Post-gel polymerization shrinkage associated with different light curing regimens.

This study compared post-gel polymerization shrinkage associated with five different light curing regimens of similar light energy density. A light-cure unit (VIP, BISCO) that allowed for independent command over time and intensity was used. The five regimens investigated were pulse delay (PD), soft-start (SS); pulse cure (PC), turbo cure (TC) and standard continuous cure (C) [control]. With the exception of TC, the light energy density for all curing regimens was fixed at 16 J/cm2. A strain-monitoring device and test configuration were used to measure the linear polymerization shrinkage of 2-mm thick composite specimens (Z100, 3M ESPE) during and post-light polymerization up to 60 minutes. Five samples were made for each curing mode. The results were analyzed using ANOVA/Scheffee's post-hoc test at significance level 0.05. Post-gel shrinkage ranged from 0.30% to 0.46 % at 60 minutes. The use of PD resulted in significantly lower shrinkage compared to PC, TC, SS and C. Shrinkage associated with SS was, in general, significantly lower than C. No significant difference in shrinkage was observed between PC, TC and C at all time intervals. The use of pulse delay and soft-start regimens decreased post-gel polymerization shrinkage.

Rapid cystic development in relation with an impacted lower third molar: a case report.

Cystic changes can arise in relation with unerupted lower third molars. This case report describes a large odontogenic keratocyst (OKC) which developed rapidly and aggressively over a short period of 2 years and presented with acute symptoms. The development of a large OKC over the mandible is evidenced by radiographs taken 2 years apart. The OKC was enucleated and the residual cavity was treated with Carnoy's solution and packed with bismuth iodoform paraffin paste dressing. The impacted third molar and second molar associated with the lesion were also extracted. This case illustrates how rapidly a cyst can develop in association with a previously asymptomatic, unerupted tooth and how quickly a radiographic diagnosis can become out of date. As such, the authors recommend the use of repeated radiographs for monitoring unerupted teeth at a tighter time frame of 6 to 12 months.