Remaining dentine thickness of root canals prepared with K-3 and ProTaper rotary systems.

OBJECTIVE: To compare the remaining dentine thickness of root canals prepared with K-3 and ProTaper files.. METHODS: This in-vitro experimental study was conducted from 1st April-30th September 2015 at the dental clinics of Aga Khan University Hospital, Karachi, and comprised human teeth. Extracted human premolars and molars were included in the study using non-probability consecutive sampling. Canals were randomly allocated into two groups i.e. K-3 and ProTaper. Changes in inner and outer walls of canals were measured using Vixwin software at 1mm, 4mm, 7mm and 10mm from the apex. SPSS 20 was used for data analysis. RESULTS: Of the 214 canals, 107(50%) were assigned to each group. No statistically significant difference was found in the remaining dentine thickness at 1mm, 4mm, 7mm and 10mm from the apex of the teeth prepared with in K-3 versus ProTapers system (p>0.05). CONCLUSIONS: The remaining dentine thickness of the root canals prepared with K-3 files was similar to that of canals prepared with ProTaper files.

Accuracy of three different apex locators and visual exam in primary teeth with and without root resorption in vitro.

AIM: The aim of this study was to evaluate the accuracy and reliability of three apex locators (EndoMaster, Raypex, DentaPort ZX) and visual assessment in primary molar teeth in vitro. MATERIALS AND METHODS: Twenty-four extracted human primary molar teeth with and without root resorption were used in this study. After endodontic access preparation, root canal length was visually measured by means of a K file; then the teeth were embedded into alginate and the roots were measured again by mans of the three apex locators. The results were collected in SPSS 15.0 and statistical evaluations were completed by one-way ANOVA and Kruksal-Wallis test. RESULTS: The measurements closest to the visually determined length were obtained with EndoMaster. No statistically significant differences were found between visual and apex locators lengths (p>0.05). CONCLUSION: Within the limitations of this study, the use of apex locators would be useful in the endodontic treatment of primary teeth.

Accuracy of electronic apex locator in enlarged root canals with different root canal irrigants: an in vitro study.

AIM: To evaluate the accuracy of Root ZX-II (J Morita Corp) apex locator in enlarged root canals with different root canal irrigants. MATERIALS AND METHODS: 48 freshly extracted single rooted mandibular premolar teeth were used. The apical enlargement was done up to #45 K-file as the master apical file (MAF). The teeth were randomly divided into 4 groups and mounted in an experimental apparatus. The following irrigants were used during electronic canal measurements: group 1: saline; group 2: 3% NaOCl; group 3: 2% chlorhexidine; group 4: 17% EDTA. The canal measurement was done with Root ZX-II apex locator using #10 and #45 K-file. Data were analyzed by two way ANOVA and Bonferroni multiple comparison test. RESULTS: Statistical analysis showed that there was statistically significant difference between #10 and #45 K-file for group 1 (p < 0.01). CONCLUSION: Root ZX-II was accurate in the presence of 3% NaOCl and 17% EDTA when measured with smaller and larger files. However, it was accurate in the presence of saline and 2% CHX when larger files were used.

A survey of endodontic practices among dentists in Nigeria.

AIM: To investigate the pattern of routine endodontic practices among Nigerian dentists. MATERIALS AND METHODS: This study was a questionnaire-based survey of samples of dentists in the Nigerian cities of Enugu and Benin. The self-administered questionnaire contained 25 close-ended questions with multiple choice options. The data collected included demographic details of respondents, root canal preparation techniques, irrigants and intracanal medicaments used, the number of appointments, method of working length determination, root filling techniques, cements used, and the scope of treatment performed. RESULTS: Most respondents used sodium hypochlorite as the irrigant, the step back technique for canal preparation, and lateral condensation with a zinc oxide-eugenol-based sealer for obturation. Most respondents did root canal treatment on all types of teeth and used radiographs to determine the working length 70% of the time. Most respondents followed up their patients for less than 12 months and most treated teeth with periapical areas larger than 10 mm by root canal therapy combined with apical surgery. CONCLUSION: Most Nigerian dentists use step back technique for canal preparation and lateral condensation for obturation. CLINICAL SIGNIFICANCE: Endodontic practice by Nigerian dentists differs from some established practice quality guidelines in many other countries, particularly in nonperfusion of modern techniques into practice, popularity of antibiotic use for endodontic emergencies and a high rate of perforations.

An in vivo evaluation of different methods of working length determination.

OBJECTIVE: The purpose of this in vivo study was to compare the ability of digital tactile, digital radiographic and electronic methods to determine reliability in locating the apical constriction. MATERIALS AND METHODS: Informed consent was obtained from patients scheduled for orthodontic extraction. The teeth were anesthetized, isolated and accessed. The canals were negotiated, pulp chamber and canals were irrigated and pulp was extirpated. The working length was then evaluated for each canal by digital tactile sensation, an electronic apex locator (The Root ZX) and digital radiography. The readings were then compared with post-extraction working length measurements. RESULTS: The percentage accuracy indicated that EAL method (Root ZX) shows maximum accuracy, i.e. 99.85% and digital tactile and digital radiographic method (DDR) showed 98.20 and 97.90% accuracy respectively. CLINICAL SIGNIFICANCE: Hence, it can be concluded that the EAL method (Root ZX) produced most reliable results for determining the accurate working length.

Evaluation Algorithm of Root Canal Shape Based on Steklov Spectrum Analysis.

In recent years, we have seen more and more interest in the field of medical images and shape comparison motivated by the latest advances in microcomputed tomography (µCT) acquisition, modelling, and visualization technologies. Usually, biologists need to evaluate the effect of different root canal preparation systems. Current root canal preparation evaluation methods are based on the volume difference, area difference, and transportation of two root canals before and after treatment. The purpose of root canal preparation is to minimize the volume difference and ensure the complete removal of the smear layer. Previous methods can reflect some general geometric differences, but they are not enough to evaluate the quality of root canal shape. To solve this problem, we proposed a novel root canal evaluation method based on spectrum and eigenfunctions of Steklov operators, which can be served as a better alternative to current methods in root canal preparation evaluation. Firstly, the ideal root canal model was simulated according to the root canal model before and after preparation. Secondly, the Steklov spectrum of the two models was calculated. Thirdly, based on the spectrum and the histogram of the Gaussian curvature on the surface, the weight of each eigenvalue was computed. Therefore, the Steklov spectrum distance (SSD), which measures shape difference between the root canals, was defined. Finally, the calculation method that quantifies the root canal preparation effect of root canals was obtained. Through experiments, our method manifested high robustness and accuracy compared with existing state-of-the-art approaches. It also demonstrates the significance of our algorithm's advantages on a variety of challenging root canals through result comparison with counterpart methods.

Treatment outcome in endodontics: the Toronto study--phases 3 and 4: orthograde retreatment.

Outcome 4-6 years after retreatment was assessed for Phases 3 and 4 of the Toronto Study. Of 477 teeth retreated, 333 were lost to follow-up, 18 were extracted, and 126 (41% recall, excluding 124 discontinuers) were examined for outcome of healed (periapical index score, < or = 2; no signs or symptoms) or diseased. When pooled with Phases 1 and 2, 187 of 229 teeth (82%) were healed. Logistic regression identified significant (P < or = .05) preoperative outcome predictors: root filling quality (odds ratio [OR], 4.18; confidence interval [CI], 1.72-10.12; healed: inadequate, 88%; adequate, 66%), perforation (OR, 4.01; CI, 1.28-12.62; healed: absent, 87%; present, 56%), and radiolucency (OR, 3.33; CI, 1.19-9.36; healed: absent, 93%; present, 80%). In teeth with radiolucency, outcome predictors were number of treatment sessions (OR, 12.08; CI, 1.84-infinity; healed: one, 100%; > or = 2, 77%) and previous root filling quality (OR, 7.68; CI, 2.36-26.89; healed: inadequate, 86%; adequate, 50%). Outcome was better in teeth with inadequate previous root filling, without perforation and radiolucency. Suggested significance of number of treatment sessions in teeth with radiolucency requires validation from randomized controlled trials.

Pre-clinical endodontics: a survey amongst German dental schools.

AIM: To evaluate the state and level of pre-clinical endodontic education in German dental schools and to evaluate differences with regard to intensity and extent of teaching, time devoted to teaching pre-clinical endodontics, personnel resources in teaching and technical equipment. METHODOLOGY: Twenty-eight questionnaires were e-mailed to those in charge of pre-clinical endodontic education in German dental schools. The extent of education, the student-teacher ratio, the teaching content as well as the application of teaching materials and technologies were asked. If, after 4 weeks, no response had been received, the questionnaire was sent out by e-mail again. In the absence of a reply, a phone call was made to the corresponding university to conduct the survey by phone. RESULTS: With feedback from 27 of 28 dental schools, the response rate was 96%. Pre-clinical endodontic education at German universities varied considerably. Theory classes ranged from 5 to 30 h (13.3 h mean), practical classes from 12.5 to 60 h (45.4 h mean). The student to staff ratio varied between 9 : 1 and 30 : 1 (16 : 1 mean). Forty-eight per cent of the universities had a specialist in endodontics or a teacher with a special interest. A dental microscope was available for pre-clinical teaching purposes in 38% of the universities. The majority (63%) of universities taught root canal preparation with rotary nickel titanium instruments. CONCLUSION: Pre-clinical endodontic education varied considerably between German universities because of differences in programme design, staff and course content.

Glide Path Enlargement of Mandibular Molar Canals by Using K-files, the ProGlider File, and G-Files: A Comparative Study of the Preparation Times.

INTRODUCTION: The preparation of a glide path before the introduction of rotary nickel-titanium instruments is a standard adjunct to ensure increased safety during root canal preparation. The aim of this study was to compare the mean preparation time of manual instrumentation with K-files, G-Files, and the ProGlider instrument to prepare a glide path in curved root canals. METHODS: The mesial canals of 90 mandibular molars (with curvature angles between 25° and 35°) were selected. The specimens were randomly divided into 3 groups with 30 canals each, and canal preparations were performed by an endodontist who used #10-15-20 stainless steel manual K-files (group KF), #10 stainless steel manual K-file followed by #12-17 G-File instruments (group GF), and #10 stainless steel manual K-file followed by #16 ProGlider instrument (group PG). The total time it took to prepare the glide paths was recorded with an electronic stopwatch. New instruments were used for each canal. RESULTS: Glide path enlargement with the PG group (27.9 ± 8.6 seconds) and GF group (41.9 ± 20.1 seconds) was shown to be statistically significantly faster than stainless steel KF group (74.9 ± 24.1 seconds) by using analysis of variance (P < .05). There was no statistically significant difference observed between the mean preparation times of the PG and GF groups (P < .05). CONCLUSIONS: Glide path preparation times with the rotary instrument groups were significantly faster than with stainless steel manual K-files.

A retrospective clinical study of incidence of root canal instrument separation in an endodontics graduate program: a PennEndo database study.

This study investigated the incidence of hand and rotary instrument separation (IS) in the endodontics graduate program at the University of Pennsylvania between 2000 and 2004. In 4,865 endodontic resident cases the incidence of hand and rotary IS was 0.25% and 1.68%, respectively. The odds for rotary IS were seven times more than for hand IS. The probability of separating a file in apical third was 33, and 6 times more likely when compared to coronal and middle thirds of the canals. The highest percentage of IS occurred in mandibular (55.5%) and maxillary (33.3%) molars. Furthermore, the odds of separating a file in molars were 2.9 times greater than premolars. Among the ProFile series 29 rotary instruments, the .06 taper # 5 and # 6 files separated the most. There was no significant difference in IS between the use of torque controlled versus nontorque controlled handpieces, nor between first and second year residency.

Development and Evaluation of an Endodontic Simulation Model for Dental Students.

The aims of this study were to develop an endodontic simulation model able to implement the electronic method of working length determination (electronic apex locators, EALs) in a dental school, to evaluate the practicality of this tool for dental students, and to compare the accuracy of working length measurements achieved by the EAL and the radiographic method. A new simulation model was constructed by embedding extracted human teeth in a self-cured resin, along with a conductive medium. After radiographic and electronic working length determinations, root canal instrumentation was performed by students at a dental school in Austria according to the working lengths obtained from the EAL. Subsequently, root apices (n=44) were longitudinally sectioned using a diamond coated bur. Measurements of the distance between the anatomical root apex (ARA) and the apical constriction (AC) as well as between ARA and the ascertained apical point of endodontic instrumentation were performed using digital photography and a 3D computer-assisted design software. The distance between ARA and the radiologic (ARA-R) or electrometric (ARA-EL) readings of the apical point of endodontic instrumentation was compared with the actual distance ARA-AC. The accuracy of both methods was determined. The difference between the actual distance ARA-AC and the targeted radiological distance was statistically significant (p=0.0001), as was the measured distance between ARA-R and ARA-EL (p=0.016). The electronic method seems to be more precisely referring to the AC (R(2)=0.0198) than the radiographic method (R(2)=0.0019). These results suggest that the endodontic simulation model described in this study can be successfully used in preclinical dental education.

Precurving of nickel-titanium files affects transportation in simulated canals.

Instrumentation studies comparing nickel-titanium with stainless-steel files have been performed without precurving the nickel-titanium files. It is unknown what influence the precurving of nickel-titanium files would have on transportation in small curved canals of varying curvatures. One hundred-sixty resin blocks with simulated canals were used. Eighty blocks had gradual (gradual curve (GC)) 30-degree curves; the remainder had abrupt (abrupt curve (AC)) 30-degree curves. Ten blocks for each curvature and for each degree of precurving (0, 15, 20, 25, 30, 35, 40, and 45) were instrumented with a machine that imparted only an in and out motion. Simulated canals were a size 30 at the apex, and size 30 nickel-titanium files were used to instrument the canals. A transportation "t" index was determined at two levels: T1 (1 mm from the apex) and TB (a line bisecting the curve of the canal). For GC at T1 and TB, 45- and 25-degree curved instruments, respectively, produced significantly less transportation (p < 0.0001). For AC at T1 and TB, 35- and 0-degree curved instruments, respectively, produced significantly less transportation (p < 0.0001). Comparing GC and AC, the transportation for GC was significantly less (p < 0.0015).

Canal transportation caused by a new instrumentation technique and three standard techniques.

The ability of three different enlarging techniques (balanced force concept, step-back, and recapitulation) and a prototype system to maintain the original canal path during root canal preparation were compared, in vitro, with a theoretical ideally prepared root canal. Measurements were made at the concave and convex sides of the canal at four different levels (1, 4, 5, and 7 mm from apical, respectively). Simulated root canals embedded in clear casting resin and an enlarging computer-supported device were used for this study. The results showed that none of the enlarging techniques used in this study was able to prepare a canal ideally. The prototype system, at level 1, showed an ideal amount of material removed from the concave side and less, in comparison with the other techniques, from the convex side of the canals. The same tendencies persisted at all levels, with the exception of the level 4 concave side.

Comparison of debris extruded apically in straight canals: conventional filing versus profile .04 Taper series 29.

The purposes of this study were to determine quantitatively the amount of debris and irrigant forced in an apical direction, the frequency of apical plug development, and the time required to prepare canals when a step-back technique using K-files was compared with the .04 Taper system. Sixty-nine extracted teeth with straight canals were divided into four statistically similar groups. Two groups were instrumented either 1 mm short of the apical foramen or to the apical foramen with K-files. The other two groups were instrumented to the same levels using .04 Taper files. The extruded debris and irrigant were collected in preweighed vials. The weight of the debris and volume of irrigant extruded using both techniques were compared and analyzed using paired t test and one-way ANOVA. Tukey's Multiple Comparisons Procedure showed K-files used to the apical foramen extruded significantly more debris than the other three groups (p < 0.01). The .04 Taper files used 1 mm short extruded less debris than the other groups. Significantly more irrigant was extruded when filing was performed to the apical foramen (p < 0.007), regardless of the technique used. More apical plugs were created in teeth filed short of the apical foramen, but the difference between the two preparation techniques was not statistically significant. It took significantly less time to instrument canals with the .04 Taper system than with K-files (p < 0.002).

Shaping ability of Lightspeed rotary nickel-titanium instruments in simulated root canals. Part 1.

The aim of this study was to determine the shaping ability of Lightspeed nickel-titanium rotary instruments in simulated canals. Forty canals consisting of four different shapes in terms of angle and position of curvature were prepared by Lightspeed instruments using the technique recommended by the manufacturer. This report describes the efficacy of the instruments in terms of preparation time, instrument failure, canal blockages, loss of canal length, and three-dimensional canal form. Overall, the mean preparation time for all canals was 8.12 min with canal shape having no significant effect on the speed of preparation. No instruments deformed or separated during the study, and none of the canals became blocked with debris. Seventeen canals retained their original working length, but 16 gained in length and 7 lost length. There was no significant difference between the canal shapes in terms of the mean loss of distance or category of distance change. Apical stops as judged from intracanal impressions were present in 23 of the canals but they were all judged to be of poor quality. The canals were found to be smooth in the apical half of the canal in 36 specimens and in the coronal half of 24 specimens. All the canals had poor taper characteristics, and only 16 specimens showed good flow characteristics. Under the conditions of this study, Lightspeed instruments prepared canals rapidly, with no fractures, canal blockages, and with minimal change in working length. The three dimensional form of the canals was compromised as flow and taper were less than ideal, presumably as a result of an ineffective stepback procedure. The results imply that either the stepback sequence should be modified or another instrument with increased taper should be used to refine the canal walls before obturation.

A comparison of canal centering ability of four instrumentation techniques.

The purpose of this study was to compare three engine driven (nickel-titanium) NiTi instrument systems with hand files for their effect on canal transportation. Mesial roots of mature lower first molars with separate canals were paired on the basis of curvature and morphology. Canal lengths were standardized to 11 mm from orifice to apical foramen. Profile, Lightspeed, McXIM, and Flex-R hand filing techniques respectively were randomly assigned to one of the four canals of each tooth pair. The roots were mounted and sectioned at 1 mm, 3 mm, and 5 mm from working length using a modified Bramante technique. All sections were video imaged preoperatively after instrumentation to size #30 and after final instrumentation to size #40. The images were computer analyzed for changes in canal area and centering at each stage of instrumentation. Preparation time was also recorded. Data were analyzed using ANOVA. The NiTi systems remained better centered in the canal than stainless steel hand files. There were no significant differences among the NiTi systems at any level. The difference between hand filing and the NiTi techniques was more pronounced at size #40 than at size #30. The NiTi systems were all significantly faster than hand filing. No significant differences in preparation were found between the NiTi systems when canals were instrumented to the size nearest #40.

Determination of the p-monochlorophenol residue in the calcium hydroxide + P-monochlorophenol combination used as an intracanal dressing in pulpless teeth of dogs with induced chronic periapical lesion.

To determine the presence of p-monochlorophenol in the calcium hydroxide (Calen) + p-monochlorophenol combination after its use as intracanal dressing, periapical lesions were induced in 60 root canals of upper and lower premolars of four dogs. After biomechanical preparation, the root canals received the intracanal medication, which was removed from the apical third after 2, 4, 7, and 14 days for chemical analysis by spectrophotometry. The results showed a p-monochlorophenol loss of approximately 50.0% in the dressing after 48 h, with no further significant loss after longer periods of times. p-Monochlorophenol was still present in the medication after 14 days.

In vitro evaluation of effects of ultrasonic root-end preparation on resected root surfaces.

This in vitro study investigated structural alterations in resected roots that had root-end preparations made with a conventional microhead handpiece and ultrasonics at two intensity levels. Root ends were examined with fluorescence confocal microscopy. Serial histologic sections to the 2 mm levels and then at the level of 3 mm and 4 mm from the resected surface were examined. Statistical analysis of the confocal data indicated no significant difference between the groups in the number and length of the fractures. Results of the histologic data indicated that root ends prepared by ultrasonics had a statistically greater number of fractures than both the control and the conventionally prepared groups. The latter did not differ significantly from each other.

Comparison of ultrasonic and high-speed-bur root-end preparations using bilaterally matched teeth.

The purpose of this study was to compare ultrasonic and high-speed-bur root-end preparations. Seventy-six roots from 29 bilaterally matched pairs of human teeth in cadavers were used in this study. In group 1 ultrasonic preparations were made in 38 roots and filled with amalgam. In group 2 high-speed bur preparations were made in 38 roots and filled with amalgam. The size of the bony crypt was measured and the teeth were extracted and radiographed mesial-distally and buccal-lingually. None of the root-end preparations resulted in root perforation. The mean mesial-distal minimum depth of ultrasonic and high-speed bur preparations were 2.11 mm and 1.39 mm, respectively. The mean buccal-lingual minimum depth of preparation was 2.51 mm for the ultrasonic and 2.05 mm for the high-speed bur preparations. The depth of the ultrasonic preparations was significantly greater for both measurements. A significantly greater bevel angle was associated with the bur preparations, 35.1 degrees versus 16.0 degrees for the ultrasonic preparations. The incidence of ultrasonic root-end preparations deviating from the uninstrumented canal spaces was found to be 2.6%. All bur root-end preparations were at an acute angle to the long axis of the root. The bony crypt size for bur preparations was significantly greater than that for ultrasonic preparations.

Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canals.

The efficacy of five instrumentation techniques for cleaning the apical third of curved root canals was assessed by histological examination. Mesial root canals of freshly extracted human mandibular molars were prepared by the following instrumentation methods: step-back technique using stainless steel files; step-back technique using nickel-titanium files; ultrasonic technique; balanced force technique; and Canal Master U technique and instruments. The apical portion of the root was histologically processed, and cross-sections were examined for remaining soft tissue, predentin, and debris. The results showed no significant differences among the techniques. Although the five instrumentation methods were effective in removal of major amounts of tissue from the canals, none totally debrided the entire root canal system, especially when variations in the internal anatomy were present.