Course and composition of the nerves that supply the mandibular teeth of the rat

Abstract

The rodent dentition has become an important model for investigations of interactions between dental tissues and peripheral neurons. Although experimental nerve injury has been widely used for such studies, there is uncertainty about the courses of nerve fibers supplying the mandibular teeth. In order to clarify this, we used a mixture of monoclonal antibodies against neurofilament proteins to enhance demonstration of nerve fibers so that small nerves could be readily traced in serial frozen sections of mandibles of Sprague Dawley rats ranging in age from embryonic day (E) 18 to postnatal day (P) 90. The 1st molar and anterior portion of the 2nd molar were innervated by small nerves that emerged as distinct branches of the IAN trunk at or near the mandibular foramen. In contrast, the nerve supply to the 3rd molar and posterior part of the 2nd molar was a branch of the lingual nerve that bypassed the mandibular canal altogether. The IAN trunk split into the mental nerve and a large branch to the incisor about 2 mm anterior to the mandibular foramen. Thick branches of the incisor nerve descended into the incisor socket to form a dense plexus of nerve fiber bundles extending along the length of the incisor periodontium. The sparse pulpal innervation of the incisor was provided by a few thin fascicles that emerged from the caudal portion of the periodontal plexus to enter the incisor apex. The dental branches of the IAN and lingual nerve seen in the adult were well established and readily identifiable at age E18 even though their targets were limited to the follicles of the developing teeth. These studies show that the trigeminal branches that supply the mandibular teeth can be identified at a wide range of ages as distinct nerves at a considerable distance proximal to their targets. This detailed information on the courses taken by the dental nerves can provide an anatomical basis for increased precision in characterization and perturbation of neural pathways from the molars and incisor.

Neurochemical Properties of Dental Primary Afferent Neurons

“…Several literatures suggested that over 60% of axons of inferior alveolar nerve neurons were myelinated [24-27], which showed discrepancyto our data in whichonly 25.7% were myelinated. In addition, more recent study reported that most of parental axons traced with horseradish peroxidase placed in upper molars of rats were myelinated [28].…”

Morphometric analysis of the mandible in growing rats with different masticatory functional demands: adaptation to an upper posterior bite block

“…However, photographic analysis can only provide cross‐sectional data. The plane formed by the mental and the mandibular foramens was chosen as a reference plane (14), since the endoskeleton of the rat mandible, including these two anatomical features, has been found to be the most stable structure during development (19).…”

“…1, the area of the external surface of the hemi-mandible, including the condylar process, excluding the teeth; 2, the area of the condylar process, delimited by the condylar tangent (tangent to both upper and posterior mandibular notches); 3, the angle formed by the perpendicular from the most posterior and superior part of the condyle to the condylar tangent and the reference plane; 4, the angle formed by the axis of the incisor alveolar process and the reference plane (incisor alveolar axis: a line from the midpoint between the upper and lower aspect of the incisor alveolar crest to the midpoint between the deepest part of the incisor alveolar curvature and the edge of the digastric fossa; 5, the angle formed by the lower border of the mandible and the reference plane; 6, the angle formed by the occlusal plane and the reference plane; 7, the maximal distance of the condyle from the condylar tangent; 8, the maximal distance between the mental foramen and the condyle; 9, the maximal distance between the mental foramen and the coronoid process; 10, the maximal distance between the mental foramen and the angular process; 11, the distance between the condylar tangent points; 12, the maximal vertical distance of the coronoid process from the reference plane; 13, the maximal vertical distance of the angular process from the reference plane; 14, the distance between the reference plane and the deepest point of the alveolar crest of the third molar; 15, the distance between the reference plane and the deepest point of the alveolar crest of the first molar; 16, the distance between the reference plane and the mesial cusp of the third molar; 17, the distance between the reference plane and the middle cusp of the first molar. ular foramens was chosen as a reference plane (14), since the endoskeleton of the rat mandible, including these two anatomical features, has been found to be the most stable structure during development (19).…”

Dental Pulp Cells Produce Neurotrophic Factors, Interact with Trigeminal Neurons in Vitro, and Rescue Motoneurons after Spinal Cord Injury

“…Even though the anatomical relation between developing teeth and trigeminal fibers has been extensively studied in the past (Byers, 1984;Luukko, 1997;Naftel et al, 1999), our knowledge of how the dental pulp becomes innervated is still only fragmentary. Trigeminal axons are present before any structural signs of tooth formation are detectable.…”