634 research outputs found
Novel Confocal-Laser-Scanning-Microscopy and conventional measures investigating eroded dentine following dentifrice dab-on and brushing abrasion
Objectives
To validate novel non-contacting Confocal-Laser-Scanning-Microscopy (CLSM) methodology with conventional Contacting Profilometry (CP) measures investigating brushing or dab-on of stannous-fluoride dentifrice on early aggressive dentine erosion.
Methods
75 polished human dentine samples were prepared and eroded in agitated 6% citric acid then randomly allocated into 5 intervention groups; artificial saliva control (1); controlled use of a pressure sensitive counter-rotating oscillatory powered toothbrush with sodium-fluoride NaF (2) or stannous-fluoride SnF2 (3), and dab-on application of NaF (4) or SnF2 (5). Samples underwent three cycles of intervention and 2-min agitated 6 % citric acid challenges. CLSM images were taken and 3D reconstructions produced of step height using a developed software algorithm. In addition, 20 % samples were randomised and profiled using CP to measure step height and surface roughness. Vickers's diamond micro-hardness testing was carried out on all samples.
Results
Comparing CLSM and CP; Pearson correlation was 0.77 and Intra-class correlation 0.81 (p = 0.01). There were no significant statistical differences in step height between groups using both CLSM and CP. From baseline, SnF2 brushing (3) increased micro-hardness more than control (1) (p = 0.03), NaF (4) and SnF2 dab-on (5) (p ≤ 0.001), and increased surface roughness more than control (p = 0.02), NaF brushing (2) and NaF dab-on (4) (p ≤ 0.017). Dab-on of SnF2 (5) produced rougher surfaces than control (1) (p = 0.014) and reduced hardness compared with NaF brushing (p = 0.04).
Conclusions
Good agreement and correlation exists between CLSM and CP measures in dentine. There were no significant differences in surface loss after interventions between groups. Compared with control, SnF2 application increased dentine surface roughness and SnF2 controlled powered brushing application increased dentine hardness, likely caused by exposure of uneroded dentine.
Clinical significance
Isosurfaces produced using CLSM can be used to represent dentine step height loss. They show good correlation and agreement with conventional CP measures, following early aggressive erosion-abrasion cycles of dentine. The CLSM and computer algorithm therefore provides an accurate, standalone and non-contacting three-dimensional measurement of early dentine wear. Stannous-fluoride brushing, and dab-on application offer no benefits following early aggressive erosion in dentine. To reduce dentine wear, limiting erosive challenges and avoiding brushing post-erosion is advised
Basic Erosive Wear Examination (BEWE): a new scoring system for scientific and clinical needs
A new scoring system, the Basic Erosive Wear Examination (BEWE), has been designed to provide a simple tool for use in general practice and to allow comparison to other more discriminative indices. The most severely affected surface in each sextant is recorded with a four level score and the cumulative score classified and matched to risk levels which guide the management of the condition. The BEWE allows re-analysis and integration of results from existing studies and, in time, should initiate a consensus within the scientific community and so avoid continued proliferation of indices. Finally, this process should lead to the development of an internationally accepted, standardised and validated index. The BEWE further aims to increase the awareness of tooth erosion amongst clinicians and general dental practitioners and to provide a guide as to its management
Metallicity Estimation of Core-Collapse Supernova Environments within 30 Mpc
This thesis researches the local metallicities of environments of Type IIP, Type Ib and Type Ic supernovae (SNe), within a luminosity distance of 30 Mpc, by long-slit spectroscopy. During the runtime of the project 76 targets out of a sample of 110 selected targets could be observed at the Isaac Newton Telescope (INT) on La Palma. For 66 observed targets the metallicities could be measured by the N2 and O3N2 strong emission line methods, using calibrations of Pettini and Pagel (2004, PP04) and Marino et al. (2013, M13). The PP04 mean values of the local metallicities are about 8.62 dex. The metallicities by M13 are about 0.1 dex less. No significant differences between the means of the three SN types have been found. The sample of the INT observations has been extended by the results of previous work of 46 targets meeting the selection criteria of the project. Again, no significant differences between the means of the three SN types have been found. Normalised cumulative distribution functions (CDFs) of the metallicities of the three SN types are presented. Type Ib and Ic distributions tend to higher metallicity than Type IIP, however Type Ic SNe are also present at lower metallicities whereas Type Ib SNe are not. The Type Ib distribution is narrower than both the Ic and IIP distributions. The Kolmogorov-Smirnov test as well as the Anderson-Darling test indicates no statistical significance for a difference in the local metallicities of the three SN types. The narrow CDFs of Type Ib SNe give some evidence for a significant fraction of single massive progenitor stars, whilst the low metallicity of Type Ic suggests a significant fraction of compact binary progenitors. More observational data and additional statistical tests such as Monte Carlo simulation by future work are required to further constrain the progenitor stars of Type Ib,c SNe
Application of cerium chloride to improve the acid resistance of dentine
OBJECTIVE: To investigate the effect of cerium chloride, cerium chloride/fluoride and fluoride application on calcium release during erosion of treated dentine. METHODS: Forty dentine samples were prepared from human premolars and randomly assigned to four groups (1-4). Samples were treated twice a day for 5 days, 30s each, with the following solutions: group 1 placebo, group 2 fluoride (Elmex fluid), group 3 cerium chloride and group 4 combined fluoride and cerium chloride. For the determination of acid resistance, the samples were consecutively eroded six times for 5 min with lactic acid (pH 3.0) and the calcium release in the acid was determined. Furthermore, six additional samples per group were prepared and used for EDS analysis. SEM pictures of these samples of each group were also captured. RESULTS: Samples of group 1 presented the highest calcium release when compared with the samples of groups 2-4. The highest acid resistance was observed for group 2. Calcium release in group 3 was similar to that of group 4 for the first two erosive attacks, after which calcium release in group 4 was lower than that of group 3. Generally, the SEM pictures showed a surface coating for groups 2-4. No deposits were observed in group 1. CONCLUSION: Although fluoride showed the best protective effect, cerium chloride was also able to reduce the acid susceptibility of dentine significantly, which merits further investigation
Poly(alkyl methacrylate) tooth coatings for dental care: evaluation of the demineralisation-protection benefit using a time-resolved in vitro method
An in vitro method for the time-resolved quantification of acid-mediated tooth demineralisation has been developed and evaluated against putative non-permanent protective formulations based on a series of poly(alkyl methacrylate)s. Using a thermostatted carousel, dentally relevant substrates consisting of hydroxyapatite discs or sections of bovine teeth have been exposed to aqueous citric acid under controlled conditions, before and after being treated with the polymeric coatings. The dissolution of phosphate was monitored by the determination of 31P by Inductively Coupled Plasma—Mass Spectrometry and by the spectrophotometric phosphovanadomolybdate method. Dose-response plots constructed for both groups of treated substrates have revealed that the coatings significantly reduce erosion rates but are less effective at inhibiting tooth demineralisation than the standard fluoride treatment. The approach has enabled an evaluation of the erosion-protection efficiency of each coating
Clinical Study Monitoring the pH on Tooth Surfaces in Patients with and without Erosion
The aim of this study was to compare tooth surface pH after drinking orange juice or water in 39 patients with dental erosion and in 17 controls. The following investigations were carried out: measurement of pH values on selected tooth surfaces after ingestion of orange juice followed by ingestion of water (acid clearance), measurement of salivary flow rate and buffering capacity. Compared with the controls, patients with erosion showed significantly greater decreases in pH after drinking orange juice, and the pH stayed lower for a longer period of time (p < 0.05). Saliva parameters showed no significant differences between the two patient groups except for a lower buffering capacity at pH 5.5 in the erosion group
Effect of a chitosan additive to a Sn2+-containing toothpaste on its anti-erosive/anti-abrasive efficacy—a controlled randomised in situ trial
Objectives: It is well known that Sn2+ is a notable anti-erosive agent. There are indications that biopolymers such as chitosan can enhance the effect of Sn2+, at least in vitro. However, little information exists about their anti-erosive/anti-abrasive in situ effects. In the present in situ study, the efficacy of Sn2+-containing toothpastes in the presence or absence of chitosan was tested. Methods: Ten subjects participated in the randomised crossover study, wearing mandibular appliances with human enamel specimens. Specimens were extraorally demineralised (7days, 0.5% citric acid, pH 2.6; 6 × 2min/day) and intraorally exposed to toothpaste suspensions (2 × 2min/day). Within the suspension immersion time, one half of the specimens were additionally brushed intraorally with a powered toothbrush (5s, 2.5N). Tested preparations were a placebo toothpaste (negative control), two experimental toothpastes (F/Sn = 1,400ppm F−, 3,500ppm Sn2+; F/Sn/chitosan = 1,400ppm F−, 3,500ppm Sn2+, 0.5% chitosan) and an SnF2-containing gel (positive control, GelKam = 3,000ppm Sn2+, 1,000ppm F−). Substance loss was quantified profilometrically (μm). Results: In the placebo group, tissue loss was 11.2 ± 4.6 (immersion in suspension) and 17.7 ± 4.7 (immersion in suspension + brushing). Immersion in each Sn2+-containing suspension significantly reduced tissue loss (p ≤ 0.01); after immersion in suspension + brushing, only the treatments with GelKam (5.4 ± 5.5) and with F/Sn/chitosan (9.6 ± 5.6) significantly reduced loss [both p ≤ 0.05 compared to placebo; F/Sn 12.8 ± 6.4 (not significant)] Conclusion: Chitosan enhanced the efficacy of the Sn2+-containing toothpaste as an anti-erosive/anti-abrasive agent. Clinical relevance: The use of Sn2+- and chitosan-containing toothpaste is a good option for symptomatic therapy in patients with regular acid impacts
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