Effects of Bioactive Agents on Dentin Mineralization Kinetics After Dentin Bleaching.

OBJECTIVES: This study evaluated effects of Bioglass 45S5 (BG) and Biosilicate (BS) remineralization on the chemical composition and bond strength of control dentin (CD) and bleached dentin (BD) surfaces. METHODS AND MATERIALS: Dentin bleaching treatment was performed using the walking bleaching technique with 0.01 g of sodium perborate and 0.5 mL of 3% hydrogen peroxide for 14 days. Remineralization treatment was carried out by rubbing a remineralization solution (0.015 g of BG or BS diluted in 1.35 mL of distilled water) on the etched dentin surface for 30 seconds. Micro-Raman spectroscopy (MRS) was used to quantitatively analyze the mineral matrix ratios of CD and BD (n=5) after remineralization treatment with BG and BS over 15 days of incubation in artificial saliva. The CD and BD discs (n=10) with and without remineralization treatment with BG and BS were restored using a two-step etch-and-rinse adhesive system (Optibond S, Kerr) and five layers of 1-mm-thick composite resin (Filtek Z250, 3M ESPE). The restored dentin discs were sectioned into nine bonded beams with cross-sectional areas of approximately 0.9 mm2 and tested for microtensile bond strength (µTBS). The dentin surface of one fractured beam per tooth was submitted to MRS to characterize the physicochemical composition (n=10) at the interface. The data were analyzed using one-way analysis of variance and the Tukey-Kramer post hoc test (p<0.005). RESULTS: MRS bioactive analyses revealed that both BG and BS promoted increased mineral matrix ratios in the CD and BD. Significantly higher µTBS values were found after CD treatment with BG (CD: 57 MPa±11; CD-BG: 78 MPa±15) and when BG and BS were applied to the BD (BD: 42 MPa±5; BD-BG: 71 MPa±14; BD-BS: 64 MPa±11) (p<0.005). The MRS analysis of the fractured dentin beam showed that the remineralization treatment significantly increased the dentin relative mineral concentration and promoted the appearance of new interface peaks, indicating a chemical interaction (p<0.005). CONCLUSION: Remineralization of BD is an effective therapy to restore damage caused by dentin bleaching and acid conditioning. This approach not only increases dentin mineral compounds but also improves dentin's ability to interact chemically with the adhesive system.

Chemical Interaction and Interface Analysis of Self-Etch Adhesives Containing 10-MDP and Methacrylamide With the Dentin in Noncarious Cervical Lesions.

OBJECTIVES: To characterize the chemical interactions and analyze the interface of adhesive systems containing 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) and N-methacryloyl glycine (methacrylamide) functional monomers with the dentin in noncarious cervical lesions (NCCLs) compared with artificial defects (ADs). METHODS AND MATERIALS: Twenty human teeth with natural NCCLs on the buccal surface were used. Class V cavities, similar to NCCLs, were created on the lingual surface to serve as controls. Teeth were randomly allocated to two groups according to the functional monomer in the adhesive (N=10): G1, 10-MDP; and G2, methacrylamide. NCCLs and ADs were characterized by their mineral composition (MC) and degree of demineralization (DD) using micro-Raman spectroscopy, adhesive/dentin chemical interactions (CIs) were assessed with infrared photoacoustic spectroscopy, and interface morphology was evaluated with scanning electron and light microscopy. MC, CI, and DD data were submitted to Shapiro-Wilk and Student t-tests ( p<0.05). RESULTS: Compared with ADs, dentin in NCCLs was hypermineralized ( p<0.05). In G1, CI, and DD in the first 2 µm, and adhesive projections in NCCLs and ADs interfaces were similar. Additionally, a thin layer of dentin collagen was observed in ADs, while it was hardly present in NCCLs. In G2, although CI could not be identified, changes in the mineral components were observed. The DD in the ADs and NCCLs were statistically similar, while SEM showed a lack of adhesion at NCCLs interface. DD and collagen exposure in the ADs and NCCLs were more pronounced than in G1. CONCLUSIONS: Results suggest that the G1 adhesive could be applied directly on the superficial sclerotic layer in NCCLs. In contrast, previous cavity preparation should be conducted to improve the micromechanical interaction of G2 with the dentin.