Matrices Dental Restoration PDF

Matrices 1  Definition Matrix is a device used during restorative procedure to hold the plastic restorative material within the tooth while it is setting. 2  Ideal requirements of a matrix band 1- Ease of application 2- Eas...

Matrices 1  Definition Matrix is a device used during restorative procedure to hold the plastic restorative material within the tooth while it is setting. 2  Ideal requirements of a matrix band 1- Ease of application 2- Ease of removal 3- Rigidity 4- Inexpensive 5- Provide proper proximal contact and contour 3 Benefits of an ideal contact and contour 1- Health of periodontium. 2- Prevents food impaction. 3- Self cleansable. 4- normal mesio-distal relationship. 4  The purpose of the matrix is to : 1- confine the amalgam so that adequate condensation forces can be applied. 2- allow reestablishment of contact with the adjacent tooth. 5 3- provide for adequate physiologic contour for the proximal surface of the restoration 4- impart an acceptable surface texture to the proximal surface, especially in the area of the contact that can not be carved and burnished. 6  Parts of matrix There are two parts in a matrix: - Band. - Retainer. 7  Matrix bands Piece of metal or polymeric material used to support and give form to the restorative material. Matrix bands are made of flexible stainless stell and are avaliable in premolar, molar, and universal sizes and thicknesses Noncontoured band Premolar band Molar band 8 The larger circumference of the band is the occlusal edge and is always placed towards the occlusal surface. The. smaller circumference of the band is the gingival edge and it is always placed toward the gingiva. 9  Retainer This is a device by which the band can be maintained in its position and shape. The retainer may be: - a mechanical device , - a metal ring - or impression compound. 10  Classification of matrix  Based on mode of retention a- with a retainer this device holds the matrix band in position. the retainer is positioned most from the buccal surface of the tooth being restored. b- without retainer Copper band matrix 11  Based on type of band a- Metallic non transparent b- non metallic transparent 12  Basesd on type of cavity for which it is used a- Matrix for class I cavity with buccal and lingual extension. b- Matrix for class II cavity preparation - Ivory No. 1 - Ivory No. 8 - Copper band - Anatomical Matrix - Automatrix 13  Ivory matrix no. 1 Consist of stainless steel band that provide the missing wall for the single proximal surface restoration (MO or DO). Indication: for restoration of class II cavity especially when the contact on the unprepared side is very tight. 14  Ivory No. 8 Matrix Consists of a band that encircles the entire crown. -To restore class II cavities on one or both proximal surfaces of posterior tooth. 15 16 17 18  Copper Band Matrix Indications - Badly broken teeth that receiving pin amalgam restorations - Class II with large buccal or lingual extension Advantages: -Excellent contour Disadvantages: Time consuming 19 20  Compound matrix - Also called as custom made matrix. - Entirely hand made as per the individual case. Indications: 1- for restoring class II cavities one or both proximal surfaces. 2- for complex situations like pin amalgam restoration. 21 Advantages: 1- Highly rigid and stable. 2- Provide good access and visibility for placing the restoration. 3- Most efficient means of reproducing contact and contour. Disadvantages: - Time consuming. 22 -The band is contoured with an egg shaped brunisher to achieve the approximate proximal and facial and lingual contours of prepared tooth. -Then the band is positioned and stabilized by applying softened impression compound facially , lingually and occlusally. 23  T Band Matrix Indications Class II cavities (mostly for primary teeth) Advantages - simple. - Inexpensive. - Rapid and easy. Disadvantages Flimsy in structure , not stable. 24  Precontoured bands - Consists of small, precontoured soft metal matrices ready for application to tooth. - The band is held in place by a flexible metal ring. - used for both amalgam and composite restorations. - Easy to apply and provides slight tooth separations. 25 26  Automatrix system - There is no retainer used to hold in place. - Bands are already formed into a circle and are available in assorted sizes in both metal and plastic. Indication: complex amalgam restoration where one or more cusp to be replaced. 27 Advantages: -improved visibility due to lack of retainer. -Rapid application. Disadvantages: - bands are flat and difficult to burnish. - expensive. 28  If matrix is not used, condensation force will tend to push the amalgam out of the preparation rather than condensing it. 29  Occasionally, as with the occlusolingual restoration of the maxillary molar, the blade of a hand instrument placed on the lingual surface of the molar and held in place during condensation may be adequate. 30  Wedges Small, tapering, triangular pieces of wood or clear plastic about ½ inch in length. 31 - Anatomical (triangular wedges) are recommended for deeper and /or wider proximal preparations. 32 - Rounded wedges are recommended for shallower and / or narrower proximal preparations. 33 Size : ½ inches (1.2cm). Wedges are available in various sizes, which may be color coded. 34 If the proper size can not be found they can be modified to fit the interproximal area by cutting the wood away. 35  Role of wedge - It should hold the matrix band firmly in position cervically. - Separate the teeth slightly so that when it and the matrix are finally removed, the teeth return to their original position closing the small space left by the thickness of the matrix band. 36  Wedging techniques A wedge should usually be inserted from the side with the widest embrasure. for example, between the first and second premolars, the largest embrasure is usually the lingual embrasure. 37 Single wedge technique 38  Piggyback wedging - Useful for the patients with gingival recession - Wedge is significantly apical of the gingival margin a second wedge may be placed on top of the first. 39  Double wedging - One from lingual embrasure and one from facial embrasure. - Indicated when proximal box is wide faciolingually. 40 41  Conclusion - 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 contacts. - No matrix band is ideal; all proximal cavities need a matrix depending on the requirements of the specific case. 42