Effects of Load Cycling on the Microleakage of Beveled and Nonbeveled Margins in Class V Resin-Based Composite Restorations

Abstract

Aim: This study evaluated the influence of mechanical loading and thermocycling on microleakage of class V resin-based composite restorations with and without enamel bevel. Methods and Materials: Sixty class V cavity preparations measuring 3.0 mm wide (mesiogingivally) x 2.0 mm high (occluso-gingivally) x 1.5 mm deep with the occlusal margin in enamel and the gingival margin in cementum were prepared on the buccal surfaces of human premolars using a #12 diamond round bur (Drendel & Zweiling Diamant GmbH, Lemgo, Germany) in a high-speed, water-cooled handpiece. The specimens were then divided into two groups of 30 specimens each, based on the type of enamel cavosurface margin configuration as beveled or nonbeveled (butt joint). After restoring the preparations with a flowable resin-based composite (Tetric Flow, Ivoclar Vivadent-AG, Schaan, Liechtenstein) and finishing and polishing with sequential discs (Sof-Lex Pop-on, 3M-ESPE, St. Paul, MN, USA), the teeth were stored at 37°C and 100 percent humidity. Twenty-four hours later, half of the specimens in each group (nonbeveled "N" or beveled "B") were exposed to a cycling loading for 250,000 cycles to simulate occlusal loading and assigned to two subgroups (NL+ or BL+), while the remainder of the specimens in each group were only maintained in a 100-percent-humidity environment, without any cyclical loading, until tested (NL-or BL-). The specimens were sealed with sticky wax (Kemdent, Associated Dental Products, Swindon, UK) and nail polish. The apical foramen of each tooth was sealed with sticky wax and the rest of the tooth was covered with nail varnish, except for an area within 1.0 mm around the composite restoration. To detect marginal leakage, all of the samples were stored in a 0.5 percent basic fuchsine solution for 24 hours. The specimens were then sectioned longitudinally using a low-speed diamond blade (IsoMet, Buehler Ltd., Lake Bluff, IL, USA), machined, and evaluated under 25X magnification using a stereomicroscope (M9, Wild Heerbrugg, Switzerland). The specimens were scored on a scale from 1 to 4 on the degree of dye penetration. The qualitative data were analyzed by the Mann-Whitney U test at a 5 percent significance level (p<0.05). The null hypothesis of this study was

Does the use of a novel self-adhesive flowable composite reduce nanoleakage?

“…This was in accordance with Kubo et al 67 and Swathi et al, 68 who stated that nanoleakage of composite restorations occurs because of stress placed along the tooth–restoration interface due to various factors, such as polymerization shrinkage, thermo-cycling in the oral environment, and mechanical fatigue through repetitive masticatory loading. Also, our findings are in agreement with Ameri et al 38 and Bedran-de-Castro et al, 43 who concluded that cyclic loading increased nanoleakage of the margins of Class V composite restorations.…”

“…The diversities in the reported data could be attributed to dissimilarities between preparation types and sizes; operator variability; materials used; and load cycle values, direction, and number. 38 , 70 On the other hand, a limitation of this study is that it was carried out in laboratory conditions, negating the effect of pulpal pressure on the used restorative systems. Thus, more clinical evaluations should be carried out as such in vitro studies do not eliminate the need for clinical ones.…”

“…During normal function and parafunctional habits, teeth are subjected to stresses. 38 Food bolus can induce vertical loading between antagonistic teeth, which is equally disseminated over the entire occlusal surface to alleviate stresses. 39 Compressive stresses arise on the tooth aspect being bent, while tensile stresses are generated simultaneously on the opposite tooth aspect.…”

Remineralizing Effect of Nanofilled Glass Ionomer Combined with Titanium Dioxide Nanoparticle and Nanohydroxyapatite in Root Caries-like Lesions

“…A round carbide bur size # 023 * with high speed hand piece was used under water coolant. The depth of the cavity was adjusted to 2 mm by inserting the entire head of the bur (14) .…”

Qualidade marginal de restaurações cervicais, feitas com materiais de diferentes módulos de elasticidade, em pré-molares submetidos a carregamento oclusal excêntrico

“…favorecer a sua longevidade, por conseguinte (Ichim et al, 2007a;Tyas, 2012;Soares et al, 2013). Nesse caso, quando as cavidades passam a ter forma de U, é que maiores tensões se concentram na margem gengival, em comparação à oclusal (Ameri et al, 2010).…”