Changes in the location of the human mandibular foramen as a function of growth and vertical facial type

The performance of inferior alveolar nerve block technique among undergraduate students

AIMS

This study aimed at evaluating the ability to feel bone touch, positive aspirations, and frequency of the success rate during the direct inferior alveolar nerve block (IANB) among dental students.

METHODS

This prospective cross-sectional study involved 203 cases of IANB injections for patients requiring extraction of mandibular posterior teeth who visited student dental clinics at Ajman University, Fujairah Campus. Students' performance of direct IANB including ability to perceive bone touch, frequency of positive aspirations, and success rate were reported.

RESULTS

Students reported feeling bone contact in 148 (72.9%), 43 (21.2%), and 12 (5.9%) of the first, second, and third attempts during the IANB, respectively. Positive aspiration was found in 46 (22.7%) of the injections. The success was in 195 (96.1%) of the total injections. Spearman's correlation coefficient indicated that there was no significant correlation between the success rate and the result of aspiration (rho = .054, p = .440). Additionally, there was no correlation between attempts to touch the bone and the outcome of the aspiration (rho = -.091, p = .198) or success rate (rho = -.083, p = .240).

CONCLUSION

There is a relatively high success rate of direct IANB technique among dental students. This confirms the inclusion of this technique in the curriculum. Furthermore, the high rate of positive aspiration reflects the awareness and competency of dental students with the aspiration technique. In turn, this will reduce the failure of anaesthesia and the subsequent systemic complications.

Evaluating Sensory Nerve Outcomes After Horizontal Osteotomy for Mandibular Distraction in Infant Robin Sequence Patients

ABSTRACT

There has yet to be a consensus on the appropriate technique for mandibular distraction in the infant Pierre Robin population nor is their sufficient data on sensory nerve outcomes. The purpose of this study is to validate the safety of the horizontal osteotomy by: (1) determining mandibular foramen location in infant Pierre Robin patients relative to the dentoalveolar plane and (2) evaluate long-term function of the inferior alveolar nerve in previously distracted Pierre Robin patients. Preoperative 3D Computed tomography (CT) scans of Pierre Robin patients < 1 year old were reviewed. A line at the level of the mandibular dentoalveolar plane was drawn across the lingual surface of the ramus and the distance to the mandibular foramen was then measured. Semmes-Weinstein monofilaments of the lower lip and chin bilaterally was performed on mandibular distraction patients in clinic. Inclusion criteria was patients >6 years of age having undergone bilateral mandibular distraction at <1 year of age. Fifteen patients' CT studies were examined. The mandibular foramen was consistently below the level of the dentoalveolar plane at an average distance of 4.7 mm. Eight patients were included in the prospective arm. Average age was 12.2. All patients had normal sensation at 2.83 through all areas. The mandibular foramen reliably exists below the dentoalveolar plane. In addition, all patients reviewed postoperatively with >10 years of follow up demonstrated normative sensation. The horizontal corticotomy performed just above the mandibular dentoalveolar plane spares the inferior alveolar nerve in young Pierre Robin patients undergoing distraction.

Position of the Mandibular Foramen in Different Facial Shapes Assessed by Cone-Beam Computed Tomography - A Cross-Sectional Retrospective Study

Purpose:

The mandibular foramen, located on the internal surface of the mandibular ramus, is an important anatomical landmark for the success during the inferior alveolar nerve block. This cross-sectional retrospective study aimed to evaluate the location of the mandibular foramen through Cone-Beam Computed Tomography (CBCT) in different facial shapes.

Materials and Methods:

The determination of the location of the mandibular foramen was performed using CBCT of mesocephalic, dolichocephalic and brachycephalic patients (n=40 each). The ramus width (W), the distance from the mandibular foramen to the deepest point of the anterior border of the mandibular ramus (D), the distance from the mandibular foramen to the lowest point of the mandibular notch (V) and the distance from the inferior border of the mandible to the lowest point in of the mandibular border (R), as well as the ratios W/D and V/R, were measured. ANCOVA, two-way ANOVA and Chi-square tests were used to analyze the variation among the facial shapes.

Results:

The ramus width (W) was greater (p<0.0001) in the brachycephalic (28.4±0.5 mm) than in both mesocephalic (26.8±0.36 mm) and dolichocephalic (25.5±0.39 mm) patients. D (p=0.0433) and R (p=0.0072) were also greater in the brachycephalic (17.7±0.36 mm; 43.4±0.75 mm, respectively) than dolichocephalic (16.5±0.3 mm; 40.3±0.63 mm, respectively), but both did not differ from mesocephalic (17.3±0.36 mm; 41.8±0.66 mm, respectively) patients. The other measurements (V, W/D and R/V) did not significantly differ among facial shapes.

Conclusion:

The localization of the mandibular foramen was, in the horizontal direction, more posterior in the brachycephalic patients and, in the vertical direction, higher in the dolichocephalic patients, when compared to the other groups analyzed. Thus, the anatomic data found in this study may help dentists to increase the success of the inferior alveolar nerve block and prevent surgical complications.

Measuring the Position of the Mandibular Foramen in Relation to the Dentoalveolar Plane in Pierre Robin Patients: Establishing Safety of the Horizontal Osteotomy

BACKGROUND

Mandibular distraction with horizontal osteotomy of the ramus and vertical distraction vector has successfully treated airway obstruction in young Pierre Robin patients. Placing the osteotomy just above the dentoalveolar plane can minimize damage to the inferior alveolar nerve. This study maps the position of the mandibular foramen relative to the height of the dentoalveolar plane to demonstrate the safety of this technique in Pierre Robin neonates.

METHODS

Retrospective review of 3D CT scans of Pierre Robin patients was performed with inclusion criteria: ≤1 year of age, bilateral micrognathia requiring surgical intervention for airway (ie, tracheostomy versus mandibular distraction), no prior mandible surgery, and pre-operative 3D CT study. Demographic information collected included: age at CT scan, age at surgery, and genetic diagnosis. Using the 3D study of each patient's right mandible, a line at the level of the mandibular dentoalveolar plane was drawn across the lingual surface of the ramus and the distance to the mandibular foramen at a length perpendicular to the dentoalveolar plane line was then measured.

RESULTS

Fifteen patients were included in the study (at least 9 Pierre Robin). Average age at time of CT scan was 71.4 days old. The mandibular foramen was below the level of the dentoalveolar plane in all cases at an average distance of 4.7 mm. Average ramus height 46.2±13.4 CONCLUSIONS:: The dentoalveolar plane was consistently above the mandibular foramen in all patients. Thus, the horizontal corticotomy at a level just above the mandibular dentoalveolar plane spares the inferior alveolar nerve in neonatal Pierre Robin patients undergoing vertical vector mandibular distraction.

Morphological analysis of mandibular foramen through anatomical planes: implications for inferior alveolar nerve block

Error in localization of mandibular foramen is attributed to a high failure rate of inferior alveolar nerve block in clinical dentistry. We hypothesized that a remodelled approach towards exploring the morphology of mandibular foramen would be useful. In the present study, the location of the mandibular foramen was analysed with respect to the anatomical planes across the ramus of the mandible and also with respect to the quadrants on the medial surface of ramus of mandible. The study was conducted on 50 dry human mandibles of unknown age and sex. The anatomical planes were defined and drawn on the mandibles. Measurements were made with digital Vernier callipers and findings were noted. It was observed that the most consistent position of the mandibular foramen was along the vertical plane, however, the foramen was most likely to be localized along the oblique plane. Morphological analysis of the foramen with respect to the anatomical planes as well as the quadrants on the medial surface of ramus led to the analysis that occlusion plane should be the preferred plane of approach. Moreover, a rectangular area on the medial surface of the ramus was identified posterior to the mid-point of occlusion plane (8 mm above mid-point, 6 mm below mid-point and 6 mm behind mid-point) where the incidence of location of the foramen was significantly high. The findings of this study may potentially reduce the failure rate of inferior alveolar nerve block and clinical complications thereof.

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

Objectives

The location of the mandibular foramen is essential for the quality of the inferior alveolar nerve block anaesthesia and has often been studied with contradictory results over the years. The aim of this study was to locate the mandibular foramen, according to the dental age of the subject, through 3D analysis.

Methods

Three-dimensional images were reconstructed from mandibular computed tomography of 260 children, adolescents and adults. The occlusal plane was determined as the average plane passing through the buccal cusps of mandibular molars, premolars, and canines, and through the incisor edge. The mandibular foramen was located three dimensionally in relation to the anterior edge of the ramus (or coronoid notch), the sagittal plane and the occlusal plane.

Results

All along mandibular growth, the three distances defining the relative position of the mandibular foramen showed negligible changes. The mandibular foramen is located from − 0.4 to 2.9 mm above the occlusal plane. The distance between the mandibular foramen and the leading edge of the mandibular ramus ranged from 17 to 19.5 mm. The angle between the ramus and the sagittal plane ranged from 3° to 5.4°.

Conclusion

In our sample, and using the occlusal plane and the anterior edge of the ramus as anatomical references, the location of the mandibular foramen was considered to be similar in all patients regardless of age.

Mechanobehaviour in dolichofacial and brachyfacial adolescents

OBJECTIVES

To test whether mechanobehaviour (temporomandibular joint (TMJ) loads, jaw muscle use) was different between facial types and correlated with ramus height (Condylion-Gonion, mm).

SETTING AND SAMPLE POPULATION

University of Missouri-Kansas City (UMKC) Orthodontic Clinic. Ten dolichofacial and ten brachyfacial adolescents (Sella-Nasion-Gonion-Gnathion (SN-GoGn) angles ≥37° and ≤27°, respectively) consented to participate.

MATERIALS AND METHODS

Numerical models calculated TMJ loads for a range of static biting based on subjects' three-dimensional anatomy. Subjects were trained to record jaw muscle electromyography (EMG) over 2 days and 2 nights in their natural environments. Laboratory EMG/bite-force calibrations determined subject-specific EMG for 20 N bite-force (T_20Nave ). Jaw muscle use via duty factors (DF=muscle activity duration/total recording time, %) was determined from day and night recordings for muscle-specific thresholds from ≥5% to ≥80%T_20Nave . ANOVA and Tukey's HSD post hoc tests assessed for group differences in mechanobehaviour (TMJ loads, DFs). Regression modelling correlated subjects' normalized TMJ loads, DFs and ramus height.

RESULTS

Dolichofacial compared to brachyfacial subjects produced significantly higher (P<.05) TMJ loads, where ipsilateral loads were ≥20% larger for some biting angles, but had significantly less (all P<.05) masseter (day, night) and temporalis (night) DFs. Regression analysis showed a significant relationship amongst normalized TMJ loads, masseter DF and ramus height (R² =.49).

CONCLUSIONS

Mechanobehaviour showed significant differences between facial types and was correlated with ramus height.

Morphological alterations in the position of the mandibular foramen in dentate and edentate mandibles

The technique of inferior alveolar nerve (IAN) block must be based on precise anatomical knowledge regarding the correct position of the mandibular foramen (MF). The aim of the investigation reported here was to determine the anatomic and topographic localization of the MF according to mandibular ramus anatomic landmarks and to identify morphological alterations in the position of the MF and size and shape of the ramus in terms of the impact of tooth socket loss in the molar and premolar region. Seventy-three dry human adult mandibles were divided into two groups according to dental status. These were measured to determine the distances from the anterior and posterior ramus border (AB, PB) to the midpoint of the MF fossa, and from the mandibular notch (MN) and inferior ramus border (IB) to the MF entering point. A number of relevant ramus anatomic features were analyzed, such as ramus width (RW), height (RH), and thickness (RT). The MF was closer to the PB and IB in edentate mandibles (right/left mean PB-MF 10.66 ± 1.84/11.06 ± 2.05 mm; right/left mean IB-MF 21.77 ± 3.23/21.8 ± 2.27 mm) compared to dentate mandibles (right/left mean PB-MF 11.87 ± 2.08/12.04 ± 1.94 mm; right/left mean IB-MF 22.94 ± 3.09/22.74 ± 3.74 mm). Edentate mandibles demonstrated reduced RW (right/left mean RW 26.03 ± 3.53/26.49 ± 3.90 mm), significantly reduced (p = 0.03) right RH (right/left mean RH 43.56 ± 4.74/45.43 ± 4.86 mm), and significantly reduced (p < 0.05) RT in the area of the MF fossa depression (right/left mean RT 5.52 ± 1.21/5.21 ± 0.91 mm) compared to dentate mandibles (right/left mean RW 27.34 ± 3.84/27.48 ± 3.80 mm; right/left mean RH 46.33 ± 4.52/47.40 ± 4.20 mm; right/left mean RT 7.86 ± 1.98/8.10 ± 1.92 mm). Alterations in MF position and mandibular ramus anatomic features in edentate mandibles increase the potential risk of complications and failure of IAN block.

The influence of mandibular skeletal characteristics on inferior alveolar nerve block anesthesia

BACKGROUND

The inferior alveolar nerve block (IANB) is the most common anesthetic techniques in dentistry; however, its success rate is low. The purpose of this study was to determine the correlation between IANB failure and mandibular skeletal characteristics.

METHODS

In total, 693 cases of lower third molar extraction (n = 575 patients) were examined in this study. The ratio of the condylar and coronoid distances from the mandibular foramen (condyle-coronoid ratio [CC ratio]) was calculated, and the mandibular skeleton was then classified as normal, retrognathic, or prognathic. The correlation between IANB failure and sex, treatment side, and the CC ratio was assessed.

RESULTS

The IANB failure rates for normal, retrognathic, and prognathic mandibles were 7.3%, 14.5%, and 9.5%, respectively, and the failure rate was highest among those with a CC ratio < 0.8 (severe retrognathic mandible). The failure rate was significantly higher in the retrognathic group than in normal group (P = 0.019), and there was no statistically significant difference between the other two groups.

CONCLUSIONS

IANB failure could be attributable, in part, to the skeletal characteristics of the mandible. In addition, the failure rate was found to be significantly higher in the retrognathic group.