Matrices In Operative Dentistry 69103s

Matrices in Operative Dentistry

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Matrix ? A matrix is defined as a properly contoured piece of metal or other material used to and give form to the restoration during its placement and hardening.

The art and science of operative dentistry,1995: Mosby-Year Book,Inc.

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Introduction 

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Unfortunately, dentistry does not have a truly satisfactory manufactured matrix for directly placed restorations. Most matrices available to the profession have some good qualities but do not meet all the requisites. The primary function of the matrix is to restore anatomical contours and areas. 3

Why do we need matrices ? 

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Gingival floor of a class II cavity is the most vulnerable area where overhang of restorative material can take place. There is no method to control the placement and contour of restoration without a matrix wall. 4

Characteristics of a good matrix        

Rigidity. Establishment of proper anatomical contour. Restoration of correct proximal relation. Easy adaptation to the tooth. Ability to be contoured. Prevention of gingival excess. Strength to offer resistance to condensation. pressure. Easy removal from the tooth. 5

Functions of matrix 

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Provision of a temporary wall of resistance to the pressure necessary for amalgam insertion. Provision of shape and contour to the restoration. Maintenance of form during placement and set of the amalgam/composite. 6

Classification    

On the basis of chemistry On the basis of thickness On the basis of rigidity On the basis of circumference

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Metallic Matrices 

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Circumferential Tofflemire (universal) Automatrix Siquveland T-band

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Sectional Palodent Composi -tight Ivory Strip-T matrix

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Circumferential Type 

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The band encircles the tooth and is secured by the retainer on the buccal or lingual aspect. Band may be straight, curved or contoured. Advantage: this type can be firmly adapted to the tooth. 9

Metallic matrices Tofflemire type

Ivory type

T-band (straight)

Curved T-Band

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Dimensions 

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The non-contoured bands are available in two thicknesses, 0.05mm and 0.038mm. Contoured matrices may have variable dimensions (depending upon the commercial product).

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Tofflemire matrix band 

The Tofflemire matrix assembly consists of the following:   

Matrix bands Matrix retainer Wedge

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Matrix bands •.

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Assembled bands

Fig 12-6

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Assembly of tofflemire retainer

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Wedges

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Wedges 

Anatomical (triangular wedges) are recommended for deeper and / or wider proximal preparations.

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Rounded wedges are recommended for shallower and / or narrower proximal preparations. Sturdevant JR et al: Conservative preparation designs for class II amalgam restorations, Dent Mater 3:144, 1987.

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Role of wedge 

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It should hold the matrix band firmly in position cervically. It should not be of such a height that it prevents the formation of a point. Another function is to separate the teeth slightly so that when it and the matrix are finally removed, the teeth return to their original positions, closing the small space left by the thickness of the matrix band. 18

Technique

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Technique

cont.

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Technique 

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Either precontoured the matrix material before placing on the tooth. Matrix band can be contoured after being adapted on the tooth with the help of an egg-shaped burnisher, back side of the blade of 15-8-14 spoon excavator or blade of a Hollenbeck carver. 21

Wedge placement  

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Simple wedging Piggy-back wedging Double-wedging Wedge-wedging

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Modification of matrices All matrices require modification when: 

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proximal surface is a guide plane for tooth/ tissue ed partial denture. Adjacent tooth has a flatter . Adjacent proximal contours are not normal.

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Clear matrices     

Polyester strips Mylar strips Cellophane strips Plastic strips Clear plastic crown form

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Wedges for composite 

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Light reflecting wedges along with clear matrices are recommended for composite restorations. Alternatively, ultra thin (0.013mm) metal matrices can be used for composites.

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Prewedging 

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Placement of wedge prior to tooth preparation is helpful especially in case of composite restorations. It allows greater separation of the teeth and more space to build a .

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Automatrix 

It’s a retainer less matrix system with four types of bands, designed to fit all teeth regardless of circumference.

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Narrow regular Wide regular Medium thin Medium regular

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(4.7mm), (0.05mm) (7.9mm), (0.05mm) (6.2mm), (0.038mm) (6.2mm), (0.05mm)

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Sectional matrices 

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Studies have shown that use of sectional matrices for composite restorations are on a rise. Sectional matrices do not only result in tighter anatomical s but also are dentist friendly. Lowe RA. The use of sectional matrix systems in class II direct composite restorations. Dent Today. 2004 Oct;23(10):108, 110-2 28

Palodent (sectional matrix)

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Apical flap matrix ? 

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Restoring a class II cavity with deeply placed proximal gingival floor or restoration of root caries in proximal surfaces with composite is a restorative challenge for the dentist. The feature of apical flap in the design of sectional has solved the issue to considerable extent. A conservative technique for restoring a tooth affected by interproximal root caries. J Prosthet Dent. 2003 Feb;89(2):2212.

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Questions ?  

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Is the matrix band stable ? Does the matrix band fit at the cervical margin ? Has the band been burnished in the area so that the point can be restored ? Is the height of the band sufficient ? Is the cavity clean and dry ? 32

Preformed Matrix Bands

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Strip-T Matrix System

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Case

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Other methods for tighter s.    

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Use of PTFE tape. Use of composite inserts. Incremental composite placement. Continuous pressure against proximal wall. Class transition technique. Dunn WJ, Davis JT, Casey JA. Polytetrafluoroethylene (PTFE) tape as a matrix in operative dentistry. Oper Dent. 2004 Jul-

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Are matrices reusable ?? 

A survey of the use of matrix bands and their decontamination in general dental practice . Lowe AH, Burke FJ, McHugh S, Bagg J. The University of Birmingham School of Dentistry.

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CONCLUSIONS: The Siquveland matrix band is the most

popular among the study group of dental practitioners. Re-use of matrix bands is common. Guidelines for the safe re-use of matrix bands are required 40

Conclusion 

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The role of matrices in operative dentistry is irreplaceable. Without a matrix there is no other way (in a directly placed restoration) to produce contours and s. No matrix band is ideal, almost all proximal cavities need a matrix depending on the requirements of the specific case.

Goldstein MB.It's all in your s! A Class II matrix roundup. Dent Today. 2003 Sep;22(9):60-5.

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Mullejans R, Badawi MO, Raab WH, Lang H. An in vitro comparison of metal and transparent matrices used for bonded class II resin composite restorations. Oper Dent. 2003 Mar-Apr;28(2):1226. El-Badrawy WA, Leung BW, El-Mowafy O, Rubo JH, Rubo MH. Evaluation of proximal s of posterior composite restorations with 4 placement techniques. J Can Dent Assoc. 2003 Mar;69(3):162-7. 42

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Rada RE. Achieving anatomic proximal s with direct composite resin restorations.Dent Today. 2000 Mar;19(3):46-50.

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Klein F, Keller AK, Staehle HJ, Dorfer CE.. Proximal formation with different restorative materials and techniques. Am J Dent. 2002 Aug;15(4):232-5 .

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Thank You

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