Three-dimensional position of the overlap relations of impacted mandibular third molar and mandibular canal
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Objective To study the method in accurately deciding the three-dimensional positional relationship when impacted mandibular third molar was overlapped with mandibular canal on the panoramic X-ray film,so as to use appropriate clinical methods to extract the mandibular third molar.Methods Fifty-seven impacted mandibular third molars were checkedby CBCT,which were overlapped with mandibular canal on the panoramic X-ray film,and then a detailed classification and appropriate surgical plan were made.Results The position relationship types on CBCT were as follows:22 impacted mandibular third molars' roots were inside the mandibular canal;30 impacted mandibular third molarsKeywords:
Mandibular third molar
Mandibular canal
Mandibular molar
Mandible (arthropod mouthpart)
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The aim of this study was to assess the reliability of four panoramic radiographic findings, both individually and in association, in predicting the absence of corticalization between the mandibular canal and the third molar on cone beam CT (CBCT) images.The sample consisted of 72 individuals (142 mandibular third molars) who underwent pre-operative radiographic evaluation before extraction of impacted mandibular third molars. On panoramic radiographs, the most common signs of corticalization (darkening of roots, diversion of mandibular canal, narrowing of mandibular canal and interruption of white line) and the presence or absence of corticalization between the mandibular third molar and the mandibular canal on CBCT images were evaluated.Darkening of roots and interruption of white line associated with the absence of corticalization between the mandibular third molar and the mandibular canal on CBCT images were statistically significant, both as isolated findings (p = 0.0001 and p = 0.0006, respectively) and in association (p = 0.002). No statistically significant association was observed for the other panoramic radiographic findings, either individually or in association (p > 0.05).Darkening of roots and interruption of white line observed on panoramic radiographs, both as isolated findings and in association, were effective in determining the risk relationship between the tooth roots and the mandibular canal, requiring three-dimensional evaluation of the case.
Mandibular canal
Mandibular molar
Cone-Beam CT
Mandible (arthropod mouthpart)
Mandibular third molar
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To evaluate impacted mandibular third molar tooth region and obtain linear measurements using CBCT images and to assess the relationship between the impacted third molar and the mandibular canal.CBCT scans of 351 patients (208 females, 143 males) were assessed. Age, gender, and impaction site were recorded for each patient. The relationship of third molars with the vertical axis of second molars, 2nd molar resorption and the relationship between third molar apices and the mandibular canal were assessed. In addition, the distance between ramus and second molar, mesiodistal width of the third molar, the angle between third molar and second molar, and width of the third molar capsule were measured. Binary Logistic Regression, Chi-Square Test, and General Linear Model were used for statistical analysis.The highest percentage of impaction was found for mesioangular followed by transversal and vertical. The transversal impacted third molars revealed a significant association with adjacent second molar root resorption (p<0.001). There was a statistical significance between the second molar resorption and distance between ramus and second molar (p<0.001). The mesioangular impacted third molars revealed significant relation with the mandibular canal (p<0.05). The most frequent variation found was the dental canal followed by the retromolar canal. In general, higher measurement values were obtained for men when compared to women (p<0.05).CBCT assessment of the third molar region provided useful information regarding impacted mandibular third molar surgery operations.
Impaction
Mandibular third molar
Panoramic radiograph
Mandibular canal
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OBJECTIVES
The aim of the present study was to evaluate the topographic relationship between mandibular third molars and the mandibular canal in panoramic tomography and cone beam computed tomography (CBCT).
METHOD AND MATERIALS
Records of all patients visiting for removal of a mandibular third molar between January 2014 and December 2015 were evaluated retrospectively. In panoramic tomography, the relationship of the roots to the mandibular canal was diagnosed according to the literature. In CBCT scans, the panoramic plane was rebuilt and orthogonal images to that plane were analyzed.
RESULTS
A total of 56 mandibular third molars were eligible for the study. Superimposition of tooth apex and mandibular canal (Class I) was similarly often found in both radiographic techniques (P = .22). In contrast, contact of tooth apex and mandibular canal (Class II) was significantly more often seen in CBCT scans than in panoramic tomography (P = .039). No contact of tooth apex and mandibular canal (Class III) was similarly often seen in both radiographic techniques (P = .59). Contact of tooth apex and the mandibular canal (Class II) was significantly more often verified by CBCT imaging than was assumed in panoramic tomography.
CONCLUSIONS
Preoperative CBCT may be helpful in Class II cases for verification of the topographic relationship between the mandibular canal and mandibular third molars.
Mandibular canal
Mandible (arthropod mouthpart)
Superimposition
Mandibular lateral incisor
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To study the developmental and morphological characteristics of the mandible in patients with impacted mandibular second molar and to predict the possible trend of mandibular development via three-dimensional (3D) measurement and analysis.A total of 88 cases of impacted group and 88 cases of control group were screened out. 3D measurements were performed by using Mimics software. A total of 23 landmark points and 17 measurements were determined. The measurements were analyzed by t-test.The mandible length, the space between the first molars, the space between mandibular angles, and the width between the first molars in the impacted group were lower than those in the control group (P<0.05). Moreover, the value of the submandibular angle was higher than that in the control group (P<0.05).The impacted mandible of patients with mandibular second molar showed lack of sagittal and width development, and the impacted mandibular second molar was a manifestation of its degeneration.目的 研究阻生下颌第二磨牙患者下颌骨的发育和形态特征，并且通过三维测量和分析预测下颌发育的可能趋势。方法 筛选出阻生组和对照组各88例，利用Mimics软件建模进行三维测量，共确定了23个标记点和17个测量值，对测量值进行t检验分析。结果 阻生组中下颌体长度、第一磨牙后萌出间隙、下颌角间距和第一磨牙间宽的值低于对照组（P<0.05），颌下角的值高于对照组（P<0.05）。结论 本研究发现下颌第二磨牙阻生患者的下颌骨呈现出在矢状向和宽度上的发育不足，下颌第二磨牙阻生是其退化的表现之一。.
Mandible (arthropod mouthpart)
Mandibular molar
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Mandibular canal
Mandibular third molar
Radiodensity
Mandible (arthropod mouthpart)
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Aim: The aim of this study was to assess the reliability of high risk injury signs to inferior alveolar nerve on panoramic radiograph, both individually and in combination, in predicting the absence of corticalisation between the mandibular canal and the third molar and cortical plate perforation on cone beam computed tomographic (CBCT) images. Methods: The sample consisted of 20 subjects (20 left and 20 right mandibular third molars) who underwent pre-operative radiographic evaluation before extraction of impacted mandibular third molars. On panoramic radiographs, the most common high risk injury signs of inferior alveolar nerve (darkening of roots, interruption of white line, deviation of mandibular canal, narrowing of mandibular canal and superimposition of mandibular canal on roots) and bucco-lingual position of mandibular canal, supero-inferior position of mandibular canal, presence or absence of corticalisation between the mandibular third molar and the mandibular canal and cortical plate perforation on cone beam computed tomographic (CBCT) images were evaluated. Results: Darkening of roots, superimposition of roots on mandibular canal were significantly associated with presence of corticalisation of mandibular canal (P value 0.05).
Mandibular canal
Inferior alveolar nerve
Mandibular third molar
Perforation
Panoramic radiograph
Superimposition
Mandible (arthropod mouthpart)
Mandibular nerve
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Mandibular molar
Mandibular third molar
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Mandible (arthropod mouthpart)
Mandibular canal
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Analysis and evaluation of relative positions of mandibular third molar and mandibular canal impacts
Objectives This study used cone-beam computed tomography (CBCT) images to categorize the relationships between the mandibular canal and the roots and investigated the prevalence of nerve damage. Materials and Methods Through CBCT images, contact and three-dimensional positional relationships between the roots of the mandibular third molar and the mandibular canal were investigated. With this data, prevalence of nerve damage according to the presence of contact and three-dimensional positional relationships was studied. Other factors that affected the prevalence of nerve damage were also investigated. Results When the mandibular third molar and the mandibular canal were shown to have direct contact in CBCT images, the prevalence of nerve damage was higher than in other cases. Also, in cases where the mandibular canal was horizontally lingual to the mandibular third molar and the mandibular canal was vertically at the cervical level of the mandibular third molar, the prevalence of nerve damage was higher than in opposite cases. The percentage of mandibular canal contact with the roots of the mandibular third molar was higher when the mandibular canal was horizontally lingual to the mandibular third molar. Finally, the prevalence of nerve damage was higher when the diameter of the mandibular canal lumen suddenly decreased at the contact area between the mandibular canal and the roots, as shown in CBCT images. Conclusion The three-dimensional relationship of the mandibular third molar and the mandibular canal can help predict nerve damage and can guide patient expectations of the possibility and extent of nerve damage.
Mandibular canal
Mandibular third molar
Mandible (arthropod mouthpart)
Mandibular molar
Mandibular nerve
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Mandibular canal
Mandible (arthropod mouthpart)
Neurovascular bundle
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Citations (4)