Influência da adição de partículas de vidro bioativas em adesivos resinosos, na cimentação de bráquetes ortodônticos / Influence of the addition of bioactive glass particles in resin adhesives in the cementation of orthodontic brackets

O objetivo deste estudo foi desenvolver e avaliar um adesivo resinoso modificado com a incorporação de partículas de vidro bioativas (SCHOTT Bioactive Glass) em diferentes concentrações. Foram avaliados a resistência ao cisalhamento (RU), o índice de remanescente dentário (IRA), o grau de conversão (GC) e a liberação de cálcio. Foram utilizados 50 incisivos bovinos que foram fixados, através de suas raízes, em um molde de PVC, com resina acrílica autopolimerizável. As amostras foram alocadas em 5 grupos (n=10): TXT - Adesivo Transbond XT (3M Unitek, Monrovia, CA, EUA) sem adição de partículas de vidro bioativas, TXT20, TXT30, TXT50 ­ Adesivo Transbond XT acrescido respectivamente de 20%, 30% e 50% de partículas de vidro bioativas e SH - Adesivo resinoso FL BOND ll (SHOFU Inc.) com biomaterial SPRG. As amostras receberam uma profilaxia com pedra pomes e condicionamento com ácido fosfórico à 37%. Em seguida foi aplicada uma fina camada do sistema adesivo indicado na face vestibular dos incisivos bovinos, em todos os grupos e fotopolimerizado por 20 segundos, utilizando-se um fotopolimerizador RADII-Cal (SDI, Victoria, Austrália). Depois foi aplicada uma pequena quantidade de pasta resinosa fotopolimerizável Transbond XT (3M Unitek, Monrovia, CA, EUA) sobre a superfície dos bráquetes autoligados (MORELLI, Sorocaba, São Paulo, Brasil) e estes foram devidamente colados na face vestibular, no centro da coroa clínica do incisivo bovino e fotopolimerizado por 20 segundos, em cada face. Posteriormente as amostras foram submetidas ao teste de resistência ao cisalhamento. O índice de remanescente adesivo foi avaliado em estereomicroscópio DISCOVERY V20 (ZEISS). Os adesivos resinosos foram submetidos ao teste de grau de conversão e liberação de cálcio. Os dados foram inicialmente submetidos ao teste de normalidade e depois submetidos ao teste de ANOVA um fator, seguido do teste de Tukey para análise de comparações múltiplas, com nível de significância de 0,05. De acordo com os resultados obtidos na resistência de união ao cisalhamento (MPa±Dp) a maior média foi observada no grupo TXT 19,50±1,40A, seguida do grupo TXT20 18,22±1,04AB, seguida do grupo SH 17,62±1,45B, seguida do grupo TXT30 14,48±1,46C e a menor média TXT50 14,13±1,02C. No grau de conversão a maior média foi observada no grupo TXT20 73,02±3,33A que foi estatisticamente semelhante ao grupo SH 68,50±1,09A, seguida do grupo TXT 60,28±1,06B e TXT30 58,84±4,06B e a menor média foi do grupo TXT50 40,67±1,21C.Para a liberação de cálcio a maior média foi TXT50 2,23±0,11D, seguida por TXT30 0,74±0,00C, TXT20 0,55±0,00B, SH 0,47±0,04B e TXT 0,14±0,00A. Concluiu-se que a incorporação de partículas de vidro bioativas influenciou na resistência de união ao cisalhamento, no grau de conversão e na liberação de cálcio (AU).

The objective of this study was to develop and evaluate a resin adhesive modified with the incorporation of bioactive glass particles (SCHOTT Bioactive Glass) in different concentrations. Shear bond strength (SBS), adhesive remnant index (ARI), degree of conversion (DC) and calcium release were evaluated. Fifty bovine incisors were used, which were fixed through their roots in a PVC mold with self-curing acrylic resin. The samples were allocated into 5 groups (n=10): TXT ­ Transbond XT Adhesive (3M Unitek, Monrovia, CA, USA) without addition of bioactive glass particles, TXT20, TXT30, TXT50 ­ Transbond XT Adhesive rescpectively increased by 20%, 30% and 50% bioactive glass particles and SH ­ FL BOND ll resin adhesive (SHOFU Inc.) with SPRG biomaterial. The samples received prophylaxis with pumice stoe and conditioning with 37% phosphoric acid. Then, a thin layer of the indicated adhesive system was applied to the buccal surface of the bovine incisors, in all groups, and light cured for 20 seconds, using a RADII-Call curing light (SDI, Victoria, Australia). Then, a small amount of Transbond XT light-curing resinous paste (3M Unitek, Monrovia, CA, USA) was applied on the surface of the self-ligating brackets (MORELLI, Sorocaba, São Paulo, Brazil) and these were duly bonded on the buccal surface, in the center of the clinical crown of the bovine incisor and light cured for 20 seconds, on each side. Subsequently, the samples were submitted to the shear bond test. The adhesive remnant index was evaluated using a DISCOVERY V20 stereomicroscope (ZEISS). The resin adhesives were submitted to the degree of conversion and calcium release test. The data were initially submitted to the normality test and then submitted to the one-way ANOVA test, followed by the Tukey test for analysis of multiple comparisons, with a significance level of 0.05. According to the results obtained in the shear bond strength (MPa±Dp), the highest average was observed in the TXT group 19.50±1.40A, followed by the TXT20 group 18.22±1.04AB, followed by the SH group 17.62±1.45B, followed by the TXT30 group 14.48±1.46C and the lowest mean TXT5014.13±1.02C. In the degree of conversion, the highest average was observed in the TXT20 73.02±3.33A group, wich was statiscally like the SH group 68.50±1.09A, followed by the TXT 60.28±1.06B and TXT30 group 58.84±4.06B and the lowest mean was for the TXT50 group 40.67±1.21C. For calcium release, the highest mean was TXT50 2.23±0.11D, followed by TXT30 0.74±0.00C, TXT20 0.55±0.00B, SH 0.47±0.04B and TXT 0.14±0.00A. It was concluded that the incorporation of bioactive glass particles influenced in the shear bond strength, in the degree of conversion and in the release of calcium (AU).

Substrate Rigidity Effect on CAD/CAM Restorations at Different Thicknesses.

OBJECTIVES: This article evaluated the effect of substrates rigidities on the post-fatigue fracture resistance of adhesively cemented simplified restorations in lithium disilicate glass ceramic. METHODS: Precrystalized computer-aided design/computer-aided manufacturing ceramic blocks were processed into disc-shaped specimens (n = 10, Ø = 10 mm), mimicking a simplified restoration at two thicknesses (0.5 and 1.0 mm). Thereafter, the discs were cemented onto different base substrates (dentin analogue [control], dentin analogue with a central core build-up of resin composite [RC], or glass ionomer cement [GIC]). The specimens were subjected to mechanical cycling in a chewing simulator (100 N, 1 × 106 cycles, 4 Hz) and then subjected to thermocycling aging (10,000 cycles, 5/37/55°C, 30 seconds). After the fatigue protocol, the specimens were loaded until failure (N) in a universal testing machine. Finite element analysis calculated the first principal stress at the center of the adhesive interface. RESULTS: The results showed that "restoration thickness," "type of substrate," and their interaction were statistically significant (one-way analysis of variance; p < 0.001). Regardless the restoration thickness a higher fracture load was observed for specimens cemented to dentin analogue. Among the base materials, RC build-up presented the highest fracture load and lower stress magnitude for both restoration thicknesses in comparison with GIC build-up. The 0.5-mm restoration showed higher stress peak and lower fracture load when submitted to the compressive test. CONCLUSION: More flexible base material reduces the fracture load and increases the stress magnitude of adhesively cemented lithium disilicate restorations regardless the ceramic thickness. Therefore, more rigid substrates are suggested to be used to prevent restoration mechanical failures.

Minimal intervention in dentistry: which is the best approach for silorane composite restoration repairs?

BACKGROUND: This study aimed to evaluate surface treatments, adhesives and composites for repairing silorane based restorations. MATERIAL AND METHODS: One hundred and twenty truncated cones (2 mm smaller diameter and 4 mm larger diameter) made of silorane composite were divided in 12 groups according with the surface treatment (diamond bur and oxide aluminum abrasion), the adhesive (Adper Scothbond Multipurpose (3M ESPE), Ecusit (Voco) and Filtek P90 Adhesive (3M ESPE)). Each group was subdivided in two according with the composite used for repair (methacrylate and silorane). The repair was made with a second truncated cone build over the first one and bond strength assssed by tensile strength. Data were submitted to ANOVA 3-way and Tukey's test (p<0.05). RESULTS: There was difference only for the adhesives and the composites, with conventional adhesives (Adper Scothbond Mutipurpose) and methacrylate-based composites (Filtek Z350) presenting superior tensile strength compared to the silorane ones (P90 Adhesive system and composite). CONCLUSIONS: Therefore, it must be concluded that silorane composite can be repaired with methacrylate base composites and adhesives. Key words:Silorane composites, composites, bond strength, minimal intervention.

Adhesive systems effect over bond strength of resin-infiltrated and de/remineralized enamel.

Background: The purpose of this study was to evaluate the effect of different bonding agents on bond-strength to demineralized enamel after remineralizing treatments and resin infiltration. Methods: Buccal enamel of 120 bovine incisors was polished and then were divided into five experimental groups: SE (sound enamel); DE (demineralized enamel); AS (demineralized enamel immersed in artificial saliva for eight weeks); NaF (demineralized enamel treated with 0.05% sodium fluoride solution (one minute) for eight weeks); Ic (demineralized enamel infiltrated with a low-viscosity resin (Icon-DGM). These groups were subdivided according to adhesive system used: self-etching adhesive Adper Easy One (3M/ESPE) and etch-and-rinse adhesive Single Bond (3M/ESPE). The composite resin blocks were fabricated using a Teflon matrix. A thermomechanical cycling machine was used to carry out the artificial aging of the specimens and thus were sectioned into sticks. The microtensile tests were performed using a universal testing machine at a cross-head speed of 1 mm/min. Data (in MPa) were subjected to two-way ANOVA and Tukey's tests (5%). Results: Significant differences were found for both factors tested and interactions (p<0.05). Tukey's test results of µTBS (mean ± SD) were: etch-and-rinse SE (28.79±3.93); DE (30.41±7.22); AS (29.03±3.33); NaF (29.81±4.06)a; Ic (29.47±5.5);  and self-etching SE (30.37±6.96); DE (14.62±4.47); AS (9.79±2.32); NaF (9.36±2.31); Ic (30.78±8.68).   Conclusions: Resin infiltration did not affect the bond strength of demineralized enamel for both adhesive systems tested. For etch-and-rinse adhesive, no differences were observed for the tested groups. For self-etching adhesive, only the resin-infiltrated group showed similar bond strength to sound enamel. Both etch-and-rinse and self-etching adhesive systems can be used in resin-infiltrated enamel, if a composite restoration needs to be further performed. In enamel that has undergone the de/remineralization process, the use of a total-etch adhesive might be preferable for the restorative procedure.

Influência do tipo de agente espessante e da viscosidade do gel de peróxido de hidrogênio na eficácia clareadora e microdureza do esmalte dental / Influence of the type the thickening agent and viscosity of hydrogen peroxide gel on dental bleaching efficacy and microhardness of dental enamel

O objetivo deste estudo foi avaliar a influência do tipo de agente espessante e da viscosidade do gel de peróxido de hidrogênio (PH) a 35%, na eficácia clareadora e microdureza do esmalte dental. Além disso, a decomposição da molécula de peróxido de hidrogênio dentro do gel clareador também foi verificada. Foram utilizados 110 dentes incisivos bovinos dos quais foram obtidos 324 espécimes em forma de discos de esmaltedentina, com 4mm de diâmetro, utilizando-se broca trefina. A leitura da cor dos referidos espécimes foi realizada em um espectrofotômetro de reflectância, enquanto a microdureza do esmalte foi analisada através de um microdurômetro com indentador Knoop. Para verificação da concentração de peróxido foi utilizado o método de titulação utilizando o permanganato de potássio. Géis clareadores experimentais foram preparados, contendo cinco diferentes tipos de agentes espessantes (Ar - Aristoflex ­ Clariant, Ca - Carbopol 980 ­ Lubrizol, CMC ­ Carboximetilcelulose, Ae ­ Aerosil 200 - Evonik e Sa - Salcare ­ BASF), os quais foram adicionados em quantidades suficientes para produzir géis com viscosidades baixa (B - 50.000 cPs), média (M - 250.000 cPs) e alta (A ­ 1.000.000 cPs). Os espécimes foram divididos em dezoito grupos: CP (Controle positivo) - de peróxido sem adição de agente espessante, CN (Controle Negativo) ­água ultra pura, CC (Controle Comercial) ­ gel de PH a 35% Whiteness HP-FGM, Ar/B, Ar/M, Ar/A; Ca/B, Ca/M e Ca/A; CMC/B, CMC/M, CMC/A, Ae/B, Ae/M, Ae/A, Sa/B, Sa/M e Sa/A. Os agentes clareadores foram aplicados sobre a superfície do esmalte por um total de 60 minutos. A cada 20 minutos, o agente clareador era trocado e uma amostra deste era coletada e as concentrações de peróxido de hidrogênio mensuradas. A microdureza do esmalte foi avaliada imediatamente após, sendo então as amostras imersas em saliva artificial por 7 dias, seguido pela leitura final da cor. Os dados foram analisados estatisticamente, empregando um nível de significância de 5%. Quanto ao percentual de redução da microdureza a ANOVA 2 fatores mostrou diferenças significativas para o tipo de espessante e viscosidade. Os resultados do testede Tukey foram: espessante ­ Ae 11,73(3,98)a, As 14,71(3,79)b, CMC 17,00(4,01)c, Ar 22,13(4,43)d e Ca 28,06(2,59); viscosidade ­ alta 15,39(8,52)a, média 18,56(5,42)b e baixa 22,22(4,40)c. Quanto ao DEab e DE00 não mostrou diferenças significativas. Com relação à concentração do peróxido de hidrogênio, as maiores reduções occorreram para o espessante Salcare. Concluiu-se que o tipo de espessante e viscosidade dos géis não influenciaram o efeito clareador, porém influenciaram na microdureza do esmalte. O tipo de espessante e viscosidade também influenciaram a concentração final do peróxido de hidrogênio, e o espessante. Sa apresentou o maior percentual de redução de peróxido. Todos os grupos apresentaram diferenças significativas e relação ao grupo CN. O grupo CA/A não apresentou diferença significativa em relação ao grupo CP e apenas o grupo Sa/M não apresentou diferença significativa em relação ao grupo CC(AU)

The aim of this study was to evaluate of the type of the agent thickener and viscosity of 35% hydrogen peroxide gel, in the bleaching efficacy and microhardness of dental enamel. In addition, the decomposition of the hydrogen peroxide molecule within the bleaching gel was also verified. We used 110 bovine incisor teeth of which 324 specimens were obtained in the form of enamel-dentin discs, with 4 mm diameter, using a trefin drill. The color reading of the aforementioned specimens was performed in a reflectance spectrophotometer, while the microhardness of the enamel was analyzed through a microdurometer with Knoop indenter. To verify the peroxide concentration, the titration method was used using potassium permanganate 0,1 N. Experimental bleaching gels were prepared, containing five different types of thickened agents (Ar ­ Aristoflex ­ Clariant, Ca ­ Carbopol 980 ­ Lubrizol, CMC ­ Carboxymethylcellulose, Ae ­ Aerosil 200 ­ Evonik and Sa ­ Salcare ­ BASF), which were added in sufficient quantities to produce gels with low viscosities (L ­ 50.000 cPs), Medium (M ­ 250.000 cPs) and High (H ­ 1.000.000 cPs). The specimens were divided into eighteen groups/subgroups: PC (positive control) ­ was applied a peroxide solution without adding thickened agent, NC (Negative control) ­ was applied ultrapure water, CC (Comercial control) and fifteen more groups, containing hydrogen peroxide at 35% associated with a specific thickened agent, in different viscosities, these being: Ar/L, Ar/Mand Ar/H (Aristoflex in low, medium and high viscosity); Ca/L, Ca/M and Ca/H (Carbopol in low, medium and high viscosity); CMC/L, CMC/M and CMC/H (Carboxymethylcellulose in low, medium and high viscosity); Ae/L, Ae/M and Ae/H medium and high viscosity). The bleaching agents were applied on the enamel surface for 60 minutes. Every 20 minutes, the bleaching agent was changed and a sample was collected and the hydrogen peroxide concentrations measued. The enamel microhardness was immersed in artificial saliva for 7 days, followed by the final color reading. Data were analyzed statistically, employing a significance level of 5%. Regarding the percentage of microhardness reduction the ANOVA 2 factors showed significant differences for the type of thickener and viscosity. The Tukey test results were: thickener ­ Ae 11.73(3,98)a, As 14.71(3.79)b, CMC 17.00(4.01)c, Ar 22.13(4.43) and Ca 28.06(2.59); viscosity ­ high 15.39(8.52)a, average 18.56(5.42)b and low 22.22(4.40)c. Regarding DEab and DE00 showed no significant differences. Regarding the concentration of hydrogen peroxide, the greatest reductions occurred for the Salcare thickener. It was concluded that the type of thickener and viscosity of the gels did not influence the bleaching effect, but influence the microhardness of the enamel. The type of thickener and viscosity also influenced the final concentration of hydrogen peroxide, and the thickener. Sa presented the highest percentage of peroxide reduction. All groups presented significant difference in relation to the CP group and only the Sa/M group did not present a significant difference in relation to the CC group(AU)