Effect of different force magnitudes on the photoelastic stress in overdenture retained by two implants

Abstract

Aim: The aim of this study was to evaluate the photoelastic stress on mandibular overdenture retained by single implant when submitted to occlusal forces exerted by maxillary conventional denture in occlusion, or single axial force on first molars. Materials and Methods: Occlusal forces of 10, 20 and 30 kgf were exerted on the maxillary denture in occlusion with the mandibular overdenture adapted in the photoelastic model. Axial forces with same magnitudes were also individually exerted on the right and left first molars of the overdenture. Qualitative analysis were made in images obtained with polariscope, and quantitative analysis with the FRINGES program. Results: Qualitative analysis showed that the stress was located predominantly around the implant in all force magnitudes. Increase of occlusal force promoted higher stress on the implant. Increased axial single force on the left and right first molars caused higher stress on the medial region of the mandible body, and higher stress was induced in the side of loading. Quantitative analysis showed that the occlusal force promoted the following values: 10 kgf (T = 252.58; N = 0.54); 20 kgf (T = 1033.87; N = 2.21) and 30 kgf (T = 1009.99; N = 2.16); axial force on left molar promoted the following values: 10 kgf (T = 256.95; N = 0.55); 20 kgf (T = 265.07; N = 0.72) and 30 kgf (T = 266.38; N = 0.70); and axial force on right molar promoted the following values: 10 kgf (T = 986.11; N = 2.11); 20 kgf (T = 969.30; N = 2.07) and 30 kgf (T = 1012.68; N = 2.16). Conclusion: In conclusion, the stresses were concentrated at around the implant and in the medial region of the mandible body when the overdentures were submitted to occlusal forces; axial forces on the molars promoted stress at the implant and the mandible body in the side of loading, and the increase of the force promoted higher stress in both loading types.