The stress distribution of a primary molar tooth restored with stainless steel crown using different luting cements.

BACKGROUND: The aim of this study is to evaluate the stress distributions of a primary molar tooth restored with a stainless steel crown (SSC) using resin and glass ionomer luting cements by Finite Element Analysis (FEA). METHODS: Original DICOM data of a primary molar was used to create a 3D model. One model was prepared as a tooth model with SSC. A 30 µm cement layer was used in model. Two different luting cements were tested in the study: self-cure adhesive resin cement, and glass ionomer cement. Vertical and oblique loads of 330 N were applied to simulate maximum bite force and lateral forces in the occlusal contact areas of the models. Maximum von Mises stress values in the models were evaluated as MPa. RESULTS: The maximum von Mises stress value was observed in the force application and general occlusal contact areas for all models. The maximum von Mises stress values were higher in the tooth model with SSC using self-cure adhesive resin cement (478.09 MPa and 214.62 MPa) than in the tooth model with SSC using glass ionomer cement (220.06 MPa and 198.72 MPa) in both vertical and oblique loading, respectively. CONCLUSIONS: Depending on the magnitude of the bite force on the SSC, fracture of the luting cement materials could occur if the stress exceeds the endurance limit of the luting cement. Cementation with glass ionomer cement may help to reduce stress levels in SSC restorations of primary molars in children.

A comparative study between zirconia and titanium abutments on the stress distribution in parafunctional loading: A 3D finite element analysis.

BACKGROUND: Zirconia has become a popular biomaterial in dental implant systems because of its biocompatible and aesthetic properties. However, this material is more fragile than titanium so its use is limited. OBJECTIVES: The aim of this study was to compare the stresses on morse taper implant systems under parafunctional loading in different abutment materials using three-dimensional finite element analysis (3D FEA). METHODS: Four different variations were modelled. The models were created according to abutment materials (zirconia or titanium) and loading (1000 MPa vertical or oblique on abutments). The placement of the implants (diameter, 5.0 × 15 mm) were mandibular right first molar. RESULTS: In zirconia abutment models, von Mises stress (VMS) values of implants and abutments were decreased. Maximum and minimum principal stresses and VMS values increased in oblique loading. VMS values were highest in the connection level of the conical abutments in all models. CONCLUSIONS: Using conical zirconia abutments decreases von Mises stress values in abutments and implants. However, these values may exceed the pathological limits in bruxism patients. Therefore, microfractures may be related to the level of the abutment.

Effect of arch wire size on orthodontic reverse closing loop and retraction force in canine tooth distalization : Three-dimensional finite element analysis.

AIM: The purpose of this study is to compare the effects of different wire size reverse closing loop and retraction forces in canine tooth distalization using the finite element analysis method. MATERIALS AND METHODS: Maxillary alveolar bone, maxillary first molar, second premolar and canine teeth were constructed in three dimensions along with their periodontal ligaments and standard edgewise brackets of 0.022 inch and stainless-steel reverse closing loop of 0.016â€¯× 0.022 inch and 0.019â€¯× 0.025 inch were designed. Force of 0.98 N and 1.96 N were applied to the arch wire from the posterior region of the molar tooth in the distal direction for activating the reverse closing loop. The stress distribution and displacement of the maxillary canine tooth were performed using the three-dimensional finite element analysis method. RESULTS: The maximum deformation on the canine tooth was higher in the x­, y­, and z­axes in both arch wires with 1.96 N force activation. Moreover, 1.96 N caused more stress on the canine tooth in both arch wires compared to the application of 0.98 N. In terms of von Mises stress distribution on alveolar bones, the amount of stress was higher during the application of 1.96 N than the application of 0.98 N. CONCLUSION: The finite element method is a reliable instrument which allows the effects of biomechanics applied in orthodontics to be evaluated. The finite element analysis method precisely predicted the mechanical effects of reverse closing loop of different wire sizes and different retraction forces.