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The purpose of this study was to evaluate the operator variability of two dentin bonding systems. Fourteen undergraduate students and ten dentists of different levels of clinical experience were selected.Tensile bond strengths between resin composite and bovine dentin using dentin adhesive systems (Clearfil Liner Bond II: LB II; Scotchbond Multi-Purpose: MP) bonding systems showed a large scatter among students and dentists.The dentists group demonstrated no statistically significant differences for mean bond strengths between LB II and MP. The student group recorded a statistically greater bond strength using LB II . The mean coefficient of variation of the dentists group showed no statistically significant difference between LB II and MP, however that of the students group was lower with LB II. When using MP, the dentist group demonstrated a lower coefficient of variation than that of the student group.In order to obtain optimal bonding performance, or when beginning the use of a new system, the operator should be aware of the technique sensitivity of some adhesive systems and sensitivity to operator variability.

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The purpose of this investigation was to measure and compare both the surface roughness and gloss of flowable composites polished with standardized silicone carbide (SiC) papers. Four flowable and two conventional composites were used in this study. Polymerized specimens were subjected to a polishing procedure comprising 12 sequential steps from coarser to finer grits of SiC paper. At the initial polishing stage, flowable composites were more sensitive to the size of the polishing particles and thus yielded surfaces rougher than the conventional composites. Surface roughness became stable when polishing particles less than 13 μm size were used. However, although surface roughness was reduced, an esthetic gloss quality was not achieved on the resultant polished surface. On the influence of filler shape, composites with spherical fillers seemed to have the upper-hand advantage of attaining a high gloss by polishing. On the influence of polishing particle size, it was suggested that polishing should be completed with polishing particles less than 12 μm size so as to achieve clinically satisfactory surface roughness and gloss.