This study evaluated the effect of the combination of three different onlay preparation designs and two restorative materials on the stress distribution, using 3D-finite element analysis. Six models of first lower molars were created according to three preparation designs: non-retentive (nRET), traditional with occlusal isthmus reduction (IST), and traditional without occlusal isthmus reduction (wIST); and according to two restorative materials: lithium-disilicate (LD) and nanoceramic resin (NR). A 600 N axial load was applied at the central fossa. All solids were considered isotropic, homogeneous, and linearly elastic. A static linear analysis was performed, and the Maximum Principal Stress (MPS) criteria were used to evaluate the results and compare the stress in MPa on the restoration, cement layer, and tooth structure (enamel and dentin). A novel statistical approach was used for quantitative analysis of the finite element analysis results. On restoration and cement layer, nRET showed a more homogeneous stress distribution, while the highest stress peaks were calculated for LD onlays (restoration: 69–110; cement layer: 10.2–13.3). On the tooth structure, the material had more influence, with better results for LD (27–38). It can be concluded that nRET design showed the best mechanical behavior compared to IST and wIST, with LD being more advantageous for tooth structure and NR for the restoration and cement layer.

Objectives: To study the effects of internal and marginal polymerization shrinkage stress and distribution in different resin composite class III dental restorations in relation to the restorative technique using numerical finite element analysis (FEA). Methods: A 3D model of a human hemi-maxilla with a sound maxillary central incisor were created. Four class III distal cavities were shaped and differently restored. Four groups of resin composite combinations were analyzed: group C (three increments of conventional composite); group B (two increments of bulk-fill composite); group FC (flowable base + three increments of conventional composite); and group FB (flowable bulk-fill base + two increments of conventional composite). The resulting four models were exported to FEA software for static structural analysis. Polymerization shrinkage was simulated using thermal analogy, and stress distribution was analyzed using the Maximum Principal Stress criterion at the marginal and internal cavity interfaces. Results: Group FC showed the highest stress at the level in the proximal region (9.05 MPa), while group FB showed the lowest (4.48 MPa). FB also exhibited the highest internal dentin stress, indicating potential risks for long-term bond degradation. In the cavo-surface incisal angle, the average peak stress across all groups was 3.76 MPa. At the cervical cavo-surface angle, stress values were 3.3 MPa (C), ~3.36 MPa (B), 3.41 MPa (FC), and 3.27 MPa (FB). Conclusions: Restorative technique did not significantly influence marginal stress distribution in class III composite restorations. However, the bevel area at the cervical margin showed the highest concentration of shrinkage stress.

This study evaluated the effect of substrate core materials and occlusal contact patterns on the fatigue mechanical behavior and stress distribution of single-unit ceramic crowns. One hundred and twenty monolithic crowns were fabricated from zirconia (YZ - IPS e.max ZirCAD, Ivoclar), lithium disilicate (LD - IPS e.max CAD, Ivoclar) and polymer infiltrated ceramic network (PICN - Enamic, Vita Zahnfabrik). The crowns were allocated considering two factors: 'substrate' (epoxy resin or cast Ni-Cr metal core) and 'occlusal contact pattern' (contact at the cusp ridges or cusp tips). The substrate models were design, milled and scanned to plan the restorations in a digital workflow. The crowns were milled, bonded to the substrates, and subjected to an accelerated fatigue test (100 N; 10,000 cycles/step; 20 Hz step-size: 100 N up to 1600 N, and after, 200 N until failure or survival at 2,800N; immersed in water). Statistical analyses were performed using two-way ANOVA, Tukey's post-hoc test, and Kaplan-Meier survival analysis (α = 0.05) considering fatigue failure load and cycles for fatigue failure (FFL/CFF). Fractographic and finite element analysis (FEA) were carried out. The results indicate that the 'substrate' factor did not influence the mechanical behavior of YZ and LD monolithic crowns (p > 0.05). However, PICN crowns bonded to epoxy resin exhibited statistically superior results for FFL and CFF (p < 0.05) compared to Ni-Cr cores. Regarding the 'occlusal contact pattern' factor, YZ and LD exhibited higher mean FFL and CFF when associated with cusp tip contact compared to cusp ridge contact (p < 0.05), except for YZ bonded to the epoxy resin substrate (p > 0.05). No differences were detected for the 'occlusal contact' factor in PICN crowns (p > 0.05). The predominant failure was Hertzian cone cracks, regardless of the restorative material. Stress measurements showed higher stress peaks at the cusp ridges. The core material did not alter the fatigue mechanical behavior of YZ or LD crowns. However, the incidence of cusp ridge contacts in YZ or LD crown increases the risk of failure. Conversely, when using PICN crowns, a core with a more similar elastic modulus enhances mechanical behavior compared to a stiffer core, and no influence on the occlusal pattern was observed.

Subgingival fractures in the anterior region present challenges for adhesive ceramic restorations. The deep margin elevation (DME) technique, using composite resin to elevate subgingival margins before indirect restoration preparation, has been reported to improve outcomes while maintaining esthetic and functional integrity. Developed for posterior teeth, DME aligns with minimally invasive principles and leverages adhesive material advancements. Its use in anterior teeth preserves gingival architecture, supports periodontal health, and ensures precise adhesive protocols, essential for successful rehabilitation. This report outlines DME's systematic application for managing anterior subgingival fractures.

Objetivos: A presente revisão de literatura teve por objetivo verificar na literatura atual a aplicabilidade da customização de pinos de fibra de vidro pré-fabricados com resina composta para situações clínicas. Materiais e métodos: Foi realizada uma pesquisa na base de dados PubMed utilizando as palavras-chave: Non-vital tooth, Post and Core Technique e Composite Resins. A busca foi limitada ao período de 2015 a 2021, de estudos publicados na íntegra, em inglês e acesso gratuito. Resultados: foram obtidos 1.981 artigos no PubMed, sendo 429 no período de 2015 a 2021. Após a leitura dos títulos e resumos foram excluídos 422 artigos. Ao final foram selecionados 5 artigos, sendo posteriormente acrescentado 4 artigos por referência cruzada, totalizando 9 artigos. Conclusão: Os pinos de fibra de vidro pré-fabricados customizados com resina composta são uma opção viável para reabilitação de dentes tratados endodonticamente com canal amplo e/ou frágil.