796 research outputs found
Effect of Conventional Mouthrinses on Initial Bioadhesion to Enamel and Dentin in situ
Aim: The study aimed to investigate the effect of a customary fluoride solution, containing sodium fluoride and amine fluoride, on initial biofilm formation on enamel and dentin in situ compared directly to chlorhexidine.
Methods: Bovine enamel and dentin specimens were mounted on maxillary splints carried by 9 subjects. After 1 min of pellicle formation, rinses with tap water (control), chlorhexidine (meridol med CHX 0.2%, GABA) and a fluoride mouthrinse (elmex, GABA) were performed for 1 min. Subsequently, the slabs were carried for another 8 h. The adherent bacteria were determined by DAPI staining, live-dead staining and determination of colony-forming units after desorption; glucan formation was visualized with concanavalin A. Additionally, energy-dispersive X-ray spectroscopy (EDX) analysis of the in situ biofilm layers was conducted, and contact angle measurements were performed. Statistical evaluation was performed by means of the Kruskal-Wallis test followed by the Mann-Whitney U test (p < 0.05).
Results: In the control group, significantly higher amounts of adherent bacteria were detected on dentin (4.8 x 10ⶠ± 5.4 x 10ⶠbacteria/cmÂČ) than on enamel (1.2 x 10ⶠ± 1.5 x 10ⶠbacteria/cmÂČ , DAPI). Chlorhexidine significantly reduced the amount of adherent bacteria (dentin: 2.8 x 10┠± 3.4 x 10â” bacteria/cmÂČ ; enamel: 4.2 x 10┠± 8.7 x 10â” bacteria/cmÂČ). Rinses with the fluoride solution also significantly reduced bacterial adherence to dentin (8.1 x 10┠± 1.5 x 10ⶠbacteria/cmÂČ). Fluoride could not be detected by EDX analysis of the biofilms. Fluoride mouthrinsing did not influence the wettability of the pellicle-covered enamel surface.
Conclusion: In addition to the reduction of demineralization and antibacterial effects, fluorides inhibit initial biofilm formation on dental hard tissues considerably, especially on dentin
Diffusion of peroxides through dentine in vitro with and without prior use of a desensitizing varnish
Different bleaching regimens are used in dentistry possibly penetrating the dentine and affecting the pulp. The aim of the present study was to investigate peroxide diffusion through dentine pre-treated with a desensitizing varnish (VivasensÂź) in a standardized in vitro setup during application of different bleaching materials. The penetration was tested using 1.3-mm-thick bovine dentine slabs. The following bleaching materials were tested with and without prior application of the desensitizing varnish on the external side of the dentine slabs: Vivastyle, Whitestrips, Simply White, Opalescence (external bleaching), and sodium perborate (internal bleaching, only tested without varnish; nâ=â8 samples per subgroup). The penetration of peroxides was measured photometrically using 4-aminoantipyrin as a substrate, the penetration of peroxides was monitored over 240Â min. All bleaching agents yielded a diffusion of peroxides through the dentine, the kinetics of penetration were approximately linear for all materials tested. The significantly highest diffusion of peroxides was observed with Opalescence, the lowest with sodium perborate. The adoption of the desensitizing varnish reduced the diffusion of peroxides significantly for all external bleaching materials. Peroxides penetrated the dentine during application of bleaching materials; the penetration of peroxides can be reduced by application of a desensitizing agent
Inferential models: A framework for prior-free posterior probabilistic inference
Posterior probabilistic statistical inference without priors is an important
but so far elusive goal. Fisher's fiducial inference, Dempster-Shafer theory of
belief functions, and Bayesian inference with default priors are attempts to
achieve this goal but, to date, none has given a completely satisfactory
picture. This paper presents a new framework for probabilistic inference, based
on inferential models (IMs), which not only provides data-dependent
probabilistic measures of uncertainty about the unknown parameter, but does so
with an automatic long-run frequency calibration property. The key to this new
approach is the identification of an unobservable auxiliary variable associated
with observable data and unknown parameter, and the prediction of this
auxiliary variable with a random set before conditioning on data. Here we
present a three-step IM construction, and prove a frequency-calibration
property of the IM's belief function under mild conditions. A corresponding
optimality theory is developed, which helps to resolve the non-uniqueness
issue. Several examples are presented to illustrate this new approach.Comment: 29 pages with 3 figures. Main text is the same as the published
version. Appendix B is an addition, not in the published version, that
contains some corrections and extensions of two of the main theorem
Hydroxyapatite-Based Solution as Adjunct Treatment for Biofilm Management: An In Situ Study
Synthetic hydroxyapatite-based solution is a bioinspired material that may present antiadhesive properties, restraining the dental biofilm formation without causing adverse effects. This
in situ study aims to evaluate the effects of three different hydroxyapatite (HAP) watery solutions
as a mouthwash against biofilm adhesion on different dental material surfaces under oral conditions. Hence, four volunteers carried maxillary splints containing enamel, titanium, ceramics, and
polymethyl-methacrylate resin (PMMA) samples. Three HAP watery solutions (5%) were prepared
with HAP particles presenting different shapes and sizes (HAP I, HAP II, HAP III). During 24 h, the
volunteers rinsed two times with one of the following selected tested solution: HAP I, HAP II, HAP
III, water, or chlorhexidine 0.2% (CHX). The first rinse was performed 3 min after pellicle formation;
the second rinse occurred after a 12 h interval. The surface analysis was performed by scanning
electron microscopy (SEM), fluorescence microscopy (FM), and transmission electron microscopy
(TEM). Statistical and microscopic analysis showed that most samples treated with any HAP solution
revealed reduced biofilm coverage presenting comparable results to CHX treated samples, however
without altering the microorganismsâ viability. In conclusion, the results of this investigation showed
that a pure hydroxyapatite-based mouthrinse could be a promising bioinspired adjunct solution for
biofilm management
Joint and individual analysis of breast cancer histologic images and genomic covariates
A key challenge in modern data analysis is understanding connections between
complex and differing modalities of data. For example, two of the main
approaches to the study of breast cancer are histopathology (analyzing visual
characteristics of tumors) and genetics. While histopathology is the gold
standard for diagnostics and there have been many recent breakthroughs in
genetics, there is little overlap between these two fields. We aim to bridge
this gap by developing methods based on Angle-based Joint and Individual
Variation Explained (AJIVE) to directly explore similarities and differences
between these two modalities. Our approach exploits Convolutional Neural
Networks (CNNs) as a powerful, automatic method for image feature extraction to
address some of the challenges presented by statistical analysis of
histopathology image data. CNNs raise issues of interpretability that we
address by developing novel methods to explore visual modes of variation
captured by statistical algorithms (e.g. PCA or AJIVE) applied to CNN features.
Our results provide many interpretable connections and contrasts between
histopathology and genetics
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