Rotary Systems Versus Manual K-File System in Primary Molar Root Canals-In Vitro Study

Aim: To evaluate and compare the cleaning ability between two, rotary shaper and manual K-files in primary molar root canals. Materials and Methods: Twenty extracted maxillary and mandibular primary molars and 10 mm length were cleaned in water and stored in 0.5% sodium hypochlorite for 1 week. Caries excavation was done. Coronal access was made. After irrigation of the root canal with normal saline, a K-file with a compatible diameter was introduced into the root canal and the canal length was determined. A K-file size #15 was introduced into the root canal and 1 ml Indian ink was injected into the orifice. The roots were then randomly divided into 2 groups. Results: Group-A (K-File) was compared at Coronal, Middle and Apical thirds using Pearson’s Chi-Square test. Results showed that Group-A (K-File) performed better at the apical thirds, reporting complete removal in 83.3% of cases followed by coronal third and the least percentage of complete removal was displayed in the middle third with only 43.3% of cases reporting complete removal. Group-B (rotary) was compared at Coronal, Middle and Apical thirds using Pearson’s Chi-Square test. Results showed that Group-B (rotary) performed better at the Coronal and middle thirds, reporting complete removal in 76.7% of cases and the least percentage of complete removal was displayed in the apical third with only 23.3% of cases reporting complete removal. Group A showed a better performance by exhibiting complete removal in 83% of the cases, while remaining comparison showed a better result with nearly 76.7% of the cases reporting complete removal, and remainder cases reporting 50% and more or lesser ink removal. Conclusion: Rotary files can be an acceptable alternative in primary teeth root canal preparation, as instrumentation time is reduced, and the prepared root canal is more conical which favors better obturation. Clinically, reduced instrumentation time would significantly improve patient cooperation and lessen fatigue of the operator.

procedural errors such as ledges, over-instrumentation and apical transportation are greatly reduced as well with reduced operating time. Rotary instrumentation characteristics have become significantly relevant when dealing with endodontic preparation of primary teeth, since appointment length is a crucial factor for pediatric patient compliance and maintaining the original path of the root canal is essential to ensure the integrity of the germ of the permanent successor. Rotary files also improve patient cooperation by shortening treatment time for cleaning canals. The study is designed to evaluate and compare the cleaning ability between rotary instruments and conventional manual K-files instruments in the preparation of primary molar root canals.

Type of Study and Source of Data
The present in vitro study was conducted in the Department of Pediatric dentistry, Turaif National Dispensary, Turaif, KSA. Twenty extracted primary maxillary and mandibular molars with at least two-thirds root remaining were collected and stored in formalin.

Methodology
Twenty extracted maxillary and mandibular primary molars with at least two thirds of intact root, and 10 mm length were cleaned in water and stored in 0.5% sodium hypochlorite for 1 week. Caries excavation was done. Coronal access was made.
After irrigation of the root canal with normal saline, a K-file with a compatible diameter was introduced into the root canal and the canal length was determined at 1 mm from the apex or root bevel.
A K-file size #15 was introduced into the root canal and 1-2 mL Indian ink was injected into the orifice until the ink leaked from apical foramen. The teeth were cleared for cleaning efficacy analysis i.e. the teeth were placed separately in jars with a lid, containing 5% formic acid and 5% nitric acid for 3 days. The acid was renewed every 24 hours until the teeth were completely decalcified. The teeth were washed under running water for 8 hours and dehydrated in 70% alcohol (for 16 hours, changed every hour), 90% alcohol (for 3 hours, changed every hour) and 96% alcohol (for 3 hours, changed every hour). After dehydration, the teeth were placed in methyl salicylate.
At first the canals were separated from CEJ and were cut at 1 mm above the working length (2 mm upper than apex or root bevel) with Diamond disc, so that the apical section could be observed.
Then the roots were cut from the mid part of the remaining canal (middle section). After clearing, each section was placed on a 1.5×2 inch red wax for easy observation. The removal of Indian ink from the cervical, middle, and apical thirds was analyzed with a stereoscopic with ×40 of magnification and four-grade scoring system was used for grading the cleaning efficacy of the root canal system (RCS).

Statistical Analysis
The data obtained was subjected to Pearson's Chi-Square test depending on the normality of data and p-value (<0.05) was considered statistically significant.

Discussion
Endodontic treatment has evolved and got revolutionized over In primary teeth, the physiologic root resorption begins soon after root completion creating difficulty in accurate working length determination [9]. The effects of instrumentation, medication, and filling materials on the succedaneum's teeth are uncertain which dissuade some clinicians from performing pulpectomy. Also, potential behavioral problems add to the dentist's reluctance to perform pulpectomy in young children. Since most of the primary molar root canals are presented with a myriad of anatomic variations due to physiologic deposition of dentine islands, the impact of these design modifications on root canal preparation on primary teeth is little known. The ink penetration and clearing technique is useful for studying the cleaning ability of the instrumentation and the morphology of human teeth as it makes the teeth transparent so that the pulp cavity and root canal walls can be diagnosed14. In our study we used India ink injection method for an analysis of the cleaning efficacy and the teeth were cleaned as reported by Silva et al. [10]. Results of present study are in accordance with [11], where it was observed that of the three groups namely manual instruments (K-files) and two rotary systems (Mtwo and Pro Taper), cleaning capacity was better in the coronal and middle thirds of the canal than in the apical third. In a study done by [12] compared cleaning

efficacy of manual instrumentation and two rotary systems namely
Mtwo and Wave.

One in the preparation of primary molar root canals, Mtwo and
Wave One systems showed significant difference in cleaning ability in the coronal and middle third of the primary molar root canal as compared to manual instrumentation (K file). In the apical third of the root canal, K file performed better than other file systems, but the difference was not found to be statistically significant. Whereas in the present study it was seen that k files performed better at apical third, while Hero shaper performed better than k-file and Mtwo in coronal and middle third which is statistically significant.

Conclusion
Rotary files can be an acceptable alternative in primary teeth root canal preparation, as instrumentation time is reduced, and the prepared root canal is more conical which favors better obturation.
Clinically, reduced instrumentation time would significantly improve patient cooperation and lessen fatigue of the operator.