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The influence of dentin adhesives on the demineralization of irradiated and non-irradiated human root dentin.

This study determined the caries-protective effects of two different dentin bonding systems (Syntac, Scotchbond) on sound and irradiated root surfaces in vitro. The root surfaces of 30 freshly extracted caries-free human molars were used. The teeth were bisected in the mesio-distal direction and all lingual halves of the teeth were irradiated. The irradiation dose of 60 Gy was fractionally applied over six weeks (2 Gy/day, 5d/wk). All halves were then coated with acid-resistant nail varnish, exposing two rectangular windows 6 mm2 each on the dentinal root surface. One window served as an untreated control, while the other was treated with one of the above mentioned dentin adhesive systems. The specimens were randomly distributed among the four experimental groups as follow: Group A: Syntac, non-irradiated; Group AR: Syntac, irradiated; Group B: Scotchbond, non-irradiated; Group BR: Scotchbond, irradiated. Subsequently, all specimens were demineralized for 14 days with acidified gel (HEC, pH 4.8, 37 degrees C). From each window, two dentinal slabs were cut. The slabs were ground to a thickness of 80 microm and submerged in water. The depth of the lesions was determined using a polarized light microscope. The non-irradiated control specimens showed lesions with an average depth of 63 microm (+/-10,2 microm). In the case of the irradiated control specimen, the lesion depth was not significantly different. In all experimental groups, the lesion depth was significantly reduced compared to the control groups. Statistical analysis revealed no significant differences between the irradiated and non-irradiated specimens. It can be concluded that demineralization of the root surface can be hampered by application of the dentin adhesive systems tested. In this study, no differences between irradiated and sound root surfaces could be detected.

Analysis of Variance↗

In vitro evaluation of fluoride varnish on overdenture abutments.

STATEMENT OF PROBLEM: No clinical study has evaluated the efficacy of fluoride varnish as a topical fluoride agent for the protection of overdenture abutments from dental caries. PURPOSE: This study assessed the efficacy of a fluoride varnish in protecting overdenture abutments from demineralization in an in vitro environment. MATERIAL AND METHODS: Eighty caries-free, extracted teeth were sectioned and domed immediately below the cementoenamel junction, simulating overdenture abutment preparations. Acid resistant nail varnish was painted on all surfaces except for a window (1 x 4 mm) on the prepared occlusal dentin surfaces. Teeth were randomly divided into 4 groups of 20 specimens: control, washed with deionized/distilled water; Daily Gel, treated with Karigel-N (5,000 ppm) for 4 minutes daily; Weekly Gel, treated with Karigel-N for 4 minutes weekly; and Weekly Varnish, treated with Duraflor (22,600 ppm) weekly. The varnish was removed using a blade 24 hours after each application to simulate the clinical loss of the varnish. Teeth were then placed in a cycle of demineralization (2.2 mMol/L CaCl(2)2H(2)O, 2.2 mMol/L KH(2)PO(4), and 50 mMol/L acetic acid at pH 4.3) for 6 hours and remineralization (1.5 mMol/L CaCl(2)2H(2)O, 0.9 mMol/L KH(2)PO(4), and 150 mMol/L KCl at pH 7.0 for 17 hours) for 21 days. Half the teeth in each group were brushed with no dentifrice for 10 seconds, twice daily. Teeth were sectioned at 100 +/- 10 microm buccolingually and evaluated under polarized light microscopy and contact microradiography. The depth of each lesion and the width of the remineralization bands were measured (mm). Analysis of variance models and T-tests were used to assess the effects of different treatments (alpha=.05). Duncan multiple range tests were then chosen as post hoc tests to evaluate the statistical significance of all pairwise comparisons. RESULTS: The control group had the deepest lesions (mean depth 400 +/- 39 microm). The lesions from the varnish and daily gel groups were significantly shallower than the lesions in both the control group and the weekly gel group. The remineralization bands in the varnish group were 52% wider than the control group bands. However, the daily gel group had the largest increase in band width (117% increase) compared with the control group. There were significant differences between all groups for net depth (lesion depth minus the remineralization band) (P<.0001). Daily application of fluoride gel was significantly more effective than the other treatments tested. Brushing was not a significant factor. CONCLUSION: Within the limitations of this in vitro study, treatment of overdenture abutment with various topical fluorides significantly inhibited demineralization and enhanced remineralization of cut occlusal dentin surfaces. Daily use of Karigel-N was the most effective treatment, followed by the weekly application of Duraflor varnish.

Analysis of Variance↗

In situ evaluation of different remineralization periods to decrease brushing abrasion of demineralized enamel.

The aim of the present in situ study was to evaluate the effect of different periods of intraoral remineralization to decrease the susceptibility of previously demineralized enamel against toothbrushing abrasion. Six human enamel specimens (A-F) were recessed in the buccal aspects of each of eight intraoral appliances which were worn for 21 days by 8 panelists. Demineralization of the samples was performed twice a day extraorally in the acidic beverage Sprite Light for 90 s. Subsequently, the enamel specimens were brushed at different times. Specimen A was brushed immediately after the demineralization. The remaining samples B-E were brushed after the intraoral appliances had been worn for various periods of remineralization: specimen B, 10 min; C, 20 min; D, 30 min and E, 60 min, respectively. Specimen F was only demineralized and remineralized, but not brushed. After 21 days, enamel wear was measured with a laser profilometer. The following values (mean +/- standard deviation) were obtained: specimen A, 6.78+/-2.71 microm; B, 5.47+/-3.39 microm; C, 6.06+/-3.18 microm; D, 5.43+/-2.58 microm; E 4.78+/-2.57 microm, and F 0.66+/-1.11 micro;m. Analysis of variance revealed a significant influence of remineralization period on abrasive wear. However, even after a remineralization period of 60 min the wear was significantly increased as compared to the demineralized, but not brushed control. It is concluded that (1) abrasion resistance of softened enamel increases with remineralization period and (2) at least 60 min should elapse before toothbrushing after an erosive attack.

Amines↗

[Inhibition of remineralization by EDTA-soluble phosphate protein in dentin].

OBJECTIVE: To investigate the effect of removing EDTA-soluble phosphate protein in dentin on the later remineralization for the purpose of better understanding of mechanism of dentin phosphate proteins on dentin mineralization. METHODS: To remove soluble phosphate protein by EDTA dissolution, then the remineralization rate was monitored by a constant composition crystal growth technique. The results were compared with those from the normal dentin and the dentin partially demineralized by acetic acid. RESULTS: Faster remineralization rates were found with dentin demineralized by EDTA (0.5 and 2 h) compared with normal dentin powder, while a slower rate was found with dentin demineralized by acetic acid. The increase of remineralization rate by removing phosphate protein from dentin was 100% more at 200 min after the start of the reaction. CONCLUSION: EDTA-soluble phosphate protein in dentin has a great potential to inhibit remineralization.

Dental Cementum↗

An intra-oral single-section demineralization/remineralization model.

This paper reviews the use of our intra-oral crown single-section model for the evaluation of in situ demineralization and remineralization. The model uses normal, healthy adults who are in need of a gold crown. A slot is placed in the working crown which can hold 3-4 single sections. A typical experiment would use an enamel lesion, root lesion, and sound root section which are characterized with polarized light microscopy and/or microradiography prior to insertion in the crown. After the experimental regimen, the sections are removed and re-characterized for any changes. The model has been used to evaluate mineral changes from the use of fluoride dentifrices and rinses, chewing gum, and food sequencing. The advantages of the model system are the before-and-after measurements on the same section, a natural plaque formation, interaction with saliva, episodic demineralization and remineralization, no bulky appliances, and the use of reasonable time frames. This model, therefore, reduces the artificiality of the in situ study to a great extent and appears to be a useful predictor of demineralization/remineralization interactions.

Adult↗

Physiological remineralization of artificially demineralized dentin beneath glass ionomer cements with and without bacterial contamination in vivo.

This study evaluated the physiological remineralization of artificially demineralized dentin beneath glass ionomer cements with and without bacterial contamination. The artificially demineralized dentin was produced on 84 monkey teeth using a decalcifying solution. Half the samples were left open to the oral cavity for one week, then, all cavities were restored with two glass-ionomer cements: Fuji IX or Fuji II LC improved (n = 7). The nanohardness of the artificially demineralized dentin at 3, 90 and 360 days was measured using a nanoindentation tester (ENT-1100, Elionix) and compared statistically by two-way ANOVA and Fisher's PLSD test (p < 0.05). Each mineral (Ca, Mg, P, F) within the demineralized dentin was also analyzed using Electron Probe Microanalysis. For the samples, the mean nanohardness of the three-day samples was significantly lower than the 360-day samples (p < 0.05). Although there was no significant difference in the mean nanohardness within all the bacterially-contaminated groups through the experimental periods (p > 0.05), the mean nanohardness of the bacterial-contaminated samples were significantly lower than the non-bacteria-contaminated samples (p < 0.05). From the EPMA results, fluoride release from both cements to the bottom of the artificially demineralized dentin was detected within three days. Although Ca density was sparse within this demineralized dentin lesion, for the Fuji IX sample, a high Mg density within this lesion was detected at 360 days.

Analysis of Variance↗

Considerations for treating adolescent patients.

Adolescence is a time of accelerated growth with increasing caloric needs. A strong attraction for the taste of sugar and its availability have had detrimental consequences for the adolescent's dentition and general health. Numerous factors combine to contribute to the demineralization and erosion that predispose the enamel to smooth surface caries. Obesity and its associated maladies, eating disorders, and pregnancy are additional issues for consideration. Determining the need for and appropriate timing of extraction of third molars should be included in the treatment plan.

Adolescent↗

Enamel demineralization during orthodontic treatment. Aetiology and prevention.

The aetiology of enamel demineralization during fixed orthodontic treatment and its sequelae are discussed. A summary is given of the various methods available to assess the risk of demineralization prior to active treatment. The best preventive strategy would appear to be an assessment of risk factors prior to banding, coupled with fluoride rinses, regular reinforcement of oral hygiene, and dietary advice throughout the course of treatment.

Cariostatic Agents↗

Effect of fluoride-releasing liner on demineralized dentin.

OBJECTIVE: The aim of this study was to evaluate the remineralization of residual demineralized dentin underneath restorations by fluoride-releasing liners in vitro. METHOD AND MATERIALS: Two glass-ionomer cement liners, Lining Cement (GC) and RK-141A (GC), and two light-cured resin liners with and without 5 wt% NaF were used in this study. The resin liners were made by mixing TEGDMA and bis-GMA. Class 5 cavities were prepared on extracted human premolars. Demineralized dentin was promoted by using a bacterial caries induction system at the cavity floor. Cavities were restored with a resin composite following application of each liner. Specimens were then stored for 4 weeks at 37 degrees C and 100% humidity. After storage, the specimens were cut through the restorations, and axial sections of about 80-microm thickness were prepared. Contact microradiographs were taken, and the radiopacity of the demineralized dentin layer underneath the liner was analyzed. RESULTS: The ratios of radiopacity of demineralized dentin under the fluoride-releasing liners were significantly higher than those under the resin liner without fluoride release. Although the amounts of fluoride release from the glass-ionomer cement liners were lower than that from the resin liner with fluoride release, there were no significant differences in the ratios of radiopacity in demineralized dentin layers among the 3 liners with fluoride release. CONCLUSION: Although the fluoride released from liners can enhance remineralization of demineralized dentin, the amount of fluoride release does not affect the ratio of radiopacity in the remineralized dentin.

Bisphenol A-Glycidyl Methacrylate↗

Effects of fluoride-supplemented sucrose on experimental dental caries and dental plaque pH.

Sucrose, 5% and 10% (w/v), supplemented with between 0 and 5 ppm fluoride (F), was tested for its influence in vitro on plaque-induced experimental in vitro enamel caries and plaque pH. Plaque growth on bovine enamel was initiated from saliva inocula and sustained in a multiple plaque growth system for up to 31 days by means of a basal medium with periodic applications of sucrose or sucrose supplemented with F. Change in enamel mineralization was assessed, before and after plaque growth, by microhardness testing and microradiography; pH was monitored with microelectrodes. It was found that enamel demineralization was inversely related to the F concentration in the range 2 to 5 ppm, for both 5% and 10% sucrose. Plaque pH responses were unaffected by the F supplements.

Analysis of Variance↗

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↗

Effect of 0.02% NaF solution on enamel demineralization and fluoride uptake by deciduous teeth in vitro.

The application of 0.02% NaF solution on teeth with a cotton swab instead of brushing with fluoride dentifrice has been suggested for young children to reduce the risk of dental fluorosis, but its anticariogenic effect has not been evaluated. Thus, we studied the in vitro effect of 0.02% NaF solution on enamel demineralization and fluoride uptake in deciduous teeth; non-fluoride dentifrice and fluoride dentifrice (1.100 mug F/g) were used, respectively, as negative and positive controls. The treatment with fluoride dentifrice was more effective in reducing enamel demineralization (p < 0.05) and on fluoride uptake by the enamel (p < 0.05) than the non-fluoride dentifrice and the 0.02% NaF solution. Data suggest that the alternative use of 0.02% NaF solution instead of fluoride dentifrice should be reevaluated especially if dental caries are to be controlled.

Analysis of Variance↗

Clinical performance and caries inhibition of resin-modified glass ionomer cement and amalgam restorations.

BACKGROUND: The authors clinically examined two restorative materials to evaluate their effectiveness in Class II restorations in primary molars and their ability to inhibit recurrent caries. METHODS: Forty subjects, each in need of two Class II restorations in primary molars, took part in this study. Each patient received one Class II restoration of resin-modified glass ionomer cement and one of amalgam. The authors evaluated the restorations at six-month, one-year, two-year and three-year recall appointments. On exfoliation, teeth with experimental restorations were retrieved and microscopically examined for inhibition of demineralization at restoration margins. RESULTS: The results of the clinical evaluation demonstrated no significant differences between the resin-modified glass ionomer cement restorations and the amalgam restorations (P < .05). Polarized light microscopic examination of the returned teeth that were restored as a part of this study indicated that the resin-modified glass ionomer cement had significantly less enamel demineralization at restoration margins than did amalgam (P < .0001). CONCLUSIONS: The resin-modified glass ionomer cement functioned clinically as well as amalgam for Class II restorations in primary molars. However, the resin-modified glass ionomer exhibited significantly less enamel demineralization at restoration margins than did amalgam. CLINICAL IMPLICATIONS: Resin-modified glass ionomer cement restorative material functions well for Class II restorations in primary molars and exhibits less recurrent caries at restoration margins than does amalgam.

Cariostatic Agents↗

Effect of a solution with high fluoride concentration on remineralization of shallow and deep root surface caries in vitro.

A root dentin single-section model was developed to compare the efficacy of different fluoride treatments on the remineralization of lesions. Shallow ( approximately 170 microm) and deep ( approximately 400 microm) lesions were produced in acetic acid buffer solutions (pH 5.0) with 0.1- and 0.5-ppm fluoride for 3 days and 2 weeks, respectively. Next, the sections were pH-cycled for 4 weeks. Following the pH cycling, all sections were first remineralized for 5 weeks, then subjected to 10 days of demineralization. The treatments were (1) no treatment (control), (2) daily 1,450-ppm NaF toothpaste, (3) weekly 4,000-ppm fluoride solution, (4) a combination of treatments 2 and 3. In the shallow lesions, the 4,000-ppm fluoride solution and the combination treatment enhanced mineral deposition at the lesion front, producing a second, slightly hyperremineralized layer. Similarly, in the deep lesions a second remineralized layer was detected. In all lesions, the fluoride solution treatment showed significantly more remineralization compared to the control and the toothpaste treatment (p<0.05), most of which was formed during the pH cycling. In the demineralization period, the control showed significantly higher mineral loss than all other treatments. These results indicate that a 4,000-ppm fluoride solution might be effective for remineralization of root dentin lesions even over 400 microm depth.

Acetates↗

Effect of fluoride/essential oils-containing mouthrinse on the microhardness of demineralized bovine enamel.

PURPOSE: To assess the ability of a fluoride mouthrinse containing a fixed combination of essential oils (thymol, menthol, eucalyptol, and methyl salicylate) to inhibit demineralization as compared with that of a clinically established NaF rinse. METHODS: Inhibition in sound bovine enamel to demineralization was assessed utilizing a cyclic T/R/D (treatment/remineralization/demineralization) in vitro model where Knoop microhardness was monitored over 6, 12, and 18 T/R/D cycles. RESULTS: Both fluoride-containing mouthrinses resulted in statistically significant increase in microhardness when compared to the non-fluoride control mouthrinse, possibly demonstrating and validating the in vitro model's ability to parallel the clinically established benefit of a 0.022% NaF rinse to inhibit demineralization. In addition, the test formulation was shown to be "at least as good as" the NaF positive control in increasing enamel microhardness following each of the 6, 12, and 18 T/R/D cycles.

Analysis of Variance↗

In vitro remineralization of in vivo and in vitro formed enamel lesions.

Thin sections of natural white spot enamel lesions (WS) and of artificial in vitro lesions (VL) were remineralized simultaneously in vitro. The sections, clamped in a PMMA holder, were microradiographed at baseline and after remineralization in a calcium- and phosphate-containing solution (pH = 7.0; 1 ppm F) after 2 and 4 weeks. All data were analyzed with respect to baseline. The results show that the lesion depth values did not change significantly during 2 and 4 weeks of remineralization. The mineral accumulation (change in DeltaZ), however, was substantial and significant in WS and VL. In WS the change in mineral accumulation was roughly proportional to the amount of mineral at baseline. The WS accumulated more than two times the amount of mineral than VL in the same periods of remineralization. After 4 weeks of remineralization the maximum mineral value Vmax in the surface layer of the WS was nearly up to the sound enamel level thick approximate87 vol%. This study shows that the technique and calculation procedure described make this single section method attractive for longitudinal demineralization-remineralization studies in vitro or in situ. Both WS and VL samples obviously remineralized in vitro similarly with respect to the baseline. Furthermore, this in vitro work indicates that remineralization inhibitors present in saliva, and previously penetrated into the enamel tissue, do not influence remineralization later on.

Absorptiometry, Photon↗

Role of saliva in caries models.

The crucial role played by the actions of saliva in controlling the equilibrium between de- and remineralization in a cariogenic environment is demonstrated by the effects on caries incidence of salivary dysfunction and by the distribution of sites of caries predilection to those were salivary effects are restricted. However, of the several properties of saliva which may confer protective effects, it is not certain which are most important. A distinction can be made between static protective effects, which act continuously, and dynamic effects, which act during the time-course of the Stephan curve. Evidence implicates salivary buffering and sugar clearance as important dynamic effects of saliva to prevent demineralization; of these, the buffering of plaque acids may predominate. Enhanced remineralization of white spot lesions may also be regarded as dynamic protective effects of saliva. Fluoride in saliva (from dentifrices, ingesta, etc.) may promote remineralization and (especially fluoride in plaque) inhibit demineralization. The design of experiments using caries models must take into account the static and dynamic effects of saliva. Some models admit a full expression of these effects, while others may exclude them, restricting the range of investigations possible. The possibility is raised that protective effects of saliva and therapeutic agents may act cooperatively.

Animals↗

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↗