Comparison of antiplaque agents using an in vitro assay reflecting oral conditions

In vitro properties of orthodontic adhesives with fluoride or amorphous calcium phosphate

This in vitro study evaluated the efficacy of orthodontic adhesives with fluoride or amorphous calcium phosphate (ACP) in reducing bacterial adhesion and enamel demineralization. Forty human premolars each sectioned buccolingually into three parts were bracketed with control resin (Transbond XT) or adhesives containing ACP (Aegis Ortho) or fluoride (QuickCure). Artificial lesions induced by pH cycling were examined by X-ray photoelectron spectrophotometry (XPS) and polarized light microscopy (PLM). After 28 days, Aegis Ortho demonstrated the lowest calcium and phosphorous content by XPS analysis. After 42 days, reductions in lesion depth areas were 23.6% for Quick Cure and 20.3% for Aegis Ortho (P < 0.05). In the presence of 1% sucrose, adhesion of Streptococcus mutans to Aegis Ortho and Quick Cure was reduced by 41.8% and 37.7% (P < 0.05) as compared to Transbond XT. Composites containing ACP or fluoride reduced bacterial adherence and lesion formation as compared to a composite without ACP or fluoride.

Evaluation of antimicrobial properties of orthodontic composite resins combined with benzalkonium chloride

An antimicrobial agent, benzalkonium chloride (BAC), was added to a chemically cured composite resin, and the antimicrobial benefits and physical properties of the modified composite were evaluated. BAC was added to Reliance Phase II composite to create modified composites with BAC concentrations ranging from 0.25 to 2.50 wt%. Specimen disks of the modified composite were incubated with Streptococcus mutans for 48 hours, and an agar disk diffusion assay was used to measure zones of bacterial inhibition. Larger disks were suspended in brain-heart infusion medium containing 2 x 10(4) colony-forming units/mL Streptococcus sobrinus (10 mL, 2 wt% sucrose, 24 hours) to measure bacterial adherence to the adhesive; adherent cells were removed from the surface with 1 N NaOH, and the optical density of the cells was measured at 550 nanometers. Traction hooks were bonded to bovine teeth with the modified composite, and tensile bond strength was evaluated with a universal testing machine. Diametral tensile stress was also measured. The modified composite samples showed that antimicrobial activity increased with higher BAC content; no antimicrobial activity was measured for the original compound in either the disk diffusion or the bacterial adherence test. There were no significant differences (P <.05) in either tensile bond strength or diametral tensile stress among the modified composite groups and the original product. The incorporation of BAC in composite material added antimicrobial properties to the original compound without altering its mechanical properties.

Potential of the aqueous extract of Terminalia chebula as an anticaries agent

The aqueous extract from Terminalia chebula was tested for its ability to inhibit the growth and some physiological functions of Streptococcus mutans. The extract strongly inhibited the growth, sucrose induced adherence and glucan induced aggregation of S. mutans. Mouthrinsing with a 10% solution of the extract inhibited the salivary bacterial count and salivary glycolysis. Mouthrinsing with the extract significantly reduced total bacterial counts and the total streptococcal counts in the saliva samples obtained up to and including 3 h after rinsing, compared with the counts obtained prerinsing or after placebo rinsing. The extract successfully inhibited glycolysis of salivary bacteria for up to 90 min postrinsing.

Incorporation of bacterial inhibitor into resin composite

Attempts to produce resin composite with antibacterial properties by incorporation of an antibacterial agent such as chlorhexidine have been reported, but problems can arise due to release of the inhibitory agent from the composite. Such problems may include toxic effects, influence on mechanical properties, and loss of effectiveness. A new monomer, methacryloyloxydodecylpyridinium bromide (MDPB), was synthesized by combining an antibacterial agent and methacryloyl group. The monomer was incorporated into resin composite to develop a non-releasing antibacterial composite. The ability of composite incorporating MDPB to inhibit growth and plaque accumulation by Streptococcus mutans in vitro was assayed, elution of antibacterial components from the material was investigated, and the influence of incorporation of MDPB on the mechanical properties of composite was studied. Uncured MDPB revealed antibacterial activity against S. mutans and six other species of oral streptococci, with the minimum inhibitory concentration for S. mutans being comparable with that of triclosan. After composite incorporating MDPB was cured, no elution of the antibacterial components was observed from the material, even after 90 days' immersion in water or other solvents. Growth of S. mutans on agar under specimens of MDPB-containing composite was inhibited compared with controls. In a bacterial accumulation study, S. mutans accumulated to a lesser degree on the surface of composite incorporating MDPB (p < 0.05) than on control. Incorporation of MDPB had no significant influence on the mechanical properties of the composite.

Evaluation of antimicrobial mouthrinses and their bactericidal effectiveness

The mechanisms of action of antimicrobials have been based in the past on in vitro data obtained from laboratory experiments performed on pure cultures of bacteria. A more complete understanding of oral antimicrobials and their mechanisms of action will results from testing of agents in systems that more closely resemble environmental areas existing in the oral cavity. It is proposed that mechanisms of drug action be studied with a drug held at suboptimal (sublethal) concentrations for short periods and in a dynamic environment that resembles the mouth. Adequate guidelines provided by the American Dental Association Council on Dental Therapeutics are available and have helped to determine the efficacy of these agents over long periods in appropriate populations.

A review of chlorhexidine and its use in special populations

The purpose of this paper is to review the mechanism of the action, safety, and side-effects of chlorhexidine, and to provide guidelines for its use in special populations. Chlorhexidine has been used orally since 1959, primarily for the control of dental plaque. Chlorhexidine is a safe material, with low toxicity potential when used correctly. The most conspicuous side-effects are the development of yellow-brown stains on the teeth, tongue, and at the margins of anterior restorations, and an alteration in taste sensation. The use of chlorhexidine is indicated in developmentally disabled, medically compromised patients, and in dependent elderly populations, since these groups are often physically unable to remove plaque by mechanical means. Clinicians should not prescribe chlorhexidine indiscriminately for all patients, however, until analyzing its efficacy, safety, and side-effects.

Enhancing the effect of oral hygiene with the use of a foam brush with chlorhexidine

The maintenance of oral hygiene for hospitalized patients, particularly medically compromised and immune compromised patients, may reduce the risk of oral and systemic infection. Foam brushes have been recommended for use in these populations, however, the use of a foam brush has not been shown to be an acceptable alternative to the use of a toothbrush. In this study, we demonstrate that the use of a foam brush saturated with chlorhexidine was equally effective in measures of plaque levels and gingivitis as was the use of a toothbrush. Therefore if a toothbrush cannot be used in hospitalized patients, an alternative may be the use of chlorhexidine applied with a foam brush.

Antimicrobial properties of human dentin impregnated with tetracycline HCl or chlorhexidine. An in vitro study

Substantivity of tetracycline HCl and chlorhexidine digluconate to human root dentin was assessed in vitro. 51 extracted single-rooted teeth, their crowns removed, were assigned to 1 of 4 treatments in groups of 12. A control groups included 3 roots. Each group was divided into 3 subgroups to allow evaluation of drug exposure for 1, 3 or 5 min. The roots were immersed in tetracycline HCl (10 or 50 mg/ml) or chlorhexidine digluconate (0.12 or 0.2%) solutions following root planning. Control roots were immersed in sterile saline (0.9%). Following drug immersion, the roots were transferred to tubes containing 2 ml tris buffered saline. The tubes were incubated at room temperature for 22 days. Desorption media were replaced at 24-h intervals. Removed media were examined for antimicrobial activity using a microtiter assay in which bacterial growth was evaluated by optical density readings. Roots immersed in tetracycline HCl 50 mg/ml released antimicrobial activity to successive desorption media for 14 days. Tetracycline HCl 10 mg/ml activity lasted 4 days. Roots subjected to chlorhexidine digluconate released antimicrobial activity for 24 h only. Within each treatment, there were no differences between the 3 exposure intervals of 1, 3 or 5 min. Our findings suggest usage of the periodontally exposed instrumented root as a depot for sustained release of tetracycline HCl, but not chlorhexidine digluconate, to the subgingival environment. The substantiveness of tetracycline HCl seems related to drug concentration rather than the exposure interval. Clinical trials are needed to confirm the clinical significance of these in vitro observations.

The antimicrobial effect of an iron-binding agent on Streptococcus mutans

The antimicrobial activity of 2,2'-bipyridine, an iron-binding agent, was investigated by incorporating this agent into Scotchbond dental adhesive resin. The growth of Streptococcus mutans on the surface of resin, media and culture vessel was determined by optical density measurements. It was observed that 2,2'-bipyridine exhibited excellent antimicrobial properties.

The efficacy of chlorhexidine gel in reduction of Streptococcus mutans and Lactobacillus species in patients treated with radiation therapy

Xerostomia may develop in patients with cancer who receive radiotherapy that includes the salivary glands in the field. These patients are at high risk of rampant dental caries. Streptococcus mutans and Lactobacillus species have been associated with dental caries. Quantitative counts of these organisms demonstrated high caries risk due to streptococci in 66% and due to lactobacilli in 100% of patients studied. Use of chlorhexidine rinse was shown to reduce S. mutans counts 1.1 logs and lactobacilli 1.1 logs. The use of chlorhexidine gel resulted in a reduction of S. mutans 1.2 logs and lactobacilli 2.2 logs. In the subjects using the rinse, caries risk due to streptococci was reduced to low levels in 44% and due to lactobacilli in only one subject, with reduction to moderate risk in one third and no change in risk in the remaining patients. The use of chlorhexidine gel was found to reduce the caries risk associated with streptococci to low levels in all patients, and the risk associated with lactobacilli to low and moderate risk in two thirds of patients.

Chlorhexidine rinse in prevention of dental caries in patients following radiation therapy

Patients who receive cancer radiotherapy, which compromises salivary gland function, may develop xerostomia. These patients are at increased risk to develop rampant dental caries. Streptococcus mutans and species of lactobacillus have been associated with dental caries. Quantitative counts of these organisms demonstrated high caries risk in 85% of patients studied. The use of chlorhexidine rinse to reduce the counts of S. mutans and lactobacillus was studied. A modest reduction in S. mutans was seen, but little effect was demonstrated on lactobacillus counts. Caries activity was shown to be related to lactobacillus count.

Inhibition of bacterial colonization by antimicrobial agents incorporated into dental resins

The antimicrobial activity of several chemical agents was determined by incorporating these agents into dentine adhesive resin and following the colonization of Streptococcus mutans on the surfaces of the resin and culture vessel, as well as in the surrounding medium, by optical density measurements. It was found that sodium fluoride and dodecylamine, an organic amine, exhibited excellent antimicrobial properties. These chemicals not only inhibited bacterial growth completely but also seemed to reduce the adhesion of the bacteria to the resin surface. A silver compound, protargin, was mildly effective in inhibiting growth of S. mutans. Copper oxide and chelating acids such as vanillic acid, syringic acid, and ethylenediamine-n, n' diacetic acid (EDDA) were not effective as antimicrobial agents against S. mutans.

Clinical and laboratory evaluation of visible light-cured denture base resins and their application to orthodontics

A series of investigations is being conducted to examine the applicability of visible light-cured resins to orthodontics. The experimental vehicle is the Hawley retainer, which is made from autopolymerized (AP), heat-cured (HC), thermoplastic Biocryl 2 (BC), and Traid visible light-cured (VLC) resins. In all physical property testing, it was found that VLC resins met or exceeded required values as established by ADA Specification No. 12 for denture base polymers. In vitro bacterial adherence studies showed that more organisms adhered to heat-cured specimens than to the other specimens. In vivo studies using split-palate Hawley retainers demonstrated slightly less bacterial adherence to BC than to the other resins. Scanning electron microscopy (SEM) observations have shown the BC surface to be the smoothest, although surface chemistry also seems important. None of the materials being tested appears to cause any significant change in the subjacent subgingival bacterial flora. There was no adverse tissue reaction under any of the materials when observed clinically. Manipulation characteristics and time of fabrication appear to be dependent on the depth of the palate and the skill of the operator.

Microbial aspects of preventive regimes in patients with overdentures

The aim of this study was to test effects of preventive regimes using fluoride and chlorhexidine to prevent caries and periodontal diseases in 34 patients with overdentures. The patients, who were treated with immediate overdentures, were distributed at random into three experimental groups. In these groups, different gels--a placebo, a fluoride, and a chlorhexidine-fluoride gel--were tested by daily application. Supragingival plaque samples from selected surfaces of two abutment teeth were taken at one week, and at one, three, and six months after initial insertion of the overdenture. The placebo and fluoride gel influenced neither total CFU nor S. sanguis and A. viscosus/naeslundii counts. In the placebo group, but not in the fluoride group, S. mutans levels increased significantly, indicating the caries risk involved in overdentures. The use of chlorhexidine-fluoride gel resulted in a long-term suppression of total CFU. Further, S. mutans was found to be selectively suppressed to below detection level. A. viscosus/naeslundii was initially strongly suppressed, but after three months a partial return of the population was noticed. S. sanguis was relatively insensitive to the chlorhexidine-fluoride gel. It is concluded that a daily application of a chlorhexidine-fluoride gel is effective against plaque formation and S. mutans on abutment teeth in overdentures.

A new visible light-cured resin system applied to removable prosthodontics

Preliminary studies of VLC resins have produced promising results; however, additional research is necessary to completely define qualities of this material. Biologic testing of VLC (Triad) resins indicated that they are nontoxic and biocompatible. They have a wide range of uses in all subdisciplines of prosthodontics. Advantages such as accuracy of fit, superior strength, complete polymerization without residual compounds, ease of fabrication and manipulation, patient acceptance, ability to bond with other denture base resins, and low bacterial adherence make this material an important addition to the choices available to dentists. As with many new materials, there are initial problems or hurdles that must be overcome before there is widespread use. Initial formulations of material had insufficient flexural strength and tended to fracture when flexed over uncut sites on a stone cast. This problem has been reduced by Dentsply International, Inc. with the introduction of the new improved formulation. The original VLC bonding agent did not provide sufficient bond strength with acrylic resin denture base materials, but this also has been improved with development of a new VLC bonding agent. The problem of microporosity and small voids produced when adapting VLC resin sheets against a stone cast may be overcome with pressure or vacuum adaptation techniques. A promising application of VLC resin material is in direct intraoral procedures such as relining of dentures. Physical and chemical properties are superior to autopolymerizing methacrylates. Preliminary studies have shown successful patient acceptance to this clinical procedure. It is of particular advantage to the patient not to be without dentures for the period of at least 1 day necessary for a laboratory-processed relining. Immediate light-curing is time-saving and convenient compared to indirect (heat-cured) relining. Until recently, most direct intraoral applications of autopolymerizing acrylic resin reliner material were considered temporary or expedient to a permanent procedure. The patient and dentist may now have another treatment choice. The release of residual methyl methacrylate, among other shortcomings of AP materials, is not a concern when using the VLC reliner material. Some patients may notice a nonobjectionable taste to the uncured material; however, they can be reassured that the taste will be only temporary until the material is completely polymerized in the curing unit. The flow of the material can be regulated by selection of appropriate viscosity, warming and cooling measures, and partial intraoral polymerization with hand-held curing lights.(ABSTRACT TRUNCATED AT 400 WORDS)

A review of the literature on use of chlorhexidine in dentistry

In addition to its plaque-inhibiting effect, chlorhexidine possesses other properties beneficial for use in dentistry. These effects are outlined, and specific recommendations are given regarding chlorhexidine's use by general practitioners. The side effects of long-term use, such as staining, and the availability of chlorhexidine also are discussed.

Inhibition of bacterial growth by tetracycline-impregnated enamel and dentin

Tetracyclines can react with enamel and dentin to form relatively insoluble fluorescent compounds. The purpose of this study was to evaluate the possible antimicrobial effect of these reaction products on various microorganisms associated with human dental plaque and periodontal disease. Slabs of native dentin and enamel as well as demineralized dentin were immersed in aqueous solutions of tetracycline HCl, oxytetracycline HCl and doxycycline HCl for periods of 1 h or 24 h. Unimpregnated enamel and dentin slabs sterilized by gamma irradiation and specimens impregnated with phenoxymethylpenicillin calcium were used as controls. Test and control specimens were placed on agar plates seeded with B. cereus, C. ochraceus, S. sanguis, F. nucleatum, B. melaninogenicus or A. viscosus and were subsequently incubated aerobically or anaerobically at 37 degrees C. With the exception of enamel impregnated for 1 h in a 0.01 mg/ml tetracycline solution, all test specimens caused growth inhibition zones, varying in size according to concentration of the drug, immersion period and bacterial species. The results indicate that tetracyclines react with enamel and dentin to form slightly soluble compounds with a pronounced antibacterial effect. In comparison, the antimicrobial effect of dentin treated with penicillin was small.

Tetracycline and its derivatives strongly bind to and are released from the tooth surface in active form

Several antibiotics were found to adsorb to saliva-coated enamel and to inhibit in vitro plaque formation by pure cultures of oral bacteria: Actinomyces viscosus, Actinomyces naeslundii and Streptococcus mutans. Tetracycline, minocycline and oxytetracycline adsorbed to the greatest degree, showing 100-fold higher adsorption than spiramycin, the test antibiotics with least adsorption. Inhibition of in vitro plaque formation was found to require both drug substantivity (capacity for adsorption) and antimicrobial activity. Inhibition of plaque formation in the in vitro assay employed correlated well with clinical efficacy.

Effect of the antibacterial agents octenidine and chlorhexidine on the plaque flora in primates

The effect of the antibacterial substance octenidine on plaque formation and on oral microflora in eight monkeys fed a sucrose diet was studied. Plaque was obtained from buccal tooth surfaces of premolars and first molars in two quadrants using a swab and a dental carver and examined using culture and fluorescent antibody procedures. A significant reduction in plaque score was observed on the buccal tooth surfaces after daily topical application of 1% solutions of octenidine and chlorhexidine for 7 d; octenidine was more effective than chlorhexidine. Placebo treatment with water was without significant effect. Octenidine and chlorahexidine affected the plaque flora in a similar manner; the proportion of S sanguis increased in relation to baseline levels while the population of Actinomyces, especially the group A. viscous and A. naeslundii, was markedly reduced. S. sanguis showed an inverse relationship to members of actinomyces in response to the action of the antimicrobial agents. Both plaque sampling methods revealed similar changes in bacterial composition as a result of treatment. The data show that octenidine is an effective inhibitor of dental plaque and its antimicrobial and antiplaque properties make it worthy of further studies.

Effect of chlorhexidine gel treatment on Streptococcus mutans population in human saliva and dental plaque

The effect of topical application of a 1% chlorhexidine gel on the population of S. mutans in dental plaque and saliva was studied in five subjects highly infected with the organism. After treatment for 5 min daily for 14 d, S. mutans was not detected in three of the subjects and counts of 700 colony-forming units or less per ml of saliva were found in the other subjects. Reappearance of S. mutans was slow and did not reach pretreatment level until 14 weeks or more after therapy. The proportion of S. sanguis in plaque increased temporarily after chlorhexidine treatment, whereas the population of lactobacilli was unaffected. These observations indicate that short-term use of chlorhexidine is of value in controlling oral infection of humans by S. mutans.

Rapid quantitative determination of the effect of antiplaque agents and antisera on the growth, acid production, and adherence of Streptococcus mutans

A rapid quantitative in vitro assay measured the effects of antiplaque agents and antiserum on growth and sucrose-mediated adherence of radio-labeled S. mutans 6715. Acid production was measured by change in pH. In this assay the primary effect of chlorhexidine and fluoride was bacteriostasis and inhibition of acid production, respectively; the primary effect of dextran, dextranase, and specific antiserum was inhibition of sucrose-mediated adherence.

Biology, immunology, and cariogenicity of Streptococcus mutans

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In vitro testing of plaque control agents

The development of a number of in vitro techniques for the evaluation of antiplaque effects of test agents has followed the characterization and culturing of plaque-forming microorganisms. Studies of the mechanism of action of chlorhexidine and clinical observations have assisted in defining critical aspects of these in vitro techniques. Such assays may play an increasingly important role in screening potential new agents as well as in the optimization of properties by chemical modification of new lead agents. In addition, data generated in the in vitro assay may assist the design of in vivo evaluations of new agents. Proper selection of in vitro techniques for these various functions in the pre-clinical development process may reduce the time and cost involved in the development of new antiplaque agents.

Effect of chlorhexidine on the relative proportions of Streptococcus mutans and Streptococcus sanguis in hamster plaque

The effect of chlorhexidine on the proportions of Streptococcus mutans and Streptococcus sanguis in plaque was studied in hamsters fed a diet containing 28% sucrose. In animals given chlorhexidine in their drinking water for 10 d a decrease in the population of S. mutans and an increase of S. sanguis occurred in the plaque. Following the removal of chlorhexidine the population of S. mutans increased again in the presence of sucrose and the number of S. sanguis returned to initial values. When animals were given a sucrose-free diet the low proportion of S. mutans observed following the short-term chlorhexidine period persisted. These data indicate that there is an inverse relationship between the number of S. sanguis and S. mutans in plaque and that the sensitivity in vivo of S. mutans to chlorheximide can be used to suppress the population of S. mutans with a concomitant rise in the proportion of S. sanguis.

The in vitro inhibition of microbial growth and plaque formation by surfactant drugs

Several cationic, mixed and amphoteric surfactants were tested for their antimicrobial activity and ability to inhibit the formation of in vitro plaque by oral microorganisms. All had antimicrobial activity against Actinomyces viscosus. Actinomyces naeslundii and Streptococcus mutans. Cationic surfactants were comparable to chlorhexidine in antimicrobial activity but were less effective in inhibiting plaque formation. Amphoteric surfactants were less effective than other detergents in antibacterial activity and had very limited capacity for the inhibition of plaque formation. Comparison of drug structure provides evidence that surfactant substantivity to saliva-coated enamel is a cation active process. Saliva was found to have an antagonistic effect on the activity of cetylpyridinium chloride but not on Triburon.