Photoelastic comparison of as-cast and laser-welded implant frameworks.
BACKGROUND
A misfit between the implant and metal framework can produce biomechanical problems.


OBJECTIVE
The purpose of this in vitro study was to evaluate the vertical misfit, passivity, and biomechanical behavior of a prosthetic protocol-shaped I-beam framework, varying the number and inclination of implants before and after laser welding.


METHODS
Two metal models with 4 or 5 implants were used. The I-beam framework for 4 or 5 implants was fabricated with cobalt-chromium alloy. The vertical misfit and passivity were evaluated with a stereomicroscope at ×80 magnification, with frameworks screwed into the respective model. The biomechanical behavior was analyzed with photoelastic studies. These analyses were performed before and after welding to observe the influence of the laser welding.


RESULTS
The misfit was not significantly different among the groups studied; laser welding did not influence the vertical misfit. However, when the groups were compared for passivity, the 5 implants before welding group were statistically different (P=.025).


CONCLUSIONS
Laser welding generated more passivity, less vertical misfit, and favorable stress distribution to the I-beam framework supported by 4 implants. To the I-beam framework supported by 5 implants laser welding did not influence the misfit or stress distribution, but there was an improvement in passivity.
Postgraduate student, Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Karina Albino
KA
Lencioni
Engineer, Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Ana Paula
AP
Macedo
Professor, Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Renata Cristina
RC
Silveira Rodrigues
Titular Professor, Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil.
Ricardo F
RF
Ribeiro
Associate Professor, Department of Dental Materials and Prosthodontics, Dental School of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil. Electronic address: rpaa@forp.usp.br.
Rossana P
RP
Almeida
D001696:Biomechanical Phenomena; D002858:Chromium Alloys / Q000737:chemistry / Q000528:radiation effects*; D015921:Dental Implants; D003764:Dental Materials / Q000737:chemistry / Q000528:radiation effects*; D007834:Lasers
D002858:Chromium Alloys; D015921:Dental Implants; D003764:Dental Materials