Blocking the buccal nerve using two methods of inferior alveolar block injection.

The anatomic relations of the buccal nerve branch of the mandibular division of the trigeminal nerve were studied to explain the rationale for the discrepancy in blocking the buccal nerve using two methods of blocking the inferior alveolar nerve, the conventional method and the Gow-Gates method. The conventional method rarely blocks the buccal nerve, while the Gow-Gates method is reported to consistently block the buccal nerve. Eight head and mandibular specimens were dissected to observe the path of buccal nerve and its relationship to the path of needles in the conventional and Gow-Gates techniques. The buccal nerve descends on the medial and then anterior aspect of the deep head of the temporalis muscle (Tdh). At the latter position the buccal nerve enters the retromolar fossa and is encased in a fascial sleeve created by a dense fascial band that spans between the temporalis muscle tendons and the buccinator muscle. At the level of the conventional block injection the buccal nerve was shielded from the path of the needle by the Tdh and the fascial band. In the Gow-Gates block injection, the buccal nerve was exposed on the medial surface of the Tdh, immediately lateral to the path of the needle and proximal to the fascial sleeve. Consequently, the anatomical relations of the buccal nerve in the conventional block method essentially shield the nerve from being bathed by anesthetic solution while in the Gow-Gates method the relations are such that the buccal nerve can be exposed to anesthetic solution and thus blocked, explaining the findings in clinical dentistry.

The viscoelastic properties of the human temporomandibular joint disc.

PURPOSE: This study evaluated the viscoelasticity of the human temporomandibular joint (TMJ) disc by comparing the moduli of elasticity generated by compressing disc specimens under two different loading rates. MATERIALS AND METHODS: Twelve TMJ disc specimens 4.25 mm +/- 0.15 mm in diameter were obtained from fresh cadavers between 65 and 75 years of age. One group of specimens was subjected to a loading rate of 0.00127 mm/sec, and the other was subjected to a loading rate of 0.000635 mm/sec. Modulus of elasticity was calculated from the stress and strain values obtained from each specimen. RESULTS: When the specimens were subjected to an average 0.00127 mm/sec loading rate, a mean modulus of elasticity of 0.541 N/mm2 was derived. When an average 0.000635 mm/sec loading rate was used, a mean modulus of elasticity value of 0.211 N/mm2 was derived. These two mean values were significantly different, as indicated by the results of a one-tailed t-test. CONCLUSIONS: Analysis of the data showed that the human TMJ disc specimens became stiffer as the loading rate increased.

Innervation of rat molar teeth: II. A quantitative analysis of primary sensory neurons innervating a mandibular molar tooth.

This study was conducted to determine the source and number of primary sensory neurons (PSNs) innervating a mandibular molar tooth of a population of 15-18-week-old Sprague-Dawley rats. The pulpal tissue was exposed to horseradish peroxidase (HRP) pellets for 24 hours. Subsequently the animals were perfusion fixed and the following PSN structures were examined for the presence of HRP-labelled cells: trigeminal (TGs) and cervical dorsal root ganglia (DRGs) and mesencephalic nucleus (MN). Only the TGs contained labelled cells and they thus were the sole source of PSN pulpal innervation. The number of TG cells was highly variable, 49-407, but most of this variability was attributable to insufficient HRP filling of the pulp chamber or leakage of HRP into periapical tissue. Selection of TGs whose respective experimental teeth demonstrated that HRP filled and was restricted to the pulp chamber revealed a narrower range of TG cells providing pulpal innervation to the first molars, 142-288, with an average of 213. A detailed mapping of these cells indicated a somatotopic distribution within the mandibular territory of the TGs. It was concluded that these findings represent TG's contribution to the pulpal innervation of this specific population of rat first molar teeth. This suggests that from animal to animal the density of innervation may be quite variable and it is hypothesized that the sensitivity of the pulp would likewise vary. In addition, these findings may contribute to the explanation of why there is variability in the stimulus strength needed to elicit a pain response in the human dentition.

Innervation of rat molar teeth: I. Distribution of neuronal cell bodies in the trigeminal ganglion from a mandibular molar tooth.

The cell bodies of neurons innervating a rat mandibular molar tooth were examined with respect to their location in the trigeminal ganglion. The study sought to determine if these cell bodies were restricted to a specific somatotopic location within the mandibular territory of the ganglion or if they were distributed throughout the entire mandibular territory. Horseradish peroxidase (HRP) pellets were placed in the cavity preparation of right first mandibular molar teeth for a 24-hour period. The animals were then perfusion fixed, and the right trigeminal ganglion was removed, sectioned and processed by the tetramethyl benzidine neurohistochemical technic. The four trigeminal ganglia constituting this experimental series demonstrated 129, 185, 236, 318 HRP-positive cell bodies. These cell bodies were dispersed throughout the extent of the mandibular territory. It was concluded from these observations that the distribution of cell bodies innervating a rat mandibular molar tooth is not restricted to a specific region of the mandibular territory of the trigeminal ganglion, but rather the distribution of these cell bodies is throughout all parts of the mandibular territory.