Prosthetic laboratory influence on the vertical misfit at the implant/UCLA abutment interface

Abstract

An inadequate fit at the abutment/implant interface can generate mechanical and biological problems. The laboratorial stages could induce misfit in such interface when the castable UCLA abutment type is used. The purpose of this study was to comparatively evaluate the performance of three prosthetic laboratories (Labs A, B and C) by vertical fit analysis of castable UCLA abutments on the casting and soldering stages of the same prosthesis. Four fixed prostheses were built by each laboratory using castable UCLA abutments. The evaluation was made by scanning electron microscopy under 500x magnification in the mesial and distal regions of each element of the prosthesis, totalizing 24 measurements per laboratory. The results were analyzed statistically by Kruskal-Wallis test (p<0.05). In the casting process, the values presented by the laboratories differed significantly to each other (p=0.004). After soldering, the values presented by the laboratories showed no significant difference (p=0.948). It may be concluded that the fit values obtained in the casting stage of UCLA abutments can be influenced when processed by different laboratories, and that conventional soldering itself increased the degree of framework misfit, regardless of which laboratory made it.

Effect of retorque on loosening torque of prosthetic screws under two levels of fit of implant-supported dentures

“…The forces created within the screw joints in the passive state are the clamping forces and preload only (13). Multi-unit implant-supported dentures do not present a perfect fit (14), thus residual static stresses are created and their magnitude depends on the misfit amplitude (15), suggesting that these residual static stresses could change the behavior of the screw joint stability of multiple-unit when compared with simpleunit implant dentures. There is very limited information about the effects of retightening some time after settling of the prosthetic screws on the joint stability in multiunit dentures.…”

Stress Analysis in Maxillary All-On-Four Model

“…The great advantage of the photoelastic models lies in that they provide us the location and pattern of the stresses (Barbosa et al, 2007), whereas the great disadvantages of this model are the homogeneity and the isotropicity of the material, completely different when compared to peri-implant tissues, which present different moduli of elasticity according to the region, whether soft tissue or bone tissue (Begg et al, 2009). Nevertheless, it is an adequate method of comparison that isolates multiple variables in terms of patients with total rehabilitation on implants.…”

External Hexagon Deformation in Implants Subjected to Internal Torque

“…The greatest changes were observed in the S60 (1.69%, 0.110 mm 2 ) and S∞ models (2.12%, 0.138 mm 2 ), exceeding the 0.1 mm 2 value, and hence hindering the EH/prosthetic abutment junction (7). The higher values of hexagon deformation for S group may be related to the morphology of the inner portion of the implant, where the connection key adapts.…”

“…Although these implants have been the most frequently performed, fatigue or overload failures such as deformation of the hexagon may occur during surgical placement of the implants, due to their different manufacturing tolerances. Higher insertion torque values reduce the risk of implant micromovements at the bone-implant interface, thereby obtaining higher rates of success of immediately loaded implants (6,7). On the other hand, implants can undergo morphological changes during torsion when inserted into bone (8).…”