SECONDARY CARIES SUSCEPTIBILITY IN PROSTHODONTICS CORRELATED TO MARGINAL GAP

Introduction: Secondary caries of abutment teeth is an unwanted complication during prosthodontics treatment and the main reason for the replacement of FPD restorations. Marginal gap space in fixed restorations is responsible for micro-leakage and cement decomposition with caries appearance due to specific demineralization process by bacteria colonization. The aim of the study was to evaluate caries lesions in correlation to the crown marginal gap. Material and methods: Marginal gap between the abutment tooth and the crown was measured using a light-body silicone for evaluating of absolute discrepancy with replica technique (RT). Twenty porcelain fused to metal crowns were fabricated on ten premolars casts. Light body polyvinylsiloxane addition silicone impression material was used to fill the discrepancies between crown and tooth. After setting, impression material was removed from the die, and the thickness of the layer was measured and evaluated by electron microscopy. Results: The measurements of marginal fit were with mean marginal discrepancies in a range between 61.5 and 75.0 microns, mean marginal gaps in a range from 40.9 - 45.3 microns, mean vertical discrepancies in a range from 22.9 - 46.0 micron, and mean horizontal discrepancies in the range of 42.0 to 58.8 micron. Statistical data analysis was performed using a non-parametric test of Kruskal-Wallis and Mann-Whitney. Conclusion: Based on the selection of 100 microns as a limit of clinical acceptability, restoration margins were presented with increased risk for caries occurrence, even when the prostheses have an acceptable fit. However, in patients with proper oral hygiene and maintenance with regular follow-ups crown margin gap was not critical