Assessment of Apical Extrusion during Root Canal Irrigation with the Novel GentleWave System in a Simulated Apical Environment.

INTRODUCTION: This study assessed apical extrusion during treatment with GentleWave (GW; Sonendo Inc, Laguna Hills, CA), a conventional open-ended 30-G needle (CN), or Endovac (EV; SybronEndo, Orange, CA) in root canals enlarged to different dimensions with and without apical constriction. METHODS: Sixteen mandibular molars were mounted in an in vitro apparatus. Roots were immersed in a pressure-regulated chamber containing distilled water with pressure kept at 5.88 ± 0.15 mm Hg to simulate periapical back pressure. Mesiobuccal (curved ≤30°) and distal (straight) canals were instrumented to the working length (WL) as follows: minimal instrumentation (MI, #15/.04), traditional instrumentation (#35/.06), or overinstrumentation (OI, #35/.06, to the WL + 1 mm). Canals were tested 5 times each with distilled water using GW, CN (at WL-3 mm), or EV and the mass (g) of extruded water recorded. Extrusion frequency and mean extruded mass were compared for each canal, irrigation group, and canal instrumentation mode (Wilcoxon t test, P < .05). RESULTS: No extrusion occurred with GW and EV, whereas the frequency of extrusion with CN was 33%. Mean extruded water mass using CN ranged in mesial canals from 0.000 ± 0.000 g (OI) to 0.047 ± 0.098 g (MI) and in distal canals from 0.123 ± 0.191 g (MI) to 0.505 ± 0.490 g (OI). With traditional instrumentation and OI instrumentation, extruded mass in distal canals was significantly higher than in mesial canals (P < .002) and distal canals with MI (P < .020). CONCLUSIONS: Within this study's limitations, root canal treatment with GW and irrigation with EV was not associated with extrusion. Extruded irrigation mass using the open-ended 30-G needle depended on the canal type and enlargement. These results have to be interpreted with caution, and further investigations are warranted to evaluate the possibility of extrusion using GW in different tooth types and clinical situations.

Evaluation of Root Canal Debridement of Human Molars Using the GentleWave System.

INTRODUCTION: Studies using conventional endodontic protocols show insufficient cleaning of root canal systems, often resulting in persistent infection and treatment failure. The GentleWave System (GWS; Sonendo, Inc, Laguna Hills, CA) has been shown to result in a higher tissue dissolution rate in a study using bovine muscle. The purpose of this study was to compare the debridement efficacy of the GWS with a traditional method for cleaning root canals. METHODS: Forty-five freshly extracted molars were randomly separated into 3 treatment groups (n = 15/group): group 1, no treatment; group 2, conventional rotary instrumentation and needle irrigation; and group 3, minimal instrumentation and the GWS treatment. Roots were prepared per standard histologic tissue processing after hematoxylin-eosin staining; sections were microscopically examined, and the percentage of soft tissue and debris remaining within the canals was morphometrically calculated. Images of the apical and middle regions of the roots were blindly analyzed. RESULTS: Significant differences (Welch's t test) were found between groups 2 and 3 in both apical (P = .0015) and middle (P = .0179) regions of the mesial roots of mandibular molars and mesiobuccal roots of maxillary molars. Groups 2 and 3 resulted in cleaning 67.8% and 97.2% of the mesiobuccal and mesiolingual root canals of mandibular molars and the mesiobuccal canals of maxillary molars, respectively, whereas the results were similar among groups 2 and 3 in the apical and middle regions of distal roots. Groups 2 and 3 revealed significantly less debris than group 1 (P < .005). CONCLUSIONS: The GWS showed a significantly greater cleaning capacity and reduction in residual debris within the mesiobuccal and mesiolingual canals of mandibular molars and the mesiobuccal canals of maxillary molars than those cleaned conventionally.

In vitro study of calcium hydroxide removal from mandibular molar root canals.

INTRODUCTION: Previous studies have shown the difficulty in removing calcium hydroxide (Ca[OH]2) paste from the root canals before root filling. METHODS: Mesial and distal canals of 30 mandibular molars were prepared with the WaveOne Primary (25/.08) and Large file (40/.08) (Dentsply Tulsa Dental Specialties, Tulsa, OK), respectively. All canals were then filled with Ca(OH)2. The teeth were divided into the following 3 treatment groups (each with n = 10): (1) instrumentation with needle irrigation, (2) instrumentation with irrigation and passive ultrasonic activation (PUI), and (3) the GentleWave system (Sonendo, Inc, Laguna Hills, CA) without instrumentation. The irrigation time in each group was 7.5 minutes. To further test the efficiency of the GentleWave system, shorter times of 90 seconds were tested using water alone. Reconstructed micro-computed tomographic scans were used to measure the volume of the canals and Ca(OH)2 after instrumentation, initial filling of Ca(OH)2, and after its removal. The percentage of Ca(OH)2 remaining in the canals was calculated. RESULTS: None of the 10 teeth (30 canals) in the conventional irrigation and PUI groups were completely cleaned of Ca(OH)2 in 7.5 minutes. In the apical third of mesial and distal canals, respectively, conventional irrigation removed 47.82% ± 16.36% and 77.68% ± 12.82%, PUI removed 61.66% ± 25.54% and 88.85 ± 12.06%, and the GentleWave system removed significantly more Ca(OH)2 (P < .05) with 100% and 98.78% ± 3.84%. Additional experiments in 10 teeth, using only water as the irrigant, revealed that the GentleWave system removed 99.85% and 99.97% of Ca(OH)2 within 90 seconds without the use of any instruments in the mesial and distal canals, respectively. CONCLUSIONS: The study confirms the difficulty to remove Ca(OH)2 from root canals using conventional methods. The GentleWave system removed the paste within 90 seconds using water irrigation alone.

Tissue dissolution by a novel multisonic ultracleaning system and sodium hypochlorite.

INTRODUCTION: This study aimed to evaluate the effectiveness of a novel Multisonic Ultracleaning System (Sonendo Inc, Laguna Hills, CA) in tissue dissolution in comparison with conventional irrigation devices. METHODS: Pieces of bovine muscle tissue (68 ± 2 mg) were placed in 0.7-mL test tubes (height: 23.60 mm, inner diameter: 6.00 mm, outer diameter: 7.75 mm) and exposed to 5 minutes of irrigation by different devices. Endodontic devices included the Multisonic Ultracleaning System, the Piezon Master 700 (EMS, Dallas, TX) ultrasonic system with agitation, the EndoVac negative-pressure irrigation system (SybronEndo, Orange, CA), and a conventional positive-pressure 27-G irrigation needle at a flow rate of 10 mL/min. The systems were tested with 0.5%, 3%, and 6% sodium hypochlorite (NaOCl) at room temperature (21°C) as well as 40°C. Irrigation with sterile water was used as a control. The mass of tissue specimens was measured and recorded before and after the use of each device, and if the specimen was completely dissolved visually within 5 minutes, the dissolution time was recorded. The rate of tissue dissolution (%/s) was then calculated. RESULTS: The Multisonic Ultracleaning System had the fastest rate of tissue dissolution (P < .05), at 1.0% ± 0.1% per second using 0.5% NaOCl, 2.3% ± 0.9% per second using 3% NaOCl, and 2.9% ± 0.7% per second using 6% NaOCl. This tissue dissolution rate was more than 8 times greater than the second fastest device tested (P < .01), the Piezon Master 700 ultrasonic system, which resulted in a tissue dissolution rate of 0.328% ± 0.002% per second using 6% NaOCl at 40°C. For all irrigation devices tested, the rate of tissue dissolution increased with a higher concentration and temperature of the NaOCl solution. CONCLUSIONS: The novel Multisonic Ultracleaning System achieved a significantly faster tissue dissolution rate when compared with the other systems examined in vitro.

Apical pressure and extent of irrigant flow beyond the needle tip during positive-pressure irrigation in an in vitro root canal model.

INTRODUCTION: This study aimed to measure the pressure generated during positive-pressure irrigation at the periapex of an in vitro tooth model using a novel method of measurement, investigating the effect of flow rate and needle design. Apical pressure was correlated with the extent of dye clearance from the end of a needle tip in a plastic root canal model with similar dimensions. METHODS: The mesiobuccal canal of a mandibular molar was instrumented to #35/06 and placed into a chamber coupled to a pressure transducer. Irrigation was performed using a digital peristaltic pump using flow rates from 1-15 mL/min with irrigation needles of different sizes and designs. A plastic root canal model instrumented to the same size filled with dye was used to measure the extent of dye clearance beyond the needle tip using the same irrigation conditions. RESULTS: Positive-pressure irrigation revealed a flow rate-dependent increase in apical pressure (P < .05). The apical pressure at high irrigation flow rates was several times higher than at low flow rates. Needle designs with safety features yielded statistically significant lower apical pressures than needles without safety features (P < .05). There was no further increase in dye clearance from the end of the needle tip in a plastic root canal model at flow rates higher than 4 mL/min. CONCLUSIONS: If apical clearance of dye beyond the needle tip is a measure of irrigation effectiveness, then maximum effectiveness with safe apical pressures can be gained at specific flow rates using specific needle tip designs. The use of an irrigation flow rate of 4 mL/min was able to achieve maximum effectiveness in this study.