Evaluation of Internal bleaching with 35% hydrogen peroxide in dentin conditioned with 37% phosphoric acid and 17% EDTA / Evaluación del blanqueamiento interno con peróxido de hidrógeno al 35% en dentina acondicionada con ácido fosfórico al 37% y EDTA al 17%

Introduction: This study aimed to evaluate the effect of dentin surface treatment with 37% phosphoric acid or 17% ethylenedia-minetetraacetic acid (EDTA) before Internal Bleaching with 35% hydrogen peroxide using the walking bleach technique. Material and Methods: This experimental in vitro study used 66 human premolars extracted for orthodontic reasons, which were debrided, endodontically prepared, and pigmented with chromogens derived from blood decomposition. The samples were randomly divided into three groups (n=22). Group A: bleaching agent without dentin conditioning; group B: bleaching agent in dentin conditioned with phosphoric acid 37%; group C: bleaching agent in dentin conditioned with 17% EDTA. 4 applications of bleaching agent were used with a separation of 4 days between each session. The initial color (baseline) and after each application was determined by spectrophotometry, recording the CIE L*a*b* values and the total color variation between the initial parameters and the different evaluation times. Results: Data were statistically analyzed with the Wilcoxon test. This showed statistically significant differences for the total variation of the color between the study groups, with the control group in no case inferior to the rest. Conclusion: The application of 37% phosphoric acid increased the effectiveness of the bleaching agent when compared to 17% EDTA. However, these did not increase the effectiveness compared to the application of the bleaching agent without a previous dentin surface treatment.

Introducción: El objetivo de este estudio fue evaluar el efecto del tratamiento de superficie dentinaria con ácido fosfórico al 37% o EDTA al 17% previo al blanqueamiento Interno con peróxido de hidrógeno al 35% por medio de la técnica Walking Bleach. Material y Métodos:Para este estudio experimental in vitro, se utilizaron 66 premolares humanos extraídos por indicación ortodóncica, los cuales fueron desbridados, preparados endodónticamente, y pigmentados con cromógenos derivados de la descomposición sanguínea. Las muestras fueron divididas aleatoriamente en 3 grupos (n=22). Grupo A: agente blanqueador sin acondicionamiento dentinario, grupo B: agente blanqueador en dentina acondicionada con ácido fosfórico 37% y grupo C: agente blanqueador en dentina acondicionada con EDTA 17%. Se utilizaron 4 aplicaciones de agente blanqueador con una separación de 4 días entre cada sesión. El color inicial (baseline) y tras cada aplicación fue determinado mediante espectrofotometría, registrando los valores CIE L*a*b* y la variación total de color entre los parámetros iniciales y los diferentes tiempos de evaluación. Resultados: Los datos fueron analizados estadísticamente con la prueba de Wilcoxon, arrojando diferencias estadísticamente significativas para la variación total del color entre los grupos de estudio, siendo en ningún caso el grupo control inferior al resto. Conclusión: La aplicación de ácido fosfórico al 37% aumenta la eficacia del agente blanqueador al compararlo con el EDTA 17%, sin embargo, no aumentan la eficacia respecto a la aplicación del agente blanqueador sin un tratamiento de superficie dentinaria previo.

Twenty-four-month clinical performance of different universal adhesives in etch-and-rinse, selective etching and self-etch application modes in NCCL - a randomized controlled clinical trial

Abstract Objective The aim of this randomized, controlled, prospective clinical trial was to evaluate the performances of two different universal adhesives and one etch-rinse adhesive for restoration of non-carious cervical lesions (NCCLs). Material and Methods Twenty patients with at least seven NCCLs were enrolled. Lesions were divided into seven groups according to adhesive systems and application modes: GSE: GLUMA Universal-self-etch, GSL: GLUMA Universal-selective etching, GER: GLUMA Universal-etch-and-rinse, ASE: All-Bond Universal-self-etch, ASL: All-Bond Universal-selective etching, AER: All-Bond Universal-etch-and-rinse, SBE (Control): Single Bond2-etch-and-rinse. A total of 155 NCCLs were restored with a nano hybrid composite (Tetric N-Ceram). Restorations were scored with regard to retention, marginal discoloration, marginal adaptation, recurrent caries and post-operative sensitivity using modified United States Public Health Service (USPHS) criteria after one week, 6, 12 and 24 months. Statistical evaluations were performed using Chi-square tests (p=0.05). Results The recall rate was 81.9% after the 24-month follow-up. The cumulative retention rates for self-etch groups (GSE: 72.2%, ASE:75%) were significantly lower than other experimental groups (GSL: 93.7%, GER: 100%, ASL: 94.1%, AER: 100%, SBE: 100%) at the 24-month follow-up (p<0.05). Regarding marginal adaptation and marginal discoloration, GSE and ASE groups demonstrated more bravo scores after 6 and 12-month observations but differences were not significant (p>0.05). Only one restoration from ASL group demonstrated post-operative sensitivity at 6 and 12-month observations. No secondary caries was observed on the restorations at any recall. At the end of 24-month observations, no significant differences were detected among groups regarding any of the criteria assessed, except retention. Conclusion GLUMA Universal and All-Bond Universal showed better results in etch-and-rinse and selective etching mode compared to the self-etch mode regarding retention. Etch-and-rinse and selective etching application modes of the current universal adhesives tended to provide better clinical outcomes considering the criteria evaluated at the end of 24-month evaluation.

Influence of pH, bleaching agents, and acid etching on surface wear of bovine enamel

ABSTRACT Development of new materials for tooth bleaching justifies the need for studies to evaluate the changes in the enamel surface caused by different bleaching protocols. Objective The aim of this study was to evaluate the bovine dental enamel wear in function of different bleaching gel protocols, acid etching and pH variation. Material and Methods Sixty fragments of bovine teeth were cut, obtaining a control and test areas. In the test area, one half received etching followed by a bleaching gel application, and the other half, only the bleaching gel. The fragments were randomly divided into six groups (n=10), each one received one bleaching session with five hydrogen peroxide gel applications of 8 min, activated with hybrid light, diode laser/blue LED (HL) or diode laser/violet LED (VHL) (experimental): Control (C); 35% Total Blanc Office (TBO35HL); 35% Lase Peroxide Sensy (LPS35HL); 25% Lase Peroxide Sensy II (LPS25HL); 15% Lase Peroxide Lite (LPL15HL); and 10% hydrogen peroxide (experimental) (EXP10VHL). pH values were determined by a pHmeter at the initial and final time periods. Specimens were stored, subjected to simulated brushing cycles, and the superficial wear was determined (μm). ANOVA and Tukey´s tests were applied (α=0.05). Results The pH showed a slight decrease, except for Group LPL15HL. Group LPS25HL showed the highest degree of wear, with and without etching. Conclusion There was a decrease from the initial to the final pH. Different bleaching gels were able to increase the surface wear values after simulated brushing. Acid etching before bleaching increased surface wear values in all groups.

Influência de diferentes ácidos fosfóricos na adesão ao esmalte / Influence of different phosphoric acids in enamel adhesion

The aim of this study was to evaluate in vitro the shear bond strength of a composite resin after acid etching with phosphoric acid 37% with and without chlorhexidine. Thirty bovine incisors were divided into two groups (n = 15), according to the type of acid etching applied in enamel – G1 (phosphoric acid 37%) and G2 (phosphoric acid 37% with chlorhexidine 2%). The conditioning of the surface followed the manufacturers’ recommendations; after this step, there was the application of adhesive and the insertion of composite resin in a rubber matrix with a center hole of 4 mm. The specimens were submitted to analysis of shear strength in a Shimadzu AGS-X Universal Testing Machine with crosshead speed of 1 mm/min and the values measured in MPa. After the test, the Adhesive Remnant Index (ARI) was assessed. Data were analyzed by descriptive and inferential statistics, adopting a significance level of 5%. The mean shear strength reported for the two groups were, respectively, 12.02 MPa and 11.86 MPa (unpaired t-test; p-value > 0.05). As for the ARI, the most frequent scores for G1 and G2 were 3 and 5, with no statistically significant difference between groups (Mann-Whitney test; p-value > 0.05). Under the experimental conditions of the study, we conclude that the addition of chlorhexidine to phosphoric acid 37% did not affect the bond strength to the enamel surface nor the type of failure found.

O objetivo deste estudo foi avaliar in vitro a resistência ao cisalhamento de uma resina composta após condicionamento com ácido fosfórico 37% com e sem clorexidina. Trinta incisivos bovinos foram divididos em dois grupos (n = 15) de acordo com o tipo de ataque ácido aplicado ao esmalte – G1 (ácido fosfórico a 37%) e G2 (ácido fosfórico 37% com clorexidina a 2%). O condicionamento da superfície obedeceu às recomendações dos fabricantes e, em seguida a esta etapa, realizou-se a aplicação do adesivo e procedeu-se a inserção da resina composta em matriz de borracha com orifício central de 4 mm. Os corpos de prova foram submetidos ao teste de resistência ao cisalhamento em máquina de ensaios mecânicos Shimadzu com velocidade de carga de 1mm/min e os valores registrados em MPa. Após o ensaio, foi observado o Índice de Remanescente Adesivo (IRA). Os dados foram analisados por estatística descritiva e inferencial, adotando-se nível de signifi cância de 5%. A média da resistência ao cisalhamento registrada para os dois grupos foi, respectivamente, 12,02 MPa e 11,86 MPa (teste t não pareado; p-valor> 0,05). Quanto ao IRA, os escores mais frequentes para G1 e G2 foram 3 e 5, não sendo observada diferença estatisticamente significante (Teste Mann-Whitney; p-valor>0,05). Nas condições experimentais do estudo, conclui-se que a adição de clorexidina ao ácido fosfórico 37% não interferiu na resistência de união à superfície do esmalte nem no tipo de fratura encontrado.

Influence of selective acid etching on microtensile bond strength of a self-adhesive resin cement to enamel and dentin

Aim: To evaluate the selective acid etching of enamel and dentin on microtensile bond strength (¦ÌTBS) of a self-adhesive resin cement. Methods: Forty-eight bovine teeth were selected and had the buccal surface ground to obtain a flat dentin (n=24) or enamel (n=24) surface. Z250 composite resin blocks (4 x 3 x 8 mm) were prepared for cementation at enamel and dentin. Each substrate received three experimental resin cementation strategies: 1) 37% phosphoric acid etching before the application of RelyX Unicem; 2) application of RelyX Unicem alone; 3) RelyX ARC as a control. Samples were light-cured using a halogen light (Optilux 501, 700mW/cm2), for 40 s. Hourglass-shaped specimens were obtained and submitted to a tensile strength at a crosshead speed of 0.5 mm/min in a universal testing machine. For statistical analysis, data were submitted to ANOVA and Tukey¡¯s test at a pre-set alpha (¨¢=0.05). Results: RelyX Unicem showed similar bond strength value (16.5 MPa) when compared to the pretreatment with acid etching (11.9 Mpa) and to the conventional resin cement (18.1 MPa) for enamel. All luting strategies presented similar dentin bond strength, but significantly lower than enamel bond strength. Conclusions: Acid etching prior to RelyX Unicem application did not improve microtensile bond strength for enamel and dentin.

Métodos de reparo em resina composta: uma revisão / Methods of repair in composed resin: a revision

Apesar de a resina composta ser amplamente conhecida e utilizada com sucesso na confecção das restaurações, em alguns casos há necessidade de reparos, os quais exigem menos desgastes dentário em comparação à substituição total das restaurações. Dessa forma, o presente trabalho tem como objetivo revisar os principais procedimentos e materiais utilizados na confecção dos reparos de resina composta, assim como os testes que avaliam a força de adesão de tais procedimentos. Meios químicos e mecânicos, isolados ou associados, tem sido propostos para analisar a força de adesão ao reparo, como a utilização do ácido fluorídrico, ácido fosfórico, jateamento de óxido de alumínio, pontas diamantadas, adesivos e silano. Com base na literatura revisada, observou-se a importância do tratamento da superfície da resina a ser reparada e concluiu-se que o jateamento com óxido de alumínio, seguido da aplicação do ácido fosfórico e do adesivo foi o modo mais eficaz de seconseguir sucesso nos reparos de resina composta.

Although the composites being widely known and used with success in the restorations, in some cases repairs are necessary, which demand less dental waste in comparison with the total substitution of the restorations. In that way, the aim of this work was to review the main procedures and materials used in repairs of composites, as well as the explaining of the tests that evaluated the bond strength of such procedures. A number of techniques have been proposed to improve bond strength of composite repair through roughening, etching the substrate surface with acidulated phosphate fluoride, HF acid gel, air-borne particle abrasion or using adhesive resins. Based on the reviewed bibliography, the importance of the treatment of the surface was observed from the resin to be repaired, and it was concluded that the air-borne particle abrasion was the most effective way for composites, followed by the application of the HF acid gel and adhesive resins.

Localized mechanics of dentin self-etching adhesive system

The bond strength of composite resins (CRs) to dentin is influenced by the interfacial microstructure of the hybrid layer (HL) and the resin tags (TAG). The contemporary self-etching primer adhesive systems overcame the inconvenient of the etch-and-rinse protocol. Studies, however, have demonstrated that HL thickness and TAG length vary according to the wetting time and additional use of acid-etching prior to self-etching primers. This study investigated the localized stress distribution in the HL and the dentin/adhesive interface. Two HL thicknesses (3 or 6 mum), two TAG lengths (13 or 17 mum) and two loading conditions (perpendicular and oblique-25°) were investigated by the finite element (FE) analysis. Five two-dimensional FE models (M) of a dentin specimen restored with CR (38 x 64 mum) were constructed: M1 - no HL and no TAG; M2 - 3 mum of HL and 13 ìm of TAG; M3 - 3 mum of HL and 17 mum of TAG; M4 - 6 mum of HL and 13 mum of TAG; and M5 - 6 mum of HL and 17 mum of TAG. Two distributed loadings (L) (20N) were applied on CR surface: L1 - perpendicular, and L2 - oblique (25°). Fixed interfacial conditions were assigned on the border of the dentin specimen. Ansys 10.0 (Ansys®, Houston, PA, USA) software was used to calculate the stress fields. The peak of von Mises (sigmavM) and maximum principal stress (sigmamax) was higher in L2 than in L1. Microstructures (HL and TAG) had no effect on local stresses for L1. Decreasing HL decreased sigmavM and sigmamax in all structures for L2, but the TAG length had influence only on the peributular dentin. The thickness of HL had more influence on the sigmavM and sigmamax than TAG length. The peritubular dentin and its adjacent structures showed the highest sigmavM and sigmamax, mainly in the oblique loading.

Cytotoxicity of dental bonding agents to human dental pulp cells in vitro / 实用口腔医学杂志

Objective:To evaluate the cytotoxicity of different dental bonding agents to human dental pulp cells. Methods:Four dental bonding agents(Prime & Bond NT,Single Bond,Xeno Ⅲ and iBond) were diluted with the culture medium by a ratio of 1∶1 000,1∶2 000 and 1∶4 000(v/v), and the fourth passage of dental pulp cells were then exposed to agent dilutions for 12, 24 and 48 h respectively, then the morphological changes of pulp cells were observed with microscopy and cytotoxicity was analyzed with modified 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay.Results:There was significant influence of the type of dental bonding agents,exposure time and concentration on the cell morphology. Total-etch system was more toxic than self-etch system.Conclusion:Dental bonding agents are toxic to pulp cells,Single Bond is the strongest cytotoxic agent among the 4 adhesive agents.