A New Technique With Sodium Hypochlorite to Increase Bracket Shear Bond Strength of Fluoride-releasing Resin-modified Glass Ionomer Cements: Comparing Shear Bond Strength of Two Adhesive Systems With Enamel Surface Deproteinization Before Etching

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By eliminating the organic substances from the enamel surface before etching (deproteinization), orthodontic bond strength can theoretically be increased because the resulting etch-pattern is predominantly type 1 and 2, instead of type 3. Fluoride-releasing resin-modified glass ionomer cements (RMGIs) might then routinely be used to bond brackets, instead of composite resins. Reducing the incidence of white spot lesions, a major current iatrogenic effect of orthodontic treatment, is a worthy cause which might be achieved due to the fluoride-releasing properties of RMGIs. The objective of this study was to determine whether deproteinization of human dental enamel surfaces, with 5.25% sodium hypochlorite (NaOCl) before etching, increases orthodontic bracket shear bond strength (SBS) of 2 adhesive systems: a composite resin and a RMGI.

Seventy-six extracted human premolars were cleaned, and randomly divided into 4 groups (2 experimental and 2 control), with 19 premolars in each group. In group 1 (experimental) and group 2 (control), brackets were bonded to the teeth using Transbond XT (3M Unitek Orthodontic Products, Monrovia, CA) and in group 3 (experimental) and group 4 (control), Fuji Ortho LC (GC America, Inc., Alsip, IL) was used. The buccal surfaces of the premolars in experimental groups 1 and 3 were deproteinized with 5.25% NaOCl for 1 minute followed by rinsing, drying, and acid etching for 30 seconds. Subsequently, the acid was rinsed off, the enamel was dried (and remoistened in the Fuji Ortho LC groups), and orthodontic brackets were bonded, either with primer and composite resin, or with RMGI. The same protocol was used in the 2 control groups (2 and 4), except that NaOCl was not used. The teeth were then stored in distilled water at room temperature for a maximum of 24 hours, thermo-cycled 500 times, between 5°C and 55°C, placed in a controlled Water Bath, at 37°C for 24 hours, mounted on acrylic rings, and debonded using a universal testing machine. The enamel surfaces were examined at 10× magnification to determine the amount of residual adhesive remaining on the tooth. An analysis of variance was used to determine whether there was a significant difference in SBSs between the 4 test groups, together with a post hoc test to determine possible significant differences among the pair of means; a χ2 test was used to compare the adhesive remnant index (ARI) scores. There were no significant differences in the SBS (P = 0.05) between the Transbond XT groups. There were significant differences in the SBS (P = 0.05) between the Fuji Ortho LC groups. The mean SBS for Transbond XT with NaOCl was 9.41 ± 4.46 megapascals (MPa); for Transbond XT without NaOCl, 8.12 ± 3.10 MPa; for Fuji Ortho LC with NaOCl, 9.64 ± 5.01 MPa; and for Fuji Ortho LC without NaOCl, 5.71 ± 3.87 MPa. The comparisons of the adhesive remnant index scores between the 2 Transbond groups (χ2 = 6.41) indicated that bracket failure mode was not significantly different (P < 0.05), and for the Fuji Ortho LC groups (χ2 = 24.08) indicated that bracket failure mode was significantly different (P < 0.05), with more adhesive remaining on the enamel bonded using Fuji Ortho LC with NaOCl. SBS was significantly increased from 5.7 to 9.6 MPa using NaOCl in the Fuji Ortho LC group (compared with 9.4 MPa in the transbond XT group with NaOCl). The Fuji Ortho LC experimental group, in which NaOCL was used, had a significantly greater amount of adhesive remaining on the enamel than the control group. It was concluded from this in vitro study that with NaOCl use, bracket bond strength with Fuji Ortho LC is similar to Transbond XT, so that fluoride-releasing RMGIs may possibly be used to bond brackets to reduce the incidence of white spot lesions.

Section snippets

Teeth

Seventy-six, freshly extracted, human premolars were collected, cleaned, and stored in distilled water at room temperature, a maximum of 6 months and a minimum of 3 days. To meet the criteria for use in the study, the teeth were selected only if they had intact buccal enamel, had not been pretreated with chemical agents (eg, H2O2), had no surface cracks from extraction forceps, and were caries-free. The premolars were randomly divided into 4 groups, (2 experimental and 2 control), with 19

Shear Bond Strength

The descriptive statistics, including mean, standard deviation, and minimum and maximum values for the 4 adhesive systems, are presented in Table 1.

The mean SBS for the brackets bonded using Transbond XT, with enamel deproteinization, was 9.41 ± 4.46 MPa, and the mean SBS for the brackets bonded using Transbond XT in the control group (without enamel deproteinization) was 8.12 ± 3.10 MPa.

The mean SBS for the brackets bonded using Fuji Ortho LC, with enamel deproteinization, was 9.64 ± 5.01 MPa,

Discussion

The present study evaluated 2 contemporary adhesive systems marketed for use to bond orthodontic brackets—a RMGI, Fuji Ortho LC, and a primer and/or composite resin system, Transbond XT. The main objective of the study was to determine whether NaOCl, applied for 1 minute before etching, increases bracket SBS.

By conditioning the enamel with 5.25% NaOCl, followed by a 30-second etching with 37% phosphoric acid, the present findings indicated that the mean SBS of brackets bonded using Fuji Ortho

Clinical Recommendations

Once Fuji Ortho LC liquid/powder has been mixed, the operator has less than a minute or two (depending on room temperature) to position the brackets before the adhesive begins to harden. This probably occurs due to the ambient light (as it is light-cured). It is therefore recommended to prepare adhesive for only 2 teeth at a time. NaOCl should also be applied to 2 teeth at a time. The saliva suction tip should be positioned in such a fashion as to suction away all NaOCl excess. As RMGIs take a

Conclusions

  • Significantly greater bracket SBS can be obtained with Fuji Ortho LC if the enamel surface is wetted for 1 minute with 5.25% NaOCL, before etching.

  • When 5.25% NaOCL is used to deproteinize the enamel surface, brackets bonded with Fuji Ortho LC have comparable SBS to brackets bonded with Transbond XT.

  • With 5.25% NaOCL use, the ARI scores are similar when either Transbond XT or Fuji Ortho LC is used to bond brackets.

  • Applying 5.25% NaOCL to the enamel surface eliminates the organic elements. This

Acknowledgments

The authors wish to express their gratitude to Dr. Jorge Guerrero from the Universidad Nacional Autónoma de México (Dental Materials Department) and to Ana Lilia Solis from the Instituto Nacional de Rehabilitación (Microscopy Department).

References (33)

  • J.L. Schmit et al.

    Effect of fluoride varnish on demineralization adjacent to orthodontic brackets bonded with RMGI cement

    Am J Orthod Dentofacial Orthop

    (2002)
  • J.S. Casko et al.

    Objective grading system for dental casts and panoramic radiographs

    Am J Orthod Dentofacial Orthop

    (1998)
  • T. Eliades

    Orthodontic materials research and applications: part 1. Current status and projected future developments in bonding and adhesives

    Am J Orthod Dentofacial Orthop

    (2006)
  • K.S. Coups-Smith et al.

    Glass ionomer cements as luting agents for orthodontic brackets

    Angle Orthod

    (2003)
  • S.E. Bishara et al.

    Shear bond strength comparison of two adhesive systems following thermocycling

    Angle Orthod

    (2007)
  • J. Rodríguez

    Bond strength of a glass ionomer cement and a light cured composite: an ex vivo study

    (1997)
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      Several methods of enamel surface preparations are proposed to increase SBS, such as sandblasting (air abrasion), laser application or enamel deproteinization with sodium hypochlorite [19,20]. Justus demonstrated that enamel deproteinization increases significantly the SBS of a resin-modified glass ionomer cement [21]. Furthermore, Espinosa et al. showed that the use of 5.25% sodium hypochlorite (NaOCl), for 1 minute before acid etching, deproteinized the enamel by eliminating its organic matter, resulting in an increased quality of the etching pattern [22,23].

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