The effect of CO2 9.3 µm short-pulsed laser irradiation in enamel erosion reduction with and without fluoride applications-a randomized, controlled in vitro study.

The aim of this in vitro study was to evaluate the protective effect of short-pulsed CO2 9.3 µm laser irradiation against erosion in human enamel without and combined with TiF4 and AmF/NaF/SnCl2 applications, respectively, as well as compared to the protective effect of these fluoride treatments alone. After polishing, ninety enamel samples (3 × 3mm) were used for 9 different treatment groups: 4% TiF4 gel (pH 1.5, 24,533 ppm F-); AmF/NaF/SnCl2 rinse (pH 4.5; 500 ppm F-, 800 ppm Sn2); CO2 laser (average power 0.58 W); CO2 laser (0.58 W) + TiF4; CO2 laser (0.58 W) + AmF/NaF/SnCl2; CO2 laser (0.69 W); CO2 laser (0.69 W) + TiF4; CO2 laser (0.69 W) + AmF/NaF/SnCl2; negative control (deionized water). TiF4 gel was brushed on only once before the first erosive cycling, while samples treated with AmF/NaF/SnCl2 were daily immersed in 5 ml of the solution before cycling. Laser treatment occurred with a CO2 laser (wavelength 9.3 µm, pulse repetition rate 100 Hz, pulse duration 14.6 µs/18 µs, average power 0.58 W/0.69 W, fluence 1.9 J/cm2/2.2 J/cm2, beam diameter 0.63 mm, irradiation time 10 s, air cooling). TiF4 was applied only once, while AmF/NaF/SnCl2 was applied once daily before the erosive challenge. Surface loss (in µm) was measured with optical profilometry immediately after treatment, and after 5 and 10 days of erosive cycling (0.5% citric acid, pH 2.3, 6 × 2 min/day). Additionally, scanning electron microscopy investigations were performed. All application measures resulted in loss of surface height immediately after treatment. After 5 days, significantly reduced surface loss was observed after applying laser irradiation (both power settings) followed by applications of TiF4 or AmF/NaF/SnCl2 solution (p < 0.05; 2-way ANOVA and Tukey test) compared to fluoride application alone. After 10 days, compared to after 5 days, a reduced tissue loss was observed in all groups treated with AmF/NaF/SnCl2 solution. This tissue gain occurred with the AmF/NaF/SnCl2 application alone and was significantly higher when the application was combined with the laser use (p < 0.05). Short-pulsed CO2 9.3 µm laser irradiation followed by additional application of AmF/NaF/SnCl2 solution significantly reduces the progression of dental enamel erosion in vitro.

Protection Against Discolouration by Two Over-the Counter Desensitising Products.

PURPOSE: To determine in vitro the protection potential against discolouration of two OTC (over-the-counter) desensitising products on enamel and dentin in comparison to a standard toothpaste and water by means of a spectrophotometer. MATERIALS AND METHODS: A total of 96 samples of bovine enamel-dentin complex and 48 of bovine dentin were alternatively immersed in red wine, tea, coffee or water after having been treated by a sodium monofluorophosphate- and calcium phosphate-based product (Curodont Protect), an amine fluoride-based toothpaste (Elmex Red), a stannous chloride-based toothpaste (Elmex Protection Erosion) or distilled water (negative control). Initial (T0) and final colour (T1, after 4 weeks of immersion in staining solutions) of each specimen were assessed by a spectrophotometer. Statistical analysis was done by means of repeated measures ANOVA followed by Fisher's LSD post-hoc test. Differences between T0 and T1 were considered stastistically significant at p ≤ 0.05. RESULTS: When enamel samples were measured over a black background, ΔE00 values (T0-T1) varied from 2.2 (SD 0.7) for amine fluoride-based product/water to 53.9 (SD 7.6) for amine fluoride-based-product/red wine. When dentin samples were measured over a black background, ΔE00 values (T0-T1) varied from 5.4 (SD 0.9) stannous chloride based product/water to 61.6 (SD 3.7) amine fluoride-based product/red wine. CONCLUSION: Specifically, the application of the sodium monofluorophosphate was able to statistically significantly (p ≤ 0.05) reduce discolouration induced by the staining solutions tested only on the enamel-dentin complex, while distilled water and the stannous fluoride-based product were able to statistically significantly (p ≤ 0.05) reduce discolouration induced by the staining solutions tested in pure dentin samples.

Effect of an experimental mouth rinse containing NaF and TiF4 on tooth erosion and abrasion in situ.

OBJECTIVE: This study compared the effect of an experimental NaF/TiF4 mouth rinse with a commercial tin/F mouth rinse on the prevention of tooth wear in situ. METHODS: Fifteen subjects took part in this crossover and double-blind study, in which they wore a palatal appliance with 8 bovine teeth samples (4 enamel and 4 root dentine) in each of 3 phases (5 days each). Half of the samples were subjected to erosive challenges, and the other half to erosive plus abrasive challenges. The phases corresponded to the use of 1) Experimental solution containing NaF/TiF4 (189 ppm Ti+4, 500 ppm F-, pH 4.4); 2) commercial solution containing SnCl2/NaF/AmF (800 ppm Sn+2, 500 ppm F-, pH 4.5, Elmex®/GABA, positive control); 3) distilled water (negative control). Erosive challenges were performed using 0.1% citric acid (pH 2.5) for 90 s 4 times per day. The abrasion was done using a toothbrush and slurry of fluoride toothpaste, for 15 s 2 times per day. Thereafter, the subjects rinsed with the tested mouth rinse for 60s. Tooth wear was measured using contact profilometry (µm) and submitted to a two-way RM ANOVA/Bonferroni test (p < 0.05). RESULTS: No significant differences were detected between the experimental and the commercial mouth rinses, regardless of the challenge. Both fluoride mouth rinses were able to significantly reduce tooth wear compared to the negative control (p < 0.0001). No significant differences were detected with respect to tooth wear between the challenges (erosion and erosion plus abrasion). CONCLUSION: The experimental NaF/TiF4 mouth rinse has a similar protective effect to the commercial one against tooth wear in situ. CLINICAL SIGNIFICANCE: The experimental NaF/TiF4 solution protected against tooth wear in situ, regardless of the challenge (erosion or erosion plus abrasion), for both enamel and dentine, similarly to a commercial solution (tin/F-Elmex®) applied for this proposal. This result supports the conduction of clinical trials and a possible application of this solution in the future.

Tin Tungstate Nanoparticles: A Photosensitizer for Photodynamic Tumor Therapy.

The nanoparticulate inorganic photosensitizer ß-SnWO4 is suggested for photodynamic therapy (PDT) of near-surface tumors via reiterated 5 min blue-light LED illumination. ß-SnWO4 nanoparticles are obtained via water-based synthesis and comprise excellent colloidal stability under physiological conditions and high biocompatibility at low material complexity. Antitumor and antimetastatic effects were investigated with a spontaneously metastasizing (4T1 cells) orthotopic breast cancer BALB/c mouse model. Besides protamine-functionalized ß-SnWO4 (23 mg/kg of body weight, in PBS buffer), chemotherapeutic doxorubicin was used as positive control (2.5 mg/kg of body weight, in PBS buffer) and physiological saline (DPBS) as a negative control. After 21 days, treatment with ß-SnWO4 resulted in a clearly inhibited growth of the primary tumor (all tumor volumes below 3 cm(3)) as compared to the doxorubicin and DPBS control groups (volumes up to 6 cm(3)). Histological evaluations of lymph nodes and lungs as well as the volume of ipsilateral lymph nodes show a remarkable antimetastatic effect being similar to chemotherapeutic doxorubicin but-according to blood counts-at significantly reduced side effects. On the basis of low material complexity, high cytotoxicity under blue-light LED illumination at low dark and long-term toxicity, ß-SnWO4 can be an interesting addition to PDT and the treatment of near-surface tumors, including skin cancer, esophageal/gastric/colon tumors as well as certain types of breast cancer.

Efficacy of stannous, fluoride and their their combination in dentin erosion prevention in vitro.

The aim of this study was to compare the protective effects of solutions containing stannous (Sn), fluoride (F) and their combination in the prevention of dentin erosion. Forty bovine root dentin specimens (4'4'2 mm(3)) were prepared and randomly assigned to 4 groups (n = 10): SnCl2 (800 ppm/6.7 mM Sn), NaF (250 ppm/13 mM F), NaF/SnCl2 (800 ppm/6.7 mM Sn; 250 ppm/13 mM F), and deionized water (DIW) as a negative control. An acquired pellicle was formed on dentin samples by incubation in clarified, pooled, stimulated human saliva for 24 hours. The specimens were subjected to 5 daily cycles, each consisting of 5 of min demineralization (0.3%/15.6 mM citric acid, pH 2.6, 6'/day) and 60 min of re-mineralization in clarified human saliva. Thirty minutes after the 1st, 3rd and 5th demineralization episodes of each day, the specimens were treated with one of the test solutions for 2 min. Surface loss was measured via optical profilometry. Mixed-model ANOVA followed by Tukey's test were used for the statistical analysis. Sn, F, and their combination significantly reduced the dentin surface loss by 23%, 36%, and 60% compared with DIW, respectively. All groups were significantly different (p < 0.05). The combination of Sn and F significantly reduced the amount of dentin surface loss compared with all other groups. The F group also significantly reduced surface loss compared with Sn and DIW, followed by the Sn group, which showed significantly greater protection compared with the DIW control. The daily use of a combined fluoride and stannous solution is promising for preventing dentin erosion.

The future of fluorides and other protective agents in erosion prevention.

The effectiveness of fluoride in caries prevention has been convincingly proven. In recent years, researchers have investigated the preventive effects of different fluoride formulations on erosive tooth wear with positive results, but their action on caries and erosion prevention must be based on different requirements, because there is no sheltered area in the erosive process as there is in the subsurface carious lesions. Thus, any protective mechanism from fluoride concerning erosion is limited to the surface or the near surface layer of enamel. However, reports on other protective agents show superior preventive results. The mechanism of action of tin-containing products is related to tin deposition onto the tooth surface, as well as the incorporation of tin into the near-surface layer of enamel. These tin-rich deposits are less susceptible to dissolution and may result in enhanced protection of the underlying tooth. Titanium tetrafluoride forms a protective layer on the tooth surface. It is believed that this layer is made up of hydrated hydrogen titanium phosphate. Products containing phosphates and/or proteins may adsorb either to the pellicle, rendering it more protective against demineralization, or directly to the dental hard tissue, probably competing with H(+) at specific sites on the tooth surface. Other substances may further enhance precipitation of calcium phosphates on the enamel surface, protecting it from additional acid impacts. Hence, the future of fluoride alone in erosion prevention looks grim, but the combination of fluoride with protective agents, such as polyvalent metal ions and some polymers, has much brighter prospects.

Efficacy of stannous, fluoride and their their combination in dentin erosion prevention in vitro

The aim of this study was to compare the protective effects of solutions containing stannous (Sn), fluoride (F) and their combination in the prevention of dentin erosion. Forty bovine root dentin specimens (4’4’2 mm3) were prepared and randomly assigned to 4 groups (n = 10): SnCl2(800 ppm/6.7 mM Sn), NaF (250 ppm/13 mM F), NaF/SnCl2 (800 ppm/6.7 mM Sn; 250 ppm/13 mM F), and deionized water (DIW) as a negative control. An acquired pellicle was formed on dentin samples by incubation in clarified, pooled, stimulated human saliva for 24 hours. The specimens were subjected to 5 daily cycles, each consisting of 5 of min demineralization (0.3%/15.6 mM citric acid, pH 2.6, 6’/day) and 60 min of re-mineralization in clarified human saliva. Thirty minutes after the 1st, 3rd and 5th demineralization episodes of each day, the specimens were treated with one of the test solutions for 2 min. Surface loss was measured via optical profilometry. Mixed-model ANOVA followed by Tukey’s test were used for the statistical analysis. Sn, F, and their combination significantly reduced the dentin surface loss by 23%, 36%, and 60% compared with DIW, respectively. All groups were significantly different (p < 0.05). The combination of Sn and F significantly reduced the amount of dentin surface loss compared with all other groups. The F group also significantly reduced surface loss compared with Sn and DIW, followed by the Sn group, which showed significantly greater protection compared with the DIW control. The daily use of a combined fluoride and stannous solution is promising for preventing dentin erosion.

Randomised in situ trial on the effect of milk and CPP-ACP on dental erosion.

OBJECTIVES: This randomised in situ study aimed to analyse the effect of milk (with or without 5ppm F) and CPP-ACP pastes (with or without 900ppm F) on dental erosion. METHODS: The study was a seven phase (5 days each) crossover design involving 15 participants wearing intraoral appliances with enamel and dentine specimens. Specimens were extraorally eroded (erosive soft drink, 6×90s/day) and brushed (2×30s/day, 2N) using a non-fluoridated toothpaste (negative control). The test products were milk, milk+5ppm F (twice daily, each 100ml/2min), CPP-ACP paste, CPP-ACP paste+900ppm F (3min/day) or a SnCl2/AmF/NaF mouthrinse (positive control, 30s/day), which were applied immediately after erosion with the appliances in the oral cavity. In an additional group, a fluoridated toothpaste was used without any additional test product. Tissue loss was determined profilometrically after 5 days and statistically analysed by linear mixed models methodologies (p<0.05). RESULTS: Compared with the negative control (non-fluoridated toothpaste only, enamel: 2.2±1.3µm; dentine: 3.8±2.2µm), enamel and dentine loss was significantly reduced by the use of fluoridated toothpaste (enamel: 1.1±1.0µm; dentine: 2.4±1.7µm) and the SnCl2/AmF/NaF mouthrinse (1.5±1.5µm; dentine: 1.8±1.9µm). CONCLUSIONS: Milk and CPP-ACP were not effective in reducing enamel and dentine loss significantly, independently of the presence of fluoride. CLINICAL SIGNIFICANCE: Enamel and dentine erosion were significantly reduced by the use of a fluoridated toothpaste or a SnCl2/AmF/NaF mouthrinse, but not by milk or CPP-ACP under the conditions of the present study. CLINICAL TRIALS REGISTRATION: NCT01566357.

Prevention of dentine erosion by brushing with anti-erosive toothpastes.

OBJECTIVE: This in vitro study aimed to investigate the preventive effect of brushing with anti-erosive toothpastes compared to a conventional fluoride toothpaste on dentine erosion. MATERIALS AND METHODS: Bovine dentine specimens (n=12 per subgroup) were eroded in an artificial mouth (6 days, 6×30 s/day) using either citric acid (pH:2.5) or a hydrochloric acid/pepsin solution (pH:1.6), simulating extrinsic or intrinsic erosive conditions, respectively. In between, the specimens were rinsed with artificial saliva. Twice daily, the specimens were brushed for 15 s in an automatic brushing machine at 2.5 N with a conventional fluoride toothpaste slurry (elmex, AmF) or toothpaste slurries with anti-erosive formulations: Apacare (NaF/1% nHAP), Biorepair (ZnCO3-HAP), Chitodent (Chitosan), elmex Erosionsschutz (NaF/AmF/SnCl2/Chitosan), mirasensitive hap (NaF/30% HAP), Sensodyne Proschmelz (NaF/KNO3). Unbrushed specimens served as control. Dentine loss was measured profilometrically and statistically analysed using two-way and one-way ANOVA followed by Scheffe's post hoc tests. RDA-values of all toothpastes were determined, and linear mixed models were applied to analyse the influence of toothpaste abrasivity on dentine wear (p<0.05). RESULTS: Dentine erosion of unbrushed specimens amounted to 5.1±1.0 µm (extrinsic conditions) and 12.9±1.4 µm (intrinsic conditions). All toothpastes significantly reduced dentine erosion by 24-67% (extrinsic conditions) and 21-40% (intrinsic conditions). Biorepair was least effective, while all other toothpastes were not significantly different from each other. Linear mixed models did not show a significant effect of the RDA-value of the respective toothpaste on dentine loss. CONCLUSION: Toothpastes with anti-erosive formulations reduced dentine erosion, especially under simulated extrinsic erosive conditions, but were not superior to a conventional fluoride toothpaste.

Erosion/abrasion-preventing potential of NaF and F/Sn/chitosan toothpastes in dentine and impact of the organic matrix.

The study investigated the erosion/abrasion-preventing potential of experimental NaF (1,400 ppm F(-)) and amine fluoride (AmF)/NaF/SnCl2/chitosan (1,400 ppm F(-), 3,500 ppm Sn(2+), 0.5% chitosan) toothpastes relative to placebo and SnF2 gel (970 ppm F(-), 3,000 ppm Sn(2+)), and the impact of the demineralised dentine matrix on toothpaste effects. The study was a cyclic erosion/intervention experiment (10 days). Samples were stored in mineral salt solution either without or with collagenase (from Clostridium histolyticum type VII; 100 U/ml) for continuous removal of the organic matrix. To produce a comparable order of tissue loss, erosion was performed 6 × 30 s/day with 0.5% citric acid in the latter and 6 × 90 s/day with 1% citric acid in the former. Intervention was toothpaste slurry immersion (2 × 2 min/day); half of the samples were additionally brushed for 15 s within this time (brushing machine, load 200 g). Tissue loss was determined profilometrically (mean ± SD; µm). Tissue loss values (without/with brushing) for placebo, NaF, AmF/NaF/SnCl2/chitosan and SnF2 gel, respectively, were 11.6 ± 3.1/12.2 ± 2.5, 12.7 ± 3.1/10.7 ± 4.5, 8.7 ± 2.1/9.7 ± 2.1 and 8.8 ± 1.8/​10.9 ± 1.8 in the presence of the organic matrix and 10.7 ± 3.2/11.9 ± 2.1, 8.2 ± 4.0/10.1 ± 4.1, 8.7 ± 2.9/9.1 ± 1.8 and 8.4 ± 1.9/7.5 ± 1.5 in the absence of the organic matrix. Relative to placebo, the NaF formulation had no significant effects; the AmF/NaF/SnCl2/chitosan formulation significantly reduced tissue loss between 20 and 25% except when applied without brushing in the absence of the organic matrix. The effects of the formulations were similar both in the presence and absence of the organic matrix. Sn(2+)/F(-)-​containing formulations have the potential to reduce erosion/abrasion even in the absence of demineralised collagen; seeking for more effective formulations is desirable.

Combined effect of a fluoride-, stannous- and chitosan-containing toothpaste and stannous-containing rinse on the prevention of initial enamel erosion-abrasion.

OBJECTIVES: The aim of this study was to assess the preventive effect of a fluoride-, stannous- and chitosan-containing (F/Sn/chitosan-) toothpaste (TP) on initial enamel erosion and abrasion. METHODS: In total, 150 human premolar enamel specimens were ground, polished and divided into 5 toothpaste/rinse groups (n=30): (G1) placebo-TP/tap water, (G2) sodium fluoride (NaF-) TP/tap water, (G3) F/Sn/chitosan-TP/tap water, (G4) F/Sn/chitosan-TP/Sn-rinse, (G5) NaF-TP/NaF-rinse. The 8-day erosion-abrasion cyclic treatment (one cycle/day) consisted of incubating the samples in artificial saliva (30min), then submitting the samples to toothbrush abrasion (2min incubation in toothpaste slurry; brushing with 20 toothbrush strokes) and rinsing (2min; 10ml) with the respective solution: tap water (G1-G3), Sn-rinse (G4) or NaF-rinse (G5). Afterwards, the samples were submitted to erosion (2min; 30ml 1% citric acid, pH=3.6). Surface microhardness (SMH) was measured initially and after every abrasion and erosion treatment. Enamel substance loss was calculated after each abrasion. Non-parametric ANOVA followed by Wilcoxon rank tests were used for analysis. RESULTS: G1 presented the greatest SMH decrease, while G4 presented the least SMH decrease (p<0.001). G3 had a similar SMH decrease to G2 and G5. Substance loss was significantly lower in G4 than all other groups (p<0.05), closely followed by G3. Both G2 and G5 showed similar calculated enamel substance loss to G1. CONCLUSION: The treatment with F/Sn/chitosan-TP and tap water provided a similar SMH decrease to both NaF-TP groups, but significantly lower substance loss. F/Sn/Chitosan-TP and Sn-rinse showed a better preventive effect, which promoted less SMH decrease and reduced substance loss. CLINICAL SIGNIFICANCE: The toothpaste containing fluoride, stannous and chitosan shows promising results in reducing substance loss from erosion and abrasion. The combination of this toothpaste with the stannous-containing rinse showed even better prevention against erosion-abrasion.

Randomized in vivo trial evaluating plaque inhibition benefits of an advanced stannous-containing sodium fluoride dentifrice used in conjunction with power brush technology.

OBJECTIVE: To compare the plaque inhibition efficacy of a novel stannous-containing sodium fluoride test dentifrice to a standard anticavity negative control dentifrice, when both were used in conjunction with an advanced oscillating-rotating (O/R) power toothbrush. METHODS: This was a randomized, two-treatment, three-period, double-blind crossover study conducted in a population using an O/R power brush. Subjects brushed twice per day with their assigned dentifrice during the three-treatment periods, each lasting for 17 consecutive days. Each period was separated by a 4-day washout period during which subjects continued to use their O/R power toothbrush. Plaque levels were assessed and averaged amongst three assessments taken on days 15, 16 and 17 at the end of each treatment period using digital plaque imaging analysis. Assessments were carried out on the facial anterior tooth surfaces in the morning before brushing (A.M. prebrush) following whole-mouth brushing (30 s per quadrant) with the assigned dentifrice (A.M. post-brush) and in the afternoon (P.M.). RESULTS: Twenty-seven subjects were randomized and completed the study. During the 17-day usage period, the stannous-containing test NaF dentifrice demonstrated a statistically significant lower mean plaque area versus the negative control dentifrice at each assessment timepoint; overnight A.M. prebrush was 33.8% lower (P < 0.0001), A.M. post-brush was 21.8% lower (P < 0.01), and P.M. was 29.2% lower (P < 0.0001). CONCLUSION: A population of O/R power toothbrush users had significantly less plaque coverage for all three measurements when using a stannous-containing NaF dentifrice than when using a negative control (fluoride) dentifrice.

Randomised in situ study on the efficacy of a tin/chitosan toothpaste on erosive-abrasive enamel loss.

Tin is a notable anti-erosive agent, and the biopolymer chitosan has also shown demineralisation-inhibiting properties. Therefore, the anti-erosive/anti-abrasive efficacy of the combination of both compounds was tested under in situ conditions. Twenty-seven volunteers were included in a randomised, double-blind, three-cell crossover in situ trial. Enamel specimens were recessed on the buccal aspects of mandibular appliances, extraorally demineralised (6 × 2 min/day) and intraorally treated with toothpaste slurries (2 × 2 min/day). Within the slurry treatment time, one-half of the specimens received additional intraoral brushing (5 s, 2.5 N). The tested toothpastes included a placebo toothpaste, an experimental NaF toothpaste (1,400 ppm F(-)) and an experimental F/Sn/chitosan toothpaste (1,400 ppm F(-), 3,500 ppm Sn(2+), 0.5% chitosan). The percentage reduction of tissue loss (slurry exposure/slurry exposure + brushing) compared to placebo was 19.0 ± 47.3/21.3 ± 22.4 after use of NaF and 52.5 ± 30.9/50.2 ± 34.3 after use of F/Sn/chitosan. F/Sn/chitosan was significantly more effective than NaF (p ≤ 0.001) and showed good efficacy against erosive and erosive-abrasive tissue loss. This study suggests that the F/Sn/chitosan toothpaste could provide good protection for patients who frequently consume acidic foodstuffs.

Pharmacokinetics in the oral cavity: fluoride and other active ingredients.

Modern commercial toothpastes contain therapeutic ingredients to combat various oral conditions, for example, caries, gingivitis, calculus and tooth stain. The efficient delivery and retention of such ingredients in the mouth is essential for good performance. The aim of this chapter is to review the literature on the oral pharmacokinetics of, primarily, fluoride but also other active ingredients, mainly anti-plaque agents. Elevated levels of fluoride have been found in saliva, plaque and the oral soft tissues after use of fluoridated toothpaste, which persist at potentially active concentrations for hours. Both experiment and mathematical modelling suggest that the soft tissues are the main oral reservoir for fluoride. Qualitatively similar observations have been made for anti-plaque agents such as triclosan and metal cations, though their oral substantivity is generally greater. Scope for improved retention and subsequent efficacy exists.

Human colon adenocarcinoma HT-29 cell: electrochemistry and nicotine stimulation.

Recently, it was demonstrated that colorectal cancer HT-29 cells can secrete epinephrine (adrenaline) in an autocrine manner to auto-stimulate cellular growth by adrenoreceptors activation, and that this secretion is enhanced by nicotine, showing an indirect relation between colorectal cancer and tobacco. The electrochemical behaviour of human colon adenocarcinoma HT-29 cells from a colorectal adenocarcinoma cell line, the hormone and neurotransmitter epinephrine, and nicotine, were investigated by cyclic voltammetry, using indium tin oxide (ITO), glassy carbon (GC) and screen printed carbon (SPC) electrodes. The oxidation of the HT-29 cells, previously grown onto ITO or SPC surfaces, followed an irreversible oxidation process that involved the formation of a main oxidation product that undergoes irreversible reduction, as in the epinephrine oxidation mechanism. The effect of nicotine stimulation of the HT-29 cells was also investigated. Nicotine, at different concentration levels 1, 2 and 15 mM, was introduced in the culture medium and an increase with incubation time, 0 to 3h and 30 min, of the HT-29 cells oxidation and reduction peaks was observed. The interaction of nicotine with the HT-29 cells stimulated the epinephrine secretion causing an increase in epinephrine release concentration, and enabling the conclusion that epinephrine and nicotine play an important role in the colorectal tumour growth.

Patient-specific dosimetry for intracavitary 32P-chromic phosphate colloid therapy of cystic brain tumours.

PURPOSE: (32)P-chromic phosphate colloid treatments of astrocytoma and craniopharyngioma cystic brain tumours in paediatric patients are conventionally based on a sphere model under the assumption of uniform uptake. The aims of this study were to determine the distribution of the absorbed dose delivered by (32)P on a patient-specific basis and to evaluate the accuracy with which this can be predicted from a pretherapy administration of (99m)Tc-Sn colloid. METHODS: Three patients were treated with (32)P-chromic phosphate colloid following (99m)Tc-Sn colloid administrations. Convolution dosimetry was performed using pretherapy and posttherapy sequential SPECT imaging, and verified with EGSnrc Monte Carlo radiation transport simulations. Mean absorbed doses to the cyst wall and dose-volume histograms were also calculated and compared with those obtained by the sphere model approach. RESULTS: Highly nonuniform uptake distributions of both the (99m)Tc and (32)P colloids were observed and characterized by dose-volume histograms to the cyst wall. Mean absorbed doses delivered to the cyst wall, obtained with the convolution method, were on average 21 % (SD 18 %) and 50 % (SD 30 %) lower than those predicted by the (99m)Tc distribution and the uniform assumption of the sphere model, respectively. CONCLUSION: Absorbed doses delivered to the cyst wall by (32)P are more accurately predicted from image-based patient-specific convolution dosimetry than from simple sphere models. These results indicate the necessity to perform personalized treatment planning and verification for intracavitary irradiation of cystic brain tumours treated with radiocolloids. Patient-specific dosimetry can be used to guide the frequency and levels of repeated administrations and would facilitate data collection and comparison to support the multicentre trials necessary to progress this therapy.

Interplay between experimental dental pellicles and stannous-containing toothpaste on dental erosion-abrasion.

The interaction between stannous-containing dentifrice slurry and experimentally formed pellicles was investigated on enamel and root dentin using an erosion-remineralization-abrasion cycling model. The remineralizing solutions contained no proteins (negative control), mucin, casein, mucin + casein or albumin, for experimental pellicle formation. Toothbrushing was performed with fluoride toothpaste, with (TP + Sn) and without (TP) 3,500 ppm Sn. TP + Sn reduced surface loss for both enamel and root dentin (p < 0.05). The association between TP + Sn and albumin resulted in a significantly lower enamel surface loss (p < 0.05), suggesting positive interaction of stannous ion and albumin on dental erosion-abrasion protection. A similar trend was observed for root dentin, although less pronounced.

Design and synthesis of (S)- and (R)-enantiomers of [4-(2-hydroxy-1-phenylethylimino)pent-2-ol]dimethyltin(iv) and 2,2-dimethyl-4-phenyl-1,3,2-oxazastannolidine: in vitro antitumor activity against human tumor cell lines and in vivo assay of (S)-enantiomers.

New dimethyltin derived antitumor drug candidates (S)- and (R)-[4-(2-hydroxy-1-phenylethylimino)pent-2-ol]dimethyltin(iv), 1 and (S)- and (R)-[2,2-dimethyl-4-phenyl-1,3,2-oxazastannolidine], 2 derived from (R)- and (S)-enantiomers of [4-(2-hydroxy-1-phenylethylimino)pent-2-ol] and 2-amino-2-phenylethanol, respectively, were synthesized and thoroughly characterized. Preliminary complex-DNA interaction studies employing various optical methods revealed that the (S)-enantiomer displayed a higher propensity towards the drug target DNA double helix. This was quantified by K(b) and K(sv) values of ligands L and L' and (S)-/(R)-1 and (S)-/(R)-2 complexes, which demonstrated a multifold increase in the case of the (S)-enantiomers in comparison to their (R)-enantiomeric forms. This clearly demonstrates the chiral preference of the (S)-enantiomer over the (R)-enantiomer, and its potency to act as a chemotherapeutic agent. Therefore, the in vitro antitumor activity of the (S)-enantiomer of 1 and 2 was evaluated by the sulforhodamine-B (SRB) assay to assess cellular proliferation against five different human cell lines viz., Hop62, DWD, K562, DU145 and MCF-7. The complex (S)-1 displayed a remarkably pronounced and specific activity for K562, while complex (S)-2 exhibited significant activity towards Hop62, DWD, DU145 and MCF-7. The in vivo antitumor activity of (S)-1 and (S)-2 was carried out, which revealed significant regression in human lung tumors.

Conventional and anti-erosion fluoride toothpastes: effect on enamel erosion and erosion-abrasion.

New toothpastes with anti-erosion claims are marketed, but little is known about their effectiveness. This study investigates these products in comparison with various conventional NaF toothpastes and tin-containing products with respect to their erosion protection/abrasion prevention properties. In experiment 1, samples were demineralised (10 days, 6 × 2 min/day; citric acid, pH 2.4), exposed to toothpaste slurries (2 × 2 min/day) and intermittently stored in a mineral salt solution. In experiment 2, samples were additionally brushed for 15 s during the slurry immersion time. Study products were 8 conventional NaF toothpastes (1,400-1,490 ppm F), 4 formulations with anti-erosion claims (2 F toothpastes: NaF + KNO(3) and NaF + hydroxyapatite; and 2 F-free toothpastes: zinc-carbonate-hydroxyapatite, and chitosan) and 2 Sn-containing products (toothpaste: 3,436 ppm Sn, 1,450 ppm F as SnF(2)/NaF; gel: 970 ppm F, 3,030 ppm Sn as SnF(2)). A mouth rinse (500 ppm F as AmF/NaF, 800 ppm Sn as SnCl(2)) was the positive control. Tissue loss was quantified profilometrically. In experiment 1, most NaF toothpastes and 1 F-free formulation reduced tissue loss significantly (between 19 and 42%); the Sn-containing formulations were the most effective (toothpaste and gel 55 and 78% reduction, respectively). In experiment 2, only 4 NaF toothpastes revealed significant effects compared to the F-free control (reduction between 29 and 37%); the F-free special preparations and the Sn toothpaste had no significant effect. The Sn gel (reduction 75%) revealed the best result. Conventional NaF toothpastes reduced the erosive tissue loss, but had limited efficacy regarding the prevention of brushing abrasion. The special formulations were not superior, or were even less effective.