Influence of dentist experience with scan spray systems used in direct CAD/CAM impressions

Statement of problem. Direct optical impression systems requiring powder opacification are widely used in prosthodontics, but little information is available about the influence of the dentist on the quality of scan sprays used for computer-aided design and computer-aided manufacturing (CAD/CAM) impressions. Purpose. The purpose of this study was to evaluate the influence of operator experience on scan spray homogeneity and thickness on tooth surfaces before direct optical impressions are made. Material and methods. A total of 36 crown-prepared acrylic resin teeth were coated (Optispray) for direct optical impressions by 3 experienced dentists and 3 inexperienced dentists (n=18 teeth per group). The teeth were visually scored for coating homogeneity (1, heterogeneous; 2, average; 3, homogeneous). To determine the coating thickness (pm), the teeth were resin-embedded, cut, and polished. A stereomicroscope (x100 magnification) was used to examine 148 areas per tooth. The results were statistically analyzed with the nonparametric Spearman and Mann-Whitney tests (alpha=.05). Results. Coating homogeneity was significantly higher (P<.001) for the experienced group (92.41 +/- 6.65%) than for the inexperienced group (66.11 +/- 12.69%). Coatings were significantly thinner for the experienced group (43.1 +/- 14.09 mu m) than for the inexperienced group (70.19 +/- 31.26 mu m) for all crown areas (P=.007). Coatings were 52 mu m thinner for occlusal areas (P<.001) for the experienced group than for the inexperienced group. Coatings were significantly thinner for buccal (P=.015) and lingual surfaces (P=.002) for the experienced group than for the inexperienced group. Coatings on cervical surfaces were significantly thinner for the experienced group (43.52 +/- 15.76 mu m) than for the inexperienced group (63.45 +/- 29.93 mu m) (P=.035). Conclusions. Experienced dentists achieved greater homogeneity and thinner coatings on crown-preparation surfaces than inexperienced dentists.