Potential of Trichloroacetic Acid in Smear Layer and Calcium Hydroxide Removal in Root Canals–Exploratory Pilot Studies In Vitro

Introduction and aims This study investigated whether trichloroacetic acid (TCA) can function as an adjuvant solution to facilitate pulp dissolution and removal of smear layer and calcium hydroxide (Ca(OH) 2 ) during endodontic procedures. Methods For pulp dissolution studies, fresh pulp was weighed before and after immersion in 90% TCA and/or 6% NaOCl. For smear layer or Ca(OH) 2 removal, each study utilized 25 extracted human teeth with prepared root canal systems. For Ca(OH) 2 removal, canals were filled with Ca(OH) 2 and stored at 37 °C for 14 days. Teeth were divided into five groups (n=5/group) and the canal irrigated with various solutions. Group I: saline; Group II: 17% EDTA; Group III-V: 90% TCA for 15, 30 or 60 seconds, respectively. Samples were subjected to scanning electron microscopy (SEM) or spectrum analysis. Results Under our experimental conditions, NaOCl alone consistently dissolved more pulp than TCA at all time points (1, 3, and 5 minutes) under static conditions at RT ( P < .01 or < .001). Some TCA groups had significantly less smear layer than the saline or EDTA group in the coronal and middle thirds ( P < .05 to < .001). In the apical third, there was significantly less smear layer in the TCA 15-second group than the control or EDTA group ( P < .01 or P < .001). In Ca(OH) 2 removal studies, the coronal third showed that TCA 30-second group and middle third TCA 60-second group had significantly less Ca(OH) 2 than the EDTA group ( P < .05). Conclusion These findings warrant further studies with a larger sample size to validate the potential use of TCA as an adjunctive agent to facilitate smear layer and Ca(OH)₂ removal from root canal walls, Clinical relevance This is the first study to evaluate whether TCA can be used as an adjunctive endodontic irrigant. Our findings suggest that a brief treatment with TCA is more effective than EDTA for canal smear layer removal and may facilitate Ca(OH) 2 removal.