Finite Element Reconstruction of a Mandibular First Molar

Introduction: Mandibular first molar is the most important tooth with complicated morphology. In finite element (FE) studies, investigators usually prefer to model anterior teeth with a simple and single straight root; it makes the results deviate from the actual case. The most complicated and time-consuming step in FE studies is modeling of the desired tooth, thus this study was performed to establish a finite element method (FEM) of reconstructing a mandibular first molar with the greatest precision. Materials and Methods: An extracted mandibular first molar was digitized, and then radiographed from different aspects to achieve its outer and inner morphology. The solid model of tooth and root canals were constructed according to this data as well as the anatomy of mandibular first molar described in the literature. Result: A three-dimensional model of mandibular first molar was created, giving special consideration to shape and root canal system dimensions. Conclusion: This model may constitute a basis for investigating the effect of different clinical situations on mandibular first molars in vitro, especially on its root canal system. The method described here seems feasible and reasonably precise foundation for investigations

An Investigation of Three types of Tooth Implant Supported Fixed Prosthesis Designs with 3D Finite Element Analysis

Objective: Tooth/implant supported fixed prostheses may present biomechanical design problems, as the implant is rigidly anchored within the alveolus, whereas the tooth is attached by the periodontal ligament to the bone allowing movement. Many clinicians prefer tooth/implant supported fixed prosthesis designs with rigid connectors. However, there are some doubts about the effect of attachment placement in different prosthesis designs. The purpose of this study was to examine the stresses accumulated around the implant and natural teeth under occlusal forces using three dimensional finite element analysis (3D FEA).Materials and Methods: In this study, different connection designs of tooth/implant fixed prosthesis in distal extension situations were investigated by 3D FEA. Three models with various connection designs were studied; in the first model an implant rigidly connected to an abutment, in the second and third models an implant connected to abutment tooth with nonrigid connector in the distal part of the tooth and mesial part of the implant. In each model, a screw type implant (5×11mm) and a mandibular second premolar were used. The stress values of these models loaded with vertical forces (250N) were analyzed.Results: There was no difference in stress distribution around the bone support of the implant. Maximum stress values were observed at the crestal bone of the implant. In all models, tooth movement was higher than implant movement.Conclusion: There is no difference in using a rigid connector, non rigid connector in the distal surface of the tooth or in the mesial surface of an implant

Biomechanical Effects of Platform Switching in Two Different Implant Systems: A Three-Dimensional Finite Element Analysis

Aims: The purpose of this study was to determine the influence of platform switching on stress distribution of two different implant systems, using three-dimensional (3D) finite element models.Methods: Six 3D finite element models were created to replicate two different implant systems with peri-implant bone tissue, in which six different implant-abutment configurations were represented: model XiVE-a: 3.8-mm-diameter implant and 3.8-mm-diameter abutment; model XiVE-b (platform-switching model): 4.5-mm-diameter implant and 3.8-mm-diameter abutment; model XiVE-c: 4.5-mm-diameter implant and 4.5-mm-diameter abutment; model 3i-a: 4.0-mm-diameter implant and 4.1-mm-diameter abutment; model 3i-b (platform-switching model): 5.0-mm-diameter implant and 4.1-mm-diameter abutment; model 3i-c: 5.0-mm-diameter implant and 5.0-mm-diameter abutment. Axial and oblique loads of 100 were applied to all models.Results: While the pattern of stress distribution was similar for both loading situations, oblique loading resulted in higher intensity and greater distribution of stress than axial loading in both cortical bone and abutment-implant interface. Stress distribution at peri-implant bone was almost identical with similar magnitudes for all six models. In both implant systems, platform switching models demonstrated lower maximum von Mises stress in cortical bone than conventional models. However, in both implant systems and under both loading situation, platform switching models showed higher stresses at the abutment-implant interface than conventional models.Conclusion: In both implant systems, platform switching design reduced the stress concentration in the crestal bone and shifted it towards the area of implant-abutment interfac

8186266913Determination of Incisal Point as Anterior Guide to Transfer Maxillary Casts to Articulator: A Pilot Study

Objectives Despite the importance to use face-bow record for transferring maxillary cast to articulator some dentists use average points to avoid the time taken and ease of use. The location of incisal point could help to set the maxillary cast or denture in an appropriate position in mounting stage. This study was designed to determine the incisal point location in antero-posterior and vertical dimensions in different facial forms and genders.Methods Dental casts were obtained from the maxillary jaw of 44 dental students (male and female) and subsequently transferred to the articulator using an ear bow. The three dimensional location of the incisal point in relation to condylar axis was determined using a Coordinated Measuring Machine (CMM).Collected data were compared between male and female participants as well as those of oval, squared and tapered faces. For data analysis Student t test was employed to make the comparisons.Results The mean distance between the incisal point and the center of the condylar axis in antero-posterior and vertical dimensions was 81.28 mm and 42.85 mm respectively. The mean antero-posterior distance was significantly higher among male students (Ρ<0.05). The mean vertical dimensions did not show any significant difference between male and female students (P>0.05). In square facial form, the mean antero-posterior distance was significantly higher compared to the ovoid facial form (P<0.05).Conclusion The differences on incisal points were significant between the two genders only in antero-posterior dimension. A similar finding was noted on square facial form when compared to ovoid facial form.  The incisal point was more consistent with the Frankfurt mounting platform compare to Bonwill index

Distraction osteogenesis for cleft palate closure: A finite element analysis

Background: Current methods of closure of the cleft palate result in the formation of scars and impairment of growth. Distraction osteogenesis (DO) might be an effective means to repair or at least reduce the size of wide clefts. This study investigates the biomechanical aspects of this process. Materials and Methods: DO simulation was applied to reduce the size of a unilateral hard palate cleft on a three-dimensional (3D) model of the maxilla. For the position of osteotomy lines, two different models were assumed, with the osteotomy line on the affected side in model A and on the intact side in model B. In each model, DO screws were placed on two different positions, anteriorly (models A1 and B1) and posteriorly (models A2 and B2). Displacement pattern of the bony island in each of the four models, reaction forces at DO locations, and von Mises stress were estimated. Mesh generation and data processing were carried out in the 3D finite element analysis package (ABAQUS V6.7-1; Simulia Corp., Providence, RI, USA). Results: In model B2, the island moved almost evenly, assuring a more complete closure of the cleft. The most uniform stress distribution was found in model B1. Conclusion: The results suggest that the best positions for the DO screw and the osteotomy line for closure of the cleft palate are posteriorly and on the intact side, respectively