Abstract
The objective of this study was to evaluate the effect of passive or active phosphoric acid (PA) application after hydrofluoric acid (HA) treatment on the microshear bond strength of lithium disilicate. Thirty ceramic discs were made with IPS Emax 2 (10 mm thick and 10 mm diameter). The specimens were divided into 3 groups, A: 9.6% HA application; AF: 9.6% HA application + cleaning with 37% PA in passive mode and AFF: 9.6% HA application + cleaning with 37% PA in active mode. For the microshear test, four tygons (0.9 mm diameter and 0.2 mm high) were filled with resin cement (RelyX Ultimate) and placed on the ceramic disks. After testing, the fracture modes were examined under scanning electron microscopy. Data were analyzed by one-way ANOVA and Tukey's post test (α=0.05). The bond strength values were significantly higher in Group AFF (11.0±2.5 MPa) compared with group A (8.1±2.6 MPa) (p<0.002). AF group was not statistically different (9.4±2.5 MPa) from Group A. It was concluded that the active application of 37% PA after 9.6% HA increases the microshear bond strength values between the resin cement and lithium disilicate ceramic.
Highlights
Great development of all ceramic systems for dental restoration occurred in the last 20 years, which provided the clinician a better aesthetic alternative for anterior and posterior restorations [1]
The micromechanical retention of the ceramic surface is crucial to adhesive bonding with a resin luting cement
When the ceramic surface of IPS Empress 2 was treated with hydrofluoric acid, stretched crystals and superficial irregularities were clearly observed
Summary
Great development of all ceramic systems for dental restoration occurred in the last 20 years, which provided the clinician a better aesthetic alternative for anterior and posterior restorations [1]. This preference is directly related to the success of ceramic-resin bond, which contributes to the restoration’s longevity [2]. Reinforced ceramics by lithium disilicate, feldspathics, leucite-reinforced feldsphatics or fluorapatite are acid sensitive, in other words, they undergo morphological changes with acid treatment in different concentrations [3] This sensitivity changes the ceramic structure [2] and may decrease the shear bond strength to enamel and/or dentin and/or resin cement. It is known that HA is toxic [8], and to wash out this agent in order to remove the excess acid may be an alternative to reduce its toxicity
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