In vivo stress behavior in cemented and screw-retained five-unit implant FPDs.
OBJECTIVE
When fixing implant-supported fixed partial dentures (FPDs), it is important to achieve passive fit. The objective of the in vivo study presented was to quantify the strain development during the fixation of screw- and cement-retained FPDs.


METHODS
After informed patient consent had been obtained (Ethics commission Approval No. 2315; FAU Erlangen-Nuremberg, Germany), four groups of five-unit FPDs (five samples per group) were fabricated and investigated in vivo. Group 1: Cementable, repositioning technique impression, burn out plastic coping; Group 2: Screwable, pickup technique impression, burn out plastic coping; Group 3: Screwable, pickup technique impression, cast to gold cylinder; Group 4: Screwable, pickup technique impression, bonded to gold cylinder. Two strain gauges (SG) were attached to the pontics of each bridge (SG-M and SG-D) to measure the strains that occurred during either the cementing or screw-in process. The final values were recorded for analysis.


RESULTS
The mean strain values (microm/m) for each SG were: Group 1: SG-M 32 microm/m, SG-D: 89 microm/m; Group 2: SG-M 302 microm/m, SG-D: 197 microm/m; Group 3: SG-M 458 microm/m, SG-D: 268 microm/m; Group 4: SG-M 269 microm/m, SG-D: 52 microm/m.


CONCLUSIONS
Although the bridges were clinically acceptable, none of them revealed a truly passive fit with zero microstrain. In contrast to conventional screw-retained bridges, cement retention seems to result in lower strain levels. Bonding bridge pontics to prefabricated implant components seems to allow both the retrievability of a screw-retained bridge and produce moderate strain values.
Karl
Matthias
M
Department of Prosthodontics, School of Dental Medicine, University of Erlangen-Nuremberg, Glückstrasse 11, 91054 Erlangen, Germany.
Taylor
Thomas D
TD
Wichmann
Manfred G
MG
Heckmann
Siegfried M
SM
D000368:Aged; D002484:Cementation; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention / Q000295:instrumentation* / Q000379:methods*; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis; D003830:Denture, Partial, Fixed; D006801:Humans; D008297:Male; D017755:Prosthesis Fitting; D013314:Stress, Mechanical