Effect of Apical Third Enlargement to Different Taper and Master Apical Preparation Size on Periapical Healing and Postoperative Pain After Primary Single Sitting Non Surgical Root Canal Treatment

The primary goal of endodontic therapy is to eradicate microbial infection within the root canal system and prevent reinfection. Thorough debridement and disinfection of the apical third are crucial, as this region serves as a reservoir for residual microorganisms.

Till date, only four clinical trials have analysed the effect of apical canal preparation size on treatment outcomes. Out of the four clinical trials one retrospective in nature, Hoskinson study no improvement in radiographic and clinical outcome with an increase in the master apical file .

Souza (2012) conducted clinical trial in necrotic pulp and concluded that apical third enlargement does not alter endodontic treatment outcomes.

Saini (2012) stated that enlarging the canal three sizes beyond the first apical binding file is sufficient.

Fatima (2021) found that preparing the apical region in two sizes larger the initial apical binding file (IABF) with a 4% taper is inadequate, leading to significantly lower success rates compared to larger preparation sizes and greater tapers .

In both studies( Fatima and saini ) determination of apical enlargement size was based on the IABF (initial apical binding file). There was no mention of master apical size in different groups. Also the taper of apical one third was different in both these studies.Both master apical size and preparation taper can influence root canal shaping in apical third Various in-vitro studies suggest that increasing the taper has no significant effect on bacterial reduction.

According to Plotino(2014) the difference in the taper of the instruments did not result in different levels of disinfection in the apical region. They observed that amount of infected residual dentin \& the smear layer in the apical third of root canals were not significantly affected by preparations with 0.04 or 0.06 tapers when the apical diameter remained the same. Other studies examining bacterial reduction and different tapers agree with these results (Alimadadi, 2021; Usta 2023).

There is no impact on bacteria reduction when using different tapers with the same apical size #25 in the preparation of the mesial root canals of mandibular molars. ( Macedo, 2024) while clinical study by Fatima suggests that increasing the taper promotes better periapical healing. In Fatima study, a significantly high success rate was observed with apical preparation 2 sizes larger than the IABF and a 6% taper compared with the same preparation size with a 4%taper (92.8% vs 57.1%.).Till date there is no clinical study that combined the effect of different master apical file size and different taper on outcome of primary nonsurgical root canal treatment. Therefore, the present study was designed as a randomized clinical trial to examine the effect of apical third enlargement to different taper and master apical preparation size on periapical healing and postoperative pain after primary single sitting non surgical root canal treatment

Primary objective :

To evaluate and compare the radiographic outcome of periapical healing after primary non surgical single sitting root canal with different tapers and different master apical file size

Secondary objective :

To assess the post operative pain using VAS scale, postoperatively every 24 hours for 1 week after primary nonsurgical single sitting root canal treatment.

• post operative pain [Time frame: Baseline and at 24 hours, Day 2, Day 3, Day 4, Day 5, Day 6 and Day 7 after the treatment]