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.

Preoperative imaging in third molar surgery - A prospective comparison of X-ray-based and radiation-free magnetic resonance orthopantomography

This study aimed to compare preoperative data relevant to third molar surgery based on radiographic orthopantomography (OPG) and orthopantomogram-like MR images (MR-OPG), using five different MR protocols. X-ray-based OPG and OPG-like MRI reconstructions from DESS, SPACE-STIR, SPACE-SPAIR, T1-VIBE-Dixon, and UTE sequences were acquired in 11 patients undergoing third molar surgery, using a 15-channel mandibular coil. Qualitative (image quality, susceptibility to artifacts, positional relationship, contact/non-contact of the inferior alveolar nerve (IAN), relationship to maxillary sinus, IAN continuity, root morphology) and quantitative (tooth length, retromolar distance, distance to the IAN, and distance to the mandible margin) parameters of the maxillary and mandibular third molars were assessed regarding inter-reader agreement and quantitative discrepancies by three calibrated readers. Radiation-free MR-OPGs generated within clinically tolerable acquisition times, which exhibited high image quality and low susceptibility to artifacts, showed no significant differences compared with X-ray-based OPGs regarding the assessment of quantitative parameters. UTE MR-OPGs provided radiographic-like images and were best suited for assessing qualitative preoperative data (positional relationship, nerve contact/non-contact, and dental root morphology) relevant to third molar surgery. For continuous and focal nerve imaging, DESS MR-OPG was superior. MR-OPGs could represent a shift towards indication-specific and modality-oriented perioperative imaging in high-risk oral and maxillofacial surgery.

Mandibular Canal Branching Assessed With Cone-Beam Computed Tomography

This study aimed to evaluate the prevalence and type of mandibular canal branching in a sample of the Iranian population through cone-beam computed tomography (CBCT) images. This cross-sectional study was performed on CBCT records of 300 patients (112 males and 188 females; mean age 30.14 ± 10.96 y). The presence of mandibular canal branch (MCB) was evaluated by reconstructing multiple panoramic views and buccolingual cross-sections, according to Naitoh's classification. The prevalence of MCB, the type of MCB, and the demographic information of all patients were recorded. The maximum number of branching and the maximum type of branching were also registered for each patient. Mandibular canal branching was observed in 131(43.7%) of 300 CBCT images without side or sex differences ( P > 0.05). The most frequent type was dental, followed by the retromolar, forward, and buccolingual types, respectively. There was a statistically higher frequency of retromolar canal in females than in males (odds ratio: 1.14 ± 4.25; P = 0.013). About 46% of patients with MCB had more than one accessory canal and 29% displayed more than one type of MCB. The coincidence of dental and retromolar canals in a patient was the most prevalent combination. Considering the relatively high prevalence of MCB (43.7%), it is recommended to keep in mind the possibility of anatomical variations of the inferior alveolar nerve during dental procedures to avoid postsurgical complications. The high possibility of observing multiple numbers and types of branching in the patients should also be considered during preoperative assessments.

Factors affecting root migration after coronectomy of the mandibular third molar

Nerve injury especially inferior alveolar nerve (IAN) is the one of the complications that occur when the mandibular third molar (M3) is extracted and in case of high risk patients, coronectomy might be an alternative to tooth extraction. The purpose of this retrospective study was to analyze root migration and its influencing factors at 6 months after coronectomy in both 2- and 3-dimensions using periapical view and cone-beam computed tomography (CBCT). We analyzed 33 cases of root remnant after coronectomy and measured the amount of migration in CBCT. The following factors that could possibly affect root migration were also analyzed: age, gender, number of M3 roots, shape of M3s, Pell, and Gregory classification, mesiodistal (MD) angulation, buccolingual (BL) angulation, contact point with the second molar, root curvature, and complete removal of the coronal portion. Migration of greater than 2 mm was found in 64% of the roots in the 2-dimensional (2D) analysis, and the average root migration was 4.11 mm in the 3-dimensional (3D) analysis. The factors affecting migration were the root morphology, complete removal of the coronal portion, impaction depth, and MD angulation in the 2D analysis, and MD and BL angulation in the 3D analysis. Ensuring sufficient space for root migration especially considering angulation, depth and complete removal of the coronal portion might be important factors after coronectomy of the M3. Root remnant after coronectomy of M3 may migrate in young patients who has sufficient empty coronal space and this may reduce the nerve damage by the separation of IAN and M3.

The unusually lower position of the mandibular foramen and the canal of the neck of mandible

BACKGROUND

The inferior alveolar nerve (IAN) courses through the mandibular foramen (MF) to enter the first segment of the mandibular canal (MC) in the mandibular ramus, to further supply with trigeminal fibers the lower teeth of that hemimandible. As the IAN also supplies the mylohyoid nerve, it is a mixed nerve.

METHODS

Unusual morphologies of the mandibular ramus were encountered during a retrospective study of archived CBCT files.

RESULTS

A previously unreported anatomic variation was found bilaterally in an edentulous mandible, consisting of a lowered position of the MF, with seemingly compensatory lengthening and enlargement of the sulcus colli, thus shortened MCs. Also, a rare neurovascular canal of the neck of the mandible was incidentally found unilaterally in another case and is reported here.

CONCLUSIONS

Such possibilities of variation could justify the individual effect of the IAN block.

Effects of inferior alveolar nerve rupture on bone remodeling of the mandible: A preliminary study

Although various animal studies have indicated that sensory nerves played an important role in bone metabolism and nerve injury could impair the process of bone remodeling, the actual effect of sensory nerve rupture on human bones remains unclear. The aim of this preliminary study was to investigate the effect of inferior alveolar nerve (IAN) rupture on mandibular bone remodeling of patients underwent bilateral sagittal split ramus osteotomy (BSSRO).Ten patients with unilateral IAN rupture during BSSRO were involved in this study. Neurosensory examinations were employed to assess the sensory function of bilateral IAN. The remodeling process of the post-operational mandible was evaluated by panoramic radiographs and computed tomography (CT) scans.Neurosensory examinations indicated that nerve rupture resulted in significant hypoesthesia at the IAN-rupture side. Assessment of panoramic radiographs showed no evident alterations of bone structure at the IAN-rupture side of mandible. Evaluation of CT images also indicated no statistical difference in bone density and thickness between IAN-rupture side and contralateral side.Accordingly, our study indicated that IAN rupture may not significantly impair the short-term bone remodeling process of human mandible.

Anatomic evaluation of the incisive canal with cone beam computed tomography and its relevance to surgical procedures in the mental region: a retrospective study in a Brazilian population

BACKGROUND AND OBJECTIVE

To evaluate the prevalence, location, length, diameter, and distances related to the incisive canal (IC) and the need for cone beam computed tomography (CBCT) as a complementary exam prior to surgery in the mental region.

MATERIALS AND METHODS

One hundred CBCT images from patients of both genders aged 27 to 73 years were evaluated. At every 3 mm, the diameter (DIAM) of the right and left ICs and their location, their distance to base of the jaw (BIC), the buccal (BAIC) and lingual (LAIC) aspects, and their length were measured.

RESULTS

The 100 patients comprised 50 men (50%) and 50 women (50%). The IC was detected in 78 patients, more frequently in women (80%) than in men (76%). Measurements were taken in millimeters. The mean measurements for the two sides and for men and women combined were as follows: BIC = 10.0, BAIC = 4.0, LAIC = 6.2, ICL = 19.9, and DIAM = 1.4.

CONCLUSIONS

The measurements show the need for care from professionals when performing intraosseous surgical procedures in the mental region. The distances between the IC and the references studied must be observed. Thus, CBCT becomes essential for surgical planning in the mental region.

CLINICAL RELEVANCE

The mental region of the mandible is considered a safe area to perform surgical procedures such as the placement of osseointegrated implants, orthognathic surgery, and the removal of bone grafts. However, this region includes important neurovascular structures that must be considered or else hemorrhage and neurologic disorders can be experienced.

Unusual array of neural communications in the infratemporal fossa: Useful for skull base surgery

Variations in the branching pattern of the mandibular nerve frequently accounts for failure to obtain adequate local anesthesia in routine oral and dental procedures, and also for unexpected injury to the nerves during surgery. The knowledge of the neurovascular relationships of the infratemporal region is relevant in odontostomatology practice. In this article we present a rare case of atypical communication between the inferior alveolar nerve and lingual nerve and the mylohyoid and lingual nerves. Further, the clinical implications of these communications on the development of the supplementary innervation and their possible role in anesthesia is discussed in detail. The communication between mylohyoid and lingual nerve was found in this case near the submandibular ganglion after the lingual nerve passes in close relation to third molar tooth, which makes it more susceptible to injury during third molar extractions. The communicating branch between the mylohyoid nerve and lingual nerve may also innervate the tongue, and surgeons should be aware of this variation to avoid post- operative complcations after oral surgeries. Thus the precise anatomy of structures of infratemporal region and its variations may prove beneficial to clinicians, especially to oral and maxillofacial surgeons.

Microcomputed tomography (microCT) and histology of the mandibular canal in human and laboratory animals

The inferior alveolar nerve (IAN) is a sensitive branch of the trigeminal nerve. It has an intra-bone path in the mandible, inside the mandibular canal, where it is accompanied by lymph, venous and arterial vessels. We have studied the mandibular canal in human mandibles and in some laboratory animals (mice, rats, rabbits and cats). Microcomputed tomography evidenced that the walls of the canal are made with thin plates of trabecular bone with numerous fenestrations. This aspect is evidenced in dentate subjects and become more evident in edentulous subjects with atrophy of the alveolar bone. In rats and mice, the wall of the canal is also clearly composed of trabecular plates coming from the surrounding alveolar bone of the mandible. In the rabbit, similar findings are also observed but the trajectory of the canal is more difficult to identify. In the cat, the floor of the canal is composed of the cortical bone from the basilar cortex of the mandible and the roof has a trabecular nature. Vascular injections of gelatin-barium evidenced the arterial trajectories inside the bone in rats and humans. Undecalcified bone sections in human evidenced the histological aspect of the IAN and its connective sheets. Some nervous bundles can be observed outside the epineurium. Bone remodeling is observed on the wall of the mandibular canal. These descriptive findings have a clinical relevance in dental implantology or mandibular surgery.

Contribution of capsaicin-sensitive innervation to the continuous eruption of the rat mandibular incisors

A major component of tooth innervation is made of capsaicin-sensitive primary afferents (CSPA). These fibers play a key role in tooth pain and inflammation; little is known, however, about the role of CSPA in tooth eruption. The aim of this study was to examine the role of the capsaicin-sensitive afferents in the process of eruption of intact rat incisors. CSPA fibers in several rat groups, were subjected to one of the following experimental procedures: systemic chemical ablation, systemic ablation followed by chemical sympathectomy and localized activation. The observed effects on incisor eruption were compared to those made on controls. The total amount of eruption in control/naïve rats, measured over a total period of 144 h, was 3.18 ± 0.07 mm and decreased to 2.43 ± 0.08 mm (n = 7; p < 0.001) following systemic ablation of CSPA. Further decrease to 2.24 ± 0.08 mm (n = 7; p < 0.001) was noticed when chemical sympathectomy was added to CSPA ablation. The average rate of eruption was 1.7 ± 0.25 mm following CSPA activation, compared to an average of 0.8 ± 0.07 mm for controls (n = 7; p < 0.001). Capsaicin sensitive fibers play an important role in tooth homeostasis, and intact neural supply is required for tooth growth under normal conditions.

Utilization of cone beam computed tomography to determine the prevalence and anatomical characteristics of bifurcated inferior alveolar nerves

The primary purpose of this study was to evaluate the prevalence of inferior alveolar nerve (IAN) bifurcations through the utilization of cone beam computed tomography (CBCT). The secondary purposes of this study were to analyze the average distance from the main trunk to its branch at the greatest point, to calculate the average distance of the bifid IAN from the apices of the teeth, and to determine the appropriate classification for each IAN bifid nerve according to the types described by Nortjé et al: type 1, 2 canals originating from a single foramen with a narrower inferior canal; type 2, 2 canals originating from a single foramen with a superior canal extending to the second or third molar; type 3, 2 canals of equal size that arise from 2 mental foramina that may link into a single canal near the molars. Examination of 194 CBCT scans revealed that IAN bifurcations were present in 13.4% (n = 26) of the study population. Bifurcation was bilateral in 4 individuals. For left bifurcated IANs, the average distance between the superior border of the main branch and inferior border of the bifurcated IAN (GDN) was 3.41 mm. The average distance from the superior border of the bifurcated IAN to the apex of the closest root (NAP) was 3.45 mm. For right bifurcated IANs, the average GDN was 4.01 mm, and the average NAP was 4.85 mm. Fourteen bifid nerves were type 1, and 16 were type 2. Preoperative CBCT studies can determine the presence of a bifurcated IAN, thereby reducing the chances of neurologic damage.

Hypoesthesia associated with mandibular movement after sagittal split ramus osteotomy

PURPOSE

This retrospective study investigated the relationship between the degree of neurosensory disturbance (NSD) and mandibular movement distance after sagittal split ramus osteotomy (SSRO) and assessed sensory recovery.

METHODS

Lower lip hypoesthesia was evaluated at 1 week, 1 month, and 2 months after SSRO in 38 patients categorized according to the distance of mandibular movement: S group (0-7 mm; n = 17, 4 males and 13 females) and L group (7-14 mm; n = 21, 7 males, 14 females). Symptoms were evaluated by visual analog scale (VAS), tactile-threshold (SW) test, static 2-point discrimination (s-2PD) test, and current perception threshold (CPT) test.

RESULTS

The two groups did not differ significantly in gender and age. The Aβ fiber results of the CPT test differed significantly between the groups at 1 week and 1 month postsurgery (P < 0.05). There were no significant differences between the groups throughout the period in terms of VAS, SW, s-2PD, Aδ fiber, and C fiber of CPT.

CONCLUSIONS

Post-SSRO, the incidence of NSD in terms of tactile sensation may be greater in the L group early postoperatively. This may assist surgeons in explaining postoperative hypoesthesia to patients preoperatively.

Tracking of the inferior alveolar nerve: its implication in surgical planning

OBJECTIVES

The objective of the study is to assess the correlation between the mandibular canal tracing done on cone beam CT (CBCT) data, with the size, shape, and position of the neurovascular bundle (NB) obtained by magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Six human cadaver mandibles were scanned with a CBCT Promax® scanner (Planmeca, Helsinki, Finland) and with an Ingenia® 3.0 T MR system (Philips, Amsterdam, The Netherlands). The NB was segmented from the MRI dataset, while the mandibular canal (MC) tracing was done on the CBCT images. Quantitative 3D analysis was made for the full-segmented nerves and for three defined regions of specific clinical interest, namely angle, body, and mental region.

RESULTS

From the 3D MRI analysis, the nerve thickness (for the angle, body, and mental region) ranges from 0.8 to 5.2 mm, while the thickness of the mandibular canal tracing is approximately 2.00 mm on both sides as chosen in the tracing software. The mean volume of the NB on the left is 828.49 ± 215.54 mm³ and on the right 792.98 ± 264.57 mm³. For the nerve tracing, the mean value is 351.92 ± 16.42 and 339.69 ± 16.12 mm³ on the left and right sides, respectively. Wilcoxon signed-rank test showed significant differences between NB and MC volume measurements (p = 0.0005). The Bland-Altman plots show an increasing slope for thickness and volume, indicating that the absolute differences between neurovascular bundle, estimated by MRI, and the mandibular canal, drawn on the CBCT images, increase with larger mean values.

CONCLUSIONS

Surgeons should be aware of the shortcomings of nerve tracing in the different regions of the mandible.

CLINICAL RELEVANCE

Tracing of the inferior alveolar nerve (IAN) underestimates shape and volume. Whenever nerve tracing instead of well-recognizable anatomical bony landmarks is used for surgical planning that need precision, a wider safe margin is recommended.

Revisiting the Topographic Anatomy of the Marginal Mandibular Branch of Facial Nerve Relating to the Surgical Approach

BACKGROUND

The marginal mandibular branch (Mbr) of the facial nerve is vulnerable to damage during rhytidoplasty, surgical reduction of the mandibular angle, parotidectomy, and excision of the submandibular gland.

OBJECTIVES

The authors sought to map the Mbr and determine the relationship between the number of Mbr offshoots and the course of the Mbr.

METHODS

The Mbr was examined in 29 hemifaces from 12 embalmed and 4 fresh cadavers (10 males, 6 females; mean age, 73.7 years).

RESULTS

The Mbr was located ≤5 mm from the gonion (Go) in 24 of 29 hemifaces (82.8%) and ≤10 mm from the intersection of the facial artery and mandible (ie, FM) in 26 hemifaces (89.7%). In 16 hemifaces (55.2%), offshoots arose from the Mbr inferior to the mandible. The Mbr ran below the Go in 14 hemifaces (48.3%) and ran below FM in 13 hemifaces (44.8%). Except for minute offshoots deep to the platysma, the Mbr was not found to pass >2 cm below the mandible. The mean (± standard deviation) quantity of Mbr offshoots was 1.5 (± 0.6). A greater number of offshoots was associated with a higher likelihood of an inferiorly located nerve. The Mbr proceeded under the lower border of the mandible in 13 hemifaces (44.8%) and reached the mandible at a mean distance of 33.1±5.2 mm anterior to the Go.

CONCLUSIONS

To avoid damaging the Mbr, surgical maneuvers should be positioned 4.5 cm anterior to the Go and 2 cm below the mandible.

Guided bone regeneration by means of a preformed titanium foil: A case of severe atrophy of edentulous posterior mandible

The aim of this case report was to evaluate the potential of preformed titanium foil (PTF) as membrane, used together with a mouldable allograft paste, for guided bone regeneration in a case of severe mandibular posterior atrophy involving the alveolar nerve. In order to create a rigid barrier to the competitive growth of soft tissues and a stable volume for the colonization of the osteoprogenitor cells, a foil of pure titanium was pre-shaped by means of a stereolithographic model, obtained from a CT-scan of the patient. This procedure showed promising results, allowing to maximize the outcome and simplifying the surgical phase.

[Dental 3d level simulators in the study of local anesthesia]

The purpose of the study was to develop a training protocol for local anesthesia in dental students. The study involved 90 2d year dental school students divided into 3 groups according to procedure training method: on skeletal preparations; by «Typodont» simulator and by combination of methods. Manipulation effectiveness criteria in skeletal preparations was penetrating the mandibular foramina by isolation of the corresponding region by latex scarf. In «Typodont» the effective injection was determined by light and sound signals. The results showed the necessity for combined approach as it gives an opportunity to identify mandible foramina by projecting on soft tissue marks with further skills developing on the simulator. When using the combined approach only 4 students successfully completed their task by initial injection while at the second attempt only 4 were not successful.

[Topographic features of lingual nerve and its relationship with other anatomical structures in maxillolingual groove]

By surgical interventions in maxillolingual groove area one should consider anatomical variations and topography of vessels, glands ducts and lingual nerve to prevent their injury. At the Department of Operative Surgery and Topographic Anatomy of the First Moscow State Medical University named after I.M. Sechenov we carried out anatomical study on cadavers (men and women, n=30).The study revealed topographical features of the lingual nerve and its relationship to other anatomical structures in the maxillolingual groove. It was found out that at the level of the second molar (96%) lingual nerve "crosses" duct of submandibular salivary gland, at the level of the third molar lingual nerve is located under the duct and lateral to it, closer to the inner surface of the body of the mandible. At the level of the first molar lingual nerve is located above and medial to Wharton duct and passes along sublingual-lingual muscles (m.hyoglossus).

Proximity of the Mandibular Canal to Teeth and Cortical Bone

INTRODUCTION

The proximity of the inferior alveolar canal to the mandibular molar roots may pose a risk of injury during various dental surgeries. The purpose of this study was to evaluate age-related and gender-related changes by using cone-beam computed tomography images between the roots of the second molars, mandibular cortex, and the inferior alveolar canal.

METHODS

One hundred fifty-five patients (68 men, 87 women), 20 years and older, who had previous cone-beam computed tomography scans were enrolled in this study. The patients were subcategorized by gender and age (group I, <21 years; group II, 21-40 years; and group III, >40 years). Distance between the mandibular canal (MC) and the second molar distal root apex as well as the 3 mandibular cortical regions (inferior cortex, buccal cortex, and lingual cortex) were measured.

RESULTS

In men, the second molar root apex to the MC distance was significantly shorter in group I than in group III (P < .01). In women, the second molar root apex to the MC distance was significantly shorter in group I than in group II and group III (P < .05). In both men and women, the buccal cortex of the mandible to the MC distance was significantly shorter on the right side compared with the left side (P < .01).

CONCLUSIONS

Our study shows that age, gender, and region have an influence on the location of the MC in the second molar area.

[Short sagittal osteotomy]

Bilateral sagittal split osteotomy has become the standard mandibular surgery for the treatment of dento-facial deformities. Even patients with less important deformities may undergo surgery. The morbidity must be as low as possible. We describe a technique with reduced split surfaces. The osseous section follows an oblique line since the thorn of Spix below and outside towards the supra-angular region. This section is completed by an osteotomy of the posterior border of the mandible. This split never reaches the inferior alveolar nerf tunnel. The protection of the alveolar nerve is increased what decreases considerably the risk of nervous complications of this intervention. The majority of the mandibular movements are possible by this technique with the exception of the important advancements and the increase of the height of the ramus.

Periosteum Metabolism and Nerve Fiber Positioning Depend on Interactions between Osteoblasts and Peripheral Innervation in Rat Mandible

The sympathetic nervous system controls bone remodeling by regulating bone formation and resorption. How nerves and bone cells influence each other remains elusive. Here we modulated the content or activity of the neuropeptide Vasoactive Intestinal Peptide to investigate nerve-bone cell interplays in the mandible periosteum by assessing factors involved in nerve and bone behaviors. Young adult rats were chemically sympathectomized or treated with Vasoactive Intestinal Peptide or Vasoactive Intestinal Peptide_10-28, a receptor antagonist. Sympathectomy depleted the osteogenic layer of the periosteum in neurotrophic proNerve Growth Factor and neurorepulsive semaphorin3a; sensory Calcitonin-Gene Related Peptide-positive fibers invaded this layer physiologically devoid of sensory fibers. In the periosteum non-osteogenic layer, sympathectomy activated mast cells to release mature Nerve Growth Factor while Calcitonin-Gene Related Peptide-positive fibers increased. Vasoactive Intestinal Peptide treatment reversed sympathectomy effects. Treating intact animals with Vasoactive Intestinal Peptide increased proNerve Growth Factor expression and stabilized mast cells. Vasoactive Intestinal Peptide_10-28 treatment mimicked sympathectomy effects. Our data suggest that sympathetic Vasoactive Intestinal Peptide modulate the interactions between nervous fibers and bone cells by tuning expressions by osteogenic cells of factors responsible for mandible periosteum maintenance while osteogenic cells keep nervous fibers at a distance from the bone surface.

Cone Beam Computed Tomography for the Dental Implant Patient

Cone beam computed tomography offers many advantages over 2-D imaging for the evaluation of potential implant sites. With the use of CBCT scans becoming more commonplace, it is important for clinicians to be knowledgeable and to use this new technology appropriately and judiciously. The purpose of this article is to describe the advantages and limitations of CBCT imaging for the presurgical and postsurgical evaluations of implant treatment and assessment of implant-related complications.

Reduced somatosensory impairment by piezosurgery during orthognathic surgery of the mandible

PURPOSE

This clinical trial aimed to test the hypothesis that piezosurgery causes reduced nerval irritations and, thus, reduced somatosensory impairment when used in orthognathic surgery of the mandible.

METHODS

To this end, 37 consecutive patients with Angle Class II and III malocclusion were treated using bilateral sagittal split osteotomies (BSSO) of the mandible. In a split mouth design, randomized one side of the mandible was operated using a conventional saw, while a piezosurgery device was used on the contralateral side. In order to test the individual qualities of somatosensory function, quantitative sensory testings (QSTs) were performed 1 month, 6 months and 1 year after surgery.

RESULTS

A comparison of the data using a two-way analysis of variance (ANOVA) revealed a significant reduction in postoperative impairment in warm detection threshold (WDT) (P = 0.046), a decreased dynamic mechanical allodynia (ALL) (P = 0.002) and a decreased vibration detection threshold (VDT) (P = 0.030) on the piezosurgery side of the mandible as opposed to the conventionally operated control side. In the remaining QSTs, minor deviations from the preoperative baseline conditions and a more rapid regression could be observed.

CONCLUSIONS

Piezosurgery caused reduced somatosensory impairment and a faster recovery of somatosensory functions in the present investigation.

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

OBJECTIVE

A previous cross-sectional investigation showed that the mandibular foramen location depends on the age and the vertical facial pattern of growing individuals. The aim of the present longitudinal study was to explain how these factors influence the distance between the foramen and the occlusal plane. It is known that a certain distance is necessary for a successful inferior alveolar nerve block in clinical dentistry.

MATERIALS AND METHODS

This distance, as well as another four cephalometric variables, were measured on both pre-treatment and 10-year post-treatment lateral cephalometric radiographs collected from 50 patients who underwent orthodontic treatment. The changes between these two sets of measurements were also calculated.

RESULTS

A multiple regression analysis was performed using the pre-treatment age, the pre-treatment inter-maxillary angle, the rotation of the occlusal plane and the change in mandibular ramus height as independent variables and the change of foramen-occlusal plane distance as a dependent variable. The independent variables under investigation were found to account for more than half of the variability of the foramen-occlusal plane distance (r = 0.732; p < 0.001).

CONCLUSION

In very young individuals the mandibular foramen is located approximately at the level of the occlusal plane. With age it moves upwards relative to the occlusal plane and more so for those individuals with a low anterior facial height (short-face vertical facial type). These observations are, at least, partially explained by the differential growth of the various elements of the maxillo-mandibular complex and the change of the inclination of the occlusal plane.

Implant-related nerve injuries

Injuries to branches of the trigeminal nerves are a known complication during dental implant placement. These injuries tend to be more severe than those experienced during other dentoalveolar procedures. This article reviews the types of nerve injuries and areas and situations of which clinicians should be cognizant when placing dental implants. Strategies to avoid injuries, and a management algorithm for suspected nerve injuries, are also discussed.

Frequency and anatomy of the retromolar canal - implications for the dental practice

The retromolar canal (RMC) is an anatomical variant of the mandibular canal. Apart from blood vessels it also contains accessory nerve fibers and is clinically important, because its presence can account for failures of mandibular block anesthesias and in rare cases, injuries of its neurovascular bundle can lead to complications such as hemorrhages and dysesthesias. The aim of this retrospective case study was to analyze the frequency and anatomy of the RMC using cone beam computed tomography (CBCT) in order to draw conclusions for the dental practice. A total of 680 CBCT scans comprising 1,340 mandibular sides were evaluated. A total of 216 RMCs (16.12%) were found. The most common appearance of the canal (39.82%) corresponded to type Al (vertical course), whereas type C (horizontal course) occurred least often (6.02%). Mean measured values were 1.03 mm (SD=0.27mm) regarding the RMC diameter, 10.19 mm (SD=2.64mm) regarding the RMC height and 15.10 mm (SD=2.83 mm) regarding the distance of the RMC to the second molar. Neither demographic factors nor the spatial resolution of the CBCT had a statistically significant impact on the frequency of the RMC. Since the present study revealed a frequency of RMCs amounting to 16.12% (corresponding approximately to every sixth retromolar area), we recommend to spare it during surgery or to consider an additional locoregional anesthesia in the retromolar region. For preoperative diagnosis the CBCT has proved suitable, offering the possibility to select the spatial resolution depending on the indication, so that radiation exposure is reduced without a decrease in validity.

Analysis of mental foramen in dry human mandibles of adult Nigerians

OBJECTIVE

This study was undertaken to investigate the dimensions number, shape and actual location of the mental foramen as well as to assess the occurrence of accessory mental foramen in dry human mandibles of adult Nigerians. It also considered the distances between the foramen and some anatomical landmarks.

METHOD

A total of 54 adult dry human mandibles obtained from bone collections in the department of Anatomy of selected Nigerian Universities were used for this study. The sliding digital caliper was used for taking measurements from mental foramen to symphysismenti, posterior border of ramus, lower and superior borders of the mandible. The vertical and transverse diameters of the mental foramen were also measured.

RESULTS

The most common location of the mental foramen was in line with the second premolar tooth (64.8%). The oval shape occurred more (63.6% on the left side and 56.6% on the right side) than the round shape. The dominant mental foramen was single mental foramen (76.9%) and there was no significant association between occurrence, location and shape of mental foramen and sides of the mandibles in this study (P > 0.05).

CONCLUSION

This study will be of clinical relevance to the dentists, oral and maxillofacial surgeons and anaesthetists. It will also be useful to the anthropologists and archeologists in identification and population studies.

[Reconstruction of inferior alveolar nerve canal based on shape feature]

It is difficult to distinguish the inferior alveolar nerve (IAN) from other tissues inside the IAN canal due to their similar CT values in the X image which are smaller than that of the bones. The direct reconstruction, therefore, is difficult to achieve the effects. The traditional clinical treatments mainly rely on doctors' manually drawing the X images so that some subjective results could not be avoided. This paper proposes the partition reconstruction of IAN canal based on shape features. According to the anatomical features of the IAN canal, we divided the image into three parts and treated the three parts differently. For the first, the directly part of the mandibular, we used Shape-driven Level-set Algorithm Restrained by Local Information (BSLARLI) segment IAN canal. For the second part, the mandibular body, we used Space B-spline curve fitting IAN canal's center, then along the center curve established the cross section. And for the third part, the mental foramen, we used an adaptive threshold Canny algorithm to extract IAN canal's edge to find center curve, and then along it established the cross section similarly. Finally we used the Visualization Toolkit (VTK) to reconstruct the CT data as mentioned above. The VTK reconstruction result by setting a different opacity and color values of tissues CT data can perspectively display the INA canal clearly. The reconstruction result by using this method is smoother than that using the segmentation results and the anatomical structure of mental foramen position is similar to the real tissues, so it provides an effective method for locating the spatial position of the IAN canal for implant surgeries.

A modified surgical technique for inferior alveolar nerve repositioning on severely atrophic mandibles: case series of 11 consecutive surgical procedures

BACKGROUND

To emphasize the characteristics and possible pitfalls of nerve reposition in cases of severe bone resorption in the posterior mandibular area, and to modify hard- and soft-tissue manipulation accordingly.

METHODS

We analyzed retrospectively, 7 patients in which we performed full arch lower jaw rehabilitation. The patients presented for oral rehabilitation having a minimal residual bone above the mandibular canal and had undergone inferioral veolar nerve (IAN) displacement with modified surgical technique for fixed prosthetic rehabilitation.

RESULTS

Eleven procedures of nerve repositioning were performed on severely atrophic mandibles. The average age of the patients was 43.29 years (12.37 SD). Residual bone above the mental foramen ranged between 0.5 mm and 1.5 mm, with an average of 0.93 mm (0.35 SD). In total, 32 dental implants were inserted into the area simultaneously with nerve displacement. The average follow-up time was 35.71 months(41.75 SD), ranging between 7 and 120 months.

CONCLUSIONS

Severe atrophic cases require special attention due to the loss of keratinized tissue around the crestal area.The use of a modified surgical approach and specific surgical instruments provides a safer working environment for the operator and ensures optimal results.

[Sensory disorders in inferior alveolar nerve after sagittal split osteotomy of the mandible]

Methodology of the sagittal split osteotomy of the mandible improved from year to year. However, there is still the problem of neurosensory disorders of inferior alveolar nerve in the early and late postoperative period is widely covered in the foreign literature. The incidence of these disorders ranges from 40 to 55%. During 2009-2013 years in Central Research Institute of Stomatology and Maxillofacial Surgery were operated 127 patients with associated deformities of the jaws: 102 according to traditional methods, 25 - by improved methods. Assessment of lower alveolar nerve conducted by electric teeth pulp test methods, blink reflex, computed tomography in 3D mode and the questionnaire. The results showed that the improved method of the sagittal split osteotomy of the mandible by using piezoelectric bone surgery saw during cutting of the cortical bone of the mandible and special splitters with replacing of damaging factors makes it possible to reduce the incidence of neurosensory disorders of inferior alveolar nerve and reduce the time of rehabilitation.

Peri-implant bone innervation: histological findings in humans

PURPOSE

The aim of the present study was to describe nerve fibres around osseointegrated implants in humans.

MATERIALS AND METHODS

Twelve mechanically failed implants, retrieved from 10 patients were collected from three dental centres over a period of 5 years. After implant removal, decalcified semi-thin sections (0.5 μm) were stained with thionic methylene blue for light microscopic analysis. In addition, an ultrastructural analysis was performed on serial ultra-thin sections (0.06 μm) using transmission electron microscopy.

RESULTS

Both myelinated and unmyelinated nerve fibres could be identified inside the Haversian canals of the osteonal bone near the implant threads. Myelinated fibres were also located at the woven bone around the implant. However, no differentiated nerve endings could be observed around the implants.

CONCLUSIONS

This study shows the presence of nerve fibres in human peri-implant bone. Previous studies in animals showed that those fibres participate in the process of bone modelling and remodelling. Yet, the role of peri-implant bone innervation in the osseoperception phenomenon cannot be ruled out since the mechanism of mechanoreception in bone is not fully understood.

Afferent and efferent aspects of mandibular sensorimotor control in adults who stutter

PURPOSE

Individuals who stutter show sensorimotor deficiencies in speech and nonspeech movements. For the mandibular system, the authors dissociated the sense of kinesthesia from the efferent control component to examine whether kinesthetic integrity itself is compromised in stuttering or whether deficiencies occur only when generating motor commands.

METHOD

The authors investigated 11 stuttering and 11 nonstuttering adults' kinesthetic sensitivity threshold and kinesthetic accuracy for passive jaw movements as well as their minimal displacement threshold and positioning accuracy for active jaw movements. They also investigated the correlation with an anatomical index of jaw size.

RESULTS

The groups showed no statistically significant differences on sensory measures for passive jaw movements. Although some stuttering individuals performed more poorly than any nonstuttering participants on the active movement tasks, between-group differences for active movements were not statistically significant. Unlike fluent speakers, however, the stuttering group showed a statistically significant correlation between mandibular size and performance in the active and passive near-threshold tasks.

CONCLUSIONS

Previously reported minimal-movement differences were not replicated. Instead, stuttering individuals' performance varied with anatomical properties. These correlational results are consistent with the hypothesis that stuttering participants generate and perceive movements on the basis of less accurate internal models of the involved neuromechanical systems.

A case report of developmentally missing mental foramen

The inferior alveolar nerve is the mandibular division of the trigeminal nerve. Studies have documented variations in the course and branching pattern of the nerve. Here the author reports a case of developmentally missing mental foramen in an individual with normal sensory function. Identification of variations in the nerve pathway is essential for treatment planning in the area.

Clinical anatomy of the lingual nerve and identification with ultrasonography

Our objective was to investigate the pathway of the lingual nerve and find out whether it can be identified using ultrasonography (US) intraorally. It is a dominant sensory nerve that branches from the posterior division of the mandibular aspect of the trigeminal nerve, and is one of the two most injured nerves during oral surgery. Its anatomy in the region of the third molar has been associated with lingual nerves of variable morphology. If surgeons can identify its precise location using US, morbidity should decrease. We searched published anatomical and specialty texts, journals, and websites for reference to its site and US. Cadavers (28 nerves) were dissected to analyse its orientation at the superior lingual alveolar crest (or lingual shelf). Volunteers (140 nerves) had US scans to identify the nerve intraorally. Our search of published books and journals found that descriptions of the nerve along the superior lingual alveolar crest were inadequate. We found no US studies of the nerve in humans. Dissections showed that the nerve was above (n=6, 21%) and below (n=22, 79%) the crest of the lingual plate. US scans showed 140 lingual nerves intraorally in 70 volunteers. The nerve lay either above or below the superior lingual alveolar crest, which led us to develop a high/low classification system. US can identify the lingual nerve and help to classify it preoperatively to avoid injury. Our results suggest that clinical anatomy of the lingual nerve includes the superior lingual alveolar crest at the third and second molars because of its surgical importance. US scans can successfully identify the nerve intraorally preoperatively.

Position of the mental foramen in Kosovarian population

The aim of this study was to determine the position, shape, number and radiographic appearance of the mental foramen in a selected Kosovarian population. Five hundred panoramic radiographs of dental Kosovarian patients were selected and analyzed according to the mental foramen position, shape, radiographic appearance, number and symmetry. The mean distance in the horizontal plane of the mental foramen to the posterior border of the mandibular ramus was 67.5 mm and for distance from the mental foramen to symphysis menti 24.84 mm. In the vertical plane the mean distance of the mental foramen to alveolar crest was 20.38 mm and 14.68 mm for distance of the mental foramen to the lower border of mandible. The majority of mental foramen was oval in shape and the most frequent radiographic appearance was the separated type. Accessory mental foramina were detected in < 1% of the cases and the mental foramen was not bilaterally symmetrical but no statistical differences were found. This study showed that the most common position of the mental foramen investigated using panoramic radiographs from a selected group in Kosovarian population was between the first and second mandibular premolars with distinct tendency to be positioned near to the second mandibular premolar.

Radiographic assessment of the mandibular retromolar canal using cone-beam computed tomography

OBJECTIVE

The 'retromolar' nerve is a collateral branch of the inferior alveolar nerve. Cone-beam computed tomography (CBCT) provides higher resolution images. This CBCT study reports the frequency of the retromolar nerve.

MATERIALS AND METHODS

From 2007-2010 the CBCT study of 233 hemi-mandibles have been examined. The CBCT study was obtained from an investigation of the posterior mandibular region in 187 patients suffering from different pathologies and it was aimed at detecting in patients the presence of a retromolar canal and foramen.

RESULTS

Thirty-four retromolar canals with a foramen were detected on 233 CBCT (14.6%) in 30 out of 187 patients (16%). In the 46 patients who underwent CBCT bilaterally, the retromolar canal was found in nine subjects (19.6%) and was present bilaterally in four subjects, for an incidence of 8.7%.

CONCLUSIONS

The results suggest that the radiological frequency of the retromolar nerve is notable, with a possible relevance in the surgical approach of the mandibular retromolar area. The presence of a retromolar canal, well detected with CBCT, may warn clinicians about the possibility of inadequate pre-surgical anaesthesia, local intra-operative bleeding and post-operative alterations of the sensation in the third molar area.

[Diagnostics and treatment of acute odontogenic osteomyelitis of the mandible considering functional state of inferior alveolar nerve]

Evaluation of functional impairment of inferior alveolar nerve in acute odontogenic inflammatory processes was carried out in this clinical study by means of stimulation electroneurography. Possibility of early diagnosis of acute odontogenic osteomyelitis by this method and effectiveness of decompression osteoperforation for its treatment was shown.

Anatomy of the pterygomandibular space - clinical implication and review

AIM

The aim of this study was to present review of the pterygomandibular space with some referrals to clinical practice, specially to the methods of lower teeth anesthesia.

CONCLUSIONS

Pterygomandibular space is a clinically important region which is commonly missing in anatomical textbooks. More attention should be paid to it both from theoretical and practical point of view, especially in teaching the students of first year of dental studies.

Mandible - clinically revisited

Based on the current literature authors revised anatomical and clinical datas considering the mandible.

[The mental foramen or "the crossroads of the mandible." An anatomic and clinical observation]

This paper presents a clinical and anatomical review of the mental foramen (MF) based on recent publications (since 1990). Usually, the MF is located below the 2nd premolar or between the two premolars, but it may also be positioned below the 1st premolar or below the mesial root of the 1st molar. At the level of the MF, lingual canals may join the mandibular canal (hence the term "crossroads"). Accessory MF are frequently described in the literature with large ethnic variations in incidence. The emergence pattern of the mental canal usually has an upward and posterior direction. The presence and extent of an "anterior loop" of the mental canal may be overestimated with panoramic radiography. Limited cone-beam computed tomography currently appears to be the most precise radiographic technique for assessment of the "anterior loop". The mental nerve exiting the MF usually has three to four branches for innervation of the soft tissues of the chin, lower lip, facial gingiva and mucosa in the anterior mandible. The clinician is advised to observe a safety distance when performing incisions and osteotomies in the vicinity of the MF.

[Retromolar mandibular anesthesia. Radiological and topographical study of an additional method of lower teeth anesthesia]

The aim of the study was to estimate the clinical efficacy of mandibular third molars anesthesia with various combinations of local anesthesia methods. Anatomical, radiological and morphological methods were used in the study. The topographic features of retromolar triangle were thoroughly examined. The neurovascular bundle revealed its relationship with retromolar area structures. According to the results of the clinical study the most effective combinations of mandibular third molars analgesia were selected.

[Anatomical and radiological studies on additional mandible teeth anesthesia considering innervation variability]

The paper presents studies on nutritional foramina of the mandible. Some nutritional foramina located in the frontal mandibular region on the lingual surface and containing significant blood vessels and nerves are found to be more typical for teeth-bearing mandible. In retromolar area in case of third molars presence intraosseous canals were revealed leading to inferior alveolar nerve canal. One should consider intraligamental and lingual anesthesia by lower incisors extraction. Intraosseous anesthesia and retromolar area infiltration significantly increase anesthesia efficiency by third molar extraction.

Comparison of orthopantomography and computed tomography image for assessing the relationship between impacted mandibular third molar and mandibular canal

BACKGROUND

Permanent mandibular third molar are most commonly impacted teeth. In planning the surgical removal of mandibular third molar, correct diagnosis requires not only their precise spatial location, but also a thorough and accurate assessment of the intimate relationship with adjacent anatomical structures. Various imaging modalities have been used for localizing the mandibular third molar but not satisfactorily.

AIM

This prospective study of 30 patients with 42 impacted mandibular third molars was carried out with the aim of finding evidence for justifying the use of computed tomography and orthopantomography as a diagnostic modality, prior to surgical intervention of impacted mandibular third molar.

MATERIALS AND METHODS

Subjective evaluation of the CT and OPG images by two observed had shown that there was significant difference between the CT and OPG for radiographic visibility of mandibular canal in relation to third molar.

RESULTS

Data analysis was done with Chi-square test (X(2)) and z-test to find the significant difference between the two radiographic modalities OPG and CT in localizing special relationship of impacted mandibular third molar. The comparison of OPG and CT showed z-value >1.5 in darkening of roots (1.98), deflection of root (2.00) interruption of z-value = 0 in narrowing of canal and dark, bifid apexes. Also it showed p-value <0.05 in all the radiographic signs except narrowing of mandibular canal and and dark and bifid apexes.

CONCLUSION

The spiral CT image provides a unique opportunity to determine the exact position of impacted mandibular third molar and their relationship to adjacent structure in all three planes.

CLINICAL SIGNIFICANCE

Computed tomography is highly instrumental in depicting the relationship of mandibular third molar with inferior alveolar nerve canal before treatment and accurate appraisal of the several aspects can be made regarding prognosis.

Appearance of anatomical structures of mandible on panoramic radiographs in Iranian population

PURPOSE

Currently panoramic radiography is used for diagnosis of dental and bone lesions, but anatomical structures also can be seen and may be useful in dental managements. This study aimed to investigate the visibility of some important mandibular features relating to neurovascular structures in Iranian population.

MATERIALS AND METHODS

Panoramic radiographs were taken by Planmeca machine from 412 patients using standard exposure. The position of patient was in compliance with standard protocol. Then mandibular incisive canal was evaluated and data were analyzed statistically.

RESULTS

Mental foramen, anterior loop of mental nerve and incisive canal could be observed in 84.2, 66 and 51.7% of the cases. Respectively, lingual foramen was observed in only 6.1% of the radiographs. Gender doesn't affect on the visibility of these structures. There was a relationship between mandibular foramen and canal with age.

CONCLUSION

Mandibular incisive canal was considered in 51.7% of cases, it was observed that the result obtained was more than those of other researches.

Different sympathetic pathways control the metabolism of distinct bone envelopes

Bone remodeling, the mechanism that modulates bone mass adaptation, is controlled by the sympathetic nervous system through the catecholaminergic pathway. However, resorption in the mandible periosteum envelope is associated with cholinergic Vasoactive Intestinal Peptide (VIP)-positive nerve fibers sensitive to sympathetic neurotoxics, suggesting that different sympathetic pathways may control distinct bone envelopes. In this study, we assessed the role of distinct sympathetic pathways on rat femur and mandible envelopes. To this goal, adult male Wistar rats were chemically sympathectomized or treated with agonists/antagonists of the catecholaminergic and cholinergic pathways; femora and mandibles were sampled. Histomorphometric analysis showed that sympathectomy decreased the number of preosteoclasts and RANKL-expressing osteoblasts in mandible periosteum but had no effect on femur trabecular bone. In contrast, pharmacological stimulation or repression of the catecholaminergic cell receptors impacted the femur trabecular bone and mandible endosteal retromolar zone. VIP treatment of sympathectomized rats rescued the disturbances of the mandible periosteum and alveolar wall whereas the cholinergic pathway had no effect on the catecholaminergic-dependent envelopes. We also found that VIP receptor-1 was weakly expressed in periosteal osteoblasts in the mandible and was increased by VIP treatment, whereas osteoblasts of the retromolar envelope that was innervated only by tyrosine hydroxylase-immunoreactive fibers, constitutively expressed beta-2 adrenergic receptors. These data highlight the complexity of the sympathetic control of bone metabolism. Both the embryological origin of the bone (endochondral for the femur, membranous for the mandibular periosteum and the socket wall) and environmental factors specific to the innervated envelope may influence the phenotype of the sympathetic innervation. We suggest that an origin-dependent imprint of bone cells through osteoblast-nerve interactions determines the type of autonomous system innervating a particular bone envelope.

[State of lower alveolar and mental nerves by mandible fractures healing under transbone osteosynthesis]

Fracture of mandibular body at the level of P3-P4 with symphysis rupture was modeled, reposition and transosseous osteosynthesis with a specially developed device were performed under anesthesia in the operating room in 17 adult mongrel dogs in order to specify the pathogenesis and the dynamics of injury and jaw nerve regeneration. It has been established, that the arrangement of the neurovascular bundle in medullary canal predetermines the development of acute and chronic compression-and-ischemic neuropathy even if accurate reposition of bone fragments takes place. The histological signs of nerve fiber regeneration, the loss of the quantity of myelin-free nerve conductors and the retrograde spreading of degenerative changes in myelinized nerve conductors, including regenerating ones, have been found beginning from 4 weeks after injury. It has been concluded, that spontaneous nerve regeneration in case of mandibular fractures should be actively supported by neuroprotective, anti-edematous and anti-inflammatory therapy.