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PubMed2000

Effects of low-energy CO2 laser irradiation and the organic matrix on inhibition of enamel demineralization.

In the past two decades, accumulated evidence has clearly demonstrated the inhibitory effects of laser irradiation on enamel demineralization, but the exact mechanisms of these effects remain unclear. The purpose of this study was to investigate the effects of low-energy CO2 laser irradiation on demineralization of both normal human enamel and human enamel with its organic matrix removed. Twenty-four human molars were collected, cleaned, and cut into two halves. One half of each tooth was randomly selected and its lipid and protein content extracted. The other half of each tooth was used as the matched control. Each tooth half had two window areas. All the left windows were treated with a low-energy laser irradiation, whereas the right windows served as the non-laser controls. After caries-like lesion formation in a pH-cycling environment, microradiographs of tooth sections were taken for quantification of demineralization. The mean mineral losses (with standard deviation) of the enamel control, the lased enamel, the non-organic enamel control, and the lased non-organic enamel subgroups were 3955 (1191), 52(49), 4565(1311), and 1191 (940), respectively. A factorial ANOVA showed significant effects of laser irradiation (p = 0.0001), organic matrix (p = 0.0125), and the laser-organic matrix interaction (p = 0.0377). The laser irradiation resulted in a greater than 98% reduction in mineral loss, but the laser effect dropped to about 70% when the organic matrix in the enamel was removed. The results suggest that clinically applicable CO2 laser irradiation may cause an almost complete inhibition of enamel demineralization.

Analysis of Variance↗
PubMed2006

A new in vivo method for measuring caries activity with a colorimeter.

The aim of this in vivo study was to assess the association between caries prevalence and changes in mineralization measured with a colorimeter (Color Compare CC 400, JENOPTIK, Jena, Germany). After a clinical examination (defs/DMFS, initial caries lesions), an area of a deciduous tooth was etched in each of the 35 children (psi = 8.11+/-2.41 years) with 37% phosphoric acid gel for 1 min. Immediately after, this demineralization was stained with 2% aqueous methylene blue and the red/green/blue spectrum measured with a colorimeter. Twenty-four hours later, the remineralization of this area was measured following the same staining procedure. Color measurements were clearly reduced after 24 h, indicating remineralization, and they correlated highly with the age of the children (Spearman correlation coefficient r = -0.48, p = 0.004). Correlations between the number of initial caries lesions in the deciduous and permanent dentition and color measurements after demineralization were statistically significant (r = 0.41 and 0.37, p = 0.02 and 0.045, respectively). The difference between the first and second measurements correlated significantly with the number of initial caries lesions in the permanent dentition (r = 0.42, p = 0.02). The values after artificial demineralization correlated with the number of initial lesions for the permanent (r = 0.368, p = 0.045) and deciduous (r = 0.408, p = 0.015) dentition. This resistance to artificial demineralization had stronger correlation coefficients with the caries incidence than the caries experience and initial lesions, which are considered to be the most valid caries predictors. In conclusion, these data suggest that the degree of demineralization after etching and its changes with time could be associated with caries parameters. Its use in prospective clinical trials on caries activity could be a successful approach.

Acid Etching, Dental↗
PubMed1999

Prevention and reversal of dental caries: role of low level fluoride.

Dental caries is a bacterially based disease that progresses when acid produced by bacterial action on dietary fermentable carbohydrates diffuses into the tooth and dissolves the mineral, that is, 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, and fluoride in saliva can balance, prevent or reverse dental caries. Fluoride works primarily via topical mechanisms which include (1) inhibition of demineralization at the crystal surfaces inside the tooth, (2) enhancement of remineralization at the crystal surfaces (the resulting remineralized layer is very resistant to acid attack), and (3) inhibition of bacterial enzymes. Fluoride in drinking water and in fluoride-containing products reduces tooth decay via these mechanisms. Low but slightly elevated levels of fluoride in saliva and plaque provided from these sources help prevent and reverse caries by inhibiting demineralization and enhancing remineralization. The level of fluoride incorporated into dental mineral by systemic ingestion is insufficient to play a significant role in caries prevention. The effect of systemically ingested fluoride on caries is minimal. Fluoride "supplements" can be best used as a topical delivery system by sucking or chewing tablets or lozenges prior to ingestion.

Adolescent↗
PubMed2004

In vitro demineralization/remineralization cycles at human tooth enamel surfaces investigated by AFM and nanoindentation.

The early stages of enamel surface dissolution (erosion) are of high scientific relevance; however, little is known about if and to what extent these early stages, which result in the softening of the enamel surface, are reversible. The present study investigated the possible rehardening of surface softened enamel in two separate experiments in vitro, employing physiologically relevant demineralization and remineralization times and remineralizing solutions possessing chemical properties close to those of human saliva. Atomic force microscopy (AFM) based nanoindentation has been used to study the nanomechanical properties and the ultrastructure of polished enamel samples as affected by demineralization/remineralization cycles. In contradiction to previous studies employing microhardness techniques, no enamel rehardening has been observed after remineralization; however, the demineralization schemes used in the present study (short treatments with a citric acid buffer) are not comparable to the ones used in previous studies, making a comparison difficult. A mineral deposition after remineralization on softened enamel samples has been observed by AFM; however, a protective effect of this deposited layer could not be revealed. The exposure of softened enamel samples to either a remineralizing solution or a mineral water led to an improved acid resistance of these samples as shown in a demineralization/remineralization cycle. The present study has demonstrated that AFM based nanoindentation is a useful tool to investigate the demineralization and remineralization of surface softened enamel with high accuracy.

Dental Enamel↗
PubMed2007

Management of postorthodontic demineralized white lesions with microabrasion: a quantitative assessment.

INTRODUCTION: The aim of this study was to quantify changes in postorthodontic demineralized enamel lesion surface areas after microabrasion. METHOD: The study group comprised 8 orthodontic patients (mean age,17.3 years) with multiple decalcified enamel lesions after fixed orthodontic therapy. Two demineralized areas were randomly selected for interventive treatment in each patient. Microabrasion was undertaken on these lesions by using a well-accepted 18% hydrochloric acid and pumice technique. Standardized intraoral images were taken of the lesions before and immediately after microabrasion. Image-processing software was used to quantify (mm2) the visible areas of the demineralized lesions before and after microabrasion. The total labial surface area of each tooth was also determined, and the area affected by demineralization was expressed as a percentage of total tooth surface. Images were reanalyzed a month later to determine the repeatability of the method. RESULTS: Microabrasion significantly reduced visible enamel demineralization (P < .001, paired t test). The mean reduction in lesion size after treatment was 83% (SD, 8.2%; range, 61%-92%). The quantification methodology was found to be highly repeatable with an intraclass correlation coefficient of 0.98. CONCLUSIONS: Microabrasion is an effective treatment approach for the cosmetic improvement of long-standing postorthodontic demineralized enamel lesions.

Adolescent↗
PubMed1993

Influence of constant fluoride levels in solution on root hard tissue de- and remineralization measured by 125I absorptiometry.

To study the effect of fluoride on de- and remineralization of root hard tissue, an automatic pH-cycling caries model, simulating Stephan curves, was used for 21 days. From each of 13 unexposed human roots, four cementum/dentin blocks were prepared. Four experiments were carried out: one block from each tooth as subjected to pH cycling without and with fluoride at the concentrations of 0.02 ppm (1.0 mumol/l), 0.20 ppm (10.5 mumol/l) and 2.00 ppm (105.3 mumol/l) in the de- and remineralizing solutions, respectively. Mineral change in the specimens was monitored by 125I absorptiometry. When no fluoride was added to the solutions the change in transmission (delta T) increased continuously over 21 days, indicating loss of mineral. In the 0.02-ppm F experiment, there was a marked decrease in delta T, but almost no change in the 0.20-ppm F experiment. pH cycling with 2.00 ppm F in the solutions resulted in a gain of mineral in or most likely on the surface of the cementum/dentin blocks, indicated by a continuously decreasing delta T. The fluoride level in the solution significantly influenced the change in the mineral content of the specimens. Microradiographs of the sectioned blocks showed radiodense surface zones, varying degrees of subsurface demineralization and signs of remineralization or mineral deposition.

Absorptiometry, Photon↗
PubMed1978

Loss of tooth structure associated with chronic regurgitation and vomiting.

In summary, a teenaged patient had generalized loss of tooth structure. As the patient previously had a normal dental history and as his family history was negative, many causative factors were quickly ruled out. Finally, after obtaining full cooperation of the patient and reviewing the complete medical records, it was concluded that the loss of tooth structure resulted from demineralization by acidic gastric contents, due to chronic regurgitation and vomiting.

Adolescent↗
PubMed1997

VariGlass fluoride release and uptake by an adjacent tooth.

PURPOSE: To quantitatively analyze in vitro the fluoride release from proximal VariGlass restorations and resulting uptake by the enamel of adjacent teeth. MATERIALS AND METHODS: Sixty impacted third molars were used and assigned to three groups: C: control, teeth without restorations; RC: teeth with resin composite restorations (Prisma APH); and PMRC: teeth with polyacid-modified resin composite restorations (VariGlass). Each group consisted of four sets of five teeth each. In the latter two sets, by alternating restored and unrestored teeth, the proximal surfaces of three unrestored teeth with an area of exposed enamel were in contact with the restored proximal surfaces of two other teeth. The sets were submitted to high caries challenge conditions with demineralizing and remineralizing solutions for 14 days. The fluoride of each solution and the fluoride uptake were determined and statistical analyses were carried out (ANOVA and Tukey's test). RESULTS: The highest mean fluoride concentration occurred with Group PMRC in both kinds of solutions (P < 0.01), but this value was higher in the demineralizing solution (P < 0.01). Over the 14 days, however, this mean gradually decreased in both solutions (P < 0.01). Group PMRC also showed the highest mean fluoride uptake (P < 0.01), which gradually decreased with depth in the enamel (P < 0.01).

Acrylic Resins↗
PubMedDate not supplied

Relationship between mineral distributions in dentine lesions and subsequent remineralization in vitro.

Though the mineral distribution of the dentine carious lesion varies largely from tooth to tooth and from patient to patient, there are two main distribution profiles that characterize natural carious lesions in dentine. These profiles include softened and subsurface lesion types. The mineral distribution relationship between the starting profile and the profile after remineralization is not known. In order to study the relational aspects, we have produced demineralized dentine samples in vitro with mineral profiles similar to those of typical natural carious lesions, and subsequently remineralized the samples in a remineralizing solution with various fluoride concentrations (0, 2 and 10 ppm F). The mineral distributions were obtained by using an improved microradiographic technique. In addition, the nature of deposited mineral was analyzed by diamond-coupled total internal reflectance spectroscopy. Definite relationship was observed between the original lesion mineral distribution and the mineral distributions following remineralization. The amount of mineral present in approximately the first 50 microm of the lesion influenced the overall mineral profile after remineralization, possibly through influencing ion transport. If the amount was high (> approximately 10 vol%), the deposited mineral was confined to the surface (0-50 microm). The original mineral at those depths acted like a nucleus of mineral regrowth when the amount of residual mineral was intermediate, and like a transport barrier when the surface layer was well mineralized. If a surface barrier was not present, mineral was deposited at deeper depths in the lesion. Fluoride effect on dentine remineralization was dependent on the original mineral content and its distribution in the lesion. Although a high concentration of fluoride was very effective in low-mineral lesions, it produced hyperremineralization on well-mineralized subsurface lesions so that it prevented effective remineralization especially in deeper lesions.

Acetic Acid↗
PubMedDate not supplied

Enamel de/remineralization on teeth adjacent to fluoride releasing materials without dentifrice exposure.

Interproximal caries presents a continual clinical concern. The purpose of this study was to evaluate the ability of fluoride-releasing materials to remineralize incipient caries lesions on adjacent teeth, at the interproximal site with and without exposure to a fluoridated dentifrice. Thirty extracted teeth had Class II preparations placed, then equal numbers were restored with amalgam (Tytin (3-Kerr), glass ionomer (Ketac Fil-ESPE) or composite (Heliomolar-Ivoclar). Thirty additional teeth had 1 x 5 mm artificial caries lesions formed at the interproximal contact point. One hundred mu thick sections were obtained at the caries sites and polarized photomicrographs were taken. The sections had varnish placed, leaving only the external section site exposed, and were situated back into the original tooth. These teeth were then mounted with the artificial lesion having an interproximal contact with the adjacent tooth restoration. Specimens were placed in closed environments of artificial saliva for two weeks; the saliva was changed every forty-eight hours. All teeth were cycled through an artificial caries system for thirty minutes, three times per day. Half the specimens in each group were brushed with Crest (Procter and Gamble) for two minutes, twice per day. The same sections were again photographed under polarized light and areas of the lesions were digitized quantitatively. Results demonstrated the mean (+/- S.D.) percent change in lesion size (water imbibition) for each material nonexposed and exposed to fluoridated dentifrice to be: Amalgam -64.1 +/- 22.0, -1.0 +/- 8.5; Glass Ionomer 2.2 +/- 10.6, 14.0 +/- 7.2; Composite -28.1 +/- 11.7, 18.2 +/- 6.7. Negative numbers represent demineralization and positive numbers represent remineralization. Duncan's analysis indicated the nonbrushed fluoride-releasing glass ionomer and composite resin to have significantly greater demineralization inhibition compared to the nonbrushed amalgam group and remineralization enhancement effects on adjacent interproximal lesions (p < 0.05) compared to the brushed amalgam group.

Acrylic Resins↗
PubMed2000

Application of quantitative light-induced fluorescence for assessing early caries lesions.

Quantitative light induced fluorescence (QLF) is a nondestructive diagnostic method for the longitudinal assessment of early caries lesions in time. When a tooth becomes carious the fluorescence radiance at the location of the caries lesion decreases. The fluorescence image of enamel with incipient lesions can be digitized and then the fluorescence loss in the lesion can be quantified in comparison to the fluorescence radiance level of sound enamel. Changes in fluorescence radiance and lesion area can be followed in time to measure lesion development. The amount of fluorescence radiance loss is related to the mineral loss in the lesion. The technique can be used in vitro, in situ and in vivo to monitor mineral changes in lesions. Applications of QLF are found in the testing of products designed to inhibit demineralization and promote remineralization of caries. The method has been successfully applied to smooth surfaces as well as occlusal surfaces, but application on approximal lesions is not yet possible.

Cariostatic Agents↗
PubMed1992

Effect of a two-solution fluoride mouthrinse on remineralization of enamel lesions in vitro.

A previous study showed that a two-solution fluoride (F) rinse deposited significantly more loosely-bound F on the tooth surface than did a sodium fluoride (NaF) rinse with the same F concentration (12 mmol/L). In the present study, this experimental rinse was evaluated for its ability to cause remineralization of enamel lesions in an in vitro pH-cycling model. Caries-like lesions were formed in the enamel of extracted human molars by means of a pH 4 demineralizing solution. Fifty-one approximately 120-microns-thick sections containing lesions were randomly divided into (1) control, (2) NaF rinse, and (3) two-solution F rinse groups. With the cut surfaces protected, the control samples were immersed in a pH 7 remineralizing solution for 12 days, and twice daily the sections were also exposed to a pH 4 demineralizing solution for 30 min. Samples in the NaF group received an additional one-minute rinse with a NaF (12 mmol/L) solution twice daily. Samples in the two-solution rinse group received the rinse treatment with a 12 mmol/L F solution prepared by combination of a Na2SiF6 and phosphate-containing solution with a calcium solution just before use. The mineral contents of the lesions were assessed by quantitative microradiography. The results showed that (1) no significant de- or remineralization was detected in the controls; (2) a 46% decrease in mineral loss (delta Z) of the lesion was produced by the NaF rinses; and (3) a 94% decrease in delta Z and a 20-microns-thick, mineral-dense surface-coating were produced by the two-solution F rinse treatment.

Apatites↗
PubMed1996

Fluoride and hard cheese exposure on etched enamel in neck-irradiated patients in situ.

OBJECTIVES: The effect of a fluoride mouth rinse with hard cheese exposure was investigated on rehardening of an etched tooth enamel surface in subjects with radiation-induced hyposalivation in situ. METHODS: Ten patients, six males and four females of mean age 48 years, irradiated with 30 Gy per week for neck and head cancer, volunteered for the present intraoral study. The unstimulated saliva flow rate varied between 0.01 and 0.15 ml min-1. Enamel slabs, approximately 2 mm x 2 mm in size, cut from human molar teeth were embedded in self-curing acrylic resin to fit a microhardness tester. Hardness measurements were carried out on the polished and subsequently etched enamel surface, rinsed for 1 min in the mouth with 10 ml Meridol (GABA INT), containing 0.025% F as amine fluoride and stannous fluoride, and exposed alternatively to mastication of 20 g cheddar cheese for 5 min. RESULTS: Surface erosion of the enamel slabs decreased the mean hardness to a similar degree in all samples. The difference between the mean increased degrees of enamel microhardness following fluoride, fluoride and hard cheese, or repeated fluoride-cheese exposures was significant compared to the etched enamel values. The rate of rehardening derived from a second fluoride-cheese treatment was found to be improved significantly. It seems that the reduced saliva flow in xerostomic patients is sufficient to release bound calcium and phosphate from cheese products. CONCLUSIONS: It is suggested that for xerostomic patients frequent exposures to low-fluoride solutions combined with hard cheese consumption may prevent and remineralize initial demineralization.

Acid Etching, Dental↗
PubMed2006

Micromorphological and micronanalytical characterization of stagnating and progressing root caries lesions.

Root caries is the predominant disease of the tooth tissues in the elderly population and differs in progression and micromorphology from coronal dentin caries. Therefore, different clinical concepts are needed for the treatment of these progressing and arrested lesions. It was the aim of this study to investigate the three-dimensional structure and volume of stagnating and progressing root caries lesions and to determine the mineral composition of the different lesion zones to achieve a better understanding of the natural history of root caries lesion formation. Of 21 extracted human teeth of patients between 42 and 77 years of age with stagnating and progressing root caries lesions serial sections were cut and investigated with polarized light and scanning electron microscopy. From the polarized light micrographs 3D reconstructions were made to determine the volumes of the lesion zones and their relations expressed in a demineralization index (DI). With increasing size of the demineralizing zone the DI increased indicating an increase in the size of the translucent zone. The 3D reconstructions showed distinct differences between stagnating and progressing root caries lesions. In the hypermineralized translucent dentin not all dentin tubules were obliterated by intratubular dentin and within the translucent dentin scattered dead tracts were found. Electron dispersive X-ray (EDX) analysis showed that the intertubular dentin of the translucent dentin was also demineralized to a certain extent. The results indicate distinct morphological differences between progressing and stagnating root caries lesions which may have consequences for treatment strategies.

Adult↗
PubMed2004

The effect of gamma radiation on enamel hardness and its resistance to demineralization in vitro.

Given the importance of sterilizing human teeth before using them in research, the effects of a 25 kGy dose of gamma radiation on the mechanical properties of enamel and its resistance to demineralization were evaluated. Thirty human teeth were sectioned longitudinally, and while one half of each tooth was irradiated, the other half was kept as a control. Abraded and unabraded enamel slabs were obtained from these halves. The surface microhardness (SMH) of abraded slabs of irradiated and non-irradiated enamel was determined to evaluate the effect of radiation on enamel structure. Further, both abraded and unabraded slabs, either irradiated or non-irradiated, were submitted to a pH-cycling model to evaluate enamel resistance to demineralization, which was quantified by mineral loss (deltaZ) using cross-sectional microhardness. The data for SMH and deltaZ were statistically analyzed by t-test and ANOVA, respectively. The difference in enamel SMH between slabs from irradiated teeth and non-irradiated teeth was not statistically significant (P > 0.05). The abraded enamel slabs showed higher values of deltaZ than unabraded enamel slabs (P < 0.05), but the irradiation effect was not statistically significant (P > 0.05). The results suggest that the medical gamma radiation dose of 25 kGy does not affect either enamel hardness or its resistance to demineralization.

Analysis of Variance↗
PubMed2000

Studies of dental root surface caries. 2: The role of cementum in root surface caries.

Artificial caries lesions were produced in roots of teeth using an acetate buffer system, when the layer of cementum was either normal in thickness, excessively thickened by hypercementosis, or had been removed completely. The rates of lesion progression were measured in each case using polarized light microscopy to measure lesion depth. Analysis of calcium (Ca) and phosphorus (P) loss during the demineralizing process was carried out. The removal of cementum was found to significantly increase the initial rate of penetration of the lesion into the root, although this rate progressively reduced to a level consistent with that found in normal roots after seven days of demineralization. The overall depth remained consistently greater than that observed in normal roots, or when lesions were produced entirely within hyperplastic cementum. Chemical analysis also showed removal of cementum resulted in an initial doubling of the Ca and P lost from the root surface. Prior direct exposure of segments of normal roots to the oral environment was found not to significantly alter the rate of artificial lesion progression, in comparison with that in the originally protected segment of the root surface. It was concluded that an intact cementum layer has the intrinsic ability to protect the underlying dentine of exposed tooth roots against acidic demineralization and that prior exposure to the oral environment does not significantly alter this ability.

Calcium↗
PubMed1991

Mechanistic aspects of the interactions between fluoride and dental enamel.

For many years after the discovery of its caries preventive effect, fluoride was thought to be primarily active by lowering the solubility of the apatitic mineral phase of the dental hard tissues. Recent findings have shed new light on the mechanisms by which fluoride inhibits or delays dental caries. Fluoride present in the oral fluids alters the rate of the naturally occurring dissolution and reprecipitation processes at the tooth-oral fluid interface. Demineralization of enamel is inhibited by concentrations of fluoride in the sub-ppm range. Likewise, remineralization of incipient caries lesions (the earliest stage of enamel caries) is accelerated by trace amounts of fluoride. As these two processes comprise dental caries the physiological balance between hard tissue breakdown and repair is favorably shifted by fluoride. The driving force for both phenomena is thermodynamic, that is, fluorapatite or a fluoridated hydroxyapatite may form when fluoride is supplied at low concentrations. This article critically reviews the current information about tooth-fluoride interactions, both from laboratory and clinical studies.

Dental Caries↗