Simple and Low-Cost Thermal Treatments on Direct Resin Composites for Indirect Use

The aim of this study was to evaluate the influence of three low-cost additional thermal treatments, available in the dental office, on the mechanical, chemical and optical properties of a light-cured resin composite indicated for direct restorations but used as indirect restorative. The direct resin composite TPH3 (Dentsply) was light-polymerized using a light-emitting diode curing unit and submitted to three experimental additional thermal treatments: dry heat at 170 °C for 5 min, autoclave at 121 °C for 6 min, or microwave oven at 450 W for 3 min. The resin composite without any thermal treatment was used as negative control group. An indirect resin composite (Vita CM LC, Vita Zahnfabrik) was tested as a reference. Flexural strength, elastic modulus, microhardness, degree of C=C conversion, roughness before and after simulated toothbrush abrasion, translucency parameter and color difference (ΔE00) were evaluated. Data were analyzed at α=0.05. The indirect resin composite presented lower C=C conversion and mechanical performance. The flexural strength was significantly higher in the dry oven group compared with the control. The roughness was not different among groups before or after brushing, but the thermal treatments caused an increase in C=C conversion, microhardness, and elastic modulus without affecting the translucency parameter or showing visible color alteration (ΔE00<1.8). These results suggest that the use of additional thermal methods of polymerization represents an economical and simple alternative to enhance the mechanical and chemical properties of direct resin composites when used as indirect restoratives

Development of experimental HEMA-free three-step adhesive system.

To evaluate the influence of Bis-EMA 30 on the resin-to-dentin microtensile bond strength (microTBS) and structural reliability of the experimental three-step etch-and-rinse adhesive systems.Five experimental primers containing different dimethacrylate monomer concentrations (0, 10, 20, 40, 60 wt% of the Bis-EMA 30, P0.P60) added to acid monomer and solvents (ethanol/water), and a resin bond (Bis-GMA/TEGDMA, 50/50 wt%) were formulated. The adhesive system Scotchbond MultiPurpose (SBMP, 3M ESPE) was tested as commercial reference. Sixty bovine incisors were randomly separated into six groups, and their superficial coronal dentin was exposed. After acid etching and rinsing, the excess water was removed from the surface with absorbent paper. Each experimental primer was actively applied (30 s), followed by a mild air stream (10 s). The experimental adhesive resin was applied and light activated for 20 s. Resin composite restorations were incrementally built up. The restored teeth were stored in distilled water at 37 degrees C for 24 h, and then sectioned to obtain sticks with a cross-sectional area of approximately 0.5 mm(2), after which 24 specimens per group were subjected to the microTBS test. Data (MPa) were analyzed by One-way ANOVA, Tukey test (alpha=0.05) and Weibull analysis.The P40 group showed microTBS means similar to those of the control (SBMP), whereas both had statistically higher values when compared with the other groups (p0.001). Moreover, P40 showed higher structural reliability, represented by the high Weibull modulus and characteristic strength values. The lowest microTBS was observed in the P0, P10 and P20 groups, which also had low structural reliability.Bis-EMA 30 is a promising monomer to be considered as a substitute for HEMA in adhesive system compositions

effect of the silane concentration on the selected properties of an experimental microfilled composite resin

The aim of present study was evaluate the effect of different percentages of an organo-functionalized silane monomer as adhesion promoter between barium borosilicate glass fillers and (co)monomer blend in experimental dental composite resin. Gamma-methacryloxypropyltrimethoxysilane (γ-MPS) was assessed in an experimental luting cement, at the concentrations of 0, 1, 3, 5, 7 and 10 (wt%). The experimental resin without fillers was used as control group. The flexural strength (FS) and elastic modulus (E) were obtained by mini-flexural test and expressed in MPa and GPa, respectively. Water sorption (WS) and solubility (SL) were determined based on ISO standard 4049:2000. Kruskal–Wallis and Student–Newman–Keuls test were used for comparisons of FS, E and WS. The comparisons of SL means were performed using one-way ANOVA and Tukey's method (α = 5 %). The treatment with 3 % silane revealed statistically higher FS, while the group treated with 1 % silane showed statistically higher E than 3 % silane (p < 0.05) and E similar to control. The experimental composite without filler content showed the highest SL (p < 0.05) while the control composite showed the highest WS (p < 0.05). Based on present findings, flexural strength and elastic modulus can sometimes be improved with lower concentrations (1–3 %) rather than higher concentrations (5–7 %) of the silane (γ-MPS) used as coupling agent on barium borosilicate glass filler microparticles of the dental composite resin

Effect of additional acid etching on bond strength and Weibull modulus of adhesive systems applied on sound and affected dentin

The aim of this study was to evaluate the effect of additional etching with phosphoric acid at 35% in the bond strength and Weibull modulus of two adhesive systems applied to sound and affected dentin. Ninety human molars with coronal carious lesion were sectioned to produce flat coronal superficies with effected dentin surrounded by sound dentin, and allocated in six experimental groups: SB-CT: Single Bond® applied to manufacture s instructions; SB+15: Single Bond® with additional etching for 15s; SB+30: Single Bond® with additional etching for 30s; CF-CT: Clearfil SE Bond® applied to manufacture s instructions; CF+15: Clearfil SE Bond® with additional etching for 15s; CF+30: Clearfil SE Bond® with additional etching for 30s. Afterwards, the crowns were built up with a composite resin and, after 24h, mesiondistal sectioned to produce 2 or 3 slices in each substratum. Thereafter (24h), the slices were trimmed in hourglass shape and submitted to micro-tensile test (n=30). The data were analyzed by three-way ANOVA, Tukey s test (p<0,05) and Weibull analysis. The bond strength to affected dentin was significantly lower than sound dentin for the adhesives systems employed, save SB+30. The additional etching increased the bond strength to affected dentin. To sound dentin, the additional etching increased the bond strength for Clearfil SE Bond®, but decreased for Single Bond®. The Weibull modulus to affected dentin was lower for both adhesives systems. On sound dentin, Single Bond® showed lower Weibull modulus than Clearfil SE Bond® and the additional etching decrease this value. Although the additional etching may increase the bond strength to affected dentin, the means were lower than sound dentin, the same for Weibull modulus. The additional etching may reduce the bond strength and Weibull modulus for Single Bond® to sound dentin and, in opposite, increase for Clearfil SE Bond®O objetivo deste estudo foi avaliar o efeito do condicionamento adicional com ácido fosfórico à 35% na resistência de união e módulo de Weibull de dois sistemas adesivos aplicados em dentina sadia e afetada por cárie. Noventa molares humanos com lesão cariosa oclusal foram desgastados produzindo superfícies oclusais planas, com DAC circundada por DS, e divididos em seis grupos experimentais: SBCT: Single Bond® aplicado conforme o fabricante; SB+15: Single Bond® com condicionamento ácido adicional de 15s; SB+30: Single Bond® com condicionamento ácido adicional 30s; CF-CT: Clearfil SE Bond® aplicado conforme o fabricante; CF+15: Clearfil SE Bond® com condicionamento ácido adicional de 15s; CF+30: Clearfil SE Bond® com condicionamento ácido adicional de 30s. Após, as coroas dos dentes foram restauradas em formato de bloco e, posteriormente (24h), seccionadas no sentido mésio-distal originando 2-3 fatias em cada substrato. Após 24h as fatias foram recortadas em formato de ampulheta e submetidas ao ensaio de microtração (n=30). Os valores de resistência de união foram analisados com ANOVA (3- fatores), teste de Tukey (p<0,05) e análise de Weibull. Em geral, a resistência de união foi significantemente menor em dentina afetada por cárie que em dentina sadia para ambos os sistemas adesivos, exceto para SB+30. O condicionamento ácido adicional resultou no aumento da resistência de união em dentina afetada por cárie. Em dentina sadia o condicionamento ácido adicional aumentou a resistência de união para o sistema Clearfil SE Bond®, mas reduziu para o sistema Single Bond®. O módulo de Weibull foi menor em dentina afetada por cárie para os dois sistemas adesivos. Em dentina sadia, Single Bond® apresentou menor módulo de Weibull que Clearfil SE Bond® e o condicionamento ácido adicional resultou na redução desse valor. Embora o condicionamento ácido adicional possa aumentar a resistência de união em dentina afetada por cárie, as médias foram menores que em dentina sadia, bem como o módulo de Weibull. O condicionamento ácido adicional 11 pode reduzir a resistência de união e o módulo de Weibull para Single Bond® em dentina sadia e, contrariamente, aumentar para o sistema Clearfil SE Bond

Development of adhesive systems employing surfactant monomers as substitute to hydroxyethyl methacrylate (HEMA)

This study evaluated the influence of surfactant dimethacrylates (SD) on the resin-to-dentin immediate and long term microtensile bond strength (μTBS) and characterized the interfacial micromorphology of hybrid layer of the experimental HEMA-free self-etching systems. Five experimental HEMA-free two step self-etching systems containing different surfactant dimetacrylates (SD) (Bis-EMA 10, Bis-EMA 30, PEG 400, PEG 1000 and PEG 400 UDMA) and a HEMA-containing systems (control) were formulated. Sixty bovine incisors were allocated into six groups according each experimental adhesive system used. The teeth had the superficial coronal dentins exposed and were restored and sectioned to obtain sticks randomly allocated into 3 storage periods: 24h, 6 and 12 months. Thereafter the specimens were subjected to the μTBS test. Immediate μTBS data were analyzed by One-way ANOVA and Tukey s test. Long term μTBS data were analyzed by Kruskall-Wallis and Dunn test (α = 0.05). Analysis of the adhesive-dentin interfaces were performed through scanning electron microscopy. Between the HEMA-free groups, the adhesive system formulated with PEG 400 UDMA produced the highest μTBS and was similar to HEMA-containing group. Specimens of the 24 hours of storage were statistically higher for all groups tested when compared those after 6 and 12 months storage. None difference was found between 6 months and 12 months storage for each group. All the adhesives systems presented similar partially demineralized hybrid layer (1.5-3.0 μm thickness) with well formed resin tags. All SD present reasonable μTBS, being the PEG 400 UDMA a promising monomer to be considered as HEMA substitute in adhesive systems compositions.Este estudo avaliou a influência de dimetacrilatos surfactantes (DS) na resistência de união à dentina por microtração (RU), imediata e após armazenagem, além de caracterizar a micromorfologia da camada híbrida de sistemas adesivos experimentais autocondicionantes livres de HEMA. Foram formulados cinco sistemas adesivos autocondicionantes de dois passos livres de HEMA contendo diferentes DS (Bis-EMA 10, Bis-EMA 30, PEG 400, PEG 1000 and PEG 400 UDMA) e um sistema contendo HEMA, empregado como controle. Foi realizada a exposição da dentina superficial de sessenta incisivos bovinos posteriormente alocados em seis grupos experimentais de acordo com o sistema adesivo empregado. Os dentes foram restaurados e seccionados para obter espécimes (palitos) posteriormente divididos em três períodos de armazenagem: 24h, 6 e 12 meses. Após, os espécimes foram sujeitos ao teste de RU. Resultados de RU imediata foram analisados por ANOVA 1-fator e teste complementar de Tukey. Resultados de RU após envelhecimento foram analisados por Kruskall-Wallis e teste de Dunn (α = 0.05). Analises das interfaces de união dente-restauração foram realizadas através de microscopia eletrônica de varredura. Entre os grupos livres de HEMA, o sistema adesivo formulado com PEG 400 UDMA produziu maior RU e foi estatisticamente similar ao grupo controle contendo HEMA. Os espécimes testados após 24 horas de armazenamento apresentaram RU estatisticamente maior para todos os grupos quando comparados os espécimes testados após 6 e 12 meses de armazenagem. Não foram observadas diferenças significativas entre os grupos testados após 6 e 12 meses. Todos os sistemas adesivos apresentaram camada hibrida parcialmente desmineralizada (1.5-3 μm de espessura) com formação de prolongamentos resinosos. Em geral os sistemas adesivos demonstraram valores de RU satisfatórios, sendo o PEG 400 UDMA um monômero promissor para o desenvolvimento de sistemas adesivos livres de HEMA

Microleakeg in class II composite restorations using different restorative techniques

O objetivo do presente estudo foi comparar a infiltração marginal de restaurações classe II com margens cervicais em dentina utilizando diferentes técnicas restauradoras. Foram utilizados quarenta e oito molares humanos hígidos com cavidades proximais padronizadas nas faces mesial e distal com margens cervicais em dentina. Ambas, cavidades e restaurações, foram realizadas pelo mesmo operador. As cavidades foram restauradas através da técnica incremental modificada de Pollack (1988). Os dentes foram aleatoriamente divididos em quatro grupos(n = 12) e restaurados como segue: Grupo 1 (controle) – Z-250 (3M/ESPE); Grupo 2 – Vitremer(3M/ESPE) + Z-250; Grupo 3 – F2000 (3M/ESPE) + Z-250; Grupo 4 – Flow-it (3M/ESPE) + Z-250. O sistema adesivo Single Bond (3M/ESPE) foi aplicado seguindo as instruções do fabricante. Após acabamento e polimento, os dentes foram termociclados por 500 ciclos, entre 5 e 55°C, e impermeabilizados com esmalte de unha, sendo imersos em corante azul de metileno a 1% por 12 horas. Os espécimes foram seccionados e a infiltração avaliada de acordo com ranking padronizado (0-3), por três avaliadores previamente calibrados. Os resultados foram submetidos à análise estatística utilizando o teste não paramétrico de Kruskal-Wallis (p < 0.05). A penetração do corante atingiu o grau máximo na maioria dos espécimes. O grupo 1 apresentou menores valores de infiltração diferindo estatisticamente dos outros grupos. Os grupos 2 e 3 apresentaram valores intermediários, enquanto o grupo 4 teve os valores mais altos, sem, porém,ser estatisticamente diferente do grupo 3. Nenhum grupo foi capaz de selar completamente a interface adesiva

Influência do comprimento de extensores de cadeia na formação de polímeros reticulados

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Resistência à flexão e módulo de elasticidade de diferentes tipos de resina composta

The aim of the study was to test whether the filler composition of resin composites influences their flexural strength and modulus of elasticity. Flexural strength and modulus of elasticity were obtained through a three-point bending test. Twelve bar shaped specimens of 5 commercially available composites – Supreme (3M/ESPE), a universal nanofilled composite; Esthet-X (Dentsply), Z-250 (3M/ESPE), Charisma (Heraeus Kulzer), universal hybrid composites; and Helio Fill (Vigodent), a microfine composite – were confectioned according to the ISO 4049/2000 specifications. The test was performed after a 7- days storage time using a universal test machine with a crosshead speed of 1 mm/min. The filler weight content was determined by the ashing technique. The data obtained on the mechanical properties were submitted to ANOVA and Tukey test (p < 0.05). Pearson’s correlation test was used to determine the correlation between the filler content and the mechanical properties. A weak but significant correlation between the mechanical properties evaluated and the filler weight content was observed (p < 0.000). The microfine composite presented the lowest filler weight and the lowest mechanical properties. Statistically different flexural strength and modulus of elasticity results were observed among the universal hybrid composites. The nanofilled composite presented intermediary results. Within the limitations of this in vitro study, it could be concluded that the filler content significantly interfered in the flexural strength and modulus of elasticity of the composites tested

Influence of surface moisture condition on the bond strength to dentin of etch and rinse adhesive systems

evaluate the immediate microtensile bond strength (&#956;TBS) of three two-step etch-andrinse adhesive systems applied under different dentin surface moisture conditions. Methods: Class V cavities were prepared in seventy-two bovine incisors. Each tooth was randomly allocated into three groups, according to the adhesive system used: Single Bond 2 (SB), Prime & Bond 2.1 (PB) and XP Bond (XPB). Each group was divided in three subgroups, according to the dentin moisture condition: over-wet, moist and dry (n=8). For the moist subgroups the adhesive was applied as to the manufacturers instructions; for the over-wet ones, without drying the cavity after the rinsing procedure; and for the dry subgroups, drying the surface for 20 s. The teeth were restored with Filtek Z-250 and stored in distilled water (24 h); next, each restoration was sectioned in beam-shaped specimens which were stored for 24 h at 37 °C. Each specimen was submitted to &#956;TBS test (EMIC), and data were analyzed using two-way ANOVA and Tukey test (p<0.05). Results: There was a statistically significant interaction between the adhesive system type and the dentin surface moisture condition (p=0.003). SB and XPB presented higher bond strength in the moist dentin condition, and PB showed high &#956;TBS values in the dry substrate. Conclusions: The moisture condition influenced the bond strength between the adhesives and dentin. SB performed better in the moist condition, whereas PB and XPB showed satisfactory bond strength in the moist and in the dry substrates. The over-wet dentin condition only impaired bond strength to SB and XPB