Deformation at the implant interface to prosthetic superstructure: an interferometric approach

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.

Clinical and radiographic outcome of dental implants supporting fixed prostheses: the relevance of cortical bone formation

PURPOSE

To evaluate the hard and the soft tissue parameters around implants supporting fixed prostheses over a period of 5 years and the possible association to the increase in periimplant bone density (IPBD).

MATERIAL AND METHODS

A total of 39 dental implants placed in 29 patients were included in the study. Periimplant clinical (gingival index, probing depth, keratinized mucosa, sulcus fluid flow rate) and radiographic variables (bone loss, bone density) were collected, and the data analysis performed.

RESULTS

Periimplant hard and soft tissue parameters remained stable throughout the follow-up period. Of the 39 implants, 20 demonstrated IPBD. The mean distance between first bone-to-implant contact and the microgap for implants with and without IPBD was significantly different at 1-year, 2-year, and 5-year follow-up. The evidence of IPBD demonstrated no influence on the periimplant soft tissue parameters. All mean values of bone density for implants with IPBD were higher than those for implants without IPBD throughout the whole observation period.

CONCLUSION

All implants were clinically successful over the period of follow-up. IPBD might be more indicative of a stable periimplant bone level.

Deflections of an implant-supported cantilever beam subjected to vertically directed loads: in vitro measurements in three dimensions using an optoelectronic method. I. Experimental set-up

AIM

The aim of this in vitro study was to develop and test an experimental set-up consisting of a video camera and computer-based optoelectronic motion analysis system, synchronized with a loading device, for studying load-dependent deflections in three dimensions of single implant-supported cantilever beams.

MATERIAL AND METHODS

One Brånemark System implant was tightly screwed into a steel plate so that the entire implant became submerged. An abutment was attached to the implant and a cast 22-mm-long cantilever gold alloy beam incorporating a prefabricated gold cylinder was attached to the abutment with a prosthetic gold screw. A force transducer was glued on the upper surface of the beam end with its centre 19.4 mm from the centre of the implant abutment gold cylinder unit to register the applied load. A specially designed loading device was used to apply increasing vertical loads of the beam end via the transducer. The motion analysis system was synchronized with the transducer to enable measurements of three-dimensional positional changes of the beam end related to known loads.

RESULTS

Vertical loads from 15.7 to 40.4 N were applied resulting in vertical positional changes of the beam end ranging from 40.8 to 225.2 μm (z-axis). The corresponding horizontal changes perpendicular to the long axis of the beam (y-axis) due to counterclockwise horizontal rotation of the beam around the abutment- and prosthetic cylinder threads varied from 7.4 to 77.4 μm. This rotation changed the position of the beam end from 11.9 to 49.3 μm along the x-axis of the coordinate system toward the supporting implant.

CONCLUSION

It was possible to arrange an experimental set-up for optoelectronic 3-D measurements within such a limited measurement volume that would permit satisfactory registrations of small load-dependent deflections of the prosthetic beam and implant components.