Presence and location of adrenergic nerve endings in the dental pulps of mouse molars

Abstract

In all, 30 adult (45-day-old) Swiss Webster mice were used for light and electron microscopic examination of the presence, number, and location of adrenergic endings in the first molar teeth. Prior to sacrifice, 10 animals received i.p. injections at 8, 6, 4, and 2 hours of 0.5 cc of 20 mg/kg solution of 5-hydroxydopamine (5-OH-DA) as a label for adrenergic endings. The animals were then anesthetized, perfused with Karnovsky's fixative, and the teeth were postfixed in Osmic acid, decalcified, embedded in methacrylate, and serial-sectioned. The sections were surveyed by light microscopy, and the number and location of nerve endings containing the reduced 5-OH-DA were recorded. Ten control mice were injected with the vehicle solution and prepared in the same manner. A third series of mice were given a single injection of 5-OH-DA, sacrificed, and prepared for ultrastructural study. The molar pulps were divided into four areas to facilitate examination: pulp horns, coronal pulp, bifurcation area, and root pulp. These four areas were further divided into three zones: odontogenic, vascular-related, and nonvascular-associated. The location and number of endings were evaluated, and an average of approximately 70 endings containing the 5-OH-DA were found in each tooth using light microscopy. These represented 35.5 +/- 5.2 in the pulp horns; 26.1 +/- 2.4 in the central coronal; 5.4 +/- 0.7 in the bifurcation, and 5.6 +/- 0.9 in the root pulp per tooth. Vascular related endings were found in greatest number, the odontogenic zone next, and free endings lease. Verification of location of 5-OH-DA by ultrastructural analysis revealed the false transmitter in vesiculated endings in the four areas and zones of the pulp.

Dynamics of the Pulpo-Dentin Complex

“…8). A qualitatively similar pattern of distribution of sympathetic nerves was reported by Avery et al (1980). They found a large number of adrenergic nerve endings in odontogenic areas near the basal ends of odontoblasts, and speculated that they may somehow modify dentinogenesis.…”

Morphological research on the sensitivity of dentin.

“…A small number of unmyelinated nerve fibers, some of which were considered to be vasomotor autonomic nerve fibers (MATTHEws, DORMAN and BISHOP, 1959;FRANK and FRANK, 1972;AVERY, Cox and CHIEGO, 1980), and many myelinated nerve fibers entered the pulp canal through the apical foramen, accompanied by blood vessels. The nerve fibers were bundled without being ensheathed in a definite perineurium .…”

Neuropeptides in Dental Pulp: The Silent Protagonists

“…Thus, neural agents are an important signal for neurogenic inflammation, for stimulation and repair, and for regulating homeostatic functions of the pulp (67). The nerve fibers in pulp are components of a larger peripheral nervous system that includes afferent (sensory) fibers originating from the trigeminal ganglion and sympathetic fibers originating from the cervical sympathetic ganglia (70,71). There are still controversies regarding the parasympathetic innervation of the human pulp (72).…”