Pictures of Errors

Placing Too Little Composite

 

Photo illustrates composite short of the cavosurface margin.  Although this was a very infrequent error that I made when first developing the Custom Matrix Technique, due to my emphasis on this factor, attendees in my hands-on workshops do make this error.  As dentists we have been trained to add more composite than we need and grind away the excess.  The ability to quickly eyeball the correct amount of composite for a restoration is most important for Class I and II, since excess composite leads to high occlusion.

 

Matrix Band Not Retighten Adequately

Occlusal anatomy and cavosurface margin are perfect and need no finishing.  The excess composite mesial to the marginal ridge is due to the Tofflemire matrix retainer not being retightened to the same degree as when the matrix was constructed prior to preparing the tooth.  Consequently, when the custom matrix was reseated, excess composite was forced up between the custom matrix and the matrix band.  The Tofflemire matrix retainer should be snug but not overly tight when placed on the tooth both before preparation and after.

 

Too Little Pressure Placed on Custom Matrix

 

Note that the surface of the composite is smooth and well formed, but the composite is not pushed to the margins on the lingual, leaving a gap (arrows) and is not thin in those areas where it extends beyond the margins (buccal and distal).  Place 5 pounds of pressure on the custom matrix for 5 to 10 seconds after seating it to allow time for the composite to flow and conform to the shape of the matrix.

 

 

Poor Marginal Ridge Contour

 

Note the lack of correct contour of the composite in the marginal ridge area (arrow). When the custom matrix was constructed prior to preparing the tooth, the clear PVS bite registration material was not injected into the embrasure between the matrix band and the tooth in this area. The custom matrix is deficient in this area and consequently, the resulting composite is over-contoured. The intraoral syringe tip needs to trace the embrasure between the matrix band and the tooth while injecting the clear bite registration material.

 

Excess Composite and Poor Wedge Placement

 

Excess composite is noted at the buccal marginal ridge and buccal groove. Since much of the cavosurface margin on the occlusal looks perfect, the custom matrix was seated all the way, but the excess composite was expressed in areas of least resistance. Over-contoured composite at gingival margin is due to not seating the interproximal wedge securely. A number 12 blade would be used to remove gingival excess and a flame-shaped carbide-finishing bur (#7901) would be utilized to remove buccal excess.

 

Deficient Interproximal Wedge Placement

 

Although no finishing would be required on the class V restoration and minimal finishing on the class IV, the excess composite forced the custom matrix and Mylar strip out of proper contour. A wooden wedge that more fully supported the Mylar strip would alleviate poor contour gingival to the proximal contact. This is actually a very good result for the attendee in the hands-on workshop.  For a large open interdental papilla area, a large wedge such as a Stim-U-Dent would be necessary to support the Mylar strip.