PHOTOELASTIC STRESS IN MANDIBULAR OVERDENTURE RETAINED BY FOUR IMPLANTS

Aim: This study verified the photoelastic stress in mandibular overdenture retained by four implants. Materials and Methods: Four implants were placed in the anterior region of the mandibular photoelastic model at 12mm distance among them. Occlusal load with intensities of 10, 20 or 30 kgf were exerted in the mandibular photoelastic model by the maxillary complete denture in maximum intercuspation. Axial single loads with same intensities were also exerted on the first left or right molar of the overdenture. Qualitative analysis was made using polariscope and quantitative analysis with images obtained by the FRINGES program. Results: Qualitative analysis: Occlusal force, similar stress between the central implants and in the posterior region of the model that increased with the force increase (Anterior view). Stress in the apex of the distal implant and in the posterior region of the model that increased with the force increase (Left view). Stress between the right implants, in the apex of the distal implant and in the posterior region of the model that increased with the force increase (Right view). Quantitative analysis for occlusal load: 10 kgf (T=230.05; N=0.49); 20 kgf (T=1057.75; N=2.26); 30 kgf (T=1105.17; N=2.36). Axial single force in the first left molar: 10 kgf (T=870.08; N=1.68); 20 kgf (T= 886.67; N=1.88); 30 kgf (T=919.86; N=1.97). Axial single force in the first right molar: 10 kgf (T=975.19; N=2.05); 20 kgf (T=998.22; N=2.13); 30 kgf (T=1016.38; N=2.17). Conclusion: The stress on overdentures retained by four implants were differently influenced by the different force types and load intensities.