Effect of dentin pretreatment and curing mode on the microtensile bond strength of self-adhesive resin cements

PURPOSE: The aim was to evaluate the effect of curing mode and different dentin surface pretreatment on microtensile bond strength (microTBS) of self-adhesive resin cements. MATERIALS AND METHODS: Thirty-six extracted human permanent molars were sectioned horizontally exposing flat dentin surface. The teeth were divided into 12 groups (3 teeth/group) according to the dentin surface pretreatment methods (control, 18% EDTA, 10% Polyacrylic acid) and curing mode (self-curing vs. light-curing) of cement. After pretreatment, composite resin blocks were cemented with the following: (a) G-CEM LinkAce; (b) RelyX U200, followed by either self-curing or light-curing. After storage, the teeth were sectioned and microTBS test was performed using a microtensile testing machine. The data was statistically analyzed using one-way ANOVA, Student T-test and Scheffe's post-hoc test at P<.05 level. RESULTS: For G-CEM LinkAce cement groups, polyacrylic acid pretreatment showed the highest microTBS in the self-cured group. In the light-cured group, no significant improvements were observed according to the dentin surface pretreatment. There were no significant differences between curing modes. Both dentin surface pretreatment methods helped to increase the microTBS of RelyX U200 resin cement significantly and degree of pretreatment effect was similar. No significant differences were found regarding curing modes except control groups. In the comparisons of two self-adhesive resin cements, all groups within the same pretreatment and curing mode were significantly different excluding self-cured control groups. CONCLUSION: Selecting RelyX U200 used in this study and application of dentin surface pretreatment with EDTA and polyacrylic acid might be recommended to enhance the bond strength of cement to dentin.

Effect of curing modes on micro-hardness of dual-cure resin cements / 대한치과보존학회지

OBJECTIVES: The purpose of this study was to evaluate curing degree of three dual-cure resin cements with the elapsed time in self-cure and dual-cure mode by means of the repeated measure of micro-hardness. MATERIALS AND METHODS: Two dual-cure self-adhesive resin cements studied were Maxcem Elite (Kerr), Rely-X Unicem (3M ESPE) and one conventional dual-cure resin cement was Rely-X ARC resin cement (3M ESPE). Twenty specimens for each cements were made in Teflon mould and divided equally by self-cure and dual-cure mode and left in dark, 36degrees C, 100% relative humidity conditional-micro-hardness was measured at 10 min, 30 min, 1 hr, 3 hr, 6 hr, 12 hr and 24 hr after baseline. The results of micro-hardness value were statistically analyzed using independent samples t-test and one-way ANOVA with multiple comparisons using Scheffe's test. RESULTS: The micro-hardness values were increased with time in every test groups. Dual-cure mode obtained higher micro-hardness value than self-cure mode except after one hour of Maxcem. Self-cured Rely-X Unicem showed lowest value and dual-cured Rely-X Unicem showed highest value in every measuring time. CONCLUSIONS: Sufficient light curing to dual-cure resin cements should provided for achieve maximum curing.

SEM evaluation of marginal sealing on composite restorations using different photoactivation and composite insertion methods.

Aim: This in vitro study evaluates the influence of marginal sealing methods in composite restorations with different adhesive systems submitted to mechanical load. Materials and Methods: Eighty bovine incisor crowns were embedded in Polyvinyl chloride (PVC) molds with the buccal surface exposed, where cavities (4mm x 4mm x 3mm) were made. Samples had the adhesive systems, Single Bond or Clearfil SE Bond, applied according to the manufacturer's recommendations. The cavities were filled with a Z-250 composite according to the restoration technique (bulk filling or three increments) and photoactivation (conventional, soft start, pulsatile light or light-emitting diode [LED]). The samples were duplicated with epoxy resin for scanning electron microscopy observations. Samples were also submitted to mechanical load (200,000 cycles; 2 Hz) and new replicas were made. Results: The results, in percentages, were submitted to ANOVA followed by Tukey's test (P < 0.05). There was statistical difference between the cycle group (23.84%) and the non cycle group (18.63%). Comparing the restoration technique, there was no statistical difference between bulk filling (19.62%) and three increments (22.84%). There was no statistical difference among the groups: Pulsatile light (24.38%), soft start (22.75%), LED (21.47%) or conventional (16.34%). Furthermore, there were no statistical differences between the adhesive systems: Clearfil SE Bond (21.32%) and Single Bond (20.83%). Conclusions: The photoactivation methods, the restorative techniques and the adhesive systems did not influence gap formation.

Influência do protocolo de fotoativação no selamento de restaurações com compósitos / Influence of light-curing mode on the sealing of resin composite restorations

O propósito deste estudo foi avaliar a influência do protocolo de fotoativação no selamento de restaurações classe V com compósitos. Sessenta cavidades com margem oclusal em esmalte e margem apical em dentina, preparadas nas superfícies vestibular e lingual de pré molares humanos, foram hibridizadas com o sistema adesivo Single Bond e restauradas com três compósitos (A110, P60 e Point 4). Para cada compósito, foram produzidos dois grupos de acordo com os protocolos de fotoativação (n = 10): Convencional-500 mW/cm2/40 segundos e Softstart-250 mW/cm2/40 segundos + 500 mW/cm2/20 segundos. Após acabamento/polimento das restaurações e armazenagem durante 7 dias em água destilada a 37°C, os dentes foram submetidos à termociclagem. Os espécimes foram impermeabilizados com esmalte de unha e imersos em solução neutra de azul de metileno a 2 % por 24 horas. Os dentes foram seccionados e o grau de penetração do corante foi avaliado em uma escala ordinal de 0-3. Os dados foram submetidos aos testes de Kruskal-Wallis e Mann-Whitney (α = 0,05). Não houve diferença estatística entre os grupos ativados com os dois protocolos de fotoativação. A microinfiltração foi maior nas margens em dentina do que nas margens em esmalte (p < 0,01). Esses achados sugerem que o protocolo de fotoativação soft-start não apresentou influência no selamento de cavidades restauradas com compósitos fotopolimerizáveis

This study investigated the effect of light-curing modes on cervical sealing of resin composite restorations. Sixty cavities with the occlusal margins in enamel and the gingival margins in dentin, prepared on the labial and lingual surfaces of human premolars were treated with Single Bond adhesive system and restored using a bulk technique with three resin composites (A110, P60 and Point 4). For each composite, two groups of 10 cavities were created according to the two light-curing modes: Standard (S)-500 mW/cm2 / 40 seconds and Soft-start (SS) - 250 mW/cm2 / 40 seconds + 500 mW/cm2 / 20 seconds. The specimens were submitted to thermocycling prior to immersion in 2% neutral solution of methylene blue for 24 hours. The teeth were sectioned and the degree of dye penetration was scored on a 0-3 ordinal scale. The data were analyzed by Kruskal-Wallis and Mann-Whitney tests (α = 0.05). No significant difference in the microleakage scores was observed among the groups polymerized with the two light-curing modes. The microleakage was greater in dentin margins than in enamel margins (p < 0.01). These results suggest that soft-start light-curing mode did not have any influence on resin composite restoration sealing