The Effect of Light Exposure on Water Sorption and Solubility of Self-Adhesive Resin Cements.

Purpose. To investigate the effect of light activation on the water sorption (WS) and solubility (SL) of resin cements after 24 h and 7 days. Methods. Disk-shaped specimens were prepared using five dual-polymerized cements (four self-adhesive [RelyX Unicem, MaxCem, SeT and G-Cem] and one conventional [Panavia F 2.0]) and divided according to the curing mode (direct light exposure or self-cure) and water immersion period (24 h or 7 days). Specimens were dry-stored and weighed daily until a constant mass was recorded (M1). Then, specimens were stored in water for either 24 h or 7 days and immediately weighed (M2). After desiccation, specimens were weighed again until a constant mass was achieved (M3). WS and SL were calculated and statistically analyzed by Kruskal-Wallis, Dunn and Mann-Whitney U tests (α = 0.05%). Results. There was a significant increase in WS for all products after one-week immersion in water. The highest water uptake was observed for autopolymerized groups. Extended water immersion significantly affected the SL for most of autopolymerized cements. Significant differences between products were observed in both tests. Conclusions. The curing mode and the water immersion period may affect the mechanical stability of the resin cements, and these differences appear to be product-dependent.

Influence of polymerization technique on microleakage and microhardness of resin composite restorations.

This study evaluated the influence of three polymerization techniques on microleakage and microhardness of Class II restorations using a microhybrid (Filtek Z250) and a "packable" resin composite (SureFil). The techniques, their respective light intensities and time used in relation to the resin composites, are: Conventional (C)--800 mW/cm2 for 40 seconds; Soft-Start (SS1)--75 mW/cm2 for 10 seconds plus 518mW/cm2 for 30 seconds; Soft-Start (SS2)-- 170mW/cm2 for 10 seconds plus 518 mW/cm2 for 30 seconds and Plasma Arc Curing (PAC)--1,468 mW/cm2 for three or six seconds. One hundred and fifty-two "Vertical Slot type Class II cavities" at the mesial and distal surfaces were prepared and divided into eight groups (n = 19). After the restorative procedures, the samples were thermocycled (1,000 cycles at 5 degrees C and 55 degrees C), then immersed in 2% methylene blue dye solution for four hours. The microleakage was evaluated and the results analyzed by the Kruskal-Wallis and Multiple Comparisons tests. Ten samples from each group were randomly selected, embedded in polyester resin, polished and submitted to the Knoop microhardness test. ANOVA (split-plot) and Tukey's test (p < 0.01) revealed significant differences among depths: the hardness at the top surface was significantly higher followed by the middle and bottom surfaces. There was no significant difference in microleakage among the techniques when microhybrid resin composite was employed. However, when using a "packable" resin composite, the conventional technique for polymerization was comparable to Soft-Start and better than PAC.

[Effect of techniques of composite resin insertion and polymerization on microleakage and microhardness]. / Efeito das técnicas de inserção e ativação da resina composta sobre a microinfiltração e microdureza.

The aim of this study was to evaluate the influence of techniques of composite resin polymerization and insertion on microleakage and microhardness. One hundred and eighty class II cavities were prepared in bovine teeth and assigned to six groups: G1 - bulk filling + conventional polymerization; G2 - bucco-lingual increments + conventional polymerization; G3 - bulk filling + soft-start polymerization; G4 - bucco-lingual increments + soft-start polymerization; G5 - bulk filling + progressive polymerization; G6 - bucco-lingual increments + progressive polymerization. All cavities were restored with the Z100/Single Bond system (3M). After thermocycling, the samples were immersed in 2% methylene blue dye solution for 4 hours. Half of the samples were embedded in polystyrene resin, and Knoop microhardness was measured. The Kruskal-Wallis test did not reveal statistical differences (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.

Efeito das técnicas de inserçäo e ativaçäo da resina composta sobre a microinfiltraçäo e microdureza / Effect of techniques of composite resin insertion and polymerization on microleakage and microhardness

O objetivo deste trabalho foi avaliar a influência da técnica de ativaçäo e de inserçäo da resina composta sobre a microinfiltraçäo marginal e microdureza em restauraçöes classe II. Foram preparadas 180 cavidades que foram divididas em 6 grupos: G1 - incremento único + ativaçäo convencional; G2 - incrementos vestíbulo-linguais + ativaçäo convencional; G3 - incremento único + ativaçäo soft-start; G4 - incrementos vestíbulo-linguais + ativaçäo soft-start; G5 - incremento único + ativaçäo progressiva; G6 - incrementos vestíbulo-linguais + ativaçäo progressiva. Todas as cavidades foram restauradas com o sistema Z100 Single Bond (3M). Após 1000 ciclos térmicos (5 e 55C), os espécimes foram imersos em soluçäo aquosa de azul de metileno a 2 por cento, por 4 horas e a microinfiltraçäo foi avaliada. Metade dos espécimes foram incluídos em resina de poliestireno e a microdureza Knoop foi avaliada. Após o teste Kruskal-Wallis, näo foi observada diferença significativa (p>0,05) entre todas as técnicas de ativaçäo e de inserçäo quanto à microinfiltraçäo. Quanto à microdureza, após os testes Análise de Variância (2 fatores) e Tukey, näo houve diferença significativa entre as técnicas restauradoras empregadas (p>0,05), porém a ativaçäo progressiva (G5 e G6) apresentou menor dureza Knoop (p<0,05): G1=144,11; G2=143,89; G3=141,14; G4=142,79; G5=132,15; G6=131,67. Concluiu-se que as técnicas de ativaçäo e de inserçäo da resina composta näo afetaram a microinfiltraçäo, mas ocorreu uma diminuiçäo na microdureza do material quando a ativaçäo progressiva foi utilizada

Evaluation of microleakage in cervical margins of various posterior restorative systems.

PURPOSE: The purpose of this in vitro study was to evaluate the microleakage and dye penetration patterns of various restorative systems in the cervical margins of Class II cavities using the dye penetration technique. MATERIALS AND METHODS: Ninety bovine incisors were selected and part of the crown was sectioned producing a standardized occlusogingival margin of 4 mm. Standardized Class II box cavities were designed on the mesial (MO) and distal (OD) surfaces with the gingival margin in dentin. The cavities were randomly divided into six groups (n = 30): group 1 (control), Etch & Prime 3.0 (Degussa AG) + Definite (Degussa AG); group 2, Prime & Bond NT (Dentsply De Trey) + Definite; group 3, Etch & Prime 3.0 + flowable composite resin Wave (SDI) + Definite; group 4 (control), Prime & Bond NT + TPH Spectrum (Denstply De Trey); group 5, Etch & Prime 3.0 + TPH Spectrum; group 6, Prime & Bond NT + Wave + TPH Spectrum. After they were finished and polished, the specimens were subjected to 1500 thermal cycles in baths of 5 degrees+/-2 degrees C and 55 degrees+/-2 degrees C with 60 seconds of dwell time for each bath. After the thermocycling, the specimens were sealed with acid-resistant varnish, leaving a 1-mm window around the cervical margin interface, and immersed in 2% methylene blue buffered solution for 4 hours. Then the specimens were sectioned longitudinally in half and qualitatively evaluated under stereomicroscopy at 45 times magnification, using ranked scores for the dentin cervical margin (0-4). The dye penetration pattern (adhesive or dentinal) was also evaluated. The data were subjected to a reproducibility kappa test, and the mean of the three examiners' scores was analyzed by the Kruskal-Wallis nonparametric test and a multiple comparison nonparametric test. Fisher's exact test was used to evaluate the dye penetration pattern. RESULTS: The rank sums of the groups were expressed in decreasing order: group 4, 67.23a; group 3, 72.58ab; group 6, 78.43ab; group 5, 93.19bc; group 2, 112.97c; group 1, 113.52c. (Statistically significant differences are expressed by different superscript letters.) The results indicate that none of the systems used in this study was able to impede microleakage, and that the use of a flowable resin decreases the values of leakage only for Definite composite resin. The dye penetration pattern for the groups that used Prime & Bond NT was predominantly dentinal, whereas the pattern for Etch & Prime 3.0 groups was adhesive. CLINICAL SIGNIFICANCE: An ormocer-based resin that was developed to improve the physical properties of composite resin and a self-etching primer adhesive system obtained higher values of microleakage compared with a one-bottle adhesive system and a microhybrid composite resin. The flowable composite resin decreased the values of microleakage only for the ormocer-based resin.

Influence of resin composite polymerization techniques on microleakage and microhardness.

OBJECTIVE: The purpose of this study was to evaluate the marginal microleakage and the extent of polymerization in Class II resin composite restorations prepared with two restorative techniques and two polymerization systems. METHOD AND MATERIALS One hundred twenty Class II cavities were prepared in bovine teeth and randomly divided into four groups: Bulk placement and conventional polymerization (Conv 1); buccolingual increments and conventional polymerization (Conv 3); bulk placement and soft-start polymerization (Soft 1); buccolingual increments and soft-start polymerization (Soft 3). All cavities were restored with the Z100/Single Bond system. After thermocycling, the specimens were immersed in 2% methylene blue solution and then evaluated for microleakage. Half of the samples were embedded in polyester resin and polished. The Knoop microhardness of the restorations was measured. RESULTS: There was no dye penetration in 54.44% of Conv 1, 70.11% of Conv 3, 42.53% of Soft 1, and 63.22% of Soft 3 specimens. There were statistically significant differences in microleakage among groups. There were no statistically significant differences in microhardness among any groups at any depth. CONCLUSION: The incremental placement technique resulted in less microleakage. The soft-start system provided adequate polymerization but could not improve marginal sealing.