Molecular analysis of primary dentin after different chemical treatments : Chemical, mechanical and morphological studies / Identificação molecular da dentina decidua em diferentes tratamentos quimicos : analise quimica, micro-mecanica e morfologica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Theoretically, it is supposed to have lower degree of mineralization for primary dentin compared with permanent one could lead different behavior of this substrate after contact with deproteinizating/demineralizating solutions, followed by composite restorations. The aim of this study was provide scientific informations at chemical, mechanical and morphological levels regarding the quality of inorganic and organic content of primary dentin compared to permanent one, as well as after deproteinizating/demineralizating solutions action. In order to facilitate the accomplishment of this thesis, it was divided into two phases, as described on the following descriptions: Study 1: To recognize the primary dentin compared to permanent dentin in the middle of crown, with or without 35% phosphoric acid total etching. The analyses were: Fourier Transformed Raman Spectroscopy (FT-Raman); Scanning Electron Microscopy/Energy-Dispersive Spectroscopy (EDS/SEM) and Hardness Micromechanical Test, related to molecular and micro-mechanical areas. Ten human molars, 5 primary and 5 permanent, were abrading with carbide bur until reach the middle dentin simultaneously to smear layer production. Four parts per tooth were obtained, half designed to FT-Raman spectroscopy and half to hardness test. The studied groups were (n=10): G1 (primary dentin smear layer); G2 (35% phosphoric acid etched primary dentin); G3 (permanent dentin smear layer); G4 (35% phosphoric acid etched permanent dentin). Result spectros from chemical analysis were subject to Cluster analysis based on identified principal components. The EDS/SEM analysis was done in order to add the FT-Raman data. To hardness test, 5 specimens were included, polished, cleaned, and etching (G2, G4) before the test. Five indentations were recorded to each specimen under middle dentin surface with 100 µm of distance each others beginning with 50 µm apart from JAD. A mean was calculated by each group and these values were recorded. The results were subjected to ANOVA and Tukey test. FT-Raman analysis showed difference among groups. Inorganic content: G3 was the most different, followed by G4, while G1 and G2 were the most similar to each other. EDS/SEM identified the C, O, P, Ca and Zn chemical elements in dentin. Organic content: G2 was the most different of all groups, followed by G4, while G1 and G3 were the most similar. There were no difference of hardness between G1 vs G3 and G2 vs G4 (p>0.05), however, there were difference between G1 vs G2 and G3 vs G4 (p<0.05). Study 2: FT-Raman and SEM were used to evaluate chemically and morphologically the coronary dentin of pulp chamber laterals walls after 1% NaOCl action followed by 35% phosphoric acid total etching. The aim of this study was to simulate the changes that can occur in endodontically treated teeth with type class I cavity restored with composite and total etching adhesive systems. Twenty human molars, 10 primary and 10 permanent, were sectioned mesio-distally paralleled to long axis of teeth. Two parts of dentin pulp chamber, buccal and lingual lateral walls, were obtained from each tooth, providing 20 parts to primary as well as to permanent teeth, followed by division into groups (n = 5): Primary teeth (Groups 1, 2, 3 and 4); permanent teeth (groups 5, 6, 7 and 8) : G1 and G5 ? pulp chamber dentin ; G2 and G6 ? pulp chamber dentin irrigated with 1% NaOCl (30 min); G3 e G7 - pulp chamber dentin irrigated with 1% NaOCl (30 min) and etched by 35% phosphoric acid; G4 e G8 - pulp chamber dentin etched by 35% phosphoric acid. After FT-Raman analysis, all specimens were prepared and evaluated by SEM. The morphological changes were classified according a score. Results: Inorganic content: There was a clear difference between primary and permanent dentin pulp chamber. Within this division, G1 and G4 showed very similar profile between them, followed by G2 that was intermediated between them and G3. G6 and G7 showed are very similar between them, followed by G8 that was intermediated between them and G5. Organic content: G7 and G8 were very similar between them; G2 showed be intermediate; G4 and G6 were very similar between them as well as G3 and G5 that, in turn, were quite similar to G1. The photomicrographs showed difference among non-treated groups, NaOCl treated groups and NaOCl treated followed by phosphoric acid etched groups. The groups only acid etched not differ from NaOCl treated followed by acid etched groups. Therefore, the inorganic content of primary teeth is qualitatively different from inorganic content of permanent ones, both in middle dentin of crown as well as in pulp chamber dentin, but not morphologically in case of NaOCl treatment followed by phosphoric acid treatment

ASSUNTO(S)

dureza hardness sodium hypochlorite hipoclorito de sodio dentition primary dentição primaria decidua espectroscopia dentin dentina decidua spectroscopy

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