Fernanda Tranchesi Sadek

Ethanol Wet-bonding Challenges Current Anti-degradation Strategy

The long-term effectiveness of chlorhexidine as a matrix metalloproteinase (MMP) inhibitor may be compromised when water is incompletely removed during dentin bonding. This study challenged this anti-bond degradation strategy by testing the null hypothesis that wet-bonding with water or ethanol has no effect on the effectiveness of chlorhexidine in preventing hybrid layer degradation over an 18-month period. Acid-etched dentin was bonded under pulpal pressure simulation with Scotchbond MP and Single Bond 2, with water wet-bonding or with a hydrophobic adhesive with ethanol wet-bonding, with or without pre-treatment with chlorhexidine diacetate (CHD). Resin-dentin beams were prepared for bond strength and TEM evaluation after 24 hrs and after aging in artificial saliva for 9 and 18 mos. Bonds made to ethanol-saturated dentin did not change over time with preservation of hybrid layer integrity. Bonds made to CHD pre-treated acid-etched dentin with commercial adhesives with water wet-bonding were preserved after 9 mos but not after 18 mos, with severe hybrid layer degradation. The results led to rejection of the null hypothesis and highlight the concept of biomimetic water replacement from the collagen intrafibrillar compartments as the ultimate goal in extending the longevity of resin-dentin bonds.

One-year stability of resin-dentin bonds created with a hydrophobic ethanol-wet bonding technique

UNLABELLED Dentin bonding performed with hydrophobic resins using ethanol-wet bonding should be less susceptible to degradation but this hypothesis has never been validated. OBJECTIVES This in vitro study evaluated stability of resin-dentin bonds created with an experimental three-step BisGMA/TEGDMA hydrophobic adhesive or a three-step hydrophilic adhesive after one year of accelerated aging in artificial saliva. METHODS Flat surfaces in mid-coronal dentin were obtained from 45 sound human molars and randomly divided into three groups (n=15): an experimental three-step BisGMA/TEGDMA hydrophobic adhesive applied to ethanol (ethanol-wet bonding-GI) or water-saturated dentin (water-wet bonding-GII) and Adper Scotchbond Multi-Purpose [MP-GIII] applied, according to manufacturer instructions, to water-saturated dentin. Resin composite crowns were incrementally formed and light-cured to approximately 5mm in height. Bonded specimens were stored in artificial saliva at 37 degrees C for 24h and sectioned into sticks. They were subjected to microtensile bond test and TEM analysis immediately and after one year. Data were analyzed with two-way ANOVA and Tukey tests. RESULTS MP exhibited significant reduction in microtensile bond strength after aging (24h: 40.6+/-2.5(a); one year: 27.5+/-3.3(b); in MPa). Hybrid layer degradation was evident in all specimens examined by TEM. The hydrophobic adhesive with ethanol-wet bonding preserved bond strength (24h: 43.7+/-7.4(a); one year: 39.8+/-2.7(a)) and hybrid layer integrity, with the latter demonstrating intact collagen fibrils and wide interfibrillar spaces. SIGNIFICANCE Coaxing hydrophobic resins into acid-etched dentin using ethanol-wet bonding preserves resin-dentin bond integrity without the adjunctive use of MMPs inhibitors and warrants further biocompatibility and patient safetys studies and clinical testing.

Tubular Occlusion Optimizes Bonding of Hydrophobic Resins to Dentin

Although hydrophobic resins may be bonded to acid-etched dentin with an ethanol wet-bonding technique, the protocol is sensitive to moisture contamination when bonding is performed in deep dentin. This study tested the hypothesis that the use of oxalate or poly(glutamic) acid-modified, diluted ceramicrete (PADC) for dentinal tubule occlusion prevents fluid contamination and improves the bonding of an experimental hydrophobic adhesive to acid-etched, ethanol-dehydrated dentin. Mid-coronal and deep acid-etched moist dentin pre-treated with oxalate or PADC was dehydrated by ethanol wet-bonding and infiltrated with the experimental three-step etch-and-rinse hydrophobic adhesive under simulated pulpal pressure. Tensile bond strengths to deep dentin without pre-treatment were severely compromised. Conversely, oxalate and PADC pre-treatments reduced dentin permeability, prevented water contamination, and improved bond strengths. Minimal nanoleakage was identified within hybrid layers created in the oxalate- and PADC-pre-treated deep dentin. The use of tubular occluding agents optimized bonding of hydrophobic resins to dentin.

Six-month evaluation of adhesives interface created by a hydrophobic adhesive to acid-etched ethanol-wet bonded dentine with simplified dehydration protocols

OBJECTIVES To evaluate the efficacy of simplified dehydration protocols, in the absence of tubular occlusion, on bond strength and interfacial nanoleakage of a hydrophobic experimental adhesive blend to acid-etched, ethanol-dehydrated dentine immediately and after 6 months. METHODS Molars were randomly assigned to 6 treatment groups (n=5). Under pulpal pressure simulation, dentine crowns were acid-etched with 35% H(3)PO(4) and rinsed with water. Adper Scotchbond Multi-Purpose was used for the control group. The remaining groups had their dentine surface dehydrated with ethanol solutions: group 1=50%, 70%, 80%, 95% and 3x100%, 30s for each application; group 2 the same ethanol sequence with 15s for each solution; groups 3, 4 and 5 used 100% ethanol only, applied in seven, three or one 30s step, respectively. After dehydration, a primer (50% BisGMA+TEGDMA, 50% ethanol) was used, followed by the neat comonomer adhesive application. Resin composite build-ups were then prepared using an incremental technique. Specimens were stored for 24h, sectioned into beams and stressed to failure after 24h or after 6 months of artificial ageing. Interfacial silver leakage evaluation was performed for both storage periods (n=5 per subgroup). RESULTS Group 1 showed higher bond strengths at 24h or after 6 months of ageing (45.6+/-5.9(a)/43.1+/-3.2(a)MPa) and lower silver impregnation. Bond strength results were statistically similar to control group (41.2+/-3.3(ab)/38.3+/-4.0(ab)MPa), group 2 (40.0+/-3.1(ab)/38.6+/-3.2(ab)MPa), and group 3 at 24h (35.5+/-4.3(ab)MPa). Groups 4 (34.6+/-5.7(bc)/25.9+/-4.1(c)MPa) and 5 (24.7+/-4.9(c)/18.2+/-4.2(c)MPa) resulted in lower bond strengths, extensive interfacial nanoleakage and more prominent reductions (up to 25%) in bond strengths after 6 months of ageing. CONCLUSIONS Simplified dehydration protocols using one or three 100% ethanol applications should be avoided for the ethanol-wet bonding technique in the absence of tubular occlusion, as they showed decreased bond strength, more severe nanoleakage and reduced bond stability over time.

The effect of long-term storage on the microleakage of composite resin restorations: qualitative and quantitative evaluation

The aim of this study was to evaluate the influence of storage periods of 24 hours and 3 months on the microleakage of class II cavities. Two methods of assessing microleakage were also compared. Class II cavities were prepared in sound human molars. MO cavities were restored using ABF experimental (Kuraray Medical Inc.) + Z250 composite resin (3M ESPE), and DO cavities were restored using Single Bond (3M ESPE) + Z250. After different storage periods, specimens were thermocycled, immersed in a dye (0.5% methylene blue solution for 4 h) and longitudinally sectioned. Dye penetration was scored according to a 0-4 scale. The extent of microleakage was measured using the ImageLab 2000 program. A statistically significant correlation was verified between both evaluation methods (r = 0.978, p < 0.001). ANOVA revealed a statistically significant difference between the tested adhesive systems regarding microleakage (p < 0.001), although it was not influenced by the different storage periods.

Microtensile bond strength of current adhesive systems when compared to cohesive strength of sound dentin and a resin-based composite

Received: March 28, 2004; Revised: September 8, 2004Purpose: To evaluate the microtensile bond strength ( µTBS) to dentin of 4 adhesive systems,the micromorphology of the adhesive/dentin interface and to compare the results to the µTS (co-hesive strength) of sound dentin and resin composite. Occlusal surfaces of 24 extracted caries-freehuman molars were cut flat to expose the dentin surface. They were randomly assigned to 4 groups(n = 6): Adper Scotchbond Multi Purpose Plus (MP), Adper Single Bond (SB), Clearfil ProtectBond (CP) and Adper Prompt (AP). Adhesive systems were applied and “crowns” were builtusing Z100. Other 5 human molars were sectioned to obtain square-shaped dentin blocks and5 resin blocks were built using a composite resin, Z100. After storage in distilled water at 37 °Cfor 24 h, stick-shaped specimens were obtained for all groups (n = 5) with 0.8 mm

Influência do tempo de armazenamento na resistência de união à dentina de dois

O objetivo da pesquisa foi estudar a influencia do tempo de armazenamento (24h e tres meses) na resistencia adesiva de dois tipos de adesivo dental, sendo um convencional, Single Bond (SB) e outro com primer autocondicionante, ABF experimental (ABF), e tambem a influencia das variacoes regionais do substrato dentinario. O esmalte oclusal de 16 terceiros molares foi removido, expondo uma superficie dentinaria plana. Nesta, foi criada uma camada de smear atraves de lixas de papel de granulacoes decrescentes. Apos a aplicacao dos sistemas adesivos, blocos de resina Z250 de 5 mm de altura foram construidos sobre a superficie dentinaria. Os dentes foram divididos em quatro grupos (n=4) de acordo com o material e o tempo de armazenagem em agua destilada a 37∞C: A)SB 24 h; B)SB tres meses; C)ABF 24 h; D)ABF tres meses. Apos o armazenamento, os dentes foram seccionados, longitudinalmente, em cortes perpendiculares entre si, a fim de se obterem corpos-de-prova (cp) em formato de palito de aproximadamente 0,8 mm2 de seccao transversal, constituidos por resina-adesivo-dentina. Esses cp foram mapeados, com esmaltes de diferentes cores, conforme suas localizacoes no dente: mais periferica ou interna, no sentido horizontal. Os especimes foram submetidos ao teste de microtracao. A analise de variância demonstrou nao haver diferenca significante entre os valores medios de resistencia dos dois adesivos com diferentes idades de armazenamento, nem entre as diferentes regioes do dente.