Effect of pH and application times of a meta-phosphoric acid on resin-dentin bonding properties

• Published in: International journal of adhesion and adhesives Vol. 74; pp. 107 - 114
• Main Authors: Millan Cardenas, Andres Felipe, Figueredo de Siqueira, Fabiana Suelen, Bandeca, Matheus Coelho, Feitosa, Victor Pinheiro, Reis, Alessandra, Loguercio, Alessandro D., Gomes, João Carlos
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-04-2017; Elsevier BV
• Subjects: Bond strength; Bonding strength; Chemical compounds; Dentin; Dentine; Etching; Experiments; Hybrid layer; Independent variables; Minerals; Nanoleakage; Phosphoric acid; Scanning electron microscopy; Teeth; Total-etch; Phosphoric acid; Total-etch; Dentine; Hybrid layer; Nanoleakage
• ISSN: 0143-7496; 1879-0127
• DOI: 10.1016/j.ijadhadh.2016.10.014

To evaluate the effect of different pHs of 40% meta phosphoric acid (MPA) in comparison with a conventional 37% ortho-phosphoric acid under different application times in terms of resin-dentin bond strength (μTBS), nanoleakage (NL) and the dentin-etching pattern.
Ninety-six molars were randomly assigned into 12 experimental conditions according to the combination of the independent variables: Acid [37% ortho-phosphoric acid (OPA), 40% meta-phosphoric acid (MPA) in the following pHs – 0.5, 1 and 2] and Application Time [7, 15 and 30s]. After restorations, specimens were sectioned into resin–dentine beams (0.8mm2) tested under tension (0.5mm/min). Selected beams from each tooth were used for NL evaluation. The dentin-etching pattern of the OPA and MPA was examined under a scanning electron microscop. Acid vs application time data were subjected to two-way ANOVA and Tukey's test (α=0.05)
MPA pH 0.5 showed μTBS means similar to OPA, independently the application time (p>0.05). A statistically higher NL was observed for OPA in comparison with MPA, regardless the application time (p<0.03). When MPA pH 0.5 was applied at the different times, the demineralised substrate showed presence of minerals along dentin surface.
The use of 40% meta-phosphoric acid with pH 0.5 is an alternative acid-etching agent with similar immediate bond strength and lower nanoleakage than the traditional 37% ortho-phosphoric acid.