Influência do uso do laser de Nd: YAG na resistência de união de materiais resinosos à dentina / YAG laser influence on bond strength of adhesive resins to dentin

The aim of this study was to evaluate the influence of Nd:YAG laser on microtensile bond strength (μTBS) of different adhesive materials to human dentin. Eighteen human third molars were divided into 6 groups. Group 1 – adhesive system, Adper Single Bond 2 (SB); Group 2 – adhesive system, Clearfil SE Bond (CSEB); Group 3 – self-adhesive resin luting cement, RelyX Unicem; Group 4 – irradiation with Nd:YAG laser and application of SB; Group 5 – irradiation with Nd:YAG laser and application of CSEB; Group 6 – irradiation with Nd:YAG laser and application of RelyX Unicem. A composite resin block was built on the dentin surfaces, and sticks with a cross-sectional area of ~0.80 mm2 were obtained. Twenty specimens per group were selected and subjected to μTBS testing in a universal testing machine. According to the analysis of variance and Tukey test (α = 0.05), the highest μTBS mean was obtained with CSEB (41.75 MPa) without laser irradiation, but this value was not statistically different from CSEB with laser irradiation (33.42 MPa). Mean μTBS of SB without (32.15 MPa) and with (35.38 MPa) laser irradiation did not differ statistically. The lowest μTBS values were obtained for RelyX Unicem, and the group without laser irradiation showed statistically higher values (14.50 MPa) than those found with laser irradiation (7.53 MPa). Nd:YAG laser did not significantly reduce bond strength of the adhesive systems under study, except for the self-adhesive resin luting cement.

O objetivo desse estudo foi avaliar a influência do laser Nd:YAG na resistência à microtração de diferentes materiais adesivos à dentina humana. Dezoito terceiros molares humanos foram divididos em 6 grupos. Grupo 1 – Adesivo Adper Single Bond 2 (SB), Grupo 2 – Adesivo Clearfil SE Bond (CSEB), Grupo 3 – Cimento resinoso autoadesivo RelyX Unicem, Grupo 4 – irradiação com laser de Nd:YAG e aplicação de SB, Grupo 5 – irradiação com laser de Nd:YAG e aplicação de CSEB e Grupo 6 – irradiação com laser de Nd:YAG e aplicação de RelyX Unicem. Um bloco de resina composta foi confeccionado sobre essas superfícies de dentina tratadas e os espécimes foram seccionados para obtenção de palitos de 0,80 mm2. Vinte espécimes foram selecionadas por grupo e submetidos a resistência adesiva à microtração (μTBS) em máquina de ensaio universal. De acordo com a análise de variância e teste de Tukey (α = 0,05), a maior média μTBS foi obtida com CSEB (41,75 MPa) sem irradiação por laser, esse valor não diferiu estatisticamente do CSEB com irradiação por laser (33,42 MPa ). A μTBS média de SB sem (32,15 MPa) e com (35,38 MPa) irradiação do laser não diferiram estatisticamente entre si. Os menores valores de μTBS foram obtidos para RelyX Unicem, sendo o valor sem irradiação por laser (14,50 MPa) estatisticamente superior ao com (7,53 MPa). O Laser de Nd: YAG não diminuiu significativamente a resistência de união dos sistemas adesivos estudados, apenas para o cimento resinoso autoadesivo.

Effect of conditioner on microtensile bond strength of self-adhesive resin cements to dentin.

OBJECTIVE: Evaluate, in vitro, the microtensile bond strength (µTBS) of RelyX ARC conventional resin cement and RelyX Unicem and Maxcem self-adhesive resin cements to dentin, and the influence of polyacrylic acid pretreatment on the µTBS. MATERIAL AND METHODS: Flat dentin surfaces were obtained in 15 third molars which were randomly divided into 5 groups: Group 1 - RelyX ARC (control); Group 2 - RelyX Unicem; Group 3 - Maxcem Elite; Group 4 - 22.5% polyacrylic acid and RelyX Unicem; Group 5 - 22.5% polyacrylic acid and Maxcem Elite. A block of composite resin was built over the resin cements. The samples were sectioned to obtain beams, and 20 specimens for each group were submitted to µTBS on a universal testing machine. Failure modes were analyzed by scanning electron microscopy. RESULTS: According to ANOVA and Tukey test, the highest µTBS mean (MPa) was obtained with RelyX ARC (21.38), which did not differ statistically from Maxcem Elite with polyacrylic acid pretreatment (19.22) and RelyX Unicem with polyacrylic acid pretreatment (17.75) (p>0.05). The latter two groups did not differ statistically from RelyX Unicem (16.98) (p>0.05). The lowest mean was obtained for Maxcem Elite (6.43), which differed statistically from the other groups (p<0.05). All failures were adhesive for Maxcem Elite without polyacrylic acid pretreatment, and mixed failures were predominant in the other groups. CONCLUSIONS: RelyX ARC achieved higher µTBS to dentin in comparison to the self-adhesive resin cements. Polyacrylic acid pretreatment was effective in improving the µTBS of Maxcem Elite, but did not influence the µTBS for RelyX Unicem.