Direct measurement of the bactericidal effect of chlorhexidine on human dental plaque

The Oral Microbiota

The oral microbiota represents an important part of the human microbiota, and includes several hundred to several thousand diverse species. It is a normal part of the oral cavity and has an important function to protect against colonization of extrinsic bacteria which could affect systemic health. On the other hand, the most common oral diseases caries, gingivitis and periodontitis are based on microorganisms. While (medical) research focused on the planktonic phase of bacteria over the last 100 years, it is nowadays generally known, that oral microorganisms are organised as biofilms. On any non-shedding surfaces of the oral cavity dental plaque starts to form, which meets all criteria for a microbial biofilm and is subject to the so-called succession. When the sensitive ecosystem turns out of balance - either by overload or weak immune system - it becomes a challenge for local or systemic health. Therefore, the most common strategy and the golden standard for the prevention of caries, gingivitis and periodontitis is the mechanical removal of this biofilms from teeth, restorations or dental prosthesis by regular toothbrushing.

Development of a biofilm inhibitor molecule against multidrug resistant Staphylococcus aureus associated with gestational urinary tract infections

Urinary Tract Infection (UTI) is a globally widespread human infection caused by an infestation of uropathogens. Eventhough, Escherichia coli is often quoted as being the chief among them, Staphylococcus aureus involvement in UTI especially in gestational UTI is often understated. Staphylococcal accessory regulator A (SarA) is a quorum regulator of S. aureus that controls the expression of various virulence and biofilm phenotypes. Since SarA had been a focussed target for antibiofilm agent development, the study aims to develop a potential drug molecule targeting the SarA of S. aureus to combat biofilm associated infections in which it is involved. In our previous studies, we have reported the antibiofilm activity of SarA based biofilm inhibitor, (SarABI) with a 50% minimum biofilm inhibitory concentration (MBIC50) value of 200 μg/mL against S. aureus associated with vascular graft infections and also the antibiofilm activity of the root ethanolic extracts of Melia dubia against uropathogenic E. coli. In the present study, in silico design of a hybrid molecule composed of a molecule screened from M. dubia root ethanolic extracts and a modified SarA based inhibitor (SarABI(M)) was undertaken. SarABI(M) is a modified form of SarABI where the fluorine groups are absent in SarABI(M). Chemical synthesis of the hybrid molecule, 4-(Benzylamino)cyclohexyl 2-hydroxycinnamate (henceforth referred to as UTI Quorum-Quencher, UTI(QQ)) was then performed, followed by in vitro and in vivo validation. The MBIC50 and MBIC90 of UTI(QQ) were found to be 15 and 65 μg/mL, respectively. Confocal laser scanning microscopy (CLSM) images witnessed biofilm reduction and bacterial killing in either UTI(QQ) or in combined use of antibiotic gentamicin and UTI (QQ) . Similar results were observed with in vivo studies of experimental UTI in rat model. So, we propose that the drug UTI(QQ) would be a promising candidate when used alone or, in combination with an antibiotic for staphylococcal associated UTI.

Effect of fluoride and chlorhexidine digluconate mouthrinses on plaque biofilms

Objective : To develop a model in which to investigate the architecture of plaque biofilms formed on enamel surfaces in vivo and to compare the effects of anti-microbial agents of relevance for caries on biofilm vitality. Materials and Methodology : Enamel discs mounted on healing abutments in the pre-molar region were worn by three subjects for 7 days. Control discs were removed before subjects rinsed with 0.1% chlorhexidine digluconate (CHX) or 0.2% sodium fluoride (NaF) for 1 minute. Biofilms were stained with Baclight Live/Dead and z-stacks of images created using confocal scanning laser micoscopy. The levels of vital and dead/damaged bacteria in the biofilms, assessed as the proportion of green and red pixels respectively, were analysed using ImageTrak^® software. Results : The subjects showed individual differences in biofilm architecture. The thickness of the biofilms varied from 28-96µm although cell density was always the greatest in the middle layers. In control biofilms, the overall levels of vitality were high (71-98%) especially in the area closest to the enamel interface. Rinsing with either CHX or NaF caused a similar reduction in overall vitality. CHX exerted an effect throughout the biofilm, particularly on the surface of cell clusters whereas NaF caused cell damage/death mainly in the middle to lower biofilm layers. Conclusion : We describe a model that allows the formation of mature, undisturbed oral biofilms on human enamel surfaces in vivo and show that CHX and NaF have a similar effect on overall vitality but differ in their sites of action.

Effect of a Chlorhexidine Mouthwash on the Risk of Postextraction Bacteremia

Objective.

To investigate the prevalence, duration, and etiology of bacteremia following dental extractions performed after a single administration of Chlorhexidine mouthwash.

Design and Setting.

A randomized, controlled trial performed in a university hospital.

Methods.

A series of 106 patients with mental and behavioral disabilities who underwent dental extractions under general anesthesia were randomly assigned to a control group or Chlorhexidine group. The exclusion criteria applied were use of antibiotics in the previous 3 months, use of oral antiseptics, any type of congenital or acquired immunodeficiency, and disease that predisposes the patient to infections or bleeding. The Chlorhexidine group had 0.2% Chlorhexidine mouthwash administered for 30 seconds before any dental manipulation. Blood samples were collected at baseline, 30 seconds, 15 minutes, and 1 hour after the dental extractions. Subculture and further identification of the isolated bacteria were performed by conventional microbiological techniques.

Results.

The prevalence of bacteremia after dental extraction in the control and Chlorhexidine groups were 96% and 79%, respectively, at 30 seconds (P = .008), 64% and 30% at 15 minutes (P <.001), and 20% and 2% at 1 hour (P = .005). The most frequently identified bacteria were Streptococcus species in both the control and Chlorhexidine groups (64% and 68%, respectively), particularly viridans group streptococci.

Conclusion.

We recommend the routine use of a 0.2% Chlorhexidine mouthwash before dental extractions to reduce the risk of postextraction bacteremia.

Effect of CPP/ACP on initial bioadhesion to enamel and dentin in situ

The present in situ study investigated the influence of a preparation containing CPP/ACP (caseinphosphopeptide-amorphous calcium phosphate) (GC Tooth mousse) on initial bacterial colonization of enamel and dentin. Therefore, pellicle formation was performed in situ on bovine enamel and dentin specimens fixed to individual upper jaw splints worn by 8 subjects. After 1 min of pellicle formation GC Tooth mousse was used according to manufacturer's recommendations. Rinses with chlorhexidine served as positive controls. Specimens carried without any rinse served as negative controls. After 8 h overnight exposure of the splints, bacterial colonization was quantified by fluorescence microscopy (DAPI and BacLight live/dead staining). Additionally, the colony forming units (CFU) were determined after desorption. Furthermore, the effects on Streptococcus mutans bacteria were tested in vitro (BacLight). There was no significant impact of CPP/ACP on initial bacterial colonization proved with DAPI and BacLight. Determination of CFU showed statistical significance for CPP/ACP to reduce bacterial adherence on enamel. The in vitro investigation indicated no antimicrobial effects for CPP/ACP on Streptococcus mutans suspension. Under the chosen conditions, CPP/ACP (GC Tooth mousse) had no significant impact on initial biofilm formation on dental hard tissues. The tested preparation cannot be recommended for biofilm management.

Confusion over live/dead stainings for the detection of vital microorganisms in oral biofilms--which stain is suitable?

BACKGROUND

There is confusion over the definition of the term "viability state(s)" of microorganisms. "Viability staining" or "vital staining techniques" are used to distinguish live from dead bacteria. These stainings, first established on planctonic bacteria, may have serious shortcomings when applied to multispecies biofilms. Results of staining techniques should be compared with appropriate microbiological data.

DISCUSSION

Many terms describe "vitality states" of microorganisms, however, several of them are misleading. Authors define "viable" as "capable to grow". Accordingly, staining methods are substitutes, since no staining can prove viability.The reliability of a commercial "viability" staining assay (Molecular Probes) is discussed based on the corresponding product information sheet: (I) Staining principle; (II) Concentrations of bacteria; (III) Calculation of live/dead proportions in vitro. Results of the "viability" kit are dependent on the stains' concentration and on their relation to the number of bacteria in the test. Generally this staining system is not suitable for multispecies biofilms, thus incorrect statements have been published by users of this technique.To compare the results of the staining with bacterial parameters appropriate techniques should be selected. The assessment of Colony Forming Units is insufficient, rather the calculation of Plating Efficiency is necessary. Vital fluorescence staining with Fluorescein Diacetate and Ethidium Bromide seems to be the best proven and suitable method in biofilm research.Regarding the mutagenicity of staining components users should be aware that not only Ethidium Bromide might be harmful, but also a variety of other substances of which the toxicity and mutagenicity is not reported.

SUMMARY

- The nomenclature regarding "viability" and "vitality" should be used carefully.- The manual of the commercial "viability" kit itself points out that the kit is not suitable for natural multispecies biofilm research, as supported by an array of literature.- Results obtained with various stains are influenced by the relationship between bacterial counts and the amount of stain used in the test. Corresponding vitality data are prone to artificial shifting.- As microbiological parameter the Plating Efficiency should be used for comparison.- Ethidium Bromide is mutagenic. Researchers should be aware that alternative staining compounds may also be or even are mutagenic.

In situ chlorhexidine substantivity on saliva and plaque-like biofilm: influence of circadian rhythm

BACKGROUND

The aim of the present study is to assess in situ substantivity of a single mouthrinse with 0.2% chlorhexidine (CHX) on saliva and on undisturbed de novo plaque-like biofilm (PL-biofilm), differentiating between two times of application: 1) CHX mouthrinse in the morning; and 2) CHX mouthrinse at night.

METHODS

The study participants were 10 healthy volunteers who wore an individualized splint with glass disks for 48 hours to boost the growth of PL-biofilm. Saliva samples were collected, and two disks were removed from each volunteer's splint at 8, 10, and 12 hours after performing a mouthrinse with 0.2% CHX at 7:00 am (M-0.2% CHX-diurnal) and 1:00 am (M-0.2% CHX-nocturnal). The saliva and plaque samples were analyzed by epifluorescence and confocal laser scanning microscopy, respectively, using a green fluorescent nucleic acid stain/propidium iodide staining.

RESULTS

With M-0.2% CHX-diurnal, the frequency of vital bacteria in saliva was significantly higher than in the PL-biofilm at 8, 10, and 12 hours after mouthrinse. After M-0.2% CHX-nocturnal, the frequency of vital bacteria in saliva was significantly lower than in the PL-biofilm at 8 hours and higher than in the PL-biofilm at 12 hours after mouthrinse.

CONCLUSION

These results support the more active physiologic dynamics of the salivary flora and the possible reservoir function associated with the structure of undisturbed de novo PL-biofilm.

Antibacterial effect of taurolidine (2%) on established dental plaque biofilm

Preliminary data have suggested that taurolidine may bear promising disinfectant properties for the therapy of bacterial infections. However, at present, the potential antibacterial effect of taurolidine on the supragingival plaque biofilm is unknown. To evaluate the antibacterial effect of taurolidine on the supragingival plaque biofilm using the vital fluorescence technique and to compare it with the effect of NaCl and chlorhexidine (CHX), 18 subjects had to refrain from all mechanical and chemical hygiene measures for 24 h. A voluminous supragingival plaque sample was taken from the buccal surfaces of the lower molars and wiped on an objective slide. The sample was then divided into three equal parts and mounted with one of the three test or control preparations (a) NaCl, (b) taurolidine 2% and (c) CHX 0.2%. After a reaction time of 2 min, the test solutions were sucked of. Subsequently, the plaque biofilm was stained with fluorescence dye and vitality of the plaque flora was evaluated under the fluorescence microscope (VF%). Plaque samples treated with NaCl showed a mean VF of 82.42 ± 6.04%. Taurolidine affected mean VF with 47.57 ± 16.60% significantly (p < 0.001, paired t test). The positive control CHX showed the lowest mean VF values (34.41 ± 14.79%; p < 0.001 compared to NaCl, p = 0.017 compared to taurolidine). Taurolidine possesses a significant antibacterial effect on the supragingival plaque biofilm which was, however, not as pronounced as that of CHX.

Visualization of adherent micro-organisms using different techniques

The visualization and quantification of adherent bacteria is still one of the most relevant topics in microbiology. Besides electron microscopic techniques such as transmission electron microscopy, scanning electron microscopy and environmental scanning electron microscopy, modern fluorescence microscopic approaches based on fluorogenic dyes offer detailed insight into bacterial biofilms. The aim of the present review was to provide an overview of the advantages and disadvantages of different methods for visualization of adherent bacteria with a special focus on the experiences gained in dental research.

Substantivity of amine fluoride/stannous fluoride following different modes of application: a randomized, investigator-blind, placebo-controlled trial

OBJECTIVE

Amine fluoride/stannous fluoride (ASF) is proven to be effective against plaque and gingivitis. The purpose of this clinical controlled study was to investigate the influence of different application modes on the substantivity of this formulation.

MATERIAL AND METHODS

Seventeen healthy volunteers received a professional dental prophylaxis. Undisturbed plaque growth was permitted for the next 48 h. In a crossover design, participants received ASF as a single mouthrinse, toothpaste, slurries with high (HA) or low (LA) air content, or a placebo. Vitality of plaque bacteria was investigated before and at 1, 2, 3, 4, 6, and 8h after application of ASF. ANOVA was applied on a 0.05 significance level.

RESULTS

Highest reduction of plaque vitality resulted after toothpaste application, followed by mouthrinse, LA, and HA slurry. No changes occurred in the placebo group. Compared to baseline and placebo, statistically significant changes were detected up to 4h in all ASF groups. Toothpaste exerted antibacterial efficacy up to 8h. Vitality reduction was higher in the LA group than in the HA group.

CONCLUSIONS

The concentration of ASF in formulations influences the time course of the antibacterial effect. Contact of ASF formulations with air might reduce their efficacy.

Effect of N-chlorotaurine mouth rinses on plaque regrowth and plaque vitality

The purpose of this 4-day plaque regrowth study was to assess the effect of N-chlorotaurine (NCT) mouth rinses on plaque inhibition and plaque vitality. Eighty volunteers participated in this investigator-blind, randomized, clinical controlled study in parallel groups. No oral hygiene was permitted except rinsing with a 2% or 3% NCT mouth rinse, a positive or a negative control. Primary parameters were the plaque index (Silness and Löe, Acta Odontol Scand, 22:121-135, 1964) and plaque vitality (Netuschil et al., J Clin Periodontol, 16:484-488, 1989) after the final rinse. In addition, another plaque index (Turesky et al., J Periodontol, 41:41-43, 1970), plaque area, and bleeding on probing were recorded. All parameters were taken at baseline and day 5. U test was applied on a 5% error level. No differences in plaque inhibition were found between the two NCT formulations and the negative control. However, a statistically significant reduction of plaque vitality compared to the negative and positive control was observed. Discoloration of the tongue and unpleasant taste were recorded in participants in the NCT groups. NCT mouth rinses did not inhibit plaque regrowth, but they did reduce the vitality of plaque bacteria. Methods of prolonging the substantivity of the NCT mouth rinses should be investigated to enhance the antibacterial properties of these formulations.

Fluorescence microscopic visualization and quantification of initial bacterial colonization on enamel in situ

OBJECTIVE

The acquired salivary pellicle has been defined as proteinaceous film free of bacteria. However, due to the large numbers of microorganisms existent in the oral fluids, it is conceivable that adherent bacteria are already present in the initial pellicle. The aim of this in situ study was to visualize and to quantify these bacteria.

DESIGN

Initial biofilm formation was performed on bovine enamel slabs mounted buccally on individual splints and carried in situ by six subjects for 3, 30 and 120 min, respectively. After intraoral exposure, the slabs were rinsed with saline solution and the adherent bacteria were investigated with the following fluorescence microscopic methods: staining with 4',6-diamidino-2-phenylindole (DAPI), staining of vital and nonvital bacteria with fluoresceinediacetate and ethidiumbromide (live/dead staining) and fluorescence in situ hybridization (FISH) of eubacteria and streptococci, respectively. In addition, determination of colony forming units after ultrasonically induced detachment of bacteria was performed.

RESULTS

With all the methods, bacteria were detected in the initial in situ biofilm irrespective of the formation time. The numbers of bacteria revealed high intraindividual and interindividual variability and the microorganisms were distributed randomly in small aggregates. The results of the epifluorescence microscopic techniques corresponded well. The mean number of adherent bacteria detected was in the range of 10-20x10(4)cm(-2).

CONCLUSION

Already after 3 min, adherent bacteria are present in the initial pellicle. For the first time, DAPI-staining as well as FISH have proven success for visualization of initial intraoral colonization of enamel specimens.

Effect of water-soluble reduced chitosan on Streptococcus mutans, plaque regrowth and biofilm vitality

The purpose of the present study was to examine the effects of a newly developed water-soluble reduced chitosan on Streptococcus mutans, plaque regrowth, and biofilm vitality. A 1.0%, water-soluble reduced chitosan, with pH ranging from 6.0 to 6.5, molecular weights between 3,000 and 5,000 Da, and 70% degree of deacetylation, was used. To determine antibacterial and antiplaque potency of chitosan, minimal inhibitory concentrations (MICs) for S. mutans and S. sanguinis (formerly S. sanguis), short-term exposure to S. mutans, and clinical trial of plaque regrowth and biofilm vitality were conducted. Twelve dental students volunteered to participate in the 6-week, double blind, randomized clinical trial using the classical 4-day plaque regrowth design. The MIC of water-soluble reduced chitosan for S. mutans was 1.25 g/l. While the cells exposed to distilled water (DW) grew rapidly, with a maximum turbidity reached by 16 h postinoculation, S. mutans exposed to chitosan (5.0 g/l) exhibited a substantial delay in growth and reached a maximum turbidity by 32 h postinoculation. The chitosan solution reduced the plaque index and the vitality of the plaque flora significantly when compared to DW, but this was less than the reductions found with the positive control of 0.1% chlorhexidine solution. The water-soluble reduced chitosan exhibited potent antibacterial effect on S. mutans, and displayed a significant antibacterial and plaque-reducing action during the 4-day plaque regrowth.

An in vitro antimicrobial comparison of miswak extract with commercially available non-alcohol mouthrinses

The aim of this study was to assess the antimicrobial activity of eight commercially available mouthrinses and 50% miswak extract against seven microorganisms. Corsodyl, Alprox, Oral-B advantage, Florosept, Sensodyne, Aquafresh Mint, Betadine and Emoform mouthrinses were used while 50% aqueous extract of miswak (Salvadora persica) was used against Streptococcus faecalis, Streptococcus pyogenis, Streptococcus mutans, Candida albicans, Staphylococcus aureus and Staphylococcus epidermidis. The ditch plate method was used to test the antimicrobial activity. Inhibition zones of microorganisms around ditches were measured in millimetres. Range, mean and standard deviations were used for comparison of antimicrobial activity. Mouthrinses containing chlorhexidine was with maximum antibacterial activity, while cetylpyridinium chloride mouthrinses were with moderate and miswak extract was with low antibacterial activity. Further research is needed for the substantivity of these mouthrinses and further in vivo/in vitro studies are needed using Biofilm model to substantiate present findings. Dental professionals must exercise caution and provide guidance in assisting their patients in making informed choices regarding their use of mouthrinses for clinical efficacy.

How to select the right mouthrinses in periodontal prevention and therapy. Part I. Test systems and clinical investigations

The use of mouthrinses is increasing, especially as adjuncts to the daily mechanical oral hygiene. Different test systems may and can be used to test their antibacterial and clinical effects: bacteriology in vitro, substantivity in vivo, 4-day plaque re-growth, experimental gingivitis and long-term use. The plaque re-growth investigations of a few days are not only of limited use but may also be dangerous because often too extensive conclusions have been drawn from their design. The 'gold standard' test is the experimental gingivitis model to reveal the antiplaque as well as the antigingivitis effects of any mouthrinse preparation during 3 weeks. The last kind of investigations are of several months' duration, where the substances are used as supplements to mechanical oral hygiene measures.

Adherence of Streptococcus mutans to various restorative materials in a continuous flow system

A continuous flow system was developed to evaluate the adhesion of Streptococcus mutans ATCC 25175 to filling materials (Ariston, Tetric, Dyract, Compoglass, Vitremer, Aqua Ionofil, Ketac Fil, amalgam, Galloy and ceramics as controls). Streptococcus mutans was added to saliva-coated test specimens, and a nutrient broth permanently supplied over a time period of 48 h and then the weight of plaque, the number and viability of the bacteria adhering to the materials were determined. The weights of artificial plaque on all filling materials tested were higher than those on ceramics, the highest values were measured on the glass-ionomers. The amount of plaque correlates with the surface roughness, whereas there was no correlation of the surface roughness with the number of colony-forming units (CFU) of S. mutans. The CFU of adhering S. mutans also depends on the viability of the bacteria. The plaque on Ketac Fil contained a high number of viable bacteria. The fluorides of glass-ionomers do not efficiently prevent the attachment and the viability of S. mutans.

Efficacy of an amine fluoride-triclosan mouthrinse as compared to the individual active ingredients

BACKGROUND

The purpose of the clinical study was to examine the antibacterial and plaque-reducing properties of mouthrinses containing triclosan (TRI), amine fluoride (AmF), and the combination of both (AFT) on 4-day plaque regrowth. A placebo solution (PLA) and a 0.2% chlorhexidine solution (CHX) served as negative and positive controls, respectively.

MATERIALS AND METHODS

After a professional tooth cleaning (day 0), 15 volunteers refrained from all mechanical oral hygiene measures for the next 96 h and rinsed instead twice daily for 1 min with 10 ml of one of the five randomly assigned solutions. Plaque index (PlI), which was assessed after 24 and 96 h (PlI1, PlI2), and plaque area of the front teeth (PA), which was planimetrically recorded from disclosed teeth after 96 h, served as clinical parameters. After 24 and 96 h a plaque sample was taken and analyzed microbiologically to evaluate biofilm vitality (VF1, VF2). The subsequent test cycles were conducted after a washout period of 10 days each.

RESULTS

No severe adverse events or allergy were seen during the study. CHX influenced all parameters at all time points in comparison to PLA. AFT and AmF showed very similar values (in all parameters), but AmF did not reach the level of significance regarding VF1, nor did AFT with VF2 and PlI1. The TRI solution only reduced PlI2 and PA significantly, but had no influence on biofilm vitality when compared to PLA.

CONCLUSION

A synergism between AmF and TRI was not observed. The results suggest that the plaque-reducing and antibacterial effects of the AFT solution are mainly based on the effects of the amine fluoride moiety.

Antimicrobial activity of garlic, tea tree oil, and chlorhexidine against oral microorganisms

OBJECTIVE

To compare the antimicrobial activity of tea tree oil, garlic, and chlorhexidine solutions against oral microorganisms.

METHOD

The five-week study consisted of thirty subjects. The first week was considered baseline. All subjects used a control solution (second week), and were randomly divided into the three groups (third week): G1-0.12% chlorhexidine; G2 - 2.5% garlic (Allium sativum, L.); and G3 - 0.2% tea tree oil (Melaleuca alternifolia). Dishes containing blood agar and Mitis Salivarius Bacitracin agar (MSB) were inoculated with the subjects' saliva (collected twice a week). Total microorganisms and mutans streptococci were counted in blood agar and MSB, respectively.

RESULTS

Chlorhexidine and garlic groups showed antimicrobial activity against mutans streptococci, but not against other oral microorganisms. The tea tree oil group showed antimicrobial activity against mutans streptococci and other oral microorganisms. Maintenance of reduced levels of microorganisms was observed only for garlic and tea tree oil during the two consecutive weeks (fourth and fifth). Unpleasant taste (chlorhexidine 40%, tea tree oil 30%, garlic 100%), burning sensation (chlorhexidine 40%, tea tree oil 60%, garlic 100%), bad breath (chlorhexidine 40%, tea tree oil 20%, garlic 90%), and nausea (chlorhexidine 0%, tea tree oil 10%, garlic 30%) were reported.

CONCLUSION

Garlic and tea tree oil might be an alternative to chlorhexidine.

Substantivity of toothpaste slurries and their effect on reestablishment of the dental biofilm

OBJECTIVES

Toothpastes are good vehicles for antibacterial substances to exert a prolonged effect. This effect depends on the substantivity and ability to interfere with plaque metabolism and/or vitality. It was the purpose of this clinical, randomized 2 x 4 cell crossover study to evaluate and to compare the antibacterial effects of two toothpastes (Colgate Total(R), COL and Parodontax(R), PAR) applied as slurries on established plaque over 24 h (Part I) and their effect on 4-day plaque regrowth (Part II). Chlorhexamed(R) (0.1%; CHX) and water served as positive and negative controls.

MATERIAL AND METHODS

After professional toothcleaning eight students were asked to refrain from all mechanical hygiene measures for the next 72 h. After 48 h plaque was sampled and vitality of the plaque flora examined (baseline, VF0%). The subjects then rinsed for 1 min with 15 mL of one of the test or control solutions. Every second hour up to 14 h and 24 h after rinsing, plaque sampling and staining was performed to assess plaque vitality (VF2-24, Part I). In Part II, the classical 4-day plaque regrowth design was used with two rinses (1 min) a day as the only oral hygiene measure. Vitality values were assessed on day 1 and day 4 (VF1, VF2). At day 4, teeth were stained to assess the whole mouth plaque index (PlI) and to evaluate the percentage of plaque area (PA) of the anterior teeth.

RESULTS

Compared to placebo, all active rinses reduced plaque vitality significantly over a period of 24 h (Part I). PAR, COL and CHX revealed reductions of 18-31%, 28-50% and 19-50%, respectively. In Part II, similar reductions of all parameters were found for all active rinses (PAR 12-30%, COL 34-51%, CHX 40-64%).

CONCLUSIONS

Colgate Total has shown a significant action on plaque regrowth and a high substantivity during 24 h, while Parodontax revealed a more moderate but still significant effect.

Effect of an amine-fluoride-triclosan mouthrinse on plaque regrowth and biofilm vitality

BACKGROUND

The purpose of this double-blind, prospective, latin-square crossover randomised study was to examine the efficacy of a mouthrinse solution containing a combination of triclosan, amine fluoride and sodium fluoride on supragingival plaque regrowth compared to a placebo and a chlorhexidine solution.

METHODS

12 volunteers refrained after professional oral prophylaxis from all mechanical hygiene measures for the following 96 h and rinsed instead cross-over in a randomised order with either chlorhexidine digluconate (0.2%, positive control), a verum solution (0.5% amine fluoride, 0.028% sodium fluoride, 0.03% triclosan) or a placebo solution. The plaque index was assessed after 24 and 96 h (PI 1, PI 2) and the plaque area (PA) photographed and calculated after 96 h of undisturbed plaque regrowth. Moreover plaque samples were taken after 24 and 96 h and examined with the vital fluorescence technique to assess the vitality of the biofilm microbiota (VF 1, VF 2).

RESULTS

The amine-fluoride-triclosan solution reduced the clinical parameters (PI and PA) as well as the vitality of the plaque flora (VF) significantly when compared to the placebo solution. The verum reached a 36.5% (p<0.05) and a 39.8% reduction (p<0.0001) in PI 1 and PI 2, respectively, concomittant with a reduction of 23.8% and 32.2% (p<0.001) in VF 1 and VF 2 and of 46.9% (p<0.0001) in PA at day 4. This was less than the reductions found with the positive control, i.e., the 0.2% chlorhexidine solution (54.2% and 71.1% reduction in PI 1 and PI 2, 40.0% and 53.4% in VF 1 and VF 2 and 71.5% in PA). However, significant differences between both active solutions were only established for PI 2 and PA.

CONCLUSION

During 4-day plaque regrowth the amine-fluoride-triclosan product displayed a significant antibacterial and plaque-reducing action in comparison to the control.

Anti-plaque effect of tempered 0.2% chlorhexidine rinse: an in vivo study

OBJECTIVES

The aim of this in vivo study was to compare the anti-plaque effect of warm and cold chlorhexidine gluconate irrigation on matured human plaque.

METHODS

In a split-mouth design, the antibacterial effect of 47 degrees C "warm" 0.2% chlorhexidine solution was compared with that of 18 degrees C "cold" rinse at the same concentration on newly-formed supragingival plaque that had been left undisturbed for 72 h. Before and 1 h after a 1-min rinse procedure, plaque was sampled from 10 test persons and vitality determined using vital fluorescence technique.

RESULTS

Cold and warm 0.2% chlorhexidine solution reduced plaque vitality significantly from 99.63% to 77.81% (p=0.014) and from 98.98% to 51.77% (p<0.001), respectively. Rinsing with warm chlorhexidine solution reduced plaque vitality to a significantly greater degree (p=0.003) than did cold chlorhexidine.

CONCLUSION

In this study, warm 0.2% chlorhexidine rinse showed a significantly more intensive anti-plaque effect than cold chlorhexidine solution at the same concentration.

The effect of dental restorative materials on dental biofilm

To investigate the arrangement of biofilms formed in vivo, volunteers wore splints with slabs of six different dental materials inserted to collect smooth surface plaque. After 5 d of undisturbed plaque accumulation, the specimens were vital stained and analyzed by the confocal laser scanning microscopy (CLSM) to evaluate the percentage of vital biofilm microflora (VF percentage). Further parameters were the area of the specimens covered by plaque (surface coating; SC, %) and the height of the biofilms (BH, pm). The metals amalgam and gold, the compomer, as well as the glass-ionomer cement harboured an almost entirely dead biofilm (VF <8%). Resin composite led to vitality values between 4 and 21%, while a very thin biofilm on ceramic revealed the highest vitality values (34-86%). SC varied from 6% on glass-ionomer cement to 100% on amalgam. BH reached its highest value on amalgam and gold of 17 and 11 microm, respectively, while heights of between 1 and 6 microm were found on the ceramic, resin composite, compomer and the glass-ionomer cement. Within their limits, the present findings indicate that amalgam, gold, compomer and glass-ionomer cement exert an influence against the adhering biofilm. No general relationship could be established between the different parameters VF percentage, SC percentage and BH (microm).

Effect of an enamel matrix protein derivative (Emdogain) on ex vivo dental plaque vitality

BACKGROUND

A common clinical observation following surgical periodontal therapy with an enamel matrix derivative (Emdogain) is the improved healing of the soft tissues and the limited inflammation of the operated areas. These clinical observations are empirical and difficult to explain. One of the factors influencing the early wound healing might be a potential antimicrobial effect of Emdogain.

AIM

To investigate the effect of Emdogain on the vitality of ex vivo supragingival dental plaque and to compare this effect to that of a standard 0.2% chlorhexidine solution.

MATERIALS AND METHODS

24 patients suffering from adult periodontitis were included in the study. At the beginning of the experiment, all participants were given a professional tooth cleaning. For the following 4 days, they had to refrain from any kind of oral hygiene measures. At day 5, from each of the volunteers, a voluminous plaque biofilm sample was taken with a sterile curette from the vestibular surfaces of the 1st lower molars and divided into 5 equal parts. Each part was mounted with 5 microl of the following solutions: (1) NaCl, (2) enamel matrix derivative dissolved in water (EMD), (3) enamel matrix derivative dissolved in the vehicle (Emdogain), (4) vehicle (propylene glycol alginate, PGA), (5) 0.2% chlorhexidine digluconate (CHX). After a reaction time of 2 min the test solutions were sucked off, and subsequently the biofilm was stained with a fluorescence dye. The vitality of the plaque flora after the treatments was evaluated under the fluorescence microscope (VF%).

RESULTS

Plaque samples treated with NaCl showed a mean vitality of 76.8+/-8%. The EMD, Emdogain, PGA and CHX showed VF values of 54.4+/-9.2, 21.4+/-10.6%, 19.6+/-11.6% and 32.3+/-11.8%, respectively. Emdogain, PGA and CHX showed statistically highly significant reductions (p<0.0001) in terms of bacteria vitality when compared to water (negative control) and EMD. Both Emdogain and PGA were found to be statistically significantly different compared to CHX (p<0.001) (positive control).

CONCLUSION

The results of this study indicate that Emdogain might have an antibacterial effect on the vitality of the ex vivo supragingival dental plaque flora.

The ability of direct fluorescence-based, two-colour assays to detect different physiological states of oral streptococci

AIMS

To investigate the ability of six fluorescent-based, two-colour viability assays to detect different physiological growth stages of two oral streptococci species.

METHODS AND RESULTS

The growth of Streptococcus sanguinis and Strep. mutans from 0 to 73 h culture periods was monitored by cell labelling with six mixtures of fluorescent stains, in addition to the growth parameters optical density (O.D.), log values of the total cell counts (log BC ml(-1)) and of the colony-forming units (log cfu ml(-1)).

CONCLUSION

In comparison with the corresponding cfu values as control, the vitality proportions determined by the Syto 9/PI test best reflected the dynamic growth pattern of both test strains. The direct fluorescent-based, two-colour assay Syto 9/PI provides valuable information about microbial viability stages.

SIGNIFICANCE AND IMPACT OF THE STUDY

The detection of viable but non-culturable bacteria requires more precise direct methods such as the fluorescent staining technique presented here, in addition to the classical plate count method.

Conofocal microscopy study of undisturbed and chlorhexidine-treated dental biofilm

Culturing of dispersed plaque samples and vitality staining of plaque smears are the most commonly used methods for evaluating the effects of antimicrobials on dental plaque. The visualization of the antimicrobial action on oral biofilm present on the substrate surface (in situ) would add valuable information to the existing knowledge about the treatment effects. This study aimed at combining the advantage of confocal laser scanning microscopy (CLSM) to visualize plaque non-destructively with a vitality staining technique to assess the immediate bactericidal effect of chlorhexidine (CHX) on biofilm. Three 200-microm-wide grooves were cut into bovine dentin discs for plaque accumulation. The discs were worn by six subjects for 6, 24, and 48 hrs, then broken into halves, one of which received a one-minute extraoral 0.2% CHX treatment, while the other served as control. Both halves were stained for vital fluorescence measurements and visualized by CLSM. Plaque vitality (in %) was quantified by image analysis in three plaque layers-outer, middle, and inner. The CHX effect was significant in six-hour samples (p < 0.001) and only in the outer layer of the 48-hour plaque (p < 0.001), demonstrating a resistant nature of dental biofilm to a single CHX treatment. With the present approach, we have shown that it is possible to visualize and quantitate the antimicrobial treatment effect on biofilm still present on the substrate on which it was grown.

Spatial distribution of vital and dead microorganisms in dental biofilms

To examine the spatial structure of dental biofilms a vital fluorescence technique was combined with optical analysis of sections in a confocal laser scanning microscope (CLSM). Enamel slaps were worn in intraoral splints by three volunteers for five days to accumulate smooth-surface plaque. After vital staining with fluorescein diacetate and ethidium bromide the specimens were processed for CLSM examination. Optical sections 1 microm apart were analysed in the z-axis of these dental biofilms. One of the films was 15 microm high, sparse and showed low vitality, i.e. <16%, while the others were taller (25 and 31 microm) and more vital, i.e. up to 30 and 69%, respectively. In all instances the bacterial vitality increased from the enamel surface to the central part of the plaque and decreased again in the outer parts of the biofilm. The spatial arrangement of the microorganisms in the biofilm showed voids outlined by layers of vital bacteria, which themselves were packed in layers of dead material.

Alcohol-free mouthrinse solutions to reduce supragingival plaque regrowth and vitality. A controlled clinical study

BACKGROUND

The aim of this study was to evaluate the clinical and antibacterial properties of alcohol-free mouthrinses, an amine fluoride/stannous fluoride mouthrinse (ASF) and two triclosan solutions in comparison with a chlorhexidine and a placebo rinse.

MATERIAL AND METHODS

In a double-blind, randomised 5-cell cross-over 4-day plaque regrowth study, 19 volunteers rinsed 2 x a day with 15 ml of each of the distributed solutions. Each test cycle was followed by a 10 days wash-out period. On day 0 of each test week, volunteers received a dental prophylaxis. Thereafter they refrained from all mechanical oral hygiene procedures for the next four days. Plaque regrowth was assessed daily by the plaque index and on day 4 by calculating the plaque area with a computer program after disclosure and photography of the front teeth. The vitality of the plaque was examined on days 1 to 4 by the vital fluorescence technique.

RESULTS

19 participants completed the study. Compared to the placebo the ASF solution showed 15.7% (p>0.5), 30.6% (p<0.001), 40.5% (p<0.001) and 44.7% (p<0.001) reductions on the consecutive days 14 in plaque index and a reduction of 61.9% in plaque area. The decrease of vitality of supragingival plaque was highly significant compared to placebo on every test day ranging between 30.9% and 36.6%. A reduction in plaque index from 19.4% (p<0.01) on day 2, 34.9% (p<0.001) on day 3 and 40.4% (p<0.001) on day 4 concommitant with a reduction in plaque area of 48.9% (p<0.001) was noted for alcohol-free chlorhexidine. Concerning the vitality chlorhexidine reduced the percentage of vital bacteria significantly on every day (16.0% to 24.9%). The reductions in mean plaque index for the 0.15% triclosan solution during the test period were 6.3%, 22.4%, 24.6% and 36% and in plaque area 41.8%. Vitality was significantly reduced at every day compared to placebo. Plaque Index reduction with the 0.02% triclosan increased from 15.3% (day 2) to 31.0% (day 4) and a reduction of 23.6% was seen in plaque area. A significant effect concerning the vitality of the plaque was only found at the first and the last day of the test cycle.

CONCLUSION

Alcohol-free mouthrinse solutions were shown to be effective in reducing both plaque accumulation and plaque biofilm vitality compared to a placebo solution.

The influence of a 0.2% chlorhexidine mouthrinse on plaque regrowth in orthodontic patients. A randomized prospective study. Part II: Bacteriological parameters

In a prospective plaque regrowth study focusing on oral hygiene during fixed appliance therapy 12 adolescent patients (mean age 14.1 +/- 1.5 years) were evaluated twice over 2-day test periods. In the randomized, double-blind study the influences of a 0.2% chlorhexidine mouthrinse (Corsodyl, CHX) and a commercially available dentifrice supplementing fluoride (Odol-med-3) were compared intra- and interindividually in a crossover design with regard to the bacteriological parameters. The bacteriological parameters of vital fluorescence, bacteriological counts (BC), colony forming units (CFU), plating efficiency (PE) and mutans streptococci (MS) were related to the clinically assessed indices of plaque and gingivitis. All parameters analyzed demonstrated significant differences between the control and the test (chlorhexidine) group. Where-as the values of BC, CFU, and PE progressively increased in the control group from T0 to T2, these parameters distinctly decreased in the chlorhexidine group. All values of vital flora (VF) scored around 75% in the control group compared to values of 30% in the test group. BC, CFU und PE correlated significantly. The score of mutans streptococci persisted or increased in the controls whereas mutans streptococci approached 0 in the chlorhexidine group. Until the 5th day of washout a clear-cut carry over of the chlorhexidine rinse on mutans streptococci as well as on the gingival index was evident. Since dead microorganisms remain on the tooth surface and in order to maintain oral health, chlorhexidine application might advisedly be supplemented by mechanical plaque control.

The effect of chlorhexidine mouthrinses on early bacterial colonization of guided tissue regeneration membranes. An in vivo study

BACKGROUND

Different membrane materials accumulate varying amounts of bacteria when exposed in the oral cavity, due to their textural and structural surface characteristics. The aim of the study was to evaluate the effect of chlorhexidine mouthrinses on the in vivo early bacterial colonization of 3 different guided tissue regeneration membrane materials.

METHODS

Rectangular-shaped strips cut from 3 periodontal membranes (expanded polytetrafluoroethylene, polyglactin 910, and polylactic acid) were glued to removable devices adapted to the 2 upper quadrants in 8 dental students. In each student 1 quadrant was randomly selected as test side while the other served as control side. The experiment was divided in 2 phases: in the first phase plaque accumulation was followed for 4 hours while the second accumulation was followed for 24 hours. During the 4-hour experiment, students rinsed the test device twice (immediately following device application and after 2 hours) with 0. 12% chlorhexidine solution. The control device was rinsed with saline. In the second phase, students rinsed the test device with chlorhexidine and the control devices with saline 3 times (after device application and at 8 and 16 hours). Both the 4-hour and the 24-hour specimens were processed for scanning electron microscopy analysis. Fifty-four fields (at 200x magnification) were randomly selected and analyzed on each strip. Magnification was increased to determine the presence and morphotype of bacteria. The presence or absence of bacteria was assessed in a binomial fashion: the field was bacteria-positive when bacteria constituted the deposits covering the membrane surface. The microscopic field was negative (bacteria-negative) when no bacteria were observed. Bacteria-positive fields showing rods and filaments as prevalent morphotypes were recorded as rod-positive fields.

RESULTS

The results of data analysis suggest that bacterial contamination of membrane materials is significantly reduced by treatment with chlorhexidine. They also suggest that other variables affect plaque accumulation as well; i.e., the time allowed (4 versus 24 hours) and the different membrane materials. The interaction between these 2 variables is also highly significant, thereby indicating a different rate of plaque accumulation on different materials, irrespective of the treatment with chlorhexidine.

CONCLUSIONS

It was concluded that chlorhexidine mouthrinses may be effective in reducing and delaying the early bacterial accumulation on membrane materials although they are not able to fully prevent it. Membrane surface characteristics seem to be a more critical factor than the use of chlorhexidine, in influencing bacterial adhesion and colonization of barrier materials.

In vitro models of biological responses to implant microbiological models

To study the etiology and explore possibilities for the therapy of implant-associated infections, investigators have developed and utilized various in vitro models. Major contributions have come from the non-oral medical field, where device-related infections can create life-threatening situations. Microbiological models may include (i) models to study the reaction of micro-organisms to the presence of implants, (ii) models to study the reaction of implant-associated micro-organisms to antimicrobial agents, and (iii) models to study the reaction of the host tissues to the presence of implants contaminated with micro-organisms. In evaluating the potential usefulness of these models for research in oral implantology, one must consider common features as well as important differences between implanted medical devices and oral implants. Although infections associated with implantable medical devices and oral peri-implant infections share a remarkable number of common features, there are also important differences that need attention when findings from in vitro experiments are extrapolated to clinical relevance.

An approach to differentiate between antibacterial and antiadhesive effects of mouthrinses in vivo

An experimental set-up allowing differentiation in vivo between antibacterial and antiadhesive properties of mouthrinses is described. The percentage of vital bacteria (= microbial vitality) and the bacterial counts were microscopically evaluated in saliva and in supragingival dental plaque both collected simultaneously at various times during de novo plaque formation. In a cross-over design, 12 healthy participants refrained from all oral hygiene for four separate periods of 2 x 4 h and 2 x 72 h after having rinsed with either an amine fluoride/stannous fluoride solution (Meridol) or 0.9% NaCl (placebo). Stimulated whole saliva was collected before and after the rinse. Together with whole-saliva samples, representative 4, 24 and 72-h-old plaque samples were separately taken from defined vestibular tooth surfaces that had been either exposed to the mouthrinse (unprotected sites) or temporarily covered with inert plastic films (protected sites) during rinsing. The pooled plaque and saliva were stained with fluorescent dyes to differentiate vital from dead micro-organisms which permitted the estimation of the percentages of vital bacteria. The total bacterial counts were quantified under the darkfield microscope. The Wilcoxon test was used for selected pairwise comparisons (alpha = 0.05). The percentage of vital bacteria in saliva fell significantly from 80-95% to about 50-60% as a result of the antibacterial activity of the test solution. These baseline values and those found in the presence of 4 and 24-h-old plaque were frequently lower than those recorded after the placebo rinse. In comparison to the placebo, microbial vitality was significantly reduced in early supragingival plaque formed on unprotected sites after applying the test solution. The similar total bacterial counts in 4-h-old plaque recorded after the use of the test solution on the unprotected and the protected areas did not point to an antiadhesive effect of the agent. It is concluded that this new experimental set-up allows decoding of the mode of action of a mouthrinse.

A pilot study of confocal laser scanning microscopy for the assessment of undisturbed dental plaque vitality and topography

Confocal microscopy and vital fluorescence techniques were combined for the first time to investigate ex vivo human dental plaque. The vital fluorescence technique used discriminates vital from dead cells, while confocal laser scanning microscopy allows the optical sectioning of undisturbed biofilms leaving the samples intact during analysis. The concomitant use of both methods made an examination of the three-dimensional architecture of dental plaque possible. The topography of plaque biofilms that were allowed to accumulate in situ on glass and enamel was recorded. The distribution of plaque microflora vitality as well as its accumulation varied according to plaque age. A plaque thickness of up to 8, 35 and 45 microm was estimated ex vivo on enamel after 1, 2 and 3 days, respectively. Young and sparse plaque biofilms consisted mainly of dead material. Vital bacteria were observed on top of this dead layers.

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.

Chemical agents for the control of plaque and plaque microflora: an overview

This presentation provides an overview of the technologies available for the chemical control of plaque. It is generally accepted that the formation of dental plaque at the interfaces of tooth/gingiva is one of the major causes of gingival inflammation and dental caries. Several therapeutic approaches have been used to control dental plaque and supragingival infections. These include fluoride preparations such as stannous fluoride, oxygenating agents, anti-attachment agents, and cationic and non-cationic antibacterial agents. Among the fluoride preparations, stable stannous fluoride pastes and gels have been shown to reduce supragingival plaque, gingivitis, hypersensitivity and caries. The effect of the oxygenating agents on the supragingival plaque has been equivocal, but recent data indicate that a stable agent which provides sustained active oxygen release is effective in controlling plaque. A polymer, PVPA, which reduced attachment of bacteria to teeth was shown to significantly reduce plaque formation in humans. A new generation of antibacterials includes non-ionics such as triclosan, which in combination with a special polymer delivery system, has been shown to reduce plaque, gingivitis, supragingival calculus and dental caries in long-term studies conducted around the world. Unlike the first generation of agents, the triclosan/copolymer/sodium fluoride system is effective in long-term clinicals and does not cause staining of teeth, increase in calculus, or disturbance in the oral microbial ecology.

Effects of chlorhexidine on the bacterial colonization and degradation of dentin and completely demineralized dentin in situ

The effects of 0.2% chlorhexidine on selected plaque microorganisms were studied in an intraoral dentin caries model. In 8 individuals wearing partial dentures, sound and completely demineralized dentin specimens were placed consecutively in 2 periods of 4 weeks, respectively. Throughout the experimental period, the specimens were treated 2 x daily with 0.2% chlorhexidine; control specimens were treated with water. Plaque accumulation on the specimens was left undisturbed. No protection against demineralization of the dentin or degradation of the dentin collagen by the chlorhexidine treatment was observed. The chlorhexidine treatment did not result in a reduction of the total cultivable flora when compared with the control specimens. A significant reduction of mutans streptococci and total streptococci recovered from completely demineralized dentin treated with chlorhexidine was observed, but the proportions of Actinomyces and lactobacilli were not affected significantly. It is speculated that areas of exposed roots, which are difficult to reach by oral hygiene measurements, such as approximal surfaces, will not be protected by a 0.2% chlorhexidine mouthrinse against the caries process.

Vital microorganisms in early supragingival dental plaque and in stimulated human saliva

The aim of this study was to compare the percentage of vital microorganisms (= microbial vitality) of saliva with that of supragingival plaque both collected at various times during the early phases of de novo plaque formation. Between intervals of optimal oral hygiene, 14 healthy participants refrained from all oral hygiene measures for periods of 1, 4, 8 and 72 h. Stimulated whole saliva was collected at the beginning (= baseline) and the end of each period. Vestibular plaque was removed from teeth 13-16, and 23-26. Analysis of the pooled plaque (p) and saliva (s) samples comprised the total number of bacterial counts and colony-forming units to estimate the percentage of viable microorganisms (PEp; PEs). The microbial vitality (VFp; VFs) was determined by using a fluorescence staining to differentiate vital from dead bacterial cells. The bulk of the PEs values reached 5-30%. At baseline VFs ranged between 70% and 90%. The VFs values recorded at baseline or in the presence of 1 h and 4 h-old plaque, were significantly (alpha = 0.05) higher than the corresponding VFp values ranging from 5% to 30%. It was concluded that there is a considerable discrepancy between the microbial vitality of a very early dental plaque and that of whole surrounding saliva sampled at the same time. Unfavourable local environmental conditions prevailing at cervical tooth surfaces are suggested to restrain the survival of the majority of the first bacteria adhering to a particular tooth area during the early phases of supragingival plaque formation.

Plaque bacteria counts and vitality during chlorhexidine, meridol and listerine mouthrinses

The aim of this double-blind study was to enumerate the total number of living and dead bacteria on defined tooth areas during the application of antibacterial mouthrinses. After prophylaxis, 40 students refrained from all oral hygiene measures for 3 d, during which they rinsed with a phenolic compound (Listerine), an amine fluoride/stannous fluoride solution (Meridol), 0.2% chlorhexidine (CHX) or a control solution (0.02% quinine-hydrochloride). The plaque index (P1I) was recorded at the start and the end of the investigation. Total bacterial counts (BC) and colony-forming units (CFU) of 1d-, 2d- and 3d-old dentogingival plaque were determined. The plating efficiency (PE) was calculated as a percentage of CFU/BC and the portion of vital microflora estimated by a vital fluorescence technique (VF). All groups started with a P1I approximating 0.1. On day 3, the P1I values were 1.21 in the control group and 0.51, 0.37 and 0.14 after Listerine, Meridol and CHX use, respectively. A tremendous variation existed between the numbers of viable bacteria found per mm2 on the enamel surface and day 3 (CHX: 0.2; Meridol: 300; Listerine; 6x10(4); control: 2x10(6)), while higher total numbers of bacteria were concomitantly present (CHX and Meridol: 1-2x10(4); Listerine: 2x10(5); control: 2x10(6)). Both vitality parameters PE and VF reached 92% in the control group at day 3, but only 7% after CHX use. With Meridol and Listerine, the corresponding PE values were 3% and 43%, respectively, while the VF values reached 48% and 54%. The PII, BC, CFU and PE values of the CHX and the Meridol groups differed significantly from those of the control group. In contrast, Listerine showed no difference as compared to the control rinse. Due to the strong antibacterial action of CHX and Meridol during their use, almost only dead or non-proliferating bacteria were found on the tooth surfaces. Thus, only a thin plaque could develop. As a clinical consequence, both substances showed retardation of plaque development as reflected by significantly reduced plaque indices.

Effects of mouthrinses with chlorhexidine and zinc ions combined with fluoride on the viability and glycolytic activity of dental plaque

Inhibition of plaque acidogenicity by a mouthrinse with chlorhexidine (CHX) or zinc ions has been ascribed to a prolonged bacteriostasis due to substantive properties of the agents. The present aim was to study the effects of mouthrinses with CHX and Zn ions combined with fluoride on the viability and glycolytic activity of dental plaque in order to assess the bacteriostatic versus possible bactericidal effects. Following 2 d of plaque accumulation, 4 groups of 10 students rinsed with either 12 mM NaF (F), 0.55 mM CHX diacetate+F (F-CHX), 10 mM Zn acetate+F (F-Zn), or with the three agents in combination (F-CHX-Zn). Plaque samples were collected before and 90 min after mouthrinsing. Thereafter, the in vivo plaque pH response to sucrose was monitored in each student using touch microelectrodes. F-CHX and F-CHX-Zn reduced the in vivo pH fall significantly as compared with F, whereas F-Zn exerted a non-significant inhibition. Pooled pre- and post-rinse plaque samples were used to measure the pH fall during fermentation of [14C]-glucose, and the glycolytic profiles were analyzed by HPLC. Bacterial viability was assessed by counting the colony-forming units (CFU). All mouthrinses except F reduced glucose consumption and acid formation and thus the pH fall. F-CHX reduced the CFU equal to the reduction of glucose consumption, indicating that inhibition of plaque acidogenicity was due to a bactericidal rather than a bacteriostatic effect. F and F-Zn did not reduce the CFU, thus F-Zn decreased glucose metabolism without affecting plaque viability. F-CHX-Zn reduced both the CFU and glucose metabolism of surviving plaque microorganisms.

Comparison of digitised and visual plaque vitality measurement

Plaque samples from 12 patients suffering from adult periodontitis (8 male, 4 female), aged 32-58 (mean age 44.3) years were stained using the technique of vital fluorescence described by Netuschil and co-workers. The proportions of vital plaque was then assessed by 2 techniques: the visual methods previously described and by an image capture system linked to a computerised image programme. A total of 94 plaque samples were included in the study. Analysis of the data from the 2 sets showed that there was no significant difference between the two methods (p = 0.26).

Patterns and rates of growth of microcosm dental plaque biofilms

Rates of growth in wet weight and changes in them over time were established for microcosm dental plaques cultured from the mixed salivary bacteria in an artificial mouth. Standardized conditions included a continuous supply of medium containing 0.25% mucin and 1.5 ml of 5% w/v sucrose in 6 min every 8 h. Plaques were weighed daily. Plaque wet weight and total protein were highly correlated. Plaque doubling times were 3-7 h over day 1 and 9-21 h over day 2, which is similar to in vivo plaques. Subsequently, growth curves were either linear or between a linear and exponential increase. Evidence was obtained for plaque blooms. Methyl paraben (0.2%) applied for 15 min (3.75 ml) 6 times daily inhibited growth but only for 3 days, after which the rate was similar to control plaques, indicating that selection for resistance had occurred. It was concluded that the regulation of plaque growth rates is complex and does not conform to simple growth pattern models. Detailed studies of plaque growth and the effects of antiplaque agents can be carried out using this experimental system.

Microbial vitality of supragingival dental plaque during initial stages of experimental gingivitis in humans

Although vital plaque micro-organisms are part of the natural ecosystem in the oral cavity they are also the key factor in the development of diseases induced by the human dental plaque. In a previous study (9) the portion of vital bacteria related to the total number of plaque micro-organisms (i.e. the microbial vitality) appeared low in small plaque samples. The objective of this investigation was to determine the exact relationship of microbial vitality and age of supragingival plaque during the early phases of human dental plaque formation. Between intervals of optimal oral hygiene, thirteen participants refrained from all oral hygiene measures for periods of 1, 2, 4, 8, 24 and 72 h. Plaque was completely sampled from a defined area situated on the vestibular surface of the teeth 13, 14, 15, 23, 24 and 25. The pooled plaque from these areas was immediately processed. Total bacterial counts (BC) as enumerated by darkfield microscopy, and colony-forming units (CFU) were recorded. The microbial vitality was calculated indirectly as plating efficiency (PE = CFU per BC) and directly assessed using a vital fluorescence (VF) technique. In the 1 h old plaque samples the median values of PE and VF were 29% and 18%, respectively. Thereafter, the microbial vitality increased significantly with plaque age. The 24 h old plaque samples yielded values of 77% (PE) and 62% (VF). It was concluded that the microbial vitality of the early dental plaque investigated was considerably lower compared to that of a more mature plaque.

Microbial generation time during the early phases of supragingival dental plaque formation

The objective of this investigation was to determine the microbial generation time during early human supragingival plaque formation. On 2 occasions, 13 participants refrained from all oral hygiene measures for periods of 1, 2, 4, 8, 24 and 72 h. Plaque was sampled from defined areas of the teeth 13, 14, 15, 23, 24 and 25. Two independent methods were used to estimate the total number of viable cells: colony-forming units BCVF, total bacterial counts (BC) as enumerated by microscopic examination, and the percentage of vital bacteria using a vital fluorescence technique (VF) were recorded. The total number of vital microorganisms was calculated by BCVF (= BC x VF). The generation time based on either colony-forming units or BCVF increased significantly with plaque age. During the first interval (1-4 h), the microbial multiplication took slightly less than 1 h. After the establishment of a more mature plaque (24-72 h), the replicating time was between 12.5 h (BCVF) and 14.8 h (colony-forming units). It was concluded that the microbial generation time recorded at the initial stages of plaque formation is considerably lower than that found in older plaque.

Bacterial penetration in vitro through GTAM membrane with and without topical chlorhexidine application. A light and scanning electron microscopic study

Premature exposure of membrane in the oral cavity is considered the most common complication as well as a reason for failure or incomplete success of guided tissue regeneration, as the exposed membrane undergoes plaque accumulation. A method to control, or at least to reduce the bacterial invasion of the membrane allowing a delay in the membrane removal, could be of clinical interest. The purpose of the present study was to evaluate the possibility of treating, with topical chlorhexidine application, the bacterial colonization of exposed membranes. A special device was developed in order to evaluate, under an experimental environment, the bacterial colonization. This device was made from a removable acrylic denture base to which 5 gold cups were attached. The cups consisted of an internal compartment, isolated from the oral cavity by a GTAM membrane, and an external compartment exposed to the oral environment. 3 healthy subjects had this device fitted, bilaterally, in the molar-premolar region of the upper jaw. The cups of one side of each subject had 0.2% chlorhexidine gluconate gel applied 2x a day for 1 min, whereas those of the other side served as controls. 12 cups were removed after 2 weeks and the remainder removed after 1 month. The non-treated control specimens were characterized by greater amounts of plaque accumulation. In all the test sites, plaque deposits increased in thickness and quantity during the 4 weeks of the experiment. Complete invasion of the membrane and initial colonization of its internal surface were observed only in 4-week specimens. A relatively simple flora consisting mainly of cocci and short rods, was found in bacterial deposits forming under the influence of chlorhexidine, whereas in non-treated specimens, it was possible to observe a more mature and complex plaque, composed mostly of filamentous bacteria. In conclusion, topical application of chlorhexidine gel is an effective method of reducing plaque and calculus formation on the surface of GTAM membranes exposed to the oral cavity for up to 4 weeks. This study has, however, failed to demonstrate the capacity of chlorhexidine to prevent or to retard bacterial penetration through the thickness of the inner portion of the membranes.