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Year : 2018  |  Volume : 5  |  Issue : 4  |  Page : 128-131

Evaluation of 5% proanthocyanidin and 30% alpha-tocopherol on shear bond strength of composite to bleached enamel: An In vitro study

Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere, Karnataka, India

Date of Web Publication25-Jan-2019

Correspondence Address:
Sonal Vakilram Nishad
Department of Conservative Dentistry and Endodontics, College of Dental Sciences, Davangere, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jdrr.jdrr_54_18

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Objective: The aim of this in vitro study is to evaluate and compare the effect of 5% proanthocyanidin and 30% alpha-tocopherol on the bond strength of composite resin to the bleached enamel. Materials and Methods: The labial enamel surface of sixty central incisors was flattened for the purpose of this study. Fifteen teeth served as control group which did not receive bleaching nor antioxidant treatment. The remaining 45 teeth then were randomly divided into three groups of 15 each. They are Group 1: bleaching with 38% hydrogen peroxide for 10 min without the use of antioxidant, Group 2: bleaching followed by treating with 5% proanthocyanidin, and Group 3: bleaching followed by treating with 30% alpha-tocopherol. The bonded specimens were stored in distilled water (37°C, 24 h) and tested for shear bond strength in a universal testing machine. The data were analyzed with one-way ANOVA and Tukey's post hoc test. Results: Higher bond strength values were seen in the control group followed by 5% proanthocyanidin group. Conclusion: Use of 5% proanthocyanidin can effectively reverse the bond strength of bleached enamel.

Keywords: 30% alpha-tocopherol, 5% proanthocyanidins, bleaching, shear bond strength

How to cite this article:
Lokhande P, Manne D, Shivanna V, Nishad SV. Evaluation of 5% proanthocyanidin and 30% alpha-tocopherol on shear bond strength of composite to bleached enamel: An In vitro study. J Dent Res Rev 2018;5:128-31

How to cite this URL:
Lokhande P, Manne D, Shivanna V, Nishad SV. Evaluation of 5% proanthocyanidin and 30% alpha-tocopherol on shear bond strength of composite to bleached enamel: An In vitro study. J Dent Res Rev [serial online] 2018 [cited 2023 Jan 30];5:128-31. Available from: https://www.jdrr.org/text.asp?2018/5/4/128/250787

  Introduction Top

Today, dentists are increasingly becoming the professionals to whom people turn first for active assistance on improving their appearance. Bleaching is now the single most common esthetic treatment. With the careful diagnosis, case selection, treatment planning, and attention to technique, bleaching is simplest, least invasive, and least expensive means available to lighten discolored teeth and diminish or eliminate many stains in both vital and pulpless teeth.[1]

Bleaching agents contain a high concentration of carbamide peroxide (35%–37%) or hydrogen peroxide (30%–38%).[2] Strong, durable bonds between the restorative material and tooth substrate are essential, not only from a mechanical standpoint but also from the biological and esthetic perspectives. Good marginal adaptation of dental materials reduces microleakage, staining, pulpal irritation, and secondary caries.[3] Studies have shown that hydrogen peroxide and carbamide peroxide can affect the bond strength of composite to etched enamel when bonding is performed immediately after the bleaching process. This is due to the presence of residual peroxide that interfaces with resin bonding and inhibits resin polymerization. Therefore, waiting period for bonding procedure after bleaching has been reported to vary from 24 h to 4 weeks.[4] However, in the present scenario, restorative procedures are possible immediately after bleaching with the use of antioxidant, which shortens the overall time needed for esthetic procedures.[5],[6]

Proanthocyanidin, a grape seed extract, is a natural antioxidant that has greater potential to scavenge oxygen-free radicals. It is 50 times more potent than sodium ascorbate.[7]

Alpha-tocopherol is the most active component of Vitamin E complex,[8] and this organic substance is the most powerful antioxidant in the lipid phase of the human body.[9]

Comparative evaluation of these two antioxidants on bleached enamel has not been done so far. Hence, the aim of this in vitro study is to evaluate and compare the effect of 5% proanthocyanidin a 30% alpha-tocopherol on bond strength of bleached enamel.

  Materials and Methods Top

Two solutions were prepared for the study:

  1. 5 g of grape seed extract in the form of powder was taken and dissolved in 100 mL of distilled water to obtain 5% proanthocyanidin
  2. 30 g of alpha-tocopherol powder dissolved in 100 mL of ethyl alcohol to make 30% alpha-tocopherol solution.

Specimen preparation

Sixty human single-rooted, caries-free maxillary central incisors which were extracted for periodontal reasons were collected. Exclusion criteria included fractured, cracked, carious, fluorosed, restored, and dried teeth. The roots were embedded in acrylic resin blocks, keeping the coronal portion of the tooth exposed. Labial enamel surfaces were flattened with 600 grit silicon carbide paper (Moyco Precision Abrasives, Montgomeryville, PA, USA).

Fifteen teeth served as control group and did not receive any bleaching procedure. The remaining 45 specimens were bleached with 38% hydrogen peroxide gel (Opalescence Xtra Boost, Ultradent Products, Inc., South Jordan, UT) for 10 min as per manufacturer's instructions. The bleaching gel was completely rinsed off with water and dried. The specimens were then randomly divided into three experimental groups of 15 teeth each, depending on the type of antioxidant used [Table 1] which are as follows:
Table 1: Description of groups

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  • Group 1: after bleaching (without antioxidant), composite buildup was done
  • Group 2: bleaching followed with 5% proanthocyanidin for 10 min then composite buildup
  • Group 3: bleaching followed with 30% alpha-tocopherol for 10 min then composite buildup.

The samples were etched with 37% phosphoric acid (total etch etching gel, Ivoclar Vivadent, Schaan, Liechtenstein) for 15s, rinsed with water for 20s, and excess water was dried. Then, the specimens were coated with two coats of Adper single bond (3M ESPE, Dental Products, St Paul, MN, USA) agitated for 10s thoroughly, air dried and light cured for 20s. Then, composite (Filtek SupremeXT, 3M ESPE) of 2 mm diameter and 2 mm height was built up and light cured for 20s.

Testing procedures

The shear bond test was performed using a knife-edge blade in a Hounsfield universal testing machine (Instron, USA) at a cross-head speed of 1 mm/min. The shear bond was calculated from the force at failure divided by cross-section area and multiplied by a constant. The values were expressed in megapascals (MPa).

Statistical analysis

The statistical method used in this study was one-way ANOVA and Tukey's post hoc test at a 95% confidence level.

  Results Top

The results of this study are shown in [Table 2] and [Table 3]. Graphical representation of the comparison of mean shear bond strength between groups is given in [Figure 1]. [Table 1] shows that when the experimental groups, i.e., Group 1, 2, and 3 were compared, Group 2 (5% proanthocyanidin) showed significantly higher bond strength (22.01 ± 0.97). Furthermore, it was seen that the mean shear bond strength of the control group (24.47 ± 1.41) was significantly higher than all other groups. Group 3 (30% alpha-tocopherol) showed an intermediate bond strength of 18.12 ± 0.91 with no significant difference. Thus, among the antioxidants, 5% proanthocyanidin showed the maximum shear bond strength followed by 30% alpha-tocopherol. Thus, the shear bond strength of the groups can be illustrated as follows:
Table 2: Comparison of shear bond strength between the study groups

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Table 3: Pairwise comparison of shear bond strength between the study groups

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Figure 1: Graph showing the mean value of bond strength between the groups

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Group 4 (control) (24.47 ± 1.41) > Group 2 (5% proanthocyanidin) (22.01 ± 0.97) > Group 3 (30% alpha-tocopherol) (18.12 ± 0.91) > Group 1 (no antioxidant) (9.89 ± 0.93).

Control group showed a higher bond strength as the specimens were not bleached and allowed for better adhesion of the composite restoration.

[Table 3] illustrates that the mean difference of Group 1 with Group 2, 3, and 4 which showed the bond strength of −12.12, −8.23, and −14.58, respectively. The mean difference of Group 2 with Group 3 and 4 was 3.90 and −2.46, respectively. Furthermore, when comparing Group 3 with Group 4, there was a mean difference of −6.36. The reduction in values indicated the decreasing bond strength with Group 2 showing the maximum bond strength among all the experimental groups.

  Discussion Top

Bleaching a vital tooth is the most commonly used conservative and effective treatment options available for the treatment of discolored teeth. In vitro studies indicate surface morphology changes in enamel and dentin after peroxide bleaching.[10]In vitro bond strength studies using Adper Single Bond (3M ESPE, Dental Products) have reported values in the range of 30–35 MPa.[4] Reduction in the bond strength of composite after bleaching is because of the fact that there is the presence of residual oxygen after bleaching procedure which in turn interferes with oxygen and hydroxyl or perhydroxyl ions that are released when a bleaching agent is applied to dental structure and are responsible for inhibiting resin penetration into enamel.[8]

Hydrogen peroxide as a bleaching agent has a low molecular weight and decomposes into oxygen and perhydroxylfree radicals. Perhydroxyl radicals attack the long-chained, dark-colored macromolecules of pigments and split them into smaller, less-colored, and more diffusible molecules which are removed from structure producing the bleaching effect.[11],[12] High concentration of hydrogen peroxide (38%) was used as it promoted a better permeability into dentin thus giving better results of tooth whitening.[13],[14] Lai et al. stated that inclusion process of peroxide ions could be reversed by the use of antioxidants.[6],[15]

Proanthocyanidin is a group of polyphenolic bioflavonoids found in high concentration in natural sources such as grape seed extract, pine bark extract, cranberries, lemon tree bark, and hazelnut tree leaves.[7] It comprises of the monomeric flavan-3-ol (+) catechin and () epicatechin. These compounds have also been reported to demonstrate antibacterial, antiviral, anticariogenic, anti-inflammatory, and antiallergic properties.[16]In vitro studies have confirmed that antioxidant property of proanthocyanidin is 50 times greater than those of Vitamin C.[7],[16]

Vitamin E is the collective name for a group of potent, lipid-soluble, and chain-breaking antioxidants.[17] Alpha-tocopherol is the most active component of Vitamin E complex, and this organic substance is the most powerful antioxidant in the lipid phase of the human body.[9]

Therefore, the present study is designed to evaluate the neutralizing effect of proanthocyanidin and alpha-tocopherol on the shear bond strength of composite resin to bleached enamel. Various mechanical tests have been used to assess the bonding performance of restorative materials. Testing in shear mode is relatively simple, reproducible, and widely accepted test.[18]

According to the present study, Group 4, i.e., control (no bleaching: 24.47 ± 1.41) showed the highest bond strength compared to the other groups.[4],[17] Bond strength was lowest for Group 1 (bleached and not treated with antioxidants: 9.89 ± 0.93) when compared with control and other antioxidant groups. This is due to the fact that the bleaching agent leaves behind a residual oxygen layer which interferes with resin infiltration and inhibits polymerization of resin.[8]

According to this study, Group 3 (alpha-tocopherol: 18.12 ± 0.89) showed better bond strength when compared to Group 1 (9.89 ± 0.93).[8] However, when compared to Group 2 (proanthocyanidin: 22.01 ± 0.97), it showed less shear bond strength.

This study showed that surface treatment with proanthocyanidin (Group 2) improves the bond strength (22.01 ± 0.97) when compared with Group 1 (bleached: 9.89 ± 0.93) and Group 3 (alpha-tocopherol: 18.12 ± 0.89). This could be due to the following:

  1. The specificity of oligomeric proanthocyanidin (OPC) complexes for hydroxyl-free radicals
  2. The presence of multiple donor sites on OPC complexes that trap superoxide radicals
  3. The esterification of epicatechin by gallic acid in OPC complexes, which enhances the free radicals' scavenging ability.[6],[7]

They are also potent scavengers of superoxide radical (O2) and hydroxyl radicals (-OH) in aqueous models. In the present study, treatment with OPCs gave bond strengths superior to that of unbleached enamel.

In vitro studies have confirmed that antioxidant property of OPCs is 50 times greater than those of Vitamin C and 20 times greater than that of Vitamin E.[7],[16]

  Conclusion Top

Under the limitations of this in vitro study, it can be concluded that

  1. Treatment of the bleached enamel surface with 5% proanthocyanidin reverses the reduced bond strength and may be an alternative to delayed bonding, especially when restoration is to be completed immediately after bleaching
  2. The use of grape seed extract as an antioxidant yields significantly greater enamel bond strength than that of 30% alpha-tocopherol.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Goldstein GR, Garber DA. Complete Dental Bleaching. Chicago: Quintessence Books; 1995. p. 2.  Back to cited text no. 1
Minoux M, Serfaty R. Vital tooth bleaching: Biologic adverse effects-a review. Quintessence Int 2008;39:645-59.  Back to cited text no. 2
Swift EJ Jr., Perdigão J, Heymann HO. Bonding to enamel and dentin: A brief history and state of the art, 1995. Quintessence Int 1995;26:95-110.  Back to cited text no. 3
Vidhya S, Srinivasulu S, Sujatha M, Mahalaxmi S. Effect of grape seed extract on the bond strength of bleached enamel. Oper Dent 2011;36:433-8.  Back to cited text no. 4
Torres CR, Koga AF and Borges AB. The effects of antioxidant agents as neutralizers of bleaching agents on enamel bond strength. Braz J Oral Sci 2006;5:971-6.  Back to cited text no. 5
Gökçe B, Cömlekoğlu ME, Ozpinar B, Türkün M, Kaya AD. Effect of antioxidant treatment on bond strength of a luting resin to bleached enamel. J Dent 2008;36:780-5.  Back to cited text no. 6
Fine AM. Oligomeric proanthocyanidin complexes: History, structure, and phytopharmaceutical applications. Altern Med Rev 2000;5:144-51.  Back to cited text no. 7
Sasaki RT, Flório FM, Basting RT. Effect of 10% sodium ascorbate and 10% alpha-tocopherol in different formulations on the shear bond strength of enamel and dentin submitted to a home-use bleaching treatment. Oper Dent 2009;34:746-52.  Back to cited text no. 8
Burton GW, Ingold KU. Vitamin E as an in vitro and in vivo antioxidant. Ann N Y Acad Sci 1989;570:7-22.  Back to cited text no. 9
Cavalli V, de Carvalho RM, Giannini M. Influence of carbamide peroxide-based bleaching agents on the bond strength of resin-enamel/dentin interfaces. Braz Oral Res 2005;19:23-9.  Back to cited text no. 10
Subramonian R, Mathai V, Christaine Angelo JB, Ravi J. Effect of three different antioxidants on the shear bond strength of composite resin to bleached enamel: An in vitro study. J Conserv Dent 2015;18:144-8.  Back to cited text no. 11
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Souza-Gabriel AE, Vitussi LO, Milani C, Alfredo E, Messias DC, Silva-Sousa YT, et al. Effect of bleaching protocols with 38% hydrogen peroxide and post-bleaching times on dentin bond strength. Braz Dent J 2011;22:317-21.  Back to cited text no. 12
Carvalho AO, Ayres AP, de Almeida LC, Briso AL, Rueggeberg FA, Giannini M, et al. Effect of peroxide bleaching on the biaxial flexural strength and modulus of bovine dentin. Eur J Dent 2015;9:246-50.  Back to cited text no. 13
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Lai SC, Tay FR, Cheung GS, Mak YF, Carvalho RM, Wei SH, et al. Reversal of compromised bonding in bleached enamel. J Dent Res 2002;81:477-81.  Back to cited text no. 15
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Kavitha M, Selvaraj S, Khetarpal A, Raj A, Pasupathy S, Shekar S, et al. Comparative evaluation of superoxide dismutase, alpha-tocopherol, and 10% sodium ascorbate on reversal of shear bond strength of bleached enamel: An in vitro study. Eur J Dent 2016;10:109-15.  Back to cited text no. 17
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  [Figure 1]

  [Table 1], [Table 2], [Table 3]

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