Sodium Hypochlorite as a Deproteinizing Agent Optimize Orthodontic Brackets Adhesion using Resin Modified Glass Ionomer Cement

Research Article

Austin J Dent. 2016; 3(3): 1037.

Sodium Hypochlorite as a Deproteinizing Agent Optimize Orthodontic Brackets Adhesion using Resin Modified Glass Ionomer Cement

Ayman E1, Amera A2* and Khursheed AM1

1Orthadontic Unit, School of Dental Sciences, University of Science Malaysia, Malaysia

2Department of Oral and Maxillofacial Surgery, University of Anbar, Iraq

*Corresponding author: Alkaisi Amera, Department of Oral and Maxillofacial Surgery, University of Anbar, Iraq

Received: May 21, 2016; Accepted: July 09, 2016; Published: July 12, 2016


Aim: The main aim of this study was to test the effect of deproteinization of human dental enamel surfaces, with 5.25% sodium hypochlorite (NaOCl) before etching on orthodontic bracket shear bond strength (SBS) of Resin Modified Glass Ionomer Cement (RMGI) adhesive system.

Materials and Methods: Sixty extracted human premolar teeth were randomly divided into two groups. Group1as an experimental and group II control, with 30 teeth each. Both groups; brackets were bonded to the teeth using, Fuji Ortho LC. The buccal surface of the premolars in the experimental group was deproteinized with 5.25% NaOCl before acid etching and orthodontic brackets were bonded with RMGI. The same protocol was used in the control group except NaOCl was not applied. The debonding force (SBS) was measured using Instron machine and the residual adhesive remain on the tooth surface was scored as well enamel roughness was measured using profilometry. Independent t test was used to determine whether there is a significant difference in SBS and the adhesive remnant index (ARI) scores between the 2 groups. Kurskal-Wallis test was used to test for Ra, Rq and Rt data analysis.

Results: The mean SBS for Fuji Ortho LC with NaOCl, was 17 (±5.37) MPa; and for Fuji Ortho LC without NaOCl, 13.86 (±4.41) MPa, the difference between the 2 groups was significant P =0.029. The mean (SD) adhesive remnant index scores for group 1 & 2 were 3.97 (±.718) and 2.90 (±.712) respectively with significant difference between the 2 groups P > 0.001..No significant difference was found in enamel roughness between cleanup methods P for Ra, Rq and Rt was = 0.340 , 0.483 and 0.280 respectively.

Conclusion: It was concluded that enamel treatment with NaOCl increase bonding strength of brackets bonded with RMGIC, and was statistically significant when compared to the untreated group.

Keywords: Deproteinization; Brackets; RMGI; SBS; ARI


The orthodontic communities have strived in the past few years to obtain and use materials and techniques that increase the bond strength between orthodontic brackets and the enamel surface of the teeth. As the attachments have to be intentionally removed upon completion of the treatment, excessive bond strength may cause unwanted damage to enamel surfaces. An acceptable range of bond strength should be sufficiently high to minimize bracket. Debonding complications and bracket debonding by the clinician should be simple, clean, and harmless to the bond restoration. Resin Modified Glass Ionomer Cement (RMGIC), poses the ability to bond in the presence of saliva and blood which can be a very good bonding agent for orthodontic attachments especially in the areas of the mouth that are difficult to access. In addition, their fluoride releasing property makes them an ideal bonding agent for patients with poor oral hygiene [1], however; their immediate bond strength is found to be too low for immediate ligation of the initial wire. Bishara, et al. [2] concluded that RMGIs have significantly lower initial bond strength, but increases more than 20-fold within 24 hrs. In comparison, composite adhesive has a significantly higher initial bond strength that doubled within 24 hrs [3,4]. The low initial bond strength of Fuji Ortho LC necessitates a second appointment for placing the arch wire; which means an increase in the total number of appointments made during the treatment and makes time management more difficult for the orthodontist [1]. Regardless of the bonding technique used to attach orthodontic brackets to the teeth, preparing the enamel surface properly to acquire a good and stable bond is necessary, proper preparation usually requires the removal of the enamel pellicle and the creation of irregularities in the surface prior to bonding, this process is called enamel conditioning [5]. Enamel conditioning is performed using one of the two techniques, the first one; is acid etching, in which an acid gel is utilized, resulting in a microetching and the second is sandblasting, in which air abrasion methods are used, resulting in a macroetching [5]. The introduction of the acid etching technique by Buonocore [6] is a milestone in dentistry, this concept is based on the acid dissolution of the enamel tooth surface resulting in the formation of micro porosities in the surface that are used to achieve a micromechanical bond. Since then, a major modifications and enhancements have ensued, including the use of decreased concentrations of phosphoric acid (80%) to 37% orthophosphoric acid and a reduction in the application time from 60 s to 15 s [6,7]. With the use of 37% phosphoric acid, 15-second treatment is recommended for the anterior teeth and premolars [8]. During routine etching with phosphoric acid, 10 µm to 50 µm enamel is removed from the surface, whereas rough surface porosities up to 10 µm to 200 µm deep are created [9], as well Fjeld and øgaard [10] reported that acid etching causes an enamel loss ranging from 3 µm to 10 µm. A non-invasive technique successfully employed in endodontic the uses of NaOCl as an irrigating solution to disinfect and remove debris and organic materials from the canals [11,12] can be used as a deproteinizing agent. It is a possible strategy to optimize adhesion by removing organic elements of both the enamel structure and the acquired pellicle before acid etching,

Espinosa, et al. [13] suggested that the use of 5.25% NaOCl as a deproteinizing agent prior to acid etching increases bond strength because organic elements are removed well. A universal testing machine (Instron) and a digital dynamometer are used to evaluate the shear bond strength (SBS) in vivo and in vitro of metallic brackets bonded to human teeth with light-cured (LC) bonding materials, It is found that tests performed by a universal testing machine resulted in larger bond strengths than those performed by a digital dynamometer in vivo and in vitro [14]. The debonding force is applied to the junction of the attachment and adhesive interfaces; this method comes closest to applying a true shear force, which never occurs clinically [15]. Adhesive remnant should be entirely removed from the tooth surface after orthodontic attachment removal. However, complete removal of the entire adhesive remnants is not easily achieved because of the colour similarity between the adhesives and enamel, however many patients may be left with unsatisfactory incomplete resin removal [16]. A wide variety of instruments and procedures are used for adhesive removal [17], include manual removal using a scalar or a pair of band-removing pliers [18], various shapes of tungsten carbide burs (TCBs) with low or high speed hand pieces [19, 20], Sof-Lex discs [21], and special composite finishing systems with zirconia paste or slurry pumice as well as ultrasonic applications [22]. Carbon dioxide laser application have also been promising [23], and the Nd:YAG laser has demonstrated potent structural degradation of the composite, suggesting that it could be used as an adjunct to the removal of residual resin [24]. Air powder abrasive systems have also been suggested for removing residual adhesive [25], but the need for rubber dam and protective mask/eye wear is an impractical aspect of this technique [26]. All these techniques produce various degrees of polish, and some introduce abrasion with significant loss of enamel, moreover, they may have adverse effects on the pulp tissues if not dissipated with an appropriate coolant. Approximately 10% of enamel is lost because of acid etching, bracket removal, and cleanup after debonding [27]. This study was aimed to determine the effect of NaOCl application before acid-etching on the shear bond strength of orthodontic brackets bonded to the teeth using resin-modified glass ionomer cement.

Materials and Methods

The experimental procedures were approved by the Research Ethics Committee, University Science Malaysia number: [11:35:30 PM] (FWA Reg. No: 00007718; IRB Reg. No: 00004494). Sixty human premolars, extracted for orthodontic reasons, were collected, the soft tissues removed and the teeth were stored in a distilled water at room temperature (7 days) until they were ready for use. The teeth were randomly divided into 2 different enamel treatment groups with 30 teeth each. Group I: experimental, was treated with sodium hypochlorite 5.25% prior to 37% Phosphoric acid etching using RMGI as an adhesive material and group II: control using 37% Phosphoric acid and RMGI only. Premolars with normal crown shape without any deformity and caries free crowns were included. Teeth which have restorations, cracks, and history of bracket bonding were excluded from the study. The roots of the teeth were embedded in acrylic base frame to make blocks measuring (20 x 20 x 40 mm) for ease of manipulation and testing purposes. Standard orthodontic premolar 0.018 metal brackets (Gemini, 3M Unitek, Monrovia, CA), with a 100-gauge mesh were used in this study.

Laboratory procedures

The buccal surfaces of the premolars were cleaned with a non fluoridated prophylaxis paste and rubber prophylactic cups for 10 seconds, rinsed and dried for both groups.

Group I (NaOCl + acid etching): Each tooth, enamel was deproteinized with 5.25% NaOCl for 1 minute using a micro brush, followed by rinsing, drying, and acid etching with 37% phosphoric acid for 30 seconds. Subsequently, the acid was rinsed off and the enamel dried, RMGI was mixed according to the manufacturer instructions and placed on the bracket mesh covering the entire base of the bracket without bubbles or voids applied to the tooth using force sufficient to produce a flash of excess adhesive around the bracket to ensure a uniform thickness of the adhesive. The excess adhesive was removed with a sharp scalar, and the bracket light cured for ten seconds on each side. A Bluedent smart LED curing light (Plovdiv, bulgaria) was used in all bonding procedures during 40 seconds (10 seconds for each mesial, distal, occlusal, and gingival margins) at emitted wave length of 430-490 nm, as maintaining a distance of 1 mm from the bracket base.

Group II (Acid ´┐Ż Etched group): Same procedures for group 1 were followed except no NaOCl was applied before etching as a control group.


Shear bond strength (SBS): After bracket bonding, the teeth were stored in distilled water for 24 hours at room temperature until they were submitted to the shear test. A Universal Test Machine (Instrone model no.8874, England) was used for bracket debonding, the force applied using a flat-end steel rod at the bracket-tooth interface, measured at a crosshead speed of 1.0 mm / min with the tooth aligned so that the applied force perpendicular to the bracket (Figure 1). Each test was recorded in mega Pascal (MPa) by a computer contact to the machine and the samples were restored in distilled water.