Factors that Affect the Shear Bond Strength of Pit and Fissure Sealants to Tooth Structure: A Systematic Review.

INTRODUCTION: Pit and fissure sealants are effective in preventing caries disease, however, they may present flaws that damage the physical barrier leading to treatment failure. OBJECTIVE: To answer the question ''Do pit and fissure sealants present good adhering to the dental structure when analyzed by their resistance to shear/microshear?". METHODS: This systematic review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) and was recorded in Open Science Framework. Embase, PubMed, SCOPUS, and Web of Science databases were used for the search strategy. The articles were selected according to the eligibility criteria. The risk of bias was performed with the adaptation of the quasi-experimental studies tool by Joanna Briggs Institute (JBI). RESULTS: 1245 studies were found in the databases when applying the search strategy, after removal of duplicates 881 were evaluated and 44 were selected. After applying the JBI tool, 30 studies presented low risk and 15 moderate risk of bias. Meta-analysis was not possible to performed due to the heterogeneity of the studies. CONCLUSION: The adhesion is dependent on the application protocol, and among the protocols evaluated, conditioning with 37% phosphoric acid for 60 seconds and contamination of the substrate, as these can affect sealant adhesion.

Effect of Protein-Based Treatment on Chemical Composition, Hardness and Bond Strength of Remineralized Enamel

Abstract This study evaluated the chemical composition and microhardness of human enamel treated with an Enamel Matrix Derivative (EMD) solution, and the bond strength between composite resin and this enamel. Thirty human enamel samples were randomly divided into three groups: Untouched Enamel (UE), Demineralized Enamel (DE) and Demineralized Enamel Treated with EMD (ET). DE and ET groups were subjected to acid challenge and ET treated with EMD (EMD was directly applied over conditioned enamel and left for 15 min). Samples from each group (n=4) had chemical composition assessed through to attenuated total reflectance Fourier transform infrared (ATR-FTIR). Knoop microhardness of enamel samples from each group (n=10) was measured. For the microshear bond strength, the samples were etched for 30 s, and the adhesive was applied and cured for 10 s. Two matrixes were placed on the samples, filled with Filtek Z350 XT composite and cured for 20 s, each. The matrix was removed, and the microshear bond strength of each group (n=10) was tested. Data were subjected to Kruskal-Wallis test (for microhardness), to analysis of variance and to Tukey's test (for microshear bond strength); (α=0.05). FTIR results have shown phosphate (hydroxyapatite indicator) in 900-1200 cm-1 bands in the UE and ET groups, which were different from the DE group. Microhardness and microshear analyses recorded higher statistical values for the UE and ET groups than for DE. EMD application to demineralized enamel seems to have remineralized the enamel; thus, the microhardness and bond strength was similar between UE and ET groups.

Resumo Este estudo avaliou a composição química e microdureza do esmalte humano tratado com solução de Derivados da Matriz do Esmalte (EMD) e a resistência de união entre compósito e este esmalte. Trinta amostras de esmalte humano foram aleatoriamente divididas em três grupos: Esmalte Intocado (UE), Esmalte Desmineralizado (DE) e Esmalte Desmineralizado Tratado com EMD (ET). Os grupos DE e ET foram submetidos a desafio ácido e ET tratado com EMD (O EMD foi aplicado diretamente sobre esmalte condicionado e deixado por 15 minutos). Amostras de cada grupo (n = 4) tiveram composição química avaliada através de espectroscopia no infravermelho por transformada de Fourier com reflectância total atenuada (FTIR-ATR). A microdureza Knoop das amostras de esmalte de cada grupo (n=10) foi mensurada. Para a resistência ao microcisalhamento, as amostras foram condicionadas por 30 s, o adesivo aplicado e foto-ativado por 10 s. Duas matrizes plásticas (1 mm de comprimento) foram posicionadas sobre as amostras, preenchidas com compósito Filtek Z350 XT e foto-atiavadas por 20 s cada. As matrizes foram removidas e a resistência ao microcisalhamento de cada grupo (n=10) foi testada. Os dados foram submetidos ao teste de Kruskal-Wallis (para análise da microdureza), à análise de variância e ao teste de Tukey (para análise da resistência ao microcisalhamento); (α=0.05). Os resultados do FT-IR mostraram fosfato (indicador de hidroxiapatita) na banda entre 900-1200 cm-1 nos grupos UE e ET, diferentemente do grupo DE. Análises de microdureza e microcisalhamento demonstraram resultados estatisticamente superiores para os grupos UE e ET quando comparados ao DE. A aplicação de EMD ao esmalte desmineralizado parece ter remineralizado o esmalte; assim, a microdureza e a resistência de união foram semelhantes entre os grupos UE e ET.

Reliability and correlation between microshear and microtensile bond strength tests of composite repairs.

The aim of this study was to evaluate the reliability of microshear (µSBS) and microtensile (µTBS) bond strength tests on composite repairs using universal adhesives with or without the application of additional silane. Cylindrical (µSBS) and block-shaped (µTBS) specimens were fabricated using nanofilled (F-Filtek One Bulk Fill) and nanohybrid (T-Tetric EvoCeram Bulk Fill) bulk-fill composites. The specimens were aged by thermocycling (5,000 cycles, 5-55 °C), sandblasted, and then divided into three groups (n = 30) as follows: non-repaired (FC and TC), repaired with universal adhesives (FA, Scotchbond Universal; and TA, Adhese Universal), and with the previous application of silane (FS and TS). After 48 h, the specimens were repaired using the same composite. The µSBS and µTBS specimens exhibited bonded areas of 1 mm2 and were subjected to shear stress and tension until failure, at a crosshead speed of 0.5 mm/min in a universal testing machine. Weibull analyses and Pearson correlation (α = 0.05) were applied to the data. At characteristic strength, FC, FA, and FS exhibited significantly higher µSBS when compared with TA and TS (p < 0.05). However when tested by µTBS at the same parameter, FA presented significantly lower bond strength when compared to FC, FS, and TA (p < 0.05). The correlation between Weibull modulus was strongly negative and not significant (p > 0.05). Both bond strength tests exhibited a material-dependent behavior. The microtensile bond strength test demonstrated more reliability than the microshear test for composite repair evaluation.

Bond stability of conventional adhesive system with MMP inhibitors to superficial and deep dentin.

PURPOSE: To evaluate the microshear bond strength (µSBS) to deep (DD) or superficial (SD) dentin (µSBS) overtime, nanoleakage (AG%), degree of conversion (DC%), water sorption (WSp), and solubility (WSl) of an adhesive system [Adper Single Bond 2(ASB)] containing matrix metalloproteinases (MMP) inhibitors [GM1489 (ASB-GM), Batimastat (ASB-BAT), or Chlorhexidine diacetate (ASB-CHX)]. ASB without inhibitor was used as control (CONTROL). MATERIALS AND METHODS: WSp and WSL were calculated based on ISO4049. DC% was analyzed using FT-IR spectroscopy. Dentin discs were used for µSBS evaluation. For AG%, resin-dentin beams were analyzed under scanning electronic microscopy. Data were analyzed using three-way ANOVA (AG% and µSBS) or ANOVA (DC%, WSp, WSl) and Tukey's HSD test. RESULTS: ASB-CHX presented the lowest DC%, lowest WSp, and highest WSl. ASB-GM reached the highest immediate µSBS in SD, only different from ASB-CHX. In DD, ASB-BAT and ASB-GM had the highest µSBS, statistically different from ASB-CHX. After twelve months, ASB-GM and ASB-BAT presented higher µSBS in SD when compared to CONTROL and ASB-CHX. In DD, ASB-GM reached the highest value, which was statistically different from CONTROL and ASB-CHX. CONTROL at both dentin depths and ASB-CHX at DD did not maintain bond stability. In SD after 12 months, ASB-BAT and ASB-GM decreased AG%. In DD, only ASB-GM reduced AG%. CONCLUSION: The ASB containing Batimastat and GM1489 maintained resin-dentin bond stability after 12 months for both dentin depths, without jeopardizing WSp, WSl, or DC% of the adhesive system. The ASB-GM presented greater µSBS after 12 months when compared with ASB. CLINICAL SIGNIFICANCE: Batimastat and GM1489 could be suitable for inclusion as an MMP-inhibitor into Single Bond to improve the bond stability to superficial and deep dentin, without jeopardize the physic-mechanical proprieties.

Influence of different resin cements and surface treatments on microshear bond strength of zirconia-based ceramics.

AIM: This study aims to evaluate the microshear bond strength of zirconia-based ceramics with different resin cement systems and surface treatments. MATERIALS AND METHODS: Forty blocks of zirconia-based ceramic were prepared and embedded in polyvinyl chloride (PVC) tubes with acrylic resin. After polishing, the samples were washed in an ultrasonic bath and dried in an oven for 10 min. Half of the samples were subjected to sandblasting with aluminum oxide. Blocks were divided into four groups (n = 10) in which two resin cements were used as follows: (1) RelyX™ U100 with surface-polished zirconia; (2) RelyX™ U100 with surface-blasted zirconia; (3) Multilink with surface-polished zirconia; and 4) Multilink with surface-blasted zirconia. After performing these surface treatments, translucent tubes (n = 30 per group) were placed on the zirconia specimens, and resin cement was injected into them and light cured. The PVC tubes were adapted in a universal testing machine; a stiletto blade, which was bolted to the machine, was positioned on the cementation interface. The microshear test was performed at a speed of 0.5 mm/min. Failure mode was analyzed in an optical microscope and classified as adhesive, cohesive, or mixed. RESULTS: The null hypothesis of this study was rejected because there was a difference found between the resin cement and the surface treatment. There was a statistical difference (P < 0.005) in RelyX™ U100 with surface-blasted zirconia, in relation to the other three groups. For Multilink groups, there was no statistical difference between them. CONCLUSION: Self-adhesive resin cement showed a more significant tendency toward bond strength in the ceramic-based zirconium oxide grit-blasted surfaces.

Effect of self-curing activators and curing protocols on adhesive properties of universal adhesives bonded to dual-cured composites.

OBJECTIVES: To measure microshear bond strength (µSBS) and nanoleakage (NL) of self-etch universal adhesives under core buildup restorations using different curing protocols, at 24h and after 6-month water storage. METHODS: Middle dentin of 55 molars was divided into: Clearfil Universal Bond [CFU], Prime&Bond Elect [PBE], and One Coat 7 Universal [OCU]. All-Bond Universal [ABU] and Clearfil SE Bond [CSE] were used as control. CFU, PBE and OCU were: light-cured [LC], dual-cured [DC] and self-cured [SC]. Data were analyzed separately (two-way ANOVA), Tukey's test (α=0.05). RESULTS: µSBS: At 24h OCU/LC resulted in statistically higher µSBS than ABU. CSE/DC showed statistically higher µSBS than all DC adhesives. PBE/LC resulted in significant lower µSBS than the respective DC/SC modes (p<0.001). At 6-month, both CFU and PBE (LC/SC), resulted in a significant decrease in µSBS. µSBS for OCU/DC decreased significantly (p<0.001) compared to the respective LC/SC modes. NL: At 24h, ABU showed %NL similar to CBU/LC and OCU/LC (p>0.05). CSE/DC resulted in significantly higher %NL than OCU/DC but significantly lower than PBE/DC. CFU/LC/SC resulted in significantly lower %NL than CFU/DC. PBE/SC resulted in significant lower %NL than PBE/LC and PBE/DC. OCU/LC and OCU/DC resulted in significant lower %NL than OCU/SC (p<0.001). At 6-month ABU, CSE, CFU/LC and CFU/SC, resulted in a significant increase in %NL. SIGNIFICANCE: Self-cured activator and different curing protocols influenced µSBS and NL of self-etch universal adhesives, but this influence was material-dependent.

New Single-bottle Ceramic Primer: 6-month Case Report and Laboratory Performance.

INTRODUCTION: This article presents a 6-month case report and an in vitro evaluation of the performance of the new self-etching glass-ceramic monobond etch and prime (MEP) when applied in a lithium disilicate (LD). The MEP contains in the same bottle, along with acid conditioner and silanes. This simplifies the bonding procedures by reducing not only the number of steps, but also the working time. A 42-year-old female patient sought for esthetic treatment, and the main complaint was the darkened appearance of the upper lateral incisor. The esthetic treatment includes dental bleaching and gingivectomy, all-ceramic zirco-nia crowns, and all-ceramic crown and laminate veneer LD. After 6 months of esthetic treatment, marginal staining, gap, or chip fracturing damaging margins after sharp explorer in the margins was not observed. Furthermore, the inferior etching pattern of MEP was compared with traditional hydrofluoric acid (HF) conditioning. The microshear bond strength to the intaglio surface of LD was statistically similar when HF was compared with MEP. This new self-etching glass-ceramic showed good in vitro and 6 months clinical results in this case report. Future long-term clinical studies with more clinical case need to be done to confirm the performance of the use of this new conditioner. CLINICAL SIGNIFICANCE: The use of a new self-etching glass-ceramic showed a good in vitro and 6 months clinical results. This new product can be an easy, simple, and alternative approach for esthetics bonding procedure.

The Effect of Hydrofluoric Acid Concentration and Heat on the Bonding to Lithium Disilicate Glass Ceramic

Abstract The aim of this study was to evaluate the effects of hydrofluoric acid (HF) concentration and previous heat treatment (PHT) on the surface morphology and micro-shear bond strength (mSBS) of a lithium disilicate glass ceramic (EMX) to resin cement. One hundred four EMX specimens were randomly assigned to two groups (n=52) according to the HF concentration: 5% and 10%. A new random distribution was made according to the PHTs (n=13): control (no PHT); previously heated HF (70 °C); previously heated EMX surface (85 °C); the combination of heated HF + heated EMX surface. The etching time was set at 20 s. All EMX blocks were silanated and received a thin layer of an unfilled resin. Five resin cement cylinders were made on each EMX surface using Tygon tubes as matrices, and then stored for 24 h at 37 °C. One random etched EMX sample from each group was analyzed using field-emission scanning electron microscopy (FE-SEM). The data were subjected to two-way ANOVA and multiple comparisons were performed using the Tukey post hoc test (a=0.05). For the control groups, 5% HF showed statistically lower mSBS values when compared to 10% HF (p<0.05). PHT increased the mSBS values for 5% HF, yielding statistically similar results to non-PHT 10% HF (p<0.05). FE-SEM images showed increased glassy matrix removal when PHT was applied to HF 5%, but not to the same degree as for 10% HF. PHT has the potential to improve the bond strength of 5% HF concentration on lithium disilicate glass ceramic.

Resumo O objetivo deste estudo foi avaliar os efeitos das concentrações de ácido fluorídrico (AF) e do prévio tratamento térmico (PTT) na morfologia da superfície e resistência de união ao microcisalhamento (mRUM) de uma cerâmica vítrea de dissilicato de lítio (EMX) ao cimento resinoso. Cento e quatro espécimes de EMX foram aleatoriamente distribuídos em dois grupos (n=52) de acordo com a concentração do AF: 5% e 10%. Os espécimes foram novamente distribuídos de forma aleatória de acordo com o PTT (n=13): controle (sem PTT); AF previamente aquecido (70 °C); superfície do EMX previamente aquecida (85 °C); combinação entre AF e EMX aquecidos. O tempo de condicionamento foi fixado em 20 s. Todos os espécimes de EMX foram silanizados e receberam a aplicação de uma fina camada de um adesivo sem carga. Cinco cilindros de cimento resinoso foram confeccionados usando tubos Tygon como matrizes e então armazenados por 24 h a 37 °C. Uma amostra condicionada de cada grupo foi aleatoriamente selecionada e analisada em um microscópio eletrônico de varredura em emissão de campo (MEVEC). Os dados foram submetidos ao teste ANOVA de dois fatores e múltiplas comparações foram feitas pelo teste de Tukey (a=0.05). Para os grupos controle, AF 5% mostrou valor de mRUM estatisticamente menor do que AF 10% (p<0.05). PTT aumentou os valores de mRUM para o AF 5%, proporcionando resultados estatisticamente similares ao grupo AF 10% controle (p<0.05). MEVEC mostrou um aumento na remoção da matriz vítrea quando o PTT foi aplicado ao grupo AF 5%, no entanto esse efeito não foi visto no grupo AF 10%. O PTT tem o potencial de melhorar a resistência de união do AF 5% na cerâmica vítrea reforçada por disilicato de lítio.

Influence of Surface Treatments and Adhesive Systems on Lithium Disilicate Microshear Bond Strength

Abstract The purpose of this study was to evaluate the microshear bond strength of ceramic prosthetic structures reinforced by lithium disilicate cemented with resin cement under conditions of different surface treatments and adhesive systems. Seventy-two rectangular blocks of lithium disilicate (6.5 mm long × 5 mm wide × 1 mm thick) were fabricated, air abraded with 50-μm Al2O3 particles and divided into six groups (n=12) depending on the surface pretreatments. The groups were as follows: 10HF/S/SBM: 10% hydrofluoric acid etched for 20 s (10HF) + silane (S) + Adper Scotchbond Multi-Purpose (SBM); 10HF/S/SB: 10HF + S + Single Bond Universal (SB); 10HF/SBM; 10HF/SB; S/SBM and S/SB. Two 1-mm-long plastic tubes were placed on the specimens, filled with RelyX ARC resin cement and cured for 20 s per tube. The plastic tube was removed, and the microshear bond strength was tested. Data were submitted to analysis of variance and Tukey's tests (α=0.05). Fractured specimens were observed under optical microscopy. For both adhesives, the bond strengths (MPa) of groups treated with acid-etching and silane (10HF/S/SB: 24.82, 10HF/S/SBM: 24.90) were higher (p<0.001) than those of groups treated with acid-etching (10HF/SB: 16.47, 10HF/SBM: 19.94) only or only silane (S/SB: 18.42, S/SBM: 13.24). All groups showed a predominance of failure adhesive. The silanization should be a clinical step in cementing ceramic structures reinforced by lithium disilicate, even with the application of universal adhesive that contains silane in its formulation.

Resumo O objetivo neste estudo foi avaliar a resistência de união ao microcisalhamento de estruturas protéticas cerâmicas reforçadas por dissilicato de lítio cimentadas com cimento resinoso sob diferentes tratamentos de superfície e sistemas adesivos. Setenta e duas barras retangulares de dissilicato de lítio (6,5 mm de comprimento × 5 mm de largura × 1 mm de espessura) foram fabricadas, tratados com partículas de Al2O3 (50 μm) e dividido em seis grupos (n=12) dependendo dos pré-tratamentos de superfície. Os grupos foram como se segue: 10HF/S/SBM: condicionamento com ácido fluorídrico 10% durante 20 s (10HF) + silano (S) + Adper Scotchbond Multi-Purpose (SBM); 10HF/S/SB: 10HF + S + Single Bond Universal (SB); 10HF/SBM; 10HF/SB; S/SBM; e S/SB. Dois tubos plásticos cilíndricos de 1 mm de comprimento foram colocados sobre os espécimes, preenchidos com cimento RelyX ARC e fotoativado durante 20 s por tubo. Os tubos plásticos foram removidos e a resistência de união ao microcisalhamento foi testada. Os dados foram submetidos à análise de variância e ao teste de Tukey (α=0,05). Espécimes fraturados foram observados sob microscopia óptica. Para ambos os adesivos, a resistência de união (MPa) dos grupos tratados com condicionamento ácido e silano (10HF/S/SB: 24,82, 10HF/S/SBM: 24,90) foram superiores (p<0.001) aos grupos tratados com condicionamento ácido apenas (10HF/SB: 16,47, 10HF/SBM: 19,94) ou apenas silano (S/SB: 18,42, S/SBM: 13,24). Todos os grupos apresentaram uma predominância de falha adesiva. A silanização deve ser um passo clínico em cimentação de estruturas cerâmicas reforçadas por dissilicato de lítio, mesmo com a aplicação do adesivo universal que contém em sua formulação um silano.

Effect of Fluoride and Simplified Adhesive Systems on the Bond Strength of Primary Molars and Incisors

The aim of this study was evaluate in vitro the influence of simplified adhesive systems (etch-and-rinse and self-etching) and 1.23% acidulated phosphate fluoride (APF) on the microshear bond strength (μ-SBS) of composite resins on primary molars and incisors. Forty primary molars and forty incisors vestibular enamel was treated with either the self-etching Clearfil SE Bond (CSE, Kuraray) or etch-and-rinse Adper Single Bond 2 (SB2, 3M/ESPE) adhesive system. Each group was subdivided based on the prior treatment of the enamel with or without the topical application of 1.23% APF. Thereafter, matrices were positioned and filled with composite resin and light cured. After storage in distilled water at 37±1°C for 24 h, the specimens were submitted to μ-SBS in a universal testing machine. Kruskal-Wallis and Mann-Whitney tests (p<0.05) showed that the prior application of 1.23% APF led to a significant reduction in bond strength. The type of adhesive exerted no significant influence bond strength. In the inter-group analysis, however, significantly bond strength reduction was found for the incisors when CSE was employed with APF. Adhesive failure was the most common type of fracture. The bond strength was affected by the prior application of 1.23% APF and type of tooth.

O objetivo deste estudo foi avaliar a influência dos sistemas adesivos simplificados (condicionamento ácido total e auto-condicionante) e fluorfosfato acidulado a 1,23% (FFA) na resistência de união ao microcisalhamento (μ-RUC) de resinas compostas em molares e incisivos decíduos. O esmalte vestibular de quarenta molares e quarenta incisivos decíduos foi tratado com Clearfil SE Bond (CSE, Kuraray) ou Adper Single Bond 2 (SB2, 3M/ESPE). Cada grupo foi subdividido com base no tratamento prévio do esmalte com ou sem aplicação tópica de FFA a 1,23%. Em seguida, matrizes foram posicionadas e preenchidas com resina composta e posterior fotopolimerização. Depois da armazenagem em água destilada a 37±1 °C por 24 h, os espécimes foram submetidos ao μ-RUC em uma máquina de ensaio universal. Teste Kruskal-Wallis e Mann-Whitney (p<0,05) mostraram que a aplicação prévia de FFA a 1,23% levou a uma redução significativa na resistência de união. O tipo de adesivo não exerceu influência significativa na resistência de união. Na análise intergrupos, entretanto, redução significativa na resistência de união foi encontrada para os incisivos quando CSE foi empregado sem FFA. Falha adesiva foi o tipo de fratura mais comum. A resistência de união foi afetada pela aplicação de FFA a 1,23% e tipo de dente.

Does active application of universal adhesives to enamel in self-etch mode improve their performance?

OBJECTIVES: To evaluate the effect of adhesion strategy on the enamel microshear bond strengths (µSBS), etching pattern, and in situ degree of conversion (DC) of seven universal adhesives. METHODS: 84 extracted third molars were sectioned in four parts (buccal, lingual, proximal) and divided into 21 groups, according to the combination of the main factors adhesive (AdheSE Universal [ADU], All-Bond Universal [ABU], Clearfil Universal [CFU], Futurabond U [FBU], G-Bond Plus [GBP], Prime&Bond Elect (PBE), and Scotchbond Universal Adhesive [SBU]), and adhesion strategy (etch-and-rinse, active self-etch, and passive self-etch). Specimens were stored in water (37°C/24h) and tested at 1.0mm/min (µSBS). Enamel-resin interfaces were evaluated for DC using micro-Raman spectroscopy. The enamel-etching pattern was evaluated under a field-emission scanning electron microscope (direct and replica techniques). Data were analyzed with two-way ANOVA and Tukey's test (α=0.05). RESULTS: Active self-etch application increased µSBS and DC for five out of the seven universal adhesives when compared to passive application (p<0.001). A deeper enamel-etching pattern was observed for all universal adhesives in the etch-and-rinse strategy. A slight improvement in etching ability was observed in active self-etch application compared to that of passive self-etch application. Replicas of GBP and PBE applied in active self-etch mode displayed morphological features compatible with water droplets. The DC of GBP and PBE were not affected by the application/strategy mode. CONCLUSIONS: In light of the improved performance of universal adhesives when applied actively in SE mode, selective enamel etching with phosphoric acid may not be crucial for their adhesion to enamel. CLINICAL SIGNIFICANCE: The active application of universal adhesives in self-etch mode may be a practical alternative to enamel etching in specific clinical situations.

Effect of Two Microshear Test Devices on Bond Strength and Fracture Pattern in Primary Teeth

This in vitro study evaluated the influence of two devices for application of shear load in microshear tests on bond strength and fracture pattern of primary enamel and dentin. Eighty primary molars were selected and flat enamel (40 teeth sectioned mesio-distally) and dentin (40 teeth sectioned transversally) surfaces were obtained. Both surfaces were polished to standardize the smear layer. Two-step etch-and-rinse adhesive systems (Adper Single Bond and XP Bond) were used. Polyethylene tubes was placed over the bonded surfaces and filled with composite resin. The microshear testing was performed after storage in water (24 h/37 °C) using two devices for application of microshear loads: a notched rod (Bisco Shear Bond Tester) or a knife edge (Kratos Industrial Equipment). Failure modes were evaluated using a stereomicroscope. Bond strength data were subjected to ANOVA and chi-square test to compare the failure mode distributions (α=0.05). No significant differences were observed between the groups for dentin and enamel bond strength or fracture patterns (p>0.05). The predominant failure mode was adhesive/mixed. In conclusion, the devices for application of shear loads did not influence the bond strength values, regardless of adhesive system and substrate.

Este estudo in vitro avaliou a influência de dois dispositivos para aplicação de força de cisalhamento em testes de resistência de união ao microcisalhamento e no padrão de fratura em dentina e esmalte de dentes decíduos. Oitenta molares decíduos foram selecionados e superficies planas em esmalte (40 dentes seccionados no sentido mésio-distal) e dentina (40 dentes seccionados transversalmente) foram obtidas. Ambas as superficies foram abrasionadas para padronização da lama dentinária. Dois sistemas adesivos de condicionamento ácido prévio (Adper Single Bond e XP Bond) foram utilizados. Tubos de polietileno foram colocados sobre as superficies, nas quais já haviam sido aplicados os sistemas adesivos, e preenchidos com resina composta. O teste de resistência de união ao microcisalhamento foi realizado após armazenamento dos espécimes em água (24 h/37 °C) utilizando dois dispositivos para a aplicação das forças de cisalhamento: cisalha côncava (Bisco Shear Bond Tester) e cisalha plana (Kratos Industrial Equipment). O padrão de fratura foi avaliado usando estereomicroscópio. Os dados de resistência de união foram submetidos à ANOVA e o teste quiquadrado foi utilizado para comparar a distribuição dos padrões de fratura (α=0,05). Não foram observadas diferenças estatisticamente significantes entre os grupos, tanto para a resistência de união a dentina e esmalte quanto para o padrão de fratura (p>0,05). O modo de falha predominante foi adesiva/mista. Em conclusão, os dispositivos para aplicação de força de cisalhamento não influenciam os valores de resistência de união, independente do sistema adesivo e substrato.

Tensile and Flexural Strength of Commercially Pure Titanium Submitted to Laser and Tungsten Inert Gas Welds

This study evaluated the tensile and flexural strength of tungsten inert gas (TIG) welds in specimens made of commercially pure titanium (CP Ti) compared with laser welds. Sixty cylindrical specimens (2 mm diameter x 55 mm thick) were randomly assigned to 3 groups for each test (n=10): no welding (control), TIG welding (10 V, 36 A, 8 s) and Nd:YAG laser welding (380 V, 8 ms). The specimens were radiographed and subjected to tensile and flexural strength tests at a crosshead speed of 1.0 mm/min using a load cell of 500 kgf applied on the welded interface or at the middle point of the non-welded specimens. Tensile strength data were analyzed by ANOVA and Tukey's test, and flexural strength data by the Kruskal-Wallis test (α=0.05). Non-welded specimens presented significantly higher tensile strength (control=605.84±19.83) (p=0.015) and flexural strength (control=1908.75) (p=0.000) than TIG- and laser-welded ones. There were no significant differences (p>0.05) between the welding types for neither the tensile strength test (TIG=514.90±37.76; laser=515.85±62.07) nor the flexural strength test (TIG=1559.66; laser=1621.64). As far as tensile and flexural strengths are concerned, TIG was similar to laser and could be suitable to replace laser welding in implant-supported rehabilitations.

Este estudo avaliou a resistência à tração e à flexão de soldas feitas com gás inerte de tungstênio (TIG) em amostras de titânio comercialmente puro (Ti CP) em comparação com a solda a laser. Sessenta amostras cilíndricas (diâmetro de 2 mm e espessura de 55 mm) foram distribuídas aleatoriamente em três grupos para cada ensaio (n=10): sem solda (controle), solda TIG (10V, 36A, 8 s) e solda com laser de Nd:YAG (380 V, 8 ms). As amostras foram radiografadas e submetidas aos testes de resistência à tração e à flexão em máquina de ensaios mecânicos à velocidade de 1mm/min com célula de carga de 500 kgf aplicada na interface soldada ou no ponto médio das amostras controle. Os dados de resistência à tração foram analisados estatisticamente por ANOVA e teste de Tukey e os dados de resistência à flexão pelo teste de Kruskal-Wallis (α=0,05). Espécimes não-soldados apresentaram resistência à tração (controle=605,84±19,83) (p=0,015) e resistência à flexão (controle=1908,75) (p=0,000) significantemente maiores que os solados com TIG ou laser. Não houve diferença estatisticamente significante (p>0.05) entre os tipos de solda no teste de resistência à tração (TIG=514,90±37,76; laser=515,85±62,07) nem no teste de resistência à flexão (TIG=1559,66; laser=1621,64). As resistências à tração e à flexão foram similares quando as amostras foram soldadas com TIG e a laser.

Resistência de união de sistemas adesivos autocondicionantes em dentina profunda / Bond strength of self-etching adhesive systems to deep dentin

Introdução e objetivo:: Os sistemas adesivos autocondicionantes têm sido largamente utilizados por dentistas e pesquisadores nos procedimentos adesivos de restaurações dentárias. O objetivo deste estudo foi avaliar a resistência de união ao microcisalhamento de sistemas adesivos autocondicionantes em dentina profunda. Material e métodos: Prepararam-se 50 terceiros molares humanos até obtenção de superfícies planas de dentina profunda (2 mm abaixo do limite amelodentinário do sulco central), abrasionadas com lixa de carbeto de silício n.º 600. As amostras foram aleatoriamente divididas em cinco grupos (n = 10), de acordo com os grupos experimentais: 1) adesivo convencional Syntac (controle), 2) adesivo autocondicionante One-Up Bond F Plus (um passo), 3) Hybrid Bond (um passo), 4) AdheSE (dois passos) – unidos ao compósito Tetric Ceram – e 5) Silorane System Adhesive (dois passos), unido ao compósito de baixa contração FiltekSilorane. Os materiais foram aplicados segundo orientações dos fabricantes e com uma matriz Tygon. Os corpos-de-prova foram armazenados em água destilada a 37±2ºC por uma semana. Determinou-se a resistência de união por meio da máquina universal de ensaios Zwick, a uma velocidade de 0,5 mm/minuto. Resultados: Os resultados obtidos em MPa (DP) foram analisados estatisticamente (Anova e teste de Tukey – p < 0,05) e apresentaram os seguintes dados: 2) 25,5 (4,4); 1) 24,9 (5,3); 3) 22,4 (8,1); 4) 21,5 (4,4) e 5) 18,1 (7,2). O teste de Tukey mostrou variações significativas entre os grupos 2 e 5, que não evidenciaram diferenças com os demais grupos testados. Conclusão: O adesivo Silorane e o compósito Filtek Silorane tiveram resistência de união similar à dos demais materiais, porém menor que o One-Up Bond F Plus, quando este foi utilizado com o Tetric Ceram. Os resultados sugerem que, em termos de resistência de união, os adesivos autocondicionantes podem ser uma boa alternativa nos procedimentos restauradores adesivos em dentina profunda.

Introduction and objecttiivee:: The self-etching adhesive systems have been widely used by dentists and researchers in the procedures of adhesive dental restorations. The purpose of this study was to evaluate the microshear bond strength of self-etching adhesive systems to deep dentin.Material and methods: Fifty freshly extracted human third molars were prepared using a diamond saw until obtaining flat surfaces of deep dentin (2 mm below the DEJ of central sulcus), wet-abraded with 600-grit SiC paper. The samples were randomly divided into five groups (n = 10) according to the experimental groups: 1) conventional adhesive Syntac (control), 2) one-step self-etching adhesive One-Up Bond F Plus, 3) onestep self-etching adhesive Hybrid Bond, 4) two-step self-etching adhesive AdheSE – bonded to Tetric Ceram resin composite; and the 5) two-step self-etching adhesive Silorane System Adhesive bonded to low shrinkage resin composite Filtek Silorane. The adhesives and the resin composite were applied according to the manufacturers’ instructions, and using a Tygon tubing mold. The samples were stored in distilled water at 37±2ºC for one week. Microshear bond strengths were determined using a Zwick universal testing machine at a crosshead speed of 0.5 mm/minute. Results: The results obtained in MPa (SD) were statistically analyzed (Anova and Tukey test, p < 0.05), and showed the following results: 2) 25,5 (4,4); 1) 24,9 (5,3); 3) 22,4 (8,1); 4) 21,5 (4,4) and 5) 18,1 (7,2). There was statistically significant variation between groups 2 and 5; which did not show difference to the other groups tested. Conclusion: The Silorane System Adhesive and the low shrinkage resin composite Filtek Silorane showed similar bond strength to Syntac, Hybrid Bond and AdheSE – bonded to Tetric Ceram resin composite; however, being lower than One-Up Bond F Plus bonded to Tetric Ceram. Regarding the bond strength, the results suggest that self-etching adhesive systems can...