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PubMed2005

Quantitative light fluorescence: a technology for early monitoring of the caries process.

Quantitative light fluorescence (QLF) can detect about twice as many demineralized precavitated enamel areas a conventional visual examination or any other caries detection instrument. This technology has been used in several controlled clinical trials with the consistent observation that it is capable of monitoring and quantifying changes in the mineral content and size of clinically visible noncavitated white spot lesions; therefore, it can be used to assess the impact of preventive measures on the remineralization and reversal of the caries process. The anticipated future use of QLF with dehydration to identify active areas of demineralization will markedly enhance the utility of this technology in clinical dental research and dental practice.

Adolescent↗

PubMed2002

A comparison of in vitro enamel demineralization potential of 3 orthodontic cements.

The objective of this in vitro study was to compare resistance to enamel demineralization after banding with 3 orthodontic cements. The 3 orthodontic cement groups and the nonbanded control group were evaluated for cariopreventive potential. One hundred twenty extracted human molars were selected for banding, embedded in resin blocks, and randomly assigned to the following 4 groups: zinc phosphate cement, zinc polycarboxylate cement, resin-modified glass ionomer (RMGI), and nonbanded control. Orthodontic bands were placed and cemented; specimens were stored in artificial saliva at 37 degrees C for 30 days, thermocycled for 24 hours, and then debanded with a customized band-removal device attached to a universal testing machine. The cement was hand removed, and 2 coats of nail varnish were applied to the teeth, leaving a 2 x 2-mm window exposed on the buccal surface of the mesiobuccal cusp. The teeth were stored in lactic acid-gelatin solution for 4 weeks at 37 degrees C to develop simulated white spot decalcification in the window. The teeth were subjected to dye (10% methylene blue) for 24 hours and then sectioned through the window. The depth of dye penetration was determined and used as a measure of the cariopreventive effect of the banding cement. Data were analyzed with a 1-way ANOVA and a Tukey test for the multiple comparisons. Dye penetration occurred as follows: the zinc phosphate and control groups were about the same; there was less dye penetration with the zinc polycarboxylate, and the least with the resin-modified glass ionomer. The 2 fluoride-releasing cements (zinc polycarboxylate and RMGI) demonstrated less demineralization than the zinc phosphate in vitro and might provide greater protection from demineralization around a band periphery in clinical settings.

Analysis of Variance↗

PubMed1993

Shrinkage of sound and demineralized human coronal dentine slabs.

In this article a method is presented for dentine shrinkage measurements. The relative shrinkage of sound dentine slabs is assessed using a Perthometer with respect to a steel reference. The relative shrinkage of lesions in dentine slabs can be estimated using combined Perthometer/microradiography measurements. The results show that the relative lesion shrinkage of lesions in thick slabs is quite different from the shrinkage of lesions in thin sections used for microradiography. The relative lesion shrinkage is, for periods up to 30 min, linear with the air drying period and increases strongly with the demineralization period. The previously published diol treatment is capable of reducing the relative lesion shrinkage in thick dentine slabs to negligible values.

Dentin↗

PubMed2002

Enamel microhardness after in vitro demineralization and role of different restorative materials.

This study aimed to evaluate the extension of enamel demineralization around the margin of restorations after immersion in cariogenic solution, in an attempt to define the role of new restorative materials in preventing secondary caries formation. For this purpose, enamel microhardness was measured. Twelve class V restorations in human extracted third molars were prepared in vitro and immersed in a demineralizing solution (lactic acid, pH 4.5) at 37 degrees C for 3 days to simulate the formation of secondary caries and its effect on the marginal integrity of composite restorations. The restorative systems tested in the study were Scotchbond 1 + Z 250 (group A), ABF + APX (group B), Fuji IX (group C), SE Bond + APX (group D), and Scotchbond 1 + F 2000 (group E). The microhardness was measured close to the margin of restoration (marginal exposed enamel), at 2.0 mm from the margin (exposed enamel), and at approximately 4 mm from the margin in a varnish-covered enamel area (protected enamel). Five measurements were made on each site at 20, 40, 60, 80, and 100 microm depth from the external enamel surface. Exposed enamel and marginal exposed enamel were greatly affected by the cariogenic solution, as confirmed by the high rate of demineralization. The marginal exposed enamel showed a higher rate of demineralization than the exposed enamel, as demonstrated by the lowest microhardness values. The materials that claimed fluoride release did not prevent any type of enamel marginal alteration. This study revealed that enamel close to the margin of restoration may be rapidly affected by secondary caries formation when immersed in a demineralizing-cariogenic solution and that fluoride-releasing materials are unable to reduce the marginal demineralization processes. These demineralization processes may be responsible for marginal secondary caries and for restoration failures.

Biomechanical Phenomena↗

PubMedDate not supplied

In situ and in vitro effects of bleaching with carbamide peroxide on human enamel.

This study evaluated in vitro and in situ the potential adverse effects of 10% carbamide peroxide on human enamel using microhardness, calcium loss and surface morphology analysis. Twenty-four enamel slices (4 mm2) were obtained from recently extracted premolars. The specimens were polished under water-cooling down to 1,200-grade sandpaper. After initial microhardness readings (100 g), the specimens were randomly divided into two groups for in situ and in vitro conditions. The specimens were covered with 10% carbamide peroxide for eight hours. After removing the bleaching gel, the in vitro specimens were stored in deionized water and the in situ specimens, included in an intra-oral appliance, were placed in the oral cavity of four volunteers. These cycling sequences took place for 14 days. Upon conclusion of the bleaching treatment, new microhardness readings were performed on all specimens. Calcium dosage was assessed from the bleaching gel collected after initial exposure on day one, then from gel collected between days two and seven and gel collected between day eight and 14 using an atomic absorption spectrophotometer. Surface morphology was observed from two non-treated control specimens and two specimens of each experimental bleached group under SEM evaluation. Statistical analysis (ANOVA and Tukey tests) disclosed that specimens bleached in situ showed similar microhardness to unbleached specimens and had statistically higher (p < 0.01) hardness than in vitro bleached specimens. The loss of calcium in the in vitro situation at 14 days was 2.5 times higher than the in situ condition. SEM micrographs demonstrated that surface alterations were more pronounced in the in vitro condition. The adverse effects of carbamide peroxide on enamel were evident in specimens bleached in vitro but were not seen in situ. The presence of saliva could prevent the demineralizing effect of bleaching gel in situ.

Analysis of Variance↗

PubMed1998

Fluoride-dependent formation of mineralized layers in bovine dentin during demineralization in vitro.

Demineralization of dentin in the presence of fluoride produces lesions with a mineralized surface layer which becomes thicker and more mineralized with higher fluoride concentrations whereas the lesion depth is hardly affected. The aim of this study was to investigate the effects of the time of fluoride treatment and the amount of fluoride taken up on the properties of the mineralized layer. Discs of bovine dentin embedded in methylmethacrylate with one surface exposed were demineralized in 50 mM acetic acid, 2.2 mM CaCl2, 2.2 mM KH2PO4, pH 5.0. At the start and/or later during the demineralization period, the specimens were incubated individually for 1 or 2 days in 10 ml of the same demineralization solution supplemented with 0.5, 2.0 or 5.0 ppm fluoride, which was then assessed for changes in calcium and fluoride concentrations. After 2, 5 and 8 days, specimens were sectioned for microradiographic analysis so as to follow development of the lesions and the mineralized layers. The results were the following: While demineralization with fluoride present at the first day led to the formation of a surface layer, fluoride present only at a later day produced a subsurface layer, not at the lesion front but closer to the surface. This layer resulted from (re)precipitation and not from preservation of the original mineral. The 'integrated mineral content' of the surface layer increased linearly with the uptake of fluoride, which resulted in an apparent fluorapatite content of about 20 vol%. The profiles of the surface layers remained unchanged during continued demineralization in the absence of fluoride. It was concluded that in the presence of fluoride mineral loss is reduced as a result of the reprecipitation of dissolved mineral ions as a layer of fluoride-enriched apatite. This layer does not offer protection of underlying dentin against continued demineralization.

Acetic Acid↗

PubMed1993

Effect of whole saliva components on enamel demineralization in vitro.

The aim of the present study was to use an in vitro enamel demineralization model (1) to confirm that whole saliva pretreatment conferred acid resistance to dental enamel and (2) to determine whether this phenomenon was attributable to specific salivary proteins, minerals, lipids, or some combination of these. Crowns of human teeth, each with one exposed window, were prepared in groups of ten. They were each pretreated by immersion individually in 4 ml of either (1) clarified whole saliva for 18, 72, or 168 h, (2) dialyzed saliva (3500 MWCO membrane), (3) the "flow-through" fraction from a DEAE separation of whole saliva (neutral and basic proteins), (4) the "eluted" fraction of a DEAE separation of whole saliva (anionic proteins), or (5) a combination of salivary lipids and the DEAE "flow-through" fraction of whole saliva (neutral and basic proteins). Control groups were group 6 with no pretreatment, group 7 pretreated for 168 h in a borate buffer (5 mmol/l), and group 8 pretreated in a mineral solution containing calcium (0.7 mmol/l) and phosphate (2.6 mmol/l). The crowns were then demineralized for 7 d in vitro (0.1 mol/l acetate, 1 mmol/l Ca and phosphate, pH 5.0) to produce artificial caries-like lesions. Lesions were assessed by cross-sectional microhardness profiles, and mineral loss (delta Z, micron x vol% mineral) calculated. Mineral loss (delta Z) values decreased linearly with the square root of time of pretreatment by whole saliva, confirming a time-dependent protective effect of salivary pellicle against demineralization of enamel.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗

PubMed2001

[A possible criteria for diagnosis of early caries in pits and fissures].

OBJECTIVE: The aim of this study was to examine pits and fissures of occlusal surfaces with severe stains by both histological and clinical methods, and to evaluate the criteria for diagnosis of early caries in pits and fissures. METHODS: Thirty-one fresh extracted molars and premolars, severely stained but no detectable defects in the surfaces, walls and floors of occlusal fissures, were collected. The teeth were longitudinally sliced across the stained fissures and ground into sections of 100-140 microns. The sections were observed using microscopy and microradiography. RESULTS: All samples showed early carious lesions in pits and fissures under microscope. Demineralization in walls or floors was identified by microradiography in 30 samples. CONCLUSION: Although without detectable defects, severely stained pits and fissures showed demineralization by using microscopy and microradiography. Thus, early caries in pits and fissures may be identified by the severely stained appearance.

Adolescent↗

PubMed1997

Clinical diagnosis of precavitated carious lesions.

During the 20th century, dental caries was usually diagnosed using tactile-visual criteria that detected the presence of cavitation rather than measured the disease process as a continuum that starts from the appearance of microporosity, as a result of demineralization, to the occurrence of cavitation. With increasing understanding of the dental caries process and the role of primary and secondary prevention in arresting it, sensitive and specific diagnostic systems are needed that could enable dentists to detect signs of early demineralization and possible progression of precavitated carious lesions before the occurrence of cavitation. In this review of the literature, published validity studies of diagnosis of precavitated lesions were reviewed. Overall, the current clinical diagnostic systems have low sensitivity and moderate specificity. Good reliability of diagnosing precavitated carious lesions could be obtained for diagnosing pits and fissures but for smooth tooth surfaces the reliability is poor. As our diagnostic capability of precavitated lesions improves, there is a need for a significant change in dental education, dental insurance, and dental practice to reward dentists for promoting oral health and preserving tooth structure. In this paper, a new model for classifying carious lesions based upon the type of intervention strategies is proposed to assist in this new approach of caries management.

Dental Care↗

PubMed1991

In vitro demineralization of enamel by F-sensitive and F-resistant mutans streptococci in the presence of 0, 0.05, or 0.5 mmol/L NaF.

Lactate production and accompanying enamel demineralization by fluoride-sensitive and fluoride-resistant mutans streptococci were studied in an in vitro demineralization model in the presence of 0, 0.05, or 0.5 mmol/L NaF. The fluoride-resistant strains were derived from laboratory strains or were recently isolated strains from xerostomic patients on high-dose fluoride therapy. The demineralization model was composed of a cell suspension in a glucose-agarose gel overlying a bovine enamel block. Lactate and calcium content of the agarose were determined after 22-hour incubations at 37 degrees C. Fluoride-resistant variants of Streptococcus sobrinus 6715-15 produced less lactate and caused less demineralization than did the parent strain even in the presence of fluoride. On the other hand, fluoride-resistant variants of Streptococcus mutans C180-2 and of S. mutans GS-5 produced more acid and caused greater demineralization than did their respective parent strains, both in the absence and presence of fluoride. Two recently isolated fluoride-resistant S. mutans strains produced more lactate and demineralized enamel more than did two recently isolated S. mutans strains from normal human subjects, both in the presence of 0 and 0.05 mmol/L NaF. It is concluded that adaptation to fluoride resistance does not invariably reduce the cariogenicity of mutans streptococci nor the effectiveness of fluoride in preventing demineralization.

Animals↗

PubMedDate not supplied

In vitro enamel effects of a resin-modified glass ionomer: fluoride uptake and resistance to demineralization.

PURPOSE: The purpose of this study was to determine the in vitro effects of a resin-modified glass-ionomer restorative material on human enamel. METHODS: Enamel specimens were restored with Photac-Fil, a resin-modified glass ionomer; Ketac-Fil, an autopolymerizing glass ionomer and silver amalgam. The samples were pH cycled and then subjected to an artificial caries challenge. Specimens were evaluated by fluoride microdrill biopsy and quantitative microradiography at 1, 2, and 3 mm from restorations. Data on fluoride content, lesion depth, and mineral content were analyzed by one-way ANOVA, Student's t test, Neuman-Keuls procedure (multiple [pairwise] comparison), and Pearson's product-moment correlation tests. RESULTS: There were significant differences in fluoride uptake, lesion depth, and mineral density between groups. Significant correlational relationships were also determined. CONCLUSION: This study demonstrates that Photac-Fil and Ketac-Fil prevent in-vitro demineralization of enamel and suggests different mechanisms of action for each material.

Analysis of Variance↗

PubMed2005

Formation of inhibition layers with a newly developed fluoride-releasing all-in-one adhesive.

This study evaluated the capability of a novel fluoride-releasing, all-in-one adhesive system on forming inhibition layer (radio-opaque layer) as compared with other adhesive systems. Dentin surface was treated with Imperva bond (IB), FL-BOND (FB), Reactmer bond (RE), or FL-BOND S-1 (FS) (which is a novel system). Untreated specimens were categorized as nonbonding group (NB). After storing for 10 days in de-ionized water, the specimens were cut into halves perpendicularly to the pulp chamber and immersed in a buffered demineralizing solution for four days. Longitudinal sections were cut and microradiographed. The width of inhibition layers adjacent to the adhesive surface--at a depth of 50 microm under the demineralization surface--was analyzed. Microradiography revealed distinct inhibition layers adjacent to the experimental surfaces of FB, RE, and FS. No inhibition layers were observed in NB and IB. In particular, the width of the inhibition layer of FS (12.5 microm) was significantly greater than those of FB and RE. These results indicated that a newly developed all-in-one adhesive system, FS, may have a superior ability of forming inhibition layers adjacent to cavity walls, and that it may also protect dentin against further demineralization in case of secondary marginal caries.

Adhesives↗

PubMed1991

[Solubility of enamel and synthetic hydroxylapatite on irradiation].

The effect of Co 60-irradiation (70 Gy) on pulverized human enamel and synthetic hydroxyapatite was studied in vitro. Irradiated and non-irradiated samples were experimentally demineralized (pH 5.1) during a period of 28 days. In terms of solubility, defined as the equilibrium of saturation, there was no statistically significant difference between irradiated and non-irradiated enamel. However, in terms of solubility rates, defined as the amount of dissolved substance during the demineralization period, irradiated enamel showed a statistically significantly higher solubility rate than non-irradiated enamel. There was no effect of Co 60-irradiation on synthetic hydroxyapatite.

Dental Enamel Solubility↗

PubMed1999

A computerized analysis of the relation between the occlusal enamel caries lesion and the demineralized dentin.

It has previously been shown that the demineralized dentin does not spread laterally along the enamel-dentin junction in non-cavitated approximal lesions. This study examined the spread of the dentinal part of occlusal lesions along the enamel-dentin junction. The material consisted of 48 well-defined occlusal lesions with histological evidence of dentin demineralization. The teeth were embedded in methylmethacrylate, serially-sectioned, ground, and contrast-stained. The sections with the deepest lesion penetration from each lesion were photographed and scanned by a high-quality scanner in order to produce images for computerized histomorphometric analysis. Two variables were measured on the images: i) the length of the contact area of the enamel lesion along the enamel-dentin junction; and ii) the length of the contact area of the demineralized part of the dentin lesion along the enamel-dentin junction. The results showed a gradual increase in the lengths of the enamel and dentin contact areas between the sections, each representing well-defined progressive stages of lesion formation. In two-thirds of the non-cavitated lesions, the enamel lesion was larger than the demineralized part of the dentin lesion, and in 50% of the cavitated cases the extension of the demineralized dentin was less than the affected enamel. Our conclusion is that the dentin demineralization did not spread significantly in a lateral direction in non-cavitated occlusal lesions.

Coloring Agents↗

PubMedDate not supplied

Light scattering properties of natural and artificially demineralized dental enamel at 1310 nm.

A fundamental understanding of how near-IR light propagates through sound and carious dental hard tissues is essential for the development of clinically useful optical diagnostic systems, since image contrast is based on changes in the optical properties of these tissues on demineralization. During the caries (decay) process, micropores are formed in the lesion due to partial dissolution of the individual mineral crystals. Such small pores behave as scattering centers, strongly scattering visible and near-IR light. The optical properties of enamel can be quantitatively described by the absorption and scattering coefficients, and the scattering phase function. Our aim is to measure the optical scattering behavior of natural and artificial enamel caries. Near-IR attenuation measurements and angular-resolved goniometer measurements coupled with Monte Carlo simulations are used to determine changes in the scattering coefficient and the scattering anisotropy on demineralization at 1310 nm. An ultra-high resolution digital microradiography system is used to quantify the lesion severity by measurement of the relative mineral loss for comparison with optical scattering measurements. The scattering coefficient increases exponentially with increasing mineral loss. Natural and artificial demineralization increases the scattering coefficient more than two orders of magnitude at 1310 nm, and the scattering is highly forward directed.

Dental Caries↗

PubMed2007

Susceptibility of acid-softened enamel to mechanical wear--ultrasonication versus toothbrushing abrasion.

The study aimed to compare the amounts of softened enamel removable by ultrasonication and by toothbrushing abrasion of briefly eroded samples. Thirty bovine enamel samples were demineralized in hydrochloric acid (pH 2.1) for 60 s and were then either brushed with 350 brushing strokes in toothpaste slurry (group A) or distilled water (group B) or were ultrasonicated for 120 s (group C). Enamel loss was measured after 10, 20, 50 and then after every 50 brushing strokes or after 5, 30, 60 and 120 s ultrasonication. Samples were indented with a Knoop diamond after erosion, and enamel loss due to abrasion or wear was calculated from the change in indentation depth after mechanical treatment. Within- and between-group comparisons were performed by ANOVA or t test. Initially, enamel loss increased with increasing brushing treatment or ultrasonication time. Enamel loss did not increase after 300 brushing strokes in group A (534 +/- 169 nm) or 250 brushing strokes in group B (423 +/- 80 nm), or after 60 s ultrasonication (231 +/- 72 nm). Enamel loss was significantly higher in groups A and B than in group C. The results confirm that ultrasonication removes only the outer, more highly demineralized part of the softened enamel layer. Results also indicate that toothbrushing abrasion removes more softened enamel from briefly eroded enamel than ultrasonication, and therefore probably removes partly demineralized enamel from the deeper part of the softened layer. In vivo, excessive toothbrushing might remove the softened enamel layer almost completely.

Animals↗

PubMed2003

A modified pH-cycling model to evaluate fluoride effect on enamel demineralization.

Since in vitro pH-cycling models are widely used to study dental caries, they should allow evaluations of fluoride effect on early stages of caries development. Therefore, acid etching on enamel surface must be avoided, enabling surface microhardness (SMH) analysis. In the present study, the pH-cycling model originally described by Featherstone et al.9 (1986) was modified to preserve the enamel surface and to produce early carious lesions that could be evaluated using SMH and cross-sectional microhardness (CSMH) measurements. In order to validate this modified model, a dose-response evaluation with fluoride was made. Human enamel blocks with known SMH were submitted to such regimen with the following treatments: distilled deionized water (DDW; control) and solutions containing 70, 140 and 280 ppm F. Data from %SMH change and deltaZ (mineral loss) showed a statistically significant negative correlation between F concentration in treatment solutions and mineral loss. In conclusion, the modified pH-cycling model allowed the evaluation of changes on the outermost enamel layer during caries development, and a dose-response effect of fluoride reducing enamel demineralization was observed.

Analysis of Variance↗

PubMedDate not supplied

Influence of olive oil emulsions on dentin demineralization in vitro.

The effect of two different concentrations of olive oil emulsions on development of artificial caries-like dentin lesions under severe demineralizing conditions was investigated. Bovine dentin samples (n = 180) were ground flat, polished, divided into four groups, and subjected to three demineralization cycles per day. Samples were stored in one of the following solutions for 5 min prior to demineralization in a buffer solution (pH 5): Group 1: 50% oil emulsion (olive oil and distilled water); group 2: 5% oil emulsion; group 3: distilled water; and group 4: 1,500 ppm sodium fluoride. Daily up to 9 days, lesion depth (ld) and mineral loss (deltaZ) were determined by means of microradiography and analyzed by ANOVA and Tukey's studentized range test (p < or = 0.05). Lesion depth increased with time for all groups. Mineral loss increased in groups 1-3. A small but significant decrease in mineral loss was observed following treatment with lipid emulsions as compared to treatment with distilled water, but fluoride treatment was considerably more effective. Mean mineral loss (means +/- SD in vol% x microm) averaged over the study period was 4,368 +/- 1,599, 4,536 +/- 1,823, 4,849 +/- 1,798, and 789 +/- 177 for group 1, 2, 3, and 4, respectively. Ratio (deltaZ/ld) remained constant around 30 vol% for groups 1-3, but decreased for group 4. In conclusion, externally provided lipids have the potential to reduce dentin demineralization in vitro.

Analysis of Variance↗