JP3693241B2 - Oral hygiene state inspection device and method for measuring the number of microorganisms in the oral cavity - Google Patents

Description

【００４４】
さらに、微生物の細胞質の比誘電率をε２、微生物を含んでいる液体の比誘電率をε１、微生物を球体と見なしたときの半径をａ、円周率をπとすると、誘電泳動力Fは（数２）の式２のように書き換えることができる。
【００４５】
【数２】

【００４６】
式２は誘電泳動による力が電位勾配、媒質と誘電体微粒子としての微生物の比誘電率の差などの影響を受けることを示している。
【００４７】
さて、図２に示すギャップ１２は櫛歯状の薄膜電極２が対向している部分である。ギャップ１２付近に浮遊する微生物は、ギャップ１２間に生じるこのような電界作用によってギャップ１２に引き寄せられ、電気力線に沿って整列する。このとき、ギャップ１２付近の微生物の整列状態は、試料液体中に存在する微生物数とギャップ１２の間隔に依存するが、十分に微生物数が多いときにはギャップ１２が微生物が鎖状に繋がって架橋されるほどになる。そして、当初からギャップ１２付近に浮遊していた微生物は直ちにギャップ１２部分へ移動し、ギャップ１２から離れたところに浮遊していた微生物は距離に応じて所定時間経過後にギャップ１２部に到達するため、所定の時間後にギャップ１２付近の所定領域に集まっている微生物の数は測定セル１内の微生物数に比例する。この比例関係を基に試料中の微生物数を算出することができる。
【００４８】
実施の形態１においては、誘電泳動を生じさせるために交流の電界を用いているが、この交流印加の条件下では、誘電率εは複素誘電率ε'で表され、導電率σの影響を受ける。例えば、微生物を含んでいる液体の複素誘電率は液体の導電率σ１との関係において（数３）の式３のようになる。
【００４９】
【数３】

【００５０】
今、微生物を含んでいる液体の導電率σ１が高くなる方向に変化した場合について考えてみると、複素誘電率で考えた式２に中の項（ε１−ε２）／（ε１＋２ε２）（ｃｌａｕｃｉｕｓ−Ｍｏｓｓｏｔｉ式と呼ばれている）の値が非常に小さくなり、誘電泳動力Fの値は小さくなる。そして、その結果微生物を電極付近に集めることができなくなり、測定感度は低下することになる。液体の導電率σ１を決定するのはほとんどが液体中に溶解している導電性物質イオンであるので、液体中からイオンを除去してやれば液体の導電率σ１は低下し、その結果誘電泳動力Ｆが増大して感度が向上することになる。
【００５１】
ところで、本実施の形態１におけるギャップ１２の間隔は５μmに設定されているが、この値に限定されるものではない。ギャップ１２の間隔は測定対象となる試料溶液中の微生物の種類や濃度に応じて調節されるのが望ましく、実施の形態１では、口腔内の微生物種を対象とした最適測定条件を本発明者らが鋭意検討した結果５μmという値を設定している。この値は試料溶液の特徴に合わせて０．２〜３００μmの範囲で適宜調節されることが望ましい。
【００５２】
以下、試料の採取から試料液中の微生物の測定、口腔内の衛生状態評価にいたるまでの一連の流れ、手順を説明する。まず、口腔内から試料を得ることが必要である。被験者の口腔内から得られる試料はいくつかの種類が考えられる。それは、第１に唾液や唾液を染みこませた布状のもの、第２に歯牙や舌や口腔内壁を拭った布や綿棒、そして第３に歯間からピック状のもので掻き取られた試料などである。
【００５３】
試料はその由来によって様々な情報をもたらす。例えば、第１の試料である唾液は、口腔内の総合的な衛生状態を評価するに適した試料であるといえる。唾液は口腔内に数カ所ある分泌線を出て口腔内を洗いながら広がっていく課程で口腔内の微生物を溶かし込む。この唾液中の特定の細菌の数と、う触の間には相関関係が存在することが従来から解明されており、サリバテストと呼ばれる一連のカリエスリスクテスト（う触危険度テスト）中で、培養法による菌数計測が行われていることからも分かるように、唾液内の微生物を調べることで口腔内全体の衛生状態を評価することができる。
【００５４】
また、第２の試料の歯牙表面などを拭った試料や歯間から得られた試料は、採取した局所部位の衛生状態を反映している。上述したように歯牙表面や歯間には微生物はプラークを形成して存在しているため、試料採取部位にプラークが付着していた場合には試料中微生物数は大変多いものになる。このため測定は比較的容易である。
【００５５】
このように口腔内の衛生状態を評価するには、例えば唾液を用いても、歯牙表面などを拭った試料を用いても、どちらでもよいが、実施の形態１においては歯牙表面を綿棒で拭ったものを試料としている。具体的に本実施の形態１での試料採取は、被験者自らが綿棒を手に持ち測定部位の歯牙表面をこすることで行う。
歯牙表面をこする回数や力はあらかじめ決めておけばよい。特定の歯牙表面から試料採取を行えばその部位のみの衛生状態が、また全体的に採取を行うと口腔内の状態が総合的に判定されることになる。もちろんサンプリング部位が多くなるとそれだけ試料中の微生物の絶対数も多くなっていくので、測定を行う前にどのパターンや条件で評価を行うのかをあらかじめ決めておき、それに従った試料採取を行う。実施の形態１における口腔内衛生状態検査装置はいくつかのパターンでの測定評価に対応したプログラムがあらかじめ内蔵されており、適宜被験者が測定パターンを選択できるようになっている。以下、歯牙表面を綿棒でふき取った一つの試料を測定する場合を説明するが、前述したように試料の形態および試料数は評価の目的にあわせて都度選択されるべきものである。
【００５６】
さて、試料採取を行う一方で、口腔内衛生状態測定装置は測定評価のための準備を行う。まず測定セル１内には試料を懸濁させるための液体が満たされる。懸濁媒としては様々な液体を用いることが可能である。例えば、水、油類、エタノール等のアルコール類、アセトン、ＤＩＭＳＯ、フラン、その他有機溶剤等およびこれらの混合物を懸濁媒として使用することができる。実施の形態１では、試料が水溶性のものであること、また入手が容易であることから懸濁媒に精製水を使用している。水道水等も測定に供することは可能であるが、地域によって溶解物のばらつきが大きいこと、また井戸を水源とするものの一部には導電率が非常に大きなものがあることから本実施の形態１では採用していない。
【００５７】
測定セル１内に懸濁媒としての精製水を満たした後、図示しない電源部スイッチを投入する。電源部が投入されると、制御部７は測定前の準備動作を行う。まず、精製水が正常な状態であることを確認するために、制御部７は泳動電源部５を制御して薄膜電極２に周波数１００ｋＨｚ、電圧０．１Vｐｐの交流を印加し、これと同時に測定部６を制御して印加している電圧、回路に流れている電流、そして位相角を測定する。測定部６は、この結果を演算して精製水の導電率を算出する。導電率算出の過程の詳細は省略するが、まず後述するインピーダンス解析から薄膜電極２間の導電率を算出し、ついでその値を精製水の導電率に換算する。薄膜電極２間の導電率は精製水の導電率と比例するので、算出された電極間導電率に電極形状で定まる係数をかけるだけで精製水の導電率を算出することができる。
【００５８】
ところで、上述したように試料液の導電率があまりに高いと測定の精度が低下するので本実施の形態１においては測定を行う試料液の導電率に一定の制限として１０ｍＳ／ｍという値を設けている。制限を設ける理由は、一つにはイオンによる上述した誘電泳動の特性を鑑み測定に一定の精度を確保するためであり、今ひとつは電極を電気分解によるダメージから保護するためである。仮に測定試料が非常に大きな導電率を持っていても、薄膜電極２が電気分解から守られるように最初に印加される電圧は０．１Ｖｐｐと低めに設定しておけば、電極が電気分解でダメージを受けることはない。ただ、１０ｍＳ／ｍという値は限定的なものではなく、条件に応じて適宜設定されるべきものである。
【００５９】
さて、精製水の導電率が１０ｍＳ／ｍ以下であることが確認されると、制御部７は表示部８を制御して測定準備が完了したことを被験者に知らせる。これにより、測定動作のすべてが終了したことになる。
【００６０】
測定準備が完了すると、被験者は測定試料としての歯牙表面を拭った綿棒を測定セル１内の精製水に浸漬して、綿棒に付着した微生物を精製水に懸濁させる。
このとき、綿棒をゆらしたり、壁面にこすりつけたり、あるいは回転子３を回転させて測定セル１内に水流を起こすなど懸濁を促進する処理をすることが望ましい。これらによって測定用の試料液が作製される。
【００６１】
試料液ができると、被験者は図示しない測定ボタンを押して装置に測定開始を指示する。測定開始の指示を受け、制御部７は薄膜電極２に周波数１００ｋＨｚ、電圧０．１Ｖｐｐの交流電圧を印加する。同時に測定部６を制御して印加中の電圧、回路に流れている電流、位相角を測定し、試料液の導電率を測定する。口腔内の状態によっては試料液の導電率が１０ｍＳ／ｍを超過することがあるが、この場合、制御部７が試料液の導電率が高すぎる旨のエラーメッセージを表示して、被験者に対して、試料液を希釈して導電率を下げるか、または試料液を再度作製するか等の作業を促す。試料液の導電率が１０ｍＳ／ｍ以下であることが確認されると、本測定がスタートする。
【００６２】
まず、制御部７は測定電極に周波数１００ｋＨｚ、５Ｖｐｐの交流電圧を印加する。これとともに電流と位相角の測定を始める。実施の形態１においては、測定データは３秒おきに採取され、その度に演算されて結果が測定部６内の図示しないメモリに蓄積されていく。以下、データが採取され演算されてからメモリに蓄積されるまでの過程を説明する。
【００６３】
測定部６が収集するデータは印加された電圧、電流、位相角の３つである。測定部６はこれら得られた測定結果から、薄膜電極２間に想定される等価回路を後述する抵抗と静電容量からなるＣＲの並列回路であるとみなしたときの抵抗成分の値を計算し、最終的に薄膜電極２間の電導度を算出する（以下、薄膜電極２間の電導度をコンダクタンスと表現する）。
【００６４】
コンダクタンスを求めるためには、まず薄膜電極２間のインピーダンスを求め、このインピーダンスに対して後述する位相角を加味した演算を行う。インピーダンスは印加電圧と電流の除算で求めることができる。コンダクタンスの算出はやや複雑であるが、インピーダンスを測定のための電圧と電流の位相の差を角周波数の角度差で表現した値（以下、位相角という）を使って複素平面上に極座標表現し、これを解析することで算出することができる。以下、インピーダンスをＺ、静電容量をＣ、リアクタンスをｘ、レジスタンスをｒとして、図３、図４と（数４）〜（数８）の式４〜８を用いて詳細に説明する。
【００６５】
【数４】

【００６６】
【数５】

【００６７】
【数６】

【００６８】
【数７】

【００６９】
【数８】

【００７０】
（数４）はＣＲ並列等価回路の合成インピーダンスを表す式４、（数５）はＣＲ並列等価回路のレジスタンス表す式５、（数６）はＣＲ並列等価回路のリアクタンスを表す式６、（数７）はＣＲ並列等価回路の抵抗値を表す式７、（数８）はＣＲ並列等価回路の静電容量値を表す式８である。
【００７１】
図３（ａ）は電極間の電気的状態を等価回路で示したものである。図３（ａ）において、５０は薄膜電極２の一方の極、５１は薄膜電極の他方の極、５２は等価回路における等価的な静電容量成分を表すコンデンサ、５３は等価回路における抵抗成分を表す電気抵抗である。また、図３（ｂ）において、５４は時間軸、５５は波形の振幅を表す軸、５６は印加される電圧波形、５７は回路を流れる電流の波形である。
【００７２】
測定開始直後のギャップ１２の間には微生物を含んだ試料液が存在しており、誘電泳動によって微生物が電極間のギャップ１２に移動する前には、試料液を電極間誘電体として構成されるコンデンサ５２と試料液による電気抵抗Ｒ５３が並列に電極５０と５１間を結んでいると考えられる。そして、誘電泳動によって微生物が移動した後は、後述するように微生物体が誘電体微粒子としてふるまうために、コンデンサ５２と抵抗Ｒ５３の絶対値は変化するが、等価回路の接続形態は変わらない。以下、この等価回路をＣＲ並列回路と呼ぶ。
【００７３】
このようなＣＲ並列回路に交流電圧を印加すると、回路に流れる電流５７と印加した電圧５６の間に図３（ｂ）に示すような位相の差が現れることが一般に知られている。位相差を印加した電圧の周波数を角周波数ωであらわしたときの角度差θを用いて複素平面上に極座標表示すると、電圧、電流、位相角の間には図４に示す関係がある。
【００７４】
インピーダンスＺは測定される印加電圧と電流の除算で得られ、図４に示されたベクトルの絶対値に相当する。この時、インピーダンスＺはＺ＝ｒ＋ｊｘ（ｊは虚数単位）の形で表現することができ、レジスタンスｒはｒ＝Ｚｓｉｎθとして図３（ａ）に示されたＣＲ並列回路の合成インピーダンスの電気抵抗成分、リアクタンスｘはｘ＝Ｚｃｏｓθとして同回路の静電容量成分の逆数に関連付けられる。
【００７５】
一方、図３（ａ）のＣＲ等価回路の合成インピーダンスは（数４）の式４で表現され、式４をＺ＝ｒ＋ｊｘの関係からレジスタンスｒとリアクタンスｘに分解して（数５）の式５と（数６）の式６を得る。式５と式６を連立させて変形すると（数７）の式７と（数８）の式８を得る。
【００７６】
式７及び式８に測定のための電圧値、その時の電流値、電圧と電流の位相角の測定値から演算したｒ、ｘ、ωを代入することにより等価回路における電気抵抗Ｒ５３とコンデンサ５２を知ることができる。得られた電気抵抗成分の逆数をとることで電極間のコンダクタンスを得ることができる。
【００７７】
このような演算で行って得られたコンダクタンスの値は、測定を行った時間または測定を行った順番を表す値と共にメモリに記録されて、一点のデータ採取に関する作業が終了する。その後、予めプログラミングされた所定の回数のデータ数を採取し、測定部６は蓄積されたコンダクタンスのデータ解析を行う。コンダクタンスのデータ解析は、時間経過に伴うコンダクタンスの変化の傾きの値を求めることである。
【００７８】
コンダクタンスの時間変化の傾きを求める方法は、得られたデータに対して最小二乗法で求められる直線近似を行うのが最も簡単である。微生物の濃度が高く、時間経過に伴ってコンダクタンスの変化の傾きが次第に小さくなっていくような曲線の場合でも、採取したデータ全体ではなく、初期の一部のデータを取り出して接線で直線近似すればよい。データ全体では曲線であっても、必要なのは初期のコンダクタンス変化の傾きである。このような微生物濃度が高い試料では、測定毎のコンダクタンス変化が大きく、はっきりとしたノイズの少ない測定結果を与えるので、初期の一部のデータだけでも十分な精度で傾きを算出することができる。
【００７９】
さて、なぜコンダクタンスの時間変化の傾きを測定すれば微生物数を算出することができるかというと、上述したように微生物は電気的には抵抗と静電容量の並列接続された素子として等価的に表現することができるからである。これは微生物がイオンリッチで比較的電気伝導率が大きな細胞壁と、リン脂質からなり電気伝導率の小さな細胞膜に囲まれていることに起因する。誘電泳動によりギャップ１２に移動する微生物によってギャップ１２が架橋されると、微生物を介して薄膜電極２間に電流が流れるようになる。ギャップ１２へ泳動される微生物の数が増え、微生物による架橋の数が増えると薄膜電極２に流れる電流が増加するから、薄膜電極２間のコンダクタンス変化を測定すればその値はギャップ１２付近に移動してきた微生物数、ひいては試料液中に存在する微生物数に相関した測定結果を得ることができるのである。このようなコンダクタンスの時間変化の一例を示したのが図５である。図５から、測定初期のコンダクタンスの時間変化の傾き（勾配）もコンダクタンスの時間変化と同様に、微生物数に対応して増加しているのが分かる。
【００８０】
コンダクタンスの時間変化で微生物数を算出する場合、過渡状態が経過して平衡状態になってからコンダクタンスを測定することも考えられるが、この場合どうしても時間が長くかかる。しかし、測定初期のコンダクタンスの時間変化の傾き（勾配）で微生物数を算出する場合は、比較的短時間で微生物数を算出できるという優れた特徴を有している。
【００８１】
さて、最終的に試料液中の微生物数を表示するためには、コンダクタンスの時間変化の傾きと試料中の微生物数の変換式が必要である。この変換式は、実際に口腔内から得られた試料で作製した試料液を、本実施の形態１で説明した口腔内衛生状態検査装置の測定系と、培養法などの従来から微生物数の測定法として確立している方法を用いて、双方の測定方法で同時に測定し、従来の確定した方法で測定した微生物数とコンダクタンスの時間変化の傾きの間の相関関係を回帰分析し、その結果得られる関数をもちいる。発明者らは測定を繰り返し、鋭意検討した結果、口腔内に存在する微生物の種類には個人差があるが、上述した二つの測定方法の間にはきわめて良好な相関関係が存在する、との知見を得ている。その一例を図６に示す。図６のグラフによれば、例えば、測定によってコンダクタンス変化の傾きが０．１と出た場合には、試料液中の微生物数は１ｍｌ当たり１０の７乗近傍と算出することができる。このような相関関係を変換式としてプログラミングし、測定部６のメモリに記憶させることによって、微生物数が未知の口腔内試料を測定する場合にも、コンダクタンスの時間変化の傾きの値を代入することにより試料液中の微生物数を算出できる。
【００８２】
さて、口腔内に関する個人の臨床的な性質には差があり、微生物数が比較的多くても口腔内疾患に全く縁がない人から、その反対に口腔内は比較的清潔であると思われるにも関わらず、う触等から逃れられないという人まで様々である。しかし、どのような体質の人であれ、歯牙表面のプラーク付着はない方が衛生的という点では違いはない。そこで、実施の形態１で測定される微生物数は、歯科医師など専門家の指導によって１度でよいから、正確に個々の被験者に応じた口腔内衛生状態の評価をしてもらい、その後はその評価に従って微生物数をカウントし健康増進を図るのが望ましい。
【００８３】
以上説明したように、試料液中の微生物数を測定し表示部８に表示を行ってすべての測定動作が終了する。被験者は試料液を捨て、再測定する場合は同様の手順で次の測定を行えばよい。このように本実施の形態１では、きわめて簡易な方法で、試薬であるとか特別な装置や訓練を必要とすることなく、客観的に被験者自らの口腔内の衛生状態を調べることが可能な機器を提供することができる。
【００８４】
（実施の形態２）
本発明の実施の形態２における口腔内衛生状態検査装置と口腔内衛生状態検査方法について図面を参照しながら詳細に説明する。なお、実施の形態１と重複する部分の説明については実施の形態１に譲り説明を割愛する。図７は本発明の実施の形態２における口腔内衛生状態検査装置の全体横成図である。
【００８５】
図７において、４０は測定セル、４１は薄膜電極、４２は回転子、４３はスターラー、４４は泳動電源部、４５は測定部、４６は制御部、４７は表示部、４８は隔膜、４９はイオン交換樹脂である。
【００８６】
実施の形態２の口腔内衛生状態検査装置が、実施の形態１の口腔内衛生状態検査装置と最も異なるところは測定セル４０の構成であり、以下、実施の形態２が実施の形態１と異なる部分について説明を行う。実施の形態２における測定セル４０内部は、隔膜４８によって機能的に２室に分割されている。実施の形態２における隔膜４８はニトロセルロース製のメンブレンフィルタであり、その細孔径は０．４５μｍである。隔膜４８はイオンなどの微細なものは通すが、微生物が通過できない程度の細孔径を持つものであれば利用することが可能である。また、実施の形態２においては隔膜４８という形で表現しているが、透過／非通過を選択的に可能にするものであれば形状はとくに制限されるものではない。
【００８７】
本実施の形態２におけるイオン交換樹脂４９は、陰イオン交換樹脂と陽イオン交換樹脂の混合物である。陰イオン交換樹脂はＯＨ型、陽イオン交換樹脂はＨ型が用いられる。陰陽それぞれのイオン交換樹脂４９は、試料液中の陰陽イオンをＯＨ^-イオンとＨ⁺イオンに交換することで試料液の導電率を低下させるものである。実施の形態２におけるイオン交換樹脂４９が、本発明における試料液の導電率を調整する導電率調整部に相当する。
【００８８】
以下、本実施の形態２における口腔内衛生状態測定装置の一連の動作と手順を実施の形態１と異なる点につき重点的に説明する。口腔内からの試料採取後試料を精製水に懸濁させ試料液を作り、測定開始ボタンを押すことによって制御部４６まず試料液の導電率を測定する過程までは実施の形態１と同様である。
【００８９】
実施の形態１においては、測定開始前の試料液の導電率が１０ｍＳ／ｍを越えていると判断した場合には、エラーを表示して試料液を測定可能な導電率になるまで希釈するか、または試料を作製し直すことを行わない限り測定を進めないような処理を行った。しかし、本実施の形態２では１０ｍＳ／ｍを越えていた場合でも測定を継続する。なお、１０ｍＳ／ｍという値は試料と測定系の組み合わせによって適宜決定されるべきものである。
【００９０】
さて、制御部４６は測定開始前の導電率が１０ｍＳ／ｍを越えていると判断した場合には、直ちに測定を開始するのではなく、予めプログラムで設定されている所定時間測定開始時間を遅延する処理を行う。そして、所定時間経過後に再度試料液の導電率測定を行い測定の可否の判断を行う。制御部４６が測定開始を遅らせている間に、測定セル４０内ではイオン交換樹脂４９によって試料液の導電率が低減される。以下、遅延処理について説明する。
【００９１】
口腔内からの試料には多数の含有イオンが含まれるが、その多くはナトリウムイオンと塩化物イオンであり、この２つのイオンを例にあげて、導電率低減に至る挙動を説明する。他にも陰陽イオンが試料液中には存在しているが、その挙動はこの２つのイオンと同様である。
【００９２】
測定セル４０内に満たされた精製水中に試料が懸濁されると同時に、精製水中にナトリウムイオンと塩化物イオンが溶解・拡散していく。濃度勾配によって拡散したナトリウムイオンと塩化物イオンは、容易に隔膜４８を抜けてイオン交換樹脂４９と相互作用し、イオン交換が生じる。ナトリウムイオンは陽イオン交換樹脂のＨ⁺イオンと交換され、塩化物イオンは陰イオン交換樹脂のＯＨ^-イオンと交換される。イオン交換によって試料液中に放出されたＨ⁺イオンとＯＨ^-イオンは直ちに結合して水分子となる。イオン交換樹脂４９近傍のナトリウムイオンと塩化物イオンは、イオン交換によってイオン交換樹脂４９に捕捉されてしまい、イオン交換樹脂付近のナトリウムイオンと塩化物イオンの濃度が低下する。その結果測定セル４０内でナトリウムイオンと塩化物イオンの濃度の不均衡が生じるため、濃度勾配に従って新たなナトリウムイオンと塩化物イオンがイオン交換樹脂付近に移動してくる。その後同様のことが繰り返され、測定セル４０内のナトリウムイオンと塩化物イオンの濃度は次第に低下していく。
【００９３】
イオン交換によって放出されるＨ⁺イオンとＯＨ^-イオンは結合した後もほとんど解離することなく、水分子として結合を保つため結果として測定セル４０内の試料液の導電率は低下していく。イオン交換樹脂近傍のイオンと樹脂とのイオン交換反応は瞬間的に終了するため、ナトリウムイオンと塩化物イオンの初期濃度が高いほど大きな濃度勾配が生じる。大きな濃度勾配はそれに比例した物質移動（移動するナトリウムイオンと塩化物イオンの絶対量）を招くので、結局測定セル４０中のナトリウムイオンと塩化物イオンの初期濃度が大きいほど急激に濃度低下、すなわち導電率の低下が生じる。このとき懸濁液中の微生物は、隔膜４８を通過することができないため測定セル４０内の隔膜４８で隔てられた電極側にとどまり測定の効率を低下させることがない。
【００９４】
さて、制御部４６が測定開始を遅らせている間に、この濃度調整が終わり、所定時間経過後に試料液の導電率を再び測定したとき、測定開始条件を満たしていればそのまま測定を実行する。上述したように試料液中のイオン濃度が高く、試料液の導電率が高いときにはイオン濃度の変化が急激に起きるが、試料液の導電率が１０ｍＳ／ｍ程度まで低下してくるとイオン濃度の変化も緩慢になり、１０ｍＳ／ｍ以下では測定中の導電率の変化は事実上無視できる程度になる。
【００９５】
実施の形態２では、試料液の導電率を変化させる導電率調整部としてイオン交換樹脂４９を使用したが、同様の目的を達成するための導電率調整部は他のものでもよい。例えば、透析を用いる調整である。試料を懸濁した試料液を、半透膜を介して蒸留水などの低イオン濃度の液体と接触させる。すると、半透膜の内外でのイオン濃度の勾配によって試料液中のイオンは半透膜を介して蒸留水側に拡散していく。蒸留水の量が試料液の量に対して十分に多いときには試料液中のイオンはほとんど蒸留水側に移行し、結果として試料液中のイオン濃度が低下する。このとき、蒸留水を流すなどして、常に試料液との間に大きなイオン濃度の勾配を保つような工夫を行うことで、迅速に試料液中のイオンを除去することができる。このように試料液中のイオン濃度を低下させ、試料液の導電率を低減する口腔内衛生状態検査装置は実施の形態２で説明したものに限られない。
【００９６】
ところで、実施の形態２においては、測定部４５は最終的に測定を行った試料液の導電率、すなわち試料液の導電率が１０ｍＳ／ｍを下回ったという判断を行った後に測定した導電率をメモリに保持し、後述する微生物数算出時の補正のための準備を行う。誘電泳動による微生物の電極への捕集と、インピーダンス変化を用いたコンダクタンスの傾き算出までの過程は、実施の形態１と同様であるので実施の形態１に説明を譲って割愛する。
【００９７】
測定部４５はコンダクタンスの傾きが得られた後に、以下の考え方に従って試料液の初期導電率によるコンダクタンス変化の傾きに補正を加える。以下に図８を用いて試料液の初期導電率によるコンダクタンス変化の傾き補正（以下、傾き補正という）の説明を行う。図８（ａ）は低イオン濃度における誘電泳動力と泳動のための電圧の周波数の関係を説明するためのグラフ、図８（ｂ）は高イオン濃度における誘電泳動力と泳動のための電圧の周波数の関係を説明するためのグラフ、図９は印加周波数１００ｋＨｚにおける資料導電率と規格化された誘電泳動力との関係を表すグラフである。
【００９８】
さて、すでに実施の形態１において（数２）の式２を引用し試料液の導電率σ１と誘電泳動力Ｆの関係の説明を行った。この中の項（ε１−ε２）／（ε１＋２ε２）（ｃｌａｕｃｉｕｓ−Ｍｏｓｓｏｔｉ式と呼ばれている）を周波数に対してプロットしたのが図８（ａ）と図８（ｂ）である。ここで、εは復素誘電率であり、例えば（数３）の式３で表現されることは既に説明したとおりである。
上述した（ε１−ε２）／（ε１＋２ε２）の値は、誘電泳動力Ｆの大きさを表す（数２）の式２の中の項であり、その値が正で大きいほど誘電泳動力も強くなることが分かる。また、値が正の時は誘電泳動力は引力として作用するが、値が負になると誘電泳動力は斥力として作用することもわかる。
【００９９】
図８（ａ）と図８（ｂ）では試料液の導電率が異なっており。導電率は図８（ｂ）の方が図８（ａ）より大である。図８（ａ），（ｂ）の２つのグラフから分かるように、試料液の導電率が大きくなると誘電泳動が引力として作用する周波数の範囲は狭くなり、値も小さくなっていくことが分かる。本実施の形態２では、微生物数を電極上に移動させ測定するために引力を使用していることから、試料液の導電率が大きくなると感度が低下する。このときの試料液の導電率と、誘電泳動力の強度の関係を印加周波数１００ｋＨｚにおいてグラフ化したものが図９である。図９のグラフの縦軸はイオン濃度が非常に小さな純度の高い水で生じると期待される誘電泳動力を１として導電率が変化した場合の誘電泳動力を規格化したものである。以下、図９に点線で示した値を例にして試料液の初期導電率によるコンダクタンス変化の傾きの補正を説明する。
【０１００】
図９において、点線で示した導電率の値は５．２ｍＳ／ｍである。このとき誘電泳動力は、イオン濃度が非常に小さな純度の高い水で生じると期待される値の、ちょうど半分の０．５になる。誘電泳動力が半分になることで一定時間内に電極上に移動してくる微生物数が減少し、コンダクタンス変化の傾きも半分になる。従って、試料液の導電率の補正を行わないと、導電率の影響で算出される微生物数が半分になり、最終的な口腔内の衛生状態の判定結果が不正確になる。そこで、採取されたデータから計算されるコンダクタンスをそのままプロットして得られる傾きに１／０．５を乗算して補正を行う。これにより、試料液の導電率が高い条件下で測定したにも関わらず、イオン濃度が非常に小さな純度の高い水で測定したときと同じ傾きに換算することができる。このような方法により、１０ｍＳ／ｍ程度以下までの試料液で測定されたコンダクタンス変化の傾きであれば、補正が可能である。試料液の導電率が１０ｍＳ／ｍを越えると、補正値がマイナスになってしまい計算結果が不正になるが、この領域は現象的には誘電泳動力Ｆが０であるかまたは斥力を及ぼす領域であり、予め試料液の導電率を測定することによって、導電率が１０ｍＳ／ｍを越えている場合は測定を行わないようにすれば、計算結果が不正になることはない。
【０１０１】
実施の形態２で説明したように、試料液の導電率を調整する機構とコンダクタンスの傾きの値を試料液の初期導電率の値で補正することで、そのままでは測定が不可能であるか、または評価結果が不正確になるような場合であっても正しい評価を行うことができる口腔内衛生状態検査装置を提供することができる。
【０１０２】
（実施の形態３）
本発明の実施形態３の口腔内衛生状態検査装置と口腔内衛生状態検査方法について図面を参照しながら詳細に説明する。なお、実施の形態１と重複する部分の説明については実施の形態１に譲り説明を割愛する。図１０は本発明の実施の形態３における口腔内衛生状態検査装置の全体横成図である。
【０１０３】
図１０において、２１は口腔内試料を懸濁させた試料液を保持するためのセル、２２は光源、２３は光源側光学系、２４は受光器、２５受光側光学系、２６は測定部、２７は表示部、２８は制御部、２９は光源からセル２１内に入射した光束、３０はセル２１内の微生物によって散乱された散乱光である。
【０１０４】
実施の形態３のセル２１は、試料液を導入／排出するための開口部を有するとともに、測定のための光束２９をセル２１内に導入し散乱光を検出する透明な開口部を有している。ここで透明な開口部というのは、測定波長において光学的に透明と評価される開口部という意味である。実施の形態３においては、セル２１は一般的なガラス製の容器を用いている。光源２２は、半導体レーザや発光ダイオード（ＬＥＤ）が小型で消費電力も少ないため望ましい。しかし、受光器の検出波長範囲と組み合わせることで、白熱電球、蛍光管、キセノンやナトリウム等のガスを封入した発光管等でも使用可能である。ただ、実施の形態３においては構成が簡単になるため、発振波長６６０ｎｍの半導体レーザ（以下、ＬＤという）を使用している。またＬＤからの照射光はセル２１の中央部で、試料液深さのほぼ中央の部分を横切るように設定されている。
【０１０５】
実施の形態３における光源側光学系２３は、光源２２としてＬＤを使用しているため光束２９が特定方向に強力に放出されるから、これをそのままセル２１に入射して測定すればよい。従って、とくに光学系を設ける必要がないのであるが、実施の形態３ではビームの断面形状を整えるためのシリンドリカルレンズや、光束２９の広がりを制御するコリメーターレンズを使用している。光源２２が白熱電球などの場合には、光源側光学系２３は上記の構成に加えて反射鏡やスリット、波長の選択透過フィルタなどを設ける必要があり、やや複雑なものになる。
【０１０６】
受光器２４は一般的なフォトダイオード（以下ＰＤとする）が使用される。受光器２４に関しては様々なタイプのものが広く知られており、使用可能な受光器２４は多い。上述したように受光器２４は光源２２側の特性に合わせて選択されればよい。また、このことは受光側光学系２５についても同様のことが言え、光源２２および受光器２４の組み合わせによって様々な光学系を使用可能である。
実施の形態３においては、受光側光学系２５には詳細に図示しないがセル２１内の光束２９からの散乱光３０をＰＤに集光するためのレンズが設けられている。
【０１０７】
以上説明したセル２１および光学系は、外部からの迷光による測定誤差を避けるために、全体が外部からの光を遮断することができる容器内に収納されている。測定部２６には図示しないマイクロプロセッサ、メモリ、光源２２用のＬＤドライバ回路、ＰＤからの信号を増幅して検出する検出回路等が備えられており、散乱光３０の強度を検出して微生物数を定量検出し、さらにその結果を口腔内の衛生状態の評価へと換算することができる。
【０１０８】
表示部２７は、本実施の形態３における最終出力としての口腔内の衛生状態の評価結果を被験者に知らしめるための表示を行う。表示の形態については既に実施の形態１において説明を行ったので割愛する。また、本実施の形態３における口腔内衛生状態検査装置の評価結果を他の機器の制御のために用いる場合はとくに表示を行う必要がない。一連の動作は制御部２８によって制御される。
【０１０９】
さて、実施の形態３における一連の測定動作と手順を以下に説明する。試料の採取については実施の形態１と同様であるので割愛する。実施の形態３における試料の懸濁媒は、散乱光を測定するという原理上微粒子やこまかな泡など光を散乱してバックグラウンドを高めるノイズ成分が混入していないようにすることに注意を払う必要がある。その組成については実施の形態１で説明したような液体が使用可能である。また、実施の形態１と異なり懸濁媒がイオンを含むものであっても測定に支障がない。
【０１１０】
実施の形態３においても、試料の性質上懸濁が容易であるという理由で、懸濁媒に精製水を使用している。イオンを含んでいても問題ないので、精製水でなくとも一般の水道水も使用可能であるが、微粒子の混入についてばらつきがあることが懸念されるため精製水としている。さらには測定前に精製水を０．２２〜０．４５μｍ径のフィルタで濾過することができれば測定の精度を向上させる意味で望ましい。
【０１１１】
試料の精製水への懸濁も実施の形態１に同様である。図１０にはセル２１内を攪拌する機構を設けてはいないが、攪拌や超音波振動など、試料の懸濁を助けるような流動促進手段をセルに設けることが望ましいのはいうまでもない。セル２１内に試料液が準備されると、被験者は図示しない装置の電源部スイッチを投入し、やはり図示しない測定開始ボタンを押して装置に測定開始を指示する。測定開始の指示を受け制御部２８は測定部２６を制御して光源２２を点灯させる。以下、制御部は各部と連携しながらメモリ上にあらかじめ保存されたプログラムに従ってスムーズに測定を進めていく。
【０１１２】
光源２２の点灯後、測定部２６は受光器２４からの信号を検出する。実施の形態３における光源２２のＬＤの波長は６６０ｎｍであり、測定対象の比較的小さな細菌でも１μｍ程度の大きさであるから、光束２９の通過する光路上にこれら微生物が存在すると光束２９の一部が散乱される。散乱された光の一部は受光側光学系２５に備えられた図示しないレンズによって集光され受光器２４に導かれる。受光器２４としてのＰＤに入射した散乱光はＰＤによって電気信号に変換され測定部２６によって検出される。
【０１１３】
受光器２４としてのＰＤからの出力電圧は入射した散乱光量に応じて変化し、散乱光量は光束２９上に存在する微生物の数によって変化するため、ＰＤの出力電圧を検出することで測定部２６は光路上に存在する微生物の数を測定することができる。
【０１１４】
光路上の微生物数はセル２１内に満たされた試料液中を浮遊している微生物の平均的な数を反映しており、光路上の微生物数から最終的に試料中の微生物数を算出することが可能になる。ここで、光を散乱するのは微生物ばかりではなく、口腔内に存在する食べカスや懸濁時に混入した泡なども同様であり、これらは微生物に対して非常に大きいので大きなノイズとして検出されてしまう恐れがある。これを防ぐために実施の形態３では、測定開始後から予め設定された所定時間連続して測定を行い、散乱光の時間変化を監視する。時間経過とともに、食べかすなどの大きな浮遊物は迅速に沈降してセル２１の底部に堆積し、また気泡は浮力によって浮上しセル上部の液面近傍へ移動するが、微生物は、ブラウン運動の影響を受けて容易に沈降せず、また浮上することもないため一定時間経過後した後には散乱光はほぼ微生物に依存したものだけになる。測定部２６は散乱光が一定時間大きな変動が無くなったことを確認した後、その時点での値を測定結果として微生物数の算出を行う。
【０１１５】
散乱光強度からの試料液中の微生物数の計算は、実施の形態１で説明した方法と同様、本実施の形態３で測定した試料液をそのまま培養法等の既に確立した微生物数の測定法で追試験し、それらの結果の相関性を関数化またはテーブル化して演算／参照することによって算出する。微生物数を最終出力である衛生状態の評価へ換算する部分も実施の形態１に同じであるので割愛する。評価結果を表示部２７に表示し、被験者にその結果を知らしめることで一連の測定動作を終了する。
【０１１６】
ここで、本実施の形態３では光束２９が貫くセル２１内の光路上に存在する微生物に起因した散乱光を測定することによって微生物数を算出し、最終的に口腔内の衛生状態の評価結果に結びつける実施の形態を説明したが、測定は散乱光だけでなく透過光によっても行うことができる。上述したように、光束２９が貫く光路上に微生物が存在すると、光束２９の一部は散乱される。光束２９の一部が散乱されるということは散乱点以降の光束２９の強度は散乱光の分弱くなるということであり、つまりは散乱光が多ければ多いほど、すなわち試料液中の微生物数が多ければ多いほど透過光の強度は低下していく。
【０１１７】
従って、散乱光と透過光の測定を行うことは同じ現象を表裏に評価することであり、測定系の構成を変更すれば透過光を測定しても実施の形態３と全く同様の考え方で試料液中の微生物が測定できる。光源２２と受光器２４を直線上に対向して配置することで容易に実現できる。散乱光の場合は微生物数が増加すればするほど受光部で検出される光量が増加し、透過光の場合は減少する。透過光の減少分を散乱光の強度測定結果と同様の取り扱いで処理すれば試料中の微生物数、ひいては口腔内の衛生状態の評価を行うことができる。
【０１１８】
このように口腔内から得られた試料を液体に懸濁した試料に対し光を用いた測定を行うことでも口腔内の衛生状態を評価する装置を実現することができる。
【０１１９】
（実施の形態４）
本発明の実施形態４の口腔内衛生状態検査装置と口腔内衛生状態検査方法について図面を参照しながら詳細に説明する。なお、前述した他の実施の形態と重複する部分については説明を割愛する。図１１は本発明の実施の形態４における口腔内衛生状態検査装置の全体構成図である。
【０１２０】
図１１において、６０は試料を収容することができる密閉可能なセル、６１はセル６０内に配置されたガスセンサ、６２は測定部、６３は表示部、６４は制御部、６５は口腔内から採取された試料を含む冶具である。
【０１２１】
セル６０は内部にガスセンサ６１を備え、試料の出し入れをするための開閉部を備えている。セル６０は開閉部によって密閉され、測定時は外部との間に空気の出入りができないようになっている。セル６０はそれ自体が揮発性物質を含まないようにガラスの容器を採用している。プラスチック等の材料でもよい。また、本実施の形態４では採用していないが、より高感度な測定を行うためには、セル６０全体をヒーター等の手段で加熱すると良い。加熱によって試料からの物質の揮発がより活発になり、加熱していない時に比較してセル６０内の揮発性物質の濃度が高まることで結果的に高感度な測定を実施することができる。
【０１２２】
実施の形態４においては、ガスセンサ６１は、酸化スズなどを焼結した酸化物セラミックスからなるセンサ本体と、図示しないがセンサ本体を加熱し測定を安定して行うためのヒーターを備えている。セル６０内の揮発性物質にセンサ本体が感応すると、セラミックスに接続された電極間の特性が変化し、電流の形でその変化を外部に取り出すことができる。ガスセンサ６１はセル６０内の揮発性物質に感応すればよく、他の構成のこのでも構わない。既に多数の方式、材料組成からなるガスセンサ６１が提案されており、それらの中から本発明の目的に適うものを適宜選択して使用することができる。さらに、ガスセンサ６１に搭載されるセンサ本体は１種類に限定されるものではなく、複数の種類のガスセンサを同時に搭載し、同時に稼働させることもできる。
【０１２３】
測定部６２は、ガスセンサ６１を使ってセル６０内の揮発性物質を測定するために必要な回路を備えている。例えば、センサ本体を加熱するために用いるヒーター用の電源回路、センサを流れる電流を検出するための検出回路、電流値を基に演算を行うための演算回路等である。こうした回路はプログラム的にマイクロプロセッサで構成するのがよい。このほか、演算結果を一時的に保存するためのメモリ等も設けられる。
【０１２４】
制御部６４と表示部６３の構成とその動作は、実施の形態１で既に説明した制御部７および表示部８と基本的に同一であるので説明を省略する。口腔内から採取された試料を含む冶具６５は、本実施の形態４においては実施の形態１同様の綿棒を用いている。
【０１２５】
ここで、口腔内の衛生状態を評価するために口腔内から得られる試料中の揮発性物質を測定する意味について説明する。口腔内から得られる試料中の揮発性物質の種類や量は、口臭と密接に関係しており、口臭は口腔内の微生物の代謝活動によって生じるものが多く、口腔内の微生物の数や種類と関連している。口腔内の衛生状態が微生物の存在によって評価できることは既に説明した通りであり、このことから、口腔内から得られる試料中の揮発性物質の種類や量は、プラーク、そして口腔内の衛生状態には密接な関係を有すことになる。
【０１２６】
例えば、先に説明した歯周ポケットの深部に生育するＰＧ菌等の微生物は嫌気的な雰囲気を好む。一般に嫌気性の微生物、特に嫌気性の細菌は、その代謝に際して硫化水素やメルカプタン化合物などの臭気の強烈な物質を生成することが多い。口腔内の衛生状態が損なわれ、歯周病に罹患するとこれら歯周ポケット内に生息する微生物によって口臭が著しく強まる。そこで、口腔内から得られる試料中の揮発性物質の種類や量を調べることで、プラークの付着状況が分かり、口腔内の衛生状態を判定することが可能となる。歯槽膿漏や虫歯により歯牙が損傷を受けるという口腔内の疾病的な弊害のほかに、試料中の揮発性物質の種類や量を調べることで、口臭によって口腔内の衛生状態が分かり、疾病のほかに口臭対策も可能になる。
【０１２７】
さて、実施の形態４における試料の採取から口腔内の衛生状態評価にいたるまでの一連の流れを説明する。実施の形態４における試料の採取は実施の形態１同様に綿棒を用いているので、手順は実施の形態１と同じである。ただ、実施の形態４における試料は、唾液よりも歯牙表面や歯牙と歯茎の境目をこすって採取したプラークなどの方がより好ましい。それは本実施の形態４における衛生状態の判定方法は、上述したように主に歯牙と歯茎の境目の歯周ポケットに生息する微生物の分析により適しているからである。試料を採取した後、被験者は冶具をセル６０内に投入して密閉する。そして図示しない測定開始ボタンを押して制御部６４に測定開始を伝える。
【０１２８】
制御部６４は、測定開始の指示を受けて直ちに測定部６２を制御し、セル６０内の揮発性物質量の測定を開始する。実施の形態４において使用しているセラミックス系のガスセンサ６１は対象ガスの選択性がそれほど高くないため、いわばあらゆる揮発性物質について検出が可能なものである。
【０１２９】
測定部６２は、ガスセンサ６１からの信号の強度を測定して口腔内のプラーク付着状況と衛生状態を評価する。ガスセンサ６１と口腔内の衛生状態評価の間の換算は、予め専門家が指導した衛生状態の評価と、本測定法によるガスセンサ６１の信号強度の間の相関性を表す関数を定め、その関数を予めプログラミングしておくことで行う。算出された評価結果は表示部６３に表示されて被験者に報知される。本実施の形態４ではガスセンサを１種類使用した場合のみを説明したが、複数のガスセンサを併用してより詳細な解析を行って評価を行うことも可能であるし、またセンサが１種類であっても、特定のガス、例えば硫化水素やメルカプタン系の化合物を選択的に測定して評価するのも望ましい。
【０１３０】
このように、口腔内から得られた試料を密閉容器に入れガスセンサを用いて試料からの揮発性物質の測定を行うことで、実施の形態４の口腔内衛生状態検査装置は疾病のほかに口臭も対策することが可能になる。
【０１３１】
【発明の効果】
本発明の口腔内衛生状態検査装置は、制御部が電源部を制御することにより電極に電圧を印加して試料液中の微生物を誘電泳動力によって該電極上に捕集し、測定部が捕集後または捕集中の電極間のインピーダンスを測定することで試料液中の微生物数を定量的に算出するから、試薬であるとか特別な装置や訓練を必要とすることなく、簡易かつ客観的に自らの口腔内の衛生状態を調べることができる。
【０１３２】
また、試料液と電極の相対位置を変化させる流動促進手段を備えたから、試料液中の微生物を効率よく電極上に集めることができ、迅速な測定を行うことができる。
【０１３３】
また、誘電泳動によって試料中の微生物を電極上に捕集する前に、測定部が試料液の導電率を測定するから、イオン濃度の高い試料液等の測定ミスを未然に防ぐことができ、信頼性の高い判定結果を導き出すことができる。
【０１３４】
また、試料液の導電率を調整する導電率調整部を備えたから、最適な条件で誘電泳動と測定を行うことができ、迅速で精度の高い測定を行うことができる。
【０１３５】
また、測定部が試料液の導電率を測定し、測定した導電率を基に測定結果を補正するから、試料の性質に寄らず常に正確な判定結果を導き出すことができる。
【０１３９】
本発明の口腔内微生物数測定方法は、測定のための電極を備えたセル内に口腔内から採取されたサンプルを含む試料液を導入し、試料液と電極の相対位置を変化させるとともに、電極に電圧を印加して試料液中の微生物を誘電泳動力によって電極上に捕集し、電極間のインピーダンスを測定することにより試料液中の微生物数を定量的に算出するから、試薬であるとか特別な装置や訓練を必要とすることなく、簡易かつ客観的に自らの口腔内の衛生状態を調べることが可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態１における口腔内衛生状態検査装置の全体横成図
【図２】本発明の実施の形態１における電極の説明図
【図３】（ａ）電極間の電気的状態を等価回路で示した説明図
（ｂ）電流と電圧の位相の差を表した説明図
【図４】インピーダンスのベクトル分解を説明する説明図
【図５】コンダクタンスの時間変化図
【図６】培養による微生物数測定とコンダクタンス変化の傾きの相関図
【図７】本発明の実施の形態２における口腔内衛生状態検査装置の全体横成図
【図８】（ａ）低イオン濃度における誘電泳動力と泳動のための電圧の周波数の関係を説明するためのグラフ
（ｂ）高イオン濃度における誘電泳動力と泳動のための電圧の周波数の関係を説明するためのグラフ
【図９】印加周波数１００ｋＨｚにおける資料導電率と規格化された誘電泳動力との関係を表すグラフ
【図１０】本発明の実施の形態３における口腔内衛生状態検査装置の全体横成図
【図１１】本発明の実施の形態４における口腔内衛生状態検査装置の全体構成図
【符号の説明】
１，４０ 測定セル
２，４１ 薄膜電極
３，４２ 回転子
４，４３ スターラー
５，４４ 泳動電源部
６，２６，４５，６２ 測定部
７，２８，４６，６３ 制御部
８，２７，４７，６４ 表示部
１０ 電極基板
１１ 導電性薄膜
１２ ギャップ
２０，２１，６０ セル
２２ 光源
２３ 光源側光学系
２４ 受光器
２５ 受光側光学系
２９ 光束
３０ 散乱光
４８ 隔膜
４９ イオン交換樹脂
６１ ガスセンサ
６５ 冶具[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oral hygiene state inspection apparatus for inspecting the hygiene state in the oral cavity and preventing crushing and periodontal disease, and a method for measuring the number of oral microorganisms used therefor.
[0002]
[Prior art]
It is bacteria in the oral cavity that affect the hygienic condition in the oral cavity and cause touch and periodontal disease. Most of the bacteria in the mouth are localized in plaques, that is, plaque.
Therefore, plaque control for removing plaque from the oral cavity is extremely important for maintaining oral hygiene, and the oral hygiene can be evaluated by knowing the state of plaque adhesion.
[0003]
By the way, there is no conventional way to know the hygiene status of the oral cavity easily without the help of others, and examinations by specialists with specialized skills such as dentists are required to check the hygiene status of the oral cavity. Was common. However, it is rare to go to a dentist just for the purpose of knowing the hygiene status of the oral cavity, and as a result, it is impossible to prevent crushing and periodontal disease, etc. There were also many.
[0004]
Therefore, as a method for a general person to know the hygiene condition in his / her mouth in a simple and objective manner, there are investigation methods represented by Japanese Patent Laid-Open Nos. 07-068552 and 08-059513. was suggested. This conventional technique uses a pigment to dye plaque.
[0005]
[Problems to be solved by the invention]
By using the conventional techniques proposed in Japanese Patent Application Laid-Open No. 07-069852 and Japanese Patent Application Laid-Open No. 08-059513, an amateur can know the state of plaque adhesion in his / her mouth easily and objectively to some extent. . However, since the entire oral cavity other than plaque is stained red by the pigment, it is not associated with humans or examined during meals, and its usage is limited. In addition, the staining was psychologically resistant by putting the reagent in the mouth and could not be examined frequently with a simple feeling.
[0006]
In addition, because the site where plaque easily adheres is in the back of the mouth and the side of the back tooth, the situation is clearly known only for the part where the staining state can be seen from the front, such as the lip side of the front tooth, There was also a risk that it would be easy for an amateur to judge that he was healthy.
[0007]
In addition, since this conventional technique determines the presence of plaque using staining, it can qualitatively grasp the state of plaque adhesion, but has a problem that the state of plaque adhesion cannot be quantitatively grasped.
[0008]
Therefore, in order to solve these problems, the present invention provides an oral hygiene state inspection device that can easily and objectively check the hygiene state of the oral cavity even by a general user who does not have specialized knowledge. With the goal.
[0009]
It is another object of the present invention to provide an oral hygiene state inspection method that allows a general user who does not have specialized knowledge to easily and objectively check the hygiene state of his / her oral cavity.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an oral hygiene condition inspection apparatus according to the present invention includes an electrode for measurement inside, a cell that can hold a sample liquid containing a sample collected from the oral cavity, and an electrode. A power supply unit that applies a voltage for performing dielectrophoresis, a measurement unit that calculates the number of microorganisms in the sample solution, and a control unit that controls the power supply unit and the measurement unit, and the control unit applies a voltage to the electrodes. Applied to collect the microorganisms in the sample solution on the electrode by dielectrophoretic force, and the measurement unit measures the impedance between the electrodes after collection or collection, thereby quantitatively determining the number of microorganisms in the sample solution It is characterized by calculating and evaluating the hygiene state in the oral cavity.
[0011]
Thereby, even a general user who does not have specialized knowledge can investigate the hygiene state in his or her mouth simply and objectively.
[0012]
In addition, the method for inspecting the oral hygiene state of the present invention introduces a sample liquid containing a sample collected from the oral cavity into a cell equipped with an electrode for measurement, and performs a dielectrophoresis by applying a voltage to the electrode. In addition to collecting microorganisms in the sample solution on the electrodes by the dielectrophoretic force, quantitatively calculating the number of microorganisms in the sample solution by measuring the impedance between the electrodes, and evaluating the sanitary condition in the oral cavity It is characterized by.
[0013]
Thereby, even a general user who does not have specialized knowledge can investigate the hygiene state in his or her mouth simply and objectively.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The present invention includes a cell having an electrode for measurement therein and capable of holding a sample liquid containing a sample collected from the oral cavity, a power supply unit for applying a voltage for performing dielectrophoresis to the electrode, and a sample A measuring unit for calculating the number of microorganisms in the liquid; and a control unit for controlling the power supply unit and the measuring unit. The control unit applies a voltage to the electrodes to cause the microorganisms in the sample liquid to move to the electrodes by dielectrophoretic force. It is collected on the top, and the number of microorganisms in the sample solution is quantitatively calculated by measuring the impedance between the electrodes after collection or collection by the measurement unit, and the hygienic condition in the oral cavity is evaluated. Therefore, it is possible to easily and objectively check the hygiene condition in the oral cavity without using a reagent or a special device or training.
[0015]
In addition, when collecting microorganisms in the sample by dielectrophoresis on the electrode, a flow promoting means is provided to change the relative position of the sample solution and the electrode, so that the microorganisms in the sample solution can be efficiently collected on the electrode. Can be performed quickly.
[0016]
In addition, since the measurement unit measures the conductivity of the sample solution before collecting the microorganisms in the sample on the electrode by dielectrophoresis, measurement errors such as a sample solution with a high ion concentration can be prevented beforehand. A highly reliable determination result can be derived.
[0017]
In addition, since the conductivity adjusting unit for adjusting the conductivity of the sample solution is provided, dielectrophoresis and measurement can be performed under optimum conditions, and quick and highly accurate measurement can be performed.
[0018]
In addition, since the measurement unit measures the conductivity of the sample solution and corrects the measurement result based on the measured conductivity, an accurate determination result can always be derived regardless of the properties of the sample.
[0022]
The present invention introduces a sample liquid containing a sample collected from the oral cavity into a cell equipped with an electrode for measurement, changes the relative position of the sample liquid and the electrode, and applies a voltage to the electrode. And collecting the microorganisms in the sample solution on the electrodes by dielectrophoretic force, and quantitatively calculating the number of microorganisms in the sample solution by measuring the impedance between the electrodes. Since it is a method for measuring the number of internal microorganisms, it is possible to easily and objectively examine the hygiene state in the oral cavity without requiring a reagent or special equipment or training.
[0025]
Embodiments 1 to 4 of the present invention will be described below with reference to FIGS. 1 to 11 and equations (Equation 1) to (Equation 8).
[0026]
(Embodiment 1)
The oral hygiene state inspection apparatus and the oral hygiene state inspection method in Embodiment 1 of the present invention will be described in detail with reference to the drawings. FIG. 1 is an overall horizontal view of an oral hygiene condition inspection apparatus according to Embodiment 1 of the present invention, FIG. 2 is an explanatory diagram of electrodes according to Embodiment 1 of the present invention, and FIG. FIG. 3B is an explanatory diagram showing the phase difference between current and voltage, FIG. 4 is an explanatory diagram explaining the vector decomposition of impedance, and FIG. 5 is a time variation diagram of conductance. FIG. 6 is a correlation diagram between the measurement of the number of microorganisms by culture and the slope of change in conductance.
[0027]
In FIG. 1, 1 is a measurement cell, 2 is a thin film electrode, 3 is a rotor, 4 is a stirrer, 5 is an electrophoretic power supply unit, 6 is a measurement unit, 7 is a control unit, and 8 is a display unit. In FIG. 2, 10 is an electrode substrate, 11 is a conductive thin film, and 12 is a gap formed between two opposing electrodes.
[0028]
The measurement cell 1 in Embodiment 1 is a cylindrical glass container, and is provided with an opening for introducing / extracting the sample liquid. Further, the measurement cell 1 includes a rotor 3 for stirring the sample liquid. The rotor is coupled to the stirrer 4 disposed adjacent to the measurement cell 1 via a magnetic force and rotates. Uses unobstructed glass. The material of the measurement cell 1 can be plastic as well as glass.
[0029]
In the measurement cell 1, in order to move microorganisms in the sample solution to a predetermined position by dielectrophoresis, a thin film electrode 2 composed of two electrodes is nested on the electrode substrate 10 with a small gap 12 facing each other. Is provided. In the first embodiment, as shown in FIG. 2, the thin-film electrodes 2 are arranged so that comb-shaped electrodes are opposed to each other, and the gap 12 is 5 μm. The thin film electrode 2 constitutes an electrode for measurement in the present invention. The thin film electrode 2 is formed by coating a conductor on the electrode substrate 2 by a method such as sputtering, vapor deposition, or plating.
[0030]
When a voltage is applied to the thin film electrode 2 in order to move the microorganisms to a predetermined position, the electric field near the gap 12 laid between the thin film electrodes 2 becomes the strongest.
Although details will be described later, the microorganisms migrate toward the gap 12 where the electric field is most concentrated.
[0031]
The stirrer 4 and the rotor 3 are provided in order to change the relative position of the sample liquid and the electrode by stirring. However, the stirrer 4 and the rotor 3 are not necessarily provided as long as the flow promoting means changes the relative position by causing the sample liquid to flow on the electrode. There is no need for the stirrer 4 and the rotor 5. For example, a water flow may be generated in the measurement cell 1 using a pump, or the electrode may be mounted on a movable mechanism, and the electrode itself may rotate, vibrate, or translate. Various types of rotors 3 can be selected. In the first embodiment, a cylindrical shape is used.
[0032]
Next, the migration power supply unit 5 supplies an AC voltage for causing dielectrophoresis between the electrode substrates 2. The alternating current referred to here is not only a sine wave but also a voltage that changes the direction of the flow at a substantially constant cycle, and the average values of the bidirectional currents are equal. In the first embodiment, a frequency of 100 kHz and a peak-to-peak voltage (hereinafter referred to as pp) of 5 V are applied as an alternating voltage for dielectrophoresis. Of course, the frequency and voltage value of the alternating voltage for dielectrophoresis are not limited to the values described above, and can be selected from a wide range. For example, the value ranges from 100 Hz to 50 MHz in frequency. However, the frequency at which the microorganism can be most efficiently dielectrophoresed on the electrode varies depending on the condition of the sample solution and the type of microorganism.
[0033]
In the first embodiment, details will be described later, but a value of 100 kHz is set as one of frequencies suitable for performing dielectrophoresis on a sample solution under a condition in which microorganisms in the oral cavity are suspended in purified water. Selected. In addition, the higher the applied voltage, the stronger the dielectrophoretic force. However, if the voltage is increased too much, phenomena such as electrolysis causing troubles and electrical destruction of microorganisms moved between the gaps 12 occur. . Therefore, the applied voltage is preferably adjusted as appropriate according to the characteristics of the sample solution to be measured. The distance between the gaps 12 is preferably about 20 Vpp / μm or less based on the distance between the gaps 12. In the first embodiment, the gap between the gaps 12 is 5 μm, and the applied voltage is 5 Vpp between electrodes, that is, 1 Vpp / μm.
[0034]
The control unit 7 includes a microprocessor (not shown), a memory for storing a preset program, a timer, and operation buttons such as a measurement start button for a subject to instruct measurement, and a preset program Accordingly, the voltage for dielectrophoresis is applied to the thin film electrode 2 by controlling the electrophoretic power source 5. The control unit 7 transmits / receives signals to / from the measurement unit 6 and manages the flow of the entire measurement operation by appropriately controlling. Further, the control unit 7 displays the measurement result, the operation state, and the like on the display unit 8.
[0035]
The measurement unit 6 includes a microprocessor (not shown), a memory for temporarily storing measurement data and calculation results, a voltage applied to the electrodes, a current flowing between the electrodes, and a difference between the phase of the voltage and the current ( It is composed of a circuit for measuring the phase angle (hereinafter referred to as a phase angle), etc., and can perform an operation for analyzing the impedance of the electrode. The number of bacteria in the sample solution can be calculated from the result of electrode impedance analysis.
This calculation method will be described later. Note that the microprocessor and memory of the measurement unit 6 can be shared with the microprocessor and memory of the control unit 7.
[0036]
The display unit 8 displays a sanitary state in the oral cavity as an evaluation result in the form of the number of microorganisms in the sample liquid by a display such as an LCD, a printer, a speaker, or the like. The display on the display unit 8 is the final output of the oral hygiene state inspection apparatus in the first embodiment. In the first embodiment, the user knows the hygiene condition in the oral cavity as an evaluation result by a quantitative display of the number of microorganisms in the sample solution. As a display method, for example, a semi-quantitative method using a bar graph or the like is used. It is also possible to display in a realistic expression, further abstractly display XX, or use voice or other communication means in addition to (or instead of) visual display, and many of these display methods What is necessary is just to select an optimal thing from among according to the objective.
[0037]
In addition, the user directly evaluates the results of the evaluation, such as switching the operation mode of the electric toothbrush automatically by checking the hygiene status in the oral cavity, controlling the amount of denture cleaning agent input, changing the temperature setting, etc. When the control related to the oral hygiene condition inspection apparatus is performed, the control may be performed without displaying on the display unit 8.
[0038]
Now, the microorganisms and plaques in the oral cavity, which are inspection targets, will be described. Major diseases in the oral cavity, such as touch and periodontal disease, are both diseases caused mainly by microorganisms. Many of the microorganisms in the oral cavity are localized in the plaque. Plaque is a state in which bacteria in the oral cavity are locally solidified by growth, and most of them are microbial masses except for metabolites such as polysaccharides described later. The number of microorganisms in 1 g of plaque actually reaches 10 to 11 to 10. Removal of the plaque from the oral cavity (hereinafter referred to as plaque control) is the most important for promoting oral hygiene. Specifically, the brushing method, so-called tooth brushing, is the main means of plaque control.
[0039]
Now, the causative agent of touch is a group of bacteria centering on Streptococcus mutans (hereinafter referred to as SM), and periodontal diseases such as alveolar pyorrhea are Porphyromonas gingivalis (hereinafter referred to as PG). It is caused by several fungal species, mainly. These bacteria are present in plaques, and cause diseases ideologically through the plaques. For example, SM bacteria, which are causative agents for palpation, produce a gum-like polysaccharide film by using food residue in the oral cavity as a nutrient source, and act in it. SM bacteria produce acid by metabolism, which dissolves the teeth and makes them feel.
[0040]
On the other hand, PG bacteria live in gaps between gums and teeth called periodontal pockets and cause opportunistic inflammation. Chronic inflammation leads to alveolar pyorrhea. Periodontal pockets exist even when the oral cavity is in a healthy state, but plaque accumulates, the accumulated plaque becomes old and transitions to a state called calculus, and many microorganisms become permanent in it. It gets deeper and deeper. The back of the deepened periodontal pocket becomes an anaerobic atmosphere and is a good place to live such as PG bacteria. Here, a vicious cycle in which inflammation progresses more and more due to the propagation of PG bacteria, eventually destroying the alveolar bone and missing the teeth.
[0041]
As described above, it has been clarified that all oral diseases are caused by the presence of plaque, but the actual condition is that brushing for plaque control is carried out by an individual person. In the conventional technique based on the above-described staining, whether or not the plaque can be surely removed is determined qualitatively, rather than based on the impression of color, and not based on the measurement data. Therefore, in order to effectively prevent intraoral diseases, an apparatus for inspecting the oral hygiene with high accuracy is expected.
[0042]
Subsequently, the dielectrophoresis used in the first embodiment will be described. A detailed description can be found further in J. theor. See Biol (1972) vo 1.37, 1-13, etc. When a high-frequency AC voltage is applied, the microorganisms in the measurement cell 1 migrate to a portion where the electric field is strongest and non-uniform due to the action of the AC electric field generated thereby. As described above, in the first embodiment, the gap 12 of the thin film electrode 2 corresponds to a portion where the electric field is strongest and is not uniform. At this time, if the dipole moment as the dielectric fine particles of the microorganism is μ, the relationship of the formula 1 of (Equation 1) exists between the dielectrophoretic force F and the electric field E.
[0043]
[Expression 1]

[0044]
Further, if the relative permittivity of the cytoplasm of the microorganism is ε2, the relative permittivity of the liquid containing the microorganism is ε1, the radius when the microorganism is regarded as a sphere is a, and the circumference is π, the dielectrophoretic force F Can be rewritten as equation (2).
[0045]
[Expression 2]

[0046]
Equation 2 shows that the force due to dielectrophoresis is affected by the potential gradient, the difference in relative permittivity of the microorganism as the medium and the dielectric fine particles, and the like.
[0047]
Now, the gap 12 shown in FIG. 2 is a portion where the comb-like thin film electrode 2 faces. Microorganisms floating in the vicinity of the gap 12 are attracted to the gap 12 by such an electric field effect generated between the gaps 12, and are aligned along the lines of electric force. At this time, the alignment state of the microorganisms in the vicinity of the gap 12 depends on the number of microorganisms present in the sample liquid and the interval between the gaps 12. However, when the number of microorganisms is sufficiently large, the gap 12 is cross-linked by linking the microorganisms in a chain form. It will become. The microorganisms floating in the vicinity of the gap 12 from the beginning immediately move to the gap 12 portion, and the microorganisms floating away from the gap 12 reach the gap 12 portion after a predetermined time according to the distance. The number of microorganisms gathered in a predetermined area near the gap 12 after a predetermined time is proportional to the number of microorganisms in the measurement cell 1. The number of microorganisms in the sample can be calculated based on this proportional relationship.
[0048]
In the first embodiment, an AC electric field is used to cause dielectrophoresis. Under this AC application condition, the dielectric constant ε is expressed by a complex dielectric constant ε ′, and the influence of the conductivity σ is affected. receive. For example, the complex dielectric constant of a liquid containing microorganisms is expressed by Equation 3 in (Equation 3) in relation to the electric conductivity σ1 of the liquid.
[0049]
[Equation 3]

[0050]
Considering the case where the electrical conductivity σ1 of the liquid containing microorganisms changes in the increasing direction, the term (ε1−ε2) / (ε1 + 2ε2) (claucus− The value of the “Mossotti equation” becomes very small, and the value of the dielectrophoretic force F becomes small. As a result, microorganisms cannot be collected in the vicinity of the electrode, and the measurement sensitivity is lowered. Since most of the conductivity σ1 of the liquid is determined by the conductive substance ions dissolved in the liquid, if the ions are removed from the liquid, the conductivity σ1 of the liquid decreases, and as a result, the dielectrophoretic force F Increases and sensitivity is improved.
[0051]
By the way, although the interval of the gap 12 in the first embodiment is set to 5 μm, it is not limited to this value. It is desirable that the gap 12 is adjusted according to the type and concentration of microorganisms in the sample solution to be measured. In the first embodiment, the present inventor sets the optimal measurement conditions for the microorganisms in the oral cavity. As a result of intensive studies, the value of 5 μm is set. This value is desirably adjusted in the range of 0.2 to 300 μm according to the characteristics of the sample solution.
[0052]
Hereinafter, a series of procedures and procedures from sampling to measurement of microorganisms in the sample solution and evaluation of the hygiene condition in the oral cavity will be described. First, it is necessary to obtain a sample from the oral cavity. There are several types of samples obtained from the oral cavity of the subject. It was first scraped with saliva or a cloth soaked with saliva, second with a cloth or cotton swab wiping the teeth, tongue or inner wall of the mouth, and third with a pick-like one between the teeth. Sample.
[0053]
The sample provides various information depending on its origin. For example, saliva, which is the first sample, can be said to be a sample suitable for evaluating the overall hygiene in the oral cavity. Saliva dissolves microorganisms in the oral cavity in a process that exits several secretory lines in the oral cavity and spreads while washing the oral cavity. It has been elucidated that there is a correlation between the number of specific bacteria in saliva and touch, and it has been cultivated in a series of caries risk tests (touch risk test) called saliva test. As can be seen from the fact that the number of bacteria is measured by the method, the hygiene condition of the entire oral cavity can be evaluated by examining the microorganisms in the saliva.
[0054]
Further, the sample obtained by wiping the tooth surface or the like of the second sample or the sample obtained between the teeth reflects the sanitary condition of the collected local part. As described above, since microorganisms are present in the form of plaques on the tooth surface and between the teeth, the number of microorganisms in the sample is very large when the plaques adhere to the sample collection site. Therefore, the measurement is relatively easy.
[0055]
Thus, in order to evaluate the hygiene state in the oral cavity, for example, either saliva or a sample wiped on the tooth surface may be used, but in the first embodiment, the tooth surface is wiped with a cotton swab. The sample is used. Specifically, sampling in the first embodiment is performed by the subject himself holding a cotton swab and rubbing the tooth surface of the measurement site.
The number and force of rubbing the tooth surface may be determined in advance. If a sample is collected from the surface of a specific tooth, the sanitary state of only that part is comprehensively determined, and if the entire sample is collected, the state in the oral cavity is comprehensively determined. Of course, as the number of sampling sites increases, the absolute number of microorganisms in the sample also increases. Therefore, it is determined in advance which pattern or condition is to be evaluated before performing the measurement, and the sample is collected according to that. The oral hygiene state inspection apparatus according to the first embodiment is preinstalled with programs corresponding to measurement evaluations in several patterns, so that a subject can select a measurement pattern as appropriate. Hereinafter, although the case where one sample which wiped off the tooth surface with a cotton swab is measured will be described, the form of the sample and the number of samples should be selected according to the purpose of the evaluation as described above.
[0056]
Now, while sampling, the intraoral hygiene state measuring device prepares for measurement evaluation. First, the measurement cell 1 is filled with a liquid for suspending the sample. Various liquids can be used as the suspension medium. For example, water, oils, alcohols such as ethanol, acetone, DIMSO, furan, other organic solvents, and mixtures thereof can be used as the suspension medium. In Embodiment 1, since the sample is water-soluble and is easily available, purified water is used as the suspension medium. Although tap water can be used for measurement, the dispersion of the dissolved material varies greatly from region to region, and some of the water sources from wells have very high conductivity. 1 is not adopted.
[0057]
After filling the measuring cell 1 with purified water as a suspension medium, a power unit switch (not shown) is turned on. When the power supply unit is turned on, the control unit 7 performs a preparatory operation before measurement. First, in order to confirm that purified water is in a normal state, the control unit 7 controls the electrophoretic power supply unit 5 to apply an alternating current with a frequency of 100 kHz and a voltage of 0.1 Vpp to the thin-film electrode 2 and measure at the same time. The voltage applied, the current flowing through the circuit, and the phase angle are measured by controlling the unit 6. The measuring unit 6 calculates the conductivity of the purified water by calculating this result. Although details of the process of calculating the conductivity are omitted, first, the conductivity between the thin film electrodes 2 is calculated from an impedance analysis described later, and then the value is converted into the conductivity of purified water. Since the conductivity between the thin film electrodes 2 is proportional to the conductivity of the purified water, the conductivity of the purified water can be calculated simply by multiplying the calculated interelectrode conductivity by a coefficient determined by the electrode shape.
[0058]
By the way, as described above, if the conductivity of the sample solution is too high, the accuracy of the measurement is reduced. Therefore, in the first embodiment, the conductivity of the sample solution to be measured is set to a value of 10 mS / m as a certain limit. Yes. The reason for providing the restriction is to secure a certain accuracy in measurement in view of the above-described characteristics of dielectrophoresis by ions, and another reason is to protect the electrode from damage due to electrolysis. Even if the measurement sample has a very high conductivity, if the voltage initially applied is set to a low value of 0.1 Vpp so that the thin film electrode 2 is protected from electrolysis, the electrode is electrolyzed. No damage is taken. However, the value of 10 mS / m is not limited and should be appropriately set according to the conditions.
[0059]
When it is confirmed that the conductivity of the purified water is 10 mS / m or less, the control unit 7 controls the display unit 8 to inform the subject that the measurement preparation is completed. As a result, all the measurement operations are completed.
[0060]
When the measurement preparation is completed, the test subject immerses the swab on the tooth surface as a measurement sample in purified water in the measurement cell 1 and suspends microorganisms adhering to the swab in the purified water.
At this time, it is desirable to perform a process of promoting suspension such as shaking the swab, rubbing against the wall surface, or rotating the rotor 3 to generate a water flow in the measurement cell 1. Thus, a sample solution for measurement is produced.
[0061]
When the sample liquid is prepared, the subject presses a measurement button (not shown) and instructs the apparatus to start measurement. In response to the measurement start instruction, the control unit 7 applies an AC voltage having a frequency of 100 kHz and a voltage of 0.1 Vpp to the thin film electrode 2. At the same time, the measuring unit 6 is controlled to measure the voltage being applied, the current flowing through the circuit, and the phase angle, and the conductivity of the sample solution is measured. Depending on the condition in the oral cavity, the conductivity of the sample liquid may exceed 10 mS / m. In this case, the control unit 7 displays an error message indicating that the conductivity of the sample liquid is too high, and Then, the work such as diluting the sample solution to lower the conductivity or preparing the sample solution again is promoted. When it is confirmed that the conductivity of the sample solution is 10 mS / m or less, this measurement starts.
[0062]
First, the control unit 7 applies an AC voltage having a frequency of 100 kHz and 5 Vpp to the measurement electrode. At the same time, measurement of current and phase angle is started. In the first embodiment, measurement data is collected every 3 seconds, is calculated each time, and the result is accumulated in a memory (not shown) in the measurement unit 6. Hereinafter, a process from when data is collected and calculated until it is stored in the memory will be described.
[0063]
The data collected by the measurement unit 6 includes three values: applied voltage, current, and phase angle. The measurement unit 6 calculates the value of the resistance component when the equivalent circuit assumed between the thin film electrodes 2 is regarded as a CR parallel circuit composed of a resistance and a capacitance, which will be described later, from the obtained measurement results. Finally, the electrical conductivity between the thin film electrodes 2 is calculated (hereinafter, the electrical conductivity between the thin film electrodes 2 is expressed as conductance).
[0064]
In order to obtain the conductance, first, the impedance between the thin film electrodes 2 is obtained, and a calculation taking into account the phase angle described later is performed on this impedance. The impedance can be obtained by dividing the applied voltage and current. Although the conductance calculation is somewhat complicated, the impedance is expressed in polar coordinates on a complex plane using a value (hereinafter referred to as phase angle) that expresses the difference between the phase of voltage and current for measurement as the angular difference of the angular frequency. It can be calculated by analyzing this. Hereinafter, the impedance is Z, the capacitance is C, the reactance is x, and the resistance is r, and will be described in detail with reference to FIGS. 3 and 4 and Equations 4 to 8 of (Equation 4) to (Equation 8).
[0065]
[Expression 4]

[0066]
[Equation 5]

[0067]
[Formula 6]

[0068]
[Expression 7]

[0069]
[Equation 8]

[0070]
(Equation 4) is Equation 4 representing the combined impedance of the CR parallel equivalent circuit, (Equation 5) is Equation 5 representing the resistance of the CR parallel equivalent circuit, and (Equation 6) is Equation 6 representing the reactance of the CR parallel equivalent circuit. 7) is an expression 7 representing the resistance value of the CR parallel equivalent circuit, and (Equation 8) is an expression 8 representing the capacitance value of the CR parallel equivalent circuit.
[0071]
FIG. 3A shows the electrical state between the electrodes in an equivalent circuit. In FIG. 3A, 50 is one pole of the thin film electrode 2, 51 is the other pole of the thin film electrode, 52 is a capacitor representing an equivalent capacitance component in the equivalent circuit, and 53 is a resistance component in the equivalent circuit. It is the electrical resistance that represents. In FIG. 3B, 54 is a time axis, 55 is an axis representing the amplitude of the waveform, 56 is a voltage waveform to be applied, and 57 is a waveform of a current flowing through the circuit.
[0072]
A sample solution containing microorganisms exists between the gaps 12 immediately after the start of measurement. Before the microorganisms move to the gaps 12 between the electrodes by dielectrophoresis, the sample solution is configured as an interelectrode dielectric. It is considered that the capacitor 52 and the electric resistance R53 due to the sample solution connect the electrodes 50 and 51 in parallel. After the microorganisms move by dielectrophoresis, the microorganisms behave as dielectric fine particles as will be described later, so that the absolute values of the capacitor 52 and the resistor R53 change, but the connection form of the equivalent circuit does not change. Hereinafter, this equivalent circuit is referred to as a CR parallel circuit.
[0073]
It is generally known that when an AC voltage is applied to such a CR parallel circuit, a phase difference as shown in FIG. 3B appears between the current 57 flowing in the circuit and the applied voltage 56. When polar coordinates are displayed on the complex plane using the angle difference θ when the frequency of the voltage to which the phase difference is applied is represented by the angular frequency ω, there is a relationship shown in FIG. 4 among the voltage, current, and phase angle.
[0074]
The impedance Z is obtained by dividing the measured applied voltage and current, and corresponds to the absolute value of the vector shown in FIG. At this time, the impedance Z can be expressed in the form of Z = r + jx (j is an imaginary unit), and the resistance r is r = Zsin θ, and the electrical resistance component of the combined impedance of the CR parallel circuit shown in FIG. The reactance x is related to the reciprocal of the capacitance component of the circuit as x = Z cos θ.
[0075]
On the other hand, the combined impedance of the CR equivalent circuit of FIG. 3A is expressed by Equation 4 of (Equation 4), and Equation 4 is decomposed into resistance r and reactance x from the relationship of Z = r + jx. 5 and Equation 6 of (Equation 6) are obtained. By transforming Equation 5 and Equation 6 simultaneously, Equation 7 in Equation 7 and Equation 8 in Equation 8 are obtained.
[0076]
The electric resistance R53 and the capacitor 52 in the equivalent circuit are substituted by substituting r, x, and ω calculated from the voltage value for measurement, the current value at that time, and the measured value of the phase angle of the voltage and the current into Expression 7 and Expression 8. I can know. The conductance between the electrodes can be obtained by taking the inverse of the obtained electrical resistance component.
[0077]
The conductance value obtained by such an operation is recorded in the memory together with the value representing the time when the measurement was performed or the order in which the measurement was performed, and the work related to data collection at one point is completed. Thereafter, a predetermined number of data items programmed in advance are collected, and the measuring unit 6 analyzes the accumulated conductance data. Conductance data analysis is to determine the slope of the change in conductance over time.
[0078]
The simplest method for obtaining the slope of the change in conductance with time is to perform linear approximation obtained by the least square method on the obtained data. Even in the case of a curve in which the concentration of microorganisms is high and the slope of the change in conductance gradually decreases with the passage of time, a portion of the initial collected data is extracted instead of the entire collected data, and a straight line approximation is made with a tangent line. That's fine. Even if the entire data is a curve, what is needed is the slope of the initial conductance change. Such a sample with a high concentration of microorganisms has a large conductance change for each measurement and gives a clear measurement result with little noise. Therefore, the slope can be calculated with sufficient accuracy even with only a part of the initial data.
[0079]
The reason why the number of microorganisms can be calculated by measuring the slope of the change in conductance over time is that, as described above, microorganisms are electrically equivalent as elements in which resistance and capacitance are connected in parallel. This is because it can be expressed. This is because microorganisms are ion-rich and surrounded by a cell wall having a relatively high electrical conductivity and a cell membrane made of phospholipid and having a low electrical conductivity. When the gap 12 is bridged by microorganisms that move to the gap 12 by dielectrophoresis, an electric current flows between the thin film electrodes 2 through the microorganisms. When the number of microorganisms migrating to the gap 12 increases and the number of cross-linking by microorganisms increases, the current flowing through the thin film electrode 2 increases. Therefore, if the conductance change between the thin film electrodes 2 is measured, the value moves to the vicinity of the gap 12 Thus, it is possible to obtain a measurement result that correlates with the number of microorganisms that have been generated, and thus the number of microorganisms present in the sample solution. An example of such a change in conductance over time is shown in FIG. From FIG. 5, it can be seen that the slope (gradient) of the conductance at the beginning of the measurement increases corresponding to the number of microorganisms, similarly to the conductance over time.
[0080]
When calculating the number of microorganisms by changing the conductance over time, it is conceivable to measure the conductance after the transient state has passed and the equilibrium state is reached, but in this case, it takes a long time. However, when the number of microorganisms is calculated based on the slope (gradient) of the change in conductance with time at the beginning of measurement, it has an excellent feature that the number of microorganisms can be calculated in a relatively short time.
[0081]
Now, in order to finally display the number of microorganisms in the sample solution, a conversion formula for the slope of the change in conductance with time and the number of microorganisms in the sample is necessary. In this conversion formula, a sample liquid actually prepared from the oral cavity is used to measure the number of microorganisms from the conventional measurement system of the oral hygiene state inspection apparatus described in the first embodiment and the culture method. Using a method established as a method, measurement is performed simultaneously with both measurement methods, and the correlation between the number of microorganisms measured with the previously established method and the slope of the change in conductance over time is analyzed by regression analysis. The function that is used is used. As a result of repeated measurement and intensive studies, the inventors found that there are individual differences in the types of microorganisms present in the oral cavity, but there is a very good correlation between the two measurement methods described above. We have knowledge. An example is shown in FIG. According to the graph of FIG. 6, for example, when the slope of the conductance change is 0.1 as a result of measurement, the number of microorganisms in the sample solution can be calculated to be around 10 7 per ml. By programming such a correlation as a conversion formula and storing it in the memory of the measuring unit 6, even when measuring an intraoral sample whose number of microorganisms is unknown, the value of the slope of the change in conductance over time is substituted. Thus, the number of microorganisms in the sample solution can be calculated.
[0082]
Now, there is a difference in the clinical characteristics of individuals related to the oral cavity, and it seems that the oral cavity is relatively clean from those who have no relation to oral disease even if the number of microorganisms is relatively large Nevertheless, there are many people who cannot escape from touching. However, no matter what the constitution, there is no difference in terms of hygiene if there is no plaque adhesion on the tooth surface. Therefore, the number of microorganisms measured in the first embodiment may be once under the guidance of an expert such as a dentist, so that the oral hygiene state is accurately evaluated according to each subject, and thereafter It is desirable to promote health by counting the number of microorganisms according to the evaluation.
[0083]
As described above, the number of microorganisms in the sample solution is measured and displayed on the display unit 8, and all measurement operations are completed. When the subject discards the sample liquid and remeasures, the next measurement may be performed in the same procedure. As described above, in the first embodiment, a device capable of objectively examining the hygiene condition of the subject's own oral cavity without using a reagent or a special device or training by a very simple method. Can be provided.
[0084]
(Embodiment 2)
The oral hygiene state inspection apparatus and the oral hygiene state inspection method in Embodiment 2 of the present invention will be described in detail with reference to the drawings. In addition, about the description of the part which overlaps with Embodiment 1, it hands over to Embodiment 1 and omits description. FIG. 7 is an overall horizontal view of the oral hygiene state inspection apparatus according to Embodiment 2 of the present invention.
[0085]
In FIG. 7, 40 is a measurement cell, 41 is a thin film electrode, 42 is a rotor, 43 is a stirrer, 44 is an electrophoresis power supply unit, 45 is a measurement unit, 46 is a control unit, 47 is a display unit, 48 is a diaphragm, 49 is It is an ion exchange resin.
[0086]
The most different point of the oral hygiene condition inspection apparatus of the second embodiment from the oral hygiene condition inspection apparatus of the first embodiment is the configuration of the measurement cell 40. Hereinafter, the second embodiment is different from the first embodiment. The part will be described. The inside of the measurement cell 40 in the second embodiment is functionally divided into two chambers by a diaphragm 48. The diaphragm 48 in Embodiment 2 is a membrane filter made of nitrocellulose, and its pore diameter is 0.45 μm. As the diaphragm 48, fine substances such as ions can be passed, but any diaphragm having a pore diameter that does not allow passage of microorganisms can be used. In the second embodiment, the shape is expressed as a diaphragm 48. However, the shape is not particularly limited as long as transmission / non-passage can be selectively performed.
[0087]
The ion exchange resin 49 in the present second embodiment is a mixture of an anion exchange resin and a cation exchange resin. The anion exchange resin is OH type, and the cation exchange resin is H type. Each of the yin and cation ion exchange resins 49 converts the anion and cation in the sample solution to OH. ^- Ion and H ⁺ The conductivity of the sample solution is lowered by exchanging with ions. The ion exchange resin 49 in Embodiment 2 corresponds to a conductivity adjusting unit that adjusts the conductivity of the sample solution in the present invention.
[0088]
Hereinafter, a series of operations and procedures of the oral hygiene condition measuring apparatus according to the second embodiment will be described mainly with respect to differences from the first embodiment. After collecting the sample from the oral cavity, the sample is suspended in purified water to prepare a sample solution, and the process until the control unit 46 first measures the conductivity of the sample solution by pressing the measurement start button is the same as in the first embodiment. .
[0089]
In the first embodiment, if it is determined that the conductivity of the sample liquid before the start of measurement exceeds 10 mS / m, whether an error is displayed and the sample liquid is diluted to a measurable conductivity Alternatively, a process was performed so that the measurement could not proceed unless the sample was remade. However, in the second embodiment, the measurement is continued even when it exceeds 10 mS / m. The value of 10 mS / m should be determined as appropriate depending on the combination of the sample and the measurement system.
[0090]
When the controller 46 determines that the conductivity before the start of measurement exceeds 10 mS / m, the control unit 46 does not start the measurement immediately, but delays the measurement start time for a predetermined time set in advance by the program. Perform the process. Then, after the predetermined time has elapsed, the conductivity of the sample solution is measured again to determine whether the measurement is possible. While the control unit 46 delays the start of measurement, the conductivity of the sample solution is reduced by the ion exchange resin 49 in the measurement cell 40. Hereinafter, the delay process will be described.
[0091]
A sample from the oral cavity contains a large number of contained ions, most of which are sodium ions and chloride ions. Taking these two ions as examples, the behavior leading to a decrease in conductivity will be described. Other anions and cations are present in the sample solution, but the behavior is similar to these two ions.
[0092]
At the same time as the sample is suspended in the purified water filled in the measurement cell 40, sodium ions and chloride ions are dissolved and diffused in the purified water. Sodium ions and chloride ions diffused by the concentration gradient easily pass through the diaphragm 48 and interact with the ion exchange resin 49 to cause ion exchange. Sodium ion is cation exchange resin H ⁺ Ions are exchanged, and chloride ions are anion exchange resin OH ^- Exchanged with ions. H released into the sample solution by ion exchange ⁺ Ion and OH ^- Ions immediately combine to form water molecules. Sodium ions and chloride ions in the vicinity of the ion exchange resin 49 are captured by the ion exchange resin 49 by ion exchange, and the concentration of sodium ions and chloride ions in the vicinity of the ion exchange resin decreases. As a result, an imbalance in the concentration of sodium ions and chloride ions occurs in the measurement cell 40, so that new sodium ions and chloride ions move to the vicinity of the ion exchange resin according to the concentration gradient. Thereafter, the same thing is repeated, and the concentration of sodium ions and chloride ions in the measurement cell 40 gradually decreases.
[0093]
H released by ion exchange ⁺ Ion and OH ^- Since the ions are hardly dissociated even after being bonded and remain bonded as water molecules, the conductivity of the sample solution in the measurement cell 40 decreases as a result. Since the ion exchange reaction between the ions in the vicinity of the ion exchange resin and the resin ends instantaneously, the higher the initial concentration of sodium ions and chloride ions, the larger the concentration gradient. Since a large concentration gradient causes mass transfer (absolute amounts of sodium ions and chloride ions to move) in proportion thereto, the concentration decreases rapidly as the initial concentration of sodium ions and chloride ions in the measurement cell 40 increases. A decrease in conductivity occurs. At this time, since the microorganisms in the suspension cannot pass through the diaphragm 48, the microorganisms stay on the electrode side separated by the diaphragm 48 in the measurement cell 40, and the measurement efficiency is not lowered.
[0094]
Now, while the control unit 46 delays the start of measurement, the concentration adjustment is completed, and when the conductivity of the sample solution is measured again after a predetermined time has passed, if the measurement start condition is satisfied, the measurement is performed as it is. As described above, when the ion concentration in the sample solution is high and the conductivity of the sample solution is high, the ion concentration changes rapidly, but when the conductivity of the sample solution decreases to about 10 mS / m, the ion concentration changes. The change also becomes slow, and at 10 mS / m or less, the change in conductivity during measurement becomes practically negligible.
[0095]
In the second embodiment, the ion exchange resin 49 is used as the conductivity adjusting unit for changing the conductivity of the sample solution. However, another conductivity adjusting unit for achieving the same object may be used. For example, adjustment using dialysis. The sample liquid in which the sample is suspended is brought into contact with a liquid having a low ion concentration such as distilled water through a semipermeable membrane. Then, the ions in the sample solution diffuse to the distilled water side through the semipermeable membrane due to the gradient of the ion concentration inside and outside the semipermeable membrane. When the amount of distilled water is sufficiently larger than the amount of sample solution, most of the ions in the sample solution move to the distilled water side, resulting in a decrease in the ion concentration in the sample solution. At this time, ions in the sample solution can be quickly removed by devising to always maintain a large gradient of ion concentration with the sample solution by flowing distilled water or the like. Thus, the oral hygiene state inspection apparatus for reducing the ion concentration in the sample liquid and reducing the conductivity of the sample liquid is not limited to that described in the second embodiment.
[0096]
By the way, in the second embodiment, the measurement unit 45 calculates the conductivity of the sample liquid that has been finally measured, that is, the conductivity measured after determining that the conductivity of the sample liquid is less than 10 mS / m. The data is stored in a memory and prepared for correction when calculating the number of microorganisms described later. The process from the collection of microorganisms to the electrode by dielectrophoresis and the calculation of the slope of conductance using the impedance change is the same as that in the first embodiment, and will not be described in the first embodiment.
[0097]
After the conductance slope is obtained, the measuring unit 45 corrects the conductance change slope due to the initial conductivity of the sample solution according to the following concept. Hereinafter, the inclination correction of the conductance change due to the initial conductivity of the sample solution (hereinafter referred to as inclination correction) will be described with reference to FIG. FIG. 8A is a graph for explaining the relationship between the dielectrophoretic force at a low ion concentration and the frequency of the voltage for electrophoresis, and FIG. 8B is a graph of the dielectrophoretic force at a high ion concentration and the voltage for the electrophoresis. FIG. 9 is a graph for explaining the relationship between frequencies, and FIG. 9 is a graph showing the relationship between the material conductivity and the normalized dielectrophoretic force at an applied frequency of 100 kHz.
[0098]
Now, the relationship between the conductivity σ1 of the sample solution and the dielectrophoretic force F has been described with reference to Equation 2 in (Equation 2) in the first embodiment. The terms (ε1−ε2) / (ε1 + 2ε2) (referred to as the Clausius-Mossoti equation) are plotted against the frequency in FIGS. 8A and 8B. Here, ε is a permittivity permittivity, and for example, it is expressed by Equation 3 in (Equation 3) as already described.
The value of (ε1−ε2) / (ε1 + 2ε2) described above is a term in Equation 2 of (Equation 2) that represents the magnitude of the dielectrophoretic force F. The larger the value, the stronger the dielectrophoretic force. I understand that. It can also be seen that when the value is positive, the dielectrophoretic force acts as an attractive force, but when the value becomes negative, the dielectrophoretic force acts as a repulsive force.
[0099]
The conductivity of the sample solution is different between FIG. 8 (a) and FIG. 8 (b). The conductivity is larger in FIG. 8B than in FIG. As can be seen from the two graphs of FIGS. 8A and 8B, it can be seen that when the conductivity of the sample solution increases, the frequency range in which dielectrophoresis acts as an attractive force becomes narrower and the value also decreases. In Embodiment 2, since the attractive force is used to move and measure the number of microorganisms on the electrode, the sensitivity decreases as the conductivity of the sample solution increases. FIG. 9 is a graph showing the relationship between the conductivity of the sample liquid and the intensity of the dielectrophoretic force at an applied frequency of 100 kHz. The vertical axis of the graph in FIG. 9 is a standardization of the dielectrophoretic force when the electrical conductivity is changed with the dielectrophoretic force expected to be generated in water having a very low ion concentration as 1. Hereinafter, the correction of the slope of the change in conductance due to the initial conductivity of the sample solution will be described by taking the value shown by the dotted line in FIG. 9 as an example.
[0100]
In FIG. 9, the conductivity value indicated by the dotted line is 5.2 mS / m. At this time, the dielectrophoretic force is 0.5, which is exactly half of the value expected to be generated in high purity water with a very small ion concentration. When the dielectrophoretic force is halved, the number of microorganisms moving on the electrode within a certain time is reduced, and the gradient of the conductance change is also halved. Therefore, if the conductivity of the sample solution is not corrected, the number of microorganisms calculated due to the influence of the conductivity is halved, and the final determination result of the oral hygiene condition becomes inaccurate. Therefore, correction is performed by multiplying the slope obtained by plotting the conductance calculated from the collected data as it is by 1 / 0.5. Thereby, although it measured on the conditions with the high electrical conductivity of a sample liquid, it can convert into the same inclination as when measuring with high water with a very small ion concentration. By such a method, correction is possible if the slope of the conductance change is measured with a sample solution up to about 10 mS / m or less. If the conductivity of the sample solution exceeds 10 mS / m, the correction value becomes negative and the calculation result becomes incorrect. This region is a region where the dielectrophoretic force F is zero or exerts repulsive force. If the electrical conductivity of the sample solution is measured in advance so that the measurement is not performed when the electrical conductivity exceeds 10 mS / m, the calculation result will not be incorrect.
[0101]
As described in the second embodiment, the mechanism for adjusting the conductivity of the sample solution and the value of the conductance slope are corrected with the value of the initial conductivity of the sample solution. Or even if it is a case where an evaluation result becomes inaccurate, the oral hygiene state inspection apparatus which can perform correct evaluation can be provided.
[0102]
(Embodiment 3)
The oral hygiene condition inspection apparatus and the oral hygiene condition inspection method of Embodiment 3 of the present invention will be described in detail with reference to the drawings. In addition, about the description of the part which overlaps with Embodiment 1, it hands over to Embodiment 1 and omits description. FIG. 10 is an overall horizontal view of the oral hygiene state inspection apparatus according to Embodiment 3 of the present invention.
[0103]
In FIG. 10, 21 is a cell for holding a sample liquid in which a sample in the oral cavity is suspended, 22 is a light source, 23 is a light source side optical system, 24 is a light receiver, 25 light receiving side optical system, 26 is a measuring unit, Reference numeral 27 denotes a display unit, 28 denotes a control unit, 29 denotes a light beam incident on the cell 21 from a light source, and 30 denotes scattered light scattered by microorganisms in the cell 21.
[0104]
The cell 21 of the third embodiment has an opening for introducing / extracting the sample liquid, and has a transparent opening for introducing a light flux 29 for measurement into the cell 21 and detecting scattered light. Yes. Here, the transparent opening means an opening that is evaluated as being optically transparent at the measurement wavelength. In the third embodiment, the cell 21 uses a general glass container. The light source 22 is desirable because a semiconductor laser or a light emitting diode (LED) is small and consumes less power. However, in combination with the detection wavelength range of the light receiver, it can also be used in incandescent bulbs, fluorescent tubes, arc tubes filled with gases such as xenon and sodium. However, in the third embodiment, since the configuration is simplified, a semiconductor laser (hereinafter referred to as LD) having an oscillation wavelength of 660 nm is used. The irradiation light from the LD is set so as to cross the central portion of the cell 21 at the central portion of the sample solution depth.
[0105]
Since the light source side optical system 23 in the third embodiment uses an LD as the light source 22 and the light flux 29 is strongly emitted in a specific direction, it may be measured by entering the cell 21 as it is. Accordingly, although it is not necessary to provide an optical system in particular, Embodiment 3 uses a cylindrical lens for adjusting the cross-sectional shape of the beam and a collimator lens for controlling the spread of the light flux 29. When the light source 22 is an incandescent light bulb or the like, the light source side optical system 23 needs to be provided with a reflecting mirror, a slit, a wavelength selective transmission filter and the like in addition to the above-described configuration, and is somewhat complicated.
[0106]
As the light receiver 24, a general photodiode (hereinafter referred to as PD) is used. Various types of light receivers 24 are widely known, and many light receivers 24 can be used. As described above, the light receiver 24 may be selected in accordance with the characteristics on the light source 22 side. This also applies to the light receiving side optical system 25, and various optical systems can be used depending on the combination of the light source 22 and the light receiver 24.
In the third embodiment, although not shown in detail in the light receiving side optical system 25, a lens for condensing the scattered light 30 from the light beam 29 in the cell 21 on the PD is provided.
[0107]
The cell 21 and the optical system described above are housed in a container that can block light from outside in order to avoid measurement errors due to stray light from outside. The measurement unit 26 includes a microprocessor, a memory, an LD driver circuit for the light source 22, a detection circuit that amplifies and detects a signal from the PD, and detects the intensity of the scattered light 30 to detect the number of microorganisms. Can be quantitatively detected, and the result can be converted into an evaluation of the hygiene condition in the oral cavity.
[0108]
The display unit 27 performs display for notifying the subject of the evaluation result of the hygiene state in the oral cavity as the final output in the third embodiment. Since the display mode has already been described in the first embodiment, it is omitted. Moreover, when using the evaluation result of the oral hygiene state inspection apparatus according to the third embodiment for controlling other devices, there is no need to perform display. A series of operations is controlled by the control unit 28.
[0109]
Now, a series of measurement operations and procedures in Embodiment 3 will be described below. The collection of the sample is the same as in the first embodiment, and is omitted. The sample suspension medium in the third embodiment pays attention to the principle that scattered light is measured so that noise components such as fine particles and fine bubbles are scattered to increase the background. There is a need. As for the composition, the liquid described in Embodiment 1 can be used. Unlike Embodiment 1, there is no problem in measurement even if the suspension medium contains ions.
[0110]
Also in Embodiment 3, purified water is used as the suspension medium because it is easy to suspend due to the nature of the sample. Since there is no problem even if ions are included, it is possible to use general tap water without using purified water, but purified water is used because there is a concern that there may be a variation in mixing of fine particles. Furthermore, it is desirable to improve the accuracy of measurement if purified water can be filtered with a filter having a diameter of 0.22 to 0.45 μm before measurement.
[0111]
The suspension of the sample in purified water is the same as in the first embodiment. Although no mechanism for agitating the inside of the cell 21 is provided in FIG. 10, it goes without saying that it is desirable to provide a flow promoting means such as agitation and ultrasonic vibration to assist the suspension of the sample in the cell. When the sample solution is prepared in the cell 21, the subject turns on the power supply switch of the device (not shown), and also presses the measurement start button (not shown) to instruct the device to start measurement. In response to the measurement start instruction, the control unit 28 controls the measurement unit 26 to turn on the light source 22. Hereinafter, the control unit smoothly proceeds with the measurement in accordance with a program stored in advance in the memory in cooperation with each unit.
[0112]
After the light source 22 is turned on, the measurement unit 26 detects a signal from the light receiver 24. The wavelength of the LD of the light source 22 in the third embodiment is 660 nm, and even a relatively small bacterium to be measured has a size of about 1 μm. Therefore, if these microorganisms are present in the optical path through which the light flux 29 passes, Part is scattered. Part of the scattered light is collected by a lens (not shown) provided in the light receiving side optical system 25 and guided to the light receiver 24. Scattered light incident on the PD as the light receiver 24 is converted into an electrical signal by the PD and detected by the measuring unit 26.
[0113]
The output voltage from the PD as the light receiver 24 changes according to the amount of incident scattered light, and the amount of scattered light changes depending on the number of microorganisms present on the light flux 29. Therefore, the measuring unit 26 is detected by detecting the output voltage of the PD. Can measure the number of microorganisms present in the light path.
[0114]
The number of microorganisms on the optical path reflects the average number of microorganisms floating in the sample liquid filled in the cell 21, and finally the number of microorganisms in the sample is calculated from the number of microorganisms on the optical path. It becomes possible. Here, light is scattered not only by microorganisms, but also by eating wastes present in the oral cavity and bubbles mixed during suspension. These are very large for microorganisms and are detected as large noises. There is a risk. In order to prevent this, in the third embodiment, the measurement is continuously performed for a predetermined time after the start of measurement, and the time change of the scattered light is monitored. Over time, large floats such as food residue settle quickly and accumulate on the bottom of the cell 21, and bubbles rise due to buoyancy and move to the liquid surface near the top of the cell. The light does not settle easily and does not float, so that after a certain period of time, the scattered light is only dependent on microorganisms. After confirming that the scattered light has not fluctuated greatly for a certain time, the measurement unit 26 calculates the number of microorganisms using the value at that time as the measurement result.
[0115]
The calculation of the number of microorganisms in the sample liquid from the scattered light intensity is the same as the method described in the first embodiment. And the correlation between these results is calculated or converted into a function or a table and calculated / referenced. The part for converting the number of microorganisms into the sanitary condition evaluation as the final output is also the same as in the first embodiment, and is omitted. The evaluation result is displayed on the display unit 27, and the series of measurement operations is completed by notifying the subject of the result.
[0116]
Here, in the third embodiment, the number of microorganisms is calculated by measuring the scattered light caused by the microorganisms existing on the optical path in the cell 21 through which the light flux 29 penetrates, and finally the evaluation result of the oral hygiene condition However, the measurement can be performed not only with scattered light but also with transmitted light. As described above, when microorganisms are present on the optical path through which the light flux 29 penetrates, a part of the light flux 29 is scattered. The fact that a part of the light beam 29 is scattered means that the intensity of the light beam 29 after the scattering point is weakened by the scattered light, that is, the more scattered light, that is, the number of microorganisms in the sample liquid. The greater the number, the lower the intensity of transmitted light.
[0117]
Therefore, measuring the scattered light and the transmitted light is to evaluate the same phenomenon on the front and back, and if the configuration of the measurement system is changed, the transmitted light can be measured in the same way as in the third embodiment. Microorganisms in the liquid can be measured. This can be easily realized by arranging the light source 22 and the light receiver 24 so as to face each other on a straight line. In the case of scattered light, as the number of microorganisms increases, the amount of light detected by the light receiving portion increases, and in the case of transmitted light, it decreases. If the decrease in the transmitted light is processed in the same manner as the measurement result of the scattered light intensity, the number of microorganisms in the sample, and thus the sanitary condition in the oral cavity can be evaluated.
[0118]
Thus, the apparatus which evaluates the sanitary condition in an oral cavity is realizable also by performing the measurement using light with respect to the sample which suspended the sample obtained from the intraoral area in the liquid.
[0119]
(Embodiment 4)
The oral hygiene state inspection apparatus and the oral hygiene state inspection method of Embodiment 4 of the present invention will be described in detail with reference to the drawings. In addition, description is abbreviate | omitted about the part which overlaps with other embodiment mentioned above. FIG. 11 is an overall configuration diagram of an oral hygiene state inspection apparatus according to Embodiment 4 of the present invention.
[0120]
In FIG. 11, 60 is a sealable cell that can contain a sample, 61 is a gas sensor disposed in the cell 60, 62 is a measurement unit, 63 is a display unit, 64 is a control unit, and 65 is collected from the oral cavity. A jig including the processed sample.
[0121]
The cell 60 includes a gas sensor 61 therein and an opening / closing portion for taking in and out the sample. The cell 60 is sealed by an opening / closing part so that air cannot enter and exit from the outside during measurement. The cell 60 employs a glass container so that it does not contain volatile substances. A material such as plastic may be used. Although not adopted in the fourth embodiment, the entire cell 60 may be heated by means such as a heater in order to perform measurement with higher sensitivity. By heating, the volatilization of the substance from the sample becomes more active, and as a result, the concentration of the volatile substance in the cell 60 is increased compared to when the sample is not heated, so that highly sensitive measurement can be performed.
[0122]
In the fourth embodiment, the gas sensor 61 includes a sensor main body made of oxide ceramics obtained by sintering tin oxide or the like, and a heater (not shown) for heating the sensor main body and performing measurement stably. When the sensor body is sensitive to the volatile substance in the cell 60, the characteristic between the electrodes connected to the ceramic changes, and the change can be taken out in the form of current. The gas sensor 61 only needs to be sensitive to the volatile substance in the cell 60, and may have another configuration. There have already been proposed gas sensors 61 having a large number of systems and material compositions, and a sensor suitable for the object of the present invention can be appropriately selected and used. Furthermore, the sensor main body mounted on the gas sensor 61 is not limited to one type, and a plurality of types of gas sensors can be simultaneously mounted and operated simultaneously.
[0123]
The measuring unit 62 includes a circuit necessary for measuring a volatile substance in the cell 60 using the gas sensor 61. For example, a heater power supply circuit used for heating the sensor body, a detection circuit for detecting a current flowing through the sensor, an arithmetic circuit for performing an operation based on the current value, and the like. Such a circuit is preferably configured by a microprocessor in a programmatic manner. In addition, a memory for temporarily storing the calculation results is also provided.
[0124]
Since the configurations and operations of the control unit 64 and the display unit 63 are basically the same as those of the control unit 7 and the display unit 8 already described in the first embodiment, the description thereof is omitted. The jig 65 including the sample collected from the oral cavity uses a cotton swab similar to the first embodiment in the fourth embodiment.
[0125]
Here, the meaning of measuring the volatile substance in the sample obtained from the oral cavity in order to evaluate the hygiene state in the oral cavity will be described. The type and amount of volatile substances in samples obtained from the oral cavity are closely related to bad breath, which is often caused by metabolic activity of microorganisms in the oral cavity. Related. As described above, the hygiene status in the oral cavity can be evaluated by the presence of microorganisms. From this, the type and amount of volatile substances in the sample obtained from the oral cavity depend on the plaque and the hygiene status in the oral cavity. Will have a close relationship.
[0126]
For example, microorganisms such as PG that grow in the deep part of the periodontal pocket described above prefer an anaerobic atmosphere. In general, anaerobic microorganisms, particularly anaerobic bacteria, often produce substances with intense odor such as hydrogen sulfide and mercaptan compounds during their metabolism. When oral hygiene is impaired and periodontal disease is affected, bad breath is remarkably increased by microorganisms living in these periodontal pockets. Therefore, by examining the type and amount of volatile substances in the sample obtained from the oral cavity, it is possible to determine the state of plaque adhesion and determine the oral hygiene condition. In addition to the disease-related harmful effects in the oral cavity, such as tooth damage caused by alveolar pyorrhea and dental caries, the type and amount of volatile substances in the sample can be examined to determine the hygiene status in the oral cavity based on bad breath, In addition, measures against bad breath are possible.
[0127]
Now, a series of flow from the collection of the sample in Embodiment 4 to the evaluation of oral hygiene will be described. Since the sample collection in the fourth embodiment uses a cotton swab as in the first embodiment, the procedure is the same as in the first embodiment. However, the sample in Embodiment 4 is more preferably a plaque collected by rubbing the tooth surface or the boundary between the tooth and gum than the saliva. This is because the sanitary condition determination method according to the fourth embodiment is suitable for analysis of microorganisms that mainly live in the periodontal pocket at the boundary between the tooth and the gum as described above. After taking the sample, the subject puts the jig into the cell 60 and seals it. Then, a measurement start button (not shown) is pressed to notify the control unit 64 of the measurement start.
[0128]
Upon receiving an instruction to start measurement, the control unit 64 immediately controls the measurement unit 62 and starts measuring the amount of volatile substances in the cell 60. Since the ceramic gas sensor 61 used in the fourth embodiment has a low target gas selectivity, it can detect any volatile substance.
[0129]
The measuring unit 62 measures the intensity of the signal from the gas sensor 61 and evaluates the plaque adhesion state and the hygiene state in the oral cavity. The conversion between the gas sensor 61 and the evaluation of the hygiene condition in the oral cavity is performed by determining a function indicating the correlation between the hygiene condition evaluation in advance by an expert and the signal intensity of the gas sensor 61 according to this measurement method. This is done by programming in advance. The calculated evaluation result is displayed on the display unit 63 and notified to the subject. In the fourth embodiment, only the case where one type of gas sensor is used has been described. However, it is possible to perform a more detailed analysis by using a plurality of gas sensors in combination, and there is only one type of sensor. However, it is also desirable to selectively measure and evaluate specific gases such as hydrogen sulfide and mercaptan compounds.
[0130]
As described above, the sample obtained from the oral cavity is placed in an airtight container and the volatile substance from the sample is measured using a gas sensor, so that the oral hygiene state inspection apparatus according to the fourth embodiment has a bad breath in addition to the disease. It becomes possible to take measures.
[0131]
【The invention's effect】
In the oral hygiene condition inspection apparatus of the present invention, the control unit controls the power supply unit to apply a voltage to the electrode, collects microorganisms in the sample solution on the electrode by the dielectrophoretic force, and the measurement unit captures it. Since the number of microorganisms in the sample liquid is quantitatively calculated by measuring the impedance between the electrodes after collection or collection, it is simple and objective without requiring reagents or special equipment or training. You can check your own oral hygiene.
[0132]
In addition, since the flow promoting means for changing the relative position between the sample solution and the electrode is provided, the microorganisms in the sample solution can be efficiently collected on the electrode, and rapid measurement can be performed.
[0133]
In addition, since the measurement unit measures the conductivity of the sample solution before collecting microorganisms in the sample on the electrode by dielectrophoresis, measurement errors such as a sample solution with a high ion concentration can be prevented in advance. A highly reliable determination result can be derived.
[0134]
Further, since the conductivity adjusting unit for adjusting the conductivity of the sample solution is provided, dielectrophoresis and measurement can be performed under optimum conditions, and quick and highly accurate measurement can be performed.
[0135]
In addition, since the measurement unit measures the conductivity of the sample solution and corrects the measurement result based on the measured conductivity, an accurate determination result can always be derived regardless of the properties of the sample.
[0139]
The method for measuring the number of microorganisms in the oral cavity of the present invention introduces a sample liquid containing a sample collected from the oral cavity into a cell equipped with an electrode for measurement, changes the relative position of the sample liquid and the electrode, Since the number of microorganisms in the sample solution is quantitatively calculated by collecting the microorganisms in the sample solution on the electrodes by the dielectrophoretic force by applying a voltage to the electrode and measuring the impedance between the electrodes, It is possible to easily and objectively check the hygiene status in the oral cavity without requiring special equipment or training.
[Brief description of the drawings]
FIG. 1 is an overall horizontal view of an oral hygiene state inspection apparatus according to Embodiment 1 of the present invention;
FIG. 2 is an explanatory diagram of electrodes in the first embodiment of the present invention.
FIG. 3A is an explanatory diagram showing an electrical state between electrodes in an equivalent circuit.
(B) An explanatory diagram showing the phase difference between current and voltage
FIG. 4 is an explanatory diagram for explaining vector decomposition of impedance;
[Fig. 5] Time variation diagram of conductance
Fig. 6 Correlation diagram of microbial count measurement by culture and slope of conductance change
FIG. 7 is an overall horizontal view of an oral hygiene state inspection apparatus according to Embodiment 2 of the present invention.
FIG. 8A is a graph for explaining the relationship between the dielectrophoretic force at a low ion concentration and the frequency of voltage for electrophoresis.
(B) A graph for explaining the relationship between the dielectrophoretic force at a high ion concentration and the frequency of voltage for electrophoresis.
FIG. 9 is a graph showing the relationship between the material conductivity and the normalized dielectrophoretic force at an applied frequency of 100 kHz.
FIG. 10 is an overall horizontal view of an oral hygiene state inspection apparatus according to Embodiment 3 of the present invention.
FIG. 11 is an overall configuration diagram of an oral hygiene state inspection apparatus according to Embodiment 4 of the present invention.
[Explanation of symbols]
1,40 measuring cell
2,41 Thin film electrode
3,42 rotor
4,43 Stirrer
5,44 Electrophoresis power supply
6, 26, 45, 62 Measuring unit
7, 28, 46, 63 Control unit
8, 27, 47, 64 Display
10 Electrode substrate
11 Conductive thin film
12 gap
20, 21, 60 cells
22 Light source
23 Light source side optical system
24 Receiver
25 Light receiving side optical system
29 luminous flux
30 Scattered light
48 Diaphragm
49 Ion exchange resin
61 Gas sensor
65 Jig

Claims (5)

A cell equipped with an electrode for measurement inside and capable of holding a sample liquid containing a sample collected from the oral cavity;
A power supply for applying a voltage for performing dielectrophoresis on the electrode;
A measurement unit for calculating the number of microorganisms in the sample solution;
A control unit for controlling the power supply unit and the measurement unit;
A flow promoting means for changing the relative position of the sample solution and the electrode;
The control unit applies a voltage to the electrode by controlling the power supply unit, and collects microorganisms in the sample solution on the electrode by dielectrophoretic force,
The flow promoting means changes the relative position of the sample solution and the electrode when collecting the microorganisms on the electrode by dielectrophoresis,
The measurement unit is configured to quantitatively calculate the number of microorganisms in the sample solution by measuring the impedance between the electrodes after collection or collection.   2. The oral hygiene state according to claim 1, wherein the measuring unit measures the conductivity of the sample solution before collecting the microorganisms in the sample solution on the electrode by dielectrophoresis. Inspection device.   The oral hygiene state inspection apparatus according to claim 1 or 2, further comprising a conductivity adjusting unit that adjusts the conductivity of the sample solution.   The oral hygiene state according to any one of claims 1 to 3, wherein the measurement unit measures the conductivity of the sample solution and corrects the calculation result of the number of microorganisms based on the measured conductivity. Inspection device.   A sample solution containing a sample collected from the oral cavity is introduced into a cell equipped with an electrode for measurement, the relative position between the sample solution and the electrode is changed, and a voltage is applied to the electrode to apply the sample. The number of microorganisms in the oral cavity is characterized by quantitatively calculating the number of microorganisms in the sample liquid by collecting microorganisms in the liquid on the electrodes by dielectrophoretic force and measuring the impedance between the electrodes. Method.

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