Six-month evaluation of adhesives interface created by a hydrophobic adhesive to acid-etched ethanol-wet bonded dentine with simplified dehydration protocols
Received 21 October 2009; received in revised form 21 November 2009; accepted 23 November 2009. published online 07 December 2009.
Abstract
Objectives
To evaluate the efficacy of simplified dehydration protocols, in the absence of tubular occlusion, on bond strength and interfacial nanoleakage of a hydrophobic experimental adhesive blend to acid-etched, ethanol-dehydrated dentine immediately and after 6 months.
Methods
Molars were randomly assigned to 6 treatment groups (n=5). Under pulpal pressure simulation, dentine crowns were acid-etched with 35% H3PO4 and rinsed with water. Adper Scotchbond Multi-Purpose was used for the control group. The remaining groups had their dentine surface dehydrated with ethanol solutions: group 1=50%, 70%, 80%, 95% and 3×100%, 30s for each application; group 2 the same ethanol sequence with 15s for each solution; groups 3, 4 and 5 used 100% ethanol only, applied in seven, three or one 30s step, respectively. After dehydration, a primer (50% BisGMA+TEGDMA, 50% ethanol) was used, followed by the neat comonomer adhesive application. Resin composite build-ups were then prepared using an incremental technique. Specimens were stored for 24h, sectioned into beams and stressed to failure after 24h or after 6 months of artificial ageing. Interfacial silver leakage evaluation was performed for both storage periods (n=5 per subgroup).
Results
Group 1 showed higher bond strengths at 24h or after 6 months of ageing (45.6±5.9a/43.1±3.2aMPa) and lower silver impregnation. Bond strength results were statistically similar to control group (41.2±3.3ab/38.3±4.0abMPa), group 2 (40.0±3.1ab/38.6±3.2abMPa), and group 3 at 24h (35.5±4.3abMPa). Groups 4 (34.6±5.7bc/25.9±4.1cMPa) and 5 (24.7±4.9c/18.2±4.2cMPa) resulted in lower bond strengths, extensive interfacial nanoleakage and more prominent reductions (up to 25%) in bond strengths after 6 months of ageing.
Conclusions
Simplified dehydration protocols using one or three 100% ethanol applications should be avoided for the ethanol-wet bonding technique in the absence of tubular occlusion, as they showed decreased bond strength, more severe nanoleakage and reduced bond stability over time.
aDepartment of Dental Materials, School of Dentistry, University of São Paulo, Av. Prof. Lineu Prestes, 2227, São Paulo, SP, Brazil
bDepartment of SAU&FAL, University of Bologna, Bologna, Italy
cDivision of Dental Sciences and Biomaterials, Department of Biomedicine, University of Trieste, Trieste and IGM-CNR, Unit of Bologna c/o IOR, Bologna, Italy
dDepartment of Endodontics, School of Dentistry, Medical College of Georgia, Augusta, GA, USA
ABSTRACT