Determination of minimum inhibitory concentrations of commercial toothpastes using an agar dilution method

Comparative Fluoride Release and Antimicrobial Analysis of Commercial and Experimental Bioactive Glass/Nano-Oxide-Based Dentifrices

OBJECTIVES

 The objectives were to measure fluoride release and assess the antimicrobial behavior of fluoride-doped nano bioactive glass (F-nBG) and nano zinc oxide (ZnO)-enriched novel dentifrices.

MATERIALS AND METHODS

 Experimental dentifrices were synthesized by incorporating ZnO nanoparticles and F-nBG (1.5 wt% and 4 wt%) as active ingredients. The fluoride release behavior of suspensions and elutes of samples were analyzed by ion selective electrode. Antimicrobial activity and minimum bactericidal concentration against Streptococcus mutans and Lactobacillus casei were evaluated. Microbial stability against contamination was also assessed by a challenge test.

RESULTS

 The fluoride release behavior of experimental dentifrices was higher than that of commercial dentifrices and was dependent on filler loading. The fluoride release was more from suspensions than elutes. Zones of inhibition (ZOIs) and minimum bactericidal concentration values for novel dentifrices showed direct proportionality with filler loading, and effectiveness was exhibited against both strains. Experimental dentifrices exhibited effective antibacterial potential, which could possibly be due to release of sufficient fluoride and zinc ions in aqueous media from F-nBG and ZnO present in their formulations.

CONCLUSION

 Combination of F-nBG and ZnO may provide a multi-benefit approach for simultaneously treating early white spot lesions, reducing bacterial growth, and providing core plaque control.

Antibacterial activity of aqueous extracts of Indian chewing sticks on dental plaque: An in vitro study

The anti-microbial efficacy of aqueous extracts of Indian chewing sticks against different kinds of plaque bacteria in vitro was investigated. Supra-gingival plaque is cultured and subjected to the antibacterial activity of the aqueous extracts of chewing sticks (Neem, Acacia, Pongamia glabra, Achyranthes aspera, Streblus asper) separately. The results of the study demonstrate that all the five chewing sticks under study possess inhibitory potential against bacteria present in dental plaque mainly on aerobes. The antibacterial efficacy of aqueous extracts has antibacterial effects and could be used as a therapeutic agent and therefore, it appears to be potent anti-microbial agents that could be considered as a medicinal plant. Results of this study showed chewing sticks contained antibacterial agents, but the concentration and composition of the active substances differed among the plants.

Evaluation of oral hygiene products: science is true; don't be misled by the facts

Most people in industrialized countries use oral hygiene products. When an oral health benefit is expected, it is important that sufficient scientific evidence exist to support such claims. Ideally, data should be cumulative derived from studies in vitro and in vivo. The data should be available to the profession for evaluation by publication in refereed scientific journals. Terms and phrases require clarification, and claims made by implication or derived by inference must be avoided. Similarity in products is not necessarily proof per se of efficacy. Studies in vitro and in vivo should follow the basic principles of scientific research. Studies must be ethical, avoid bias and be suitably controlled. A choice of controls will vary depending on whether an agent or a whole product is evaluated and the development stage of a formulation. Where appropriate, new products should be compared with products already available and used by the general public. Conformity with the guidelines for good clinical practice appears to be a useful way of validating studies and a valuable guide to the profession. Studies should be designed with sufficient power to detect statistically significant differences if these exist. However, consideration must be given to the clinical significance of statistically significant differences between formulations since these are not necessarily the same. Studies in vitro provide supportive data but extrapolation to clinical effect is difficult and even misleading, and such data should not stand alone as proof of efficacy of a product. Short-term studies in vivo provide useful information, particularly at the development stage. Ideally, however, products should be proved effective when used in the circumstances for which they are developed. Nevertheless, a variety of variable influence the outcome of home-use studies, and the influence of the variable cannot usually be calculated. Although rarely considered, the cost-benefit ratio of some oral hygiene products needs to be considered.

Studies on stannous fluoride toothpaste and gel (1). Antimicrobial properties and staining potential in vitro

Stannous fluoride (SF) in a toothpaste vehicle has the potential to provide anticaries and plaque inhibitory benefits through the fluoride and antimicrobial stannous moieties respectively. Dental staining, however, can occur by precipitation of dietary chromogens onto the tooth surface by stannous ions. These studies in vitro compare the antimicrobial profile and propensity to cause tea staining of a number of stannous fluoride formulations. The formulations used were 2 SF toothpaste products (SF1, SF2), 2 experimental SF plus stannous pyrophosphate toothpastes (SFSP1, SFSP2), a SF gel (G) and a NaF toothpaste (C). Maximum inhibitory dilution values against a range of oral bacteria were determined by agar dilution. Tea staining was measured spectrophotometrically on saliva coated clear acrylic blocks exposed to slurries of the paste or gel. All formulations showed antimicrobial activity with the order of greatest activity downwards being C, SF2, SF1, SFSP1, SFSP2 and G. Tea staining at 10 exposures was in the following descending order of optical density SFSP1, SFSP2, G. C, SF1, SF2, water control. The antimicrobial profile of G was similar to that of SF, whereas that of the other formulations were varied but similar to a detergent profile. The difference in staining suggested considerable variation in availability of stannous ions in the formulations. However, the propensity for stannous ions to stain must be balanced against the stain removal propensity of the contained detergents in the toothpaste formulations. In conclusion, the variation in antimicrobial activity and more particularly staining activity of the formulations suggest the products will vary in activity in vivo.

The substantivity of a number of oral hygiene products determined by the duration of effects on salivary bacteria

The persistence of action, or substantivity, of antimicrobial agents in the mouth appears to be a major variable influencing plaque inhibition. Such substantivity can be assessed by measuring the duration and magnitude of suppression of salivary bacterial numbers produced by antimicrobial agents. Although this has been determined for some agents, there is little information on the substantivity of the numerous products which contain these and other antimicrobial agents. This study was commissioned on the basis that efficacy cannot be assumed merely because a product contains a known active agent. Nine formulations or products were chosen: 2 rinses containing chlorhexidine or C31G, 4 rinses containing cetylpyridinium chloride (CPC) (with and without fluoride and/or alcohol), a minus-CPC control rinse, and 2 toothpastes with and without stannous fluoride. Additionally, water was used as a placebo control. Twenty health dentate volunteers took part in this blind, 10 cell randomized, single rinse, cross-over study, which was balanced for carryover. Mouthrinses were 15 ml volumes and toothpastes 3 gm in 10 ml water slurries rinsed for 60 seconds. On the day of each study volunteers suspended oral hygiene habits and at approximately 9:00 a.m. rinsed with the allocated formulation. Unstimulated saliva samples were obtained immediately before and 30, 60, 180, 300, and 420 minutes after rinsing. The samples were immediately processed for total anaerobic bacterial counts. All rinses except water and the minus CPC control rinse produced significant falls in counts to 30 minutes. Of more relevance in this inter-treatment comparison-designed study, the C31G rinse showed significant substantivity compared to water only for 60 minutes. C31G was highly significantly less substantive than chlorhexidine from 30 minutes to 420 minutes. The CPC rinses were similar and significantly more substantive than their control rinse to between 180 and 300 minutes. The stannous fluoride and control pastes were similarly substantive to 300 minutes, with the stannous fluoride paste remaining substantive compared to water to 430 minutes. Based on antimicrobial action these formulations varied considerably in substantivity and this is likely to reflect their comparative plaque inhibitory properties.

The choice of controls in toothpaste studies. The effect of a number of commercially available toothpastes compared to water on 4-day plaque regrowth

Toothpastes have been shown to have an antimicrobial activity both in vitro and in vivo; this activity variably translates into a plaque inhibitory effect in vivo. Commercially available toothpastes have a complex chemical make-up and some contain additional chemicals for which improved effects against plaque have been claimed. The aim of this study was to assess the plaque inhibitory properties of 5 commercially available toothpastes compared to a rinse of water over 4 days. The study was a randomised, single-blind, cross-over design balanced for residual effects. Volunteers were rendered plaque-free at each baseline and rinsed for 1 min, under the supervision of an assistant, 2x a day with the allocated mouthrinse or toothpaste slurry. At the end of the 4-day test period, the plaque was disclosed and measured by plaque index and plaque area. The plaque measurements indicated a significant difference between the toothpastes. The order of efficacy was Colgate Total, Crest regular, Crest Tartar, Colgate regular, Colgate 0-6 gel and water. This confirms previously reported data confirming the plaque inhibitory properties of certain toothpastes compared to water. These data indicate that the choice of control toothpaste with which to compare toothpastes formulated for plaque control is important and could influence conclusions drawn from clinical trials of such products.

The effect of a commercially available triclosan-containing toothpaste compared to a sodium-fluoride-containing toothpaste and a chlorhexidine rinse on 4-day plaque regrowth

Many compounds could be added to toothpaste to assist plaque inhibition, but ionic interactions can cause formulation difficulties. Moreover, the actual chemical action of a plaque inhibitory agent added to a toothpaste is difficult to assess when the product is used in the conventional manner, i.e., in addition to toothbrushing. The non-ionic antimicrobial triclosan has been incorporated in toothpastes and shown to have variable plaque inhibitory activity both alone and in conjunction with certain polymers or metal ions. Little is known of the efficacy of triclosan toothpastes compared to conventional fluoride toothpastes. The aim of this study was to compare a commercially available toothpaste containing 0.3% triclosan/co-polymer with a sodium fluoride toothpaste for chemical plaque inhibitory effects over a 4-day period. The study was designed to stratify the relative efficacy plaque inhibitory action of the products, comparisons were made with a positive control, chlorhexidine rinse and a negative control, saline. The study design was a randomised single blind crossover design balanced for first-order carryover. A total of 18 healthy, dentate volunteers participated in the study. On day 1 of each period the volunteers suspended toothcleaning and rinsed 2 x daily with the allocated mouthrinse or toothpaste slurry. On day 5, the plaque on the teeth was disclosed and scored by index and area. Increasing plaque scores were in the order chlorhexidine, triclosan toothpaste, fluoride toothpaste, and saline. Chlorhexidine was significantly more effective than all the other agents tested, and both toothpaste preparations were significantly better than the saline rinse. There was no significant difference between the two toothpaste rinses. Consistent with other studies the triclosan toothpaste offers only moderate plaque inhibitory properties when compared to a conventional toothpaste.

Surfactants and experimental irritant contact dermatitis

Surface-active agents (surfactants) are characterized by the possession of 2 different moieties, both polar and non-polar regions on the same molecule. Surfactants are broadly classified as anionic, cationic, amphoteric, or non-ionic, according to the nature of the hydrophile yielded in aqueous solution. In currently marketed household, personal, and industrial cleaners, anionic surfactants are the most common class because of their relative ability to solubilize fats and oils, lower the surface tension of aqueous solutions, or form microemulsions. Many surfactants elicit irritant reactions when applied to the skin, partially due to their relative ability to solubilize lipid membranes. Hence, surfactants have become important implements in skin irritation investigations. In general, the physicochemical properties of surfactants are a crucial factor in eliciting skin irritation. Anionic surfactants are broadly accepted as potent irritants to human and animal skin. Cationic surfactants are reputedly at least equally irritating, but more cytotoxic than anionic, while the irritation potential of non-ionic surfactants is considered the lowest. Such classification of innumerable surfactants is convenient and held in high practical esteem. however, the categorization does not permit the exact determination of irritation and cytotoxicity potential of each surfactant. Ranking of surfactant skin irritancy and cytotoxicity obtained by both in vitro and in vivo assays provides a helpful orientation for future work.

The effects of Acacia arabica gum on the in vitro growth and protease activities of periodontopathic bacteria

The antibacterial activity of acacia gum was assessed using fresh isolates and reference strains of Actinobacillus actinomycetemcomitans, Capnocytophaga spp., Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola. A fine aqueous suspension of gum was produced by sonication and then a soluble fraction isolated by centrifugation and membrane filtration. These preparations were incorporated into columbia agar at doubling concentrations. Growth of P. gingivalis and P. intermedia cultures on the agar was inhibited by whole gum sonicate at concentrations of 0.5-1.0% w/v. Both species showed reduced susceptibility when horse blood was present in the agar. The gum soluble fraction did not inhibit growth of any bacterial culture. The effect of acacia on bacterial proteases was examined with cell sonicates from log phase broth cultures. Enzyme activities were determined by fluorimetric assay with various synthetic peptide substrates. Most protease activities reduced in the presence of 0.5% w/v gum sonicate, with the trypsin-like activities of P. gingivalis and P. intermedia proving most sensitive. The gum soluble fraction was nearly always less inhibitory than the sonicate. The action of acacia gum against suspected periodontal pathogens and their enzymes suggests that it may be of clinical value.

The plaque removal effects of single rinsings and brushings

Chemical plaque removal is one mechanism whereby an agent could improve oral hygiene and gingival health. As with toothpastes most agents, when delivered as rinses, would be considered adjunctive to mechanical tooth cleaning procedures. The aim of this study was to determine whether selected commercial rinses exhibited clinically significant plaque removal properties alone or when combined with toothbrushing with water or a toothpaste. A group of 12 volunteers took part in this single blind, randomized placebo-controlled, 12 cell cross-over study, employing 6 rinses. During each regimen subjects accumulated plaque from a zero baseline over 72 hours. Plaque removal was then measured by index and area after first a single rinse of product and second a subsequent brushing with water or toothpaste. Prebrushing rinsing removed less than 5% of the plaque with little difference between agents. No rinse was more adjunctive than water to postrinse brushings. Most statistically significant differences arose with the chlorhexidine rinse being apparently less effective. However, the possibility of a disclosing dye interaction cannot be discounted as explaining this anomalous result. This study could not support any claim of a direct prebrushing rinse benefit greater than that provided by water to mechanical plaque removal by any of the products tested.

A 6-month home usage trial of a 1% chlorhexidine toothpaste (1). Effects on plaque, gingivitis, calculus and toothstaining

Research and development has been aimed towards the development of toothpastes for oral hygiene and gingival health benefits. The most effective antiplaque agent to date, chlorhexidine, is difficult to formulate into active toothpaste products. Despite some encouraging findings for experimental chlorhexidine toothpastes, there are to date no commercially available products. Based on positive findings from an experimental gingivitis study, this investigation evaluated 2 chlorhexidine toothpastes, one with fluoride, as adjuncts to oral hygiene. The study was a double-blind controlled, parallel, balanced group design, extending over 6 months. A total of 297 volunteers commenced the study after screening for a minimum acceptance level of gingivitis. At baseline, 6, 12 and 24 weeks, stain, gingival, bleeding and plaque indices were recorded, together with a calculus index at 6, 12 and 24 weeks. After a baseline prophylaxis, volunteers used the allocated product 2 x per day, with no other oral hygiene instructions given. Plaque, gingival and bleeding scores improved in all 3 groups, but to an overall significantly greater extent in the active groups. However, staining and calculus indices were significantly increased in the active compared to the control group. If the local side-effects of chlorhexidine are considered to be acceptable, these chlorhexidine toothpastes could be recommended for the same clinical applications as other chlorhexidine products. The apparent compatibility of fluoride with chlorhexidine in the one product may be pertinent to caries prevention.

Antibacterial Activity of Some Triclosan-Containing Toothpastes and Their Ingredients

The antibacterial activity of 4 triclosan-containing toothpastes was compared to a conventional fluoride dentifrice and triclosan and sodium lauryl sulphate (SLS), both singly and in combination. A panel of 17 bacteria was tested by an agar dilution method. At concentrations typical of those found in toothpastes, triclosan and SLS displayed approximately equal antibacterial activity. A paste containing triclosan and zinc citrate appeared more active than the other triclosan pastes which, in general, showed marginal superiority over the conventional paste. SLS, although included in dentifrice formulations for its detergent properties, may significantly contribute to the antibacterial profile of a product. The need for appropriate controls when evaluating experimental toothpastes is emphasized.

Triclosan and sodium lauryl sulphate mouthwashes (I). Effects on salivary bacterial counts

A number of commonly used toothpaste ingredients, such as detergents, possess not inconsiderable antimicrobial activity. Additionally, specific ingredients including triclosan are now added to toothpastes to enhance such activity and to improve plaque inhibition. To date, there have been few studies of the antimicrobial properties in vivo of individual toothpaste ingredients. Most investigations have evaluated the whole toothpaste product. Persistence of antimicrobial action in vivo has been shown to relate to potential plaque inhibitory action. The aim of this study was to compare the magnitude and duration of salivary bacterial count reductions produced by a single rinse of 0.2% triclosan, 1% sodium lauryl sulphate (SLS) and 0.2% chlorhexidine mouthwashes. 16 volunteers took part in a single-blind latin-square randomised crossover designed study with balanced residual effects. Before and for time periods up to 420 min following rinsing with the allocated mouthwashes, saliva samples were obtained and processed for total anaerobic counts. With the exception of the saline control rinse, the 3 test solutions produced considerable reductions in bacterial counts which remained significant to 3 h for triclosan and 7 h for SLS and chlorhexidine. However, at most time periods after baseline, the effects of chlorhexidine were significantly greater than triclosan and SLS. Overall, SLS had significantly greater effects than triclosan. Incremental values from 30 min post rinsing were always positive for SLS and triclosan, indicating bacterial recovery, whereas these values were negative for chlorhexidine. The results indicate that triclosan and SLS provide some persistence of antimicrobial activity in the oral cavity when used at relatively high dose compared to a toothpaste vehicle.

The effect of triclosan, stannous fluoride and chlorhexidine products on: (II) Salivary bacterial counts

A previous study demonstrated that triclosan and stannous fluoride containing oral hygiene products reduced plaque regrowth compared to saline but were not more effective than a conventional commercial fluoride/anionic detergent toothpaste. To further understand these results, this study measured the persistance of antimicrobial activity of the same products by recording the duration of salivary bacterial count reductions following a single exposure to each product. Comparison was also made with a chlorhexidine rinse as the positive control. From a panel of 16 volunteers, in an 8-cell randomised cross-over designed study, salivary bacterial counts were recorded at baseline and to 420 min. All test and control products were significantly more effective than saline and significantly less effective than chlorhexidine at suppressing bacterial counts. Unlike chlorhexidine, evidence of bacterial recovery was apparent after the 30-min sampling time. There were essentially no significant differences between the test and control products, although the stannous fluoride toothpaste performed marginally better than other products. The findings are consistent with the plaque regrowth results previously obtained and again demonstrate to date that it is difficult to surpass the antimicrobial and plaque inhibitory properties of conventional commercially available toothpastes by the addition of antimicrobial agents such as triclosan and metal salts.

Studies on the effect of toothpaste rinses on plaque regrowth. (II). Triclosan with and without zinc citrate formulations

Encouraging findings have been reported for the effects of Triclosan/zinc citrate toothpastes on plaque regrowth and in some studies gingival health. To date, commercially-available toothpastes contain 0.2% Triclosan with or without 0.5% zinc citrate. The aim of this study was to evaluate the effects on 4-day plaque regrowth, of a number of 0.2% Triclosan toothpastes with or without zinc citrate. All of the toothpastes contained varying levels of anionic detergent sodium lauryl sulphate and were compared with a commercially available toothpaste without Triclosan or zinc citrate and a 0.2% chlorhexidine mouthrinse. The toothpastes were used as slurry twice a day and plaque regrowth scored by area and the criteria of the debris index. Plaque inhibition was significantly greater with the chlorhexidine mouthrinse than with all of the toothpastes. There were no significant differences in plaque scores between any of the toothpastes. It would appear that at the concentration of 0.2% Triclosan with or without 0.5% zinc citrate provides little if any additional benefit to plaque inhibition to that produced by a conventional toothpaste containing sodium lauryl sulphate.

Studies on the effect of toothpaste rinses on plaque regrowth. (I). Influence of surfactants on chlorhexidine efficacy

A number of compounds have been added to toothpastes to inhibit plaque regrowth. The inclusion of cationic antiseptics, such as chlorhexidine, poses formulation difficulties because of interactions with other ingredients particularly anionic detergents. More recently, Triclosan/zinc citrate formulations have been shown effective plaque inhibitors. The aim of this study was to compare a commercially available 0.2% Triclosan/0.5% zinc citrate toothpaste with a number of experimental 0.5% chlorhexidine/detergent toothpastes for effects on plaque regrowth over 4 days. Subjects rendered plaque free at each baseline rinsed twice a day with toothpaste slurries and disclosed plaque was scored at the end of each period. All toothpastes significantly reduced plaque by comparison with a control toothpaste, but were significantly less effective than a 0.2% chlorhexidine rinse. Some significant differences in favour of one chlorhexidine toothpaste were noted but these were small in magnitude. Whether the plaque inhibition obtained with Triclosan/zinc citrate toothpaste was greater than would be expected from other commercially available preparations cannot be determined from this study and is the subject of a further investigation.

Comparison of the effect of toothpastes containing enzymes or antimicrobial compounds with a conventional fluoride toothpaste on the development of plaque and gingivitis

Many toothpastes have been formulated over recent years to contain antimicrobial compounds with the aim of preventing or reducing plaque, calculus, gingival inflammation or dental caries. For many, if not all of these toothpastes, it has yet to be proven whether they are significantly better at reducing plaque and gingivitis than conventional toothpastes, for which no such therapeutic effects have been claimed. This 12-day, incomplete block designed, cross-over study compared the development of plaque and gingivitis following rinsing with toothpaste slurries containing the following active ingredients: (1) hexetidine/zinc citrate, (2) 0.2% triclosan, (3) amyloglucosidase/glucose oxidase, (4) sodium fluoride/sodium monofluorophosphate (NaF, MFP). By the 8th day of the study, a significant difference in gingival crevicular fluid (GCF) and GI was found between the groups. By day 12, however, no significant difference in plaque index and gingival inflammation was found between the 4 toothpastes, although plaque area was significantly reduced with the hexetidine/zinc citrate paste when compared to the conventional fluoride paste. It was concluded that the active ingredients added to the toothpastes evaluated in this study provided little or no more additional benefit to oral hygiene and gingival health than could be achieved with a conventional fluoride toothpaste.

The effect of a cetylpyridinium chloride (CPC) detergent foam compared to a conventional toothpaste on plaque and gingivitis. A single blind crossover study

A CPC-detergent formulation in a foam vehicle, was compared with a fluoride toothpaste for its ability to prevent plaque and gingivitis over a period of 12 days. Whilst refraining from all other oral hygiene procedures, the foam or toothpaste was applied to the teeth in fluoride application trays, in a group of 14 volunteers. At days 8 and 12 of this crossover study, the following assessments were made: gingival crevicular fluid; gingival index; bleeding on probing; plaque index; plaque area. Except for plaque area at day 8 of the study, there were no significant differences between the 2 products at either day 8 or day 12. It is therefore concluded that the CPC-detergent formulation, in its present form, does not inhibit plaque and gingivitis more effectively than a conventional fluoride toothpaste.