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PubMedDate not supplied

[Quantitative evaluation of permeability of root canalicular system].

The purpose of this study was to evaluate the rate of permeability of the canalicular system of the root (apical and central portion) using albumin labelled with 131J-radioisotope. Freshly extracted central maxillar incisors were divided in three groups: I 10 specimens were used to quantity the rate of the tracer penetration through the apical foramen and apical ramification; II 10 specimens were used for the measurement of central root portion permeability for the same tracer; III. This group was the control group; it consisted of 5 samples which were tested to the sealing ability of the used sticky-wax. The results showed: 1). Through an apical foramen and ramification 56% of radiolabelled albumin penetrated into an external saline eluent; 2). When albumin was used as an eluent another amount of 6.5% of 131J-albumin was released; 3) About 38% of total albumin tracer was irreversibly bound to the components of root dentine and cement; 4). Through the central portion of the root canalicular system 50% of radiolabelled albumin penetrated from the root canal; 5). Penetration of large molecules (m.w. 67000), like bacterial endotoxins and protein metabolic products, is absolutely possible and penetration occurs primarily through a system of apical ramification and pulpo-periodontal communication as well as through a canalicular pattern of root dentine and cement.

Dental Pulp Cavity↗
PubMedDate not supplied

[Changes in the properties of the enamel of the permanent teeth in children using fluoride-containing toothpastes].

Focal demineralization of the enamel of permanent teeth was studied in 104 schoolchildren aged 9 to 12 over the course of prophylaxis (cleaning the teeth with fluorine-containing toothpastes). The parameters checked up were the intensity of coloring, size and electric conductivity of the spots, and the rate of remineralization of the enamel of permanent teeth. For a year a strong correlation between the tested characteristics of the enamel and saliva was observed. Some age-specific characteristics of permanent teeth enamel were detected. Age group of 11 to 12 years should be distinguished in prophylactic and control groups, because it is at this age that all the tested properties of the enamel are the most liable to change: electric conductivity, permeability, and remineralization rate. This period seems to be characterized by a specific reaction of all systems and organs of the body to environmental exposures. Remineralizing prophylaxis was found to be the most effective at the age of 9 to 10 years. The findings permit us emphasize the contribution of fluorine contained in the Blendax fluorine-containing toothpaste used by the children to the major components of the pathologic process (white spots) and enamel remineralization at the stage of its maturation.

Child↗
PubMed1997

The carbon dioxide laser as an aid in apicoectomy: an in vitro study.

OBJECTIVE: To achieve the required goal of optimally sealing the apical section and the root-canal when performing an apicoectomy, the authors decided to use the CO2 laser as an additional aid. SUMMARY BACKGROUND DATA: The CO2 laser has previously shown to have an excellent sealing effect on dentin surfaces. METHODS: In this in vitro study, the authors examined the effects of CO2 laser application in apicoectomies with the help of color penetration tests and scanning electron microscopic (SEM) examinations. Sections and root canals were irradiated with low power (0.5 W) in continuous wave mode for totally 20 sec. The thermal stress for the adjacent tissues attaching thereto is moderate as shown by infrared-spectroscopy. RESULTS: A comparison with nonirradiated samples revealed that CO2 laser irradiation reduced color penetration at the section to a minimum. Also, irradiation of the root-canal wall resulted in satisfactory sealing of the surface. These findings were supported by the results of the SEM examinations. CONCLUSIONS: CO2 laser treatment optimally prepares the tooth for final intraoperative filling because of sealing of the dentinal tubules, the resultant elimination of niches for bacteria and the sterilizing effect of the laser.

Apicoectomy↗
PubMed1999

In vitro permeability and scanning electron microscopy study of acid-etched and ground enamel surfaces protected with dental adhesive coating.

Clinical procedures, such as acid etching and reshaping of the teeth supporting removable partial dentures by grinding off some enamel surface, increase the permeability of dental enamel. Teeth take several months in vivo to partially recover from such damage. In the meantime, the tooth is more susceptible to carious decay. To prevent this the ground or etched enamel should be effectively protected. Using electron paramagnetic resonance (EPR) and a two-chamber diffusion cell the authors studied the influence of adhesive resin applied to the ground and acid-etched enamel surfaces on the diffusion of spin label TMAPO (2,2,6-6 tetramethyl-4-acetamido-piperidine-1-oxyl) molecules through the enamel. The enamel permeability was measured in samples exposed to 1-min etching with 37% phosphoric acid, in samples etched for 5 min, and in samples ground with a diamond bur. Next, all the treated enamel surfaces were coated with Scotchbond Multi-Purpose Plus(R) dental adhesive system and the permeability measurements repeated. Scanning electron microscopy (SEM) was used to study the porosity of enamel surfaces. The adhesive resin film covering the etched or ground enamel surfaces was found to decrease significantly the diffusion through dental enamel. This finding confirms the clinical value of dental adhesives used to protect ground or accidentally acid-etched enamel surfaces. SEM analysis showed that adhesive resin covers the porous surface of the acid-etched and ground enamel tightly.

Acid Etching, Dental↗
PubMed1995

Effect of bleaching agents on dentin permeability to Streptococcus faecalis.

Bacterial contamination of dentin may be a contributing factor in the development of bleaching-associated root resorption. In this study, the effect of commonly used bleaching agents on the permeability of dentin tubules to Streptococcus faecalis was evaluated. Sixty extracted bovine incisors were horizontally sectioned apically to the cementoenamel junction. In each tooth, a standard cavity was prepared, the pulp tissue extirpated, and remnants of soft tissue and smear layer were removed. Following rinsing and repeated autoclave sterilization, the teeth were divided into four groups, each treated with one of the following materials: 30% hydrogen peroxide, sodium perborate mixed with 30% hydrogen peroxide, sodium perborate mixed with distilled water, and distilled water alone that served as control. The bleaching agents were sealed in the teeth and incubated at 37 degrees C for 7, 14, and 21 days. At each time interval the bleaching agents were removed and the teeth incubated at 37 degrees C in brain heart infusion infected with S. faecalis. Histological sections were prepared, and the maximal bacterial penetration for each group was measured using a computerized morphometric system. Statistical analysis of the results revealed that teeth treated with either 30% hydrogen peroxide alone or in combination with sodium perborate were significantly more permeable to S. faecalis than those treated with sodium perborate mixed with water (p < 0.0001). Sodium perborate mixed with water did not cause an increase in dentin permeability to S. faecalis and was similar to the water control. In conclusion, it seems that bleaching agents containing hydrogen peroxide in high concentrations may increase bacterial penetration through dentinal tubules.

Analysis of Variance↗
PubMed2000

Cementoenamel junction: microscopic analysis and external cervical resorption.

There is a lack of data regarding the shapes and distribution of the mineralized tissue that composes the cementoenamel junction. A sample of 198 permanent human teeth was analyzed by optical microscopy and scanning electron microscopy. Scanning electron microscopy showed three types of tissue interrelations: enamel overlapped by cementum; enamel and cementum edge-to-edge; and a gap, revealing a strip of exposed dentin. Using optical microscopy, a fourth type of cementoenamel junction was observed: cementum overlapped by enamel. The distribution of the hard tissues found at the cementoenamel junction is unpredictable and irregular both for any tooth type (e.g. on cuspids) and on any one individual tooth. Based on these results and on analysis of the mechanisms involved in cervical root resorption, it is possible to consider the cervical region as prone to external resorption.

Dental Cementum↗
PubMed1999

Dealing with sensitive teeth.

Dental pain is extremely common in the UK and can severely reduce the quality of life when it is associated with eating, drinking or speech. Patients often present complaining of a short, sharp, stabbing pain from hot or cold air, foods or drinks: while this may be caused by tooth decay, failing fillings or cracks in teeth, a major cause is sensitivity from exposed dentine. Treatment varies from dietary control, desensitising toothpastes to protection with dentine-bonding agents and glass ionomers. In extreme cases elective devitalisation is necessary.

Dentin Permeability↗
PubMed1995

Multilayer culture of periodontal ligament epithelial cells: a model for junctional epithelium.

The unique features of junctional epithelium involve lack of keratinization, limited differentiation and a relatively permeable structure. In order to study the relationship between differentiation and permeability of stratified epithelium a model system was developed. Porcine periodontal ligament epithelial cells were cultured on the polycarbonate nucleopore membrane of the Transwell two-compartment culture system. Within 5 days of culture the cells formed a confluent multilayered structure. Subsequently, maturation of the structure and differentiation of surface cells took place. Transmission electron microscopy showed that the cells were arranged into basal and suprabasal layers with sparse desmosomal attachments and wide intercellular spaces resembling the organization of junctional epithelium. The basal cells attached to a subepithelial basal lamina through numerous hemidesmosomes. The cytokeratin profile of the cultured epithelium (K5, 6, 14, 16, 19) resembled that of the cells of junctional epithelium attached to the tooth surface. The older cultures expressed differentiation markers, K4, K13 and involucrin, thereby resembling sulcular epithelium. The epithelial permeability, measured by diffusion of phenol red, radioactive dextran or methionine tracers, and as transepithelial electrical resistance, decreased with the increased cell number and maturation of the cultures. The new model provides an organotypic culture system which allows to control differentiation of a multilayered periodontal epithelium. It thus may serve as a valuable new tool for studies on the permeability and behaviour of periodontal epithelium under the influence of exogenous and endogenous factors.

Analysis of Variance↗
PubMed2004

Effect of remaining demineralised dentine on dental microleakage accessed by a dye penetration: how to inhibit microleakage?

OBJECTIVES: To demonstrate that microleakage has taken place at the defect, which was analysed previously by a tensile test using dumbbell shaped specimens trimmed from bonded resin/dentine restorations, and to suggest how microleakage can be inhibited reliably in dental treatment. METHODS: A total of 60 Class V box cavities were prepared at the cemento-enamel junction on fresh bovine incisors and randomly divided into four groups of 15 specimens each. Exposure times of etching for 10:3 conditioner were set at 10, 30 or 60 s, and for 10% phosphoric acid (positive control) at 10 s. The cavity walls were rinsed with water for 10 s, air-dried for 10 s and hybridised with 4-META/MMA-TBB resin. All the cavities were filled with a light cured resin composite and stored in 37 degrees C water for 24 h and then immersed in 15% methylene blue for 2 h. The length of dye penetration along the interface was graded by defined criteria and analysed using Kruskal-Wallis and Mann-Whitney tests. The dye penetration patterns were examined by light microscopy and the remaining demineralised dentine was analysed by Transmission Electron Microscopy (TEM). RESULTS: The least leakage score was obtained in 10s-10:3 etched group with 12 out of 15 specimens demonstrating no leakage. Leakage was significantly lower at the cementum margin than for the other three groups. No significant difference in the extent of greatest dye penetration was found between the 60s-10:3 and 10s-phosphoric etched groups. Dye penetration along the cementum margins was significantly higher than that of the enamel margins in all groups, except the 10s-10:3 etched group. TEM examination confirmed that there were exposed collagen fibrils in the remaining demineralised dentine, where microleakage had taken place. SIGNIFICANCE: It could be concluded from this study that microleakage has taken place at the defect in the bonded specimens which has correlations with zones of incompletely infiltrated demineralised dentine that was observed using TEM. A reliable method of inhibiting microleakage is the presence of well prepared hybridised dentine.

Acid Etching, Dental↗
PubMed1993

Migration of a Streptococcus sanguis strain through the root dentinal tubules.

The persistent presence of bacteria in the root canal system often leads to the failure of treatment. The aim of this study was to study the in vitro penetration of root dentinal tubules by bacteria. Bovine dentin was inoculated with a strain of Streptococcus sanguis, NCTC 7863; samples were taken at 10, 20, and 28 days, and bacterial penetration of the tubules was demonstrated using two techniques, scanning electron microscopy and light microscopy after Brown and Brenn staining. The results showed that S. sanguis can penetrate deep inside the tubules (792 microns). The maturity of the dentin blocks seems to be a major factor in tubule penetration.

Animals↗
PubMed1992

Cervical canal leakage after internal bleaching.

The effects that walking bleach procedures had on root canal filling leakage and the extent of dentinal penetration were studied. Forty teeth were divided into four groups: 1--GP, set sealer, no base; 2--GP, set sealer, 2-mm Cavit base; 3--GP, unset sealer, no base; and 4--GP, unset sealer, 2-mm Cavit base. All were bleached for 7 days, fresh bleach was added for another 7 days, then methylene blue dye was placed for 5 days. The extent of dye penetration apically along the root canal filling and through the dentinal tubules was evaluated. The results indicate that 2 mm of Cavit was sufficient to significantly reduce linear leakage and dentinal penetration. The Cavit should be placed to a level slightly coronal to the facial cementoenamel junction. Teeth with cemental defects demonstrated greater perpendicular dye penetration in the areas of the defects than those with intact cementum. The data from this study suggest the use of a base material over gutta-percha in clinical practice prior to internal walking bleach procedures.

Analysis of Variance↗
PubMed2002

Dentin shear strength: effect of distance from the pulp.

OBJECTIVE: Dentin structure varies with orientation and location. Ultimate shear strength (USS) has also been found in previous studies to vary with location. The present study further explores this relationship between USS and various locations in coronal dentin as well as distance from the pulp. METHODS: Stick specimens were prepared from coronal dentin located in the center or under cusps of human molar teeth. These were tested in the shear mode at various distances from the pulp. RESULTS: Median values ranged from 52.7 (range 29.0-73.1) MPa near the pulp to 76.7 (range 53.9-104.0) MPa near the dentino-enamel junction. No differences were found among the buccal, central or lingual locations, however, the USS near the pulp was found to be significantly lower. SIGNIFICANCE: The properties of coronal dentin vary with distance from the pulp, which may affect adhesion and other aspects of restorative dentistry.

Anisotropy↗
PubMed2001

The structure of dentine in the apical region of human teeth.

AIM: To study the structure of the apical region of human teeth with emphasis on dentinal tubules and their branches. METHODOLOGY: This descriptive histological study employed demineralized stained sections for light microscopy, demineralized unstained sections for scanning electron microscopy, and undemineralized, acid-etched specimens for confocal tandem scanning microscopy. RESULTS: The apical portion of human teeth showed marked variations in structure, including accessory root canals, areas of resorption and repaired resorptions, occasional attached, embedded and free pulp stones, varied amounts of irregular secondary dentine, and even cementum-like tissue lining the apical root canal wall. The apex often deviated from the long axis of the root canal. Primary dentinal tubules were irregular in direction and density. Some areas were devoid of tubules. CONCLUSIONS: The irregular and variable structure of the apical region of human teeth represent special challenges during endodontic therapy. Obturation techniques based on the penetration of adhesives into dentinal tubules are unlikely to be successful and adhesive techniques must depend on impregnation of a hybrid layer.

Adult↗