Tissue levels of bone resorptive cytokines in periodontal disease

The levels of 3 bone resorptive cytokines, interleukin 1 alpha (IL-1 alpha), IL-1 beta, and tumor necrosis factor alpha (TNF alpha), were assessed in tissues from sites of periodontal disease. As determined by ELISA of tissue extracts, IL-1 beta and TNF alpha were detected in all diseased sites, whereas IL-1 alpha was present in 8/22 sites, IL-1 beta was present in highest concentration (mean +/- SEM: 11,695 +/- 2,888 pg/ml; 672 pM), followed by TNF alpha (434 +/- 135 pg/ml; 26 pM), and IL-1 alpha (342 +/- 160 pg/ml; 20 pM). The levels of all 3 mediators were significantly lower in clinically healthy tissues. There was a highly significant correlation between levels of IL-1 beta and TNF alpha (rs = 0.61, P less than 0.001), suggesting coordinated expression of these 2 mediators. The numbers of cells containing each mediator was also determined by indirect immunofluorescence on frozen tissue sections. Consistent with findings from tissue extracts, IL-1 beta-containing cells were present in approximately 5-fold higher numbers than TNF alpha-containing cells, and 40-fold higher numbers than IL-1-alpha-containing cells. Taken together with previous findings, these results indicate that IL-1 beta is likely to be an important mediator in the pathogenesis of periodontal disease.

The biomechanical characteristics of the bone-periodontal ligament-cementum complex

The relative motion between the tooth and alveolar bone is facilitated by the soft-hard tissue interfaces which include periodontal ligament-bone (PDL-bone) and periodontal ligament-cementum (PDL-cementum). The soft-hard tissue interfaces are responsible for attachment and are critical to the overall biomechanical efficiency of the bone-tooth complex. In this study, the PDL-bone and PDL-cementum attachment sites in human molars were investigated to identify the structural orientation and integration of the PDL with bone and cementum. These attachment sites were characterized from a combined materials and mechanics perspective and were related to macro-scale function. High resolution complimentary imaging techniques including atomic force microscopy, scanning electron microscopy and micro-scale X-ray computed tomography (Micro XCT) illustrated two distinct orientations of PDL; circumferential-PDL (cir-PDL) and radial-PDL (rad-PDL). Within the PDL-space, the primary orientation of the ligament was radial (rad-PDL) as is well known. Interestingly, circumferential orientation of PDL continuous with rad-PDL was observed adjacent to alveolar bone and cementum. The integration of the cir-PDL was identified by 1-2 microm diameter PDL-inserts or Sharpey's fibers in alveolar bone and cementum. Chemically and biochemically the cir-PDL adjacent to bone and cementum was identified by relatively higher carbon and lower calcium including the localization of small leucine rich proteins responsible for maintaining soft-hard tissue cohesion, stiffness and hygroscopic nature of PDL-bone and PDL-cementum attachment sites. The combined structural and chemical properties provided graded stiffness characteristics of PDL-bone (E(r) range for PDL: 10-50 MPa; bone: 0.2-9.6 GPa) and PDL-cementum (E(r) range for cementum: 1.1-8.3 GPa), which was related to the macro-scale function of the bone-tooth complex.

Bone sialoprotein in developing porcine dental tissues: cellular expression and comparison of tissue localization with osteopontin and osteonectin

Bone sialoprotein (BSP) is a highly sulphated and glycosylated phosphoprotein that is a major constituent of bone and other mineralized connective tissues. Although BSP can mediate cell attachment through an RGD sequence and binds selectively to hydroxyapatite, its precise function in mineralized tissues is unknown. To provide insights into its possible function, affinity-purified polyclonal antibodies directed against porcine BSP were used to demonstrate the histological distribution of this protein in developing porcine mandibular alveolar bone and the associated tooth tissues from 35- and 50-day fetuses. In addition, a porcine cRNA probe was used to determine the cellular expression of BSP in the same tissues by in situ hybridization. Immunoreactivity to BSP protein was restricted to the cells and matrix of the mineralized tissues of alveolar bone and dentine. In dentine, BSP was localized to the odontoblasts and their processes and to the peritubular dentine. In the alveolar bone, immunoreactivity for BSP was evident in osteoblastic cells and osteocytes and in the bone matrix; the older bone stained more strongly than newly formed bone. In addition, BSP appeared to be concentrated in the reversal lines of the rapidly remodelling bone. The distribution of BSP in these tissues revealed distinct differences when compared to osteopontin and SPARC/osteonectin, which are also prominent non-collagenous proteins of mineralized tissues. Most notable was the localization of osteopontin and especially osteonectin in non-mineralizing tissues. The immunoreactivity of osteoblasts and osteocytes for BSP in bone was consistent with the high levels of BSP mRNA revealed by in situ hybridization. However, much lower levels of hybridization were evident in the odontoblasts of developing mandibular molars. These studies demonstrate that BSP is expressed during the early formation of dentine and alveolar bone and that the protein accumulates in the peritubular dentine and bone matrix.

Immunohistochemical localization of the matrix glycoproteins--tenascin and the ED-sequence-containing form of cellular fibronectin--in human permanent teeth and periodontal ligament

The expression of two matrix glycoproteins, tenascin and cellular fibronectin (cFN), has been studied in fully developed human permanent teeth, periodontal ligament, and alveolar bone, in both frozen and paraffin-processed material. Polyclonal antibodies to tenascin and a monoclonal antibody recognizing the ED sequence specific to at least some forms of cFN were used. Staining for both tenascin and cFN was positive in the dental pulp, odontoblastic layer, cementoblast-pre-cementum zone, and on the periosteal as well as endosteal surfaces of the alveolar bone. In the periodontal ligament, cFN was evenly distributed, whereas tenascin was accumulated in the attachment zones. Pre-dentin stained for tenascin but not for cFN. Mineralized dentin and cementum were tenascin- and cFN-negative. The relative staining intensity for tenascin was greater than that for cFN in the cementoblast-pre-cementum layer and in the attachment zones of the periodontal ligament, whereas cFN stained more intensely in the pulp. In frozen material, antigenicities were well-preserved. Paraffin processing facilitated precise recognition of tissue morphology, but the antigenicity of cFN was lost. The co-expression of tenascin and cFN in the dental pulp, cementogenic zone, and on the surfaces of the alveolar bone may reflect the ability of the cells to deposit mineralized tissue matrices. The pronounced expression of tenascin in the interfaces between mineralized and non-mineralized tissues suggests that it is functionally associated with mechanical stress and may thus have at least two distinct functions. The relative amounts of the two matrix glycoproteins may contribute to regulation of tissue structure.

Immunohistological localization of cell adhesion proteins and integrins in the periodontium

The distribution of the cell adhesion proteins vitronectin, fibronectin, tenascin, and laminin as well as several integrin subunits, alpha 2, alpha 5, and alpha v, was studied in primate periodontal tissues. Full baboon mandibular sections were analyzed by immunohistochemical methods in order to localize the molecules studied in both soft and hard tissues. Vitronectin was associated with the connective tissue of the marginal gingiva, the periodontal ligament, as well as the endosteum and periosteum. A notable finding was the particularly high staining intensity of vitronectin in the periodontal ligament. Fibronectin was widely distributed in the periodontal connective tissue and was also localized to the pericellular matrix of osteocytes and blood vascular elements. Epithelial basement membranes stained positively for both fibronectin and tenascin. These proteins were also expressed in the periosteal and endosteal connective tissues and the periodontal ligament. The staining intensity for tenascin was higher in zones along the cementum and bone surfaces. Laminin was, characteristically, limited to basement membranes of epithelium and endothelium. The distribution of fibronectin, tenascin, and laminin is related to previous findings in other species. The localization of the several integrin alpha-subunits is also described in full baboon mandibular sections. The vitronectin receptor (alpha v) had a uniquely strong expression in osteoclasts of the alveolar bone and was found, at lesser intensity, on periodontal ligament fibroblasts. The fibronectin receptor alpha subunit, alpha 5, was also observed on osteoclasts, and, in addition, was widely distributed on fibroblasts, cementoblasts, and osteoblasts.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of types I, V, and VI collagen in human permanent teeth and periodontal ligament

Types I, V, and VI collagen were immunohistochemically localized in frozen and paraffin sections of human permanent teeth, periodontal ligament, and alveolar bone, by means of polyclonal antibodies. Hyaluronidase was effective in exposing epitopes of the various collagen types. The expression of type I collagen in predentin was strong in frozen sections, whereas the dental pulp stained relatively weakly. Staining intensity in the dentin matrix decreased toward enamel and cementum. Reactivity in the periodontal ligament was moderate, and it was weaker in the alveolar bone and also in cementum, which stained more intensely in paraffin sections. Staining for type V collagen was strong in the pulp. Weak reactivity in predentin became uniformly evident in frozen sections only, and dentin was negative. The periodontal ligament stained with moderate intensity, and a weak staining reaction was seen in cementum and bone. Staining for type VI collagen in the pulp and periodontal ligament was strong, whereas predentin and dentin were negative. The alveolar bone stained moderately, and non-uniform reactivity was present in cementum. In non-mineralized dental tissues, the use of frozen material enabled good immunohistochemical localization of the distinct collagen types to be carried out. Their distribution patterns in dental tissues not only differed, but the relative staining intensities for each collagen type in the pulp and predentin were inversely related. However, differences may exist in the exposure of the epitopes of collagen(s) between soft and mineralized tissues.

Structural characterization of human alveolar bone proteoglycans

Proteoglycans were extracted from EDTA-demineralized human alveolar bone under dissociative conditions using 4 M guanidinium chloride in the presence of protease inhibitors. The extract was further purified by anion-exchange chromatography on DEAE-Sephacel, using a step-wise salt gradient. The proteoglycan-rich fraction was analysed for carbohydrate, protein and amino acid composition and molecular size by SDS-PAGE. Glycosaminoglycan content was determined by cellulose acetate electrophoresis after proteolysis. The sulphate isomers of the glycosaminoglycans were confirmed by Fourier-transformed infra-red spectroscopy. Two chondroitin sulphate-proteoglycan species were identified with molecular weights of 79 and 55-65 kDa, respectively. The core proteins had molecular weights of 49 kDa for both proteoglycans, with the amino acid content rich in glycine, leucine, glutamate and aspartate. The chondroitin sulphate chains were mainly as the 4-sulphate isomer forms although low but detectable amounts of 6-sulphate isomer were also present.

A review of the association between osteoporosis and alveolar ridge augmentation

OBJECTIVE

Because of increasing life expectancy and popularity of dental implants, surgeons face a larger number of osteoporotic patients who require bone augmentation. Relationship between low bone density/osteoporosis and bone graft success is still not clear. The purpose of this article is to review and summarize the literature regarding the success of alveolar bone augmentation in osteoporosis.

STUDY DESIGN

The study design includes a literature review of relevant preclinical and clinical articles that address the association between osteoporosis and alveolar bone augmentation.

RESULTS

Increased rate of complications such as resorption of bone graft, non-integration of bone graft, delayed healing time, and implant failure in augmented bone especially in the maxilla may be associated with compromised bone health.

CONCLUSIONS

Despite the decreased success rate, osteoporosis is not an absolute contraindication for bone augmentation and dental implant placement. The modifiable risk factors for osteoporosis should be eliminated before surgery.

Human cementum tumor cells have different features from human osteoblastic cells in vitro

Cells obtained from human cementoblastoma and alveolar bone were isolated and cultured. Initial and late stages of mineralization were assessed by using atomic force microscopy, scanning electron microscopy and X-ray microanalysis. In cultures of cementoblastoma-derived cells the initial stages of mineralization showed well-defined spherical-shaped structures, while the osteoblastic cells showed plaque-like deposits. These morphological patterns of mineral deposition could serve as nucleation centers for hydroxyapatite crystals. Late stages of mineralization at 28 and 35 d maintained those morphological differences established in initial cultures. The material deposited by cementoblastoma and osteoblastic cells, analyzed by EDX spectra, revealed similar Ca/P ratios for both cell types. These values were similar to those reported for hydroxyapatite in enamel and bone. Alkaline phosphatase specific activity (AlP), of osteoblastic cells at 3, 7 and 11 d, showed an increase of 27.9, 50.9 and 37.0% (p < 0.001), respectively. However, at 15 and 19 d there was an increase of AlP activity of cementoblastoma cells by 39.4 and 34.5% over osteoblastic cells (p < 0.001). Immunostaining of cementoblastoma and osteoblastic cells using a specific mAb against a cementum-derived attachment protein revealed strong immunostaining of cementoblastoma cells which was localized to the cell membrane and fibril-like structures (96.2 +/- 1.3). A few osteoblastic cells also stained weakly with the anti-CAP mAb (6.4 +/- 0.6). Sections of decalcified paraffin embedded cementoblastoma specimens, when immunostained with anti-CAP mAb, showed strong immunostaining of the cells surrounding the regular and irregularly-shaped calcified masses of the tumor. Putative cementocytes also stained positively. Immunostaining with a polyclonal antibody against osteopontin strongly stained the osteoblastic cells (89.0 +/- 3.6). Cementoblastoma cells showed weaker staining (54.2 +/- 2.4). The results suggest that cementoblastoma cells could be a major source of specific cementum proteins. These cells could provide the opportunity to elucidate the regulation of the cementogenesis process.

Expression of growth hormone receptor by immunocytochemistry in rat molar root formation and alveolar bone remodeling

Growth hormone (GH) may regulate tooth formation and bone remodeling associated with tooth eruption. This study reports the distribution of growth hormone receptor/binding protein in developing rat molars and adjacent alveolar bone by immunocytochemistry using well-characterized anti-growth hormone receptor monoclonal antibodies. These tissues represent an excellent model for studying the ontogenic changes that occur in odontogenic and osteogenic cells, as these cells are found in linear arrays displaying the various stages of morphological and functional differentiation, and differentiated function. Immunoreactivity was first seen in precementoblasts in contact with the epithelial root sheath, and preodontoblasts. However, growth hormone receptor immunoreactivity was associated primarily with the cytoplasm of odontogenic and osteogenic cells forming their respective matrices. Thus, cementoblasts and odontoblasts at sites of new matrix formation showed intense immunoreactivity whereas cementocytes and mature odontoblasts at later stages of tooth development were nonreactive. Osteoblasts engaged in intramembranous ossification in the alveolar bone were positive, although osteocytes and endosteal cells were immunonegative. Osteoclasts at sites of alveolar bone remodeling resorption were also immunopositive. These patterns of receptor expression parallel the ontogenic sequences of odontogenic and osteogenic cells and suggest that GH promotes the functional state of these cells. Our results also imply that GH may influence differentiation or differentiated functions associated with odontogenesis, osteogenesis, and bone remodeling independent of systemic insulin-like GF-I.

Micrometer-Sized Magnesium Whitlockite Crystals in Micropetrosis of Bisphosphonate-Exposed Human Alveolar Bone

Osteocytes are contained within spaces called lacunae and play a central role in bone remodelling. Administered frequently to prevent osteoporotic fractures, antiresorptive agents such as bisphosphonates suppress osteocyte apoptosis and may be localized within osteocyte lacunae. Bisphosphonates also reduce osteoclast viability and thereby hinder the repair of damaged tissue. Osteocyte lacunae contribute to toughening mechanisms. Following osteocyte apoptosis, the lacunar space undergoes mineralization, termed "micropetrosis". Hypermineralized lacunae are believed to increase bone fragility. Using nanoanalytical electron microscopy with complementary spectroscopic and crystallographic experiments, postapoptotic mineralization of osteocyte lacunae in bisphosphonate-exposed human bone was investigated. We report an unprecedented presence of ∼80 nm to ∼3 μm wide, distinctly faceted, magnesium whitlockite [Ca₁₈Mg₂(HPO₄)₂(PO₄)₁₂] crystals and consequently altered local nanomechanical properties. These findings have broad implications on the role of therapeutic agents in driving biomineralization and shed new insights into a possible relationship between bisphosphonate exposure, availability of intracellular magnesium, and pathological calcification inside lacunae.

Identification, distribution and expression of osteoadherin during tooth formation

Osteoadherin (OSAD) is a keratan sulfate-containing proteoglycan, belonging to the small leucine-rich proteoglycan (SLRP) family. In bone OSAD has been localized in primary spongiosa within the bovine fetal rib growth plate. Moreover, in situ hybridization has shown expression of OSAD in osteoblasts close to the cartilage and bone border in the growth plate of rat femur. mRNA expression has also detected OSAD in mature osteoblasts on the surface of bone trabeculae. We have identified OSAD in extracts of bovine dentin, and the identity was verified by N-terminal sequencing. Western blot analysis detected two bands in bovine bone and dentin at 85 kDa and 60 kDa. Northern blot analysis of RNA samples from 5-d-old-rat tooth and femur showed a 1.9-kb transcript for OSAD in both tissues. OSAD was located to the mineralized dentin matrix, cementum and surrounding alveolar bone by immunohistochemistry, and in situ hybridization showed OSAD to be highly expressed during early crown formation in the entire odontoblast cell layer, in the area of Hertwig's epithelial root sheath, in the cells of the newly formed mantle dentin, and in the odontoblasts at the fissures. Ultrastructural studies indicated that OSAD might be associated with collagen fibrils. Thus, OSAD may play an important role during tooth development and biomineralization of dentin.

Immunohistochemical localization of collagenous components in healthy periodontal tissues of the rat and marmoset (Callithrix jacchus). I. Distribution of collagen types I and III

The distribution of collagen types I and III was demonstrated in healthy periodontal tissues of the rat and marmoset using immunofluorescent localization after decalcification of the maxillae and mandiblae in 0.2 N HCl. An intense fluorescence in the alveolar bone and cementum matrix, as well as in the soft periodontal tissue, was demonstrated with anti-collagen type I antibodies. In the gingival connective tissue and in the periodontal ligament thick fibers of collagen type I could be observed. The fluorescent reaction in the rat periodontal ligament was not strong in comparison to the marmoset periodontal ligament. Sharpey's fibers, inserting into the cementum and alveolar bone, were also stained. On the other hand, collagen type III could not be demonstrated in the hard periodontal tissues, but could be in the bone marrow stroma and the incremental lines as well as around the Sharpey's fibers of the cementum, in accordance to previous studies. In the gingival connective tissue a strong staining was evident, especially near the basement membrane. The periodontal ligament showed an intense fluorescence that was, in some areas, continuous with Sharpey's fibers inserting into the cementum. The distribution of collagen types I and III was demonstrated with immunohistochemical techniques in the rat and marmoset periodontium. These results provide necessary information on healthy tissues that will be required for future studies on the effects of pathological, reparative and regenerative processes.

Histomorphometric and biochemical study of osteoclasts at orthodontic compression sites in the rat during indomethacin inhibition

Prostaglandins affect the number of osteoclasts at compression sites in orthodontic tooth movement. They may also have a role in tooth movement and influence the extent of root resorption. The purpose was to examine the effect of indomethacin on the activity of resident osteoclasts, recruitment of new osteoclasts and root resorption at orthodontic compression sites. Two separate populations of osteoclasts were studied: those resident at the sites after initial appliance activation and those recruited by a subsequent activation. Orthodontic appliances were activated to provide mesially directed forces of 40 g on the maxillary molars of rats. The appliances were activated with the same force after 4 days. The rats were killed at 1, 3, 6 and 10 days after initial activation. Half of the rats were injected with indomethacin. Tooth movement was measured cephalometrically; osteoclast numbers, sizes, numbers of nuclei per osteoclast and root resorption were assessed histomorphometrically; tartrate-resistant acid phosphatase (TRAP) in alveolar bone was measured biochemically. Indomethacin inhibited both initial tooth displacement and that following the delay. It also reduced the increase in osteoclast numbers, total osteoclast surface and alveolar bone TRAP at day 10. It had no effect on the surface area of each individual osteoclast or number of nuclei in each osteoclast. Root resorption increased in both groups but it was enhanced at day 10 in the indomethacin group. These data suggest that orthodontic tooth movement after appliance activation requires the recruitment of osteoclasts to sites of compression and that this is indomethacin-sensitive. Furthermore, indomethacin enhances root resorption at compression sites 10 days after appliance reactivation.

Ultrastructural and histochemical examination of alveolar bone at the pressure areas of rat molars submitted to continuous orthodontic force

It is usually believed that repair in alveolar bone during orthodontic movement occurs after decreasing of force. However, we have recently observed signs of repair in previously resorbed cementum from human teeth exposed to continuous forces. In order to test the hypothesis that bone resorption and deposition occur concomitantly at the pressure areas, a continuous 15 cN force was applied in a buccal direction to upper first molars from eight 2.5-month-old male Wistar rats for 3 d (n = 4) and 7 d (n = 4). As a control, two additional rats did not have their molars moved. Maxillae were fixed in 2% glutaraldehyde + 2.5% formaldehyde, under microwave irradiation, decalcified in ethylenediaminetetraacetic acid, and processed for transmission electron microscopy. Specimens from one rat from each group were processed for tartrate-resistant acid phosphatase (TRAP) histochemistry. At both the times studied, the alveolar bone surface at the pressure areas showed numerous TRAP-positive osteoclasts, which were apposed to resorption lacunae. In addition, osteoblasts with numerous synthesis organelles were present in the neighboring areas overlying an organic matrix. Thus, this study provides evidence that the application of continuous forces produces concomitant bone resorption and formation at the pressure areas in rat molars.

Effect of orthodontic appliance reactivation during the period of peak expansion in the osteoclast population

BACKGROUND

Delays in the appearance ofosteoclasts at compression sites occur following orthodontic appliance reactivation when this is done during the period of osteoclast recruitment. This study examined changes in alveolar bone after appliance reactivation at a time coinciding with the peak expansion of the osteoclast population following the first appliance activation.

METHODS

Orthodontic appliances were activated with 40 g on maxillary molars followed by a reactivation with the same force after 4 days in one group and sham reactivation in the other. Rats were killed at 0, 1, 3, 6, and 10 days thereafter. Orthodontic movement was measured cephalometrically. TRAP and interleukin-1 alpha (IL-1alpha) were measured biochemically, and changes in osteoclasts and root resorption were assessed at both compression and tension sites histomorphometrically.

RESULTS

Teeth in the reactivated group displayed more initial displacement than controls but no more tooth movement 10 days following appliance reactivation. Also, increases in osteoclast numbers and surface percent, as well as alveolar bone Tartrate-resistant acid phosphatase (TRAP), became evident in the treated animals only 10 days after reactivation. However, IL-1alpha was elevated in alveolar bone within 1 hr following appliance reactivation but returned to baseline by day 1. There were no treatment-related difference in nuclear number per osteoclast or trabecular surface per osteoclast. Significant treatment-related increases in root resorption were evident at compression sites by day 10.

CONCLUSIONS

These findings indicate that after appliance reactivation during the height of osteoclastic stimulation, a second cohort of osteoclasts can be recruited, but only after a delay of several days. This delay is not due to a failure to produce IL-1alpha in the tissues.

The effect of glycosylaminoglycans on the mineralization of sheep periodontal ligament in vitro

The effect of removal of glycosylaminoglycans on the mineralization of sheep periodontal ligament was determined using enzyme digests followed by incubation in solutions supersaturated with respect to hydroxyapatite at pH 7.4. TEM revealed that control periodontal ligament remained unmineralized. However, tissue from which glycosylaminoglycans had been removed contained plate-like crystals arranged parallel to and within the collagen fibrils. Electron probe and electron diffraction studies suggested that the crystals were apatitic with a similar order of crystallinity to dentine, and a Ca:P ratio of 1.61. In addition, the glycosylaminoglycan content of periodontal ligament, cementum and alveolar bone was compared using cellulose acetate electrophoresis. Periodontal ligament contained predominantly dermatan sulfate while cementum and alveolar bone contained mostly chondroitin sulfate. A role for glycosylaminoglycans in maintaining the unmineralized state of the periodontal ligament is suggested. Control of expression of specific proteoglycan species on a spatially restricted basis is presumably central to this role.

Analysis of chondroitin sulfate isomers in the periodontium of the monkey using high-performance liquid chromatography

Glycosaminoglycan (GAG) was extracted from monkey periodontium, consisting of gingiva, periodontal ligament, alveolar bone and cementum, and from dental pulp and dentin by digestion with Pronase E. Unsaturated disaccharide isomers formed by chondroitinase AC digestion from chondroitin sulfate were labeled with dansylhydrazine and analyzed by high-performance liquid chromatography. These tissues showed different molar ratios of the unsaturated chondroitin sulfate disaccharides. The ratio of delta Di-4S to delta Di-6S was lowest in the dental pulp, followed by the gingiva, periodontal ligament, dentin, alveolar bone, and cementum, in that order. It was greater in the calcified than in the uncalcified tissues.

Roxithromycin penetration into gingiva and alveolar bone of odontoiatric patients

The concentrations of the new macrolide antibiotic roxithromycin in plasma, saliva, gingiva, and alveolar bone were studied in 24 odontoiatric patients treated with a first dose of 300 mg p.o. followed by three maintenance doses of 150 mg p.o., 12-hourly. Samples of blood, saliva, gingiva, and bone were collected at various time points up to 24 h after the last dosing, and the roxithromycin concentration was measured microbiologically, using Bacillus subtilis ATCC 6633 as the reference organism. Pharmacokinetic analysis was performed according to a two-compartment open model with first-order absorption. The plasma, gingiva, and alveolar bone peak concentrations were 6.12 +/- 1.94 mg/l, 6.55 +/- 2.54 mg/kg, and 5.09 +/- 1.60 mg/kg, respectively. Low levels of roxithromycin were detected in saliva (0.67 +/- 0.12 mg/l at the 3rd h). The values of the area under the concentration-time curve for plasma, gingiva, and bone were 59.47 mg/l.h, 51.88 mg/kg.h and 46.80 mg/kg.h, respectively; the half-life values were 7.52 h for plasma and 6.36 and 5.20 h for gingiva and bone, respectively. These results indicate that roxithromycin reaches high levels in periodontal tissues.

An unusual disordered alveolar bone material in the upper furcation region of minipig mandibles: A 3D hierarchical structural study

Teeth are subjected to compressive loads during mastication. Under small loads the soft tissue periodontal ligament (PDL) deforms most. However when the loads increase and the PDL is highly compressed, the tooth and the alveolar bone supporting the tooth, begin to deform. Here we report on the structure of this alveolar bone in the upper furcation region of the first molars of mature minipigs. Using light microscopy and scanning electron microscopy (SEM) of bone cross-sections, we show that this bone is hypermineralized, containing abundant small pores around 1-5 μm in diameter, lacunae around 10-20 μm as well as larger spaces. This bone does not possess the typical lamellar motif or other repeating structures normally found in cortical or trabecular mammalian bone. We also use high resolution focused ion beam scanning electron microscopy (FIB-SEM) in the serial surface mode to image the 3D organization of the demineralized bone matrix. We show that the upper furcation bone matrix has a disordered isotropic structure composed mainly of individual collagen fibrils with no preferred orientation, as well as highly staining material that is probably proteoglycans. Much larger aligned arrays of collagen fibers - presumably Sharpey's fibers - are embedded in this material. This unusual furcation bone material is similar to the disordered material found in human lamellar bone. In the upper furcation region this disordered bone comprises almost all the volume excluding Sharpey's fibers. We surmise that this most unusual bone type functions to resist the repeating compressive loads incurred by molars during mastication.

Gingival swelling in a 13-year-old girl with multiple recurrences

We present a challenging case of gingival swelling that recurred several times in 3.5 years in a 13-year-old girl. Histologic evaluation of the initial biopsy revealed groups of epithelioid cells surrounded by lymphocytes in the submucosal fibrous connective tissue, and it was diagnosed as noncaseating granulomatous inflammation. With the tissue specimens from subsequent multiple excisions and several immunohistochemical studies, the diagnoses evolved to benign cellular infiltrate of undetermined origin, epithelioid hemangioma, proliferating endothelial cell neoplasm of uncertain biologic potential, atypical vascular tumor, epithelioid hemangioendothelioma, and kaposiform hemangioendothelioma. We discuss the list of differential diagnoses from various pathologists and propose our diagnosis of epithelioid hemangioendothelioma based on its clinical behavior, histologic features, and immunohistochemical findings.

X-ray microanalytical and morphological observations of the interface region between ceramic implant and bone

In 8 monkeys both the maxillary lateral incisors were extracted. In the 16 extraction sites an Al2O3-ceramic dental implant (Frialit) was immediately inserted. Eight implants were submerged under the oral mucosa and the other 8 were allowed to penetrate through the mucosa during the observation period. None of the implants was loaded during the observation periods. After experimental periods of 1, 2, 4 and 8 months, the interface region between the implant and bone was examined using scanning-electron microscopy, X-ray microanalysis, back scatter, microradiography and light microscopy. The results showed that osseointegration of Al2O3-ceramic dental implant was obtained. The newly formed bone around the implant filled exactly the contours of the implant. Newly formed bone had a mineral content and a phosphorus-to-calcium ratio similar to that of the adjacent older mature jaw bone. There were no differences in the osseointegration rate between the submerged and the nonsubmerged implants. No leakage of aluminium from the implant could be detected in the bone.

Distribution of fluoride in the dental tissues and their supporting mandibular bone from the same individual

Dental and skeletal tissues have their own distinct fluoride distribution profiles. It was thought useful to compare these within individuals as normally comparisons are made between different groups of individuals. The average fluoride concentration decreased in the following order; cementum, alveolar bone, cancellous bone, mandible, dentine and enamel.

Localization of pro-collagen type II mRNA and collagen type II in the healing tooth socket of the rat

Sprague-Dawley rats (50 days old) were anaesthetized and the maxillary right molars extracted. The rats were killed at 2, 3, 6, 8 and 10 days after extraction. The maxillae were dissected and prepared for either routine histology, in situ hybridization for pro-collagen type II mRNA, or immunohistochemical detection of collagen type II. Pro-collagen type II mRNA was expressed maximally in the healing tooth socket at 8 days after the extractions, but the protein was not expressed at any time. This suggests that the translation of pro-collagen type II mRNA does not occur in osteoblasts following tooth extraction. Ossification was present in the socket at 6 days after the extractions, which is consistent with the suggestion that an early feature of osteoblastic differentiation may be the expression of type II pro-collagen mRNA.