The purposes of this study are to establish and validate a finite element (FE) model using finite element analysis methods and to identify optimal loading conditions to simulate masticatory movement. A three-dimensional FE model of the maxillary and mandibular cortical bone, cancellous bone, and gingiva was constructed based on edentulous cone-beam-computed tomography data. Dental computer-aided design software was used to design the denture base and artificial teeth to produce a complete denture. Mesh convergence was performed to derive the optimal mesh size, and validation was conducted through comparison with mechanical test results. The mandible was rotated step-by-step to induce movements similar to actual mastication. Results showed that there was less than a 6% difference between the mechanical test and the alveolar bone-complete denture. It opened 10° as set in the first stage, confirming that the mouth closed 7° in the second stage. Occlusal contact occurred between the upper and lower artificial teeth as the mouth closed the remaining angle of 3° in the third stage while activating the masseter muscle. These results indicate that the FE model and masticatory loading conditions developed in this study can be applied to analyze biomechanical effects according to the wearing of dentures with various design elements applied.

Wol Kang, Min-Su Kim, and Won-Gi Kim. J Dent Hyg Sci 2019;19:238-44. https://doi.org/10.17135/jdhs.2019.19.4.238

This study aimed to evaluate the needs of dentists, dental technicians, dental hygienists, and dental-related workers in terms of dental computer-aided design (CAD) software and artificial intelligence (AI). Based on a factor analysis, 57 survey items were assigned to six categories: (a) considerations when purchasing dental CAD software; (b) prosthesis design process; (c) dental CAD function; (d) use of AI dental CAD crown and denture design; (e) impact of AI; and (f) improvements in AI features. Overall, 93 participants were included in the study, and the reliability of the resultant survey data was estimated using Cronbach’s alpha coefficient. Statistically significant factors in each category were identified using one-way analysis of variance and Tukey’s honestly significant difference test (α = 0.05). The results revealed that design quality, design convenience and reproducibility, margin line setting, and automatic margin setting were considered most important in their respective categories (p < 0.05). There were also significant differences in the importance of certain items, such as branding importance and functional diversity, among different dental personnel groups (p < 0.05). Design speed and convenience were also found to be more important to dentists and dental hygienists compared to other dental personnel (p < 0.05). The importance of specific survey items varied significantly based on age, dental personnel, and work experience groups. Dental personnel, such as dentists and dental technicians, assigned greater importance to certain factors, such as branding, functional diversity, design speed, and compatibility with CAM equipment, compared to other occupational groups.

1) 탈지 공정에서는 온도 조건 변화에 따른 무게감소율은 큰 차이를 보이지 않으나, 수축률의 경우 상대적으로 덜 발생하는 저온 조건에서 소폭 개선됨을 확인하였다. 온도 증가에 따라 수축률이 증가하였고, 1300°C부터 소결이 진행되는 것을 확인하였다. 휨 특성의 경우 온도가 낮아질수록 잔류응력이 덜 발생하여 휨 정도가 개선되는 것을 알 수 있었다. 급가열의 경우 결합체인 폴리머의 급격한 팽창으로 인해 출력물에 크랙을 발생시켰다.

Denture base elastic-property assignment may influence how mechanical stress is distributed between a complete denture and its supporting tissues. This study compared rigid and flexible denture base material conditions in an idealized maxillomandibular finite element (FE) model at the final static bilateral clenching step. The model represented a fully edentulous geometry with coincident denture–gingiva surfaces connected by a tie constraint. The model did not include an initial interface gap, interface separation or sliding, extraction sockets, tissue remodeling, or time-dependent misfit. Geometry, mesh, boundary conditions, and loading were identical between the two conditions, whereas both the Young’s modulus and Poisson’s ratio assigned to the denture base differed. The peak magnitude of the minimum principal stress in the gingiva and the model-predicted local peak von Mises stress in the denture base elements were evaluated. Under the adopted mesh configuration, the flexible property assignment was associated with reductions of 28.6% and 35.3% in gingival compressive stress magnitude and increases of 70.5% and 73.9% in local denture base peak stress in the maxilla and mandible, respectively. These local peak differences are exploratory, model-dependent observations and have not been demonstrated to be mesh-independent. The findings do not establish clinical adaptation, contact pressure, tissue protection, deformation, durability, or performance in immediate dentures.

Wol Kang, Won-Gi Kim. Journal of Technologic Dentistry 2021;43:77-83. https://doi.org/10.14347/jtd.2021.43.3.77