Objective: The objective of this study was to evaluate which bar material (BioHPP or Cobalt Chromium) induced less stresses on the supporting structures of implant retained mandibular overdenture
Materials and methods: Completely edentulous mandibular educational cast was scanned. Designing an STL file including; implants beds, mucosal space and vertical slots for strain gauges was done. A bar joint design was selected & STL files were transferred to 5-axis milling machine to mill bars as follow: group I: Six bars were milled from BioHPP blank, group II: Six bars were milled from cobalt chromium blank. For each model, four strain gauge sensors were placed and a universal testing machine were used to apply a static load of 100N bilaterally between lower second premolar and first molar then unilaterally on the right side. The mean and the standard deviation of the recorded readings were collected, tabulated, and statistically analyzed.
Results: The result of this study showed no significant difference between the two groups regarding bilateral loading as the mean micro strain was 314.83 &313.5 μm/m for group I & II respectively.Under unilateral loading, the results showed that the mean micro strain in the loaded side was 495.16 &493.83 μm/m for group I & II respectively and the result was statistically non-significant
Conclusion: Within the limitations of this study, it could be concluded that:
-BioHPP and Cobalt-Chromium milled bars have no differences regarding micro strains developed in the supporting structures either upon bilateral or unilateral loading in implant retained mandibular overdenture.