Mesenchymal stem cell-encapsulated collagen microspheres for bone tissue engineering.

There is a demonstrated clinical need for alternatives of autologous fresh bone graft with excellent biological performance in osteoconductivity, osteoinductivity, and osteogenicity. We previously developed a collagen microencapsulation technology entrapping bone marrow-derived mesenchymal stem cells (MSCs) in a biomimetic collagen fiber meshwork and produced injectable collagen-MSC microspheres. In this study, we hypothesize that injectable microspheres with osteoconductivity, osteogenicity, and osteoinductivity can be fabricated by differentiating the encapsulated MSCs, from either human or mouse sources, toward osteogenic lineages in these three-dimensional microspheres. The osteogenicity, osteoconductivity, and osteoinductivity of the microspheres were evaluated in vitro. Osteogenic markers of the differentiating MSCs including alkaline phosphatase and calcium deposition showed positive staining. Osteoconductivity of the collagen meshwork in the microsphere was demonstrated by the presence of calcium phosphate deposits among the collagen fibers and by the significantly increased calcium content extracted from the microspheres. Moreover, osteoinductivity of the MSC-encapsulated microspheres was demonstrated by the ability to induce osteogenic differentiation of undifferentiated MSCs in both contact and noncontact coculture. This study contributes toward the future development of injectable alternatives for fresh bone grafts using autologous MSCs.

Prolonged exposure to bacterial toxins downregulated expression of toll-like receptors in mesenchymal stromal cell-derived osteoprogenitors.

BACKGROUND: Human mesenchymal stromal cells (MSCs, also known as mesenchymal stem cells) are multipotent cells with potential therapeutic value. Owing to their osteogenic capability, MSCs may be clinically applied for facilitating osseointegration in dental implants or orthopedic repair of bony defect. However, whether wound infection or oral microflora may interfere with the growth and osteogenic differentiation of human MSCs remains unknown. This study investigated whether proliferation and osteogenic differentiation of MSCs would be affected by potent gram-positive and gram-negative derived bacterial toxins commonly found in human settings. RESULTS: We selected lipopolysaccharide (LPS) from Escherichia coli and lipoteichoic acid (LTA) from Streptococcus pyogenes as our toxins of choice. Our findings showed both LPS and LTA did not affect MSC proliferation, but prolonged LPS challenge upregulated the osteogenic differentiation of MSCs, as assessed by alkaline phosphatase activity and calcium deposition. Because toll-like receptors (TLRs), in particularly TLR4 and TLR2, are important for the cellular responsiveness to LPS and LTA respectively, we evaluated their expression profiles serially from MSCs to osteoblasts by quantitative PCR. We found that during osteogenic differentiation, MSC-derived osteoprogenitors gradually expressed TLR2 and TLR4 by Day 12. But under prolonged incubation with LPS, MSC-derived osteoprogenitors had reduced TLR2 and TLR4 gene expression. This peculiar response to LPS suggests a possible adaptive mechanism when MSCs are subjected to continuous exposure with bacteria. CONCLUSION: In conclusion, our findings support the potential of using human MSCs as a biological graft, even under a bacterial toxin-rich environment.

The hierarchical cluster analysis of oral health attitudes and behaviour using the Hiroshima University--Dental Behavioural Inventory (HU-DBI) among final year dental students in 17 countries.

OBJECTIVE: To explore and describe international oral health attitudes/ behaviours among final year dental students. METHODS: Validated translated versions of the Hiroshima University-Dental Behavioural Inventory (HU-DBI) questionnaire were administered to 1,096 final-year dental students in 17 countries. Hierarchical cluster analysis was conducted within the data to detect patterns and groupings. RESULTS: The overall response rate was 72%. The cluster analysis identified two main groups among the countries. Group 1 consisted of twelve countries: one Oceanic (Australia), one Middle-Eastern (Israel), seven European (Northern Ireland, England, Finland, Greece, Germany, Italy, and France) and three Asian (Korea, Thailand and Malaysia) countries. Group 2 consisted of five countries: one South American (Brazil), one European (Belgium) and three Asian (China, Indonesia and Japan) countries. The percentages of 'agree' responses in three HU-DBI questionnaire items were significantly higher in Group 2 than in Group 1. They include: "I worry about the colour of my teeth."; "I have noticed some white sticky deposits on my teeth."; and "I am bothered by the colour of my gums." CONCLUSION: Grouping the countries into international clusters yielded useful information for dentistry and dental education.

Sealing ability of dentin coating using adhesive resin systems.

PURPOSE: To assess the sealing ability of dentin coating using adhesive resin systems to verify its potential in protecting the dentin/pulp from the oral environmental stimuli. MATERIALS AND METHODS: 15 extracted human premolars were prepared for complete crowns and the electrical resistance of their coronal dentin was measured. The prepared teeth were then randomly divided into three groups, and the prepared dentin surface of five teeth in each group was coated using one of three adhesive resin systems (All-Bond 2, Clearfil Liner Bond II, Super-Bond D-Liner) with low viscosity resins. Measurements for electrical resistance of the prepared coronal dentin was repeated after the first and second coat of the low viscosity resins, and at 1 and 4 weeks of storage in a physiological saline solution. Additionally, three prepared teeth were exposed to either cold (37 degrees C --> 4 degrees C) or heat (37 degrees C --> 60 degrees C) stimulus and the temperature change was monitored inside the pulp chamber. Time-temperature curve was obtained before and after the first and the second dentin coating. RESULTS: Before dentin coating electrical resistance of the coronal dentin ranged from 1 to 11 k(omega), and increased significantly after the first coating by 3-15 times, and by 5-185 times after the second coating. Thermal diffusion was significantly smaller in the dentin after the coating. Before coating, the temperature change inside the pulp chamber ranged from 2-5 degrees C at 5 seconds after the thermal stimuli were applied. This decreased significantly to between 0.3-0.5 degrees C after the coating.

Rehabilitating a patient with bruxism-associated tooth tissue loss: a literature review and case report.

Tooth tissue loss from bruxism has been demonstrated to be associated with various dental problems such as tooth sensitivity, excessive reduction of clinical crown height, and possible changes of occlusal relationship. A literature search revealed a number of treatment modalities, with an emphasis on prevention and rehabilitation with adhesive techniques. Rehabilitating a patient with bruxism-associated tooth tissue loss to an acceptable standard of oral health is clinically demanding and requires careful diagnosis and proper treatment planning. This article describes the management of excessive tooth tissue loss in a 43-year-old woman with a history of bruxism. The occlusal vertical dimension of the patient was re-established with the use of an acrylic maxillary occlusal splint, followed by resin composite build-up. Full-mouth oral rehabilitation ultimately involved constructing multiple porcelain veneers, adhesive gold onlays, ceramo-metal crowns, and fixed partial dentures.