Effect of load cycling on nanoleakage of butt joint and beveled occlusal enamel margins in class V composite resin restorations / Efeito do ciclo de carga na nanoinfi ltração de margens de esmalte oclusal com e sem bisel em restaurações classe V

Objectives: This study evaluated the infl uence of mechanical and thermal cycling on the nanoleakageof Class V composite resin restorations with and without enamel beveling. Material and method:Using 60 Class V cavities prepared on the buccal surfaces of human molars, specimens were dividedinto two groups (n = 30) based on the confi gurations of the enamel cavosurface margins. (beveled andnon-beveled) After restoring the cavity preparations with a fl owable composite, half of the specimenswere mechanically load-cycled. The specimens were sealed leaving a 1 mm window around the cervicaland enamel margins. Specimens were placed in a 50% (W/V) silver nitrate solution then immersedin photodeveloping solution and exposed to fl uorescent light for 8h. The teeth were buccolinguallysectioned, gold sputter coated and examined with a SEM to evaluate the nanoleakage values. The datawere analyzed using two-way ANOVA (α = 0.05). Results: Enamel margin confi guration had no significant effect on nanoleakage (p > 0.05). However, the nanoleakage value was signifi cantly higher inthe load-cycled group than in the group not load-cycled (p < 0.05). Conclusion: Since enamel margin confi guration does not affect nanoleakage, there is no need to bevel enamel margins of Class V cavitypreparations for composite restorations.

Objetivos: O presente estudo avaliou a infl uência dos ciclos de carga mecânico e térmico na nanoinfi ltração derestaurações Classe V em resinas compostas, com e sem biselamento do esmalte. Material e método: Os espécimes(60 cavidades Classe V preparadas na superfície vestibular de molares humanos) foram divididos em dois grupos(n = 30) baseados nas confi gurações das margens cavosuperfi ciais do esmalte (biseladas e não biseladas). Após restauraçãodos preparos cavitários com um compósito tipo fl ow, metade dos espécimes foi carregada mecanicamente.Os espécimes foram selados mantendo janela de 1 mm em torno das margens cervical e de esmalte. Os espécimesforam colocados em solução de nitrato de prata (50%), imersos na sequência em solução processadora fotográfi cae expostos à luz fl uorescente por oito horas. Os dentes foram cortados em sentido vestíbulo-lingual, revestidos emouro e observados em microscopia eletrônica para avaliar os valores de nanoinfi ltração. Os dados foram analisadospelo ANOVA (α = 0,05). Resultados: A confi guração das margens do esmalte não teve efeito signifi cante nananoinfi ltração (p > 0,05). Entretanto, os valores da nanoinfi ltração foram signifi cativamente mais altos no grupode carga que no grupo sem carga (p > 0,05). Conclusão: Uma vez que a confi guração da margem do esmalte nãoafeta a nanoinfi ltração, não há necessidade de biselar as margens do esmalte nos preparos de cavidades Classe V emrestaurações de compósitos.

Comparison of microleakage after load cycling for nanofilled composite resin fillings with or without flowable resin lining / 대한치과보철학회지

STATEMENT OF PROBLEM: when using resin for class II restoration, micoleakage by instrumentation can be regarded as the primary negative characteristic. A review of the available literature suggests that using flowable resin as liner to decreased microleakage. PURPOSE: The aim of this study was to determine the influence of the nanofilled flowable resin lining on marginal microleakage after load cycling in class II composite restoration fillings using nanofiller resin. MATERIAL AND METHODS: 24 extracted premolars were prepared with class II cavity. F group was restored the nanofilled resin with the nanofilled flowable resin as liner. NF group was restored the nanofilled resin only. After restoration, an experiment was performed on 2 groups using a 300N load at 104, 105 and 106 cycles. Prior to and before each load cycling, it was gauged length on total marginal microleakage, axial marginal microleakage and buccal, gingival, lingual marginal microleakage. Data were analyzed with the Mann-Whitney test & Kruskal-Wallis test. RESULTS: There were statistically significant differences between 2 groups and between individual groups. (P < .05) The result showed less microleakage in teeth restored by the nanofilled resin, which was lined by the nanofilled flowable resin. CONCLUSION: There was significant reduction in microleakage when the nanofilled flowable resin lining was placed underneath the nanofilled resin in class II composite restoration fillings.

The nanoleakage patterns of experimental hydrophobic adhesives after load cycling / 대한치과보존학회지

The purpose of this study was: (1) to compare nanoleakage patterns of a conventional 3-step etch and rinse adhesive system and two experimental hydrophobic adhesive systems and (2) to investigate the change of the nanoleakage patterns after load cycling. Two kinds of hydrophobic experimental adhesives, ethanol containing adhesive (EA) and methanol containing adhesive (MA), were prepared. Thirty extracted human molars were embedded in resin blocks and occlusal thirds of the crowns were removed. The polished dentin surfaces were etched with a 35% phosphoric acid etching gel and rinsed with water. Scotchbond Multi-Purpose (MP), EA and MA were used for bonding procedure. Z-250 composite resin was built-up on the adhesive-treated surfaces. Five teeth of each dentin adhesive group were subjected to mechanical load cycling. The teeth were sectioned into 2 mm thick slabs and then stained with 50% ammoniacal silver nitrate. Ten specimens for each group were examined under scanning electron microscope in backscattering electron mode. All photographs were analyzed using image analysis software. Three regions of each specimen were used for evaluation of the silver uptake within the hybrid layer. The area of silver deposition was calculated and expressed in gray value. Data were statistically analyzed by two-way ANOVA and post-hoc testing of multiple comparisons was done with the Scheffe's test. Silver particles were observed in all the groups. However, silver particles were more sparsely distributed in the EA group and the MA group than in the MP group (p < .0001). There were no changes in nanoleakage patterns after load cycling.

Microleakage of microfill and flowable composite resins in class V cavity after load cycling / 대한치과보존학회지

Low-viscosity composite resins may produce better sealed margins than stiffer compositions (Kemp-Scholte and Davidson, 1988; Crim, 1989). Flowable composites have been recommended for use in Class V cavities but it is also controversial because of its high rates of shrinkage. On the other hand, in the study comparing elastic moduli and leakage, the microfill had the least leakage (Rundle et al. 1997). Furthermore, in the 1996 survey of the Reality Editorial Team, microfills were the clear choice for abfraction lesions. The purpose of this study was to evaluate the microleakage of 6 compostite resins (2 hybrids, 2 microfills, and 2 flowable composites) with and without load cycling. Notch-shaped Class V cavities were prepared on buccal surface of 180 extracted human upper premolars on cementum margin. The teeth were randomly divided into non-load cycling group (group 1) and load cycling group (group 2) of 90 teeth each. The experimental teeth of each group were randomly divided into 6 subgroups of 15 samples. All preparations were etched, and Single bond was applied. Preparations were restored with the following materials (n=15): hybrid composite resin [Z250(3M Dental Products Inc. St.Paul, USA), Denfil(Vericom, Ahnyang, Korea)], microfill [Heliomolar RO(Vivadent, Schaan, Liechtenstein), Micronew(Bisco Inc. Schaumburg, IL, USA)], and flowable composite [AeliteFlo(Bisco Inc. Schaumburg, IL, USA), Revolution(Kerr Corp. Orange, CA, USA)]. Teeth of group 2 were subjected to occlusal load (100N for 50,000 cycles) using chewing simulator(MTS 858 Mini Bionix II system, MTS Systems Corp., Minn. USA). All samples were coated with nail polish 1mm short of the restoration, placed in 2% methylene blue for 24 hours, and sectioned with a diamond wheel. Enamel and dentin/cementum margins were analyzed for microleakage on a sclale of 0 (no leakage) to 3 (3/3 of wall). Results were statistically analyzed by Kruscal-Wallis One way analysis, Mann-Whitney U-test, and Student-Newmann-Keuls method. (p=0.05) RESULTS: 1. There was significantly less microleage in enamel margins than dentinal margins of all groups. (pA=H=M>D>Z. But there was no significant differences. 6. In enamel margins, load cycling did not affect the marginal microleakage in significant degree. 7. In dentin margins, load cycling did affect the marginal microleakage only in Revolution. (p<0.05)