Influencia das tecnicas de polimerização das resinas compostas na microinfiltração, microdureza, formação de fendas e resistencia a microtração

Orientador : Luiz Andre Freire PimentaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaDoutorad

Avaliação da microinfiltração marginal e da dureza de restaurações classe II de resina composta, utilizando dois sistemas de polimerização e duas tecnicas restauradoras

Orientador : Luiz Andre Freire PimentaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O objetivo deste trabalho foi avaliar a microinfiltração marginal e a dureza de restaurações classe II de resina composta, usando duas técnicas restauradoras e dois sistemas de polimerização. Foram preparadas 120 cavidades simulando classe II em dentes bovinos, que foram divididas em 4 grupos: DEME 1 - único incremento + polimerização convencional (Optilux 500/DEMETROM); DEME 3 - incrementos vestíbulo-linguais + polimerização convencional; SOFT 1 - único incremento + polimerização soft-start (Degulux Soft-Start/DEGUSSA); SOFT 3- incrementos - vestíbulo-linguais +polimerização soft-start. Todas as cavidades foram restauradas com o sistema Single Bondl ZlOO (3M). Após a termociclagem (1000 ciclos a 5 e 55 °c), os dentes foram imersos em solução de azul de metileno a 2%, por 4 horas, e a microinfiltração foi avaliada. Metade das amostras foi incluída em resina de poliestireno, polida e a microdureza Knoop foi mensurada. Quanto à microinfiltração, o Teste Exato de Fisher mostrou diferença estatisticamente significante entre os grupos (p<0,05). Não foi encontrada diferença estatisticamente significante (ANOV A) na dureza entre todos os grupos, em qualquer profundidade. A técnica incremental exibiu menor infiltração marginal, independente do sistema de polimerização utilizado. O sistema soft-start promoveu polimerização semelhante ao convencional, mas não melhorou o selamento marginalAbstract: The aim of this study was to evaluate the marginal microleakage and the microhardness of class II composite resin restorations using two restorative techniques and two polymerization systems. One hundred twenty class II cavity were prepared in bovine teeth and it were randomly divided into four groups: DEME 1- Bulk increment + conventional polymerization (Optilux 500/DEMETROM); DEME 3- Bucco-lingual increments + conventional polymerization; SOFT 1- Bulk increment + soft-start polymerization (Degulux Soft-StartlDEGUSSA); SOFT 3- Bucco-lingual increments + soft-start polymerization. All cavities were restored with the ZlOO/Single Bond system (3M). After thermocycling (1000 cycles at 5 °C and 55°C), the samples were immersed in methilene blue 2% dye solution, for 4 hours, and the microleakage was evaluated. Half of samples was embedded in polyester resin, polished and the Knoop microhardness was measured. Fisher Exact test showed statistical significant difference of microleakage among groups (p<0,05). No statistical differences (ANOV A) were found for hardness for all groups at any depth. Incremental technique showed less leakage, regardless of the polymerization systems used. The soft-start system provided polymerization similar to conventional system, but could not improved the marginal sealingMestradoDentísticaMestre em Clínica Odontológic

The effect of light-curing source and mode on microtensile bond strength to bovine dentin

PURPOSE: The purpose of this study was to evaluate the effects of different light-curing techniques on the microtensile bond strength of hybrid and packable resin composite to dentin. The null hypotheses were that different light-curing techniques do not affect the adhesion of resin composites to tooth structure and that different resin composites do not have a similar bond to dentin. MATERIALS AND METHODS: One hundred four box-shaped buccal preparations were made and dentin/enamel adhesive was applied according to the manufacturer's instructions (Single Bond 3M ESPE). A hybrid resin composite (Filtek Z250, A2, 3M ESPE) or a packable resin composite (Solitaire 2, A2, Heraeus Kulzer) were inserted in bulk and polymerized using one of these techniques (n = 13): (a) Soft-start (SS) using a halogen lamp (QTH); (b) LED low intensity; (c) Plasma arc (PAC) curing for 6 s for packable resin composite and 3 s for the hybrid resin composite; (d) Conventional (C) QTH curing for 40 s. Afterwards, specimens were thermocycled 1,000 times between 5 degrees C and 55 degrees C in tap water, and were sectioned into beams with a rectangular cross-sectional area of approximately 1 mm2. Microtensile bond strength testing was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. RESULTS: Bond strength means +/- (SD) in MPa were: Filtek Z250: SSQTH = 17.9 (5.4); LED = 17.9 (6.4); PAC = 16.8 (6.8); CQTH = 16.1 (4.6). Solitaire 2: SSQTH = 12.4 (6.4); LED = 15.5 (4.3); PAC = 16.2 (4.4); CQTH = 13.8 (5.7). The data were structured in a split-plot design and analyzed by a two-way ANOVA and Tukey's tests (alpha = 0.05). CONCLUSION: The light-curing method did not significantly affect bond strengths. However, the bond strengths of the packable resin composite were significantly lower than those of the hybrid resin composite for all polymerization techniques, suggesting that the restorative material itself might be a more critical factor in adhesion than the curing method

Resin-dentin bond stability of etch-and-rinse adhesive systems with different concentrations of MMP inhibitor GM1489

Enzymatic degradation of the hybrid layer can be accelerated by the activation of dentin metalloproteinases (MMP) during the bonding procedure. MMP inhibitors may be used to contain this process. Objective: To evaluate the degree of conversion (DC%), dentin bond strength (µTBS) (immediate and after 1 year of storage in water), and nanoleakage of an experimental (EXP) and a commercial (SB) adhesive system, containing different concentrations of the MMP inhibitor GM1489: 0, 1 µM, 5 µM and 10 µM. Methodology: DC% was evaluated by FT-IR spectroscopy. Dentin bond strength was evaluated by µTBS test. Half of beams were submitted to the µTBS test after 24 h and the other half, after storage for 1 year. From each tooth and storage time, 2 beams were reserved for nanoleakage testing. Data were analyzed using ANOVA and Tukey’s test to compare means (α=0.05). Results: All adhesive systems maintained the µTBS after 1 year of storage. Groups with higher concentrations of inhibitor (5 µM and 10 µM) showed higher µTBS values than groups without inhibitor or with 1 µM. The nanoleakage values of all groups showed no increase after 1 year of storage and values were similar for SB and EXP groups, in both storage periods. The inhibitor did not affect the DC% of the EXP groups, but the SB5 and SB10 groups showed higher DC% values than those of SB0 and SB1. Conclusions: The incorporation of GM1489 in the adhesive systems had no detrimental effect on DC%. The concentrations of 5 µM GM1489 for SB and 5 µM or 10 µM for EXP provided higher μTBS than groups without GM1489, in the evaluation after 1 year of storage; whereas the concentration of inhibitor did not affect adhesive systems nanoleakage

Effect of techniques of composite resin insertion and polymerization on microleakage and microhardness

O objetivo deste trabalho foi avaliar a influência da técnica de ativação e de inserção da resina composta sobre a microinfiltração marginal e microdureza em restaurações classe II. Foram preparadas 180 cavidades que foram divididas em 6 grupos: G1 - incremento único + ativação convencional; G2 - incrementos vestíbulo-linguais + ativação convencional; G3 - incremento único + ativação "soft-start"; G4 - incrementos vestíbulo-linguais + ativação "soft-start"; G5 - incremento único + ativação progressiva; G6 - incrementos vestíbulo-linguais + ativação progressiva. Todas as cavidades foram restauradas com o sistema Z100/Single Bond (3M). Após 1.000 ciclos térmicos (5 e 55ºC), os espécimes foram imersos em solução aquosa de azul de metileno a 2%, por 4 horas e a microinfiltração foi avaliada. Metade dos espécimes foram incluídos em resina de poliestireno e a microdureza Knoop foi avaliada. Após o teste Kruskal-Wallis, não foi observada diferença significativa (p >; 0,05) entre todas as técnicas de ativação e de inserção quanto à microinfiltração. Quanto à microdureza, após os testes análise de variância (2 fatores) e Tukey, não houve diferença significativa entre as técnicas restauradoras empregadas (p >; 0,05), porém a ativação progressiva (G5 e G6) apresentou menor dureza Knoop (p ; 0.05) between the polymerization and insertion techniques as to microleakage. Regarding microhardness, the two-way ANOVA and the Tukey test did not reveal statistical differences between the restorative techniques (p >; 0.05), but progressive polymerization (G5 and G6) was associated with smaller Knoop microhardness values (p < 0.05): G = 144.11; G2 = 143.89; G3 = 141.14; G4 = 142.79; G5 = 132.15; G6 = 131.67. It was concluded that the evaluated polymerization and insertion techniques did not affect marginal microleakage, but a decrease in microhardness occurred when progressive polymerization was carried out

Sodium fluoride and casein phosphopeptide-amorphous calcium phosphate cream plus sodium fluoride efficacy in preventing enamel erosion in a simulated oral environment study model

Aim: The aim of this study was to evaluate the effectiveness of dentifrices containing high concentrations of sodium fluoride (NaF) and casein phosphopeptide-amorphous calcium phosphate cream plus fluoride (CPP-ACPF) in prevention of the erosion in a simulated oral environment study model. Subjects and Methods: Fifteen flat human enamel specimens were polished and half of the surfaces were protected with adhesive tape. Initial Knoop microhardness (KHN) and surface roughness (SR) were measured, and specimens were assigned to four groups: Control (placebo toothpaste - G1); CPP-ACPF (G2), NaF 1450 ppm (G3), and NaF 5000 ppm (G4). Enamel surfaces were brushed 3 times daily in association with demineralization-remineralization cycles (5s in cola drink + 5s in artificial saliva/10 cycles/twice daily) and the specimens were maintained in a salivary flow simulator apparatus. After 14 days, KHN and SR were measured again, and the enamel surfaces were analyzed by scanning electronic microscopy (SEM). Statistical Analysis Used: Data were analyzed using the two-way ANOVA and Student-Newman-Keuls multiple range test (α =0.05). Results: All the tested groups presented a decrease in KHN after 14 days (P < 0.05). There was no statistical significance among materials tested. Significant increase in SR was observed for all groups. SEM analysis showed morphological alterations with honeycomb structures in enamel surfaces in the four experimental groups. Conclusions: It was concluded that tooth brushing with dentifrices with high concentration of NaF and CPP-ACPF cream was not able to prevent enamel erosion in simulated oral environment