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Quantification of formation and remineralization of artificial enamel lesions with a new portable fluorescence device.

Quantitative laser fluorescence has been reported as a useful method for the non-destructive in vitro and in vivo diagnosis of early enamel caries. A portable system for intraoral use has been developed with a new light source and filter system replacing the laser light to facilitate clinical application. This new device was validated with microradiographic and chemical analyses for assessment of mineral changes in enamel during lesion formation and remineralization in vitro and compared with the laser light equipment. A significant correlation was found between fluorescence changes and mineral loss: r = 0.79 (laser system) and r = 0.84 (portable lamp system). The correlation between the two fluorescence methods was r = 0.93. The portable fluorescence device seemed to be a promising new tool for reproducible and sensitive assessment of the severity of incipient enamel lesions.

Animals↗

Assessment of the effect of selected snack foods on the remineralization/demineralization of enamel and dentin.

This study utilized volunteer subjects to examine caries-like lesions for remineralization and demineralization patterns in dentin and enamel when nine different snack foods were eaten between meals. Caries progression was observed in enamel and dentin when apple juice, a cola beverage, and sweetened (strawberry) yogurt were consumed as snacks. Remineralization of enamel was observed when cheddar cheese, skim milk, 2% milk, whole milk, chocolate milk, and orange juice were used as between meal snacks. Dairy products, with the exception of the sweetened yogurt, generally reduced the amount of demineralization produced in dentin. This study helps establish a scientific basis for appropriate between-meal snacks for patients who are concerned about their dietary habits as a part of their overall preventive oral health plan.

Adult↗

Fluorides in the new millennium.

Water fluoridation is known to be the most successful public health measure of the 20th century. More than half a century later, we are still reaping the benefits of fluoridation. We now know that the most important mechanism of fluoride action occurs through daily low-dose exposures. The battle between demineralization and remineralization occurs constantly, and fluoride shifts the balance to the latter. This dynamic, daily process far supersedes the pre-eruptive fluoride incorporation in importance. Fluoride, however, is now available in a variety of very different forms, useful in waging the war on caries. Nevertheless, opponents of this therapeutic agent maintain that its widespread use should be curtailed. Although the benefits of fluoride can no longer be disputed, fluoride supplementation must be supported and approached with consideration of total fluoride exposure.

Cariostatic Agents↗

The effect of a triclosan/copolymer/fluoride liquid dentifrice on interproximal enamel remineralization and fluoride uptake.

BACKGROUND: The authors measured the enamel remineralization of dental interproximal surfaces by a triclosan/copolymer/fluoride liquid dentifrice to test its performance against that of a standard toothpaste. METHODS: In a randomized, crossover, blinded, in situ protocol, the authors fitted 19 healthy adult subjects with mandibular appliances holding bilateral, interproximal bovine enamel slabs. They measured initial abrasion levels and fluoride content. In a two-phase crossover protocol, they evaluated the percentage of surface mineral recovery, or SMR, and fluoride uptake caused by the experimental dentifrice and a fluoride-containing traditional control toothpaste. RESULTS: Abrasion depths were similar and not different statistically (P > .05). The interproximal blocks exposed to the triclosan-containing liquid dentifrice had a mean fluoride uptake that was nearly 100 parts per million (13.1 percent) greater than that achieved with the American Dental Association-accepted control dentifrice. This finding, while not statistically significant, may indicate enhanced performance of the experimental dentifrice because the initial enamel slab abrasion depths were shown to be quite uniform. Moreover, the blocks exposed to the experimental toothpaste had a 49.8 percent SMR, while the positive control blocks had an SMR of only 36.9 percent. This enhanced remineralization performance was statistically significant (P < .05). CONCLUSIONS: This is the first study to show enhanced performance of a triclosan-containing liquid dentifrice in preventing interproximal dental caries. The difference in percentage of SMR was statistically significant and is likely to be clinically relevant. CLINICAL IMPLICATION: The results of this preliminary study offer evidence supporting clinicians' recommendation of the new liquid dentifrice to patients who are prone to developing interproximal carious lesions.

Adolescent↗

Practical fluoride and remineralization protocols for adult patients.

There is a wealth of information on preventive measures and procedures that can be used to care for paediatric and adolescent patients. However, few studies have been conducted in adult or geriatric populations, and an understanding of preventive and non-surgical treatment regimens for these patients is lacking. Traditionally, caries incidence is high among risk groups of low income, low dental IQ and certain ethnic subgroups, but we are now witnessing a high incidence of caries among middle-income and healthy adult patients with an imbalance of protective factors and cariogenic factors. We will direct our attention to the adult population and attempt to address some of the most common questions.

Adult↗

Influence of the mineral content and morphological pattern of artificial root caries lesion on composite resin bond strength.

Dentine substrates with different mineral contents and morphological patterns were created by submitting root slabs to the following treatments: (A) immersion in artificial saliva during the experimental period (control), (B) demineralization for 32 h to induce caries lesion (demineralized group), and (C) demineralization for 32 h followed by remineralization for 8 d (remineralized group). The slabs were longitudinally sectioned, the mineral content was determined by cross-sectional microhardness, and the bond strength of an adhesive system/composite resin was assessed using a microtensile bond strength test. The dentine morphology after the treatments as well as the failure pattern of the debonded specimens was examined by scanning electron microscopy. Statistically significant differences were found in mineral content. Morphological analysis showed marked differences between the patterns of demineralized and remineralized substrates. The bond strength mean value of the control A did not differ from the group B, but was statistically higher than the group C. Since no linear relationship was found between dentine mineral content and bond strength values, it could be suggested that the morphological pattern may be more relevant than the mineral content to explain the bond strength of composite resin to dentine.

Analysis of Variance↗

The relative efficacy of fluoride toothpastes assessed with pH cycling.

This study addressed the dose response between fluoride toothpastes and in vitro de- and remineralization, to predict the efficacy of toothpastes and understand the mode of action in the range 0-3,000 ppm F. Enamel lesions were pH-cycled with calcium uptake and loss being assessed daily. Both 'shallow' (about 50 microm deep) and 'deep' (about 200 microm deep) lesions were studied. F treatments were given in 30 (w/v)% toothpaste dilutions for up to 5 min daily. Calcium loss during the demineralization periods showed a dose response, resulting in 72% reduction for 3,000 ppm F compared to 0 ppm F. Calcium uptake during remineralization was increased in the F compared to non-F groups, with F concentration being less important than its mere presence. Significant differences were observed in F response between shallow and deep lesions, suggesting that this parameter should be included when testing caries-preventive products. Microradiographic analysis showed that lesion depth and severity had increased significantly in the non-F groups. In the F groups, the original lesion was partly remineralized, while a new lesion had formed beyond the original lesion front. Mineral loss of this second lesion correlated inversely with the F concentration of the treatments. These data revealed that fluoride can drive demineralization further into enamel by making the surface tissue less soluble, hence by not neutralizing acids penetrating into the tissue. It is also concluded that depth analysis of mineral uptake and loss is important to understand the mode of action of different F products.

Analysis of Variance↗

Influence of polymers for use in saliva substitutes on de- and remineralization of enamel in vitro.

A number of polymers which have previously been tested for their applicability as thickening agents in saliva substitutes were studied in vitro for their caries-protective properties. These were: polyacrylic acid, carboxymethylcellulose, xanthan gum, guar gum, hydroxyethylcellulose and porcine gastric mucin. The polymers were tested for their effects on: (1) growth of hydroxyapatite crystals in a supersaturated calcium phosphate solution, (2) dissolution of hydroxyapatite crystals in 50 mM acetic acid, pH 5.2 and (3) demineralization and remineralization of bovine enamel in a pH-cycling model. Growth of hydroxyapatite crystals was strongly inhibited by polyacrylic acid and carboxymethylcellulose at very low concentrations (0.005% w/v). Other polymers displayed lower inhibition of hydroxyapatite crystal growth. Hydroxyapatite dissolution was inhibited by all polymers except by hydroxymethylcellulose and xanthan gum. This occurred both in the presence of the polymers as well as after a 30-min preincubation. In the pH-cycling experiment, bovine enamel specimens with preformed lesions were alternately exposed to a demineralization buffer and a remineralization buffer containing the polymers hydroxyethylcellulose, carboxymethylcellulose, xanthan gum, polyacrylic acid, or porcine gastric mucin. A remineralization buffer containing 1 ppm NaF was used as a positive control. Under the experimental conditions, the control experiment without additives resulted in a net mineral loss (30.6 mumol Ca/cm2 after 14 days of pH cycling). In the presence of 1 ppm NaF, a small mineral gain was observed (8.6 mumol/cm2). All polymers largely inhibited further demineralization (1.2-12.3 mumol/cm2) except polyacrylic acid which, inhibited of its high calcium-binding capacity, caused demineralization, especially in the remineralization buffer (17.1 mumol/cm2). In conclusion, polymers tested in this study, except the polyacrylic acid, reduced the demineralization of enamel in vitro. The precise mechanism of the protective effect is not clear but it is speculated that formation of an absorbed polymer layer on the hydroxyapatite or enamel surface may provide protection against acidic attacks.

Acetic Acid↗

Effect of fluoridated milk on progression of root surface lesions in vitro under pH cycling conditions.

The aim of this study was to assess the effect of milk with 0, 2.5 or 5 ppm F on progression and remineralization of caries-like root surface lesions using a pH cycling model. The root surface lesions were created utilizing a partially saturated lactic acid buffer at pH 4.6. Longitudinal sections were cut through the lesion and analyzed using polarized light microscopy (PLM) and microradiography (MRG). The sections were then coated with an acid resistant varnish, except the outer natural surface that would be exposed to water, milk or fluoridated milk and cycled in a de- and remineralizing system for 2 weeks. The lesions were characterized again by PLM and MRG after treatment. A significant reduction in lesion progression was found by PLM and MRG after treatment with either non-fluoridated or fluoridated milk when compared to the control group. Using quantitative MRG, mineral change and distribution in the lesions were recorded. A possible protective effect of fluoridated milk on root surface caries was supported by a reduction in the progression of the lesions and an increase in the mineral within the lesion.

Analysis of Variance↗

An in situ interproximal model for studying the effect of fluoride on enamel.

This crossover study determined the ability of an interproximal, intra-oral model to demonstrate a fluoride dose response to 0-, 250- and 1,100-ppm fluoride (sodium fluoride) dentifrices with respect to fluoride uptake into, and remineralization of, incipient subsurface enamel lesions. Following a 1 week 'lead in' period during which 30 panelists were randomly assigned to use one of the products, two enamel specimens with artificial carious lesions were mounted into a specially designed functional partial denture worn by each panelist. Panelists continued to brush three times daily with their test dentifrice for 4 weeks, after which the specimens were removed and analyzed for fluoride uptake and remineralization. The procedure was repeated until each panelist had followed all three treatment regimens. Fluoride analyses were performed using a microdrill biopsy technique, and mineral content changes were determined by transverse microradiography. Fluoride uptake data were significantly different (p < 0.01) for all three products with the effect of 1,100 ppm F > 250 ppm F > placebo. The 1,100 ppm F dentifrice also effected significantly greater remineralization (p < 0.01) than did the 250-ppm-F or placebo dentifrices. Relative efficacy of the three fluoride dentifrices tested in this study was similar to that established in a clinical trial, and, therefore, supports the use of this model for in situ studies of the effects of fluoride-containing products on enamel lesions.

Adult↗

Effect of calcium in model plaque on the anticaries activity of fluoride in vitro.

The uptake of calcium by a polysaccharide (agarose) gel used as a model for plaque from a two-step treatment (consisting of a calcium rinse followed by a fluoride treatment) and the effect of the deposited calcium in model plaque on caries lesion formation in enamel were determined. Calcium uptake was measured by treatment of the model plaques with [45Ca]-CaCl2 solutions with or without NaF. A two-step treatment consisting of calcium followed by fluoride produced a 100% increase in calcium content of model plaque, presumably due to the formation of CaF2, compared with a treatment with artificial saliva followed by calcium alone. The effects of these increased plaque minerals on caries lesion formation were studied by subjecting model-plaque-covered enamel blocks to a cyclic demineralization-remineralization treatment. Artificial-plaque-covered enamel blocks were treated daily with 180 ppm calcium for ten min, then 100 ppm fluoride for ten min, followed by demineralization for 16 h, and finally, remineralization for seven h and 40 min. After five days, the blocks were sectioned, and lesion formation was determined by microradiography-microdensitometry. Artificial plaque treated with a calcium rinse followed by a fluoride rinse reduced lesion size by 90%, compared with a 68% reduction by a fluoride rinse alone. When the experiment was repeated with a simulated pre-brush calcium rinse (180 ppm calcium) followed by a fluoride dentifrice suspension (110 ppm fluoride), lesion size was reduced by 46%, compared with a 32% reduction by the fluoride dentifrice suspension alone.

Absorptiometry, Photon↗

Anticaries profile qualification of an improved whitening dentifrice.

A series of pH cycling "profile" laboratory studies was conducted to confirm the anticaries potential of an enhanced cleaning and whitening dentifrice based on a novel abrasive polishing silica and pyrophosphate tartar control source, with sodium fluoride as the anticaries ingredient. Under pH cycling remineralization conditions, the whitening dentifrice produced lesion fluoridation comparable to a conventional tartar control dentifrice containing combinations of pyrophosphate anion and a NaF fluoride ion source. Under pH cycling lesion progression conditions, the whitening dentifrice produced enamel protection against caries development, comparable to control dentifrices containing NaF alone or in combination with tartar control pyrophosphate anion. These results are consistent with clinical data supporting the effectiveness of NaF dentifrices combined with anionic tartar control inhibitors such as pyrophosphate. These results support the anticaries effectiveness of the enhanced cleaning and whitening dentifrice based upon "Stain-Specific Soft Silica."

Analysis of Variance↗

The caries balance: the basis for caries management by risk assessment.

Dental caries progression or reversal depends upon the balance between demineralization and remineralization. The 'Caries Balance' is determined by the relative weight of the sums of pathological factors and protective factors. Minimally invasive dentistry aims at the least possible removal of enamel or dentin, including reducing pathological factors and enhancing remineralization to avoid any removal of hard tissues. A structured caries risk assessment should be carried out based upon the concept of the caries balance. Following the risk assessment a treatment plan is devised which leads to the control of dental caries for the patient. The balance between pathological and preventive factors can be swung in the direction of caries intervention and prevention by the active role of the dentist and his/her auxiliary staff. Much is now understood about the mechanism of dental caries. We have known for a long time that demineralization of enamel, dentin or cementum is caused by organic acids that are generated by so-called acidogenic bacteria in the plaque when these bacteria feed upon fermentable carbohydrates (Silverstone, 1973; Featherstone, 2000; Loesche, 1986). The natural repair process is remineralization, which occurs when the pH rises again and calcium and phosphate from saliva together with fluoride enter the subsurface region of the lesion and form a new veneer on the existing crystal remnants in the lesion (Ten Cate and Featherstone, 1991). This veneer is less soluble than the original mineral and resists further acid attacks. The key to improved dental health for all is now for the dental profession to embrace this knowledge and put it into practice in the real world, to inhibit caries formation and progression, and to enhance the natural repair process.

Anti-Infective Agents, Local↗

Caries prevention and reversal based on the caries balance.

The science behind caries prevention and reversal is well understood. A recent clinical trial has confirmed that reducing caries risk results in a reduction in dental decay. Dental caries progression or reversal depends upon the balance between demineralization and remineralization and can be visualized for clinical purposes as the "caries balance." This balance is determined by the relative weights of the sums of pathological factors and protective factors. A structured caries risk assessment should be carried out based upon the concept of the caries balance. Following the risk assessment, a treatment plan is devised which leads to the control of dental caries for the patient. The balance between pathological and preventive factors can be swung in the direction of caries intervention and prevention by the active role of the dentist and his/her auxiliary staff.

Adolescent↗

Application of the Zürich biofilm model to problems of cariology.

The term biofilm is increasingly replacing 'plaque' in the literature, but concepts and existing paradigms are changing much more slowly. There is little doubt that biofilm research will lead to more realistic perception and interpretation of the physiology and pathogenicity of microorganisms colonizing plaques in the oral cavity. There is clear evidence that the genotypic and phenotypic expression profiles of biofilm and planktonic bacteria are different. Several techniques are available today to study multispecies biofilms of oral bacteria, each having its particular advantages and weaknesses. We describe a biofilm model developed in Zürich and demonstrate a number of applications with direct or indirect impact on prophylactic dentistry: spatial arrangement and associative behavior of various species in biofilms; multiplex fluorescent in situ hybridization analysis of oral bacteria in biofilms; use of the biofilm model to predict in vivo efficacy of antimicrobials reliably; mass transport in biofilms; de- and remineralization of enamel exposed to biofilms in vitro. The potential of biofilm experimentation in oral biology has certainly not yet been fully exploited and dozens of possible interesting applications could be investigated. The overall physiological parameters of multispecies biofilms can be measured quite accurately, but it is still impossible to assess in toto the multitude of interactions taking place in such complex systems. What can and should be done is to test hypotheses stemming from experiments with planktonic cells in monospecies cultures. In particular, it will be interesting to investigate the relevance to biofilm composition and metabolism of specific gene products by using appropriate bacterial mutants.

Animals↗

[Appositional rate of incisor dentin and hematic calcium level in rats. Application of time marking method using lead acetate].

Matsumoto et al. have reported that the remineralization of rat incisor dentin following administration of various drugs depends upon the hematic calcium (hCa) level in parathyroidectomized (PTX) rats. It is known that injected lead according to a time marking method deposits at the mineralizing front in hard tissues. In the present study, we observed the alteration of the mineralizing front of the incisor dentin and examined the dependency of the dentin remineralization on the hCa level in PTX rats given 1,25 (OH)2D3. Male Wistar rats (7-8 weeks old) were used. They were fed a synthetic diet containing 0.3% Ca or 0.02% Ca (Ca-deficient) from 3 days before PTX. In order to mark the time in the incisor dentin, lead acetate was injected at 3 day intervals. Exp. I: A group of rats fed a diet containing 0.3% Ca was given a single injection (400 ng/kg) of 1,25 (OH)2D3 on the 9th day after PTX. Exp. II: four groups of rats were given daily injections of various doses (vehicle, 25, 50 and 100 ng/kg) of 1,25 (OH)2D3 from the 11th day after PTX for 13 days. The distance between the two lead-lines observed in the histological sections of the incisor was measured as an indicator of the appositional rate of dentin. In rats given a diet containing Ca below 0.3%, the hCa level was about 5 mg/dl after PTX. Mineralization of the incisor dentin was suppressed markedly, and a hematoxylin unstained zone was observed in the histological sections, indicating that the mineralizing front had been stagnant. In Exp I, a high dosage of 1,25 (OH)2D3 raised the hCa level to over 8 mg/dl within 12 hours; formation of a new mineralizing front and remineralization of the dentin were observed. In Exp. II, daily injections of 1.25 (OH)2D3 raised the hCa levels gradually and dose dependently. The hCa levels in groups of rats given 50 and 100 ng/kg of 1,25 (OH)2D3 were over 8 and 10 mg/dl respectively after the 6th day from the beginning of the drug administrations. The distance between the two lead-lines deposited in dentin also increased gradually. Therefore, the appositional rate of the incisor dentin seemed to increase in accordance with the rise in the hCa level. The correlation coefficient between the appositional rate of lingual dentin and the hCa level was estimated to be 0.922 (p less than 0.001, y = 4.4x + 19.2).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Effect of fluoride on overdenture abutments.

This study evaluated the caries preventive effects of high concentrations of fluoride on overdenture abutment teeth. Twenty-four extracted caries-free teeth were randomly selected from a pool of patients aged 50-70 and prepared as for overdenture abutments. The teeth were sectioned mesiodistally into two halves. All surfaces on the teeth were painted with a protective varnish except for a window on the root surface and one on the cut dentin of the occlusal. The 48 root halves were randomly divided into four groups of 12 specimens. Each group received a different 4-minute treatment prior to being placed in a demineralizing solution for 6 hours. The treatment groups were (1) distilled H2O only; (2) 1,000 ppm F-; (3) 5,000 ppm F-; and (4) 10,000 ppm F-. The teeth were cycled for 6 hours in the demineralizing solution and 17 hours in a fluoride-free remineralizing solution for 17 days. Sections were cut at 100 +/- 10 microns through the windows. Standardized photomicrographs were made under polarized light using distilled H2O and quinoline as the imbibing media. Microradiographs were made of the same specimens and these were also photographed at the same magnification. The depths of the lesions were measured from drawings of the lesions projected on a digitizer screen. The amount of demineralization was calculated by subtracting the width of the mineralizing bands from the depth of the lesion. The conclusions were: (1) Lesions on the root surface were much shallower than on the occlusal; (2) A dose response to the fluoride concentration of the topical application was evident.

Aged↗

The use of topical fluoride to prevent or reverse dental caries.

Topical fluoride has been the main stay of caries prevention for many decades. There are several mechanisms which make it beneficial including inhibiting demineralization, enhancing remineralization, and inhibiting bacterial growth. Topical fluoride is available in many different forms. The concentrations of various fluoride preparations range from 225 parts per million (ppm) fluoride in over-the-counter oral rinses to 22,600 ppm in the fluoride varnishes. The clinician must decide which type of topical preparation is best suited for their patient. Patients with high caries risk may benefit from prescription strength fluorides (along with the other chemical and dietary therapies described in this issue of Special Care in Dentistry). The application of fluoride varnish is an excellent topical form for those patients who have access to dental care and for whom it is difficult to comply with the use of other topical forms.

Cariostatic Agents↗