A comparison of the shear bond strength of orthodontic brackets bonded after enamel conditioning with sodium hypochlorite and papain gel: An in vitro study

Ferin Fathima; Ravi Shantaraj; Subbaiah Pradeep; Dhakshaini Mysore Rajashekar; I Girish Kumar

doi:10.4103/jms.jms_116_21

ORIGINAL ARTICLE

Year : 2022 | Volume : 36 | Issue : 3 | Page : 101-105

A comparison of the shear bond strength of orthodontic brackets bonded after enamel conditioning with sodium hypochlorite and papain gel: An in vitro study

Ferin Fathima¹, Ravi Shantaraj¹, Subbaiah Pradeep², Dhakshaini Mysore Rajashekar³, I Girish Kumar²
¹ Department of Orthodontics and Dentofacial Orthopedics, JSS Dental College and Hospital, JSS Academy of Higher Education and Research, Mysuru, Karnataka, India
² Department of Orthodontics and Dentofacial Orthopedics, JSS Dental College and Hospital, Mysuru, Karnataka, India
³ Department of Pharmacognosy, Drug Centre, JSS Hospital; Department of Prosthodontics and Crown and Bridge JSS Dental College and Hospital, JSS Academy of Higher Education and Research, Mysuru, Karnataka, India

Date of Submission	06-Sep-2021
Date of Decision	22-Mar-2022
Date of Acceptance	26-Aug-2022
Date of Web Publication	25-Feb-2023

Correspondence Address:
Dr. Subbaiah Pradeep
Department of Orthodontics and Dentofacial Orthopaedics, JSS Dental College and Hospital, Mysuru - 570 015, Karnataka
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jms.jms_116_21

Abstract

Objectives: The objective of this research was to evaluate the effect of conditioning the enamel surface with 10% papain gel and 5.25% sodium hypochlorite (NaOCl) on the shear bond strength (SBS) of orthodontic brackets and correlate it with the conventional bonding mechanism utilizing a universal testing machine.
Materials and Methods: Ninety extracted human premolars divided into three groups: In Group 1, treatment with 5.25% NaOCl for 60 s on enamel surface followed by etchant and primer application. In Group 2, treatment with 10% Papain gel for 40 s followed by etching and primer application. In Group 3, etching was followed by primer application. A universal testing machine was used to record the SBS of the orthodontic brackets.
Results: About 5.25% NaOCl (15.10 ± 2.66) and 10% papain gel (15.66 ± 2.83) treatment on enamel before acid etching when compared to the control group (12.82 ± 2.03) increased the SBS with a statistically significant difference between them (P = 0.002, P < 0.001). The experimental groups, NaOCl (15.10 ± 2.66) and papain gel (15.66 ± 2.83) group, were comparable but did not show any statistically significant difference between them (P = 0.665).
Conclusion: SBS of orthodontic brackets can be significantly increased if the enamel is deproteinized with 5.25% NaOCl and 10% papain gel before acid etching with 37% phosphoric acid compared to the conventional bonding technique. Deproteinizing enamel can be considered a cost-effective ally to increase orthodontic brackets' bond strength and thereby reduce the duration of orthodontic treatment.

Keywords: Deproteinization, enamel conditioning, papain gel, shear bond strength, sodium hypochlorite, whitespot lesion

How to cite this article:
Fathima F, Shantaraj R, Pradeep S, Rajashekar DM, Kumar I G. A comparison of the shear bond strength of orthodontic brackets bonded after enamel conditioning with sodium hypochlorite and papain gel: An in vitro study. J Med Soc 2022;36:101-5

How to cite this URL:
Fathima F, Shantaraj R, Pradeep S, Rajashekar DM, Kumar I G. A comparison of the shear bond strength of orthodontic brackets bonded after enamel conditioning with sodium hypochlorite and papain gel: An in vitro study. J Med Soc [serial online] 2022 [cited 2023 Jun 9];36:101-5. Available from: https://www.jmedsoc.org/text.asp?2022/36/3/101/370591

Introduction

Dentistry in general and orthodontics in particular strongly rely on advances in the material science. Nonetheless, advanced research on material development has had significant effect on the practice of orthodontics since the advent of modern orthodontics by Edward H. Angle.^[1] The implementation of direct bonding was another headway in orthodontics. In the early days, Brackets and auxillary attachments were welded onto gold or stainless steel bands. Sufficient space should have been made around each tooth before treatment.

To seat the bands, after which it was cumbersome to close the spaces postorthodontic treatment. This was prolonged and difficult for the patient. Attached and banded attachments often induced gingival damage and below the band decalcification may occur. Orthodontic bracket bonding to the enamel surface was pioneered by Dr George Newman in the mid-1960s.^[2] Enamel etching patters were categorized into three by Gwinnet (1971) and Silverstone (1975), on the basis of the dissolution of the hydoxyapetite crystals.^[3]

Type 1 – Sequence that dissolves the enamel rods
Type 2 – The interrods are dissolved
Type 3 – All rods and interrods are dissolved.

Clinically, it provides a frosty white appearance that reveals only the quantity but not the quality of the etching. However, it was later established by silverstone that majority of the etching patterns were of Types 1 and 2 based on the retentive component produced by the porous layer. The micro retention provided by the other two lacked Type 3 pattern.

The organic components are still tethered to the enamel surface (the acquired dental pellicle) even after pumicing of the surface. Through controlling mineral dissolution dynamics on the enamel surface, the acquired pellicle has a major role in preserving the structure of teeth and offers resilience against chemical depletion and damage by acid etching. Therefore, the pellicle prohibits the enamel surface from being etched completely, contributing to bracket debonding and whitespot lesion (WSL) creation on the bonded surface. Because of its proteolytic properties, sodium hypochlorite (NaOCl) solutions have been used to irrigate wounds from 1915. Various NaOCl concentrations (1%–5%) are now commonly recognized as a root canal irrigant^[4],[5] In 2008, it was found by Espinosa et al., 2010 that treating the superficial surface with 5.25%. NaOCl before etching increased the quality of the etching pattern because NaOCl separated organic matter from this surface (deproteinization).^[6] Papain was introduced into the dental field recently. The product, Papaca'rie was used in the chemomechanical dissolution of carious activity. The objective was of eliminating affected tissue without harming any healthy structure in the oral cavity. Papain is an enzyme obtained from the parts of Carica papaya. The enzyme has been included in various antibacterial and deproteinization agents.^[7] Because of these properties, it was used in the dental field. It can also remove debris from teeth and increase acid penetration of enamel. It produces a rough surface and it is helpful to enhance the bond strength between adhesive and tooth enamel.^[6] Enamel conditioning is an inevitable part in dentistry but the surface area conditioned majorly is only 2%.^[8] This is majorly noticed in procedures wherein restorations and orthodontic brackets are defective. This results in numerous dental visits thus increasing the treatment time and hiking its cost.

Since research on the effects of enamel deproteinization and its importance on orthodontic bracket shear bond strength (SBS) is limited in the literature, the idea of this research is to study the effect of 10% papain gel and 5.25% NaOCl on the increase of orthodontic bracket SBS and also to correlate it with the standard bonding mechanism by means of a universal testing machine.

Materials and Methods

Collection of samples

Extracted teeth used in this study were extracted for orthodontic purposes from patients-seeking orthodontic treatment at the Department of Orthodontics, JSS Dental College and Hospital. Ninety premolar samples extracted for orthodontic treatment purpose were used. It was randomly divided into three groups of 30 samples each The collected specimen is stored at the room temperature in distilled water solution of 0.1% thymol for disinfection and to inhibit bacterial growth.

Preparation of 10% papain gel

Papain, an anti-oxidant (α-tocopherol acetate), emulsifier (amylopectin), thickener (Carbomer) pH adjuster (Triethanolamine) Preservative (methyl paraben and propyl paraben), Metalcomplexing agent (ethylene diaminetetraacetic acid), Distilled water as a vehicle. C. papaya extract 25 mg was obtained from Hi-media laboratory and 10% papain gel, was then formulated with the above-mentioned raw materials in the Department of Pharmacognosy, JSS College of Pharmacy, JSS AHER, Mysuru.

Group A (pink)

Initially, 5.25% NaOCl is applied with a applicator tip for 60 s washed and dried followed by etching with 37% phosphoric acid. Primer was then applied and light cured. The orthodontic bracket was bonded with 3M Transbond™ XT composite resin.

Group B (green)

About 10% Papain gel is applied on the enamel surface with an applicator tip for 40 s, washed, and dried. Etching with 37% phosphoric acid is done. Primer was then applied and light cured. The orthodontic bracket was bonded with 3M Transbond™ XT composite resin.

Group C (brown)

Etched with 37% phosphoric acid washed and dried. Primer was then applied and light cured. The orthodontic bracket was bonded with 3M Transbond™ XT composite resin.

Evaluation of shear bond strength

After the pretreatment of enamel using 5.25% NaOCl, 10% papain gel and control group, respectively, the brackets are bonded onto the buccal surfaces of the tooth using 3M™ Transbond™ XT composite resin. A universal testing machine with a load cell of 1000 N was used, operating at a cross-head speed of 0.5 mm/min. In the universal testing machine, each sample was placed with its long axis parallel to the direction of the applied force. A jig was made using 0.01” stainless steel wire and the end of the wire was embedded in acrylic block (to secure the stainless steel wire), which was fixed to the upper jaw. The loop was engaged under wings of bracket on which shear force is to be applied. The maximum force necessary to debond or initiate bracket failure was recorded in Newton. The SBS in Mega-pascals (MPas) was computed as a ratio of force in Newton to the surface area of the bracket. Profile projector Microscope (Mitutoyo–PJ-A3000), Mitutoyo South Asia Pvt. Ltd., screen 0315 mm, measuring range of 100 mm × 100 mm, ×10 projector lens, 100 mm × 100 mm XY stage with linear scales and Halogen lamp of 24 V, 15W was used to measure the bracket base surface area. Bracket base was measured and calculated to derive the total surface area value of 10.5 mm².

Statistical analysis

The data obtained were subjected to the statistical analysis, which was performed using SPSS (Statistical Package for the Social Sciences, IBM, SPSS Inc., IBM SPSS Statistics) software version 14 for Windows with the one-way analysis of variance (ANOVA) and Tukey's post hoc tests to compare the SBS values of all the groups. All the tests were performed at 95% confidence level with the level of significance set at 0.05 (5%).

Results

[Table 1] shows statistical differences between the test parameters in the study according to one-way-ANOVA. In ANOVA, there is a statistically significant difference between the Groups A, B, and C with P < 0.001. The mean SBS of Papain gel group is (15.66 Mpa) which is the highest followed by NaOCl group (15.10 Mpa) and least mean SBS was shown by the control group (12.82 MPa). From Tukey's post hoc test [Table 2], it is observed that there is significant difference in mean bond strength 5.25% NaOCl (15.10 ± 2.66) treatment on enamel before acid etching when compared to the control group (12.82 ± 2.03) wherein conventional technique was used did increase the SBS with a statistically significant difference between them (P = 0.002). Ten percent papain gel (15.66 ± 2.83) treatment on enamel before acid etching when compare to the control group (12.82 ± 2.03) wherein conventional technique was used did increase the SBS with a statistically significant difference between them (P < 0.001). The experimental groups, NaOCl (15.10 ± 2.66) and papain gel (15.66 ± 2.83) group, were comparable but did not show any statistically significant difference between them (P = 0.665).

Table 1: Groups, minimum, maximum, mean and standard deviation, and range and significance of the shear bond strength values and statistical analysis of the groups evaluated

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Table 2: Descriptive statistics, including mean difference, standard error, and P value

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Discussion

Dental enamel is made up of 96% of inorganic matter and <1% of organic matter, <50% protein is present. Orthophosphoric acid primarily works on the mineral portion, that is, the inorganic part of the enamel, although the organic portion of the enamel surface is not removed.^[9] Phosphoric acid is prevented from etching the enamel surface successfully because of this additional organic coating, resulting in a variable pattern and a superficial enamel surface for bonding. To multiply the type of etch patterns in turn gave rise about idea of removing protein composition of enamel. Researchers have shown that the organic material and salivary proteins present in saliva are typically located in the superficial zone and can create obstacles in the traditional etching technique as well as in the deepest resin penetration. Researches have shown that the organic material along with saliva components consisting in saliva is attributed in the outermost layer and can create obstacles. It is notable that Gurneyand Rapp in 1946 published an original research paper entitled “A Technique for Observing small Changes on Tooth Surface.^[10] These authors did enamel and dentin etching of tooth surface which was previously treated with a NaOCl derivate, sodium hydroxide (NaOH) solution, at various concentrations to procure adequate surfaces evaluated under SEM. The tooth specimens were then immersed for etching with results analyzed at appropriate times by creating additional micro-impressions. The surfaces looked cleaner after the application of the NaOH solvent, possibly because of the dissolution of small part of the organic coats from the surfaces.^[11]

While the bond strength of traditional etching systems has been tested in several studies, few studies have considered the potential effects of enamel protein levels on etching efficiency.

Pithon et al., 2011 stated that deproteinization of enamel with 10% papaingel tends to multiply the SBS, independent of the etching agent, and therefore, this makes papain gel a good alternative for deproteinization for enamel surface before bonding orthodontic brackets.^[12] The mean SBS recorded after deproteinization was 23.6 ± 50.88 which is not comparable to the results obtained in the present study which is 15.66 ± 2.83. The reason for varying results could be due to the use of bovine incisors in the above study.

The impact of various types of concentrations of gel form of papain on orthodontic bonding of bracket was also consequently studied by Pithon et al., 2012 to confirm the hypothesis that deproteinization of enamel with papain concentrations of 2%, 4%, 6%, 8%, and 10% increases SBS with different concentrations. The conclusion was that the deproteinization with 8% and 10% gel of papain strengthens SBS of orthodontic brackets bonded with RMGIC.^[13] Similarly, 10% papain gel was found to be the ideal concentration by Sharafeddin and Safari 2019 in their study. Effect of Papain and Bromelain Enzymes on SBS of Composite to Superficial Dentin in Different Adhesive Systems evaluated the 10% papain gel as a deproteinizing agent before the self-etching adhesive system and it showed the highest SBS.^[14] Taking into consideration the results of these studies, concentration of 10% was found ideal for papain gel and was used for the present study.

Espinosa et al.,2010 in the study showed that conditioning of the surface of enamel using 5.25% NaOCl for 1 min, before acid etching, improves the etching pattern quality because NaOCl eliminates the organic matter which causes deproteinization of enamel surface. The researchers demonstrated that the outermost organic layer prevents standard 37% phosphoric acid from etching the enamel surface, resulting in in-consistent etch patterns and a unreliable enamel surface for bonding orthodontic brackets. Types 1 and 2 patterns of etching results when NaOCL were used, whereas Type 3 etch pattern was mostly seen when NaOCl was not used. Deproteinizing agent to phosphoric acid etching became twice the enamel's retentive surface notably, from 48.8% to 94.47% and more commonly Type I andType II etching patterns.^[6]

Saroğlu et al., 2006 showed that deproteinization following the acid etching resulted in enhancement of the enamel bonding in hypo-calcified amelogenesis imperfect (HCAI) teeth and was used to decrease the high breakage rates of adhesive restorative treatments in HCAI cases. HCAI enamel may have 3%–4% protein by weight in contrast with 0% for normal enamel. As the adhesion of enamel with restoration highly depends on the alterations in the enamel surface, excess proteins removal may have provided advantage on the adhesion of the restorative procedures.^[15] Effect of bromelain enzyme for dentin deproteinization on bond strength of adhesive systems was studied by Chauhan et al., 2019. Thirty extracted human premolars were used in the study. In Group 1, teeth were etched; in Group 2, teeth were etched and deproteinized with bromelain enzyme; in Group 3, teeth were etched and deproteinized with 5% NaOCl. The conclusion states that the bond strength results were significantly influenced by the application of bromelain enzyme. Statistically significant was not demonstrated in the control group and NaOCl-treated group. However, NaOCl may exert different effects on bond strength depending on the chemical structure of the adhesive system and the type of the initiator in the adhesive system used which could be the reason for the contrary results compared to the present study.^[16]

Enamel surface deproteinization before orthodontic bracket bonding was suggested by Justus et al., 2010 using NaOCl. They stated that Enamel-deproteinization with 5.25% NaOCl improves the SBS, independent of the etching agent.^[17] Transbond XT with NaOCL Deproteinization recorded mean SBS values of 9.41 ± 4.46 which was comparable to the results achieved in the present study. Enamel deproteinization after acid etching was studied by Harleen et al., 2014 where 5.25% NaOCl was applied on the enamel surface after acid etching. They concluded that no significant enhancive effect of enamel deproteinization after acid etching with respect to the occurrence of Type I–II etching patterns as well as on the SBS of adhesive resin and composite resin complex to the enamel surface was observed in this study which was in contrast with the present study.^[18] The contrary results could be due to the use of extracted permanent molar teeth and bonding of composite resin block on the treated enamel surface differing from the present study where orthodontic brackets were bonded on the buccal surfaces of extracted premolar teeth.

To conclude, this study states that enamel deproteinization using 5.25% NaOCl and 10% Papain gel significantly increased the SBS of orthodontic brackets. As innovations and advancements happen, newer deproteinizing agents such as bromelain gel have also been introduced. Deproteinization treatment can be considered a new ally in orthodontic treatment as it helps to decrease bracket failure and treatment duration and can also aid in reducing WSL formations.

Conclusion

Within the limitations of the present study, the following conclusions were drawn:

Significantly greater SBS of orthodontic brackets can be obtained with conventional composite if the enamel is deproteinized with 5.25% NaOCl or 10% papain gel before acid etching with 37% phosphoric acid
Similar efficiency was shown by 5.25% NaOCl and 10% papain gel in deproteinizing enamel and thereby increasing the bond strength
Deproteinization with 5.25% NaOCl and 10% papain gel before acid etching offers a noninvasive and cost-effective method of enhancing bond strength of orthodontic brackets.

Since 10% papain gel and 5.25% NaOCl has been proved as an effective enamel deproteinizing agent, it will help the orthodontists to achieve effective bonding before orthodontic bracket bonding procedure, but newer studies with larger sample sizes and clinical trials are recommended for these deproteinization agents before its clinical application. Increasing the SBS significantly decreases the treatment time and can be considered a new ally in the current orthodontic perspective.

Acknowledgment

JSS College of Pharmacy, Mysore
Sri Jayachamarajendra College of Engineering, Mysore.

Author's contribution

Dr. Ferin Fathima – Principle Investigator
Dr. Ravi S – Guiding Throughout The Research Project
Dr. Pradeep. S-Guiding Throughout The Research Project
Dr. K. Mruthunjaya-Preparation of 10% Papain Gel
Dr. Girish Kumar I-The Research Project.

Financial support and sponsorship

Self-funded.

Conflicts of interest

There are no conflicts of interest.

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