WO2002043609A1

WO2002043609A1 - Self adjusting matrix

Info

Publication number: WO2002043609A1
Application number: PCT/IN2000/000116
Authority: WO
Inventors: Lakshmi Nagesh Chakka
Original assignee: Lakshmi Nagesh Chakka
Priority date: 2000-12-01
Filing date: 2000-12-01
Publication date: 2002-06-06
Also published as: AU2001230491A1

Abstract

The present invention discloses a self-adjusting matrix system for tooth restoration without a tightness retainer. It consists of a stainless steel band having 'U' shaped wire springs which links the band ends together. The band is rolled up around the tooth to be restored and held in position by means of said 'U' springs. The 'U' springs are soldered, or fastened through code-coloured matrices and part of the band could be in cellophane for light hardening of the amalgam.

Description

TITLE OF INVENTION - SELF ADJUSTING MATRIX

Field of Invention and Description:

The present invention discloses a modified dental matrix system (self adjusting matrix system). A restoration involving tooth surface requires the use of matrix to guide the restoration material to natural shape of tooth structure.

Self Adjusting Matrix is an instrument which consists of a "C" shaped Stainless Steel Band. The free ends of the Stainless Steel Band are joined by 3 "U" shaped stainless steel loops. The thickness of this wire ranges from 0.5 mm to 0.7 mm. The width of the Stainless Steel Band is 6 mm.

Since the tooth size varies from one another, the circumference(s) also varies. The normal range is s=20 to 36 mm. These dimensions are also subject to changes if the circumference(s) is less than 25 mm. Hence the inner circumference of the instrument ranges from 22 mm to 38 mm depending on circumference(s) and the dimensions of the "U" loop. The Self Adjusting Matrix can be fabricated by two methods depending on the methods employed for joining the Stainless Steel Band with the "U" loops.

1. Locking method

2. Resistance welding method

Locking Method: In locking method, the ends of the Stainless Steel Bank has 3 holes on either ends with a gap of 1 mm each at different levels. The ends of the "U" loop have bends. These bends fit into the holes on either end of the Stainless Steel Band, which are locked into the holes. Resistance Welding Method: In the resistance welding method, the ends of the Stainless Steel Band does not have any holes. The free ends of the "U" loops are also straight without any bends. The band and the loop are held in position using fixture and are welded. The advantage of using Resistance Welding is that there are no inner bends of the ^Λ,U" loops making the application of the instrument easier. The following article deals with the fabrication and comparison of 3 different Matrix System.

Though there are several matrix systems available, none of those are flexible enough to adapt to the tooth surface and rigid enough to resist the condensation pressure. This is because of the fact that the crown converges both coronally and cervically and to contain the amalgam in the prepared proximal cavity, the matrix band has to adapt more tightly at the cervical aspect. This means that, since the contour of the tooth surface varies at difference levels, the forces exerted by the matrix band on the tooth surface should also vary at different levels.

Philips and associates (1) evaluated eight matrix bands - ovoid, square, and tapering teeth. They concluded that none of the techniques produced perfect proximal contours, that the ovoid tooth had the contour most difficult to reproduce.

The purpose of this study is to show that a Matrix. System can be development to exert varied forces on the tooth surface at different levels of the tooth with the added advantage of the absence of the retainer handle. This paper describes the evaluation of observations made on invitro restorations done on Columbiodento form teeth No. 860 with mesioocclusal cavity using 3 different Matrix Systems. 1. Self Adjusting Matrix System

2. Tofflemire Matrix System

3. Siqveland Matrix System

The experiment includes:

1. Selection of teeth

2. Fabrication of Self Adjusting Matrix

3. Restoration using the 3 types of systems

4. Calculation of the percentage error in each system

5. Comparing the results

1. SELECTION OF TEETH:

30 Columbia dentoform teeth No. 860 with cavities on the Mesiocclusal surface of the mandibular right first molars were taken, which can fit into the Columbia dentoform M860 jaw and articulator.

The outline of the Proximal box was traced under 10 times magnification. This was done by painting the Proximal box on 5 teeth using a water soluble dye and the outline of the Proximal box was traced on a tracing sheet using a profile projector.

All the 5 tracings thus obtained were superimposed. It was seen that all the outlines coincide exactly. Hence it was assumed that the same outline form applies to all 30 cavities. The teeth were then numbered from 1 to 30. TECHNIQUE FOR FABRICATION OF SELF ADJUSTING MATRIX:

It employs materials present commonly available in the dental office which include.

1. Wide siqveland matrix band strip

2. ASH No.l scissors

3. 0.5 mm Stainless steel orthodontal wire

4. Rubber dam punch

5. Snipe nose pliers

6. No. 65 pliers

7. Mosquito forceps

8. Measuring scale

STEP 1: The matrix band was taken and a point was marked at 34 mm from one of the ends. Using the ASH No.l scissors, the band was cut at this point (Fig 6A).

STEP 2: 2 mm away from either ends, 3 holes measuring 1 mm in diameter were punched on either side using the rubber dam punch at 3 different levels and 1 mm away from each other.

STEP 3: Now the orthodontal wire was bent using No. 65 pliers.

STEP 4: The ^Λ,U" loops are then held in a mosquito forceps and the free ends are engaged into the holes punched in the matrix band. The "U" loops are tightened to the Matrix band using a Snipe nose pliers. Now the overall circumference of the matrix band is 36 mm which is the circumference of the teeth being used for the experiment. 15 numbers of such Matrix Bands were made. RESTORATION:

It was then decided that the teeth numbering from 1 to 10 will be packed using self Adjusting Matrix system. Teeth numbering from 11 to 20 be packed using Tofflemire Matrix System and teeth number 21 to 30 to be packed using Siqveland Bank Matrix System.

Before the test could be started, a small experiment was conducted to determine the amount of amalgam needed, number of increments needed and total number of thrust needed. This was done on 5 teeth. Instruments required for this experiment are.

1. Amalgamator

2. Tytin single spill amalgam capsule (slowest, 400 mg alloy, 300 mercury)

3. Amalgam carrier

4. Amalgam pot

5. Probe

6. Burnisher

Each of the 5 cavities were then packed using the amalgam obtained by vibrating the amalgam capsule in the amalgamator for 6 seconds under slow speed category. The amalgam was packed using Self-adjusting Matrix System in incremental fashion and each increment was condensed thoroughly.

After packing all the 5 teeth, the following inferences were made:

(i) A single amalgam capsule Tytin Single Spill amalgam capsule was needed. (ii) A total number of 4 increments were needed and the first increment to be placed in the occlusal preparation and the second and third to be placed in the proximal preparation and the last increment to be placed in both proximal and occlusal preparations.

(iii) A total no. of 26 thrusts were needed for condensation. The excess amalgam in the coronal aspect of the proximal box was removed using a probe. The outer layer was burnished using a burnisher. These conditions to be standardized to all the 30 restorations.

Teeth numbering from 1 to 10 were then packed using the Self Adjusting Matrix System.

This was done by placing each tooth in the Columbia dentoform M860 jaw model and the Self Adjusting Matrix System was applied onto the tooth. Before the application, the band was activated. According to the surface contour, the loops at different levels are compressed using a plier. Once the matrix band is forced over the tooth the "U" loops stretch. The stretched "U" loops, due to the elastic property of Stainless Steel, tries to regain its original shape. This will exert force on the Matrix band which in turn exerts force on the tooth surface.

Since the "U" loops at different levels are activated in a varied fashion, the Matrix Band exerts varied forces on the tooth surface, with the greatest force being applied on the cervical aspect. After the application of the matrix band the cavity is restored in the previously determined method. After the initial set, the Matrix Band was removed by sliding it occlusally. The same procedure was done to all the 10 cavities. Teeth numbering from 11 to 20 were packed using Siqveland Matrix System using the same technique.

Since the aim of the experiment is to show the adaptability of the matrix band onto the tooth surface using different Matrix Systems, a wedge was not used at any stage of restoration which enables in recording the actual efficacy of the individual matrix system which can be calculated by the amount overhanging obtained in each case.

Since the purpose of the experiment was to record the amount of overhangings, and compare the results, the occlusal carving and marginal ridge reconstruction was not considered as they do not influence in the amount overhangings.

Now the outline of the amalgam restoration was traced under the same magnification and numbered according to the tooth. Each outline of the restoration was then superimposed by the previously obtained outline of the proximal box. This will show the amount of excess amalgam flown out of the proximal box in each case.

CALCULATION OF THE PERCENTAGE ERROR IN EACH OFTHE SYSTEMS USED

In order to calculate the percentage of error in each of the systems, the following method was employed.

1. The tracing sheet was cut alongwith the outline drawn. This was done to all the 30 restorations and also to the outline of the proximal box. Each paper cutting was then weighed in a sensitive balance and the values were recorded.

Claims

CLAIMS:

1. I claim that this self-adjusting matrix can be used in restoration of tooth involving the reconstruction of tooth surface as in Blacks Class 2 cavity, either mesial occlusal or distal occlusal or mesial occlusal distal, Blacks Class 1 with buccal or palatal extension.

2. I claim that the matrix works on the principle of elasticity of the stainless steel.

3. I claim that the matrix does not have a retainer to tighten the matrix band around the tooth and the tightening is done by the spring back action of the stainless steel wire loop.

4. I claim that this self-adjusting matrix can be made by two methods, that is, locking method and welding method.

5. I claim that the matrix comes in various sizes depending on the size of the tooth.

6. I claim that the various size matrix are colour coded for easy selection.

7. I claim that each colour indicates a different size of the matrix coinciding with the colour-coding on the polyethelene band.

8. I claim that the activation is done by compressing one of the "U" loops, using pliers..

9. I claim that the modification to adult matrix can be used for pediatric patients, which is a miniature version of the adult form.

10. I claim that the pediatric matrix band has two ^λU" loops as compared to three in the adult matrix.

11. I claim that a modification of the adult matrix can be made to incorporate a cellophane sheet to permit the transfer of light in light cure composite restoration.

12. I claim that the matrix comes in kit form and that it contains many chamber with different colours pertaining to the known size of the matrix.

13. I claim that the kit contains the self-adjusting matrix and colour-coded stripes.

14. I claim that this self-adjusting matrix can be autoclaved other than the self-adjusting matrix with collophano, which needs chemical sterilization.