Abstract
Rabbit molars are continuously erupting laminated teeth. The fine structure of blood vessels in the molars of domestic rabbits has not been extensively studied yet. The present study demonstrates the fine structure of blood vessels of dental pulp by means of: 1) transmission electron microscopy (TEM) and 2) scanning electron microscopy (SEM).
Adult domestic rabbits (Oryctolagus cuniculus) weighing 3-5 kg were perfused with 2% glutaraldehyde in 0.1M cacodylate buffer (pH 7.2) through the canulated thoracic aorta in this study. For TEM, small pieces of pulp were decalcified, postosmicated, embedded in Araldite 502, sectioned and observed with a JEM-100cx transmission electron microscope. For SEM, the blood vessels were visualised by a cast method injecting low-viscosity methacrylate (Mercox CL-2B, Dainihon Ink Chemical Company, Tokyo, Japan). The specimens were macerated with 10% NaOH solution, washed in tap water, and then dried in air. After being sputter-coated (Eiko sputter coater 1B-2, Mito, Japan) with gold, the casts were observed with a JEM-50A scanning electron microscope.
The fine structure of arterioles consisted of three layers; however, the tunica adventitia was always obscure or often lacking. Arterioles possessing thickened endothelial cells which almost completely occlude the lumen were rarely observed. Adjacent to the outer layer of such arterioles, small individual non-myelinated nerve terminals were observed. These structures are similar to the arteriovenous anastomosis previously observed by TEM in human dental pulp.
A peculiar feature observed in the pulpal capillaries adjacent to arterioles was the partial unevenness of their diameters which ranged from 0.5 to 7μm. The length of each contracted or dilated portion varied from 4 to 40 μm. Contraction-dilation intervals also varied considerably with the distance between contracted and dilated parts, ranging from 1 to 30mμ. Consequently, the overall external morphology of these capillaries showed a marked irregularity. These capillaries showed several gaps between endothelial cells and were enveloped with basement membrane. These structural features were observed by SEM as well as by TEM and seem to be related to capillary permeability in this area.
