A Comparison of the Retention of Three Endodontic Dowel Systems Following Different Surface Treatments

Purpose: Practitioners have several options during the selection of a dowel for core restoration, including metal and glass fiber materials. Retention of the cemented dowel is critical for the success of this type of restoration. The purpose of this in vitro study was to evaluate the effect of two surface treatments on the retention of three types of dowels placed into prepared canals with a resin cement. Materials and Methods: Following the removal of the clinical crown, gutta percha was used to restore canals prepared to size 40 in 90 extracted human anterior teeth. The access openings were then sealed, and the teeth stored in water for 3 weeks at 37°C. Post preparations were made to a depth of 9 mm, and parallel ParaPost, FibreKleer, and FibreKor dowels were each used to restore 30 teeth. Ten dowels in each group received no surface roughening treatment, 10 were air abraded with 50 μ aluminum oxide, and 10 were air abraded with CoJet. The specimens were stored in water for 24 hours at 37°C following dowel placement and prior to debonding with an Instron Testing Machine. Results: The forces (N) required in tensile load to dislodge the dowels for each group were: ParaPost/CoJet 214.04 ± 91.72, FibreKleer/AlOxide 196.07 ± 57.69, ParaPost/AlOxide 184.46 ± 35.05, FibreKleer/CoJet 176.36 ± 42.43, FibreKor/AlOxide 174.32 ± 53.64, ParaPost/Unroughened 174.14 ± 40.74, FibreKor/CoJet 167.16 ± 35.94, FibreKor/Unroughened 116.69 ± 37.01, and FibreKleer/Unroughened 96.88 ± 33.45. Post hoc analysis demonstrated that the unroughened FibreKor and FibreKleer dowels had significantly less retention than all other test groups (p≤ 0.05). Conclusion: Surface roughening with air abrasion increases retention in dowels cemented with a resin cement. Both the aluminum oxide and CoJet systems were equally effective in this regard.