Abstract
This study evaluated comparatively by scanning electron microscopy (SEM) the effect of different dental conditioners on dentin micromorphology, when used according to the same protocol. Forty dentin sticks were obtained from 20 caries-free third human molars and were assigned to 4 groups corresponding to 3 conditioners (phosphoric acid 37%, Clearfil SE Bond and iBond) and an untreated control group. After application of the conditioners, the specimens were immersed in 50% ethanol solution during 10 s, chemically fixed and dehydrated to prepare them to SEM analysis. In the control group, dentin surface was completely covered by smear layer and all dentinal tubules were occluded. In the phosphoric acid-etched group, dentin surface was completely clean and presented exposed dentinal tubule openings; this was the only group in which the tubules exhibited the funnel-shaped aspect. In the groups conditioned with Clearfil SE Bond primer and iBond, which are less acidic than phosphoric acid, tubule openings were occluded or partially occluded, though smear layer removal was observed. SE Bond was more efficient in removing the smear layer than iBond. In the Clearfil SE Bond group, the cuff-like aspect of peritubular dentin was more evident. It may be concluded all tested conditioners were able to change dentin morphology. However, it cannot be stated that the agent aggressiveness was the only cause of the micromorphological alterations because a single morphological pattern was not established for each group, but rather an association of different aspects, according to the aggressiveness of the tested conditioner.
Highlights
Adhesive dentistry has undergone remarkable changes since the introduction of phosphoric acid as an enamel conditioner1 and the same principles still guide adhesion, that is, partial demineralization of the dental structure and impregnation of the etched area with resin monomers
The adhesive systems can be classified in two major groups, according to the need or not of acid etching prior to the impregnation of the dental substrate with resin monomers
The materials that require previous acid etching are classified as total-etch adhesive systems, whereas those that perform the conditioning of the dental surface simultaneously to resin monomer interdiffusion are classified as self-etching adhesive systems4,12,15
Summary
Adhesive dentistry has undergone remarkable changes since the introduction of phosphoric acid as an enamel conditioner and the same principles still guide adhesion, that is, partial demineralization of the dental structure and impregnation of the etched area with resin monomers. The technique of dentin hybridization and the concept of hybrid layer caused a significant advance in adhesive dentistry. The adhesive systems can be classified in two major groups, according to the need or not of acid etching prior to the impregnation of the dental substrate with resin monomers. The total-etch adhesive systems use a strong acid agent, like phosphoric acid, that removes the smear layer and demineralizes enamel and dentin, exposing the collagen fibrils and increasing the surface free energy. Overdrying causes tissue dehydration, especially in dentin, and can compromise the performance of these adhesive systems
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