The mandibular plane: a stable reference to localize the mandibular foramen, even during growth

Investigating the characteristics of the mandibular canal in cone beam CT

CONTEXT

The mandibular canal (MC) is an essential landmark that should be considered before any surgeries. Therefore, accurately assessing the location and characteristics of the MC in cone beam computed tomography (CBCT) imaging is very important.

AIMS

To determine the characteristics of the MC in relation to adjacent anatomical structures in CBCT projections.

SETTINGS AND DESIGN

The convenience sampling method.

METHODS AND MATERIAL

This was a retrospective study of 112 CBCT images of Vietnamese patients aged 18 to 69 years, taken for clinical indications between 2018 and 2023. The evaluation was carried out by comparing and arranging the anatomical structures of different planes in three-dimensional space to assess and measure relevant dimensions.

STATISTICAL ANALYSIS USED

Independent samples T-test.

RESULTS

The average diameter of the MC from the apex of the second premolar to the distal apex of the second molar, if there were no missing teeth in this segment, was 2.58 ± 0.52 mm (right) and 2.55 ± 0.54 mm (left). If there were a missing tooth in this segment, the measurements were 2.51 ± 0.79 mm (right) and 2.47 ± 0.45 mm (left). The difference between the two sides regarding the presence or absence of a missing tooth was not statistically significant.

CONCLUSIONS

The precise localization of the MC related to the tooth apex and the diameter of the MC can vary in each person. CBCT indications should be considered when establishing treatment planning to avoid damaging the inferior alveolar nerve in the MC.

3D X-ray microscope acts as an accurate and effective equipment of pathological diagnosis in craniofacial imaging

Craniofacial structure and dental hard tissue used to be researched on by traditional imaging tools such as light microscope, electron microscope and micro-CT. Due to the limitations of imaging principle, resolution and 3D rendering reconstruction technique, traditional imaging tools are constrained for presenting fine structure and precise measurements. Here a brand-new imaging equipment-3D X-ray microscope is introduced to realize a more efficient scanning by demonstrating the comparison of the craniofacial structures and dental hard tissue of diabetes and normal DBA mouse. To explore a higher resolution, more efficient imaging measurement and 3D reconstruction method on craniofacial structure and dental hard tissue. The study included 12 DBA mice which were divided into two groups (control group and diabetes group). The heads were separated and scanned by 3D X-ray microscope, after which regions of interest were selected, followed by measurement and 3D reconstruction based on microscope attached software Dragonfly pro©. Hemi-mandibles were collected for enamel mineral density assessment supported by QRM-MicroCT-HA phantom. Data was submitted to paired t-tests at a 95% confidence level. The automatic assessed enamel thickness of diabetes mice decreased on average, whereas the rest of manual measurements and automatic assessed density showed no statistical difference. We constructed HA phantom assisted enamel density procedure in Dragonfly software. Craniofacial structure and dental hard tissue were well-presented both in 2D slide and 3D reconstruction viewport by 3D X-ray microscope which can be routinely used as craniofacial structure and dental hard tissue imaging tool.

Accuracy of Mandibular Foramen Localization Using Digital Orthopantomogram (OPG) in Middle Eastern Population

BACKGROUND/OBJECTIVES

Locating the mandibular foramen (MF) through imaging is clinically important for inferior alveolar nerve (IAN) anesthesia and mandibular ramus osteotomies. Although cone-beam computed tomography (CBCT) is superior in imaging the mandible, an orthopantomogram (OPG) is preferred for its ease of use and availability. Therefore, the present study aimed to evaluate the accuracy of digital OPG in localizing the MF, in a subset of the Middle Eastern population.

METHODS

Radiographic images (OPG and CBCT) of selected patients (adults, dentulous and no mandibular abnormalities) were used to locate the MF through digital measurements (mm) of the anteroposterior distance from the anterior border of the ramus (MF-AP) and the superoinferior position from the mandibular occlusal plane (MF-SI). Measurements were statistically compared between OPG and CBCT for accuracy. Differences in measurements between OPG and CBCT were compared against the anatomic location (right/left), age and biological sex, assuming a p-value < 0.05 as significant.

RESULTS

A total of 204 radiographic records (males: 100/females: 104/mean age: 34.65 ± 11.55 years) were evaluated. The measurements for the MF were MF-AP-OPG (right: 13.53 ± 2.44/left: 13.19 ± 2.25), MF-AP-CBCT (right: 13.61 ± 2.39/left: 13.36 ± 2.19), MF-SI-OPG (right: 5.25 ± 1.71/left: 5.41 ± 1.65) and MF-SI-CBCT (right: 5.59 ± 1.66/left: 5.52 ± 1.61). Measurements between OPG and CBCT were not significantly different, except for MF-SI (right) (p = 0.042). While the overall difference between OPG and CBCT (MF-AP/MF-SI) measurements showed a significant association (p < 0.01) with the anatomic location (right/left), a significant association (p < 0.05) with biological sex was observed only for MF-AP.

CONCLUSIONS

Based on this study's outcomes, digital OPG is an accurate modality to locate the MF based on anteroposterior (MF-AP) and superoinferior (MF-SI) measurements. This would be clinically beneficial for dental and oral surgeons to achieve the optimum IAN block anesthesia based on preoperative panoramic radiographs. Similarly, it would assist maxillofacial surgeons in planning mandibular orthognathic surgeries and ramus osteotomies without complications.

Cone Beam CT Assessment of Mandibular Foramen and Mental Foramen Positions as Essential Anatomical Landmarks: A Retrospective Study in Vietnam

INTRODUCTION

The mandibular foramen (MnF) and the mental foramen (MF) are essential anatomical landmarks that should be considered before any surgical procedures in the mandible. This study aimed to investigate the characteristics of the MnF and MF in relation to adjacent anatomical structures, as well as age and gender differences, using cone beam computed tomography (CBCT) projections.

METHODS

The study was conducted from August 2023 to January 2024 at the Can Tho University of Medicine and Pharmacy Hospital, Vietnam. In this retrospective study, 50 CBCT images of Vietnamese patients were randomly taken for various clinical purposes. Furthermore, relevant data, such as gender and age groups, were selected to evaluate the correlations, along with specific inclusion criteria. Patients within the age range of 18-69 with a symmetrical mandible were included.

RESULTS

The distance of the MnF-MN was 29.6±5.0 mm (right) and 30.1±4.6 mm (left) in males and 25.0±4.2 mm (right) and 26.3±5.0 mm (left) in females. The distance of the MnF-posterior border of the ramus (P) was 16.2±3.6 mm (right) and 15.0±2.3 mm (left) in males. For females, it was 17.1±2.9 mm (right) and 13.8±1.7 mm (left). The distance of the MF-body mandible (MB) was 15.4±2.4 mm (right) and 15.6±2.0 mm (left) in males and 14.0±2.1 mm (right) and 14.3±1.6 mm (left) in females. The distance of the MF-mandibular midline (MM) was 27.0±2.6 mm (right) and 27.0±2.9 mm (left) in males and 25.3±2.0 mm (right) and 25.1±2.2 mm (left) in females. These distances showed statistically significant differences depending on gender (P<0.05).

CONCLUSION

It can be said that CBCT provides comprehensive information about the MnF and the MF for dentists in research and clinical practice.

The inferior alveolar nerve and its relationship to the mandibular canal

Previous work on the mandibular canal, mental foramen, and mandibular foramen has focused on humans and some other non-primate mammals (with small sample sizes), but little work has investigated the mandibular canal and inferior alveolar nerve (IAN) across primates. However, it is important to understand the relationship between the IAN and mandibular canal due to the IAN's close relationship to the teeth and mastication, and thus dietary adaptations. While it is assumed that most bony canals within the skull grow around and form to pre-existing nervous structures, this relationship has never been validated for the IAN and mandibular canal. MicroCT scans of 273 individuals (131 females, 134 males, and 8 unknown sex) from 68 primate species and three mammalian outgroups, and diceCT scans of 66 individuals (35 females, 23 males, and 8 unknown sex) from 33 primate species and the same mammalian outgroups were used to create 3D models of the IAN and mandibular canal from which cross-sectional areas were taken at various points on the structures. Using qualitative descriptions, phylogenetic generalized least squares analysis, and phylogenetic ANOVAs, we were able to establish three main conclusions: (1) the mandibular canal is most often not a defined canal within the mandible of primates, (2) when the canal can be identified, the IAN does not comprise most of the space within, and (3) there are significant relationships between the IAN and the corresponding canals, with most showing isometry and the mental foramen/nerve showing negative allometry.

A detailed radiomorphometric analysis of the mandibular foramen, lingula and anti-lingula with a special emphasis on mandibular prognathism

INTRODUCTION

The aim of this study was to evaluate radiomorphometric differences of mandibular foramen (MF), lingula (Li), and anti-lingula (AL) between prognathic and non-prognathic patients, using cone-beam computed tomography (CBCT).

METHODS

A total of 228 3D CBCT images of 57 prognathic and 57 non-prognathic patients were retrospectively evaluated. The distances between MF or Li to occlusal plane (OP), anterior border of ramus (AR), posterior border of ramus (PR), sigmoid notch (SN), gonion (Go) and distances Li to MF were measured. The presence of AL, and the distances to Li were also assessed in both groups.

RESULTS

In prognathic patients the mean distances of MF-AR and Li-PR were lesser, and Li-OP was greater (p < 0.05). However, distances from MF or Li to the other ramal landmarks were similar in both groups (p > 0.05). Presence of AL was found at 53 sides in prognathic and 20 sides in non-prognathic groups (p < 0.05). The horizontal distance of Li-MF was greater in prognathic patients (p < 0.05). On the other hand, there was no difference between groups regarding the horizontal distance of Li-Al, and the vertical distances of Li-MF and Li-AL (p > 0.05).

CONCLUSION

The present study provided valuable data regarding morphological differences of MF-AR, Li-MF and Li-OP, which should be considered in the preoperative assessment of patients with mandibular prognathism. Presence of AL was more common in prognathic patients and mainly located above Li. 3D CBCT applications facilitated assessment of AL and its relationship with Li.

Skeletal maturation and the location of the mandibular foramen within the ramus mandibulae

PURPOSE

It is well documented that the mandible does not grow at a constant rate. There are significant correlations between the increase of mandibular size and cervical vertebral maturation. The peak growth velocity of the mandible occurs after the third stage of cervical vertebral maturation. The location of the mandibular foramen (MF) and its changes subsequent to growth are of great interest to clinicians as they relate to the anesthesia of the inferior alveolar nerve and to mandibular surgical procedures. Therefore, the aim of the present study was to assess the influence of the mandibular growth spurt on the location of the MF in various skeletal growth patterns.

METHODS

Panoramic and lateral cephalometric radiographs of 98 (32 orthognathic, 50 retrognathic, 16 prognathic) patients before and after the growth peak were collected. For each subject, the maturational stage of the cervical vertebrae was defined on successive lateral cephalograms and the vertical and horizontal position of the MF was evaluated on two panoramic radiographs, one before and one after the growth peak.

RESULTS

The MF-Post/MF-Ant ratio (MF distance to the posterior border of the ramus/MF distance to the anterior border of the ramus) significantly increased after the growth peak in orthognathic and retrognathic subjects (P = 0.015 and 0.02, respectively). This ratio did not significantly increase in prognathic subjects (P = 0.882). No statistically significant changes in the vertical position of the MF were found in the three groups after the growth spurt.

CONCLUSION

The horizontal position of the MF moves in an anterior direction in orthognathic and retrognathic subjects during the mandibular growth spurt. The vertical position of the mandibular foramen remains unchanged during this period.

Variability associated with mandibular ramus area thickness and depth in subjects with different growth patterns, gender, and growth status

INTRODUCTION

The purpose of this study was to quantitatively evaluate the ramus bone parameters (ramus thickness and ramus depth) for miniscrew placement. An additional aim was to compare and contrast the ramus bone parameters in growing and nongrowing male and female subjects with hyperdivergent, normodivergent, hypodivergent facial types.

METHODS

Cone-beam computed tomography scans of 690 subjects were evaluated. They were classified in terms of growth status, gender, and facial type. Ramus thickness was measured as the distance from the outer (buccal) to the inner (lingual) aspects of the mandibular ramus. Ramus depth was measured as the distance from the anterior border of the ramus to the inferior alveolar nerve canal. The measurements for ramus thickness and ramus depth were performed at 3 different levels bilaterally: (1) occlusal plane (OP), (2) 5 mm above the occlusal plane (5OP), and (3) 10 mm above the occlusal plane (10OP).

RESULTS

Males showed a significantly higher ramus thickness than females (P <0.05). Ramus thickness decreased significantly (P <0.05) as we moved superior from the level of OP to 5OP and 10OP in all 3 facial types in both females (growing and nongrowing) and males (growing and nongrowing). Growing females and growing males had significantly higher ramus thickness than nongrowing females and nongrowing males, respectively. Ramus depth increased as we moved higher from the OP to 10OP. Hyperdivergent facial type showed a significantly reduced ramus depth compared with hypodivergent and normodivergent facial type in growing and nongrowing males and females at all 3 locations, namely OP, 5OP, and 10OP (P <0.05).

CONCLUSIONS

Because of adequate ramus depth and ramus thickness, 5OP was considered the optimal insertion site for the placement of miniscrews. Patients with a hyperdivergent facial type showed significantly reduced ramus depth than hypodivergent and normodivergent facial types. Ramus thickness in males was significantly higher than in females in all facial types.

Morphometric Analysis of Mandibular Foramen in Saudi Children Using Cone-Beam Computed Tomography

OBJECTIVES

This study evaluated the position of the mandibular foramen (MF) with regard to the occlusal plane (OP) and the anterior border (AB) of the mandibular ramus (AB) in a sample of 7-12-year-old Saudi children using cone-beam computed tomography (CBCT) images.

MATERIALS AND METHODS

In this descriptive, observational study, 155 CBCT scans were selected and analyzed for positional changes in the MF. Reconstructed panoramic and axial sections were used to measure the MF-OP and MF-AB distances, respectively, on both the right and left sides of the mandible. Data were analyzed using paired t-test, independent t-test, one-way analysis of variance, and Tukey's honest significant difference post hoc tests where applicable, at a significance level of P < 0.05.

RESULTS

The mean distance of MF from the AB of the ramus was 14.68 mm, with no significant differences between the genders (P > 0.05). The MF moved upward from a position below the OP to above it, according to age in both males and females, and the difference between the age groups was significant (P < 0.05). No significant differences (P < 0.05) in the mean values of distances between the right and left sides of the mandible were seen.

CONCLUSIONS

The location of the MF varies with respect to age and should be considered while administering inferior alveolar nerve block in children to achieve a more effective anesthesia.

The correlation between surgical reference points: antilingula, lingula, and mandibular foramen

The purpose of the present study was to investigate and determine the anatomical relationship between the antilingula, lingula, and mandibular foramen using cone-beam computed tomography (CBCT).

METHODS

CBCT images of 90 participants (180 mandibular ramus) were collected. The locations of and distances between the antilingula, lingual, and mandibular foramen according to side (right and left) and skeletal patterns were measured and then evaluated by statistical analysis.

RESULTS

Only 27 participants (15%) had bilateral distinct antilingula, lingula, and mandibular foramen. The antilingula was located anteriorly (4.28 mm and 3.59 mm) and above (1.99 mm and 8.52 mm) the lingula and mandibular foramen. The lingula was behind (0.69 mm) and above (6.53 mm) the mandibular foramen. Skeletal Class III was anterior and inferior to Class II and Class I in the antilingula, lingula, and mandibular foramen. Considering the correlations of landmarks, we found that the lingula was strongly correlated with the mandibular foramen on the X axis (r = 0.757) and Y-axis (r = 0.878).

CONCLUSION

The antilingula is located anteriorly and above the lingula and mandibular foramen. The lingula is behind and above the mandibular foramen. The osteotomy line of orthognathic surgery can only be safely designed through actual measurement of the locations of the antilingula, lingula, and mandibular foramen.