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.

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.

This paper presents an experimental application of the fringe projection method for evaluating the pre-molar teeth deformations, under different load conditions. It was developed an algorithm for digital images reconstruction, which is able to process and evaluate the teeth deformation behavior. The teeth samples were placed in polystyrene resin and fixed in a support with a rod, for load application. The different workloads were 25N, 50N, 75N and 100N, applied in the long axis of the teeth. The levels of displacements were as low as 1.4 x 10 −3 mm, for applied load of 25 N and 1.85 x 10 −3 mm for 100 N, giving a displacement-load slope of approximately of 6 nm/N.

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.