| With the development in preservative dentistry, more and more residual teeth have been restored using posts and crowns. Fiber posts have been widely used due to their excellent biocompatibility and suitable elastic modulus. However in clinical practice, a high failure rate of fiber post-retained restorations was still reported. Loss of bonding was considered as the predominant failure mode in fiber post-retained restorations, which account for 50 percent of its complications. An in vitro research pointed out that the integrity of the dentine-cement-post ‘sandwich interface' was essential for post retention. Resin cements, which have high mechanical strength and high bonding strength immediately, were applied for luting fiber posts as the predominant preference. However, a large number of studies reported that resin cements had a big shrinkage after polymerization and were prone to degradation in water environment. These changes would compromise the bonding durability of fiber posts. A previous study evaluated the effects of the type of luting cements(conventional glass-ionomer cement Fuji I, resin-modified glass ionomer cement Fuji CEM, self-adhesive resin cement RelyX Unicem and etch-and-rinse resin cement RelyX ARC) and thermo-mechanical loading on the retention of glass fiber posts to root canal. After artificial ageing, the bonding strength of two resin cements decreased, while that of resin-modified glass ionomer cements increased significantly.The results suggest the resin-modified glass ionomer cement after absorbing water features such as mild inflation may increase interface sealing performance, thus improve the stability of fiber posts restoration.Based on these findings, the present study designed a clinical randomized trial to compare the clinical bond durability of fiber post-retained restorations using resin modified glass ion cement(Fuji CEM), self-adhesive resin cement(RelyX Unicem) and self-etch adhesive resin system(DC Bond and DC Core) respectively. According to the inclusion and exclusion criteria, 285 teeth were included which need post-core restoration. The included teeth were randomly assigned into one of three groups according to the cements employed for luting posts, involving group RGI: a self-cured resin glass-ionomer cement(Fuji CEM, GC Corp., Tokyo, Japan); group SAR: a self-adhesive dual-cured resin cement( RelyX Unicem; 3M ESPE, St. Paul, MN, USA), and group SER: a self-etch adhesive resin cement system(Clearfil DC Bond and Core Automix ONE, Kuraray Noritake Dental), following a random number list. The base line condition of the each fiber-post restoration was recorded, including the basic information of the subjects, tooth position, completion time of root canal filling, the defect reason, with or without night molar habits, the amount of dentin left after endodontic treatment and abutment preparation, the length of fiber post in the root canal and the type of restoration. The patients were recalled at 6 months and 12 months, checking whether there was any loss of bonding or broken of fiber post, root fracture, periapical lesions, crown mobility and so on. The success rate and retention rates were calculated. Results of the present study showed that, after 12 months of follow-up, the survival rate of group RGI and SAR were both 100% and that of group SER was 98.77%. No post fracture, crown dislodgement or periapical lesion was found and the occurrence of post debonding was limited to only one case. The latter was seen in premolar with no ferrule effect.With the limits of present study, the success rate and survival rate of RGI was 100% after a year of follow-up observation. This indicated that resin-modified glass ionomer cement was reliable for bonding fiber post in the first year. Based on the previous in vitro study, the authors inferred that with the extension of time, an increase in bonding durability would be expected for resin-modified glass ionomer cement. However, further long time follow up is necessary to obtain more reliable data. |
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