Evaluation of Bonding to Root Caries Using Complementary Microscopic Techniques

Objective: Root caries is a growing, significant oral health problem in the United States. The purpose of this investigation was to evaluate bonding to caries-affected root surfaces using complementary microscopic techniques. Methods: Five extracted, single-rooted human teeth with root caries were prepared by removing the infected dentin. Five healthy teeth were prepared such that cavitations resembling root surface caries were made on the cervical third of the root. The prepared teeth were then treated with Single-Bond-Plus adhesive per manufacturer's instructions. After the adhesive was applied, the teeth were cut into two slabs. 5 micron sections were obtained from each slab for FTIR analysis and differential staining with Goldner's Trichrome. The remaining slabs were examined using micro-Raman mapping. Then the specimens were treated with 5N HCl (30s) and 5% NaOCl (30min), analyzed with SEM. Results: Staining revealed that the healthy specimens showed a uniform interface with a better adhesive-dentin connection, whereas the caries-affected specimens showed a non-uniform, rough interface with thick exposed collagen zone. The FTIR images showed that the caries-affected specimens had a larger demineralized layer and a wider area of demineralized dentin without adhesive penetration. These results were confirmed by the detailed micro-Raman mapping results. The SEM images showed that the healthy specimens contained a thicker acid-resistance hybrid layer and more resin tags compared to the caries-affected specimens, which suggests more penetration. Conclusion: The results indicated that forming a good adhesive/dentin interface in both healthy and caries-affected root surface substrates was difficult to achieve because of poor dental adhesive penetration. However the healthy root surface specimens had better adhesion than the caries-affected root surface specimens. Supported by NIH K25 DE015281, R03 DE15735