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PubMed1989

Distribution and central projections of primary afferent neurons that innervate the masseter muscle and mandibular periodontium: a double-label study.

A double-label strategy was used to determine the distribution and central projections of primary afferent neurons that innervate the periodontium and muscles of mastication in cats. Central injections of either Fast Blue (FB) or a mixture of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) and HRP were made into one of three cytoarchitectonically distinct regions of the spinal trigeminal nucleus. These regions included the subnucleus oralis (Vo), the subnucleus interpolaris (Vi), and the medullary dorsal horn (MDH). In each case, injections were also made into the periodontium of the ipsilateral mandibular teeth or into the ipsilateral masseter muscle. FB injections preceded the peroxidase injections by at least 48 hours and total survival time ranged from 72 to 96 hours. Animals were perfused with phosphate-buffered paraformaldehyde (4%; pH 7.2). Serial frozen sections were made through the brainstem and trigeminal ganglion. Tetramethylbenzidine was used as a chromagen to demonstrate HRP and sections were viewed with brightfield and epifluorescent illumination. Cells containing peripherally injected tracer were observed in the lateral portion of the ganglion and in the mesencephalic nucleus (Vmes). Double-labeled ganglion cells were observed in most cats that received periodontal injections in combination with central injections in the dorsal part of spinal trigeminal nucleus regardless of the rostrocaudal level of the central injection. In the animals that received intramuscular injections, double-labeled ganglion cells were observed only in the animals that received central injections caudal to the Vo. Double-labeled Vmes perikarya were observed in cats that received either intramuscular or periodontal injections in combination with central injections into the MDH and Vo but not in animals that received injections into the Vi. These results demonstrate that ganglion cell periodontal afferents project to the three major rostrocaudal subdivisions of the spinal trigeminal nucleus while ganglion cell muscle afferents have more limited central projections to caudal regions of the nucleus. Masseter and periodontal Vmes afferents also project ot the spinal trigeminal nucleus--specifically, to the Vo and MDH. These findings are consistent with physiological observations regarding the role of periodontal and masseteric afferents in oral and facial reflexes and somesthetic mechanisms.

Afferent Pathways↗

PubMed1992

Effect of traumatic occlusion on CGRP and SP immunoreactive nerve fibre morphology in rat molar pulp and periodontium.

Traumatic occlusion provides a trauma that affects the whole tooth and its supporting tissues. To study the effect of this trauma on CGRP and SP immunoreactive nerve morphology in pulp and periodontium, traumatic occlusion was induced in 2-months-old rats. The occlusal surface of the first maxillary molar in 30 rats were unilaterally raised 1 mm with a composite material. At different observation periods up to 30 days, the rats were transcardiacally perfused, the jaws demineralized, sectioned and processed for immunohistochemistry with the avidin-biotin-peroxidase method. Changes in nerve morphology, distribution and density in first and second molars and their supporting tissues were analyzed and compared in experimental (n = 30) and control rats (n = 14). Already after 5 days with traumatic occlusion, 22% of the experimental teeth had increased density of CGRP and SP immunoreactive nerves locally in gingiva, the periodontal ligament and the pulp, while in 15%, axonal proliferation and changed nerve morphology were found in the whole pulp (severe reaction). During a 20-day period, the pulpal nerve reactions progressed and included the whole pulp in 46% of the experimental teeth. The periodontal nerve responses were still localized only to the cervical and apical regions, and they remained local in these areas throughout the experimental periods. After 20 days the number of teeth with severe nerve changes seemed to decrease. The study shows that an unilateral change in occlusion of the first molar initiate nerve responses in the total molar dentition. In this experimental model the pulpal axons containing CGRP and SP reacted more serious to occlusal trauma than the nerves in the periodontium. The results indicate that the nerve changes in some cases might be transient.

Animals↗

PubMed1983

Autoradiographic and cytochemical studies of phagocytic cells in selected fibre tracts of the mouse periodontium.

Proliferative and protein synthetic activities of phagocytic cells of specific fibre tracts of the periodontium of C57Bl mice were employing autoradiographic techniques; these were combined with a histochemical technique for horseradish peroxidase (HRP) as a marker for phagocytic activity. Animals were injected either with [3H]thymidine as a marker for proliferative activity, or with [3H]proline as a marker for protein synthetic activity prior to HRP injection. Blocks from the maxillae of experimental and control animals were fixed, decalcified, and sectioned at 50 micrometers. These were incubated with HRP localization media, dehydrated and flat embedded in Epon 812 wafers. The entire length of the periodontium, including adjacent tooth and bone, were selectively cut from the wafers, mounted on epoxy blocks and serially sectioned at 2 micrometers. Slides containing these sections were then dipped in NTB-3 nuclear track emulsion, and after appropriate exposure times, were developed and post-stained. Sections were examined microscopically, employing an ocular grid, and phagocytic cells within each area examined were delineated as either 'fibroblast-like' (FL cells) or 'endothelial/macrophage-like' (EML cells) according to criteria such as morphology, location, orientation and proximity to a vascular channel. They were then subclassified as labelled or unlabelled with respect to the autoradiographic markers. The thymidine labelling index obtained for non-phagocytic FL cells was 3.09%; this was more than twice that for phagocytic FL cells (1.35%). Similarly phagocytic FL cells in all regions studied incorporated less than half as much [3H]proline as did their non-phagocytic counterparts. This was determined by silver grain counts over HRP-stained and unstained cells using a matched pair system. In addition, the variation of the relative number of phagocytic FL cells in specific fibre tracts suggested a relationship to functional demand. The distribution of these cells was closely related to experimentally determined rates of protein turnover. Phagocytic FL cells have a markedly reduced proliferative rate and synthesize proline-containing proteins at a reduced rate. This may reflect protein production primarily for the purpose of cell maintenance. These findings are consistent with the presence of subpopulations of fibroblasts (or fibrocytes) developmentally or functionally modified for phagocytosis; alternatively, this could signify modulation of fibroblasts from primarily biosynthetic activities to degradative functions in response to varying microenvironmental conditions.

Animals↗

PubMed1978

A continuous-flow culture system for organ culture of large explants of adult tissue: effect of oxygen tension on mouse molar periodontium.

A modified continuous-flow culture system (CFCS) was developed to maintain large explants of periodontium from adult mouse in organ culture. The culture medium was stored in a reservoir outside of the incubator, pumped via polyvinyl tubing into small glass culture chambers that were placed in the oxygenator and then collected in a waste flask. Medium was analyzed for pO2, pCO2 and pH during the culture period. Three-molar and single-molar explants of periodontium were maintained for 48 hr in the CFCS at two different pO2 ranges: 100 to 120 mm Hg and 400 to 420 mm Hg. [3H]Proline was added 24 hr prior to sacrifice. Light-microscope morphological and radioautographic observations suggested that cell viability and incorporation of [3H]proline, probably into newly synthesized protein, increased with an increase in pO2 and was related to a pO2 gradient extending from the periphery to the center of the explants.

Animals↗

PubMed2003

An experimental method for in vivo analysis of biomechanical asymmetries of the periodontium.

For analysis of the initial tooth movement in vivo, an optical measuring apparatus with a resolution of 0.001 degree for rotation or 0.5 micron for translation respectively has been developed. Its design is described in detail. Because of its high sensitivity it is experimentally feasible to investigate the biomechanical properties of the periodontium under force application and to determine if it makes any difference whether a tooth is rotated mesially or distally out of its neutral position. For that purpose moments with defined time responses are buccally applied to premolars by means of a cardan shaft and the corresponding rotational angle-time characteristics are recorded. As expected, first measurements show sign symmetry for widely spaced teeth. In the case of pronounced anterior crowding, however, asymmetry seems to occur in such a manner that the force system has to overcome a threshold in order to rotate the tooth distally. Additionally, the periodontium may be subject to a sign-dependent rigidity. In all cases, the movement is limited to some degree.

Bicuspid↗

PubMed1982

Effects of incisor repositioning on monkey periodontium after expansion through the cortical plate.

The anterior teeth of five adult pigtail monkeys were moved lingually to correct a previously induced extreme labial displacement. (Roots had been moved through the labial bone to create bone dehiscence, loss of attachment, and gingival recession.) Eight months later, repositioning was performed with fixed appliances (Fig. 3). The teeth were retained in their more normal arch position for 5 months, after which clinical and histologic measurements were made of several periodontal parameters. The canines were not moved and served as reference teeth. Measurements were made to record changes in the levels of the gingival margin, the mucogingival junction, and the marginal bone relative to a fixed point on the tooth crowns, and the width of keratinized gingiva. Oxytetracycline was administered three times to label areas of osteogenesis in the periodontium. The incisors were retracted lingually a mean of 1.8 mm. The marginal bone level increased (moved coronally) a mean of 2.5 mm. and 3.1 mm. for maxillary and mandibular incisors, respectively (Table II). The tetracycline labels showed that osteogenesis occurred in the periodontium to a significant degree. The anchor canines had a loss of 1.1 mm. marginal bone (moved apically). Effects on gingival clefts and keratinized gingiva were slight. These observations demonstrate that in monkeys reapposition of labial bone can occur in a coronal direction, once teeth in extreme labial position with bone dehiscence and gingival recession are moved to a more normal environment. The effects on the periodontal soft tissues (width of keratinized gingiva, recession, attachment level) were, on the other hand, negligible in this study.

Alveolar Process↗

PubMed2002

Effects of oestrogen deficiency on osteoclastogenesis in the rat periodontium.

This study was designed to investigate quantitative changes in osteoclast generation in rat periodontium following ovariectomy. Wistar rats, aged 9 weeks, were subjected to either ovariectomy (OVX) or sham surgery. Osmotic pumps were implanted in 24 rats and either 17beta-oestradiol or vehicle solution were infused continuously. The rats were assigned to one of the following groups: (1) OVX+vehicle; (2) sham+vehicle; or (3) OVX+ 17beta-oestradiol. On the days 7 and 14 after surgery, four rats in each group were killed. Mandibles were demineralized and embedded in paraffin. Frontal sections of alveolar bone in the region of the first molar were cut for enzyme histochemistry and immunohistochemistry. On day 7, there was no significant difference in the number of tartrate-resistant acid phosphatase (TRAP)-positive cells located on bone surfaces in either group. However, the number of TRAP-positive mononuclear cells that were separated from the bone surface was significantly higher in group 1 than in groups 2 and 3. On the day 14, the number of TRAP-positive cells in group 1, which were attached to the bone surface, was significantly higher than had been apparent on day 7. There were also significant increases in the number of nuclei of TRAP-positive cells attached to the bone in group 1 compared with groups 2 and 3 on day 14. These findings demonstrate that oestrogen deficiency induces of osteoclastogenesis in the rat periodontium and that quantitative changes in osteoclastogenesis could be prevented by E2 infusion.

Acid Phosphatase↗

PubMed2003

Immunohistochemical localisation of extracellular matrix proteins in the periodontium during cementogenesis in the rat molar.

OBJECTIVE: The development of the periodontium involves the coordinated expression of numerous extracellular matrix (ECM) macromolecules and their receptors (integrins). The aim of this study was to determine the expression of selected hard and soft tissue matrix molecules and the integrin alpha5beta1 in the periodontal tissues, during cementogenesis in the rat molar. METHODS: Using immunohistochemical methods, the distribution of the extracellular matrix proteins, fibronectin, tenascin, and bone sialoprotein (BSP), as well as the integrin subunits alpha5 and beta1 were studied in rats aged 3, 5 and 8 weeks. RESULTS: Fibronectin was widely distributed in the gingival epithelium, gingival connective tissue and in the periodontal ligament. Tenascin expression was less marked compared with fibronectin, but was more distinctly associated with cells and peri-cellular areas of the epithelial-connective tissue interface, the gingiva and within the periodontal ligament. The fibronectin-receptor alpha5beta1 integrins were expressed by epithelial cells, periodontal ligament cells and gingival fibroblasts. A notable finding was the increased staining intensity of fibronectin, tenascin and alpha5beta1 integrin in all 5-week old molar sections in the periodontal ligament matrix and cells, apical to the cemento-enamel junction (CEJ) along the alveolar crest (AC) ridge height. Bone sialoprotein was distinctly associated with the hard tissues of the periodontium as acellular cementum and alveolar bone matrix expressed bone sialoprotein throughout all sections, in all age groups. CONCLUSIONS: In conclusion, this study has demonstrated the selective distribution of several hard and soft tissue matrix molecules during periodontogenesis. The results highlight the complex nature of interactions of various proteins and molecules during development. The interactions between these molecules and their specific roles in development and regeneration await further investigation.

Animals↗

PubMed1980

Localization of some enzymes in the periodontium of the rat molar.

The authors studied alkaline and acid phosphatase, nonspecific esterase and NADH2 tetrazolium reductase localization in the periodontium of the rat molar. The activity of all enzymes studied remained preserved in spite of decalcification in EDTA. The activity of the enzymes was relatively high, the most intense reaction was observed, with the exception of alkaline phosphatase, in the gingival epithelium. In the junctional epithelium the reaction was less intense and decreased towards the end of the epithelial attachment. Only NADH2 tetrazolium reductase exhibited high activity in this region. The periodontal ligament displayed positive reaction in all enzymes studied with the exception of alkaline phosphatase, which was active only in the dentoalveolar ligament. The results of the present study indicate that highly active metabolic processes take place in the periodontium. The results and literature are discussed in the paper.

Acid Phosphatase↗

PubMed1999

Analysis of stress in the periodontium of the maxillary first molar with a three-dimensional finite element model.

The aim of this study was to simulate the stress response in the periodontium of the maxillary first molar to different moment to force ratios, and to determine the moment to force ratio for translational movement of the tooth by means of the finite element method. The three-dimensional finite element model of the maxillary first molar consisted of 3097 nodes and 2521 isoparametric eight-node solid elements. The model was designed to dissect the periodontal ligament, root, and alveolar bone separately. The results demonstrate the sensitivity of the periodontium to load changes. The stress pattern in the periodontal ligament for a distalizing force without counterbalancing moments showed high concentration at the cervical level of the distobuccal root due to tipping and rotation of the tooth. After various counterrotation as well as countertipping moments were applied, an even distribution of low compression on the distal side of the periodontal ligament was obtained at a countertipping moment to force ratio of 9:1 and a counterrotation moment to force ratio of 5:1. This lower and uniform stress in the periodontal ligament implies that a translational tooth movement may be achieved. Furthermore, high stress concentration was observed on the root surface at the furcation level in contrast with anterior teeth reported to display high concentration at the apex. This result may suggest that the root morphology of the maxillary first molar makes it less susceptible to apical root resorption relative to anterior teeth during tooth movement. The stress patterns in the periodontal ligament corresponded with the load types; those on the root appeared to be highly affected by bending and the high stiffness of the root.

Alveolar Process↗

PubMed2000

Expression and distribution of cell-surface proteoglycans in the normal Lewis rat molar periodontium.

Cell-surface proteoglycans participate in several biological functions such as cell cell and cell-matrix interactions, cell adhesion, the binding to various growth factors as co-receptors and repair. To understand better the expression and distribution of cell-surface proteoglycans in the periodontal tissues, an immunohistochemical evaluation of the normal Lewis rat molar periodontium using panels of antibodies for syndecan-1, -2, -4, glypican and betaglycan was carried out. Our results demonstrated the expression and distribution of all proteoglycans in the suprabasal gingival epithelium, soft and hard connective tissues. Both cellular and matrix localization was evident within the various periodontal compartments. The presence of these cell-surface proteoglycans indicates the potential for roles in the process of tissue homeostasis, repair or regeneration in periodontium of which each function requires further study.

Animals↗

PubMed1998

An evaluation of the biomechanical response of the tooth and periodontium to orthodontic forces in adolescent and adult subjects.

This study was designed to quantify the magnitude of tooth mobility in adolescents and adults, and to investigate the differences in the biomechanical response of tooth and periodontium to orthodontic forces. The initial displacement of the maxillary central incisor was measured in 50 adolescent and fifty adult patients and the biomechanical properties of the periodontium were examined using the finite element method (FEM) and supporting experimental data. The magnitude of tooth mobility was significantly greater in the adolescent group than in the adult group. By integrating the differences in tooth mobility in both subject groups with analytical tooth displacements, the Young's modulus of the periodontal ligament (PDL) was demonstrated to be greater in the adults than in the adolescent subjects. The differing biomechanical properties of the PDL in adults were demonstrated to result in almost equivalent or somewhat increased stress levels in the PDL in adult subjects. It is suggested that this might produce a reduction in the biological response of the PDL and thus lead to a delay in tooth movement in adults.

Adolescent↗

PubMed2000

Enzyme-histochemical demonstration of lymphatic vessels in the golden hamster periodontium: an attempt to reactivate the 5'-nucleotidase activity with Mg++ ion supply.

Enzyme-histochemical demonstration of lymphatic vessels in the golden hamster periodontium was performed on cryostat sections using the 5'-nucleotidase (5'-Nase) staining method by light microscopy and backscattered electron imaging of scanning electron microscopy. The inhibition of the 5'-Nase activity by decalcification was cancelled by the Mg++ ion supply. The reaction products of 5'-Nase activity were produced on the lymphatic endothelial cells and the tubular structures of lymphatic vessels were seen as highlights by backscattered electron imaging. The invasion of 5'-Nase-positive lymphatic vessels into the alveolar bone from the periodontium was found in the present study.

5'-Nucleotidase↗

PubMed1983

Bacterial invasion of the periodontium; an important factor in the pathogenesis of periodontitis?

Tissue samples from 2 humans suffering from severe periodontitis were investigated by transmission electron microscopy. Confirming earlier observations in gnotobiotic rats, bacteria were found in various regions of gingival tissues. We observed bacteria invading the pocket epithelium, the underlying connective tissue, and microorganisms were also present deep in the connective tissue. The bacterial invasion of the periodontium was accompanied by different stages of tissue degradation. Various morphologically distinct types of Gram-negative and Gram-positive bacteria were evident. These microorganisms were found in the apical part of the periodontium. More coronally, a heavy infiltrate consisting predominantly of plasma cells was present. It is suggested that bacteria cannot invade regions of connective tissue protected by a massive cellular infiltrate. It seems that they rather circumvent this strong defense by penetrating more apically through the pocket epithelium while producing as camouflage leukochemophobic compounds which paralyze the chemotactically regulated mobile defense. It seems to us that bacterial invasion is a consistent feature of advanced periodontitis, leading to focal necrosis or microabscesses, and may well explain the cyclic nature of this disease.

Bacteria↗

PubMed1989

Ultrasonic B-scans of the facial/oral periodontium in pigs.

In vitro ultrasonic scans of the oral/facial periodontium of pigs were obtained using a special experimental design and with the help of a newly developed ultrasonic measuring and analysis system. These two-dimensional images distinguish themselves from the one-dimensional RF-echograms and A-scans in that they enable the viewer to have a quick overview of the relationship between different interfaces in a scanned sector. A selection of ultrasonic B-scans proves that the scanned tissues such as gingiva, bone, periodontal ligament, tooth surface and even structures of the inner part of the tooth may be clearly imaged and distinctly differentiated. Furthermore, we demonstrate with manipulations of the pigs periodontium, that the interpretation of the pictures is correct. The primary goal of our investigation was to assess whether the ultrasonic procedure is suitable for the determination of the height of the facial/oral bone crest. On the basis of this study, we may confirm this supposition for the imaging in ultrasonic B-scans.

Alveolar Process↗

PubMed1989

Determination of the facial/oral alveolar crest using RF-echograms. An in vitro study on the periodontium of pigs.

This study is a part of a research project in which we have been investigating the use of the ultrasonic pulse echo technique as a means of determining in vivo the facial/oral alveolar crest precisely and routinely. Here, RF-echograms are presented, showing the facial/oral periodontium of pigs. These echograms have been produced using a focussed 20 MHz transducer and a special design of an ultrasonic measuring and analysis system. In one series of measurements on macerated periodontia of pigs we found out that RF-echograms characteristic of a particular level of the facial/oral pericrestal aspect can be achieved. Based upon these results, we succeeded in determining exactly the height of the facial/oral alveolar crest in a 2nd experimental group using the intact periodontium of pigs. In all experiments, we tried to image separately both the echo amplitudes of the facial/oral alveolar plate and of the tooth surface. In other words, the periodontal ligament space is imaged sonographically. In our experience, the imaging of the space is an important aspect for the correct interpretation of echograms. Possibilities and limits of this method are demonstrated and explained.

Alveolar Process↗

PubMed1993

Platelet-derived growth factor and dexamethasone combined with a collagen matrix induce regeneration of the periodontium in monkeys.

Platelet-derived growth factor (PDGF) and the glucocorticoid dexamethasone combined with a collagen carrier matrix (CM) induced regeneration of the periodontium in monkeys. Regeneration was stringently defined as: (1) new cementum, (2) new supra-crestal bone extending coronally from the residual alveolar interdental septum and (3) functionally-oriented periodontal ligament fibers attaching new cementum to new bone. A single application of PDGF/dexamethasone/CM or CM was placed in debrided lesions of experimental periodontitis displaying 3-5 mm of attachment loss associated with horizontal and angular bony defects. Regeneration, judged histologically by these criteria and quantified by computer assisted histomorphometry after 4 weeks, was present only in PDGF/dexamethasone/CM treated lesions and not in those treated with CM or debridement alone. PDGF/dexamethasone/CM induced 5-fold more new cementum and ligament, and 7-fold more supra-crestal bone than control treatments. The presence of substantial amounts of regenerated periodontium including increased height of the alveolar bone; fill of vertically resorbed interdental alveolar septa in PDGF/dexamethasone/CM treated lesions suggests that this combination may provide a new therapeutic agent for the regeneration of lesions of periodontitis associated with horizontal as well as angular bony defects.

Alveolar Process↗

PubMed1994

Microradiography of the feline marginal periodontium with a microfocal high-resolution x-ray system.

The present paper is a cross-sectional microradiographic study. Postmortem hemimandibles were radiographed with a microfocal high-resolution method. Microradiographic appearances of the feline periodontium are described and discussed. Mean relative alveolar bone support in clinically and histologically normal cats was 46.9%. Site-specific alveolar bone support (ABS) was calculated twice (blind). The 95% confidence limits of the method error for one observation were estimated. Differences between two site-specific measurements did not exceed +/- 2.72%. Microfocal radiography yielded valuable additional information about the feline periodontium and made it possible clearly to identify important dental and periodontal structures such as the CEJ (cementoenamel junction) and the bottom of infrabony defects.

Alveolar Bone Loss↗