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Introduction A thorough knowledge of root canal anatomy is critical for successful root canal treatments. This study evaluated the internal anatomy of the palatal roots of maxillary first molars with micro–computed tomography (microCT). Methods The palatal roots of extracted maxillary first molars ( n = 169) were scanned with microCT to determine several anatomic parameters, including main canal classification, lateral canal occurrence and location, degree of curvature, main foramen position, apical constriction presence, diameters 1 and 2 mm from the apex and 1 mm from the foramen, minor dentin thickness in those regions, canal volume, surface area, and convexity. Results All canals were classified as Vertucci type I. The cross sections were oval in 61% of the canals. Lateral canals were found in 25% of the samples. The main foramen did not coincide with the root apex in 95% of the cases. Only 8% of the canals were classified as straight. Apical constriction was identified in 38% of the roots. The minor and major canal diameters and minor dentin thickness were decreased near the apex. The minor dentin thickness 1 mm from the foramen was 0.82 mm. The palatal canals exhibited a volume of 6.91 mm 3 and surface area of 55.31 mm 2 and were rod-shaped. Conclusions The root canals of the palatal roots were classified as type I. However, some factors need to be considered during the treatment of these roots, including the frequent ocurrence of moderate/severe curvatures, oval-shaped cross-sections, and lateral canals, noncoincidence of the apical foramen with the root apex, and absence of apical constriction in most cases.

Introduction The morphology of the palatal root of maxillary first and second molars was analyzed and compared using micro–computed tomographic scanning. Methods Forty-seven extracted maxillary molars were scanned with a micro–computed tomographic device to analyze the palatal radicular dentin dimensions, canal working width, root length, canal curvature, lateral canals, and apical constriction anatomy. Quantitative data were analyzed with mean and standard deviation for first and second molars, respectively. Comparison was made between first and second molars using an unpaired t test. Results The palatal root of maxillary first molars was found to have statistically significantly thinner dentin than second molars on the palatal aspect of the root 8–11 mm from the apex, correlating to the coronal and middle thirds of the root. First molar palatal roots also had a statistically significantly wider canal mesiodistally than second molars at 13–15 mm from the apex, correlating approximately to the level of the cementoenamel junction and pulpal floor. Significant canal curvature was present. These findings suggest the need for conservative coronal flaring and instrumentation. Conclusions The absence of an apical constriction in 76.6% of the specimens highlights the importance of creating an apical seat through instrumentation to maintain obturation materials. A minimum master apical file size of 40 is recommended based on preoperative working widths in the apical 0.5–1.0 mm. A root-end resection of 3.5 mm would remove a greater majority of lateral canals.

Introduction Apical constriction has been proposed as the most appropriate apical limit for the endodontic working length. Despite being the most used, some limitations are attributed to the radiographic method of working length determination. It lacks precision because it is based on the average position of the apical constriction. The electronic apex locators have been presented as an alternative to the odontometry performed by radiography. These devices detect the transition of the pulp to the periodontal tissue, which is anatomically very close to the apical constriction and may perform with improved accuracy. Methods A systematic review was performed to compare the radiographic and electronic methods. Clinical studies that compared both methods were searched for on 7 electronic databases, a manual search was performed on the bibliography of articles collected on the electronic databases, and the authors were contacted to ask for references of more research not detected on the electronic and manual search. Results Twenty-one articles were selected. The majority were comparative or evaluation studies, and very few clinical studies comparing both methods are available. Several methodological limitations are present on the collected articles and debated in this review. Conclusions Although the available scientific evidence base is short and at considerable risk of bias, it is still possible to conclude that the apical locator reduces the patient radiation exposure and also that the electronic method may perform better on the working length determination. At least one radiographic control should be performed to detect possible errors of the electronic devices.

Introduction: The purpose of this study was to compare the accuracy of working length (WL) measurements by using the Root ZX II, Apex NRG XFR, and Mini Apex Locator with rotary nickel-titanium (NiTi) instruments. Methods: Twenty-eight teeth had their WLs determined with each electronic apex locator (EAL) by using 0.04 taper ProFiles sizes 40–20 in a crown-down technique until WL was reached. Four control teeth had their WL determined by using stainless steel hand files. The files were cemented at WL, and the teeth were extracted. The apical 4 mm of each root was shaved to the apical constriction, exposing the file. Photographs were taken under 15 and 30 magnification and projected at 360 and 720 for evaluation. Results: The accuracy of the Root ZX II, Apex NRG XFR, and Mini Apex Locator in locating the minor diameter within 0.5 mm was 50%, 46.43%, and 39.29%, respectively. There was no statistically significant difference between the EALs in locating the minor diameter. The determination of WL by using hand files in the control teeth was more accurate. Conclusions: The Root ZX II, Apex NRG XFR, and Mini Apex Locator used with rotary NiTi files were able to locate the apical constriction within 0.5 mm only 50% or less of the time. (J Endod 2009;35:962–965)

This study aimed to evaluate the safety and efficacy of a method of using nickel-titanium rotary instruments for preparing the C-shaped root canal system. Forty-three human mandibular second molars with a C-shaped canal configuration were prepared with a crown-down approach to an apical dimension of size 30 by using a combination of ProFile and HERO instruments. Micro-computed tomography was used to examine the canal diameter and the remaining thickness of the dentin wall along the root canal. Results showed that only isolated regions in cross section of the C-shaped canal were physically prepared by the rotary instruments. The furcal wall (concave aspect of the "C" in cross section) of all clinically identifiable canals had a similar thickness at a distance 1-7 mm from the apical constriction both before and after instrumentation. More dentin was removed from the outer (convex aspect of the "C") than the furcal aspect at the apical region, but the converse was true more coronally. All prepared canals showed a taper that matched that of the last instrument used. It was concluded that cleaning of the C-shaped canal system is incomplete with the use of rotary instruments and should be assisted by ultrasonic irrigation. Although rotary instruments seemed to be safe in such canals, further enlargement to an apical dimension greater than size 30 (0.06 taper) is not recommended.

The aim of this in vitro investigation was to determine the accuracy of 4 different electronic apex locators (EALs) with 3 different instrument sizes. For this study 146 roots were embedded in an agar solution. Electronic measurements were made to the physiologic foramen (apical constriction) with the Elements Apex Locator, Justy II, Raypex 5, and ProPex II and K-type files sizes 08, 10, and 15. Statistical significances were calculated with the sign test (P < .001). Exact measurements to the physiologic foramen were made with the Elements Apex Locator, 36.99%, 39.04%, and 44.93%; Justy II, 38.62%, 32.41%, and 43.41%; Raypex 5, 42.76%, 39.31%, and 39.06%; and ProPex II, 38.62%, 43.45%, and 40.63% of the time with instrument sizes 08, 10, and 15, respectively. No significant differences were found between the actual working length and EALs/instrument size. A nonsignificant higher number of unstable measurements were observed in all EALs with instrument size 15.

One aim of this study was to attempt to relate the position of the cementodentinal junction (CDJ) and the apical constriction to that of the apical foramen in mandibular premolars, as well as to measure the canal diameter at these various points. Another aim was to evaluate how electronic working length determination by Root ZX and radiographic method of working length determination correlated to the location of these various positions. The results showed that CDJ was detected at average distance of 0.3 mm from apical foramen with average canal diameter of 0.32 mm, whereas the apical constriction was detected at average distance from apical foramen of 1.2 mm with canal diameter of 0.22 mm. There was a statistically significant difference between file-tip position from apical foramen in group I working length measured by Root ZX and group II working length measured radiographically. Also this significant difference was found between file-tip position in both groups and CDJ and apical constriction. The average canal diameter at 0.5, 1, and 1.5 mm from apical foramen was 0.33 ± 0.11, 0.28 ± 0.06, and 25 ± 0.05 mm, respectively.

The cemento-dentino-canal junction, the apical constriction, and the apical foramen are the principal reference points used to determine the apical limit for instrumentation and root canal filling. For a better understanding of these structures, the objective of this study was to evaluate histologically the localization of the cemento-dentino-canal junction and the diameters of the apical foramen and root canal at the cemento-dentino-canal junction. Eighteen anterior maxillary teeth (canines, central, and lateral incisors) were used, from which 269 histological sections were obtained and evaluated by optical microscopy. The results indicated that the longest extension of the cementum into the root canal was observed in the canines, this value decreasing in the lateral incisors, and even more so in the central incisors. The widest diameter of the apical foramen corresponded to the lateral incisors, followed by the canines and the central incisors. The diameter of the root canal at the cemento-dentino-canal junction was greatest in the canines and lowest in the central and lateral incisors. Great variability was observed in the measurements of the extension of the cementum into the root canal. AQ: 1.

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 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 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.

To better assess the efficiency of the mechanical preparation of root canals, 1085 transparent specimens of extracted mandibular incisors were examined for canal configuration, thickness and curvature of the root canals, condition of any accessory canals, and location of the apical foramen. Greater than 85% of the root canals possessed a single canal (Type I). Of specimens in which furcation was observed, only 3% possessed two separate canals (Type III and IV). Fewer than 30% of the specimens showed accessory canals that were mechanically impossible to clean. The majority of the lateral branches were small, greater than 80% of the specimens were smaller than a #15 reamer, and none of the branches were larger than a #30 reamer. Although apical foramina located distal to the apex were observed in about 50% of the specimens, 83.6% of all apical foramina were within 0.5 mm of the apex, and 99.5% were within 1.0 mm. Data on the thickness of the root and main canal in the apical portion and curvature of the root canal suggest that for adequate apical preparation, a #40 reamer must be able to reach the apical constriction.

Introduction The existence of the apical constriction has been repeatedly questioned. The aim of the present study was to validate the existence of the apical constriction and determine its location and dimensions in molars by using substantial micro–computed tomography analysis. Methods: Ninety human molars with 271 canals were evaluated. Teeth with resorption, defects, or incomplete root formation as well as wisdom teeth were excluded. Patients' age was categorized into 3 groups. Teeth were scanned by micro–computed tomography with a resolution of 27 μm. Multi-threshold segmentation was performed to trace the canal outline in a total of 25,093 sections. In each cross section, 88 parameters, eg, area, circumference, and maximum and minimum diameter were recorded and analyzed. The apical constriction (AC) was defined to be the narrowest area extending along a distance of 0.1 mm or more at the apex. Size and form of the constriction were recorded as well as the distance to the apical foramen (AC-AF) and apex (AC-A). Results The mean distance of AC-AF was 0.2 mm (99% confidence interval, 0.15–0.24; range, 0–0.6 mm), and of AC-A it was 0.9 mm (99% confidence interval, 0.86–1.0; range, 0.1–1.7 mm). The type of canal had no influence on AC-AF and AC-A. In 76% of all canals the apical constriction was parallel. The mean size of constriction in molars was instrument size 30. Patients aged 30 or younger had significantly wider constrictions. Conclusions The apical constriction was found to be located at or close to the foramen. The most common form was the parallel form.

Two different electronic apex locators were used before extraction to determine working length in 116 root canals belonging to 34 molars. The results were then compared with postextraction working length measurements. The determinations were made before and after eliminating the canal contents and drying the interior. The results showed that 84.8% and 79.3% of the Odometer, and 89.6% and 88.7% of the Endocater readings for dry and nondry canals, respectively, occurred within the two 0.5-mm intervals closest to the apical constriction.

The purpose of this study was to relate the relationship of the apical constriction to the anatomical apex and to determine the ability of the Endocater (Hygenic Corp., Akron, OH), using commercially bonded coated probes to locate the position of the apical constriction, in permanent teeth that were intact and had not been subjected to previous endodontic manipulation. Using local anesthesia and rubber dam isolation, conventional access cavities were prepared at ultra high speed with water coolant in teeth treatment planned for extraction. The Endocater was used to determine the working length. The probes were sealed in place with autopolymerizing composite resin and the teeth extracted. The teeth were sectioned buccolingually, and the position of the probe in relation to the anatomical apex and apical constriction was measured with the use of an ocular microscope. In 17.1% of the canals, the probes bound in the coronal portion of the canals and would not reach the apical portion of the root. In those teeth in which the probes reached the apical portion of the root, the Endocater was able to locate the apical constriction within 0.5 mm in 93.4% of the canals.

Small-diameter hand files are systematically used to determine the initial working length and to establish patency of the root canal. In wide canals, electronic apex locator accuracy might be influenced by file size. This article reports on a study to assess the influence of apical constriction diameter on the precision of the Root ZX apex locator by using files of varying diameter on teeth with 3 different degrees of apical widening: 0.37, 0.62, and 1.02 mm. Ten extracted single-root teeth, stored in saline solution at 37 degrees C, were sectioned at the enamel-cement junction and embedded in an alginate mold. Initial working length (L0) was determined with a #10 Kerr file, and canals were irrigated with either 50% citric acid or 5.25% sodium hypochlorite. To assess the ability of the locator to identify the narrowest area of the root canal as constriction diameter increased, the canal was progressively widened by insertion of files of increasing diameter (10-100) at a point L0+1 mm. After each enlargement, the working length (L) was redetermined, with files from #10 (L10) up to the file used for widening. Comparison of statistical results was based on the difference between final working length and initial length (L10) for each apical width. Statistical analysis was carried out with analysis of variance test for comparison of means. Results showed that at apical constriction widths of 0.37 and 0.62 mm, there was no significant difference between initial working lengths as determined by a Kerr #10 file and final working lengths after widening with files of up to #60. In those teeth whose apical width had been increased to 1.02 mm, there was no statistically significant difference between initial and final working lengths as measured by files from #10-#25; however, significant differences were apparent between #10 and #30, #35, or #40 (P

In cases of disrupted apical constriction effort is made to create an apical stop and subsequently instrument and obturate the canal up to this point. The aim of this study was to in vitro evaluate the sealing ability of three root canal sealers used with the lateral compaction technique in teeth with enlarged constriction. Thirty-six single rooted premolars with straight canals were instrumented up to the apical constriction using a step-back technique. The constriction was enlarged and root canal instrumentation 1.5 mm short of the original working length was performed, to create a new apical stop. Teeth were obturated using lateral compaction technique with either Topseal, Roth 811, or Apexit. Teeth were subjected to area-metric analysis of dye penetration in transverse root sections, up to the most coronal extend of the dye. Sections were studied under the stereomicroscope, digital images were processed and leakage area was estimated. Statistical analysis was performed using Student’s t test and Wilcoxon matched-pairs signed-rank test. No gutta-percha was extruded into the space between the apical constriction and the new iatrogenically created constriction. Topseal showed statistical significant less leakage. No significant difference was found between Apexit and Roth 811 (t = 0.99; p = 0.75).

The efficacy of tactile detection of the apical constriction in flared and nonflared root canals was examined in 120 root canals of adult patients. In 68 nonflared (group 1) root canals, a #15 or #20 K-file was used to detect ("feel") the apical constriction. In 52 teeth (group 2), Hedstrom files, Gates Gliden drills #2 to #4, and ultrasonic files were used to enlarge the canal orifice and flare the coronal portion of the root canals before testing the apical constriction. After placing a #15 or #20 file in each root canal, a radiograph was taken, and the distance between the tip of the file and the radiographic apex was measured. The location of the file tip was classified into three categories: (a) within 1 mm short of the radiographic apex; (b) underextended, more than 1 mm short of the radiographic apex; and (c) overextended beyond the radiographic apex. In group 1 (nonflared), 32.3% of the root canals were classified in category a, as compared with 75.0% in group 2 (preflared). Over 26% of the root canals in group 1 and approximately 4% of the canals in group 2 were included in category b. Files inserted in preflared root canals had a significantly lower incidence of overextension than those placed in nonflared canals (21% versus 41%). The ability to determine the apical constriction by tactile sensation was significantly increased when the canals were preflared (p < 0.0001).

The purpose of this study was to compare the ability of radiographic and electronic methods to determine reliably the location of the apical constriction. The working length of root canals in human cadaver teeth was determined by positioning an endodontic file at the apical termination point as indicated by an apex locator. These same teeth were radiographed at various angles with the file in place. The radiographs were evaluated by five examiners to determine a radiographic termination point for each canal. Teeth were extracted and examined histologically to determine the ideal termination point. The deviations of the two experimental termination points from the ideal termination point were compared. The mean of the absolute value of the deviations from the apical constriction for the apex locator was significantly less (p0.05) than that for the radiographic method. Thus, the method using the apex locator was slightly more reliable.

The purpose of this study was to investigate anatomically the apical portion of the root canal of human maxillary anterior teeth. Thirty maxillary central incisors, 30 maxillary lateral incisors, and 30 maxillary cuspids were used. These were teeth from patients ranging in age from 11 to 73 yr. The root apex and main apical foramen coincided in 16.7% of central incisors and cuspids and in 6.7% of the lateral incisors. The labiolingual diameter of the root canal at the apical constriction of the central incisors, lateral incisors, and cuspids averaged 0.425 mm, 0.369mm, and 0.375 mm, respectively; and the respective vertical distances between apex and apical constriction were 0.863 mm, 0.825 mm, and 1.010 mm.

A new method for locating the apical constriction and foramen in vivo has been developed and tested on an in vitro model prepared with an extracted human tooth. The results indicate the feasibility of this method for clinical use. Comment: The device described permits length determination in an electrolyte-filled canal. The problem with such devices seems to be that prior to instrumentation (when length determination is usually desired), the exact degree and nature of canal hydration are unpredictable. After instrumentation, canals likely have to be open to at least a #35 instrument before a solution of any kind can be predictably delivered throughout the canal. This may be too large a size to take the apical several millimeters of a fine or tortuous canal. Nevertheless, the device seems an advance over previous electrical gadgets.

One of the authors (J. U.) previously reported a new method of making root canal measurements and described the equipment for doing this. The original report described tests on bovine and human teeth in vitro. The applicability of the voltage gradient method to human root canal measurement in vitro was reported. Clinical use of the method was tested, using human teeth in situ but scheduled for extraction for therapeutic reasons. The method is based on the principle that current density through an electrolyte-filled canal is highest at the narrowest point and minimum at the apical foramen. The data obtained from this clinical investigation demonstrated that the location of the apical constriction can be directly determined without concern for the tooth to tooth morphological variation of the distance of the constriction from the root apex.

A recently reported method for locating the apical constriction and foramen utilizes the principle that current density through the electrolyte-filled canal is highest at the narrowest point and the conformation of the electric field changes suddenly at the apical foramen. The reliability and safety of this method were determined using severed bovine mandibles and anesthetized dogs. In the animal models, it was found that this method is reasonably accurate and possesses a high degree of safety.

Extracted human maxillary and mandibular molars displaying curved roots and closed apices were used to determine the effect of orifice enlargement prior to biomechanical canal preparation. When this was accomplished, files could be passed more easily to the apex, indicating the elimination of interferences cervical to the apical constriction. The Peezo reamer was a more effective instrument for orifice enlargement than the Gates-Glidden drill.