Journal of the International Clinical Dental Research Organization

REVIEW ARTICLE
Year
: 2021  |  Volume : 13  |  Issue : 2  |  Page : 80--85

Chlorhexidine in operative dentistry - A review


Tanvi Sanjay Satpute1, Sanjyot A Mulay2,  
1 Department of Conservative Dentistry and Endodontics, MGM Dental College and Hospital, Navi Mumbai, Maharashtra, India
2 Department of Conservative Dentistry and Endodontics, Dr. DY Patil Dental College and Hospital, Dr. DY Patil Vidyapeeth, Pune, Maharashtra, India

Correspondence Address:
Dr. Tanvi Sanjay Satpute
Department of Conservative Dentistry and Endodontics, MGM Dental College and Hospital, Junction of NH4 and Sion-Panvel Expressway, Sector 1, Kamothe, Navi Mumbai - 410 209, Maharashtra
India

Abstract

This review aims to explore existing literature and provide information about techniques that have been employed to incorporate chlorhexidine (CHX) in dental materials, its antimicrobial effectiveness, and its effects on the pulp and dental restorations, in addition to its possible side effects. For both dentists and patients, one of the most important aspects of dental restorations is its longevity. Thus, the objective should be elimination of bacteria and bacterial remnants that can be responsible for recurrent caries, postoperative sensitivity, and ultimately failure of the restoration. Searches were carried out on various online databases including PubMed. Keywords were chosen to assess the properties of various dental materials containing CHX. Methods of introducing CHX in restorative materials were also searched. Studies were selected based on relevance, with a preference given to recent research. A range of antibacterial agents have been incorporated into experimental as well as commercial dental restorative materials to provide antibacterial activity. CHX has demonstrated to be effective and safe against bacterial plaque and biofilms. In addition to its plaque-inhibiting effect, CHX displays other properties beneficial for use in Operative Dentistry.



How to cite this article:
Satpute TS, Mulay SA. Chlorhexidine in operative dentistry - A review.J Int Clin Dent Res Organ 2021;13:80-85


How to cite this URL:
Satpute TS, Mulay SA. Chlorhexidine in operative dentistry - A review. J Int Clin Dent Res Organ [serial online] 2021 [cited 2022 Jul 3 ];13:80-85
Available from: https://www.jicdro.org/text.asp?2021/13/2/80/335870


Full Text



 Introduction



One of the most common reasons for failure of a restoration is secondary caries,[1] which is mainly caused by oral bacteria.[2] The development of secondary caries can occur because of the lack of antibacterial properties in the restorative material followed by subsequent demineralization caused by the acid production by microorganisms.[3] Therefore, antibacterial agents that can eliminate cariogenic bacteria and retard the growth of their biofilms are highly desirable.

Any chemical that interferes with the growth and reproduction of bacteria, thereby eliminating its harmful effects, is an antibacterial agent. Three types of antibacterial agents have been employed most commonly in dental materials which include leachable agents, polymerizable agents, and fillers.[4] Leachable agents are usually water soluble and therefore can be released into the area adjacent to the restoration, under certain oral conditions. Apart from benzalkonium chloride, one of the most frequently used leachable antibacterial agents in dental materials is chlorhexidine (CHX).[5]

Streptococcus mutans is an important etiologic agent in human dental caries.[6] S. mutans has been implicated as a causative agent for the initiation of dental caries as well as the occurrence of secondary caries. The amount of plaque and the degree of cariogenicity at restoration margins depend on the restorative material.[7] González-Cabezas et al.[8] reported the distribution of three cariogenic bacteria, S. mutans, Actinomyces naeslundii, and Lactobacillus casei in secondary carious lesions around amalgam restorations. Svanberg et al.[9] detected higher total colony forming unit counts for S. mutans at margins of composite restorations as compared to amalgam fillings. A study by Splieth et al.[10] also showed that a variety of microbes found under composite fillings were much greater as compared to amalgam.

CHX is currently the most potent antimicrobial agent against S. mutans and dental caries.[11],[12],[13] The efficacy of CHX in caries prevention has been established in various clinical trials.[14] The role of CHX in endodontics is well documented, but there is no adequate review of the literature regarding CHX and its applications in operative dentistry. Hence, the purpose of this paper is to review different aspects of CHX and its relevance to operative dentistry.

 Structure and Mechanism of Action



Structurally, CHX consists of a symmetrical cationic molecule made up of two 4-chlorophenyl rings and two biguanide groups which are connected by a central hexamethylene chain [Figure 1]. It was found that it is most stable in the form of its salts. The most common preparation is with digluconate salt since it has high water solubility.[15]{Figure 1}

CHX has a broad spectrum of activity against Gram-positive and Gram-negative organisms, yeast, fungi, facultative anaerobes, and aerobes.[16],[17],[18] It has been shown that CHX has an affinity to bacteria, because an interaction occurs between the negatively charged groups on the bacterial cell wall and the positively charged CHX molecule.[19] This interaction increases permeability of the bacterial cell wall and thus allows the agent to infiltrate into the cytoplasm and cause death of the microorganism.[20] The mode of action of CHX has been exhaustively reviewed by Hugo[21] whose own classical study has showed that CHX at low concentrations is a potent membrane active agent against both Gram-positive and Gram-negative bacteria. At higher concentrations, CHX can be bactericidal. It induces precipitation of cytoplasmic protein and nucleic acids, thereby markedly inhibiting acid production.[22],[23] Another beneficial property of CHX is its substantivity where it has an inherent ability to be retained by oral surfaces and gradually released into oral fluids over a period of time.[24]

 Applications



Antibacterial agents have been previously incorporated in various dental materials in operative dentistry including cleansers, etchants, bonding agents, cements, and resin composites.[4]

To facilitate the understanding in this context, this literature review underlines four vital objectives related to CHX, which include (1) cavity disinfectants, (2) bonding agents, (3) cements, and (4) resin composites. The substantial amount of literature on CHX determined that discussions should be focused on studies and literature reviews. There are studies mentioned having unfavorable results too since they could help in outlining the clinically relevant aspects.

Cavity disinfectants

The presence of bacteria in the smear layer, after cavity preparation, is a major cause of secondary caries and these bacteria can remain viable for a long period of time.[25] The amount of success in the elimination of bacteria during cavity preparation, before it is restored, may prolong the survival of the restoration and therefore the success of the procedure. To reduce the possibility of residual caries and sensitivity, an antibacterial solution, which could be applied after cavity preparation and has the capacity to disinfect the dentin, would be valuable.[26]

Numerous disinfectants have been used clinically, with a goal to reduce or eliminate bacteria during cavity preparation and before the placement of restorations.[27] Different concentrations of CHX are available commercially. Among them, it has been reported that the 2% solution is the most widely used in clinical dentistry and research.[28] In the form of 2% aqueous solution, CHX is considered as a biocompatible[29] and toxicologically safe disinfectant.[30],[31]

Cavity disinfection can be carried out before application of various restorative materials or restorative techniques. While managing deep carious lesions, pretreatment by CHX has been reported to increase the clinical success of both direct[32] and indirect[33] pulp-capping procedures. Application of 2% CHX neither affects the bond strength of Resin-Modified Glass Ionomer cement (RMGIC) to dentin.[34] This is supported by the studies carried out by Cunningham et al.,[35] Aykut-Yetkiner et al.,[36] and Ersin et al.[37] In regard to acid-etching technique, the application of CHX has no untoward effect on immediate composite adhesive bonds in dentin,[38] enamel,[39] or with RMGIC.[35] Use of CHX aids in preservation of dentin bond strength with etch-and-rinse adhesives.[40],[41],[42],[43] There are studies that have also examined the use of CHX after acid etching. They demonstrated that the initial bond strengths were comparable with those of the controls.[44],[45],[46] CHX enhances the durability of the restorative bond with dentin because of its anticollagenolytic action. This is attributed to the inhibitory action of CHX on matrix metalloproteinases (MMPs).[47] However, in other studies carried out using self-etching adhesives, it has been demonstrated that the use of CHX as a cavity disinfectant could result in higher microleakage[48] or increased gap formation around the margins.[49]

The use of a cavity-disinfecting agent with restorative adhesive material yields contrasting results depending on the material used and its interactions and reactions with different bonding systems.[50],[51],[52] The sequence of the application of disinfecting agents depends on the bonding system used. Since the smear layer and the surrounding dentin are removed with the total-etch adhesive system, it is rational to apply the disinfecting agent after etching the cavity. However, the self-etch systems with a weaker acidic primer only modify the smear layer, and it is obligatory to use the disinfecting agent before applying the acidic primer.[53]

Cements

Various additives have been included to enhance the antimicrobial activity of dental cements. The additional antibacterial property can be beneficial for atraumatic restorative treatment or restoration of noncarious cervical lesions in geriatric patients. However, the impact of these additives on the physical properties of the materials and on the longevity of restorations must be studied.

A study conducted by Duque et al.[54] showed that incorporating CHX improved the antimicrobial action without altering the chemical or mechanical properties of Glass Ionomer cement (GIC). Türkün et al.[55] added CHX to ChemFil Superior GIC and demonstrated that it can exhibit long-term antibacterial effects against S. mutans and Lactobacillus acidophilus without influencing the physical properties of the material. For prolonged release of CHX, a preparation containing antimicrobial nanoparticles based on hexametaphosphate salt of CHX was studied. It was observed that the formulation did not negatively influence the bond strength of GIC to dentin.[56]

Various concentrations of CHX have been added in RMGIC. Amongst them, 1.25% CHX exhibits good biological and mechanical behavior and hence could be a favorable option for clinical use.[57] Another study added various concentrations of CHX to GIC and concluded that CHX at 0.5% concentration is a favorable option since it exhibited enhanced antibacterial activity with physical and mechanical properties unchanged.[58]

Bonding agents

Dental bonding agent (DBA) is a resin-based material employed to bond restorations to tooth structures. DBAs are in direct proximity to the teeth but are not exposed to the oral medium. As secondary caries at resin–teeth interface is the most common reason for restoration failure, examination of whether application of an antibacterial DBA would help reduce recurrent caries and thereby improve longevity of dental restorations is highly relevant.[4]

One method that can be used to achieve antibacterial effects via dental bonding is by integrating antibacterial agents into dental adhesives. Even though routine dental adhesives possess almost no antibacterial effect,[5],[59] dental adhesives with low pH values exhibit antibacterial effects against some bacteria, such as S. mutans, but not against acid-tolerant bacteria such as Lactobacilli.[60],[61] Notably, the low pH of adhesives activates MMPs, which causes degradation of the adhesive bond.[62] MMPs are a class of zinc- and calcium-dependent endopeptidases effective at degrading all the components of extracellular matrix. Human dentin contains MMP-2, MMP 8, MMP-9, and MMP-20.[63],[64],[65],[66] They are confined within the mineralized dentin matrix during tooth development and play an important role in dentinal caries.[67]

All self-etching dental adhesives are acidic (pH 1.5–2.7) and hence release MMPs. Even simplified etch-and-rinse adhesives can reactivate endogenous enzymatic activities in dentin that are previously inactivated by phosphoric acid etching.[68],[69],[70] These MMPs that get activated can slowly hydrolyze unshielded collagen fibrils of hybrid layers which is thought to be responsible for the evidence of thinning and disappearance of collagen fibrils from incompletely infiltrated hybrid layers in aged, bonded dentin.[71],[72],[73]

CHX when added directly to a primer can preserve bond strength when the concentration of CHX in the primer is higher than or equal to 0.1%.[74] In another study where CHX was incorporated in the adhesive system, CHX demonstrated inhibition of dentin proteolytic activity, and no difference was observed in the bond strength.[75] Incorporation of CHX into the primer has also displayed significant antibacterial activities.[76] To maintain a sustained release of CHX for an extended period of time, feasibility of CHX-loaded mesoporous silica as a modifier in dentin adhesives was studied. It was demonstrated that CHX-encapsulated mesoporous silica can potentially extend the service life of adhesive restoration since it inhibited the growth of S. mutans biofilm.[77]

Resin composites

Resin composites are composed principally of inert inorganic fillers and organic monomers. The fillers incorporated in composites are commonly silica based which are inert in nature and possess no antibacterial activity. The quantity of monomers and other components leached out from composites is much lower than the minimum concentration required for bacterial inhibition. There are basically two methods that can be employed to produce an antibacterial resin composite. An antibacterial agent could be dissolved in the composite's resin monomers, or it could be blended with the filler particles.[4]

CHX is released faster in a medium of lower pH value because of its higher solubility at lower pH.[78] Release rate is also said to be affected by the hydrophilicity of resin. The most hydrophilic resin exhibits the highest CHX release rate, while the most hydrophobic resin exhibits the lowest rate. It probably is because CHX release from resins may be related to water-induced swelling, which in turn is enhanced by the hydrophilicity of cured polymer matrix.[79]

It was observed through a study that addition of chlorhexidine gluconate and chlorhexidine dihydrochloride to a composite resin increases the antibacterial activity without compromising the mechanical properties.[80] Studies have also been carried out with modified experimental composite resins to check if the addition of CHX could enhance the various properties of the material. Halloysite nanotubes (HNTs) have been used as a nanocarrier system for drug delivery. A study incorporating CHX-loaded HNT fillers was carried out. It was found that incorporating HNT/CHX considerably enhanced mechanical properties with remarkable antibacterial activity.[81] CHX fillers were also experimentally incorporated in nanocomposites containing amorphous calcium phosphate and calcium fluoride. There was an appreciable increase in the antimicrobial capability, therefore imparting it both antimicrobial and remineralizing properties.[82]

 Disadvantages and Side Effects



Chlorhexidine digluconate reportedly has a tendency to cause brownish staining of the teeth. Nevertheless, this consequence is seen after long-term use.[83],[84] Even though CHX allergy is rare, it may cause contact dermatitis, desquamative gingivitis, or taste alteration.[29] It has been reported that CHX in a high concentration of around 18% has toxic effects. However, concentrations of up to 10% are acceptable for contact with tissue.[85] The proposed mechanisms for discoloration are degradation of CHX molecule to parachlor aniline, catalysis of maillard reactions, protein denaturation with chromogens, metal sulfide formation, and precipitation of anionic dietary compounds. Nevertheless, there is no sufficient evidence to support the above-mentioned mechanisms. The more conclusive evidence to date is in favor of precipitation of dietary compounds onto adsorbed CHX molecule.[86]

 Conclusion



Currently, many antibacterial agents have been tested in experimental formulations. Few of them have also been employed in commercially available products. Among them, CHX has shown promising results.

Its effect on long-term clinical performance is still unknown. There is a need to improve study designs to mimic the oral environment in vivo and to develop standardized methods to help understand and optimize the material.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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