The Effect of the Ultrasonic Irrigant Activation Protocol on the Removal of a Dual-species Biofilm from Artificial Lateral Canals.

INTRODUCTION: Lateral canals are particularly challenging to clean and disinfect. The aim of this study was to compare the removal efficacy of a dual-species biofilm from a lateral canal model by different ultrasonic irrigant activation protocols in vitro. METHODS: Artificial root canal models with 270 simulated lateral canals were made of polydimethylsiloxane. A dual-species biofilm (Streptococcus oralis and Actinomyces naeslundi) was grown in vitro in the lateral canals using a constant depth film fermenter. Two percent NaOCl or demineralized water was delivered by a syringe and an open-ended needle for 30 seconds and subsequently activated by an ultrasonic file for a total activation time of 30, 60, or 90 seconds divided in 1 or 3 consecutive activation cycles. In the control groups, the irrigant was allowed to rest for 30, 60, or 90 seconds. The volume of the biofilm in the lateral canal was evaluated before and after the final irrigation protocol by optical coherence tomography. The results were analyzed by 3-way factorial analysis of variance (α = 0.05). RESULTS: Irrigation with NaOCl rather than demineralized water resulted in more effective biofilm removal from the lateral canal (P < .001). Three cycles of intermittent ultrasonic activation were significantly more effective than no activation (P = .029). The total irrigant contact time did not affect biofilm removal (P = .403). CONCLUSIONS: The type of the irrigant and the ultrasonic activation protocol affected biofilm removal from artificial lateral canals. None of the compared protocols was able to eradicate the biofilm.

Ultrasonic Irrigant Activation during Root Canal Treatment: A Systematic Review.

INTRODUCTION: The aim of this study was to systematically review the evidence on the cleaning and disinfection of root canals and the healing of apical periodontitis when ultrasonic irrigant activation is applied during primary root canal treatment of mature permanent teeth compared with syringe irrigation. METHODS: An electronic search was conducted of the Cochrane Library, Embase, LILACS, PubMed, SciELO, and Scopus databases using both free-text key words and controlled vocabulary. Additional studies were sought through hand searching of endodontic journals and textbooks. The retrieved studies were screened by 2 reviewers according to predefined criteria. The included studies were critically appraised, and the extracted data were arranged in tables. RESULTS: The electronic and hand search retrieved 1966 titles. Three clinical studies and 45 in vitro studies were included in this review. Ultrasonic activation did not improve the healing rate of apical periodontitis compared with syringe irrigation after primary root canal treatment of teeth with a single root canal. Conflicting results were reported by the in vitro microbiological studies. Ultrasonic activation was more effective than syringe irrigation in the removal of pulp tissue remnants and hard tissue debris based on both clinical and in vitro studies. Ultrasonic activation groups were possibly favored in 13 studies, whereas syringe irrigation groups may have been favored in 3 studies. CONCLUSIONS: The level of the available evidence was low, so no strong clinical recommendations could be formulated. Future studies should focus on the antimicrobial effect and healing of apical periodontitis in teeth with multiple root canals.

Uncontrolled Removal of Dentin during In Vitro Ultrasonic Irrigant Activation in Curved Root Canals.

INTRODUCTION: The aim of this study was to examine the effect of file type and activation time on the uncontrolled removal of dentin during in vitro ultrasonic irrigant activation in prepared curved root canals. METHODS: Seventy-two curved mesial root canals of human mandibular molars were prepared to size 35/.04 taper. The specimens were randomly allocated to 4 groups (n = 18). Two milliliters of 2% sodium hypochlorite were delivered 3 times to each root canal, and the irrigant was ultrasonically activated every time for 10 seconds at 35% power either by a ultrasonic K-file (group A), an Irrisafe file (Acteon Satelec, Merignac, France) (group B), or a smooth wire (group C). The same specimens also received further activation continuously for another 30 seconds. No activation took place in group D. Specimens were scanned by micro-computed tomographic imaging before and after preparation and after the first and second activation period. Scans were coregistered and segmented, and the amount of dentin removed during activation was quantified by morphological operations. Results were analyzed by nonparametric statistical tests (α = 0.05). RESULTS: Defects with a maximum depth of 0.18 mm were identified. Both the type of file and activation time affected the removal of dentin (P ≤ .002 and P ≤ .031, respectively). K-files removed more dentin than Irrisafe files and smooth wires in the coronal and middle third. All files removed comparable amounts in the apical third. CONCLUSIONS: All 3 types of files may result in uncontrolled removal of dentin. A longer activation time may increase this effect.