The vasculature of the rat molar periodontal ligament

The vascular architecture of the rat molar periodontal ligament was investigated using the SEM vascular casting technique. Vascular patterns varied within the different regions of the tooth socket. A different microvascular arrangement was found to be associated with (i) the buccal and lingual walls (ii) the interdental septum and (iii) the interradicular septum. Tracts of four to six vessels coursed occluso‐apically down the buccal and lingual walls. A similar pattern existed at the interdental septum except that the vessels were more closely packed. At the interradicular septum, the postcapillary venules coursed within the ligament for only 100 to 400 μm before re‐entering the bone. Overall, vessels were predominantly postcapillary venules with a lesser number of capillaries. Anastomoses between adjacent vessels coursing in the ligament occurred infrequently, although many communications with the alveolar plexus were noted. Except at the interradicular septum, ligament vasculature arose mainly from the deeper gingival vessels. A few vessels originated from branches of the alveolar plexus, forming a hairpin loop as they entered the plexus. These findings differed markedly from Kindlova & Matěna's (1962) description of morphologically paired arterial and venous systems. On a morphological basis vascular flow was considered to be directed from the coronal down to the apical region of the socket. However, Ligament vessels adjacent to the vertical walls of the interradicular septum received a greater arterial supply than the crestal region, where venous drainage was more prolific. Therefore, the vascular arrangement over the septum suggested a direction of vascular flow opposite to that occurring at the outer walls of the socket, although tidal flow could occur in either direction in the interradicular area.