Temperature rise during photo-polymerization under ceramic restorations

Method: Three light-curing units were used; a high intensity quartz-tungsten-halogen unit Elipar 2500 (3M ESPE) and two LED units: Translux Power Blue (Hereaus) and Excelled 1400 (Jovident). The 15 ceramic specimens (CEREC Blocks, Sirona) used in this study were of 2.5 mm thickness, 5 mm wide and 6 mm long and made using a slow speed saw (Isomet, Buehler). Using the same slow speed saw the occlusal enamel portion of 15 mandibular third molars was removed and 15 dentin discs of 1 mm height were prepared. The thickness of the luting cement (Rely X Unicem, 3M ESPE) was delimited to 0.5 mm, using a Teflon mold and then brought into contact with the dentin disc. Light-curing time for all the groups was 20 sec. The temperature rise was measured placing underneath the dentin disc a K-type thermocouple wire connected to a data logger. Five measurements were carried out for each group. The difference between the initial and highest temperature readings was recorded and the 5 calculated temperature changes were averaged to determine the mean value in temperature rise. Statistical analysis was performed using ANOVA at a level of significance of a=0.05. 

Result: The results indicated that there was a lower temperature rise induced from Translux Power Blue than from the other two light-curing units, which did not present statistically significant difference (p<0.05). However, temperature rise from the light-curing units used in this study is lower than 5.5^oC, which is the limit of pulpal damage.

Conclusion: Within the limitations of this study, although the type and characteristics of light-curing units may affect temperature rise under ceramic restorations, this influence is possibly not of clinical significance.