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The purpose of this article is to present a simple and easy method for in vitro analysis of root canal instrumentation that permits one to observe and measure the diameter of a root before and after instrumentation, using the teeth themselves as control.
Furcation grooves on the palatal aspect of the buccal roots of 35 maxillary first premolars, randomly selected, were assessed and found to exist in 97% of the sample. The buccal roots were sectioned into slices, 1 mm thick, and morphometric horizontal and vertical measurements were taken by a Toolmaker Microscope. The slice with the deepest invaginations served as the reference plane. The deepest invaginations were found to be at a mean distance of 1.18 mm from the bifurcation, with a mean depth of 0.4 mm. The canal had a kidney-shaped appearance in cross-section, and the mean distance from the invagination to the canal wall was 0.81 mm. It is thus hazardous to use rotary instruments for flaring these roots and any circular-shaped post space preparation at this level is contraindicated. The outcome of such procedures might be root thinning, perforation, or vertical root fracture, thus causing a poor prognosis.
The purpose of this study was to determine the effect of using electronic apex locators on the number of radiographs taken and the adequacy in length of the final obturation. Patients in an undergraduate student endodontics clinic participated in the study. The working length (WL) was estimated by the authors for all cases (36 teeth; 58 canals), using both a preoperative standardized radiograph and an electronic measurement. The students were then asked to place WL files to one of the estimates (electronic or radiographic; chosen by random assignment) and take a WL radiograph. Neither the students nor their instructors knew which method was chosen for the estimates. Once treatment was completed, the total number of working radiographs was counted. The number of cases with acceptable (0 to 2 mm short of the apex) or unacceptable obturation was also blindly registered. An electronic estimate of the WL improved length quality of the final obturation, compared with a radiographic estimate. The number of working radiographs taken was less in the electronic apex locator group in anterior and premolar teeth, but not in molars.
The purpose of this study was to evaluate the accuracy of the Root ZX in vitro in the presence of a variety of endodontic irrigants. The in vitro model, described by Donnelly, consisted of refrigerated gelatin made with 0.9% sodium chloride instead of water. The following irrigants were tested: 2% lidocaine with 1:100,000 epinephrine, 5.25% sodium hypochlorite, RC Prep, liquid EDTA, 3% hydrogen peroxide, and Peridex. A total of 30 extracted, single-rooted teeth were used. The experimental measurements in the presence of the various irrigants were compared with the actual canal lengths. The present data indicate that the Root ZX electronic apex locator reliably measured canal lengths to within 0.31 mm and that there was virtually no difference in the length determination as a function of the seven irrigants used. These results strongly support the concept that the Root ZX is a useful, versatile, and accurate device for the determination of canal lengths over a wide range of irrigants commonly used in the practice of endodontics.
A minimum thickness of 1 mm has been suggested for the residual root wall in post preparation. The objective of this paper is to evaluate the reliability of radiography when used to measure root thickness. In 106 upper first premolars with one and two root canals, post preparations were made with Peeso reamers to a depth in the root equal to the crown length. Bucco-palatal radiographs were taken of each tooth. The films were processed and projected with a magnification of x20. The smallest thickness of the mesial and distal walls of each root at the apical end of the preparation was measured and recorded. The teeth were then cut at the level of the measurement, and the smallest thickness of the proximal walls was measured using a microscope with a micrometric eyepiece. Fourteen percent of the teeth with one root canal and 27% of the teeth with two root canals could not be measured due to blurred radiographic contours. Variance analysis showed a highly significant difference (p < 0.001) when radiographic and anatomical measurements were compared. The radiograph showed greater thicknesses than were actually present and should not therefore be considered to be a reliable method for measuring residual thickness of tooth walls after post preparation.
This in vitro study investigated the prevalence, location, and pathway of the second mesiobuccal canal (MB-2) in 45 first and second maxillary molars using the operating microscope (OM). Initially location and negotiation of MB-2 were attempted without magnification. Teeth in which MB-2 was not located or could not be negotiated were further explored under OM. Roots where MB-2 could not be negotiated even with OM were cross-sectioned and inspected microscopically. Morphometric measurements were performed to map the location of MB-2. Without magnification an apparent MB-2 orifice was located in 42 teeth and the canal negotiated in 31 (69%). With OM one additional apparent MB-2 orifice was located, and five previously identified canals were negotiated (total 80%). The root cross-sections confirmed the absence of MB-2 in all nine teeth where it was not negotiated. Location of MB-2 varied randomly. In conclusion MB-2 can be negotiated in 80% of maxillary molars, although an orifice is apparent in 96% of the teeth. Ability to negotiate MB-2 is facilitated by OM.
The purpose of this study was to compare the influence of the root canal status on the determination of the root canal length by an electronic apex locator in vital and necrotic canals and canals with root canal filling retrieval. One hundred seven teeth with a total of 171 canals with various contents (105 vital pulp, 47 necrotic pulp, and 19 retrieval of root canal filling materials) were measured for root canal length in vivo with the AFA Apex Finder. The distance between the file tip and the radiographic apex was also determined on radiographs. In 86% of the evaluated roots, the file tip position as indicated by the Apex Finder was located within 0.5 mm of a point 1.0-mm short of the radiographic apex. The Apex Finder showed higher accuracy for determining the apical constriction in vital canals (93.9%) than in necrotic canals (76.6%), and this difference was statistically significant (p < or = 0.05). The Apex Finder indicated the point -1 mm +/- 0.5 mm in canals with retrieval of root canal filling materials in 68.4% of these cases, but because of the small number of retrieval cases, this is not comparable statistically with vital and necrotic cases. The authors concluded that the AFA Apex Finder is highly accurate in vital canals.
The aim of this in vitro study was to evaluate the ability of the Root ZX device to avoid instrumentation beyond the apical foramen in premolars after conventional working length radiography. Thirty extracted premolars with 43 root canals were subjected to radiographic and electronic working length determination. Radiographic working length determination resulted in overestimation in 51% of the root canals, although the measuring file tip was located to be 0 to 2 mm short of the radiographic apex. Electronic working length measurements with the Root ZX reduced the percentage of overestimation to 21%. In 6 root canals (14%), both radiographic and electronic working length measurements led to overestimation. It is concluded that complementing radiographic working length determination with electronic apex locator measurements may help to avoid overestimation beyond the apical foramen in premolars.
This study aimed to evaluate Root ZX accuracy with different NaOCl concentrations and to observe effects of the alginate model when NaOCl was used in the canal during electronic measurements. Fifty extracted single-rooted, single-canal human teeth were used in five experimental groups. NaOCl concentrations of 5.25%, 2.65%, 1.00%, and 0.50%, respectively, were injected into the root canals of teeth in four groups and distilled water in control group 5. After measuring root lengths with Root ZX, the files were locked in place. There were no statistically significant differences among all the groups (p > 0.95) when evaluating the distance of the file tips and apical constriction or for the distance from file tip to apical foramen. Root ZX could be used in root canal length measurements with various NaOCl concentrations. Designation of apical constriction needs more care. The alginate model could be used for in vitro electronic measurements with various NaOCl concentrations.
Canal curvatures of 700 permanent human teeth were determined by measuring the angle and the radius of the curvatures and the length of the curved part of the canal. For each type of tooth (except third molars) 50 were selected at random and were investigated. Size 08 silver points were inserted into the canals, and the teeth were radiographed from a facial and proximal view by using a standardized technique. All radiographs were analyzed by a computerized digital image processing system. Of the 1163 root canals examined, 980 (84%) were curved and 65% showed an angle < or = 27 degrees with radii < 40 mm. Thirteen percent displayed angles between 27 degrees and 35 degrees with radii not greater than 15 mm, and 9% of all canals that were investigated had curves > 35 degrees with the greatest radius of 13 mm. The greatest angle of all the teeth was 75 degrees with a radius of 2 mm. To define the canal curvature mathematically and unambiguously, the angle, the radius, and the length of the curve should be given.
This in vitro investigation examined pre- and postinstrumentation working length (WL) measurements in curved root canals. The conditions compared were combinations of (a) stainless steel hand files + Gates Glidden drills (SS) versus nickel-titanium rotary files (Ni-Ti); and (b) early coronal flaring (flaring completed before WL determination) versus late coronal flaring (flaring completed after WL determination). Coronal flaring was accomplished for the SS group using Gates Glidden drills and for the Ni-Ti group using rotary Ni-Ti files (n = 15/group). WL was determined before coronal flaring, immediately after coronal flaring, and again after canal preparation. Results indicated that WL decreased for all canals as a result of canal preparation. The mean decrease in WL was significantly greater for the SS group (-0.48 mm +/- 0.32) than for the Ni-Ti group (-0.22 mm +/- 0.26). Less change in WL occurred in both groups when initial WL was determined after coronal flaring (SS: -0.12 mm +/- 0.13, Ni-Ti: -0.14 mm +/- 0.25).
The purpose of this in vitro study was to evaluate the accuracy of Root ZX apex locator to determine the working length in teeth with simulated apical root resorption. Fifty extracted, single-rooted, human teeth with mature apices were used in this study. An irregular cavity defect was drilled at the apex of each tooth simulating an apical root resorption. Three operators used the Root ZX to measure the working lengths, comparing the electronic readings with the direct visual measurements. The Root ZX was 62.7%, 94.0%, and 100.0% accurate to within 0.5 mm, 1 mm, and 1.5 mm of the direct visual measurements, respectively. Statistically significant differences were observed between operator A and B and A and C (p < 0.01), but no significant differences were detected between operator B and C (p > 0.01).
The object of this study was to determine if canal length is altered as a result of straight-line access (SLA) and coronal flaring (CF). Selected were 86 canals of extracted molars and premolars from two groups: straight or severely curved (Schneider curvature <5 degrees and >20 degrees). The reference cusp tip and root-end were flattened to produce reproducible measurements. A #10 file was placed such that the tip extended slightly beyond the apex, with the handle on the referenced cusp. The amount of file protrusion was measured with a stereomicroscope. Then, SLA and CF were performed and the corresponding file replaced to the same coronal reference position. Apical file protrusion was measured again. The change in canal length was determined by the difference in the pre- and post-SLA/CF measurements. A Wilcoxon signed rank test statistically verified that there was a measurable, significant (p < 0.001) change in canal length after SLA and CF. The mean change overall was slight, with a decrease of 0.17 mm. Severe curvature had a slightly greater, significant effect on the amount of change. Tooth type had no significant effect. Changes in working length from SLA and CF, although statistically significant, were very small and clinically unimportant.
The objective of this study was to investigate whether the use of an electronic apex locator results in a reduction in X-ray exposure during endodontic therapy. Fifty, sound, extracted, single-rooted canine and incisor teeth were selected and randomly divided into two groups (A and B) of 25 teeth. The working length was determined radiographically with (group B) and without (group A) adjunctive use of an apex locator by one operator. After working length determination, the teeth were sectioned and the actual working length measured for comparison. For group A, 14 retake radiographs were required to determine the working length, whereas group B required no retake radiographs; this difference was highly significant (p < 0.001). The electronic apex locator was extremely accurate in locating the apical foramen with all teeth tested within 0.5 mm of the anatomical apex and 11 (44%) teeth at the apical foramen. In contrast, 15 (60%) teeth tested using radiographs alone were within 0.5 mm of the anatomical apex and only 4 (16%) teeth were actually at the anatomical apex. It was concluded that using an electronic apex locator as an aid to endodontic therapy could potentially reduce the number of diagnostic radiographs required for working length determination. Location of the apical foramen using a combination of an electronic apex locator and radiographs to determine working length is more accurate than using radiographs alone.
A new circuit was designed to automatically compensate for measurement errors of an electronic apex locator in various electrolytes. Thirty-one root canals were clinically tested for accuracy. A file was inserted into the canal until the apex signal was obtained, at which point the file was immobilized with glass-ionomer cement. After extraction, the apical area was exposed and the position of the file tip was examined under an operating microscope. Distances from the major foramen and cemento dentinal junction (CDJ) were recorded. The average distance from the major foramen was -0.13 mm with a range of -1.28 mm and +0.46 mm. The average distance in 26 detectable CDJ samples was +0.18 mm with a range of -0.98 mm and +0.65 mm. The measurements, which were within +/- 0.5 mm, were 94% (29/31) from the major foramen and 92% (24/26) from the CDJ. Measurement consistencies within one SD were 81% for the major foramen and 65% for the CDJ, respectively. Measurements within two SD were 97% for the major foramen and 92% for the CDJ. There were no differences between the smaller (< # 25) and larger apical foramens (< or = 25) or vital and nonvital pulps.
The purpose of this study was to assess the effects of five electronic apex locators on pacemaker function in vitro. A Biotronik Actros DR+ pacemaker was evaluated at maximum sensitivity on a flat bench top. The pacemaker lead, electronic apex locator, and oscilloscope were connected across a 150-ohm resistor. Pace monitoring was carried out with a Biotronik EPR 1000 programmer and a Tektronix TDS 220 2-channel digital real-time oscilloscope. Four of five electronic apex locators tested did not cause inhibition or interfere with normal pacemaker function. It seems that electronic apex locators can be used safely in patients with pacemakers.
The purpose of this study was to determine if a buccal curvature in the palatal roots of maxillary molars affected the clinician's ability to accurately determine working length. Twenty-seven extracted, human maxillary molars were sorted by palatal root curvatures as J- and C-type, and the angle of curvature was determined. Straight-line access was made and a #20 file was placed into the canal until the tip was visible at the apical foramen then withdrawn. The file, tooth, and calibration wire were radiographed on one image using the RadioVisioGraphy system. Actual (file) and radiographic (tooth) lengths were determined using the RadioVisioGraphy ruler. Radiographic length appeared shorter on average than the actual length. Canal curvatures larger than 25 degrees had differences greater than 0.5 mm. This represents a statistically significant difference between the actual and radiographic lengths as the degree of curvature increases. There was no significant difference between the J- and C- types.
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.