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.

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 the study was to analyze and quantify the influence of isthmus extension and depth of MOD cavity of upper premolars on stress distribution by means of two-dimensional finite element method. Seven different homogeneous and elastic models were created:Model 1, intact teeth;Model 2, MOD cavity with 2 mm isthmus, 2 mm depth and composite resin restoration;Model 3, MOD cavity with 2 mm isthmus, 3 mm depth and composite resin restoration;Model 4, MOD cavity with 2 mm isthmus, 4 mm depth and composite resin restoration;Model 5, MOD cavity with 4 mm isthmus, 2 mm depth and composite resin restoration;Model 6, MOD cavity with 4 mm isthmus, 3 mm depth and composite resin restoration;Model 7, MOD cavity with 4 mm isthmus, 4 mm depth and composite resin restoration. Each model were submitted to a 100N load and analyzed. The greater the depth extent of MOD cavity, the greater the stress generated in the cavity pulp wall and in the cervical region of the tooth. Increasing the extension of the cavity isthmus intensifies stress in these regions and generates stress concentration on palatal and vestibular faces. Stress generated in the cavity pulp wall was predominantly tensile stress. The loss of marginal ridges influences the stress distribution pattern of upper premolars. It is indicated restorative techniques that allow greater conservation of tooth structure.

Devido a crescente valorização da harmonização facial, faz grande a procura de tratamentos estéticos nas clínicas odontológicas, devido aos fatores que interferem na harmonia do sorriso. Com isso, cada vez mais se torna um desafio satisfazer as exigências estéticas de cada paciente. Portanto, o objetivo deste trabalho foi relatar o impacto psicossocial em um caso clínico que foi realizado reabilitação estética anterior com resina composta direta. O paciente, gênero masculino, 32 anos, compareceu à clínica de Dentística da Faculdade de Odontologia da Universidade Federal de Mato Grosso do Sul (FAODO-UFMS) em 2019, queixando-se da aparência do seu sorriso devido ao “espaço” que havia entre os dentes e “cor amarelada”. No exame clínico detalhado foi verificado a presença de diastema entre os elementos 11 e 21, devido a desproporção do tamanho dos dentes nessa região. Foi proposto, então, clareamento de consultório combinado com caseiro e realização de facetas diretas de resina composta nos elementos 11,12,13, 21, 22 e 23. Para isso, foi realizado fotografias, enceramento diagnóstico inicial e teste com mock-up. As facetas foram confeccionadas pela técnica estratificada com auxílio de guia de silicone para confecção da face palatina. Foi aplicado o questionário OHIP-14 antes e após o tratamento para analisar a eficácia do tratamento na qualidade de vida do paciente. Concluiu-se o tratamento baseado no clareamento dental seguido por facetas diretas com resina composta foi capaz promover uma melhor qualidade de vida.

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This study applied the finite element method (FEM) and the moiré strip projection method to evaluate the biomechanical behavior of healthy and endodontic-treated premolar teeth. The finite element method and the moiré strip projection method were applied to evaluate the influence of restored materials in association with cervical lesions and were considered as strain estimates for a tooth sample with 21 units, under loads of 25, 50, 75, and 100 N, frontal and oblique applied. The focused cases were: tooth H healthy; tooth A-MOD amalgam; tooth AL-MOD amalgam + lesion; tooth ALR-MOD amalgam + injury restored; tooth R-MOD resin; tooth RL-MOD resin + lesion; tooth RLR-MOD resin + injury restored. The results obtained by FEM simulation can be considered perfectly validated by the results presented by the experimental moiré projection analysis, demonstrating that the FEM numerical analysis can be used to evaluate the biomechanical behavior of healthy and endodontically treated teeth. Developing an alternative protocol to generate FEM three-dimensional models will lead to a ready and inexpensive tool since there is no need for costly equipment for tooth extraction prognosis.