Context:Polymerization shrinkage in composite resins is responsible for microleakage. Methacrylate-based composite resins have linear reactive groups resulting in high polymerization shrinkage. A recently introduced composite resin Filtek P90 is based on siloxanes and oxiranes which polymerize by cationic “ring opening” polymerization resulting in reduced polymerization shrinkage.Objectives:Aim of this study was to compare microleakage in class II cavities restored with a nanoceramic restorative (Ceram X) and a silorane composite (Filtek P90).Materials and Methods:Standardized class II box type cavities were prepared on mesial (Groups Ia and IIa) and distal (Groups Ib and IIb) surfaces of twenty extracted permanent molar teeth with gingival floor ending 1 mm coronal and apical to the cementoenamel junction, respectively. The teeth in Group Ia and Ib were restored with Ceram X and Group IIa and IIb with Filtek P90. The specimens were thermocycled and microleakage evaluated.Statistical Analysis Used:The data were statistically analyzed using Wilcoxon Signed-Rank test at the 0.05 level of significance.Results:Mean microleakage score of group la and lb was 1 ± 2.260 and 2.8 ± 1.229, respectively. And that of group Ila and llb was 0.2 ± .869 and 0.3 ± .588, respectively. When groups I and II were compared, results were statistically significant (P<0.05).Conclusion:It was concluded that silorane-based composite may be a better substitute for methacrylate-based composites.

Aims:The purpose of this study was to compare the sealing ability of Mineral Trioxide Aggregate (MTA) and Glass Ionomer Cement (GIC) when used over gutta-percha as intracanal sealing materials. The study also evaluated the sealing ability of Zinc oxide eugenol (ZOE) cement and Acroseal sealer.Materials and Methods:Teeth were obturated with gutta-percha using sealer ZOE (group A, C, D) and Acroseal (group B). The groups were further divided into 2 subgroups (15 premolars each) on the basis of intracanal sealing material used: GIC subgroups (A1, B1) and MTA in subgroups (A2, B2). The clearing technique was used in this study for leakage evaluation. Seventy mandibular premolars were prepared using step-back technique and divided into experimental groups A and B (30 premolars each) and the positive and negative control groups C and D (5 premolars each).Statistical analysis used:Coronal microleakage was determined under stereomicroscope using 15X magnification. Data was statistically analyzed using one-way ANOVA followed by Post-Hoc Multiple comparison (Bonferroni).Results:MTA group leaked significantly less than GIC group (P < 0.05). Acroseal exhibited better sealing ability than ZOE sealer. Teeth with no intracanal barrier showed almost complete leakage.Conclusions:MTA may be preferred over GIC as an intracanal barrier.

It was suggested that lower modulus composites can flex with the tooth structure decreasing the bond failure and that the stresses are much lesser when there is absence of an occlusal restoration. Occlusal composite restorations reinforce the tooth structure and reduce the cuspal flexure as compared to silver amalgam.

Background:Abfraction, a type of non-carious cervical tooth loss, is a poorly understood condition. One factor thought to contribute to the development of these lesions is the effect of occlusal loading and the presence of occlusal restoration.Aim and Objectives:The aim of this paper is to study the stress profile in the cervical region of mandibular first premolar with variation of occlusal loads, and to compare the stress profile between sound and occlusally restored tooth under variation of occlusal load, using two-dimensional plane strain finite element model.Materials and Methods:A mandibular first premolar was sectioned and modeled in the finite element software, along with its peridontium. Varying occlusal loads were applied along the cuspal inclines, with and without an occlusal restoration. The software used was NISA II EMRC.Result:It was found that higher occlusal loads caused more cuspal flexure and that the maximum shear stress was much higher and closer to the cervical area. It was also observed that there was a slight increase in shear stress when occlusal restoration was present.Conclusion:It was suggested that high occlusal loading and the presence of an occlusal amalgam restoration increased the stress concentration at the cervical area, which may lead to the breakdown of enamel at the cervical region.