In situ induced demineralization in irradiated and non-irradiated human dentin

The objective of this study was to evaluate the onset of initial demineralization in irradiated and non-irradiated human dentin. Dentin specimens were prepared from the cervical regions of 48 third molars. Either the lingual or the buccal dentin specimen of each tooth was irradiated fractionally up to 60 Gy (2 Gy/d, 5 d/wk). The remaining dentin sample was not irradiated. Two irradiated and two non-irradiated dentin specimens were inserted into both buccal aspects of each 12 intraoral mandibular appliances. The appliances were worn by 12 persons for 5 wk day and night. One side was brushed daily with a fluoride-free toothpaste. On the other side, plaque was allowed to grow. Individual oral hygiene techniques were performed without any fluorides. During meals, the appliance was stored in 10% sucrose solution. After the in situ period, slabs (150 microm) were ground and studied by means of transversal microradiography and microscopic techniques. Concerning mineral loss and lesion depth, ANOVA revealed significant differences between brushed and non-brushed specimens, whereas no differences between irradiated and non-irradiated dentin lesions were found. It is concluded that (in vitro) irradiated dentine is not more susceptible to caries than non-irradiated, if adequate oral hygiene techniques are implemented.