[A study on the vascular permeability of the periodontal membrane in relation to tooth movement (author's transl)].
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Animals↗
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Results for “Tooth Permeability”
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Dentin permeability: effects of crown preparation.
Sequential crown reductions of extracted human teeth were made to evaluate both regional differences in dentin permeability and the effects of tooth reduction. Two different methods of tooth reduction were used. In group 1, tooth reduction was nonuniform but was done in a manner similar to conventional crown preparations. Maximum, total crown permeability was measured using a pressurized fluid filtration technique after removing the smear layer. Regional reductions in permeability were accomplished by creating smear layers on mesial, distal, buccal, lingual, and occlusal surfaces sequentially. Between each step, changes in dentin permeability were measured. In group 2, tooth reductions were uniform and regional permeability was reduced by localized application of potassium oxalate. Both methods demonstrated increased permeability of dentin as the prepared surfaces approached the pulp chamber. Generally, the mesial surfaces were more permeable than the distal surfaces. The occlusal and lingual surfaces were the least permeable regions.
Adult↗
Should etching be performed as a part of a vital bleaching technique?
Many clinicians advocate etching the teeth before vital bleaching as a way to enhance the permeability of the tooth surface to hydrogen peroxide and thus to enhance the bleaching effect. However, no studies have been published to date to document the effect of etching on vital bleaching. In this study, ten patients received a bleaching treatment regimen of several appointments. Half of the teeth in one arch of each patient were etched with phosphoric acid for 20 seconds before they were bleached with 35% hydrogen peroxide. The teeth in the other half of the same arch were treated with tap water prior to bleaching. Evaluations of the patients after 3 and 6 weeks failed to confirm any enhanced lightening effect from etching.
Acid Etching, Dental↗
Reversible azide inhibition of water influx into individual radish root-hair cells.
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Azides↗
Detection of lead in human teeth by exposure to aqueous sulfide solutions.
A recent study has shown that the presence of lead (Pb) as well as other base metals in esthetic restorative materials, especially dental cements, is detectable by color shifts induced by exposure of hardened specimens to a 0.1% (w/v) aqueous solution of sodium sulfide, Na2S. The present study was initiated to determine the applicability of this simple exposure test to the detection of Pb in human teeth. Extracted whole teeth as well as sectioned, thin specimens were exposed first to either a 0.01% or a 0.001% (w/v) aqueous solution of lead nitrate, Pb (NO3)2, at 37 degrees C for 24 h. After rinsing with distilled H2O and a subsequent 24 h exposure to the 0.1% Na2S solution at 37 degrees C, the tooth specimens were examined visually and by a dental color analyzer for color changes. The latter color measurements were evaluated by the Lab system of Hunter, and the color difference, delta E, was determined. Neither control specimens exposed to distilled H2O only or to 0.1% Na2S only exhibited any significant change in appearance after 24 h of storage at 37 degrees C. However, specimens exposed first to the Pb (NO3)2 solutions showed discernible delta E values after exposure to the Na2S solution. Delta E was greatest for specimens exposed to the more concentrated Pb (NO3)2 solution. Most of the discoloration in both thin and intact tooth specimens was confined to the outermost layers of the tooth structure. For the intact specimens, the greatest degree of discoloration occurred in the cementum, the most permeable part of the tooth structure.
Adult↗
Measurement of the permeability of dental enamel and its variation with depth using an electrochemical method.
To investigate the permeability of the dental enamel of erupted and unerupted human pre-molars and its variation with depth, we determined the resistivity of successive 100-micron-thick layers. The electrical resistance of halved tooth crowns at zero Hertz, which according to Scholberg et al. (1982, 1984) is inversely related to the permeability, was measured before and after removal of successive enamel layers from the outer surface toward the dentino-enamel junction (D.E.J.). The resistivity of the successive enamel layers increased from the D.E.J. toward the outer surface in approximately the same way in erupted as well as in unerupted pre-molars, except within the outermost layer of 100 to 200 microns thickness. The resistivity of this layer in erupted pre-molars was considerably higher than that in unerupted pre-molars, which may be due to post-eruptive mineralization.
Adolescent↗
Demineralization and remineralization evaluation techniques--added considerations.
Methods used for the analysis of tooth de- and remineralization include techniques with various degrees of sophistication and quantitative capabilities, ranging from direct measures of mineral gain/loss (e.g., microradiography) to indirect measures (e.g., iodide permeability) of changes in tooth mineral properties. In all instances, the capabilities of methods for accurate determination of changes in tooth mineral properties are affected by procedures used in the preparation of specimens for analysis, the magnitude of change taking place in the test (vs. the detection limits of the techniques), and protocols for specimen analysis. In specific instances, such as in the case of dentin, unique specimen-handling and analysis procedures must be used to prevent artifacts. The choice of techniques for the assessment of de- and remineralization depends strongly upon study protocols and laboratory capabilities; however, 'quantitative' measures of mineral gain and loss are possible only if direct chemical or radiographic techniques are used. Either radiographic, cross-sectioned microhardness or polarized light can be used for the determination of lesion depth. Porosity, light-scattering, and surface microhardness are indirect techniques which complement direct measures of mineral gain and loss. Whatever methods are used in the analysis of de- and remineralization, researchers must take care to differentiate accurately among the quantitative capabilities of techniques used in analysis.
Dental Enamel↗
Effects of fibrinogen in vivo on dentine permeability in the dog.
Dentine permeability measurements were made each hour for 6 h in tooth cavities prepared in control dogs or dogs which had been pretreated with a purified fraction of snake venom to deplete their plasma of fibrinogen. The control dogs exhibited a progressive fall in dentine permeability (approximately 50 per cent reduction in 6 h); the permeability in the fibrinogen-depleted dogs only fell 15 per cent in 6 h. The results implicate plasma proteins, particularly high molecular-weight proteins such as fibrinogen, as agents which reduce dentine permeability in vivo.
Animals↗
Tissue-engineered hybrid tooth and bone.
Tooth loss accompanied by alveolar bone resorption presents a significant clinical problem. We have investigated the utility of a tissue-engineering approach to provide corrective therapies for tooth-bone loss. Hybrid tooth-bone tissues were bioengineered as follows. Tooth implants were generated from pig third molar tooth bud cells seeded onto polyglycolide (PGA) and polyglycolide-colactide (PLGA) scaffolds, and grown for 4 weeks in the omenta of adult rat hosts. Bone implants were generated from osteoblasts induced from bone marrow progenitor cells obtained from the same pig, seeded onto PLGA fused wafer scaffolds, and grown for 10 days in a rotational oxygen-permeable bioreactor system. The tooth and bone implants were harvested, sutured together, reimplanted, and grown in the omenta for an additional 8 weeks. Histological and immunohistochemical analyses of the excised hybrid tooth-bone constructs revealed the presence of tooth tissues, including primary and reparative dentin and enamel in the tooth portion of hybrid tooth-bone implants, and osteocalcin and bone sialoprotein-positive bone in the bone portion of hybrid tooth-bone constructs. Collagen type III-positive connective tissue resembling periodontal ligament and tooth root structures were present at the interface of bioengineered tooth and bone tissues. These results demonstrate the utility of a hybrid tooth-bone tissue-engineering approach for the eventual clinical treatment of tooth loss accompanied by alveolar bone resorption.
Animals↗
The epithelial attachment and the dental junctional epithelium: ultrastructural features in porcine molars.
The region of epithelial apposition with a tooth surface is the site of an unusual stratified integument, the junctional epithelium, which combines tight attachment to the tooth, cell turnover, tissue permeability, and epithelial versatility into the first line of defense against periodontal destruction by oral pathogens. To better understand the structure and function of the junctional epithelium we have reviewed its developmental and cell biology, and undertaken a multidisciplinary analysis of its composition in the pig, an omnivore whose dietary and dental development and occlusion patterns are similar to the human condition, and which, because of its size, is more readily amenable to experimental manipulation. The porcine junctional epithelium was also compared with this well-described epithelium in the rat. Morphological analyses by light microscopy and scanning and transmission electron microscopy showed the porcine junctional epithelium and epithelial attachment were similar to that in the rat except that apically, extracellular matrix lamellae associated with the internal basal lamina were more complex, and more coronally there was extensive layering of a dental cuticle-like material. Biochemical analysis of the porcine junctional epithelium by dissociative extraction and SDS-PAGE revealed the presence of some proteins not present in gingival epithelium. Together, these studies show that the porcine junctional epithelium has predictable morphological and biochemical features which establish the pig as an advantageous model to study the basic and clinical biology of this unique epithelium.
Animals↗
A comparison between the occluding effects of the Nd:YAG laser and the desensitising agent sensodyne on permeation through exposed dentinal tubules of endodontically treated teeth: an in vitro study.
OBJECTIVE: Dentine hypersensitivity may occur due to loss of covering enamel and/or loss of cementum after gingival recession, resulting in exposure of cervical dentine and patency of dentinal tubules. The effect of thermally cooled pulsed neodymium:yttrium-aluminium-garnet (Nd:YAG) laser on the permeability and structural appearance of the root canal wall was investigated in vitro. The aim of this study was to compare the occluding effect of Nd:YAG laser with that of sensodyne on exposed dentine. MATERIAL AND METHODS: Forty freshly extracted human maxillary anterior teeth were collected at random. Root canal obturations were performed using master apical file no. 60 k-type for obturated teeth. All teeth were stored in 100% humidity at 37 degrees C for 48h to allow time for the sealer to set. Dentine of 35 teeth was exposed by removing the cementum, and the remaining five teeth represented a negative control group. Specimens were examined using stereomicroscopy to show the surface topography of the dentine substrate before and after treatment with Nd:YAG laser or sensodyne. RESULTS: A double-blind technique was used when taking measurements of ink penetration (in mm) for each group. Teeth treated by Nd:YAG laser showed the least ink penetration, followed by teeth treated by sensodyne. The positive control group demonstrated complete ink penetration and the negative control group showed no ink penetration. Stereomicroscopic examination of specimens treated with Nd:YAG laser showed deposition on the dentinal surface, and specimens treated with sensodyne showed partial deposition. Untreated specimens were free of deposition and the tubules remained patent. CONCLUSION: There is no significant difference in the occluding effect of Nd:YAG laser and sensodyne toothpaste. Both treatments have a promising effect on the reduction of permeation through exposed dentinal tubules. However, the occluding effect of Nd:YAG laser occurs within seconds whereas that of sensodyne takes at least 3 weeks.
Analysis of Variance↗
[Permeability of fluoride-treated teeth to uranium salts].
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Fluorides↗
[Endosseous integrated implantation: multiple post-extraction implantationing threaded cyclindric titanium. Use of a semipermeable reabsorbable membrane].
On the basis of their experience of postextractive oral grafts, the authors examine all the surgical possibilities of this technique, at times using osteoinducing materials or at others semipermeable reabsorbable membrane; on other occasions an ostroinducing material associated with reabsorbable membrane is used to stimulate piloted regeneration of underlying bone tissue. Although not widely used, the post-extractive technique is presented as a fascinating reality that certainly, if used with due care, produces satisfactory and gratifying results. The authors are convinced that the contribution to simplifying surgical procedures and the reduced number of sessions that a patient has to undergo is without doubt a considerable advantage. In fact, using the postextractive technique with reabsorbable membrane the patient only undergoes a single operation. The authors have experience of three hundred post-extractive grafts with a very low failure rate (loss of seven grafts). These results can be attributed to clear rules: respect for antisepsis precautions, minimum surgery involving bone tissue, design of access flap to bone arch, positioning of fixture in correct spatial and occlusal direction, instant graft stability and perioplantar bone neoformation free of interference. The use of grafts has become a routine technique and is a valid alternative to prosthetic rehabilitation stages. It has become a true field with precise characteristics in the context of modern dentistry.
Adult↗
Clinical considerations of microleakage.
Most dental materials permit the microleakage of bacteria and bacterial products from oral fluids to reach dentin. Thus, an understanding of the clinical consequences of microleakage demands that we analyze the permeability characteristics of dentin. The more dentin surface that is exposed during tooth preparation, the greater the potential for microleakage. Thicker dentin is less permeable than thin dentin. Dentin over pulp horns is more permeable than central dentin. Similarly, the dentin making up axial walls is more permeable than dentin forming the pulpal floor of cavities. Coronal dentin is much more permeable than root dentin. In addition to the number of tubules per unit area, tubule diameter, and the location of the dentin in a tooth, another extremely important variable is the presence or absence of a smear layer. When smear layers are created, grinding debris are forced into each tubule to form a smear plug. Smear plugs are usually 1- to 2-microns long but may be 10-microns long. They are much longer than the smear layer thickness and they reduce dentin permeability more than the overlying smear layer. Smear layers constitute a natural cavity liner that reduces the permeability of dentin far more than any cavity varnish. However, its presence limits the strength of dentin bonding agents because of the relatively low cohesive forces holding the smear layer together and to dentin. If it is removed, the bond strengths of dentin adhesive resins increases, but removal also increases the potential liability for pulpal inflammation if the bond is not uniformly perfect.(ABSTRACT TRUNCATED AT 250 WORDS)
Dental Cements↗
Permeability of normal versus carious dentin.
Although a number of reports have been published demonstrating that carious dentin is less permeable than normal dentin, these reports have been qualitative rather than quantitative. The purpose of this in vitro study was to apply a quantitative technique to the study of the permeability of carious human teeth before and after excavation, before and after removal of the smear layer and before and after preparation of a control cavity of similar size and depth in normal dentin subjected to the same measurements, for comparative purposes. Dentin permeability was measured as a hydraulic conductance. The permeability values measured at each step in the protocol were expressed as a percent of the maximum permeability of both cavities, permitting each tooth the serve as its own control. Carious lesions exhibited a slight degree of permeability (2.3 +/- 0.6% of controls) which remained unchanged after excavation of the lesions. Removal of the smear layer in the excavated carious lesions increased the permeability significantly to 6.9 +/- 3.2%. Preparation of a control cavity of the same area and depth increased the permeability slightly. Removal of its smear layer increased the permeability of the dentin 91%. These results confirm previous qualitative studies that carious dentin, even after excavation and removal of the smear layer has a very low permeability.
Acid Etching, Dental↗
Diffusion in mammalian tooth enamel in relation to the caries process.
For the rate of demineralization of enamel during caries, three physicochemical processes are of importance: the diffusion into and out of the enamel, the dissolution of mineral and the complexation of ions. The interpretation of diffusion experiments in conjunction with artificial caries experiments and computer simulations is described. In the caries process, relevant diffusion coefficients of small ions and molecules are of the order of magnitude 10(-9)--10(-7) cm2 s-1.
Animals↗
Changes in permeability caused by connexin 32 mutations underlie X-linked Charcot-Marie-Tooth disease.
The relationship between the loss of connexin 32 function and clinical manifestations of X-linked Charcot-Marie-Tooth (CMTX) disease is unknown. Here, we report that eight of nine CMTX mutations investigated form channels with measurable electrical conductance. Single-channel studies of two mutations demonstrate reduced junctional permeability caused by a decrease in either pore size (S26L) or open channel probability (M34T) that favors residency in a low-conductance substate. Permeation of second messengers such as cAMP through reflexive gap junctions between adjacent cytoplasmic loops of myelinating Schwann cells is likely to be reduced or absent in these channels. We propose that CMTX mutations impair the transduction of signals arising from normal glial-neuronal interactions and thereby cause demyelination and axonal degeneration.
Animals↗