Marginal fit and photoelastic stress analysis of CAD-CAM and overcast 3-unit implant-supported frameworks.

Anna Gabriella Camacho Presotto, Cláudia Lopes Brilhante Bhering, Marcelo Ferraz Mesquita, Valentim Adelino Ricardo Barão

Journal: The Journal of prosthetic dentistry 2018;117(3):373-379

PMID: 27666497

Full Text on Elsevier Science View on PubMed

Abstract

STATEMENT OF PROBLEM

Several studies have shown the superiority of computer-assisted design and computer-assisted manufacturing (CAD-CAM) technology compared with conventional casting. However, an advanced technology exists for casting procedures (the overcasting technique), which may serve as an acceptable and affordable alternative to CAD-CAM technology for fabricating 3-unit implant-supported fixed dental prostheses (FDPs).

PURPOSE

The purpose of this in vitro study was to evaluate, using quantitative photoelastic analysis, the effect of the prosthetic framework fabrication method (CAD-CAM and overcasting) on the marginal fit and stress transmitted to implants. The correlation between marginal fit and stress was also investigated.

MATERIAL AND METHODS

Three-unit implant-supported FDP frameworks were made using the CAD-CAM (n=10) and overcasting (n=10) methods. The frameworks were waxed to simulate a mandibular first premolar (PM region) to first molar (M region) FDP using overcast mini-abutment cylinders. The wax patterns were overcast (overcast experimental group) or scanned to obtain the frameworks (CAD-CAM control group). All frameworks were fabricated from cobalt-chromium (CoCr) alloy. The marginal fit was analyzed according to the single-screw test protocol, obtaining an average value for each region (M and PM) and each framework. The frameworks were tightened for the photoelastic model with standardized 10-Ncm torque. Stress was measured by quantitative photoelastic analysis. The results were submitted to the Student t test, 2-way ANOVA, and Pearson correlation test (α=.05).

RESULTS

The framework fabrication method (FM) and evaluation site (ES; M and PM regions) did not affect the marginal fit values (P=.559 for FM and P=.065 for ES) and stress (P=.685 for FM and P=.468 for ES) in the implant-supported system. Positive correlations between marginal fit and stress were observed (CAD-CAM: r=0.922; P<.001; overcast: r=0.908; P<.001).

CONCLUSIONS

CAD-CAM and overcasting methods present similar marginal fit and stress values for 3-unit FDP frameworks. The decreased marginal fit of frameworks induces greater stress in the implant-supported system.

Address: Doctoral student, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas, Sao Paulo, Brazil.; Assistant Professor, Department of Restorative Dentistry, School of Dentistry, Federal University of Minas Gerais, Minas Gerais, Brazil; and Associate Professor, School of Dentistry, Newton Paiva University Center, Minas Gerais, Brazil.; Professor, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas, Sao Paulo, Brazil.; Assistant Professor, Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas, Sao Paulo, Brazil. Electronic address: [email protected].

DOI: 10.1016/j.prosdent.2016.06.011