Effect of acid etching duration on tensile bond strength of composite resin bonded to erbium:yttrium–aluminium–garnet laser-prepared dentine. Preliminary study

Abstract

The purpose of this study was to compare the tensile bond strength of composite resin bonded to erbium:yttrium-aluminium-garnet (Er:YAG) laser-prepared dentine after different durations of acid etching. The occlusal third of 68 human third molars was removed in order to expose the dentine surface. The teeth were randomly divided into five groups: group B (control group), prepared with bur and total etch system with 15 s acid etching [37% orthophosphoric acid (H(3)PO(4))]; group L15, laser photo-ablated dentine (200 mJ) (laser irradiation conditions: pulse duration 100 micros, air-water spray, fluence 31.45 J/ cm(2), 10 Hz, non-contact hand pieces, beam spot size 0.9 mm, irradiation speed 3 mm/s, and total irradiation time 2 x 40 s); group L30, laser prepared, laser conditioned and 30 s acid etching; group L60, laser prepared, laser conditioned and 60 s acid etching; group L90, laser prepared, laser conditioned and 90 s acid etching. A plot of composite resin was bonded onto each exposed dentine and then tested for tensile bond strength. The values obtained were statistically analysed by analysis of variance (ANOVA) coupled with the Tukey-Kramer test at the 95% level. A 90 s acid etching before bonding showed the best bonding value (P < 0.05) when compared with all the other groups including the control group. There is no significance difference between other groups, nor within each group and the control group. There was a significant increase in tensile bond strength of the samples acid etched for 90 s.

Impact of Er:YAG laser pulse duration on ultra-structure of dentin collagen fibrils

“…Although literature has used settings of 10 Hz [7,10,25,28] for dentin pretreatment, the current study and former ones [8,26,36] demonstrated that the use of lower frequency, as low as 2 Hz, provides effective ablation rates to the target tissues. These lower frequencies allow suitable ablation and decrease the heat generated from this energy transference.…”

“…This absorbed residual energy is transformed into heat that will accumulate into dentin. The main concern when laser heating occurs is the occurrence of thermal damage to the underlying dentin collagen matrix [23] which may cause collagen denaturation in deep regions of dentin [24,25].…”

Laser Application for Restorative Dentistry

“…Chousterman et al reported signifi cant increase in tensile bond strength of the samples when the etching time was prolonged up to 90 s [ 44 ].…”

Color Stability of Enamel following Different Acid Etching and Color Exposure Times

“…Ito et al 17 found that a short etching duration (10s) provided higher bond strength than extended etching (30s, 60s) of samples contaminated with saliva and blood. Chousterman et al 18 recommended that extension of acid etching time to 90s will improve tensile bond strength of composite bonded to Er:YAG laser-prepared dentin. On the other hand, according to Oliveira et al 19 etching time had no significant effect on the bond strength of the adhesives to dentin.…”