ABSTRACT
Precise knowledge regarding the topography of the tooth apex and location of the apical assessing the constriction are necessary for good and efficient root canal treatment and its long term prognosis. Since radiography is among the most commonly used methods for termination point, it is essential to be able to determine the exact location of apical constriction by radiography. The aim of this study is to evaluate the distance of apical constriction from anatomic and radiographic apices in extracted maxillary second premolars using clearing technique. It also compared the reliability of radiographic results with that of histologic findings. In this in-vitro experimental study, 50 extracted maxillary second premolars of patients presenting to various dental care centers in Tehran were selected. After cleaning and disinfecting the root surfaces and preparing the access cavity, 2% methylene blue was injected into the canals along with the use of negative pressure. Then, demineralization and clearing process were done using 5% nitric acid and methyl salicylate. Samples were evaluated under stereomicroscope at X16 magnification. In order to evaluate the distance between apical constriction and radiographic apex, a #10 file was fixed at the apical constriction under the stereomicroscope. Covering the apices with sealer, radiographs were taken from all samples. The reliability of radiographic results was compared with that of histologic findings. The mean distance of apical constriction from the anatomic and radiographic apices was 0.9 and 1.05 mm, respectively. Sensitivity, specificity, positive and negative predictive values of radiographic results were 87.8%, 88.8%, 93% and 62%, respectively. The likelihood ratio for positive and negative radiographic results was 7.9 and 0.1%, respectively. The diagnostic odds ratio was 57.6% which is indicative of the acceptable accuracy and validity of the radiographic results in assessing the distance of apical constriction from the anatomic apex. This study demonstrated that the distance of apical constriction from the anatomic and radiographic apices in the maxillary second premolars was approximately 1 mm and therefore, the process of cleaning, shaping and obturation should end at this point. This study emphasizes on the accuracy of radiographic findings and importance of having sufficient anatomic knowledge for achieving a good treatment outcome in a clinical setting