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 ß-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.

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.

Sister-chromatid exchange, chromosomal aberrations and delays in cell-cycle kinetics in human lymphocytes induced by dental composite resin eluates.

We have investigated eluates derived from commercially available composite resin-based materials used for direct (Tetric Ceram/Ivoclar-Vivadent, Simile/Pentron, Filtek Z-250/3M ESPE) and indirect (Adoro/Ivoclar-Vivadent and Conquest Sculpture/Pentron) dental restorations, with respect to their genotoxic effects on human peripheral lymphocytes. Primary lymphocyte cultures obtained from blood samples of three healthy donors were exposed to eluates of freshly cured specimens of all the materials tested. Metaphases were induced with phytohaemagglutinin, collected after a 72-h treatment using colchicine and stained with the Fluorescence Plus Giemsa (FPG) procedure. Preparations were scored for sister-chromatid exchange (SCE) and chromosomal aberrations (CAs). The proliferation rate index (PRI) and the mitotic index (MI) were also calculated. Our results show that eluates derived from the three direct composites (Filtek Z-250, Simile and Tetric Ceram) increased the frequencies of SCE and CAs and markedly reduced PRI and MI. Tetric Ceram's eluate, being the most genotoxic of all eluates tested, increased the frequencies of SCE up to 24.40 per cell (control, 9.87 per cell) and of CAs up to 424 per 100 metaphases scored (control, 5). Moreover, it caused a pronounced decrease of the PRI down to 1.31 (control, 2.44) and of the MI down to 9.8 per thousand (control, 19.2 per thousand). In contrast, eluates derived from the laboratory-processed composites (Adoro and Conquest Sculpture) induced much less cytogenetic damage. Overall, the degree of genotoxicity and cytotoxicity decreased as follows: Tetric Ceram>Filtek Z-250>Simile>Adoro=Conquest Sculpture. These results indicate that composite resins used for direct and indirect dental restorations differ extensively in their cytotoxic and genotoxic potential and in their ability to affect chromosomal integrity, cell-cycle progression, DNA replication and repair. This underlines the impact of improved polymerization with respect to their biological behavior.

Attachment and proliferation of human periodontal ligament fibroblasts on bioactive glass modified ceramics.

In this study, six groups of modified ceramic specimens were constructed and were studied comparatively with dental porcelain (P:control) for their ability to support human periodontal ligament fibroblasts attachment and proliferation. The dental porcelain was initially coated with bioactive glass (PCB) or with a mixture of porcelain and bioactive glass (PCBP) and then calcium-phosphate rich (Ca-P) or hydroxy-carbonate apatite (HCAp) layers were bio-mimetically developed on both surfaces (PCB and PCBP) after immersion in simulated body fluid. The development and characterization of Ca-P and HCAp layers on PCBCa-P, PCBHCAp, PCBPCa-P, PCBPHCAp specimens' surfaces were evaluated by Scanning Electron Microscopy (SEM) and further confirmed by Fourier Transform Infrared Spectroscopy (FTIR). The modified ceramics differed from their controls concerning their surface morphology as evaluated by SEM, and their surface chemical composition (Al, P, Si, Ca, Na and K) as evaluated by Energy Dispersive Spectroscopy (EDS). Almost all modified specimens supported cell attachment, spreading and proliferation at higher extent than the control porcelain specimens. The additional layers of Ca-P or HCAp on PCBP and PCB specimens were found to positively affect cell attachment and proliferation. The highest cell population, of all specimens tested, was observed on PCBPCa-P and PCBPHCAp. The Ca-P particles present on all Ca-P and HCAp coated specimens seemed to be involved in cell adhesion.

Ultrasonographic thickness and electromyographic activity of masseter muscle of human females.

The aims of this study were to assess the thickness of the masseter muscle by means of ultrasonography and to investigate the relationship between masseter electromyographic activity and muscle thickness bilaterally, during maximum voluntary clenches. Participants in the study consisted of 52 young female adults (mean age 23.7 +/- 2.5 years) without craniomandibular disorders and with full natural dentitions. The thickness of the masseter muscle was measured with a real-time ultrasound equipment. Electromyographic activity was recorded with bipolar surface electrodes, during maximum voluntary clenches. The error of the methods was calculated by double recordings in 15 subjects in a 4-week interval. The measurement error for the right muscle was 0.16 mm in thickness and 16.44 microV in electromyographic activity. For the left masseter the corresponding values were 0.19 mm and 18.01 microV. The relationship of masseter muscle thickness to its electromyographic activity was estimated by Pearson's correlation coefficient. The mean masseter thickness under contracted conditions was 13.9 +/- 1.5 mm for the right side and 13.9 +/- 1.4 mm for the left side. The mean maximum electromyographic activity was 379.0 +/- 56.0 microV for the right muscle and 372.3 +/- 73.2 microV for the left. Muscle thickness was strongly correlated to electromyographic maximum activity in the right masseter (r = 0.721, P < or = 0.001) and moderately correlated in the left muscle (r = 0.407, P < or = 0.01). The difference between the two sides is possibly because of the larger method error in the left side. It is apparent that ultrasonography can be used as a useful tool to assess masseter muscle functional capacity during full effort in healthy individuals.

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.

Effectiveness of conservative treatment for craniomandibular disorders: a 2-year longitudinal study.

The severity of symptoms of craniomandibular disorders was studied during a 2-year period in 195 patients treated with conservative therapeutic schemes. Results revealed a continuing improvement and a statistically significant tendency for the great majority of patients to become asymptomatic or show a decrease in the severity of symptoms. By the end of the 2 years, 66.7% of the patients were symptom free, 25.6% presented with slight symptomatology, and 3.1% were recorded with a fluctuating recurrence of symptoms. This investigation provided the data to develop an exponential model for the hypothesis that stabilization of effectiveness of conservative treatment is achieved between 6 months and 1 year after the initiation of treatment.

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.

[Influence of the sprue casting design on the surface porosity of the silver-palladium dental alloys]. / E epidrase tes schediases ton agogon chyteuses sten epiphaneiake porose ton argyropalladiouchon kramaton. (Anakoinotheke sto 70 Panellenio Odontiatriko Eunedrio. Athena, Oktobrios 1987).

The purpose of this work is to investigate and find out the best "design" of the casting sprues on the area and the number of the surface porosity when we cast silver-palladium dental alloys for metalloacrylics fixed partial dentures. Our observation and research have been done on 216 external surfaces from 72 M.O.D. specimens, which were casted using four different designs of casting sprues and three types of silver-palladium dental alloys (Panag, Pangold and Palliag M.). The evaluation of our findings and statistical analysis have been done. The findings of our study are the following. 1. It has been found that the "alloy" factor doesn't influence the area and the number of the surface porosity we examined, on the contrary it has been found that the "design" factor has great influence on the area and the number of the dental alloys. 2. The use of chill-sets and the securing of sprue button alloy decrease the area and the number of the surface porosity when we cast silver-palladium dental alloys. 3. The straight sprues and the placing of the specimens near the heat-center of the mold created much better conditions for decreasing the number and the area of the surface porosity than when we use the preci-roto system.

Complete mandibular subperiosteal implants for edentulous mandibles.

The complete mandibular subperiosteal implant is one of the oldest implant modalities. It has been serving thousands of people for over 25 years. All failures and problems created in the past have been due to the inadequate support and improper architectural design of the implant substructure. Through the mistakes made in experimentation over the years, better results have been achieved because of the improvement of the implant design. Proper evaluation and utilization of the available bone is essential for a successful prognosis for the edentulous mandible. The crossbar attachment that joins the four implant posts of the substructure provides better force distribution and less potential for resorption below the primary struts of the complete mandibular subperiosteal implant. The cast substructure rests on the bone and is covered by the mucoperiosteum. Satisfactory retention and stability is given to the definitive overdenture which is fitted over the protruding posts and crossbar design. The complete mandibular subperiosteal implant is a definite solution to the problem mandibular edentulous patient. Proper, careful, and conservative diagnosis is important. Skill, experience, and accuracy are major criteria for the success of a dental implant.