Dependence of in vitro demineralization of apatite and remineralization of dental enamel on fluoride concentration

Testing mechanical properties and degree of conversion of resin-based composite material containing contact killing antibacterial agent in comparison with fluoride composite resin

Background

A major drawback of resin composites is their tendency to accumulate microbial biofilms that can lead to secondary caries. The objective of this study was to compare the mechanical properties and the degree of conversion of commercial resin-based composite materials containing a contact-killing antibacterial agent, dimethylaminohexadecyl methacrylate (DMAHDM), at different concentrations, with a fluoride-releasing composite material.

Materials and methods

Four groups were tested: Tetric N Ceram composite material (G1), Tetric Evo Ceram (G2), and Tetric N Ceram with the addition of contact-killing antibacterial agent DMAHDM at concentrations of 3% (G3) and 5% (G4). The mechanical properties, including flexural strength, elastic modulus, and Vickers microhardness and the degree of conversion were investigated.

Results

Adding 3 % and 5 % DMAHDM resulted in flexural strength values that were comparable to Tetric Evo Ceram. Tetric N Ceram was comparable to the group containing 3 % DMAHDM (p > 0.05). However, it was significantly greater when compared to Tetric Evo Ceram (93.3 ± 9.4) and 5 % DMAHDM (p < 0.05). Both the elastic modulus and Vickers microhardness values of Tetric N Ceram were significantly higher than those of the other groups (p < 0.05). Furthermore, the elastic modulus of Tetric Evo Ceram showed similar results to groups with 3 % and 5 % DMAHDM. Nevertheless, the Vickers microhardness value is significantly higher when compared to 5 % DMAHDM (0.394 ± 0.021) (p < 0.05) while it was comparable to that of 3 % DMAHDM (0.484 ± 0.016) (p > 0.05). There was no statistically significant difference in the degree of conversion between the groups (p > 0.05).

Conclusion

Adding 3% DMAHDM to Tetric N Ceram resulted in flexural strength values that were similar to those of Tetric N Ceram and Tetric Evo Ceram. DMAHDM did not affect the degree of conversion of Tetric N Ceram composite.

The Effect of a Bioactive Oral System and CO2 Laser on Enamel Susceptibility to Acid Challenge

This study evaluated the structural changes of enamel treated by the Regenerate system and carbon dioxide (CO2) laser against acid challenge. Thirty human enamel slabs were prepared and assigned into three groups: Group I: untreated (control); Group II: treated with the Regenerate system; and Group III exposed to CO2 laser. All specimens were subjected to an acid challenge (pH 4.5–7.0) for 14 days. Specimens were evaluated and compared at 120 points using five Raman microspectroscopic peaks; the phosphate vibrations ν1, ν2, ν3, and ν4 at 960, 433, 1029, and 579 cm−1, respectively, and the carbonate at 1070 cm−1, followed by Vickers microhardness test. The ratio of carbonate to phosphate was correlated to the equivalent microhardness numbers. The intensities of phosphate peaks ν1, ν2, and ν4 were reduced in all groups post-acid challenge, while the carbonate and ν3 were significantly increased (p < 0.000). Surfaces treated by Regenerate exhibited higher peak intensity of phosphate and carbonate before and after pH-cycling (p < 0.05). The mineral content in enamel had a direct effect on tissue microhardness, and the CO2-lased surfaces showed a reduced carbonate content and higher microhardness values. Both approaches induced surface changes that can protect enamel against acid challenge resulting in a significant benefit for dental healthcare.

The Fluoride Ion Release from Ion-Releasing Dental Materials after Surface Loading by Topical Treatment with Sodium Fluoride Gel

The study aimed to investigate the rechargeability of ion-releasing dental material specimens immersed in distilled water for 25 months, which depleted their ion-releasing ability. Four restorative dental materials (alkasite composite, giomer, glass-ionomer, and composite material) presented with 24 specimens were studied after topical treatment with a concentrated fluoride gel. The effect of resin coating on the ion uptake and release was investigated on additional 42 specimens of restorative dental materials with coatings. The composite materials were coated with two adhesive systems, whereas the glass-ionomer was coated with the special coating resin. After topical fluoride exposure, ion release and specimen mass were measured at 1, 2, 3, 4, 5, 6, 7, and 14-day intervals using an ion-selective electrode and an analytical balance, respectively. The cumulative fluoride levels for the uncoated specimens of alkasite composite were significantly higher than those of giomer and glass-ionomer cement, with no statistically significant difference between the latter two materials. The conventional composite had the lowest cumulative concentration of fluoride ions (p < 0.05). The adhesive systems affected the fluoride recharge and reduced the ion concentrations absorbed by the specimens. Specimens coated with universal adhesive showed significantly higher ion release compared to universal fluoride-releasing adhesive or special coating resin for glass-ionomers (p < 0.05). No statistically significant change in specimen mass was observed during the 14-day period. Surface coating with adhesive systems as well as special coating resin for glass-ionomers affects the fluoride recharge process.

Direct and indirect effects of different dentifrices on the initial bacterial colonization of enamel in situ overnight

OBJECTIVE

The aim of this study was to investigate the direct and indirect influence of fluoridated toothpastes and fluoride-free toothpaste with hydroxyapatite (HAP) as active ingredient on initial bacterial colonization on enamel in situ.

METHODS

For this clinical-experimental pilot study, eight subjects were instructed to brush their teeth with three different toothpastes (Elmex^® : 1400 ppm AmF, Meridol^® : 1400 ppm AmF +SnF2, Karex^® : HAP), using each for two consecutive days. As a control, brushing without toothpaste was performed. To evaluate bacterial colonization, subject wore splints with buccally placed bovine enamel platelets overnight. Two modes were tested. In a first pass (regimen A), the splints were inserted after toothbrushing to examine the indirect effects of the dentifrices. In order to investigate the direct effects, the specimens were brushed in situ in a second pass (regimen B). Biofilm formation was visualized and quantified using fluorescence microscopy (DAPI and BacLight) and transmission electron microscopy (TEM).

RESULTS

For brushing regimen A (indirect effect of dentifrices), no statistical differences were detected between any of the tested dentifrices or the control. Likewise, no statistically significant differences were recorded for brushing regimen B (direct effect of dentifrices). Furthermore, no differences between the different brushing techniques were determined with regard to the ultrastructure of the overnight biofilm.

CONCLUSION

Within the limitations of the present pilot study, it can be concluded that in patients with good oral hygiene, dentifrices and their chemical composition have no statistically significant effect on the initial bacterial colonization of enamel platelets in situ, irrespectively of the mode of application.

Effectiveness of applying proximal enamel caries with fluoride-releasing sealant and fluoride varnish on caries progression in permanent teeth: A 12-month split-mouth randomized clinical trial

BACKGROUND

Few studies report on managing initial proximal caries with sealants, and no reports focus on fluoride-releasing sealants.

AIM

To compare the effectiveness between applications of a fluoride-releasing sealant and fluoride varnish on proximal enamel caries to control caries progression in permanent teeth.

DESIGN

This was a split-mouth randomized controlled trial in forty-four 11- to 16-year-old children with radiographic caries in at least one contralateral pair of teeth with proximal enamel caries. The lesions were evaluated using DIAGNOdent and were also assessed visually after tooth separation. The lesions in each subject were randomly sealed with a fluoride-releasing sealant (Helioseal® F) or applied with fluoride varnish (Duraphat®). The fluoride varnish-treated lesion was reapplied at 3 and 6 months. Clinical examination, bitewing radiograph evaluation, and DIAGNOdent assessment were performed at 6 and 12 months. The caries progression outcome variables were regression, no change, and progression. The data were analyzed with the McNemar-Bowker test.

RESULTS

Radiographic examination and DIAGNOdent assessment demonstrated no significant differences in the percentages of regression, no change, or progression at the 12-month follow-up (p > .05).

CONCLUSION

Applications of a fluoride-releasing sealant and of fluoride varnish three times resulted in a nonsignificant difference in caries progression of initial proximal caries at the 12-month follow-up.

Ion Capture and Release Ability of Glass Ionomer Cement Containing Nanoporous Silica Particles with Different Pore and Particle Size

This study prepared glass ionomer cement (GIC) containing nanoporous silica (NPS) (GIC-NPS) at 5 wt% concentrations using 3 types of NPS with different pore and particle sizes and evaluated the differences in their cationic ion capture/release abilities and mechanical properties. The cationic water-soluble dye was used as cationic ion. The test GIC-NPS complexes captured dyes by immersion in 1 wt% dye solutions. All the GIC-NPS complexes released dyes for 28 d, and the amount of dye released from the complexes increased with decreasing pore size; however, the particle size of NPS did not affect the amount of dye released. Additionally, GIC-NPS was able to recharge the dye, and the amount of released the dye by the complexes after recharge was almost identical to the amount released on the first charge. Although not significantly different, the compressive strength of GIC-NPS was slightly greater than that of GIC without NPS regardless of the type of NPS. These results suggest that the degree of capture and release of cationic molecules, such as drugs, can be controlled by optimizing the pore size of NPS without sacrificing its mechanical strength when its content is 5 wt%.

A modified TEGDMA-based resin infiltrant using polyurethane acrylate oligomer and remineralising nano-fillers with improved physical properties and remineralisation potential

OBJECTIVES

This study aimed to modify an experimental triethylene glycol dimethacrylate (TEGDMA) based resin infiltrant using PUA oligomer and two remineralising fillers, including fluorohydroxyapatite (FHA) and fluoride-doped bioactive glass (FD-BG), to improve the mechanical and physical properties and induce remineralising potential.

MATERIALS AND METHODS

The polyurethane acrylate oligomer (PUA) was synthesised and characterised. Experimental resin infiltrant was prepared by mixing 10% of synthesised PUA with 88% TEGDMA. Water contact angle, penetration coefficient, and penetration depth were then measured. The FHA and FD-BG fillers were synthesised and characterised. To prepare nano-filled resin infiltrant, 5% of each powder was mixed with the prepared resin infiltrant. The prepared resin infiltrants were characterised to evaluate their degree of conversion, mechanical properties, water sorption, and solubility. The ion release of filled resin was also assessed. The non-infiltrated and infiltrated enamel specimens underwent fourteen days of pH-cycling, and a surface microhardness was done to assess the resistance to demineralisation.

RESULTS

The results showed that the addition of PUA to TEGDMA increased the mechanical properties and decreased water sorption and solubility. The addition of synthesised FD-BG fillers to resin infiltrant significantly improved the resistance to demineralisation of enamel samples compared with other groups (p ≤ 0.001). The FHA fillers also improved the resistance to demineralisation; however, the produced changes were not statistically meaningful (p > 0.05).

CONCLUSIONS

Based on the results, the PUA+TEGDMA+ FD-BG/FHA composite can be used as an alternative material for pure TEGDMA in enamel infiltration approaches owing to its better mechanical properties, lower water sorption and solubility, and also remineralisation potential.

CLINICAL SIGNIFICANCE

A resin infiltrant with remineralisation potential, lower water sorption and solubility and higher mechanical properties may enhance the management of early caries lesions.

Demineralization prevention with a new antibacterial restorative composite containing QASi nanoparticles: an in situ study

OBJECTIVES

To investigate whether a newly developed dental composite with quaternary ammonium silica dioxide (QASi) nanoparticles incorporated with other fillers into the restorative material demonstrates antibacterial activity by reducing enamel demineralization in an in situ gap model.

MATERIALS AND METHODS

Twenty subjects wearing a lower removable partial denture (RPD) with acrylic flanges on both sides of the mouth were recruited into the 4-week in situ study. The gap model consisted of an enamel slab placed next to a composite, separated by a 38-μm space. In the split-mouth design on one side of the RPD, the composite was the Nobio Infinix composite (Nobio Ltd., Kadima, Israel), and the contralateral side used a control composite. Each participant received enamel slabs from one tooth. The gap model was recessed into the RPD buccal flange, allowing microbial plaque to accumulate within the gap. After 4 weeks of continuous wearing, decalcification (∆Z mineral loss) of the enamel slabs adjacent to the gap was determined by cross-sectional microhardness testing in the laboratory.

RESULTS

The ∆Z for the antibacterial composite test side was 235±354 (mean±standard deviation [SD]; data reported from 17 participants) and statistically significantly lower compared to ∆Z of the control side (774±556; mean±SD) (paired t-test, P<0.0001; mean of test minus control -539 (SD=392), 95% confidence interval of difference: -741, -338).

CONCLUSIONS

This in situ clinical study showed that composites with QASi antibacterial particles significantly reduced demineralization in enamel adjacent to a 38-μm gap over a 4-week period in comparison to a conventional composite.

CLINICAL RELEVANCE

Composites with QASi nanoparticle technology have the potential to reduce the occurrence of secondary caries.

TRIAL REGISTRATION

ClinicalTrials.gov #NCT04059250.

Novel Nano Calcium Fluoride Remineralizing and Antibacterial Dental Composites

OBJECTIVE

Composites with remineralizing and antibacterial properties are favorable for caries inhibition. The objectives of this study were to develop a new bioactive nanocomposite with remineralizing and antibiofilm properties by incorporating dimethylaminohexadecyl methacrylate (DMAHDM) and nano-calcium fluoride (nCaF₂).

METHODS

nCaF₂ was produced via a spray-drying method and integrated at 15% mass fraction into composite. DMAHDM was added at 3% mass fraction. Mechanical properties and F and Ca ion releases were assessed. Colony-forming units (CFU), lactic acid and metabolic activity of biofilms on composites were performed.

RESULTS

The new composites had flexural strengths of (95.28±6.32) MPa and (125.93±7.49) MPa, which were within the ISO recommendations. Biofilm CFU were reduced by 3-4 log (p<0.05). The composites achieved high F releases of (0.89±0.01) mmol/L and (0.44±0.01) mmol/L, and Ca releases of (1.46±0.05) mmol/L and (0.54±0.005) mmol/L.

CONCLUSIONS

New nanocomposites were developed with good mechanical properties, potent antibacterial activity against salivary biofilms, and high F and Ca ion releases with potential for remineralization.

CLINICAL SIGNIFICANCE

Novel nanocomposites using nCaF₂ and DMAHDM were developed with potent antibacterial and remineralizing effects and high F and Ca ion releases. They are promising to inhibit recurrent caries, promote remineralization, and possess long-term sustainability.

Association between population-based fluoride varnish application services and dental caries experience among schoolchildren in Taiwan

BACKGROUND/PURPOSE

Taiwan government has provided population-based fluoride varnish application services for all preschool children since July 2004. This study investigated the association providing such services on dental caries experiences among schoolchildren.

METHODS

A cross-sectional study was conducted on schoolchildren aged 8-9 years. A questionnaire collected information on sociodemographic background, parents' oral health status, children's oral health-related behavior, and dietary habits. Dental caries was recorded through standardized oral examinations. The number of services was retrieved from the Taiwan National Health Insurance Research Database. Univariate, multivariable linear, and logistic regression analyses were performed.

RESULTS

The study involved 1246 children. The mean dental caries indices were 3.97 for decayed, extracted, and filled teeth (deft) and 0.94 for decayed, missing and filled teeth (DMFT). After adjustments for confounding factors, it was revealed that children receiving services were not associated with significantly lower deft and DMFT indices (P > 0.05). The adjusted odds ratio (OR) for untreated primary teeth of children receiving 3 or more services was 0.64 (95% CI = 0.44-0.95) compared with those who received no services (P = 0.025). However, subgroup analyses demonstrated that children in the low-risk group were mainly affected (adjusted OR = 0.36-0.89, P = 0.013).

CONCLUSION

This study revealed that children receiving 3 or more services were associated with a 36% decreased risk of having untreated caries in primary dentition, but these children were mainly in the low-risk group. These results illustrate real data that provides dentists and policymakers with valuable information.

Effect of the S-PRG filler content in the multi-ion releasing paste on the acid resistance of the enamel surface after polishing with the paste

This study aimed to investigate the effect of the multi-ion releasing paste (MP) on the acid resistance of the enamel surface of an extracted human tooth. Five kinds of MP were prepared according to the content (wt%) of S-PRG fillers: 0 wt% (MP0, control), 1 wt% (MP1), 5 wt% (MP5), 20 wt% (MP20), and 30 wt% (MP30). The buccal coronal surfaces of the extracted anterior teeth were polished with each kind of MP for 1 min. After removing radicular parts, the coronal parts underwent a pH cycling, and then sliced to make thin sections. The lesion depth of each section was measured using a polarization microscope. Each lesion's depth of enamel polished with MP5, MP20, and MP30 was significantly shallower than that polished with MP0.

Effects of bioactive glass incorporation into glass ionomer cement on demineralized dentin

The effects of the incorporation of sodium-free bioactive glass into glass ionomer cement (GIC) on the demineralized dentin are studied. Four experimental groups with various amounts of BAG in GIC were considered: BG0 group: 0 wt% (control); BG5 group: 5 wt%; BG10 group: 10 wt%; BG20 group: 20 wt%. The GIC surface and GIC-approximated demineralized dentin surfaces were evaluated using field emission scanning electron microscopy (FE–SEM). X-ray diffraction (XRD) analysis was performed to evaluate the chemical changes in the GIC-approximated dentin surface. In addition, a shear bond strength test was performed to evaluate the effects of BAG incorporation on the bond strength of GIC. FE–SEM analysis indicated that BAG-incorporated GICs formed distinct precipitates on their surface. Precipitates were also formed on the GIC-approximated demineralized dentin surface. It was more obvious when the amount of BAG increased. In the XRD analysis, fluorapatitie (FAP) peaks were detected in the BG5, BG10, and BG20 groups. There was no significant difference in the shear bond strength among all experimental groups. BAG-incorporated GIC precipitated FAP crystals underlying demineralized dentin surface without affecting bond strength. This study suggests the possibility of BAG as a beneficial additive in GIC.

Synthesis and characterization of an anti-caries and remineralizing fluorine-containing cationic polymer PHMB-F

Dental caries have become a major global public health problem. Plaque control and remineralization of initial enamel lesions are paramount for the prevention and control of caries. Polyhexamethylene biguanide (PHMB) is a type of cationic amphipathic antibacterial agent with broad-spectrum antibacterial properties and good biological safety. Fluoride delays demineralization and promotes the remineralization of hard dental tissues. However, a high concentration is needed for it to function as an antibacterial agent. In order to create a PHMB with the benefits associated with fluoride, we synthesized a fluorine-containing cationic polymer, PHMB-F. Fourier transform-infrared spectroscopy and solid state nuclear magnetic resonance characterization confirmed the successful synthesis of PHMB-F. Antibacterial tests showed that PHMB-F had better antiseptic efficacy for Streptococcus mutans compared with just PHMB. Moreover, positively-charged PHMB-F allows fluoride ions to exist closer to the enamel surface with negative potential, which markedly lowers the ion concentrations in the microenvironment adjacent to hard dental tissues needed to maintain equilibrium. Thus, only low concentrations of PHMB-F are required for enamel remineralization.

Infrared imaging confirms the role of the transparent surface zone in arresting dental caries

Several studies have demonstrated the potential of short wavelength infrared (SWIR) reflectance, thermal imaging and optical coherence tomography for the nondestructive assessment of the activity of caries lesions. The purpose of this study was to test the hypothesis that the activity of arrested caries lesions on the coronal surfaces of extracted teeth would be changed by reducing the thickness of the highly mineralized transparent surface layer, which was measured using polarization sensitive optical coherence tomography (PS-OCT). The lesion activity was assessed using SWIR reflectance and thermal imaging during forced air drying of the lesion before and after mechanical removal of a surface layer ~ 50-μm thick covering the lesion. Both the intensity change in SWIR reflectance images at 1500-1750-nm wavelengths after drying the lesions and the change in thermal emission measured with a thermal camera at 8-13-μm wavelengths increased significantly (P<0.05) after reducing the thickness of the mineralized surface layer in the lesions indicating the permeability of the lesion to fluids increased. These results provide further evidence that the presence of a highly mineralized outer surface layer is a key indicator of lesion arrest.

Randomised study of intra-oral kinetics of fluoride-containing toothpastes

OBJECTIVES

This randomised, controlled, analyst blind, crossover study aimed to evaluate and compare salivary fluoride and calcium ion concentration over 60 min following brushing with an assigned treatment and following an orange juice (OJ) or deionised (DI) water rinse 60 min post-brushing.

METHODS

Study treatments, both containing 1150 ppm fluoride as NaF and 5% w/w KNO₃, were the Test (including 1.2 % w/w cocamidopropyl betaine) and Comparator (including tetrasodium pyrophosphate and sodium lauryl sulphate) toothpastes. Twenty nine participants were randomised to treatment.

RESULTS

A sharp increase in salivary fluoride ion concentration immediately post-brushing with either toothpaste decreased over time. Fluoride concentration following Test toothpaste use was numerically higher than the Comparator at all timepoints, with a significant difference from 10 min post-brushing (p < .05). Following the 60 min rinse, there were no significant differences between the Test or Comparator + OJ groups in salivary fluoride concentration but the Test + DI water group was significantly lower than Test (p < .001) or Comparator (p < .001) + OJ groups. A reduction in salivary calcium ion concentration was seen immediately post-brushing and after the OJ rinse with both toothpastes. Significant differences were observed in favour of the Test toothpaste at all timepoints (p < .05) and for Test and Comparator + OJ group (p < .001) compared with Test + DI water rinse. Both treatments were generally well-tolerated.

CONCLUSIONS

This study demonstrated that toothpaste formulations with identical declared fluoride concentrations and the same fluoride source give rise to differing intraoral fluoride concentrations over time, which are potentially related to different formulation excipient effects.

CLINICAL SIGNIFICANCE

By understanding the interaction of toothpaste formulation excipients in the oral environment, formulations can be developed that maximise retention of fluoride in the oral environment.

Combined effect of casein phosphopeptide-amorphous calcium phosphate and sodium trimetaphosphate on the prevention of enamel demineralization and dental caries: an in vitro study

OBJECTIVE

To evaluate the effect of treatment with fluoridated toothpaste supplemented with a combination of sodium trimetaphosphate (TMP) and casein phosphopeptide-amorphous calcium phosphate (MI Paste Plus^®) on the demineralization of dental enamel.

METHODS

Bovine enamel blocks selected by initial surface hardness (SHi) were randomly allocated into six groups (n = 12), according to the test toothpastes: (1) without F-TMP-MI Paste Plus^® (Placebo); (2) 1100 ppm F (1100F); (3) MI Paste Plus^®; (4) 1100F + MI Paste Plus^® (1100F-MI Paste Plus), (5) 1100F + 3 % TMP (1100F-TMP); and (6) 1100F-TMP + MI Paste Plus^® (1100F-TMP-MI Paste Plus). Blocks were treated two times per day with slurries of toothpaste (1 min), and groups 4 and 6 received an application of MI Paste Plus (3 min). Next, the samples were subjected to five pH cycles (demineralizing/remineralizing solutions) at 37 °C, to produce subsurface enamel lesions.Thereafter, the blocks were maintained for 2 days in fresh remineralizing solution. After pH cycling, the following were obtained: percentage of surface hardness loss (%SH); integrated loss of subsurface hardness (ΔKHN); profile analysis and lesion depth subsurface through polarized light microscopy (PLM); scanning electron microscopy (SEM); and fluoride (F), calcium (Ca), and phosphorus (P) in the enamel. The data were subjected to ANOVA (1-criterion), followed by the Student-Newman-Keuls test (p < 0.001).

RESULTS

The 1100F-TMP-MI Paste Plus group showed better results for SHR, ΔKHN, and PLM (p < 0.001). The F concentration was similar among all groups (p > 0.001). The 1100F-TMP-MI Paste Plus group showed the highest concentration of Ca and P in the enamel (p < 0.001).

CONCLUSION

The application of 1100F-TMP-MI Paste Plus promoted a higher inhibitory effect against enamel demineralization.

CLINICAL SIGNIFICANCE

The combination of treatments with F, TMP, and MI Paste Plus^® can be an effective alternative to improve the oral health of individuals, especially those with high activity of dental caries and at high risk for its development.

Evaluation of antibacterial and cytocompatible properties of multiple-ion releasing zinc-fluoride glass nanoparticles

Zinc-fluoride glass nanoparticles (Zinc-F) release several ions, such as fluoride, zinc and calcium ions, through acid-base reactions. The aim of this study was to evaluate the antibacterial and cytotoxic properties of Zinc-F. Antibacterial tests showed that a Zinc-F eluting solution significantly reduced the turbidity and colony-forming units of Streptococcus mutans and Actinomyces naeslundii, compared to that of calcium-fluoroaluminosilicate glass nanoparticles without zinc ions. In live/dead staining, Zinc-F eluate significantly decreased green-stained bacterial cells, indicating live cells, compared with the control (no application). Human dentin coated with Zinc-F showed suppressed S. mutans and A. naeslundii biofilm formation. Additionally, Zinc-F eluate showed low cytotoxic effects in osteoblastic and fibroblastic cells. Therefore, our findings suggested that Zinc-F exhibits antibacterial and biocompatible properties through multiple-ion release.

Fluoride Mode of Action: Once There Was an Observant Dentist

The discovery and implementation of fluoride in the prevention of dental caries is often praised as one of the most important achievements in health care. In the early 20th century, it took 30 y to identify fluoride as the cause of enamel mottling but also of reduced caries prevalence in a population drinking water containing fluoride. Similarly, from 1960 to 1990, it took major efforts to unravel the working mode of fluoride in such detail that a rational scheme of caries prevention could be formulated. This article describes the scientific struggle leading to a consensus on the topic. For a historic purpose, the field, the actors, and their main research achievements are described. Ultimately it was generally agreed that the effect of fluoride is primarily topical by fluorides in the oral fluids rather than systemic by incorporation of fluoride in the enamel mineral crystals. Fluoride concentrations, even <1 mg/L, enhance the deposition of calcium phosphates during remineralization of enamel (and dentin). Similarly, such low levels of fluoride are effective in reducing the dissolution of the calcified tissues. This understanding has led to the development of fluoride-containing caries-preventive products that had an undisputed beneficial effect on the levels of dental caries.

The Effect of Bioactive Glass-Enhanced Orthodontic Bonding Resins on Prevention of Demineralization: A Systematic Review

At present, bioactive glasses (BAGs) are demonstrating promising results in the remineralization of hard tissues. Their bioactive properties can potentially overcome the demineralization effect accompanying orthodontic treatment. This review aimed to evaluate the effectiveness of bioactive glass enhanced orthodontic bonding resins on enamel remineralization, in addition to their antibacterial, ion release and acid neutralization effect. Four databases (PubMed, MEDLINE, Web of Science and Scopus) were searched. Two hundred and fifty-one full-text articles were screened independently, out of which seven studies satisfied the inclusion criteria. Quality appraisal was performed by two independent reviewers. Methodologies used to assess the anti-demineralization effect included Micro-Computed Tomography, Polarized Light Microscopy and Hardness Testing (Knoop and Berkovich). All seven articles confirmed the superior remineralization effect of BAG orthodontic bonding resins compared to their non-BAG counterparts. A proportional relationship was proved between BAG concentrations and increased anti-demineralization effect. The addition of antibacterial agents to BAG does not necessarily improve its anti-demineralization effect. Although studies have confirmed the effectiveness of BAG orthodontic bonding resins on enamel remineralization, there was a degree of heterogeneity across studies due to the lack of an in vitro studies standardized protocol.

Plaque Fluoride Levels as a Predictor of Caries Development in Early Childhood with High Sugar Exposure - A Preliminary Study

Objective

This longitudinal study aimed to investigate if the plaque fluoride (PF) concentration can predict the early childhood caries onset. Design: As part of a larger study, 188 preschoolers were clinically evaluated for early childhood caries diagnosis, at baseline and after 1-year follow-up. After that, the final sample comprised: 1. children who had already caries at baseline (decayed, missing or filled surfaces, as well as white chalky white spot lesions adjacent to gingival margins) and developed at least one more cavitation after one year (n=16), and 2. children who never had or developed any caries lesions, including active white spots lesions (n=15). Before the clinical examinations, dental plaque was collected. PF concentration was determined with an ion-specific electrode. A chart was used to estimate the mean daily sugar exposure. The results were statistically analyzed by Spearman correlation and logistic regression analyses (α=0.05).

Results

After one year, a positive significant correlation between caries development and liquid sucrose, total sugar and total sucrose consumption increments was found (p<0.05). Moreover, the solid sugar, solid sucrose and total sugar exposure at baseline were positively correlated with the presence of dental plaque at follow-up (p<0.05). To top it all, children with PF concentrations ≤0.1 μg/mg at baseline were 10 times more likely to develop caries.

Conclusion

In conclusion, this study demonstrated for the first time in vivo that low PF concentration is a predictor of caries development in primary teeth.

In vitro CO2 9.3-μm short-pulsed laser caries prevention-effects of a newly developed laser irradiation pattern

Caries prevention with different lasers has been investigated in laboratory studies and clinical pilot trials. Objective of this in vitro study was to assess whether 9.3-μm microsecond short-pulsed CO₂ laser irradiation enhances enamel caries resistance without melting, with and without additional fluoride application. Seven groups of enamel, totaling 105 human enamel samples, were irradiated with 2 different carbon dioxide lasers with 2 different energy application systems (original versus spread beam; 9.3 μm wavelength, pulse repetition rate 43 Hz vs 100 Hz, fluence ranges from 1.4 to 3.9 J/cm², pulse duration 3 μs to 18 μs). The laboratory pH-cycling was performed with or without additional fluoride, followed by cross-sectional microhardness testing. To assess caries inhibition, the mean relative mineral loss delta Z (∆Z) was determined. To evaluate for melting, scanning electron microscopy (SEM) examinations were performed. For the non-laser control groups with additional fluoride use, the relative mineral loss (ΔZ, vol% × μm) ranged between 512 ± 292 and 809 ± 297 (mean ± SD). ΔZ for the laser-irradiated samples with fluoride use ranged between 186 ± 214 and 374 ± 191, averaging a 58% ± 6% mineral loss reduction (ANOVA, P < 0.01 to P < 0.0001). For the non-laser-treated controls without additional fluoride, the mineral loss increased (ΔZ 914 ± 422 to 1224 ± 736). In contrast, the ΔZ for the laser-treated groups without additional fluoride ranged between 463 ± 190 and 594 ± 272 (P < 0.01 to P < 0.001) indicative of 50% ± 2% average reduction in mineral loss. Enhanced caries resistance was achieved by all applied fluences. Using the spread beam resulted in enhanced resistance without enamel melting as seen by SEM. CO₂ 9.3-μm short-pulsed laser irradiation with both laser beam configurations resulted in highly significant reduction in enamel mineral loss. Modifying the beam to a more homogenous profile will allow enamel caries resistance even without apparent enamel melting.

Shear Bonding Strength and Thermal Cycling Effect of Fluoride Releasable/Rechargeable Orthodontic Adhesive Resins Containing LiAl-F Layered Double Hydroxide (LDH) Filler

This study aims to investigate the shear bonding strength (SBS) and thermal cycling effect of orthodontic brackets bonded with fluoride release/rechargeable LiAl-F layered double hydroxide (LDH-F) contained dental orthodontic resin. 3% and 5% of LDH-F nanopowder were gently mixed to commercial resin-based adhesives Orthomite LC (LC, LC3, LC5) and Transbond XT (XT, XT3). A fluoroaluminosilicate modified resin adhesive Transbond color change (TC) was selected as a positive control. Fifteen brackets each group were bonded to bovine enamel and the SBS was tested with/without thermal cycling. The adhesive remnant index (ARI) was evaluated at 20× magnification. The fluoride-releasing/rechargeability and cytocompatibility were also evaluated. The SBS of LC, LC3, and LC5 were significantly higher than XT and TC. After thermal cycling, the SBS of LC, LC3, and LC5 did not decrease and was significantly higher than TC. The changes of ARI scores indicate that failure occurred not only cohesive but also semi-cohesive fracture. The 30 days accumulated daily fluoride release of LC3, LC5, and TC without recharge are higher than 300 μg/cm². The LDH-F contained resin adhesive possesses higher SBS compared to positive control TC. Fluoride release and the rechargeable feature can be achieved for preventing enamel demineralization without cytotoxicity.

Tri-(2-picolyl)amine-modificated triarylborane: Synthesis, photophysical properties and distinguish for cyanide and fluoride anions in aqueous solution

We designed and synthesized a tri-(2-picolyl) amine (TPA) functionalized triarylborane, 1-(6-(4-(dimesitylboryl)phenyl)pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine (PB2). The photophysical properties of PB2 were thoroughly explored. Moreover, PB2 can capture CN^- and F^- in aqueous solution through strong chelation induced by the synergy of a boron atom and metal ion gripped by TPA to display entirely different fluorogenic responses such as fluorescence enhancement for CN^- and fluorescence quenching for F^-. The results of TOF-MS-EI analysis and theoretical calculations indicate that the complexing of PB2 with CN^- formed a 2-to-2 adduct with a stabilized configuration, resulting in strong emission. The complexing of PB2 with F^- formed a 1-to-1 adduct with a loose configuration, resulting in weak emission. In pure water, the detection limit of PB2 for CN^- is 0.79 μM, and in H₂O/THF (1:9 v/v) system, the detection limits of PB2 for CN^- and F^- can reach 0.39 and 2.12 μM, respectively, indicating its potential application for effective detection and discrimination of CN^- and F^-.

"Setting the scene in early childhood" - an MID approach for life

This article presents a discussion paper for both consideration and implementation of Minimal Intervention Dentistry (MID) principles by the general dental practitioner. It argues that if these concepts can be adopted in early childhood by both the community and the profession, "Teeth for Life" can become a reality for all. Oral Health promoting behaviours can be nurtured and supported from infancy and developed into everyday living practice for a lifetime thereby maintaining an optimal quality of life. MID techniques have become more refined and supported by scientific research in the recent times and should be considered an essential clinical guideline for the future disease management.

Comparison of fluoride ion release and alkalizing potential of a new bulk-fill alkasite

AIM

This study was conducted to evaluate and compare fluoride ion release by Cention-N (self-cure and light-cure) and conventional glass-ionomer cement (GIC) at different pH and time intervals.

METHODOLOGY

Cavities of similar dimensions were prepared in mandibular molars and restored with Cention-N (by self-cure and light-cure techniques) and GIC. Samples were stored in deionized water, and the cumulative fluoride ion release and change in pH were assessed utilizing spectrophotometer and pH meter, respectively, at the end of 7 days, 14 days, and 21 days. The data thus obtained were statistically analyzed.

RESULTS

All the tested materials released fluoride ions in both acidic and neutral pH at all time intervals, and the fluoride ion release was significantly higher (<0.05) in acidic pH as compared to neutral pH except in GIC. All the groups showed a statistically significant increase in pH in acidic medium, whereas no significant increase was observed in neutral medium.

CONCLUSIONS

Cention-N (self-cure) has the highest fluoride ion release and alkalizing potential in acidic pH as compared to Cention-N (light-cure) and GIC.

Randomised study of the effects of fluoride and time on in situ remineralisation of acid-softened enamel

OBJECTIVES

This single-centre, randomised, crossover study used a short-term in situ dental erosion remineralisation model to explore the remineralisation of acid-softened enamel in the 4-h period immediately following brushing with an anti-erosion, dentin hypersensitivity test dentifrice containing 1150 ppm fluoride (as sodium fluoride [NaF]) or a placebo dentifrice with no fluoride.

MATERIALS AND METHODS

Fifty participants wearing a palatal appliance holding surface-softened bovine enamel specimens brushed their natural teeth with their assigned dentifrice. Specimens were removed at 5-, 10-, 15-, 30-, 60-, 120- and 240-min post brushing. Enamel remineralisation effect was evaluated at each timepoint by percent surface microhardness recovery (%SMHR) and enamel fluoride uptake (EFU). After a second in vitro erosive challenge, the percent relative erosion resistance (%RER) was calculated.

RESULTS

Statistically significant differences in %SMHR were observed for the test dentifrice compared with the placebo dentifrice from the 60-min timepoint onwards (all p < 0.02; mean difference of 8.66 [95% CI 3.46, 13.87] at 60 min). At each specimen removal time, %RER and EFU were statistically significantly higher for the test dentifrice compared with the placebo dentifrice (p < 0.0001 for all). No treatment-related or serious adverse events were reported.

CONCLUSIONS

The NaF-containing anti-erosion, dentin hypersensitivity dentifrice improved remineralisation of acid-softened enamel starting at 60 min of intra-oral exposure. It also improved enamel erosion resistance and fluoride uptake as early as 5 min after exposure to fluoridated dentifrice slurry.

CLINICAL RELEVANCE

Brushing with a NaF-containing dentifrice can rapidly improve remineralisation, enamel erosion resistance and fluoride uptake.

Phosphoryl oligosaccharides of calcium enhance mineral availability and fluorapatite formation

OBJECTIVES

Phosphoryl oligosaccharides of calcium (POs-Ca) are a highly soluble calcium source and can keep the solubility of calcium and fluoride ions. The aim of this study was to investigate the effect of calcium (from POs-Ca) and fluoride ions penetrate into subsurface enamel lesions in vitro.

DESIGN

Demineralized bovine enamel slabs were remineralizedin vitro for 24 h at 37 °C with artificial saliva (AS) containing POs-Ca and various fluoride concentrations (0-100 ppm), or AS containing different levels of POs-Ca adjusted to a Ca/P ratio of 0.4-3.0 and fluoride, then were analyzed using Transversal microradiography. From those results, remineralization effects with optimal conditions were compared between POs-Ca and calcium chloride (CaCl₂). To determine the form of incorporated fluoride, we analyzed the chemical state and local structure of fluorine atoms integrated into enamel subsurface lesions using micro X-ray absorption near-edge structure (μ-XANES) spectroscopy.

RESULTS

A significant mineral recovery rate was observed with POs-Ca and fluoride at 0.5 or 1.0 ppm (n = 6, p < 0.05), as well as a Ca/P molar ratio of 1.67 (n = 5, p < 0.05). Under those conditions, the mineral recovery rate of AS containing POs-Ca (37.9 ± 7.3%) was significantly greater than that of CaCl₂ (15.0 ± 9.6%) (n = 5, mean ± SD, p < 0.05). μ-XANES spectra analysis of the samples indicated that the dominant form of fluorine atoms in enamel subsurface lesions was fluorapatite.

CONCLUSIONS

POs-Ca with fluoride-derived diffusion into subsurface enamel lesions facilitated formation of fluorapatite phases.

Enhanced Delivery of F-, Ca2+, K+, and Na+ Ions into Enamel by Electrokinetic Flows

As the outermost layer of the tooth crown, dental enamel is the most mineralized tissue in mammals, consisting of hydroxyapatite crystallites separated by long and narrow nanochannels. A major challenge in dentistry is how various molecules can be infiltrated into these nanopores in an efficient and controlled way. Here we show a robust method to transport various ions of interest, such as fluoride (F^-), potassium (K⁺), calcium (Ca⁺⁺), and sodium (Na⁺), into these nanopores by electrokinetic flows. It is verified by fluorescence microscopy, laser-scanning confocal microscopy, mass spectrometry, and ion selective electrode technique. Different ions are demonstrated to infiltrate through the entire depth of the enamel layer (~1 mm), which is significantly enhanced penetration compared with diffusion-based infiltration. Meanwhile, transport depth and speed can be controlled by infiltration time and applied voltage. This is the first demonstration of reliably delivering both anions and cations into the enamel nanopores. This technique opens opportunities in caries prevention, remineralization, tooth whitening, and nanomedicine delivery in clinical dentistry, as well as other delivery challenges into various biomaterials such as bones.

Protocols to Study Dental Caries In Vitro: pH Cycling Models

As laboratory models are bridges to in vivo caries studies, they must mirror clinical conditions, where demineralization and remineralization alternate constantly (i.e., pH cycling) and are only interrupted during the very short period of application of investigational products, such as toothpaste or mouth rinse. In view of this, models have been developed, based on pH cycling, to study the anticaries or caries remineralizing effects of substances. The pH cycling models have long been accepted and utilized by the scientific community and the toothpaste industry as an appropriate alternative to animal caries testing, particularly for ionic fluoride-based dentifrices. Several pH cycling models have been developed and described in the literature over the years. However, in this chapter, we crudely categorize them into two types: according to what the investigational product is tailored to achieve, i.e., prevention of caries development (net demineralization) or remineralization of early caries (net remineralization). Thus the models are termed "demineralization" or "remineralization" models and are described in details here together with their disadvantages and applications.

Influence of Ultrapulsed CO2 Laser, before Application of Different Types of Fluoride, on the Increase of Microhardness of Enamel In Vitro

Objective

To evaluate the influence of ultrapulsed CO₂ laser in combination with commercial fluoride products in order to verify the increase of microhardness of artificial enamel caries lesions.

Materials and Methods

Bovine enamel specimens were prepared, and artificial enamel caries lesions were created. Teeth were randomly divided into 5 groups (n=10): treated with laser (L), laser + neutral fluoride gel 2% (LNF), laser + acidulated phosphate fluoride gel 1.23% (LAFG), laser + acidulated fluoride mousse 1.23% (LAFM), and laser + fluoride varnish 5% (LFV). Microhardness was evaluated at baseline, after caries induction, after CO₂ laser irradiation + fluoride treatment in the 1st week, and after fluoride treatment at 3rd and 5th week.

Results

There was a decrease in microhardness in all groups after artificial enamel caries lesion formation; no increase in microhardness was found in the first and third weeks in all groups (p > 0.05). In the fifth week, an increase in microhardness occurred in all groups (p < 0.05).

Conclusion

Although CO2 laser irradiation in combination with different commercial fluoride products was capable of increasing microhardness on enamel caries lesions in bovine tooth enamel it is necessary to confirm these results by testing the isolated effect of fluoride on enamel surface microhardness. Also, although microhardness was higher in the fluoride varnish group than in the other groups in the fifth week it is not possible to discard the best effect of fluoride varnish treatment on absence of artifacts that may occur with the other fluoride treatments.

Clinical Relevance

In order to prove that CO2 laser may contribute to an increase in microhardness when applied to enamel lesions in combination with different commercial fluoride products it is necessary to conduct additional studies. Also, higher microhardness of fluoride varnish group should be carefully considered.

Selective Ablation of Carious Lesions using an Integrated Near-IR Imaging System and a Novel 9.3-µm CO2 Laser

Previous studies have shown that reflectance imaging at wavelengths greater than 1200-nm can be used to image demineralization on tooth occlusal surfaces with high contrast and without the interference of stains. In addition, these near-IR imaging systems can be integrated with laser ablation systems for the selective removal of carious lesions. Higher wavelengths, such as 1950-nm, yield higher lesion contrast due to higher water absorption and lower scattering. In this study, a point-to-point scanning system employing diode and fiber lasers operating at 1450, 1860, 1880, and 1950-nm was used to acquire reflected light images of the tooth surface. Artificial lesions were imaged at these wavelengths to determine the highest lesion contrast. Near-IR images at 1880-nm were used to demarcate lesion areas for subsequent selective carious lesion removal using a new compact air-cooled CO₂ laser prototype operating at 9.3-µm. The highest lesion contrast was at 1950-nm and the dual NIR/CO₂ laser system selectively removed the simulated lesions with a mean loss of only 12-µm of sound enamel.

Effects of nicomethanol hydrofluoride on dental enamel and synthetic apatites: a role for anti-caries protection

Aim

To analyse the anti-caries properties of nicomethanol hydrofluoride (NH) and the benefit of its combination with siliglycol, a coating agent.

Methods

Fluoride (F) uptake by dental enamel and synthetic apatite treated with NH was measured in vitro and compared to treatment with mineral fluorides. The addition of siliglycol was also tested. The effect of NH (as a mouthwash) on salivary pH was also investigated in healthy human subjects and compared to the effect of a placebo and of nicomethanol alone.

Results

In vitro experiments showed a greater and faster F uptake on dental enamel or synthetic apatite treated with NH compared to sodium fluoride. F uptake was improved further by the addition of siliglycol. In healthy human subjects, pH reduction was strongly inhibited 5 min after two mouthrinses with NH. This effect was less pronounced but still statistically significant at 15 and 30 min (p < 0.05).

Conclusions

NH was able to promote the fixation of F ions and strengthen the dental structure. Its combination with siliglycol further improved F uptake by the tooth and the control/inhibition of dental biofilm development.

Fluoride supplementation (with tablets, drops, lozenges or chewing gum) in pregnant women for preventing dental caries in the primary teeth of their children

BACKGROUND

Dental caries (tooth decay) is one of the most common chronic childhood diseases. Caries prevalence in most industrialised countries has declined among children over the past few decades. The probable reasons for the decline are the widespread use of fluoride toothpaste, followed by artificial water fluoridation, oral health education and a slight decrease in sugar consumption overall. However, in regions without water fluoridation, fluoride supplementation for pregnant women may be an effective way to increase fluoride intake during pregnancy. If fluoride supplements taken by pregnant women improve neonatal outcomes, pregnant women with no access to a fluoridated drinking water supply can obtain the benefits of systemic fluoridation.

OBJECTIVES

To evaluate the effects of women taking fluoride supplements (tablets, drops, lozenges or chewing gum) compared with no fluoride supplementation during pregnancy to prevent caries in the primary teeth of their children.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 25 January 2017); the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 11) in the Cochrane Library (searched 25 January 2017); MEDLINE Ovid (1946 to 25 January 2017); Embase Ovid (1980 to 25 January 2017); LILACS BIREME Virtual Health Library (Latin American and Caribbean Health Science Information database; 1982 to 25 January 2017); and CINAHL EBSCO (Cumulative Index to Nursing and Allied Health Literature; 1937 to 25 January 2017). We searched the US National Institutes of Health Ongoing Trials Register (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform for ongoing trials to 25 January 2017. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of fluoride supplements (tablets, drops, lozenges or chewing gum) administered to women during pregnancy with the aim of preventing caries in the primary teeth of their children.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the titles and abstracts (when available) of all reports identified through electronic searches. Two review authors independently extracted data and assessed risk of bias, as well as evaluating overall quality of the evidence utilising the GRADE approach. We could not conduct data synthesis as only one study was included in the analysis.

MAIN RESULTS

Only one RCT met the inclusion criteria for this review. This RCT showed no statistical difference on decayed or filled primary tooth surfaces (dfs) and the percentage of children with caries at 3 years (risk ratio (RR) 1.46, 95% confidence interval (CI) 0.75 to 2.85; participants = 938, very low quality of evidence) and 5 years old (RR 0.84, 95% CI 0.53 to 1.33; participants = 798, very low quality of evidence). The incidence of fluorosis at 5 years was similar between the group taking fluoride supplements (tablets) during the last 6 months of pregnancy and the placebo group.

AUTHORS' CONCLUSIONS

There is no evidence that fluoride supplements taken by women during pregnancy are effective in preventing dental caries in their offspring.

Remineralizing potential of a 60-s in vitro application of Tooth Mousse Plus

BACKGROUND

No published studies exist on the remineralizing potential of Tooth Mousse Plus^® (TMP) when applied for less than 3 min.

AIM

To evaluate (i) the remineralizing potential of TMP on artificial carious lesions, when applied thrice daily for 60 s, and (ii) the benefit of using a fluoridated dentifrice prior to TMP application.

DESIGN

Carious lesions, 120-200 μm deep, were produced by placing molars in demineralizing solution for 96 h, and sections 100-150 μm thick were then randomly assigned to four groups. Specimens were treated thrice daily with a non-fluoridated (Group A), or 1000 ppm F dentifrice (Group B), or TMP (Group C), or a 1000 ppm F dentifrice followed by TMP application (Group D), and then subjected to a 10-day pH cycling model. Lesion evaluation involved polarizing light microscopy and microradiography.

RESULTS

Post-treatment maximum mineral content at the surface zone (V_max ) was significantly increased and lesion depth (LD) significantly decreased in Group C, while only the V_max increased in Group D. Increase in LD was observed in Group B; however, no significant differences were noted in percentage LD changes between groups B, C, and D (P > 0.05).

CONCLUSIONS

TMP applied for 60 s significantly remineralized the artificial carious lesions. No additional benefit was evident when TMP was preceded by treatment with 1000 ppm F dentifrice.

The innovative applications of therapeutic nanostructures in dentistry

Nanotechnology has paved multiple ways in preventing, reversing or restoring dental caries which is one of the major health care problems. Nanotechnology aided in processing variety of nanomaterials with innovative dental applications. Some showed antimicrobial effect helping in the preventive stage. Others have remineralizing potential intercepting early lesion progression as nanosized calcium phosphate, carbonate hydroxyapatite nanocrystals, nanoamorphous calcium phosphate and nanoparticulate bioactive glass particularly with provision of self-assembles protein that furnish essential role in biomimetic repair. The unique size of nanomaterials makes them fascinating carriers for dental products. Thus, it is recentlyclaimedthat fortifying the adhesives with nanomaterials that possess biological meritsdoes not only enhance the mechanical and physical properties of the adhesives, but also help to attain and maintain a durable adhesive joint and enhanced longevity. Accordingly, this review will focus on the current status and the future implications of nanotechnology in preventive and adhesive dentistry.

Review of Fluoride Release and Secondary Caries Reduction by Fluoridating Composites

Secondary caries is one of the main reasons to replace restorations. Due to the pressure to eliminate or reduce the number of amalgam restorations in many countries, fluoride-releasing composites have gained in importance. This review limits itself to information relevant to secondary caries near fluoride-releasing anterior or posterior composites. Although many parameters are very important in composite functioning, a weak spot near a filling is always the interface and the locally present interfacial gap between the composite and the hard tissues, where secondary caries takes place due to plaque action. Relevant parameters such as the amount of fluoride released in vitro in μg.cm-2, the rate of fluoride release, and the period of fluoride release are compared for several composites. In vitro F release has been measured for some fluoridating composites for more than five years. Unfortunately, F release in vivo or in situ cannot be measured adequately.

The fluoride released by the composites considered is partly taken up by the surrounding tissues, partly released to the saliva, and partly efficacious in possible marginal gaps and defects. A major part of this paper pertains to in vitro, in situ, and in vivo secondary caries reduction experiments. In vitro caries reductions in the order of 40% from F-releasing composites vs. controls have been found. In in situ model investigations under plaque and saliva conditions, secondary caries reduction percentages of between 40 and 50% have been experimentally measured in gaps in enamel near F composites.