Enamel Caries Lesion Depth Obtained by Optical Coherence Tomography and Transverse Microradiography: A Comparative Study.

INTRODUCTION: Visual imaging of subsurface caries lesions is of vital interest in dentistry, which can be obtained by invasive radiography technique as well as by available non-destructive imaging approaches. Thus, as a first step toward the development of a new innovative approach, Spectral-domain optical coherence tomography (SD-OCT) was applied to detect the lesion depth in comparison to the established reference technique (transverse microradiography [TMR]). METHODS: Bovine enamel specimens were demineralized for 5 days, following previous studies. For OCT, the resulting artificial lesions were scanned three-dimensionally (SD-OCT) and semi-automated measured (CarLQuant). For TMR, specimens were sectioned and the lesion depth was manually determined (Inspektor Research System). RESULTS: The range of lesion depth detected with OCT was 24.0-174.0 µm (mouth rinse study), 18.0-178.0 µm (toothpastes study) and with TMR 59.2-198.0 µm (mouth rinse study), 33.2-133.4 µm (toothpastes study). We found a strong correlation between both methods in terms of lesion depth (Spearman rankwith outlierp < 0.001, Rho = 0.75, Spearman rankwithout outlierp = 0.001, Rho = 0.79). The two methods produce similar results (Passing-Bablok regression, 1.16). As deeper is the lesion, the smallest is the difference between both methods as indicated by Bland-Altman-plots. CONCLUSION: Especially in the case of deep lesions, the values obtained by both methods are in agreement, and OCT can potentially substitute TMR to detect and assess lesion depth with the benefit of being non-destructive.

Accuracy of the DIAGNOcam and bitewing radiographs in the diagnosis of cavitated proximal carious lesions in primary molars.

AIMS: To evaluate the diagnostic abilities of near-infrared light transillumination (using the DIAGNOcam) and bitewing radiographs in detecting cavitated proximal carious lesions in primary molars. SUBJECTS AND METHODS: The study was a cross-sectional analytical, clinical study. The proximal surfaces of primary molars of healthy 5- to 8-year-old children were radiographically screened for the presence of carious lesions in the enamel or outer third of dentin (D1). Two trained and calibrated examiners evaluated the depth of caries in bitewing radiographs and DIAGNOcam images and then verified the presence of cavitation by direct visual examination using the "International Caries Detection and Assessment System" after temporary tooth separation. RESULTS: A total of 236 proximal lesions were included in the study. Most of the clinically cavitated lesions (51.9%) were D1 radiographically and in outer dentin lesions (scores 3 and 4) by the DIAGNOcam (37% and 48.1%, respectively). Although DIAGNOcam showed higher sensitivity (0.852) compared to the radiographs (0.519), it showed slightly less specificity (0.569) compared to the radiographs (0.579). However, DIAGNOcam showed higher value of the area under the curve (AUC = 0.722; P < 0.001) compared to the radiographic method (AUC = 0.561; P = 0.308). CONCLUSIONS: The DIAGNOcam showed higher sensitivity and better accuracy than bitewing radiographs in diagnosing cavitated proximal lesions in primary molars and can be generally considered as an alternative to radiographs to detect cavitation without the hazards of ionizing radiation in children.

X-Ray Micro- and Nanodiffraction Imaging on Human Mesenchymal Stem Cells and Differentiated Cells.

Adult human mesenchymal stem cells show structural rearrangements of their cytoskeletal network during mechanically induced differentiation toward various cell types. In particular, the alignment of acto-myosin fibers is cell fate-dependent and can serve as an early morphological marker of differentiation. Quantification of such nanostructures on a mesoscopic scale requires high-resolution imaging techniques. Here, we use small- angle x-ray scattering with a spot size in the micro- and submicrometer range as a high-resolution and label-free imaging technique to reveal structural details of stem cells and differentiated cell types. We include principal component analysis into an automated empirical analysis scheme that allows the local characterization of oriented structures. Results on freeze-dried samples lead to quantitative structural information for all cell lines tested: differentiated cells reveal pronounced structural orientation and a relatively intense overall diffraction signal, whereas naive human mesenchymal stem cells lack these features. Our data support the hypothesis of stem cells establishing ordered structures along their differentiation process.

Use of Adipose-Derived Mesenchymal Stem Cells to Accelerate Neovascularization in Interpolation Flaps.

OBJECTIVE: Interpolation flaps are commonly used in plastic surgery to cover wide and deep defects. The need to, wait for 2 to 3 weeks until the division of the pedicle still, however, poses a serious challenge, not only extending treatment and hospital stay, but also increasing hospital expenses. To solve this problem, we have aimed to use the angiogenic potential of stem cells to selectively accelerate neovascularization with a view to increasing the viability of interpolation flaps and achieving early pedicle removal. MATERIALS AND METHODS: A total of 32 rats were allocated to 2 groups as control (N = 16) and experiment (N = 16). The cranial flaps 6 × 5 cm in size located on the back of the rats were raised. Then, a total suspension containing 3 × 10(6) adipose-derived mesenchymal stem cells (ADSC) tagged with a green fluorescent protein (GFP) was injected diffusely into the distal part of the flap, receiving bed, and wound edges. In the control group, only a medium solution was injected into the same sites. After covering the 3 × 5 cm region in the proximal part of the area where the flap was removed, the distal part of the flap was adapted to the uncovered distal area. The pedicles of 4 rats in each group were divided on postoperative days 5, 8, 11, and 14. The areas were photographed 7 days after the pedicles were released. The photographs were processed using Adobe Acrobat 9 Pro software (San Jose, CA) to measure the flap survival area in millimeters and to compare groups. Seven days after the flap pedicle was divided, the rats were injected with 250 mCi Tc-99 mm (methoxy-isobutyl-isonitrie) from the penile vein, and scintigraphic images were obtained. The images obtained from each group were subjected to a numerical evaluation, which was then used in the comparison between groups. The flaps were then examined by histology to numerically compare the number of newly formed vessels. Neovascularization was also assessed by microangiography. In addition, radiographic images were obtained by mammography and evaluated quantitatively. RESULTS: An evaluation of statistical results revealed a significant increase in the flap survival area of the group on stem cell treatment in comparison to the control group. In scintigraphic examinations, the rate of radioactive substance retention was significantly higher in the stem cell group, relative to the control group. Histopathologic examination showed that the capillary density in the stem cell group was higher than that in the control group. Green fluorescent protein had been used to label ADSC in the experiment and it was found by immunofluorescence staining that endothelial samples of control animals did not have GFP (+) cells, whereas all the animals in the experiment group had GFP (+) cells. The comparison of microangiographic images of the experiment and control groups demonstrated significantly elevated vascularity in the former, relative to the latter. DISCUSSION: It has been established in the current study that ADSC injection worked well in speeding up the neovascularization of interpolated flaps and reducing the time of pedicle division. It seems possible to minimize the morbidity of interpolated skin flaps with mesenchymal stem cell therapy at an appropriate dose and for an appropriate length of time.

Remineralizing efficacy of a CPP-ACP cream on enamel caries lesions in situ.

The aim of this double-blind, randomized, cross-over in situ study was to compare the remineralizing effects induced by the application of casein phosphopeptide-stabilized amorphous calcium phosphate complexes (CPP-ACP)-containing cream (without fluoride) after the use of fluoride toothpaste with the prolonged use of fluoride toothpaste on enamel caries lesions in situ. During each of three experimental legs of 4 weeks, 13 participants wore intra-oral mandibular appliances with 8 pre-demineralized bovine enamel specimens in the vestibular flanges mimicking either 'easily cleanable' or 'proximal' surfaces (n = 312). The three randomly allocated treatments were as follows: (1) application of CPP-ACP-containing cream (GC Tooth Mouse, non-fluoride) after the use of fluoride toothpaste (1,400 ppm NaF; TM), (2) prolonged application of fluoride toothpaste (1,400 ppm NaF; positive control, PC) and (3) prolonged application of fluoride-free toothpaste (negative control, NC). Additionally, one of each of the two flanges was brushed twice daily with the respective toothpaste. The differences in integrated mineral loss as assessed by transversal microradiography were calculated between values before and after the in situ period. Changes in mineral loss were analysed for those pairs of subgroups differing in only one of the three factors (intervention, brushing and position). The PC treatment induced a significantly higher mineral gain compared with the TM and NC treatments. No significant differences between TM and NC for both positions were observed. In conclusion, the additional use of a CPP-ACP-containing cream seems to be less efficacious in remineralizing caries lesions than the prolonged application of fluoride toothpaste.

In vitro Induction of residual caries lesions in dentin: comparative mineral loss and nano-hardness analysis.

Artificially inducing dentinal lesions mimicking those remaining after selective excavation should allow to investigate the effects and limits of such selective excavation, for example regarding the mechanical properties of treated teeth or the remineralisation of sealed residual lesions. Such analyses might otherwise be limited by the variability of natural lesions or ethical and practical concerns. This study compared different demineralisation protocols for their suitability to induce lesions similar to natural residual caries. Twelve natural deep lesions were excavated until leathery dentin remained, and analysed for their mineral loss (ΔZ), lesion depth (LD), mineral loss ratio (R), the slope of the mineral gradient and their nano-hardness profile. Artificial lesions were induced using four different demineralisation protocols (acetic acid pH = 4.95; 0.1 M lactic acid gel pH = 5.0; 0.5 M ethylenediaminetetraacetic acid pH = 7.2; Streptococcus mutans biofilms) and their depths monitored over different demineralisation times. Lesions with depths most according to those of natural lesions were analysed using transversal microradiography. Lesions induced by acetic acid solution did not significantly differ with regards to LD, ΔZ, R and mineral profile. Seven dentin specimens were subsequently submitted to a moderately acidic (pH = 5.3) methylhydroxydiphosphonate-buffered acetate solution for 12 weeks. Natural and artificial residual lesions were similarly deep (mean ± SD: LD = 626 ± 212 and 563 ± 88 µm), demineralised (R = 19.5 ± 4.7 and 29.8 ± 4.1%), showed a flat and continuous mineral gradient (slope = 0.10 ± 0.05 and 0.13 ± 0.06 vol%/µm) and did not significantly differ regarding their nano-hardness profile. The described protocol induces lesions with mineral content and mechanical properties similar to natural residual lesions.

Microradiographic and histological evaluation of the bone-screw and bone-plate interface of orthodontic miniplates in patients.

OBJECTIVES: To describe the tissue reactions at the bone-titanium interface of orthodontic miniplates in humans. MATERIALS AND METHODS: Forty-two samples, consisting of tissue fragments attached or not to miniplates or their fixation screws, were collected from 24 orthodontic patients treated with miniplate anchorage, at the time of removal of their miniplates. The samples were embedded in methylmethacrylate and cut into undecalcified sections which were submitted to microradiographic analysis. The sections were also stained and examined under ordinary light. RESULTS: Three types of reactions were observed both on the histological sections and on the microradiographs. 1. The majority of the stable miniplates were easy to remove (34/42). The tissue samples collected consisted mainly in mature lamellar bone with some medullary spaces containing blood vessels, 2. two screws were highly osseointegrated and required the surgeon to remove them by trephining (2/42). They were surrounded by bone tissue which extended to the miniplate. The histological features were similar to the previous group, though the bone-screw contact was higher, and 3. in six samples obtained after unstable miniplate removal during the treatment, we observed either some woven bone trabeculae or loose connective tissue, without any histological sign of inflammation. LIMITATIONS AND CONCLUSION: For evident ethical reasons, our data were limited by the size of the tissue fragments and the limited number of patients and variety of clinical presentations. The healing reactions consisted mainly in mature lamellar bone tissue sparsely in contact with the screw or the miniplate, with signs of a moderate remodelling activity.

Validation of a novel microradiography device for characterization of bone mineralization.

In order to simplify bone mineralization measurements, a system using radiographic films has been updated with a digital detector. The objective of this paper was to validate this new device. Technologies and physical phenomena involved in both systems (radiographic films and digital detector) are different. The methodology used to compare the two systems was based on image quality and assessed on two main parameters: contrast to noise ratio and spatial resolution. Results showed that the contrast to noise ratio was similar between the two systems, provided that acquisition parameters were optimized. With regard to spatial resolution, a magnification factor of at least 4 or more was required to achieve the same resolution as films. A final validation was also shown on a real image of a bone sample. The results showed that both systems have similar image quality performances, and the system using digital detector has several advantages (easier to use than films, no consumables and faster acquisition time).

Erosion Prevention Potential of an Over-the-Counter Stabilized SnF2 Dentifrice Compared to 5000 ppm F Prescription-Strength Products.

OBJECTIVE: To determine the relative ability of various F-containing products to protect enamel against the initiation and progression of tooth surface loss due to erosive acid challenges. METHODS: Cores of enamel were prepared from extracted human teeth, soaked in pooled human saliva (pellicle formation), and then treated in a 1:3 slurry (product:saliva) of either OTC level (1100 ppm F) or prescription level (5000 ppm F) products, followed by a standardized erosion cycling procedure (five days of cycling) that included 10-minute challenges with an erosive dietary acid (1% citric acid at pH 2.3) applied 60 minutes after each dentifrice treatment (repeated four times per day). Enamel surface loss was measured using transverse microradiography. Two studies were conducted. Study 1 included: A) 1100 ppm F as NaF; B) 1100 ppm F as stabilized SnF; C) 5000 ppm F as NaF; and D) 5000 ppm F as NaF + acidulated phosphate. Study 2 included: 1) 1100 ppm F as stabilized SnF; 2) 5000 ppm F as NaF + tricalcium phosphate; and 3) 1100 ppm F as NaF. RESULTS: Study 1: Treatment B (1100 ppm F as SnF), where specimens lost only 8.0 µm of the enamel surface, was significantly more effective than Treatments A, C, and D at protecting enamel against the initiation and progression of erosive acid damage (p < 0.05). Specimens treated with product A exhibited 22.8 (1.25) µm (mean ± sem) of enamel loss; 20.0 (0.71) µm of enamel loss with treatment C and 24.0 (1.4) µm of enamel loss with Treatment D. Study 2 also demonstrated significantly greater erosion protection with the stabilized SnF2 dentifrice (p < 0.05), with only 5.8 (1.93) µm of tooth surface loss, while groups 2 and 3 lost 19.8 (0.75) µm and 18.0 (2.16) µm, respectively. CONCLUSION: Results from both studies demonstrated the OTC dentifrice formulated with stabilized SnF2 provides significantly greater protection against erosive acid attack compared to some of the most popular prescription level (5000 ppm F) fluoride treatments available.

A microautoradiographic method for fresh-frozen sections to reveal the distribution of radionuclides at the cellular level in plants.

Microautoradiography (MAR) is a conventional imaging method based on the daguerreotype. The technique is used to visualize the distribution of radionuclide-labeled compounds within a tissue section. However, application of the classical MAR method to plant tissue sections is associated with several difficulties. In this study, we report an MAR method applicable to fresh-frozen plant sections. Our method had two features: (i) the sample was kept frozen from plant tissue collection to radioisotope detection, making it possible to fix solutes without solvent exchange; and (ii) 1.2 µm thick polyphenylene sulfide film was inserted between the fresh-frozen plant section and the photosensitive nuclear emulsion to separate the section from the emulsion before autoradiography was conducted, which significantly improved the quality of the section until microscopic detection, the quality of the MAR image and the success rate. Then, the passage of cadmium (Cd) through vegetative rice stem tissue after 24 h of (109)Cd absorption was described for the first time using the MAR method. MAR clearly revealed the distribution of (109)Cd at the tissue level with high resolution. The (109)Cd concentration in phloem cells was found to be particularly high, whereas the xylem cells contained only small amounts of (109)Cd. The MAR method was also applicable for detecting (109)Cd and [(33)P]phosphate in roots. The MAR method developed here is expected to provide distribution images for a variety of compounds and ions in plant tissue.

Bone formation in peri-implant defects grafted with microparticles: a pilot animal experimental study.

AIM: This study aimed to evaluate the healing of peri-implant defects grafted with microparticles (MPs). MATERIAL AND METHODS: Six domestic pigs received nine standardized defects at the calvaria, and an implant was inserted in the middle of each defect. The space between the implant and lateral bone portion was filled with MP pellets (n = 18) or MP supernatant (n = 18) or left unfilled (n = 18). After 14 and 28 days, three animals were sacrificed and specimens removed for further processing. Samples were microradiographically and histologically analysed. In addition, we immunohistochemically stained for anti-vWF as a marker of angiogenesis. RESULTS: In the case of bone regeneration and vessel formation, the null hypothesis can be partially rejected. After 14 and 28 days, no significant difference was observed within groups regarding de novo bone formation, bone density and osseointegration. However, superior vessel formation was found at both time points. CONCLUSION: Microparticles represent a promising treatment option to accelerate peri-implant vessel formation. Further studies are needed to investigate the regenerative properties of MPs more precisely.

Micro- and nano-CT for the study of bone ultrastructure.

Micro-computed tomography (micro-CT)-a version of X-ray CT operating at high spatial resolution-has had a considerable success for the investigation of trabecular bone micro-architecture. Currently, there is a lot of interest in exploiting CT techniques at even higher spatial resolutions to assess bone tissue at the cellular scale. After recalling the basic principles of micro-CT, we review the different existing system, based on either standard X-ray tubes or synchrotron sources. Then, we present recent applications of micro- and nano-CT for the analysis of osteocyte lacunae and the lacunar-canalicular network. We also address the question of the quantification of bone ultrastructure to go beyond the sole visualization.

Cariogenic effects of probiotic Lactobacillus rhamnosus GG in a dental biofilm model.

Probiotic bacteria have been suggested to inhibit Streptococcus mutans (SM) and thus prevent dental caries. However, supporting evidence is weak and probiotic species might be cariogenic themselves. Thus, we compared and combined the probiotic Lactobacillus rhamnosus GG (LGG) with SM and analysed the resulting mineral loss (ΔZ) in dental tissues. We simulated three biofilm compositions (SM, LGG, SM × LGG), two lesion sites (smooth enamel, dentin cavity) and two nutrition supply frequencies (twice/day, 6 times/day) in a multi-station, continuous-culture biofilm model. A total of 240 bovine enamel and dentin samples were cut, polished and embedded. All experimental procedures were performed in independent duplicates, with 10 samples being allocated to each group for each experiment (final sample size n = 20/group). Biofilms were cultured on the specimens and supplied with 2% sucrose medium and artificial saliva in consecutive pulses. After 10 days, ΔZ and bacterial numbers were assessed. SM × LGG biofilms caused significantly increased ΔZ compared with SM or LGG biofilms (p < 0.01, Mann-Whitney test), and ΔZ was significantly increased in dentin cavities compared with smooth enamel lesions (p < 0.01). Bacterial numbers did not significantly differ between biofilms of different species (p > 0.05, ANOVA). Frequent nutrition supply significantly increased bacterial numbers (p < 0.01). Biofilms in dentin cavities compared to smooth enamel harboured significantly more bacteria (p < 0.05). LGG induced mineral loss especially in dentin cavities and under highly cariogenic conditions. LGG did not have inhibitory effects on SM, but rather contributed to the caries process in vitro.

Dentifrice fluoride and abrasivity interplay on artificial caries lesions.

Incipient caries lesions on smooth surfaces may be subjected to toothbrushing, potentially leading to remineralization and/or abrasive wear. The interplay of dentifrice abrasivity and fluoride on this process is largely unknown and was investigated on three artificially created lesions with different mineral content/distribution. 120 bovine enamel specimens were randomly allocated to 12 groups (n = 10), resulting from the association of (1) lesion type [methylcellulose acid gel (MeC); carboxymethylcellulose solution (CMC); hydroxyethylcellulose gel (HEC)], (2) slurry abrasive level [low (REA 4/ RDA 69); high (REA 7/RDA 208)], and (3) fluoride concentration [0/275 ppm (14.5 mM) F as NaF]. After lesion creation, specimens were brushed in an automated brushing machine with the test slurries (50 strokes 2×/day). Specimens were kept in artificial saliva in between brushings and overnight. Enamel surface loss (SL) was determined by optical profilometry after lesion creation, 1, 3 and 5 days. Two enamel sections (from baseline and post-brushing areas) were obtained and analyzed microradiographically. Data were analyzed by analysis of variance and Tukey's tests (α = 5%). Brushing with high-abrasive slurry caused more SL than brushing with low-abrasive slurry. For MeC and CMC lesions, fluoride had a protective effect on SL from day 3 on. Furthermore, for MeC and CMC, there was a significant mineral gain in the remaining lesions except when brushed with high-abrasive slurries and 0 ppm F. For HEC, a significant mineral gain took place when low-abrasive slurry was used with fluoride. The tested lesions responded differently to the toothbrushing procedures. Both slurry fluoride content and abrasivity directly impacted SL and mineral gain of enamel caries lesions.

Effect of gallium on growth of Streptococcus mutans NCTC 10449 and dental tissues.

Gallium-doped phosphate-based glasses (Ga-PBG) were assessed for their impact on Streptococcus mutans and dental mineralisation, firstly by disc diffusion assays followed by biofilms grown on nitrocellulose filter membrane (NFM) and constant-depth film fermentor (CDFF). Short-time exposure (10 min) effects of Ga-PBG on S. mutans biofilm were compared with that of 0.2% chlorhexidine. The effects of Ga-PBG on bovine enamel (which was investigated under pH-cycling condition) and dentine were analysed using transverse microradiography (TMR), profilometry and inductively coupled plasma optical-emission spectrometry (ICP-OES). The disc diffusion assays showed inhibition zones of 24.5 ± 0.5 mm for Ga-PBG compared with controls (C-PBG). Ga-PBG showed statistically significant growth inhibition of S. mutans biofilms on NFM (p = 0.001) and CDFF (p < 0.046) compared with hydroxyapatite (HA) and C-PBG. The CDFF assay revealed a maximum of 2.11 log colony-forming unit (CFU) reduction at 48 h, but short-time exposure effects were comparable with that of 0.2% chlorhexidine only on older biofilms (maximum of 0.59 vs. 0.69 log CFU reduction at 120 h). TMR analyses of the enamel revealed non-significant mineral loss (p = 0.37) only in the case of Ga-PBG samples compared with controls including sodium fluoride. ICP-OES analyses indicated transient gallium adsorption into dentine by calcium displacement. The results confirmed that gallium inhibited S. mutans growth and appears to have the potential to protect the enamel surface under conditions representative of the oral environment. Further work is needed to establish whether it has an application in daily oral hygiene procedures to prevent or reduce caries.

Cephalometric assessment of craniofacial dysmorphologies in relation with Msx2 mutations in mouse.

OBJECTIVES: To determine the role of Msx2 in craniofacial morphology and growth, we used a mouse model and performed a quantitative morphological characterization of the Msx2 (-/-) and the Msx2 (+/-) phenotype using a 2D cephalometric analysis applied on micrographs. MATERIALS AND METHODS: Forty-four three-and-a-half-month-old female CD1 mice were divided into the following three groups: Msx2 (+/+) (n = 16), Msx2 (+/-) (n = 16), and Msx2 (-/-) (n = 12). Profile radiographs were scanned. Modified cephalometric analysis was performed to compare the three groups. RESULTS: Compared with the wild-type mice, the Msx2 (-/-) mutant mice presented an overall craniofacial size decrease and modifications of the shape of the different parts of the craniofacial skeleton, namely the neurocranium, the viscerocranium, the mandible, and the teeth. In particular, dysmorphologies were seen in the cochlear apparatus and the teeth (taurodontism, reduced incisor curvature). Finally contrary to previous published results, we were able to record a specific phenotype of the Msx2 (+/-) mice with this methodology. This Msx2 (+/-) mouse phenotype was not intermediate between the Msx2 (-/-) and the wild-type animals. CONCLUSION: Msx2 plays an important role in craniofacial morphogenesis and growth because almost all craniofacial structures were affected in the Msx2(-/-) mice including both intramembranous and endochondral bones, the cochlear apparatus, and the teeth. In addition, Msx2 haploinsufficiency involves a specific phenotype with subtle craniofacial structures modifications compared with human mutations.

Comparative study of the measurement of enamel demineralization and remineralization using transverse microradiography and electron probe microanalysis.

Transverse microradiography (TMR) and electron probe microanalysis (EPMA) are commonly used for characterizing dental tissues. TMR utilizes an approximately monochromatic X-ray beam to determine the mass attenuation of the sample, which is converted to volume percent mineral (vol%min). An EPMA stimulates the emission of characteristic X-rays from a variable volume of sample (dependent on density) to provide compositional information. The aim of this study was to compare the assessment of sound, demineralized, and remineralized enamel using both techniques. Human enamel samples were demineralized and a part of each was subsequently remineralized. The same line profile through each demineralized lesion was analyzed using TMR and EPMA to determine vol%min and wt% elemental composition and atomic concentration ratio information, respectively. The vol%min and wt% values determined by each technique were significantly correlated but the absolute values were not similar. This was attributable to the complex ultrastructural composition, the variable density of the samples analyzed, and the nonlinear interaction of the EPMA-generated X-rays. EPMA remains an important technique for obtaining atomic ratio information, but its limitations in determining absolute mineral content indicate that it should not be used in place of TMR for determining the mineral density of dental hard tissues.

Erosion protection comparison of stabilised SnF2 , mixed fluoride active and SMFP/arginine-containing dentifrices.

PURPOSE: To investigate the relative erosion protection potential of marketed dentifrices formulated with either stabilised stannous fluoride (SnF2 ), sodium fluoride (NaF) and/or sodium monofluorophosphate (SMFP) using an established laboratory erosion cycling model. METHODS: Sound enamel cores from extracted, human enamel were cleaned, ground and polished, soaked in pooled saliva (pellicle formation) and treated with a 1:3 slurry of dentifrice and saliva. Specimens were subjected to daily challenges with 1% citric acid, a potentially damaging acid found in common food and drinks. Marketed dentifrices compared were: (1) a stabilised stannous fluoride product formulated with 1,100 ppm F as SnF2 ; (2) a cavity protection product containing 1,100 ppm F as NaF; (3) a cavity protection product comprising a mixed active fluoride system with 1,000 ppm F as SMFP + 450 ppm F as NaF; and (4) a sensitivity product containing 1,450 ppm F as SMFP + 8% arginine bicarbonate. RESULTS: Specimens from Group 1 demonstrated an average loss of 5.5 (±1.2) µm of tooth surface enamel; Groups 2, 3 and 4 lost an average of 18.3 (±0.9) µm, 16.0 (±2.0) µm and 17.1 (±1.1) µm, respectively, of tooth surface enamel. Group 1 provided a statistically significant difference in protection compared with the other products. CONCLUSIONS: These results suggest that the marketed dentifrice formulated with stabilised SnF2 may provide enhanced protection of exposed tooth surfaces against dietary acid attack compared with the other products tested.

Protective benefits of a stabilised stannous-containing fluoride dentifrice against erosive acid damage.

PURPOSE: To assess the potential of a stabilised stannous (Sn)-containing NaF dentifrice (Oral B/blend-a-Med(®) Pro-Expert), in addition to a number of other marketed European dentifrices formulated with various fluoride actives and two control dentifrices, to protect enamel against erosive acid damage. METHODS: Cores of human enamel (four per group) were soaked in pooled human saliva, and then treated with a 1:3 slurry (dentifrice:saliva) using a standardised in vitro erosion model (5-day cycling) that includes 10-minute challenges with 1% citric acid applied 60 minutes after each dentifrice treatment. Enamel surface loss was measured using transverse microradiography (TMR). RESULTS: Specimens treated with the Sn-containing NaF dentifrice showed 6.5 µm of surface loss ± 1.2 (SEM), which was not significantly different (P < 0.05, Fisher LSD) from that of a clinically proven, stabilised SnF2 positive control [Crest(®) Pro-Health, 1,100 ppm F as SnF2 : 3.0 µm of surface loss ± 1.1 (SEM)]. The Sn-containing NaF dentifrice and the clinically proven positive control both provided significantly greater protection (P < 0.05, Fisher LSD) compared with all of the other products tested. Enamel loss (SEM) values for other European products and the reference control (active agents) were: Meridol(®) : (1,400 ppm F as AmF + SnF2 ) 12.0 µm (1.47); Colgate(®) Cavity Protection: (1,450 ppm F as SMFP + NaF) 12.9 µm (1.66); Odol med 3(®) (1,400 ppm F as NaF) 14.2 µm (1.49); Elmex(®) (1,400 ppm F as AmF) 14.5 µm (1.76); Colgate(®) Enamel Protect: (1,450 ppm F as NaF + KNO3 ) 16.3 µm (2.02); Lacalut(®) aktiv: (1,400 ppm F as AlF3 ) 18.5 µm (1.71); Sensodyne(®) ProNamel(™) : (1,450 ppm F as NaF + KNO3 ) 20.5 µm (1.26); Crest Cavity Protection (1,100 ppm F as NaF, reference control) 22.00 µm (2.04); and Mentadent(®) : (1,450 ppm F as NaF + Zn citrate) 22.3 µm (0.63). CONCLUSION: These results support the potential for the stabilised, Sn-containing NaF dentifrice to provide erosion protection benefits that are not significantly different from the positive control benchmark for erosion protection (stabilised SnF2 ), and are significantly better than a broad range of dentifrice formulations available on the European market.

Hydraulic characteristics of water-refilling process in excised roots of Arabidopsis.

Plants have efficient water-transporting vascular networks with a self-recovery function from embolism, which causes fatal discontinuity in sap flow. However, the embolism-refilling process in xylem vessel is still unclear. The water-refilling processes in the individual xylem vessels of excised Arabidopsis roots were visualized in this study using synchrotron X-ray micro-imaging technique with high spatial resolution up to 1 µm per pixel and temporal resolution up to 24 fps. In normal continuous water-refilling process, we could observe various flow patterns affected by the morphological structures of the xylem vessels, especially when water passed through perforation plates. A simple criterion based on the variation in dynamic pressure was suggested to evaluate the contribution of individual perforation plates to the water-refilling process. Meanwhile, the water-refilling embolized sections of xylem vessels through radial pathways were also observed. Separated water columns were formed from this discontinuous water-refilling process and the water influx rates through the radial pathways were estimated to be 478 and 928 µm(3) s(-1). The dynamic behavior of the separated water columns were quantitatively analyzed from the stoppage of volume growth to the translational phase. These water-refilling processes in excised roots of Arabidopsis may shed light on understanding the water refilling in the embolism vessels of intact plants and the interconnectivity of xylem vessel networks in vascular plants.