An in vitro comparison of three endodontic techniques for primary incisors.

Fifty-four extracted primary maxillary central incisors with some incisal edge intact as a reference point and no more than 25% of root resorption, signs of canal obstructions, or root anomalies were included. 3 The sample was equally and randomly distributed to pressure syringe, lentulo spiral, or incremental groups. Immediately following extraction, each tooth was placed in 10% formalin then placed in saline for I hr. Then each tooth was dried and its apex protected with a small piece of paper and covered with a ball of wax approximately 4 mm in diameter. The apical one-third of the root was then embedded in plaster of Paris. After the plaster hardened, pink base plate wax was placed over the hardened plaster. Another mix of plaster then was poured above the wax sheet to the level of the cervical area of each tooth. After the second layer hardened, the apical plaster block was separated. The inner wax layer, the soft paper, and the wax ball around the apex of each tooth were peeled off to create an apical void. The two separate plaster pieces then were sealed back together with cyanoacrylate. Each tooth was assigned to a predetermined sequence to control for improvement of the operator’s skills and also to allow each technique equal chance of being first, second, and third in the order of treatment. The teeth were classified as having either an open or a closed apex based on their radiographic appearance. Before preparing the teeth for endodontic treatment, the principal investigator practiced by filing and obturating 15 teeth (not included in this study) divided equally among the three techniques. Anterior/posterior (AP) and lateral baseline standardized radiographs were exposed for each tooth. The canal length was determined only from the AP radiograph. Access to the pulp was obtained with #2 and #3 high-speed carbide burs; a barbed broach was used to remove it. The working length of the canal was established 1 mm short of the radiographic apex. Biomechanical preparation of root canals was initiated with a number 10 H-file and finished with number 60. The canal then was irrigated and dried.