Fixation of 5-unit implant-supported fixed partial dentures and resulting bone loading: a finite element assessment based on in vivo strain measurements.
OBJECTIVE
It is believed that implant-supported fixed partial dentures (FPDs) should display passive fit. The objective of this in vivo-based finite element analysis (FEA) was to quantify the magnitude of bone loading occurring on account of the fixation of cemented or screw-retained 5-unit superstructures.


METHODS
Based on a patient situation with 3 implants, 4 different groups of restorations with 10 samples each were fabricated. Strain gauges on the pontics of the restorations were used for in vivo measurements. Using the values obtained, bone loading in 3-dimensional FE models was simulated as von Mises equivalent stress.


RESULTS
The in vivo measured mean strain values ranged from 32 microm/m to 458 microm/m at the different sites. FEA revealed stresses between 5 and 30 MPa in the cortical area, while in trabecular bone values ranging from 2 MPa to 5 MPa were observed. Stress of a similar magnitude was found for axial implant loading with 200 N.


CONCLUSIONS
Assuming that the axial loading of a single implant with 200 N is within the realm of the bone's adaptation ability, it would appear that the amount of stress resulting from the fixation of superstructures alone does not constitute a risk.


CONCLUSIONS
The level of precision of fit which can be obtained in superstructure fabrication would appear to suffice to produce restorations that do not cause bone damage.
Karl
Matthias
M
Department of Prosthodontics, School of Dental Medicine, University of Erlangen-Nuremberg, Germany.
Winter
Werner
W
Taylor
Thomas D
TD
Heckmann
Siegfried M
SM
D001732:Bite Force; D002484:Cementation; D003758:Dental Implantation, Endosseous; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods*; D003781:Denture Retention / Q000295:instrumentation / Q000379:methods*; D003830:Denture, Partial, Fixed; D020342:Finite Element Analysis; D006801:Humans; D013314:Stress, Mechanical