[Effect of mechanical load cycling on class V glass- ionomer and composite restorations; a microleakage and scanning electron microscopic evaluation]

Microleakage is an important problem with direct restorations and familiarity with its contributing factors is of utmost importance. The aim of this study was scanning electron microscopic evaluation of marginal integrity in three types of class V tooth-colored restorations and the effect of load cycling on their microleakage. In this in vitro study, class V cavity preparations were made on the buccal and lingual surfaces of 30 bovine incisors [60 cavities]. The specimens were divided into three groups [n=10 each or 20 cavities] and restored as follows: group 1: with Filtek Z350[nanocomposite], group 2: Fuji IX/G Coat Plus[CGIC], and group 3: Fuji II LC[RMGI]. All specimens were finished and polished immediately and were thermocycled [_2000,5-50 °C]. In each group, half of the teeth were load cycled .Epoxy resin replicas of 12 specimens were evaluated under FE-SEM and interfacial gaps were measured. Finally the teeth were immersed in 0.5% basic fuchsine dye for 24 hours at room temperature, sectioned and observed under stereomicroscope. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests and a comparison between incisal and cervical microleakage was made with Wilcoxon test. It was shown that the mechanical load cycling caused a statistically significant increase in cervical microleakage of Fuji IX and Fuji II LC and in incisal microleakage of Fuji II LC. Microleakage in Z350 with load-cycling and Fuji IX with and without load-cycling was significantly higher in cervical compared with incisal area. Both incisal and cervical microleakage were significantly different among these materials under load-cycling.[Fuji II LC>Fuji IX>Z350]. It was concluded that the marginal sealing ability of Fuji IX under loadcycling was better than that of Fuji II LC. Z350 showed better marginal integrity while being load-cycled than both Fuji II LC and Fuji IX

[SEM evaluation and comparison of marginal integrity of glass-ionomer and composite restorations with immediate or delayed polishing]

Marginal seal in class V cavities and determining the best restorative material to decrease microleakage is of great importance in operative dentistry. The aim of this study was to evaluate the effect of polishing time on the microleakage of three types of tooth-colored restorative materials in class V cavity preparations and to assess the marginal integrity of these materials using scanning electron microscope [SEM]. In this in vitro study, class V cavity preparations were made on the buccal and lingual surfaces of 30 bovine incisors [60 cavities]. The specimens were divided into three groups each containing 10 teeth [20 cavities]: group 1, Filtek Z 350 [nanocomposite]; group 2, Fjui IX/G Coat Plus [CGIC]; and group 3, Fuji II LC [RMGI]. In each group, half of the specimens [n=20] were finished/polished immediately and the rest of them were finished/polished after 24 hours. All the specimens were thermocycled for 2000 cycles [5-50 [degree sign] C]. epoxy resin replicas of 12 specimens [2 restorations in each subgroup] were evaluated using SEM and the interfacial gaps were measured. Finally, the teeth were immersed in 0.5% basic fuchsin dye for 24 hours at room temperature, sectioned and observed under stereomicroscope. The data were analyzed using Kruskal-Wallis and Mann-Whitney U tests and the comparison between incisal and cervical microleakage was made with Wilcoxon test. Incisal and cervical microleakage were not affected by polishing time in none of the three restorative materials [P>0.05]. Cervical microleakage only in Fuji IX with immediate polishing was significantly higher than incisal microleakage [P<0.05]. Incisal and cervical microleakage with immediate or delayed polishing were not significantly different in Fuji IX, Fuji II LC, and Z350 [P>0.05]. Immediate polishing is recommended in tooth-colored class V restorations