GB2374015A

GB2374015A - Orthodontic calibrating ruler

Info

Publication number: GB2374015A
Application number: GB0108731A
Authority: GB
Inventors: Colin Wallis
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-04-06
Filing date: 2001-04-06
Publication date: 2002-10-09
Anticipated expiration: 2021-04-06
Also published as: GB0108731D0; GB2374015B

Abstract

An apparatus and method to quantitatively assess dental arch form using an orthodontic ruler as illustrated in FIG.3. The orthodontic ruler is a rigid transparent plate marked with a plurality of arch templates converging at a midline anterior point of each arch template and also calibrated along a length of each arch. When placed on a study model of a dental arch it is possible to observe and record the shape of the dental arch in terms of a specific arch template and a specific length calibration.

Description

ORTHODONTIC DEVICE Field of the Invention The present invention relates, in general, to a measuring device used in the field of orthodontics. The invention is particularly, but not exclusively, concerned with measurements taken during an orthodontic assessment.

Background to the Invention In the field of orthodontics, an orthodontic assessment of an upper dental arch and a lower dental arch is performed to determine the type of treatment required or to analyse the state of treatment in progress. A problem sometimes requiring orthodontic treatment is curvature of the arch, known as the'curve of Spee', which may be associated with arch crowding.

The orthodontic assessment may include a space analysis of one or both arches. The aim of the analysis is to estimate the space available to align the teeth and level the arch antero-posteriorly. The measurement of interest in this aspect of the analysis is the minimum length that extends along the line of the arch from a pre-determined anterior point to a pre-determined posterior point.

One method of space analysis involves taking a direct measurement between the pre-determined anterior and posterior points, along the occlusal (biting) surface. A total length that would be occupied by the teeth, if they were in alignment, can be measured by adding the individual mesio-distal dimension of every tooth between the pre-determined points. This may be carried out with dividers and a simple ruler. (A half arch length for a left side or a right side may also be obtained by the addition of the individual mesio-distal dimension of every tooth within the half of the arch under analysis. ) An estimation is then made, usually visually, of any additional space factors

resulting from arch curvature. This method is clearly subject to human error and misjudgement.

There is, therefore, a need to accurately measure the length of the theoretical line of proper alignment of the upper or lower arches without using expensive equipment or time consuming methods. Furthermore, there is a need to utilise the accurate measurement of the theoretical length of the line of proper alignment to quantify the progress and aim of the treatment followed.

Summary of the Invention According to a first aspect of the present invention there is provided an orthodontic ruler comprising a form marked with at least part of a dental arch template, the template being calibrated.

In a second aspect of the present invention there is provided an orthodontic ruler comprising a plurality of substantially flat plates each marked with an at least part dental arch template of varying sizes, the templates being calibrated.

In a third aspect of the present invention there is provided an orthodontic ruler comprising a substantially flat plate marked with a plurality of graduated at least part dental arch templates converging at an apex of each at least part dental arch, the templates being calibrated.

In a fourth aspect of the present invention there is provided an orthodontic ruler comprising a plurality of substantially flat plates each marked with a plurality of graduated at least part dental arch templates converging at an apex of each at least part dental arch, the templates being calibrated.

The form may also comprise a plurality of substantially flat plates each marked with an at least part dental arch template of varying sizes, the templates being calibrated.

The form may also comprise a substantially flat plate marked with a plurality of graduated at least part dental arch templates converging at an apex of each part dental arch, the templates being calibrated.

The form may remain substantially flat in use.

A calibrated midline may be marked at the apex of each at least part dental arch template, perpendicular to the at least part dental arch.

The form may be a transparent or a substantially transparent material.

The form may be articulated into different at least part dental arch templates whilst remaining substantially flat.

In a fifth aspect of the present invention there is provided a method of quantitatively assessing at least part of a dental arch form, the method comprising placing an orthodontic ruler on at least part of a dental arch, with an arch apex in close proximity with a predetermined front point determining a part dental arch template similar in form to the part dental arch, observing a position of a predetermined posterior point with reference to a length calibration marked on the part dental arch template.

The invention may also comprise a method of quantitatively assessing at least part of a dental arch form wherein a mesio-distal dimension of each tooth in the part dental arch is measured using a pair of dividers and a total mesio-distal dimension of teeth in the part dental arch is calculated by addition and the total mesio-distal dimension of teeth is compared with an actual dental arch length previously observed.

It is an object of the present invention to provide an orthodontic ruler which does not deform from the measurement plane, thereby enabling accurate measurement of a theoretical line of proper alignment.

It is an object of the present invention to provide an orthodontic ruler which can be used to measure a variety of dental arches of different sizes.

It is an object of the present invention to provide an orthodontic ruler through which a study model of a dental arch or a dental arch in vivo can be observed by a user.

It is an object of the present invention to provide an orthodontic ruler which enables measurement of the position of incisors with reference to a calibrated midline marked on the ruler at the apex of, and perpendicular to, the dental arch template.

Advantageously, the present invention provides an orthodontic ruler for use in an orthodontic assessment which is simple and quick to use. Furthermore, the orthodontic ruler can be easily cleaned. Advantageously, the orthodontic ruler can be a single use or multiple use apparatus. Furthermore, the orthodontic ruler can be manufactured cheaply.

The present invention is generally applicable to the field of orthodontics and, whilst being particularly applicable to an orthodontic space analysis, can be employed more widely.

Brief Description of the Drawings Several embodiments of the present invention will now be described by way of illustration only and with reference to the accompanying drawings, in which: FIG. 1 is an illustration of a side view of a lower arch exhibiting curvature;

FIG. 2 is an illustration of an occlusal view of the lower arch of FIG. 1 ; FIG. 3 is an illustration of an embodiment of the present invention in which a plurality of dental arch templates are marked on a single orthodontic ruler ; FIG. 4 illustrates an embodiment of the present invention in which a single dental arch template is marked on each of four orthodontic rulers ; and FIG. 5 illustrates an embodiment of the present invention in which a half dental arch template is marked on an orthodontic ruler and shown in position over a study model.

Detailed Description of a Preferred Embodiment FIG. 1 is an illustration of a side view of a lower arch 10 with a pronounced curvature problem which is demonstrated in the departure of occlusal surfaces of the teeth from a straight solid reference line 12. Reference line 12 represents a theoretical line of proper alignment (as described in the Background to the Invention) which spans from a molar 14 to an incisor 16. A dotted reference line 18 shows a half of a current total dental arch length (as described in the Background to the Invention) of the lower arch 10. Clearly, an aim of orthodontic treatment for lower arch 10 would be to ensure 12 and 18 are substantially parallel.

FIG. 2 illustrates a lower arch of FIG. 1 in an occlusal view 20. It can be seen that a left side and a right side of the lower arch 20 are not symmetrical, which is a common feature of a dental arch. Reference numerals 22 and 24 denote suitable predetermined posterior contact points and reference numeral 26 denotes a suitable predetermined anterior contact point.

FIG. 3 illustrates an orthodontic ruler 30 of the present invention which comprises a thin transparent rigid material 32 with a plurality of arch templates 34 marked. A series of length calibrations 36 are marked on the arch templates 34. The present embodiment illustrated in FIG. 3 shows, by way of example only, centimetre calibrations 36 marked on the arch

templates 34 and a midline 38 is marked perpendicular to the arch templates 34 and is calibrated in millimetres. In operation, a cast may be taken of an upper and a lower dental arch of the patient and a study model may be produced. With reference to FIG. 2, the ruler is placed on posterior contact points 22,24, and an anterior contact point 26. In an initial stage of an orthodontic space analysis, the orthodontic ruler of FIG. 3 is positioned such that a convergence of midline 38 and arch templates 34 is directly above a central anterior point on the study model. A user may then select the arch template 34 which is a best fit for each side of the study model (where the arch template runs approximately along a centre line of the occlusal surface of each tooth). Frequently, a dental arch is asymmetrical about midiine 38 and therefore a different arch template of the graduated arch templates 34 may be recorded for a left side and a right side.

The user may then observe the location of contact points 22,24 and 26 in relation to length calibrations 36 and may record the measurements.

A subsequent stage of the orthodontic space analysis involves taking a direct measurement between the pre-determined anterior 26 and posterior points 22,24 along the occlusal surface of each arch. As described in the Background to the Invention section, a pair of dividers and a simple ruler may be utilised to measure an individual mesio-distal dimension of each tooth of the study model.

A further stage of the orthodontic space analysis involves a comparison of the distance between the pre-determined posterior point of the arch and the predetermined anterior point of the arch along the theoretical line of proper alignment as measured by the orthodontic ruler 30 and the measurement between the pre-determined anterior and posterior points along the mesiodistal aspects of the teeth as recorded by use of the pair of dividers. (Where crowding is present, the former measurement will be smaller than the latter measurement. ) The user may use this comparison to accurately determine

the most suitable path of treatment to follow. Furthermore, proposed changes to tooth position or arch form may be precisely quantified. For example, where a treatment objective is to move incisor teeth forward or backward, this may be quantified by reference to the calibrations on midline 38. Or, where a treatment objective is alteration to the overall form of a patient's dental arch, quantitative assessment can be made in terms of several different arch templates before, during, and after treatment.

There is a large variation in sizes and forms of dental arches and therefore numerous arch templates may be required to cover all possibilities. A plurality of dental arch templates may be marked on a single orthodontic ruler (as illustrated in FIG. 3) and one embodiment of the present invention provides a separate orthodontic ruler for each of several categories of dental arch form, such as standard, broad and progressive. In another embodiment, each orthodontic ruler 40a, 40b, 40c, 40d may include a single arch template 44a, 44b, 44c, 44d, and a set of orthodontic rulers 41 would be supplied.

Each orthodontic ruler 40a, 40b, 40c, 40d would be marked with a different arch template (as illustrated simplistically in FIG. 4). FIG. 4 also shows rigid plastics material 42a, 42b, 42c, 42d marked with calibrations 46a, 46b, 46c, 46d and midlines 48a, 48b, 48c, 48d.

An orthodontic ruler of the present invention may be made from various materials such as a transparent plastics material or a semi-opaque material or any combination thereof. Furthermore, the material of construction may be any material capable of maintaining a rigidity in an occlusal plane, such that it rests on contact points 22,24 and 26 (see FIG. 2) and does not deform to inaccurately record the theoretical line of proper alignment. As previously mentioned, the left and right side of a dental arch may not be symmetrical and therefore an orthodontic ruler 50 comprising half a dental arch template 54 and associated markings 56,58, for a left or a right side of the dental arch may be used (as illustrated simplistically in FIG. 5). FIG. 5 also shows rigid plastics material 52. Again, a user could be supplied with a set of varying half

templates (not shown) to accommodate the large variation in sizes and forms of dental arches.

A further embodiment of the orthodontic ruler of the present invention may comprise a flat plate calibrated as described above with an exterior edge in the same shape as the dental arch template, but, for example, 0. 5cm outside an outermost dental arch template. Alternatively, the orthodontic ruler of the present invention may comprise a calibrated, flexible, articulated apparatus with limited degrees of freedom enabling the user to bend it to a required arch shape whilst always maintaining a flat occlusal plane. Also, this narrow apparatus has a midline marked perpendicular to the longest dimension of the orthodontic ruler. Clearly, the latter two embodiments, in particular, could be utilised in vivo, without the need to produce a study model.

In summary, according to an underlying inventive concept, an apparatus of a preferred embodiment enables a user to accurately quantify features of a dental arch, which apparatus is simple to use, portable and cheap to manufacture.

It will be appreciated that the above description has been given by way of example only and that modifications may be made within the scope of the invention. For example, whilst the present invention has been generally described with reference to calibrations in millimetres and centimetres, clearly, any markings on the orthodontic ruler may be used which are consistent, thus enabling a comparison of contact points throughout treatment.

Claims

Claims 1. An orthodontic ruler comprising a form marked with at least part of a dental arch template, the template being calibrated.
2. The orthodontic ruler of claim 1, wherein said form comprises a plurality of substantially flat plates each marked with an at least part dental arch template of varying sizes, the templates being calibrated.
3. The orthodontic ruler of claim 1, wherein said form comprises a substantially flat plate marked with a plurality of graduated at least part dental arch templates converging at an apex of each part dental arch, the templates being calibrated.
4. The orthodontic ruler of any preceding claim, wherein the form remains substantially flat in use.
5. An orthodontic ruler comprising a plurality of substantially flat plates each marked with an at least part dental arch template of varying sizes, the templates being calibrated.
6. An orthodontic ruler comprising a substantially flat plate marked with a plurality of graduated at least part dental arch templates converging at an apex of each at least part dental arch, the templates being calibrated.
7. An orthodontic ruler comprising a plurality of substantially flat plates each marked with a plurality of graduated at least part dental arch templates converging at an apex of each at least part dental arch, the templates being calibrated.
8. The orthodontic ruler of any preceding claim, further comprising a calibrated midline marked at the apex of each at least part dental arch template, perpendicular to the at least part dental arch.
9. The orthodontic ruler of any preceding claim, wherein the form is a transparent or a substantially transparent material.
10. The orthodontic ruler of claim 1, wherein the form is articulated into different at least part dental arch templates whilst remaining substantially flat.
11. A method of quantitatively assessing at least part of a dental arch form, the method comprising: placing an orthodontic ruler on at least part of a dental arch, with an arch apex in close proximity with a predetermined front point; determining a part dental arch template similar in form to the part dental arch; observing a position of a predetermined posterior point with reference to a length calibration marked on the part dental arch template.
12. The method of claim 11, further comprising: measuring a mesio-distal dimension of each tooth in the part dental arch using a pair of dividers and calculating a total mesio-distal dimension of teeth in the part dental arch by addition; comparing the total mesio-distal dimension of teeth with an actual dental arch length previously observed.
13. An orthodontic ruler substantially as herein described.
14. An orthodontic ruler substantially as illustrated in the accompanying drawings.
15. A method for quantitatively assessing a dental arch form substantially as herein described.