Importance of anatomy in dental implant surgery.

BACKGROUND: The knowledge of nerves and vessels in the maxillofacial region, particularly the anatomical structures in the maxilla, mandible, tongue muscles, and salivary glands, is essential for dental surgeons. In addition, the structures in the mandibular canal, palate, and maxillary sinus should be understood well. HIGHLIGHT: The arteries and nerves in the maxillofacial region were observed in this study. Some variations in the origin of the inferior alveolar artery were found. Notably, the variations in the origin of the inferior alveolar artery from that of the external carotid artery and a double origin of the inferior alveolar artery were observed. Thus, the maxillary artery may originate from the external carotid and stapedial arteries. The following points are important. (1)The greater palatine artery is always located deeper than the greater palatine nerve. (2)The posterior superior alveolar artery often runs through the compact bone of the maxilla. Using CT scans, the canal of the artery can be observed. (3)Variations in origins of the inferior alveolar artery have been observed. The origin of the inferior alveolar nerve may differ depending on the course of the maxillary artery. CONCLUSIONS: Dental practitioners should, therefore, have a comprehensive knowledge of the anatomy of the maxillofacial region and its variations. Without this knowledge, they should not operate on patients.

The lingual nerve: overview and new insights into anatomical variability based on fine dissection using human cadavers.

This article, for both researchers and clinicians, presents an overview of the lingual nerve and highlights how new insights into human anatomical variability can be gained by integrating fine dissection of cadavers with neuroanatomical approaches, microscopic studies, and morphometric techniques. Textbooks mainly provide descriptions of the typical or common gross anatomical appearance of structures in the human body with little reference to the nature and extent of variation that may be encountered within and between populations. Furthermore, few texts attempt to integrate descriptions of the regional distribution and branching of neural structures with their central connections or their microscopic anatomy. Using the lingual nerve as an example from the head and neck region, we show that there is still an important place for detailed fine dissections of human cadavers when they are also integrated with morphometric techniques applied to data representing observed variation at both macro- and micro-levels. It is essential that health professionals have a sound understanding of the nature and extent of anatomical variation displayed normally by their patients so that they can perform procedures, such as local anaesthesia and surgery, safely and also be able to correctly diagnose pathology when it is present.

The facial nerve: anatomy and associated disorders for oral health professionals.

The facial nerve, the seventh cranial nerve, is of great clinical significance to oral health professionals. Most published literature either addresses the central connections of the nerve or its peripheral distribution but few integrate both of these components and also highlight the main disorders affecting the nerve that have clinical implications in dentistry. The aim of the current study is to provide a comprehensive description of the facial nerve. Multiple aspects of the facial nerve are discussed and integrated, including its neuroanatomy, functional anatomy, gross anatomy, clinical problems that may involve the nerve, and the use of detailed anatomical knowledge in the diagnosis of the site of facial nerve lesion in clinical neurology. Examples are provided of disorders that can affect the facial nerve during its intra-cranial, intra-temporal and extra-cranial pathways, and key aspects of clinical management are discussed. The current study is complemented by original detailed dissections and sketches that highlight key anatomical features and emphasise the extent and nature of anatomical variations displayed by the facial nerve.

Aberrant distribution of the trochlear nerve: A cadaveric study supported by immunohistochemistry.

The trochlear nerve is generally considered to be a purely motor nerve supplying one extraocular muscle, the superior oblique. In the current study, 28 orbits were dissected and in one orbit (3.6%), the trochlear nerve divided into two main branches. The medial branch followed the classical course, entered the superior oblique muscle and was presumed to be motor in function. However, before entering the muscle, it partially fused with the frontal nerve, and gave a bundle of nerve fibres to the frontal nerve. The lateral branch gave a communication to the frontal nerve, travelled along the lacrimal nerve, received a branch from the lacrimal nerve then penetrated the lacrimal gland. The lateral branch was presumed to be sensory. Paraffin sections from the two branches were stained using immunohistochemistry. The two branches had different nerve fibre populations and showed distinct differences in neurofilament proteins (NFP) immuno-labelling. While both branches showed intense labelling for NFP-H, the lateral branch showed no staining or faint staining for NFP-M and NFP-L respectively, but the medial branch showed moderate labelling for both the NFP-M and NFP-L. Staining for substance P, a marker for nociceptive fibres, showed intense staining in a subset of fibres in the lateral branch, but no staining in the medial branch. Calcitonin gene-related peptide labelling was evident in some axons and some Schwann cells in the medial branch but widespread, weak and fine granular in the lateral branch. These findings indicate that, in some individuals (3.6%), the trochlear nerve may contain motor and sensory fibres, suggesting inter-nuclear communication within the brainstem during embryogenesis or mixing of nerve fibres in their extra-axial pathways.

Nerve fiber analysis on the morphology of the lingual nerve.

The route of fine fascicles of nerve fibers in the lingual nerve was clarified. Contemporary anatomy textbooks describe the lingual nerve as supplying sensory innervation to the mucous membrane of the presulcal part of the tongue, the floor and side wall of the mouth, and the mandibular gums. In addition to receiving the chorda tympani and a branch of the inferior alveolar nerve, the lingual nerve is connected to the submandibular ganglion by a few branches. It carries preganglionic fibers from the chorda tympani and postganglionic fibers from the submandibular ganglion to the submandibular and sublingual glands. The branch from the mylohyoid nerve is described as a sensory nerve. However, we observed that this branch was directly connected to the submandibular ganglion. Furthermore, the branch from the submandibular ganglion innervated thin membranous tissue that originated in the petrous part of the temporal bone and inserted into the lateral surface of the superior constrictor. These branches have not been described in the anatomy textbooks and literature. Therefore, we studied the morphological features of the lingual nerve and discovered the route of fine fascicles of nerve fibers in the lingual nerve. These findings will likely improve the neurological and physiological understanding of the function of the lingual nerve.

Newly identified thin membranous tissue in the deep infratemporal region.

Recently, the importance of deglutition has attracted attention due to its role in the prevention of aspiration pneumonia. We therefore observed the anatomy of the pharynx of 57 hemi-sections of adult Japanese cadavers (male 32 sides, female 25 sides). A previously unidentified tissue was observed in the infratemporal fossa. This unidentified tissue was a thin membranous tissue that existed between the medial pterygoid and the superior constrictor in all of the cadavers examined. The previously unknown membranous tissue consisted of collagenous and muscular fibers and was innervated mainly by a branch of the mandibular nerve.