Comparison of two preventive interventions on dental caries among children in Democratic People's Republic of Korea.

OBJECTIVES: The aim was to compare the change in dental caries status in two different intervention groups of the Children's Oral Health Promotion Programme (COHPP). METHODS: A longitudinal study among 500 children who had participated into the COHPP for 6 years was conducted in Pyongyang, Democratic People's Republic of Korea (DPRK). Children in Group I received intensified school-based intervention and were clinically examined at the age of 7 years in 2007 (n = 250), 10 years in 2010 (n = 250) and 13 years in 2013 (n = 242). Children in Group II (n = 250) joined the programme at the age of 4 years in kindergarten in 2007, were provided with early preschool-based intervention and were clinically examined at the age of 7 years in 2010 and 10 years in 2013. RESULTS: Both the prevalence and the mean number of dt + DT decreased significantly in both groups during the follow-up. This was due to decrease in the number of dt, whereas the number of DT remained relatively constant. Poisson regression showed that the association between the group status and the change in the number of dt + DT was statistically significant when adjusted for gender but disappeared when the school was included in the analysis. CONCLUSIONS: The decrease in dental caries may be partly due to the exfoliation of deciduous teeth and dental treatment received. However, the study gave some reference emphasizing the early starting of the prevention.

The role of physiological markers of health in the association between demographic factors and periodontal disease.

BACKGROUND AND OBJECTIVE: Age is highly related to oral health status. The higher prevalence of oral disease within subgroups of the population may reflect a tendency towards "early aging" and dysregulation of multiple physiological systems. This study examines whether the association between periodontal disease and demographic factors is mediated by physiological measures of health. MATERIAL AND METHODS: Logistic regression was used to examine whether biomarkers and demographic factors, such as socio-economic status (SES) and race/ethnicity, were associated with periodontal disease, and then whether the strength of these relationships could be attributed to associations between demographic variables and physiological measures of systemic health. RESULTS: Periodontal disease was associated with measures of SES and race/ethnicity. Furthermore, 1-unit increases in cytomegalovirus (CMV), optical density, C-reactive protein (CRP) and glycated hemoglobin (HbA1c) were associated with a 25% [odds ratio (OR) = 1.25; 95% confidence interval (CI): 1.14-1.36], 13% (OR = 1.13; 95% CI = 1.03-1.24) and 19% (OR = 1.19; 95% CI = 1.12-1.27) increased likelihood of periodontal disease, respectively. However, when biomarkers and socio-demographic variables were both included in the model, their associations with periodontal disease were significantly reduced or eliminated. CONCLUSIONS: The risk of periodontal disease is higher among black and/or low-income individuals; however, these associations appear to be partly due to the greater probability of elevated levels of CRP, CMV or HbA1c among these groups.

Comparison of polyvinyl alcohol coated nasal packing with non-absorbable nasal packing.

BACKGROUND: A number of different nasal packing materials are available for prevention of nasal bleeding after endoscopic sinus surgery. Polyvinyl alcohol (PVA) coated nasal packing is an expandable packing for use in rhinological surgery. This innovative surf- ace treatment helps to reduce the possibility of adherence to tissue and of blood clotting within the sponge. The present study investigated the effects of PVA coated packing and non-absorbable packing with respect to pain, healing site and postoperative bleeding following endoscopic sinus surgery. METHODOLOGY: Patients between 18-80 years of age undergoing sinus surgery were enrolled. Each patient`s ethmoid cavities were randomised to receive PVA coated packing material or the standard non-absorbable sinus packs. The remaining nasal packing material was removed on the 2nd day in the clinic. We determined visual analog scale score, bleeding time and wound healing status. A single rhinologist graded postoperative endoscopic appearance. Length of follow-up was 3 months. RESULTS: Thirty three patients were recruited. There was a significant difference in the bleeding time between the two groups, but pain and wound healing were not significantly different between the two groups. CONCLUSION: PVA-coated nasal packing presents comparable characteristics with traditional nasal packing.

Up-regulation of the expression of major histocompatibility complex class I antigens by plasmid DNA transfection in non-hematopoietic cells.

The effect of DNA on the surface expression of major histocompatibility (MHC) class I antigens was examined in non-hematopoietic tumor cell lines. Transfection with plasmid DNA via liposome or electroporation significantly increased the surface expression of MHC class I molecules in a transient manner. Northern blot analysis showed that levels of MHC class I mRNA were increased by DNA transfection, probably via transcriptional activation. In contrast, the expression of the MHC class II and beta-actin genes was not affected, suggesting that the up-regulation of MHC class I expression by plasmid DNA works in a gene-specific manner.

Characterization of UV-irradiated dense/porous collagen membranes: morphology, enzymatic degradation, and mechanical properties.

Collagen-based membranous materials of various shapes (gel, film, sponge) are known to be the most promising materials in terms of facilitating the regeneration of dermal defects. In this study, dense and porous collagen membranes were fabricated using air-drying and freeze-drying processes, respectively, and the effect of ultraviolet (UV) radiation on the degree of membrane crosslinking was evaluated by in vitro biodegradation and mechanical testing. A non-irradiated membrane group was used as the negative control and a glutaraldehyde (GA) treated group as the positive control. Scanning electron microscopy showed that, as the freezing temperature decreased to -196 degrees C, the resultant mean pore sizes also decreased; optimal pore size was obtained at a freezing temperature of -70 degrees C. In vitro biodegradation and mechanical testing demonstrated that GA treatment or 4 hours of exposure to UV radiation significantly increased both resistance to collagenase and mechanical strength versus the untreated controls, regardless of the collagen membrane type (dense or porous). Our results suggest that UV treatment is a useful tool for the fabrication of collagen membranes designed to be used as dermal dressings.

Fatigue properties and stem subsidence in wire coil reinforced PMMA bone cement: a preliminary in vitro study.

The longevity of the cemented total hip joint replacement depends on the integrity of the cement fixation with respect to the interfaces of the metal stem and bone, and stress/strain transmission and its distribution. A simple stainless steel wire coil was placed around a tapered stem in a simulated cement mantle to counteract radial- and hoop-stress and dynamic compression-compression tests were performed. The results showed that the wire coil reinforced cement group had a higher fatigue (30%) and strength (35%) up to 10(5) loading cycles. The amount of stem subsidence during fatigue tests of the wire reinforced group was significantly reduced (2.5 times) compared with the control group.

Reinforcement of bone cement around prostheses by pre-coated wire coil: a preliminary study.

The longevity of the cemented total hip joint replacement depends on the integrity of the cement fixation with respect to the interfaces of the metal stem and bone, and stress/strain transmission and its distribution. A simple coil made of stainless steel wires was placed around a tapered stem in a simulated cement mantle to counteract the radial- and hoop-stress and static push-out mechanical tests were performed. The results show statistically significant increases in ultimate strain (+17.62%), ultimate load (+110.34%), stiffness (+117.63%), and fracture toughness (+153.63%) exhibited by the wire reinforcement over the control. Precoating with thin layer of polymethylmethacrylate may also enhance the mechanical properties of the reinforced cement mantle. This simple device may contribute to the longevity of the cement mantle by virtue of the enhanced mechanical properties, which in turn will be able to absorb more energy transmitted through the metal stem.

Reinforcement of bone cement around the femoral prosthesis tip by pre-coated wire coil: a human cadaver bone study.

In order to alleviate fixation-related problems of cemented total hip arthroplasty (THA), a wire coil was incorporated within the cement mantle at the distal end of femoral prosthesis in a sectioned human cadaver specimen. Mechanical push-out test results showed that the wire reinforcement reduces the hoop strain by 50% at the exterior surface of the bone. The reinforced specimen also showed less axial stem displacement. The use of wire coil within the cement mantle could reduce hoop strain and axial stem displacement in the femoral prosthesis of total hip joint implants.

Reinforcement of bone cement around prostheses by pre-coated wire coil: a finite element model study.

The longevity of cemented total joint replacements, namely total hip arthroplasty (THA), depends on the integrity of the cement per se and interfaces of the metallic stem-cement and bone-cement, and stress/stress transmission and its distribution. A simple coil made of stainless steel wire was placed around a tapered stem in a simulated cement mantle to counteract the radial- and hoop-stresses created by the stem loading. Two-dimensional axisymmetric finite element analysis was performed to elucidate the level of the stress and its distribution with and without the wire coil. The results suggest that the peak stresses distributed throughout the cement may be reduced by more than one half, via the incorporation of a wire coil, confirming the mechanical test results, which showed an average fracture load of 3.70 +/- 1.13 kN for pure bone cement control and 9.02 +/- 1.54 kN for the wire coil reinforced specimens. These results indicate that the reinforcement of the cement mantle with a wire coil in the distal end of the hip stem prosthesis could reduce the hoop-stresses, which may results in reduced stresses in the bone and cement interface. Consequently, loosening of the interfaces of the bone-cement and cement-stem could be reduced due to the enhanced fatigue life of the bone cement mantle with favorable stress distribution at the distal tip of the stem.

Effect of bone mineral particles on the porosity of bone cement.

Bone particle-impregnated bone cement is investigated in vitro, which could be used to improve fixation between bone and cement interface by ingrowth of tissues that may replace bone particles. Inorganic bone particles (150-300 microns diameter) were mixed with regular bone cement powder by 0, 10, 20, and 30% by weight and implanted into the pre-drilled intramedullary canal (11cm long, 10mm diameter) of canine femur. A 4mm diameter, 10mm long stainless steel rod was implanted to simulate the prosthesis. The specimens were cut into 2mm thick discs transversely along the long axis of the bone and ground to examine with a confocal laser microscope. Diametral tensile strength tests were performed for the 0, 10, 20, and 30% bone particle impregnated bone cement discs without the intramedullary implant. Present results show that mixing bone particles with bone cement decreased the number of pores and porosity but increased the size of pores. The analysis of porosity distribution showed no significant difference between bone cement and bone particle-impregnated bone cement. Also, the strength of the bone particle-impregnated bone cement decreased linearly with increased amount of bone particles in spite of the decreased percent porosity. Using a bone particle-impregnated bone cement along with a pre-coated implant could be one of the solutions to the problems in the fixation of total joint arthroplasty.

Effect of shock wave treatment on femoral prosthesis and cement removal.

The present study has examined the efficacy of shock wave treatment to aid in the removal of bone cement in human cadaver femora after femoral prosthesis implantation. The shock waves were applied to the specimens at four points, in the circumference 90 degrees apart, at three levels. Four hundred shocks were applied at each point with intensity level of 25 kV. Extraction time of the bone cement was significantly (p < 0.002) faster in the treated versus untreated control groups. The average extraction time was decreased by 32%. Shock wave treatment also reduced the amount of residual cement inside the bone surface by an average of 55% (p < 0.006). The number of shocks needed to remove the prosthesis from bone cement also decreased significantly (p < 0.001) after shock wave treatment.

A new approach for the calculation of photon dose conversion factors in the PMMA slab phantom.

A new simple method using the computer code MCNP is proposed for calculation of photon dose conversion factors in the PMMA slab phantom. Absorbed dose is calculated by multiplying fluence buildup in the PMMA slab phantom by virtual energy deposition in the ICRU tissue substance. This method does not need auxiliary calculations to determine the dose conversion factors, such as calculation of backscatter factors in the ICRU tissue cube and the PMMA slab phantoms. The discrepancies between the results of the direct method presented here and a more conventional indirect method is less than 2%, except for low energy photons (<100 keV) at large depths. As the direct method reduces the number of calculational steps, the results are more reliable than those of the indirect method.

A novel thermosensitive polymer with pH-dependent degradation for drug delivery.

A class of thermosensitive biodegradable multiblock copolymers with acid-labile acetal linkages were synthesized from Pluronic triblock copolymers (Pluronic P85 and P104) and di-(ethylene glycol) divinyl ether. The novel polymers were engineered to form thermogels at body temperature and degrade in an acidic environment. The Pluronic-based acid-labile polymers were characterized using nuclear magnetic resonance, gel permeation chromatography and differential scanning calorimetry. In vitro biocompatibility of the synthesized polymers was evaluated using calorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. The polymers showed reverse thermogelling behavior in water around body temperature. The sol-gel transition temperatures of the polymers synthesized from Pluronic P85 and P104 were lowered from 70.3 to 30 degrees C and from 68.5 to 26.9 degrees C, respectively, when the synthesized polymers were compared with corresponding Pluronic block copolymers at a concentration of 25wt.%. The hydrophobic dye solubilization confirmed the formation of polymeric micelles in the aqueous solution. The sizes of the multiblock copolymers increased on a rise in temperature, indicating that thermal gelation was mediated by micellar aggregation. The thermally driven hydrogels showed preferential polymer degradation at acidic pH. At pH 5.0 and 6.5, the release of 40kDa fluorescein isothiocyanate-dextran (FITC-dextran) from the thermally formed hydrogels was completed within 2 and 9 days, respectively. However, FITC-dextran was continuously released up to 30 days at neutral pH. The mechanism of FITC-dextran release at pH 5.0 was mainly an acid-catalyzed degradation, whereas both diffusion and pH-dependent degradation resulted in FITC-dextran release at pH 6.5. The novel polymers hold great potential as a pH-sensitive controlled drug delivery system owing to their interesting phase transition behavior and biocompatibility.

Differentiating dental pulp cells via RGD-dendrimer conjugates.

Traumatic dental injuries are often irreversible, underscoring the need for therapies that protect dental pulp cells and enhance their regeneration. We hypothesized that generation 5 poly amido amine (PAMAM) dendrimers (G5), functionalized with fluorescein isothiocyanate (FL) and αVß3-specific, cyclic arginine-glycine-aspartic acid (RGD) peptides, will bind to dental pulp cells (DPCs) and modulate their differentiation. Dental pulp cells and mouse odontoblast-like cells (MDPC-23) (±) treated with G5-FL-RGD were analyzed via Western blot, RT-PCR, and quantitative PCR. Transcription of dental differentiation markers was as follows: Dentin matrix protein (DMP-1), dentin sialoprotein (DSPP), and matrix extracellular phosphoglycoprotein (MEPE) as well as vascular endothelial growth factor (VEGF) all increased via the JNK pathway. Long-term G5-RGD treatment of dental pulp cells resulted in enhanced mineralization as examined via Von Kossa assay, suggesting that PAMAM dendrimers conjugated to cyclic RGD peptides can increase the odontogenic potential of these cells.

Membrane immunoglobulins of spontaneous B lymphomas of aged BALB/c mice.

Four cell lines derived from spontaneous BALB/c lymphoma tumors were analyzed with regard to the type of their membrane immunoglobulins (Ig). Using lactoperoxidase iodination of membrane proteins combined with immunoprecipitation and electrophoresis on polyacrylamide gel, three of these cell lines (X16c, L10A and K46) were found to express the monomeric form of IgM and IgD as well as half molecules. One cell line (M12) lacked both IgM and IgD. The apparent mol. wt of the lymphoma micro chain was about 80 000 and exceeded the mol. wt. of 75 000 determined for micro chains secreted by myeloma cells. The mol. wt. of the delta heavy chain was found to be 66 000. Immunofluorescence showed that the L10A and X16c lines expressed lambda light chains on their cell surface. Another Ig-bearing cell line (K46) expressed both lambda and kappa chains. Thus, three out of the four B lymphomas examined expressed both IgM and IgD with light chains of the Lambda type. These results, together with our previous findings which demonstrate the presence of Ia and Fc receptors on the same cells, indicate that spontaneous B lymphomas in BALB/c mice are the malignant counterpart of mature B lymphocytes.

Catabolism of the murine IgG1 molecule: evidence that both CH2-CH3 domain interfaces are required for persistence of IgG1 in the circulation of mice.

Site-directed mutagenesis of a recombinant Fc-hinge fragment has previously been used to identify a region of the murine IgG1 molecule that controls catabolism, and this site encompasses amino acid residues at the interface of the CH2 and CH3 domains. In the current study the nature of this 'catabolic site' has been further analysed using recombinant techniques. Fc-hinge, CH2-hinge, CH2 and CH3 fragments have been expressed in Escherichia coli, purified and analysed in pharmacokinetic studies in mice. The CH2-hinge has been analysed as both a monomer and dimer, and the dimer has a longer beta phase half-life (61.6 h) than the monomer (29.1 h). This suggests that two catabolic sites per Fc fragment are required for serum persistence. The need for two functional sites per molecule has been confirmed by the analysis of a hybrid Fc-hinge fragment comprising a heterodimer of one Fc-hinge with the wild type (WT) IgG1 sequence and a mutant Fc-hinge with a defective catabolic site (mutated at His310, Gln311, His433 and Asn434). This hybrid is cleared with a beta phase half-life of 37.9 h and this is significantly shorter than that of the WT Fc-hinge fragment (82.9 h). In contrast to the CH2-hinge dimer, the CH3 domain is cleared rapidly (beta phase half-life of 21.3 h) indicating that the region of this domain (His433 and Asn434) previously identified as being involved in the control of catabolism is not sufficient in the absence of the CH2 domain for the serum persistence of an IgG fragment. The data extend our earlier observations concerning a region of the murine IgG1 molecule that is involved in the control of catabolism and have implications for the design of engineered antibodies for therapy.

Involvement of hydrogen peroxide in the differentiation of clonal HD-11EM cells into osteoclast-like cells.

The present study uses the osteoclast precursor clonal line, HD-11EM, to study the potential of hydrogen peroxide (H2O2) in mediating the differentiation of HD-11EM into osteoclast-like cells. HD-11EM cells are a newly established clonal cell line that, in response to 1alpha,25-(OH)2D3, differentiate into osteoclast-like cells that are multinucleated (more than three nuclei), express tartrate-resistant acid phosphatase (TRAP), and excavate resorption pits when cultured on dentin slices in the presence of osteoblasts (Hsia et al., 1995, J. Bone Miner. Res., 10(Suppl 1):S424; Hsia, and Hauschka, 1997, unpublished data). Here we demonstrate that HD-11EM express the reduced nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase specific cytochrome b558 subunits, and that stimulation of HD-11EM with 1 or 10 nM 1alpha,25-(OH)2D3 increases the extracellular release of H2O2 within 5-10 min. Ours is the first report that stimulation of a cell with 1alpha,25-(OH)2D3 enhances the activation of NADPH-oxidase and increases the basal release of superoxide and the formation of its dismutation product, H2O2. To determine the possible involvement of H2O2 in the differentiation of HD-11EM, these cells were exposed to glucose/glucose oxidase. This enzyme system was used to deliver a pure and continuous source of H2O2 in nanomole amounts consistent with quantities produced by HD-11EM in response to 1alpha,25-(OH)2D3. Both 1alpha,25-(OH)2D3 and the exogenously generated H2O2 stimulated a dose- and time-dependent increase in TRAP activity/cell and the number of multinucleated cells 24-48 hr after treatment. Northern analysis confirmed an increase in expression of TRAP mRNA in response to either 1alpha,25-(OH)2D3 or H2O2. Decreases in cell proliferation and v-myc mRNA were also observed in response to these agents. Taken together, our findings indicate that production of H2O2 by HD-11EM is an important local factor involved in differentiation of HD-11EM into osteoclast-like cells, and suggest that H2O2 may play a role in native osteoclast differentiation.

Complications of total hip arthroplasty: MR imaging-initial experience.

PURPOSE: To investigate the use of standard magnetic resonance (MR) imaging sequences with simple parameter modifications for the detection and characterization of total hip arthroplasty (THA) complications. MATERIALS AND METHODS: An initial phantom study was performed with cobalt-chrome and titanium prostheses to establish the imaging parameters for a subsequent clinical study. In the clinical study, coronal and transverse MR imaging of 14 THA prostheses was performed before and after intravenous contrast material administration in 12 patients who were being considered for revision arthroplasty. The images were reviewed for evidence of juxtaarticular or periprosthetic abnormalities, patterns of contrast enhancement, and quality of periprosthetic tissue depiction. RESULTS: Phantom study results showed improved periprosthetic tissue depiction with use of thin sections, increased frequency-encoding gradient strength, and fast spin-echo sequences. The clinical study results demonstrated periprosthetic abnormalities in 11 cases: mechanical loosening in two cases (including one case with an associated periprosthetic fracture); granulomatosis, eight; and infection, one. In 100% of cases, tissue depiction around the femoral component was judged to be of "diagnostic quality." Tissue depiction around the acetabular component was of diagnostic quality in five (36%) cases. In all seven surgically confirmed cases, a correct diagnosis was made preoperatively with MR imaging. CONCLUSION: By using simple modifications to standard MR imaging sequences, diagnostic-quality MR imaging of THA complications can be performed, particularly around the femoral prosthetic stem.

Dissolution of poorly crystalline apatite crystals by osteoclasts determined on artificial thin-film apatite.

Poorly crystalline apatite (PCA) crystals introduced into bone tissue should be stable for a definite period before they are dissolved as a result of a host response. In this report, the dissolution of PCA crystals by the action of osteoclasts was studied on artificial thin films. These consisted of PCA crystals having similar crystallographic properties to bone crystals which were developed for assaying the osteoclast activity in vitro. The dissolution of minerals by osteoclasts decreased along with the decreased amount of labile phosphate and hydrogen phosphate domains of apatite crystals, which were caused by the crystal maturation temperature. A profound effect on mineral dissolution by pH in the culture medium was also shown. Low acidity considerably increased mineral dissolution, whereas a slight alkalinity totally blocked mineral dissolution. There was little difference in the mineral dissolution behavior of osteoclasts near the physiologic pH. In addition, it was determined whether mineral dissolution by osteoclasts was dependent on the destruction of the organic matrix. Nocodazole was introduced to inhibit the secretion of hydrolytic enzymes, and acetazolamide was added to inhibit acid production by the osteoclasts. There was no significant change as a result of nocodazole addition on mineral dissolution or by the addition of acetazolamide on degradation of collagen. These results indicate that small changes in the physicochemical properties of apatite crystals can decrease resorption by osteoclasts, which can be highly activated at low pH. These results also suggest that mineral dissolution and organic degradation by osteoclasts are self-regulating.