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PubMed1988

A model to investigate xerostomia-related dental caries.

The aim of this study was to develop an in vivo model in which onset, progression, and prevention of xerostomia-related dental caries can be studied. The progress of the caries process was investigated on ground and polished human enamel blocks placed in the lower denture of 7 edentulous subjects suffering from xerostomia. During a period of 6 weeks the samples were analyzed at weekly intervals by means of scanning optical monitoring, scanning longitudinal microradiography, scanning electron microscopy, and hardness measurements. Although the indentation length increased significantly within 2 weeks, no demineralization could be yet observed with scanning optical monitoring, longitudinal microradiography, and electron microscopy in most samples. Starting from the 3rd week a progressive demineralization could be observed by all methods. The mineral loss (hydroxyapatite) in the 3rd week was 0.0126 kg.m-2 (median) which increased to 0.0761 kg.m-2 after 6 weeks. Scanning electron microscopy showed a destruction which resembled that of natural xerostomia-related dental caries. From this study it may be concluded that the in vivo model developed is suitable for studying onset, progression, and prevention of xerostomia-related dental caries.

Aged↗

PubMed1989

Remineralization of bovine dentine in vitro. The influence of the F content in solution on mineral distribution.

In this paper remineralization of bovine dentine is reported. After demineralization of the dentine in an acidic gel system creating lesions of about 180 microns depth, the tissue was remineralized in a 1.5 mM Ca and 0.9 mM phosphate containing solution at pH 7 and 37 degrees C for 8 or 21 days. The F content in the remineralization solution was 0.02, 2, or 10 ppm as NaF. Samples were analyzed by means of microradiography and scanning electron microscopy. The results show that remineralization (without F added in solution) causes a decrease in mineral loss and in lesion depth. With 2 or 10 ppm in solution, however, a substantial mineral accumulation in the lesion, but particularly on the original dentine surface, was observed. During 3 weeks of remineralization, mineral accumulations of 67 and 70 vol% of mineral for 2 and 10 ppm F in solution, respectively, were found near the original outer surface, with the sound dentine mineral value being 48 vol%. The combined microradiography and scanning electron microscopy data show that the mineral accumulated is for a major part deposited on the dentine tissue and partly inside. The latter deposition occurred both inside the tubules as well as in the intertubular areas. Inside the tubules dense precipitates were observed. Because several differences exist between bovine and human dentine, an extrapolation to the human in vivo situation is speculative. The results indicate that the presence of fluoride in the parts per million range is important for dentine remineralization efficacy and that the outer surface area in dentine can be 'overremineralized'.

Animals↗

PubMed1994

Secondary caries in dentine around composites: a wavelength-independent microradiographical study.

Composite restorations are prone to develop secondary caries if a gap exists between tissue and restoration. The aim of this article was to quantify the effects of a fluoridating and non-F composite on secondary dentine caries in vitro as a function of time. The mineral loss in dentine was assessed in an artificial gap of 200 microns width at the composite/dentine interface; the samples were demineralised in a carboxymethylcellulose gel (pH = 5, 37 degrees C) for 8 weeks. Once a week the mineral content of the samples was determined using non-destructive wavelength-independent microradiography (WIM). After 8 weeks transversal microradiography (TMR) was done on the samples to investigate the mineral distribution of the dentine lesions. The WIM results show that the fluoride-releasing composite decreased the dentine demineralisation statistically significantly with respect of the non-F control by approximately 45%. The mineral loss values are found to be strictly proportional to time; the demineralisation reduction is expected to continue over extended periods of clinical relevance. The TMR results show that the fluoridating composite reduced the mineral loss values significantly with respect to the non-F control by approximately 55%, but had a negligible effect on the lesion depth values. This study indicates that WIM is an accurate and reliable technique to measure in vitro secondary dentine caries next to a composite restoration as a function of time.

Animals↗

PubMed1996

Preparation and measurement of artificial enamel lesions, a four-laboratory ring test.

Transversal microradiography is the most widely accepted method used to study changes in mineral content profiles. In spite of its widespread use, relatively little information is available on its validity and reproducibility. Following the recommendation of the Consensus Conference on Intraoral Model Systems, this study was designed to explore reproducibility of lesion analysis within a laboratory and comparability of analysis among various laboratories. Incipient enamel lesions were produced by four research groups using both a common ('standard') and a local ('preferred') protocol. Sections were produced by each group and allocated to 'mixed' bags of specimens, which were analysed by the groups. With the chosen scheme some sections were analysed six times by the same group (as an internal reference standard) while others were analysed by all four groups. The data for the mineral content profiles were expressed as the integrated mineral loss (IML) value and lesion depth. The results showed the lesions produced with the standard protocol to be in the range 2,000-3,000 vol% mineral x microns for IML. The IML of the lesions produced with the preferred protocol varied between 1,800 and 6,300 vol% mineral x microns. Variation in IML values could be attributed to the biological variation between lesions, but also to time (of microradiograph production) and measurement effects, calibration of the magnification of the specimens, and the parameters used in the algorithm to calculate IML. Some of these parameters also affected the lesion depth. It is advised to standardise (or at least report) the method of calculation of IML, and to include a reference lesion between analyses in a longitudinal study as an internal standard. With the data produced, it was calculated that the number of lesions required to differentiate between preventive treatments varied substantially among laboratories. The recommendations given will improve the power of the screening methods for caries-preventive agents for which microradiography is an essential analytical method.

Analysis of Variance↗

PubMed2003

Human aortic valve calcification is associated with an osteoblast phenotype.

BACKGROUND: Calcific aortic stenosis is the third most common cardiovascular disease in the United States. We hypothesized that the mechanism for aortic valve calcification is similar to skeletal bone formation and that this process is mediated by an osteoblast-like phenotype. METHODS AND RESULTS: To test this hypothesis, we examined calcified human aortic valves replaced at surgery (n=22) and normal human valves (n=20) removed at time of cardiac transplantation. Contact microradiography and micro-computerized tomography were used to assess the 2-dimensional and 3-dimensional extent of mineralization. Mineralization borders were identified with von Kossa and Goldner's stains. Electron microscopy and energy-dispersive spectroscopy were performed for identification of bone ultrastructure and CaPO4 composition. To analyze for the osteoblast and bone markers, reverse transcriptase-polymerase chain reaction was performed on calcified versus normal human valves for osteopontin, bone sialoprotein, osteocalcin, alkaline phosphatase, and the osteoblast-specific transcription factor Cbfa1. Microradiography and micro-computerized tomography confirmed the presence of calcification in the valve. Special stains for hydroxyapatite and CaPO4 were positive in calcification margins. Electron microscopy identified mineralization, whereas energy-dispersive spectroscopy confirmed the presence of elemental CaPO4. Reverse transcriptase-polymerase chain reaction revealed increased mRNA levels of osteopontin, bone sialoprotein, osteocalcin, and Cbfa1 in the calcified valves. There was no change in alkaline phosphatase mRNA level but an increase in the protein expression in the diseased valves. CONCLUSIONS: These findings support the concept that aortic valve calcification is not a random degenerative process but an active regulated process associated with an osteoblast-like phenotype.

Aortic Valve↗

PubMed1988

Abrasion biopsy in studies of mineral density of experimental enamel lesions.

The profile of mineral density of experimental enamel lesions was determined by means of sampling with a new abrasion biopsy technique. Three types of lesions were produced on bovine enamel slabs: (1) pre-softened in lactic acid buffer for 16 hr; (2) pre-softened and exposed to a test for acid resistance for seven days; and (3) pre-softened, exposed to the seven-day Intra-oral Cariogenicity Test with extra-oral immersions in 1000 ppm F solutions for one min twice daily (ICT/F), plus the seven-day test for acid resistance. Lesions were assessed with measurements of surface microhardness, microradiography of thin sections, and abrasion biopsy. For abrasion biopsy of the experimental lesions, 15 parallel layers of approximately 10 microns each were abraded simultaneously with reference slabs of sound enamel on strips of lapping film. The depth of abrasion for each sample was calculated from the phosphorus content of the reference sample. Exposure to the ICT/F formed an acid-resistant zone within the lesion which diminished the microhardness change, although it did not have an appreciable effect on the total lesion depth as assessed with microradiography; abrasion biopsy indicated the formation of a mineral-dense zone within the lesion. This recently-developed technique of abrasion biopsy of experimental lesions offers the opportunity to link the composition of the lesion to controlled experimental conditions which will improve our understanding of demineralizing and remineralizing reactions on a standard tooth substrate.

Animals↗

PubMed1988

Mineral density and fluoride content of in vitro remineralized lesions.

This in vitro investigation studied the remineralization of experimental caries lesions in bovine enamel by use of three methods: (1) surface microhardness, (2) microradiography, and (3) abrasion biopsy for mineral density and fluoride content. The lesions were produced by a two-day exposure to 0.01 mol/L lactic acid/sodium hydroxide buffer partially saturated with 3.0 mmol/L Ca, 1.8 mmol/L P, in 1% CMC, at pH 4.0 and 37 degrees C. The lesions were exposed to a remineralizing solution containing 3.0 mmol/L Ca, 1.8 mmol/L P, and 3 ppm F in 1% CMC at pH 7.0 and 37 degrees C for two, six, and ten days, with solution changes every two days. The data derived from the three methods are presented in sequence from the baseline and at days two, six, and ten of the remineralizing treatment. Microhardness measurements showed hardness recoveries of 35.9, 78.9, and 87.5%, respectively. Microradiography suggested complete recovery with the ten-day remineralization. Abrasion biopsy of successive 10-micron layers to a depth of 100 micron indicated 15.2, 39.8, and 68.8% mineral density recoveries, with fluoride content of the surface layer increasing from a baseline of 300 ppm to 4600, 9000, and 9800 ppm F for the 2, 6, 10 days of remineralization, respectively. Subsequent acid-etching of thin sections from the ten-day-remineralized specimens showed that the fluoride-enriched remineralized area was more resistant to acid dissolution than was the underlying normal enamel.

Animals↗

PubMed1995

High-resolution and analytical electron microscopic studies of new crystals induced by a bioactive ceramic (diopside).

Diopside has been developed for use in dental root implants and for the filling of bone defects. In previous studies, diopside developed hydroxyapatite (HA) on its surface and achieved a direct bond with bone. The purpose of this study was to investigate the mechanism of crystal formation on the diopside surface. We ultrastructurally evaluated the interface between new diopside-induced crystals and diopside. Specimens were prepared in three experiments: (1) Granular diopside was immersed in simulated body fluid (SBF); (2) granular diopside was implanted into a cavity in rabbit bone; and (3) a diopside dental root implant was implanted into a Japanese monkey. The specimens were examined by contact microradiography, high-resolution transmission electron microscopy, and analytical electron microscopy. In the experiment with SBF, many platelet-like crystals formed in the diopside surface layer. The lattice of diopside and that of the new crystals were very close, but no clear continuation of the lattice was observed. In the experiments which used a rabbit and a monkey, contact microradiography showed close contact between bone and diopside. High-resolution transmission electron microscopy revealed crystal growth from the diopside surface layer, and continuity between the diopside lattice and that of the new crystals. The morphological characteristics of the new crystals and the results of these analyses suggest that these new crystals are HA. With regard to the mechanism by which crystals are formed on the diopside surface layer, it is possible that epitaxial crystal growth could originate as a nucleus on the surface. In this case, epitaxial crystal growth of primarily octacalcium phosphate (OCP) may have occurred, and this may have changed to HA by a phase transition. However, epitaxial growth of OCP on the diopside surface is still highly speculative, since there is no direct supporting evidence.

Animals↗

PubMed1991

Effect of HEBP (1-hydroxyethylidene-1,1-bisphosphonate) on experimental osteoporosis induced by ovariectomy in rats.

The present study was undertaken to test whether long term administration of HEBP could prevent the progress of bone loss induced by ovariectomy in rats. Administration of HEBP was started from day 111 after ovariectomy. The animals received subcutaneous injections of HEBP, at a dose of 0, 2, 4, or 8 mg/kg, every other day for 92 days. Tibiae, femora and incisor teeth were investigated by chemical analyses and by contact microradiography. Effects on calcium, phosphorus, and alkaline phosphatase activity in the plasma were also examined. Progress in the loss of bone density and ash content caused by ovariectomy was prevented by the administration of 2 mg/kg HEBP for 92 days and was partially prevented by the administration of 4 mg/kg. At a dose of 8 mg/kg, however, HEBP did not prevent the bone loss but, rather, potentiated it. These chemical findings were qualitatively confirmed by contact microradiography. A dose-dependent inhibition was observed in the mineralization of incisor dentin. These results suggest that HEBP, at least at low dose levels in which the inhibition of mineralization is not predominant, has a potency to prevent the progress of bone loss induced by ovariectomy. At higher doses, however, this compound seems not to be effective, because of the severe inhibition of mineralization.

Animals↗

PubMed1978

Bone changes induced by diphenylhydantoin in chicks on a controlled vitamin D intake.

Florid rickets developed in chicks receiving doses of diphenylhydantoin analogous to doses used in humans as anticonvulsants, vitamin D3 being given in amounts sufficient for normal bone mineralization in controls. The changes in the bones were directly related to the dose of diphenylhydantoin and inversely related to the dose of vitamin D3. Bone mineralization was assessed by roentgenography, histological examination, microradiography, and measurement of bone ash. Of these methods, roentgenography was the least sensitive. Rachitic changes were detectable by light microscopy and microradiography in chicks whose skeletons appeared normal roentgenographically. Roentgenographic evidence of rickets became detectable only when the rickets was far advanced. Rickets developed at serum levels of diphenylhydantoin similar to those found in patients taking anticonvulsant medication.

Animals↗

PubMedDate not supplied

Bone mass determination from microradiographs by computer-assisted videodensitometry. II. Aluminium as a reference substance.

Aluminium was evaluated as a reference substance in the assessment of rabbit cortical bone by microradiography followed by videodensitometry. Ten dense, cortical-bone specimens from the same tibia diaphysis were microradiographed using prefiltered 27 kV roentgen radiation together with aluminium step wedges and bone simulating phantoms for calibration. Optimally exposed and processed plates were analysed by previously described computer-assisted videodensitometry. For comparison, the specimens were analysed by physico-chemical methods. A strict proportionality was found between the 'aluminium equivalent mass' and the ash weight of the specimens. The total random error was low with a coefficient of variation within 1.5 per cent. It was concluded that aluminium is an appropriate reference material in the determination of cortical bone, which it resembles in effective atomic number and thus x-ray attenuation characteristics. The 'aluminium equivalent mass' is suitably established as the standard of expressing the results of bone assessment by microradiography.

Aluminum↗

PubMed1987

[Microradiographic study of prehistoric skeletal remains].

Microradiography is a standard technique for determining small differences in mineral content in histological sections of calcified tissues by using soft X-rays. Such differential mineralization points on physiological and pathological processes in bone and teeth, and is frequently conserved both in excavated skeletal remains and in cremations. Continuing from this, microradiography gives diagnostic criteria for histological and palaeopathological investigations on historic and prehistoric skeletal remains rather than ordinary light microscopy. In addition, this technique helps in reconstructing the genesis of special dead bone decomposition phenomena.

Bone and Bones↗

PubMed1982

Birefringence and mineral content of the first stage of artificial carious lesion formation (a combined polarizing microscopic, microradiographic and scanning electron microscopic investigation).

Artificial carious lesions were made using acetic buffer solutions of pH 6.0 containing calcium and phosphate. The solutions were highly undersaturated with respect to hydroxyapatite. Out of 72 lesions 51 showed subsurface demineralization, whereas in 21 only a superficial demineralization occurred. These superficial lesions were examined using polarized light microscopy, microradiography and scanning electron microscopy. This superficial breakdown of enamel material, considered as the initial demineralization of the enamel, appeared to occur at the prism junctions. This was indicated by the polarizing microscope technique and was made clearly visible using scanning electron microscopy. Quantitative polarizing microscopy and microradiography revealed results which correlated very well. From this it is probable that the initial superficial demineralization of the enamel is--under the described conditions--a simple dissolution reaction.

Birefringence↗

PubMed1993

Long-term osteopenic changes in cancellous bone structure in ovariectomized rats.

Cancellous bone mass decreases following ovariectomy in rodents, providing a useful model for post-menopausal bone loss in humans. This study describes and quantifies the longer-term changes in cancellous bone structure in the ovariectomized (OVX) rat. Rats were OVX or sham-OVX at 100 days of age and bones were collected 540 days later. Lumbar vertebral bodies were prepared for microradiography and structural analyses (nodal analyses and star volume analyses) of cancellous bone. Proximal humerii were prepared for scanning electron microscopy (SEM). Microradiography confirmed the loss of cancellous bone from the central spongiosa regions of the vertebral bodies and the humerii in the OVX rats. Changes in trabecular structural elements included relative increases in the number of free to free, cortical to free, cortical to node struts and decreases in the node to node struts in the OVX animals compared with controls. There were increases in average lengths of the node to free, node to node, and free to free trabecular struts in the OVX animals. The marrow star volume was increased in the OVX animals indicating a greater trabecular separation in these animals compared with controls. Viewed by SEM, metaphyseal trabeculae in the controls consisted of rods and plates but in the OVX animals the remaining trabeculae were mostly longitudinal rods with smaller transverse connecting rods. The remaining bone in the OVX animals was found in the lateral metaphyseal areas and is consistent with maintenance of the structural capacity of the bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Comparison of osteopenic changes in cancellous bone induced by ovariectomy and/or immobilization in adult rats.

BACKGROUND: Ovariectomy (OVX) and immobilization (IMM) in rats are useful models of osteopenia, replicating some aspects of osteoporosis in humans. The purpose of this study was to compare changes in cancellous bone after OVX and/or IMM. METHODS: Differences in cancellous bone were determined at 6 and 12 weeks after OVX or IMM. Comparisons were also made when rats were ovariectomized or immobilized for 6 weeks and then immobilized (OVX/IMM) and ovariectomized (IMM/OVX), respectively, for 6 more weeks. The femurs were used to determine bone mineral content (BMC) using single photon absorptiometry (SPA) and for scanning electron microscopy (SEM). Tibias were collected for microradiography, image analysis, and histomorphometry of metaphyseal cancellous bone. RESULTS: Six and 12 weeks after OVX, there was less cancellous bone mass, compared with controls, as indicated by SPA, SEM, microradiography, image analyses, and histomorphometry. Bone was lost primarily from the central metaphyseal regions in the OVX animals, whereas the loss occurred throughout the metaphyses in the IMM animals. There were more rodlike bone spicules and fewer platelike trabeculae in the OVX and IMM groups compared with controls. Differences in the structural aspects of the cancellous bone, including differences in the types of bone struts and marrow star volumes, indicated less trabecular connectivity and greater trabecular separation in the OVX and IMM animals, compared with controls. Endochondral growth indices in the IMM groups tended to be less, whereas the OVX groups tended to be greater than controls. Cancellous bone formation rates were generally greater in the OVX groups but less in the IMM groups compared with controls. Osteoclastic resorption surfaces were substantially elevated in the IMM and OVX groups, particularly the IMM groups. Changes reflecting OVX and IMM, independently, were apparent in the OVX/IMM and IMM/OVX groups and indices of osteopenia were different from controls, including less bone mass, trabecular connectivity, and greater trabecular separation, bone turnover rates, and osteoclastic surface. CONCLUSIONS: These results demonstrate differences in the osteopenic changes that occur in cancellous bone following OVX or IMM. The changes were generally more dramatic in the IMM than in the OVX animals. When OVX and IMM were applied in combination, the osteopenic changes are particularly severe, emphasizing the importance of mechanical usage even with a deficiency of gonadal hormones.

Animals↗

PubMed1994

Stimulation of bone healing by transforming growth factor-beta 1 released from polymeric or ceramic implants.

The ability to transforming growth factor-beta 1 (TGF-beta 1), to stimulate bone healing was evaluated in a rat critical calvarial defect model. Both a low dose and a high dose of TGF-beta 1 were incorporated into two different types of implants: one made from a composite of poly(lactic-co-glycolic acid) (PLPG) (50:50) and demineralized bone matrix (DBM), and the other from calcium sulfate (CaSO 4). Scanning electron microscopy showed that the CaSO 4 implants were more porous than the PLPG/DBM samples. Both types of implants released biologically active TGF-beta 1 for over 300 h in vitro. The samples were implanted in a 9-mm diameter rat calvarial defect for 6 weeks along with contralateral control implants containing no TGF-beta 1. Microradiography and histological analysis were used to assess the bone healing in the defects. Microradiography revealed that the greatest amount of calcified bone (67.5%) was present in in the CaSO 4 implants containing a high dose of TGF-beta 1 while minimal new bone formation occurred in the PLPG/DBM implants. Histologically, the PLPG/DBM implants exhibited an inflammatory response with little mineralization or bone formation. The defects containing the PLPG/DBM implants consisted of a connective tissue stroma with large void spaces. Giant cells and numerous polymorphonuclear leukocytes were present throughout the implants. In contrast, the CaSO 4 implants had only a few inflammatory cells and the presence of mineralization and true bone was a more consistent feature. These preliminary studies show that TGF-beta 1 is capable of inducing new bone formation. Furthermore, the materials used to deliver the growth factor can play a significant role in the bone healing process.

Animals↗

PubMed2006

The biocompatibility and osteoconductivity of a cement containing beta-TCP for use in vertebroplasty.

A new composite bone cement designated "G2B1" was developed for percutaneous transpedicular vertebroplasty. G2B1 contains beta tricalcium phosphate particles and methylmethacrylate-methylacrylate copolymer as the powder components, and methylmethacrylate, urethane dimethacrylate, and tetrahydrofurfuryl methacrylate as the liquid components. Biocompatibility and osteoconductivity were evaluated using scanning electron microscopy, contact microradiography, and Giemsa surface staining 4, 8, 12, 26, and 52 weeks after implantation into rat tibiae. To evaluate osteoconductivity, affinity indices (%) were calculated. Scanning electron microscopy and contact microradiography revealed that bone contact with G2B1 was attained within 4 weeks (affinity index: 50.2 +/- 11.8 at 4 weeks) and at most of the margin within 26 weeks (affinity index: 87.4 +/- 7.2 at 26 weeks). Specifically, G2B1 contacted bone via a wide calcium-phosphate-rich layer, and its degradation started within 8 weeks, mainly in the marginal area. Giemsa surface staining showed that there was almost no inflammatory reaction around the G2B1. These results indicate that G2B1 is a biocompatible and osteoconductive bone cement.

Animals↗

PubMed1979

Structure and formation of ankylosis in Xenopus laevis.

The structure of ankylotic teeth in Xenopus laevis was studied by light, transmission, and scanning electron microscopy as well as by microradiography in decalcified and undecalcified specimens. The mature teeth of Xenopus laevis are calcified from the crown to the base, fused to the jaw bone, and have no uncalcified area, such as a fibrous ring separating the tooth into the crown and pedicle. Microradiography shows that the mature tooth and jaw bone appear as an X-ray opaque area, except for the basal region of the dentine. This region is composed of an X-ray translucent area and an X-ray opaque thin layer on the lingual side of the translucent area. The mature tooth is composed of two differently calcified areas: (1) a highly calcified area, which makes up almost all of the tooth and contains a thin layer of the basal dentine on the lingual side, and (2) a lowly calcified basal dentine, which is fused to the jaw bone. Therefore, the lowly calcified area does not completely separate the dentine and jaw bone. Repeating banding patterns among the collagen fibrils differ among the dentine-forming area and the matrices of dentine and jaw bone. During the formation of ankylosis of the tooth germ, collagen bundles in the dentine-forming area accumulate directly on the surface of the jaw bone. Consequently, the mature teeth of Xenopus laevis fuse to the jaw bone directly without the mediation of the other structures.

Animals↗