Photoelastic Stress in Mandibular Overdenture Retained by Two Implants

Objectives: The aim of this study was to verify the effect of occlusal and axial single loads in the photoelastic stress in overdenture retained by two implants placed in the anterior region of the mandible. Materials and Methods: Occlusal load (10, 20, and 30 kgf) was exerted by the conventional maxillary complete denture in occlusion with the overdenture adapted in the mandibular photoelastic model. Axial single load was also exerted on the first left or right molar of the overdenture. Qualitative analysis was made in polariscope images and quantitative analysis by the FRINGES program. Results: Qualitative analysis: The occlusal load showed similar stress in the region between the two implants. Axial single load induced in the first molars promoted stress in the implant apexes, and between the implant and mandible posterior region for the three loads. Quantitative analysis for occlusal load: 10 kgf (T = 265.03; N = 0.57); 20 kgf (T = 989.81; N = 2.11); 30 kgf (T = 1055.40; N = 2.26). Axial single load in the left molar: 10 kgf (T = 267.38; N = 0.57); 20 kgf (T = 270.07; N = 0.58) and 30 kgf (T = 281.84; N = 0.60). Axial single load in the right molar: 10 kgf (T = 952.14; N = 2.03); 20 kgf (T = 1038.58; N = 2.22); and 30 kgf (T = 926.92; N = 1.98). Conclusions: Different photoelastic stress levels occurred in the overdenture retained by two implants when submitted to occlusal or axial single load in the first left or right molar. Clinical Relevance: Artificial teeth intercuspation in the overdenture supported by two implants must have the same importance given to the vertical relationship to relieve the chewing effort.