The only difference in these two resin composites was the addition of barium aluminum silicate to make one of them radiopaque. Lindberg et al. [20] indicated no significant differences in 9-year survival rates of Class II restorations between hybrid resin composite restorations and open sandwich restorations, in which

a polyacid-modified resin composite was placed as first layer in the cervical part of the cavity and following layers were placed with a resin composite. By contrast, Opdam et al. [30] reported that a total-etch technique showed a significantly higher 9-year survival rate of Class II restorations compared to a closed-sandwich technique in which a thin layer of resin-modified glass-ionomer lining cement was applied on the entire dentin surface. Wilder et al. [25] revealed that the 12-year clinical performance of a dual-cured adhesive was excellent and was not affected by dentin acid etching. Qvist and Strøm DAPT purchase [6] reported no significant difference in survival click here rates of Class III restorations at 11 years between restorative techniques,

mainly with or without an enamel bevel. With respect to the comparison between Class I and Class II restorations, there are inconsistent findings [13], [14], [18], [32], [33] and [40]. In addition, there are contradictory outcomes even in the articles, which demonstrated significant differences between cavity designs. Rodolpho et al. [18] reported that Class I resin composite restorations showed mafosfamide significant better survival function

compared to Class II restorations, whereas Kubo et al. [33] indicated opposite results. In our earlier study [32], there were no significant differences in the longevity between Class I, II, III and V restorations. In the later study [33], however, significant differences were found between classes (Fig. 4). Although the sample sizes of Class I restorations in both studies were markedly smaller compared to those of other classes, the later study may provide more reliable information since the relatively high recall rate of 91% was obtained. Concerning the effect of cavity size, there are also inconsistent findings [13], [14], [18], [29] and [30]. All three articles [18], [29] and [30], which showed significant effects on longevity demonstrated that failure rates significantly increased with the number of the restored surfaces. Although three articles showed no significant effect of tooth type on the longevity of posterior resin composite restorations [10], [13] and [31], four articles demonstrated that restorations placed in premolars showed significant better survival rates compared to those in molars [15], [17], [18] and [30]. This may be due to the greater occlusal forces on molar restorations compared to premolar restorations. Another possible explanation is poorer access to operating field in molars, and which may require more extensive restorations. Fig. 5 shows survival curves of resin composite restorations by tooth type obtained from our data.