Influence of Irrigant,Dowel Type,and Root‐Reinforcing Material on Fracture Resistance of Thin‐Walled Endodontically Treated Teeth

Purpose: Unresolved controversy exists concerning the optimum restorative material to reinforce the thin‐walled roots of endodontically treated teeth to improve their fracture resistance under occlusal load. This study evaluated the effectiveness of irrigant, dowel type, and root‐reinforcing material on the fracture resistance of thin‐walled endodontically treated teeth. Materials and Methods: The root canals of 140 maxillary central incisors were enlarged and equally divided into seven groups according to the canal irrigant: no irrigant (control), 5% hydrogen peroxide, 5% sodium hypochlorite, a combination of 5% hydrogen peroxide and sodium hypochlorite, 15% ethylenediaminotetraacetic acid (EDTA), 10% lactic acid, or 20% lactic acid. Within each group, root canals were lined with composite resin (PermaFlo) or glass ionomer cement (Fuji II LC). A light‐transmitting plastic dowel (Luminex) was used to create space for a quartz fiber‐reinforced dowel (Aestheti Post) or a titanium alloy dowel (ParaPost XH) and to cure the restorative materials. Following dowel cementation and restoration of the roots with composite core, the teeth were submitted to fracture resistance testing, and data were analyzed with 3‐way ANOVA followed by Ryan‐Einot‐Gabriel‐Welsch Multiple Range Test (α= 0.05). Results: Fracture resistance values were significantly different among irrigants, restorative materials, and their interaction (p < 0.001); however, the dowel type was not significantly different (p= 0.51). Conclusions: Thin‐walled roots that had the smear layer removed with lactic acid and that were then lined with composite resin had a higher fracture resistance.