Microleakage in Overflared Root Canals Restored with Different Fiber Reinforced Dowels
Howard E. Strassler, DMD
Erut S, Gulsahi K, Caglar A, et al. Oper Dent. 2008;33: 96-105.
This study evaluated microleakage in overflared root canals restored with four different types of adhesively luted fiber-reinforced dowels: DT Light Post (LP), Glassix (GL), Ribbond (RB) and StickTech Post (ST). Forty non-carious, single-rooted mandibular human premolars with straight root canals were prepared using a step-back technique and obturated with gutta-percha using lateral condensation. The restored roots were randomly divided into four groups (n = 10). The root canals were overprepared, creating an overflared dowel space, and each dowel was adhesively luted using a total-etched adhesive (Single Bond) and dual-polymerizing luting agent (RelyX ARC). All specimens were thermal cycled 1,000 times between 5° C and 55° C and stored in 2% methylene-blue solution for 1 week. The teeth were cut horizontally into three consecutive sections: apical (A), middle (M), and coronal (C). Each section was digitally photographed from the occlusal direction under a stereomicroscope. The images were transferred to a PC and stored in TIFF format. For each image, dye penetration was estimated as the ratio of methylene-blue-infiltrated surface divided by total dentin surfaces. The data were compared and statistically analyzed using the Kruskal-Wallis test (P < .05). The Mann-Whitney U test was used to compute multiple pairwise comparisons to determine differences between the experimental groups (P = .083). Dentin-luting agent fiber-reinforced dowel (FRD) interfaces were evaluated under a scanning electron microscope. Scanning electron microscopy (SEM) showed detachment of the luting resin from the dentin surface in varying degrees in all specimens evaluated. All groups showed considerable leakage at the sections evaluated. Significant differences were demonstrated between LP-RB for the apical and middle sections and between GL-RB, LP-RB and ST-RB for the coronal sections (P < .0083). Among the FRDs evaluated, the individually shaped polyethylene-reinforced dowel (Ribbond) showed the least overall leakage.
If the goal is to maintain an intact dentition, this research may have implications in the use of adhesive composite fiber as reinforcement for large tooth preparations of vital and non-vital endodontically treated teeth. This research parallels two other research papers concerning improvement in adhesion and tooth reinforcement when using UHMWPE fiber ribbons during restoration of an endodontically treated tooth. In one study, it was shown that the UHMWPE ribbon embedded within flowable composite adjacent to the dentin walls increases the microtensile bond strength to the dentin floor in cavities with a high c-factor.1 Another research study concluded that the insertion of a lock-stitch, leno weave UHMWPE fiber ribbon (Ribbond) inside the cavity had a positive effect on fracture strength of endodontically treated molar teeth with MOD cavity preparation and cuspal fracture.2
Dr. Strassler has received grant/research support from Ribbond.
1. Belli S, Dönmez N, Eskitaflcio¤lu G. The effect of c-factor and flowable resin or fiber use at the interface on microtensile bond strength to dentin. J Adhes Dent. 2006;8: 247-253.
2. Belli S, Cobankara FK, Eraslan O, et al. The effect of fiber insertion on fracture resistance of endodontically treated molars with MOD cavity and reattached lingual cusps. J Biomed Mater Res B Appl Biomater. 2006; 79:35-41.
About the Author
Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School