Surface quality achieved by polishing and by varnishing of temporary crown and fixed partial denture resins

Studies have suggested that coating a temporary restoration with varnish material could replace time-consuming polishing procedures needed for achieving an optimally smooth surface.

This study examined the surface roughness of acrylic resins after having been polished or coated with different varnish materials.

A total of 360 cylindrical specimens were fabricated from 9 brands of resin. One surface on each specimen was machined flat and subsequently either polished with rubber polishers or coated with 1 of 9 varnishes. Selected specimens were subjected to thermal cycling (5 degrees C to 55 degrees C, 2000 cycles). Surface quality was assessed by means of a profilometer and by SEM examination.

Polished specimens had average surface roughness values (Ra) of 0.8 microm; differences in roughness between materials were small, but statistically significant. Type of coating had a significant influence on surface quality. Depending on the combination of materials used, the coating produced both smoother and rougher surfaces than polishing (0.4 microm < Ra < 4.6 microm). Five coatings were deemed not to be clinically applicable because of poor wetting properties. Thermal cycling did not significantly influence surface quality, but caused minute cracks in the cyanoacrylate coating.

In regard to surface quality and applicability, the use of varnishes on temporary restorations is not advisable.