Einfluss von Trocknung und Schmelzrandanschrägung auf die Randspaltbildung von Klasse-II-Kompositfüllungen

Resin composites are characterized by a polymerization shrinkage of about 3%, which would lead to marginal gaps without the use of appropriate adhesive systems. Adhe-sive systems should guarantee stable bonding between tooth and resin composite and therefore inhibit marginal gaps and recurrent caries. In this study, by use of the Solobond M adhesive system, marginal quality of Class II resin composite fillings was investigated with regard to the influence of various drying techniques as well as enamel bevelling. 64 extracted human molars, free of caries and fillings, received Class-II cavities with cervical margins having been located below the amelocemental junction. 50% of cavi-ties were prepared with enamel bevel. Enamel and dentin were etched with 35% phosphoric acid and rinsed with water, thereafter various drying techniques were implemented: 1) 3 brief air blows, 2) 5 s air blow, 3) 15 s air blow + rewetting, 4) 30 s air blow. Then, according to the manufacturer’s instruction, the application of the adhesive sys-tem Solobond M (Voco, Cuxhaven, Germany) followed. A horizontal incremental tech-nique was used to fill the cavities with the microhybrid resin composite Clearfil AP-X (Kuraray, Osaka, Japan). For evaluation of marginal gaps, a scanning electron microscope (SEM) was used. Rep-licas of the teeth were made, before and after the treatment with a specific thermocy-cling load (10,000 cycles, 5°C/55°C). Thermocycling fatigue of the resin composite fillings led to a significant increase of marginal gaps (p<0.05). A 100% marginal seal in enamel was achieved prior to fatigue of the resin composite fillings. The various drying techniques showed no significant difference in the marginal quality after thermal stress (p>0.05). However, bevelled groups showed significantly better results than those without bevelling (p<0.05). In dentin, more intensive drying technique caused less satisfactory results (p<0.05). Group 3 (rewetting group) showed the most stable results with least scatter before and after thermocycling, followed by group 1 (3 s air blow) and group 2 (5 s air blow). The worst results were achieved by Group 4 (p<0.05), with the most intensive drying technique. In this Group, no perfect marginal seal was achieved in dentin even initially. In enamel, successful adhesion is easier to achieve and it is less technique sensitive than in dentin. Therefore, in deep Class-II cavities, marginal gap are diffcult to avoid. By use of Solobond M (Voco, Cuxaven, Germany), a short drying method and subse-quent rewetting technique should be used. Overdrying of the dentin should be omitted to obtain stable results. Enamel bevelling shows advantages.