P. Garefis

Comparative analysis of in vitro osteo/odontogenic differentiation potential of human dental pulp stem cells (DPSCs) and stem cells from the apical papilla (SCAP).

OBJECTIVE The aim of this study was to compare the in vitro osteo/odontogenic differentiation potential of mesenchymal stem cells (MSCs) derived from the dental pulp (dental pulp stem cells - DPSCs) or the apical papilla (stem cells from the apical papilla - SCAP) of permanent developing teeth. DESIGN DPSCs and SCAP cultures were established from impacted third molars of young healthy donors at the stage of root development. Cultures were analysed for stem cell markers, including STRO-1, CD146, CD34 and CD45 using flow cytometry. Cells were then induced for osteo/odontogenic differentiation by media containing dexamethasone, KH(2)PO(4) and β-glycerophosphate. Cultures were analysed for morphology, growth characteristics, mineralization potential (Alizarin Red method) and differentiation markers (dentine sialophosphoprotein-DSPP, bone sialoprotein-BSP, osteocalcin-OCN, alkaline phosphatase-ALP), using immunocytochemistry and reverse transcriptase-polymerase chain reaction. RESULTS All DPSCs and SCAP cultures were positive for STRO-1, CD146 and CD34, in percentages varying according to cell type and donor, but negative for CD45. Both types of MSCs displayed an active potential for cellular migration, organization and mineralization, producing 3D mineralized structures. These structures progressively expressed differentiation markers, including DSPP, BSP, OCN, ALP, having the characteristics of osteodentin. SCAP, however, showed a significantly higher proliferation rate and mineralization potential, which might be of significance for their use in bone/dental tissue engineering. CONCLUSIONS This study provides evidence that different types of dental MSCs can be used in tissue engineering/regeneration protocols as an approachable stem cell source for osteo/odontogenic differentiation and biomineralization that could be further applied for stem cell-based clinical therapies.

Molecular Toxicology of Substances Released from Resin-Based Dental Restorative Materials

Resin-based dental restorative materials are extensively used today in dentistry. However, significant concerns still remain regarding their biocompatibility. For this reason, significant scientific effort has been focused on the determination of the molecular toxicology of substances released by these biomaterials, using several tools for risk assessment, including exposure assessment, hazard identification and dose-response analysis. These studies have shown that substances released by these materials can cause significant cytotoxic and genotoxic effects, leading to irreversible disturbance of basic cellular functions. The aim of this article is to review current knowledge related to dental composites’ molecular toxicology and to give implications for possible improvements concerning their biocompatibility.

Effects of HEMA and TEDGMA on the in vitro odontogenic differentiation potential of human pulp stem/progenitor cells derived from deciduous teeth

OBJECTIVES The aim of this study was to investigate the effects of HEMA and TEGDMA on the odontogenic differentiation potential of dental pulp stem/progenitor cells. METHODS Dental stem/progenitor cell cultures were established from pulp biopsies of human deciduous teeth of 1-3 year-old children (Deciduous Teeth Stem Cells-DTSCs). Cultures were characterized for stem cell markers, including STRO-1, CD146, CD34, CD45 using flow cytometry. Cytotoxicity was evaluated with the MTT assay. DTSCs were then induced for osteo/odontogenic differentiation by media containing dexamethasone, KH(2)PO(4),β-glycerophosphate and L-ascorbic acid phosphate in the presence of nontoxic concentrations of HEMA (0.05-0.5mM) and TEGDMA (0.05-0.25mM) for 3 weeks. Additionally, the effects of a single exposure (72 h) to higher concentrations of HEMA (2mM) and TEGDMA (1mM) were also evaluated. RESULTS DTSCs cultures were positive for STRO-1 (7.53±2.5%), CD146 (91.79±5.41%), CD34 (11.87±3.02%) and negative for CD45. In the absence of monomers cell migration, differentiation and production of mineralized dentin-like structures could be observed. Cells also progressively expressed differentiation markers, including dentin sialophosphoprotein-DSPP, bone sialoprotein-BSP, osteocalcin-OCN and alkaline phosphatase-ALP. On the contrary, long-term exposure to nontoxic concentrations of HEMA and TEGDMA significantly delayed the differentiation and mineralization processes of DTSCs, whereas, one time exposure to higher concentrations of these monomers almost completed inhibited mineral nodule formation. BSP, OCN, ALP and DSPP expression were also significantly down-regulated. SIGNIFICANCE These findings suggest that HEMA and TEGDMA can severely disturb the odontogenic differentiation potential of pulp stem/progenitor cells, which might have significant consequences for pulp tissue homeostasis and repair.

Effect of age and sex on craniomandibular disorders

The purpose of this study was to investigate the effect of age and sex on craniomandibular disorders. A total of 195 subjects were examined, 148 women and 47 men. The range of age was 16 to 70 years. Clinical and anamnestic examination data established the ratio of women to men as 4:1. The prevalence of clicking, headache, teeth-clenching, hypomobility, difficulty in mastication, and neuromuscular symptoms was greater among young women than in other age and sex groups. There was a statistically significant correlation between severity of symptoms and age among women, and a relative decline by age in the prevalence of symptoms for both sexes. Finally, younger patients showed a greater prevalence of neuromuscular symptoms, whereas older patients had more peripheral symptoms.

Genotoxic and cytotoxic effects of different types of dental cement on normal cultured human lymphocytes

In this study we have investigated the genotoxic and cytotoxic effects of eluates derived from different types of commercially available dental cements, including glass ionomer cements (GICs) (Ketac Cem/3M ESPE and GC Fuji I/GC Corp), resin-modified glass ionomer cements (RM-GICs) (RelyX Luting/3M ESPE and Vitrebond/3M ESPE) and dual-cure resin cements (RCs) (Variolink II/ Ivoclar-Vivadent and Panavia F 2.0/Kuraray) on normal cultured human lymphocytes. Lymphocyte primary cultures obtained from blood samples of three healthy donors were exposed to serial dilutions of eluates derived from specimens of each material tested. Metaphases were induced with phytohaemagglutinin, collected after 72h treatment by use of colchicine and stained according to the fluorescence plus giemsa (FPG) procedure. Preparations were scored for sister chromatid exchange (SCE) and chromosomal aberrations (CAs), while the proliferation rate index (PRI) was also calculated. Our results show that eluates derived from the RM-GICs and RCs caused severe genotoxic effects by significantly increasing the frequencies of SCEs and CAs in cultures of peripheral blood lymphocytes and by decreasing the relevant PRI values in a dose-dependent manner, whereas the two GICs caused only minor cytogenetic effects. Eluates of the two RM-GICs (Vitrebond and RelyX) were also very cytotoxic, as the first serial dilutions of both materials caused a complete mitotic arrest in lymphocyte cultures. Overall, the degree of genotoxicity and cytotoxicity caused by dental cements decreased as follows: Viterbond>Rely X>Panavia F 2.0>Variolink II>Ketac Cem=GC Fuji I. These results indicate that different types of dental cement differ extensively in their genotoxic and cytotoxic potential and their ability to affect chromosomal integrity, cell-cycle progression, DNA replication and repair. Although these results cannot be directly extrapolated to the clinical situation, the potential occurrence of adverse effects caused by the RM-GICs and RCs tested in this study should be considered when making a clinical decision about dental cements.

Comparison of cell proliferation on modified dental ceramics

The aim of this study was to investigate the influence of substrate characteristics such as chemical composition and surface morphology of dental ceramics to support cell attachment and proliferation. Thus, body (B) and shoulder (S) porcelain differing on their surface morphology and composition were treated with oxides CaO or CaO and P(2)O(5) and four modified ceramics BCa, BCaP, SCa, SCaP were constructed, respectively. The modified ceramics differ from their controls concerning their surface morphology as evaluated by Scanning Electron Microscope (SEM), and their surface chemical composition (Na, KP and Ca) as evaluated by Energy Dispersing Spectroscopy (EDS). All modified ceramics support better than the control ceramics the cell proliferation over 72 h incubation period. Furthermore, higher rates of cell proliferation was detected in shoulder modified ceramics (SCa and SCaP) than in all other cases.

Shear bond strength of techniques for bonding esthetic veneers to metal

STATEMENT OF PROBLEM New composites with improved qualities have been introduced to the dental profession as alternatives to porcelain. There is concern about the strength and reliability of new metal-resin bonding systems when these composites are used as esthetic veneers over metal frameworks. PURPOSE This in vitro study compared the shear bond strength of 2 metal-resin bonding techniques with the bond strength of conventional porcelain fused-to-metal (PFM). Effects of water storage and thermocycling were also evaluated. MATERIAL AND METHODS Ninety disks, cast in a medium gold, high noble PFM alloy, were divided equally into 6 groups, and received 3 treatments for veneering: conventional feldspathic porcelain on 1 group, and a composite (Artglass) bonded to the metal, using 2 metal-resin bonding techniques. Specimens were tested in shear, half of them after a 24-hour dry storage at room temperature and the rest after 10-day storage in normal saline solution at 37 degrees C and thermocycling. Fractured specimens were evaluated under x10 magnification to determine the nature of failure. Statistical analysis was performed with 2-factor analysis of variance (ANOVA). RESULTS Mean shear bond strength values before and after wet storage and thermocycling were 29.66 and 22.91 MPa for the PFM group; 21.43 and 17.92 MPa for the Siloc group; and 19.34 and 15.64 for the etched group, respectively. The PFM group exhibited significantly higher bond strength values compared with the other 2 groups (P<.001). All groups showed a significant decrease in bond strength values after wet storage and thermocycling (P<.001). CONCLUSION Wet storage and thermocycling caused a significant decrease in shear bond strength of all specimens. Shear bond strength of conventional feldspathic PFM was significantly higher than that of the 2 metal-resin bonding techniques tested. The 2 latter techniques did not reveal any statistically significant differences.

Attachment and Proliferation of Human Periodontal Ligament Fibroblasts on Fibronectin-Coated Bioactive Glass Modified Ceramics

The effect of fibronectin (FN) on human periodontal ligament fibroblasts (PDLF) attachment and proliferation on Bioglass® (PerioGlas® Synthetic Bone Graft Particulate, US Biomaterials) modified dental ceramics, was investigated in vitro. FN introduced limited alterations in cell attachment on Bioglass®-modified dental ceramics in comparison with the corresponding non-FN-coated specimens but had a profound positive effect on Bioglass®-coated specimens that weakly supported both cell attachment and proliferation. The amount of protein adsorbed on the specimens was not proportional to its biological activity, i.e. cell attachment, spread and proliferation, probably due to surface energy variations and FN conformational changes induced by differences in surface composition and morphology of the different dental ceramics modifications.

Expression of Bioactivity and Biocompatibility Testing of Bioactive Glass Modified Zinc Phosphate Luting Cement

The bioactivity and biocompatibility of a zinc phosphate luting cement (HARVARD, Richter & Hoffmann, Dental-GmbH, Berlin) which was modified by Bioglass® (PerioGlas® Synthetic Bone Graft Particulate, US Biomaterials), was evaluated in vitro with human lung fibroblasts (MRC-5), baby hamster kidney fibroblasts (BHK) and rat pulp cells (RPC) by XTT and BrdU assays. A thin Ca-P layer was grown on the surface of Bioglass®-modified zinc phosphate cement specimens after immersion in SBF for 7 days and remained constant after 16 days immersion time. The incorporation of Bioglass® powder in zinc phosphate specimens resulted in equal or increased cell attachment and activity for almost all cell lines examined without any apparent impact on mechanical or physicochemical properties of the cement, although this needs further documentation. The combination of these two methods in determining the biocompatibility of Bioglass®-modified zinc phosphate cements showed that cells not only attached well on modified specimens but were actively synthesizing DNA after 72h of incubation.