Evaluation of chemical and/or mechanical treatments of the smear layer as revealed by scanning electron microscopy - a blind comparative study

Abstract

A blind comparative study of chemical and/or mechanical treatments of the smear layer, according to scanning electron microscopy images, was carried out. The effect of the treatments was analyzed on the smear layer of mesio-occlusodistal cavity walls prepared in vitro in human third molars. The agents used were air/water spray, 37% phosphoric acid, 5% tannic acid, biologic detergent, 0.5% sodium hypochlorite, and enamel hatchet alone or in association with the previous agents. Electron micrographs were evaluated by three professionals according to the degree of visualization of underlying dentin or enamel. Phosphoric acid received the highest scores due to the complete removal of the smear layer. However, statistical analyses revealed diverse performances of non or slightly demineralizing agents, according to the cavity walls in dentin, while there was equivalent effect on the enamel of gingival walls.

Evaluation of the smear layer and hybrid layer in noncarious and carious dentin prepared by air abrasion system and diamond tips

“…Phosphoric acid, a cleaning demineralizer agent, was efficient in smear layer removal and opening of the dentinal tubules (Fig. 1B), as demonstrated by Luz et al (2000). Fig.…”

Effects of cleaning agents on bond strength to dentin

“…The use of different treatments on the dentin surface causes different effects on the smear layer, from its total removal by the action of 37% phosphoric acid 4 to its partial removal when non-demineralizing or slightly demineralizing treatments are used 10 . These effects help the physicochemical interaction between some adhesive systems and the dentin, providing a satisfactory restorative material/tooth interaction.…”

“…The recent evolution of adhesive systems has brought on the refinement of all-etch adhesive systems (using 32% or 37% phosphoric acid) 2,6 , and the development of self-etching adhesive systems (organic acids and/or acidic monomers in the primer), reducing clinical steps 15 . Differences among adhesive systems require important considerations regarding the adhesion to dentin, such as: treatment used in the dental surface, humidity of dentin 2 , smear layer removal 10 , collagen network collapse 15 , and depth of resin tag formation inside dentinal tubules 5,9 .…”

“…The related literature reports a great number of other cavity cleaning agents for dentinal surface, such as: phosphoric acid 4,9 , sodium hypochlorite 6,10 , EDTA 4,5,6 , hydrogen peroxide 6 , polyacrylic acid 6 , prophylactic pastes 5,14 , and aluminum oxide jet 5 .…”

“…Their effect ranges from the simple removal of some contaminants to the total or partial removal of the smear layer, promoting demineralization that can facilitate the interaction between resin and dentin, although changing dentinal permeability and all the phenomena related to it 10 .…”