Restorative - Outcome 9 Flashcards
What is a matrix?
A matrix is used as a supportive wall to replace a missing wall in a prepared tooth while the restoration is being placed. This would include Class II, III or IV cavity preparations. The matrix may be mde of metal or plastic. It is shaped to resemble the normal contour of the missing wall, positioned and placed while the restorative material is being placed (or shaped) and is removed when the restoration is completed.
The shape and material of matrices
The shape of a matrix system, and or the material used is determined by its location and for what type of cavity preparation.
Matrices that are circumferential - are usually used to replace proximal, facial, or lingual walls.
Sectional matrices - are used for missing proximal walls
cervical matrices - are used for Class IV restorations.
Clear Plastic Matrix systems
A matrix system made of clear plastic will allow the operator to utilize the curing light more effectively when placing a light cured restorative material. They are often used for anterior restorations of Class IV buccal restorations.
What are wedges?
Wedges may be used in conjunction with a matrix system to achieve proper interproximal contacts. They are placed next to the matrix band using wedge placement forceps or cotton forceps, into the embrasure space for each missing proximal wall.
The function of wedges:
Hold the matrix band firmly against the gingival margin of the preparation
-To prevent overhangs on restorations.
- Provide slight separation between the teeth, ensuring an accurate contact space and compensating for the thickness of the matrix band, creating a tight contact between the finished restoration and the adjacent tooth
Wedge Sizes and Shapes
Wedges are made in various sizes and shapes (triangular or round), and materials (wood or plastic). The most commonly used type of wedge is triangular.
Considerations of Wedges include..
- The wedge must be wide enough so that pressure is applied to the apical and gingival walls of the preparation.
- The wedge presses the band against the tooth and causes a slight separation of the teeth.
- The wedge is slightly wider than the distance between the cervical portions of adjacent teeth.
Celluoid Matrix System
A clear plastic matrix is used with anterior composite resin or glass ionomer materials. The clear plastic matrix is also referred to as the celluloid strip or Mylar strip. It is used for a Class III or IV restoration when the proximal wall of an anterior tooth is missing. No retainer is needed to hold the matrix in place, making this system an easier application.
Celluloid Strip
The plastic matrix and wedge serve the following purposes during the restoration process:
-The matrix is placed interproximal before the etching and bonding of the tooth to protect adjacent teeth from these materials.
-After the placement of composite material, the matrix is pulled tightly around the tooth to help in reconstructing its natural contour.
-The clear plastic matrix allows the curing light to penetrate the material, thereby completing the curing process.
T-Band matrix system
The T-band is a band in the shape of a T that can be easily placed, contoured and removed. When formed, the top portion of the T allows the straight portion to adjust and fit the circumference of a primary molar.
About the T-Band Matrix
The T-band is available in two types, narrow width, and wide width, with a choice of stainless steel or brass material.
The material is sturdy but can be adequately contoured.
The loop may be prepared in advance and slipped over the tooth and tightened before the preparation is made to save time.
Sectional Matrix System
The sectional matrix system facilitates the implementation of tight, anatomically correct contacts for Class II and MOD posterior composite restorations. The sectional system uses small contoured sections, rather than long circumferential bands, which are placed interproximally and secured by tension rings.
Sectional Components
Different sizes of contoured sectional matrix beans.
Two tension rings with differing tine lengths (long and short). The ring is applied to the tooth after the matrix bean is in place.
Tension ring forceps used to open the ring.
One sectional matrix bean is applied for each interproximal surface being restored. The system allows for the overlapping of tension rings when doing a MOD or for multiple restorations in one quadrant. Using the tension ring forceps, the tension rings are applied to the tooth after the sectional matrix bean and wedge is in place. The tension ring is placed with the tines between the sectional matrix bean and the wedge.
3 types of retainers:
- Universal (buccal): The buccal retainer has guide channels that are flat or even with the diagonal slot vise. This retainer sits flat against the teeth in the mucco-buccal fold and the retainer is always placed on the buccal surface of the tooth.
- Contra-angle (lingual): The lingual retainer has the guide channels set at an angle to the diagonal slot vise and this retainer is always placed on the lingual surface of the teeth. When the retainer is in place, it lies at an angle to the teeth so the metal does not damage the enamel surface of the remaining teeth in the arch.
- Pediatric: The pediatric tofflemire retainer is smaller in all dimensions than the Universal or Lingual retainers to accommodate the smaller mouth of a child.
Tofflemire Retainer
The Tofflemire matrix system is a metal device consisting of a retainer and a band used for posterior restorations. It is one of the oldest systems and most commonly used.
