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PubMed1986

Matrix proteins of the teeth of the sea urchin Lytechinus variegatus.

The teeth of the sea urchin Lytechinus variegatus grow continuously. The mineral phase, a high magnesium calcite, grows into single crystals within numerous compartments bounded by an organic matrix deposited by the odontoblasts. Electron microscopic examination of glutaraldehyde-fixed Ethylene Diamine Tetra acetic acid (EDTA) demineralized teeth shows the compartment walls to be organized from multiple layers of cell membrane which might contain cytoplasmic protein inclusions. Proteins extracted during demineralization of unfixed teeth were examined by gel electrophoresis, high performance liquid chromatography, and amino acid analysis. The tooth proteins were acidic, they contained phosphoserine, and they were rich in aspartic acid. By contrast, the proteins of similarly extracted mineralized Aristotle's lantern skeletal elements were nonphosphorylated and were rich in glutamic acid. Vertebrate tooth and bone matrix proteins show similar differences. Surprisingly, an antibody to the principle rat incisor phosphoprotein showed a significant cross-reactivity with the urchin tooth protein, by dot-blot and enzyme-linked immunosorbent assay procedures. Thus, the urchin tooth proteins contain epitope regions similar to those which are phenotypic markers of vertebrate odontoblasts. Whether this is an expression of convergent or divergent evolutionary processes, it is likely that the matrix proteins play a similar role in matrix mineralization. The sea urchin tooth may thus be an excellent model for the study of odontoblast-mediated mineral-matrix relationships.

Amino Acids↗
PubMed2002

A clinical, microbiologic, and radiographic study of deep caries lesions after incomplete caries removal.

OBJECTIVE: Clinical, radiographic, and microbiologic changes in deep caries lesions were assessed after incomplete carious dentin removal and tooth sealing. METHOD AND MATERIALS: Thirty-two teeth with deep caries lesions were studied. Treatment consisted of incomplete excavation of the demineralized dentin, application of calcium hydroxide, and sealing for a 6- to 7-month period. The color and consistency of the dentin were clinically assessed. Differences in radiographic density were assessed by digital image subtraction. Microbiologic samples were obtained from the demineralized dentin before the temporary sealing and after the experimental period. The samples were cultivated on blood agar under aerobic and anaerobic conditions, in Mitis Salivarius agar, and Rogosa selective Lactobacillus agar. RESULTS: Two cases were lost during the study; one presented pulpal necrosis. In the other case, there was pulpal exposure during removal of provisional sealing. In all teeth, the initial demineralized dentin was soft and wet; one lesion was yellow, 21 were light brown, and eight were dark brown. After treatment, the dentin was dry, and 80.00% of specimens were hard, 16.67% were leathery, and 3.33% remained soft. The dentin was light brown in five teeth and dark brown in 25. There was a statistically significant mean difference in radiographic density (pixel intensity), 88.77 +/- 7.02 in the control areas and 94.66 +/- 6.75 in the test areas. The counts of anaerobic and aerobic bacteria, lactobacilli, and Streptococci mutans had decreased significantly by the end of treatment. CONCLUSION: Incomplete removal of carious dentin and subsequent tooth sealing resulted in the arrest of the lesions, suggesting that complete dentinal caries lesion removal is not essential to the control of caries lesions.

Adolescent↗
PubMed2000

The odontoclasts of Ambystoma mexicanum.

The resorption of teeth in Ambystoma mexicanum during postembryonal ontogenesis and induced metamorphosis occurs by means of light-microscopic detectable giant-cells. These have morphological and functional characters similar to those of odontoclasts of other vertebrates. The multinucleated odontoclasts resorb not only the pedicel (base), but the stalk of the tooth, too. When active, the cells form a ruffled border and a sealing zone. In this way they are able to demineralize the hard tissues of teeth (dentin and mineral of the pedicel) and to dissolve the extracellular matrix. Resorption of enamel has not been observed. Marks of resorption resemble the Howship's lacunae of other tetrapods. TRAP as a typical enzyme of odontoclasts could not be detected histochemically. Dependence of PTH, which is supposed to be necessary for the formation and activation of odontoclasts as well as of thyroxine can be excluded, although the resorbing cells are functionally and cytologically identical with those of other vertebrates. This demands some other mechanism for the formation and regulation of the odontoclasts in A. mexicanum.

Ambystoma mexicanum↗
PubMed2003

Automatic quantitative analysis of ore content of human tooth enamel based on image processing.

Introducing the theory of fuzzy set, mathematical morphology and computerized mask fast scanning, we developed the TOOTH.SCA software and method to analyze the effect of fluoride (NaF) on ore content of human tooth enamel automatically and quantitatively. And we obtained some characteristic parameters, such as the depth, the type and the demineralized content of every scathing layer of dental caries. The smallest scale of mask scanning is 0.1 microm x 0.1 microm and the time required to analyze a sample is only 12 s. The applied software and method we built play an important role to the research on the mechanism of pathological changes of teeth and preventing dental caries.

Bone Density↗
PubMed1997

Shear bond strength of Dyract compomer material to dentin of primary molars.

The purpose of this study was to measure and compare the shear bond strength and fracture pattern of Dyract compomer material with and without use of PSA prime/adhesive as well as 35% phosphoric acid etching to the buccal dentin of primary first and second molars. In addition, micromorphology of the restorative surfaces opposing the tooth structure following these different surface treatments was evaluated. For shear bond strength measurement and fracture pattern evaluation, 36 extracted non-restored human primary molars with mild to moderate caries divided into 3 groups of 12 teeth each were used. Dyract with and without use of PSA prime/adhesive as well as 35% phosphoric acid etching for 15 seconds prior to placement of PSA prime/adhesive was applied to the buccal surface of exposed dentin. A standardized tube of Dyract was placed on each dentin surface and polymerized. The tubes were sheared off with a Universal testing machine at a cross head speed of 12.7 mm/min. For evaluation of the restorative surfaces opposing the tooth structure, 9 teeth divided into 3 groups of 3 teeth each were used to prepare the specimens, which were then demineralized in 10% hydrochloric acid for 24 hours. Fitting surfaces of these specimens were prepared and examined using scanning electron microscope. Tukey's multiple range test showed that the shear bond strength of Dyract with PSA prime/adhesive (group 1) was statistically significantly higher than Dyract without PSA prime/adhesive (group 2) and phosphoric acid etching (group 3). The shear bond strength in group 1 averaged 5.89 +/- 1.40 (X + SD MPa) while for groups 2 and averaged 1.49 +/- 0.69 and 3.69 +/- 0.89 respectively. Pretreatment of dentin surface with 35% phosphoric acid increased resin tags formation but it did significantly lower shear bond strength of Dyract with PSA prime/adhesive to dentin of primary molars. Bond failure patterns for all groups were only adhesive and mixed type failures.

Adhesives↗
PubMed1992

Growth hormone regulates nucleolar organizer regions during odontogenesis in the rat.

Nucleolar organizers are major sites of ribosomal RNA synthesis and provide an index of transcriptional activity. In order to further define growth hormone actions on nucleolar organizer regions in tooth forming cells, hypophysectomized rats treated with growth hormone for 4 and 24 h, hypophysectomized and sham-operated animals were used. After demineralization and standard paraffin embedding, longitudinal sections of maxillary incisors were stained by a silver stain technique to reveal nucleolar organizer regions. The area of these regions per nucleus was measured using a modified microdensitometer. Analyses of variance of the resulting data showed that preameloblasts and preodontoblasts have greater silver stained nucleolar organizer region values than ameloblasts and odontoblasts. Hypophysectomy reduced and growth hormone partly restored the level of nucleolar organizer regions in preameloblasts and preodontoblasts, but not in mature ameloblasts or odontoblasts. In the case of the younger preameloblasts and preodontoblasts, the effect of growth hormone was seen within 4 h of growth hormone injection. In conclusion, rRNA synthesis, as revealed by the specific silver staining of nucleolar organizer regions in tooth forming cells, appears to be regulated by growth hormone over a relatively short time frame.

Ameloblasts↗
PubMed1997

Citric acid demineralization of cementum and dentin: the effect of the storage medium.

The purpose of this study was to see if the root surface topography of teeth, stored in saline and subsequently treated with citric acid, differred from the root surface topography of teeth that were treated immediately upon extraction, 12 freshly extracted adult human permanent teeth, with proximal surfaces free of caries and periodontal disease, were treated in succession. The crowns were removed at the level of periodontal attachment, the teeth sectioned buccal-lingually and a treatment area deligniated on each proximal section. The treatment area of 6 teeth was root planed to expose dentin (D) and scaled to remove adherent tissue and leave a cementum surfaces (C) on the other 6 teeth. A coronal-apical groove down the middle of the treatment area divided it into approximately equal parts or experimental regions. One proximal section of each tooth was placed in physiologic saline (S) and treated after 6 weeks of storage while the other proximal section was freshly treated (F). Treatment consisted of applying a 30% citric acid (CA) solution (pH = 1.60) for 5 min. Cotton pellets soaked in the citric acid solution were placed (P) on one half of the experimental area and heavily burnished (B) on the other half. Treatment areas were subsequently prepared for scanning electron microscopy analysis. Assessment was made of (i) the % of surface area tufted, (ii) fibril tufting depth (0.3) and (iii) fibril tufting density (1.3). Similarities were found in the data for both storage methods (F and S) across each application technique (P or B) and each tooth surface (D or C) with respect to the (i) % area tufted and (ii) frequency distribution of tufting depth scores. As for the application techniques, the data for burnishing was greater than placed across each storage method (F or S) and each tooth surface (D or C) for the same two parameters. The results of the study indicated that 6-week physiologic saline storage does not affect root surface demineralization by citric acid, as assessed by SEM.

Adult↗
PubMed1994

Saliva stimulation and caries prevention.

The protective role of saliva is demonstrated by the rampant caries seen in human subjects with marked salivary hypofunction, and in desalivated animals. In normal cases, however, the relationship between saliva flow and coronal or root caries experience is doubtful, and to examine the concept that stimulation of saliva might have protective effects against caries, one must look beyond a simple correlation between caries and flow rate. Protective properties of saliva which increase on stimulation include salivary clearance, buffering power, and degree of saturation with respect to tooth mineral. These benefits are maximized when saliva is stimulated after the consumption of fermentable carbohydrates, by reducing the fall in plaque pH leading to demineralization and by increasing the potential for remineralization. Plaque acid production is neutralized, and experimental lesions in enamel are remineralized, when gum is chewed to stimulate saliva after a carbohydrate intake. The pH-raising effects are more easily explained by the buffering action of the stimulated saliva than by clearance of carbohydrates. The remineralization action depends upon the presence of fluoride. These findings suggest that the protective actions of saliva can be mobilized by appropriate salivary stimulation, and that in addition to established procedures such as tooth cleaning and fluoride regimens, eating patterns which lead to saliva stimulation to increase the potential for saliva protection might be included in recommendations for caries prevention. Confirmation of this concept in clinical tests is required.

Dental Caries↗
PubMed1999

Esthetic compomer restorations in posterior teeth using a new all-in-one adhesive: case presentation.

UNLABELLED: Compomers have continually gained in importance since their introduction in 1993, especially because of their ease of handling. The main indications are cervical lesions, Class III restorations, and restorations in the primary dentition. To extend the indications of compomers to esthetic Class I and II restorations in the permanent dentition, improvements in wear resistance and bond strength need to be accomplished. Studies have shown an improved bond strength and less marginal gap formation between compomers and enamel and dentin with acid etching of the tooth before application of conventional mild self-etching adhesives. Newly formulated, improved self-etching adhesives with a higher demineralization potential recently have been developed. The objective of this case presentation is to demonstrate step-by-step the clinical procedure for the application of a newly developed self-etching adhesive with high demineralization potential in combination with a compomer material in occlusal cavities. CLINICAL SIGNIFICANCE: Improved self-etching adhesives provide a faster and simplified application technique and allow effective conditioning and priming of enamel and dentin in one step, without waiving sufficient bond strengths. With limited indications, compomers are used in combination with these self-etching primers to restore occlusal cavities in posterior teeth. Evidence-based dentistry requires exact scientific data to evaluate whether this new trend results in benefits for patients. However, until clear evidence from controlled clinical studies supports the use of improved compomer systems in Class I and II cavities in the permanent dentition, dentists should be careful with this indication.

Bicuspid↗
PubMed1990

Root hard-tissue demineralization rate measured by 125I absorptiometry: comparison with lesion-depth measurements.

The aim of the present study was to compare demineralization of root hard tissue, monitored by 125I absorptiometry, with lesion-depth measurements under polarized light microscopy. The intact roots of ten human molars, which had not been exposed to the oral environment, were divided into 39 cementum/dentin blocks and exposed to a buffer solution of pH 4.5 containing 2.2 mmol/L calcium and inorganic phosphate. After demineralization for 3.5, 7, 14, and 21 days, transmission measurements by 125I absorptiometry were performed, and one block from each tooth was taken out of the solution for lesion-depth measurement. The results showed a high degree of correlation (r = 0.952) between lesion depth and change in transmission, with a more rapid increase initially in both variables. A linear relationship with the square root of time was found. Conversion of transmission data to lesion-depth data was possible when this caries model system was used on cementum dentin blocks.

Absorptiometry, Photon↗
PubMedDate not supplied

Dentine caries: take it or leave it?

In modern dentistry the primary aim when excavating carious dentine is to eradicate only the highly infected, irreversibly demineralized and denatured biomass in order to allow effective restoration of the cavity, restoration of the surface anatomy of the tooth and to prevent disease progression. However, the boundary between this superficial zone of dentine requiring excavation and the deeper, affected but repairable tissue is not always obvious either in the clinic or in the research laboratory. The inherent subjectivity in detecting this excavation boundary can result in clinically significant differences in the quality and quantity of dentine removed by different operators and makes the in vitro comparison of newer excavation techniques more difficult. This article discusses the rationale behind carious dentine excavation and the criteria available to the dentist, both clinical and laboratory, to help identify the dentine requiring removal.

Bacteria↗
PubMed1976

[Attempt at a comparison of healthy coronal dentin and carious coronal dentin].

The amino acid composition of normal human coronal dentine has been studied. The amino acid composition of carious coronal dentine was compared to that of the normal coronal dentine. The study was conducted on non demineralized samples. The results lead to a reconsideration of the so-called "normal dentine" in relation to different parameters: tooth age, sample location. A precise comparison between normal and carious dentine appears difficult to make.

Amino Acids↗
PubMed1989

[Staining of carious dentin with Kariesdetektor].

In a histological study of the staining effect of the staining solution Kariesdetektor 60 human teeth with carious lesions of varying sizes were separated into one control half and one test half each immediately following their extraction. Non-decalcified thin ground sections were prepared with the aid of the saw-cut-and-grind technique. The test halves were stained with Kariesdetektor, the control preparations with toluidine blue. The staining effect of the disclosing dye was evaluated under the light microscope and compared with the control preparations. In enamel the disclosing dye stained all carious areas except the dark and the more peripheral transparent zones. In dentinal caries the zones of necrosis and penetration were safely stained. Zones of demineralization, dead tracts, and transparency zones were not stained. Kariesdetektor is a reliable optical aid in removing infected carious hard tooth structures.

Dental Caries↗
PubMed1999

Autogenous masticatory mucosal grafts in extraction socket seal procedures: a comparison between sockets grafted with demineralized freeze-dried bone and deproteinized bovine bone mineral.

Successful preservation of the edentulous ridge after extractions may eliminate or reduce the need for ridge augmentation procedures. It has been claimed that grafting fresh extraction sockets and sealing them with autogenous soft tissue grafts promote ridge preservation after tooth extraction. In this study, the survival of free autogenous connective tissue grafts sealing extraction sites was evaluated. In 24 healthy patients, 42 maxillary anterior teeth were extracted. After socket debridement, soft tissue margins of the socket orifice were carefully cut to remove epithelial debris, Sockets were filled with either demineralized freeze-dried bone allografts (DFDBA) or deproteinized natural bovine bone mineral xenograft (DBBMX) to the level of the alveolar bone crest. Circular connective tissue grafts, slightly larger in diameter than the soft tissue socket orifice, were obtained and placed on top of the filler graft material sealing the sockets. Grafts were stabilized and secured by sutures and inspected weekly for the first month. The grafts were classified into 3 groups according to clinical parameters: vital, partially vital and non-vital. After 1 week, 18 grafts were vital, 13 partially vital and 11 non-vital. When only 1 sample unit (1 site per patient) was compared between DFDBA and DBBMX grafted sockets, no significant difference in graft vitality was shown (P = 0.34 for vital; P = 0.67 for vital plus partially vital). After 1 month, all socket orifices were sealed with mucosa. Based on the present observations, it seems that connective tissue grafts sealing fresh extraction sites are mainly dependent on underlying tissue vascularization and that sealing grafted fresh extraction sockets filled with bone substitute allograft or xenograft materials may be beneficial but an unpredictable procedure.

Adolescent↗