Incidence and Anatomical Properties of Retromolar Canal in an Iranian Population: A Cone-Beam Computed Tomography Study.
ABSTRACT: Objectives:Retromolar canal (RC) is an anatomic structure, and due to increasing demand for surgical procedure in the retromolar area of the mandible, the identification of the retromolar canal has become an issue of clinical concern. It can innervate the third molar and some of the muscles around the posterior segment of the mandible, complicating surgical procedures in the retromolar area and root canal treatment of third molars. The aim of this study was to evaluate the incidence and anatomical properties of RC in a western Iranian population using cone-beam computed tomography (CBCT) images. Materials and Methods. Two hundred bilateral CBCT images were collected and screened in the three spatial planes for the presence of an RC. Anatomical properties and location of the RCs were assessed according to their course and distance from the surrounding structures. The relationship between the presence of RC and age, sex, side, and presence of second and third molars was also evaluated. Independent samples t-test, ANOVA, Tukey's post hoc test, paired t-test, ANOVA, Tukey's post hoc test, paired. Results:At least one RC was observed in 22% of the mandibles. Its bilateral incidence was 5.5%. Two major types of canals were detected, namely, type I, following a straight or curved course from the mandibular canal (MC) to the retromolar area (47.3%), and type II, coursing from the retromolar area to the radicular part of the third molar (52.7%). Regarding linear measurements, the mean RC diameter and the mean distance to the MC, second, and third molars were 0.68?±?0.31, 13.7?±?2.8, 15.3?±?3.0, and 7.3?±?2.3?mm, respectively. Conclusion:Based on the results of this study, RC was found in 22% of the cases; thus, it should be considered as a normal anatomical variation in the Iranian population rather than a rare finding.
Project description:To investigate the anatomical variations of the mandibular canal through assessment in situ, panoramic radiography, CT or CBCT and assess their frequency.Articles were selected from databases (Cochrane Library, LILACS, ProQuest, PubMed, Scopus, Web of Science and Google Scholar), articles without limitations of language, in which the main objective was to evaluate the frequency of bifurcation of the mandibular canal through assessment in situ, panoramic radiography, CT or CBCT were selected. A meta-analysis of prevalence using random effects was performed.Using a selection process in two phases, 15 articles were identified, and a meta-analysis was conducted. The results from these meta-analyses showed that the overall prevalence of anatomical variations for in situ studies was 6.46%, and through assessment of panoramic radiography and CT or CBCT the overall prevalence shown was 4.20% and 16.25%, respectively.There are two types of variations of the mandibular canal: the retromolar canal and bifid mandibular canal. The frequency variations through assessing in situ, panoramic radiography and CT or CBCT were 6.46%, 4.20% and 16.25%, respectively.
Project description:The aim of this study was to evaluate the reproducibility of the third molar assessment, comparing five observers and two cone beam CT (CBCT) units. 28 patients, each with two impacted mandibular third molars, were included. Each patient was randomly examined with a Scanora(®) 3D (Soredex, Helsinki, Finland) CBCT unit in one mandibular third molar region and with a Cranex(®) 3D (Soredex) CBCT unit in the other region. Five observers with varying CBCT experience assessed all third molars and recorded the following variables: number and morphology of the roots, relation to the mandibular canal in two directions, shape of the canal and whether there was a direct contact between the roots of the molar and the mandibular canal. The radiographic assessments were compared pairwise among all observers for all variables. Wilcoxon's signed-rank test was used to test the differences in observer accordance percentages among the recorded variables in the images from the two units, and kappa statistics expressed interobserver reproducibility. The mean percentages for observer accordance ranged from 65.4 to 92.9 for Scanora 3D and 60.3 to 94.8 for Cranex 3D. There was no significant difference between the observer accordance in the two CBCT units (p > 0.05), except for assessing root flex in the mesiodistal direction, for which the observer accordance was higher for Scanora 3D (p < 0.05). Kappa values ranged from 0.1 to 1.0 for Scanora 3D and from 0.2 to 0.9 for Cranex 3D. For the variable "direct contact", the interobserver reproducibility was excellent for the two trained radiologists. The two units had almost similar interobserver reproducibility for mandibular third molar assessment. Observer variation existed, and experienced radiologists demonstrated the highest interobserver reproducibility for canal-related variables.
Project description:Preoperative radiographic examination of mandibular third molars (MTM) is essential to prevent inferior alveolar nerve (IAN) injury. The aim of this study was to assess the panoramic radiography (PAN) signs considered as indicators of increased risk of IAN injury and to correlate them with the cone beam CT (CBCT) findings. 58 patients who had MTMs extraction between January 2012 and January 2018. OPG were evaluated for the following signs: interruption of the roof of the canal, root darkening, roots deflection and narrowing, canal deviation, superimposition between the MTM roots and mandibular canal. Loss of canal cortication, root grooving, thinning and perforation of lingual cortex were assessed in CBCT images. Chi-square test and multivariate logistic regression tests were used to test the relationship between PAN signs and CBCT findings. A total of 79 MTMs were examined. Loss of canal cortication in CBCT was seen in 22 (27.8%) of the cases. Root darkening in PAN images was the most frequent radiographic sign. Canal deviation and interruption of white line in PAN demonstrated a statistically significant correlation with the loss of canal cortication between the MTM and the mandibular canal on CBCT images (p?=?0.004 and p?=?0.012, respectively). No statistically significant association was observed for the other PAN signs and CBCT findings. Canal deviation and interruption of white lines were associated with loss of canal cortication on CBCT, indicating a direct contact between the roots and the mandibular canal which required a further assessment prior to the extraction.
Project description:BACKGROUND:The posterior regions of the jaws usually represent a significant risk for implant surgery. A non-valid assessment of the available bone height may lead to either perforation of the maxillary sinus floor or encroachment of the inferior alveolar nerve and consequently to implant failure. This study aimed to evaluate the reliability of surgeon's decision in appraising the appropriate implant length, in respect to vital anatomical structures, using panoramic radiographs. METHODS:Only implants that are inserted in relation to the maxillary sinus (MS) or the mandibular canal (MC) were enrolled (first premolars [1P], second premolars [2P], first molars [1M], and second molars [2M]). All preoperative panoramic radiographs were evaluated under standard conditions. The postoperative estimation (under/over) was determined depending on the available bone height (ABH) measured from the apical end of the implant to the floor of the MS and the roof of the MC using cone beam computed tomography (CBCT). Any complication or side effect that associated with overestimated implants insertion was recorded. RESULTS:The study sample included 73 patients (predominantly females) who had consecutively received 148 implants, of which 68 were inserted in the posterior maxilla and 80 in the posterior mandible. Underestimation was recorded in 93.2% of the measurements. The remaining bone height after implants insertion was <?2?mm in the majority of underestimated cases (73.9%); they were significantly (P?<?0.01) more than sites with remaining bone ? 2?mm (26.1%). In the posterior mandible, overestimation was significantly higher than posterior maxilla. Five cases with transient paresthesia were reported in the mandibular overestimated implants. CONCLUSIONS:This study specified that surgeon's choice of implants length, based on panoramic radiographs, was reliable regarding the incapability to insert implants with further length in the majority of underestimated cases, the low percent of overestimated measurements, and the minor associated complications.
Project description:The aim of this investigation was to evaluate root canal morphology of maxillary first and second molars and also to assess the prevalence and morphology of the second mesiobuccal canal (MB2) in these teeth, using cone-beam computed tomography (CBCT).In this cross-sectional study, the total of 470 CBCT images from the archive of Radiology Department of Isfahan University of Medical Sciences (IUMS), Iran, was evaluated and 295 images were selected. The number of roots, and canal configuration were determined based on Vertucci's classification system. The data was analyzed using SPSS 20, and P-values less than 0.05 were considered significant.A total of 295 images from 295 patients (165 females and 130 males), including 389 maxillary first (197 right and 192 left) and 460 maxillary second (235 right and 225 left) molars were evaluated. The prevalence of MB2 canals were 70.2% and 43.4% in the maxillary first and second molars, respectively. The most common type of Vertucci's classification was type II (53.1%), followed by type I.The second mesiobuccal canal was present in almost two thirds of first and less than half of second molars. The morphology and canal configuration of a maxillary molar can almost predict the morphology of contralateral molar. However, it does not relate to the ipsilateral molar.
Project description:Objectives:To evaluate the prevalence, location and configuration of bifid mandibular canals so as to avoid injury to the nerve and inadequate anesthesia during surgical procedures. Materials and Methods:CBCT scan of 203 patients (125 males and 78 females) was evaluated for the presence and the type of the bifid mandibular canal. They were classified according to Nortje et al. The prevalence rates were determined according to gender, location, and type of bifid mandibular canal. Statistical analysis was performed using IBM SPSS software version 24. Results:The prevalence rate of bifid mandibular canals was found to be 10.3% with 12.8% in males and 6.4% in females. The Chi-square test reveals there is a statistically significant difference between the different locations of bifid mandibular canals and most of the canals were present on the right side. The most frequent type of bifid mandibular canal observed was type II dental canal (38.1%), followed by type III forward canal (28.6%), type I retromolar canal (14.3%), and type IV buccolingual canal (14.3%). Conclusion:CBCT is suggested for a detailed evaluation and identification of bifid mandibular canals before any surgical procedures to avoid post-operative complications.
Project description:Selecting either buccal or lingual approach for the mandibular third molar surgical extraction has been an intense debate for years. The aim of this observational retrospective study was to classify the molar based on the proximity to the external cortical bone, and analyze the position of inferior alveolar canal (IAC) of each type. Cone-beam CT (CBCT) data of 110 deeply impacted mandibular third molars from 91 consecutive patients were analyzed. A new classification based on the mean deduction value (MD) of buccal-lingual alveolar bone thickness was proposed: MD≥1 mm was classified as buccal position, 1 mm>MD>-1 mm was classified as central position, MD≤-1 mm was classified as lingual position. The study samples were distributed as: buccal position (1.8%) in 2 subjects, central position (10.9%) in 12 and lingual position (87.3%) in 96. Ninety-six molars (87.3%) contacted the IAC. The buccal and inferior IAC course were the most common types in impacted third molar, especially in lingually positioned ones. Our study suggested that amongst deeply impacted mandibular third molars, lingual position occupies the largest proportion, followed by the central, and then the buccal type.
Project description:OBJECTIVES: The aim of this study was to analyse the position and relationship of juxta-apical radiolucency (JAR) to the mandibular canal and buccal and/or lingual cortical plates using cone beam CT (CBCT). METHODS: A retrospective study was carried out to analyse the JAR on CBCT for 27 patients. These findings were compared with 27 age- and sex-matched patients without the presence of JAR, which acted as the control group. The CBCT images were analysed according to a checklist, to evaluate the position of the JAR and its relationship to the mandibular canal. Then, any thinning or perforation of either the buccal or lingual cortical plate due to JAR was noted, and a classification to quantify the thinning of cortical plates was proposed. The findings in the two groups were analysed using a paired comparison by McNemar test. RESULTS: A statistical increased thinning of cortical plates was seen in the JAR group compared with the control group, and most of the cases were in the J3 group. None of the patients in either the JAR or the control group showed perforation of the buccal and/or lingual cortical plate on CBCT images. CONCLUSIONS: A classification to quantify the thinning of cortical plates was proposed, which may be used for objective evaluation of the thinning of the cortical plates in future studies. The present study gives an insight into the relationship of the juxta-apical area with the mandibular canal and cortical plates in the mandible using CBCT.
Project description:BACKGROUND: Bone density at the interradicular area plays an important role during orthodontic treatment. In view of this fact, the study was designed to quantitatively evaluate the bone density at the interradicular areas of the alveolar and basal bones of maxilla and mandible by computed tomography. METHODS: One hundred and nine computed tomographic images were randomly selected, and bone density was measured in Hounsfield units (HU) with bone mineral density software (Siemens VA20A_SP3A). The sample consisted of 78 males (mean age 29.5 years, range 20 to 40 years) and 31 females (mean age 27.6 years, range 20 to 40 years). Cortical and cancellous bone density was measured at the interradicular areas at the alveolar and basal bone levels of the maxilla and mandible, and the data was subjected to statistical analysis for comparisons. RESULTS: The highest cortical bone density was observed between the second premolar and first molar at the alveolar bone level and between the first and second molars at the basal bone level in the maxilla. Maxillary tuberosity showed the least bone density. The density of the cortical bone was greater in the mandible than in the maxilla and showed a progressive increase from the incisor to the retromolar area. The basal bone showed a higher density thanthe alveolar bone. CONCLUSION: Different qualities of the bone were found in the anatomic regions studied, which confirms the importance of knowledge of site-specific bone tissue density to correlate with various clinical findings.
Project description:In this pilot study, a volumetric analysis of retromolar onlay bone grafts over a period of 12?months was conducted, using repeated CBCT imaging combined with automated image registration.Eleven patients being treated with 16 bone grafts taken from the retromolar area were examined by CBCT scanning prior to bone augmentation (T0), immediately after bone augmentation (T1) and after a healing time of 12?months after augmentation (T2). Graft volumes were measured at each time point after automated image registration of consecutive CBCT scans.The mean volume of the augmented site was 372.2 ± 179.4?mm<sup>3</sup>. Resorption relative to the original augmented volume was 43.7% ± 19.0% after 12?months.Three-dimensional graft resorption could be precisely depicted by the use of automated image registration for CBCT data over a period of 12?months and demonstrated extensive volumetric changes of bone grafts taken from the ascending ramus of the mandible.Graft resorption and continuous bony remodeling of the grafted site before and after implant insertion have to be carefully considered by the clinician.