Straight and offset implant placement under axial and nonaxial loads in implant-supported prostheses: strain gauge analysis.
OBJECTIVE
The aim of this in vitro study was to quantify strain development during axial and nonaxial loading using strain gauge analysis for three-element implant-supported FPDs, varying the arrangement of implants: straight line (L) and offset (O).


METHODS
Three Morse taper implants arranged in a straight line and three implants arranged in an offset configuration were inserted into two polyurethane blocks. Microunit abutments were screwed onto the implants, applying a 20 Ncm torque. Plastic copings were screwed onto the abutments, which received standard wax patterns cast in Co-Cr alloy (n = 10). Four strain gauges were bonded onto the surface of each block tangential to the implants. The occlusal screws of the superstructure were tightened onto microunit abutments using 10 Ncm and then axial and nonaxial loading of 30 Kg was applied for 10 seconds on the center of each implant and at 1 and 2 mm from the implants, totaling nine load application points. The microdeformations determined at the nine points were recorded by four strain gauges, and the same procedure was performed for all of the frameworks. Three loadings were made per load application point. The magnitude of microstrain on each strain gauge was recorded in units of microstrain (με). The data were analyzed statistically by two-way ANOVA and Tukey's test (p < 0.05).


RESULTS
The configuration factor was statistically significant (p= 0.0004), but the load factor (p= 0.2420) and the interaction between the two factors were not significant (p= 0.5494). Tukey's test revealed differences between axial offset (με) (183.2 ± 93.64) and axial straight line (285.3 ± 61.04) and differences between nonaxial 1 mm offset (201.0 ± 50.24) and nonaxial 1 mm straight line (315.8 ± 59.28).


CONCLUSIONS
There was evidence that offset placement is capable of reducing the strain around an implant. In addition, the type of loading, axial force or nonaxial, did not have an influence until 2 mm.
Department of Prosthodontics and Periodontology, Piracicaba School of Dentistry, UNICAMP, Piracicaba, Brazil. celwanderley@hotmail.com
Celina Wanderley
CW
Abreu
Renato Sussumu
RS
Nishioka
Ivan
I
Balducci
Rafael Leonardo Xediek
RL
Consani
D000539:Alveolar Process / Q000502:physiology; D002858:Chromium Alloys; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D003799:Dental Stress Analysis / Q000379:methods; D003830:Denture, Partial, Fixed; D006801:Humans; D013314:Stress, Mechanical; D016474:Weight-Bearing
D002858:Chromium Alloys; D015921:Dental Implants