Effect of Preparation Depth on the Marginal and Internal Adaptation of Computer-aided Design/Computer-assisted Manufacture Endocrowns.

The aim of the study was to evaluate the effect of preparation depth and intraradicular extension on the marginal and internal adaptation of computer-aided design/computer-assisted manufacture (CAD/CAM) endocrown restorations. Standardized preparations were made in resin endodontic tooth models (Nissin Dental), with an intracoronal preparation depth of 2 mm (group H2), with extra 1- (group H3) or 2-mm (group H4) intraradicular extensions in the root canals (n=12). Vita Enamic polymer-infiltrated ceramic-network material endocrowns were fabricated using the CEREC AC CAD/CAM system and were seated on the prepared teeth. Specimens were evaluated by microtomography. Horizontal and vertical tomographic sections were recorded and reconstructed by using the CTSkan software (TView v1.1, Skyscan).The surface/void volume (S/V) in the region of interest was calculated. Marginal gap (MG), absolute marginal discrepancy (MD), and internal marginal gap were measured at various measuring locations and calculated in microscale (µm). Marginal and internal discrepancy data (µm) were analyzed with nonparametric Kruskal-Wallis analysis of variance by ranks with Dunn's post hoc, whereas S/V data were analyzed by one-way analysis of variance and Bonferroni multiple comparisons (α=0.05). Significant differences were found in MG, MD, and internal gap width values between the groups, with H2 showing the lowest values from all groups. S/V calculations presented significant differences between H2 and the other two groups (H3 and H4) tested, with H2 again showing the lowest values. Increasing the intraradicular extension of endocrown restorations increased the marginal and internal gap of endocrown restorations.

Pulp reactions to light-cured glass ionomer cements.

This study compared the pulp responses to two light-cured glass ionomer liners with a chemically set glass ionomer lining cement and zinc oxide-eugenol. Deep Class V cavities were prepared at high-speed with carbide burs under a water coolant in 96 teeth of three young adult beagle dogs. The smear layer was left intact according to the manufacturers' recommendations. The cavities in each quadrant were lined with either Vitrebond light-cured glass ionomer liner, X-R Ionomer light-cured liner, GC lining cement or ZOE which served as a control. All cavities were restored with Silux Plus resin composite. The ZOE liner was covered with a varnish prior to the resin composite placement. The animals were terminated at 1, 4 and 12 weeks. Jaws were excised, fixed in 10% formalin and decalcified in 5% formic acid. Teeth were sectioned at 7 microns, and stained with hematoxylin and eosin. Selected slides were stained with the Brown and Hopps method for histologic demonstration of bacteria. The microscopic findings indicated that pulpal reactions to the two light-cured glass ionomer liners were minimal and comparable to those elicited by the chemically-cured glass ionomer lining cement and ZOE. Bacteria were observed in nine specimens but only one of these revealed a moderate pulp reaction.