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PubMed1992

Odontoblast-mediated regulation of the progression of dentinal caries.

Osteoblasts and odontoblasts are both derived from the same mesenchymal cell line. Our aim was to investigate whether the processes of bone destruction and dentinal caries are biologically similar. The working hypothesis was that after the initiation of caries in the enamel, its rate of progression in the dentine is regulated by cell-mediated factors. Experimental caries was induced in the rat with a high sucrose diet combined with Streptococcus sobrinus infection. Both destruction of dentine and its apposition in the pulp under the carious lesions were measured after vital staining with tetracycline. Caries progression and dentine apposition were higher in developing teeth prior to apex "closure" than in adult, fully-formed teeth. Rats placed on a cariogenic diet during tooth development had an increased rate of caries progression. Fluoride administration via the drinking water was associated with decreased dentine apposition and little progression of dentine caries during the developmental stages. Dentine apposition was enhanced in adult rats placed on fluoride administration, while caries progression was reduced, whereas in animals subjected to metabolic acidosis dentine caries progression was enhanced, with reduced dentine apposition. In contrast, alkalotic animals had less dentinal lesions and smaller ones than the controls. Three theories are advanced to explain the observed changes: (i) They may be associated with changes in alkaline phosphatase activity in the pulpo-dentinal complex, (ii) they may be mediated by ionic changes in the dentinal fluid, or (iii) they may reflect the liberation of growth factors from dentinal matrix.

Acidosis↗
PubMed1992

Changes in pulpal blood flow and in fluid flow through dentine produced by autonomic and sensory nerve stimulation in the cat.

We have recorded the flow of fluid through exposed dentine in cat canines. The effects on this flow of electrical stimulation of the cervical sympathetic trunk (CST) and of the inferior alveolar nerve (IAN) were investigated. In some preparations, pulpal blood flow was also monitored with a laser Doppler flow meter and the compound action potentials evoked by IAN stimulation were recorded from the tooth. CST stimulation (0.5-5/s) resulted in a significant decrease in the rate of outward flow of fluid through the dentine or, with the higher frequencies tested, a reversal of the flow. CST stimulation also produced vasoconstriction. IAN stimulation caused a significant increase in the rate of outward flow of fluid from the dentine. This effect required the recruitment of A delta fibres: A beta fibres alone had no effect. Pulpal vasodilatation occurred with the same threshold. Mechanical stimulation of dentine in an acutely denervated tooth also caused vasodilatation, indicating that pulpal afferents were involved. The results show that the rate of fluid flow through dentine, and hence the rate of inward diffusion of chemicals from the oral cavity, can be influenced by changes in the state of the pulpal microvasculature.

Action Potentials↗
PubMed1991

[Studies on the specific electric resistance of the dentin of human teeth].

Electric current produced by corrosion of metals or used for diagnostic or therapeutic purposes has to pass through the dentin to reach the pulp. The electric resistance of the dentin, which influences the dentinal current intensity, is poorly documented in the literature. In this study 140 cylindrical dentin samples of human teeth were collected from four different regions of the tooth crown and their specific electrical resistance was measured. The recorded values vary with the orientation of the dentinal tubules ranging between 12.5 ohms and ohms. The linear temperature coefficient of the specific resistance is -0.0132 degrees C-1 for the temperature interval of 20 to 34 degrees C. It is assumed that the mechanism underlying electric conduction in dentin is related to the transport of ions in the dentinal fluid.

Adult↗
PubMed2001

Odontoblast function seen as the response of dentinal tissue to dental caries.

Microbes are responsible for the initiation and maintaining of carious processes. They have an efficient machinery for dissolving crystalline hydroxyapatite. When initiating carious processes, microbial acid formation determines the rate of the process in enamel. When the process reaches dentin, the micro-environment changes. Dential fluid in dentin tubules is the liquid where dissolving products of apatites are destroyed. Inorganic composition of dentinal fluid, however, is not altered much during the carious process, indicating that a functional secretory domain is working to pump the dissolved calcium and phosphate ions out of the fluid. Activation of odontoblast alkaline phosphatase and dentin latent collagenases is the known cellular event during the carious process in dentin. Because the caries lesion is by definition undermining, this suggests that, in this degradation process, the extracellular compartment, crystalline hydroxyapatite is dissolved by microbial acids, and a mixture of proteinases degrades the organic matrix. The degradation products of collagen and other matrix components in dentinal fluid must be transported either through the caries lesion in the enamel to saliva or through the odontoblast to the pulp (active transport). This facilitates further processing of the degradation products intracellularly during the passage through the cell.

Alkaline Phosphatase↗
PubMed2006

Marginal quality in enamel and dentin after preparation and finishing with an Er:YAG laser.

PURPOSE: To find the most appropriate Er:YAG laser parameters for an optimal marginal adaptation of Class V restorations in enamel and dentin. METHODS: Six saucer-shaped mixed Class V cavities were prepared in each of the eight experimental groups with an Erbium:YAG hard laser (Opus Duo) on extracted human molars in near contact mode with a conical 800 microm sapphire tip under continuous water spray by using different pulse energy and pps (pulse per second) parameters. The cavities were restored under the simulation of dentin fluid with Clearfil SE Bond and Clearfil APX PLT composite applied in two layers and light-cured. Marginal adaptation in enamel and dentin was quantified before and after simultaneous thermal (5-50-5 degrees C, 2 minutes each) and mechanical (max. 49N; 1,200,000 cycles) stresses by using the replica technique in a SEM under x200 magnification. RESULTS: With the exception of dentin margins before loading, significant differences for percentages of "continuous margin" and "enamel fractures" were detected before and after loading (P < 0.05, ANOVA, Student's t-test). A pulse energy of 100 mJ both on dentin and enamel was found optimal for finishing and smoothing the preparation margins after cavity preparation with 500 mJ or more.

Analysis of Variance↗
PubMed1988

[Changes induced by ouabain and colchicine in the transdentinal flow estimated in vivo by perfusion: the "push-pull" of the incisors of rats].

The active or passive mechanisms regulating the various movements of dentinal fluid have not yet been sufficiently studied. For this reason different "in vivo" factors that may modulate the kinetics of transdentinal flow were investigated. After systemic administration of a radiotracer in rats, the kinetics were examined with a push-pull perfusion device fixed to the incisor dentin. The drugs chosen, i.e. ouabain and colchicine, were for their respective effects on microtubules and on the ATPase-dependent Na+ K+ pump, since these two factors are involved in the transport process. Anesthetized animals were prepared to allow intravenous injection of iodine 125 (0,5 to 0,7 mCi), carotid sampling, and perfusion of upper incisors. Ouabain induced a very significant decrease in transdentinal flow, which was particularly evident in younger animals (2,81 x 10(-2) % vs 0,04 x 10(-2)%, p less than 0,05). However, colchicine produced two different kinds of results : at low doses (3,5 to 5 mg/100 g) the pulsatile pattern of the curves was partially inhibited, whereas, at higher doses (6 to 7 mg/100 g), the transdentinal flow of radioactivity increased. These results suggest that a combination of active and passive transport may be involved in the various movements of this fluid.

Animals↗
PubMed1984

Effects of air-drying in vitro on human dentine permeability.

The effects of evaporation produced by air blasts of 0, 0.5, 2 or 5 min to dentine in vitro were evaluated by measuring dentine hydraulic conductance before and after each trial. When the tubules were filled with water, even prolonged evaporation had no effect on dentine permeability. Tubules filled with physiological salt solution produced a time-dependent decrease in dentine permeability. Tubules filled with 1.5 per cent albumin in water gave the largest reductions in dentine permeability. These effects were more marked in unetched as opposed to acid-etched dentine. The results suggest that part of the reduction in dentine sensitivity produced clinically by prolonged air blasts may be due to precipitation of organic and inorganic constituents of dentinal fluid at the surface.

Acid Etching, Dental↗
PubMed1977

The morphologic relationship between dental resins and etched dentin.

A scanning electron microscopic examination of the interface between etched dentin and several different commercial resins showed that pretreatment with othophosphoric acid enlarged the dentinal tubules facilitating penetration of the resin. The depth of penetration increased from approximately 0.2 mm to 2.0 mm when dentin was dried for 24 hours compared to using the normal clinical protocol. The hydration of dentin and/or the presence of dentinal fluid probably influences the degree of resin penetration. While penetration would provide a means of mechanical retention of resin it would probably do so at the expense of dentin and pulp viability particularly where remaining dentin thickness is less than 1.0 mm. Penetration of toxic resin would account in part for the enhanced inflammatory pulpal response observed following application of acid etch restorative procedures.

Absorption↗
PubMed2006

Spectroscopic investigation of the function of aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution as a dentin desensitizer.

Fourier-transform (FT)-Raman and -infrared (IR) spectroscopy were employed to investigate the function of the aqueous 2-hydroxyethylmethacrylate/glutaraldehyde solution (Gluma) as a desensitizer. 2-Hydroxyethylmethacrylate (HEMA), glutaraldehyde (GA), and the mixture of HEMA/GA (i.e. Gluma) were used to interact with dentin, collagen, hydroxyapatite (HAP), and bovine serum albumin (BSA) individually. All the interactions were monitored by an FT-Raman spectrometer. FT-IR spectroscopy was also used in this study. The results show that HEMA could be absorbed by dentin and collagen; GA could cross-link collagen and BSA; and when BSA was added to Gluma, polymerization of HEMA occurred. The results suggest that Gluma acts as a desensitizer whereby, first, GA reacts with part of the serum albumin in dentinal fluid, which induces a precipitation of serum albumin, then, second, a reaction of GA with serum albumin induces polymerization of HEMA. The function of Gluma as a desensitizer to block dentinal tubules occurs via these two reactions.

Absorption↗
PubMed1985

The movement of radioactive molecules across dentine in vivo in the dog.

Using a technique for measuring the movement of circulating molecules across the odontoblast-dentinal complex, the movement of water and alpha-aminoisobutyric acid through dentine and into a flow cell prepared on the tooth is described. The movement of water depended on dentine thickness, and varied from 0.40 microliter/min per cm2 in a flow cell overlying an average thickness of 0.74 mm of dentine, to 1.23 microliter/min per cm2 in a flow cell with a dentinal floor of 0.40 mm average thickness. The data suggest that alpha-aminoisobutyric-acid concentrations were lower in dentinal fluid than in blood plasma.

Aminoisobutyric Acids↗
PubMedDate not supplied

[Microbial permeability of dentin].

This is a review of the literature about the contemporary aspects of microbial permeability of dentin. They are discussed the factors that are responsible for this question and analytically: the structure of dentin, the composition of dentin in organic and inorganic ingredients, the response mechanisms of dentin, that is the irritation dentin and sclerotic dentin, the hypermineralized zone under carious lesions, the role of saliva and dentinal fluid, the role of pulp and its microcirculation against the invasion of microbes and, the role of smear layer. Also this article refers to the immunological reaction of the pulp and finally to the role of dentist in the permeability of dentin, because the more conservative is a tooth preparation the less is the permeability of dentin. In conclusion, the microbial permeability of dentin is a very complicated biological phenomenon that needs more study and further investigations.

Dental Pulp↗
PubMedDate not supplied

In vivo adhesive interface between resin and dentin.

V-shaped cervical cavities prepared in monkey teeth were restored with several dentin bonding systems, and the in vivo resin-dentin interfacial structures were observed under the scanning electron microscope using an argon-ion etching technique. The hybrid layer could be clearly observed; its depth was dependent on the conditioner/primer used and tended to be thinner at the deep part of the cavity. Resin tags were also clearly observed, and their structure at the inner part was noted to be rougher than that closer to the tubule orifices. When 37% phosphoric acid gel was used, the tags in the deeper parts of the cavity were much rougher. Hemispherical and spherical roughened structures were observed directly above the tubule orifices, which were thought to be a mixture of dentinal fluid and bonding resin that had flowed out from the tubules. The acidic primer containing maleic acid and HEMA could not remove the smear plugs, and undissolved smear particles were observed in the tubules.

Acid Etching, Dental↗
PubMed1987

Physiological factors affecting secretion of parotid hormone.

A parotid hormone (PH) that stimulates a dentinal fluid transport (DFT) mechanism in rat teeth is part of the hypothalamic parotid gland endocrine axis (HPEA). Infusion of a porcine hypothalamus-thalamic tissue extract (PHTE) into anesthetized rats stimulates the DFT mechanism in intact animals but is ineffective in parotidectomized rats. Infusion of PHTE into intact conscious pigs raises the plasma titer of immunoreactive PH (iPH) five- to eightfold. Parotidectomy prevents the response. The feeding of pig chow is a potent stimulus for iPH secretion: an 11-fold increase is reached within 10-20 min, and the response is directly related to the length of the feeding stimulus. No response is obtained after parotidectomy. The secretion of saliva and iPH from the parotids occurs independently of each other, suggesting different control mechanisms for each function. The immediate secretion of iPH in response to feeding and its relationship to DFT stimulation may represent a systemic physiological process by which resistance of teeth to decay is enhanced at a time when the acidogenic potential of the oral microbes is maximum.

Animals↗
PubMed2005

Fluorescence microscopy for the evaluation of the margins of Class V restorations in vitro.

PURPOSE: First, to elucidate the cause of the appearance of "white lines" in Class V restorations as seen under the light microscope and their enhancement when using a fluorescent microscope (FM); second, to compare the results of the FM quantitative marginal analysis to those of the SEM quantitative marginal analysis. MATERIALS AND METHODS: Thirty-two standardized Class V fillings, with half of the preparation in dentin and half in enamel, were placed in 16 human caries-free premolars on the buccal and lingual surface using 4 adhesive systems (Clearfil SE, Syntac, 2 experimental self-etching adhesives) and the composite Tetric Ceram. All teeth were connected to a device containing horse serum to simulate dentinal fluid and subjected to thermomechanical loading (1,200,000 cycles at 49 N, 3000 cycles at 5 degrees C/55 degrees C). The restoration margins of 24 fillings were directly evaluated with FM--after the fabrication of replicas--and with SEM. Eight fillings were used to elucidate the cause of the fluorescent signal, by examining them with FM and different filters under dry and moist conditions, and also with dark field microscopy and CLSM. Further, two Class V fillings with the same composite but without the fluorescent substances were made and evaluated. Selected specimens were cut in the bucco-oral direction to analyze the restorative interface on section replicas with SEM. To detect differences between FM and SEM, the Wilcoxon test was performed (p < 0.05). To evaluate the degree of agreement between the two evaluation methods, a linear regression analysis was performed and the Spearman correlation coeffcient was calculated. RESULTS: The evaluation of Class V restorative margins by SEM, dark field microscopy, and CLSM revealed that the phenomenon seems to be an optical effect caused by the debonding of the composite from the underlying substrate creating another refractive environment when air penetrates into the gap. The effect depends on the geometry of the cavity design, the absence of moisture, and the use of a fluorescent composite material. The light source that produced the best visible results covered both ultraviolet and the blue part of white light (350 to 460 nm), producing light green lines and green areas. Those green or white areas as seen with the light microscope were related to gaps in the interface between tooth substance and composite. With the exception of one of the experimental self-etching adhesives, the mean percentage of continuous margin of the 4 groups showed no statistically signifcant dfference for the two test methods. Linear regression analysis revealed a good correlation between the two test methods for dentin margins and a moderate correlation for enamel margins. CONCLUSION: Fluorescence microscopy seems to be a useful tool for evaluating dentinal and enamel margins of Class V restorations in vitro.

Adhesives↗
PubMed2006

Proximal direct composite restorations and chairside CAD/CAM inlays: marginal adaptation of a two-step self-etch adhesive with and without selective enamel conditioning.

The aim of this study was to evaluate the marginal adaptation of CEREC ceramic inlays, CEREC composite inlays and direct composite restorations in unbeveled proximal slot cavities under artificial aging conditions. Two groups of each restoration type were prepared (n = 6), one group with a self-etch adhesive, the other group with H(3)PO(4) enamel etching before the self-etch adhesive application. Replicas were generated before and after long-term thermo-mechanical loading under dentinal fluid simulation and margins were evaluated at x200 magnification in the scanning electron miscroscope (SEM). Statistically, significant differences were found before and after loading with respect to the percentages of "continuous margins", the direct composite filling with H(3)PO(4) enamel etching giving the lowest percentages of "continuous margins" after loading (p < 0.05). The highest percentage of "continuous margin" was attained by composite inlays without H(3)PO(4) enamel etching. However, these results were not significantly different from ceramic inlays after stressing. Polymerization shrinkage is still one critical property of composite restorative materials. The marginal adaptation of indirect adhesive proximal slot restorations without enamel bevels both fabricated out of composite and ceramic is better than that of directly placed composite restorations.

Acid Etching, Dental↗
PubMed1991

Correlation of in vivo and in vitro performance of adhesive restorative materials: a report of the ASC MD156 Task Group on Test Methods for the Adhesion of Restorative Materials.

Before a standard designed to test the adhesion of adhesive restorative materials can be accepted, it is necessary to identify those parameters which are of clinical relevance and which can be studied under in vitro testing conditions. The goal of this report has been to identify information related to how dentinal fluid, intra-tubular pressure, polymerization shrinkage, cavity preparation, cavity shape, placement technique, curing method, tooth age, environmental conditions, masticatory forces, thermal cycling, and microleakage influence the bond strength++ of adhesive restorative materials. This review is also intended to function both as an information base of past experimental data as well as a source of guidance for further, needed research.

American Dental Association↗
PubMed1997

An in vitro study of various instruments for root planing.

Rotating instruments are becoming increasingly significant in the scaling and planing of the root surface. The objective of this in vitro study was to test various root-planing instruments on extracted teeth and then to compare the treated surfaces using scanning electron microscopy. Two manual instruments (scaler and curette) and five mechanically rotating instruments (Desmo-Clean; Perio-Set; Viking-Set; and 40-microns and 15-microns diamond finishers) were investigated. From a total of 42 teeth, six root surfaces were treated with each instrument. The results confirm the clear superiority of the manual instruments (especially the curette). The manual instruments permit good root planing with minimum ablation from the root surface and only a thin smear layer (a compound of grinding dust, dentinal fluid, and water). The best planing results by rotating instruments were achieved with the Desmo-Clean and the 15-microns diamond finisher, whose performance was almost equal to that of the manual instruments. The rotating instruments, however, were associated with higher ablation and a marked smear layer. Manual instruments remain the media of choice on easily accessible root surfaces; however, rotating instruments are of advantage in inaccessible areas (eg, furcations) because of their handling properties.

Bicuspid↗
PubMed1992

In vitro evaluation of dynamic fluid displacement in dentinal tubules activated on pin placement.

The use of cemented, friction-lock, and self-threading pins for improving retention has been essential for treatment in restorative dentistry, with the self-threading pin considered to be the most retentive. Cavity varnish has been suggested to prevent microleakage around pins. This study investigated the insertion of a self-threading pin when the pinhole was filled with a liquid dye. The results showed that pinholes filled with dye before pin placement had measurable dye displacement. Pinholes without pins displayed no measurable dye displacement through the dentin; this was also true when the dye fluid was removed before the pin placement. However, the dye in pinholes was displaced toward the path of least resistance, and fluid in a pinhole can contribute to crazing of the dentin during placement.

Dental Leakage↗