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PubMed2003

The in vitro detection of early enamel de- and re-mineralization adjacent to bonded orthodontic cleats using quantitative light-induced fluorescence.

The purpose of this study was to determine whether quantitative light-induced fluorescence (QLF) could detect very early demineralization and remineralization longitudinally adjacent to orthodontic components in an in vitro model. Extracted human premolars (n = 13) were sectioned sagittally to produce two equal halves and an orthodontic cleat was bonded to the buccal surface of each tooth. Transparent nail varnish was placed over the remaining surface, leaving exposed enamel windows adjacent to the cleat on the coronal and gingival aspects. Each half-tooth was placed into the lid of an Eppendorf tube and randomly assigned to either control (distilled water) or experimental (lactic acid demineralizing buffer, pH 4.5) regimes. Digital photographs and QLF baseline images were taken. The tubes were mounted into a rotating holder and left for 24 hours. QLF and digital photographs were taken, the solutions refreshed and the teeth returned. This was continued every 48 hours for 288 hours. At this time the lactic acid buffer was replaced with a remineralizing solution (artificial saliva, fluoride, calcium) and the experiment continued with weekly examinations. QLF images were analysed and deltaQ at the 5 per cent threshold recorded. Analysis of the QLF images showed that both demineralization and remineralization were identified and monitored. Statistical differences between each of the timed examinations were found (P < 0.05). Analysis of the photographs demonstrated that QLF detected subclinical lesions. This initial pilot study has demonstrated the potential for QLF to longitudinally monitor de- and re-mineralization of enamel adjacent to orthodontic cleats in vitro.

Dental Caries Activity Tests↗

PubMed2001

Further observations on tertiary dentin in human deciduous teeth.

The structure of reparative tertiary dentin in human deciduous teeth has been studied. Reparative dentin is secreted by a new generation of odontoblast-like cells which have been subject to strong stimuli, e.g., trauma or deep active caries lesions with associated pulp inflammation. Ground sections of 25 teeth were prepared, and contact microradiographs were produced. Another 30 teeth were demineralized, embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Some demineralized sections from each tooth were also studied in the scanning electron microscope. Most of the teeth showed some type of tertiary dentin formation. Mineralized tissue with a varied morphology was observed. In teeth which had been subject to trauma, the entire pulp chamber was sometimes obliterated. Mineralization seemed to start in the incisal region, and the central part of the pulp was the last part to be obliterated. Radiolucent voids and canals were seen. The organic matrix was dense and fibrous. In the pulp chamber and especially in the root canals, resorption had often occurred, indicating that signals giving rise to odontoclasts were also present. Resorption was often followed by deposition of various amounts of cementum-like repair tissue. The cells responsible for the formation of reparative dentin are believed to be subodontoblasts or undifferentiated ectomesenchymal cells. The varied morphology of the reparative dentin, observed in the pulp of the teeth examined, indicates that different stimuli lead to induction of hard-tissue-forming cells which produce different types of hard tissue.

Cementogenesis↗

PubMedDate not supplied

Composite cure and pulp-cell cytotoxicity associated with LED curing lights.

This study compared the cure and pulp-cell cytotoxicity of composites polymerized with light-emitting diode (LED) and halogen-based light curing units. A mini-filled resin composite (Tetric Ceram, Vivadent), two LED (E-light [EL], GC and Freelight [FL], 3M-ESPE), a conventional halogen (Max [MX], Dentsply) and a high-intensity halogen light (Astralis 10 [AS], Vivadent) were evaluated. Cure associated with the different lights was determined by measuring the top and bottom surface hardness (KHN; n = 5) of 2-mm thick specimens using a digital microhardness tester (load = 500 gf; dwell time = 15 seconds). Pulp-cell cytotoxicity was assessed using a direct contact method involving incisor tooth slices dissected from 28-day old Wistar rats maintained in Dulbecco's Modified Eagle's Medium (DMEM) and 1% agarose. The bottom surfaces of the cured composite specimens (7-mm diameter and 2-mm deep) were placed in contact with the openings of each tooth slice. After incubation in 5% CO2 atmosphere at 37 degrees C for 48 hours, the tooth slices were fixed, demineralized and processed for histological examination. Pulp fibroblasts and odontoblasts were counted histomorphometrically at 400x magnification within a 1500 microm2 area using a computerized micro-imaging system. Eighteen readings were obtained for each curing light. Data was subjected to ANOVA/Scheffe's test and Pearson's correlation at significance level 0.05 and 0.01, respectively. At the top surfaces, the cure with AS was significantly greater than the other curing lights, with MX and FL being significantly greater than EL. At the bottom surfaces, MX, AS and FL had significantly better cure than EL. Specimens cured with MX were less cytotoxic than those polymerized with other curing lights. Specimens cured with AS and EL were significantly less cytotoxic than FL. Composite cure and cytotoxicity associated with LED lights is device dependent. Composite cure was not correlated to pulp-cell cytotoxicity. The response of pulpal fibroblasts to unreacted/leached components of composites differs somewhat from odontoblasts.

Analysis of Variance↗

PubMed2001

Laser-matrix-fluoride effects on enamel demineralization.

Laser and fluoride have been shown to inhibit enamel demineralization. However, the role of organic matrix and their interactions remains unclear. This study investigated the interaction among CO2 laser irradiation, fluoride, and the organic matrix on the demineralization of human enamel. Twenty-four molars were selected and cut into halves. One half of each tooth was depleted of its lipid and protein. The other half served as a matched control. Each tooth half had two window areas, treated with a 2.0% NaF gel. All left windows then received a laser treatment. Next, the tooth halves were subjected to a four-day pH-cycling procedure that created caries-like lesions. Tooth sections were cut from the windows, and microradiographs were used for quantification of the demineralization. The combined fluoride-laser treatment led to 98.3% and 95.1% reductions in mineral loss for enamel with and without organic matrix, respectively, when compared with sound enamel.

Analysis of Variance↗

PubMed1985

Intercellular junctions between human odontoblasts. A freeze-fracture study after demineralization.

Intercellular junctions in the odontoblastic layer have been studied with a freeze-fracture technique. Children's tooth germs were fixed, sliced and demineralized. Samples of the pulpodentinal border were routinely prepared for freeze-fracture. Three kinds of intercellular junctions were detected between human odontoblast cell bodies: gap junctions, desmosomes and tight junctions. Numerous gap junctions are responsible for intercellular communication at different levels of the cell bodies. Focal tight junctions, parallel to the axis of the cell, and desmosomes are sites of cell-to-cell adhesion between lateral plasma membranes. At the distal end of the cell bodies, junctional complexes consist of zonular tight junctions and gap junctions. These zonular tight junctions, never before described between odontoblasts, contribute to the pseudo-epithelial organization of the odontoblastic layer. They constitute a predentin-pulp barrier, the permeability of which must be studied to establish their role in relation to dentin formation.

Adolescent↗

PubMedDate not supplied

Utilization of laser fluorescence to monitor caries lesions development in primary teeth.

PURPOSE: The objective of this study was to analyze and evaluate laser fluorescence (LF) performance in monitoring and quantifying smooth-surface incipient caries lesions in primary teeth. METHODS: Artificial caries lesions were produced in 2 delimited windows on the buccal surface of 24 primary incisors using a pH-cycling procedure. LF (DIAGNOdent) readings were collected on the windows on each tooth surface before (sound enamel) and after (artificial caries lesions) the demineralization process. The left lesion of each tooth was used for the polarized light microscopy analysis. Statistical tests were performed to observe the performance of the method and correlation between LF readings and caries lesions depth. RESULTS: There was a significant increase in the LF readings after demineralization (P < .0001). The area under receiver operating characteristic curve was 0.956, showing a good result of the method. The best cut off LF value to detect incipient caries was 5, and with this value, sensitivity, specificity, and accuracy was 0.78, 1, and 0.89, respectively. Pearson's correlation coefficient between DIAGNOdent values and caries lesion depth was 0.68. CONCLUSIONS: Although LF was good at detecting artificial caries lesions in primary teeth, the quantification of mineral loss was undesirable.

Dental Caries↗

PubMed2001

[Comparison of the effect of fluoride and non-fluoride dentifrices on enamel demineralization and remineralization in vitro].

OBJECTIVE: The purpose of the experiment is to investigate the effect of fluoride dentifrices in China on the intact and artificial caries-like bovine enamels. METHODS: The artificial caries-like lesions were created by dipping the teeth into an acid buffered solution. Both the bovine intact enamels and the artificial caries-like enamels were assigned tooth brushing 20 times every half an hour with 3 kinds of fluoride dentifrices and one kind of non-fluoride dentifrices respectively. The amount of calcium dissolved by lactic acid was determined as the susceptibility of demineralization by atomic adsorption spectrometry (AAS). RESULTS: The group treated with fluoride dentifrice showed significantly less demineralization than the non-fluoride group (P < 0.02). The effect of inhibition of acid solubility in artificial caries-like enamel after tooth brushing is significantly greater than that in intact enamel. CONCLUSION: Fluoride dentifrices in this experiment can prevent both intact enamel and artificial caries-like enamel from acid solubility after tooth brushing, and it seems that the effect of the fluoride dentifrices on the redemineralization is greater than the reduction of enamel solubility.

Animals↗

PubMed1995

Collagen formation at the tooth-cell interface: comparative ultrastructural study on the effect of partial demineralization of cementum with dentin.

In order to compare the effect of partial demineralization with root planing and partial demineralization of cementum with that of dentin on healing, the ultrastructural morphology of the interface between the layer of human periodontal ligament-derived, fibroblast-like cells (HPF) and the treated root surface was studied in an in vitro culture system. Sixty (60) pairs made from transversally-cut root slices, 500 microns thick, were obtained from extracted human periodontally diseased teeth. Thirty (30) pairs of the root slices were preliminarily root planed (RP). The remaining half were root planed and then partially demineralized in a solution of citric acid (RP+CA). The opposite surface of paired slices was made uniform by using either cementum or dentin. Consequently, all root slices were classified into four experimental groups: RP-cementum and RP-cementum pairs (group 1), RP-dentin and RP-dentin pairs (group 2), RP+CA-cementum and RP+CA-cementum pairs (group 3), and RP+CA-dentin and RP+CA-dentin pairs (group 4). Each pair of root slices was placed on the floor of a 35-mm culture dish. HPF were seeded at a concentration of 4 x 10(5) cells/dish. Co-cultures of HPF and the root slices were examined using phase contrast and electron microscope after 4, 6, and 10 weeks. Electron-dense material covered non-demineralized root surfaces and the lining cells in accumulating cell layers were oriented parallel to the root surface and attached to the material in groups 1 and 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Adhesion↗

PubMed1999

Evaluating the effects of fluoride-releasing dental materials on adjacent interproximal caries.

BACKGROUND: The authors examined several restorative materials to evaluate their ability to inhibit demineralization and enhance remineralization of incipient carious lesions on the interproximal enamel of teeth adjacent to those restored with the materials. METHODS: Twenty-one subjects in need of a crown on a mandibular molar and a Class II inlay on an adjacent tooth took part in this six-phase study. Artificial enamel lesions were created and positioned within the interproximal portion of a crown. Lesions were photographed with polarized light microscopy and characterized before and after 30-day intraoral exposures. Each phase included the placement of a new section in the crown model and a new Class II inlay restorative material in the adjacent tooth. RESULTS: Results demonstrated that nonfluoridated resin composite, fluoridated resin composite and resin-modified glass ionomer restorative materials, when placed in subjects who brushed with a fluoridated dentifrice, demonstrated significantly (P < .05) less enamel demineralization than the nonfluoridated resin composite control placed in subjects who brushed with a nonfluoridated dentifrice. The resin-modified glass ionomer cement, however, even when brushed with a nonfluoridated dentifrice, exhibited significantly (P < .05) less demineralization than the nonfluoridated resin composite control brushed with a nonfluoridated dentifrice. CONCLUSIONS: Resin-modified glass ionomer cement appears to significantly inhibit demineralization of interproximal enamel of teeth adjacent to those restored with the material. CLINICAL IMPLICATIONS: Resin-modified glass ionomer cement restorations can enhance prevention of enamel demineralization on adjacent teeth.

Acrylic Resins↗

PubMed2000

The science and practice of caries prevention.

BACKGROUND AND OVERVIEW: Dental caries is a bacterially based disease. When it progresses, acid produced by bacterial action on dietary fermentable carbohydrates diffuses into the tooth and dissolves the carbonated hydroxyapatite mineral--a process called demineralization. Pathological factors including acidogenic bacteria (mutans streptococci and lactobacilli), salivary dysfunction, and dietary carbohydrates are related to caries progression. Protective factors--which include salivary calcium, phosphate and proteins, salivary flow, fluoride in saliva, and antibacterial components or agents--can balance, prevent or reverse dental caries. CONCLUSIONS: Caries progression or reversal is determined by the balance between protective and pathological factors. Fluoride, the key agent in battling caries, works primarily via topical mechanisms: inhibition of demineralization, enhancement of remineralization and inhibition of bacterial enzymes. CLINICAL IMPLICATIONS: Fluoride in drinking water and in fluoride-containing products reduces caries via these topical mechanisms. Antibacterial therapy must be used to combat a high bacterial challenge. For practical caries management and prevention or reversal of dental caries, the sum of the preventive factors must outweigh the pathological factors.

Adolescent↗

PubMed2004

Effect of dentinal fluid composition on dentin demineralization in vitro.

Dentin demineralization is reduced by perfusion with water. We hypothesized that a simulated dentinal fluid (SDF) that contains albumin, in addition to electrolytes, would be more effective in reducing dentin demineralization than water alone, and this effect would increase with increasing flow rate of SDF. Perfusion rate in tooth segments that carried buccal cervical dentin windows was measured in a fluid transport set-up. These windows were then demineralized under perfusion with water, or SDF at 1.47 kPa for 31 days. We analyzed integrated mineral loss and lesion depth with the use of transverse microradiography (TMR), which revealed that 38% more mineral dissolved from dentin lesions perfused with water than from those perfused with SDF. The former were also 18% deeper. Flow rate of dentinal fluid showed no correlation with demineralization. We concluded that composition of dentinal fluid is an important determinant of the rate of lesion formation and progression in dentin.

Albumins↗

PubMed1999

The in vitro demineralization potential of a sodium fluoride, calcium and phosphate ion-containing dentifrice under various experimental conditions.

While fluoride has had a dramatic effect in reducing the rate of caries, it has failed to provide complete protection against caries development, and tooth decay is still widely prevalent. The objective of this study was to determine the demineralization prevention potential of a remineralizing dentifrice with fluoride (Enamelon), and an assured supply of calcium and phosphate ions on bovine enamel in a cyclic remin/demin regimen using various experimental conditions. A conventional fluoride toothpaste, Crest, and a placebo dentifrice were used as controls. One-hundred and forty-four ground and polished 4 mm bovine enamel cores were prepared and assigned to various test treatments using six specimens per treatment group. They were subjected to six cyclic treatments consisting of one-minute exposures at room temperature to the test product diluted 1:2 in water, remineralization for a specified time at 37 degrees C, and demineralization for a specified time at 37 degrees C. The enamel specimens were tested for micro-hardness initially, and after the first, third and sixth treatment, remineralization and demineralization cycles using a Buehler Micro-hardness Tester with a 200 g load. Differences in micro-hardness between the test groups were analyzed for significance by performing multiple pair-wise comparisons using Bonferroni significance levels at the 95% confidence level. The results of this study showed that Enamelon Toothpaste was generally more effective in preventing demineralization of enamel than the fluoride dentifrice at 0.5 and 1.5 hours, and the non-fluoride control dentifrice at all time measurements. Prevention of enamel demineralization by the dentifrices was affected by changes in demineralization time and pH, but not by changes in remineralization time.

Animals↗

PubMedDate not supplied

In vitro evaluation of fluoride-releasing restorative materials for sealing the root canals of overdenture abutments.

PURPOSE: The purpose of this study was to evaluate the ability of newer fluoride-releasing restorative materials to protect the root surface from acid attack. MATERIALS AND METHODS: The materials used were glass-ionomer cement (GIC), resin-modified glass-ionomer cement (RM-GIC), and a compomer (Comp). A composite resin (CR) was used as the control. The restored teeth were stored in deionized, distilled water for 14 days and subjected to 300 thermocycles (55 degrees C and 5 degrees C). The teeth were cycled in a demineralizing solution (pH 5.0 or 4.0) for 6 hours and in a remineralizing solution (pH 7.0) for 17 hours for 10 days. The depths of lesions created by acid challenge were measured at the interface of the tooth and the restorative material and then at a distance of 50, 100, and 300 microns from the tooth-restoration margin using polarized light microscopy and contact microradiography. RESULTS: At pH 4.0, there was significant difference in the depth at the interface between the tooth and the restorative material (P < .001). The GIC and RM-GIC were protective, and the lesion depths were significantly shallower than for Comp or CR. The protective effect varied depending on the distance from the interface of the tooth and the restorative material. At pH 5.0, the GIC and RM-GIC had no lesions at the interface, while the Comp and the CR had lesions (P < .001). CONCLUSION: Fluoride-releasing glass-ionomer cement seems to be an appropriate material to seal the root canals of overdenture abutments, because it has an inhibiting effect on demineralization at the cavity wall in vitro.

Aged↗

PubMed2006

Effect of fluoride on artificial caries lesion progression and repair in human enamel: regulation of mineral deposition and dissolution under in vivo-like conditions.

OBJECTIVE: This study was carried out to determine in vitro the effect of fluoride on (1) the demineralization of sound human enamel and (2) the progression of artificial caries-like lesions, under relevant oral conditions. METHODS: Thin sections of sound human enamel were exposed to solutions undersaturated with respect to tooth enamel to a degree similar to that found in dental plaque fluid following sucrose exposure in vivo, containing fluoride concentrations (0-0.38ppm) found in plaque fluid. Mineral changes were monitored for 98 days, using quantitative microradiography. The effect of fluoride (1.0-25.0ppm) on the progression of artificial caries-like lesions was similarly studied. RESULTS: Fluoride concentrations of 0.19ppm and greater were found to prevent the demineralization of sound enamel in vitro. However, significantly higher concentrations of fluoride (25.0ppm) were required to prevent further demineralization of artificial caries-like lesions. Demineralizing solutions with intermediate fluoride concentrations (2.1-10.1ppm) induced simultaneously remineralization in the outer portion of the lesion and demineralization in the inner portion. Simultaneous remineralization and demineralization were also observed in hydroxyapatite pellets. CONCLUSIONS: Our results show that the observed effect of fluoride on enamel demineralization is not solely a function of bulk solution properties, but also depends on the caries-status of the enamel surface. A mechanistic model presented indicates that, in comparison to sound enamel surfaces, higher concentrations of fluoride are required to prevent the progression of artificial caries-like lesions under in vivo-like conditions since the diffusion of mineral ions that promote remineralization is rate-limiting.

Analysis of Variance↗

PubMedDate not supplied

Influence of two dentin bonding systems on the demineralization of the root surface.

It has been assumed that dentin adhesives can prevent root surface caries. The aim of this study was to determine the caries-protective effect of two different dentin bonding systems on the demineralization of root surfaces in vitro. The root surfaces of 60 freshly extracted caries-free human molars were thoroughly cleaned and polished, thereby removing the cementum. The teeth were then coated with acid-resistant nail varnish, exposing two rectangular windows of 6 mm2 each. One window served as an untreated control, while the other window was treated with a dentin bonding system. The specimens were distributed among the following experimental groups--Group 1: Syntac, Heliobond (no air thinning); Group 2: Syntac, Heliobond (as recommended); Group 3: Syntac, without Heliobond; Group 4: Prime & Bond 2.0 (no air drying); Group 5: Prime & Bond 2.0 (as recommended); Group 6: Prime & Bond 2.0 (dentin pretreated with 36% phosphoric acid). Subsequently, all specimens were demineralized for 6 days with acidified gel (HEC, pH 4.8, 37 degrees C). From each tooth, three dentinal slabs were cut perpendicular to the polished surface of the windows. The slabs were ground to a thickness of 80 microns and imbibed with water. The depth of the respective demineralized areas was determined using a polarized light microscope. All control specimens exhibited lesions with a mean depth of 67 microns. In Groups 2, 3, and 5 the lesion depth was reduced significantly, while in Groups 1, 4, and 6 no lesions could be detected. It was concluded that the demineralization of the root surface can be impeded by application of the dentin adhesives tested.

Acrylates↗

PubMed1980

Enamel remineralization as a factor in the pathogenesis of dental caries.

This paper described an investigation of local resistance acquired in response to cariogenic attacks and remineralization periods from environmental fluids. Surfaces from extracted human teeth with yellow and brown areas indicative of consolidated carious lesions were exposed to acid buffers. Subsurface lesions were developed on areas of sound enamel adjacent to, but not in areas of, consolidated lesions. The development of higher tooth resistance to acid through demineralization and remineralization was demonstrated experimentally on bovine enamel presoftened in acid, treated with fluoride, exposed to the oral environment, and finally exposed to acid buffers for development of subsurface lesions. These results are interpreted as an extension of theory of tissue adaptation to an injurious challenge, in that the tooth surface is primed by the challenge for possible remineralization and the development of higher resistance. This, cariogenic challenges can result in either local adaptation of the enamel to the challenge through lesion consolidation or to open cavitation. As in any biological adaptation, the determining factors for the final outcome are: (a) the frequency and duration of the challenge, (b) the frequency and duration of remineralizing conditions, and (c) the composition of the remineralizing fluid. The implications of the theory in the pathogenesis of caries are discussed in the light of clinical and laboratory investigations.

Animals↗

PubMed2006

Effect of CHX on the decalcifying effect of 10% citric acid, 20% citric acid, or 17% EDTA.

The objective of this study was to measure the demineralization capacity of 10% and 20% citric acid and 17% EDTA after three time periods and to determine whether it was modified by the addition of 1% of commercial chlorhexidine (CHX). Three slices of 2-mm thickness were cut from the cervical third of the root of ten bovine incisors and sectioned into two equal parts, obtaining six specimens per tooth. Specimens were assigned to one of six groups (n = 10) for immersion in 25 ml of the above mentioned solutions or 25 ml of these same solutions plus 1% CHX (Hibimax). At 3, 10, and 15 min of immersion, the concentration of Ca2+ was measured by atomic absorption spectrophometry. The demineralization effect of all solutions was time-dependent (F = 158,448; p < 0.001), without significant differences among them (p = 0.783). Addition of 1% CHX did not modify the demineralizing capacity of these solutions. In the first three minutes, significantly more [Ca2+] was obtained when 17% EDTA was used in comparison with the other solutions.

Animals↗

PubMedDate not supplied

In vitro demineralization inhibition of enamel caries utilizing an unfilled resin.

Smooth surface caries remain a concern in children, particularly those that are diagnosed with "baby bottle caries." The purpose of this study was to evaluate the caries inhibition of an unfilled resin placed on smooth enamel surfaces. Incisors were obtained and painted with an acid-protective varnish, excluding 2 mm x 6 mm windows on the labial surface. Each tooth had an unfilled resin placed over half the area of the window; the remaining area was not treated. One hundred microns longitudinal sections were obtained from the treated and non-treated sites. Polarized photomicrographs were taken of each section, in imbibition media of air, water and Thoulet's (R.I.: 1.41, 1.47), representing a minimum of 1%, 5%, 10%, and 25% pore volume respectively. The sections were then painted with an acid-protective varnish so that only the external surface was exposed and placed in separate closed environments of a non-fluoridated artificial saliva. One section from each tooth had unfilled resin on the external surface, one section had only natural enamel exposed, and a third section had the external surface varnished to act as a control. The teeth were thermocycled at 10 degrees C and 50 degrees C, 20 cycles per day for three months; they were also cycled through artificial caries challenge (pH 4.4) for 35 minutes, three times per day. Sections were then photographed under polarized light, as before, and areas of lesions were digitized. Results demonstrated caries to be present on all non-treated enamel surfaces exposed to the artificial caries challenge. Significantly less enamel demineralization occurred when an unfilled resin was placed on it (p < 0.001).

Composite Resins↗