Effect of physical activity on bone turnover in young boys

AIMS: To evaluate the effect of the physical activity on bone turnover in young male soccer players at the Tanner's stage of 1-2. MATERIAL AND METHODS: 61 young soccer players (13,4 +/- 0,3 years old) who actively participated in soccer since 3,7 +/- 0,7 years were compared to 60 age and sex- matched non active subjects. Bone mineral density (BMD) of whole body, and in specific skeleton sites, fatty body mass (FBM) and lean body mass (LBM) were determined by a dual energy X-ray absorptiometry (DXA). Total plasma alkaline phosphatase (ALP) and plasma bone alkaline phosphatase (BALP), plasma osteocalcin (OC) and plasma collagen type I cross-linked C-telopeptide (CTX) were measured. RESULTS: BMD of the whole body and at the lumbar spine (L2-L4), femoral, lower limbs and LBM were significantly higher in young soccer players than in controls. The biochemical markers of bone turnover: ALP (6,7%), BALP (8,9%), OC (3%) and CTX (3,1%) were not significantly higher in sportsmen than in controls. The calcium was significantly higher in sportsmen than in controls. CONCLUSION: These results suggest that soccer practice induced an increase of bone mass in boys. The increase in the level of bone turnover evaluated by the new biochemical markers was not significant in the sportsmen.     

Cancer‐associated somatic DICER1 hotspot mutations cause defective miRNA processing and reverse‐strand expression bias to predominantly mature 3p strands through loss of 5p strand cleavage

Our group recently described recurrent somatic mutations of the miRNA processing gene DICER1 in non‐epithelial ovarian cancer. Mutations appeared to be clustered around each of four critical metal‐binding residues in the RNase IIIB domain of DICER1. This domain is responsible for cleavage of the 3′ end of the 5p miRNA strand of a pre‐mRNA hairpin. To investigate the effects of these cancer‐associated 'hotspot' mutations, we engineered mouse DICER1‐deficient ES cells to express wild‐type and an allelic series of the mutant DICER1 variants. Global miRNA and mRNA profiles from cells carrying the metal‐binding site mutations were compared to each other and to wild‐type DICER1. The miRNA and mRNA profiles generated through the expression of the hotspot mutations were virtually identical, and the DICER1 hotspot mutation‐carrying cells were distinct from both wild‐type and DICER1‐deficient cells. Further, miRNA profiles showed that mutant DICER1 results in a dramatic loss in processing of mature 5p miRNA strands but were still able to create 3p strand miRNAs. Messenger RNA (mRNA) profile changes were consistent with the loss of 5p strand miRNAs and showed enriched expression for predicted targets of the lost 5p‐derived miRNAs. We therefore conclude that cancer‐associated somatic hotspot mutations of DICER1, affecting any one of four metal‐binding residues in the RNase IIIB domain, are functionally equivalent with respect to miRNA processing and are hypomorphic alleles, yielding a global loss in processing of mature 5p strand miRNA. We further propose that this resulting 3p strand bias in mature miRNA expression likely underpins the oncogenic potential of these hotspot mutations. Copyright © 2012 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Die Stone Disinfection: Incorporation of Sodium Hypochlorite

Purpose Previous research has shown that dental gypsum casts may be effectively disinfected by the substitution of 10% of the gauging water with 5.25% solution of sodium hypochlorite. The purpose of this investigation was to determine the properties of gypsum produced from such a solution as opposed to tap water alone. Materials and Methods Tests included setting time, compressive strength, rigidity, diametral tensile strength, setting expansion, hardness, and detail reproduction. Results The addition of sodium hypochlorite to the gauging water resulted in a statistically significant increase in the compressive strength and rigidity, and a decrease in setting time (p .5). All other properties remained unchanged. Conclusions This substitution may be an effective and convenient method of disinfecting gypsum casts in the laboratory without adversely effecting physical and mechanical properties.     

Enamel demineralization adjacent to orthodontic brackets bonded with hybrid glass ionomer cements: An in vitro study

Enamel demineralization is recognized as a possible side effect of bonding orthodontic brackets with composite resins. Fluoride-releasing restorative materials have been shown to inhibit tooth demineralization. The purpose of this study was to evaluate two fluoride-releasing hybrid glass ionomer bonding agents for inhibition of enamel demineralization surrounding orthodontic brackets under two experimental conditions. This in vitro study used 72 extracted human premolars. Twenty-four teeth were bonded with Advance resionomer, 24 were bonded with Fuji Ortho LC hybrid glass ionomer and 24 were bonded with Transbond XT composite resin as the control. The teeth were cycled in an artificial caries challenge three times daily for 30 days. Half of the teeth in each group were brushed twice daily with a fluoridated dentifrice, and the other half were not brushed. Demineralization of enamel surrounding orthodontic brackets was evaluated with polarized light microscopy. Enamel lesions were photographed under maximum illumination. Images were projected, and demineralized areas were traced. Both average depth and area were measured with a sonic digitizer. Analysis of variance (P < .0001) and Duncan’s test (P < .05) indicated significant differences in depth and area of demineralized enamel such that lesion size was: Transbond XT no brush > Transbond XT brush > Advance no brush = Advance brush = Fuji Ortho LC no brush = Fuji Ortho brush. The promising results of this in vitro study warrant further clinical investigation of hybrid glass ionomer adhesives as orthodontic bonding agents to minimize enamel demineralization. (Am J Orthod Dentofacial Orthop 1998;114:668-74)     

Crown retention with use of a 5% glutaraldehyde sealer on prepared dentin

Statement of problem. A previous study showed that a resin sealer decreased casting retention with zinc phosphate cement.Purpose. This study determined whether a nonresin sealer applied to prepared dentin affected the retention of cemented castings.Material and methods. Extracted molars were prepared with a flat occlusal, 20-degree taper and 4 mm axial length. The axial surface area of each preparation was determined and samples were distributed to achieve equivalent groups. Gluma Desensitizer sealer was used to seal the dentin before provisionalization and again before crown cementation. An Olympia alloy casting was produced for each preparation and cemented with a seating force of 20 Kg with either Mizzy’s zinc phosphate, Ketac-Cem glass ionomer, or Resinomer material in combination with One Step adhesive. Castings were thermocycled, then removed along the path of insertion with an Instron testing machine. A two-factor analysis of variance was used with α = 0.05 and n = 9-10.Results. Mean dislodgment stresses for unsealed and sealed conditions were 6.3 and 6.4 MPa for zinc phosphate, 9.1 and 10.1 MPa for glass ionomer, and 12.1 and 12.6 MPa for the resin cement. The means for the three cements were statistically different (p < 0.001). The effect of sealer (p = 0.369) and cross product interactions (p = 0.820) were not significant.Conclusions. The use of the glutaraldehyde-based system as a desensitizing treatment for prepared teeth had no effect on crown retention for any of the three cements evaluated and the modified resin cement produced the highest mean dislodgment stress that exceeded the strength of the tooth. (J Prosthet Dent 1998;79:671-6.)