Cone beam CT findings of retromolar canals in a Korean population

Purpose

The identification of the variation involving the mandibular canal is important during surgical procedures in the mandible. This study aims to investigate the incidence, course, width, and location of retromolar canals in a Korean population using cone beam CT.

Methods

The cross-sectional, sagittal, and three dimensional images from volumetric cone beam CT data of 446 patients were reconstructed using imaging analysis software for the presence of a retromolar canal. Retromolar canals were classified into three types according to the courses. The width and location (distance from the second molar) of retromolar canals were evaluated.

Results

A retromolar canal was observed in 8.5 % of patients (38/446). Most retromolar canals had vertically curved courses (Type 1, 66.7 %), followed by horizontally curved courses (Type 2, 20 %). Type 3 retromolar canals, which run independently from separate foramina in the mandibular ramus, were rare (13.3 %). The mean width of a retromolar canal was 1.13 mm (SD ± 0.38, 0.60–2.00), and the mean distance to the second molar was 14.08 mm (SD ± 3.85, 8.50–24.00).

Conclusions

The incidence of retromolar canals in the Korean population was lower than that reported in the investigated ethnic groups. In the presence of a retromolar canal, local anesthesia may be ineffective. The damage to a retromolar canal may be unavoidable during surgical procedures involving the mandible and may result in paresthesia, excessive bleeding, postoperative hematoma, or traumatic neuroma.     

Risk assessment of inferior alveolar neurovascular bundle by multidetector computed tomography in extractions of third molars

Purpose

This study aimed to assess the reliability of multidetector computed tomography (MDCT) in determining the surgical risk of the inferior alveolar neurovascular bundle in extractions of third molars.

Methods

The sample comprised thirty-three individuals (63 third molars) who underwent preoperative evaluation by MDCT before extraction of impacted mandibular third molars. MDCT was used to determine the relationship between the roots of the third molars and the mandibular canal, and the course of the mandibular canal. Inferior alveolar nerve (IAN) exposure and the presence of hemorrhage were analyzed after removal of the teeth. IAN neurosensory deficit was recorded after 7?days. Clinical and MDCT findings were compared using Fisher’s exact test (P?Results There was a statistically significant association between IAN exposure and the tomographic relationship between the roots of third molars and the mandibular canal (P?=?0.015). Conventionally, all cases of IAN neurosensory deficit and hemorrhage occurred when the roots of the third molar presented in an at-risk relationship with the mandibular canal, however, this association was not statistically significant (P?>?0.05). A statistically significant association was found between the lingual course of the mandibular canal and IAN exposure (P?=?0.03).

Conclusions

MDCT is an effective tool for determination of the surgical risk to the inferior alveolar neurovascular bundle in extraction of mandibular third molars.     

Evaluation of the morphological changes in the mandible for dentate and totally edentate elderly population using cone-beam computed tomography

Purpose

The loss of teeth considerably modifies the mandibular shape. The aim of this study was to compare the morphological changes in the mandible for dentate and totally edentate elderly subjects using cone-beam computed tomography.

Methods

In total, 50 cone-beam computed tomography patients (25 dentate, 25 edentate) without any maxilla-mandibular dysmorphosis were analyzed retrospectively. Panoramic representations of the mandible with superimposed axial slices and cross-sectional slices were developed with the cone-beam computed tomography scans. Values of the mandibular cortical index, bone quality index, gonial angle, antegonial angle, antegonial depth and condyle angle in the left and right side were measured.

Results

There was a significant difference in the mandibular cortical index between the total edentate group and the dentate group in the left side of the mandible (p < 0.001). There was a significant difference in the bone quality index between the total edentate group and the dentate group in the right side and the left side (p < 0.001). There was a significant difference in the bone quality index between the right side and the left side (p < 0.005). When comparing gender, there was only a difference in the right side (p < 0.05).

Conclusions

Our study concluded that the mandibular basal bone morphology changes as a consequence of tooth loss. Cone-beam computed tomography is shown to be a good tool in investigating and achieving these results.     

Visibility of mandibular canal on panoramic radiograph after bilateral sagittal split osteotomy (BSSO)

Purpose

This study aimed to assess the visibility of the mandibular canal (MC) on panoramic radiographs after bilateral sagittal split osteotomy (BSSO), and to investigate what factors affect this MC visibility.

Methods

We assessed MC visibility on panoramic radiographs of 200 BSSO patients. Images were acquired preoperatively (T0), immediately postoperatively (T1), 6 months postoperatively (T2), and 1 year postoperatively (T3), from three different predetermined regions of the mandible: the angle (Angle), distally to the second molar (M2), and mesially to the first molar (M1). All analyses were performed using SAS version 9.22.

Results

The visibility of the MC was registered preoperatively in over 96 % (387/400) of the measurements at the angle of the mandible, 79 % (317/400) at M2, and <63 % (251/400) at M1. MC visibility decreased immediately after the operation and increased thereafter. Region of the mandible (P ≤ 0.0001), plate removal (P ≤ 0.0001), time of assessment (P ≤ 0.0001), and age (P = 0.0034) were the important predictors of whether MC would be radiographically visible.

Conclusions

The visibility of the MC decreased immediately after BSSO, especially at the operation site (M2 and M1), while maximum MC visibility was achieved at 12 months postoperatively in our series. Since MC was not visible at the operation site after BSSO for 50 % of the subjects, it may be necessary to use additional visualization modalities for postoperative patient assessment in this region.     

Double mandibular foramen leading to the accessory canal on the mandibular ramus

Purpose

The knowledge of the variation in the mandibular foramen and canal is clinically significant in surgical procedures of the mandible. This study aims to evaluate the anatomical characteristics of double mandibular foramen leading to the accessory canal on the mandibular ramus using cone beam CT.

Methods

The sagittal, cross-sectional, and three-dimensional images of cone beam CT data from 446 patients were evaluated in the presence of double mandibular foramen and the accessory canal passing through the foramen. The accessory canals were classified into two types according to the configuration (forward and retromolar type), and the location of double mandibular foramen was recorded.

Results

The eight double mandibular foramina leading to the accessory canals were observed in six patients out of 446 patients (1.35 % of population). Regarding the configuration of the accessory canal, there were two forward types and six retromolar types. All double mandibular foramina were located above the mandibular foramina on the medial aspect of the mandibular ramus.

Conclusion

Three-dimensional images of cone beam CT data are useful in confirming the presence of double mandibular foramen leading to the accessory canal. The variation may cause failure in the routine mandibular nerve block anesthesia and it is often vulnerable during surgical procedures involving the mandibular ramus. Also, double mandibular foramen is considered as an easy route for tumor cell to spread following the radiotherapy. Therefore, the variation should be carefully investigated using reconstructed cone beam CT images in planning of dental surgery or radiotherapy in the mandible.     

Morphodigital study of bone quality in the mandibular angle in patients with third molar impacted

The aim of this study was to analyze if the presence of impacted third molars, and their positions in the mandibular angle, can change the bone quality in this area, considering the measure of the cortical thickness in this region as representative or not for mandible fracture risk. Software was used to analyze 50 digital images from panoramic radiographs of patients who had one or two impacted third molars in the mandible, and 30 digital images of patients with agenesis of the mandibular third molar. The thickness of the cortical region of the mandible was measured; it was possible to draw a parallel line to the posterior portion of the mandible and a parallel line to the body of this bone on each side of the image. At the intersection of these lines near the distal portion of the second molar, another line was set up to serve as reference in the cortical thickness measurement. It could be concluded that the cortical thickness of the mandibular angle in male patients without impacted third molars was greater than the thickness in patients with these teeth, and no difference in thickness was found for the female group.     

Anatomical configuration of the inferior alveolar neurovascular bundle: a histomorphometric analysis

Purpose

The inferior alveolar neurovascular bundle (NVB) is important in implant placement and many other surgeries in dentistry because it is a major supplier of sensation and blood to the mandible via the mandibular canal. The purposes of the present study were to determine the areas and diameters of the NVB, the inferior alveolar nerve (IAN), and the inferior alveolar artery (IAA), and to verify the buccolingual location of the mandibular canal.

Methods

The anatomical configuration of the NVB was examined by histomorphometrically analyzing 20 embalmed dentulous hemimandibles. The areas and maximum horizontal and vertical diameters of the NVB, IAN, and IAA were measured according to tooth region. The distances from the internal border of the mandibular canal to the outer surface of the buccal and lingual cortical plates were also measured.

Results

The areas of the vertically oval-shaped NVB and IAN appeared to be constant between the molar and premolar regions, which contain the mental branch, and decreased sharply in the lateral incisor after branching off of the mental branch via the mental canal. The mandibular canal was located close to the lingual cortical plate in the posterior tooth region before passing through the mental canal, immediately after which it was situated quite close to the buccal cortical plate, and then closer to the middle toward the anterior tooth region.

Conclusions

The findings of this study provide useful anatomical information that should help to minimize the risk of injury to the NVB during surgical procedures in the mandibular region.

     

Mandibular lingual canals distribute to the dental crypts in prenatal stage

Purpose

To describe configurations of human prenatal mandibular, lingual canals using a limited-field cone beam computed tomography (CBCT) to examine their origin and anatomical significance.

Materials and methods

Nine fetal mandibles were examined using a CBCT. Mandibular maturity was assessed according to the mandibular size measured directly and image findings on development of dental crypts. Mandibular, lingual canals and the related foramina (mandibular, mental, and lingual foramina) were observed on axial, sagittal, and cross-sectional images. The horizontal position of mental and lingual foramina was assessed by direct observation using a loupe.

Results

In all nine mandibles, CBCT images depicted three separate mandibular canals, which individually occurred at the ramus area. One was a short canal directly connecting to the permanent molar crypt. The other two showed a parallel course, following the mandibular corpus toward the frontal area; the upper one connected to the mental foramen, and the lower one distributed anterior area of canine and incisor crypts. Lingual foramina were observed bilaterally in eight of nine mandibles, whose horizontal position was lingual against the crypt of deciduous canine. The lingual canals occurred from lingual foramina, and connected to the close deciduous tooth crypt or the mandibular canal distributing in the frontal area.

Conclusions

It was suggested human dentition could be developed by plural mandibular and lingual canals.     

Cone beam computed tomographic evaluation of nutrient canals and foramina in the anterior region of the mandible

Purpose

To investigate the incidence and anatomical location of mandibular nutrient canals (NCs) originating from the mandibular canal using dental cone beam computed tomography (CBCT).

Methods

CBCT images from 105 patients were examined to evaluate the presence, number, diameter, and course of NCs.

Results

NCs and their foramina were bilaterally located in 17 (16.2 %) images. The mean diameters of NCs and foramina were 0.9 ± 0.4 (range, 0.2–3.2) mm and 0.9 ± 0.4 (0.2–2.1) mm, respectively. NCs coursed through the mandibular incisor region up to the lingual surface of the alveolar bone crest.

Conclusion

The present study revealed the frequency and distribution of NCs using CBCT image analysis. NCs are important because surgical injury to the neurovascular bundle within these canals can lead to excessive bleeding and postoperative paresthesia. The identification of NC on CBCT images may be useful during the harvesting of bone blocks or placement of endosseous implants in the anterior region of the mandible.

     

A retrospective comparison of the location and diameter of the inferior alveolar canal at the mental foramen and length of the anterior loop between American and Taiwanese cohorts using CBCT

Purpose

The aim was to retrospectively compare the measurements of the location and size of the inferior alveolar canal at the mental foramen and the length of the anterior loop between two cohorts of Americans and Taiwanese using cone-beam computed tomography (CBCT).

Methods

CBCT was performed with an I-CAT^® Cone-Beam 3D Dental Imaging System and reconstructed into multiple-plane views to measure two populations.

Results

There was no statistically significant difference (P = 0.2681) in the distance from the mental foramen to the inferior border of the mandible (mandibular border height) between Americans (9.84 ± 2.01 mm) and Taiwanese (10.13 ± 1.66 mm). No significant difference was found (p = 0.1161) in the inferior alveolar canal diameter between these two cohorts (2.26 ± 0.67 and 2.13 ± 0.47 mm, respectively). However, the anterior loop length of Taiwanese (7.61 ± 1.81 mm) was significantly longer than that of Americans (6.22 ± 1.68 mm) (P < 0.0001).

Conclusion

Our study indicated that (1) the location of mental foramen of Americans was closer to the inferior border of the mandible than Taiwanese; (2) the diameter of the inferior alveolar canal of Americans was larger than Taiwanese; (3) the anterior loop of Taiwanese was longer than Americans. These differences may be, at least partly, due to the racial influence and this information may possess potential valuable clinical relevance.     

Prevalence of bifid mandibular canals in panoramic radiographs: a maxillofacial surgical scope

Purpose

The present study aims to estimate the prevalence of bifid mandibular canals in patients treated at the Dental Clinic of the Federal University of Paraná, Brazil.

Methods

The sample consisted of 3,024 panoramic radiographs from male (n = 1,155) and female (n = 1,869) patients (mean age 30 years). An experienced radiologist analyzed the panoramic radiographs according to the study of Langlais et al. (J Am Dental Assoc 110:923–926, 1985), which classifies bifid mandibular canals into four different types.

Results

Sixty patients (1.98 %) presented bifid mandibular canals. Specifically, 50 patients revealed bifid mandibular canals type I, while 10 patients revealed bifid mandibular canals type II. All the variations were unilateral. In addition, statistically significant results were not observed for gender distribution.

Conclusion

The present findings indicate a low prevalence of morphologic alterations of the mandibular canal in the studied population. However, the present outcome highlights the clinical relevance of investigating the radiologic morphology of the mandibular canal prior to surgical interventions.     

Use of CBCT to investigate the root canal morphology of mandibular incisors

Purpose

To investigate the root canal morphology of mandibular incisors using cone-beam computed tomography (CBCT).

Materials and methods

A total of 353 patients with 1,412 healthy, well-developed mandibular incisors were enrolled. Radiographic examination by CBCT was conducted as part of their routine examination, diagnosis and treatment planning. The following observations were made using CBCT: (1) the number of roots; (2) the number of canals; (3) canal configuration according to Vertucci’s classification; (4) the position of root canal bifurcations.

Results

Two canals were found in 10.9 % of mandibular central incisors, 25.5 % of lateral incisors and in 18.2 % of all the 1,412 mandibular incisors. Significantly, more lateral incisors possessed two canals than central incisors (p < 0.05). Of the teeth with two canals, type III incisors were the most prevalent, followed by types II, IV and V. Furthermore, 37.7 % of teeth were found to have root canal bifurcations that were at or near to the cortical-middle third junction regions of the roots.

Conclusion

Routine mode CBCT imaging was clinically useful for detection of two canals and determines the position of root canal bifurcations in mandibular incisors.     

Radiological patterns of the bony roof of the superior semicircular canal

Objectives

To study the radiological patterns of the bony roof of the superior semicircular canal with a view for obtaining readily applicable conclusions.

Design

84 patients (163 petrous bones) have been studied by Multi-slice Helical Computed tomography (Philips Brilliance 6). We have determined the distribution of the different types of bone cover of the superior semicircular canal, taking some previously notified, standardised measurements of normality as reference.

Results

During the analysis of the roof of the superior semicircular canal, we have distinguished five different types, depending on their thickness and tomodensitometric aspect. Normal pattern in 121 cases (74.2 %), with a thickness of between 0.6 and 1.7 mm, papyraceous pattern or fine thickness ≤0.5 mm that appears in 23 of our cases (14.1 %), thick pattern ≥1.8 mm that we have observed in 11 cases (6.7 %), and pneumatised pattern in 5 cases (3.1 %), which is characterised by having supralabyerinthine cells. Finally, a dehiscent pattern was observed in three cases (1.8 %).

Conclusion

We describe five patterns of superior semicircular canal roofs: normal, thick, papyraceous, pneumatised and dehiscent. The papyraceous type and the dehiscent type would be subject to producing pathology, and in some cases the latter could be a consequence of the former.     

Evaluation of bifid mandibular canals with cone-beam computed tomography in a Turkish adult population: a retrospective study

Purpose  

Knowing the anatomic location and also variations of the mandibular canal is especially important for surgical procedures on mandible such as dental implant surgery, impacted molar extraction and sagittal split ramus osteotomy. The purpose of this study was to clarify the incidence and location of bifid mandibular canals in an adult Turkish population to avoid complications during surgical procedures.     

下颌神经管全长三维走向的测量及其临床意义

目的　研究下颌管的全长走行位置及其与四周骨板的毗邻关系 ,为临床下颌手术提供解剖学依据。方法　对14 0侧成人下颌骨进行冠状、矢状及水平三维剖面的测量。找出下牙槽神经管全长在下颌骨中走行的基本位置及其与四周骨松质、骨皮质的毗邻关系值。结果　下牙槽神经管在下颌骨中走行虽有变化 ,但下颌管全长的总体走行是紧贴着舌侧骨板 ;在下颌第一、二磨牙区下颌管走行与下颌下缘成平行状 ;在近颏孔时才折转向外和向颊侧出颏孔。结论　在牙种植术、下颌各类截骨术中按正常解剖方位并侧重于颊侧骨板操作 ,可以避免损伤下牙槽神经血管。     

Localizing the mandibular canal on dental CT reformatted images: usefulness of panoramic views

Purpose

The aim of this study was to compare panoramic and paraxial views of dental CT reformatted images to detect the mandibular canal, and to evaluate the usefulness of the dental CT software function of “Outlining the Mandibular Canal in the Panoramic View”.

Methods

One hundred and fifty-five patients (310 sides), who underwent multi-slice computed tomography examination for pretreatment planning of dental implant were analyzed. After scanning, two types of dental CT reformatted image, panoramic and paraxial views were obtained. Two oral radiologists evaluated both views for the visibility of the mandibular canal using a 5-point rating scale: score 5, 100–80 % visible, to score 1, 20–0 % visible. The visibility scores of the two views were evaluated and compared by Wilcoxon’s signed rank test.

Results

The mean ± standard deviations of panoramic and paraxial views were 4.2 ± 1.1 and 3.5 ± 1.2, respectively, and the former was significantly higher than the latter (p < 0.001). On the basis of these results, we attempted to apply the function of “Outlining the Mandibular Canal in the Panoramic View” to cases with poor visibility of the canal (score 1, 2 or 3) on paraxial views. Consequently, we could reduce the number of such cases from 128 (41 %) to 56 (18 %).

Conclusions

The detectability of the mandibular canal was significantly higher in panoramic views than in paraxial views. Using the function of “Outlining the Mandibular Canal in the Panoramic View”, the precision for identifying the canal on paraxial views was considered to be improved.     

下颌神经管的解剖结构

背景:在下颌后牙种植术中,由于下颌神经管走行于下颌骨体内,有时可损伤下齿槽神经,因而制约了牙种植术的应用。 因此,牙种植术的应用需详细了解下颌神经管的解剖结构。 目的：观察下颌神经管在下颌骨内的走行及管内的解剖结构。 方法：共纳入15具成人牙下颌骨标本与4具新鲜下颌骨动脉灌注标本。纳入对象均牙列完整,后牙无缺失,牙槽骨无吸收。测量15具成人牙下颌骨标本下颌管走行及其管腔各径长度,包括下颌管横径与纵径,下颌管至上下内外缘距离。观察4具新鲜下颌骨动脉灌注标本管内下颌神经管内神经、血管位置关系。 结果与结论：下颌管内缘至舌侧骨板的距离比下颌管外缘至颊侧骨板距离短(P < 0.01);下颌管上缘至牙槽嵴顶的距离较下颌管下缘至下颌骨下缘的距离大(P < 0.01)。表明下颌管在下颌骨体部走行中偏舌侧、偏下颌骨下缘。下颌神经管在下颌骨体部的部分横径小于纵径(P < 0.05),亦即下颌管截面形态为上下径略长的椭圆形。神经管横纵径于前后牙位区差异无显著性意义。实验还发现在暴露的下颌管腔中下牙槽神经及伴随血管有一层被膜包绕成神经血管束,血管位于神经上方,而且位置恒定,并发出小分支包绕神经。结果提示,下牙槽血管神经束在下颌管内走行中血管位于神经之上。     

Evaluation of location and dimensions of mandibular lingual foramina using cone-beam computed tomography

Objectives

The aim of this study was to assess the regional frequency and anatomical properties of mandibular lingual foramina (MLF) and their bony canals with cone-beam computed tomography (CBCT).

Materials and methods

A retrospective study was conducted by selecting images of the mandible from CBCT examination of 500 patients. MLF were located according to tooth areas and were grouped into midline, paramedian, and posterior foramina. In addition, the frequency of bony canals originating from lingual foramina was calculated, and the course and anastomoses were examined.

Results

In total, 491 areas with lingual foramina were observed. The highest regional frequency was recognized in the midline area (95.2 %), followed by left first premolar (15.1 %) area. The frequency of foramina in the midline was different from the paramedian and posterior (p < 0.01) regions. 95.6 % of lingual vascular canals originating from midline lingual foramina had a perpendicular course into the symphysis, whereas 60.3 % of canals from paramedian foramina and 83.6 % of canals from lateral lingual foramina presented with an anteriorly directed course.

Conclusions

CBCT examination easily demonstrates the presence of the lingual vascular canals. MLF are frequently present in a Turkish population; radiologists and oral surgeons should be aware of this anatomic feature and its possible implications.     

Impact of chlorhexidine mouth rinse use on postextraction infection via nitric oxide pathway

Objective and design

Nitric oxide (NO) has been linked to inflammatory reactions, tissue destruction, host defense, and wound healing in oral diseases. It is known that arginase enzyme controls the synthesis of NO through arginine depletion. This study evaluated the arginase–NO pathway alteration in response to tissue injury after dental extraction surgery and the effect of postoperative use of 0.2% chlorhexidine gluconate rinse (CHX).

Materials and methods

This study included 28 individuals who had impacted mandibular third molars. They were randomly divided into two groups. Group A was comprised of 13 individuals who used postoperative CHX (0.2%) rinse, while group B included 15 individuals who did not use postoperative CHX rinse. For each patient, periodontal inflammatory status was evaluated. Salivary and gingival tissue samples were obtained before and 1 h and 1 week after the surgery to determine the NO level and arginase activity using spectrophotometric methods.

Results

NO level of tissue samples displayed an insignificant decrease in both groups postoperatively. However, arginase activity of tissue samples was significantly higher in group B compared to group A 1 week after surgery (p ≤ 0.01). There were no significant changes in salivary arginase activity and NO level in both groups before or after the third molar surgery.

Conclusion

Results indicated that good oral hygiene following periodontal treatment prior to third molar surgery was related to an increase in arginase activity, which may improve wound healing. However, use of CHX rinse following periodontal treatment had no pronounced effect on the arginase–NO pathway.