New Restoration Technique Vs Fracture Resistance of Endodontically Treated Teeth

Objectives: The aim of this in vitro study was to evaluate the effect of a new restoration technique on fracture resistance of endodontically treated mandibular premolars with MOD cavity preparation. Materials & Methods: 60 recently extracted single-rooted mandibular premolar teeth were used and randomly assigned to four groups (n=15). Group 1 didnot receive either cavity preparation or root canal treatment (negative control). From Group 2 to 4, the teeth received root canal treatment and a MOD cavity preparation. Group 2 kept unrestored (positive control). Group 3 restored with dentin bonding system (Clearfil SE Bond, Kuraray) and composite resin (Clearfil AP-X, Kuraray). In Group 4, a piece of polyethylene ribbon fiber (Ribbond, Ribbond Inc.) was inserted inside the cavity from buccal cusp to lingual cusp direction during restoring teeth with dentin bonding system and composite resin. After finishing and polishing, the teeth were placed in a specially designed steel pad at an angle of 45 to the long axis of the root and subjected to compressive fracture tests in a universal testing machine at crosshead speed of 1 mm/min. The mean load necessary to fracture the samples in each group were recorded in N. Data were statistically analyzed by Kruskal-Wallis ANOVA and Mann-Whitney U tests. Results: The results indicated that MOD preparation with superimposed endodontic access of the teeth 83% weakened the tooth structure in comparison with intact teeth (p<0.05). Teeth reinforced with a combination of polyethylene fiber and composite resin were not significantly different than only composite resin restoration (p>0.05). However, the failure mode of reinforced teeth was limited to enamel level while other three group showed fracture in level of cemento-enamel junction or more below (p<0.05). Conclusions: As a result, intercuspal fiber reinforcement by Ribbond of endodontically treated teeth may be very beneficial when compared to conventional composite restoration.