Clear Custom Matrix Technique
Frequently Asked Questions

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Clear Custom Matrix in place with sectional matrix and ring clamp.

Can the Clear Custom Matrix Technique be used with a sectional matrix band and a Garrison Clamp? (The Garrison Clamp is also known as, or is similar to, the Composi Tight and G Ring clamp.)

Yes, the custom matrix can be used with a Garrison Clamp. See the photo above showing its use with a clear custom matrix. The problem in using a sectional matrix with the Clear Custom Matrix Technique is inserting the sectional matrix between the proximal contacts of unprepared teeth. This can be done if the contacts are not too tight by working the sectional matrix through the contact.

If you have normally tight contacts, working a commonly thin sectional matrix through the proximal contacts can be difficult, but not impossible. How I do it is to obtain good local anesthesia and then work a wooden wedge between the teeth, splitting the contact. Once you get the sectional matrix through the contact you can remove the wedge, position the Garrison Clamp, and make your clear custom matrix adjacent to the sectional matrix band. Another option is to place the Garrison clamp; in a couple of minutes, the contact may be open enough to work a sectional matrix band into the contact. Then replace the Garrison Clamp, and make your custom matrix.

2. Can a custom matrix be made for a class II restoration without placing a matrix band around the tooth prior to preparing the tooth?

You can inject the clear PVS bite registration material over and around the tooth to be prepared for a class II restoration without a matrix band in place, but then that custom matrix needs to be trimmed to fit inside or adjacent to the matrix band prior to using the custom matrix to conform the composite. The problem with this method is that you cannot trim it perfectly, and this leaves incorrectly contoured composite right where the custom matrix ends and the matrix band begins, due to inexact trimming. This will require additional finishing in an area that is often near an adjacent tooth, leading to the possibility of iatrogenic damage to the adjacent tooth.

3. When curing the final layer of a class I or class II composite restoration through the clear custom matrix, does curing the entire composite at one time lead to extensive polymerization shrinkage and the potential for post-operative sensitivity?

The final increment can be made as thin as you want, if you feel that thicker layers will lead to problems. There has never been a problem with post-operative sensitivity when curing a final 1.5 mm thick layer with this technique. The reason for this may be due to the following:

When curing through a clear custom matrix, the light energy is reduced. This is the reason that after all finishing is completed, you cure the last layer again to make sure all the composite is cured completely. By reducing the light energy, the composite is cured more slowly. This allows the composite a chance to flow before it becomes so rigid that it can't relax and reduces some of the polymerization shrinkage stress. Placing pressure on the custom matrix while curing aids in the flow of the polymerizing composite.

Post-operative sensitivity has never been a problem in over 15 years of using this technique.

If the dentist still wants to place and light-cure composite in small increments in an effort to reduce polymerization shrinkage, that can still be done if no increment is above the original surface of the tooth. If any increment is above the original surface of the tooth, the custom matrix cannot be seated all the way and the occlusion will be high.

In any case, it is important to note that both light-cured and chemical-cured composite continue to cure and shrink for over 24 hours after the initial set. It is true that much of the shrinkage takes place during the initial set, yet most of the shrinkage takes place after the curing light is turned off. (Causton BE. Miller B. Sefton J. The deformation of cusps by bonded posterior composite restorations: an in vitro study. [Journal Article] British Dental Journal. 159(12):397-400, 1985 Dec 21)


What happens if you do not get the Tofflemire matrix retainer and band assembly back in the same position when using the custom matrix to contour the unset composite?

The custom matrix is slightly flexible. It will conform to slight positioning errors in the replacement of the Tofflemire matrix retainer. To make your job easier, the metal matrix band has a memory that helps indicate its original position on the tooth. In addition, I try to position the matrix retainer so its longitudinal axis is in line with the buccal groove of a molar or cusp tip of a bicuspid.


After you construct a custom matrix to close a diastema, how do you prevent the composite in the contact area from bonding together and closing the contact?  I am closing a space between the right and left maxillary central incisors using the Clear Custom Matrix Technique.  I don't want to end up with a closed contact between 8 and 9.

           In the diastema closure case I sometimes show at my presentation, I took advantage of the fact that the space between #8 and #9 was quite large, and to close it completely would have made the central incisors too wide.  Consequently, I left a very slight space between the centrals. In that way, the clear bite registration material can be injected between the waxed-up teeth and the contacts will not end up closed.


If you want to have the teeth in contact, then after you wax the teeth into contact, use a very thin metal matrix band to create a very small space between the waxed-up teeth, then place a Mylar strip in that space between the teeth. Now make two custom matrixes, one for each tooth, with the Mylar strip between them.  You will need to place a wedge or something to hold the Mylar strip against each tooth while you make each custom matrix.  Then just slightly roughen the teeth to break any glaze where there will be bonding, and etch and apply

bonding agent.  Condense the composite into each matrix, then with the Mylar strip and wedged in place, seat your custom matrix.  Remember when making the custom matrix, include adjacent teeth distal to the space in the matrix to assist in indexing the matrix.  (This is done on the side away form the diastema closure).

When placing the composite in the mouth, I do one side of the diastema closure at a time.  This allows me to finish those areas of the composite that will be difficult to access when the other half of the closure is placed.

When placing the other composite, you will need to wedge the Mylar strip adjacent to the other tooth and place composite into the matrix (make sure you condense it into the matrix to capture all the contours you waxed up on your model).  Seat that custom matrix adjacent to the Mylar strip with pressure for 5 to 10 seconds.

Since common wedges are usually not big enough for large diastemas, use a Stim-U-Dent or other large wedge.  Whether these diastema closures are done by hand or with a custom matrix, it is difficult to get nice contours where the composite joins the tooth at the gingival -- another reason not to try to close the entire space if it is a large diastema. 

The height of the Stim-U-Dent or wedge may affect the mesial contour of the composite.  Additionally, since a Mylar strip is flat, it may be difficult to get it to contour the mesial surface of the composite, especially where the composite meets the tooth at the gingival.  This is another good reason to leave a slight space (1/32 of an inch is enough) so the clear bite registration material can be injected between the contact areas is the contours of the proximal surfaces are exactly as you waxed them, and you do not need a Mylar strip.



What happens if you place too little composite as the last layer and end up with a void in your composite or at your margin?

       As mentioned previously, this is a rare occurrence, since we were all taught to place more composite than we need and then grind away the excess. Placing excess composite is a difficult habit to break.

       If you have a void, in my experience it is small and can easily be filled in with a small increment of composite and cured without reapplying the custom matrix again. The void contained air and has an air-inhibited layer. Consequently, the composite added to the void will bond to the air-inhibited layer once the air (oxygen) has been excluded. The curing of this small layer can be done at the same time as the composite is cured again to ensure that adequate light energy has reached the composite.

      If the void is large, the custom matrix can be reseated to aid in contouring the added composite. If the void is very small, I will sometimes use a flowable composite to aid in penetrating long narrow voids.