Many dental students struggle for visual recognition when irst exposed to the study of tooth cavity preparation in the operative dentistry laboratory. Rapid prototypes and virtual models of different cavity preparations were developed for the incoming irst-year class of 2010 at the Dental School of Federal University of Uberlândia, Brazil, to help them to visualize the subtle differences in cavity preparations and are described in this article. Rapid prototyping techniques have been used in dental therapy, mainly for the fabrication of models to ease surgical planning in implantology, orthodontics, and maxillofacial prostheses. On the other hand, the application of these technologies associated with 3D-virtual models in dental education is waiting to be exploited, once they have signiicant potential to complement conventional training methods in dentistry.

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The MOD cavity restored with composite resin is a better option than amalgam to improve the biomechanical behavior of wedge-shaped lesion, avoiding dental failure. In addition, the occlusal interferences must be removed, allowing homogeneous contact distribution and preventing WS lesion progression.

Combined assessment of computer-based and experimental techniques provide an holistic approach to characterize the biomechanical behaviour of teeth with both unrestored and restored NCCLs.

ABSTRACT:The aim of this study was to analyze the biomechanical behavior of lower premolars regarding the non-carious cervical lesion (NCCL) depth, load type and restoration status, using finite element analysis. Twodimensional virtual model simulating a healthy lower premolar were created using the CAD software. Based on this image, five models were generated: healthy (H), three types of NCCLs: small lesion (SL -0.5 mm deep), medium lesion (ML -1.0 mm), deep lesion (DL -1.5 mm), and restored lesion (RL). The models were export to a CAE software (ANSYS Finite Element Analysis Software), the areas of all structures were plotted and each model was meshed using a control mesh device. All of the virtual models were subjected to two occlusal load types, (100N each): occlusal load (OL) and buccal load (BL) on buccal cusp. The magnitude and the stress distribution were obtained using the von Mises and maximum principal stress criteria (σ1), in MPa. The quantitative analysis of stress (MPa) was identified at three points of the NCCLs: enamel surface on its upper wall , dentin at the bottom wall and dentin on the lower wall. The results showed a direct relation between sequential removal of cervical structure and higher stress concentration for any groups and for both loads types. For OL the highest value of stress was 8.8 MPa for DL on upper wall of NCCLs.The BL exhibited higher stress values in comparison to the OL for all models.In addtion, the BL was responsible for providing the highest stress accumulation on the bottom wall, 38.2 MPa for DL. The restoration with composite resin was able to restore a stress distribution close to the healthy model, for both load types. In conclusion, the extent of non-carious cervical lesion and loading conditions influenced the stress distribution pattern of lower premolar. The outer load seems to be more critical in affecting the biomechanical behavior of lower premolars, regardless of the lesion size. The restoration of NCCLs with composite resin appears to recover the biomechanical behavior, similar to healthy model.

The aim of this study was to evaluate the effect of parallel and tapered threaded post placement on the strain and stress distribution of endodontically treated teeth. Fifteen bovine incisors were sectioned 15 mm from their apices, endodontically treated, and divided into three groups (n = 5) according to three different threaded posts: parallel threaded post (Radix-Anker, RA); tapered threaded post (Euro-Post, EP) and tapered threaded post (Reforpost II, RII). A strain-gauge was fixed on the proximal surface perpendicular to the long root axis, 2 mm from the cervical limit. Strain generated during post placement was recorded and compared using one-way ANOVA and Tukey's test (α = .05). A scanning electron microscope was used to examine the longitudinal root sections. Stress was evaluated for each group in a two-dimensional finite element analysis. The models were meshed with tetrahedron elements and loaded with 2 N at an angle of 135° to the lingual face. The equivalent Von Mises stress was calculated. The one-way ANOVA showed significant difference among the groups. The RA group (150.0 ± 12.2 A) produced higher external strain than the RII (80.0 ± 12.2 B) and the EP (70.0 ± 6.1 B) groups. The inner strain was approximately five times greater than the external dentin strain. High stress concentrations in each thread of the posts were observed. Scanning electron micrographs showed cracks that started in the threads of the posts. The threaded post placement induced root strain mainly on the parallel side post. Root strain and stress concentration on the post threads tended to create cracks in the inner root canal dentin.

Introdução: este é o terceiro de seis artigos que abordam uma análise geral da literatura sobre resinas compostas nos últimos dez anos. Visto que as resinas compostas são amplamente utilizadas, essa revisão tem como objetivo analisar a relação dos diversos tipos de aparelhos fotoativadores usados em relação à composição de diversas resinas compostas estudadas. Métodos: pesquisa realizada pela plataforma PubMed, utilizando MeSH sobre fotoativação e resinas compostas. Os artigos foram escolhidos de acordo com a relevância para o tema pesquisado e pela data de publicação de 2008 a 2018. Após a leitura completa, foram selecionados 28 artigos para essa revisão de literatura. Resultados: os resultados foram distribuídos em duas tabelas. A primeira tabela apresenta os dados dos aparelhos fotoativadores associados ao grau de conversão de resinas compostas comercializadas. O melhor resultado foi dos aparelhos fotoativadores de LED, poliwave e monowave, já que a maioria das resinas apresenta como fotoiniciador a canforoquinona (CQ). A segunda tabela relaciona o espectro de luz emitido pelos aparelhos com os fotoiniciadores das resinas experimentais e seu grau de conversão. A CQ foi o fotoiniciador que apresentou melhor resultado, assim como os aparelhos fotoativadores de luz halógena e de LED poliwave. Conclusões: os melhores resultados de grau de conversão estão relacionados ao uso de fotoiniciadores compatíveis com o comprimento de onda emitido pelo fotoativador utilizado.

Objective: The aim of this study was to perform an acid wear properties review (pH, entitlement and buffering effect) of diets that can influence dental and restorative aging. Methodology: Manuscripts from the Pubmed database were collected. The search terms were: “Dental erosion”, “Erosion”, “Food habits”, “acidity”, “tooth enamel solubility”, “carbonated drinks”, “hydroxyapatite” and “alcoholic beverage consumption” between the years of 1995 and 2020. Result: 755 manuscripts were initially obtained, but after analyzing the inclusion and exclusion criteria, 15 manuscripts were selected at the end. After analyzing the 15 manuscripts included in the literature review, the results of the study showed that most of the diets evaluated had a pH lower than 5.5, except for coffee and mineral water. The soft drinks and Kombucha had lower pH values and therefore more corrosive potential. Conclusion: Based on the results of this study, it may be concluded that most of the diets evaluated present a corrosive potential for dental structure and restorative materials.