White light scanner-based repeatability of 3-dimensional digitizing of silicon rubber abutment teeth impressions

PURPOSE: The aim of this study was to evaluate the repeatability of the digitizing of silicon rubber impressions of abutment teeth by using a white light scanner and compare differences in repeatability between different abutment teeth types. MATERIALS AND METHODS: Silicon rubber impressions of a canine, premolar, and molar tooth were each digitized 8 times using a white light scanner, and 3D surface models were created using the point clouds. The size of any discrepancy between each model and the corresponding reference tooth were measured, and the distribution of these values was analyzed by an inspection software (PowerInspect 2012, Delcamplc., Birmingham, UK). Absolute values of discrepancies were analyzed by the Kruskal-Wallis test and multiple comparisons (alpha=.05). RESULTS: The discrepancy between the impressions for the canine, premolar, and molar teeth were 6.3 microm (95% confidence interval [CI], 5.4-7.2), 6.4 microm (95% CI, 5.3-7.6), and 8.9 microm (95% CI, 8.2-9.5), respectively. The discrepancy of the molar tooth impression was significantly higher than that of other tooth types. The largest variation (as mean [SD]) in discrepancies was seen in the premolar tooth impression scans: 26.7 microm (95% CI, 19.7-33.8); followed by canine and molar teeth impressions, 16.3 microm (95% CI, 15.3-17.3), and 14.0 microm (95% CI, 12.3-15.7), respectively. CONCLUSION: The repeatability of the digitizing abutment teeth's silicon rubber impressions by using a white light scanner was improved compared to that with a laser scanner, showing only a low mean discrepancy between 6.3 microm and 8.9 microm, which was in an clinically acceptable range. Premolar impression with a long and narrow shape showed a significantly larger discrepancy than canine and molar impressions. Further work is needed to increase the digitizing performance of the white light scanner for deep and slender impressions.

Complications of Perfluorocarbon Liquids as an Intraoperative Tool

Perfluorocarbon liquids(PFCLs) have recently been used to facilitate surgery in a variety of condition, including proliferative vitreoretinopathy, giant retinal tears, diabetic tractions, retinal detachment with a rhegmatous component, dislocated crystalline lenses. Although the ocular toxicity of PFCLs has been evaluated in a number of animal studies, few reports have focused on ocular complications associated with their clinical use. We evaluated complications of PFCLs as an intraoperative tool in a series of 55 patients. We had used two kinds of PFCLs, Vitreon(perfluorophenanthrene) and DK-line(perfluorodecaline) intraoperatively. 10 eyes had intraoperative complications. Subretinal PFCLs(6 eyes), subretinal hemorrhage(3 eyes), subretinal hemorrhage with subretinal PFCLs(1 eye) were observed. Postoperative complications of PFCLs as an only intraoperative tool were preretinal small dreplets(4 eyes), subretinal small droplets(4 eyes) and small dreplets in anterior chamber(2 eyes). In case of posterior retinal break, careful injection should be considered. Postoperative small residual droplet of perfluorocarbon in sub- and preretinal space did not cause any toxic effects in these patients. But remained droplet in anterior chamber should be removed to avoid significant corneal toxity.