INFLUENCE OF RADIATION DOSE IN COLLAGEN DEGRADATION, COLLAGEN-MMP IMMUNOEXPRESSION AND IMMEDIATE ADHESIVE PROPERTIES

Objective Radiation-related caries are a collateral effect of head and neck cancer radiotherapy, with rapidly progressive, asymptomatic, and ample lesions. The aim was to determine the alterations of collagen degradation, collagen IV, and MMP20 immunoexpression in the amelodentin junction and its influence on the immediate adhesive properties of enamel and dentin according to the radiation dose. Study Design Forty caries-free extracted third molars were divided into 8 groups according to radiation dose (0, 20, 40, and 70 Gy) for the experiments. Collagen degradation was measured with hydroxyproline test. The immunoexpression was performed with immunofluorescence confocal microscopic analysis. Immediate adhesive properties were measured according to μTBS and μSBS. Data from immunofluorescence was analyzed descriptively and adhesive properties were analyzed using 2-way analysis of variance and Tukeys test (α = .05). Results A progressive degradation of collagen was observed when the radiation dose is increasing. Decreasing levels of collagen IV and increasing MMP20 levels were also directly associated with the dose of radiation. When radiation doses were applied between 40 and 70 Gy, the adhesive values were significantly lower for both strategies in the 2 tests performed. Conclusion High doses of radiation above 40 Gy affect the collagen degradation, collagen-MMP immunoexpression, and immediate adhesive properties.