Periodontal Vasculature Research Articles

Gingival Micro Circulation: Nature of Vasculature

Microcirculation is defined as the flow of blood in the minutest blood vessels present in the tissues. These micro-vessels in the organs and tissues comprises the microvasculature. These micro-vessels are made up of four components that includes arterioles metarterioles capillaries and venules. Arterioles carry oxygenated blood to the capillaries. Blood in the capillaries in turn flows out into veins via venules. Microcirculation differs from macro-circulation which involves circulation of blood to and from the organs. The maximum vascular supply of the periodontal tissues is from the microcirculation. Every blood vessel that supplies the periodontal tissues including the gingiva in both maxilla and mandible emerges out from the maxillary artery. These blood vessels branch into the alveolar bone marrow and gets distributed within the periodontium ultimately as micro-vessels microcirculation. Changes in the periodontal vasculature is evident as the periodontal condition shifts from health to disease. This review paper highlights the structure of microcirculation its functions vascular distribution of gingiva differences in the maxillary and mandibular blood flow rates aging and microcirculatory dynamics in human gingiva effects of smoking and changes in gingival microcirculation from health through gingivitis to periodontitis.

Movement analysis of primate molar teeth under load using synchrotron X-ray microtomography

Mammalian teeth have to sustain repetitive and high chewing loads without failure. Key to this capability is the periodontal ligament (PDL), a connective tissue containing a collagenous fibre network which connects the tooth roots to the alveolar bone socket and which allows the teeth to move when loaded. It has been suggested that rodent molars under load experience a screw-like downward motion but it remains unclear whether this movement also occurs in primates. Here we use synchroton micro-computed tomography paired with an axial loading setup to investigate the form-function relationship between tooth movement and the morphology of the PDL space in a non-human primate, the mouse lemur (Microcebus murinus). The loading behavior of both mandibular and maxillary molars showed a three-dimensional movement with translational and rotational components, which pushes the tooth into the alveolar socket. Moreover, we found a non-uniform PDL thickness distribution and a gradual increase in volumetric proportion of the periodontal vasculature from cervical to apical. Our results suggest that the PDL morphology may optimize the three-dimensional tooth movement to avoid high stresses under loading.

Coculture With Endothelial Cells Enhances Osteogenic Differentiation of Periodontal Ligament Stem Cells via Cyclooxygenase‐2/Prostaglandin E2/Vascular Endothelial Growth Factor Signaling Under Hypoxia

During periodontitis and orthodontic tooth movement, periodontal vasculature is severely impaired, leading to a hypoxic microenvironment of periodontal cells. However, the impact of hypoxia on periodontal cells is poorly defined. The present study investigates responses of cocultured endothelial cells (ECs) and periodontal ligament stem cells (PDLSCs) to hypoxia. Osteogenic differentiation, molecular characterization, and various behaviors of PDLSCs and human umbilical venous ECs under hypoxia were assessed by quantitative real-time reverse-transcription polymerase chain reaction, Western blot, and enzyme-linked immunosorbent assay. Moreover, the effect of ECs on PDLSC osteogenic differentiation was tested using NS398 (cyclooxygenase 2 blocker), SU5416 (vascular endothelial growth factor [VEGF] receptor inhibitor), AH6809, L-798106, and L-161982 (EP1/2/3/4 antagonists). First, hypoxia promoted osteogenic differentiation in PDLSCs and enhanced EC migration, whereas PD98059 (extracellular signal-regulated protein kinase [ERK] inhibitor) blocked, and cocultured ECs further enhanced, hypoxia-induced osteogenic differentiation. Second, NS398 impaired EC migration and prostaglandin E2 (PGE2)/VEGF release, whereas cocultured PDLSCs and exogenous PGE2 partially reversed it. Third, NS398 (pretreated ECs) decreased PGE2/VEGF concentrations. NS398-treated ECs and AH6809/SU5416-treated PDLSCs impaired cocultured EC-induced enhancement of PDLSC osteogenic differentiation. Hypoxia enhances ERK-mediated osteogenic differentiation in PDLSCs. Coculture with EC further augments PDLSC osteogenic differentiation via cyclooxygenase-2/PGE2/VEGF signaling.

The osteogenic differentiation of PDLSCs is mediated through MEK/ERK and p38 MAPK signalling under hypoxia

PurposeDuring orthodontic treatment and chronic periodontitis, the periodontal vasculature is severely impaired by overloaded mechanical force or chronic inflammation. This leads to the hypoxic milieu of the periodontal stem cell niche and ultimately affects periodontal tissue remodelling. However, the role of hypoxia in the regulation of periodontal ligament stem cell (PDLSC) behaviours still remains to be elucidated. The present study was aimed at investigating the effects of hypoxia on osteogenic differentiation, mineralisation and paracrine release of PDLSCs and further demonstrating the involvement of mitogen-activated protein kinase (MAPK) signalling in the process. MethodsFirst, PDLSCs were isolated and characterised. Second, the effects of different periods of hypoxia on PDLSC osteogenic potential, mineralisation and paracrine release were investigated. Third, extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 kinase activities under hypoxia were measured. Finally, specific MAPK inhibitors PD98059 and SB203580 were employed to investigate the involvement of two kinases in PDLSC osteogenesis under hypoxia. ResultsImmunocytochemical staining and multilineage differentiation assays verified that the isolated cells were PDLSCs. Cell viability, alkaline phosphatase (ALP) activity, messenger RNA (mRNA) and protein levels of runt-related transcription factor 2 (Runx2) and Sp7, mineralisation and prostaglandin E2 (PGE2) and vascular endothelial growth factor (VEGF) release were significantly increased by hypoxia. ERK1/2 and p38 were activated in different ways under hypoxia. Furthermore, hypoxia-stimulated transcription and expression of the above-mentioned osteogenic regulators were also reversed by PD98059 and SB203580 to different degrees. ConclusionsExposure of PDLSCs to hypoxia affected their osteogenic potential, mineralisation and paracrine release, and the process involved mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) and p38 MAPK signalling.

Effects of vascular endothelial cells on osteogenic differentiation of noncontact co‐cultured periodontal ligament stem cells under hypoxia

During periodontitis or orthodontic tooth movement, the periodontal vasculature is severely impaired by chronic inflammation or excessive mechanical force. This leads to a hypoxic microenvironment of the periodontal cells and enhances the expression of various cytokines and growth factors that may regulate angiogenesis and alveolar bone remodeling. However, the role of hypoxia in regulating the communication between endothelial cells (ECs) and osteoblast progenitors during the remodeling and repair of periodontal tissue is still poorly defined. The aim of this study was to investigate the effects of vascular ECs on osteogenic differentiation, mineralization and the paracrine function of noncontact co-cultured periodontal ligament stem cells (PDLSCs) under hypoxia, and further reveal the involvement of MEK/ERK and p38 MAPK pathways in the process. First, PDLSCs were obtained and a noncontact co-culture system of PDLSCs and human umbilical vein endothelial cells was established. Second, the effects of different time-periods of hypoxia (2% O(2) ) on the osteogenic potential, mineralization and paracrine function of co-cultured PDLSCs were investigated. Third, ERK1/2 and p38 MAPK activities of PDLSCs under hypoxia were measured by western blotting. Finally, we employed specific MAPK inhibitors (PD98059 and SB20350) to investigate the involvement of ERK1/2 and p38 MAPK in PDLSC osteogenesis under hypoxia. We observed further increased osteogenic differentiation of co-cultured PDLSCs, manifested by markedly enhanced alkaline phosphatase (ALP) activity and prostaglandin E(2) (PGE(2)) levels, vascular endothelial growth factor (VEGF) release, runt-related transcription factor 2 (Runx2) and Sp7 transcriptional and protein levels and mineralized nodule formation, compared with PDLSCs cultured alone. ERK1/2 was phosphorylated in a rapid but transient manner, whereas p38 MAPK was activated in a slow and sustained way under hypoxia. Furthermore, hypoxia-stimulated transcription and expression of osteogenic regulators (hypoxia-inducible factor-1α, ALP, Runx2, Sp7, PGE(2) and VEGF) were also inhibited by PD98059 and SB203580 to different degrees. Further increased osteogenic differentiation and mineralization of co-cultured PDLSCs under hypoxia were regulated by MEK/ERK and p38 MAPK pathways. And the ECs-mediated paracrine of PGE(2) and VEGF may facilitate the unidirectional PDLSC-EC communication and promote PDLSCs osteogenesis.

Soluble products from Eikenella corrodens induce cell proliferation and expression of interleukin‐8 and adhesion molecules in endothelial cells via mitogen‐activated protein kinase pathways

The periodontal vasculature is profoundly affected during the progression of periodontitis, and several specific bacteria are believed to be involved in this inflammatory disease. Eikenella corrodens is one of the common bacteria detected in periodontitis diseased lesions; however, the function of this organism in periodontitis is not well understood. In this study, we investigated the E. corrodens-induced endothelial cell alteration and inflammation process that leads to leukocyte infiltration in inflamed regions. Soluble products from E. corrodens (EcSP) induced the gene expression and protein production of vascular endothelial growth factor in oral epithelial cells and human umbilical vein endothelial cells (HUVEC). Direct stimulation by EcSP also activated endothelial cell proliferation. Moreover, EcSP induced ERK1/2 (p44/42) and p38 mitogen-activated protein kinase (MAPK) phosphorylation within 10-30 min in HUVEC, as demonstrated by Western blot analysis and up-regulated intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), E-selectin and interleukin-8 (IL-8) production demonstrated by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. The specific p38 MAPK inhibitor SB203580 reduced the expression of ICAM-1, VCAM-1 and IL-8, whereas the blockade of p44/42 by MAPK kinase (MEK1) inhibitor, PD98059, inhibited only IL-8 expression. Our results indicate that E. corrodens can trigger a cascade of events that induce inflammatory responses in periodontal tissue via the MAPK cascade and may promote chronic periodontitis without bacteria-cell contact.

The blood vessel system in the periodontal ligament of the equine cheek teeth – Part I: The spatial arrangement in layers

Corrosion casts of blood vessels in the periodontium of cheek teeth from eight horses were observed three-dimensionally with a dissection microscope. Selected specimens were examined in a scanning electron microscope. Periodontal blood vessels communicated with those from the gingiva, the alveolar bone, and the apical region. In the upper jaw, there were anastomoses with the blood vessels of the mucosa of the maxillary sinus. The periodontal vascular system was organized in two or three layers. The peripheral layer was mainly composed of large venules, the inner one consisted of capillaries. In the intermediate layer, blood vessels were post-capillary venules. This layer was developed only in horses under 10 years of age. In all layers the vascular orientation was mainly occluso-apical, this was defined as the standard pattern. There were many variations displayed in different courses of certain blood vessels. The vascular organization is discussed with regard to the specialized functions of the periodontal ligament (PDL). The wide vessels of the outer layer are thought to play a mechanical role as part of a shock absorbing system. The capillaries of the inner layer meet nutritional requirements. The disappearance of the intermediate layer in horses older than 10 years is taken as an adaptation to the remodelling of the PDL. Modifications in the standard pattern of vascular arrangements are also interpreted as adaptations to life-long changes in the periodontal space. Anastomoses between the periodontal vasculature and the blood vessels of the maxillary sinus indicate that periodontal disease may be transferred into the sinus.

Histomorphometric study of the periodontal vasculature during and after experimental tipping of the rat incisor

The periodontal vasculature encircling the entire length of the rat lower incisor was studied at the time of tipping movement and 3 months later. In 12 rats (212±4 g b.w.), loads (0.19±0.016 N) were applied to the lower left incisor in a linguointrusive direction. After 2 weeks of loading, six experimental animals were killed with the loading springs in place. The springs were removed in the six remaining rats, which were killed 12 weeks later. Six additional rats with intact teeth served as control. All incisors were fixed, demineralized, embedded in glycol methacrylate and cross-sectioned perpendicular to the long axis of the tooth. The distance of each section (2 μm) from the apex was calculated. A computerized image-analysis program was used to measure the width and area of the labial and lingual periodontal ligament to establish whether the measured segments corresponded to the compressed or expanded zones. In each cross-section, the various types of blood vessels were counted and the cross-sectional area of all venous vessels was measured. The results showed that after 2 weeks of loading (1) the general trend of vascular changes was similar under pressure and tension; (2) the large-diameter vessels were unaffected by loading; (3) the mean number of terminal arterioles had decreased significantly, while the number of capillaries and postcapillary venules had increased significantly in the apical tooth part; (4) the venous blood vessel area had decreased significantly in the apical tooth part; (5) the intensity of the vascular reaction was dependent on the degree of tissue distortion; and (6) after 12 weeks’ recovery the vascular changes were still present, demonstrating a rebound effect. The findings suggest that microvascular alterations following tooth loading are not directly related to the spatial effect of loading itself and are of a much longer duration than expected.

Nonsteroidal anti-inflammatory drugs in orthodontic tooth movement: Metalloproteinase activity and collagen synthesis by endothelial cells

Orthodontic treatment is based on the biologic principle that prolonged pressure on teeth results in remodeling of periodontal structures, allowing for tooth movement. Periodontal remodeling is a complex process regulated in part by prostaglandins and adversely affected by the use of nonsteroidal anti-inflammatory drugs. We investigated the effects of indomethacin on collagenase activity and procollagen synthesis in rat endothelial cell cultures. Cyclooxygenase inhibition resulted in exacerbation of IL-1β–mediated collagenase B (MMP-9) production and activity, as well as attenuation of type IV procollagen synthesis levels by endothelial cells in vitro. Hence, the use of over-the-counter nonsteroidal anti-inflammatory drugs during tooth movement may result in aberrant remodeling of periodontal vasculature and other structures, ultimately affecting orthodontic treatment efficacy. Further studies are needed to establish novel pain relievers that do not interfere with orthodontic processes. (Am J Orthod Dentofacial Orthop 2000;118:203-9)

Vascular changes in the periodontal ligament after removal of orthodontic forces

Vascular changes in the periodontal ligament after release of orthodontic force and their possible contribution to relapse of relocated teeth are poorly understood. This study documented the periodontal vascular changes after 2 weeks of tooth movement and during a 3-week period after release of orthodontic force. This study is the first comprehensive quantitative description of these events. Changes in blood vessel number and density were correlated with the direction of tooth movement (initially mesial in response to force but later distal because of relapse). Application and removal of orthodontic force produced significant changes in blood vessel number and density, which were not related to changes in tissue volume. The vascular changes were dependent on the site of evaluation and the size of the blood vessel. The periodontal vascular distribution and density can be summarized as follows: (1) increased after application of orthodontic force, (2) transient decrease subsequent to removal of force, (3) transient increase during reactivated distal drift, and (4) normalization. Normalization was achieved during an interval equivalent to the duration of orthodontic force, suggesting that the vasculature could modulate interstitial tissue pressures, resulting in relapse of relocated teeth. The role of the periodontal vasculature in alveolar remodeling and in modifying interstitial tissue fluid pressures coincident to human tooth movement requires further study.

弱い機械的刺激に対する血管透過性こう進反応の研究

The purpose of the study was to investigate the early response of microvasculature, especially increased vascular permeability (IVP) to the light-continuous mechanical pressure stimulation. The hamster cheek pouch was used as an in vivo model of periodontal vasculature. FITC-dextran (molecular weight 150,000) was injected intravenously as a tracer and then intravital and electron microscopic observations were made and also the role of histamine in IVP to the mechanical stimulation was studied. The results were as follows: 1. Blood flow in postcapillary venules (PCV) (about 50 microns in diameter) was not interrupted under the stimulation of 0.1g. IVP at PCV was observed at 5 minutes after the beginning of this stimulation by fluorescein intravital microscopy. 2. Electron microscopic observations revealed that this IVP was attributed to the formation of gaps (0.1 approximately 0.5 microns) between endothelial cells of PCV without stasis and degranulation of mast cells and that monocytes and platelets were attached to the endothelial cells in the lumen. These gaps were seen until 30 minutes after the beginning of the stimulation. 3. Pretreatment with pyrilamine, a histamine H1-receptor antagonist, inhibited the appearance of IVP at 5 minutes after the beginning of the stimulation, but it didn't completely reduce IVP appearing after 10 minutes of stimulation. It was suggested that histamine played some roles in IVP which appeared at 5 minutes after the beginning of the stimulation, but was not essential after 10 minutes.

Fenestrated capillaries in the periodontal ligaments of the erupting and erupted rat molar

Quantitative ultrastructural studies were conducted on eight rats (four aged 21 days and four aged 8 weeks) using the periodontal tissues around the mesial root of the mandibular first molar. The periodontal ligament of the erupting tooth contained significantly more capillary fenestrations than the erupted tooth, both in terms of the number per unit area of endothelium (2.2/microns2) and in terms of total number per cubic millimetre of tissue (30.5 X 10(6)/mm3). Differences were also discerned with respect to the percentage of capillaries in the tissue. Thus, the periodontal vasculature demonstrates marked morphological changes which may be related to the eruptive phase of the tooth.

Effects of sympathetic nerve activity on changes in the position of the rabbit incisor tooth evoked by acute alterations in arterial blood pressure

The influence of the sympathetic innervation of periodontal blood vessels on the responses of the upper incisor tooth to sudden changes in mean arterial pressure was studied in 15 anaesthetized rabbits. Changes in axial position of the tooth were measured by ultrasonic transit time technique. With intact sympathetic nerves, the tooth showed small, if any, intrusive movements in response to 6–42 mm Hg reductions in arterial pressure evoked by stimulation of the aortic baroreceptor nerve. When exposed to similar periods of hypovolaemic hypotension, the intrusions were, on an average, 1 μm larger ( p < 0.01). After bilateral sectioning of the cervical sympathetic nerves, tooth intrusions in response to both types of pressure reduction became more marked, as did the extrusive movements evoked by abrupt increases in aortic pressure (produced by inflation of intra-aortic balloon). After sympathectomy, a 19 ± 6 mm Hg rise in pressure caused extrusions of 6 ± 3 μm, or 2 μm more than before the sympathectomy ( p < 0.01). The results suggest that the activity in sympathetic nerves to periodontal blood vessels may be inhibited by central nervous mechanisms and that the sympathetic innervation of the periodontal vasculature serves to minimize changes in tooth position brought on by sudden alterations in arterial pressure.

The influence of vascular beta-adrenoceptors on the position and mobility of the rabbit incisor tooth.

The influence of vascular beta-adrenoceptors on the tooth-supporting functions of the periodontal ligament were studied in 30 anesthetized rabbits. Propranolol and the beta 2-adrenoceptor antagonists ICI 118,551 and H 35/25 induced a marked extrusion of the incisor, probably due to reduced vasodilator tone in periodontal postcapillary blood vessels. Isoprenaline reversed the movement. beta 1- and beta 2-receptor antagonists decreased the intrusive responses to sympathetic nerve stimulation in teeth close to control position, but had no effect on responses in fully extruded teeth. Intrusive mobility, as tested by intermittent loading with 5-10 g, remained unaffected by beta-adrenoceptor blockade. The results suggest that vascular beta 2-adrenoceptors are important in the regulation of tooth position by their control of periodontal postcapillary resistance. Prejunctional beta-receptors enhancing the vasoconstrictor--and intrusive--responses to sympathetic nerve stimulation are probably a mixture of beta 1- and beta 2-receptors. It would seem that the periodontal vasculature is important for the position of the rabbit tooth but, due to rapid adaptive mechanisms of the tooth-supporting tissues, the vasculature contributes little to the resistance against load-induced intrusive movements of the tooth.

Effects of tooth loading on the periodontal vasculature of the mandibular fourth premolar in dogs

A surgical technique was developed to isolate the arterial supply to the periodontal ligament, pulp and gingiva of the canine mandibular 4th premolar, and to measure the pressure and flow therein. This model system was used to study the interaction between tooth loading and periodontal blood flow. Intrusive forces of less than 350 N were found to produce negligible alteration of the measured blood flow, while loads of 1050 N produced a reduction of flow equivalent to an increase in vascular resistance of approximately 10 per cent, with no effect on arterial pressure. The increase in flow on removal of load was greater than the reduction seen on application, suggesting that reactive hyperemia may occur in the periodontal tissues. The phenomenon of periodontal pulsation first studied by Parfitt ( J. dent. Res. 39, 608–618) in humans, was examined in the dog as a part of the present work. It was found that the pulsation of the canine mandibular 4th premolar was still in evidence under applied loads 230 times that which Parfitt found to obliterate the movement of the human incisor. This may be taken to indicate that the density and architecture of the periodontal vasculature may, in part, be determined by the loads applied to the teeth during function.

A model of the periodontal vasculature in tooth support

Previous studies have suggested that the blood vessels in the periodontal space may be the most important of all the components of the periodontal ligament in providing support for the teeth. Since the relationship between intrusion of the teeth and applied load has been studied and the mathematical form of this relationship established to be f = ( αx + k) x, it was decided to determine whether the relationship could be accounted for by the mechanical characteristics of the blood vessels. The results reported here represent a preliminary study conducted on samples of man-made tubing in order to assess the load-deflection behaviour of a fluid-carrying, internally-pressurized cylinder subjected to transverse forces. The effects of the resulting occlusion of the tube on flow rates were also studied. The results of this work indicate that an equation of the form f = x( αx + k) will indeed adequately describe the load-deflection characteristics of a transversely loaded tube. The ratio α k , however, is several orders of magnitude less than that found for the periodontal ligament, suggesting that the vasculature does not predominate in tooth support. The effect of occlusion on flow, on the other hand, is quite similar to the observed effect of load on periodontal blood flow, suggesting that the periodontal vessels do, nonetheless, contribute measurably to the support of the teeth. The various observations concerning the periodontal vasculature and tooth support can be reconciled by means of a simple mathematical model, which is presented.

Oxytalan Fiber System of Molars in the Mouse Mandible

The periodontal ligament of molars in mice includes an oxytalan fiber system that extends uninterruptedly from the first to the third molar. These fibers are not anchored in bone but they coordinate the movement of the tooth to the periodontal vasculature. The hypothesis is proposed that oxytalan fibers may be part of a mechanism that regulates vascular flow.

Effect of aging on the marmoset periodontium

The periodontium of old marmosets is characterized by a narrow, serrated cribriform plate of alveolar bone, a loss of tinctorial identification of Sharpey's fibers and a decrease in the cellular elements of the periodontal ligament. The attachment fibers are frequently calcified. In contrast to the blue periodontal ligament and pink alveolar bone in alcian blue‐PAS stained sections of adult marmosets, the periodontal ligament stains pink and the alveolar hone deep red in old animals. Aged marmosets also have degenerative changes in the periodontal vasculature not seen in younger adults. The changes are similar to those described in aged human periodontal tissues.

Effect of aging on the marmoset periodontium

The periodontium of old marmosets is characterized by a narrow, serrated cribriform plate of alveolar bone, a loss of tinctorial identification of Sharpey's fibers and a decrease in the cellular elements of the periodontal ligament. The attachment fibers are frequently calcified. In contrast to the blue periodontal ligament and pink alveolar bone in alcian blue‐PAS stained sections of adult marmosets, the periodontal ligament stains pink and the alveolar bone deep red in old animals. Aged marmosets also have degenerative changes in the periodontal vasculature not seen in younger adults. The changes are similar to those described in aged human periodontal tissues.

Revascularization of the periodontium after tooth grafting in monkeys.

In replanted and homo transplanted teeth a vascular network developed in the blood clot between the two parts of the torn periodontium, which allowed the grafted ligament to regain its vascularity. When dentoalveolar ankylosis developed, the periodontal vasculature was split into a number of vascular clusters. In homotransplants, a definite cellular immunologic response by the host was absent. An acrylic radicular obturator was used.