Quality of apical seal in curved canals using three types of spreaders

The aim of the present study was to evaluate the influence of spreader shape on the quality of obturation. Forty-five single canal teeth with varying degrees of apical curvature were used throughout. The canals were prepared using the step-back technique and obturated with lateral condensation. The teeth were classified into three groups (A, B, and C) and treated as follows. Group A was treated with markedly conical, flat-ended spreaders (A to D; Dentsply-Maillefer, Ballaigues, Switzerland). Group B was treated with slightly conical (15 to 40) sharp-pointed CC-cord spreaders. Group C was treated with CC-cord, slightly conical but flat-ended spreaders. The obturated teeth were decalcified in 7.5% nitric acid to obtain four cross-sections: the first at 2 mm from the apex and then the following three sections at 1-mm intervals. Section thickness was approximately 1 mm. Each section was photographed under a stereoscopic microscope. The following areas were measured on each of the microphotographs using a planimeter: (a) gutta-percha mass, (b) mass of sealer, (c) foreign bodies, and (d) empty spaces. These four areas were added to determine total cross-sectional canal area and then the percent of that area attributable to a and to b + c + d was calculated. The statistical analysis of the data (parametric Student's t test for independent groups) revealed that only in group B was the area occupied by a, the gutta-percha mass, significantly greater at all levels than the area occupied by b + c + d. Next in obturation effectiveness was group C, followed by group A.