Radiographic reproduction of endodontic "working length" comparing the paralleling and the bisecting-angle techniques

Evaluation of changes in root canal length and accuracy of the electronic apex locator during different stages of endodontic treatment and retreatment

This study evaluated changes in the root canal length (RCL) and the accuracy of the electronic apex locator (EAL) during the different stages of endodontic treatment and retreatment. Fifty-six mesial root canals of mandibular molars were selected. The actual root canal length (AL) of the canals was obtained by inserting a size 15 hand file up to the apical foramen, under magnification. The electronic lengths were obtained at the "APEX" mark of Root ZX II, using an alginate model. Both measurements were performed at three different stages of the initial root canal treatment-unflared, flared, and concluded-and at two stages of retreatment, after achieving patency and repreparation. Data were statistically analyzed and the significance level established was 5%. All stages produced a significant reduction in the AL (p < 0.05). The greatest variation was observed between the unflared-flared stages (0.2 mm) and between concluded-patency stages (0.09 mm), with no difference between them (p > 0.05). The accuracy of Root ZX II was negatively affected after achieving patency, presenting statistically significant difference compared to the other stages (p < 0.05). A significant reduction in the RCL was observed along the different stages of endodontic treatment and retreatment. The EAL was accurate to measure the root canals in most stages, except after achieving patency for endodontic retreatment. Determining and monitoring the RCL is an essential step towards a favorable prognosis, since it reduced along the different stages evaluated. Root ZX II was not accurate for endodontic retreatment.

Evaluation of Different Techniques of Working Length Determination in Comparison with CBCT

AIM

To estimate the working length of teeth using conventional tactile technique, radiovisiography technique, Apex locator, and confirmation of working length by cone beam computed tomography technique.

MATERIALS AND METHODS

Forty patients with the age group between 20 and 50 years with irreversible pulpitis were included in this study. After taking a preoperative radiograph, the procedure was started. The cavity wall buildup was done using composite in the cases needed and then rubber dam application was done. The working length of mesiobuccal and mesiolingual canal was taken using cone beam computed tomography and this was considered as the standard value. Then using tactile method, length of the canal was measured using radiovisiographic software followed by apexlocator.

RESULT

The Apex locator has showed best result as compared to tactile and radiovisiography.

CONCLUSION

Apex locator values were closest to cone beam computed tomography working length measurement values and electronic apexlocator can be used efficiently as an alternative method for working length determination. The quality of various techniques according to ranks of working length determination was found to be Cone beam computed tomography (CBCT) > Apexloc > Radiovisiography (RVG) > Tactile. Thus, Apex locator can be used as an alternative to cone beam computed tomography for working length determination.

The Performance of Paralleling Technique and Bisecting Angle Technique for Taking Periapical Radiographs: A Systematic Review

Periapical radiography is a routine radiographic procedure performed by dentists on a daily basis. It can be taken with two techniques, the paralleling technique (P tech) and the bisecting angle technique (B tech). This systematic review aimed to identify the relevant literature, compare the use of P and B techs across various dental specialties, and determine the most appropriate technique to be used for different purposes in taking periapical radiographs. In January 2023, we searched PubMed, Web of Science, Scopus, and Google Scholar to identify the studies that compared the two radiographic techniques. The search string was: (paralleling AND ("bisecting angle" OR "bisected angle")). Manual reference tracing was also performed to identify the studies potentially missed. After screening, 26 studies were included for the qualitative review. The 26 included studies were published between 1976 and 2021. Ten of the studies were about general dentistry (dental radiology in general applications), whereas another ten studies were related to endodontics, such as working length estimation. Most studies advocated the use of the P tech for general, endodontics, implantology, and other indications. B tech was advocated for patients with a low palatal height. More future studies are needed to evaluate their performance in different scenarios with standardized equipment and radiographic positioning.

Preoperative Estimation of Endodontic Working Length with Cone-Beam Computed Tomography and Standardized Paralleling Technique in comparison to Its Real Length

An accurate estimation of the working canal length is essential for successful root canal treatment. This study is aimed at investigating the diagnostic accuracy of root canal length estimation on cone-beam computed tomography (CBCT) scans and digital paralleling radiographs (PAs), using the real canal length as a gold standard, and at evaluating the influence of canal curvature on this estimation. Sixty extracted human premolar teeth were selected for this study. Root canal length measurement was performed on CBCT scans (NewTom, Giano, Verona, Italy) and digital paralleling radiography (EzRay Air W; Vatech, Korea). The real working length was established by subtracting 0.5 mm from the actual canal length. No significant difference was found between CBCT and digital paralleling radiography. There was a tendency for underestimation of the root canal length measured on the CBCT images in 52 (86.7%) of the examined teeth and overestimation in 5 teeth (8.3%). All the digital radiographs slightly overestimated the real canal length. The analysis revealed a strong correlation between the estimation from moderate to severe curvature for digital radiography and CBCT images. Preoperative working length estimation can be made closest to its real clinical canal length on the standardized paralleling technique, using a long (16-inch) target-receptor distance.

Applying the paralleling technique in intraoral periapical radiographs for Japanese patients by analyzing CT images

OBJECTIVES

The aim of this study was to investigate the size of the teeth and palatal heights to determine if it is possible to apply the paralleling technique in the upper molar region in Japanese patients.

METHODS

The medical computed tomography (CT) data of ten patients were analyzed. A minimum intensity projection image with 8-mm slice thickness was created for each second premolar, first molar, and second molar tooth. We traced the tooth, the alveolar bone, the plate bone surface, and the cheek skin surface on a tracing paper. Tooth length (TL), palatal height (PH), distance between a tip of the cheek and each tooth (D1), and distance between each tooth and the receptor (D2) were measured. The measurements were performed by two observers, and the measurements were repeated twice by each observer. Two potential situations were considered for application of the paralleling technique.

RESULTS

We analyzed whether there was a possibility for application of the paralleling technique comparing the TL and the PH for each case by considering the magnification rate calculated from D1 and D2, the palatal mucosa thickness, and the safety margin within the resultant image. The data suggested that applying the paralleling technique was impossible in 95% of cases. In the cases where application of the paralleling technique was impossible, the incident angle of X-ray increased by 31.6°.

CONCLUSIONS

We concluded that the paralleling technique could not be applied in Japanese patients due to insufficient space for the image receptor in the upper maxilla region.

A clinical evaluation of two electronic apex locators and conventional radiography in working length determination in primary molar and its influence on children's behavioral responses

BACKGROUND

Accurate root canal length determination, simplicity of the procedure, and patient's cooperation are important determinants in the success of endodontic treatment in primary teeth.

AIM

The aim of the study was to clinically compare the accuracy of Propex Pixi and Formatron D10 apex locators with conventional radiography in determining working length in mandibular primary second molars with and without varying degrees of physiological root resorption.

DESIGN

A nonrandomized clinical trial was conducted in 115 mandibular primary second molars indicated for pulpectomy in 90 pediatric dental patients. A single calibrated examiner determined the working length by conventional radiographic method and electronic apex locator (EAL) methods in a total of 376 canals. Behavior of the children during execution of each method in each tooth was recorded using the Frankl's behavior rating scale. The data obtained were tabulated and subjected to statistical analysis.

RESULTS

Significant correlation (intraclass correlation = 0.80 and 0.81, P < 0.001) could be detected between working length measurements obtained using Propex Pixi and Formatron D10 and measurements obtained using conventional radiography. Higher percentage of negative behaviors (negative and definitely negative) was observed during the conventional radiographic method (68.6%) as opposed to the Propex Pixi (16.5%) and Formatron D10 (20.8%) methods.

CONCLUSIONS

Both the apex locators were as accurate as conventional radiography in determining working length in primary teeth; Formatron D10 being more accurate than Propex Pixi. The EALs were far better accepted by children than conventional radiography.

Apicoectomy on an Incisor Tooth of a Victorian Koala (Phascolarctos cinereus victor)

An eight year old Victoran Koala was presented with a discharging mandibular sinus of at least one month duration. On examination, a dental abscess of the right mandibular incisor tooth was found. During the course of endodontic treatment, a size 2 Gates Glidden bur separated from the shank and was lodged in the canal. Due to the anatomy of the tooth the bur could not be removed and an apicoectomy was performed. Following the apicoectomy (follow-up period two years), the periapical pathology resolved.

Comparison of three different apex locators in determining the working length of mandibular first molar teeth with irreversible pulpitis compared with an intraoral periapical radiograph: A block randomized, controlled, clinical trial

AIM

The aim of the present study was to assess the clinical accuracy APEX and 0.5 marks of three different apex locators - iPex II, Root ZX, and Apex ID - before and after canal preparation in the mandibular first molar.

METHODS

Sixty patients between the ages of 13-60 years participated in the study. After access gaining and canal preparation stages files were inserted with the apex locator clip attached until the electronic apex locators (EALs) shows readings of APEX and 0.5 marks and same is confirmed with periapical radiographs. Eighteen apex locator readings were recorded from each tooth, and 1080 readings were obtained from the 60 patients.

RESULTS

Differences among readings from apex locators and radiographic readings were assessed using paired t test. Only in two patients (1 male and 1 female) were the APEX mark readings different from the radiograph estimation. When the 0.5 mark readings of three different EALs were compared with each other, we could observe that the readings from Root ZX differed significantly (P < 0.05).

CONCLUSIONS

In the present study, we observed the negligible differences in readings between the EAL at the APEX mark readings, coinciding with the radiographic observation. Clinically, we recommend the apical foramen be located with the apex locators' APEX mark readings prior to identifying the apical constriction position.

Premature exposure of dental implant cover screws. A retrospective evaluation of risk factors and influence on marginal peri-implant bone level changes

OBJECTIVES

The objectives of this study were to identify risk factors associated with the premature cover screw exposure (pCSE) at dental implants and to evaluate the influence of a pCSE on peri-implant marginal bone level (MBL) change compared to non-exposed implants.

MATERIALS AND METHODS

Retrospective data assessment from 165 patients (mean age = 54.0 ± 14.4 years) who received 395 submerged implants included demographic, health-related, and therapeutic variables which were analyzed for their respective impact. MBL change was detected at digital radiographs obtained from first- and second-stage surgeries.

RESULTS

pCSE were detected in 43 patients (26.1%) and 53 implants (13.4%). An increased frequency of exposure was significantly associated with (I) male gender (p = 0.012) at patient level and (II) the posterior region of the jaws (p = 0.005), implant systems with platform-matching cover screws, and a vertical distance of ≥0.5 mm between bone crest and the implant platform (both p < 0.001) at implant level. The decrease in mesial, distal, and total MBL differed significantly (mean total = 0.8 ± 0.7 vs. 0.3 ± 0.5; mean mesial = 0.8 ± 0.8 vs. 0.3 ± 0.6; mean distal = 0.8 ± 0.8 vs. 0.3 ± 0.6 mm; p < 0.001) between non-exposed and pCSE implants.

CONCLUSIONS

Male patients, implants with platform-matched cover screws, or when placed supracrestally or in posterior sites revealed significantly more pCSE, resulting in significantly decreased peri-implant MBL compared with non-exposed implants.

CLINICAL RELEVANCE

Patients with an enhanced risk of pCSE should follow frequent regular recalls during the healing period to enable for early diagnosis and intervention.

An ex vivo comparison of working length determination by three electronic root canal length measurement devices integrated into endodontic rotary motors

AIM

The objective of this study was to compare the accuracy of working length (WL) determination by X-Smart Dual, ENDOAce, and Gold Reciproc motor, in manual mode and mechanical preparation set to auto apical reverse (AAR) mode.

MATERIALS AND METHODS

Forty-five anterior teeth were included in the study. The canal length was determined by introducing #10 file into the canal until it emerged at the apical foramen. The incisal edges were adjusted to obtain 18 mm standard length. The teeth were embedded in Plexiglas tubes, filled with alginate, and measured in manual and AAR modes.

RESULTS

Within and between the groups, there was no significant difference in WL measurements, both in manual and AAR modes. In the X-Smart Dual group, all manual measurements were within root canal limits, while 13 % of AAR mode measurements were recorded when the file tip passed the apical foramen. In the ENDOAce group, 13 and 7 % of the measurements, in manual and AAR modes respectively, were recorded when the file tip passed the foramen. In the Gold Reciproc motor group, 27 and 33 % of the measurements, in manual and AAR modes respectively, were recorded when the file tip passed the foramen.

CONCLUSION

With the limitation of this ex vivo study, the tested devices presented no significant differences in length measurements and were within the clinical accepted margin of error.

CLINICAL RELEVANCE

Mechanical preparation must be confined to the root canal system. The adverse results of overinstrumentation emphasize the need to reconsider the ±0.50 mm margin of error that is clinically acceptable for WL measurements.

Femoral imaging artifacts associated with dorsal recumbency craniocaudal radiographic positioning. Description of a modified bisecting angle technique

OBJECTIVES

To describe the radiographic length distortion associated with femoral tilt during cranio-caudal positioning. To describe a modified bisecting angle technique to alleviate image foreshortening.

METHODS

Five pairs of femurs were imaged. The femurs were tilted from 0 to 50 degrees and the X-ray anode was tilted from 0 to 40 degrees. Femoral length was measured on the resulting images. A geometric model depicting sagittal femoral positioning was described with two trigonometric formulas. Trigonometric formula 1 (TF¹) was designed to predict apparent femoral length. Data generated by TF¹ were compared to the cadaveric study results. Trigonometric formula 2 (TF²), based on the same model, was used to predict the ideal anode angle (iAA) to alleviate foreshortening. Unrelated to the model, a simplified linear formula (SF) was created to approximate the TF². Data generated with the SF and the TF² were compared.

RESULTS

When the femoral specimens were tilted to 20 degrees or greater, significant foreshortening was appreciated (p <0.001). Increasing the anode angle increased apparent length, eliminating foreshortening. Data generated by the TF¹ agreed closely with the results of the cadaveric study (R² = 0.999). The SF and the TF² demonstrated close agreement and were able to predict an iAA consistent with the results of the cadaveric study.

CLINICAL SIGNIFICANCE

A femoral tilt of 20 degrees or greater results in significant image foreshortening and may warrant alternate radiographic techniques. If the femur is tilted, adjusting the anode angle can alleviate femoral foreshortening.

Clinical efficacy of electronic apex locators: systematic review

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.

A comparative assessment of the accuracy of electronic apex locator (Root ZX) in the presence of commonly used irrigating solutions

Objectives: This study aimed to evaluate the accuracy of Root ZX in determining working length in presence of normal saline, 0.2% chlorhexidine and 2.5% of sodium hypochlorite. Material and Methods: Sixty extracted, single rooted, single canal human teeth were used. Teeth were decoronated at CEJ and actual canal length determined. Then working length measurements were obtained with Root ZX in presence of normal saline 0.9%, 0.2% chlorhexidine and 2.5% NaOCl. The working length obtained with Root ZX were compared with actual canal length and subjected to statistical analysis. Results: No statistical significant difference was found between actual canal length and Root ZX measurements in presence of normal saline and 0.2% chlorhexidine. Highly statistical difference was found between actual canal length and Root ZX measurements in presence of 2.5% of NaOCl, however all the measurements were within the clinically acceptable range of ±0.5mm. Conclusion: The accuracy of EL measurement of Root ZX within±0.5 mm of AL was consistently high in the presence of 0.2% chlorhexidine, normal saline and 2.5% sodium hypochlorite. Clinical significance: This study signifies the efficacy of ROOT ZX (Third generation apex locator) as a dependable aid in endodontic working length.

Key words:Electronic apex locator, working length, root ZX accuracy, intracanal irrigating solutions.

The reliability of artificial neural network in locating minor apical foramen: a cadaver study

INTRODUCTION

The purpose of this study was to evaluate the accuracy of the artificial neural network (ANN) in a human cadaver model in an attempt to simulate the clinical situation of working length determination.

METHODS

Fifty single-rooted teeth were selected from 19 male cadavers ranging in age from 49-73 years. Access cavities were prepared, a file was placed in the canals, and the working length was confirmed radiographically by endodontists. The location of the file in relation to the minor apical foramen was categorized as long, short, and exact by the ANN, by endodontists before extraction, and stereomicroscopically after extraction. The results were compared by using Friedman and Wilcoxon tests. The significance level was set at P <.05.

RESULTS

The Friedman test revealed a significant difference among groups (P < .001). There were significant differences between data obtained from endodontists and ANN (P = .001) and data obtained from endodontists and real measurements by stereomicroscope after extraction (P < .002). The correct assessment by the endodontists was accurate in 76% of the teeth. ANN determined the anatomic position correctly 96% of the time. The confidence interval for the correct result was 64.16-87.84 for endodontists and 90.57-101.43 for ANN.

CONCLUSIONS

ANN was more accurate than endodontists' determinations when compared with real working length measurements by using the stereomicroscope as a gold standard after tooth extraction. The artificial neural network is an accurate method for determining the working length.

Cone beam computed tomography in endodontics

Cone beam computed tomography (CBCT) is a contemporary, radiological imaging system designed specifically for use on the maxillo-facial skeleton. The system overcomes many of the limitations of conventional radiography by producing undistorted, three-dimensional images of the area under examination. These properties make this form of imaging particularly suitable for use in endodontics. The clinician can obtain an enhanced appreciation of the anatomy being assessed, leading to an improvement in the detection of endodontic disease and resulting in more effective treatment planning. In addition, CBCT operates with a significantly lower effective radiation dose when compared with conventional computed tomography (CT). The purpose of this paper is to review the current literature relating to the limitations and potential applications of CBCT in endodontic practice.

A new approach for locating the minor apical foramen using an artificial neural network

AIM

To develop a new approach for locating the minor apical foramen (AF) using feature-extracting procedures from radiographs and then processing data using an artificial neural network (ANN) as a decision-making system.

METHODOLOGY

Fifty straight single-rooted teeth were selected and placed in a socket within the alveolar bone of a dried skull. Access cavities were prepared and a file was place in the canals to determine the working length. A radiograph was taken to evaluate the location of the file in relation to the minor foramen and further checked after retrieving the tooth from the alveolar socket. The location of the file tip was categorized into: beyond the AF (long), within the root canal (short) and just at the minor AF (exact). Each radiograph was used to extract relevant features using K-means, Otsu method and Wavelet protocol. Thirty-six extracted features were used for training and the rest were used for evaluating the multi-layer Perceptron ANN model.

RESULTS

Analysis of the images from radiographs (test samples) by ANN showed that in 93% of the samples, the location of the AF had been determined correctly by false rejection and acceptation error methods.

CONCLUSION

Artificial neural networks can act as a second opinion to locate the AF on radiographs to enhance the accuracy of working length determination by radiography. In addition, ANN can function as a decision-making system in various similar clinical situations.

Direct digital radiography versus conventional radiography for estimation of canal length in curved canals

Purpose

The purpose of this study was to compare the conventional and digital radiography in the estimation of working length in mandibular molars.

Materials and Methods

Sixty molar teeth were selected and divided into three groups in the basis of canal curves (0-15°, 15-30°, >30°). After the placement of a 15 K-file, radiographs were taken with a conventional film (F-speed) and a digital sensor. Canal lengths were measured in these images by two observers. Statistical analysis was performed with repeated measures of ANOVA and paired sample t-test with 95% confidence.

Results

There was a high inter-observer agreement on the measurements of working length in conventional and digital radiographs. There was no significant difference between the mean values of measurements in conventional and digital radiography. Moreover, there was no significant difference between conventional and digital radiography with the actual values in the basis of canal curves.

Conclusion

The accuracy of conventional and digital radiography in the determination of the working length was in an acceptable range.

A comparative study of three periapical radiographic techniques for endodontic working length estimation

AIM

To compare the diagnostic quality of endodontic working length estimation films produced using film holders with those taken using the bisecting angle technique and to assess the level of acceptance of film holders by operator and patient.

METHODOLOGY

Five post-graduate and 20 final year undergraduate students attending a UK Dental School produced working length radiographs using either the paralleling or the bisecting angle technique. The paralleling group used one of two film holders, the Endoray II or the XCP Endodontic Instrument, on alternate patients. An assessment of the ease of use of the device and the patients' views on the comfort of the examination were recorded. Each radiograph was examined simultaneously by two assessors, scored for film faults and diagnostic acceptability. Statistical data was derived using the Mann-Whitney U test and Cohen's kappa.

RESULTS

The rates of unacceptable radiographs for the XCP Endodontic Instrument, Endoray II and the bisecting angle techniques were 12.2%, 21.4% and 48.6%, respectively. The combined percentage of unacceptable paralleling technique films (16.7%) was highly significantly different (P < 0.001) when compared with the bisecting angle technique (48.6%). The paralleling technique produced a significant reduction in incorrect vertical angulation (P < 0.001), cone cutting (P < 0.001) and incorrect film placement (P < 0.001). Film holders were rated either excellent or good in 90% of examinations by operators and 47.5% of patients reported no discomfort.

CONCLUSIONS

These results support the use of the film holders for endodontic working length estimation.

The fundamental operating principles of electronic root canal length measurement devices

It is generally accepted that root canal treatment procedures should be confined within the root canal system. To achieve this objective the canal terminus must be detected accurately during canal preparation and precise control of working length during the process must be maintained. Several techniques have been used for determining the apical canal terminus including electronic methods. However, the fundamental electronic operating principles and classification of the electronic devices used in this method are often unknown and a matter of controversy. The basic assumption with all electronic length measuring devices is that human tissues have certain characteristics that can be modelled by a combination of electrical components. Therefore, by measuring the electrical properties of the model, such as resistance and impedance, it should be possible to detect the canal terminus. The root canal system is surrounded by dentine and cementum that are insulators to electrical current. At the minor apical foramen, however, there is a small hole in which conductive materials within the canal space (tissue, fluid) are electrically connected to the periodontal ligament that is itself a conductor of electric current. Thus, dentine, along with tissue and fluid inside the canal, forms a resistor, the value of which depends on their dimensions, and their inherent resistivity. When an endodontic file penetrates inside the canal and approaches the minor apical foramen, the resistance between the endodontic file and the foramen decreases, because the effective length of the resistive material (dentine, tissue, fluid) decreases. As well as resistive properties, the structure of the tooth root has capacitive characteristics. Therefore, various electronic methods have been developed that use a variety of other principles to detect the canal terminus. Whilst the simplest devices measure resistance, other devices measure impedance using either high frequency, two frequencies, or multiple frequencies. In addition, some systems use low frequency oscillation and/or a voltage gradient method to detect the canal terminus. The aim of this review was to clarify the fundamental operating principles of the different types of electronic systems that claim to measure canal length.

Accuracy of electronic apex locators in comparison to actual length—an in vivo study

OBJECTIVES

The measurement precision of four electronic apex locators (Root ZX, Morita, Tokyo, Japan; Endy, Loser, Leverkusen, Germany; Justy II, Hager-Werken, Duisburg, Germany; Endox Lysis, Milan, Italy) was examined in the present in vivo study.

METHODS

The root canal length of 40 single-rooted and multi-rooted teeth was determined with the four devices prior to tooth extraction. To determine the actual root canal length, the apical third was longitudinally sectioned, the root canal instrument was positioned and the apex was examined using a microscope.

RESULTS

The average measurement deviation (+/-SD) in relation to the apical constriction was 0.3 mm (+/-0.6) for the Root ZX, 0.7 mm (+/-1.0) for the Endy, 0.2 mm (+/-0.7) for the Justy II and 1.3 mm (+/-1.7) for the Endox. The limit of +/-0.5 mm from the apical constriction was attained by the Root ZX in 78%, by the Endy in 67%, by the Justy II in 80% and by Endox in 31% of all measurements.

CONCLUSIONS

The latest generation of apex locaters provide the clinician with an accurate and useful adjunct for the determination of root canal length.

Difference in root canal length between Asians and Caucasians

AIM

To investigate whether there is a racial difference in canal length between the Asians and Caucasians.

METHODOLOGY

Five hundred and fifteen Asian patients who had received root canal treatment at the Yonsei University Hospital, Korea between 1995 and May 2001 and 324 Caucasoid patients who had received root canal treatment at the Graduate Endodontic Clinic at the University of Pennsylvania, US were selected. The clinical endodontic procedures at both clinics were similar. An electronic apex locator (Root-ZX; J. Morita Co., Kyoto, Japan) was used to measure the initial working lengths and this was verified by conventional radiography. The measurements from both Asian and Caucasian teeth were compared using a Student's t-test and a Mann-Whitney test.

RESULTS

The mean difference in canal length of pooled teeth between the Asian and Caucasian teeth was 1.2 mm, with a range from 0 to 2.5 mm. The greatest difference was in the distobuccal canal (2.5 mm) of maxillary first molar teeth followed by the mesiolingual canal (2.3 mm) of mandibular second molar, the buccal canal (2.1 mm) of the maxillary second premolar, the maxillary first molar and the mandibular second molar.

CONCLUSION

Tooth lengths in Asians were shorter than Caucasians.

Radiographic practices of dentists undertaking endodontics in New Zealand

OBJECTIVES

To determine the radiographic practices of New Zealand dentists undertaking root canal treatment, and to investigate the relationship between radiographic practices and educational and clinical factors.

METHODS

A questionnaire was sent to all 1200 general dental practitioners and five specialist endodontists in New Zealand. Data were subjected to descriptive and analytical statistics.

RESULTS

The response rate was 79%. The mean number of root canal treatments done by general dentists in the previous 12 months was 103, and for the specialists 938. Pre-operative views were taken by 57.1% of respondents all the time and by 34.8% in most cases. The long cone paralleling and bisecting angle techniques were in regular use by similar numbers of respondents, and over one half of the practitioners regularly used film holders and electronic apex locators. Working length films were taken by 67% of practitioners all the time and by 18% in most cases. One-quarter of practitioners took a master point view all the time, and 15% did this for most cases. Almost 65% always took a film of the completed root filling and 21% did for most cases. Twenty-three per cent of practitioners did not follow up their work.

CONCLUSIONS

The majority of respondents used radiographs pre-operatively, for working length assessment and to assess the final root filling. There was a general improvement in radiographic practices compared with data from a previous national survey held in 1980.

Canal length evaluation of curved canals by direct digital or conventional radiography

OBJECTIVES

The purpose of this study was to compare the accuracy of a digital radiograph imaging system (DDR) with conventional radiography for the purpose of estimating endodontic file lengths in curved canals of mandibular molars.

STUDY DESIGN

Sixty extracted human mandibular molars with root curvatures ranging from 5 degrees to 52 degrees were mounted in plastic blocks. Canal length was estimated by using on-screen DDR with both 2- and 3-click measurement and from conventional E-speed radiographs by using a millimeter ruler and x2 magnification. Two operators familiar with both radiographic methods performed the estimates.

RESULTS

One-way analysis of variance and Newman-Keuls tests revealed no significant differences between the groups. Although both conventional and DDR methods of analysis overestimated the true canal length, the DDR accuracy improved as the curvature severity increased.

CONCLUSIONS

The image quality of DDR systems has improved to the point that they can now be used for estimating canal lengths, even for curved canals, with accuracy comparable to that of conventional radiographs. However, further work remains to be done to optimize image quality.

A mathematically based classification of root canal curvatures on natural human teeth

Testing of root canal-shaping instruments on natural human teeth has many difficulties, because of the different anatomical forms of root canals. There is a lack of an internationally accepted and mathematically based classification of root canal morphology. The aim of this study was to give a mathematical description of root canal forms with the help of differentiated geometrical pattern analysis and computer graphics. The measurements of 433 roots were conducted on isometric radiographs taken from the clinical view. Measured points of the same radiographs were approximated using fourth degree polynomial functions describing the imaginary axis of canals. The classification of root canal morphology on the basis of Schneider's angle differs from the classification of geometrical pattern analysis. Fourth-degree function approximation as a new method for the description of the shape of root canal curvatures seems to be exact and reliably repeatable. This type of classification of root canals is suitable for standardizing test specimens, including natural human teeth used for testing root forms: I (straight), J (apical curve), C (entirely curved), or S (multicurved).

Radiographic simulation of a periapical lesion comparing the paralleling and the bisecting-angle techniques

Sixty apical areas of single-rooted teeth were examined in this study. A simulated periapical lesion was produced using an acrylic sphere (diameter 2.0 mm), the surface of which was covered with a thin layer of zinc cement. The sphere was placed in close contact with the apical foramen using a thin orthodontic wire inserted into the apical portion of the root canal. The correctly adjusted parallel projection depicted the simulated lesion with a very low degree of error. Overangulation of the central beam with maintenance of parallelism between tooth and film resulted in a moderate degree of magnification. When correctly adjusted, the bisecting-angle technique produced images with almost the same accuracy as the paralleling technique. Over-angulation resulted in most images showing a reduced size of the simulated lesion. Moderate under-angulation most often recorded the correct dimension of the globe. In some cases a magnified image of the sphere was produced. Generally, this was associated with a palatally curved root. The investigation thus clearly indicated that the paralleling technique provides the most reliable information about the extent of a pathological process.

Tooth length determination: a review

Tooth length determination is a crucial step in endodontic treatment. Until the late 1970s, tooth length determination was based mainly on radiographic interpretation. The advent of apex locators, which identify the difference in the electrical resistance between the root canal and the periodontal membrane, ushered in a new era for measuring tooth length. However, the accuracy of these devices has been questioned. Pertinent literature is discussed with the aim of providing information on the development of the concept, techniques, and devices for tooth length determination.

Shortened dental arches and periodontal support

The periodontal support of subjects with shortened dental arches (SDA, n = 74), and of subjects with SDA and free-end removable partial dentures in the lower jaw (SDA and RPD, n = 25) was compared with that of subjects with complete dental arches (CDA, n = 72). The periodontal support was determined by tooth mobility and alveolar bone height, measured on a radiograph, of the distal alveolar bone of the premolars. Significant differences in tooth mobility were found between the three groups of subjects. The relative bone height showed a trend towards lower values for the SDA group and the SDA and RPD group. For some teeth these differences were significant. Premolars that are the most posteriorly located occluding teeth in the dental arch tend to have a lower relative alveolar bone height than premolars in an intermediate location. This effect is more marked in the upper jaw than in the lower jaw. Premolars in the lower jaw, that serve as abutment teeth for free-end RPDs, tend to show lower values for the relative bone height. It is concluded that the differences between the three groups with regard to the periodontal support are small. The large amount of crowns and bridges in both the SDA and SDA and RPD groups, and the dental history of these subjects, resulting in SDA, should be taken into account. However, as indicated by the periodontal breakdown of premolars in some subjects with SDA, the combination of an existing severe periodontal involvement and a SDA is considered to be an unfavourable situation.