Strontium-90 in Deciduous Teeth Collected in Northern Finland from Children Born in 1952–1964.

Strontium-90 content was measured by means of Cerenkov radiation in deciduous teeth collected in three areas in northern Finland from children bom in 1952–1964.

The ⁹⁰Sr levels in tooth crowns in areas I and II showed a continuous increase in children born in 1952–1958, no further increase during the years 1959–1961, a sharp increase in 1962–1963, and no further change in 1964. In the northernmost part of Finland (area III) the strontium-90 contents of deciduous teeth when plotted against year of birth showed a slightly different trend with no increase during the years 1952–1957 and a steep rise in 1958 and 1959. These changes occurred in both Lapp and non-Lapp children. These differences in the strontium-90 content of deciduous teeth were presumably related to environmental peculiarities and specific dietary habits in area III. The maximum strontium-90 level, 16.76 pCi/gCa, was found in a sample of tooth roots of four Skolt children born in 1963.

The strontium-90 contents in the crowns of the four types of deciduous teeth were related as follows: second molars > cuspids > first molars > incisors.     

Organic Tissue Dissolution in Clodronate and Etidronate Mixtures with Sodium Hypochlorite

IntroductionMixtures of clodronate with sodium hypochlorite (NaOCl) better maintain free available chlorine (FAC) than etidronate-hypochlorite mixtures. This research aimed to compare organic tissue dissolution and residual FAC between clodronate and etidronate mixtures. Additionally, clodronate-hypochlorite mixtures lose no FAC over several hours. The second aim was to examine how well such mixtures dissolve organic material 6 hours from mixing.MethodsSoon after mixing, porcine palatal mucosa samples were added to 32°C solutions containing 0.26 mol/L clodronate and 5% NaOCl (0.26 mol/L-5% NaOCl), 0.26 mol/L etidronate-5% NaOCl, 5% NaOCl, 0.26 mol/L clodronate, 0.26 mol/L etidronate, or phosphate-buffered saline. Weights and FAC, where applicable, were recorded initially and at 15 minutes. FAC was measured by iodometric titration. Secondly, 6 hours after mixing, mucosa was added to 0.26 mol/L clodronate-2.5% NaOCl, 2.5% NaOCl, 0.52 mol/L clodronate-5% NaOCl, 5% NaOCl, or phosphate-buffered saline. Sample weights at 0, 5, 10, and 15 minutes were recorded. Analysis of variance was used for statistical analyses (α < .05).ResultsSoon after mixing, 0.26 mol/L clodronate-5% NaOCl dissolved mucosa as well as 5% NaOCl and better than 0.26 mol/L etidronate-5% NaOCl compared with which it retained more FAC. At 6 hours after mixing, 0.26 mol/L clodronate-2.5% NaOCl dissolved organic material as well as 2.5% NaOCl. However, 0.52 mol/L clodronate-5% NaOCl dissolved less mucosa than 5% NaOCl.ConclusionsSoon after mixing, clodronate mixtures better dissolve organic material than etidronate mixtures and have higher residual FAC. Six hours from mixing, 0.26 mol/L clodronate-2.5% NaOCl mixtures dissolve organic material similarly to controls.     

A novel and easy-to-prepare strontium(II) modified calcium phosphate bone cement with enhanced mechanical properties

The aim of this study was to evaluate two different approaches to obtaining strontium-modified calcium phosphate bone cements (SrCPCs) without elaborate synthesis of Sr-containing calcium phosphate species as cement precursors that could release biologically effective doses of Sr²⁺ and thus could improve the healing of osteoporotic bone defects. Using strontium carbonate as a strontium(II) source, it was introduced into a hydroxyapatite-forming cement either by the addition of SrCO₃ to an α-tricalcium phosphate-based cement precursor mixture (A-type) or by substitution of CaCO₃ by SrCO₃ during precursor composition (S-type). The cements, obtained after setting in a water-saturated atmosphere, contained up to 2.2 at.% strontium in different distribution patterns as determined by time-of-flight secondary ion mass spectrometry and energy-dispersive X-ray spectroscopy. The setting time of CPC and A-type cements was in the range of 6.5–7.5 min and increased for substitution-type cements (12.5–13.0 min). Set cements had an open porosity between 26 and 42%. Compressive strength was found to increase from 29 MPa up to 90% in substituted S-type cements (58 MPa). SrCPC samples released between 0.45 and 1.53 mg g^?1 Sr²⁺ within 21 days and showed increased radiopacity. Based on these findings, the SrCPC developed in this study could be beneficial for the treatment of defects of systemically impaired (e.g. osteoporotic) bone.     

A novel strontium(II)-modified calcium phosphate bone cement stimulates human-bone-marrow-derived mesenchymal stem cell proliferation and osteogenic differentiation in vitro

In the present study, the in vitro effects of novel strontium-modified calcium phosphate bone cements (SrCPCs), prepared using two different approaches on human-bone-marrow-derived mesenchymal stem cells (hMSCs), were evaluated. Strontium ions, known to stimulate bone formation and therefore already used in systemic osteoporosis therapy, were incorporated into a hydroxyapatite-forming calcium phosphate bone cement via two simple approaches: incorporation of strontium carbonate crystals and substitution of Ca²⁺ by Sr²⁺ ions during cement setting. All modified cements released 0.03–0.07 mM Sr²⁺ under in vitro conditions, concentrations that were shown not to impair the proliferation or osteogenic differentiation of hMSCs. Furthermore, strontium modification led to a reduced medium acidification and Ca²⁺ depletion in comparison to the standard calcium phosphate cement. In indirect and direct cell culture experiments with the novel SrCPCs significantly enhanced cell proliferation and differentiation were observed. In conclusion, the SrCPCs described here could be beneficial for the local treatment of defects, especially in the osteoporotic bone.     

The effects of fluoride,strontium, theobromine and their combinations on caries lesion rehardening and fluoridation

ObjectiveThe aim was to investigate the effects of fluoride, strontium, theobromine and their combinations on caries lesion rehardening and fluoridation (EFU) under pH cycling conditions.DesignHuman enamel specimens were demineralized at 37 °C for 24 h using a pH 5.0 solution containing 50 mM lactic acid and 0.2% Carbopol 907 which was 50% saturated with respect to hydroxyapatite. Lesions were assigned to nine treatment groups (n = 16) based on Knoop surface microhardness indentation length.Treatmentaqueous solutions were: placebo, 11.9 mM sodium fluoride (F), 23.8 mM sodium fluoride (2 × F), 1.1 mM strontium chloride hexahydrate (Sr), 1.1 mM F theobromine, Sr + theobromine, F + Sr, F + theobromine, F + Sr + theobromine. Lesions were pH cycled for 5d (daily protocol: 3 × 1min-treatment; 2 × 60min-demineralization; 4 × 60 min & overnight-artificial saliva). Knoop indentation length was measured again and%surface microhardness recovery (%SMHr) calculated. EFU was determined using the acid-etch technique. Data were analysed using ANOVA.ResultsModel showed fluoride dose-response for both variables (2 × F > F > placebo). For%SMHr, F + Sr+/−theobromine resulted in more rehardening than F, however less than 2 × F. F + theobromine was similar to F. For EFU, F + Sr was inferior to F, F + theobromine and F + Sr + theobromine which were similar and inferior to 2 × F. In absence of fluoride, Sr, theobromine or Sr + theobromine were virtually indistinguishable from placebo and inferior to F.ConclusionsIt can be concluded that a) strontium aids rehardening but not EFU and only in presence of fluoride; b) theobromine does not appear to offer any anti-caries benefits in this model; c) there are no synergistic effects between strontium and theobromine in the presence or absence of fluoride.     

Radiation-induced meningeal and pituitary tumors in the rat after prenatal application of strontium-90

Summary Strontium-90 was injected i. v. into pregnant rats on day 18 post conception (p. c.). This caused a remarkable transplacental radioactivity uptake and accumulation in the ossification centers of the skull basis. The total radiation dose within the surface of these regions was consequently calculated to be 0.6–1.2 Gy within the entire lifespan. About 50% of it was delivered during the 7 days following the injection of the isotope. the pathologic examination of the offspring throughout their lifetime revealed a pituitary tumor frequency in the exposed groups which was about tenfold in the males and threefold in the females in comparison to the controls. A very outstanding result in the animals treated was the occurrence of metastasizing meningeal sarcomas in about 6% of all cases. In four cases (=2%) the simultaneous occurrence of a pituitary adenoma and of a meningeal sarcoma could be observed.     

依替二膦酸锶对大鼠腰椎及股骨骨密度的影响

目的观察新合成的抗骨质疏松化合物依替二膦酸锶对骨代谢的影响。方法以去势SD大鼠为基础,对依替二膦酸锶、依替二膦酸二钠和二氯化锶以及不同剂量依替二膦酸锶对大鼠股骨及腰椎的骨密度的影响进行动态观察和比较。结果依替二膦酸锶与相同摩尔剂量的依替二膦酸二钠和二氯化锶相比,对去势大鼠腰椎和股骨骨密度的影响更为明显。其干预后去势大鼠骨密度增加的出现更早,且其升高的幅度也较高。50 mg/(kg·d)、100 mg/(kg·d)和150 mg/(kg·d)3种不同剂量的依替二膦酸锶均能有效地增加去势大鼠椎体和股骨的骨密度,且其增加骨密度的能力无明显差异。结论新化合物中的骨吸收抑制物依替二膦酸和骨形成促进物锶进入大鼠体内后,两者的生物学效应可能存在互补性。     

Bone formation induced by strontium modified calcium phosphate cement in critical-size metaphyseal fracture defects in ovariectomized rats

The first objective was to investigate new bone formation in a critical-size metaphyseal defect in the femur of ovariectomized rats filled with a strontium modified calcium phosphate cement (SrCPC) compared to calcium phosphate cement (CPC) and empty defects. Second, detection of strontium release from the materials as well as calcium and collagen mass distribution in the fracture defect should be targeted by time of flight secondary ion mass spectrometry (TOF-SIMS). 45 female Sprague–Dawley rats were randomly assigned to three different treatment groups: (1) SrCPC (n = 15), (2) CPC (n = 15), and (3) empty defect (n = 15). Bilateral ovariectomy was performed and three months after multi-deficient diet, the left femur of all animals underwent a 4 mm wedge-shaped metaphyseal osteotomy that was internally fixed with a T-shaped plate. The defect was then either filled with SrCPC or CPC or was left empty. After 6 weeks, histomorphometric analysis showed a statistically significant increase in bone formation of SrCPC compared to CPC (p = 0.005) and the empty defect (p = 0.002) in the former fracture defect zone. Furthermore, there was a statistically significant higher bone formation at the tissue–implant interface in the SrCPC group compared to the CPC group (p < 0.0001). These data were confirmed by immunohistochemistry revealing an increase in bone-morphogenic protein 2, osteocalcin and osteoprotegerin expression and a statistically significant higher gene expression of alkaline phosphatase, collagen10a1 and osteocalcin in the SrCPC group compared to CPC. TOF-SIMS analysis showed a high release of Sr from the SrCPC into the interface region in this area compared to CPC suggesting that improved bone formation is attributable to the released Sr from the SrCPC.     

雷奈酸锶通过TGF-β1/Smad通路促进骨髓间充质干细胞向成骨细胞分化

 [摘 要] 目的:研究转化生长因子β1（TGF-β1）/Smad通路在雷奈酸锶（strontium ranelate,Sr）促进大鼠骨髓间充质干细胞（BMSCs）向成骨细胞分化中的作用。方法: 在大鼠BMSCs向成骨细胞的诱导分化过程中,用Sr处理细胞,用Western blotting法检测磷酸化Smad2（phosphorylated Smad2,p-Smad2）和Runx2的表达。用TGF-β1特异性阻断剂SB431542或Smad2小干扰RNA（Smad2-siRNA）预处理BMSCs后加入Sr,再观察p-Smad2和Runx2表达的改变。应用试剂盒检测碱性磷酸酶（alkaline phosphatase,ALP）活性及钙结节水平。结果: 在大鼠BMSCs向成骨细胞的诱导分化过程中,Sr可增加p-Smad2和Runx2的表达,Sr 浓度为1 mmol/L、作用1 h时,p-Smad2表达最多;Sr 浓度为1 mmol/L、作用5 d时,Runx2表达最多;用SB431542或Smad2-siRNA预处理BMSCs后再加入Sr,不仅可以抑制p-Smad2和Runx2的表达,且ALP活性与钙结节数量也受到明显的抑制。结论: Sr可通过TGF-β1/Smad通路促进大鼠BMSCs向成骨细胞分化。