Influence of fixation mode and superstructure span upon strain development of implant fixed partial dentures.
OBJECTIVE
Implant-borne fixed partial dentures (FPDs) should fit passively in order to avoid complications ranging from screw loosening to loss of osseointegration. The aim of this study was to measure the strain development of three-unit and five-unit screw- and cement-retained implant-supported FPDs. Additionally, the influence of the parameters retention mechanism and FPD span were evaluated.


METHODS
Three Straumann implants were anchored in a measurement model based on a real-life patient situation and strain gauges (SGs) were fixed mesially and distally adjacent to the implants and on the pontics of the superstructures. During cement setting and screw fixation of 40 implant FPDs (10 samples from each group: three-unit cementable; five-unit cementable; three-unit screw-retained; five-unit screw-retained), strain development was recorded. For statistical analysis, multivariate two-sample tests were performed with the level of significance set at p= 0.1.


RESULTS
The mean strain values for the four FPD groups at the different SG sites ranged from 26.0 to 637.6 microm/m. When comparing the four groups, no significant differences in strain magnitude could be detected. Similarly, a comparison of the two FPD spans revealed no significant difference (p= 0.18 for cementable FPDs; p= 0.22 for screw-retained FPDs). A comparison of the two fixation modes also revealed no significant difference (p= 0.67 for three-unit FPDs; p= 0.25 for five-unit FPDs).


CONCLUSIONS
FPD span and retention mechanism appear to have only a minor influence on strain development in implant FPDs. As implant-supported restorations have proven to be successful over time, the question arises as to whether an "absolute" passive fit is a prerequisite for successful implant restorations.
Karl
Matthias
M
Department of Prosthodontics, School of Dental Medicine, University of Erlangen, Glueckstrasse 11, Nuremberg, Germany.
Wichmann
Manfred G
MG
Winter
Werner
W
Graef
Friedrich
F
Taylor
Thomas D
TD
Heckmann
Siegfried M
SM
D002484:Cementation / Q000379:methods; D003738:Dental Cements; D003758:Dental Implantation, Endosseous; D015921:Dental Implants; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods*; D003779:Denture Design; D003781:Denture Retention / Q000295:instrumentation / Q000379:methods*; D003830:Denture, Partial, Fixed; D006801:Humans; D017755:Prosthesis Fitting
D003738:Dental Cements; D015921:Dental Implants