JP2004506472A - Method and apparatus for drilling teeth using pressurized water injection - Google Patents

Abstract

An apparatus and method for removing corroded tool material by piercing teeth using high pressure water jets is disclosed. The system according to the present invention may include a pressurized water source (12) operatively connected to an applicator (16) used to define a water flow (28) on the corroded portion of the tooth (32). The present invention utilizes a water flow utilizing a single or multiple water flow orifices, pure water or particle entrained flow, and constant high pressure or pulsating pressure to achieve the removal of oral material, including enamel.

Description

上記式中、
Ｐ_１＝システム内部の液体の圧力
Ｐ_２＝オリフィスから退出する液体の圧力
Ｖ_１＝システム内部の液体の速度
Ｖ_２＝オリフィスから退出する液体の速度
ρ＝液体の密度
ｇ＝重力
ｚ_１＝システム内部の液体の高さ
ｚ_２＝オリフィスから退出する液体の高さ
【００２７】
この式によって、種々の設計パラメータに応じて水噴射システムの特徴を形成することができる。歯科水噴射用途において重要な要因は、液体流の退出速度、アプリケータと歯との間の距離、液体の内圧、水流の大きさ、および液体の密度である。例えば、退出速度が既知であるとすると、上述の式を用いれば、既知の退出速度を得るために必要な内圧について解くことができる。これは、歯科医がスラリ流の切除速度と切除深さの関係を理解している場合に有用であろう。しかしながら、圧力計算を簡略化するために、いくつかの仮定を設けることが可能であり、そうするべきである。第１に、液体がシステムを通過する際の最少摩擦損失の仮定がある。摩擦損失は生ずるが、この損失を無視しても、精度が幾分落ちるだけで、計算が大幅に簡略化する。第２に、液体がノズルから退出するときの圧力を大気圧（約１４．７ｐｓｉ）と仮定する。液体退出位置における圧力は実際には多少変動する場合もあるが、大したことはない。第３に、第１点および第２点間における高さの変化は、２つの圧力の差圧と比較した場合、極小さいものであると仮定する。最後に、水の第１速度は、第２点における退出速度と比較した場合、０であると仮定することができる。これらの仮定に従い、水の内圧について式を解く。
【００２８】
【数２】

この式は、毎秒１００インチ乃至毎秒１０００インチの速度を得るためには、システム内の圧力はそれぞれ約２００ｐｓｉ乃至１８，０００ｐｓｉでなければならないことを示す。したがって、較正の目的のために、退出速度を関連する圧力に対して評価 （ｓｃａｌｅ）することができる。図２および図３に示す実施形態では、好ましい動作圧力は１．７２ＭＰａ乃至１１７ＭＰａ（２５０ｐｓｉ乃至１７，０００ｐｓｉ）の間である。最適な圧力範囲は、好ましい研磨材の種類、体積濃度、オリフィスのサイズ、液体の種類、およびその他の要因によって左右される得る。異なる値や材料を用いる場合には、別の圧力範囲が好ましい場合もある。例えば、研磨材のサイズが大きく濃度が高い場合、特定の用途に対して本システムは全体的に低い圧力で作動することもできる。係る実施形態は、本発明の水噴射歯科用工具の範囲に該当するものとする。
【００２９】
本発明のシステムでは１．７２ＭＰａ乃至１１７ＭＰａ（２５０ｐｓｉ乃至１７，０００ｐｓｉ）の圧力範囲が好ましいが、現在好ましいスラリの特性では、水噴射が最も実用的に動作するのは３．４５ＭＰａ乃至１７．２ＭＰａ（５００ｐｓｉ乃至２，５００ｐｓｉ）の範囲である。現在好ましいスラリは、体積濃度が１１％の２０ミクロン酸化アルミニウム／水スラリである。この圧力範囲にすれば、低価格の機器および安全性の高い操作で歯の穿孔が制御可能である。直感的にわかるように、液体の圧力が高い程、水流が歯を穿孔する速度は高い。したがって、穿孔処置の最適制御を可能とするには、低圧を維持するとよい。用いる圧力が低い程、必要な機器も安価ですむ。高圧ポンプ、バルブ、およびホースのコストのために、水噴射歯科用工具の価格実現可能性が制限される場合もある。低圧動作であれば、機械を手頃な価格に抑えることができる。更に、低圧範囲は高圧範囲よりも安全である。何故なら、液体に蓄積されるエネルギが少ないからである。単一の処置中に高圧および低圧の双方を用いる別の実施形態も可能である。本システムは、流体の圧力を変動させ、これによってオリフィスから退出する液体の速度を変動させるように構成することもできる。変動装置は、流体に圧力スパイクを生成可能なポンプ、または種々の間隔で流体流を切断するバルブであり得る。
【００３０】
図に戻ると、図４は、射出後研磨材ミキサを有する水噴射システムの別の実施形態を示している。図２のシステムと同様、水噴射システムは、液体を加圧する増強ポンプ１０８に液体を供給する低圧液体源１０４を有する。典型的な増強ポンプ１０８は、端部と端部とが整合された２つのシリンダで構成することができ、一方のシリンダが大きく、他方のシリンダは小さい。ポンプ１０８では、圧力は力を面積で除算した値に等しいという単純な原理を用いている。面積が減少すれば、その結果、力は増大する。したがって、大きなピストンが液体を小さいシリンダ内に送り込むと、２つのシリンダ面積間の差に比例して圧力は上昇する。圧力が増大する一方で、その系は液体の流量を犠牲にする。しかしながら、水噴射は低流量である必要があるので、増強ポンプは水噴射歯科用工具には非常に適している。増強ポンプ１０８内のピストンは、油圧１１２または空気ポンプで駆動して、液体を加圧するとよい。一旦液体を加圧すると、高圧導管１１６を通過してアプリケータ１２０に向かう。アプリケータ１２０は、研磨材源１２４から研磨材を受容する。アプリケータにおいて、研磨材は液体と混合され、得られたスラリが歯またはその他の口腔物質に向けて射出される。
【００３１】
本水噴射歯科用工具において、アプリケータ１２０は、歯科用ドリル型機器と同様、手持ち操作が可能である。これによって、歯科医が熟知した方法で工具を柔軟に使用することが可能となる。あるいは、患者の口の上の場所に配した位置決め装置にアプリケータを取り付け、自在アーム（ｆｌｅｘｉｂｌｅ ａｒｍ）またはその他の位置決め装置によって、異なる操作位置に水噴射流を設定することもできる。別の実施形態では、液体流が歯に衝突する場所を較正し、歯科医がアプリケータ１２０を位置決めし易くすることもできる。アプリケータ１２０にスタイラスを設け、水流衝突位置を示すようにしてもよい。あるいは、アプリケータは、穿孔位置を示す光またはレーザを有してもよい。本アプリケータ１２０では、本開示の目的および機能を同じくする別の実施形態も存在可能である。
【００３２】
図５は、射出後研磨材ミキサを有するアプリケータの断面図を示す。同様のアプリケータと同じように、液体１４０はアプリケータ１２０のチャネル１４４を通過する。チャネル１４４は、アプリケータの本体１４８内に固定されており、図５では、ホース状導管として示されている。液体１４０は、ノズル１５２に進入する際には、研磨材が全く懸濁されていない。図５のノズルは、図３のノズル６４と全体的に同一である。液体はノズル１５２に入り、オリフィス・ディスク１６０のオリフィス１５６から高圧で押し出される。射出の時点では、水流１６４には研磨材が含まれていない。図５の実施形態では、研磨材１６８は、オリフィス１５６を離れた後、再合焦ノズル（ｒｅｆｏｃｕｓｉｎｇ ｎｏｚｚｌｅ） １７２において高圧水流１６４に混合される。研磨材１６８は、退出する液体流によって発生する減圧によって、研磨材供給管１７６を通って再合焦ノズル１７２に引き込まれる。一旦研磨材が再合焦ノズル１７２に入ると、液体流１６４と混合されてスラリが形成される。再合焦ノズルのテーパ部によって、液体流１６４は再度細流に再合焦され、作業領域１７８に射出される。
【００３３】
図３および図５に示すように、水噴射除去工具は、オリフィス・ディスク９６，１６０を支持するコレット９２，１５８を有する。スラリは、オリフィス・ディスク９６，１６０からそれぞれ射出される。図６は、コレット１８２内に保持され、円形オリフィス１８４を有するオリフィス・ディスク１８０の図である。円形オリフィス１８４は、歯の一点にスラリ流を合焦させることができる。コレットにネジ部を設けると、ノズルに着脱可能に取り付けることができるので、コレットおよびノズル構造体全体を交換することなく、オリフィス・ディスクを容易に交換することが可能となる。図７は、楕円形オリフィス１９４を有するオリフィス・ディスク１９０の別の実施形態を示す。楕円形オリフィス１９４は、虫歯またはその他の口腔物質の矩形領域を除去することができる。このような形状のオリフィスは、歯の中に広く浅い孔を形成することができる。しかしながら、広範囲の歯科用途のための水噴射においては、別の形状のオリフィスを装備することができる。加えて、オリフィス・ディスク内のオリフィスは、更にテーパ状出口を有することもでき、こうすれば、水流がオリフィスから退出する際に、水流の直径を広げることができる。種々のテーパ角を用いて多数の水流および噴霧特性を得ることができる。
【００３４】
これらのオリフィス・ディスク１８０， １９０は、一般にサファイアまたはダイアモンドのように、研磨材によって容易に磨耗しない材料で形成される。オリフィスのサイズおよび形状も、水噴射歯科用工具の重要な設計要素である。出口オリフィスのサイズが、退出するスラリの量および歯における切除の直径を決定する。好適な実施形態のサイズは、０．００３インチ（０．０７６ｍｍ）乃至０．００８インチ（０．２０３ｍｍ）の範囲である。しかしながら、種々の用途毎に別のサイズにすることは、当業者に周知であろう。一定流過程の間にオリフィスのサイズを変化させると、次の式にしたがって絞り効果が得られる。
【００３５】
Ｖ_１Ａ_１＝Ｖ_２Ａ_２
上記式中、
Ｖ_１＝システム内部の液体速度
Ｖ_２＝オリフィスから退出する液体速度
Ａ_１＝管の断面積
Ａ_２＝オリフィスの断面積
【００３６】
この式は、液体がオリフィスから退出する際にはその速度が上昇することを示すが、絞りの効果は、一般に、システム内の大きな圧力と比較すると、取るに足りない程度である。しかしながら、圧力が低い場合、絞り効果は水噴射システムに対して著しい効果を有する場合がある。
【００３７】
図８は、第１オリフィス２０４および第２オリフィス２０８を有するオリフィス・ディスク２００を示す。オリフィス２０４，２０８に多少角度を付けると、２つの水流２１２，２１６が歯の上の同一位置で合流し、歯質を除去する速度を高めたり、あるいは孔の形状を変化させることができる。用途に応じて、２つよりも多いオリフィスを有する別の実施形態も可能である。
【００３８】
本水噴射歯科用工具には複数の用途や変形があり、これらは本開示の一部として実施することができる。水噴射を用いて歯質を除去するために開示した方法は、以下のステップの多くを実行することができるが、別のパラメータ範囲を含んでもよい。第１に、液体を加圧する。典型的な圧力は１．７２ＭＰａ乃至１１７ＭＰａ（２５０ｐｓｉ乃至１７，０００ｐｓｉ）であるが、３．４５ＭＰａ乃至１７．２ＭＰａ（５００ｐｓｉ乃至２，５００ｐｓｉ）が好ましい。次に、加圧液体をアプリケータに送り、歯に孔を開けるのに十分な速度でオリフィスから射出させる。オリフィスの範囲は、０．００３インチ（０．０７６ｍｍ）乃至０．００８ｍｍ（０．２０３ｍｍ）とするとよい。また、本方法は、液体内に研磨材を混合し、この研磨材をスラリに懸濁させるステップも含むことができる。現時点における好ましい研磨材の１つは、体積濃度が４％乃至２０％の研磨用酸化アルミニウムを含むスラリである。研磨材のサイズは、４乃至７ミクロンの範囲とするとよい。
【００３９】
本発明は、ここに広義に記載し以下に特許請求する、その構造、方法、またはその他の本質的な特性から逸脱することなく、他の具体的形態でも実施可能である。本装置およびシステムは、骨や指の爪のエッチングのような、当業者には公知の別の用途でも使用可能である。先に記載した実施形態は、あらゆる観点において、限定ではなく、例示としてのみ解釈するものとする。したがって、本発明の範囲は、前述の説明ではなく、添付した特許請求の範囲によって示される。特許請求の範囲の意味および均等の範囲に該当するあらゆる変更は、本発明の範囲に包含されるものとする。
【図面の簡単な説明】
【図１】水噴射歯科用工具の概略ブロック図。
【図２】研磨材ミキサを備えた、水噴射歯科用工具の別の可能な実施形態の概略ブロック図。
【図３】スラリ・アプリケータの断面図。
【図４】研磨材供給源および増強ポンプを備えた、水噴射歯科用工具の別の可能な実施形態の概略ブロック図。
【図５】射出後研磨材ミキサを有するアプリケータの断面図。
【図６】円形オリフィスを備えた液体スラリ・オリフィス・ディスクの端面図。
【図７】楕円オリフィスを備えた液体スラリ・オリフィス・ディスクの端面図。
【図８】第１および第２オリフィスを備えたアプリケータの可能な実施形態の断面図。[0001]
(Background of the Invention)
1. Field of the invention
The present invention relates to the field of drilling teeth to remove corroded enamel or other tooth matter and to provide a surface of appropriate size and shape to receive a dental restoration filler. More specifically, the present invention relates to a method and apparatus for drilling teeth using one or more high pressure water streams, with or without abrasive suspended in water.
[0002]
2. Technical background
According to the American Dental Association Survey Office, an estimated 151,810,000 dental fillings were performed in the United States in 1990 alone. Currently, the most prevalent and well-known method for removing dentin in a recess filling procedure is by a high speed drilling process. Perforations are often accompanied by considerable discomfort and anxiety. Most people find going to a dentist to fill a depression is a very unpleasant and painful experience. Some people dislike visiting a dentist because of the sound, smell, and pain associated with a typical drilling process.
[0003]
High speed dental drills are mechanical drills with a bit at the end and driven by an electric or pneumatic power source. The drill bit is designed to remove a small piece of tooth when its rotating head contacts the tooth. This removal method works exactly like an industrial drill when removing metal or ceramic parts. Dental drills are generally hand-held and can be easily positioned in most areas of the tooth to remove caries. The drilling process often requires water to cool the tooth to be drilled and a vacuum to remove this water and debris. The perforation process has the advantage of being low cost and widely accepted in the dental field. However, perforation in dental applications has many disadvantages. The cutting action of the rotating bit can damage the enamel and weaken the tooth structure. This process is invasive to the patient and, due to the size of the drill bit, often requires much more healthy material to be removed than necessary.
[0004]
In many cases, patients experience discomfort due to grinding or vibration near the dental nerve, which may have been stressed by enamel corrosion. During this process, the patient will hear a constant, high pitch groan of the drill motor, which is accompanied by pain and discomfort, and some will feel unmistakable fear. Large amounts of analgesics may be needed to offset the pain and discomfort of the perforation procedure, but need to wait for the drugs to take effect, which can further lengthen the process. The use of drugs also increases the cost of the procedure. As a result of these problems, the process of perforating the teeth is accompanied by discomfort and anxiety in the patient for minutes or even hours.
[0005]
To overcome the disadvantages of dental perforation, alternative methods of removing corroded tooth material are being investigated. One such method is air polishing. The air polishing device polishes and removes the surface by propelling and delivering small abrasive particles onto the teeth using pressurized air. Air polishing devices are very effective for shallow surface depressions and can often preserve more healthy teeth than high-speed drills. Also, the impact of the abrasive particles on the teeth is so small that vibrations are not a concern and injections of pain killers are usually unnecessary. This saves time and increases patient comfort. However, the air polishing method is not very time efficient when piercing below the outer enamel layer of the tooth and extending into soft tissue. This is because, in part, the soft tissue immediately below the enamel surface, called dentin, partially absorbs the impact of the abrasive particles. The particles tend to bounce off of this part of the tooth, reducing the effectiveness of the abrasive stream drilling.
[0006]
Another alternative to drilling recently introduced is laser drilling and ablation techniques. Lasers are the most accurate method of removing tooth material in the dental industry. They are well controlled and can penetrate the tooth surface and underlying tissue with the smallest resection width of all currently available methods. Although the use of a laser creates a heat-affected zone in the area adjacent to the tooth to be ablated, studies have shown that this effect is not large enough to cause permanent damage to dental health. It is shown. Although lasers have been very effective in dental applications, very few dentists use them. The main reason is that these costs are significantly higher than alternatives. Also, most dentists are not willing to invest in technology without realizing that there are significant improvements over current methods.
[0007]
In developing a new corrosion removal method, there is a need for an apparatus and method that is capable of removing corroded tooth material while preserving as much healthy tooth material as possible. Leaving more healthy tooth material in place is helpful in maintaining the strength of the entire tooth and minimizing the possibility of subsequent toothing. For high speed drills, the minimum cut size is limited by the width of the cutting tool. In order to reach the corroded area sufficiently, a relatively large amount of healthy tooth must be removed. Air polishing and laser methods can reduce the amount of ablation and thus preserve much more healthy teeth than was previously possible. However, even more accurate ablation limits the speed of the process, the type of material that can be removed, and the cost of the equipment required. Since these methods can only remove relatively small areas of the tooth at a time, the larger the area of material to be removed, the longer the required time.
[0008]
In view of the above, there is a need for improved tooth drilling devices and methods. Such a method should be effective in removing enamel and other corrosive substances quickly with minimal patient discomfort. Accordingly, it is naturally preferred that such devices be quiet and minimize the number of instruments that must be simultaneously inserted into the patient's mouth. Further, such devices should be inexpensive to operate and work with equipment that can be easily integrated with current dental clinic systems. Such devices must be self-cooling, highly accurate and capable of preserving healthy tooth structure. In addition, such a method should minimize the patient's distress and avoid psychological stress on patients who would already be in great anxiety just by considering going to a dentist.
[0009]
(Summary of the Invention)
The method and apparatus utilize high pressure liquid, i.e., water jets, through small orifices to cut and remove corroded teeth for a dental restoration procedure. Water jets can ablate much more material than other methods without damaging the surrounding material. The apparatus includes a pressure source configured to supply a flow of pressurized liquid, such as water, to the applicator through a high speed conduit. The applicator has a first orifice positioned to direct the first liquid flow to the oral surface, and the velocity of the liquid flow emitted from the orifice can pierce into the dentin, such as a tooth enamel. .
[0010]
The water-jet dental tool can also have an abrasive suspended in a pressurized liquid. The abrasive is typically mixed with a liquid to create a substantially homogenized slurry. The abrasive in the slurry may be between 1 and 30 microns in diameter and has an abrasive volume concentration in the range of 3% to 20%. In the present apparatus and method, any number of abrasives can be used. Aluminum oxide, pumice, baking soda, and illminite are abrasives currently used in the dental field and can also remove sufficient amounts of tooth and oral matter when used in water jet systems. . The slurry is ejected from the applicator under high pressure. Typically, the pressure of the slurry is in the range of 1.72 MPa to 117 MPa (250 psi to 17,000 psi), and preferably in the range of 3.45 MPa to 17.2 MPa (500 psi to 2,500 psi). Depending on other factors, such as the size of the slurry and orifice, in other embodiments, a slurry pressure of less than 250 psi may be useful.
[0011]
The orifices in the applicator can also have different shapes for different drilling requirements. In one embodiment, the orifice is circular, and in another embodiment, the orifice is elliptical. However, for a wide range of dental applications, other shapes of orifices can be implemented in the water jet. The size of the orifice may range from 0.003 inches (0.076 mm) to 0.008 inches (0.203 mm). In addition, the applicator may have more than one orifice to direct water flow to the teeth and may be able to introduce periodic changes in liquid pressure.
[0012]
Also, the method may be performed by another device by embodying the procedure. The process involves pressurizing the liquid. The pressure can be in any number range, depending on the composition of the slurry. Next, the pressurized liquid is fed into the applicator. The applicator can include any number of orifices having a diameter sufficient to pierce the teeth. The applicator then ejects a high pressure liquid or slurry stream from the orifice at a rate sufficient to pierce the teeth.
[0013]
The operation, features and advantages of the present apparatus and method will become more apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
[0014]
(Detailed description)
The presently preferred embodiment of the present invention will be best understood by reference to the drawings. Throughout the drawings, similar parts are denoted by the same reference numerals. Although the components of the present invention are generally described and illustrated herein, it will be readily understood that they can be arranged and constructed in a wide variety of different configurations. Accordingly, the following more detailed description of the embodiments of the apparatus, system, and method of the present invention is intended to limit the scope of the claimed invention, as illustrated in FIGS. Rather, they represent merely the presently preferred embodiments of the invention.
[0015]
Referring to FIG. 1, a water jet dental tool 10 is shown having a source of pressurized liquid 12 and a liquid flow applicator 16. The pressurized liquid source 12 and the applicator 16 are operably connected such that the applicator 16 receives high pressure liquid from the pressure source 12. The source of pressurized liquid may be a high pressure liquid pump or other pressure generating device such as a pressurized gas tank, a weighted piston, or a compressed flexible bladder. The pressurized liquid source 12 and the applicator 16 may be connected by any liquid transfer device that can withstand high pressure. The system 10 may use a high pressure hose, a drilled section of a block, or any other similar high pressure conduit 20. Once the high pressure liquid reaches the applicator 16, it is ejected from the water jet 10 through the orifice 24. The diameter of the orifice 24 is smaller than the diameter of the high-pressure conduit 20.
[0016]
Due to the constant volumetric flow rate of such a nozzle system, high pressure liquid is converted to high velocity liquid as it passes through the orifice. A trickle of liquid 28 is directed by applicator 16 to a desired oral substance, such as teeth 32 shown in FIG. The high velocity liquid stream 28 impacts the tooth surface, thereby slowing down the water. The deceleration of the liquid flow 28 causes a reaction force at the teeth 32 in the direction toward the teeth 32 and in the same direction of the liquid flow 28. Since the force is equal to the product of the mass and the acceleration, the product of the deceleration of the liquid and the mass of the liquid impinging on the teeth 32 produces a force on the teeth 32 sufficient to remove the dentin. FIG. 1 illustrates a possible caries removal procedure. However, the water-injected dental tool 10 can also remove healthy tooth material, such as when smoothing a missing part, or soft oral material, such as during root treatment. The water injection dental tool 10 can be used for many of the same applications as conventional drills.
[0017]
There are various embodiments of the dental tool shown in FIG. For example, in the water injection shown in FIG. 2, a polishing slurry is created by combining a liquid with an abrasive. A slurry is a mixture of a liquid, often water, with any of several types of finely divided particulate matter. The slurry travels through the water injection system, similar to a liquid, but in addition to polishing, to facilitate removal of dentin or other similar materials. In the oral environment, the particles selected for mixing with the liquid must be selected taking into account the health standards to which they apply. Abrasives such as aluminum oxide are preferred because they are already used in dental applications and the material has been approved for dental applications by the United States Food and Drug Administration. Other abrasives, such as pumice, baking soda, and illminite, are also safe in the oral environment and can be used to remove dentin. In addition to being safe, the abrasive must have other important physical properties, such as particle size, volume concentration, hardness, and insolubility.
[0018]
The particle size of the slurry abrasive is a factor in determining and controlling the amount of material removed by the liquid flow. In one embodiment for removing caries material, the abrasive particle size preferably ranges from 1 to 30 microns. Typically, the classification of particle size is based on the size of the filter net or filter through which the abrasive passes. References in this and other sections to particle size should not be construed as limiting the abrasive to any one particle size. For example, an amount of 20 micron aluminum oxide may also include some percentage of particles larger or smaller than 20 microns. This is common in the screening process. Rather, an amount of 20 micron aluminum oxide will be comprised of particles that are not perfect, but approximately 20 microns. In addition, other substances may be present in the slurry in addition to the liquid and abrasive particles. For example, various types of painkillers and cleaning materials may be included in the slurry to widen the variety of uses and types of the slurry. In addition, various materials that facilitate suspending the abrasive particles in the slurry may be used.
[0019]
In a preferred embodiment, the liquid in the slurry has a 4% to 17% volume concentration of abrasive. This preferred range allows the slurry to remain entirely liquid while retaining a suitable amount of abrasive for ablation. By optimizing the ratio of abrasive to liquid, the function of water injection can be optimized. The slurry must remain substantially liquid to allow for pressurization of the liquid in a pump, pressure amplifier, or other pressure source. However, it is also desirable to operate the system in the low pressure range for safety and power generation reasons.
[0020]
In one embodiment, a volume concentration of 4% to 17% is preferred, but other ranges are within the scope of this disclosure. For example, the present device can remove oral matter without using abrasives. This can be used in highly corroded teeth and in situations involving treatment of the gums. In this water injection system, it is possible to use a higher concentration of the abrasive, but care must be taken to prevent the slurry from becoming sludge. In addition, increasing the concentration of the abrasive can create dirty residues around the work area. A volume concentration of 17% provides a good mixture that can be efficiently excised, but leaves spray residues from the abrasive particles around the work area. At 11% by volume of the mixture, the contamination is much less than with a more concentrated abrasive, but not as efficiently ablated as with a 17% abrasive. Therefore, individual environments and applications must be considered when selecting the volume concentration of the abrasive in the pressurized liquid.
[0021]
At present, the preferred liquid for the slurry is water because of its safety and availability. However, other liquids can be used as long as they can create pressure and suspend the abrasive. Water is an excellent solvent, which limits the types of abrasives that can be used in water jets. For example, baking soda can be used for water injection, but it dissolves in water, so its characteristics as an abrasive cannot be used. In addition, it may be difficult to keep such abrasives homogeneous throughout the system. Keeping the slurry homogeneous helps to calibrate and time the exposure of the teeth to the high pressure stream of slurry. Liquids other than water can be used for water injection if the solubility of the abrasive is low.
[0022]
Returning to FIG. 2, this embodiment shows a system having two possible devices and locations for mixing a slurry in a water-injected dental tool 40. The system has a pump or other pressure source 44 that receives liquid from a liquid source 48. The abrasive mixers 50, 52 may be located on either side of the pump. The system does not require both mixers 50, 52, but typically has one or the other. A mixer 50 upstream of the pump 44 receives a quantity of abrasive from the abrasive supply 56 based on the volume of liquid passing through the system. The upstream mixer 50 receives both the liquid and the abrasive and mixes them to form a slurry of the appropriate concentration. Next, the slurry enters the pump and is pressurized to high pressure. Once the slurry is pressurized, it exits through high pressure conduit 60. The slurry enters the applicator 64 and is directed to the material to be ablated. However, this embodiment has several disadvantages. Slurries that are pressurized in the pump can wear the components of the pump, causing the pump to leak or fail.
[0023]
To avoid this damage, the abrasive may be added to the pressurized liquid by the downstream mixer 52. In this abrasive mixing process, the abrasive must be injected into the high differential pressure water stream in one batch or intermittently as a slurry in the pressurized liquid. In a single batch injection procedure, a single dose suitable for limited drilling time and depth is typically delivered into the system. However, in dental restorative operations, only a small number of dental perforations are usually performed at each visit, so the downstream mixer configuration is very suitable for dental procedures. Alternatively, in low pressure embodiments, the abrasive may be suitably added downstream of the pressure source without any additional changes or work. In yet another embodiment, the system may not mix the abrasive and liquid at all, and may perform the ablation function using only abrasive-free liquid.
[0024]
In selecting a design for a particular application, the advantages and disadvantages of each abrasive injection method must be considered. Here, it is preferable to place the mixer 52 downstream of the pump or other pressure source to prolong the life of the pump or pressure source. By loading the abrasive material for one time into the abrasive material supply device, a fixed amount of abrasive material can be supplied to a number of oral treatments. However, it is desirable to have a pump that can pressurize the slurry with minimal wear on the system.
[0025]
Regardless of where the slurry is mixed, the mixture enters the applicator 64 as a slurry and exits the orifice 68. FIG. 3 shows a cross-sectional view of the applicator 64 of FIG. Within the body 76 of the applicator is a tube or channel 72 that can withstand high pressures as in a water injection system. Channel 72 is shown as having a slurry passing therethrough, which is represented by particles 80 within liquid 84. The slurry mixture passes through channel 72 and enters a nozzle 88 that is connected to the end of channel 72. The nozzle 88 has a collet 92 that supports an orifice 96. The slurry is forced through a small orifice 96 by the internal pressure of the mixture. The mechanical relationship between slurry pressure and velocity can be best related by Bernoulli's equation. Bernoulli's equation relates the pressure, velocity, density, and elevation of a liquid to two points in a fluid system having a constant flow rate. With water injection, the volume of liquid entering the system is equal to the volume of water exiting orifice 96. This is because there is no other liquid input / output source. For this reason, Bernoulli's equation is suitable for calculating water injection. In the following equation, a first measurement is taken at the pressurization point of the system and a second measurement is taken immediately after the liquid exits the orifice. The equation is shown below.
[0026]
(Equation 1)

In the above formula,
P₁= Pressure of the liquid inside the system
P₂= Pressure of liquid exiting the orifice
V₁= Liquid velocity inside the system
V₂= Velocity of liquid exiting the orifice
ρ = density of liquid
g = gravity
z₁= Liquid level inside the system
z₂= Height of liquid exiting the orifice
[0027]
This equation can shape the characteristics of the water injection system depending on various design parameters. Important factors in dental water jet applications are the exit velocity of the liquid stream, the distance between the applicator and the tooth, the internal pressure of the liquid, the size of the water stream, and the density of the liquid. For example, assuming that the exit speed is known, the internal pressure required to obtain a known exit speed can be solved using the above equation. This may be useful if the dentist understands the relationship between slurry flow ablation rate and ablation depth. However, to simplify the pressure calculation, some assumptions can and should be made. First, there is an assumption of a minimum friction loss as the liquid passes through the system. Friction losses do occur, but ignoring this loss, with some loss of accuracy, greatly simplifies the calculations. Second, assume that the pressure at which the liquid exits the nozzle is atmospheric pressure (about 14.7 psi). The pressure at the liquid exit position may actually fluctuate somewhat, but this is not a big deal. Third, assume that the change in height between the first and second points is minimal when compared to the pressure difference between the two pressures. Finally, it can be assumed that the first velocity of the water is zero when compared to the exit velocity at the second point. Following these assumptions, solve the equation for the internal pressure of water.
[0028]
(Equation 2)

This equation shows that to achieve a speed of 100 inches per second to 1000 inches per second, the pressure in the system must be about 200 psi to 18,000 psi, respectively. Thus, for calibration purposes, the exit speed can be scaled against the associated pressure. In the embodiment shown in FIGS. 2 and 3, the preferred operating pressure is between 1.72 MPa and 117 MPa (250 psi and 17,000 psi). The optimal pressure range may depend on the preferred abrasive type, volume concentration, orifice size, liquid type, and other factors. If different values or materials are used, different pressure ranges may be preferred. For example, if the size of the abrasive is large and the concentration is high, the system may also operate at a lower overall pressure for a particular application. Such an embodiment shall fall within the scope of the water injection dental tool of the present invention.
[0029]
While a pressure range of 1.72 MPa to 117 MPa (250 psi to 17,000 psi) is preferred in the system of the present invention, the currently preferred slurry characteristics make water jets most practically operational at 3.45 MPa to 17.2 MPa ( 500 psi to 2,500 psi). The currently preferred slurry is a 20 micron aluminum oxide / water slurry with a volume concentration of 11%. With this pressure range, the perforation of the teeth can be controlled with low-cost equipment and safe operation. Intuitively, the higher the pressure of the liquid, the higher the rate at which the water stream perforates the teeth. Therefore, a low pressure may be maintained to allow optimal control of the drilling procedure. The lower the pressure used, the cheaper the equipment needed. The cost of high pressure pumps, valves and hoses may also limit the price feasibility of water jet dental tools. With low pressure operation, the machine can be kept affordable. Furthermore, the low pressure range is safer than the high pressure range. This is because less energy is stored in the liquid. Other embodiments that use both high and low pressure during a single procedure are possible. The system can also be configured to vary the pressure of the fluid, thereby varying the velocity of the liquid exiting the orifice. The variator may be a pump capable of producing a pressure spike in the fluid, or a valve that cuts off the fluid flow at various intervals.
[0030]
Returning to the figure, FIG. 4 illustrates another embodiment of a water injection system having a post-injection abrasive mixer. Like the system of FIG. 2, the water injection system has a low pressure liquid source 104 that supplies liquid to a boost pump 108 that pressurizes the liquid. A typical boost pump 108 may be comprised of two end-to-end aligned cylinders, one large and the other small. Pump 108 uses the simple principle that pressure equals force divided by area. As the area decreases, the force increases as a result. Thus, when a large piston pumps liquid into a small cylinder, the pressure rises in proportion to the difference between the two cylinder areas. While the pressure increases, the system sacrifices liquid flow. However, since water jets need to be at low flow rates, boost pumps are very well suited for water jet dental tools. The piston in the intensifier pump 108 may be driven by a hydraulic 112 or air pump to pressurize the liquid. Once the liquid is pressurized, it passes through the high pressure conduit 116 to the applicator 120. Applicator 120 receives abrasive from abrasive source 124. In the applicator, the abrasive is mixed with a liquid and the resulting slurry is injected towards teeth or other oral material.
[0031]
In the present water injection dental tool, the applicator 120 can be hand-held, similarly to a dental drill-type device. This allows the dentist to use the tool flexibly in a manner familiar to him. Alternatively, the applicator can be mounted on a positioning device located above the patient's mouth, and the water jet can be set to different operating positions by a flexible arm or other positioning device. In another embodiment, the location where the liquid stream impacts the teeth may be calibrated to help the dentist position applicator 120. A stylus may be provided on the applicator 120 to indicate the location of the water stream collision. Alternatively, the applicator may have a light or laser indicating the location of the perforation. There may be other embodiments of the present applicator 120 that have the same purpose and function of the present disclosure.
[0032]
FIG. 5 shows a cross-sectional view of an applicator having a post-injection abrasive mixer. As with similar applicators, liquid 140 passes through channel 144 of applicator 120. The channel 144 is fixed within the body 148 of the applicator and is shown in FIG. 5 as a hose-like conduit. When the liquid 140 enters the nozzle 152, no abrasive is suspended. The nozzle of FIG. 5 is generally the same as the nozzle 64 of FIG. Liquid enters the nozzle 152 and is forced out of the orifice 156 of the orifice disk 160 at high pressure. At the time of the injection, the water stream 164 contains no abrasive. In the embodiment of FIG. 5, abrasive 168 is mixed with high-pressure water stream 164 at refocusing nozzle 172 after leaving orifice 156. The abrasive 168 is drawn into the refocusing nozzle 172 through the abrasive supply tube 176 by the reduced pressure generated by the exiting liquid flow. Once the abrasive enters the refocusing nozzle 172, it is mixed with the liquid stream 164 to form a slurry. With the taper of the refocusing nozzle, the liquid stream 164 is refocused again into a trickle stream and ejected to the working area 178.
[0033]
As shown in FIGS. 3 and 5, the water jet removal tool has collets 92,158 that support orifice disks 96,160. Slurry is ejected from orifice disks 96 and 160, respectively. FIG. 6 is an illustration of an orifice disk 180 held within a collet 182 and having a circular orifice 184. Circular orifice 184 can focus the slurry flow at a point on the tooth. If the collet is provided with a threaded portion, it can be detachably attached to the nozzle, so that the orifice disk can be easily replaced without replacing the collet and the entire nozzle structure. FIG. 7 illustrates another embodiment of an orifice disk 190 having an elliptical orifice 194. Oval orifice 194 can remove a rectangular area of caries or other oral material. Such an orifice can form a wide and shallow hole in the tooth. However, in water jets for a wide range of dental applications, other shaped orifices can be equipped. In addition, the orifice in the orifice disk may further have a tapered outlet, which may increase the diameter of the water flow as it exits the orifice. Numerous water flow and spray characteristics can be obtained using various taper angles.
[0034]
These orifice disks 180, 190 are formed of a material that is not easily worn by abrasives, such as sapphire or diamond. The size and shape of the orifice are also important design factors of the water jet dental tool. The size of the exit orifice determines the amount of slurry exiting and the diameter of the cut at the tooth. The size of the preferred embodiment ranges from 0.003 inches (0.076 mm) to 0.008 inches (0.203 mm). However, different sizes for different applications will be known to those skilled in the art. Changing the size of the orifice during the constant flow process results in a throttling effect according to the following equation:
[0035]
V₁A₁= V₂A₂
In the above formula,
V₁= Liquid velocity inside the system
V₂= Liquid velocity exiting the orifice
A₁= Tube cross-sectional area
A₂= Cross section of orifice
[0036]
This equation shows that the velocity increases as the liquid exits the orifice, but the effect of the throttle is generally insignificant when compared to the high pressures in the system. However, at low pressures, the throttling effect can have a significant effect on the water injection system.
[0037]
FIG. 8 shows an orifice disk 200 having a first orifice 204 and a second orifice 208. A slight angle of the orifices 204, 208 allows the two streams 212, 216 to merge at the same location on the tooth, increasing the speed at which the dentine is removed or changing the shape of the holes. Other embodiments with more than two orifices are possible, depending on the application.
[0038]
The present water-injection dental tool has multiple uses and variations, which can be implemented as part of the present disclosure. The disclosed method for removing tooth material using water jets can perform many of the following steps, but may include other parameter ranges. First, the liquid is pressurized. Typical pressures are from 1.72 to 117 MPa (250 psi to 17,000 psi), with 3.45 MPa to 17.2 MPa (500 psi to 2,500 psi) being preferred. The pressurized liquid is then sent to the applicator and ejected from the orifice at a rate sufficient to pierce the teeth. The range of the orifice may be between 0.003 inches (0.076 mm) and 0.008 mm (0.203 mm). The method can also include the step of mixing the abrasive in the liquid and suspending the abrasive in the slurry. One currently preferred abrasive is a slurry containing 4-20% by volume aluminum oxide for polishing. The size of the abrasive may range from 4 to 7 microns.
[0039]
The present invention may be embodied in other specific forms without departing from its structure, methods, or other essential characteristics, which are broadly described herein and claimed below. The devices and systems can be used in other applications known to those skilled in the art, such as etching bones and fingernails. The embodiments described above are to be interpreted in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. Any modification falling within the meaning and equivalent scope of the claims is intended to be included in the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of a water injection dental tool.
FIG. 2 is a schematic block diagram of another possible embodiment of a water jet dental tool with an abrasive mixer.
FIG. 3 is a cross-sectional view of the slurry applicator.
FIG. 4 is a schematic block diagram of another possible embodiment of a water jet dental tool with an abrasive source and a boost pump.
FIG. 5 is a cross-sectional view of an applicator having a post-injection abrasive mixer.
FIG. 6 is an end view of a liquid slurry orifice disk with a circular orifice.
FIG. 7 is an end view of a liquid slurry orifice disk with an elliptical orifice.
FIG. 8 is a cross-sectional view of a possible embodiment of an applicator with first and second orifices.

Claims (43)

A tooth-perforating device,
A source of pressurized liquid configured to provide a stream of pressurized liquid;
An applicator operably connected to the liquid source and receiving the pressurized liquid, the applicator selectively delivering a first stream of the pressurized liquid toward the dentin. A first orifice disposed in the perforation device, wherein the liquid stream is capable of perforating dentin. The apparatus according to claim 1, further comprising an abrasive suspended in the pressurized liquid. 3. The device of claim 2, wherein the abrasive is selected from aluminum oxide, pumice, baking soda, and illuminite. 3. The apparatus of claim 2, wherein the abrasive has an average particle size of 1 to 30 microns. The apparatus of claim 2, wherein the abrasive is aluminum oxide. 3. The apparatus of claim 2, wherein the volume concentration of the abrasive in the pressurized liquid ranges from about 3% to 20%. 3. The apparatus of claim 2, wherein the abrasive is mixed substantially homogeneously throughout the pressurized liquid. The apparatus of claim 1, wherein the liquid is pressurized to a pressure in a range from 1.72 MPa to 117 MPa (250 psi to 17,000 psi). The apparatus of claim 1, wherein the liquid is pressurized to a pressure in the range of 3.45 MPa to 17.2 MPa (500 psi to 2,500 psi). The apparatus of claim 1, wherein the liquid is pressurized to a pressure in a range from 1.72 MPa to 17.2 MPa (250 psi to 500 psi). The device of claim 1, wherein the diameter of the first orifice is between about 0.003 inches (0.076 mm) and 0.008 inches (0.203 mm). The device of claim 1, wherein the diameter of the first orifice is between about 0.004 inches (0.076 mm) and 0.006 inches (0.152 mm). The device of claim 1, wherein the first orifice is circular. The device of claim 1, wherein the first orifice is one of an elliptical and other non-circular orifices. The device of claim 1, further comprising a second orifice. The device of claim 1, wherein the source of pressurized liquid is adapted to induce a periodic change in the liquid pressure. A tooth-perforating device,
A pump capable of pressurizing the liquid to a pressure in the range of 1.72 MPa to 117 MPa (250 psi to 17,000 psi);
An applicator operably connected to the pump for receiving the pressurized liquid, the orifice having an orifice size of 0.003 inches (0.076 mm) to 0.008 inches (0.203 m) in diameter; An applicator,
A punching device comprising: The apparatus of claim 17, further comprising an abrasive source that mixes abrasive with the liquid after the liquid exits the orifice. 19. The apparatus of claim 18, further comprising a refocusing nozzle coupled to the applicator for refocusing the mixture of liquid and abrasive. A tooth-perforating device,
A pressure source configured to pressurize the slurry of aluminum oxide and water;
A slurry applicator operably coupled to the pressure source and capable of injecting the slurry with a force suitable for removing a predetermined amount of dentine;
A punching device comprising: A method of piercing a tooth,
Pressurizing the liquid;
Delivering the pressurized liquid to an applicator having an orifice;
Squeezing and injecting a pressurized liquid flow from a first orifice onto a tooth surface, wherein the velocity of the liquid is sufficient to pierce the tooth;
Consisting of: 22. The method of claim 21, further comprising suspending an abrasive suspended in the pressurized liquid. 23. The method of claim 22, wherein the abrasive is selected from aluminum oxide, pumice, baking soda, and illuminite. 23. The method of claim 22, wherein the abrasive has an average particle size of 1 to 30 microns. 23. The method of claim 22, wherein the volume concentration of the abrasive ranges from about 3% to 20%. 23. The method of claim 22, wherein the abrasive is mixed substantially uniformly throughout the pressurized liquid. 22. The method of claim 21, wherein the pressurized liquid is water. 22. The method of claim 21, wherein the liquid is pressurized to a pressure in a range from 1.72 MPa to 117 MPa (250 psi to 17,000 psi). 22. The method of claim 21, wherein the liquid is pressurized to a pressure in a range from 500 psi to 2500 psi. 22. The method of claim 21, wherein the liquid is pressurized to a pressure in a range from 250 psi to 500 psi. 22. The method of claim 21, wherein the diameter of the first orifice is between about 0.003 inches (0.076 mm) and 0.008 inches (0.203 mm). 22. The method of claim 21, wherein the diameter of the first orifice is between about 0.004 inches (0.076 mm) and 0.006 inches (0.152 mm). 22. The method according to claim 21, wherein said first orifice is circular. 22. The method of claim 21, wherein the first orifice is elliptical. 22. The method according to claim 21, further comprising a second orifice. A method for removing corroded parts of teeth,
Pressurizing the polishing slurry;
Injecting a stream of pressurized slurry into the corroded part of the tooth;
Perforating and removing the corroded portion of the tooth;
Consisting of: A method of perforating a tooth material,
Pressurizing the slurry to a pressure of about 1.72 to 117 MPa (250 to 17,000 psi), wherein the slurry contains aluminum oxide particles in a volume concentration of 4% to 20%, and the diameter of the aluminum oxide particles is Having an average particle size of 1 to 30 microns;
Squirting the pressure slurry through a circular orifice having a diameter of 0.004 inches (0.102 mm) to 0.006 inches (0.152 mm) to the tooth material;
Consisting of: A tooth removal system,
A pressurized liquid source;
A pump capable of generating a high pressure in a liquid, the pump being operatively coupled to the liquid source;
A high pressure conduit,
A hand-held applicator for injecting the pressurized liquid stream toward the tooth with a force effective to controllably pierce the tooth enamel;
A system comprising: 39. The system of claim 38, further comprising an abrasive supply connected to the system prior to the pump. 39. The system of claim 38, further comprising an abrasive supply connected to the system after the pump. A tooth removal system,
A liquid source;
A hydraulic pump,
An intensifier pump operably coupled to the liquid source and receiving operational input from the hydraulic pump, the intensifier pump generating a high pressure in the liquid;
A high pressure conduit,
A hand-held applicator for injecting the pressurized liquid stream toward the tooth with a force effective to controllably pierce the tooth enamel;
A system comprising: 42. The apparatus of claim 41, further comprising an abrasive source releasably coupled to the applicator, wherein abrasive is mixed with the ejected liquid stream. A tooth-perforating device,
A pump for pressurizing the slurry of aluminum oxide and water to a pressure in the range of 250 to 17,000 psi (1.72 MPa to 117,000 psi), the slurry having a volume concentration of aluminum oxide of 4% to 20%; The aluminum oxide has a particle size of approximately 1 to 30 microns;
Injecting the high pressure flow of the slurry through a circular orifice or a non-circular orifice.

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