Constricted Canal Research Articles

Phase Transformation and Mechanical Behaviour of Different Heat-Treated Nickel-Titanium Rotary Instruments

ObjectivesThis study evaluated the phase composition, phase transformation behaviour, and mechanical properties of five heat-treated NiTi instruments. MethodsProTaper NEXT (M-wire, PTN), ProTaper Gold (Gold-wire, PTG), One Curve (C-wire, OC), EdgeTaper Platinum (Fire-wire, ETP), NeoNiTi (electrical discharge machining-wire, NNA), and ProTaper Universal (conventional wire, PTU, control) with #25-tip size were tested (n = 12/group) for cyclic fatigue resistance (number of cycles to failure; NCF) and torsional resistance (angle of rotation to fracture and maximum torque at fracture [ultimate torsional strength]). The geometry and fracture surfaces of the tested instruments were examined by scanning electron microscopy. The phase transformation temperature and phase composition of the instruments were evaluated using differential scanning calorimetry and X-ray diffraction. Data were statistically analysed using one-way ANOVA and Tukey's post hoc test, with the significance level set at 5%. ResultsPTG showed the highest NCF (P < .05) at 37°C, while ETP exhibited the highest angle of rotation to fracture, ultimate torsional strength, and stiffness (P < .05). Scanning electron microscopy demonstrated typical clusters of fatigue striations and numerous cracks after cyclic fatigue fracture, whereas there was a concentric abrasion pattern with a dimple and microvoids at the centre after torsional fracture. In differential scanning calorimetry curves, austenite-finishing temperatures of heat-treated instruments were higher than 37°C, whereas that of PTU was lower than 37°C. PTU showed strong peaks of austenite at 25 and 37°C, whereas ETP showed a strong peak of R-phase at 25°C, but mostly austenite phase at 37°C in X-ray diffraction. ConclusionsGeometry, alloy type, and phase transformation temperatures of NiTi instruments affected their mechanical behaviour. Clinical relevancePTG showed the highest NCF, suitable for markedly curved canals. ETP had the highest torsional resistance, appropriate for narrow and constricted canals.

Endodontic management of curved canals in mandibular molars- A case series

A tooth with a straight root canal and a single foramen is the exception rather than the rule. Most of the canals have multiple curvatures along their length, which poses difficulty in root canal instrumentation. Because of the presence of curved canals in mandibular molars, Endodontic treatment is very challenging. Curved canals have been found to be relatively higher in mandibular molars, ranging from 3.3 to 30.92% when compared to maxillary molars. Constricted canals and curvatures introduce factors that can increase the risk of procedural errors during root canal preparation. A thorough assessment of the preoperative radiographs, careful and a meticulous approach can yield into a safe and a successful endodontic treatment of such teeth. The current case series presents two such interesting cases of endodontic management of curved canals in mandibular molars.

Mechanical Properties of NiTi Rotary Files Fabricated through Gold-Wire, CM-Wire, T-Wire, and R-Phase Heat Treatment

Although nickel–titanium (NiTi) rotary files are invaluable tools in dentistry, the relationship between their properties and performance has not been elucidated. Herein, the performance of gold heat-treated (ProTaper Gold and ProfaTaper Gold), controlled memory (CM)-wire (HyFlex CM and V Taper 2H), T-wire (2Shape), and R-phase heat-treated (K3XF) NiTi files was evaluated; the non-heat-treated ProFile was used as the control. The bending, buckling, cyclic fatigue, and torsional resistances of the NiTi files were determined, and their phase transformation behavior was studied through differential scanning calorimetry (DSC). The angle of rotation until fracture (ARF), ultimate torsional strength (UTS), and stiffness were evaluated via torsional resistance testing. One-way analysis of variance (ANOVA) and post hoc analyses were conducted using the Games–Howell test and Tukey’s test. ProFile displayed the highest buckling resistance (8 N), CM-wire NiTi files exhibited the lowest bending resistance (0.660–0.758 N cm), and HyFlex CM displayed the highest cyclic fatigue resistance. ProTaper Gold exhibited high UTS and low ARF. K3XF demonstrated high bending resistance and the lowest cyclic fatigue resistance. The CM-wire NiTi files were the most suitable for use in curved canals, while the gold-wire NiTi files were ideal for constricted canals. ProFile was recommended for use in re-treatment cases.

A comparison of glide path preparation times of three different techniques in constricted canals

A comparison of glide path preparation times of three different techniques in constricted canals

NEGOTIATING THE CURVES WITH AF-F ONE FANTA ROTARY FILE: A CASE REPORT

The Posterior teeth often present with curved and dilacerated roots, a significant challenge for the clinicians during the endodontic treatments. The efficient biomechanical preparation is also affected by improper instrumentation in the curved or constricted canals. The use of conventional instruments and techniques in the dilacerated roots may develop ledges, fractured instruments, and canal blockages which further complicate the endodontic treatments. The introduction of Fanta AF-F One rotary file instruments has significantly impacted the biomechanical preparation of root canals systems. The Fanta AF-F One rotary file has noted advantages such as increased flexibility, higher strength, and wear resistance over the conventional rotary endodontic systems. The present case series discusses the endodontic treatment of two severely curved root canal systems successfully treated with Fanta AF-F One rotary file endodontic system.

Effect of Blue Heat Treatment on Vertical Force Induced with Endodontic Files.

To evaluate the vertical forces induced with Reciproc (R) and Reciproc Blue (RB) systems during canal shaping. Maxillary premolar teeth with two separate straight and constricted canals were chosen (n=26). After access cavity preparation, each tooth was fixed in a standing position on a stage connected to a force analyzing device (M5-20 Advanced Digital Force Gauge; Mark-10 Corporation, NY, USA). The glide path was prepared manually until K file sizes #15. Then, canals in all the groups were completely shaped with an R25/RB25 file (size 25,.08 taper). The canal shaping was done with a steady and gentle pressure on the file to give a slow 'in-and-out' movement of 2 mm amplitude. The file was inserted three times until it reached the WL successfully. After each insertion, the canal was recapitulated and irrigated with a 1% sodium hypochlorite solution. The shaping time was analyzed by Student's t-test. The inward and upward peak forces were used for analysis by using the Mann-Whitney test. All statistical analyses were performed using SPSS software at a 95% confidence level. Each root canal was shaped successfully with a single file inserted three times until the WL was reached. Within each group, the overall real-time force increased with the successive insertions of the file. The inward peak forces in both groups ranged from 1.71 to 8.38 N and the R group showed minimal peak forces than the RB group in the three insertions (P<0.05). The upward peak forces ranged from 1.50 to 3.26 N wherein both groups showed comparable peak forces at each insertion (P>0.05). The R and RB systems required average times of 22.01±3.08 and 23.93±4.15 s, respectively, to shape the canals completely (P>0.05). In this experiment, no file fracture took place during canal shaping. The blue heat treatment influenced the forces developed during canal shaping. RB file was associated with higher inward peak forces than R file.

Comparison of canal transportation and centering ability of manual K-files and reciprocating files in glide path preparation: a micro-computed tomography study of constricted canals

BackgroundOptimum Glide Path (OGP) is a new reciprocating motion aiming to perform efficient glide path preparation in constricted canals. The aim of this study was to investigate and compare manual and OGP movement in terms of canal transportation and centering ability in glide path preparation of constricted canals.MethodsThirty constricted mesial root canals of mandibular molars, with initial apical size no larger than ISO#8, were selected and negotiated with #6–#8 K-files under the microscope. Canals were randomly divided into two experimental groups: Group 1 (MAN, n = 15): Glide path was established by using #10-#15 stainless steel K-files manually; Group 2 (OGP, n = 15): #10-#15 Mechanical Glide Path super-files were used with OGP motion (OGP 90°, 300 rpm). Each instrument was used to prepare only 2 canals (as in one mesial root). Canals were scanned before and after glide path preparation with micro-computed tomography (micro-CT) to evaluate root canal transportation and centering ratio at 1, 3 and 5 mm levels from the root apex. File distortions and separations were recorded. Paired t-test was used to statistically evaluate the data (P < .05).ResultsGroup 2 showed a significantly lower transportation value than group 1 at 1-mm and 3-mm levels (P < .05), however the difference at 5-mm level was not significant. There was no significant difference regarding the centering ratio between the groups. Six #10 K-files were severely distorted in group 1, while no file separation or distortion was found in group 2.ConclusionsOGP motion performed significantly less canal transportation (apical 3 mm) and file distortion during glide path establishment in constricted canals comparing to manual motion, while the centering ability between the two was similar.Clinical relevanceOGP reciprocating motion provides a safer and efficient clinical approach compared to traditional manual motion in glide path establishment with small files in constricted canals.

A comparison of different hand and rotary endodontic glide path files for buckling resistance: An in vitro study

Introduction: The purpose of the present study was to compare the buckling resistance between the hand files and rotary files and compare the buckling resistance between pathfinding files made out of different alloys.Materials and Method: The test instruments were divided into two major groups based on the mode of use, hand instruments and rotary instruments. These groups were further divided into six subgroups. Six subgroups of endodontic files containing three samples were tested for buckling resistance by applying load in axial direction using a universal testing machine. The maximum load required to generate a lateral elastic displacement of 1 mm was recorded for each instrument. Data were analyzed using two-way analysis of variance and Newman–Keuls multiple post hoc tests using software SPSS version 19. P value was considered < 0.05.Results: The results indicated that the buckling resistance decreased in the following order: Hand C Plus file > Rotary One G file > Hand C pilot files > Rotary ProGlider file > Hand PathFinder Carbon Steel > Rotary HyFlex Electric Discharge Machining (EDM) file.Conclusion: The stainless steel instruments (C + and C-Pilot) were more resistant to buckling than carbon steel (Pathfinder CS) and nickel-titanium instruments (ProGlider and HyFlex EDM). Buckling resistance may influence instrument's performance during the negotiation of constricted canals, and the C Plus in hand file group showed significantly better results than the other instruments tested. Metallurgy and modulus of elasticity of the instruments play a significant role in buckling resistance as One G file in rotary file group showed highest buckling resistance (conventional austenite nickel-titanium) than ProGlider (M-wire NiTi) and HyFlex (EDM + Controlled Memory).

Evaluation of the Cyclic and Torsional Fatigue Resistance of Thermally Treated Hyflex CM versus Aurum Blue Nickel-titanium Rotary Instruments.

We aim to evaluate the cyclic and torsional fatigue resistance of two rotary instruments, Hyflex CM 25/0.06 (HCM) (Coletene-Whaledent, Allstetten, Switzerland) and Aurum Blue (AB) 25/0.06 (Meta-Biomed, Republic of Korea). Forty rotary instruments, HCM 25/0.06 and AB 25/0.06 (n=20 each) were used. The instruments were rotated in an artificial stainless steel canal with a 60° angle and a 5-mm radius of curvature (n=10) at body temperature (35°±1°C). The torsional test evaluated the torque and angle of rotation at failure of new instruments (n=10) in the portion 3 mm from the tip according to ISO 3630-1. The fractured surface of each fragment was observed by scanning electron microscopy. The data were analyzed using unpaired student's t- test, and the level of significance was set at 5%. AB 25/0.06 had significantly greater number of cycles to failure than HCM 25/0.06 (P<0.05). The torsional test showed there were no significant differences in the torsional strength and angular rotation to fracture between the groups (P>0.05). Based on this in vitro study, AB 25/0.06 instrument was more resistant to cyclic fatigue than the HCM 25/0.06 instrument, suggested that these instruments are safer than HCM 25/0.06 for the preparation of severely curved canals. However; there was no significant difference in the torsional properties of the two instruments then appear to have similar performance during constricted canal preparation.

Constricted canals: a new strategy to overcome this challenge.

Negotiation of constricted canals can be a challenge during endodontic treatment. Over the years, several strategies have been presented in order to overcome the difficulties imposed by this anatomical feature. This paper presents three cases using a different protocol from that recommended by the manufacturer of the Protaper System in order to facilitate the negotiation of constricted canals. These cases suggest that the modified protocol shown is able to perform the shaping process with less resistance, reducing the risk of instrument separation and performing an effective process to reach the apical thirds in constricted canals.

Buckling Resistance of Pathfinding Endodontic Instruments

IntroductionThis study compared the buckling resistance of the following endodontic pathfinding instruments: C-Pilot file (VDW, Munich, Germany), C+ file (Maillefer/Dentsply, Ballaigues, Switzerland), and PathFile (Maillefer/Dentsply). MethodsThe test instruments were subjected to a devised buckling resistance test, which consisted of the application of an increasing load in the axial direction of the instrument by using a universal testing machine. The maximum load required to generate a lateral elastic displacement of 1 mm was recorded for each instrument. ResultsThe results indicated that the buckling resistance decreased in the following order: C+ file > C-Pilot file > PathFile. The difference was statistically significant (P < .05). ConclusionsThe stainless steel instruments (C+ and C-Pilot) were more resistant to buckling than the nickel-titanium instrument (PathFile). Considering that buckling resistance may influence the performance of instruments during the negotiation of constricted canals, the C+ files showed significantly better results than the other instruments tested.

Penetration of constricted canals with modified K files

A technique using K files with modified tips has been developed for the penetration of constricted canals. The tip of a #10 K file was sliced diagonally to make it thinner. Because this modified K file has an especially fine tip and an appropriate stiffness, it followed constricted or sharply curved canals well and had a high penetration potential. The author attempted to penetrate to the apical foramen in all 1844 canals of 977 teeth treated from 1987 to 1994. In 263 canals (14.3%) that could not be penetrated with conventional #10 K files, further attempts were made with the modified K files. As a result, the number of the nonpenetrated canals was reduced to 75 (4.1%). There were 7 file breakages and 14 accidental perforations.

Helical tubulate inclusion compounds

Abstract The inclusion properties of the first helical tubuland diol hosts 1–5 have been surveyed and are reported. Bicyclic diol 1 forms helical tubulate inclusion compounds with most small solvent molecules, but with certain phenols hydrogen bonded co-crystalline materials are produced instead. Diol 2 yields helical tubulates with larger guest molecules, but if smaller solvents are used then an alternative host system is obtained. This has the guests trapped in ellipsoidal cavities located along constricted canals and is termed the ellipsoidal clathrate type. In some cases both inclusion types can be produced from 2 by varying the experimental conditions. The free volume present in the helical tubuland lattices of 3 and 5 is insufficient for guest inclusion. Diol 4 has the largest void space and can form inclusion compounds with large molecules such as ferrocene and squalene. X-ray crystal structures of representative examples of these compounds are discussed.

Fine structural study of the statocysts in the veliger larva of the nudibranch, Rostanga pulchra.

The two statocysts of the veliger larva of Rostanga pulchra are positioned within the base of the foot. They are spherical, fluid-filled capsules that contain a large, calcareous statolith and several smaller concretions. The epithelium of the statocyst is composed of 10 ciliated sensory cells (hair cells) and 11 accessory cells. The latter group stains darkly and includes 2 microvillous cells, 7 supporting cells, and 2 glial cells. The hair cells stain lightly and each gives rise to an axon; two types can be distinguished. The first type, in which a minimum of 3 cilia are randomly positioned on the apical cell membrane, is restricted to the upper portion of the statocyst. The second type, in which 9 to 11 cilia are arranged in a slightly curved row, is found exclusively around the base of the statocyst. Each statocyst is connected dorso-laterally to the ipsilateral cerebral ganglion by a short static nerve, formed by axons arising from the hair cells. Ganglionic neurons synapse with these axons as the static nerve enters the cerebral ganglion. The lumen of the statocyst is continuous with a blind, constricted canal located beneath the static nerve. A diagram showing the structure of the statocyst and its association with the nervous system is presented. Possible functions of the statocyst in relation to larval behavior are discussed.

Role of endodontics in current dental practice

The findings presented in this statistical study are applicable to a representative sample of dentists in general practice in Illinois. Almost 90% of the respondents in this survey do some or all of their root canal therapy. The majority of those who do some or all of their root canal therapy do so because they enjoy it. Most of the respondents (77.3%) do not take root canal cultures. Kerr's Root Canal Sealer is the most widely used sealer, followed by Kerr's Tubli-Seal and Dr. Wach's sealer, respectively. The preferred technique of filling root canals among the respondents is by means of guttapercha and lateral condensation for most canals and the use of silver points for narrow or constricted canals. A technique that is not taught in any American dental school, the Sargenti N2 technique, is used by almost 20% of the responding dentists. Most of the respondents try to fill the canal 0.5 to 1 mm from the apex. Although dozens of intracanal medicaments exist, the most commonly used one is camphorated parachlorophenol, which is used by more than 50% of the dentists who participated in this survey. A chelating agent is used by almost two fifths of the dentists surveyed and use of such an agent is increasing. More than half the respondents carry out some sort of endodontic surgery in their practice' apicoectomy is the most common endodontic surgery performed. The data show that 48.9% of the dentists who participated in this survey feel that dental schools should devote more time to teaching endodontics, 50.5% believe that the amount of time should remain the same, and only 0.5% feel that the amount of time should be decreased. About 70% of those who feel that the amount of time for teaching endodontics should be increased specified an increase in clinical training.