Slow-release fluoride devices: a literature review

Intraoral medical devices for sustained drug delivery

OBJECTIVES

The oral cavity constitutes an attractive organ for the local and systemic application of drug substances. Oromucosal tablets, gels, or sprays are examples of the formulations applied. Due to the elution through the saliva, the residence time of the formulation at the application site is relatively short. Medical devices placed in the oral cavity, with a reservoir for an active substance, play an important role in solving this problem.

MATERIALS AND METHODS

In this review, we discuss the devices described in the literature that are designed to be used in the oral cavity, highlighting the advantages, disadvantages, and clinical applications of each of them.

RESULTS

Among the intraoral medical devices, special types are personalized 3D-printed devices, iontophoretic devices, and microneedle patches.

CONCLUSION

We anticipate that with the development of 3D printing and new polymers, the technology of flexible and comfortable devices for prolonged drug delivery in the oral cavity will develop intensively.

CLINICAL RELEVANCE

The presented review is therefore a useful summary of the current technological state, when in fact none of the existing devices has been widely accepted clinically.

Preparation and characterization of NaF/Chitosan supramolecular complex and their effects on prevention of enamel demineralization

Fluoridated mouthrinse is indicated for individuals with high risk of caries. Chitosan (Chit) exhibits antibacterial properties, but little is known about its effects on enamel when combined with sodium fluoride (NaF) to form NaF/Chit supramolecular complexes. In our study, NaF/Chit supramolecular complexes structured as microparticles were synthetized and characterized, and their effects on human enamel were evaluated after cariogenic challenge simulating the daily mouthrinse use. Initially, NaF/Chit complex formation was investigated based on several titrations by measuring the zeta potential, electrical conductivity (κ), hydrodynamic diameter (Dh), viscosity (η) and heat flow (by isothermal titration calorimetry) against the molar ratio [NaF]/[Chitmonomer], which allowed us to identify the interactions between Chit-NaF with a stoichiometry of approximately 0.68. Spontaneous microparticle formation was observed. Samples of enamel blocks were prepared and divided into eight groups (n = 10/group): (i) 0.2% Chit; (ii) 0.2% NaF; (iii) 0.2% NaF/Chit suspension; (iv) 0.2% acetic acid; (v) 0.05% Chit; (vi) 0.05% NaF; (vii) 0.05% NaF/Chit suspension; and (viii) 0.05% acetic acid. Cariogenic challenge was performed in each sample by cycling in demineralization and remineralization solutions for 7 days. Before each demineralization cycle, the corresponding substances were passively applied daily for 90 s, even in groups with 0.02% concentration. After 7 days, samples were examined for Knoop hardness (KHN) measurements. The data were analyzed by repeated-measures ANOVA and Tukey tests (α = 0.05). The 0.2% NaF and 0.2% NaF/Chit groups showed higher KHNpost-challenge values than the other groups. The 0.2% NaF/Chit microparticle suspension reduced the enamel hardness loss after cariogenic challenge as effectively as the 0.2% NaF solution and demonstrated potential for use in a formulation with anti-caries effects.

3D hydrogel/ bioactive glass scaffolds in bone tissue engineering: Status and future opportunities

Repairing significant bone defects remains a critical challenge, raising the clinical demand to design novel bone biomaterials that incorporate osteogenic and angiogenic properties to support the regeneration of vascularized bone. Bioactive glass scaffolds can stimulate angiogenesis and osteogenesis. In addition, natural or synthetic polymers exhibit structural similarity with extracellular matrix (ECM) components and have superior biocompatibility and biodegradability. Thus, there is a need to prepare composite scaffolds of hydrogels for vascularized bone, which incorporate to improve the mechanical properties and bioactivity of natural polymers. In addition, those composites' 3-dimensional (3D) form offer regenerative benefits such as direct doping of the scaffold with ions. This review presents a comprehensive discussion of composite scaffolds incorporated with BaG, focusing on their effects on osteo-inductivity and angiogenic properties. Moreover, the adaptation of the ion-doped hydrogel composite scaffold into a 3D scaffold for the generation of vascularized bone tissue is exposed. Finally, we highlight the challenges and future of manufacturing such biomaterials.

3D printing of a controlled fluoride delivery device for the prevention and treatment of tooth decay

Dental decay is a highly prevalent chronic disease affecting people from all ages. Clinically, fluoride supplementation is the primary strategy in the prevention of dental decay. However, the current existing self-application formulations such as gels or mouthwashes are rapidly cleared after administration, resulting in modest efficacy even after repeated applications. Therefore, a user-friendly formulation that can provide sustained fluoride release in the oral cavity is of great interest for dental decay prevention. Herein, we report the utilization of fused deposition modelling to fabricate personalised mouthguards, which allow local and prolonged fluoride elution. Composite filaments comprising sodium fluoride and polymers with tuneable hydrophobicity were produced using blends of poly(ε-caprolactone) (PCL) and poly(vinyl alcohol) or poly(ethylene glycol) (PEG). The materials exhibited suitable mechanical properties for dental devices as well as different release kinetics depending on their composition. Ex vivo studies were performed on decayed human teeth using the 3D printed tooth caps that precisely fit the complex geometries of each specimen. A significant elevation of fluoride content in the lesion mineral in contact with the PCL/PEG tooth caps was achieved compared to the ones in contact with solutions mimicking dental care products. In conclusion, this study suggested that a sustained localized drug release of fluoride from personalised 3D printed mouthguards at the device-enamel interface can improve the incorporation of fluoride in the tooth matrix and prevent lesion progression.

The effect of layered double hydroxide on fluoride release and recharge from a commercial and an experimental resin varnish

OBJECTIVES

Layered Double Hydroxide (LDH) is capable of fluoride anion exchange and release. This study investigated the effects of incorporating ZnAl-LDH in commercial and experimental dental varnishes, on fluoride release and re-release after charging in NaF.

METHODS

Five discs of each material (commercial ClinproXT varnish and experimental light cured resin varnish), with and without 9%ZnAl-LDH were immersed and agitated in deionised water (DW) at 37 °C. A fluoride ion selective electrode measured fluoride release in DW daily over two-weeks. At 3, 6, 9 and 12 days the discs were recharged in 15 ml 0.05 M NaF solution (37 °C) for five minutes followed by immersion in DW. Energy dispersive X-ray spectra (EDS), weight changes and SEMs were performed on discs, before and after each cycle.

RESULTS

Evidence of ZnAl-LDH was confirmed by the presence of peaks for zinc and aluminium in EDS spectra. Cumulative fluoride and mean fluoride released between Clinpro, Clinpro + LDH and resin were significantly different (ANOVA, Tukey's HSD post-hoc test, p < 0.001) except between the resin and resin + LDH. Mean fluoride concentrations differed significantly after every recharge between Clinpro, Clinpro + LDH and resin, but not between the resin and resin + LDH (p < 0.01). The weights and SEMs of the experimental resins +/-LDH, appeared to be stable whilst the weights of Clinpro samples +/-LDH, fluctuated and fragmented.

SIGNIFICANCE

ClinproXT and experimental resin containing ZnAl-LDH recharged with fluoride did not significantly increase fluoride release compared to the unmodified materials. However, all LDH-F incorporated materials demonstrated fluoride recharging properties which appear beneficial to dentistry and thus further work is required to improve these properties.

Clinical and Antimicrobial Evaluation of Copaifera langsdorffii Desf. Dental Varnish in Children: A Clinical Study

Background

The objective of this study was to evaluate the clinical and microbiological efficacies of (C. langsdorffii) dental varnish in children at high risk of dental caries..

Methods

This is a longitudinal, randomized, controlled clinical trial. Ninety high-risk caries-free children (ICDAS II = 0) were recruited and randomly divided into three groups: C. langsdorffii, chlorhexidine, or fluoride. The varnishes were applied on the second deciduous molars for three times: baseline (D0), after 90 days (D90), and after 180 days (D180). Saliva was collected on D0, D90, D180, and D360 to evaluate S. mutans reduction. Statistics were carried out by ANOVA, Tukey's test, and the paired t-test.

Results

Copaiba varnish demonstrated significant S. mutans reduction: D360 versus D0 (p < 0.0001), D180 versus D0 (p < 0.001), D360 versus D90 (p < 0.001), D180 versus D90 (p < 0.001), and D360 versus D180 (p < 0.05). Chlorhexidine varnish significantly reduced S. mutans at D180 versus D0 (p < 0.05). Fluoride reduced at D180 versus D0 (p < 0.001).

Conclusions

Three annual applications of this varnish showed substantial antimicrobial activity against S. mutans and caries prevention for up to 12 months.

Unravelling the dissolution mechanism of polyphosphate glasses by 31P NMR spectroscopy: ligand competition and reactivity of intermediate complexes

Phosphate glass dissolution can be tailored via compositional and subsequent structural changes, which is of interest for biomedical applications such as therapeutic ion delivery. Here, solid-state ³¹P nuclear magnetic resonance characterisation of 45P₂O₅-xCaO - (55 -x)Na₂O glasses was correlated with dissolution studies using time-dependent liquid ³¹P NMR spectroscopy and quantitative chemical analysis. Glasses dissolved congruently in aqueous media, and the first dissolution stage was the hydration of phosphate chains. In deionised water and Tris buffer (pH₀ 7.4 or 7.9), trimetaphosphate rings and orthophosphates were the predominant species in solution, indicating relatively fast degradation. By contrast, long phosphate chains were identified in EDTA (pH₀ 10.0). Besides pH differences, coordination of phosphate species by metal cations appears to play a catalytic role in the hydrolysis mechanism via turning phosphorus atoms into suitable electrophiles for the subsequent nucleophilic attack by water. Hydrolysis rates were proportional to phosphate complex stability, with stronger complexes for chains than for rings. A competition between solvent and phosphate species for the metal ion occurred in the order EDTA > Tris > deionised water.

Emerging Applications of Drug Delivery Systems in Oral Infectious Diseases Prevention and Treatment

The oral cavity is a unique complex ecosystem colonized with huge numbers of microorganism species. Oral cavities are closely associated with oral health and sequentially with systemic health. Many factors might cause the shift of composition of oral microbiota, thus leading to the dysbiosis of oral micro-environment and oral infectious diseases. Local therapies and dental hygiene procedures are the main kinds of treatment. Currently, oral drug delivery systems (DDS) have drawn great attention, and are considered as important adjuvant therapy for oral infectious diseases. DDS are devices that could transport and release the therapeutic drugs or bioactive agents to a certain site and a certain rate in vivo. They could significantly increase the therapeutic effect and reduce the side effect compared with traditional medicine. In the review, emerging recent applications of DDS in the treatment for oral infectious diseases have been summarized, including dental caries, periodontitis, peri-implantitis and oral candidiasis. Furthermore, oral stimuli-responsive DDS, also known as "smart" DDS, have been reported recently, which could react to oral environment and provide more accurate drug delivery or release. In this article, oral smart DDS have also been reviewed. The limits have been discussed, and the research potential demonstrates good prospects.

Dose-response evaluation of a copaiba-containing varnish against streptococcus mutans in vivo

INTRODUCTION

Dental caries is the most prevalent disease in humans and its incidence is particularly high during childhood. The use of medicinal plants is a common practice in Brazil.

OBJECTIVE

To evaluate the optimal antimicrobial concentration of Copaifera langsdorffii (copaiba) oil-resin, in the form of dental varnish, against Streptococcus mutans (S. mutans) in children.

METHODS

Twenty-four children, caries-free, aged until 6 years old, were selected to participate in this study. The varnish was applied to the occlusal surfaces of all deciduous molars. The antimicrobial activity was analyzed in saliva, whose collection was conducted in two phases: before applying the copaiba varnish and after use to verify the instantaneous effectiveness of Copaifera langsdorffii dental varnish in the reduction of S. mutans. The microbiological analysis was repeated twice, establishing dilutions of 1:10 mL and 1:100 mL.

RESULTS

Comparisons between different times within the same dilution were carried out by repeated measures analysis of variance (ANOVA) associated with Tukey's multiple comparisons test. Comparisons of conditions prior to and after treatment were performed using the t test for paired samples and it indicated that the 1% formulation promoted a more significant decrease in the number of S. mutans colonies (p = 0,0026).

CONCLUSION

Copaiba oil-resin, in the form of dental varnish, has antimicrobial activity against S. mutans in all the concentrations studied. Further studies to identify the long-term activity and anticaries effect of this varnish are required to establish its use in caries prevention.

3D printing of a wearable personalized oral delivery device: A first-in-human study

Despite the burgeoning interest in three-dimensional (3D) printing for the manufacture of customizable oral dosage formulations, a U.S. Food and Drug Administration-approved tablet notwithstanding, the full potential of 3D printing in pharmaceutical sciences has not been realized. In particular, 3D-printed drug-eluting devices offer the possibility for personalization in terms of shape, size, and architecture, but their clinical applications have remained relatively unexplored. We used 3D printing to manufacture a tailored oral drug delivery device with customizable design and tunable release rates in the form of a mouthguard and, subsequently, evaluated the performance of this system in the native setting in a first-in-human study. Our proof-of-concept work demonstrates the immense potential of 3D printing as a platform for the development and translation of next-generation drug delivery devices for personalized therapy.

Change of salivary fluoride level with intake of fluoride releasing lozenges: A pilot study

AIM

Long-term, low-level fluoride concentrations in saliva are highly effective in caries prevention and remineralization. The aim of the present two-phased study was to test whether fluoride-releasing lozenges compared to placebo significantly raise salivary fluoride levels above baseline achieved by 1100 ppm fluoride toothpaste in a double-blind, crossover pilot study.

METHODS

In phase 1, a four-arm crossover basic study, four participants used one dissolvable lozenge with .25, 0.5, 1 or 1.5 mg fluoride for 1 hour. In phase 2, the three-arm crossover main study, 11 participants used three lozenges per day for 1 hour for 1 week, establishing long-term salivary fluoride levels dissolving 0 (control), 0.5 and 1.5 mg fluoride lozenges. Saliva was collected at baseline; during lozenge use; 5, 15, 30, and 60 minutes later; and early the next morning. Salivary fluoride levels were determined by laboratory diffusion analysis.

RESULTS

In phase 1, 5 minutes after using one lozenge, salivary fluoride levels were above baseline (0.03 ppm), reaching 0.13 ± 0.19 ppm for the 0.25 mg and 0.73 ± 0.75 ppm for the 1.5 mg fluoride lozenge, dropping to baseline after 60 minutes. In phase 2, after 1 week use of 0.5 and 1.5 mg lozenges, respectively, for the 0.5 mg lozenge for 15 minutes and the 1.5 mg lozenge 30 minutes after use, the salivary levels were significantly higher than baseline/control (0.02 ppm). During 1-hour lozenge use, fluoride levels >0.1 ppm were consistently achieved.

CONCLUSIONS

Fluoride lozenges achieved elevated salivary fluoride levels during use, but only for short periods after use.

Antimicrobial activity of copaiba oil (Copaifera ssp.) on oral pathogens: Systematic review

Copaifera ssp. produces an oil-resin that presents antiinflammatory, antitumor, antiseptic, germicidal, antifungal, and antibacterial activity. This systematic review aimed to analyze the antimicrobial action of Copaiba oil against oral pathogens, when compared to that of control substances. A search on Medline/PubMed, LILACS, SciELO, EMBASE, and SCOPUS databases were performed up to March 2017. To be included, the studies needed to perform any antimicrobial activity essay, using copaiba oil and a control substance. The antimicrobial effect of each substance, in each study, was extracted. Eleven studies were included, and several copaiba species were used. All studies showed that copaiba oil, regardless of its species, presented a bactericidal and/or bacteriostatic effect in in vitro analyzes. Only one study showed that the antimicrobial effect of the Copaifera officinalis was similar to the one found in chlorhexidine. A higher risk of bias was detected in most of the included studies. The studies demonstrated that the antimicrobial activity of copaiba oil, in most cases, is lower than chlorhexidine, which is considered the gold standard. However, there is great potential against oral bacteria. Further high quality studies are warranted in order to assess the efficacy of copaiba oil on oral pathogens.

The history of public health use of fluorides in caries prevention

AIM

The aim of our study was to chronologically analyse various public health measures of fluoride use in caries prevention.

METHODS

We systematically searched the PubMed database on the preventive role of fluorides in public health, published from 1984 to 2014. The search process was divided into four steps, where inclusion and exclusion criteria were defined. Qualitative methodology was used for the article analysis. In the research process, the described forms of F use, diversity of the described F agents, and the observed population group were analysed.

RESULTS

In our systematic review, 40 relevant reviews were revealed. Fluorides have been used in many different forms, but only a few studies showed their significant role in public health. Water fluoridation was the most important public health measure. In the recent decades, the number of studies on topical fluorides is constantly rising. The most extensively described topical forms of fluorides are professionally applied fluoride agents and fluoride toothpaste for home-use. The use of fluoride containing toothpaste in caries prevention is a safe and successful public health measure (PHM) if their use is widespread, and it is recommended for all. The results on other topical forms of fluorides are insufficient to be suggested as an important PHM.

CONCLUSIONS

The role of fluorides in public health prevention has changed in accordance with the knowledge about the fluoride cariostatic mechanism. Previously the most important pre-eruptive effect of fluorides was supplemented by the post eruptive effect. Abundant evidence exists to show the effectiveness of systemic and topical fluorides.

Fluoride loaded polymeric nanoparticles for dental delivery

The overall aim of the present paper was to develop fluoride loaded nanoparticles based on the biopolymers chitosan, pectin, and alginate, for use in dental delivery. First, the preparation of nanoparticles in the presence of sodium fluoride (NaF) as the active ingredient by ionic gelation was investigated followed by an evaluation of their drug entrapment and release properties. Chitosan formed stable, spherical, and monodisperse nanoparticles in the presence of NaF and tripolyphoshate as the crosslinker, whereas alginate and pectin were not able to form any definite nanostructures in similar conditions. The fluoride loading capacity was found to be 33-113ppm, and the entrapment efficiency 3.6-6.2% for chitosan nanoparticles prepared in 0.2-0.4% (w/w) NaF, respectively. A steady increase in the fluoride release was observed for chitosan nanoparticles prepared in 0.2% NaF both in pH5 and 7 until it reached a maximum at time point 4h and maintained at this level for at least 24h. Similar profiles were observed for formulations prepared in 0.4% NaF; however the fluoride was released at a higher level at pH5. The low concentration, but continuous delivery of fluoride from the chitosan nanoparticles, with possible expedited release in acidic environment, makes these formulations highly promising as dental delivery systems in the protection against caries development.

Prevention and Treatment of White Spot Lesions in Orthodontic Patients

Decalcification of enamel, appearing as white spot lesions (WSLs), around fixed orthodontic appliances is a major challenge during and after fixed orthodontic treatment by considering the fact that the goal of orthodontic treatment is to enhance facial and dental esthetic appearance. Banded or bonded teeth exhibit a significantly higher rate of WSLs compared to the controls with no braces as fixed appliances and the bonding materials promote retention of biofilms. These lesions are managed in the first step by establishing good oral hygiene habits and prophylaxis with topical fluorides, including high-fluoride toothpastes, fluoride mouthwashes, gels, varnishes, fluoride-containing bonding materials, and elastic ligatures. Recently, other materials and methods have been recommended, including the application of casein phosphopeptides-amorphous calcium phosphate, antiseptics, probiotics, polyols, sealants, laser, tooth bleaching agents, resin infiltration, and microabrasion. This article reviews the currently used methods to manage enamel demineralization during and after orthodontic treatment and the risk factors and preventive measures based on the latest evidence.

Prevention of enamel demineralization with a novel fluoride strip: enamel surface composition and depth profile

There is no topically applicable low concentration fluoride delivery device available for caries prevention. This study was aimed to assess the use of a low concentration (1450 ppm) fluoride strip as an effective fluoride delivery system against enamel demineralization. The enamel surface composition and calcium-deficient hydroxyapatite or toothpaste treatments were investigated using X-ray photoelectron spectroscopy. In vitro enamel demineralization was assayed using a pH cycling model and the dissolution of calcium ions from the treated specimens was quantified using ion chromatography. After 24-hr fluoride-strip treatment, the enamel was covered with a CaF₂ layer which showed a granular morphology of 1 μm in size. Below the CaF₂ layer was a region of mixed fluorapatite and CaF₂. Fluoride infiltrated extensively in enamel to produce highly fluorinated fluorohydroxyapatite. In comparison, low-fluoride-level fluorinated fluorohydroxyapatite was formed on the enamel specimen exposed to toothpaste. The treatments with the fluoride strip as short as 1 hr significantly inhibited enamel demineralization. The fluoride strip was effective for topical fluoride delivery and inhibited in vitro demineralization of enamel by forming CaF₂ and fluoride-containing apatites at the enamel surface. It exhibited the potential as an effective fluoride delivery device for general use in prevention of caries.

31P NMR characterisation of phosphate fragments during dissolution of calcium sodium phosphate glasses

Phosphate glasses in the system P₂O₅-CaO-Na₂O dissolve in aqueous solutions, and their solubility can be varied by changing the glass composition. This makes them of interest for use as controlled release materials, e.g. as degradable implants, devices for the release of trace elements or as fertilizers, but in order to tailor glass solubility to meet specific requirements, we need to further our understanding of their dissolution behaviour and mechanism. The structure of P₂O₅-CaO-Na₂O glasses (P₂O₅ between 55 and 35 mol%; glass structure analysed by ³¹P MAS NMR) changed from a network (55 mol% P₂O₅) to short chains (35 mol%) with decreasing phosphate content. Solubility in Tris buffer showed significant differences with phosphate content and glass structure; dissolution varied between 90% (50 mol% P₂O₅) and 15% (35 mol%) at 24 h. Glasses with high phosphate contents significantly lowered the pH of the solution, while glasses with low phosphate contents did not. Glasses consisting of a phosphate network dissolved by a mechanism involving P-O-P bond hydrolysis, as no Q³ groups but increasing concentrations of Q⁰ (orthophosphate) were found in solution by solution ³¹P NMR. Glasses consisting of chains, by contrast, can dissolve by hydration of entire chains, but hydrolysis also occurred, resulting in formation of Q⁰ and small ring structures. This occurrence of hydrolysis (and thus formation of P-OH groups, which can be deprotonated) caused the pH decrease and explains the variation in solution pH with structure.

Propolis--based chitosan varnish: drug delivery, controlled release and antimicrobial activity against oral pathogen bacteria

Background

Dental caries is the most prevalent oral disease in several Asian and Latin American countries. It is an infectious disease and different types of bacteria are involved in the process. Synthetic antimicrobials are used against this disease; however, many of these substances cause unwarranted undesirable effects like vomiting, diarrhea and tooth staining. Propolis, a resinous substance collected by honeybees, has been used to control the oral microbiota. So, the objective of this study was to develop and characterize sustained-release propolis-based chitosan varnish useful on dental cariogenic biofilm prevention, besides the in vitro antimicrobial activity.

Methods

Three formulations of propolis - based chitosan varnish (PCV) containing different concentrations (5%, 10% and 15%) were produced by dissolution of propolis with chitosan on hydro-alcoholic vehicle. Bovine teeth were used for testing adhesion of coatings and to observe the controlled release of propolis associated with varnish. It was characterized by infrared spectroscopy, scanning electron microscopy, casting time, diffusion test in vitro antimicrobial activity and controlled release. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were tested for the main microorganisms involved in the cariogenic biofilm through the microdilution test in 96-well plates.

Results

The formulations presented a tooth surface adherence and were able to form films very fast on bovine tooth surface. Also, propolis-based chitosan varnishes have shown antimicrobial activity similar to or better than chlorhexidine varnish against all oral pathogen bacteria. All microorganisms were sensitive to propolis varnish and chitosan. MIC and MBC for microorganisms of cariogenic biofilme showed better results than chlorhexidine. Propolis active components were released for more than one week.

Conclusion

All developed formulations turn them, 5%, 10% and 15% propolis content varnish, into products suitable for clinical application on dental caries prevention field, deserving clinical studies to confirm its in vivo activity.

Preparation and optimization of calcium fluoride particles for dental applications

Fluorides are used in dental care due to their beneficial effect in tooth enamel de-/remineralization cycles. To achieve a desired constant supply of soluble fluorides in the oral cavity, different approaches have been followed. Here we present results on the preparation of CaF2 particles and their characterization with respect to a potential application as enamel associated fluoride releasing reservoirs. CaF2 particles were synthesized by precipitation from soluble NaF and CaCl2 salt solutions of defined concentrations and their morphology analyzed by scanning electron microscopy. CaF2 particles with defined sizes and shapes could be synthesized by adjusting the concentrations of the precursor salt solutions. Such particles interacted with enamel surfaces when applied at fluoride concentrations correlating to typical dental care products. Fluoride release from the synthesized CaF2 particles was observed to be largely influenced by the concentration of phosphate in the solution. Physiological solutions with phosphate concentration similar to saliva (3.5 mM) reduced the fluoride release from pure CaF2 particles by a factor of 10-20 × as compared to phosphate free buffer solutions. Fluoride release was even lower in human saliva. The fluoride release could be increased by the addition of phosphate in substoichiometric amounts during CaF2 particle synthesis. The presented results demonstrate that the morphology and fluoride release characteristics of CaF2 particles can be tuned and provide evidence of the suitability of synthetic CaF2 particles as enamel associated fluoride reservoirs.

Iatrogenic possibilities of orthodontic treatment and modalities of prevention

The benefits of orthodontic treatment are numerous and in most cases, the benefits outweigh the possible disadvantages. Orthodontic treatment can play an important role in enhancing esthetics, function, and self-esteem in patients. However, it carries with it the risks of enamel demineralization, tissue damage, root resorption, open gingival embrasures in the form of triangular spaces, allergic reactions to nickel, and treatment failure in the form of relapse. These potential complications are easily avoidable by undertaking certain precautions and timely interventions by both the orthodontist and the patient. The orthodontist must ensure that the patient is aware of the associated risks and stress the importance of the patient's role in preventing these untoward outcomes. The decision whether to proceed with the orthodontic treatment is essentially a risk-benefit analysis, where the perceived benefits of commencing treatment outweigh the potential risks. This article provides an overview of the iatrogenic possibilities of orthodontic treatment and the role of the patient as well as the orthodontist in preventing the associated risks.

Dose-response effects of zinc and fluoride on caries lesion remineralization

The present mechanistic in vitro study aimed to investigate dose-response effects of zinc and fluoride on caries lesion remineralization and subsequent protection from demineralization. Artificial caries lesions were created using a methylcellulose acid gel system. Lesions were remineralized for 2 weeks using citrate-containing artificial saliva which was supplemented with zinc (0-153 μmol/l) and fluoride (1.1 or 52.6 μmol/l) in a 7 × 2 factorial design. Lesions were also remineralized in the absence of zinc and citrate, but in the presence of fluoride. After remineralization, all lesions were demineralized for 1 day under identical conditions. Changes in mineral distribution characteristics of caries lesions after remineralization and secondary demineralization were studied using transverse microradiography. At 1.1 μmol/l fluoride, zinc exhibited detrimental effects on remineralization in a dose-response manner and mainly by preventing remineralization near the lesion surface. At 52.6 μmol/l fluoride, zinc retarded remineralization only at the highest concentration tested. Zinc enhanced overall remineralization at 3.8-15.3 μmol/l. At 76.5 and less so at 153 μmol/l, zinc showed extensive remineralization of deeper parts within the lesions at the expense of remineralization near the surface. Citrate did not interfere with remineralization at 1.1 μmol/l fluoride, but enhanced remineralization at 52.6 μmol/l fluoride. Lesions exhibiting preferential remineralization in deeper parts showed higher mineral loss after secondary demineralization, suggesting the formation of more soluble mineral phases during remineralization. In summary, zinc and fluoride showed synergistic effects in enhancing lesion remineralization, however only at elevated fluoride concentrations.

Intraoral Fluoride-Releasing Devices: A Literature Review

Dental caries still continues to be a problem for majority of the individuals and it can be a serious problem for medically compromised, developmentally disabled and elderly individuals. Water fluoridation, systemic and topical fluorides are used for past many years to supply supplemental fluoride in order to combat dental caries. The latest fluoride research is investigating the use of slow-release devices for the long-term intraoral provision of fluoride. The present review addresses two main types of intraoral fluoride-releasing devices like the copolymer membrane device, glass device containing fluoride and some variations of these devices. These devices can significantly increase the salivary fluoride concentration without substantially affecting the urinary fluoride levels. A significant number of studies have confirmed that intraoral fluoride-releasing devices have great potential for use in preventing dental caries in children, high-caries-risk groups, and irregular dental attenders in addition to a number of other applications. As most of the studies done on these devices are in vitro and in vivo studies, more well-designed clinical trials are necessary to evaluate the results so that these devices can be used clinically.

How to cite this article

Gambhir RS, Kapoor D, Singh G, Singh J, Kakar H. Intraoral Fluoride-Releasing Devices: A Literature Review. World J Dent 2012;3(4):350-354.

Effect of topical application of fluoride gel NaF 2% on enzymatic and non-enzymatic antioxidant parameters of saliva

OBJECTIVE

The aim of the study was to evaluate the effect of topical fluoride gel NaF 2% application on antioxidant parameters of whole saliva from children.

DESIGN

The saliva mechanically stimulated with parafilm was collected from 25 children (6-12 years) attending the Clinic of Paediatric Dentistry of Universidade Cruzeiro do Sul, São Paulo, Brazil, before (control group) and immediately after application of neutral fluoride gel NaF 2% (fluoride-gel group), according to the Standards for Research Using Human Subjects, Resolution 196/96 of the USA National Health Council of 10/10/1996. Afterwards, pre-post ferric-reducing antioxidant power (FRAP), trolox-equivalent antioxidant capacity (TEAC), uric acid, reduced/oxidised glutathione content (GSH/GSSG) and total peroxidase activity (TPO) were evaluated in whole saliva of both groups.

RESULTS

All non-enzymatic antioxidant parameters were augmented by fluoride-gel NaF 2% application, whereas a notable reduction (31%) of peroxidase activity was concomitantly observed in the children's saliva (p ≤ 0.05). Nevertheless, the reducing power of saliva was kept unaltered under these circumstances (p ≤ 0.05).

CONCLUSIONS

Despite the reduced activity of peroxidase (an important antimicrobial and antioxidant enzyme), the topical fluoride gel NaF 2% favourably stimulated the release of non-enzymatic antioxidant components of saliva, sustaining the reducing power of saliva and the natural defences of the oral cavity.

The effect of fluoride slow-releasing devices on fluoride in plaque biofilms and saliva: a randomised controlled trial

AIM

To investigate the effect of the fluoride sustained slow-releasing device (FSSRD) on F levels in unstimulated saliva and undisturbed plaque biofilms over 7 days. The investigation also aimed at studying the effect of patient age on fluoride (F) concentrations in dental plaque biofilms and unstimulated saliva while using the FSSRD.

STUDY DESIGN

This was a randomised control double blind cross-over study.

METHODS

Sixty-five participants between the ages of 6-35 years took part in this study. The mean age of all the participants was 19.22 years with 24 participants aged between 6-16 years (mean age=11.8 years) and 41 participants aged between 16-35 years (mean age=23.57 years). Plaque biofilms were collected using a modification of the plaque generating device (MPGD) [Robinson et al., 1997]. During the whole study period, including a 7 day washout period before the first leg, all participants were asked to use only non-fluoridated toothpaste and to avoid where possible high fluoride containing foods or drinks. Whenever possible, the FSSRD/placebo device (PD) was attached to the second permanent molar, while the MPGD was attached to the first permanent molars in the same upper dental quadrant. At the end of each leg of the study whole, mixed unstimulated saliva was collected from all participants and analysed for F concentration.

STATISTICS

Statistical analysis using paired sample t-test was used to compare the results of F level between test and control groups, while, Spearman's correlation coefficient was used to test the relationship between patient's age and plaque weight against F concentration in plaque and saliva.

RESULTS

There was no statistically significant difference in F concentration in plaque and saliva between the test and control groups when analysed using paired sample t-test (p>0.05). There was no correlation between patient's age and F concentration in dental plaque and saliva (p>0.05), in both the test and control groups.

CONCLUSIONS

Our data showed no effect of the FSSRD in raising F concentrations in dental plaque and unstimulated whole saliva after 7 days. Such levels may require longer periods to become established.

A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics

Several inorganic materials such as special compositions of silicate glasses, glass-ceramics and calcium phosphates have been shown to be bioactive and resorbable and to exhibit appropriate mechanical properties which make them suitable for bone tissue engineering applications. However, the exact mechanism of interaction between the ionic dissolution products of such inorganic materials and human cells are not fully understood, which has prompted considerable research work in the biomaterials community during the last decade. This review comprehensively covers literature reports which have investigated specifically the effect of dissolution products of silicate bioactive glasses and glass-ceramics in relation to osteogenesis and angiogenesis. Particularly, recent advances made in fabricating dense biomaterials and scaffolds doped with trace elements (e.g. Zn, Sr, Mg, and Cu) and investigations on the effect of these elements on the scaffold biological performance are summarized and discussed in detail. Clearly, the biological response to artificial materials depends on many parameters such as chemical composition, topography, porosity and grain size. This review, however, focuses only on the ion release kinetics of the materials and the specific effect of the released ionic dissolution products on human cell behaviour, providing also a scope for future investigations and identifying specific research needs to advance the field. The biological performance of pure and doped silicate glasses, phosphate based glasses with novel specific compositions as well as several other silicate based compounds are discussed in detail. Cells investigated in the reviewed articles include human osteoblastic and osteoclastic cells as well as endothelial cells and stem cells.

Dental caries: A complete changeover, PART III: Changeover in the treatment decisions and treatments

Comprehensive management of dental caries should involve the management of disease as well as the lesion. Current decision making process in cariology is influenced by numerous factors such as the size/ depth/ activity of the carious lesion and age/ the caries risk status of the patient. Treatment decisions should involve planning the non-operative/ preventive treatment for non-cavitated or early cavitated lesions and also formulating operative treatment for cavitated lesions. Apart from these two responsibilities, a clinician should also be knowledgeable enough to decide when not to interfere in the caries dynamics and how frequently to recall the patient for follow-ups. The non-operative treatment prescriptions vary in dose, intensity and mode of delivery according to the caries risk status. Minimal invasion and maximal conservation of tooth structure has become the essence of current operative treatments. This part of the series elaborates on the paradigm shift in the management of dental caries.

Novel technologies for the prevention and treatment of dental caries: a patent survey

IMPORTANCE OF THE FIELD

Dental caries is one of the most common preventable childhood diseases; people are susceptible to this ailment throughout their lifetime. In the US, 90% of late adolescents and young adults have dental caries, while 94% of all dentate adults had evidence of treated or untreated coronal caries. Dental caries is often not self-limiting and without proper care can progress until the tooth is destroyed.

AREAS COVERED IN THIS REVIEW

In this paper, the etiology of dental caries is briefly introduced. It is followed by a thorough review of patents and literatures on the recent development of various novel technologies for the prevention and treatment of dental caries.

WHAT THE READER WILL GAIN

Recent advances in anti-plaque agents, including chemoprophylactic agents, antimicrobial peptides, vaccines, probiotics/replacement therapy and sugar substitutes, and remineralization agents including fluorides and casein phosphopeptides are analyzed. TAKE HOME MASSAGE: Both the discovery of new anti-caries agents and the development of dentotropic delivery systems will be the future focus of this research field.

A review of slow-release fluoride devices

BACKGROUND

Fluoride has been used to combat dental caries using a number of different clinical approaches. An exciting relatively new development is fluoride slow-releasing devices that consistently elevate intra-oral fluoride levels of plaque and saliva for prolonged periods of up to two years.

METHODS

The literature on the use of slow-releasing fluoride devices in dentistry were reviewed. A Medline search on key words was carried out. All papers in English were individually reviewed.

RESULTS

Slow-releasing fluoride devices have been shown to be effective in elevating salivary fluoride levels in both animals and human studies and to enhance the remineralisation of dental enamel. They have been demonstrated to be safe to use and without the risk of fluoride toxicity. A double blind randomised clinical trial demonstrated 76% fewer new carious surface increment in high caries-risk children after two years.

CONCLUSIONS

These devices have a number of potential uses in dentistry and in particular have great potential for caries prevention of non-compliant high caries-risk groups.

In vitro remineralization of enamel by polymeric amorphous calcium phosphate composite: quantitative microradiographic study

OBJECTIVE

This study explores the efficacy of an experimental orthodontic amorphous calcium phosphate (ACP) composite to remineralize in vitro subsurface enamel lesions microradiographically similar to those seen in early caries.

METHODS

Lesions were artificially created in extracted human molars. Single tooth sections a minimum of 120microm thick were cut and individually placed in holders exposing only the carious enamel surface. The exposed surfaces were either left untreated (control) or coated with a 1mm thick layer of the experimental ACP composite (mass fraction 40% zirconia-hybridized ACP and 60% photo-activated resin), or a commercial fluoride-releasing orthodontic cement. The composite-coated sections were then photo-cured and microradiographic images were taken of all three groups of specimens before the treatment. Specimens were then cyclically immersed in demineralizing and remineralizing solutions for 1 month at 37 degrees C to simulate the pH changes occurring in the oral environment. Microradiographs of all specimens were taken before and after treatment.

RESULTS

Quantitative digital image analysis of matched areas from the contact microradiographs taken before and after treatment indicated higher mineral recovery with ACP composites compared to the commercial orthodontic F-releasing cement (14.4% vs. 4.3%, respectively), while the control specimens showed an average of 55.4% further demineralization.

SIGNIFICANCE

Experimental ACP composite efficiently established mineral ion transfer throughout the body of the lesions and restored the mineral lost due to acid attack. It can be considered a useful adjuvant for the control of caries in orthodontic applications.