Effect of cementation delay on bonding of self-adhesive resin cement to yttria-stabilized tetragonal zirconia polycrystal ceramic treated with nonthermal argon plasma.

STATEMENT OF PROBLEM: Nonthermal argon plasma (NTAP) has been reported to improve the bond strength of resin cements to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics. However, the effect of the inevitable delay before cementation and after treating Y-TZP ceramics with NTAP is unclear. PURPOSE: The purpose of this in vitro study was to investigate whether delays of 8, 12, and 24 hours between the Y-TZP ceramic treatment with NTAP and the cementation would affect the surface energy and the bond strength of a self-adhesive resin cement to Y-TZP ceramic. MATERIAL AND METHODS: Sixty plates and 50 blocks of 3Y-TZP ceramic were divided into 2 groups (n=30 and n=25): as-sintered (AS) and airborne-particle abraded with 50-µm Al2O3 (APA). These groups were further divided into 5 subgroups (n=6 and n=5) according to the delay between the NTAP treatment and the measurement of surface energy and microtensile bond strength (µTBS) evaluation: (0, 8, 12, and 24 hours). For both 3Y-TZP surface conditions (AS and APA), a control group without NTAP treatment was used (ASC and APAC). The surface energy (SE) was evaluated with a goniometer and the 3Y-TZP elemental composition with X-ray photoelectron spectroscopy (XPS). For the µTBS test, the 3Y-TZP ceramic blocks were cemented to composite resin blocks with a self-adhesive resin cement. After storage in distilled water at 37 °C for 24 hours, the 3Y-TZP-composite resin blocks were sectioned into beams and submitted to a µTBS test. Data were submitted to 2-way ANOVA and the Tukey HSD test (α=.05). RESULTS: For the AS group, NTAP increased the SE irrespective of the delay before measurement: ASC<0 hour=8 hours=12 hours=24 hours (P<.05). For the APA group, except after 12 hours, NTAP also increased the surface energy (P<.05). XPS analysis showed an increase in the oxygen/carbon ratio after NTAP treatment for both groups. For the AS group, NTAP increased the µTBS after 0, 8, and 12 hours (P<.05), whereas for the APA group this occurred only after 8 hours (P<.05). For the AS and APA groups, the highest µTBS was reached after 8 hours (P<.05). CONCLUSIONS: Treatment of 3Y-TZP ceramic with NTAP improved the SE and increased the µTBS of self-adhesive resin cement to 3Y-TZP ceramic. These effects were time dependent, with better results at 8 hours after NTAP treatment.

Simulação de textura de lesão cariosa para treinamento pré-clínico / Carious lesion's texture simulation for preclinical training

O objetivo deste estudo foi apresentar uma metodologia simples para a simulação de duas texturas de cárie em dentina em dentes de acrílico no treinamento pré-clínico. A proposta de desenvolvimento desta metodologia surgiu da necessidade de, durante o treinamento de remoção de cárie seletiva (parcial) por profissionais que atuavam em saúde pública, melhorar a compreensão em termos teóricos e práticos do que seriam as camadas da lesão cariosa em dentina: amolecida, em lascas, firme e endurecida. A metodologia permite identificar qual camada deve ser removida completamente, qual deve ser removida parcialmente e qual deve ser mantida intacta. O sucesso obtido no treinamento de mais de 1000 profissionais capacitados em diferentes prefeituras brasileiras foi o incentivo para a redação deste artigo, descrevendo detalhadamente a metodologia (AU).

The aim of this study was to present a simple method to simulate two dentin carious textures in acrylic teeth for preclinical training. The proposed development of this methodology arose from the need for the training of selective (partial) caries removal by professionals working in public health, improving the theoretical and practical understanding regarding the lesions' layers: soft, leathery, firm, and hard dentine. This method allows to identify which layer should be removed completely, which should be partially removed and what should be left intact. The success in training over 1000 professionals working at Brazilian Dental Public Health System was the incentive for writing this article, detailing the methodology (AU).