Influence of Surface Treatment of Lithium Disilicate on Roughness and Bond Strength.

PURPOSE: To evaluate the effect of different concentrations of hydrofluoric acid (HF) on the surface roughness of a ceramic reinforced by lithium disilicate and on the bond strength formed between the ceramic and self-adhesive resin cement. MATERIALS AND METHODS: A total of 100 disks of IPS e.max Press ceramic (Ivoclar Vivadent) reinforced by lithium disilicate were prepared as follows: group 1 remained untreated (control group); in groups 5-20, 5-40, and 5-60, the surfaces were etched with 5% HF for 20, 40, and 60 seconds, respectively; in groups 10-20, 10-40, and 10-60, the surfaces were etched with 10% HF for 20, 40, and 60 seconds, respectively; and in groups 10-20P, 10-40P, and 10-60P, the surfaces were etched with 10% HF for 20, 40, and 60 seconds, respectively, followed by treatment with 37% phosphoric acid for 5 seconds. Surface roughness and bond strength were analyzed with confocal microscopy and microshear testing, respectively. The values obtained were statistically analyzed using paired t test and two-way ANOVA followed by Tukey post hoc test at a 5% significance level. RESULTS: Surface roughness was influenced by the concentration and exposure time of acid applied (P < .05) and by the combination of these two factors (P < .05). Treatment with 10% HF for 40 seconds (group 10-40) achieved the highest roughness value. In contrast, bond strength was affected only by the acid exposure time (P < .05). CONCLUSION: Conditioning of lithium disilicate ceramics can change the surface morphology, thereby affecting bond strength with resin cement.

Micromorfologia da interface da união sistema restaurador-dentina decídua em função do sistema adesivo e do instrumento cortante rotatório / Micromorphology of the restorative system-primary dentin adhesive interface as a function of the adhesive system and rotary cutting instrument

Objetivo: Avaliar, in vitro a micromorfologia da interface da união sistema restaurador-dentina decídua, em função do sistema adesivo e do instrumento cortante rotatório. Método: Foram utilizados 20 segundos molares decíduos divididos aleatoriamente em dois grupos (n=10). No grupo C, foi realizado desgaste, até atingir a dentina, com ponta carbide. No grupo D, foi feito o mesmo desgaste, porém com ponta diamantada. A superfície preparada de cada dente foi dividida ao meio, sendo que em uma metade foi aplicado um sistema adesivo convencional de duas etapas (Single-Bond - 3M) e na outra um sistema autocondicionante de etapa única (One Up Bond F - Tokuyama). Todos os dentes foram restaurados com a resina composta híbrida (Filtek Z250 - 3M). As amostras foram termocicladas, embutidas em resina, seccionadas para obtenção da interface de união e preparadas para observação ao MEV. Resultados: Os dois sistemas adesivos utilizados foram capazes de formar camada híbrida. O sistema adesivo convencional de duas etapas proporcionou melhor selamento da interface de união, quando comparada ao autocondicionante e o emprego da ponta diamantada com o adesivo autocondicionante, mostrou o pior selamento da interface de união, com os maiores valores de gap. Conclusão: O instrumento cortante rotatório (ponta diamantada) só apresentou influência negativa na qualidade da interface sistema restaurador-dentina decídua quando se empregou sistema adesivo autocondicionante de etapa única.

Purpose: To evaluate, in vitro, the micromorphology of therestorative system-primary dentin interface as a function of theadhesive system and rotary cutting instrument.Method: Twenty primary second molars were randomly assignedto two groups (n=10). In group C, the teeth were ground with acarbide bur until reaching the dentin. In group D, the same procedurewas done however using a diamond bur. The prepared surface ofeach tooth was bisected. In one half, a 2-step total-etch adhesivesystem (Single-Bond - 3M) was applied and in the other half, a 1-step self-etching adhesive system (One Up Bond F - Tokuyama)was applied. All teeth were restored with a hybrid composite resin(Filtek Z250 - 3M). The specimens were thermocycled, embeddedin resin, sectioned to obtain the adhesive interface and preparedfor SEM analysis.Results: Both adhesive systems were capable of forming a hybridlayer. The 2-step total-etch adhesive system provided a bettersealing of the adhesive interface, in comparison to the self-etchingadhesive system. The use of a diamond bur together with the selfetchingadhesive system yielded the worst sealing of the adhesiveinterface, with presence of larger gaps.Conclusions: The rotary cutting instrument (diamond bur) had anegative influence on the quality of the restorative system-primarydentin interface only when a 1-step self-etching adhesive systemwas used.