Abstract
Objective: Evaluate the microtensile bond strength (µTBS) in different dentin thicknesses, under simulated pulpal pressure (SPP), submitted to an adhesive technique using laser irradiation. Material and methods: Forty sound human molars were sectioned and randomly divided into two groups (n=20): Group 1 – 1 mm of dentin thickness; Group 2 – 2 mm of dentin thickness. Each group was divided into two subgroups (n=10): Subgroup A – Absence of SPP; Subgroup P – Presence of SPP (15 cm H2O). The samples were sequentially treated with: 37% phosphoric acid, adhesive system (Adper Single Bond 2), Nd:YAG laser irradiation (60 s, 1064 nm, 10 Hz) using 60 and 100 mJ/pulse energy parameters and photopolymerization (10 s). A composite resin block (Filtek Z350) was built up onto the irradiated area. After 30 days stored in water, the samples were sectioned and submitted to microtensile test (10 kgf load cell, 0.5mm/min). Data were analyzed by three-way ANOVA and Tukey tests. Results: Three-way ANOVA revealed no significant differences for SPP (p=0.0821) and for dentin thickness p= 0.9405) on bond strength. The laser energy parameters (p=0.001) indicated that 100 mJ showed greater µTBS means compared to the group irradiated with 60 mJ. Dentin thickness did not affect on µTBS. The presence of SPP reduced the mean µTBS values. Conclusions: Simulated pulpal pressure did not affect the µTBS using 60 mJ of laser energy parameter. At 100 mJ, the presence of SPP negatively influenced the bond strength, regardless of dentin thickness. KEYWORDSBond strength; Dentin; Intrapulpal pressure; Nd:YAG laser.
Highlights
The development and regular use of adhesive materials has revolutionized many aspects of restorative and preventive dentistry [1]
When considering the laser energy parameters (p < 0.0001), the highest bond mean values was observed in the group irradiated with 100 mJ and restored in the absence of simulated pulpal pressure (SPP) (49.61 ± 9.59)Ab
For the group irradiated with 60 mJ, there were no significant differences between the presence or absence
Summary
The development and regular use of adhesive materials has revolutionized many aspects of restorative and preventive dentistry [1]. The adhesion mechanism to enamel and dentin is essentially an exchange process that involves the replacement of minerals removed from dental tissue, as a result of etching, by resin monomers with low surface tension and high diffusion capacity [2,3]. In an attempt to minimize the negative effects of excess moisture on adhesive procedures and standardize the morphology of hybridization zone, studies had been evaluated the effects of Nd:YAG (neodymium-doped yttrium aluminium garnet) laser irradiation on dental tissues [6,7,8,9,10,11]. The laser was applied to sound dentin prior to the adhesive system, resulting in heat denaturation of the organic components, as well as obliteration of the dentin tubules by melting and recrystallization of the inorganic components and low bond strength values [6,10,12]
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