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The effect of two polishing pastes on the surface roughness of bis-acryl composite and methacrylate-based resins.

STATEMENT OF PROBLEM
A highly polished restoration surface is necessary to promote a plaque-free environment.


PURPOSE
The purpose of this study was to compare the surface roughness of 3 different bis-acryl composite-based and 3 different methyl methacrylate-based provisional crown and fixed partial denture resins after being polished with aluminum oxide and diamond paste.


MATERIAL AND METHODS
Six different materials were used (Iso-Temp, Protemp II, Structer 2, Dentalon Plus, Tab 2000 Kerr, Temdent). A total of 180 specimens were fabricated: 30 specimens of each material using circular stainless steel molds 10 mm in diameter and 2 mm high. Each material was mixed and polymerized according to manufacturer's instructions. The bis-acryl composite specimens were polymerized with a laboratory light-initiating unit for 30 seconds on each side (400 to 525 nm, 75 W quartz-halogen light source). All specimens were kept in a water bath at 37 degrees C for 45 minutes. Ten specimens of each group were left as untreated controls, 10 specimens of each group were polished with the aluminum oxide paste (Composite Polish), and 10 specimens of each group were polished with the diamond paste (Insta glaze). Surface roughness was determined with a profilometer. The data were analyzed with one-way analysis of variance (Post Hoc Scheffe's S test) (P<.001). In addition, the profilometric evaluations photographic images were recorded with a scanning electron microscope to examine the surface roughness after polishing.


RESULTS
The mean of the surface characteristics of the bis-acryl composites were 1.33 microm for aluminum oxide and 0.90 microm for diamond polishing paste; the mean of the results of the methyl methacrylate resins were 1 microm for aluminum oxide and 0.50 microm for diamond polishing paste. The difference between the mean values of bis-acryl resins groups and methacrylate-based resin groups were significant (P<.001). The difference between the subgroups of bis-acryl resins group (Iso-Temp, Protemp II, Structer 2) were not significant (P>.05). The difference between the subgroups of methacrylate-based resin group (Dentalon, Tab 2000, Temdent) were not significant (P>.05).


CONCLUSION
Within the limitations of this study, single-phase polishing of the bis-acryl composites tested and the methacrylate resins tested with diamond-based paste produced a smoother surface than when polished with aluminum oxide paste.