Stress Analysis of Implant-Supported Removable Partial Denture with Anterior Fixed Prostheses and Conventional Implant-Supported Overdentures in the Edentulous Mandible

Aim: To compare new design implant-supported removable partial dentures retained with anterior fixed prosthesis with a conventional locater and bar attached implant overdenture prostheses retained by two or four implants via photoelastic stress analysis. Materials and Methods: Seven edentulous mandibuler acryclic models prepared and divided into two main groups; two to four implant models, subgroup separation as stated; for two implant models overdenture with locator attachment, crown design retained removable prosthesis with clasp retention, bridge design retained removable prosthesis with clasp retention, bridge design retained removable prosthesis with precision attachment retention; and for four implant models prosthesis with bar attachment overdenture, fixed bridge design retained removable prosthesis with clasp retention, fixed retained removable prosthesis with precision attachment retention. A 300 N load was applied to the first premolars. Photoelastic stress analysis method that is a specific method concerning stress visualization, and does not require statistical analysis, was used. The stress distributions were seen in optically using a poloriscope. Results: In the models with two implant-retained removable partial dentures, the stress distribution was found to be lower than that with the four implant-retained removable partial dentures. Nonsplinted implants caused high stress around the distal implant on the loading side. Conclusion: The stress loads were transmitted to other implants by splinting. Implant-supported removable partial dentures with an anterior fixed prosthetic design show lower stress distributions compared with bar retained prosthesis. These dentures appear to be advantageous in terms of stress transmission.

Photoelastic Stress Response of Complex 3D-Printed Particle Shapes

Stress visualization within 3-dimensional particles undergoing dynamic processes can greatly advance our understanding of complex particle behaviors. Traditional photoelastic stress visualization methods suffer inherent limitations from lack of available technology for complex particle production. Recently, 3D-printing has created new possibilities for enhancing the scope of stress analysis within physically representative granules. Here, we investigate opportunities offered by 3D-printing a granular material with photoelastic properties. We report the results of X-ray computed tomography and 3D-printing, combined with traditional photoelastic analysis, to visualize strain exhibited within simple discs to reproduced coffee beans. We find that the choice of print layer orientation with respect to the force load affects the optical properties of the discs, without a significant difference in their mechanical properties. Furthermore, we present a first, semi-quantified, measurement of stresses within 3D-printed particles of complex shape. The promising data shows potential for applying this method to complex assemblies of 3-dimensional particles.

Effect of mucosa thicknesses on stress distribution of implant-supported overdentures under unilateral loading: Photoelastic analysis

Introduction: The aim of this study was to evaluate the effect of different heights of attachment and mucosa thicknesses on the stress distribution of two implant-retained mandibular overdenture designs under loading using the photoelastic stress analysis method. Materials and methods: Six photoelastic models of an edentulous mandibula were fabricated with two solitary implants that were placed in the canine regions. The attachment systems studied were ball and locator stud attachments. Both the ball and locator groups included three models that had different residual ridge heights so as to provide different mucosa thicknesses (1 mm–1 mm, 1 mm–2 mm, 1 mm–4 mm). A static vertical force of 135 N was applied unilaterally (each on the right then the left side) to the central fossa of the first molars. Models were positioned in the field of a circular polariscope to observe the distribution of isochromatic fringes around the implants and the interimplant areas under loading. The photoelastic stress fringes were monitored and recorded photographically. Results: The ball attachment groups showed higher stress values than did the locator groups under loading. Both attachment systems produced the lowest stress values in stimulated 1 mm–1 mm mucosa thickness models. The models with 1 mm–2 mm mucosa thicknesses showed higher stress values than did other models for both attachment systems. The highest stress value observed around both attachment systems was the moderate level in all test models. Conclusion: In different height mucosa thicknesses, locator attachment models distributed the load to the other side of the implant and its surrounding tissue, whereas the ball attachment did not. Regardless of mucosal thickness and attachment type, the implant on the loading side was subjected to the highest stress concentration.