Effect of different fluoride levels in dentifrice on the development of approximal caries

Detection of artificial enamel caries-like lesions with a blue hydroxyapatite-binding porosity probe

OBJECTIVES

This in vitro study investigated the ability of a blue protein-based hydroxyapatite porosity probe to selectively detect artificial enamel caries-like lesions of varying severities.

METHODS

Artificial caries-like lesions were formed in enamel specimens using a hydroxyethylcellulose-containing lactic acid gel for 4/12/24/72 or 168 h. One untreated group was used as a control. The probe was applied for 2 min and unbound probe rinsed off with deionized water. Surface color changes were determined spectrophotometrically (L*a*b* color space) and with digital photography. Lesions were characterized using quantitative light-induced fluorescence (QLF), Vickers surface microhardness, and transverse microradiography (TMR). Data were analyzed using one-way ANOVA.

RESULTS

Digital photography did not reveal any discoloration in unaffected enamel. However, all lesions stained blue with color intensity positively correlated with demineralization times. The color data reflected similar trends: lesions became significantly darker (L* decreased) and bluer (b* decreased), while overall color differences (ΔE) increased significantly after probe application (4-h lesion, mean±standard deviation: ΔL*=-2.6 ± 4.1/Δb*=0.1 ± 0.8/ΔE=5.5 ± 1.3 vs. 168-h lesion: ΔL*=-17.3 ± 1.1/Δb*=-6.0 ± 0.6/ΔE=18.7 ± 1.1). TMR analysis revealed distinct differences in integrated mineral loss (ΔZ) and lesion depth (L) between demineralization times (4-h lesion: ΔZ=391±190 vol%min × µm/L = 18.1 ± 10.9 µm vs. 168-h lesion: ΔZ=3606±499 vol%min × µm/L = 111.9 ± 13.9 µm). QLF and microhardness were also able to differentiate between demineralization times. L and ΔZ strongly correlated (Pearson correlation coefficient [r]) with Δb* (L vs. Δb*: r=-0.90/ΔZ vs. Δb*: r=-0.90), ΔE (r = 0.85/r = 0.81), and ΔL* (r=-0.79/r=-0.73).

CONCLUSION

Considering the limitations of this study, the blue protein-based hydroxyapatite-binding porosity probe appears to be sufficiently sensitive to distinguish between unaffected enamel and artificial caries-like lesions.

CLINICAL SIGNIFICANCE

Early detection of enamel caries lesions remains one of the most critical aspects in the diagnosis and management of dental caries. This study highlighted the potential of a novel porosity probe in detecting artificial caries-like demineralization by objective means.

In vitro demineralization prevention by fluoride and silver nanoparticles when applied to sound enamel and enamel caries-like lesions of varying severities

OBJECTIVES

To investigate the effect of fluoride and silver nanoparticles on the prevention of in vitro demineralization of sound enamel and enamel caries-like lesions of varying severities.

METHODS

Caries-like lesions of different severities (1/6/15 days) were created in bovine enamel specimens. One group remained sound. All specimens were demineralized again using a partially saturated acetic acid solution. Mimicking the intra-oral retention of fluoride and silver in vitro, this solution was supplemented with fluoride (0/1/10 ppm) and/or silver nanoparticles (0/10 ppm) in a factorial design. Changes in lesion depth (ΔL) and integrated mineral loss (ΔΔZ) were evaluated by digital transverse microradiography. Data was analyzed using three-way ANOVA.

RESULTS

Lesion severity significantly affected ΔΔZ and ΔL, after no treatment and after the treatment of fluoride and silver independently (p = 0.012 and p = 0.037, respectively). Fluoride and the fluoride × lesion severity interaction were shown to be significant (p < 0.001) on ΔΔZ and ΔL. Silver nanoparticles significantly affected ΔΔZ (p = 0.041), but not ΔL (p = 0.15). The silver nanoparticles × lesion severity interaction was significant for ΔΔZ and ΔL (p = 0.032 and p = 0.024, respectively). No interaction was observed for ΔΔZ and ΔL between fluoride and silver (p = 0.962 and p = 0.971, respectively) as well as lesion severity and the use of fluoride and silver combined (p = 0.722 and p = 0.158, respectively).

CONCLUSION

Fluoride and silver nanoparticles had a significant effect on the prevention of in vitro demineralization of sound enamel and enamel caries-like lesions of varying severities.

CLINICAL SIGNIFICANCE

Fluoride and silver nanoparticles may potentially allow for more tailored caries prevention.

Effects of potassium and sodium fluoride in different concentrations on micro-shear bond strength and inhibition of demineralization

The aim of this study was to investigate the effects of potassium fluoride (KF) and sodium fluoride (NaF) in different concentrations on micro-shear bond strength (µSBS) and their protective effects against acid. The enamel blocks were treated with several concentrations of KF and NaF. For µSBS, Clearfil SE Bond 2 was applied to the treated surface and resin composite was light-cured, then examined using a universal testing machine. For acid resistance test, the specimens were immersed in acidic solution (pH 4.5), then examined under 3D confocal laser scanning microscope (CLSM). In µSBS, KF at 1,000, 9,000, and 10,000 ppm did not show differences compared with the control, while other concentrations of KF and NaF led to decreased µSBS. Higher concentrations of NaF and KF showed higher resistance to the acid challenge. So, we concluded that various concentrations of KF and NaF solutions had specific effects on µSBS and acid resistance.

The effect of theobromine on the in vitro de- and remineralization of enamel carious lesions

OBJECTIVES

This in vitro study investigated the effect of theobromine on the de- and remineralization of enamel carious lesions under plaque fluid-like conditions.

METHODS

Early carious lesions were created in 272 bovine enamel specimens and assigned to sixteen groups (n=17) based on Knoop surface microhardness (SMH). Lesions were demineralized again under plaque fluid-like conditions in the presence of fluoride (0.2 or 1ppm) and theobromine (0; 10; 100 or 200ppm) at different pH values (5.5 or 7.0) in a factorial design. SMH was determined again and percent SMH recovery (%SMHr) calculated. Three-way ANOVA was used for the fixed effects of fluoride, theobromine and pH levels to compare the differences between each level.

RESULTS

The three-way interaction was not significant (p=0.712). The two-way interaction between fluoride and pH was significant (p=0.030), whereas those between fluoride and theobromine as well as that for pH and theobromine were not (p=0.478 and p=0.998, respectively). Theobromine did not affect %SMHr at any of the tested concentrations. There were trends for the higher fluoride concentration and the higher pH resulting in more rehardening with the lesions exposed to 0.2ppm fluoride at pH 5.5 displaying significantly less rehardening than those exposed to 0.2ppm fluoride at pH of 7.0 and lesions exposed to 1ppm fluoride at pH of 5.5.

CONCLUSION

Theobromine, when continuously present in a plaque fluid-like medium at various concentrations and at different pH values, does not affect de- or remineralization of enamel carious lesions under the presently studied conditions.

CLINICAL SIGNIFICANCE

Based on the presently available evidence, theobromine cannot be recommended as an anticaries agent.

Comparative efficacy of a hydroxyapatite and a fluoride toothpaste for prevention and remineralization of dental caries in children

Objective

This in situ study compared the effectiveness of two toothpastes containing hydroxyapatite or 500 ppm fluoride in promoting remineralization and inhibiting caries development.

Materials and methods

Two enamel blocks (human primary teeth), one sound and one with artificially-produced caries lesion, were exposed to toothpaste containing either 10% hydroxyapatite or 500 ppm F⁻ (amine fluoride) via intra-oral appliance worn by 30 adults in two-arm double blind randomized crossover study lasting 14 days per arm (ClinicalTrials.gov: NCT03681340). Baseline and post-test mineral loss and lesion depth (LD) were quantified using microradiography. One-sided t-test of one group mean was used for intragroup comparison (baseline vs. post-test), while two-sided t-test of two independent means was used to compare the two toothpaste groups.

Results

Pairwise comparison (baseline vs. test) indicated significant (p < 0.0001) remineralization and LD reduction by either toothpaste; however, when compared against each other, there was no statistically significant difference in remineralization or LD reduction between the two toothpastes. No demineralization could be observed in sound enamel blocks exposed to either toothpaste. While F⁻ induced lesion surface lamination, HAP produced a more homogenous lesion remineralization.

Conclusions

10% hydroxyapatite achieved comparable efficacy with 500 ppm F⁻ in remineralizing initial caries and preventing demineralization. Thus the HAP toothpaste is confirmed to be equal to the fluoride toothpaste in this study.

Effects of Self-Assembling Peptide P11-4, Fluorides, and Caries Infiltration on Artificial Enamel Caries Lesions in vitro

The application of a self-assembling peptide on noncavitated caries lesions is supposed to be a feasible approach to facilitate remineralization and mask their unfavorable appearance. However, demineralizing conditions are common in the oral environment, so the aim of this pH-cycling study was to compare recommended and novel treatment methods regarding their ability to hamper demineralization and as a consequence mask artificial enamel caries lesions. Artificial caries lesions were prepared in bovine enamel and randomly allocated to 11 groups (n = 22). Treatments before pH-cycling were as follows: the application of a self-assembling peptide (Curodont™ Repair [C]), a low-viscosity resin (Icon® [I]), 2 fluoride solutions (10,000 ppm F-: Elmex fluid [E] and 43,350 ppm F-: Tiefenfluorid® [T]), and no intervention (N). During pH-cycling (28 days, 6 × 60 min demineralization/day) half of the specimens in each group were brushed (10 s; 2 ×/day) with either fluoride-free (named e.g., C0) or NaF (1,100 ppm F-; e.g., C1) dentifrice slurry. In another subgroup specimens were pH-cycled but not brushed (NNB). Differences in integrated mineral loss (ΔΔZ), lesion depth (ΔLD), and colorimetric values (ΔΔE) were calculated between values after pre-demineralization, surface treatment, and pH-cycling. Specimens of C0, C1, NNB, N0, N1, T0, and E0 showed significantly increased ΔZ and LD values after pH-cycling (p ≤ 0.003; paired t test). C0, C1, NNB, and N0 showed significantly higher changes in ΔΔZ than E1, I0, I1, and T1 (p < 0.001; ANOVA). Significantly reduced colorimetric values could only be observed for I1, I0, E1, and E0 after treatment and after pH-cycling (p ≤ 0.027; paired t test). In conclusion, under the conditions chosen only the application of a low-viscosity resin could mask caries lesions significantly, whereas self-assembling peptides could neither inhibit lesion progression nor mask the lesions considerably.

Effect of Enamel Caries Lesion Baseline Severity on Fluoride Dose-Response

This study aimed to investigate the effect of enamel caries lesion baseline severity on fluoride dose-response under pH cycling conditions. Early caries lesions were created in human enamel specimens at four different severities (8, 16, 24, and 36 h). Lesions were allocated to treatment groups (0, 83, and 367 ppm fluoride as sodium fluoride) based on Vickers surface microhardness (VHN) and pH cycled for 5 d. The cycling model comprised 3 × 1 min fluoride treatments sandwiched between 2 × 60 min demineralization challenges with specimens stored in artificial saliva in between. VHN was measured again and changes versus lesion baseline were calculated (ΔVHN). Data were analyzed using two-way ANOVA (p < 0.05). Increased demineralization times led to increased surface softening. The lesion severity×fluoride concentration interaction was significant (p < 0.001). Fluoride dose-response was observed in all groups. Lesions initially demineralized for 16 and 8 h showed similar overall rehardening (ΔVHN) and more than 24 and 36 h lesions, which were similar. The 8 h lesions showed the greatest fluoride response differential (367 versus 0 ppm F) which diminished with increasing lesion baseline severity. The extent of rehardening as a result of the 0 ppm F treatment increased with increasing lesion baseline severity, whereas it decreased for the fluoride treatments. In conclusion, lesion baseline severity impacts the extent of the fluoride dose-response.

Re- and Demineralization Characteristics of Enamel Depending on Baseline Mineral Loss and Lesion Depth in situ

Objectives: The aim of this double-blinded, randomized, cross-over in situ study was to evaluate the re- and demineralization characteristics of sound enamel as well as lowly and highly demineralized caries-like enamel lesions after the application of different fluoride compounds. Methods: In each of three experimental legs of 4 weeks, 21 participants wore intraoral mandibular appliances containing 4 bovine enamel specimens (2 lowly and 2 highly demineralized). Each specimen included one sound enamel and either one lowly demineralized (7 days, pH 4.95) or one highly demineralized (21 days, pH 4.95) lesion, and was positioned 1 mm below the acrylic under a plastic mesh. The three randomly allocated treatments (application only) included the following dentifrices: (1) 1,100 ppm F as NaF, (2) 1,100 ppm F as SnF2 and (3) 0 ppm F (fluoride-free) as negative control. Differences in integrated mineral loss (ΔΔZ) and lesion depth (ΔLD) were calculated between values before and after the in situ period using transversal microradiography. Results: Of the 21 participants, 6 did not complete the study and 2 were excluded due to protocol violation. Irrespectively of the treatment, higher baseline mineral loss and lesion depth led to a less pronounced change in mineral loss and lesion depth. Except for ΔΔZ of the dentifrice with 0 ppm F, sound surfaces showed significantly higher ΔΔZ and ΔLD values compared with lowly and highly demineralized lesions (p < 0.05, t test). Conclusion: Re- and demineralization characteristics of enamel depended directly on baseline mineral loss and lesion depth. Treatment groups should therefore be well balanced with respect to baseline mineral loss and lesion depth.

Remineralization agents - new and effective or just marketing hype?

This is a review of the need for better remineralization and of the status of calcium-based remineralizing agents for use in anti-caries toothpastes. Use of fluoride toothpastes has markedly reduced caries. However, the decline may be over or in reverse. There is a limit to what fluoride alone can do; complementary agents are needed. Using plaque as a reservoir for calcium-based agents holds promise. Plaque fluid is already supersaturated with respect to relevant calcium phosphates at neutral pH; extra calcium may lead to surface-blocking and sub-optimal lesion consolidation. However, at cariogenic pH, lesions may be more porous to the ingress of mineral, leading to fuller consolidation, and controlled release of calcium should reduce undersaturation with respect to enamel and accelerate deposition of fluorhydroxyapatite. Clinical data to validate in vitro screening models are scarce. Direct progression to in situ models may often be appropriate. The spectrum of lesion types, from softening to relatively advanced subsurface, and lesion activity should be considered. Far from being 'marketing hype', progress with calcium-based remineralizing agents is both encouraging and scientifically sound. Clinical evidence exists for the efficacy of some agents, but further unequivocal clinical data are needed before these agents might be considered 'effective' when delivered from toothpaste.

In vitro cariostatic effects of various iron supplements on the initiation of dental caries

Previous animal and laboratory studies have shown the possible cariostatic effect of iron. The purpose of this study was to in vitro study the effect of different concentrations of four iron supplements on the initiation of dental caries.

MATERIALS AND METHODS

Four products of iron supplements were used namely fre-in-sol, ferotonic, feromin and ferose. Two hundred extracted teeth were distributed randomly into 10 groups. Eight groups were from the four iron products in two concentrations (100% and 50%) in addition to the positive and negative control groups. Mutans streptococci bacteria (6715) grown in Todd Hewitt Broth were used. Assessment of decalcification and cavitation was done daily for 60 days.

RESULTS

It showed that different iron - supplement products play cariostatic effect in the initiation of the dental caries. With the exception of 100% and 50% ferose, both 100% and 50% concentrations of all supplements have cariostatic effect. The mean dates for decalcification varied with lowest for the positive control (12.2 days) and the highest was for 50% feromin. Cavitation was seen in the positive control and 100% ferose groups with mean on the first day of cavitation of 57 days.

CONCLUSION

It was concluded that iron may have cariostatic effect on the in vitro development of dental caries in human teeth.

Remineralization of initial carious lesions in deciduous enamel after application of dentifrices of different fluoride concentrations

The aim of the present study was to evaluate the remineralization potential of five dentifrices with different fluoride concentrations. Initial caries lesions were created in 72 cylindrical enamel blocks from deciduous teeth. The specimens were randomly distributed among six experimental groups corresponding to six experimental periods. Each of the six volunteers carried two deciduous enamel specimens fixed in an intraoral appliance for a period of 4 weeks. They brushed their teeth and the enamel blocks at least two times a day with dentifrices containing 0 ppm (period 1), 250 ppm (period 2), and 500 ppm fluoride (period 3), respectively. A second group of volunteers (n = 6) used dentifrices with a fluoride content of 0 ppm (period 4), 1,000 ppm (period 5), or 1,500 ppm (period 6). At the end of the respective period, the mineral content was determined by transversal microradiography (TMR). The use of dentifrices containing 500 ppm fluoride (38% MR), 1,000 ppm fluoride (42% MR), and 1,500 ppm fluoride (42% MR) resulted in a statistically significant higher mineral recovery compared to the control group (0 ppm fluoride). Mineral recovery was similar after use of dentifrices containing 0 and 250 ppm fluoride (24%; 25%). It is concluded that it is possible to remineralize initial carious lesions in deciduous enamel in a similar way as it has been described for enamel of permanent teeth.

The effect of fluoride gel on incipient carious lesions in a low-caries child population

OBJECTIVES

Secondary analyses were performed to study the cariostatic efficacy of semi-annual professional fluoride gel application on incipient carious lesions in low-caries children initially aged 9.5-11.5 years.

METHODS

Double-blind randomized controlled clinical trial.

RESULTS

The mean treatment effect of fluoride gel for enamel and dentinal caries lesions after 4 years' follow-up was 0.92 D(2,3)FS and 0.20 D(3)FS, respectively. When enamel lesions were included in the DFS count (i.e. D(2,3)FS), the preventive fraction (PF) showed borderline significance (23%; P = 0.05). No significant treatment effect of professionally applied fluoride gel was found for D(2,3)FS and D(3)FS scores of the second molars. The PF for D(2,3)FS of occlusal, approximal, buccal and lingual surfaces and for buccal and palatal pits and fissures differed not significantly.

CONCLUSION

Professionally applied fluoride gel showed no statistically significant caries-inhibiting effect on both enamel and dentine lesions in the permanent dentition of low-caries children.

Caries Prevention by Professional Fluoride Gel Application on Enamel and Dentinal Lesions in Low-Caries Children

In a double-blind randomized controlled clinical trial, the caries-reducing effect of semi-annually applied fluoride gel in a low-caries child population initially aged 4.5-6.5 years (n = 773) has been investigated. Secondary analyses of the data were performed to study the caries reduction including non-cavitated lesions. The treatment effect of fluoride gel was calculated as preventive fraction (PF). When enamel lesions were included in DFS count (D(2) grade), the PF was 22% as compared to 26% counting dentinal lesions. The PFs showed that the mean effect of professionally applied fluoride gel was highest (71%) for D(3)S in the permanent dentition and lowest for d(3)s in the primary dentition (5%). The PFs for approximal and buccal and lingual surfaces of the permanent dentition significantly decreased from 80 to 25% and from 60 to 37% when enamel lesions (D(2)S) were included. With the exception of the buccal and lingual surfaces, in the primary dentition the PFs varied slightly when enamel lesions were included. Inclusion of non-cavitated lesions in the treatment effect statistics did not change the former conclusion that the treatment effect of fluoride gel application on dental caries reduction in a low-caries child population was considered not clinically relevant.

Remineralisation study of artificial root caries lesions after fluoride treatment. An in vitro study using Electric Caries Monitor and Transversal Micro-Radiography

AIMS

To evaluate and compare remineralisation of root caries lesions after in vitro treatment with various fluoride (F) agents using an Electric Caries Monitor (ECM) and Transversal Micro-Radiography (TMR).

MATERIALS

Permanent human teeth were extracted and root surface specimens were sectioned, prepared (n = 35), and randomly allocated into seven different experimental groups (groups 1-7).

METHODS

Root surfaces were demineralised in an acidified gel (pH = 5.0) for 3 weeks followed by various F treatments and stored in a standardised remineralising solution at 37 degrees C for 6 weeks. The root surfaces were treated twice daily with different dentifrice slurries for 2 min, either with a neutral placebo dentifrice without F (group 5); or a neutral sodium fluoride (NaF) 1400 p.p.m. F dentifrice (group 1); or a neutral 1250 p.p.m. F dentifrice (group 6); or an acid dentifrice (pH 4.7) with 1400 p.p.m. F containing amine fluoride (AmF) (groups 3 and 4) or a 1250 p.p.m. (pH 4.7) AmF dentifrice (group 6). In groups 1, 2, 5, 6, and 7, the root surfaces were additionally rinsed for 2 min with a neutral non-F placebo solution. In groups 3 and 4, rinsing were performed for 2 min with an acid (pH 4.7) 250 p.p.m. F solution, containing 125 p.p.m. F as AmF and 125 p.p.m. F as potassium fluoride (KF), once or twice per day respectively. ECM was used to measure electrical resistance on root surfaces at baseline and after 3 and 6 weeks respectively. TMR technique was used to measure and compare root surface lesion depths and mineral loss.

RESULTS

Six weeks daily treatment with a dentifrice slurry containing AmF followed by rinsing with a combination of equal amounts of AmF and KF solution twice a day showed a statistical significant higher ECM values compared with the other groups. TMR data measuring lesion depths and mineral loss reduction supported the results of the ECM findings.

CONCLUSIONS

Daily application of a dentifrice slurry containing 1400 p.p.m. F as AmF combined with twice daily rinsing with a 250 p.p.m. F solution containing equal amount of AmF and KF significantly remineralise primary root caries lesions in vitro. ECM and TMR are valuable complementary methods in order to analyse the remineralisation processes.

In situ caries models

By using in situ models, we have the potential to study both fundamental aspects of the caries process as well as more applied research problems such as the effect of food on dental caries and the role of fluoride in caries prevention in human subjects without actually causing caries in the natural dentition. The key experimental parameters that need to be considered in the development of an in situ model are the characteristics of the subject panel, the physical design of the model, the type of hard tissue substrate and the method of assessing mineral status, and the study design and clinical protocol. Each parameter must be carefully considered in relation to the objectives of the research, study design requirements, ethical considerations, impact on clinical relevance, and impact on the control of variation. The major source of variation associated with in situ models should be of biological and not experimental origin. The design and conduct of proper in situ model studies require a clear understanding of the caries process, sound analytical support, and a knowledge of how to work with research subjects to achieve a high level of compliance. Given the complex nature of caries, a combination of hard tissue substrates--including sound, surface-softened lesions and subsurface lesions--may be necessary to model all aspects of caries progression and prevention successfully. Internal validation of in situ models using fluoride dose-response controls is considered to be necessary for studies evaluating the efficacy of new fluoride dentifrice formulations.

Four-year study of caries inhibition of intensive Duraphat application in 11-15-year-old children

The purpose of the study was to evaluate the caries preventive effect and cost of an intensive application of Duraphat varnish, added to the regular preventive program for 11-15-yr-old children in a Swedish Dental Community Clinic. In 1987, the 134 11-yr-old children in Floda were divided into two groups, every second child to each. Children with fixed orthodontic appliances were excluded. The test group received three applications of Duraphat varnish during 1 week, once a year, by a dental nurse. The control group received one application at the annual check-up. Both groups were included in the regular preventive program at the clinic. The total time cost for the clinic was estimated and used to calculate the cost per hour for dentists and nurses. The caries increment and progression were estimated both by routine diagnosis and by a careful study of radiographs taken at the beginning and end of the study period. There was a small caries increment and progression in the test group as compared to the control group. The difference was statistically significant for all aspects studied. The costs were about the same in both groups but more time was used in the test group. The administrative effort for the staff was considerable for the intensive Duraphat application.