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Biomedical subjects

Y Haikel

Publications and source records attributed to Y Haikel.

At least 19 recordsLinked to original sources
PubMed2006

Polyelectrolyte multilayer film coating and stability at the surfaces of oral prosthesis base polymers: an in vitro and in vivo study.

A new type of coating involving a layer-by-layer technique has been recently reported. This coating is composed of a polyelectrolyte multilayer film that confers specific properties on surfaces to which it is applied. Here, we studied the applicability of such a technique to the coating of oral prostheses, by first testing the construction of polyelectrolyte multilayer films on several polymers used in oral prosthesis bases, and, subsequently, by studying the stability of these coatings in vitro, in human saliva, and in vivo in a rat model. We demonstrated that the multilayered films are able to coat the surfaces of all tested polymers completely, thus increasing their wettability. We also showed that saliva does not degrade the film after 7 days in vitro and after 4 days in vivo. Taken together, our results establish that the layer-by-layer technique is suitable for the coating of oral devices.

Acrylates↗
PubMed2004

Multilayer polyelectrolyte films functionalized by insertion of defensin: a new approach to protection of implants from bacterial colonization.

Infection of implanted materials by bacteria constitutes one of the most serious complications following prosthetic surgery. In the present study, we developed a new strategy based on the insertion of an antimicrobial peptide (defensin from Anopheles gambiae mosquitoes) into polyelectrolyte multilayer films built by the alternate deposition of polyanions and polycations. Quartz crystal microbalance and streaming potential measurements were used to follow step by step the construction of the multilayer films and embedding of the defensin within the films. Antimicrobial assays were performed with two strains: Micrococcus luteus (a gram-positive bacterium) and Escherichia coli D22 (a gram-negative bacterium). The inhibition of E. coli D22 growth at the surface of defensin-functionalized films was found to be 98% when 10 antimicrobial peptide layers were inserted in the film architecture. Noticeably, the biofunctionalization could be achieved only when positively charged poly(l-lysine) was the outermost layer of the film. On the basis of the results of bacterial adhesion experiments observed by confocal or electron microscopy, these observations could result from the close interaction of the bacteria with the positively charged ends of the films, which allows defensin to interact with the bacterial membrane structure. These results open new possibilities for the use of such easily built and functionalized architectures onto any type of implantable biomaterial. The modified surfaces are active against microbial infection and represent a novel means of local host protection.

Adsorption↗
PubMed2004

Immunolocalization of BMP-2/-4, FGF-4, and WNT10b in the developing mouse first lower molar.

Intercellular signaling controls all steps of odontogenesis. The purpose of this work was to immunolocalize in the developing mouse molar four molecules that play major roles during odontogenesis: BMP-2, -4, FGF-4, and WNT10b. BMP-2 and BMP-4 were detected in the epithelium and mesenchyme at the bud stage. Staining for BMP-2 markedly increased at the cap stage. The relative amount of BMP-4 strongly increased from E14 to E15. At E15, BMP-4 was detected in the internal part of the enamel knot where apoptosis was intense. In contrast to TGFbeta1, BMP-2 and -4 did not show accumulation at the epithelial-mesenchymal junction where the odontoblast started differentiation. When odontoblasts became functional, BMP-2 and BMP-4 were detected at the apical and basal poles of preameloblasts. BMP-2, which induces ameloblast differentiation in vitro, may also be involved physiologically. The decrease in FGF-4 from E14 to E15 supports a possible role for the growth factor in the control of mesenchymal cell proliferation. The relative amount of FGF-4 was maximal at E17. The subsequent decrease at E19 showed correlation with the withdrawal of odontoblasts and ameloblasts from the cell cycle. WNT10b might also stimulate cell proliferation. At E14-15, WNT10b was present in the mesenchyme and epithelium except for the enamel knot, where the mitotic activity was very low. At E19 there was a decreasing gradient of staining from the cervical loop where cells divide to the tip of the cusp in the inner dental epithelium where cells become postmitotic. The target cells for FGF-4 and WNT10b appeared different.

Ameloblasts↗
PubMed2000

Expression of mRNAs encoding for alpha and beta integrin subunits, MMPs, and TIMPs in stretched human periodontal ligament and gingival fibroblasts.

The biological mechanisms of tooth movement result from the cellular responses of connective tissues to exogenous mechanical forces. Among these responses, the degradation of the extracellular matrix takes place, but the identification of the molecular basis as well as the components implicated in this degradation are poorly understood. To contribute to this identification, we subjected human fibroblasts obtained from the periodontal ligament (PDLs) and from the gingiva (HGFs) to a continuous stretch to quantify the mRNAs encoding for various metalloproteinases (MMPs), their tissue inhibitors (TIMPs), and alpha and beta integrin subunits. Both cell lines reacted by inducing the expression of the mRNAs encoding for MMP-1, MMP-2, TIMP-1, and TIMP-2, while other mRNAs did not vary (MT1-MMP, TIMP-3) or were not expressed (MMP-9). PDLs expressed selectively the mRNAs encoding for alpha4 and alphav, with no difference measurable under stretching, while the mRNAs encoding for alpha6 and beta1 were increased and the one encoding for alpha5 was decreased. HGFs increased the mRNAs encoding for alpha2, alpha6, beta1, and beta3 and decreased the one encoding for alpha3. Analysis of our data indicated that stretched HGFs and PDLs induced the same pattern of mRNAs encoding for MMPs and TIMPs but differed for those encoding various integrin subunits, known to act as protein receptors in mechanotransduction.

Cells, Cultured↗
PubMed2000

[IgE allergy due to formaldehyde paste during endodontic treatment. Apropos of 4 cases: 2 with anaphylactic shock and 2 with generalized urticaria].

We report 4 cases of allergic reaction to formaldehyde-containing root canal sealant after endodontic care: 2 anaphylactic shocks and 2 local reactions with generalized urticaria. Allergic IgE mediated mechanisms were suggested by the clinical presentation, skin tests and high levels of anti-formaldehyde IgE. These infrequent but potentially severe reactions after canal treatment led us to examine the involved mechanisms, the diagnostic procedure and the possibility of prevention in odontostomatology.

Adult↗
PubMed1999

Dissolution of synthetic hydroxyapatite in the presence of acidic polypeptides.

This article deals with the effect of two acidic polypeptides [polyaspartic acid (PA) and polyglutamic acid (PG)] onto hydroxyapatite (HAP) dissolution by separately considering their influence when they are present only at the HAP interface and when they are both adsorbed and present in the bulk solution. We first determined the amount of adsorbed PA and PG at pH 7.0 and 5.0 onto 10 mg of HAP. Dissolution experiments were performed at pH 5.0 under pH stat conditions by continuously following the consumed protons and released calcium versus time with the aid of specific electrodes. The released phosphate ions were determined by spectrophotometric analysis. The data show that, because of their calcium chelating properties, the polypeptides act as a driving force for HAP dissolution when PA and PG remain present in solution and the interfacial beneficial effect of the adsorbed peptides is erased by the chelating properties of PA and PG present in the solution. When the polypeptides are only adsorbed at the interface, even if a partial PA or PG desorption occurs, HAP dissolution inhibition is still observed.

Adsorption↗
PubMed1999

Aspects of cell proliferation kinetics of the inner dental epithelium during mouse molar and incisor morphogenesis: a reappraisal of the role of the enamel knot area.

First lower E-14 and E-16 mouse molars and E-13 lower incisors were cultured in vitro and either sequentially or continuously labelled with BrdU (5-bromo-2'-deoxyuridine). The behaviour of the non-cycling inner dental epithelial cells emerging from the enamel knot area of the molars was analysed by 3D (three dimensional) reconstructions of serial sections. These cells, as well as slow cycling cells underwent a coordinated temporo-spatial patterning leading to their patchy segregation at the tips of the forming cusps. In incisors (in vitro and in vivo), non-cycling cells were also present in the inner dental epithelium of the enamel knot area. However, these cells were not redistributed during incisor morphogenesis. These non-dividing inner dental epithelium cells of the enamel knot area which are either redistributed or not according to the tooth type specific morphogenesis might represent the organizers of morphogenetic units (OMU), the cusps.

Animals↗
PubMed1994

In vitro efficiency of endodontic irrigation solutions on protein desorption.

The use of irrigating solutions is widely accepted as a necessary adjunct to biomechanical preparation to obtain adequate cleansing of the root canal system. In this study, the efficiency of three solutions was tested in an in vitro experimental system for the removal of protein from apatite surfaces: Salvizol (a bis-dequalinium acetate solution) and sodium hypochlorite at 0.5, 1, 3 and 6% at pH 7.4 and 11.5. Buffered Tris-HCl solutions at pH 7.4 and 11.5 were used as controls. All chemicals showed rapid kinetics effects since no variation of the process could be detected after 5 min. Salvizol was the least efficient solution since it induced only a 2% protein desorption. Sodium hypochlorite efficiency increased with concentration to reach a 70% protein desorption from the apatite surface. In general, alkaline solutions were more efficient than buffered ones, and the ionic strength did not appear to have a major effect on the protein desorption process.

Absorption↗
PubMed1994

The effect of prebrushing mouthrinse solutions on the desorption of albumin from apatite.

This study evaluated the desorption of radiolabelled albumin from synthetic hydroxypatite by 4 commercial prebrushing solutions: Lysoplac (containing chlorhexidine), Plax (sodium benzoate), Acti-Brush (triclosan), and Sanogyl (sodium fluoride). In 3 min, Lysoplac and Plax were found to desorb about 90% of albumin while Acti-Brush and Sanogyl failed to desorb hardly any albumin in 15 min. The desorbing effectiveness of the test solutions was not due to their pH, because when buffer solution was being tested in different ionic strengths at pH range 6-8, it appeared to desorb less than 3% of adsorbed albumin, irrespective of the pH used. The results obtained cannot, however, be directly applied to the clinical situation where much more complex interactions occur than what were tested under the present in vitro conditions.

Adsorption↗
PubMed1992

Critical analysis of an experimental set-up generally used for the permeability evaluation of dental lining material.

The diffusion constants of iodide through dentine membranes were determined. The DI-values were within the range generally obtained by other investigators. When the estimation of the diffusion coefficient through a well defined polycarbonate membrane was calculated the value was strongly affected by the diffusion through the unstirred diffusion layer. By using such an experimental approach it seems necessary to develop a new cell equipped with a double stirring system (one in each compartment) in order to reduce strongly the thickness of the unstirred diffusion layer.

Dental Cavity Lining↗
PubMed1991

Dynamic fracture of hybrid endodontic hand instruments compared with traditional files.

The purpose of this study was to analyze in vitro the dynamic fracture of some endodontic hand instruments. The K file and H file were tested as reference traditional files; the K-Flex, Flexofile, Unifile, and Helifile were tested as newly developed hybrid instruments. The files were mounted in a lathe and rotated with cyclical axial motion in the lumen of a curved tempered steel groove until failure occurred. The results showed that the life span of instruments, the distance between the instrument tip and the rupture point, and the resistance to fracture were dependent on the size and design of the instruments. Moreover, scanning electron microscopic photographs revealed two types of breakage patterns. The K file, H file, Unifile, and Helifile showed a distinct fracture starting point with crack striations and ductile fractures. The K-Flex and Flexofile showed only plastic deformations and axial fissures.

Equipment Failure↗
PubMed1990

Exposure to mercury vapor during setting, removing, and polishing amalgam restorations.

The level of mercury vapors in the oral cavity was determined by analyzing 242 samples of intra-oral air before and after removing, setting, and polishing dental amalgam. The analysis was effected using atomic absorption spectrometry in cold vapors with the detection limit of 6 micrograms/m3. A score of 1 to 3 was assigned to each restoration to adjust the differences of the amalgam sizes. The present study showed that the vapor was released during any procedure: removing, setting, and polishing amalgam. The mean levels were between 85 and 326 micrograms/m3. However, before the restorative procedures, no mercury vapors had been detected in the oral cavity. This investigation has also demonstrated a significant direct correlation between Hg vapor concentrations in intra-oral air and the sizes of amalgam restorations during each procedure: removing, setting, and polishing. The statistic analysis showed no significant difference of mercury vapors in the oral cavity between the use or nonuse of water coolant during the amalgam polishing.

Air↗
PubMed1989

Periodontal treatment needs in populations of high- and low-fluoride areas of Morocco.

The purpose of this study was to determine the periodontal status and treatment needs, using the CPITN index, in a population aged 7 to 60 years residing in the fluorosis area of Khouribga and the non-fluorosis area of Beni-Mellal, Morocco. A total of 2378 subjects was studied. In the youngest age groups, more subjects and sextants from Khouribga than from Beni-Mellal were free of periodontal diseases. Conversely, in Beni-Mellal, subjects in the youngest age groups presented a higher mean number of sextants with calculus than those from Khouribga. In combining the 2 areas, 1.3% of the 2319 dentate subjects examined needed no treatment and 98.7% needed at least oral hygiene instructions (TN1). The present study, based on the CPITN index, demonstrated in both areas a high prevalence of gingivitis, and a relatively low prevalence of deep pocketing, occurring on the average in less than half a sextant in the total populations.

Adolescent↗
PubMed1989

The effects of airborne fluorides on oral conditions in Morocco.

The purpose of this study was to determine the prevalence and severity of dental caries and dental fluorosis, as well as various other oral conditions, in 2378 subjects (ages seven to 60) living in the fluoridated area of Khouribga and the non-fluoridated area of Beni Mellal, Morocco. The community index of dental fluorosis (CFI) ranged from 1.99 to 2.80 in the high-fluoride area: Over 90% of the population was affected, and more than one-third of the subjects showed moderate dental fluorosis. However, in Beni Mellal, more than 96% of the dentate subjects examined were free of dental fluorosis, and the CFI of 0.02 was considered not significant. Significant differences were observed between the two areas with respect to caries prevalence. DMFT and DMFS indices were markedly lower in the fluorosis area of Khouribga. The oral conditions of subjects appeared to be better in Khouribga, where the gingival and calculus indices were significantly lower than in Beni Mellal. The analyses of covariance showed no significant differences in plaque accumulation (PI) between the Khouribga and Beni Mellal samples. However, a close statistical correlation was found between PI and GI in Beni Mellal and Khouribga.

Adolescent↗
PubMed1989

[Magnetic resonance imaging and dentistry].

At the present time, the research in and the utilization of magnetic resonance imaging in odontostomatology remains limited. It appeared interesting to access the advances made in this technic and to attempt an evaluation of the longrange perspectives of MRI in this field. In order to more clearly understand the images produced by this technic, the principles of nuclear magnetic resonance are summarized, followed by an account of the principle applications with respect to the buccal cavity and the temporo-mandibular joints. Studies showing the influence of different alloys used in dentistry on the quality of the nuclear magnetic images remain for the moment, rather limited. MRI of the oropharyneal area permits a glimpse of interesting perspectives such as the detection of tumorous lesions or the visualization of meniscus of the TMJ. Nevertheless, three factors constitute considerable obstacles in the broad utilization of MRI in the field of odontostomatology: the time lapse of image production, the relatively limited special resolution and finally the prohibitive cost of examinations.

Dental Alloys↗