Influence of pulse repetition rate of Er:YAG laser and dentin depth on tensile bond strength of dentin–resin interface

Abstract

The study evaluated the in vitro influence of pulse-repetition rate of Er:YAG laser and dentin depth on tensile bond strength of dentin-resin interface. Dentin surfaces of buccal or lingual surfaces from human third molars were submitted to tensile test in different depths (superficial, 1.0 and 1.5 mm) of the same dental area, using the same sample. Surface treatments were acid conditioning solely (control) and Er:YAG laser irradiation (80 mJ) followed by acid conditioning, with different pulse-repetition rates (1, 2, 3, or 4 Hz). Single bond/Z-250 system was used. The samples were stored in distilled water at 37 degrees C for 24 h, and then the first test (superficial dentine) was performed. The bond failures were analyzed. Following, the specimens were identified, grounded until 1.0- and 1.5-mm depths, submitted again to the treatments and to the second and, after that, to third-bond tests on a similar procedure and failure analysis. ANOVA and Tukey test demonstrated a significant difference (p < 0.001) for treatment and treatment x depth interaction (p < 0.05). The tested depths did not show influence (p > 0.05) on the bond strength of dentin-resin interface. It may be concluded that Er:YAG laser with 1, 2, 3, or 4 Hz combined with acid conditioning did not increase the resin tensile bond strength to dentin, regardless of dentin depth.

Influence of femtosecond laser treatment on shear bond strength of composite resin bonding to human dentin under simulated pulpal pressure

“…Other investigations also concluded that bond strength of teeth treated with laser irradiation before bonding was weaker than that of teeth in the control group. 5,28,36 Previous studies on teeth conditioned by laser treatment confirm the results of our study. The control groups treated conventionally with adhesive systems attained the highest bond strengths.…”

“…Subsequently, all samples were exposed to a thermocycling device (Willytech Thermocycler V.2.8, Haake, Munich, Germany). Thermocycling consisted of 5000 cycles in water between 5 C and 55 C, starting after storage in water at 37 C for 24 h as an accelerated aging test, which corresponded approximately to 6 months of functioning in vivo.…”

“…Other lasers, such as Er:YAG, minimize thermal effects but cannot compete with the quality of conventional preparation techniques such as mechanical drills in combination with etching procedures. 5 Only few studies describing dental applications and the specific interactions between ultrashort laser pulses and enamel or dentin are available in the literature. A main advantage of ultrashort laser pulses is the ablation of tissue with negligible heat damage, thus creating structures with minimal damage to the surrounding tissue enabling better SBS.…”

Influência dos níveis de energia do laser Er:YAG na capacidade de ablação, microdureza e morfologia da dentina superficial e profunda

“…[34][35][36][37] The amount of tissue removed is thought to increase in proportion to the Er:YAG laser energy. However, with increased ablation efficiency, the dentin microstructure may be affected by the thermal effect and the resulting surface may vary from a white spot to charring, fusion, roughening, melting, recrystallization, cracking, and both de/remineralization and deproteinization.…”

“…The literature available on the Er:YAG laser still presents varying parameters of energy settings, and, besides the fact that little is known about the effect of Er:YAG laser irradiation on different dentin depths [33,34], there are divergent results as well.…”