The Depth of Cure of a Light Cured Temporary Crown and Bridge Material

Abstract

Background and Aim of study: Light cured temporary crown and bridge materials have been recently used in prosthetic dentistry to fabricate provisional bridges in a single bulk increment. The photo-polymerization of thick layers of this material, such as pontics and connectors, may be problematic due to the inability of the light to reach the center of the material. This study aims at measuring the maximum thickness of the material that can be completely cured.

Materials and methods: ISO specification number 4049 has been used in this study to test the depth of cure. Forty specimens of a light cured temporary crown and bridge material (Transcen Temp C&B LC, color A1, Nexbio co, Korea) has been prepared. Each specimen been cured with LED curing light  for 30,40,50,70 and 100 seconds curing times. The uncured mass of the material at the bottom of each specimen has been scraped away and the remaining thickness  measured with a mechanical caliper and divided by two.

  Results: When the material was cured for 30 seconds, the depth of cure reached 3.7mm.  Prolonging the curing time to 40 seconds increased significantly the depth of cure by 0.5 mm (4.14mm. depth of cure, P=0.001). The depth of cure further increased as the time of cure prolonged. The maximum depth of cure reached 4.8 mm  has been reached with 100 seconds application time.However, applying the light for 70 seconds resulted  in 4.6 mm depth of cure which is  nearly the same depth of cure as  when applying the light for 100 sec.(P=0.31).

Conclusion:   The depth of cure reached with light application for 30 seconds doesn’t guarantee the polymerization of the mass. Increasing the curing time will improve the depth of cure significantly. The optimal recommended curing time concluded from this study is 70 seconds.