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PubMed1989

[Effects of sealing of dentinal tubules of root canal wall with Ag (NH3)2F (3.8%) solution].

In this study, in order to determine a method for obtaining a good reaction, the reactive products of 3.8% Ag (NH3)2F, using formalin as a reducing agent, were studied. Saforide RC was used as the 3.8% Ag (NH3)2F solution and 10% neutral formalinsolution was used as a reducing agent. The silver mirror test and reaction products on the root canal wall were investigated under the scanning electron microscope, along with observation of dye penetration using a stereoscopic microscope. Reaction of periapical tissue to the materials was studied histologically in dogs. In the natural reduction group, less amounts of reactive products were seen, and sealing of the dentinal tubules of the root canal wall was inadequate. In the formalin reduction group, large amounts of reactive products were found, and the dentinal tubules of the root canal wall were sealed. CaF2, Ag3PO4, Ag2O and Ag were identified as reactive products. In the natural production groups, obstruction was present but incomplete. In Formalin groups, dye osmosis obstruction was recognized. No harmful action of the solution on the surrounding tissue of the dog's tooth was recognized.

Ammonium Compounds↗
PubMed2006

Selective defects in channel permeability associated with Cx32 mutations causing X-linked Charcot-Marie-Tooth disease.

The X-linked form of Charcot-Marie-Tooth disease (CMTX) is caused by mutations in connexin32 (Cx32), a gap junction protein expressed by Schwann cells where it forms reflexive channels that allow the passage of ions and signaling molecules across the myelin sheath. Although most mutations result in loss of function, several studies have reported that some retain the ability to form homotypic intercellular channels. To gain insight into the molecular defect of three functional CMTX variants, S26L, Delta111-116 and R220stop, we have used several fluorescent tracers of different size and ionic charge to compare their permeation properties to those of wild-type Cx32. Although all mutations allowed the passage of the dye with the smallest molecular mass, they exhibited a clear reduction in the permeability of either one or all of the probes with respect to wild-type channels, as assessed by the percentage of injections showing dye coupling. These data reveal that a lower size cutoff distinguishes these functional CMTX variants from wild-type channels and suggest that this defect may be of pathophysiological relevance.

Blotting, Western↗
PubMedDate not supplied

["In vitro" analysis of root dentin permeability during endodontic instrument use, as a function of change of instruments and number of times used].

The increase of dentinal permeability is a very important issue related to root canal disinfection. Beside the auxiliary substance used for the chemical/mechanical preparation, time and type of instruments were also considered. Based on these facts, we have studied the percentage of dentinal penetration of a stain (Patent blue V), in recently extracted teeth. By this way, areas of tooth hemisection and dentinal stain penetration could be assessed. Two different brands of type Kerr files (kerr and Maillefer) and a type K-Flex file were used for root canal preparation. They were used with the Endo PTC as an auxiliary chemical substance. The number of time used by each file was also considered. Results have shown no significant statistical differences of percentage of dentin stained, when different instruments were used. Less stain penetration could be observed when an increase of instrument action was placed, mainly observed in the apical area and tooth hemisection.

Dentin Permeability↗
PubMed1989

Barriers to diffusion of Ledermix paste in radicular dentine.

Freshly extracted human single-rooted teeth with a single root canal were used to study the effects of 2 irrigation regimens and the effect of cementum on the diffusion of corticosteroid and antibiotic tracer molecules from Ledermix paste placed in the pulp space. An irrigation regime that combined the use of 15% EDTAC and 1% NaOCl resulted in a significant increase in the permeation of the trace molecules through dentine compared with teeth that were irrigated with Savlon solution. Mechanical removal of the cementum also resulted in a significant increase in the permeation of the trace molecules. This study demonstrated that neither the smear layer nor the cementum were complete barriers to diffusion. The data obtained appeared to be of clinical relevance and provided further understanding of the dynamics of drugs in tooth roots.

Adult↗
PubMed1976

[Effect of an electric field on the penetration of fluorides into dental enamel, studied in vitro and in vivo].

The aim of the present study is to determine the influence of iontophoresis on the deposition of fluorine in dental enamel. A micromethod of fluorine-deposition and of dental enamel-sampling was perfected in vitro; it was then applied in vivo. Fluorine was layed down by topical and iontophoretical way, under the form of sodium fluoride in neutral solution. In in-vitro and in 2 in-vivo asseys 18F was used as an indicator, while in other ones fluorine was titrated by mean of a specific lanthan-fluoride electrode. Results from both methods agree. It is stated that the fluorine deposition on enamel remains lightly but significantly higher, in vivo as well as in vitro, when the tooth is subjected to a continuous electrical field.

Adolescent↗
PubMed2000

The permeability of the dentine and other tissues that are exposed at the tip of a rat incisor.

The tissues that form the incisal surface of a rat incisor include dentine, an atubular calcified tissue which lines the last-formed dentine, and calcified pulp remnants. The permeability of these tissues was investigated in vitro and in vivo using Evans blue dye. The incisal surface was prepared by etching it with acid or removing 1 mm by fracturing or with a diamond disc followed by etching. In some cases, 1.5-3.0 mm was removed to expose the soft tissue of the pulp. The dye was applied for 30 min, then longitudinal sections of the crown were cut and examined microscopically to determine the extent to which the dye had diffused into the underlying tissues. In only those teeth in which the dye had been applied direct to the pulpal soft tissue could any be detected below the exposed tooth surface. In previous experiments, it was found that both cat and human dentines were freely permeable to Evans blue when they were tested in vitro. It is concluded that the dentine and other tissues that form the incisal surface of a rat incisor are less permeable than cat or human dentine.

Acid Etching, Dental↗
PubMed1985

The reliability of the iodide permeability test applied to the natural dentition.

The purpose of this study was to assess the reliability of the iodide permeability test when applied to the human dentition. Twenty-two subjects were seen once a week for three weeks. At each visit, consecutive iodide permeability measurements were obtained: four from the right central incisor and four from the left. Results of these trials were examined for the degree of variability from one replication to another within the same day, as well as for the variability from one week to the next. Within-day and between-week reliability of the test results was assessed by two indices: the Hoyt Index, which estimates the reliability of the average of the four replicate measurements per tooth, and the Intraclass correlation, which estimates the reliability of a single measurement. The results indicate that the iodide permeability test produces sufficiently replicable measurements for use in future clinical studies.

Adult↗
PubMed1986

Effects of neutral salts in a bench-scale caries model.

In an earlier paper on bench-scale simulation of the caries process, it was shown that the passage of ions through ion-permselective barriers could have profound effects on the composition of the solution within the "lesion" at steady state. As indicated in earlier papers, these changes are produced by unequal rates of diffusion of Ca and PO4 ions prior to reaching steady state. Comparable effects are attributable to F ions when present. Here, we used the same two-compartment diffusion apparatus and membranes, as described in the earlier paper, to show that a neutral salt, such as NaCl, disproportionates under the influence of membrane potential. Thus, although the Na and Cl concentrations are nearly equal in the "plaque-saliva" compartment, they become very different in the "lesion" solution. An excess of Na over Cl is equivalent to the presence of the component NaOH, and an excess of Cl over Na is equivalent to the presence of HCl. With the highly permselective commercial membranes used in these experiments, the Ca/P ratio in the "lesion" solution changed from an initial value of 1.6 to a value as high as 53 or as low as 0.1 at steady state. These phenomena are relevant to the events taking place in a caries lesion and must be taken into account in devising physicochemical models of the caries process. A valid caries model, in turn, offers the possibility of identifying steps in the caries mechanism which might be blocked to prevent tooth decay.

Calcium↗
PubMed2002

The effects of post-extraction time on the hydraulic conductance of human dentine in vitro.

The permeability characteristics of dentine have been used in many in vitro studies to evaluate longitudinally the efficacy of various restorative and preventative procedures. However, the permeability of human dentine increases over time after tooth extraction. The aim here was to determine if there is a steady phase in dentine permeability in vitro over time. The convective permeability of dentine discs cut from extracted human third molars to 0.8% albumin solution was measured initially on day 7 after extraction using a fluid-transport model and the hydraulic conductance was calculated. The permeability of each disc was then re-measured de- and re-mounting the split-chamber 1h after the initial measurement as well as on days 8, 9, and 37 after extraction. No significant difference was found between the initial and 1h hydraulic conductances. A significant increase in hydraulic conductance was seen from day 7 to 9, but there was no significant difference between the hydraulic conductances on days 9 and 37. These results suggest that the measurements were reproducible and that a steady phase of dentine permeability is established 9 days after extraction under these study conditions in vitro.

Albumins↗
PubMed1992

Effects of Nd:YAG laser on apical seal of teeth after apicoectomy and retrofill.

The application of Nd:YAG laser to tooth surface can change its surface permeability. The purpose of this study was to investigate the effects of Nd:YAG laser on the permeability of dentin following apicoectomy and retrofill. Sixty single-rooted teeth were randomly assigned to six groups of 10 teeth each. The six groups were arranged in three pairs, experimental and control groups. The canals of teeth in pairs 1 and 2 were cleaned, shaped, obturated, and their apical 2 mm were resected. A class I preparation was prepared and filled with amalgam in each tooth in pair 1. The apical 2 mm of each tooth in pair 3 was removed, and a class I preparation was prepared and filled with amalgam. The apical surface of resected roots in half of the samples in each pair was lased twice by using Nd:YAG laser. The duration of lasing and the number of pulses were recorded for each tooth. After application of nail polish to the unoperated surface of each tooth, the teeth were placed in 0.5% methylene blue dye for 48 h. The amount of dye penetration in sagittal sections of each tooth was measured. The amount of dye penetration was significantly lower in lased roots than in nonlased ones (p < 0.05). Based on our results, it appears that application of Nd:YAG laser reduces the permeability of resected roots.

Analysis of Variance↗
PubMed1992

A permeability barrier to lanthanum and the presence of collagen between odontoblasts in pig molars.

Previous experiments in rat incisors indicate that the odontoblasts form an impermeable barrier which prevents fluid movement between pulp and dentine. The permeability of the odontoblast layer has now been investigated in pig molars which are more analogous to human teeth. The heads and necks of anesthetised piglets were perfused intra-arterially with lanthanum nitrate in Ringer's solution or with Ringer's solution alone. Molar tooth germs were removed, sliced, fixed by immersion and embedded in resin. Ultrathin sections including pulp and dentine were examined by transmission electron microscopy. Fenestrated capillaries were permeable to the electron dense lanthanum which thus entered the extracellular space between the odontoblast cell bodies. The lanthanum was excluded from predentine indicating that a barrier to permeability is present. In the above specimens and in others from 2 animals which were fixed by perfusion fixation, longitudinally oriented bundles of collagen fibrils were found passing from dentine through predentine into the odontoblast layer. Longitudinal collagen was also present between odontoblast cell bodies and entering the pulp at their basal ends. This suggests that classical von Korff fibres are present during primary circumpulpal dentinogenesis. In some sections longitudinally oriented collagen was absent. The junctions showed features of classical tight junctions but open tight junctions containing longitudinal collagen were also observed, suggesting that the junctions may modulate. Despite a trace of evidence that lanthanum can leak through adjacent to longitudinally penetrating collagen we concluded that the biological permeability barrier is maintained. The presence of the barrier indicates that other than the longitudinal collagen fibrils of which the source is unknown, all molecules incorporated into dentine are deposited there by the odontoblasts. An advantage of the barrier may be that it provides a closed environment for the orderly process of matrix deposition and mineralisation of dentine.

Animals↗
PubMed1983

The effects of acid etching on the in-vivo permeability of dentine in the dog.

Cavities were cut in both lower molars of 11 anaesthetized dogs. Dentine permeability was quantitated in these teeth using a filtration technique before and after acid etching to remove the smear layer. Acid-etching increased 5-fold the ease with which fluid could flow across dentine. Under conditions of high fluid filtration, an opening into the pulp chamber from the opposite side of the tooth produced only slight increases in filtration rate, indicating that the rate-limiting step is filtration of fluid across dentine, rather than removal of the fluid by the pulp circulation.

Acid Etching, Dental↗
PubMed1994

Permeability and microleakage of Class II resin composite restorations.

The aim of this study was to evaluate the variations in microleakage of large Class II (MOD) restorations over time. Three different combinations of dentine bonding agents and posterior resin composites which had previously shown promise were used: Vitrebond/Scotchbond 2 plus P50, Tripton plus Occlusin and Clearfil Photo Bond plus Clearfil Photo Posterior. Conventional Class II cavities were prepared in freshly extracted third molars. All gingival margins were terminated at the cemento-enamel junction. A fluid-under-pressure apparatus connected with the pulp chamber of each tooth was used to evaluate the permeability and marginal leakage of the restorations at 0.069 MPa. Microleakage was tested after insertion of restorations at 2, 15, 45, 150 min, after 1, 2, 7, 14 days, after 1, 2, 3 months, after thermal cycling and 10 months later, after occlusal loading. Finally, all specimens were exposed to silver nitrate solution to measure microleakage as dye penetration. Immediately after insertion of the restorations, all the materials showed a higher microleakage than after 1-2 days. After 4-8 weeks, all the restorations exhibited an increased permeability suggesting that hygroscopic expansion was not sufficient to keep pace with hydrolytic degradation of the restorations. Neither thermocycling or occlusal stresses increased the microleakage of the restorations.

Composite Resins↗
PubMed1989

Correlation between physical changes in tooth enamel and changes in iodide penetrability following in vitro or intraoral demineralization.

Demineralization of bovine tooth enamel was assessed by various physical means, and results were compared to measured changes in penetrability to iodide ions (delta Ip). Blocks of bovine enamel were exposed in vitro to lactate buffer (pH 4.3) containing 25 mM CaCl2 and 10 mM KH2PO4 for up to 4 days. Delta Ip increased over a wide range with time. A plot with respect to microhardness exhibited a pronounced inflection, with delta Ip rising rapidly at indentation depths greater than 2.5 microns. Microradiography and polarized light microscopy demonstrated subsurface lesions coincident only with the higher delta Ip values. The limited demineralization during the early time periods, therefore, was associated with only minimal changes at or near the enamel surface, yet could be detected readily with the delta Ip system. Demineralization produced intraorally in subjects rinsing with 5% sucrose was accompanied by increases in delta Ip, but no changes in surface microhardness or microscopic appearance of the enamel. It appeared that, under these conditions, demineralization was limited to the surface and corresponded to the very early phases of lesion formation.

Animals↗
PubMed1976

Fissures at risk.

Explore the source record for details and available documents.

Bicuspid↗
PubMed1986

Calculus revisited. A review.

Although there is no doubt that gingivitis can develop in the absence of supragingival calculus, it is not clear to what extent the presence of mineralized deposit enhances gingival inflammation. Partial inhibition of plaque mineralization can be accomplished by chemical agents, but there has been no demonstration in humans of a reduction in gingivitis. It remains to be established what level of inhibition (if any) is required to have more than a cosmetic effect. Since the accepted scenario is that apical growth of supragingival plaque precedes the formation of subgingival calculus, there is no longer an issue of whether subgingival calculus is the cause or the result of periodontal disease. Subgingival mineralization results from the interaction of subgingival plaque with the influx of mineral salts that is part of the serum transudate and inflammatory exudate. This chronology, however, should not be the basis for relegating calculus to the ash heap. Morphologic and analytical studies point to the porosity of calculus and retention of bacterial antigens and the presence of readily available toxic stimulators of bone resorption. When coupled with the increased build up of plaque on the surface of the calculus, the combination has the potential for extending (beyond that of plaque alone) the radius of destruction and the rate of displacement of the adjacent junctional epithelium. The centrality of thorough scaling and root planing in the successful maintenance of periodontal health supports the view that subgingival calculus contributes significantly to the chronicity and progression of the disease, even if it can no longer be considered as responsible for initiation.

Bacteria↗