Level Of Mental Foramen Research Articles

The mental foramen, anatomical parameters through a radiographic approach to aid in dental implantology: A retrospective analysis in a sample of a Palestinian population

PurposeThis study aims at analyzing the mental foramen (MF) structure, dimension, position, and emergence profiles among a sample of a Palestinian population. Methods212 mental foramina (106 patients) were analyzed on two panoramic views (CBCT reformatted (CRP) & conventional (CP)) and CBCT coronal views. The visibility score, position, size, presence of loop & supplementary foramina, distances coronal and apical to the foramen, and the emergence profiles of the mental canals with associated course angles were all noted. ResultsNo statistically significant relationship was found between the type of panoramic radiographic view used (i.e., CP & CRP) and the resultant visibility level and position of MF. The majority of the MF showed an intermediate visibility score on both CP & CRP. The highest percentage of MF's position was under the 2nd mandibular premolar. The emergence profile was shown to be, in most, superior (S) in 47.6% of the sample and posterosuperior (PS) in 28.3%. The MF mean height and width were 4.08 mm & 4.11 mm, respectively. The coronal and axial angles averages were 46.25° and 91.49°, respectively. The distance superior and inferior to the MF showed averages of 12.39 mm and 13.52 mm, respectively. 28.3% of the sample presented with a mental loop, with a mesial extension average of 2 mm. ConclusionOn both panoramic views (CBCT & conventional), the majority of the mental foramina displayed an intermediate visibility level, with no significant difference between the two techniques. The MF was found mostly under the second premolar. The majority of the examined mental canals had a superior emergence profile.

An Observational Study for Localization of Temporal and Marginal Mandibular Branch of Facial Nerve in Indian Cadavers

The aim of this study was to observe the variation in the course of frontotemporal and marginal mandibular branch of the facial nerve in Indian cadavers, by using fixed anatomical landmarks. A total of 30 hemi faces of 15 embalmed formalin-preserved cadavers were aged between 18 and 70 years, and dissection was carried to expose parotid and submandibular gland. Fronto-temporal and marginal mandibular branch of facial nerve were identified within the parotid gland. Retrograde dissection and identification of the fronto-temporal branch and marginal mandibular branch of the facial nerve were done to measure the distance, and anatomical landmarks were given. We found that mean distance between temporal branch of facial nerve and root of the zygomatic arch was 25.4 ± 4.6 mm. Mean distance from the lateral canthus to the temporal nerve was 21.1 ± 4.0 mm. Mean distance from the lateral canthus to the temporal nerve, superiorly was 17.7 ± 4.2 mm. Marginal mandibular branch of the facial nerve runs with the mean distance of 6.3 ± 1.7 mm inferiorly from anatomical angle. Mean distance from the antegonial notch to the marginal mandibular nerve was 6.1 ± 1.6 mm. Mean distance from the lower border of the mandible at the level of mental foramen was 1.1 ± 6.3 mm. Course and variations of the facial nerve in relation to fixed anatomical landmarks can guide the surgeon to avoid facial nerve injuries and further postoperative complications.

Cross sectional analysis of positional and numerical variations of mental foramina in dry human mandibles

Introduction: During lower jaw surgeries, mental nerve block is given at mental foramen level. However, mental foramen is prone for variations in its location and number, which could lead to iatrogenic injuries to neurovascular structures in this region. Aim and Objective: The aim of this study is to provide precise information of variations of site and number of mental foramen for helping dental surgeons to avoid injuries to mental nerve and vessels. Hence, the objective of the study is to analyze changes in site and number of mental foramen in the form of accessory foramina osteologically in Gujarat’s population. Materials and Methods: Three hundred dry mandibles of unknown sexes, and bearing all teeth or intact alveolar margin were included in the study. In 37.33% of mandibular sides, mental foramens were found between 2nd premolar and the 1st molar teeth. Numerical variations in the form of accessory foramina were found in 16.66% mandibles, more on the left side, showing statistically significant difference in laterality distribution. Conclusion: Iatrogenic injuries of mental neurovascular structures could better be avoided with precise idea of variations in site and numbers of mental foramen, which may ease the work of dental surgeon. Keywords: Dry mandibles, Mental foramen, Anaesthesia, Anatomical variation.

Mandibular radiomorphometric assessment of bone mineral density in survivors of pediatric hematopoietic stem-cell transplantation

OBJECTIVE:Hematopoietic stem-cell transplantation (HSCT) childhood survivors of hematologic malignancies are prone to develop late osteopenia and osteoporosis. The purpose of this retrospective study was to quantitatively and qualitatively assess bone mineral density (BMD) in HSCT childhood survivors and to compare the effectiveness of both qualitative and quantitative assessment methods.METHODS:DESIGN BMD assessment using panoramic radiographs of childhood HSCT survivors aged 3.69-18.88 years using two radiomorphometric indexes. Case-control double-blinded comparison of panoramic radiographic images from childhood HSCT survivors and age- and sex-matched healthy controls. Quantitative assessment was performed by measuring the cortical bone width bilaterally at the mental foramen level. Qualitative assessment was performed using the mandibular cortical index bilaterally on all panoramic images.RESULTS:Radiographs were taken 6.59-83.95 months after bone marrow transplantation [median±SD=25.92±24.9 months]. Fifty-two panoramic radiographic images were analyzed: 21 from HSCT survivors and 31 from healthy controls aged 3.69-25.1 years [mean±SD=11.89±5.28 years]. The mandibular cortical bone width was 17% smaller in childhood HSCT survivors than in healthy controls (case group: 2.420, control group: 3.307; p=0.00617). Qualitative analysis revealed an increased frequency of severe mandibular cortical erosion in childhood HSCT survivors, although no significant difference was observed (case group: 1.540, control group: 1.490; p=0.32). The interobserver agreement was 85% (Kappa index).CONCLUSIONS:HSCT childhood survivors exhibit quantitative and qualitative mandibular bone impairments. Further studies are needed to establish an association between mandibular cortical bone impairment and osteoporosis.

Somatosensory Evoked Potentials of Inferior Alveolar Nerve: confirmation of a possible non-invasive neurophysiological approach.

The use of inferior alveolar nerve (IAN) somatosensory evoked potentials (SEPs) may represent a non-invasive method to evaluate the sensory nerve function in the maxillofacial region. The aim of this work is to confirm the feasibility of a technique, previously reported in the literature, and the data previously obtained. SEPs were obtained following electrical stimulation (square wave pulses 0.2 millisecond [ms] in duration, 4 to 6.5 mA, 0.7/second repetition rate, 200 averages) of the gum at the mental foramen level, in the IAN region, via a new designed type of intraoral surface electrodes and recorded from the contralateral central scalp sites. We recognized waveforms of sufficient quality and consistently recorded a "W"-shaped response. Peak latencies of waves were at 14, 20, 27, 34 and 43 ms respectively. One side of the lower lip can be compared with the contralateral side. IAN SEPs, obtained with the present technique, may represent an objective, non-invasive, and reliable way of testing sensory nerve function in the maxillofacial region.

Origin of the torus mandibularis: An embryological hypothesis

Torus mandibularis, a well-known protuberance in the dental field, has been defined as a hyperostosis in the lingual aspect of the body of the mandible above the mylohyoid line. However, the origin of the torus mandibularis has not yet been clarified. The aim of this study was to provide a better understanding on the origin of the torus in view of the specific development of Meckel's cartilage at the site corresponding to the adult torus. A total of 40 mid-term human fetuses at 7-16 weeks of gestation were examined. The 10-13 weeks stage corresponded to the critical period in which Meckel's cartilage with endochondral ossification underwent a bending at the beginning of the intramandibular course. At the level of mental foramen, which was located between the deciduous canine and the first deciduous molar germs, the medial lamina of the mandible protruded medially to reach Meckel's cartilage. Thus, the medial lamina covered the posterior and superior aspect of the bending Meckel's cartilage just above the attachment of the developing mylohyoid muscle (i.e., in the oral cavity). We considered a bony prominence, which composed the protruding medial lamina and the bending Meckel's cartilage as the fetal origin of the torus mandibularis. A new theory is proposed for the origin of the torus mandibularis based on the existence of an anlage formed during the development of the mandible, variable in morphology and size, but always constant.

Letter to the Editor

To the Editor: Recently, an interesting research article by Romanos et al1 was published that related the frequency, and the importance, of the mandibular incisive canal (MIC) and its nerve in preoperative planning for implant surgery. For most surgeons, the anatomy and content of the MIC are controversial,2–5 and in many books or articles, there is no reference to its existence,6–8 whereby the anterior mandible region is considered a safe area for implant placement. However, the high rate of incidence reported in anatomical and imaging studies conclude that the MIC (and its nerve) corresponds to a constant anatomical structure rather than an anatomical variation,5,8 with an origin at the level of mental foramen, term at the apex of the mandibular lateral incisor, and an average diameter between 1.8 (±0.5)5,9 and 1.48 (±0.57) mm.1 Neurosensory disorders have been reported after installation of implants in the anterior region of the mandible.6,10,11 Other complications such as bruising and swelling during or after surgical procedures, or even a traumatic neuroma,10 can arise due to direct7,10 or indirect6,9 trauma of the canal or it's nerve. Another complication is the failure of osseointegration because of the migration of soft tissue around the implant.7 The high detection rate of MIC by cone beam computed tomography indicates the high value of the analysis for preoperative surgical procedures in the anterior mandibular area.3 Current evidence has described the microsurgical approach by endoscopic visualization of neurovascular structures in oral surgery and implantology, including MIC and its nerve,2,3,12 as we can see in Figure 1, which uses an immersion endoscopic technique for precise location and removal of the mandibular incisive nerve after implant placement. Mandibular incisive nerve and other nerves of the maxillofacial area have rarely been seen with this quality and amplification.Fig. 1: A, Evaluation of the visibility and the course of the mandibular incisive canal using cone-beam computed tomography. B, Intraoperative visualization by immersion endoscopy (Karl Storz 1.9mm diameter) of mandibular incisive nerve (terminal branch) prior to resection in the area of implant placement. Red arrow indicates the osseous border of the mandibular incisive canal and white arrow its nerve.The presence, and anatomy, of the MIC and its nerve should not be ignored in the planning of implants and other surgical procedures in the anterior mandible. This could play a fundamental role in avoiding any risk of neurovascular damage and obtaining successful osseointegration. We agree with Romanos et al1 that there is no doubt that orthopantomographs underestimate the real presence of MIC and a more precise examination should be taken into consideration when surgical procedures in this anatomical area have to be performed. Cone beam computed tomography is recommended to identify these structures before any surgical procedure in this region, along with the use of intraoperative endoscopy for a successful outcome (see Fig. 1 A and B).

Cone beam CT image artefacts related to head motion simulated by a robot skull: visual characteristics and impact on image quality

The aim of this study was to assess artefacts and their impact on cone beam CT (CBCT) image quality (IQ) after head motion simulated by a robot skull. A fully dentate human skull incorporated into a robot simulated pre-determined patient movements. Ten head motion patterns were selected based on the movement of the C-arm of the CBCT units (no motion as reference). Three CBCT units were used [a three-dimensional eXam (K) (KaVo Dental GmbH, Biberach, Germany), a Promax 3D MAX (P) (Planmeca Oy, Helsinki, Finland) and a Scanora(®) 3D (S) (Soredex Oy, Tuusula, Finland)]. Axial images were qualitatively assessed at three levels: mental foramen (MF), infraorbital foramen and supraorbital foramen, and artefacts characterized as stripe-like, double contours, unsharpness or ring-like. A 100 mm visual analogue scale (VAS) was used to quantitatively assess IQ. Cross-sectional images of the lower third molar and MF bilaterally were also evaluated by VAS. Four blinded examiners assessed the images. For all units and motion patterns, stripe-like artefacts were the most common. The four observers agreed on the presence of at least one artefact type in 90% of the images. Axial images showed lower overall IQ after motion (VAS = 72.4 ± 24.0 mm) than reference images (VAS = 97.3 ± 2.6 mm). The most severe artefacts were seen at the MF level. For cross-sectional images, IQ was lowest after tremor. The mean IQ range was 74-89 and 57-90 for isolated (tilting, rotation and nodding) and combined (nodding + tilting and rotation + tilting) movements, respectively. IQ for MF was lower than for third molar for any movement except tremor. Head motion of any type resulted in artefacts in CBCT images. The impact on IQ depended on the region and level in the skull.

Anatomic measurement of the depth and location of the sublingual fossa

The purpose of this study was to measure the depth and location of the sublingual fossa, a potential site of sublingual bleeding/lingual cortical perforation during endosseous implant placement in the mandibular interforaminal region (MIR), to clarify anatomical variation. Using the mandibles of 37 Japanese cadavers, the lingual depth (LD) between the lingual surface and the line perpendicular to the inferior margin of the mandible (IMM), as well as the vertical distance (VD) between the lingual surface and the IMM or the mental foramen (MF) level, were measured at defined points and lines within the MIR. The definite sublingual fossa (SF) was identified by the LD (≥1.0mm) and the VD, and the depth and location of the SF were determined. The depth ranged between 1.0mm and 5.8mm, and the vertical location ranged between 9.2mm and 15.7mm from the IMM and between 2.2mm and 6.1mm from the MF level. These results revealed certain tendencies in the depth and location of the SF but the variation was substantial. The SF should be identified in each case as accurately as possible by CT before implant placement in the MIR to minimize the risk of the potential complications.

Somatosensory Evoked Potentials of Inferior Alveolar Nerve

The use of inferior alveolar nerve somatosensory evoked potentials may represent an objective means of evaluating sensory nerve function in the maxillofacial region. The aim of this work was to confirm the existence of a standard sequence of prominent events in the trigeminal somatosensory evoked potentials (TSEPs) of inferior alveolar nerve (IAN) waveform, examine those components and their normal variability by statistical analysis, and discuss TSEPs' nervous origin and some patterns of TSEPs' abnormalities due to dysfunctional nerves. TSEPs were obtained following electrical stimulation (square wave pulses 0.2 millisecond [ms] in duration, 4 to 6.5 mA, 0.7/second repetition rate, 200 averages) of the gum at the mental foramen level via intraoral surface electrodes and recorded from the contralateral central scalp sites. We successfully recognized steady waveforms of sufficient quality and consistently recorded a "W"-shaped response: latency onset and peak of the initial deflection of positive polarity were approximately 12 ms and 20 ms, respectively. Negative and positive deflections followed with respective peak latencies at around 26 ms and 36 ms. One side of the lower lip can be compared with the contralateral side and patients may serve as their own control in cases of unilateral nerve injury. The anaesthetic block showed the total abolition of responses. Reproducible TSEP waveform was only obtained during nerve stimulation and not during masseter muscle stimulation. TSEPs, obtained with the present technique, may represent an objective, low-invasive, and reliable way of testing sensory nerve function in the maxillofacial region.