Influence of Implant Inclination and Prosthetic Abutment Type on the Biomechanics of Implant-Supported Fixed Partial Dentures
Obtaining parallelism during implant placement is often difficult, leading to inclination of implants. The present study evaluated the stress distribution in 3-unit fixed partial dentures supported by 2 implants with different inclinations and prosthetic abutments. Universal castable long abutments (UCLAs) or tapered abutments were used considering 17° of implant angulation in different directions (mesial, distal, buccal, or lingual). To do so, 3-dimensional finite element models were built and exported to specific analysis software. Forces were applied to the functional cusps. Data were obtained with regard to the maximum principal and von Mises stresses (in MPa). No relevant differences were observed in the stress values in the cortical and cancellous bone nor in the prosthesis with UCLA or tapered abutments. However, a relevant stress reduction in the prosthetic screws of the tilted implant was observed when using UCLA abutments. According to the obtained results, it is possible to suggest that both UCLA or tapered abutments can be used for 3-unit fixed partial dentures when 1 of the implants is tilted. UCLA abutment might lead to less biomechanical problems related to screw loosening or fracture.
Schematic representation of the different inclination adopted in the study. (a) Cross-section view of the models: tapered abutment (b) or universal castable long abutment (c).
Figure 2. Distribution of the von Mises stress in models with universal castable long abutment–type abutments and tapered abutments in parallel implants. Figure 3. Distribution of von Mises stresses in prosthesis and abutments made with (a) universal castable long abutment or (b) tapered abutments when the anterior implant was tilted 17° lingually. Note the higher stress concentration in the porcelain-framework interface in (a) and a more homogeneous dissipation along the entire prosthesis and the conical tapered abutments in (b). Figure 4. Maximum principal stress distribution, in MPa, in the peri-implant bone tissue in the situation that presented the highest stress concentration values (17° lingual) for both the universal castable long abutment and tapered abutment groups.
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