Identification of plasmids in Actinobacillus actinomycetemcomitans and construction of intergeneric shuttle plasmids

A collection of 39 isolates of Actinobacillus actinomycetemcomitans , obtained from laboratories located in 5 different geographical regions of the United States, was examined for the presence of plasmid DNA. Only 2 of the strains examined, designated VT736 and VT745, harbored detectable plasmids. Strain VT736 contained a 1.9 kb plasmid species (pVT736-1) and a larger (>30 kb) species (pVT736-2). Both plasmids were detected in the covalently closed circular DNA fraction of dye buoyant density gradients. However, only the smaller plasmid was observed in agarose gels containing plasmid-enriched cell lysates prepared by a rapid screening procedure. Strain VT745 contained a single, 24 kb, plasmid (pVT745) that was observed consistently in plasmid-enriched lysates, as well as in the plasmid band of dye buoyant density gradients. A restriction endonuclease map of pVT736-l was constructed. The plasmid contained one site each for the enzymes Hinc II, Kpn I and Xho I, located 600 to 700 bp from each other on the pVT736-1 map. Hinc II-digested pVT736-1 DNA could not be cloned in Escherichia coli. However, intact pVT736-1 digested with Kpn I or Xho I could be cloned in E. coli on pUC19 or pGEM7Zf(-), respectively. Kpn I-digested pVT736-1 was cloned in both orientations on pUC19, but Xho I-digested pVT736-1 was clonable in only one orientation on pGEM7Zf(-). Each of the 3 types of chimeric plasmid constructs provided a potential A. actinomycetemcomitans/E. coli shuttle plasmid for the development of a genetic transfer system in A. actinomycetemcomitans.     

SHED repair critical-size calvarial defects in mice

Objective:  Stem cells from human exfoliated deciduous teeth (SHED) are a population of highly proliferative postnatal stem cells capable of differentiating into odontoblasts, adipocytes, neural cells, and osteo-inductive cells. To examine whether SHED-mediated bone regeneration can be utilized for therapeutic purposes, we used SHED to repair critical-size calvarial defects in immunocompromised mice.
Materials and methods:  We generated calvarial defects and transplanted SHED with hydroxyapatite/tricalcium phosphate as a carrier into the defect areas.
Results:  SHED were able to repair the defects with substantial bone formation. Interestingly, SHED-mediated osteogenesis failed to recruit hematopoietic marrow elements that are commonly seen in bone marrow mesenchymal stem cell-generated bone. Furthermore, SHED were found to co-express mesenchymal stem cell marker, CC9/MUC18/CD146, with an array of growth factor receptors such as transforming growth factor β receptor I and II, fibroblast growth factor receptor I and III, and vascular endothelial growth factor receptor I, implying their comprehensive differentiation potential.
Conclusions:  Our data indicate that SHED, derived from neural crest cells, may select unique mechanisms to exert osteogenesis. SHED might be a suitable resource for orofacial bone regeneration.     

Ganglion cyst of the temporomandibular joint

We report a case of cystic lesion in a 37-year-old woman. The patient had an oval-shaped lesion adjacent to the temporomandibular joint. Thick fibrotic tissue and muscle were observed microscopically, but the epithelium lining was not observed. The lesion was diagnosed as a ganglion cyst. The patient's general medical history was non-contributory. High performance liquid chromatography (HPLC) and mass spectrophotometry (MS) revealed some proteins from the fluid in the lesion, such as a filaggrin precursor, dystroglycan, a polyprotein of the hepatitis C virus, and proteins originating from bacteria. The follow-up examinations revealed no recurrence. The probable pathogenesis of the lesion is discussed.     

Prospective clinical trial comparing the effects of conventional Twin-block and mini-block appliances: Part 1. Hard tissue changes.

PURPOSE: The aim of this prospective clinical trial was to compare the dentoskeletal effects of a conventional and a modified Twin-block (TB) appliance. The conventional TB appliance was constructed with a large, single-step advancement. The modified appliance, termed the mini-block (MB), was incrementally advanced, incorporated a maxillary incisor torquing spring, and had a reduced bite-block height. MATERIAL: Seventy patients were placed into age- and sex-matched pairs. Patients in each pair were allocated to opposing appliance groups. Active treatment lasted 9 months, irrespective of the final overjet attained, and final cephalometric records were taken at 12 months (+/-1 month). Both groups showed pretreatment equivalence for age, sex, overjet, and cephalometric variables. RESULTS: The TB group experienced a significantly greater reduction in overjet (median, -8 mm; P = .02) compared with the MB group (median, -4 mm). This improved overjet reduction was associated with significantly greater forward movement of pogonion (median change, TB: 3.3 mm; MB: 2.1 mm; P = .02) and greater retroclination of the maxillary incisors (median change, TB: -5 degrees ; MB: -1.9 degrees ; P = .04). No significant intergroup difference was found for changes in total anterior facial height (median change, TB: 4.4 mm; MB: 4.3 mm) and mandibular incisor proclination (median change, TB: 1.3 degrees ; MB, 2.4 degrees ). CONCLUSIONS: Progressive mandibular advancement was not associated with greater mandibular growth compared with single-step advancement. The maxillary incisor torquing spring seems to be effective at reducing maxillary incisor retroclination. Reduced bite activation in the MB group did not result in less mandibular incisor proclination. There was considerable individual variation in appliance effects within both groups.     

Leached components from dental composites in oral simulating fluids and the resultant composite strengths

The aim of this study was to analyse the leached moieties of dental composites after storage in ethanol and organic acids of plaque and further evaluate the resultant effect on the diametral tensile strength (DTS) of the composites. Three commercial composites were used: Bis-GMA-based Z100, Bis-GMA/UDMA-based Heliomolar, and Bis-MPEPP-based Marathon One. The solutions used were: 99·9% acetic acid, 99% propionic acid and 75% ethanol. Specimens (4 mm diam. × 2 mm thick) were stored at 37°C in 3 mL of solution for up to 30 days. Gas chromatography/mass spectrometry was used to characterize the leached moieties and DTS of the specimens after immersion was evaluated. Data were analysed using ANOVA and Tukey LSD test. The eluted substances were not all the same in different solutions and composites but mostly increased with immersion time, and included diluents (TEGDMA and decamethacrylate) and some additives, such as an ultra-violet stabilizer (TINUVINP), plasticizers (dicyclohexyl phthalate and bis(2-ethylhexyl) phthalate), initiator (triphenyl stibine), coupling agent (γ-methacryloxypropyl trimethoxysilane), and phenyl benzoate. The chief polymerizing monomers were not found. More kinds of components were found in the acetic acid and ethanol groups studied. The fewest kinds and quantities of leached moieties were found for Bis-GMA specimens and then Bis-GMA/UDMA ones, most of which are diluent agents. Bis-MPEPP specimens leached the most substances, which were composed mostly of a short phenyl group chain structure. The BisGMA composite showed the highest DTS (54·8 ± 5·7 MPa), which was not greatly affected by the length of storage. Bis-GMA/UDMA (36·2 ± 6·8 MPa) and Bis-MPEPP (26·1 ± 4·5 MPa) composites were significantly reduced (P < 0·05) after 30 days storage in the ethanol (35–50%), in the propionic acid (25–30%), and in the acetic acid (40–60%). Irreversible processes such as the leaching of components occur in fluids simulating an oral environment, which may contribute to irreversible material degradation, especially for non-Bis-GMA-based composites.     

Effects of sonicated Enterococcus faecalis extracts on interleukin-2 and interleukin-4 production by human T cells

In the present authors' previous study, sonicated Enterococcus faecalis extracts were shown to suppress the cell cycle progression of human lymphocytes. To study the effect of this microorganism on the function of lymphocytes, the authors investigated the levels of interleukin-2 (IL-2) and interleukin-4 (IL-4) production by T lymphocytes before and after the addition of sonicated E. faecalis extracts. In this study, levels of IL-2 and IL-4 produced from T cells were evaluated by using the quantitative sandwich enzyme immunoassay technique. In response to phytohemagglutinin (PHA) stimulation, T cells produced increased levels of IL-2 and IL-4. However, the expressions of both cytokines were significantly inhibited when PHA-activated T cells were preexposed to 12.5 microg/ml and 25 microg/ml of sonicated E. faecalis extracts (p < 0.05). This effect was concentration-dependent, because the levels of IL-2 and IL-4 expressions were not affected by the addition of a low concentration (5 microg/ml) of sonicated extract. These findings suggest that Th1 and Th2 immunosuppression mediated by E. faecalis could be a part of the pathogenic mechanism of the endodontic failure associated with this microorganism.     

Precipitation hardening in a dental low-gold alloy

Age-hardening characteristics in a dental low-gold alloy composed of 40.0 wt% Au-35.0 wt% Ag-7.9 wt% Pd-7.0 wt% Cu-5.0 wt% In-3.5 wt% Zn-1.5 wt% Sn, were investigated by means of the hardness test, XRD study, SEM observations and EPMA. The following results were obtained. The age-hardening was characterized by a precipitation of Cu-rich alpha2 phase in the a phase. The softening that occurred following prolonged ageing was due to the heterogeneous formation of the fine nodular precipitates composed of the Ag-rich alpha1 phase and the Cu-rich alpha2 phase at the grain boundaries of the a phase.     

A scoring system for the early detection of oral submucous fibrosis based on a self-administered questionnaire

OBJECTIVES: The aims of the present study were to evaluate the frequent clinical complaints of oral submucous fibrosis (OSF) and to develop a scoring system for early detection of the disease by a self-administered questionnaire. METHODS: A total of 296 subjects were recruited, including 123 OSF patients without oral cancer and 173 betel quid chewers without OSF or oral cancer. A self-administered questionnaire was used to collect the symptom profile from study subjects. Their maximal mouth opening (MMO) between upper and lower incisor edges was measured and recorded by well-trained nurses. A binary logistic regression model examining the likelihood of OSF based on the eight symptoms of interest was used to develop the scoring system. RESULTS: Among 79 OSF subjects with an MMO < 35 mm, the most frequent complaint was trismus (87.3%), followed by burning sensation (76.0%) and xerostomia (72.2%). Among 44 OSF subjects with an MMO > or = 35 mm, burning sensation (68.2%) was the most frequent complaint, followed by trismus (54.5%) and xerostomia (54.5%). Six frequent complaints including trismus, burning sensation, xerostomia, sore throat, numbness, and oral ulceration were utilized to develop a scoring system for the early detection of OSF. The scoring system had an area under the receiver operating characteristic curve of 0.90. CONCLUSION: This study suggests a screening questionnaire of frequent complaints for the early detection of OSF.     

Infection-mediated early-onset periodontal disease in P/E-selectin-deficient mice

BACKGROUND: Retrospective and correlation studies suggest that early-onset periodontal disease may be due to a deficiency in phagocyte function, a pathogenic oral biofilm, and/or dysregulated gingival cytokine expression. Increased susceptibility to periodontal disease is therefore thought to result from multiple risk factors. METHODS: We tested this hypothesis prospectively using P/E-selectin adhesion molecule deficient mice that mimic the human syndrome leukocyte adhesion deficiency II. RESULTS: Our studies demonstrate that, in comparison to wild type animals, P/E-/- mice exhibit: spontaneous, early onset alveolar bone loss which is significant by 6 weeks of age; a 10-fold elevation in bacterial colonization of their oral cavities; and elevated gingival tissue levels of the bone resorptive cytokine IL-1alpha. Alveolar bone loss is completely prevented by prophylactic antibiotic therapy. CONCLUSIONS: These experiments provide the first prospective evidence for the multiple risk factor hypothesis of periodontal disease, and validate the first animal model for early onset periodontitis in which both the microbiota and host response can be systematically manipulated. P/E-/- animals should be useful in testing the virulence of putative periodontal pathogens, in determining the role of host resistance factors in periodontitis, in exploring the proposed relationship(s) between infection mediated alveolar bone loss and systemic health disorders, and exploring their genetic relationships.