Differences between enamel and dentine: diffractometric spectroscopic and thermal analysis

OBJECTIVES: The aim of the study was to investigate the effect of fluoride ions on crystalline domains of human dentin and enamel.

METHODS: Ten coronal enamel samples and twenty root dentine fragments from healthy extracted third molars were used. Each fragment was grinded to produce a fine powder that was deproteinized by immersion in sodium hypochlorite solution (NaOCl 5%, Niclor 5, Ogna-Italy) for 8 days. The solution was then filtered in a millipore filter 0.8 ìm (Millipore Corporation, Bedford, MA, USA), dried at 37°C for 24 hours and split in two equal parts (controls and samples powders respectively). The samples were fluoridated by immersion for 7 days in sodium fluoride solution (NaF 1100 ppm) and then filtered and dried. Thermal (TG, ÄTG, DTA), diffractometric (XRD) and spectroscopic (FTIR) analyses were carried out on dental enamel and dentine powders.

RESULTS: Analysis showed two energetically different systems. The results depended on the defectiveness crystal lattice. The progress of thermal analysis curves showed presence of reactive sites either in the fluoridated samples and in the controls; fluoride-treated specimens showed a shifting to higher temperatures. Trend of weight loss (expressed as percentage) of mineral phase connected to the temperature variations confirmed greater stability of fluoride-treated enamel (-2.8%) compared to the untreated enamel (-3.0%), while a higher but not statistically significant weight loss occurred in both fluoridated dentine (-4.1%) and untreated dentine (-3.7%).

CONCLUSION: Analysis demonstrated that fluoride ions produce a crystal lattice stabilization of dental enamel. Fluoride-treated dentin showed small structural destabilizations caused by the nano-dimensional structure and were affected by higher weight loss.