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PubMed2000

Histologic response to intraligament injections using a computerized local anesthetic delivery system. A pilot study in mini-swine.

BACKGROUND: Intraligamentary (periodontal ligament) injection has been used to locally control pain with minimal anesthetic dose. The purpose of the present study was to determine the histologic effect of using a computer-controlled local anesthesia delivery system (CCLADS) for the administration of a periodontal ligament injection in the mini-swine model system. METHODS: Thirty-two sites in 3 mini-swine pigs with healthy periodontium were selected. Each site was notched on the mesial-lingual line angle of the tooth to allow a reference for needle placement and provide a histologic marker. An anesthetic cartridge was used with a 30-gauge needle attached to the handpiece of the CCLADS. This provided a controlled flow rate for 2 minutes. The control sites were treated with the same needle in place for 20 seconds. The animals were sacrificed and provided observation periods of 1 hour, 1, 4, 7, 21, and 49 days. Specimens were stained with hematoxylin and eosin and trichrome. RESULTS: Twenty-four hours after injection, limited localized inflammation was present. By 7 days, the ligament appeared within normal limits. Apical migration of the junctional epithelium extended to the apical limit of the notch and was similar in test and control specimens. CONCLUSIONS: Within the limits of this study, the histologic results showed that tissue responses following intraligament injections using a CCLADS demonstrated limited inflammatory responses within the first 24 hours, which abated by 7 days postinjection. Similar migration of the junctional epithelium was seen in test and control specimens and was probably related to tooth injury rather than anesthetic injections. Further investigations are warranted using CCLADS to determine whether clinical benefits will translate in the human model system.

Anesthesia, Dental↗
PubMed1996

Periodontal ligament cell population: the central role of fibroblasts in creating a unique tissue.

BACKGROUND: Fibroblasts are the predominant cells of the periodontal ligament (PL) and have important roles in the development, function, and regeneration of the tooth support apparatus. Biological processes initiated during the formation of the PL contribute to the long-lasting homeostasic properties exhibited by PL fibroblast populations. DEVELOPMENT: The formation of the PL is likely controlled by epithelial-mesenchymal and epithelial hard tissue interactions, but the actual mechanisms that contribute to the development of cellular lineages in the PL are unknown. Fibroblasts in the normally functioning PL migrate through the tissue along collagen fibres to cementum and bone and in an apico-coronal direction during tooth eruption. ADULT TISSUE: Cell kinetic experiments have shown that PL fibroblasts comprise a renewal cell system in steady-state and the progenitors can generate multiple types of more differentiated, specialized cells. Progenitor cell populations of the PL are enriched in locations adjacent to blood vessels and in contiguous endosteal spaces. In normally functioning periodontal tissues, there is a relatively modest turnover of cells in which apoptotic cell death balances proliferation. Large increases of cell formation and cell differentiation occur after application of orthodontic forces or wounding. As PL cells comprise multiple cellular phenotypes, it has been postulated that after wounding, the separate phenotypes repopulating the site will ultimately dictate the tissue form and type. CONCLUSIONS: PL fibroblasts play an essential role in responses to mechanical force loading of the tooth by remodelling and repairing effete or damaged matrix components. In consideration of the important roles played by fibroblasts in PL homeostasis, they could be described as "the architect, builder, and caretaker" of the periodontal ligament.

Adult↗
PubMedDate not supplied

A study of physiologic angiogenesis in the human using the dental pulp as an in vivo model.

With the commonly used in vivo animal models of angiogenesis, direct extrapolation of results to the human is not possible. The results presented from this study exemplify various phases of angiogenesis, from cell migration to apoptosis. This supports the use of the dental pulp of the developing human tooth as a viable model of in vivo physiologic angiogenesis.

Apoptosis↗
PubMed1998

Class II MHC antigen-expressing cells in the pulp tissue of human deciduous teeth prior to shedding.

The distribution and ultrastructure of the class II major histocompatibility complex (MHC) antigen-expressing cells in the pulp tissue of human deciduous teeth during the process of physiological root resorption was surveyed by histochemical and immunocytochemical methods using an anti-human leukocyte antigen (HLA)-DR-monoclonal antibody. Dental pulp was found to contain numerous HLA-DR-positive cells of various shapes; those showing a dendritic appearance were located mainly in the periphery of the pulp tissue, associated closely with the odontoblasts. The immunopositive cells sometimes extended their cytoplasmic processes into the dentinal tubules and increased in number in the areas affected by dental caries, attrition or restorative procedures, implicating their role in immunosurveillance. The immunopositive cells were located consistently at the pulp-dentin border during the stage of active resorption, adjacent to the preodontoclasts or odontoclasts, and covered the exposed dentin surface after the detachment of the odontoclasts until the onset of cementum formation. These data suggest that the HLA-DR-immunopositive cells in the coronal pulp of human deciduous teeth play an inductive role in the differentiation, migration and/or activation of the odontoclasts and cementoblast-like cells during the stages of tooth resorption.

Dental Pulp↗
PubMed1994

Effect of loading on the migration of periodontal fibroblasts in the rat incisor.

The influence of occlusal loading on periodontal fibroblasts was investigated in hypoloaded (shortened out of occlusion), functionally loaded and hyperloaded (constant linguointrusive mechanical loads of 9.4 +/- 0.06 g) lower left rat incisors. One hour following injection of 3H-thymidine, half of the animals in each group were killed, while the remaining rats were killed 2 weeks later. The decalcified incisors were embedded in glycolmethacrylate and sectioned (2 microns) serially, perpendicularly to the long tooth axis. Labeled and unlabeled fibroblasts in the tooth-related periodontal ligament were counted in 8 x 80 microns consecutive layers. Cell density (CD) and labeling index (LI) were plotted according to their location on the apico-incisal and cementum-bone axes. Loading caused a decrease in CD and a shift of cells from the cementum towards the middle of the ligament, proportionally to load intensity and duration. The average tooth-to-bone movement of the cells was 2 microns/day in the hypoloaded and 4 microns/day in the two loaded groups. The mean daily tooth eruption rate was 975 +/- 60 microns, 499 +/- 18 microns and 103 +/- 27 microns in the hypo-, functionally- and hyperloaded teeth, respectively. The respective concomitant average daily cell migration rates in the incisal direction were 786 microns, 500 microns, and 500 microns, i.e. 80%, 100% and 485% of the tooth eruption rates. The gross disparity between cell velocity and tooth movement under conditions of restrained eruption indicates active motility of the fibroblasts, rather than their passive tooth-eruption dependent translation.

Analysis of Variance↗
PubMed1998

Proteolytic activity of opossum tooth extracts.

Amelogenins are the main component of the developing enamel matrix. In placental mammals, amelogenins are rapidly cleaved following their secretion. HPLC fractionation of tooth extracts produces a complex chromatographic profile. The fractions are rich in amelogenin cleavage products that generally retain the amino-terminus of the parent protein but have varying lengths of peptide removed from the original carboxyl-terminus. In contrast, HPLC fractionation of opossum tooth extracts produces a simple profile with a single major chromatographic peak. SDS-and Western blot analyses demonstrated that most of the amelogenin consisted of a prominent protein band that migrated at 28 kDa. Mass spectroscopy confirmed the presence of two uncleaved, alternatively spliced forms of opossum amelogenin, Op202 and Op57, but did not detect major amelogenin cleavage products evident in tooth extracts from placental mammals. Amino acid composition analysis supported the conclusion that uncleaved amelogenin is the major component in the developing enamel matrix. Enzymogram analyses using gelatin, casein and recombinant amelogenin as substrates, comparing porcine, rat and opossum tooth extracts, suggested that fewer proteinases are present in opossum. These results identify potentially significant differences in the proteolytic processing of amelogenins between metatherian and eutherian mammals.

Amelogenin↗
PubMed1981

Palate morphogenesis. VI. Identification of stellate cells in culture.

Mesenchymal cells from the palate of mouse embryos at day 14.5 of gestation produce a minor population of stellate cells in culture. These cells are often bipolar and spindle-shaped with long cytoplasmic processes similar to neural-crest cells. Culturing of explants of palatal mesenchyme enriched for this type of cell. Stellate cells were the first to migrate from explants, followed by fibroblast-like cells and then by squamous cells. The majority of the cells in the explant were fibroblast-like. Squamous cells were present mostly in the anterior and mid-palate and least frequently in those from the posterior palate. They may represent tooth-germ epithelium. When pieces of palate were dissected out and cultured for enrichment of non-muscle contractile systems, most of the migrating cells were stellate. These may represent the highly migratory cells that are, in part, responsible for elevation of the palate shelf. Serotonin was measured in cultured mesenchymal cells from the palate. Its occurrence is consistent with regulation of movement of palate cells.

Animals↗
PubMed1990

[An immunohistochemical study on the response of nerve fibers in the periodontium of rat molars during experimental tooth movement].

It is well known that orthodontic forces induce pain during tooth movement. However there have been few neurohistological studies on sensational periodontal tissue response to orthodontic tooth movement. So we have many unknown problems about reactions of periodontal nerve fibers during tooth movement. The present study deals with the response of nerve fibers in periodontal ligament of rat molar during experimental tooth movement by means of immunohistochemical method for calcitonin gene-related peptide (CGRP). The results obtained in this study were as follows: 1. In control sections, CGRP-immunopositive nerve fibers were observed both around the root apex and in the intermediate region of the periodontal ligament. Although most of those fibers was distributed around the blood vessels, a few nerves were recognized to terminate in the periodontal fibers. 2. At three days after tooth movement, the CGRP-positive nerves gradually increased in number around the blood vessels. After that, the number of CGRP-positive nerves decreased and no difference of distribution of CGRP-positive nerves was observed between the control sections and the experimental sections at seven days. 3. Especially, at three days when active remodeling of alveolar bone was taking place, a few nerve fibers showing CGRP-immunoreactivity were observed to concentrate around osteoclasts or to migrate Howship's lacunae. These findings showed the dynamic changes of CGRP-immunoreactive nerves in the periodontal ligament during tooth movement, and suggested that this reaction of the periodontal nerves might induce pain in patients. In addition to neurotransmitter function, it was supposed that CGRP directly or indirectly effected the cellular elements and surrounding tissues on peripheral organs such as vascular system and osteoclasts.

Animals↗
PubMed1995

[A study on the interrelation of growth changes of upper apical base and alignment of permanent upper anterior teeth].

A comparative study was made between the crowding group and the normal aligned group to clarify the relationship between the growth of the maxilla, occlusion and the alignment of teeth. The material consisted of longitudinal dental casts and lateral cephalograms (II A, III A, III C of Hellman's dental age) taken from each of the 10 children. Differences between the two groups were investigated concerning the size of teeth dental arches and the coordinates of the landmarks. Then a factor analysis on the growth change, which the coordinates of landmarks showed, was performed. The results were as follows: 1. The differences of both the tooth size and the coordinates of the landmarks on the cephalograms were not significant. 2. From the factor analysis, it was observed that in the crowding group the migrations of the upper anterior teeth and molars were related more closely to the cranial base, the palate and the apical base, and also the dental arch migrated in unity. 3. It was suggested from the above results that although, in the normal group, the anterior teeth and molars migrated independently, stringently controlled migration of the teeth in the crowding group caused the united migration of the arch, resulting in uncompensatory accommodation of the teeth.

Child↗
PubMed2000

Fate of the mammalian cranial neural crest during tooth and mandibular morphogenesis.

Neural crest cells are multipotential stem cells that contribute extensively to vertebrate development and give rise to various cell and tissue types. Determination of the fate of mammalian neural crest has been inhibited by the lack of appropriate markers. Here, we make use of a two-component genetic system for indelibly marking the progeny of the cranial neural crest during tooth and mandible development. In the first mouse line, Cre recombinase is expressed under the control of the Wnt1 promoter as a transgene. Significantly, Wnt1 transgene expression is limited to the migrating neural crest cells that are derived from the dorsal CNS. The second mouse line, the ROSA26 conditional reporter (R26R), serves as a substrate for the Cre-mediated recombination. Using this two-component genetic system, we have systematically followed the migration and differentiation of the cranial neural crest (CNC) cells from E9.5 to 6 weeks after birth. Our results demonstrate, for the first time, that CNC cells contribute to the formation of condensed dental mesenchyme, dental papilla, odontoblasts, dentine matrix, pulp, cementum, periodontal ligaments, chondrocytes in Meckel's cartilage, mandible, the articulating disc of temporomandibular joint and branchial arch nerve ganglia. More importantly, there is a dynamic distribution of CNC- and non-CNC-derived cells during tooth and mandibular morphogenesis. These results are a first step towards a comprehensive understanding of neural crest cell migration and differentiation during mammalian craniofacial development. Furthermore, this transgenic model also provides a new tool for cell lineage analysis and genetic manipulation of neural-crest-derived components in normal and abnormal embryogenesis.

Animals↗
PubMed2001

Msx2 is a repressor of chondrogenic differentiation in migratory cranial neural crest cells.

During early mouse embryogenesis, cranial neural crest cells (CNCC) emigrate from the posterior midbrain and rhombomeres 1 and 2 of the anterior hindbrain into the first branchial arch-derived maxillary and mandibular processes and there provide cell lineages for several phenotypes, including cartilage, bone, and tooth. Here, we report that Sox9 and Msx2 were coexpressed in a subpopulation of CNCC during their migration. Because Sox9 is a transactivator of chondrogenesis, and Msx genes can act as transcriptional repressors, we hypothesized that Sox9 expression indicates the determination of CNCC-derived chondrogenic cell lineage and that Msx2 represses chondrogenic differentiation until CNCC migration is completed within the mandibular processes. To test whether Msx2 represses chondrogenesis, we designed experiments to inhibit Msx2 function in migratory CNCC in primary cultures through the expression of loss-of-function Msx2 mutants. We showed that infection of migratory CNCC with adenovirus Msx2 mutants accelerated the rate and extent of chondrogenesis, as indicated by the expression level of type II collagen and aggrecan, and the amount of alcian blue staining. Adenovirus infections did not apparently interfere with CNCC proliferation or migration. These findings suggest that an important early event in craniofacial morphogenesis is a transient expression of both Sox9 and Msx2 during emigration into the forming mandibular processes followed by restricted expression of Sox9 within CNCC- derived chondroprogenitor cells. We conclude that Msx2 serves as a repressor of chondrogenic differentiation during CNCC migration.

Adenoviridae↗
PubMed1995

Scanning electron microscope study of the healing molar tooth extraction socket in the rat.

Healing molar tooth extraction wounds in rats were examined by scanning electron microscopy from 15 minutes to 40 days following tooth removal. The wound epithelium, which was derived mainly from the gingiva but also from the cheek and hard palate, migrated beneath the superficial socket contents. The contents were lost between 5 to 11 days, thus leaving a central epithelial-lined depression. This decreased in width with time as the level of the wound epithelium approached that of the hard palate but was still present at 40 days. Between 5 and 7 days, the wound epithelium became more regular. However, from 11 days on, it became more irregular with increasing numbers of saucer-shaped depressions, circular defects and circular whorls of epithelial cells. The surface structure of the epithelial cells changed as it migrated and matured. The initially plump, then flattened cells mostly had smooth areas along with variable numbers of irregular microridges and microvilli, although cells derived from the cheek had only smooth surfaces. With further maturation, all cells developed a regular honeycomb surface pattern of interconnecting microridges similar to that on the hard palate. Why the wound epithelium became more uneven after 11 days is not known.

Animals↗
PubMed1996

Keratinocyte integrins in wound healing and chronic inflammation of the human periodontium.

Periodontal epithelium plays a critical role in protection, destruction and repair of human periodontium. During optimal repair, epithelium migrates and covers the wound surface to prevent infection and damage of the vulnerable underlying connective tissue. During periodontal destruction, junctional epithelium undergoes transformation to pocket epithelium that has quite different characteristics from junctional epithelium. In the course of periodontal disease the epithelial attachment to the tooth surface is lost and the epithelium proliferates and extends pseudo-rete ridges deep into the inflamed connective tissue. Both scenarios, repair and destruction, involve active epithelial migration either in the wound provisional matrix or in the inflamed connective tissue matrix, respectively. This review covers recent research data on cellular receptors, integrins, that mediate epithelial cell migration during wound healing and destruction of human periodontium.

Basement Membrane↗
PubMed1991

The tilted molar: a prosthetic and periodontal dilemma.

The tilted molar presents both prosthetic and periodontal problems. Typically, the loss of a lower first molar or second premolar produces a space and allows the molar, distal to the space, to tilt mesially. The major tilting force is produced by the opposing occlusion. Although a tightly locked occlusion can prevent excessive movement, once the tooth begins to tilt, the vector of force tends to increase the tilting. The severity of both prosthetic and periodontal problems is directly related to the amount of tilting and treatment becomes complex when adjacent teeth begin to migrate.

Dental Abutments↗
PubMed2006

Neural crest cells and patterning of the mammalian dentition.

The mammalian dentition is composed of serial groups of teeth, each with a distinctive crown and root morphology, highly adapted to its particular masticatory function. In the embryo, generation of individual teeth within the jaws relies upon interactions between ectoderm of the first branchial arch and the neural crest-derived ectomesenchymal cells that migrate into this region from their site of origin along the neural axis. Classic tissue recombination experiments have provided evidence of an essential role of the ectoderm in initiating tooth development; however, the underlying ectomesenchyme rapidly acquires dominance in establishing shape. A key question is how these cells acquire this positional information. One theory suggests that ectomesenchymal cells are pre-patterned with respect to shape generation. Alternatively, this cell population acquires positional information within the first branchial arch itself, following migration. Recent molecular evidence suggests a high degree of plasticity within these ectomesenchymal cells. In particular, signalling molecules within the ectoderm exert a time-dependent influence upon the ectomesenchyme by establishing specific domains of homeobox gene expression. Initially, these ectomesenchymal cells are plastic and able to respond to signalling from the ectoderm, however, this plasticity is rapidly lost and pattern information becomes fixed. Therefore, in the first branchial arch, local regulation between the ectoderm and neural crest-derived ectomesenchyme is crucial in establishing the appropriate tooth shape in the correct region of the jaw.

Animals↗
PubMed2003

Intrabony migration of impacted teeth.

Intrabony migration of impacted teeth is a rare dental anomaly, which occurs only in the permanent dentition of the lower jaw. The teeth involved in this phenomenon are the mandibular lateral incisor, canine, and second premolar. Migration of the lateral incisor is usually in a distal direction, resulting in transposition with the canine. Migration of the canine is most frequently in a mesial direction, resulting in transmigration across the mandibular symphysis to the opposite side of the dental arch. The second premolar most often migrates distally, sometimes past the gonial angle and as far as the coronoid process. Surgical and orthodontic treatment options are presented for the three intrabony migrating teeth.

Bicuspid↗
PubMed1990

Repair potential in localized juvenile periodontitis. A case in point.

An aggressive form of localized juvenile periodontitis (LJP) in a 12-year old West African female is reported. The case was treated with scaling, root planing, debridement, and tetracycline therapy, which resulted in complete resolution of the disease, including elimination of periodontal inflammation, regeneration of lost periodontal structures, and spontaneous repositioning of teeth that had pathologically migrated. A hopelessly involved mandibular right first molar was successfully replaced by an incompletely developed maxillary third molar tooth bud whose roots and pulp structure continued to develop after autotransplantation. It is suggested, that LJP can be successfully treated without periodontal surgery and that the potential for repair in LJP cases is apparently greater than what one can anticipate in adult forms of periodontitis.

Aggressive Periodontitis↗