NaOCl and etching acid effects on primary and permanent dentin

Objectives: The dentin quality (Inorganic and Organic contents) of primary and permanent pulp chamber was inspected by Fourier Transformed Raman Spectroscopy (FT-Raman) and Scanning Electron Microscopy (SEM). Slices of pulp chamber dentin were obtained from twenty human molars crowns (primary and permanent). Methods: The slices were assigned into 8 groups (n = 5): Primary Teeth: G1 – pulp chamber dentin; G2 – pulp chamber dentin irrigated with NaOCl 1% (30 min); G3 - pulp chamber dentin irrigated with NaOCl 1% (30 min) and etched by 35% phosphoric acid; G4 - pulp chamber dentin etched by 35% phosphoric acid. Permanent Teeth: G5 - pulp chamber dentin; G6 - pulp chamber dentin irrigated with NaOCl 1% (30 min); G7 - pulp chamber dentin irrigated with NaOCl 1% (30 min) and etched by 35% phosphoric acid; G8 - pulp chamber dentin etched by 35% phosphoric acid. The spectra were subjected to the Cluster Analysis. The SEM images were scored and evaluated in a descriptive way. Results: Inorganic Content: There was difference between primary and permanent dentin. The groups treated with NaOCl were statistically similar between them, differing from the groups not treated. Organic Content: There was no difference between primary and permanent dentin. The groups became totally mixed after NaOCl and phosphoric acid treatments. The microscopic images showed the presence of calcospherites on permanent dentin and their absence on primary dentin. Conclusions: The NaOCl changed the inorganic content in both dentitions; regardless the following phosphoric acid etching. However, the chemical changes caused by NaOCl were not detected by SEM when it was followed by etching.