A review of instrumentation kinematics of engine-driven nickel-titanium instruments.

Over the years, NiTi alloys have become indispensable materials in endodontic treatment. With technological advancements in metallurgy, manufacturers have attempted to produce instruments with enhanced features. In parallel with these developments, endodontic motors have undergone improvements in terms of torque control and kinematics that are adjustable in different directions. This review presents an overview of the advancements in instrumentation kinematics and the effect of instrumentation kinematics on root canal shaping procedures and instrument performance. The literature search for this narrative review was conducted in Google Scholar, Scopus, PubMed and Web of Science using the keywords 'kinematics and endodontics' and 'reciprocation and endodontics'. In addition, historical literature was searched using the keyword 'nickel-titanium and endodontics'. Overall, 143 articles were included up to 2015.

Comparison of apically extruded debris after root canal instrumentation using Reciproc(®) instruments with various kinematics.

AIM: To assess the amount of apically extruded debris using Reciproc(®) instruments with different kinematics (150° counter clockwise [CCW]-30° clockwise [CW], 270° CCW-30° CW, 360° CCW-30° CW and continuous rotation). METHODOLOGY: Forty-eight maxillary central incisors were selected and assigned to four root canal shaping groups as follows (n = 12): 150° CCW-30° CW, 270° CCW-30° CW, 360° CCW-30° CW and continuous rotation. Reciproc R25 and R50(®) instruments were used in all groups. Apically extruded debris was collected and dried in preweighed Eppendorf tubes. The weight of extruded debris was assessed with an electronic balance. The data were analysed with one way analysis of variance and LSD post hoc tests (P = 0.05). RESULTS: The 150° CCW-30° CW and 270° CCW-30° CW reciprocating motions extruded significantly less debris than continuous rotation (P < 0.05). However, no significant differences were found between the 360° CCW and 30° CW reciprocating motion and the continuous rotation (P > 0.05). CONCLUSIONS: All instrument movements were associated with apically extruded debris. However, the 150° CCW-30° CW and 270° CCW-30° CW reciprocating motions were associated with less extrusion than continuous rotation.

Effect of movement kinematics on the cyclic fatigue resistance of nickel-titanium instruments.

AIM: To compare the cyclic fatigue resistance of new generation OneShape and WaveOne instruments when used with different kinematics. METHODOLOGY: An artificial canal, made of stainless steel with an inner diameter of 1.5 mm, a 60° angle of curvature and a curvature radius of 3 mm, was used for cyclic fatigue test of new generation OneShape and WaveOne instruments. Groups were as follows (n = 20): 150°-30°, 210°-30°, 360°-30° and continuous rotation. The time to fracture was recorded in seconds, and the data were analysed statistically using a two-way anova and LSD tests (P = 0.05). RESULTS: Cyclic fatigue resistance was significantly affected by the movement kinematics (P < 0.001). The cyclic fatigue resistance of the new generation OneShape instruments increased significantly when operated in various reciprocation motions (150° CW-30° CCW, 210° CW-30° CCW and 360° CW-30° CCW) compared with the continuous rotation mode. New generation OneShape instruments had significantly more resistance to fracture under cyclic loading than WaveOne instruments (P < 0.001). CONCLUSIONS: When using new generation OneShape and WaveOne instruments, all the reciprocating motions (150° CW-30° CCW, 210° CW-30° CCW and 360° CW-30° CCW) resulted in extended fatigue life when compared with continuous rotation.

Effectiveness of laser-assisted irrigation and passive ultrasonic irrigation techniques on smear layer removal in middle and apical thirds.

The purpose of this study was to investigate the evaluation of laser-assisted irrigation (LAI) on the removal of the smear layer as compared to passive ultrasonic irrigation (PUI). Forty-eight single-rooted, upper-central incisor teeth were selected and prepared with ProTaper rotary instruments up to size #40 (F4) at the working lengths. Specimens were divided into four groups, as follows: (a) PUI with 5 mL of 2.5% NaOCl for 60 s; (b) PUI with 2.5 mL of 17% EDTA and 2.5 mL of 2.5% NaOCl each for 30 s; (c) LAI with 5 mL of 2.5% NaOCl for 60 s; and (d) LAI with 2.5 mL of 17% EDTA and 2.5 mL of 2.5% NaOCl each for 30 s. In the PUI groups, the ultrasonically activated file was inserted 1 mm short of the working length, but in the LAI groups, the fiber tip was applied into the pulp chamber. LAI in the pulp chamber with the combination of 17% EDTA and 2.5% NaOCl removed more of the smear layer than the other groups (p < 0.018). LAI in the pulp chamber with the combination of 2.5% NaOCl and 17% EDTA better removed the smear layer than LAI applied similarly but without EDTA or PUI with the same NaOCl and EDTA combinations using an ultrasonically activated file inserted 1 mm short of the working length.

Quantitative evaluation of apically extruded debris with Twisted File Adaptive instruments in straight root canals: reciprocation with different angles, adaptive motion and continuous rotation.

AIM: To evaluate the influence of movement kinematics when using Twisted File Adaptive instruments (SybronEndo, Orange, CA, USA) (TF Adaptive) on the amount of apically extruded debris. METHODOLOGY: Forty-eight extracted mandibular incisor teeth were selected. The teeth were randomly divided into four groups (n ꞊ 12), and the root canals were instrumented using the following movement kinematics: TF Adaptive motion, 90° clockwise (CW) to 30° counterclockwise (CCW) reciprocating motion, 150°CW to 30°CCW reciprocating motion or continuous rotation. TF Adaptive instruments were used for all groups. Debris extruded apically during instrumentation was collected in pre-weighed Eppendorf tubes, and after drying, the mean weight of the debris was assessed with an electronic balance. The data were analysed statistically using a one-way analysis of variance. RESULTS: The 90° CW to 30° CCW reciprocating motion produced the highest mean extrusion value, and this was significantly greater when compared with continuous rotation (P < 0.05). 150° CW to 30° CCW reciprocating, adaptive and continuous rotation motions produced similar amounts of debris extrusion (P > 0.05). CONCLUSION: Movement kinematics affected the amount of apically extruded debris when using Twisted File Adaptive instruments.

Effectiveness of ProTaper Universal retreatment instruments used with rotary or reciprocating adaptive motion in the removal of root canal filling material.

AIM: To compare the effectiveness of ProTaper Universal retreatment instruments with continuous rotation and adaptive motion (AM; a modified reciprocating motion that combines rotational and reciprocating motion) in the removal of filling material. METHODOLOGY: Mesiobuccal root canals in 36 mandibular first molars were instrumented up to size F2 with the ProTaper Universal instrument (Dentsply Maillefer, Ballaigues, Switzerland) and filled using sealer and ProTaper Universal F2 gutta-percha cones. Gutta-percha was then down-packed and the root canal backfilled using the extruder hand-piece of the Elements Obturation System (SybronEndo, Orange, CA, USA). The teeth were assigned to two groups (n = 18), and removal of the root fillings was performed using one of the following techniques: group 1) ProTaper Universal retreatment files used with rotational motion (RM) and group 2) ProTaper Universal retreatment files used with adaptive motion (AM) (600° clockwise/0° counter-clockwise to 370° clockwise/50° counter-clockwise). The teeth were sectioned, and both halves were analysed at 8 × magnification. The percentage of remaining filling material was recorded. The data were analysed statistically using the Student's t-test at a 95% confidence level (P < 0.05). RESULTS: There was no significant difference between the groups with respect to the total time required for retreatment (P = 0.481). The AM technique left significantly less filling material than the RM method (P = 0.013). CONCLUSION: The use of ProTaper Universal retreatment files with adaptive motion removed more filling materials from root canals than the rotational movement.

An in vitro comparison of irrigation using photon-initiated photoacoustic streaming, ultrasonic, sonic and needle techniques in removing calcium hydroxide.

AIM: To evaluate the effect of various techniques including photon-initiated photoacoustic streaming (PIPS), ultrasonic, sonic and needle irrigation on the removal of calcium hydroxide [Ca(OH)2 ] from artificial grooves created in root canals. METHODS: The root canals of 48 extracted single-rooted teeth with straight canals were prepared using ProTaper rotary instruments up to size 40. After the specimens had been split longitudinally, a standardized groove was prepared in the apical part of one segment that was filled with Ca(OH)2 powder mixed with distilled water. Each tooth was reassembled and the apices closed with wax. The specimens were irrigated for 60 s with one of the following techniques: needle irrigation using 17% EDTA, PIPS with 17% EDTA, ultrasonic irrigation using 17% EDTA and sonic irrigation (EndoActivator) using 17% EDTA. The root segments were then disassembled, and the amount of remaining Ca(OH)2 evaluated under a stereomicroscope at 25× magnification. A pixel count of Ca(OH)2 remaining on the artificially created grooves was recorded as a percentage of the overall groove surface. The data were evaluated statistically using one-way analysis of variance and the least significant difference post hoc tests at 95% confidence level (P = 0.05). RESULTS: Photon-initiated photoacoustic streaming was superior in removing Ca(OH)2 as compared to needle irrigation (P < 0.001), sonic irrigation (P < 0.001) and ultrasonic irrigation (P = 0.046). CONCLUSION: Photon-initiated photoacoustic streaming provided complete removal of Ca(OH)2 from artificial grooves in straight root canals. Ultrasonic irrigation enhanced the Ca(OH)2 removal capacity of irrigating solution but did not provide complete removal from artificial grooves.

Effect of photon-initiated photoacoustic streaming on removal of apically placed dentinal debris.

AIM: To compare the efficacy of photon-induced photoacoustic streaming (PIPS) technique with conventional, sonic and ultrasonic irrigation on the removal of apically placed dentinal debris from an artificial groove created in a root canal. METHODOLOGY: Root canal preparation was performed up to size 40 on 48 extracted single-rooted teeth using ProTaper rotary instruments. The specimens were then split longitudinally, and a standardized groove was prepared in the apical part of each segment. Each groove was filled with dentinal debris mixed with 5% NaOCl. Each tooth was reassembled and irrigated as follows: (i) conventional irrigation with 1% NaOCl, (ii) sonic, (iii) ultrasonic irrigation, and (iv) PIPS. The root segments were disassembled, and the amount of remaining dentinal debris was evaluated under a stereomicroscope at 20× magnification, using a four-grade scoring system. The data were evaluated statistically using Kruskal-Wallis and Mann-Whitney U-tests with a 95% confidence level (P = 0.05). RESULTS: Photon-induced photoacoustic streaming removed significantly more dentinal debris than conventional irrigation (P < 0.001), sonic irrigation (P < 0.001) or ultrasonic irrigation (P = 0.005). There was no significant difference between sonic and ultrasonic irrigation (P = 0.377). CONCLUSIONS: Photon-induced photoacoustic streaming was more effective than conventional, sonic and ultrasonic irrigation in the removal of apically placed dentinal debris.

Efficacy of various irrigation protocols on the removal of triple antibiotic paste.

AIM: To compare the efficacy of irrigation protocols on the removal of triple antibiotic paste (metronidazole, ciprofloxacin and minocycline) (TAP) from artificial grooves in root canals. METHODOLOGY: Root canals in 72 extracted single-rooted teeth were prepared using ProTaper rotary instruments up to size F5. The roots were split longitudinally and a standardized groove was prepared in the apical part of one segment. TAP was placed in the grooves, and the root halves were reassembled. The roots were randomly divided into six experimental groups according to the irrigation protocol used: distilled water, 1% NaOCl, 2.5% NaOCl, 100% ethanol, 17% EDTA and passive ultrasonic irrigation (PUI) with 1% NaOCl. The root segments were disassembled, and the amount of TAP remaining was evaluated under a stereomicroscope at 20× magnification using a four-grade scoring system. The data were evaluated statistically using Kruskal-Wallis and Mann-Whitney U-tests with a 95% confidence level (P = 0.05). RESULTS: There were significant differences amongst the groups (P < 0.001). Passive ultrasonic irrigation (PUI) with 1% NaOCl removed significantly more TAP than the other irrigating solutions (P < 0.05). Distilled water, 1% NaOCl, ethanol and EDTA were associated with significantly more remaining TAP. CONCLUSIONS: PUI with 1% NaOCl was more effective in removing TAP from artificial grooves in root canals than other irrigating solutions without ultrasonic agitation. It was not possible completely to remove TAP from root canals.

The effect of calcium silicate-based sealer on the push-out bond strength of fibre posts.

BACKGROUND: The aim of this study was to assess the effect of the iRoot SP root canal sealer on the push-out bond strength of fibre posts cemented with self-adhesive resin cement. METHODS: Forty-eight extracted maxillary incisors were randomly divided into four groups according to the tested sealer (n = 12): group 1 - control (only gutta-percha points, no sealer); group 2 - AH Plus Jet (resin-based sealer); group 3 - Endofill (zinc oxide-eugenol-based sealer); and group 4 - iRoot SP (calcium silicate-based sealer). All root canals were filled with gutta-percha, and groups 2-4 additionally received one of the sealers. Fibre posts were cemented with the self-adhesive resin cement Clearfil SA Cement. The specimens were sectioned in the coronal, middle and apical regions, producing three slices of 1 mm thickness. The push-out test was performed. All data were submitted to ANOVA and Tukey tests (α = 0.05). RESULTS: No statistically significant differences were found between the control group, AH Plus Jet and iRoot SP (p > 0.05). The Endofill sealer showed significantly lower bond strength compared to the other sealers and the control group (p < 0.05). CONCLUSIONS: The calcium silicate-based sealer did not adversely affect the bond strength of the fibre posts cemented with self-adhesive resin cement.