1. Matrix Systems for Restorative Dentistry
Chapter 49
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2. Chapter 49 Lesson 49.1
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3. Learning Objectives Pronounce, define, and spell the Key Terms.
Describe the use of matrix systems in class II, III, and IV restorations.
Describe the type of matrices used for posterior restorations.
Describe the purpose and use of a wedge.
Discuss alternative methods of matrix systems used in restorative dentistry.
Assemble a universal retainer and matrix band.
(Cont’d)
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4. Learning Objectives
(Cont’d)
Place and remove a matrix band and wedge for a class II restoration.
Place and remove a matrix band and wedge for a class III restoration.
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5. Introduction
A matrix system provides a “temporary wall” for the restoration process in class II, III and IV preparations.
What are class II, III, and IV preparations? Which teeth do they involve? (Class II: proximal surfaces of molars and premolars; class III: proximal surfaces of incisors and canines; class IV: proximal surfaces of incisors and canines that include the incisal edge.)
“Matrices” is the plural term for “matrix.”
There are different systems for posterior and anterior teeth.
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6. Posterior Matrix System
Universal retainer
Also referred to as Tofflemire retainer
Holds the matrix band in position
Positioned most commonly from the buccal surface of the tooth being restored
Usually assembled before the start of restoration process.
How does the posterior matrix system create a temporary wall during the restorative phase?
Why is the universal retainer placed from the buccal position?
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7. Components of Universal Retainer
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8. Matrix Bands Thin, flexible stainless steel Common designs
Universal
Extension
Guidelines for placement
Larger circumference: occlusal edge
Smaller circumference: gingival edge
Extension bands are used for class II preparations when a universal band cannot reach the height of the tooth.
What instrument would be needed to contour a band?
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9. Fig. 49-2 Most commonly used posterior matrix bands.
Top diagram: universal band.
Middle diagram: extension band.
The larger circumference is placed toward which surface?
The smaller circumference is oriented toward which surface?
Bands must be contoured to make proper contact with the adjacent teeth.
What instrument is used to contour bands?
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10. Wedges
Positioned into the lingual embrasure of a class II preparation after band placement
Positions the matrix band firmly against the gingival margin of the preparation
Various sizes
Triangular/round
Wood/plastic
What is an embrasure? (A V-shaped space in a gingival orientation between the proximal surfaces of two adjoining teeth in contact.)
Used to add pressure to the interproximal area during the restorative phase.
Used to prevent overhangs.
What is an overhang?
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11. Fig. 49-5 Assortment of precontoured wedges.
During transfer, ask the dentist what size wedge is appropriate.
Wedges are transferred and applied with the use of cotton pliers or 110 pliers.
How many wedges are used in an MOD/amalgam preparation?
How many wedges are used in a DI/resin preparation?
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12. Anterior Matrix Systems
Plastic matrix
Also referred to as:
Celluloid matrix
Mylar strip
Used in Class III and IV restorations
Metal bands are not used because the resin/composite material can be scratched or marked by the stainless steel.
No retainers are used.
Why are clear strips used in resin/composite restorations?
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13. Fig. 49-7 A clear matrix system. (Courtesy of Premier Dental Products
Examples of clear matrix systems.
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14. Using an Anterior Matrix
Placed interproximally before the etching and bonding of a tooth.
After the placement of composite material, a matrix is pulled tightly around the tooth to help reconstruct its natural contour.
A clear plastic matrix allows curing light to penetrate the material and complete the curing process.
Anterior matrices can be contoured with the use of the end of a mouth mirror.
Why would the matrix be placed before etching or bonding?
Why would a wedge be used with a celluloid or Mylar strip?
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15. Automatrix System
The automatrix system is an alternative to a universal retainer.
No retainer is used to hold the band in place.
Preformed bands available in assorted sizes in both metal and plastic.
Each band has a coil-like auto-lock loop.
A tightening wrench is inserted into the coil and turned clockwise to tighten the band.
When the band is to be removed, a tightening wrench is inserted into the coil and turned counterclockwise to loosen the band.
Removing pliers are used to cut the band.
Wedges are still used with this system.
The tightening wrench and removing pliers are sterilized after each use.
The band is removed and placed in the sharps container.
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16. Fig. 49-9 Automatrix system. (Courtesy of Dentsply Caulk.)
The blue-handled instrument is removing pliers. It has a cover to “catch” the cut piece of band for easy removal.
The tightening wrench is the small “wand” in the box.
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17. Sectional Matrices
A thin, polished palodent-type band and tension ring produce tight anatomic contact for composite resin materials in class II restorations.
These are not commonly used.
They are small, oval, and made of stainless steel.
The tension ring is the “retainer.”
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18. Fig. 49-10 Sectional matrices. (Courtesy of Garrison Dental Solutions
Used on posterior teeth only.
Why would a sectional matrix be used instead of a universal retainer?
How many rings would be used on a DO restoration?
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19. Matrix Systems for Primary Teeth
T-band
When formed, the top portion of the T allows the straight portion to adjust and fit the circumference of the primary molar.
Spot-welded band
Form-fitted band placed around a prepared tooth; removed and placed in a smaller form of a welder, fusing the metal together to make a custom band.
A T-band is made of copper and adjusted to fit a primary tooth.
A spot-welded band requires premeasurement of stainless-steel matrix material and hence more prep time.
Why would a universal retainer not be used on primary teeth?
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20. Fig. 49-11 Copper T-band used for primary molars.
After placing the end of the band through the “wings” of the other end, secure the wings around the band.
Why would this system not be used on permanent teeth?
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21. Preparing the T-Band Matrix
The wings of the T-band are bent to form a U-shaped trough.
The free end of the band is slipped loosely through the U formation.
The wings are closed, and the free end is pulled to make a small circle of the band.
Holding the free end toward the facial surface, place the band on the tooth to be prepared.
Wedges are still used with T-band matrices.
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22. Fig. 49-12 Spot welder used for primary molars
Fig Spot welder used for primary molars. (Courtesy of Unitek, Monrovia, Calif.)
A spot welder is used for the spot-welded bands.
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23. Preparing a Spot-Welded Matrix Band
Measure ¾ to 1 inch of stainless-steel matrix material.
Fit the matrix band around the prepared tooth.
Adapt the band, making sure that the ends of the matrix material are at the facial surface for the sake of visibility and control.
Using Howe pliers, hold the ends tightly and remove the band in an occlusal direction.
Place the band in the spot welder.
Spot-weld the matrix at three positions.
This requires the use of a spot-welder.
The process requires additional preparation time.
The spot-welded band is form-fitted around the tooth.
What size of pliers is generally used?
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