Methods: An epoxy resin model simulating the mandibular jaw bone was made for the experimental test with a combination of acrylic resin replicas of the first premolar and second molar and threaded implants replacing the second premolar and first molar. Splinted (G1 and G3) and non-splinted (G2 and G4) metal-ceramic screw-retained crowns were fabricated and loaded with (G1 and G2) or without (G3 and G4) the presence of a second molar that provided proximal contact. A single-camera, 2-dimensional DIC system was used to record deformation of the resin model surface at a frequency of 1.0 Hz until the load reached 250 N. Corresponding 3-dimensional FE models were constructed using computer-aided design (CAD) software for both splinted and non-splinted crowns.
Results: Surface strains were used for comparison between the two methods, while internal strains at the implant/resin block interface were calculated using FEA. Both methods found similar regions of compression and tension, and both found insignificant differences in surface strains between the splinted and non-splinted groups (P>0.05). However, FEA gave higher strain values (P<0.05), possibly due to an underestimated elastic modulus for the epoxy resin. The internal strains predicted by FEA at the implant-resin interface were at least 12 times higher than those on the surface of the models, but differences between the groups were again insignificant (P>0.05).
Conclusions: Within the limitations of this study design, it can be concluded that DIC is a useful tool for validating finite element models, and FEA is effective in qualifying the bone strain induced by implants.
Keywords: Digital image analysis, Finite analysis, Implants, Implants and Prosthodontics