[Changes in the microvascular pattern of the periodontium in an experimental tooth movement].

The purpose of the present investigation was to observe changes in the microvasculature related to the reorganization of periodontal tissue during tooth movement and to evaluate the role of periodontal vasculature. The experimental study, employing cats, was done by injection of acrylic resin into the microcirculatory system of the periodontal membrane to make visible vascularization and remodeling of the alveolar bone structure when orthodontic force was placed on a tooth. 1. Pressure side New blood vessels arose from pre-existing vessels, entered resorption lacunae, connected with each other, and formed the vascular layer for alveolar bone resorption, covering the bone surface. The blood vessels of the root side around the degenerate tissue initially had spear-like ends because of imperforation, but the vessels gradually became interconnected, forming capillary loops, and encircling the degenerate tissue. This vascular layer for capillary-loop formation and the inner circumferential vascular layer for alveolar bone resorption were completed after 3 weeks. Newly formed blood vessels ran into the resorption lacunae and formed two networks. The networks enhanced metabolic activities such as resorption by multinuclear giant cells and the proliferation of osteoblasts and fibroblasts, resulting in regeneration of the periodontal membrane. 2. Tension side The vascular pattern on the crest area in the controls showed a two-layered structure with one vascular network on the root side and one on the alveolar bone side. After 1 week, the latter was stretched to the former, forming a canopy-like structure, and causing the two-layered structure to disappear. The canopy-like structure disappeared with time, and vascularization occurred at the sites of bone formation and fibroblast proliferation. These vascular changes seemed to contribute to the regeneration of the periodontal membrane. Blood vessels responded rapidly to the environmental changes in the periodontal membrane, adjusting their morphology to functional changes, and these vascular changes preceded the deposition or resorption of bone.