Sodium hypochlorite effects on dentin bond strength and acid-base resistant zone formation by adhesive systems

Aim: To evaluate the effects of 10% NaOCl gel application on the dentin bond strengths and morphology of resin-dentin interfaces formed by three adhesives. Methods: Two etch-and-rinseadhesives (One-Step Plus, Bisco Inc. and Clearfil Photo Bond, Kuraray Noritake Dental) and oneself-etch adhesive (Clearfil SE Bond, Kuraray Noritake Dental) were applied on dentin accordingto the manufacturers’ instructions or after the treatment with 10% NaOCl (ED-Gel, Kuraray NoritakeDental) for 60 s. For interfacial analysis, specimens were subjected to acid-base challenge andobserved by SEM to identify the formation of the acid-base resistant zone (ABRZ). For microtensilebond strength, the same groups were investigated and the restored teeth were thermocycled(5,000 cycles) or not before testing. Bond strength data were subjected to two-way ANOVA andTukey’s test (p<0.05). Results: NaOCl application affected the bond strengths for One-Step Plusand Clearfil Photo Bond. Thermocycling reduced the bond strengths for Clearfil Photo Bond andClearfil SE Bond when used after NaOCl application and One-Step Plus when used asrecommended by manufacturer. ABRZ was observed adjacent to the hybrid layer for self-etchprimer. The etch-and-rinse systems showed external lesions after acid-base challenge and noABRZ formation when applied according to manufacturer’s instructions. Conclusions:10% NaOClchanged the morphology of the bonding interfaces and its use with etch-&-rinse adhesives reducedthe dentin bond strength. Formation of ABRZ was material-dependent and the interface morphologieswere different among the tested materials.

Effect of dentin desensitizers on resin cement bond strengths

Introduction: The crown preparation promotes the exposure of dentin tubules. Thus, to avoid post-operative sensitivity, the first approach involves the use of dentin adhesives, and the second one the use of dentin desensitizers. Objective: This study evaluated the effect of dentin desensitizers on microtensile bond strengths (μTBSs) of a resin cement to dentin. Material and methods: Twenty bovine teeth were prepared until obtaining flat dentin surfaces. A standardized smear layer was created (#600-grit SiC paper). The samples were randomly divided into the following four groups (n = 5): no treatment (Control), treatment with Gluma Desensitizer (Heraeus Kulzer), Super Seal (Phoenix Dental) and Teethmate Desensitizer (Kuraray Noritake Dental). The dentin surfaces were then treated with ED Primer II (Kuraray Noritake Dental). Twenty composite blocks, 4 mm thick (Estenia CeB, Kuraray Noritake Dental) were used. The composite surfaces were abraded with aluminum oxide (50 μm), and then silanized. The composite block was bonded to the dentin surface with a resin cement (Panavia F 2.0, Kuraray Noritake Dental) according to the manufacturer's instructions. After 24-hour storage (37ºC, 100% RH), the bonded samples were cut into beam-shaped microtensile specimens and loaded in tension until failure. Data were analyzed with one-way ANOVA and the Dunnett's test (α = 0.05). An SEM was used to examine the failure modes. Results: The μTBSs (MPa ± SD) were: 24.4 ± 3.2 (Control), 14.0 ± 5.6 (Gluma Desensitizer), 8.6 ± 4.7 (Super Seal), and 34.7 ± 4.6 (Teethmate Desensitizer), in which there were significant differences among the four groups (p < 0.05). The Teethmate Desensitizer group showed the highest μTBS, while the Super Seal group showed the lowest mean of μTBS to dentin. Conclusion: The efficacy of the desensitizers is material-dependent; Gluma Desensitizer and Super Seal decreased the μTBSs, however, Teethmate Desensitizer improved it.

Avaliação da resistência de união à dentina de um compósito indireto fixado com diferentes técnicas e cimentos resinosos / Evaluation of bond strength of an indirect composite luting fixed by different techniques and resin cements to dentin

O objetivo deste estudo foi avaliar a resistência de união (RU) em dentina utilizando diferentes técnicas de fixação de restaurações indiretas de compósito e cimentos resinosos. Molares humanos foram utilizados para obtenção de superfícies dentinárias oclusais planificadas a meia distância da polpa dental. Os dentes foram divididos em seis grupos experimentais, de acordo com as técnicas de cimentação (IF: instruções do fabricante; AC: adesivo + cimento; AFC: adesivo + resina Flow + cimento) e os materiais cimentantes (PF: Panavia F; RX: RelyX Unicem). Blocos de compósito indireto Estenia foram cimentados de acordo com o grupo experimental e os dentes restaurados foram armazenados em água a 37ºC por 24 horas. Os espécimes foram preparados a partir das restaurações para o ensaio de microtração. A RU foi calculada e expressa em MPa (mega pascal). Os foram analisados pela ANOVA (2 fatores) e teste de Tukey (p<0,05). Os valores médios de RU foram: PF/IF; 17,7 (4,2); PF/AC: 20,9 (8,2); PF/AFC: 25,9 (4,5); RX/IF:8,6 (4,5); RX/AC: 23,0 (7,7) e RX/AFC: 24,2 (4,8). O compósito fixado com os agentes cimentantes pode apresentar melhores resultados, em termos de RU, à dentina com a aplicação de um adesivo ou através da combinação do adesivo com uma resina flow antes da cimentação.