Primary root canals(n=20) were instrumented using rotary P1 Kedo-S Square files (Reeganz Dental Care Pvt. Ltd. India) at 300 rpm and 2.2N cm torque. The rotary files were used with an Endo-Mate DT endodontic motor (NSK, Tokyo, Japan) and EDTA gel 17% (Meta Biomed Co. Ltd, Chungbuk, Korea) was used before instrumentation.

Primary root canals(n=20) were instrumented using Fanta AFTM-Baby rotary system (Shanghai Fanta Dental Materials, SUNGO Certification Company Limited, London, England) at 350 rpm and 2 N cm torque. Four files were used sequentially in the following order; open file #17/0.08, #20/0.04 yellow, #25/0.04 red and #30/0.04 blue. The rotary files were used with an Endo-Mate DT endodontic motor (NSK, Tokyo, Japan) and EDTA gel 17% (Meta Biomed Co. Ltd, Chungbuk, Korea) was used before instrumentation.

Primary root canals(n=20) were instrumented using No.15 till 35 size manual K-files (Mani, Inc, Japan) using the quarter-turn-pull technique.

single visit pulpectomy was performed under strict aseptic conditions by a single operator. Peri-operative evaluation was done using intraoral digital senso. The teeth were anesthetized with 2% mepivacaine with 1:20,000 levonordefrin & isolated using rubber dam. caries was removed using no. 330 round carbide burs in high-speed contra angle headpiece. Access opening was gained & the roof of the pulp chamber was removed. Working length was determined by apex locator, then confirmed by periapical radiograph. Working length will be determined 1 mm shorter than apex. mechanical preparation was done using the tested files according to each group. Then, canals were irrigated with 1% sodium hypochlorite between each file followed by irrigation with normal saline. The root canals were dried using paper points & root canals were filled with Metapex. Intermediate restorative material was placed, and the tooth was restored with a preformed stainless-steel crown in the same appointment.

by evaluation of the obturation quality using immediate post-operative CBCT which is assessed by two trained pediatric dentists, blinded to instrumentation technique .

The quality of obturation was assessed by evaluating the length of the Metapex filling according to Coll and Sadrian criteria :

• Under filling (Score 1): Canal filled with metapex more than 2 mm short of the apex.
• Optimal filling (Score 2): Canal filling ending at the radiographic apex or up to 2 mm short of apex.
• Overfilling (Score 3): Any canal showing filling outside the root apex.

using four-point pain intensity scale. This scale categorizes pain as follows: (1) no pain; (2) slight pain; (3) moderate pain; and (4) severe pain.

The parents of the children were given a questionnaire to record the intensity of postoperative pain at six, twelve, twenty-four and forty-eight hours after the pulpectomy procedure.

A nursing officer who was blind to the study groups, had trained all parents on how to record the postoperative pain.

To ensure standardization, the same parent was asked to record the child's pain intensity at all time intervals.

To reduce the possibility of the parents failing to record the pain at a given time, the investigator also recorded findings via telephonic conversation with the parents.