Comparative Study Of Two Methods Of Determining Root Canal Working Length

Objective: To determine root canal working length(WL) is one of key procedures in root canal therapy. This study bring forward a method which units tooth average length, radiographic length and digital-tactile length and be called as 'triple-united method' to determine WL. The purpose of this study was to evaluate the accuracy and influence factors of this method, meanwhile, we compared this method with electronic measurement. Methods: This study was divided into two parts, namely in vitro and clinical experiments. In vitro experiment contained two groups, normal group used forty extracted single-root teeth and apical resorption group used twenty extracted single-root teeth with apical root resorption. In vitro model was established and WL was measured by triple-united method and electronic method. Clinical experiment contained 96 teeth, 147 root canals. The accuracy of two methods was observed, meanwhile, the influence of patients age and tooth position to triple-united method was analyzed, the relatedfactors including tooth integrity and apical disease to two methods was still analyzed. Results: The outcome of in vivo experiment showed triple-united method was not as good as electronic measurement. In apical resorption group, the accuracy of triple-united method was 45.0% and electronic measurement was 70.0%, p<0.05, both accuracy was decreased. As well, the outcome of in vivo experiment showed triple-united method was not as good as electronic measurement. The related factors including patients age, tooth position did not influence the accuracy of triple-united method. But if tooth was not integrity or had apical disease, the accuracy of triple-united method was decreased(78.9% to 63.6%, 86.4% to 62.1%, both p<0.05), while the accuracy of electronic method was not influenced(90.3% to 90.9%, 90.1% to 90.9%, p>o.l). Conclusions: The results suggested triple-united method was better than traditional digital-tactile measurement and could approximately satisfy clinic requirement, but was not as good as electronic method. When tooth was not integrity or had apical disease, triple-united method was not suitable very well, while electronic measurement was excellent.