Wettability Analysis of Experimental Resin-Infiltrants Containing Chlorhexidine

Research Article

Austin Dent Sci. 2017; 2(1): 1011.

Wettability Analysis of Experimental Resin-Infiltrants Containing Chlorhexidine

Cibim DD1, Inagaki LT2, Dainezi VB1, Pascon FM1, Alonso RC3, Kantoviz KR1,4 and Puppin-Rontani RM1*

1Department of Pediatric Dentistry, School of Dentistry of Piracicaba, University of Campinas, Brazil

2Department of Oral Medicine and Pediatric Dentistry, Londrina State University, Brazil

3School of Dentistry, Anhanguera University of S&aTilde;o Paulo (UNIAN-SP), Brazil

4S&aTilde;o Leopoldo Mandic Institute and Dental Research Center, Brazil

*Corresponding author: Puppin-Rontani RM, Department of Pediatric Dentistry, School of Dentistry of Piracicaba, University of Campinas, Avenida Limeira 901 Arei&aTilde;o, Piracicaba, S&aTilde;o Paulo, Brazil

Received: May 23, 2017; Accepted: June 22, 2017; Published: June 29, 2017

Abstract

Background: The purpose of this study was to determine the impact of Chlor Hexidine diacetate salt (CHX) to the wettability of experimental resininfiltrants on smooth or rough glass surfaces.

Methods: Three experimental resin-infiltrants were produced: 1) TEGDMA Infiltrant (TI) + (0.5%camphorquinone + 1%DMAEMA and 0.1%BHT); 2) TI + 0.1% CHX; 3) TI + 0.2% CHX. TEGDMA was used as control. Wettability of experimental resin-infiltrants was assessed by sessile drop method for contact angle measurements with Digidrop (n = 12 per surface type). An image of each drop was captured and analyzed with the GBX Digidrop software. Data were subjected to two-way ANOVA followed by the Tukey’s test (a = 0.05).

Results: A significant interaction between materials and surface types was found (p<0.01). For smooth surfaces, there was no statistical difference among the materials (p>0.05). In contrast, the contact angleon rough surfaces was significantly reduced by the addition of 0.1% or 0.2% CHX (38±3° and 35±4° respectively) as compared to the control group (TEGDMA, 47±2° and TI 44±5°) (p<0.05).

Conclusion: The addition of CHX improved the wettability of experimental infiltrants on rough surfaces, regardless of the CHX concentration, suggesting that it might be an alternative approach for incipient enamel caries lesions.

Keywords: Resin infiltrant; Contact angle; Wettability; Chlorhexidine

Introduction

Although the prevalence of dental caries has declined remarkably in most industrialized countries over the recent years, population subgroups continue to experience a high incidence of dental caries [1]. Accordingly, it continues to be a large health issue for high-risk patients with approximately 70-96% of the children and adolescents presenting initial caries lesions, specifically in proximal surfaces [2,3]. In adults, up to 50% of patients show carious or restored proximal surfaces [3]. The lack of compliance with preventive behavior, e.g. good oral hygiene practices, eating habits and regular exposure to fluoride, has been reported as the major factor responsible for the prevalence of dental caries lesions in this group [4].

A promising non-drilling strategy to arrest and control proximal surface caries lesions has been extensively studied, which is typically referred as resin infiltration [5-10]. This strategy aims to occlude the porous structure of incipient enamel lesions by using low-viscosity light-curing resins mixtures. Resin infiltrates allow material to penetrate into the lesion body by promoting mechanical support in this fragile structure, reducing the enamel solubility and preventing the progression of the caries lesion [7]. Resin infiltration is a microinvasive approach to arrest and camouflage white spot lesions [8,10]. In this case, the wettability property becomes a critical factor, once the resin infiltrant covers and penetrates into the white spot lesion [5]. In order for infiltrants to be effective, they should shield and penetrate the enamel in problematic areas and have a relative low contact angle (wettability) [11].

Currently, the only commercially available infiltrant is Icon® (DMG, Hamburg, Germany), which has been described as a methacrylate-based resin matrix, initiators and additives by the manufacturer. Although a good performance to arrest initial caries lesions has been demonstrated, studies have shown that Icons’ properties must be improved. In a clinical trial study, Martignon et al. [12] (2012) showed the an increased efficacy of stabilization in the progression of proximal lesion by using Icon® as infiltrant (68%), with no statistical differences between Icon® and Prime Bond NT (60%) on white spot lesions. The rough tooth surface after the application of Icon® was questioned also, once the Icon® group exhibited an increased surface roughness even after polishing proceedings [13]. It is well known that a rough surface would increase biofilm accumulation, which can degrade the material surface, compromising resin durability and increasing staining and caries development [10,14].

It has been suggested that the addition of antibacterial agents, such as Chlor Hexidine diacetate (CHX) or digluconate in resin infiltrants may improve the ability of arresting incipient caries lesions and inhibit plaque accumulation on the surface of the material and surrounding dental tissue [15]. The hypothesis is that the addition of antimicrobial agents to resin infiltrants will result in a reduced biofilm growth in the infiltrated enamel because of their antibacterial properties. Such strategy seems highly attractive; especially considering that resin infiltrants are indicated for high caries risk patients [12].

Chlor Hexidine diacetate salt (CHX) is the most popular compound for antibacterial application in dental materials due to its wide spectrum of action [15,16]. It has been included in several classes of dental materials, such as glass-ionomer cements, resin-modified glass-ionomer cements, composites and adhesives improving and/ or extending the antimicrobial properties of these materials against cariogenic bacteria [15,17-19]. Other studies have confirmed the inhibition of bacterial growth on the tooth/restoration interface [20,21]. Furthermore, CHX can suppress the growth of Streptococcus mutans, and consequently, prevent dental caries development [16]. Therefore, the addition of CHX into the resin matrix is a promising approach to assure the releasing of CHX to local sites in the oral environment [15-17,19]. CHX is a symmetrical cationic molecule consisting of two 4-chlorophenyl rings and two biguanide groups connected by a central hexamethylene chain, which is considered a strong base and it is stable in the form of salts [22]. At low concentrations, small molecular weight substances, such as potassium and phosphorus, will leach out, exerting a bacteriostatic effect [22]. Nevertheless, in higher concentrations, CHX has bactericidal action due to precipitation or coagulation of bacteria’s cytoplasm, probably caused by protein cross-linking [22].

At concentrations of 0.1 and 0.2% Inagaki et al. 2013 [23] found that CHX did not impair the degree of conversion nor the Knoop hardness of experimental infiltrants based on TEGDMA (Triethylene Glycol Dimethacrylate), and that CHX-containing infiltrants presented antibacterial activity against Streptococcus mutans and Lactobacillus acidophilus [17]. Although, these findings were the first promising steps towards the characterization of CHX-containing resin infiltrants [15,17], further studies are required to access the potential of such association as a reliable strategy to deal with white spot lesions. In the current investigation, it was tested the hypothesis that the addition of CHX would affect the infiltrant wettability depending on whether the surface was rough or smooth.

Materials and Methods

Experimental design

The factors under analysis were

Materials: Neat monomer (TEGDMA=Triethylene Glycol Dimethacrylate-T); TEGDMA Infiltrant (TI) + [0.5% camphorquinone + 1% DMAEMA (2-Di-Methyl Amino Ethyl Meth- Acrylate) and 0.1% BHT (Butylated Hydroxy Toluene)]; TI + 0.1% CHX; TI + 0.2% CHX; and

Surface types: Smooth and rough. Twelve sessile drops were assigned to either smooth or rough (n = 12), and the wettability determined by the sessile drop method for contact angle measurements with Digidrop.

Experimental resin infiltrant preparation

In this study, three low viscosity resin infiltrants were prepared using the highly fluid dimethacrylate monomer TEGDMA (Sigma- Aldrich, St. Louis, USA). The photoinitiator system used in all infiltrants was 1.0 wt% DMAEMA and 0.5 wt% CQ (2-Dimethylaminoethyl Methacrylate and Camphoroquinone, Sigma-Aldrich, St. Louis, USA, respectively). The inhibitor BHT (Butylated Hydroxytoluene, Sigma-Aldrich, St. Louis, USA) was added at 0.1 wt% in order to prevent spontaneous initiation and propagation of the freeradical polymerization reaction [22]. The mentioned antibacterial/ antimicrobial agent CHX (Sigma-Aldrich, St. Louis, USA) was used at 0.1 and 0.2 wt%. In order to avoid premature polymerization, the resin components and blends were stored in dark glass opaque recipients at 4°C until use. The neat monomer TEGDMA was used as control group.

Evaluation of wettability-Contact angle

The surfaces used to evaluate the wettability of experimental infiltrants were on rough and smooth glass surfaces. In this way, both smooth and rough type microscope glass slides (Bioslide, Walnut, CA, USA) dimensions (25x76x1mm) were used with the rough surface being the frosted end of the slide. The smooth glass slide with a regular polished glass has a mean roughness (Ra) of 0.101μm and it was selected in order to evaluate the contact angle in an ideal situation for liquid spreading into the solid surface. The rough glass slide had mean roughness (Ra) of 0.553μm and it was selected to simulate the acid etching previously the infiltrant application.

Wettability of experimental resin infiltrant was evaluated by contact angle measurements [5]. The sessile drop method was performed using Digidrop GBX goniometer (Labometric Lda, Leiria, Portugal) with distinct glass surfaces (smooth and rough) (Figure 1). Briefly, each material was loaded into a 2mL syringe (insulin type) with a 22-gauge needle (Injex Ltda, S&aTilde;o Paulo, SP, Brazil) attached and coupled to the goniometer. Droplets (approximately 4μL) were applied onto the different glass surfaces. Twelve drops (n = 12) of each material were dispensed onto each of the glass surfaces. The measurement of contact angle was accomplished immediately after the infiltrant drop had formed on a glass slide (Figure 2). The test was accomplished at room temperature. Each drop’s corresponding image was captured without external light interferences. Images were frozen by PixeLink system (Barrington, IL, USA) and the measurements were made by the GBX Digidrop Windrop software (GBX Company, Bourg de Péage, France). The camera’s focus was adjusted in relation to the position of the table with glass slide surface and the needle tip for each image. The right and left angles were measured in degrees of the contact angle and average automatically calculated by GBX Digidrop software.