In situ Effect of Frequent Sucrose Exposure on Enamel Demineralization and on Plaque Composition after APF Application and F Dentifrice Use

Effectiveness of non-operative approaches in active enamel carious lesions: a retrospective longitudinal study

The aim of the study was to investigate the effectiveness of non-invasive and micro-invasive treatments in active enamel carious lesions in high-caries-risk children. Clinical records of children treated in a dental school setting were retrospectively screened for active enamel carious lesions treated non-invasively (topical fluoride applications, oral hygiene instruction, or dietary guidance) or micro-invasively (sealant). The control of active carious lesions was set as the main outcome established by the combination of inactivation and non-progression of the lesions based on Nyvad and ICDAS criteria, respectively. Individual and clinical factors associated with the outcome were analyzed by Poisson regression. The sample consisted of 105 high-caries-risk children with a mean age of 8.3 (± 2.4) years. From a total of 365 active enamel carious lesions, most lesions (84.1%) were active non-cavitated carious lesions (ICDAS scores 1 and 2) and only 15.9% presented localized enamel breakdown (ICDAS score 3). Of these, 72.6% were inactivated and 92.1% did not progress (mean time of 6.5 ± 4.1 months). The prevalence of controlled carious lesions was higher among children older than 6 years (PR:1.43; 95%CI:1.00-2.03; p = 0.04) and in those with better biofilm control (PR:0.99; 95%CI: 0.98-0.99; p = 0.03). Non-operative approaches are effective for controlling active enamel carious lesions. The majority of active enamel carious lesions became inactive and did not progress after treatment. Caries control was associated with older children and better biofilm control.

Is professionally applied topical fluoride effective in treating incipient caries? A systematic review

The present systematic review aimed to investigate the effectiveness of professionally applied topical fluoride as therapeutic agent for incipient carious lesions in permanent teeth. Randomised clinical trials (RCTs) comparing the effectiveness of professionally applied topical fluoride (varnish or gel) with that of placebo, no intervention, and toothbrushing (control group) in the treatment of incipient carious lesions in permanent dentition were included. An electronic search was performed in the PubMed, Web of Science, Scopus, Virtual Health Library, Embase, and Cochrane databases, in the grey literature, and in clinical trials registered until January 2021. Two reviewers independently screened titles and abstracts and assessed the risk of bias using the Cochrane tool. The certainty of evidence was classified using GRADE. A total of 2,223 articles were screened using titles/abstracts. After full-text reading of the 22 selected studies, nine RCTs were included. Five RCTs found that topical fluoride may be effective in reversing incipient carious lesions in permanent teeth. Overall, five studies were classified as having a low risk of bias and four as having some concerns. Only descriptive analysis was performed because of the heterogeneity of the data. Studies comparing fluoride varnish with usual home care oral hygiene have demonstrated topical fluoride does not appear to be more effective in improving the appearance of incipient carious lesions. Therefore, usual home care oral hygiene with fluoride toothpaste may be sufficient to treat incipient carious lesions in permanent dentition. Further studies with greater methodological rigor are, however, required to reduce bias, to allow a meta-analysis, and to draw well-founded conclusions (CRD42019120406).

Engineered Salivary Peptides Reduce Enamel Demineralization Provoked by Cariogenic S. mutans Biofilm

Engineering of the acquired enamel pellicle using salivary peptides has been shown to be a promising anticaries strategy. However, the mechanisms by which these peptides protect teeth against tooth decay are not fully understood. In this study, we evaluated the effect of the engineered salivary peptides DR9-DR9 and DR9-RR14 on enamel demineralization in two experimental conditions: (1) adsorbed onto the enamel surface forming the AEP, and (2) forming the AEP combined with their use to treat the biofilms 2×/day, using a validated cariogenic Streptococcus mutans in vitro biofilm model. Biofilms were grown for 144 h on enamel slabs and then collected to determine the bacterial viability (CFU/biofilm) and biofilm mass (mg protein/biofilm), and to extract cellular/extracellular proteins, which were characterized by mass spectrometry. The culture medium was changed 2×/day to fresh medium, and pH (indicator of biofilm acidogenicity) and calcium concentration (indicator of demineralization) was determined in used medium. DR9-RR14 peptide significantly reduced enamel demineralization (p < 0.0001) in both experimental conditions. However, this peptide did not have a significant effect on biofilm biomass (p > 0.05) nor did it modulate the expression of cellular and extracellular bacterial proteins involved in biofilm cariogenicity. These findings suggest that DR9-RR14 may control caries development mainly by a physicochemical mechanism.

Effects of the association of high fluoride- and calcium-containing caries-preventive agents with regular or high fluoride toothpaste on enamel: an in vitro study

OBJECTIVES

The aim of this in vitro study was to compare the caries-preventive effect of various high fluoride- and calcium-containing caries-preventive agents (> 22.000 ppm F^- [ppm]) in adjunct to use of regular (1450 ppm) or high (5000 ppm) fluoride toothpaste on sound as well as demineralized enamel.

MATERIALS AND METHODS

Bovine enamel specimens (n = 276; 5 mm × 3.5 mm × 3 mm) having one sound surface [ST] and one artificial caries lesion [DT] were randomly allocated to 12 groups. Interventions before pH-cycling were no intervention ([SC₁/SC₅]), application of varnishes/solutions containing NaF (22,600 ppm; Duraphat [NaF₁/NaF₅]); NaF + tricalcium phosphate (22,600 ppm; Clinpro White Varnish [TCP₁/TCP₅]); NaF + CPP-ACP (22,600 ppm; MI Varnish [CPP₁/CPP₅]); silver diammine fluoride (35,400 ppm; Cariestop 30%[SDF₁/SDF₅]); and NaF + calcium fluoride (45,200 ppm; Biophat[CaF₁/CaF₅]). During pH-cycling (28 days, 6 × 120 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 × /day) with either 1,450 (NaF; named, e.g., TCP₁) or 5,000 ppm (NaF; e.g., TCP₅) dentifrice slurry. Differences in integrated mineral loss (∆∆Z) and lesion depth (∆LD) were calculated between values after initial demineralization and after pH-cycling using transversal microradiography.

RESULTS

After pH-cycling, SC₁/SC₅ showed significantly increased ∆Z_DT/LD_DT values, indicating further demineralization (p < 0.05; paired t-test). Decreased ∆Z_DT values, indicating non-significant remineralization, could only be observed in CaF₁/CaF₅ (p > 0.05; paired t-test). Additional use of all varnishes/solutions significantly decreased ∆∆Z_DT/∆∆Z_ST and ∆LD_DT/∆LD_ST compared to SC₁/SC₅ (p < 0.05;ANCOVA). Between 1450 and 5000 ppm dentifrices, a significant difference in ∆∆Z_DT/∆∆Z_ST and ∆LD_DT/∆LD_ST could only be observed for SC₁/SC₅ (p < 0.05; ANCOVA).

CONCLUSION

Under the conditions chosen, all fluoride varnishes/solutions significantly reduced demineralization. Furthermore, a significant dose-response characteristic for fluoride varnishes could be revealed. However, no additional benefit could be observed, when varnishes were combined with high fluoride instead of regular fluoride dentifrices.

CLINICAL RELEVANCE

For children and adolescents with high caries risks varnishes containing more than 22,600 ppm should be further investigated, as they offered higher caries-preventive effects in vitro. Furthermore, there seems to be no difference in the demineralization-inhibitory capacity of fluoride varnishes when used in combination with either standard or highly fluoridated dentifrices.

The effect of arginine-fluoride varnish on biochemical composition of multi-species biofilm

OBJECTIVE

To examine the biochemical components of multi-species biofilm on the arginine (Arg)-sodium fluoride (NaF) varnish-treated enamel following bacterial pH-cycling.

METHODS

l-arginine (at 1%, 2%, & 4% w/v.) was incorporated in a 5% NaF varnish. The experimental and control groups were: 1%, 2%, 4% Arg-NaF, NaF, and no treatment. Enamel blocks were prepared, acid-etched, varnish-treated and then subjected to 72 h bacterial pH-cycling in an oral biofilm reactor. The organic (carbohydrates, proteins, amyloids, and eDNA) and inorganic components (calcium, inorganic phosphate, F) were assayed for the obtained biofilm suspensions. The biofilms were stained for exopolysaccharides (EPS)/bacteria and the respective proportions of live/dead bacteria was determined using confocal imaging.

RESULTS

The total carbohydrate content of the biofilm was the lowest for the 2% and 4% Arg-NaF (p < 0.05). Except for 2% Arg-NaF, the biofilm proteins for 4% Arg-NaF were significantly higher than the other groups (p < 0.05). The amyloids for Arg-NaF groups were significantly lower than the controls (p < 0.05). The eDNA for 4% Arg-NaF was significantly higher than the controls (p < 0.05). The 2% and 4% Arg-NaF-treated enamel had increased biofilm Pi and F compared to the NaF-treated enamel (p < 0.05). The proportion of biofilm EPS matrix to bacteria was significantly reduced in Arg-NaF groups compared to the controls (p < 0.05). The dead bacterial proportions of 4% Arg-NaF were significantly higher than the controls (p < 0.05).

CONCLUSION

Higher concentrations (i.e. 2%/4%) of Arg in 5% NaF varnish have the potential to modulate the biochemical composition of the biofilm growing on the treated enamel.

Low-Temperature Plasma as an Approach for Inhibiting a Multi-Species Cariogenic Biofilm

This study aimed to determine how low-temperature plasma (LTP) treatment affects single- and multi-species biofilms formed by Streptococcus mutans, Streptococcus sanguinis, and Streptococcus gordonii formed on hydroxyapatite discs. LTP was produced by argon gas using the kINPen09™ (Leibniz Institute for Plasma Science and Technology, INP, Greifswald, Germany). Biofilms were treated at a 10 mm distance from the nozzle of the plasma device to the surface of the biofilm per 30 s, 60 s, and 120 s. A 0.89% saline solution and a 0.12% chlorhexidine solution were used as negative and positive controls, respectively. Argon flow at three exposure times (30 s, 60 s, and 120 s) was also used as control. Biofilm viability was analyzed by colony-forming units (CFU) recovery and confocal laser scanning microscopy. Multispecies biofilms presented a reduction in viability (log10 CFU/mL) for all plasma-treated samples when compared to both positive and negative controls (p < 0.0001). In single-species biofilms formed by either S. mutans or S. sanguinis, a significant reduction in all exposure times was observed when compared to both positive and negative controls (p < 0.0001). For single-species biofilms formed by S. gordonii, the results indicate total elimination of S. gordonii for all exposure times. Low exposure times of LTP affects single- and multi-species cariogenic biofilms, which indicates that the treatment is a promising source for the development of new protocols for the control of dental caries.

Root dentine demineralisation according to frequency of sucrose exposure using high-fluoride dentifrice

OBJECTIVE

To evaluate root dentine demineralisation, biomass and loosely bound fluoride (CaF₂ ) concentration according to different frequencies of sucrose exposure using a high-fluoride dentifrice.

BACKGROUND

Although high-fluoride dentifrice has been recommended to arrest root dentine lesions, it is not clear whether it can protect dentine from increased frequencies of sucrose exposure.

METHODS

An in situ, crossover, split-mouth study was conducted in 3 phases with 7 days each, in which 10 volunteers used a palatal device containing 4 bovine root dentine slabs (2 on each side) with predetermined initial hardness. Cariogenic challenge consisted in dripping a 20% sucrose solution 0 (control), 2, 4, 6, 8 or 10 times/d in each block. Volunteers used high-fluoride dentifrice (NaF, 5000 µg F/g) 3 times/d. After each phase, final hardness was measured and the percentage of surface hardness loss (%SHL) calculated. Also, biomass and CaF₂ concentration on dentine were determined. The data were processed and analysed by ANOVA and Tukey test with significance level set at 5%. The relationship between the variables was analysed by linear regression and Pearson correlation (r).

RESULTS

%SHL and biomass were significantly greater than control for sucrose frequencies higher than 6 times/d (P < 0.001), while CaF₂ concentration decreased from sucrose frequency higher than 2 times/d (P < 0.001). Regression analysis data showed a significant linear fit between sucrose exposure frequency and the studied variables with a strong correlation (r) for %SHL and CaF₂ and moderate for biomass (P < 0.05).

CONCLUSION

High-fluoride dentifrice is able to reduce root dentine demineralisation if sucrose consumption is not higher than 6 times/d.

Assessment of Inhibition of Mineral Loss from Human Tooth Enamel by Carbon Dioxide Laser and 1.23% Acidulated Phosphate Fluoride

Aims and Objectives

The efficacy of carbon dioxide (CO₂) laser irradiation combined with fluoride in inhibiting enamel demineralization has been demonstrated by several laboratory investigations. However, there are very few reports about the in situ or in vivo caries preventive effect of CO₂ laser combined with topical fluoride on dental enamel. Hence, an in situ study was designed and carried out to assess inhibition of mineral loss from human tooth enamel by CO₂ laser and 1.23% acidulated phosphate fluoride (APF).

Material and Methods

Impressions of upper and lower arch of the volunteers were made in alginate impression material. Study models were poured, duplicated, and duly labeled. On the working model, appliances were fabricated in acrylic resin to fit the upper dental arch of the volunteers. Four enamel slabs (one from each group) were fitted on the palatal surface of the appliance as close as possible to posterior teeth. Surfaces of slabs were kept below the outer surface of acrylic. The analysis was done using SPSS version 15 (SPSS Inc., Chicago, IL, USA) Windows software program.

Results

Statistically significant increase in inhibition of mineral loss of enamel slabs when treated individually or in a combination of low power CO₂ laser and 1.23% APF solution. The application of 1.23% APF solution after low power CO₂ laser treatment showed maximum inhibition of mineral loss.

Conclusion

The combined use of this specific laser treatment plus fluoride was more successful than either laser treatment or fluoride alone in the inhibition of mineral loss in the mouth. The results of this study also suggest that the combination of low power laser treatment with fluoride therapy may be effective as a caries inhibition treatment.

In situ Effect of Arginine-Containing Dentifrice on Plaque Composition and on Enamel Demineralization under Distinct Cariogenic Conditions

There is limited evidence that arginine-containing fluoridated dentifrices (AFD) have a better anticaries effect than regular fluoridated dentifrices (FD), especially in subjects at a higher risk for caries development. This study aimed to assess the effect of AFD on enamel demineralization and on the microbial and biochemical compositions of biofilm formed under different frequencies of sucrose exposure. It consisted of an in situ split-mouth design, where 12 adult volunteers who used FD for at least 2 months prior to the beginning of this study wore acrylic palatal appliances containing 4 bovine enamel specimens (1 pair at each side of the appliance) during 2 phases of 14 days each. FD slurry (3×/day) and 20% sucrose solution (4× and 8×/day) were dripped on the specimens during the first experimental phase. The same volunteers then used AFD during a 2-month washout period, followed by a second experimental phase where the AFD slurry and sucrose solution were applied onto a new subset of specimens. The percentage of enamel surface hardness loss (%SHL), the lesion depth (LD), the integrated mineral loss (IML), microbial counts on biofilms, the biomass, and inorganic and insoluble extracellular polysaccharide (IEPS) biofilm concentrations were determined. Higher %SHL, biomass, and IEPS and lower fluoride values were found at sucrose 8×/day exposure. Lower IEPS were found in the presence of AFD compared to FD. Similar %SHL, LD, and IML values were found between FD and AFD, irrespectively of the cariogenic challenge. The results suggest that AFD have an anticaries effect similar to that of regular FD.

In situ effect of the combination of fluoridated toothpaste and fluoridated gel containing sodium trimetaphosphate on enamel demineralization

OBJECTIVE

This in situ study evaluated the effect of the association of low-F (4500μg F/g) gel containing TMP and FT (1100μg F/g) on enamel demineralization.

METHODS

This crossover and double-blind study consisted of five phases of seven days each. Volunteers (n=12) wore palatal appliances containing four enamel blocks. The cariogenic challenge was performed with 30% sucrose solution (six times/day). Treatments were: placebo toothpaste (PT, no fluoride/TMP); 1100μg F/g toothpaste (FT); FT+4500μg F/g+5%TMP gel (FT+TMP gel); FT+9000μg F/g gel (FT+9000 gel) and FT+12,300μg F/g (FT+Acid gel). After topical application of treatments for one min, two blocks were removed for analysis of loosely bound fluoride (CaF₂), calcium (Ca), phosphorus (P) and firmly bound fluoride (FA) formed in enamel. After the seven-day experimental periods, the percentage of surface hardness loss (%SH), integrated subsurface hardness loss (ΔKHN), CaF₂, Ca, P and FA retained were determined. Moreover, the biofilms formed on the blocks were analyzed for F, Ca, P and insoluble extracellular polysaccharide (EPS) concentrations.

RESULTS

FT+TMP gel promoted the lowest%SH and ΔKHN (p<0.001). The highest concentration of CaF₂ formed was observed for the FT+Acid gel (p<0.001), followed by FT+9000 gel > FT+TMP gel > FT > PT. CaF₂ retained on the blocks was reduced across all groups (p<0.001). Similar values were observed for the Ca/P/F and EPS in enamel and biofilm for all fluoride groups.

CONCLUSION

The association of FT+TMP gel significantly reduced enamel demineralization in situ.

CLINICAL SIGNIFICANCE

The association of treatments may be an alternative for patients with high caries risk.

Exopolysaccharides regulate calcium flow in cariogenic biofilms

Caries-associated biofilms induce loss of calcium from tooth surfaces in the presence of dietary carbohydrates. Exopolysaccharides (EPS) provide a matrix scaffold and an abundance of primary binding sites within biofilms. The role of EPS in binding calcium in cariogenic biofilms is only partially understood. Thus, the aim of the present study is to investigate the relationship between the calcium dissolution rates and calcium tolerance of caries-associated bacteria and yeast as well as to examine the properties of EPS to quantify its binding affinity for dissolved calcium. Calcium dissolution was measured by dissolution zones on Pikovskaya's agar. Calcium tolerance was assessed by isothermal microcalorimetry (IMC) by adding CaCl2 to the bacterial cultures. Acid-base titration and Fourier transform infrared (FTIR) spectroscopy were used to identify possible functional groups responsible for calcium binding, which was assessed by isothermal titration calorimetry (ITC). Lactobacillus spp. and mutans streptococci demonstrated calcium dissolution in the presence of different carbohydrates. All strains that demonstrated high dissolution rates also revealed higher rates of calcium tolerance by IMC. In addition, acidic functional groups were predominantly identified as possible binding sites for calcium ions by acid-base titration and FTIR. Finally, ITC revealed EPS to have a higher binding affinity for calcium compared, for example, to lactic acid. In conclusion, this study illustrates the role of EPS in terms of the calcium tolerance of cariogenic microbiota by determining the ability of EPS to control free calcium concentrations within the biofilms as a self-regulating mode of action in the pathogenesis of dental caries.

Comparison of the Effect of Fluoride Varnish, Chlorhexidine Varnish and Casein Phosphopeptide- Amorphous Calcium Phosphate (CPP-ACP) Varnish on Salivary Streptococcus mutans Level: A Six Month Clinical Study

INTRODUCTION

Dental caries is the most widespread disease which has a multi factorial origin. Streptococcus mutans is considered to be the chief pathogen in its development. Different varnishes are available which can be used for the prevention of the carious process.

AIM

To compare the effect of fluoride varnish, chlorhexidine varnish and fluoride varnish containing Casein Phosphopeptide - Amorphous Calcium Phosphate (CPP-ACP) on salivary Streptococcusmutans count in children with mixed dentition over a period of six months.

MATERIALS AND METHODS

Seventy two children of age 6-12 years with mixed dentition were selected fulfilling inclusion and exclusion criteria and divided into three groups: Group I- Fluoride varnish group; Group II- Chlorhexidine varnish group; Group III- MI varnish (fluoride varnish containing CPP-ACP) group. After thorough oral prophylaxis and restorative treatment the varnishes were applied to the teeth once a week for four consecutive weeks in the respective groups. Salivary Streptococcus mutans count (CFU/ml of saliva) was estimated at baseline, 1 month, 3 months and 6 months after varnish application. Bonferroni post-hoc test and paired t-test for inter group and intra group comparison was used in the study.

RESULTS

A statistically significant reduction in salivary S. mutans colony count was seen with all three groups at all the different time intervals. Maximum reduction was noted in chlorhexidine varnish group at all the intervals after varnish application.

CONCLUSION

Prevention of dental caries plays a vital role in paediatric dental practice. The use of dental varnish has proved to be effective in reducing the dental caries. Chlorhexidine varnish was found to show maximum reduction in salivary S. mutans count for six month period, when compared to MI varnish and fluoride varnish. Thus, chlorhexidine varnish can be used as potent caries inhibiting agent and promote good oral health.

Cariogenic Potential of Sucrose Associated with Maltodextrin on Dental Enamel

Maltodextrin is a hydrolysate of cornstarch and has been widely used in the food industry associated with sucrose. The addition of starch can increase the cariogenic potential of sucrose; however, there are sparse data regarding the cariogenicity of sucrose associated with maltodextrin. Therefore, the aim of this study was to test in situ if maltodextrin could increase the cariogenic potential of sucrose. This was an in situ, randomized, crossover, split-mouth, and double-blind study. Volunteers wore palatal appliances containing bovine enamel blocks for 2 periods of 14 days. They dripped the following solutions on the enamel blocks 8 times per day: deionized distilled water (DDW), maltodextrin (M), sucrose + maltodextrin (S+M), or sucrose (S). At the end of each experimental period, biofilms were collected and analyzed for microbiological (mutans streptococci, lactobacilli, and total microorganisms counts) and biochemical (calcium, inorganic phosphate, fluoride, and insoluble extracellular polysaccharides concentrations) compositions. The enamel demineralization was assessed by microhardness. Treatments S and S+M resulted in a lower inorganic composition and higher concentration of insoluble extracellular polysaccharides in the biofilms, and higher enamel mineral loss compared to DDW and M. It can be concluded that the cariogenic potential of sucrose is not changed when this carbohydrate is associated with maltodextrin (dextrose equivalent 13-17).

In situ Mineral Loss Inhibition by CO2 Laser and Fluoride

Laser and fluoride treatments have been shown to inhibit enamel demineralization in the laboratory. However, the intra-oral effects of this association have not been tested. This study assessed in situ the effect of a Transversely Excited Atmospheric CO2 laser (λ = 9.6 μm) and the use of pressure fluoridated dentifrice on enamel demineralization. During two 14-day phases, 17 volunteers wore palatal appliances containing human enamel slabs assigned to treatment groups, as follows: (1) non-fluoride dentifrice, (2) CO2 laser irradiation plus non-fluoride dentifrice, (3) fluoride dentifrice, and (4) CO2 laser irradiation plus fluoride dentifrice. A 20% sucrose solution was dripped onto the slabs 8 times per day. The specimens treated with laser and/or fluoridated dentifrice presented a significantly lower mineral loss when compared with those from the non-fluoride dentifrice group. The results suggested that CO2 laser treatment of enamel inhibits demineralization in the human mouth, being more effective when associated with fluoride.

Ca, Pi, and F in the Fluid of Biofilm Formed under Sucrose

Calcium (Ca), inorganic phosphorus (Pi), and fluoride (F) concentrations are low in the whole plaque biofilm formed under exposure to sucrose. It was hypothesized that this would be reflected in the biofilm fluid, where these low values should greatly influence the de/remineralization process. Dental biofilms were formed in situ over enamel blocks mounted in palatal appliances and exposed 8 times/day to distilled water, glucose+fructose, or sucrose solutions for 14 days. While Ca, Pi, and F concentrations in the whole biofilms were significantly lower in the glucose+fructose and sucrose groups, no effect on biofilm fluid was observed, even after a cariogenic challenge. An increase in whole biofilm mineral ions was observed 24 hrs after the carbohydrate treatments were suspended, but this effect was also not observed in the fluid. These results suggest that there is a homeostatic mechanism that maintains biofilm fluid mineral ion concentration, regardless of its total concentration in the whole biofilm.

Devices for In situ Development of Non-disturbed Oral Biofilm. A Systematic Review

Objective: The aim of this review was to assess the types of devices used for in situ development of oral biofilm analyzed microbiologically.

Materials and Methods: A systematic search of the literature was conducted to identify all in situ studies of oral biofilm which used an oral device; the Ovid MEDLINE and EMBASE databases complemented with manual search were used. Specific devices used to microbiologically analyze oral biofilm in adults were included. After reading of the selected full texts, devices were identified and classified according to the oral cavity zone and manufacturing material. The “ideal” characteristics were analyzed in every group.

Results: The search provided 787 abstracts, of which 111 papers were included. The devices used in these studies were classified as palatal, lingual or buccal. The last group was sub-classified in six groups based on the material of the device. Considering the analyzed characteristics, the thermoplastic devices and the Intraoral Device of Overlaid Disk-holding Splints (IDODS) presented more advantages than limitations.

Conclusions: Buccal devices were the most commonly used for the study of in situ biofilm. The majority of buccal devices seemed to slightly affect the volunteer's comfort, the IDODS being the closest to the “ideal” model.

Clinical Relevance: New devices for in situ oral biofilm microbiological studies should take into account the possible effect of their design on the volunteer's comfort and biofilm formation.

Calcium Prerinse before Fluoride Rinse Reduces Enamel Demineralization: An in situ Caries Study

A calcium (Ca) prerinse before a fluoride (F) rinse has been shown to increase oral F levels. We tested the anticaries effect of this combination in a dose-response in situ caries model. In a double-blind, crossover experiment, 10 volunteers carried enamel slabs in palatal appliances for 14 days, during which they rinsed twice/day with one of four rinse combinations: (1) a placebo prerinse (150 mM sodium lactate) followed by a distilled water rinse (negative control); (2) a placebo prerinse followed by a 250 ppm F rinse; (3) a placebo prerinse followed by a 1,000 ppm F rinse, or (4) a Ca prerinse (150 mM Ca, as calcium lactate) followed by a 250 ppm F rinse. Sucrose solution was dripped onto the slabs 8×/day to simulate a high cariogenic challenge. The percent surface hardness loss (%SHL) was significantly lower in the Ca prerinse used with the 250 ppm F rinse group (%SHL = 38.0 ± 21.0) when compared with the F rinse alone (%SHL = 59.5 ± 24.1) and similar to the 1,000 ppm F rinse group (%SHL = 42.0 ± 18.3). Compared with the 250 ppm F rinse, the Ca prerinse increased biofilm fluid F only twice (nonsignificant). However, it greatly increased F in biofilm solids (∼22×). The Ca prerinse had little effect on loosely or firmly bound enamel F. The results showed an increased level of protection against demineralization by the use of a Ca prerinse, which seems to be caused by the enhancement of F concentration in the biofilm.

Functional Relationship between Sucrose and a Cariogenic Biofilm Formation

Sucrose is an important dietary factor in cariogenic biofilm formation and subsequent initiation of dental caries. This study investigated the functional relationships between sucrose concentration and Streptococcus mutans adherence and biofilm formation. Changes in morphological characteristics of the biofilms with increasing sucrose concentration were also evaluated. S. mutans biofilms were formed on saliva-coated hydroxyapatite discs in culture medium containing 0, 0.05, 0.1, 0.5, 1, 2, 5, 10, 20, or 40% (w/v) sucrose. The adherence (in 4-hour biofilms) and biofilm composition (in 46-hour biofilms) of the biofilms were analyzed using microbiological, biochemical, laser scanning confocal fluorescence microscopic, and scanning electron microscopic methods. To determine the relationships, 2nd order polynomial curve fitting was performed. In this study, the influence of sucrose on bacterial adhesion, biofilm composition (dry weight, bacterial counts, and water-insoluble extracellular polysaccharide (EPS) content), and acidogenicity followed a 2nd order polynomial curve with concentration dependence, and the maximum effective concentrations (MECs) of sucrose ranged from 0.45 to 2.4%. The bacterial and EPS bio-volume and thickness in the biofilms also gradually increased and then decreased as sucrose concentration increased. Furthermore, the size and shape of the micro-colonies of the biofilms depended on the sucrose concentration. Around the MECs, the micro-colonies were bigger and more homogeneous than those at 0 and 40%, and were surrounded by enough EPSs to support their structure. These results suggest that the relationship between sucrose concentration and cariogenic biofilm formation in the oral cavity could be described by a functional relationship.

Tooth enamel properties and morphology after microabrasion: an in situ study

AIM

This study evaluated the effect of saliva on enamel after microabrasion with different microabrasive compounds under in situ conditions.

METHODS

Enamel/dentin blocks (16 mm² ) from bovine incisors were divided into nine groups (n = 19): one control group (no treatment), four groups treated with microabrasion using 35% phosphoric acid (H₃ PO₄ ) + pumice, and the last four groups treated with microabrasion using 6.6% hydrochloric acid (HCl) + silica. The treated groups were subdivided according to the in situ regimen: without salivary exposure, 1 h, 24 h, or 7 days of saliva exposure. Surface microhardness (SMH) and cross-sectional microhardness (CSMH) were tested. Scanning electron microscopy (SEM) was used to evaluate enamel morphology. Microhardness data were tested by analysis of variance, and Tukey's and Dunnett's tests (α = 0.05).

RESULTS

The SMH analysis revealed that all the microabrasion-treated groups presented significantly-reduced SMH values when compared to the control group (P < 0.05). Treatment with HCl + silica was more prone to the effect of saliva than H₃ PO₄ + pumice, even for CSMH analysis, once the superficial layers reached the same microhardness of that of the control group (P > 0.05). These results were confirmed by SEM, which demonstrated the mineral recovery effect over time.

CONCLUSION

Saliva was effective in promoting the rehardening of enamel after microabrasion, mainly for the surfaces treated with HCl + silica.

Validation of a Cariogenic Biofilm Model to Evaluate the Effect of Fluoride on Enamel and Root Dentine Demineralization

Due to gingival recession both enamel and root dentine are at risk of developing caries. Both tissues are exposed to a similar environment, however there is not a validated model to evaluate the effect of fluoride on these dental substrates simultaneously. Hence, this study aimed to validate a caries model to evaluate the effect of fluoride to prevent demineralization on enamel and root-dentine. Streptococcus mutans UA159 biofilms were formed on saliva-coated bovine enamel and root dentine slabs (n = 12 per group) mounted in the same well of culture plates. The biofilms were exposed 8×/day to 10% sucrose and treated 2×/day with fluoridated solutions containing 0, 150, 450, or 1,350 ppm F; thus, simulating the use of low to high fluoride concentration toothpastes. The pH values of the culture medium was monitored 2×/day as a biofilm acidogenicity indicator. After 96 h, biofilms were collected for fluoride concentration analysis. The percentage of surface hardness loss (%SHL) was calculated for slabs. The fluoride uptake by the enamel and dentine was also determined. The model showed a dose-response because the biofilm and fluoride uptake increased and %SHL decreased at increasing fluoride concentrations (p < 0.05). Fluoride in the biofilm formed on dentine and fluoride uptake by dentine were higher than those for enamel. With the same fluoride concentration treatment, the percentage of reduction of demineralization was lower for dentine than for enamel. In conclusion, the model was validated in terms of a dose-response effect of fluoride on enamel and root dentine. Furthermore, the findings support the clinical data, suggesting that higher fluoride concentrations are necessary to control caries of root dentine than of enamel.

An in vitro dynamic microcosm biofilm model for caries lesion development and antimicrobial dose-response studies

Some dynamic biofilm models for dental caries development are limited as they require multiple experiments and do not allow independent biofilm growth units, making them expensive and time-consuming. This study aimed to develop and test an in vitro dynamic microcosm biofilm model for caries lesion development and for dose-response to chlorhexidine. Microcosm biofilms were grown under two different protocols from saliva on bovine enamel discs for up to 21 days. The study outcomes were as follows: the percentage of enamel surface hardness change, integrated hardness loss, and the CFU counts from the biofilms formed. The measured outcomes, mineral loss and CFU counts showed dose-response effects as a result of the treatment with chlorhexidine. Overall, the findings suggest that biofilm growth for seven days with 0.06 ml min(-1) salivary flow under exposure to 5% sucrose (3 × daily, 0.25 ml min(-1), 6 min) was suitable as a pre-clinical model for enamel demineralization and antimicrobial studies.

Diet and Dental Caries: The Pivotal Role of Free Sugars Reemphasized

The importance of sugars as a cause of caries is underemphasized and not prominent in preventive strategies. This is despite overwhelming evidence of its unique role in causing a worldwide caries epidemic. Why this neglect? One reason is that researchers mistakenly consider caries to be a multifactorial disease; they also concentrate mainly on mitigating factors, particularly fluoride. However, this is to misunderstand that the only cause of caries is dietary sugars. These provide a substrate for cariogenic oral bacteria to flourish and to generate enamel-demineralizing acids. Modifying factors such as fluoride and dental hygiene would not be needed if we tackled the single cause--sugars. In this article, we demonstrate the sensitivity of cariogenesis to even very low sugars intakes. Quantitative analyses show a log-linear dose-response relationship between the sucrose or its monosaccharide intakes and the progressive lifelong development of caries. This results in a substantial dental health burden throughout life. Processed starches have cariogenic potential when accompanying sucrose, but human studies do not provide unequivocal data of their cariogenicity. The long-standing failure to identify the need for drastic national reductions in sugars intakes reflects scientific confusion partly induced by pressure from major industrial sugar interests.

Enamel morphology after microabrasion with experimental compounds

BACKGROUND

Enamel microabrasion is an esthetic treatment for removing superficial stains or defects of enamel.

AIM

This study evaluated the roughness after enamel microabrasion using experimental microabrasive systems.

MATERIALS AND METHODS

One hundred and ten samples (5 × 5 mm) were obtained from bovine incisors and divided into 11 groups (n = 10) in accordance with the treatment: Microabrasion using 6.6% hydrochloric acid (HCl) or 35% phosphoric acid (H3PO4) associated with aluminum oxide (AlO3) or pumice (Pum) with active application (using rubber cup coupled with a micro-motor of low rotation) or passive application (just placing the mixture on the enamel surface); just the use of acids in a passive application (negative control), and a group without treatment (positive control). Roughness analysis was performed before and after treatments. The statistical analysis used analysis of variance (PROC MIXED), Tukey-Kramer and Dunnet tests (P < 0.05). Representative specimens were evaluated using scanning electron microscopy (SEM).

RESULTS

There was no significant difference between the acids used (P = 0.0510) and the applications (P = 0.8989). All of the treated groups were statistically different from the positive control. When using passive application, the use of HCl + AlO3 resulted in higher roughness when compared with HCl + Pum. Additionally, this treatment was statistically different from the passive application of H3PO4 (negative control) (P < 0.05). However, SEM analysis showed that the treatment with AlO3 resulted in an enamel surface with a more polished aspect when compared with Pum.

CONCLUSION

AlO3 may be a suitable particle for use in microabrasive systems.

Salivary fluoride levels after use of high-fluoride dentifrice

The aim of the study was to evaluate salivary fluoride (F) availability after toothbrushing with a high-F dentifrice. Twelve adult volunteers took part in this crossover and blind study. F concentration in saliva was determined after brushing with a high-F dentifrice (5000 µg F/g) or with a conventional F concentration dentifrice (1100 µg F/g) followed by a 15 mL distilled water rinse. Samples of nonstimulated saliva were collected on the following times: before (baseline), and immediately after spit (time = 0) and after 1, 2, 3, 4, 5, 10, 15, 20, 30, 45, 60, 90, and 120 min. F analysis was performed with a fluoride-sensitive electrode and the area under curve of F salivary concentration × time (µg F/mL × min⁻¹) was calculated. At baseline, no significant difference was found among dentifrices (P > 0.05). After brushing, both dentifrices caused an elevated fluoride level in saliva; however salivary F concentration was significantly higher at all times, when high-F dentifrice was used (P < 0.01). Even after 120 min, salivary F concentration was still higher than the baseline values for both dentifrices (P < 0.001). High-F dentifrice enhanced the bioavailability of salivary F, being an option for caries management in patients with high caries risk.

In situ study of the anticariogenic potential of fluoride varnish combined with CO2 laser on enamel

OBJECTIVE

This in situ study evaluated the effect of fluoride varnish combined with CO2 laser in controlling enamel demineralization caused by cariogenic challenges.

DESIGN

In a crossover study conducted in 2 phases of 14 days each, 14 volunteers (n = 14) wore palatal appliances with bovine enamel slabs treated with fluoride varnish + CO2 laser (FV + CO2), fluoride varnish (FV), nonfluoride placebo varnish (PV) and nonfluoride placebo varnish + CO2 laser (PV + CO2). Drops of sucrose solution were dripped onto enamel slabs allowing the accumulation of biofilm. At the first phase, half of the volunteers received 4 enamel slabs treated with FV while the remainders received slabs exposed to the PV with and without CO2 laser. In the second phase, the vonlunteers were reversed treatments. The slabs were evaluated for cross-sectional microhardness (CSMH) and the concentration of loosely bound fluoride (CaF2) and firmly bound fluoride (FAp). The concentration of fluoride in biofilm were also determined.

RESULTS

Two-way ANOVA showed that the CSMH values were higher in laser-irradiated enamel, regardless of the fluoride varnish. Friedman test showed that FV group presented significantly larger amount of fluoride in biofilm (P < 0.05). In the enamel, the largest amount of fluoride was found in the groups FV + CO2, which was not different from FV (P > 0.05).

CONCLUSION

The synergistic effect of fluoride varnish and CO2 laser on enamel demineralization was not observed, however, CO2 laser reduces enamel demineralization.

CLINICAL SIGNIFICANCE

CO2 laser might reduce the demineralization of subsurface enamel, although its association with a high concentrated fluoride therapy may not result in a positive synergistic interaction.

Light-activated bleaching: effects on surface mineral change on enamel

AIM

This study evaluated the in vitro effect of 35% hydrogen peroxide (HP) on surface enamel change when activated with different light curing units (LCUs).

MATERIALS AND METHODS

Enamel blocks (4 × 4 × 2 mm) were obtained from bovine incisors. The initial microhardness of the enamel was determined for each specimen. After this enamel blocks were randomly divided into four groups (n = 10) and treated as follows: Control, no bleaching procedure performed; HP - LCU, application of 35% HP gel without light activation; HP + QTH, application of 35% HP gel and light activation with a Quartz Tungsten-Halogen (QTH); and HP + Light Emitting Diode, application of 35% HP gel and light-activation with a LED. New microhardness measurements were obtained, immediately, 7 and 14 days after treatment. The percentage of surface mineral change was calculated according to the baseline and post-treatment microhardness values. Additionally, six samples from each group were randomly selected and prepared for scanning electron microscopy (SEM) characterization. The data were analyzed using an analysis of variance (ANOVA) to detect differences between the three time periods, and an ANOVA and Tukey's test with a confidence level of 95%.

RESULTS

There was no significant difference between the initial hardness values and hardness values after treatment in any of the groups or time periods (p > 0.05). No major surface alterations were detected with SEM when comparing control groups to those undergoing bleaching treatments.

CONCLUSION

The use of 35% HP in combination to QTH or LED light curing units LCU does not have detrimental effect on the enamel surface topography or in the mineral content, when compared with unbleached enamel or enamel submitted to 35% HP treatment alone.

Efficacy of 1.23% APF gel applications on incipient carious lesions: a double-blind randomized clinical trial

The aim of this double-blind randomized clinical trial was to evaluate the efficacy of 1.23% APF gel application on the arrest of active incipient carious lesions in children. Sixty 7- to 12-year-old children, with active incipient lesions were included in the study. Children were divided randomly into 2 groups: 1.23% APF gel and placebo gel applications. Each group received 8 weekly applications of treatment. The lesions were re-evaluated at the 4th and 8th appointments. Poisson regression analysis was used to estimate relative risks of the presence of active white spot lesions. Groups showed similar results (PR = 1.67; CI 95% 0.69-3.98). The persistence of at least 1 active lesion was associated with a higher number of lesions in the baseline (PR = 2.67; CI 95% 1.19-6.03), but not with sugar intake (PR = 1.06; CI 95% 0.56-2.86) and previous exposure to fluoride dentifrice (PR = 1.26; CI 95% 0.49-2.29). The trial demonstrates the equivalence of the treatments. The use of the APF gel showed no additional benefits in this sample of children exposed to fluoridated water and dentifrice. The professional dental plaque removal in both groups may also account for the resulting equivalence of the treatments.

Enhanced penetration of fluoride particles into bovine enamel by combining dielectrophoresis with AC electroosmosis

Fluoride deposition into the pores of enamel is necessary at high concentrations to reduce enamel demineralization and with a high degree of penetration to account for loss by ingestion. Current diffusion and electrochemical methods are inadequate for effectively transporting fluoride greater than 20 μm into enamel. The study explores the coupling of dielectrophoresis (DEP) and AC electroosmosis (ACEO) to selectively concentrate fluoride particles from fluoride gel excipients and enhance their penetration into enamel. By measuring the frequency response of approximately 10-μm-sized sodium fluoride particles in an aqueous gel media, appropriate frequencies for positive DEP, negative DEP, and ACEO are identified. An assembly composed of two cross-planar interdigitated electrode (IDE) arrays with open slots is driven successively by fields at appropriate frequencies to drive fluoride particles through the slots of the IDE and into the enamel pores using a combination of DEP and ACEO methods. Fluoride uptake and penetration of 1.23% acidulated phosphate fluoride gel into bovine tooth enamel at various depths is measured using wavelength dispersive spectrometry to compare deposition by diffusion, DEP, and DEP plus ACEO. Fluoride levels in all DEP groups were significantly higher than diffusion groups at depths 10 and 20 μm. The highest fluoride concentrations at 10, 20, 50, and 100 μm depths occur under deposition conditions combining DEP with ACEO. Fluoride levels at 50 μm were equivalent to long-term prophylactic exposure. These methods may potentially benefit populations at high risk for development of caries and periodontal disease, including underserved children and disparate groups.

Remineralization of demineralized enamel by toothpastes: a scanning electron microscopy, energy dispersive X-ray analysis, and three-dimensional stereo-micrographic study

Remineralization of hard dental tissues is thought to be a tool that could close the gap between prevention and surgical procedures in clinical dentistry. The purpose of this study was to examine the remineralizing potential of different toothpaste formulations: toothpastes containing bioactive glass, hydroxyapatite, or strontium acetate with fluoride, when applied to demineralized enamel. Results obtained by scanning electron microscopy (SEM) and SEM/energy dispersive X-ray analyses proved that the hydroxyapatite and bioactive glass-containing toothpastes were highly efficient in promoting enamel remineralization by formation of deposits and a protective layer on the surface of the demineralized enamel, whereas the toothpaste containing 8% strontium acetate and 1040 ppm fluoride as NaF had little, if any, remineralization potential. In conclusion, the treatment of demineralized teeth with toothpastes containing hydroxyapatite or bioactive glass resulted in repair of the damaged tissue.

Topical effect of a medically prescribed pediatric antibiotic on dental biofilm: a cross-over, in situ study

Objective

This study aimed to investigate the possible topical effect of a broad-spectrum antibiotic on dental biofilm formed in situ in the absence or presence of sucrose.

Methods

A crossover study was conducted in three phases of 14 days each, during which 11 volunteers wore palatal devices containing 6 enamel blocks covered with meshes to allow biofilm formation. Dental blocks were extraorally submitted to a 20% sucrose solution at three different frequencies of exposure (0, 3 and 8 times/day), and to a suspension of amoxicillin/clavulanate potassium (A/CP) or a placebo (P) suspension at an 8-hour time interval application regimen. On the 14^th day of each phase, biofilms were collected for microbiological (conventional culture) and molecular (Denaturing Gradient Gel Electrophoresis – DGGE) analyses.

Results

In the absence of sucrose exposure (SE) and at the 3-time daily frequency, dental biofilms treated with A/CP showed lower total biofilm weight and lower counts of total microbiota than the ones treated with P (p>0.05). A/CP presented higher counts of Candida spp. when compared with P in the presence of SE, especially at the 8-time daily frequency (p<0.05). Considering the DGGE analysis, the mean number of bands was higher for P (p>0.05), regardless of SE. However, DGGE profiles demonstrated large interindividual variability.

Conclusion

Both conventional culture and DGGE have demonstrated some differences on total microbiota of dental biofilms when exposed to the A/CP or P suspensions, mainly in the absence of sucrose, which suggests a possible topical effect of the sugar-free A/CP suspension on dental biofilm.

Salivary retention after application of fluoride gel using toothbrush or tray: a crossover trial

Currently, there are no studies in the literature evaluating salivary fluoride retention after small amounts of fluoride gel are applied to children's teeth. Therefore, the objective of the present study was to compare salivary retention after gel application using a toothbrush or by traditional application with trays. In this crossover study, children with active caries (n = 10) were randomized into one of the following treatment groups: a) application of fluoride gel using a tray (control), or b) application of fluoride gel with a toothbrush (treatment). After a 7-day washout period, the treatments were inverted. Unstimulated saliva samples were collected at baseline and 0.5, 5, 15, 30, 60 and 120 minutes after acidulated phosphate fluoride (APF) gel application in order to analyze fluoride retention in saliva. The area under the curve (AUC) was also calculated. There were no differences in fluoride retention after application of small amounts of APF with a toothbrush compared to traditional gel application using trays at all time points studied, and no differences in AUC were observed (Student t-test, p > 0.05). These results suggest that application of fluoride gel in children using a toothbrush can be utilized as an option rather than traditional trays, since the same salivary retention of fluoride is obtained using a lower dose.

Effect of Hydrogen Peroxide at 35% on the Morphology of Enamel and Interference in the De-remineralization Process: An In Situ Study

This study evaluated the microhardness and histomorphology of bovine enamel when 35% hydrogen peroxide is used. A total of 44 specimens were adapted to removable devices used by 11 individuals subjected to dental caries challenge. A decrease in microhardness was observed for all groups after the cariogenic challenge. Microscopic analysis revealed that fragments subjected to cariogenic challenge associated with bleaching had more intense superficial histologic changes, but the depth of the lesions remained unchanged. It was concluded that 35% hydrogen peroxide enhanced the reduction in hardness and histomorphologic changes in the enamel surface exposed to cariogenic challenge.

An in vitro biofilm model for enamel demineralization and antimicrobial dose-response studies

Microcosm biofilms formed in microplates have demonstrated complex community dynamics similar to natural dental biofilm. No simplified microcosm models to evaluate enamel demineralization and dose-response effect to anticariogenic therapies have yet been established, thus this study was designed to develop a pre-clinical model fulfilling this purpose. Experiments were carried out to establish the time of biofilm formation and the sucrose concentration and exposure regimen. Biofilms were initiated from saliva and grown for up to 10 days on bovine enamel discs in 24-well plates, with a saliva analogue medium. Data were collected as pH readings and the percentage enamel surface hardness change. A dose-response evaluation was performed with chlorhexidine, which significantly affected the pH and mineral loss. Overall, the established model parameters, 5 days of biofilm growth with intermittent 1% sucrose exposure of 6 h per day, was suitable as a pre-clinical model for enamel demineralization and dose-response studies.

Fluoride: its role in dentistry

In spite of decades of research on fluoride and the recognition of its role as the cornerstone of dental caries reduction in the last fifty years, questions still arise on its use at community, self-applied and professional application levels. Which method of fluoride delivery should be used? How and when should it be used? How can its benefits be maximized and still reduce the risks associated with its use? These are only some of the challenging questions facing us daily. The aim of this paper is to present scientific background to understand the importance of each method of fluoride use considering the current caries epidemiological scenario, and to discuss how individual or combined methods can be used based on the best evidence available.

Effect of different frequencies of fluoride dentifrice and mouthrinse administration: an in situ study

The effect of a combination of topical fluoridation methods for inhibition of enamel demineralization in the face of a cariogenic challenge has not been clearly established. This in situ crossover study aimed to assess whether the addition of daily use of fluoride mouthrinse (FR) to that of fluoride dentifrice (FD) is equivalent to increasing the frequency of FD application in terms of the effect on enamel demineralization and fluoride content. Over 3 phases of 14 days each, 12 volunteers wore appliances containing enamel blocks exposed to a 20 % sucrose solution 8 times/day. During each phase the blocks underwent one of the following treatments: 2x/day FD, 2x/day FD + 1x/day FR, and 3x/day FD. The blocks were assessed for hardness and fluoride content. Three x/day FD did not differ from 2x/day + 1x/day FR, however it enhanced demineralization protection when compared to 2x/day FD. All treatments produced an increase in enamel fluoride content compared to no treatment (sound blocks) (p < 0.05), but the differences between them were not significant. The results of this study suggest that the daily use of fluoride mouthrinse combined with that of fluoride dentifrice has similar effects on enamel demineralization and fluoride content when compared to increasing the frequency of fluoride dentifrice use.

APF and dentifrice effect on root dentin demineralization and biofilm

Because dentin is more caries-susceptible than enamel, its demineralization may be more influenced by additional fluoride (F). We hypothesized that a combination of professional F, applied as acidulated phosphate F (APF), and use of 1100-ppm-F dentifrice would provide additional protection for dentin compared with 1100-ppm-F alone. Twelve adult volunteers wore palatal appliances containing root dentin slabs, which were subjected, during 4 experimental phases of 7 days each, to biofilm accumulation and sucrose exposure 8x/day. The volunteers were randomly assigned to the following treatments: placebo dentifrice (PD), 1100-ppm-F dentifrice (FD), APF + PD, and APF+FD. APF gel (1.23% F) was applied to the slabs once at the beginning of the experimental phase, and the dentifrices were used 3x/day. APF and FD increased F concentration in biofilm fluid and reduced root dentin demineralization, presenting an additive effect. Analysis of the data suggests that the combination of APF gel application and daily regular use of 1100-ppm-F dentifrice may provide additional protection against root caries compared with the dentifrice alone.

Evaluation of fermented milk containing probiotic on dental enamel and biofilm: in situ study

OBJECTIVES

The aim of this study was to in situ evaluate the pH before and after the application of the fermented milk product; the fluoride (F), calcium (Ca), phosphate (P), and insoluble extracellular polysaccharides (EPS) concentration on the dental biofilm; the demineralisation of the bovine dental enamel.

DESIGN

Ten volunteers wore palatine devices containing four blocks of bovine dental enamel during three phases of 14 days each. In each phase, the treatment was accomplished with either fermented milk A (Yakult), or 20% sucrose solution (control) or fermented milk B (Batavito). Then, dental biofilm was collected, processed and the ionic concentration and insoluble extracellular polysaccharides appraised. For evaluation of the mineral loss, both the initial and final microhardness were determined.

RESULTS

The results showed that the ionic concentration (F, Ca and P) was significantly higher in the fermented milk B in comparison with both the fermented milk A and the 20% sucrose solution. There was no significant difference amongst these last two. With regarding EPS was significantly lower in fermented milk B compared to fermented milk A and sucrose (P<0.05), without significant difference amongst these last two. The two experimental groups did not differ significantly but had smaller mineral losses than control group.

CONCLUSION

It was concluded that all treatment decreased the pH of dental biofilm and promoted demineralisation of the enamel, although fermented milk B presented the lowest EPS content and percentage change and integrated loss of surface hardness. More studies should be developed to evaluate the action of probiotics on the bacterial activity and its interference on demineralisation, once the literature has been showing probiotics as a promissory caries reducing agent.

Effect of APF gel application time on enamel demineralization and fluoride uptake in situ

This in situ crossover and blind study was conducted to investigate the effect of professional acidulated phosphate fluoride (APF) gel application time on the subsequent inhibition of enamel demineralization. During 3 phases of 28 days each, 15 volunteers wore palatal appliances containing 4 enamel blocks, which were subjected to 3 treatment groups: not treated (control) and pre-treated with APF gel for 1 or 4 min. Dental plaque was allowed to accumulate on the blocks and the appliances were immersed in 10% sucrose solution 3 times a day simulating a cariogenic challenge. After each phase, the blocks were removed to evaluate enamel demineralization and concentration of fluoride (F) remaining after the cariogenic challenge. F formed on enamel was determined in additional enamel blocks subjected only to APF gel application. APF gel was efficient in reducing enamel demineralization (p<0.05), irrespective of the application time (p>0.05). Also, the concentration of the F formed and retained on enamel was significantly higher after APF gel application (p<0.05), but the effect of time of application was not statistically significant (p>0.05). The results suggest that APF application for either 1 or 4 min is equally efficient to increase F concentration in enamel and reduce enamel demineralization.

pH-cycling models to evaluate the effect of low fluoride dentifrice on enamel de- and remineralization

Since the currently available pH-cycling models do not differentiate the anti-caries potential of dentifrices with low fluoride (F) concentration, two models were developed and tested in the present. Bovine enamel blocks were subjected to the models and treated with F solutions containing from 70 to 280 microg F/mL in order to validate them in terms of dose-response effect. The models were also tested by evaluating the dentifrices Colgate Baby (500 microg F/g, as a low fluoride dentifrice), Tandy (1,100 microg F/g, as an active F-dentifrice) and Crest (1,100 microg F/g, as positive control). Enamel mineral loss or gain was assessed by surface and cross-sectional microhardness, and lesion depth was analyzed by polarized light microscopy. The pH-cycling models showed F dose-response effect either reducing enamel demineralization or enhancing remineralization. The low F dentifrice presented anti-caries potential, but it was not equivalent to the dentifrices containing 1,100 microg F/g. These data suggest that the models developed in this study were able to evaluate the anti-caries potential of low F dentifrice either on resistance to demineralization or on enhancement of remineralization.