Plaque accumulation on composite surfaces after various finising procedures.

A clinical study was undertaken to determine the rate at which plaque accumulates on the surfaces of composite restorations on which four finishing techniques were used. Plaque on these surfaces was compared with that on control surfaces with polished metallic or glazed porcelain restorations, and unrestored enamel surfaces. Composite surfaces were covered with plaque after 24 hours regardless of the finishing technique used. Plaque did not collect on adjacent control teeth to this degree until the third day, although the diffence remained statistically significant. Surface discrepancies on the polished composites were shown in scanning electron micrographs and with laboratory measurements.

Pulpal response in rhesus monkeys to cementation agents and cleaners.

The purpose of these studies was to compare pulpal inflammatory responses induced by cementation of precision amalgam inlays with zinc phosphate cement, with and without a Hydroxyline liner, Durelon cement, and ZOE controls. Hydraulic force was induced by the inlay insertion procedure. Cavilax, water, and polyacrylic acid were compared with ZOE controls. Both studies also used untreated teeth for comparison. The use of zinc phosphate luting cement in the 48-hour inlay study was the only condition provoking moderate to severe responses. Zinc phosphate cement over Hydroxyline liner and Durelon cement in the study of inlays and Cavilax cleaner, water, and polyacrylic acid in the study of cleaners showed mild responses comparable to the ZOE control in the 48-hour and in the 45-day periods.

Techniques to improve the seating of castings.

A convergence of 20 degrees for full crowns is the most likely to be seen clinically, as determined by random measurements taken at a dental laboratory. Castings did not seat without cement, by an average of 215 micron at 10 degrees of convergence, or by 99 micron at 20 degrees of convergence. Biting forces will seat a casting approximately 150 micron, but will cause random concentrations of force against tooth structure, thus compressing it. All castings tend to rebound from this position. Zinc phosphate and polycarboxylate cemented crowns seated to 33 micron and 20 micron respectively when relieved, but each were elevated to 112 micron when not relieved. A silicophosphate cement displaced crowns with 20 degrees of convergence 122 micron under "ideal" clinical conditions, even when relieved; and with CBA 9080 cement, more than 500 micron. A die relief method was found to be the most suitable of the three casting compensation techniques. Casting retention, after cementation, was increased by 25%.