Nanoindentation and Raman Spectroscopy Measurements on Root Canal Treatment

Dental restoration treatments are increasingly reliable, with natural teeth often outlasting implants when properly treated. However, the longevity of root canal-treated teeth remains challenged by radicular fractures often linked to changes in dentin. Despite extensive studies, the mechanisms underlying dentin fragility and its progression over time are not fully understood. This study investigates the chemical and mechanical properties of freshly treated (RCT) and long-term root canal-treated and re-treated (RCR-T) dentin by employing a combined nanoindentation and Raman spectroscopy measurement approach, offering a framework to address critical challenges in dental practice. For this in vitro analysis, anterior teeth from patients aged 45-55 were selected and categorized as either vital or aged (≥ 15 years) endodontically treated. Nanoindentation measured Young's modulus and hardness of the root canal, revealing that freshly treated dentin exhibited significantly higher mechanical properties than aged dentin. Complementary Raman spectroscopy analysis assessed mineral-collagen ratios, collagen structure, crystallinity, and carbonate/phosphate ratios. Raman spectroscopy highlighted significant chemical changes, including increased carbonate-phosphate ratios and reduced collagen quality in RCR-T dentin. This measurement-driven approach proved to offer valuable insights for advancing restorative dentistry and improving patient care. In particular, the consistent findings from both mechanical and chemical analyses highlighted that endodontic treatment and aging contribute to structural degradation through altered mineral composition and collagen organization, weakening the dentin substrate and potentially compromising its durability. This integrated measurement approach effectively provided a comprehensive understanding of age-related dentin changes and their implications for adhesive performance.