Influence of design and clinical factors on the removal force ratio in tapered implant-abutment interfaces.
BACKGROUND
A previous study investigated the effects of the preload and taper-angle mismatch in tapered implant systems on the removal force characteristics of the self-locking mechanism. The present study builds upon the previous one and introduces the effects of the time elapsed between insertion and removal and the presence of saliva in the implant-abutment interface as 2 new additional parameters.


OBJECTIVE
The purpose of this in vitro study was to elucidate the influences of design and clinical parameters on the removal force for implant systems that use tapered interference fit (TIF) type connections by measuring the force needed to remove an abutment from an implant.


METHODS
Ninety-six implants with tapered abutment-implant interfaces specifically built for an unreplicated factorial design were tested on a custom-built workbench for removal force. Four levels were chosen for the preload, FP, and the taper mismatch Δθ; 3 levels for the wait time t; and 2 levels for the saliva presence s at the interface. A regression model was used based on physical reasoning and a theoretical understanding of the interface. A 4-way ANOVA was used to evaluate the influence of the main effects and interactions (α=.05).


RESULTS
The experiments strongly indicated that preload, taper mismatch, and saliva presence are relevant variables in removal force. The wait time becomes important when its effect is evaluated along with the preload.


CONCLUSIONS
The results of this study can be used for decision making in the design and use of TIF type systems. The study supports the use of artificial saliva in any implant design experiment because of its significance in the removal force of the abutment.
Associate Professor, Department of Mechanical Engineering, School of Engineering at Bilbao, University of the Basque Country, Bilbao, Spain. Electronic address: josu.aguirrebeitia@ehu.es.
Josu
J
Aguirrebeitia
Lecturer, Department of Mechanical Engineering, School of Technical Engineering at Bilbao, University of the Basque Country, Bilbao, Spain.
Mikel
M
Abasolo
Professor, Department of Mechanical and Industrial Engineering, Snell Engineering Center, Northeastern University, Boston, Mass.
Sinan
S
Müftü
Associate Professor, Department of Mechanical Engineering, School of Engineering at Bilbao, University of the Basque Country, Bilbao, Spain.
Javier
J
Vallejo
D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D019094:Dental Prosthesis, Implant-Supported / Q000379:methods; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D006801:Humans; D012463:Saliva / Q000378:metabolism; D013314:Stress, Mechanical