Influence of intraoral scanning coverage on the accuracy of digital implant impressions - An in vitro study.

OBJECTIVES: To evaluate the influence of intraoral scanning coverage (IOSC) on digital implant impression accuracy in various partially edentulous situations and predict the optimal IOSC. METHODS: Five types of resin models were fabricated, each simulating single or multiple tooth loss scenarios with inserted implants and scan bodies. IOSC was subgrouped to cover two, four, six, eight, ten, and twelve teeth, as well as full arch. Each group underwent ten scans. A desktop scanner served as the reference. Accuracy was evaluated by measuring the Root mean square error (RMSE) values of scan bodies. A convolutional neural network (CNN) was trained to predict the optimal IOSC with different edentulous situations. Statistical analysis was performed using one-way ANOVA and Tukey's test. RESULTS: For single-tooth-missing situations, in anterior sites, significantly better accuracy was observed in groups with IOSC ranging from four teeth to full arch (p < 0.05). In premolar sites, IOSC spanning four to six teeth were more accurate (p < 0.05), while in molar sites, groups with IOSC encompassing two to eight teeth exhibited better accuracy (p < 0.05). For multiple-teeth-missing situations, IOSC covering four, six, and eight teeth, as well as full arch showed better accuracy in anterior gaps (p < 0.05). In posterior gaps, IOSC of two, four, six or eight teeth were more accurate (p < 0.05). The CNN predicted distinct optimal IOSC for different edentulous scenarios. CONCLUSIONS: Implant impression accuracy can be significantly impacted by IOSC in different partially edentulous situations. The selection of IOSC should be customized to the specific dentition defect condition. CLINICAL SIGNIFICANCE: The number of teeth scanned can significantly affect digital implant impression accuracy. For missing single or four anterior teeth, scan at least four or six neighboring teeth is acceptable. In lateral cases, two neighboring teeth may suffice, but extending over ten teeth, including contralateral side, might deteriorate the scan.

Characteristic-preserving Latent Space for Unpaired Cross-domain Translation of 3D Point Clouds.

This paper aims at unpaired shape-to-shape transformation for 3D point clouds, for instance, turning a chair to its table counterpart. Recent work for 3D shape transfer or deformation highly relies on paired inputs or specific correspondences. However, it is usually not feasible to assign precise correspondences or prepare paired data from two domains. A few methods start to study unpaired learning, but the characteristics of a source model may not be preserved after transformation. To overcome the difficulty of unpaired learning for transformation, we propose alternately training the autoencoder and translators to construct shape-aware latent space. This latent space based on novel loss functions enables our translators to transform 3D point clouds across domains and maintain the consistency of shape characteristics. We also crafted a test dataset to objectively evaluate the performance of point-cloud translation. The experiments demonstrate that our framework can construct high-quality models and retain more shape characteristics during cross-domain translation compared to the state-of-the-art methods. Moreover, we also present shape editing applications with our proposed latent space, including shape-style mixing and shape-type shifting, which do not require retraining a model.

The influence of crown coverage on the accuracy of static guided implant surgery in partially edentulous models: An in vitro study.

OBJECTIVE: To evaluate the influence of crown coverage of surgical guides on the accuracy of static computer-assisted implant surgeries (sCAISs) in different partially edentulous situations. METHODS: Acrylic models with five types of partially edentulous situations were fabricated in this study. In coDiagnostiX software (Dental Wings, Montreal, Canada), surgical templates were designed and fabricated with reduced crown coverage (RCC), standard crown coverage (SCC) and extended crown coverage (ECC). Then, fully guided implant placement into the acrylic models was performed by dental surgeons with more than 10 years of experience. In total, 120 models and 120 guides were manufactured, and 168 bone-level Straumann replica implants (4.1 × 10 mm, Institut Straumann AG, Basel, Switzerland) were inserted. Postoperative implant positions were scanned (Trios 3, 3 shape, Copenhagen, Denmark) and compared with the preplanned virtual positions via coDiagnostiX (Dental Wings, Montreal, Canada). The angular, coronal and apical deviations were measured and analyzed to evaluate the accuracy of implant insertion. Statistical analysis was performed using one-way ANOVA and Tukey's test. RESULTS: For single tooth missing situations, the RCC group was similar to the SCC group and ECC group in anterior sites. In premolar or molar sites, the SCC and ECC groups had no statistically significant difference (p > .05), while the RCC group had more coronal and apical deviation (p < .05). For multiple teeth missing situations, there was no difference among the RCC, SCC and ECC groups (p > .05). No difference was found among the five edentulous situations with different CCs (p > .05). CONCLUSION: The CC of templates can significantly affect the accuracy of guided surgeries when implants are inserted in a single gap at posterior sites. Templates with CC extended to the undercut line may be an optimal choice for static guided surgeries. CLINICAL SIGNIFICANCE: The accuracy of static guided implant surgery can be influenced by the CC of templates, and proper CC with the guide covering extending to the undercut line may contribute to improved accuracy. CC should be taken into consideration when designing surgical templates.

Anti-Obesity Properties of the Dietary Green Alga, Codium cylindricum, in High-Fat Diet-Induced Obese Mice.

Marine carotenoids have been reported to prevent and alleviate lifestyle-related diseases including diabetes and obesity. We previously reported that siphonaxanthin, a green algal carotenoid, effectively suppresses adipogenesis in 3T3-L1 cells and prevents lipid accumulation in mesenteric adipose tissue of KK-Ay mice. Thus, we expect that dietary siphonaxanthin-rich marine green algae may effectively prevent obesity. Here, we assessed the effect of dietary siphonaxanthin-rich green algae (Codium cylindricum) on the development of diet-induced obesity in C57BL/6J mice. The mice were fed a low-fat diet (LF; 7% fat, w/w), a high-fat diet (HF; 35% fat, w/w), or a high-fat diet supplemented with 1% or 5% green algal powder (1GA or 5GA) for 78 d. Our results showed that weights of body and perirenal white adipose tissue (WAT) in the 5GA group were significantly lower than that in the HF group. The mesenteric and total WAT, as well as plasma and hepatic cholesterol concentrations tended to be lower in both the 1GA and 5GA groups compared to the HF group. Dietary green algal powder reduced the expression of lipogenesis-related genes and enhanced the expression of energy expenditure-related genes in the mesenteric WAT. Siphonaxanthin accumulated in the mesenteric WAT may contribute to the prevention of adiposity in mesenteric WAT. Furthermore, the reduction in the weight of WAT was attributed to the inhibitory effect on fat absorption of dietary fiber contained in the green algae. Overall, these results indicated that siphonaxanthin-rich green algae may be beneficial for the prevention of obesity and regulation of lipid metabolism.