Calcium hydroxide placement by preclinical dental students using three delivery techniques: a CBCT-based volumetric and radiographic study

Effective calcium hydroxide (CH) placement is essential for intracanal disinfection, but achieving homogeneous filling without apical extrusion may be challenging for preclinical dental students. This in vitro study aimed to compare the effectiveness of CH placement performed by preclinical dental students via manual file, Lentulo spiral, and injector-type application techniques via cone-beam computed tomography (CBCT) analysis and to evaluate the presence of apical extrusion associated with each technique. A total of 264 extracted mandibular single-rooted premolar teeth were allocated to three experimental groups according to the calcium hydroxide delivery technique: manual file, Lentulo spiral, and injector-type application ( n = 88/group). Following standardized root canal preparation, each preclinical dental student applied calcium hydroxide using all three techniques. CBCT and three-dimensional volumetric analysis were used to compare medicament volume, fill ratio, homogeneity, and apical reach among the groups. Apical extrusion was evaluated using periapical radiographs. Repeated-measures statistical analyses were performed to account for the within-student study design (α = 0.05). The injector-type technique produced significantly greater medicament volume, fill ratio, and homogeneity than the manual file and Lentulo spiral techniques ( p <0.001). No significant differences were observed in apical extrusion, apical reach, or optimal placement ( p >0.05). Apical extrusion rates were low across all groups. The injector-type technique improved CH filling volume, fill ratio, and homogeneity; however, none of the techniques consistently achieved ideal intracanal placement. These findings highlight the importance of both application technique and structured preclinical training.