Evaluation of the substantivity of chlorhexidine in association with sodium fluoride in vitro

Avaliação da substantividade da clorexidina na associação com fluoreto de sódio in vitro

PREVENÇÃO

Evaluation of the substantivity of chlorhexidine in association with sodium fluoride in vitro

Avaliação da substantividade da clorexidina na associação com fluoreto de sódio in vitro

Carolina Saliba de Freitas^I; Henrique França Oliveira Diniz^I; Jânderson Breder Gomes^I; Rubén Dário Sinisterra^II; María Esperanza Cortés^III

^IUndergraduate students, School of Dentistry

^IIAssistant Professor, Department of Chemistry, Institut of Exact Science

^IIIAssistant Professor, Department of Restorative Dentistry, School of Dentistry – Federal University of Minas Gerais

ABSTRACT

The efficacy of the fluoride-chlorhexidine association in the prevention of gingivitis and caries has been advocated for a number of years^5,7,14. The objective of the association of these therapeutic agents is a synergistic action. The aim of the present study was to determine the substantivity of chlorhexidine associated or not to sodium fluoride at different intervals of time, in vitro. Bovine enamel surfaces were treated with 0.12% chlorhexidine gluconate (Periogard^® – Colgate^®) or 0.05% sodium fluoride with 0.12% chlorhexidine (Duplak^® – Dentsply^®) solutions for one minute. Fragments were placed in distilled water and samples were collected at intervals of 5, 30 and 360 minutes and analyzed by spectrophotometry in the visible ultraviolet region. Substantivity was evaluated by the measurement of chlorhexidine desorption from the treated slabs. The mean values obtained were statistically analyzed by Student's t-test. The results showed that the concentration of chlorhexidine decreased when it was used in association with sodium fluoride. The difference between the groups was statistically significant (p < 0.05). These in vitro results suggest that the association between sodium fluoride and chlorhexidine in the studied concentrations appears to have no beneficial effect because of the decrease in the substantivity of chlorhexidine.

Descriptors: Chlorhexidine; Sodium fluoride; Substantivity.

RESUMO

A efetividade da associação fluoreto-clorexidina na prevenção da gengivite e da cárie vem sendo defendida há alguns anos^5,7,14. O propósito dessa associação é obter um desempenho sinérgico. O objetivo do presente estudo foi avaliar a substantividade da clorexidina em associação ou não ao fluoreto de sódio em diferentes intervalos de tempo, in vitro. Foram tratadas superfícies de esmalte bovino com soluções de digluconato de clorexidina 0,12% (Periogard^® – Colgate^®) ou fluoreto de sódio 0,05% com clorexidina 0,12% (Duplak^® – Dentsply^®), durante um minuto. A substantividade foi medida pela dessorção da clorexidina a partir dos fragmentos previamente imersos nas soluções teste e colocados em água destilada. Alíquotas foram removidas em intervalos de 5 minutos, 30 minutos e 6 horas e analisadas através de espectroscopia na região do ultravioleta visível. Os valores obtidos foram analisados estatisticamente pelo teste t de Student. Os resultados mostraram que a concentração da clorexidina foi significativamente reduzida quando em associação com fluoreto de sódio (p < 0,05). Os resultados in vitro sugerem que a associação da clorexidina ao fluoreto de sódio nas concentrações estudadas parece não ter efeito benéfico, devido à redução da substantividade da clorexidina.

Descriptores: Clorexidina; Fluoreto de sódio; Substantividade.

INTRODUCTION

Chemotherapeutic agents are used as adjuncts to the mechanical control of plaque¹⁵. In 1890, Miller¹⁰ suggested an appropriate and intelligent use of antiseptic to destroy bacteria, or limit bacterial activity, as a way of inhibiting the destruction caused by dental decay. The main challenge in preventive dentistry continues to be the reduction or control of the acquired film in order to prevent caries and periodontal disease. Several researches have been carried out and the industry continually launches new formulations capable of interfering either in the metabolic activity or the bacterial adhesion to the dental plaque.

Fluoride is the most prominent drug used as an auxiliary in the prevention by enamel remineralization. Fluoride has been used in caries prevention since 1940. Modern concepts of the mechanism of action of fluoride recommend daily fluoride supply to establish and maintain a significant concentration in saliva and in plaque fluids, thus preventing and controlling enamel dissolution¹⁵. Furthermore, the basis of its application is that after application, either as topical solutions or as toothpaste, the free fluoride is incorporated into the enamel in the form of calcium fluoride on the tooth surface and serves as a fluoride reservoir whenever it is necessary in the demineralization/remineralization process. The use of this agent as chemoprophylaxis or chemotherapeutics in dental decay is still stimulated by the lack of evidence of harmful effects.

Although fluoride acts in the demineralization/remineralization equilibrium, this function is not exercised in pH lower than 4.5, because at this levels the dental plaque is not saturated by fluorapatite. Furthermore, there are no evidences to show the direct benefits of fluoride on individuals with gingivitis alone¹⁷. At low concentrations, chlorhexidine can reduce plaque acid production. Based on these principles, the fluoride-chlorhexidine association would be quite beneficial¹¹, probably because chlorhexidine reduces plaque acid formation for several hours, preventing the decrease in pH, and additionally, this drug has great effectiveness in the reduction of gingivitis.

Chlorhexidine, a cationic agent, has been used for more than fifteen years in Europe, and its hydrophobic and hydrophilic properties are responsible for its efficacy. Chlorhexidine is a very potent chemoprophylactic agent. It has a broad-spectrum action, and is more effective against Gram-positive than Gram-negative bacteria. Streptococcus of the mutans group is especially susceptible to chlorhexidine, which acts by binding to the bacterial cellular wall and affecting its functions¹⁵. Chlorhexidine binds readily to negatively charged bacterial cell walls and can thereby disrupt membrane integrity. In high concentrations, chlorhexidine is bactericidal and acts as a detergent by damaging cell membrane. One positive property of chlorhexidine is its intrinsic ability to be retained by oral surfaces, and gradually released into oral fluids over many hours, which is defined as substantivity¹⁵.

The fluoride-chlorhexidine association was proposed three decades ago based on results obtained firstly by in vitro and later by in vivo studies. Luoma et al.⁷ (1978) and Emilson et al.³ (1976) justified this association as the search for a synergistic effect of the two drugs to control caries and gingivitis. Ullfoss et al¹⁵ (1994) reported that a combination of a 2.2 millimolar chlorhexidine mouth rinse used twice a day with single daily rinses of 11.9 millimolar NaF resulted in mineral loss only slightly larger than that observed in sound enamel.

MATERIALS AND METHODS

Bovine teeth were sectioned with a water-cooled diamond saw to obtain the crowns. The 40 fragments obtained were embedded in polystyrene resin and vestibular surfaces of 4 x 8 mm were left exposed. After that, the resin surfaces were covered with nail polish and randomly divided to evaluate the substantivity in Group 1, by one-minute immersion in 0.12% chlorhexidine gluconate solution (Periogard^®), or the association of 0.05% fluoride sodium and 0.12% chlorhexidine (Duplak^®) in Group 2. The samples were immersed in 1 ml of distilled and sterilized water and kept in glass tubes. After 5, 30 and 360 minutes, an aliquot was taken from the tubes and the same volume was immediately replaced and analyzed by ultraviolet in a spectrophotometer at 260 nm. The values obtained were analyzed with Student's t-test.

RESULTS

Graph 1 shows the chlorhexidine release from teeth impregnated with 0.12% chlorhexidine gluconate and those impregnated with 0.05% sodium fluoride and 0.12% chlorhexidine. The peak desorption of chlorhexidine in the first 5 minutes (Table 1) was lower for the sodium fluoride-chlorhexidine association (12.14 mg/ml) than that of the chlorhexidine gluconate solution (16.68 mg/ml). After 30 minutes, there was a sharp fall in the concentration of the two groups as follows, Group 1, 45% (9.16 mg/ml), and Group 2, 82% (2.10 mg/ml). Chlorhexidine concentration corresponding to 360 minutes was 4 mg/ml for chlorhexidine gluconate, whereas sodium fluoride-chlorhexidine had a concentration of only 1.51 mg/ml. However, one of the most important properties of chlorhexidine is its substantivity, which was shown to be reduced in all time intervals analyzed for the association.

DISCUSSION

Progresses in science and pharmacology facilitate the access of dentists to a larger number of drugs everyday. However, the professional knows that for the use of new agents to be beneficial for the patient, more comparative studies should be carefully performed to establish the appropriate therapy strategy.

As previous papers^5-7 focused on the beneficial effect of the fluoride-chlorhexidine therapy to arrest caries and to remineralize incipient lesion, the substantivity was assumed to be satisfactory in relation to the current dose. However, Melo et al.⁹ (1999) advised that the fluoride-chlorhexidine association was not beneficial, because it reduced the agent concentration.

Brambilla et al.¹ (1998) concluded that this associative mouth rinse might be used in caries prevention programs for pregnant women, because it reduces Streptococcus mutans scores in the saliva and because it retards colonization in children up to four months.

Diverse studies justified the value of the fluoride-chlorhexidine association on the synergistic effect of the two drugs^3,7. Due to the low molecular weight of fluoride molecules, they could link to places of difficult access for chlorhexidine and reach Streptococcus mutans retention niches and incipient decay lesions, where the pH is low, thus inhibiting acid production with a concomitant prolonged preventive effect⁸. Nonetheless, the fluoride-chlorhexidine association could generate low chlorhexidine concentration in certain retention places, and therefore suppress the potential reservoirs of the drug, such as tongue, mucosa, tonsils and saliva, which is favorable to inhibit the recolonization of treated lesions.

As verified in this study, the maximum concentration of chlorhexidine observed after 5 minutes was larger for chlorhexidine gluconate than for the association (Graph 1). The initial lower concentration of chlorhexidine in relation to the association was due to the competition between the fluoride ions and the chlorhexidine molecules for the adsorption surface. Other authors^3,7 suggest that there are ionic reactions between fluoride and chlorhexidine, generating a decrease in the concentration of chlorhexidine, and inhibiting the bactericidal effect of the association. However, the fact that chlorhexidine has several positive charges and that it is in larger concentration in the association would neutralize the effect of the drug by fluoride⁹.

In agreement with the related literature⁷, in the present study it was observed that the substantivity of chlorhexidine was reduced. A strategy to increase the substantivity of fluoride on enamel surface is its association with amine groups, which would link to the negative charges available in teeth and enamel film. This would be interesting because it would prolong fluoride readiness on the dental surface. However, Etemadzadeh et al.⁴ (1985) showed that the amine fluoride-chlorhexidine association does not inhibit plaque growth. However, the potential to inhibit caries through the use of the fluoride-chlorhexidine association was verified by long-term studies^2,6,7,13,14, even in the treatment of incipient root lesions, with which the association was used⁶.

The change in the concentration profile of chlorhexidine shown in this study raises new concerns about its interaction with sodium fluoride, and consequently about the benefit of the association of these two drugs.

CONCLUSION

Based on in vitro experimental conditions of this work and the results obtained, we can conclude that the fluoride-chlorhexidine association is unfavorable, due to the significant decrease in the substantivity of chlorhexidine.

Recebido para publicação em 24/04/02

Enviado para reformulação em 29/11/02

Aceito para publicação em 07/02/03

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Publication Dates

• Publication in this collection
  05 Aug 2003
• Date of issue
  Mar 2003

History

• Accepted
  07 Feb 2003
• Reviewed
  29 Nov 2002
• Received
  24 Apr 2002