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PubMed2004

Monitoring of demineralized dentin microhardness throughout and after bleaching.

PURPOSE: To evaluate the effect of six bleaching agents: Nite White [NW] 10% and 22% Excel 2Z (Discus Dental), Rembrandt (REM) 10% and 22% (DenMat), Opalescence (OPA) 10% and 20% (Ultradent) and a placebo agent on demineralized dentin microhardness at different time intervals. METHODS: 105 human dentin slabs (3 x 3 mm) were embedded, planed and submitted to cariogenic challenges, composed of de- and remineralization cycles. For 42 days, specimens were exposed to bleaching agents, consisting of applying them daily for 8 hours, removing and storing the specimens in artificial saliva for 16 hours. At the end of the bleaching treatment, specimens were kept in artificial saliva for 14 days. Knoop Microhardness tests were performed on specimens' surface before (baseline), during (8 hours, 7, 14, 21, 28, 35 and 42 days) and after bleaching procedures (7 and 14 days). RESULTS: The ANOVA for split-plot showed significant effect on the interaction between bleaching agent and time (alpha =0.05). Tukey's test revealed no significant differences on demineralized dentin microhardness exposed to bleaching agents until Day 7. Regression analyses demonstrated that NW 10% and 22% and OPA 10% and 20% increased dentin microhardness in different magnitudes, whereas REM 10% and 22% induced mineral loss during bleaching agent application, followed by microhardness recovery in the post-treatment period.

Analysis of Variance↗

PubMed2006

In-vivo effects of fluoridated antiplaque dentifrice and bonding material on enamel demineralization adjacent to orthodontic appliances.

INTRODUCTION: The effect of a fluoridated antiplaque dentifrice on the development of caries lesions adjacent to dental appliances bonded with ionomeric material is unknown. METHODS: Fourteen orthodontic patients were randomly divided into 2 groups of 7. One group brushed 3 times a day with a fluoridated dentifrice, and the other used an experimental antiplaque fluoridated formulation. Bracket bases were randomly bonded with either resin-modified glass ionomer cement or composite resin to the buccal surfaces of either the maxillary left or right premolars in each subject. The teeth were banded, leaving a space on the buccal surface to allow dental plaque accumulation. After 28 days of dentifrice use, the teeth were extracted, and mineral loss in the enamel adjacent to the bonded material was assessed by cross-sectional microhardness. RESULTS: Mineral loss in the enamel surrounding the bond with the resin-modified glass ionomer cement was lower (P <.05) than around the composite bond. Enamel demineralization was lower (P <.05) in subjects who used the experimental antiplaque fluoridated formulation than in those who used the fluoridated one. CONCLUSIONS: The data suggest that an antiplaque fluoridated dentifrice is superior to one that is only fluoridated for reducing enamel demineralization adjacent to dental material bonded with composite, but the effect seems irrelevant when bonding is done with the ionomeric material.

Acrylic Resins↗

PubMed2000

In vitro dentin demineralization inhibition effects of an experimental fluoridated HEMA and water wetting agent.

The ability of fluoride-releasing resins to inhibit dentin demineralization remains controversial. The purpose of this study was to evaluate the caries inhibition of resin composite restorations with an experimental fluoridated hydroxyethyl methyl methacrylate (HEMA) and water wetting agent. Standardized Class V preparations were placed in 40 molars, the gingival margin placed below the cementoenamel junction. Two dentin primers (sodium fluoride, HEMA and water; HEMA and water) were placed in equal numbers of 20 preparations, then One-Step Dental Adhesive (Bisco) was applied as recommended by the manufacturer, followed by the placement of a resin composite restoration. Amalgam restorations with no primer/adhesive were placed in 10 preparations and 10 preparations were restored by placing One-Step Dental Adhesive, then resin composite. All teeth were subjected to an artificial caries challenge (pH 4.4) for 5 days. Results demonstrated the mean areas (microm2 +/- s.d.) of demineralization 100 microm from the restoration/dentin margin to be: amalgam 5,570 +/- 873; One-Step 7,038 +/- 2,099; HEMA and water 6,126 +/- 634; fluoridated HEMA and water 3,411 +/-593. ANOVA and Duncan's test (P < 0.05) demonstrated the fluoridated HEMA and water wetting agent to have significantly less adjacent dentin demineralization than the other three groups. Eighty percent of HEMA and water wetting agent, 80% of One-Step Dental Adhesive and 100% of amalgam restorations demonstrated wall lesions. One hundred percent of restorations with fluoridated HEMA and water wetting agent demonstrated inhibition zones in adjacent dentin.

Analysis of Variance↗

PubMedDate not supplied

Demineralization of Er:YAG and Er,Cr:YSGG laser-prepared enamel cavities in vitro.

The aim of the present study was to establish whether cavity preparation by means of an erbium laser with efficient water cooling is capable of reducing the susceptibility of the prepared dental enamel to demineralization and thus of achieving a potential caries-protective effect in the region of cavity margins. To this end, cavities limited to the enamel were prepared in the crowns of 10 teeth each using an Er:YAG (lambda = 2,940 nm) and an Er,Cr:YSGG laser (lambda = 2,780 nm). A control cavity prepared conventionally with a diamond drill in the same occlusal zone was assigned to each of these cavities. The specimens were then subjected to a pH-cycling caries model. Analysis was performed by quantitatively measuring the demineralization front under a polarized-light microscope. The results of the study showed that enamel cavities prepared with the erbium lasers used display a statistically significant acceleration of demineralization compared to conventionally prepared cavities (p < 0.01). The Er:YAG laser cavities revealed demineralization to a depth of 133.9 (SD 25.7) microm, while the value observed with the Er,Cr:YSGG laser was 133.8 (SD 25.8) microm. The depth of demineralization in the control groups was only 77.4 (SD 13.8) microm and 79.3 (SD 37.6) microm. No difference could be found between the two lasers (p = 0.98). Based on these in vitro tests, it cannot be assumed that use of the erbium laser for cavity preparation offers any advantages in terms of resistance to secondary caries in clinical practice.

Dental Caries Susceptibility↗

PubMed2003

Relationship between the fluoride concentration of the fluoride-releasing elastomers and the acquired acid resistance of human enamel in vitro.

The objective of the study was to evaluate the relationship between the fluoride concentration of the fluoride-releasing elastomers and the acquired acid resistance of human enamel. Four kinds of fluoride concentration of the experimental fluoride-releasing elastomers were 1.25, 2.5, 3.75 and 5.0 wt%. An enamel block was cut into two smaller enamel blocks, one of which was set with an elastomer, the other as a control not set with elastomer. A plastic block that had the same shape as the small enamel block was also set with elastomer. Fluoride release and acid resistance tests were carried out. The mineral loss of the demineralized enamel was measured by microradiography. The results showed that the fluoride-releasing ability significantly increased with the increase of fluoride concentration in the elastomer (p < 0.05). The acid resistance of the enamel appeared to be enhanced greatly, however, its change was not proportional to the fluoride concentration in the elastomers.

Absorption↗

PubMed1994

Effect of frequent consumption of starchy food items on enamel and dentin demineralization and on plaque pH in situ.

The aim of this cross-over study was to determine the cariogenic potential of starchy food items as between-meal snacks. This was done by measuring demineralization of human enamel and dentin as well as the pH of dental plaque in situ. Eight volunteers with complete dentures carried two enamel and two dentin specimens, mounted in the molar regions of their mandibular prostheses. There were three test periods, each lasting for 21 days, followed in a randomized order: (1) consumption of starchy food products, 12-15 times a day, in addition to the normal diet (starch period); (2) consumption of sucrose products, 12-15 times a day, in addition to the normal diet (sucrose period); and (3) no addition of test products to the normal diet (control period). Both the starch and the sucrose diets increased the demineralization of enamel and dentin compared with the control period. However, only the sucrose period resulted in significant demineralization of dentin compared with the control period. The plaque pH, followed during 60 min after a one-minute mouthrinse with 10% sucrose, was lower at all time points after both the starch and the sucrose periods compared with the control period.

Aged↗

PubMed1994

Prevention of root caries with dentin adhesives.

This in vitro investigation determined the feasibility of using dentin adhesives to protect root surfaces against caries. The roots of 22 recently extracted human teeth were all painted with a protective lacquer leaving two unprotected small windows. On each specimen, one window (control) was left untreated and the other window (experimental) was treated using a dentin adhesive (Scotchbond Multi-Purpose). The roots were then immersed in an in vitro acetate/calcium/phosphate demineralization model at pH 4.3. After 70 days, the samples were removed and sectioned through the windows. The undecalcified ground sections were examined under transmitted and polarized light. Lesions characteristic of natural root caries were seen in the untreated control windows. No such lesions were apparent in the experimental windows. The results of this preliminary study suggest that dentin adhesives may provide protection against root caries.

Dentin-Bonding Agents↗

PubMed2001

Demineralization of caries-affected transparent dentin by citric acid: an atomic force microscopy study.

OBJECTIVES: This study determined recession rates of peritubular dentin and intertubular dentin in citric acid solution (0.018M, pH=2.5) for caries-affected transparent dentin, one of the major components of dentin substrate as altered by caries, with comparisons made with non-carious dentin. METHODS: Transparent dentin was identified by sagittally sectioning five obviously carious teeth. Sections were then cut through the transparent dentin area perpendicular to the course of the dentinal tubules. Polished dentin samples of the transparent dentin and non-carious dentin were prepared with an internal reference layer and studied at specific intervals for citric acid etching in an atomic force microscope (AFM). RESULTS: At baseline, transparent dentin was identified by dentinal tubules that were largely occluded with mineral deposits that on etching proved to be acid resistant. Peritubular dentin etched rapidly and linearly over time until it could no longer be measured, yielding etching rates for transparent dentin that could not be distinguished from normal dentin. The normal and transparent intertubular dentin surfaces began etching at nearly the same rate, but then surface recession stabilized after less than 1 microm depth change for both dentin types. SIGNIFICANCE: Most previous studies have focused on demineralization and bonding to normal dentin, although many bonding procedures involve altered dentin substrates, such as those modified by caries. In this study, peritubular and intertubular dentin from normal and caries-affected dentin exhibited similar behavior. The major difference was the presence of acid resistant mineral in most of tubule lumens in the transparent dentin.

Acid Etching, Dental↗

PubMed2005

Detection of incipient carious lesions formed on human teeth in vitro using ultraviolet laser.

OBJECTIVE: A 325-nm ultraviolet (UV) laser was tested for effectiveness in the detection of incipient carious lesions on teeth. BACKGROUND DATA: The combination of early detection with new intervention methods and caries management will be the preferred dentistry of the future. METHODS: Carious lesions from extracted teeth or from demineralized teeth were irradiated by UV laser, and the fluorescence spectrum was measured. The peak ratio between two peak intensities in the spectrum was determined. RESULTS: Fluorescence peak intensity of approximately 425 nm was gradually decreased as carious lesions formed, whereas the change 625 nm was less significant. The peak ratio change between peak intensities of approximately 425 and at 625 nm was observed after 30 min of demineralization. Morphological changes were barely observable in this range. CONCLUSIONS: A 325-nm UV laser showed high efficacy in the detection of incipient carious lesions. By evaluating peak ratio, the incipient carious lesions could be detected.

Dental Caries↗

PubMed1995

Effect of air-drying on demineralized and on sound coronal human dentine: a study on density and on lesion shrinkage.

Recently, several papers investigated the linear dimensional changes in dentine after air-drying. This paper pertains to weight changes, volume changes, and density changes caused by air-drying of sound and demineralized intact dentine. The densities of sound and artificially demineralized human coronal dentine were measured in the wet state and after various drying periods of up to 24 h. The volume was assessed either by means of a pyknometer (wet samples) or by means of dimension measurements. The air-drying experiments were done using a Mettler thermobalance at room temperature. The density of wet sound coronal dentine was found to be 2.24 +/- 0.12 g.cm-3; the value of wet demineralized dentine was about 1.6 g.cm-3. The data show that previously published density values of powdered sound dentine may have been influenced by powdering effects, air-drying, and air inclusion. In whole demineralized air-dried dentine, air inclusion can be very severe: up to 30% by volume. The results show furthermore that in demineralized dentine we have two drying stages: during the first one (up to about 10 min of air-drying), the lesions shrink about 23%, while a main part of the water in the lesion evaporates, and air is incorporated into the tissue; during the second stage (drying longer than 10 min), the lesions hardly shrink anymore, but water is evaporated mainly from underlying sound dentine, followed by air incorporation.

Air↗

PubMed1998

The effect of intrinsic fluoride in cows' milk on in vitro enamel demineralization.

The fluoride concentration in cows' milk has been reported to vary with the fluoride levels in drinking water but it seldom exceeds 0.5 microg/ml. This raised a question as to whether any caries-protective effect could be attributed to the intrinsic fluoride of milk. Two samples of cows' milk with intrinsic fluoride concentrations of 0.03 and 0.3 microg/ml, respectively, were assessed for their protective effect on enamel in an in vitro demineralization model at relatively severe and mild acidic challenges (pH 4.6 and 5.0, respectively). Polished enamel discs were incubated individually in 5.0 ml of demineralization solution for 20 h per day alternated with 1-hour incubations in 1.0 ml of milk or control buffers: group 1, demineralization solution only (negative control); group 2, milk with 0.03 microg/ml fluoride; group 3, milk with 0.03 microg/ml fluoride; supplemented with NaF to 0.3 microg/ml fluoride; group 4, milk with 0.3 microg/ml fluoride; group 5, 0.3 microg/ml fluoride in 20 mM HEPES, pH 6.7; group 6, milk with 0.03 microg/ml fluoride supplemented with NaF to 5.0 microg/ml fluoride (positive control). The solutions were renewed each day and the calcium concentration in the demineralization solutions was followed during 4 days. The results showed that the protective effect of intrinsic milk fluoride on enamel is limited by the severity of the acidic challenge: There was a significant inhibition of the demineralization in groups 3-6 compared to groups 1 and 2, but only at pH 5.0 (p<0.0001) and not at pH 4.6 (p = 0.2). The organic components of milk had limited protection against demineralization because milk and HEPES with the same fluoride concentration gave similar results. The 36% reduction in calcium loss at pH 5.0 by treatment with milk with only 0.3 microg/ml fluoride is an indication that intrinsic milk fluoride has some caries-protective properties.

Acetates↗

PubMed2006

Ultrastructure of intraradicular dentin after irrigation with BioPure MTAD. II. The consequence of obturation with an epoxy resin-based sealer.

In addition to an initial report on the creation of thick demineralized collagen matrices in root dentin that were irrigated with BioPure MTAD or EDTA as final rinses for 5 minutes, this study examined the effect of a 2-minute irrigation time of these final irrigants on the extent of demineralization of intact intraradicular dentin and on interfacial nanoleakage after obturation with AH Plus and gutta-percha using warm vertical compaction. Transmission electron microscopy confirmed that the reduction in irrigation time did not compromise the smear layer removing capacity of these two irrigants when 1.3% NaOCl was employed as the initial rinse. BioPure MTAD created 5 to 6 microm thick demineralized dentin matrices, while 17% EDTA produced 1 to 2 microm thick matrices that were suboptimally infiltrated by the epoxy resin-based sealer, as manifested by the occurrence of silver tracer deposits within the hybrid layers.

Chelating Agents↗

PubMedDate not supplied

[Determination of calcium content in dentine after application of ZOE paste].

The calcium in dentine after the application of zinc oxide/eugenol paste (ZOE) was determined. The results were compared with the values valid for normal dentine calcium content in order to check some hypothesis suggesting that the effects of ZOE paste on dentine could reduce the calcium content and cause demineralization of dentine. The results obtained for calcium content in various layers of dentine have shown that only the layer of dentine-enamel junction (which should be removed before the application of ZOE paste) contained the increased concentration of calcium in comparison to anatomically deeper layers. The average calcium content in deeper dentine layers are very similar, especially in dentine layers directly exposed to action of ZOE paste, as well as in the layer on which ZOE paste was not applied.

Calcium↗

PubMed1998

Inhibition of demineralization in vitro around amalgam restorations.

OBJECTIVE: The purpose of this in vitro study was to evaluate some forms of preventing or avoiding demineralization within enamel cavity walls adjacent to amalgam restorations. METHODS AND MATERIALS: Third molar teeth were sectioned to obtain 72 specimens, divided into one control and five experimental groups: amalgam only; varnish plus amalgam; acidulated phosphate fluoride plus amalgam; adhesive amalgam; glass-ionomer cement plus amalgam; control (amalgam only, not subjected to a demineralization challenge). The experimental groups were subjected to PH and thermal cycling and then submitted to enamel hardness determinations. RESULTS: Significant differences between the treatment groups revealed that the bonded amalgam technique offered the best resistance to demineralization. The use of cavity varnish resulted in greater mineral loss than amalgam placed alone. CONCLUSION: The use of an adhesive system, glass-ionomer cement, or acidulated phosphate fluoride under amalgam restorations may interfere with development of secondary caries.

Acidulated Phosphate Fluoride↗

PubMed1991

Effect of fluoride mouthrinsing on caries lesion development in shark enamel: an in situ caries model study.

Shark enamel consists of nearly pure fluorapatite and has been shown to demineralize in an in situ caries model. The present study was conducted to investigate whether additional fluoride supplementation in the form of mouthrinsing would inhibit lesion development in shark enamel. The study slabs of shark enamel were mounted in dental appliances. Six individuals wore the appliances while rinsing daily with a neutral 0.2% NaF solution for 4 wk. The specimens were analyzed by means of quantitative microradiography, and the data compared with a previous study using untreated shark enamel and the same participants. It was found that fluoride rinsing did not measurably inhibit enamel demineralization in 4 wk. Scanning electron microradiographs showed that calcium fluoride-like material was not formed on shark enamel after neutral fluoride treatment, supporting a previous study. The present study indicates, therefore, that formation of a calcium fluoride-like material on the enamel surface may be essential for the cariostatic effect of topical agents.

Adolescent↗

PubMedDate not supplied

A novel in vitro microbial-based model for studying caries formation--development and initial testing.

We report on the development and the initial testing of a new microbial-based caries model. Specimens were fixed on a rotating mount within a reaction chamber hermetically surrounded by a sterilised glove box. A cariogenic environment was obtained by inoculation with Streptococcus mutans (ATCC 25175) combined with a continuously repeating supply of sucrose solution, trypticase soy broth and artificial saliva applied by dripping. Twenty-five caries-free upper premolars were used. The mesial parts of the occlusal fissures had been sealed with a resin-based fissure sealant (test group 1). To produce marginal gaps, the distal parts had been moistened with saliva before resin application (test group 2). Five teeth served as control and were exposed to all fluids under sterile conditions before being removed from the system after 7 days. Test specimens were infected with S. mutans and were incubated for another 14 days. No unintentional contamination occurred during the 3-week period of operation. Demineralizations were evaluated by using confocal laser scanning microscopy. Only the test specimens showed clearly visible signs of biofilm formation and caries-like lesions. The mean primary lesion depth did not differ significantly between test groups. Wall lesion depths and surface areas of demineralizations underneath the fissure sealants were significantly higher in test group 2. Thus, our model allows the simultaneous production of primary and secondary caries-like enamel lesions in a considerable number of specimens and facilitates the possibility to manipulate and transfer them without necessarily terminating the experiment, opening new possibilities for in vitro caries research.

Bicuspid↗

PubMed1998

Microhardness of in vitro caries inhibition zone adjacent to conventional and resin-modified glass ionomer cements.

OBJECTIVE: This study was conducted to correlate Knoop and triangular hardness numbers by measuring the microhardness of in vitro caries-inhibited and -demineralized dentin adjacent to a conventional and two resin-modified glass ionomer cements. METHODS: Box-shaped cavities were prepared on bovine root dentin and restored with either Fuji II, Fuji II LC, or Vitremer. The teeth were then decalcified in an acid buffered solution of 50 mmol l-1 acetic acid adjusted to pH = 4.5 for 3 days. Knoop and triangular microhardness indentations were performed perpendicular to the surface and parallel to the cavity wall, in the demineralized lesion and inhibition zone. Calcium and phosphorous contents of the outer lesions and inhibition zones were compared using energy-dispersive X-ray spectrometry (EDS). The correlation between Knoop and triangular hardness was analyzed by correlation coefficient. The statistical significance of hardness data was analyzed by one-way ANOVA and Fisher's PLSD test (p < 0.05). RESULTS: Triangular hardness (HT) correlated well with Knoop hardness number (KHN) (r2 = 0.81, p < 0.05). The microhardness of the inhibition zone created by Fuji II was of 59.2 +/- 3.8 HT and was statistically significantly higher than the zone produced by Fuji II LC and Vitremer. Fuji II LC and Vitremer produced inhibition zones with similar microhardness [48.3 +/- 3.5 HT and 44.0 +/- 7.6 HT, respectively (p > 0.05)]. Calcium and Phosphorous were present in the inhibition zone, but did not exist in the demineralized lesion. SIGNIFICANCE: Knoop and triangular hardness numbers correlated significantly (p < 0.05), and the latter seems to be a promising alternative method for measuring very narrow surfaces. Despite the fact that all glass ionomer materials used in this study were effective in producing an acid-resistant layer, microhardness and intensity of these layers were material dependent.

Analysis of Variance↗

PubMed2004

Dental plaque as a biofilm: a pilot study of the effects of nutrients on plaque pH and dentin demineralization.

Direct or in situ methods (e.g., confocal microscopy, microsensors) are used to study non-oral biofilms for almost two decades, and they have recently been introduced in the research of dental plaque. We combined a pH microsensor technique and transversal microradiography (TMR) in a pilot study where the effects of nutrient availability on plaque acidogenicity and on the development of caries-like lesions were assessed. One volunteer accumulated dental plaque for 7 days in 0.2-mm-wide and 0.8-mm-deep dentin grooves at four conditions: (1) saliva only, (2) 8 x 5 min/day dipping in 10% sucrose solution, (3) 7 x 5 min/day consumption of sweet cookies plus one meal/day, and (4) subject's regular diet. Plaque pH versus time and depth profiles in the grooves were recorded ex vivo before and after sugar challenge. 'Saliva' plaque responded to sugar with slow pH decrease--minimum pH 5.6-5.8 was reached after 30 min, while sugar dipping resulted in metabolically active plaque (minimum pH 5.3-5.5 within 4-8 min). TMR analysis revealed no demineralization after these two periods. Metabolically active plaque leading to distinct lesions resulted from frequent plaque exposure to diets rich in starch and carbohydrates (groups 3 and 4). These findings strengthen the view that the plaque acidogenicity does not necessarily reflect cariogenicity, and that retention of food components may account for increased cariogenicity at plaque retention sites in the mouth.

Animals↗