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PubMed1997

Caries progression of white spot lesions sealed with an unfilled resin.

This study evaluated the artificial caries resistance provided to white spot lesions by sealing with an unfilled resin. Twenty extracted molar teeth were coated with an acid-resistant varnish (ARV), except for two 5 mm x 2 mm enamel windows (mesial and distal), and immersed for 5 weeks in an acidified gel brought to a pH of 4.2 with lactic acid. White spot lesions (not frank caries) were created in each window. The teeth were removed from the gel, rinsed and dried. One window was divided into two equal parts; one half was covered with the ARV (Group 1); the other half was not covered (Group 2). The other window was treated with 37% phosphoric acid for 20 sec, rinsed with water for 20 sec, dried and sealed with Prisma Universal Bond 2 Adhesive (Group 3). The teeth were reimmersed in the acidified gel for 40 days until frank caries was induced in Group 2. Specimens were then removed from the gel, rinsed, and sectioned occlusogingivally. Sections were polished to approximately 100 microns, imbibed in water, and analyzed using polarized light microscopy. Depth of demineralization was evaluated in the varnished, sealed and frankly carious areas. The mean (SD) lesion depths were as follows: Group 1 (under ARV) 366 microns (103 microns); Group 2 (frank caries) 746 microns (219 microns); Group 3 (under sealed area) 298 microns (111 microns). ANOVA and Student-Newman-Keuls procedure were used to compare group means. The mean depths of demineralization under the ARV (Group 1) and the unfilled resin sealant (Group 2) were significantly less than for the unprotected enamel (Group 2) (p > 0.0001). Results indicate the potential effectiveness of sealing white spot lesions with an unfilled resin to prevent further demineralization.

Analysis of Variance↗

PubMed2006

Effect of loading and pH on the subsurface demineralization of dentin beams.

It is important to understand subsurface dentin demineralization and caries from the clinical perspective as dentin properties are modified under acidic conditions and mechanical loading. This study was conducted to observe the subsurface demineralization of dentin beams at three different pH levels under tension and compression. Bovine dentin beams (10 x 3.75 x 1.45 mm) were fixed at one end and immersed in 0.1 M lactic acid solution at pH levels 4.5, 7, and 10 for 5 days under a load of 6.5 N (663 g), and the subsurface demineralization depth was measured using a polarized light microscope. The mean subsurface demineralization depth was more subjacent to the surface under compression than that under tension at pH 4.5 and decreased as the distance from the fixed end increased. No subsurface demineralization was observed at pH 7 or 10. It was concluded that both stress and low pH are associated with increased subsurface demineralization at the fixed end of the beam.

Animals↗

PubMed1993

Effect of fluoride incorporation into human dental enamel on its demineralization in vitro.

Coronal surfaces of extracted human teeth were ground to a depth of about 1 mm and then cut in half labiolingually. One half was used as a control; the other half was exposed, for 3 days, to a fluoride-enriching buffer (0.1 mol/l lactic acid, 19.7 mmol/l CaCl2, 10.8 mmol/l KH2PO4, 3 mmol/l NaN3; pH adjusted to 4.68 with KOH) having fluoride concentrations from 0.0002 to 2.2 parts/10(6). This exposure resulted in an uptake of fluoride by the enamel to a depth of 2 microns without any apparent demineralization. The fluoride uptake was proportional to the F concentration of the enriching solution, reaching concentrations of about 8000 parts/10(6) within the first micrometre of enamel exposed to the highest F concentration; the controls had uniform F concentrations not exceeding 50 parts/10(6) along the 2.5 microns of enamel depth sampled. Thin sections (140-160 microns) were cut perpendicularly to the lingual surface, coated with protective resin except for a window about 1 mm long on the ground lingual surface, and exposed to a demineralizing buffer. The mineral losses of the sections were followed over 5 days by microradiography and image analysis. Fluoride enrichment resulted in reduced demineralization and the reduction was inversely related to the enamel fluoride content. The controls displayed a uniform erosion of the surface enamel whereas all the treatments below 1.5 parts/10(6) in the enriching solutions developed typical subsurface 'lesions'. The mineral content of the surface layer increased with increasing time of exposure to the demineralizing buffer.(ABSTRACT TRUNCATED AT 250 WORDS)

Buffers↗

PubMed1999

Protective effects of resin impregnation on demineralization of enamel.

PURPOSE: To determine if resin penetrated into the enamel etch pattern, in the absence of a polymerized outer surface film, could reduce the degree of demineralization of enamel subjected to a simulated caries challenge, and to evaluate whether the addition of fluoride to the resin would enhance reductions in demineralization. MATERIALS AND METHODS: Enamel surfaces of extracted human incisors were acid-etched. One-half of the etched area was treated with an unfilled bonding resin, while the other one-half was left untreated as a control. In another group, this same procedure was followed except the unfilled bonding resin contained fluoride. The applied resin was aggressively air thinned to ensure oxygen inhibition throughout the external surface film thickness. The thinned film was visible light-cured and the area was wiped with an ethanol swab to remove the inhibited layer. The specimens were exposed to a buffer solution of pH = 4.7 for 4 days, and were sectioned and examined by polarized light microscopy and microradiography. RESULTS: In each of the two test groups, the demineralization of the resin-treated side was significantly lower than the control side (P < 0.015). Under the conditions of this study, the experimental fluoride resin did not produce statistically significant reductions in demineralization compared with the non-fluoride resin.

Acid Etching, Dental↗

PubMedDate not supplied

Progression of dental demineralization with and without modified tunnel restorations in vitro.

This study evaluated the caries-inhibitory effects of a glass-ionomer cement restoration. As a model to assess these effects, a Ketac-Fil restoration was placed beneath the mesial or distal enamel layer in 14 extracted human molars by means of access from the occlusal fossa. The teeth were insulated in all but two areas on the approximal surfaces. The prepared teeth were mounted on a hollow cylinder and a localized progressing demineralization of the approximal surfaces was induced by storage of the samples in an acidified gel. Immediately before and 14, 21, 28, 35, and 42 days after initiation of demineralization, standardized radiographs were obtained to assess the progression of demineralization. On each radiograph, the demineralized lesions were assessed by measurement of the coronoapical extension (CA) and the central depth (CD). At 28, 35, and 42 days after initiation of the demineralization, the CD of the lesions of the glass-ionomer cement group was revealed to be statistically significantly smaller than the lesions of the control group (no tunnel restoration) (P < 0.1). A multiple linear regression analysis identified CA and time as factors correlated to CD positively and the glass-ionomer restoration as a factor related to CD negatively (P < 0.001). It seems that modified tunnel restorations utilizing glass-ionomer cement inhibit progression of dental demineralization in vitro.

Cariostatic Agents↗

PubMed1992

Surface topography of demineralized dentin preceded by formalin fixation.

Formalin treatment of dentin, prior to burnishing demineralization, results in a "tufted" collagen surface that may optimize bonding of hydroxyethyl methacrylate dentinal bonding agents. The purpose of this study was to determine if there is a clinically acceptable formalin treatment time that will yield a deeply tufted collagen surface. The exposed dentin of periodontally healthy and periodontally diseased human teeth was treated with formalin for various treatment times before "burnishing" demineralization with citric acid. Photographs of the specimens revealed that there was a statistically significant difference in the number of tufted surfaces found in the healthy group, as a whole, and the number found in the diseased group. No statistically significant difference was found among fixation times within either tooth group. It was concluded that 2 minutes of fixation was sufficient to produce a tufted fibrillar surface.

Adult↗

PubMed1986

The influence of chemically-induced modifications of root surfaces on cell migration, attachment, and orientation.

Surface demineralization of tooth root surfaces has been shown to improve re-attachment of cells and to promote tissue reconstruction following periodontal surgery. Exposure of collagen fibers has been thought to facilitate migration, attachment, and orientation of fibroblasts on the root surface. However, using an in vitro assay, we have found that both attachment and orientation of human gingival fibroblasts on demineralized dentin surfaces are further improved following digestion of the exposed collagen with bacterial collagenase. In contrast, pronase and trypsin digestion of the surface collagen had no significant effect, whereas heat denaturation had an inhibitory effect. Dissociative extraction of the demineralized dentin slices with 4 mol/L guanidine hydrochloride (GuHCl) also improved attachment and orientation, and when undemineralized dentin was subjected to dissociative extraction, cell attachment was comparable and orientation superior to that on demineralized surfaces. These studies indicate that demineralization is not a prerequisite for facilitating attachment, and that enhanced attachment and orientation of cells are not dependent upon a collagenous substratum.

Animals↗

PubMed2000

In vitro caries inhibition at the enamel margins of glass ionomer restoratives developed for the ART approach.

OBJECTIVES: To assess the ability of conventional glass ionomer cements manufactured specifically for the atraumatic restorative treatment (ART) approach to inhibit the in vitro demineralization of enamel. METHODS: Twenty-four sound permanent premolar teeth, extracted for orthodontic reasons, had cervical cavities (4x2x1. 5mm(3)) prepared in enamel. These were restored with Fuji IX, Fuji IX GP, Ketac-Molar and Compoglass, and then thermocycled 300 times between 5-55 degrees C before being placed in a demineralizing solution (0.1M lactic acid with 1g/l dissolved hydroxyapatite at pH 4.7) for four weeks. Buccolingual planoparallel sections were cut axially through the restorations, and subsequently lapped to approximately 100 microm thickness. The sections were examined with a polarized light microscope, and lesion measurements made using image analysis software. ANOVA and coefficients of variance were used to compare the findings. RESULTS: Compoglass and Ketac-Molar showed significantly less surface erosion than did the other two cements (p<0.0001). Inhibition of enamel demineralization immediately adjacent to the restoration margins was more frequent with the glass ionomer cements (20.5-25.0%) than with Compoglass (13.0%). However, the widths of the inhibition zones varied between materials and sites. CONCLUSIONS: Fluoride ion release from the restorative materials afforded some degree of protection to the adjacent enamel against in vitro demineralization.

Analysis of Variance↗

PubMed2000

The effect of triclosan toothpaste on enamel demineralization in a bacterial demineralization model.

Triclosan has been incorporated into toothpaste to enhance inhibitory effects on bacterial metabolism in dental plaque. Many studies have confirmed these effects by showing a reduction of accumulation of dental plaque, gingivitis and calculus. However, there is no evidence for triclosan having an inhibitory effect on the dental plaque-induced demineralization of the dental hard tissues. Therefore, the effect of 0.3% triclosan added to non-fluoride and fluoride toothpaste was tested in an in vitro model, in which bovine enamel specimens were to be demineralized by acids produced in overlaying Streptococcus mutans suspensions. In a first set of experiments the toothpastes were added to the S. mutans suspensions at 1:100, 1:1000 and 1:10,000 (w/v) dilutions. After 22 h incubation at 37 degrees C the suspensions were removed and assessed for calcium and lactate content, and pH. In this set of experiments, triclosan had no additive protective effect to the non-fluoride or fluoride toothpaste. In a second set of experiments, the enamel specimens were immersed daily for 3 min in 30% (w/v) slurries of the toothpastes before the 22 h incubation with the S. mutans suspensions. Under these conditions, triclosan showed an additional protective effect compared with non-fluoride toothpaste at a low concentration of S. mutans cells (0.07 mg cells dry weight per 600 microL suspension). It is concluded that the enamel surface may act as a reservoir for triclosan, which may protect the enamel surface against a mild acid attack. In combination with fluoride, however, as in toothpaste, triclosan has no additional protective effect against demineralization.

Animals↗

PubMed1994

A quantitative study of calcium binding by isolated streptococcal cell walls and lipoteichoic acid: comparison with whole cells.

Calcium-binding by surface components of oral bacteria may have important effects on remineralization/demineralization phenomena and plaque cohesion. Additionally, some species export large quantities of lipoteichoic acid, possibly as a protective measure. Measurement of calcium-binding can facilitate prediction of how this will effectively buffer plaque fluid calcium concentration and affect these processes. Using equilibrium dialysis, we measured calcium-binding capacities and affinities at pH 7.0 in isolated cell walls of Streptococcus downei, S. sanguis, and purified lipoteichoic acid (LTA) of S. sanguis. Mean binding capacities were: 56.5 mumol Ca/g wet weight for S. downei cell walls and 47.2 mumol Ca/g wet weight for S. sanguis cell walls, and 1.11 mol Ca/mol LTA phosphate were found. Mean dissociation constants (mmol/L) for cell wall calcium binding were 2.16 mmol/L (S. downei) and 2.69 mmol/L (S. sanguis). These constants were not significantly different from those for whole cells of the same species (Rose et al., 1993), but the dissociation constant for LTA (7.82 mmol/L) was significantly higher and suggested a different mode of binding. At neutral pH, at the known calcium concentration of plaque fluid, whole cells and cell walls are likely to be completely saturated with calcium, whereas free LTA is only 30% saturated. The large amounts of LTA exported by some sucrose-grown streptococci may therefore act as a calcium buffer and so protect the organisms against high local concentrations of calcium produced during demineralization.

Bacterial Adhesion↗

PubMed2006

[Dentin demineralization in situ during frequent exposures to bananas or sucrose].

The aim of the study was to compare sucrose solution and bananas on demineralizing potential in situ, and to address the question if fluoride toothpaste is equally effective in preventing dentin demineralization at open, smooth surfaces and at plaque stagnation sites (grooves). Four volunteers wore an appliance containing bovine dentin specimens with narrow grooves and a smooth surface for two 1-week in situ periods, with 8 1-minute exposures daily: either by a rinse with 10% sucrose, or by consumption of a piece of banana. Twice daily, the appliance was dipped in toothpaste slurry of a fluoride-free toothpaste at one side and a fluoride toothpaste at the contralateral side. Demineralization was assessed by tranversal microradiography. No difference in dentin demineralization was found after frequent exposure to either sucrose solution or bananas. Fluoride toothpaste effectively protected dentin only at the smooth surfaces. In the grooves, fluoride affected the demineralization pattern; it drove lesions towards the bottom of the groove.

Cariogenic Agents↗

PubMed1999

Correlation of transversal microradiography and microhardness on in situ-induced demineralization in irradiated and nonirradiated human dental enamel.

The objective was to evaluate whether a correlation exists between microhardness (MH) and transversal microradiographical (TMR) data for in situ-induced caries lesions in irradiated and nonirradiated human enamel. Enamel specimens were prepared from the lingual and buccal surfaces of 20 freshly extracted, caries-free third molars. The surfaces were polished (4000 grit). Either the lingual or the buccal specimen of each tooth was irradiated with 60 Gy; the other sample was not irradiated. Two irradiated and two nonirradiated specimens were inserted into both buccal aspects of each of five intraoral mandibular appliances. The appliances were worn by five persons for 6 weeks day and night. One side was brushed daily with a fluoride-free toothpaste; on the other side, dental plaque was allowed to grow. Individual oral hygiene was performed without any fluorides. During meals, the appliance was stored in 10% sucrose solution. Then the enamel specimens were cut perpendicular to their oral surface. The cut surface was polished (4000 grit) and the Knoop hardness number (KHN) was measured across the lesions, at 25, 50 and 75 microm from the oral surface. After MH testing the samples were polished again, thereby reducing the surface by about 10 microm. Subsequently, the slabs were ground to a thickness of 90 microm, and studied by means of TMR. Mineral loss was calculated with dedicated software at the locations corresponding to the MH testing. A total of 120 paired data was submitted to linear-regression analysis. Neither MH nor TMR showed significant differences between irradiated and nonirradiated enamel lesions. A linear relation was found between square root of KHN and the mineral volume percent. In naturally induced caries lesions, MH values can be converted to mineral volume percent using the equation [21.19 + 3.66 x square root of KHN]. This equation fits the data with a reliable correlation coefficient (r2=0.915).

Adult↗

PubMed1992

Rate and mechanism of enamel demineralization in situ.

In this paper, data are presented on the in situ demineralization of human enamel as a function of the demineralization period. To quantify the mineral loss parameters versus time, it is important to obtain information on the kinetics, and thus on the mechanism of dental caries. The results show that for in situ enamel demineralization, the lesion depth as well as the mineral loss parameter both vary linearly with the demineralization time. This is in contrast to in vitro lesion formation where the third power, or the square power of the lesion depth is linearly related to the demineralization time. In in situ demineralization, the rate-determining step of the demineralization process is the inhibitor-controlled dissolution process at the enamel crystallite surfaces, while the inhibitor content (F-, proteins etc.) in the lesion originating from the plaque, saliva and enamel is high. Furthermore, the study indicates that in in situ demineralization, interprismatic mineral loss is very important.

Dental Enamel↗

PubMed1995

Effect of dentine and collagen on the lethal photosensitization of Streptococcus mutans.

Suspensions of the cariogenic bacterium, Streptococcus mutans were treated with either toluidine blue O or aluminium disulphonated phthalocyanine and then exposed to light from a helium-neon or gallium-aluminium-arsenide laser, respectively, after passing through demineralized dentine slices. Bacteria were also embedded in a collagen matrix prior to sensitization and exposure to the laser light. When dentine slices were interposed between the laser light and the bacterial suspension, substantial kills (10(7) CFU) were achieved at energy doses of 876, 1,752, and 3,504 mJ with the helium-neon laser and of 1,188, 2,376, and 4,752 mJ with the gallium-aluminium-arsenide laser. There was no apparent relationship between the extent of killing and the degree of demineralization of the dentine. Prolonging the exposure of the sensitized bacteria to the laser light increased the kill achieved. Substantial numbers (10(8) to 10(10) CFU) of S. mutans were also killed when embedded in a collagen matrix and exposed to 438 and 1,314 mJ of helium-neon laser light and 594 and 1,782 mJ of light from the gallium-aluminium-arsenide laser. These results imply that lethal photosensitization may be effective at killing S. mutans in a carious lesion, even when the organism is embedded in demineralized dentine.

Animals↗

PubMedDate not supplied

Optical profilometric study of changes in surface roughness of enamel during in vitro demineralization.

The application of non-contact optical profilometry for non-destructive study of changes in the surface roughness of natural enamel surfaces during in vitro demineralization was investigated. Repeated measurement of profiles of the same enamel surfaces after successive demineralization episodes was achieved by a kinematic specimen mount that could be removed, then accurately repositioned. Surface roughness parameters and reflectivity of natural enamel surfaces exposed to either a demineralizing solution (test) or deionized water (control) for up to 6 days were measured at 6- to 24-hour intervals. The results prior to demineralization showed that surface roughness varies with position on the enamel surface. During demineralization there was an approximately linear increase in surface roughness for the first 70 h followed by somewhat erratic behaviour, and a saturating exponential with time increase in reflectivity for the first 70 h which subsequently remained constant. Changes in enamel surface during in vitro demineralization were also observed using scanning electron microscopy.

Dental Enamel↗

PubMed2001

Critical pH in resting and stimulated whole saliva in groups of children and adults.

OBJECTIVE: The concentrations of calcium and phosphate in saliva have significant influence on the protective mechanisms of dental hard tissues within the oral environment. A lower calcium concentration means: 1) a lower thermodynamic driving force for hydroxyapatite precipitation at normal oral pH; 2) a higher driving force for hydroxyapatite dissolution at low pH; 3) a lower critical pH. The aims of this study were to: 1. determine the calcium and phosphate concentrations 2. calculate the critical pH for enamel and 3. determine the driving forces for demineralization and remineralization in a group of children and adults. METHODS: In this comparative study, calcium and phosphate concentrations were measured in the resting and stimulated saliva of child and adult volunteers using a spectrophotometric system used in routine blood analysis. Salivary flow rates were also measured in each group. RESULTS: The calcium concentrations were lower in children than adults, but the phosphate concentrations were not significantly different. The critical pH was significantly higher for children than adults in both resting and stimulated saliva. Therefore, the thermodynamic driving forces for; (1) demineralisation at low oral pH, is greater, and (2) for remineralisation at normal oral pH, is lower, in children compared to adults. CONCLUSION: The results of this study show that from thermodynamic considerations alone, there is increased risk of demineralization in children compared with adults.

Adult↗

PubMed1994

Radiopacities in dentine under amalgam restorations.

Radiopacities, caused by tin or zinc deposits in partly demineralized dental tissue, are frequently seen under amalgam restorations. The aim of this study was to determine to what extent these radiopaque areas could be identified by Caries Detector (1% acid red in propylene glycol) which is claimed to stain the irreversibly demineralized dentine. Twenty-eight extracted teeth showing radiopacities under amalgam fillings were selected. The restorations were removed, and Caries Detector was applied. Caries was excavated until the dentine did no longer stain with the Caries Detector. Standardized radiographs were taken at different stages. In all teeth the radiopaque areas stained with the Caries Detector. Visual inspection of the radiographs, taken after excavation, revealed that the radiopacities had disappeared completely in 6 teeth; in 5 teeth a very small part of the radiopaque area remained; in 17 teeth the cavity floor appeared as a thin white line on X-ray. Overall, line scan analysis confirmed the data obtained by visual observation. The residual radiopacities and radiopaque lines were a very small fraction of the initial radiopacities. Therefore, it is concluded that the radiopaque zone under amalgam fillings represents almost entirely an area of irreversibly demineralized dentine as indicated by the Caries Detector.

Coloring Agents↗

PubMedDate not supplied

The effect of 10% carbamide peroxide, carbopol and/or glycerin on enamel and dentin microhardness.

This study evaluated the effects of 10% carbamide peroxide, carbopol and glycerin and their associations on microhardness over time on enamel and dentin. Eight treatment agents were evaluated: a commercial bleaching agent containing 10% carbamide peroxide (Opalescence 10% Ultradent), 10% carbamide peroxide, carbopol, glycerin, 10% carbamide peroxide + carbopol, 10% carbamide peroxide + glycerin, carbopol + glycerin and 10% carbamide peroxide + carbopol + glycerin. Three hundred and twenty human dental fragments, 80 sound enamel fragments (SE), 80 demineralized enamel fragments (DE), 80 sound dentin fragments (SD) and 80 demineralized dentin (DD) fragments, were exposed to the treatment agents (n=10). These agents were applied onto the surface of the fragments eight hours a day for 42 days. After eight hours, they were washed from the dental fragment surfaces after five back-and-forth movements with a soft bristle toothbrush under distilled and deionized running water. During the remaining time (16 hours per day), the fragments were kept in individual vials in artificial saliva. After the 42-day treatment period, the specimens were kept individually in artificial saliva for 14 days. Knoop microhardness measurements were performed at baseline, after eight hours, and 7, 14, 21, 28, 35 and 42 days, and 7 and 14 days post-treatment (corresponding to 49 and 56 days after the initial treatment agent applications). The non-parametric Kruskal-Wallis analysis showed significant differences among the agents at each time interval, except at baseline for sound and demineralized enamel and dentin. For SE, SD and DD, there was a decrease in microhardness values during treatment with all agents. There was a tendency towards lower microhardness values after treatment with carbopol and its associations for sound tissues. DD showed low microhardness values during and after treatment with CP and its associations. For DE, there was an increase in microhardness values during treatment with all agents and in the post-treatment phase. The baseline microhardness values were not recovered during the 14-day post-treatment phase. Opalescence 10%, carbamide peroxide, carbopol, glycerin and their associations may change the microhardness of sound and demineralized dental tissues, even in the presence of artificial saliva.

Acrylic Resins↗