In vivo force measurements on maxillary implants supporting a fixed prosthesis or an overdenture: a pilot study.
BACKGROUND
In this preliminary study, an attempt was made to measure in vivo forces simultaneously on 5 maxillary implants with different types of superstructure.


METHODS
Force measurements were carried out on 1 test patient with 5 ITI implants in the edentulous maxilla. A screw-retained fixed complete denture and an overdenture were fabricated for comparative measurements of forces. The overdenture could be mounted to 2 different types of bars. The measuring method was used with piezo-electric force transducers that were directly mounted onto the implants. This allowed for simultaneous measurements of forces in 3 dimensions, ie, in axial and transverse directions. Static and functional forces such as maximum biting (clenching), biting on a bite plate, and chewing food were registered. All measurements were repeated in the same way 2 years later.


RESULTS
The registered forces exhibited similar force patterns with both types of superstructure and both types of bars for overdenture connection. The force magnitudes were significantly different for the 3 dimensions (P<.05) with highest forces along the implant axis. On the posterior implants, force magnitudes were significantly higher (P<.05) than on the anterior implants in all 3 dimensions. On the anterior implants, under some test conditions, the transverse force components reached up to 100% of the axial force or even exceeded it during the chewing of food. During maximum biting, no upward force (tensile force) was found on any implant with the fixed complete denture, but upward force was found on one anterior implant with the overdenture. When chewing food, small force magnitudes in upward directions were regularly found with both superstructures. The force patterns between the first and second registrations showed similar trends, and no obvious differences were found.


CONCLUSIONS
From these results it was concluded that similar patterns of force transmission onto the implants are observed with a fixed complete denture and an overdenture connected to maxillary implants. The bar design did not significantly influence the force pattern.
Mericske-Stern
R
R
Department of Prosthodontics, School of Dental Medicine, University of Bern, Switzerland. regina.mericske@zmk.unibe.ch
Venetz
E
E
Fahrländer
F
F
Bürgin
W
W
D002138:Calibration; D003758:Dental Implantation, Endosseous / Q000706:statistics & numerical data; D017267:Dental Prosthesis Design / Q000706:statistics & numerical data; D019094:Dental Prosthesis, Implant-Supported / Q000706:statistics & numerical data; D003799:Dental Stress Analysis / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D003779:Denture Design / Q000706:statistics & numerical data; D003827:Denture, Complete, Upper / Q000706:statistics & numerical data; D003828:Denture, Overlay / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D008437:Maxilla; D008875:Middle Aged; D010865:Pilot Projects; D014159:Transducers