Effect of varying the vertical dimension of connectors of cantilever cross-arch fixed dental prostheses in patients with severely reduced osseous support: a three-dimensional finite element analysis

Structural Integrity of Anterior Ceramic Resin-Bonded Fixed Partial Denture: A Finite Element Analysis Study

This study was conducted as a means to evaluate the stress distribution patterns of anterior ceramic resin-bonded fixed partial dentures derived from different materials and numerous connector designs that had various loading conditions imposed onto them through the utilization of the finite element method. A finite element model was established on the basis of the cone beam computed tomography image of a cantilevered resin-bonded fixed partial denture with a central incisor as an abutment and a lateral incisor as a pontic. Sixteen finite element models representing different conditions were simulated with lithium disilicate and zirconia. Connector height, width, and shape were set as the geometric parameters. Static loads of 100 N, 150 N, and 200 N were applied at 45 degrees to the pontic. The maximum equivalent stress values obtained for all finite element models were compared with the ultimate strengths of their materials. Higher load exhibited greater maximum equivalent stress in both materials, regardless of the connector width and shape. Loadings of 200 N and 150 N that were correspondingly simulated on lithium disilicate prostheses of all shapes and dimensions resulted in connector fractures. On the contrary, loadings of 200 N, 150 N, and 100 N with rectangular-shaped connectors correspondingly simulated on zirconia were able to withstand the loads. However, two of the trapezoidal-shaped zirconia connectors were unable to withstand the loads and resulted in fractures. It can be deduced that material type, shape, and connector dimensions concurrently influenced the integrity of the bridge.

Increased Stress Concentration in Prosthesis, Adhesive Cement, and Periodontal Tissue with Zirconia RBFDPs by the Reduced Alveolar Bone Height

PURPOSE

To investigate the risk of debonding of resin-bonded fixed dental prosthesis frameworks and the effects on the periodontal tissue in patients with reduced alveolar bone levels.

MATERIALS AND METHODS

The abutment teeth were the upper central incisor and the canine. Resin-bonded fixed dental prosthesis framework fabricated using zirconia was set to models with five different alveolar bone levels. A 200-N load (the maximum clenching force of the anterior teeth) was applied to the center of the pontic to analyze the internal stress on the framework, adhesive cement, and periodontal tissue using finite element analysis.

RESULTS

The mean maximum principal stress generated in the framework was 25.33 and 29.35 MPa in the models with the normal and the lowest alveolar bone level, respectively. Regarding shear stress on the adhesive cement, stress concentration was observed on the connector side in all models, and it increased on the cervical side of the central incisor as the alveolar bone level decreased. In addition, the mean maximum and minimum principal strains generated on the periodontal ligament of the central incisor and canine tended to increase as alveolar bone loss progressed. Furthermore, the mean maximum principal stress on the cortical bone was the greatest in the model with the most significant bone loss at 5.10 MPa.

CONCLUSIONS

This study suggested that the risk of debonding and periodontal tissue damage might be higher when resin-bonded fixed dental prosthesis frameworks were used in patients with reduced alveolar bone levels compared to those in a healthy state.

Effects of Prosthetic Material and Framework Design on Stress Distribution in Dental Implants and Peripheral Bone: A Three-Dimensional Finite Element Analysis

BACKGROUND The purpose of this study was to evaluate the effects of prosthetic material and framework design on the stress within dental implants and peripheral bone using finite element analysis (FEA). MATERIAL AND METHODS A mandibular implant-supported fixed dental prosthesis with different prosthetic materials [cobalt-chromium-supported ceramic (C), zirconia-supported ceramic (Z), and zirconia-reinforced polymethyl methacrylate (ZRPMMA)-supported resin (ZP)] and different connector widths (2, 3, and 4 mm) within the framework were used to evaluate stress via FEA under oblique loading conditions. Maximum principal (smax), minimum principal (smin), and von Mises (svM) stress values were obtained. RESULTS Minimum stress values were observed in the model with a 2-mm connector width for C and ZP. The models with 3-mm and 4-mm connector widths showed higher stress values than the model with a 2-mm connector width for C (48-50%) and ZP (50-52%). Similar stress values were observed in the 3- and 4-mm models. There was no significant difference in the amount of stress with Z regardless of connector width. The Z and ZP models showed similar stress values in the 3- and 4-mm models and higher stress values than in the C model. Z, ZP, and C showed the highest stress values for the model with a 2-mm connector width. CONCLUSIONS Changes in the material and width of connectors may influence stress on cortical bone, cancellous bone, and implants. C was associated with the lowest stress values. Higher maximum and minimum principal stress values were seen in cortical bone compared to cancellous bone.

Effect of proximal contact strength on the three-dimensional displacements of implant-supported cantilever fixed partial dentures under axial loading

OBJECTIVE

This study investigated the effect of proximal contact strength on the three-dimensional displacements of cantilever fixed partial denture (CFPD) under vertically concentrated loading with digital laser speckle (DLS) technique.

METHODS

Fresh mandible of beagle dog was used to establish the implant-supported CFPD for specimen. DLS technique was employed for measuring the three-dimensional displacement of the prosthesis under vertically concentrated loading ranging from 200 to 3000 g. The effect of the contact tightness on the displacement of CFPD was investigated by means of changing the contact tightness.

RESULTS

When an axial concentrated loading was exerted on the pontic of the implant-supported CFPD, the displacement of the CFPD was the greatest. The displacement of the prosthesis decreased with the increase of contact strength. When the contact strength was 0, 0.95, and 3.25 N, the displacement of the buccolingual direction was smaller than that of the mesiodistal direction but greater than that of the occlusogingival direction. When the force on the contact area was 6.50 N, the mesiodistal displacement of the prosthesis was the biggest while the buccolingual displacement was the smallest.

CONCLUSIONS

The implant-supported CFPD is an effective therapy for fully or partially edentulous patients. The restoration of the contact area and the selection of the appropriate contact strength can reduce the displacement of the CFPD, and get a better stress distribution. The most appropriate force value is 3.25 N in this study.