Increased apical enlargement contributes to excessive dentin removal in curved root canals: a stepwise microcomputed tomography study.

INTRODUCTION: To determine whether increased apical enlargement would result in a complete preparation of curved canals and to progressively assess shaping quality using multiple microcomputed tomography (MCT) scans. METHODS: Ninety root canals with a curvature of 25° to 50° were selected. Five MCT scans, 1 preoperative and 4 postoperative, were acquired from each canal. Canal preparation was performed up to size 50 using 3 techniques, nickel-titanium (NiTi) hand files, Mtwo (VDW, Munich, Germany), and ProTaper (Maillefer, Ballaigue, Switzerland), by experienced operators in a dental mannequin so as to simulate the clinical conditions. At a level of 1 mm short of the working length, 2 parameters were evaluated in each of the 4 postoperative acquisitions: the percentage of the prepared outline and the amount of dentin removed (the prepared area). RESULTS: Statistically, there was no significant difference between the 3 systems used regarding the prepared outline. The maximum prepared outline was achieved by the use of NiTi hand files (63%; confidence interval [CI], 54%-73%), whereas Mtwo and ProTaper amounted to 58% (CI, 50%-66%) and 60% (CI, 51%-70%), respectively. In contrast, the dentin area removed by ProTaper was significantly higher than that of Mtwo and NiTi hand files. CONCLUSIONS: Increased apical enlargement of curved canals did not result in a complete apical preparation, whereas it did lead to the unnecessary removal of dentin.

Consistency of apex locator function: a clinical study.

The consistency of apex locators was determined by calculating the dysfunction frequency. Electronic working length (EWL) was determined in 507 patients requiring endodontic treatment. Different clinical parameters were recorded including tooth vitality, presence of obliteration, and metallic restoration. Two apex locators were used (Root ZX [Morita, Tokyo, Japan] and Raypex5 [VDW, Munich, Germany]). Apex locator performance was considered "consistent" when the scale bars were stable and moved only in correspondence to the movement of file in the root canal. A working length radiograph with files set to the EWL was performed. EWL were considered "acceptable" when the file tip was located 0 to 2 mm short of the radiographic apex. The function of apex locators was consistent in 85% of the patients (429/507 [99% confidence interval, 80-88]). The inconsistent measurements were strongly associated with partially or totally obliterated root canals (p < 0.0001). Radiographically, 97% of consistent measurements were "acceptable."