Influence of Radiotherapy on Dentin Enzymatic Activity

Objectives: Head and neck cancer patients present high incidence of radiation-related caries and early restorations failures. Since dentin endogenous enzymes are involved in hybrid layer degradation, the aim of this study was to evaluate the dentin enzymatic activity of teeth that underwent in vivo radiotherapy using zymography assay.
Methods: Irradiated teeth were extracted for periodontal reasons 3 to 12 months after RT conclusion from patients who underwent clinical radiation protocols with a cumulative dose of radiation that ranged from 40 to 70 Gy after the approval by the Research Ethics Committee of the School of Dentistry at the University of São Paulo (protocol 1.946.959). Teeth from irradiated and non-irradiated groups were submitted to zymographic analysis and divided in two subgroups: 1) mineralized (control) or 2) demineralized with 10% phosphoric acid. Dentin proteins were extracted and submitted to zymographic analysis in accordance with Mazzoni et al., 2007.
Results: In vivo irradiated teeth showed stronger activity on the bands of the pro- and active form of MMP-9 regardless of dentin etching. Demineralized irradiated in vivo teeth presented stronger enzymatic activity when compared to all other groups.
Conclusions: Endogenous enzymatic activity seems to be more pronounced in irradiated teeth. Further studies are ongoing to confirm these findings and investigate the possible implications in the durability of the bonding to irradiated dentin in combination with different adhesive systems.