Effect of HEMA on bonding of Er:YAG laser‐irradiated bovine dentine and 4‐META/MMA‐TBB resin

Abstract

The purpose of this study was to evaluate the priming effect of 2-hydroxyethylmetaclirate (HEMA) following acid treatment on resin bonding to prototype Er:YAG laser-irradiated dentine. Extracted bovine dentine following laser irradiation was acid treated by aqueous solution of 10% citric acid (10-0) or 10% citric acid/3% ferric chloride (10-3), and additionally treated with 35% HEMA. Pre-treated dentines were bonded to the polymethyl-methacrylate (PMMA) rod with 4-META/MMA-TBB resin (Super Bond C & B) and miniaturized dumbbell-shaped bonded specimens were prepared. These specimens profiled for tensile bond testing and fractured surfaces were observed by scanning electron microscopy (SEM). Cross-sections of resin-dentine interface were also examined. The HEMA treatment following acid conditioned by 10-3 or 10-0 for both laser-irradiated and non-irradiated dentines was significantly higher than that without HEMA treatment. SEM view of a fractured specimen showed some cohesive failure in cured resin, but almost all of the fractured surface shows boundary failure between the penetrated resin and underlying dentine. A cross-sectional view of the interface showed a very thick hybrid layer between the hybridized dentine and underlying dentine. It was concluded that HEMA treatment following acid conditioning provided a slightly higher bond strength for both the Er:YAG laser-irradiated and non-irradiated dentines. However, the bond strength of Er:YAG laser irradiated dentine was significantly lower than that of the non-irradiated dentine.

XPS analysis of the dentin irradiated by Er:YAG laser

“…The bonding strength of adhesives to Er:YAG laserirradiated dentine is lower than that to bur-cut dentine [11][12][13] . Dentine after Er:YAG laser-irradiation had a denatured surface structure 21,22) .…”

“…When irradiated by Er:YAG laser pulses, the dentin surface becomes microscopically rough, and dentinal tubules are opened without smear layers 8,10) . Although these characteristics are considered to be advantageous for resin bonding, the bond strength of resin to Er:YAG laser-irradiated dentin is lower than that to conventionally ground dentin [11][12][13][14][15][16][17] . The formation of a hybrid layer is thought to be necessary for excellent resin-dentin bonding.…”

Tensile Bond Strength of Single-Step Self-Etch Adhesives to Er:YAG Laser-Irradiated Dentin

“…12,19 In order to irradiate uniformly, some studies employed laser irradiation with the dentine specimen fixed to a moving stage. 11,12,20 However, this study employed freehand irradiation, since our previous data indicated no significant difference between uniform irradiation using a moving stage and freehand irradiation.…”

Pathological Study of Pulp Treated with Chemicals after Er:YAG Laser Preparation

“…[5][6][7][8][9][10][11] Fixation of denatured layers by application of 5% glutaraldehyde, 19 or removal by application of 37% phosphoric acid and 10% sodium hypochloride have been proven effective in improving resin bond strength. 20,21 There is a greater possibility of irritation and inflammation of pulp with chemical procedures than with conventional methods of composite restoration, and very little is yet known about such pulp reaction to such chemical procedures.…”

“…[1][2][3][4] This denatured layer, according to recent reports impairs restoration with composite resin by disturbing adhesion between the dentin and the composite resin. [5][6][7][8][9][10][11] It differs from non-irradiated dentin, both chemically and physically. 4,9,[12][13][14][15][16][17] These differences can be disadvantageous, as the denatured layer tends to be brittle and to break easily when subjected to bond strength tests after the Er:YAG-laser-irradiated dentin is filled with composite resin.…”