Bond strengths of one-step self-etch adhesives to laser-irradiated and bur-cut dentin after water storage and thermocycling.

OBJECTIVE: The objectives of this study were to evaluate the microtensile bond strength (µTBS) of one-step self-etch adhesive systems to Er:YAG laser-irradiated and bur-cut dentin after water storage and thermocycling. BACKGROUND DATA: The Er:YAG laser is a promising alternative method for cavity preparation; however, no study has compared the effect of laser irradiation and aging procedures on the adhesion of one-step self-etch adhesives to dentin. METHODS: Seventy-two third molars were selected and randomly divided according to cavity preparation method (Er:YAG laser and bur-cut). One-step self-etch adhesive systems (Clearfil S(3) Bond, AdheSE One and Adper Easy One) were used to bond the composite to dentin. Following the adhesive procedure, the specimens were subdivided according to aging conditions (24 h in water control [C], 6 months of water storage [WS] and 10.000 thermocycles [TC]). The µTBS was determined in a universal testing machine. Three-way ANOVA, independent samples t test, and post-hoc comparisons test (α=0.05) were performed on all data. RESULTS: There was no statistical difference in µTBS between Er:YAG laser-irradiated and bur-cut dentin (p>0.05). Similarly, no significant difference was found in µTBS between C, WS, and TC specimens (p>0.05). Moreover, Clearfil S(3) Bond presented the highest µTBS to dentin in both laser-irradiated and bur-cut cavity preparation methods. CONCLUSIONS: Neither bur-cut nor Er:YAG laser-irradiated dentin was affected by the aging methods used to simulate degradation of the adhesive interface. Er:YAG laser treatment may be used as an alternative cavity preparation method.

Effect of thermocycling on the bond strength of composite resin to bur and laser treated composite resin.

The objective of this study was to investigate the effect of two different surface treatments (Er:YAG laser and bur) and three different numbers of thermal cycling (no aging, 1,000, 5,000, and 10,000 cycles) on the micro-shear bond strength of repaired composite resin. Ninety-six composite blocks (4 mm × 4 mm × 1 mm) obtained with a micromatrix hybrid composite were prepared. The composite blocks were then randomly divided into four groups (n = 24), according to the thermal cycling procedure: (1) stored in distilled water at 37°C for 24 h (control group), (2) 1,000 cycles, (3) 5,000 cycles, and (4) 10,000 cycles. After aging, the blocks were further subdivided into two subgroups (n = 12), according to surface treatment. Bur and laser-treated composite surfaces were treated with an etch&rinse adhesive system. In addition, a microhybrid composite resin was bonded to the surfaces via polyethylene tubing. Specimens were subjected to micro-shear bond strength test by a universal testing machine with a crosshead speed of 0 and 5 mm/min. The data were analyzed using one-way analysis of variance and Tukey tests (α = 0.05) for micro-shear bond strengths. After conducting a bond strength test, it was found that the laser and bur-treated specimens had similar results. Aging with 10,000 thermocycles significantly affected the repair bond strength of composite resins.

Effect of external tooth bleaching on dental plaque accumulation and tooth discoloration

No disponible

Objectives: Treatment of dental discolorations with external bleaching is becoming very common in dentistry, however, possible irreversible alterations on enamel surface due to bleaching procedures is a topic of discussion. The aim of this study was to evaluate the clinical effects of bleaching by measuring the dental plaque accumulation on human enamel and tooth discoloration in vivo. Study Design: Forty-four teeth in eleven patients not revealing any restorations or periodontal problems were enrolled in this study. Bleaching agent applied only to labial surfaces of incisors using commercial 35 % hydrogen peroxide gel. Dental plaque and tooth color measured in the same group of participants, at the end of non-brushing periods lasting 3 and 5 days, respectively, before and after bleaching.Results: The results of the comparison of pre- and post-bleaching measurements showed that, after a non-brushingperiod lasting 3 day, discoloration scores and plaque accumulation scores for bleached surfaces were lower than the non-bleached surface scores. However, at the end of a non-brushing period lasting 5 day, even the color measurement score in post-bleaching period was lower than the pre-bleaching counterpart, plaque index measurements showed higher plaque accumulation scores in the bleached group.Conclusions: According to these results, bleaching with 35 % hydrogen peroxide seem to favor plaque accumulation after non-brushing period lasting 5 day and tooth discoloration after bleaching is not in correlation with the amount of plaque accumulation