| Objective: The aim of this study was to compare the morphology similarity between original upper anterior teeth and all-ceramic virtual crowns reconstructed by computeraided design(CAD) mirror-image, biogeneric reconstruction and conventional waxedup, which may facilitate the dentists with selecting a suitable CAD methodology for the restoration of anterior teeth.Methods: Twenty patients with symmetric incisors, intact dentitions, normal tooth arrangment and occlusion, and non-parodontopathy were selected for the study. Then the progress of impression, bite registration, generation type separation, and scan of the original tooth morphology were conducted accordingly. Preparations for all-ceramic full crowns were randomly simulated on the stone replicas of an upper anterior tooth and the samples were then scanned by in Eos X5(sirona). The virtual all-ceramic rescontructions were designed with CAD mirror-image(MI), CAD biogeneric reconstruction(BR) and waxed-ups(WU) respectively. All the virtual reconstructions and original tooth image data were saved. With original tooth morphology as a reference standard, all virtual reconstructions were superimposed with their original surface according to a best-fit method by a software(Geomagic qualify 2013). The deviation of three dimensional(3D) distance and the rate of volume change(RVC) between original tooth and reconstructions were calculated, the grade assessment was carried out to analyze the proximal contact parameters of reconstructions with regard to contact tightness, shape and position. Furthermore, the esthetic effect of reconstructions as well as the degree of morphological similarity and symmetry between the reconstructions and the contralateral teeth were assessed by the dentists with visual perception, and the outcomes were expressed as visual analogue scale(VAS). Statistical analysis included one-way ANOVA and rank sum test were performed to analyse the discrepancies among the reconstructions of MI, BR, and WU models with setting the ? level at 5 %.Results: The 3D distances of MI(0.062±0.122mm) and BR group(0.068±0.147mm) were significantly less than that of the WU group(0.098±0.151mm)(P<0.05), but the difference between MI and BR group was not statistically significant(P>0.05). The significant difference in RVC data was found between MI(5.7±3.0%) and WU group(9.0±6.7 %), whereas both MI and WU group showed no significant differences compared with BR group which was 8.1±4.0%(P>0.05). The mesio and distal proximal contact grades of MI and BR groups were significantly superior than that of WU group(P<0.05), but there was no significant difference between MI and BR group(P>0.05). The results of visual evaluation showed that the VAS scores of MI(85.6±5.4) and WU groups(86.5±3.9) presented higher degree of satisfaction than the BR group(78.5±8.0)(P<0.05), and no significant difference was observed between MI and WU group(P>0.05).Conclusions: CAD MI enables a closer virtual reconstruction of natural tooth than reconstructions made by CAD BR and WU. The software could effectively perform a morphologic reconstruction of the natural tooth and may be ideal for the restoration of upper anterior teeth. |
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