Sustained-release delivery systems for treatment of dental diseases

Potential Combinatory Effect of Cannabidiol and Triclosan Incorporated into Sustained Release Delivery System against Oral Candidiasis

Candida albicans is a common fungal pathogen. Biofilm formation on various surfaces is an important determinant of C. albicans pathogenicity. Our previous results demonstrated the high potential of cannabidiol (CBD) to affect C. albicans biofilms. Based on these data, we investigated the possibility of incorporating CBD and/or triclosan (an antimicrobial agent that is widely utilized in dentistry) in a sustained-release varnish (SRV) (SRV-CBD, SRV-triclosan) to increase their pharmaceutical potential against C. albicans biofilm, as well as that of the mixture of the agents into SRV (SRV-CBD/triclosan). The study was conducted in a plastic model, on agar, and in an ex vivo tooth model. Our results demonstrated strong antibiofilm activity of SRV-CBD and SRV-triclosan against C. albicans in all tested models. Both formulations were able to inhibit biofilm formation and to remove mature fungal biofilm. In addition, SRV-CBD and SRV-triclosan altered C. albicans morphology. Finally, we observed a dramatic enhancement of antibiofilm activity when combined SRV-CBD/triclosan was applied. In conclusion, we propose that incorporation of CBD or triclosan into SRV is an effective strategy to fight fungal biofilms. Importantly, the data demonstrate that our CBD/triclosan varnish is safe, and is not cytotoxic for normal mammalian cells. Furthermore, we propose that CBD and triclosan being in mixture in SRV exhibit complementary antibiofilm activity, and thus can be explored for further development as a potential treatment against fungal infections.

Sustained release of a novel anti-quorum-sensing agent against oral fungal biofilms

Thiazolidinedione-8 (S-8) has recently been identified as a potential anti-quorum-sensing/antibiofilm agent against bacteria and fungi. Based on these results, we investigated the possibility of incorporating S-8 in a sustained-release membrane (SRM) to increase its pharmaceutical potential against Candida albicans biofilm. We demonstrated that SRM containing S-8 inhibits fungal biofilm formation in a time-dependent manner for 72 h, due to prolonged release of S-8. Moreover, the SRM effectively delivered the agent in its active form to locations outside the membrane reservoir. In addition, eradication of mature biofilm by the SRM containing S-8 was also significant. Of note, S-8-containing SRM affected the characteristics of mature C. albicans biofilm, such as thickness, exopolysaccharide (EPS) production, and morphogenesis of fungal cells. The concept of using an antibiofilm agent with no antifungal activity incorporated into a sustained-release delivery system is new in medicine and dentistry. This concept of an SRM containing a quorum-sensing quencher with an antibiofilm effect could pave the way for combating oral fungal infectious diseases.

Comparison of the efficacy of a novel sustained release clotrimazole varnish and clotrimazole troches for the treatment of oral candidiasis

OBJECTIVES

Candida albicans is a common fungal infection and is commensal in 40-65 % of healthy adults. The development and pharmacokinetics of a novel sustained release clotrimazole varnish (Clot-SRV) for topical oral use have been reported. The aim of this study was to compare the efficacy of this varnish with clotrimazole troche treatment of oral candidiasis.

MATERIALS AND METHODS

Of the 12 patients with denture stomatitis treated for 14 days, six used Clot-SRV (study group) and six clotrimazole troches (control). The patients were instructed to use Clot-SRV (50 mg of clotrimazole) once a day, and the control group was instructed to use five troches of 10 mg clotrimazole/day. Microbiological samples were obtained from saliva, buccal mucosa, palate, and denture. The degree of erythema was recorded at three time points, and subjective opinions noted using a questionnaire.

RESULTS

At the end of the study, the control group had relatively more cases of erythema on all examined surfaces; patients who applied the Clot-SRV had significantly lower levels of candida on the denture surfaces and in saliva, and had better compliance to the medication.

CONCLUSIONS

The novel clotrimazole sustained release varnish may be an important part of a new protocol for oral candidiasis, with improved clinical outcomes.

Levels of sirolimus in saliva and blood following mouthwash application

OBJECTIVES

Sirolimus (rapamycin) is a mammalian target of rapamycin (mTOR) inhibitor with antiproliferative activity. Its systemic administration is currently evaluated for the management of squamous cell carcinoma and various oral disorders. Topical oral application can enhance availability, efficacy and improve safety and compliance. Our objective was to evaluate the release profile and the safety of a sirolimus mouthwash.

SUBJECTS AND METHODS

A sirolimus mouthwash (0.05 mg ml(-1) ) was applied to ten healthy male volunteers. Saliva and blood samples were taken after rinsing. Mass spectrometry and chemiluminescent microparticle immunoassay were used to determine saliva and blood levels of sirolimus. A topical oral release profile measurement and safety evaluation were performed.

RESULTS

After rinsing with the mouthwash, a classic immediate release profile was noted in the oral cavity. Extremely high initial sirolimus levels rapidly declined over a 4-hour period. Systemic exposure was limited, with a maximum level significantly lower than therapeutic doses, and safety was confirmed.

CONCLUSIONS

A single rinse with sirolimus mouthwash leads to high transient levels of the drug in the saliva. Although levels were variable, a therapeutic concentration was achieved topically along with minimal systemic absorption. These results broaden the potential clinical use of oral topical rapalogs.

Fluoride and chlorhexidine release from filled resins

Resin-based materials that release either fluoride or chlorhexidine have been formulated for inhibiting caries activity. It is not known if the two agents, when incorporated into one material, would interact and affect their release potential. We hypothesized that the ratio of fluoride to chlorhexidine incorporated into a resin, and the pH of the storage medium, will affect their releases from the material. The material investigated contained 23 wt% of filler, and the ratios of calcium fluoride to chlorhexidine diacetate were 8/2, 5/5, and 2/8. The release was conducted in pH 4, 5, and 6 acetate buffers. The results showed that release of either agent increased as the pH of the medium decreased. The presence of fluoride salt substantially reduced the chlorhexidine release, while the presence of a specific quantity of chlorhexidine significantly increased fluoride release. This interaction can be utilized to optimize the release of either agent for therapeutic purposes.

A novel sustained-release clotrimazole varnish for local treatment of oral candidiasis

The use of dental varnish for therapeutic purposes has been reported for fluoride or antibacterial drugs. Our objectives were to develop a sustained-release varnish containing an antifungal drug (clotrimazole) for topical application and to evaluate the release rate of the drug in human saliva in comparison with an available commercial troche and their acceptance by healthy volunteers. Following in vitro optimization of the release rate from the varnish, we have embarked on a crossover comparative study assessing the oral sensations and pharmacokinetics of a 10-mg clotrimazole oral troche versus a 10-mg sustained-release clotrimazole varnish in 14 human volunteers over a period of 5 h. Saliva samples were assessed for clotrimazole concentration by high performance liquid chromatography analysis. The volunteers' evaluation of the varnish and troche (taste, other sensory changes, convenience, and oral suitability) were recorded. At all time points, salivary clotrimazole concentrations were higher, and the terminal half-life was significantly prolonged in the varnish group in comparison to the control group. This can be attributed to continuous release of clotrimazole from the varnish formulation. The duration of the drug over the minimal inhibitory concentration, following application of the varnish, was more than threefold longer than following administration of the troche. The developed sustained-release varnish can be applied in patients at a lower frequency than troches, thus, achieving higher patient compliance and efficacy. This novel varnish application can serve as the basis for a new treatment approach to oral candidiasis, a very common chronic opportunistic infection with improved clinical outcome.

Drug delivery strategies for common orofacial diseases

There are many types of diseases associated with the oral cavity. As an adjunct to professional oral dental care, various drug delivery systems have been developed to improve the treatment or prevention of these diseases. In this manuscript, the current status of drug delivery strategies for these common orofacial diseases is reviewed. Biomineral-binding drug delivery and on-demand drug release are suggested to be considered in the future design of drug delivery systems for orofacial diseases. Apparently, this research field deserves much more attention from both pharmaceutical scientists and dental health professionals.

Preparation and characterization of triclosan nanoparticles for periodontal treatment

The aim of this work was to produce and characterize triclosan-loaded nanoparticles (NPs) by the emulsification-diffusion process, in an attempt to obtain a novel delivery system adequate for the treatment of periodontal disease. The NPs were prepared using poly(D,L-lactide-co-glycolide) (PLGA), poly(D,L-lactide) (PLA) and cellulose acetate phthalate (CAP). Poly(vinyl alcohol) (PVAL) was used as stabilizer. Batches were prepared with different amounts of triclosan (TCS) in order to evaluate the influence of drug on NP properties. Solid NPs of less than 500 nm in diameter were obtained. Entrapment efficiencies were higher than 63.8%. The characterization by scanning electron microscopy and light scattering indicated that high concentrations of TCS seemingly caused the increase of NP mean size. A decrease in the PLGA glass transition temperature was observed by differential scanning calorimetry. This could indicate that TCS in PLGA-NPs behaves as a non-conventional plasticizer. Subsequently, in vitro release studies were carried out under sink conditions using a device designed in our laboratory to allow a direct contact between the particles and the dissolution medium. A fast release of TCS from NPs was detected. A preliminary in vivo study in dogs with induced periodontal defects suggested that TCS-loaded NPs penetrate through the junctional epithelium.

Development of a system to adsorb drugs onto calcium phosphate materials

Several studies were carried out in order to reduce the systemic use of antibiotics due to the high concentration required to provide the minimum inhibitory concentration (MIC) at infected sites. The aim of this study was to develop a system of drug adsorption onto commercial hydroxyapatite (HA, Ca10(PO4)6(OH)2) and glass reinforced hydroxyapatite (GR-HA) granules. The drug will then be released for the local treatment of periodontitis. The antibiotics used in this study were metronidazole, a specific antibiotic indicated for the systemic treatment of periodontitis, and ampicillin, a wide spectrum antibiotic. UV spectroscopy was used to measure the amount of drug adsorbed onto HA and GR-HA granules. Results showed that metronidazole was unable to adsorb on the material's surface, as opposed to ampicillin which adsorbed both onto HA and GR-HA. Preliminary release kinetics studies were carried out using a flow through dissolution system. Results are discussed in terms of the influence of the different surface characteristics of the materials on the adsorption processes.

Bone as an effect compartment : models for uptake and release of drugs

"Bone-seeking agents" are drugs characterised by high affinity for bone, and are disposed in bone for prolonged periods of time while maintaining remarkably low systemic concentrations. As a consequence, the bone becomes a reservoir for bone-seeking agents, and a site of both desirable and adverse effects, depending on the pharmacological activities of the specific agent. For some agents, significant systemic effects may also be produced following their prolonged release from bone, a process that is governed mostly by the rate of bone remodelling. This review covers the pharmacokinetic and pharmacodynamic features of bone-seeking agents with different pharmacological properties, including drugs (bisphosphonates, drug-bisphosphonate conjugates, radiopharmaceuticals and fluoride), bone markers (tetracycline, bone imaging agents) and toxins (lead, chromium, aluminium). In addition, drugs that do not possess bone-seeking properties but are used for therapy of bone diseases (such as antibacterials for treatment of osteomyelitis) are discussed, along with targeting of these drugs to the bone by conjugation to bone-seeking agents, local delivery systems, and other approaches. The pharmacokinetic and pharmacodynamic behaviour of bone-seeking agents is extremely complex due to heterogeneity in bone morphology and physiology. This complexity, accompanied by difficulties in human bone research caused by ethical and other limitations, gave rise to modelling approaches to study bone drug disposition. This review describes the pharmacokinetic models that have been proposed to describe the pharmacokinetic behaviour of bone-seeking agents and predict bone concentrations of these agents for different doses and patient populations. Models of different types (compartmental and physiologically based) and of different complexity have been applied, but their relevance to drug effects in the bone tissue is limited since they describe the behaviour of the "average" drug molecule. Understanding of the cellular and molecular processes responsible for the heterogeneity of bone tissue will provide better comprehension of the influence of microenvironment on drug bone disposition and the resulting pharmacological response.

A direct-staining method to evaluate the mucoadhesion of polymers from aqueous dispersion

A novel technique to evaluate polymer adhesion to human buccal cells following exposure to aqueous polymer dispersion, both in vitro and in vivo, is described. Adhering polymer has been visualised by staining with 0.1% (w/v) of either Alcian blue (60 min) or Eosin (10 min) solution, uncomplexed dye being removed by 0.25 M sucrose washings. The extent of polymer adhesion was quantified by measuring the relative staining intensity of control and polymer-treated cells by image analysis. In vitro, Carbopol 974P, polycarbophil (Noveon AA-1) and chitosan (CL 113) were found to adhere to human buccal cells from 0.10% (w/w) aqueous dispersions of these polymers. Following in vivo administration as a mouthwash, these polymers persisted upon the human buccal mucosa for at least 1 h.

The effect of parabens in a mouthwash and incorporated into a sustained release varnish on salivary bacteria

OBJECTIVES

The purpose of this study was to evaluate the antimicrobial efficacy of parabens, in a mouthwash and in a slow release device, against cariogenic bacteria in the oral cavity.

METHODS

Parabens were formulated in a mouthwash or in a topical slow release varnish preparation. In two separate studies, volunteers were asked to use the mouthwash or the slow release varnish applied in a personal night guard device. The levels of mutans streptococci (MS), Lactobacilli (LB) and total cultivated bacteria were measured before and after using the mouthwash or the slow release varnish.

RESULTS

The mouthwash containing parabens had a minor and a short-term effect on MS and LB counts in human saliva. The use of slow release varnish containing parabens, applied in a night guard, had a prolonged antibacterial effect on both MS and LB counts.

CONCLUSIONS

Parabens in a mouthwash had little effect on oral bacteria counts; however, paraben in the slow release device had a significant and an extended effect in reducing oral bacteria. Although substantial reductions in oral bacterial counts were recorded after the use of parabens in a slow release device, this effect could probably be enhanced by an improved pharmaceutical formulation.

Characterization of soluble, salt-loaded, degradable PLGA films and their release of tetracycline

A local drug delivery system has been designed to release tetracycline over a period of 30 days from poly (lactide-co-glycolide) films. Incorporation of either soluble salt excipients or low molecular weight polymeric species has been found to modulate the release kinetics of the system. The following research describes the fabrication of the delivery system, monitors tetracycline release from the system, and fully characterizes the degradation of the polymer films via scanning electron microscopy, gel permeation chromatography, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and X-ray diffraction techniques. Results show that the modulation via use of salts occurs without changing the inherent degradation rate of the system. We suggest that this phenomenon may be due to the increased amount of swelling and uptake of buffer by the films loaded with soluble salt. Uptake, therefore, may be creating microscopic pores that permit further diffusion of tetracycline from the polymer matrix as well as allow the free monomers to leave the system, thereby preventing autocatalysis within the system.

The unusual routes of administration

A wide range of administration routes can be drawn on to optimise drug absorption. Though the oral route remains the favourite one for most drugs in many disease states, other routes are routinely used. Each has its strengths and weaknesses and needs to be selected carefully with full consideration of the drug, its target and the release pattern required. Advances in pharmacology and biopharmaceutics have led to exciting developments in the ways drugs can now be administered. Optimising drug administration means finding answers to a number of questions. These questions include: what, how, when and where to deliver, and how to retain the drug long enough for it to be fully effective. These issues are linked; route of administration, drug and therapeutic systems are interrelated; thus the choice of what to deliver influences how, when and where to deliver. Various definitions of 'usual/unusual' administration routes are presented, depending on the factors that determine the fate of the active ingredients, on the delivery device, and on the therapeutic objectives to be met. The various dosage forms designed for these routes, and the administration strategies developed to achieve the desired effects are described.

Topical metronidazole as an adjunct to subgingival debridement in the treatment of chronic periodontitis

The purpose of this study was to evaluate the clinical effects of a single application of a 5% metronidazole collagen device in periodontal pockets deeper than 5 mm, in association with debridement and without reinforcement of home care and hygiene as practiced by the patient at any time. Pocket depth, attachment level, bleeding on probing, gingival index and plaque index were assessed at baseline, and on days 15, 30 and 90. Analysis of data from 28 patients indicated that both debridement and metronidazole therapy decreased pocket depth, bleeding on probing and gingival index, but results were significantly better with metronidazole. These results indicate that topical metronidazole provides an effective adjunctive treatment of advanced periodontitis.

Microbiological evaluation of the efficacy of chlorhexidine in a sustained-release device for dentine sterilization

The aim of this in-vitro study was to evaluate the effect of chlorhexidine in solution and in a sustained-release device as an intracanal medication. Hollow cylindrical dentine specimens prepared from bovine incisors were incubated with Streptococcus faecalis for a period of 3 weeks. The intracanal medicaments tested were 0.2% chlorhexidine gluconate solution (CH), chlorhexidine in a sustained-release device (1.2 mg) (SBD), camphorated paramonochlorophenol (CMCP), and a control (no medication). Each medicament was introduced into the lumen of one dentine specimen and incubated for 5 min, 24 h, 48 h or 7 days at 37 degrees C. The bacteriological samples were taken by shaving the dentine inside the lumen with dental burs ranging in size from ISO 023-033. The dentine powder was collected in test-tubes containing growth medium and incubated for 24 h. The optical density of the medium was recorded by means of a spectrophotometer at a wavelength of 540 nm. There was a statistically significant difference between the control group and all the medicaments tested.

Efficacy of a sustained-release device containing chlorhexidine and Ca(OH)2 in preventing secondary infection of dentinal tubules

This study was conducted to evaluate the efficacy of the antibacterial activity of Ca(OH)2 and a sustained-release device containing chlorhexidine (SRD) in both sterilization and prevention of secondary infection of the root canal system. Bovine root dentine specimens previously incubated with Streptococcus faecalis were used in this experiment. Two different formulations of the SRD (differing in their cross-linkage), Ca(OH)2 and normal saline (control) were evaluated. The degree of bacterial infection of the root canal was tested after incubation periods of 24 h, 72 h and 7 days with these medicaments. Their efficacy in preventing secondary infection after recontamination was tested after 72 h and 7 days. The results demonstrated that both formulations of the SRD significantly reduced the bacterial population in the primary infected groups, as well as preventing secondary infection of the dentinal tubules in the recontaminated group. By contrast, Ca(OH)2 did not show any antibacterial activity, and failed to sterilize the dentinal tubules or prevent secondary infection after recontamination at the time periods examined.

Preventive dental materials: sustained delivery of fluoride and other therapeutic agents

In the 1940's, it was observed that silicate restorative cements were seldom associated with secondary caries. Fissure sealants, designed to protect caries-prone surfaces, appeared in the 1960's. The 1970's and 1980's have seen an increasing emphasis on the use of dental materials for preventive purposes. Glass ionomers, the modern version of silicates, release fluoride and have been available for some time. Polymeric materials that release various therapeutic agents are currently under development for use in topical anesthetic, endodontic, prosthodontic, and periodontal applications. An attachable membrane-reservoir device for oral fluoride delivery will soon be available for general clinical use. Several fluoride-releasing filling and adhesive resins have recently been marketed. These materials are the leading edge of a new class of preventive materials that serve as controlled-release and/or site-specific sources of therapeutic agents. This trend is expected to continue, and the near future should see the introduction of additional oral sustained-delivery systems for use in periodontal and other applications.