Effect of Implant Design and Thread Geometry on Stress Distribution in the Surrounding Bone-A Photoelastic Stress Analysis

Aim and objective: The aim of this study was to investigate the stress distribution observed in alveolar bone surrounding the dental implants of different designs and thread geometries. Materials and Methodology: Photoelastic models were fabricated using photoelastic resin and an implant was incorporated in each model. One such model had an implant with micro threads (dimensions 3.8 X 10.5 mm) whereas the other had buttress thread design (dimensions 3.8 X 10.5 mm). Respective abutments were connected to the implants by torquing the abutment to 25N cm. The models were positioned in a circular polariscope, and 450N of axial and oblique loads were applied on the abutments. The results were photographed and analyzed. Results: Implant with microthreads showed favorable stress distribution as compared to the implant with buttress thread design. Higher stresses were encountered in the apical region as compared to cervical region irrespective of the type of load and implant used. Oblique load generated highest stress in all the models as compared to axial load. Conclusion: It was concluded that the implant with microthread design showed a favorable stress distribution as compared to the implants with buttress thread design. Department of Prosthodontics, M.A.Rangoonwala College of Dental Sciences And Research Centre, Pune, India. 1Department of Oral Pathology and Microbiology, Dr. D. Y. Patil Vidyapeeth’s Dr.D. Y.Patil Dental College, Pimpri, Pune, India. Correspondence to: tabrezlakha@gmail.com Implant design and thread geometry 3 © 2016 Journal of Dental Research and Scientific Development | 2016 |Volume 3 |Issue 2 having morse taper connection by using photoelastic stress analysis. Material and Methods A stainless steel mould of (30 x 20 x 10 mm) was constructed to maintain standardization of the model fabrication. Each implant was held in place by a custom made stainless steel rod in the mould assembly (Figure 1). Separating medium i.e., silicone grease, was applied on all sides of the stainless steel components. Figure 1: Implant positioned in stainless steel mould Photoelastic resin (Pooja Polymers, Pune, India) was mixed as per manufacturer’s recommendations and was poured into the mould to obtain two blocks of 30 x 20 x 10 mm. One model had an implant with micro threads (Myriad Plus, Equinox Medical Technology, Amersfoort, NL) (Group1) whereas the other model had an implant with buttress thread design (Biohorizons Tapered Internal, Biohorizons Inc, Alabama, USA) (Group 2). Respective standard abutments were connected to the implants by torquing the abutment screws to 25N cm (Figure 2). The models were positioned in a circular polariscope, and 450N of axial and oblique (15) loads were applied on the abutments. Figure 2: Abutments connected to implants The results were recorded by a digital camera (Canon EOS 1200D, Canon Inc, Taiwan) and analyzed using a graphic software (Adobe Photoshop CC, Adobe Systems, San Jose, California) to allow visualization, comprehension, and interpretation of the localization and intensity/concentration of stress distributed surrounding the implants. Qualitative analysis was performed as suggested by Caputo and Standlee,[14] French et al,[11] Clelland et al[15], and Da Silva et al.[16] According to these authors, the number and the order of the fringes indicate stress intensity. Accordingly, the higher the fringe order (N) and number of fringes the greater the stress intensity. Similarly, principal stresses were calculated depending on the fringe order (N). All images were evaluated by the same person.