Original article
Bisphenol A release from an orthodontic adhesive and its correlation with the degree of conversion on varying light-curing tip distances

https://doi.org/10.1016/j.ajodo.2010.02.037Get rights and content

Introduction

The aims of this research were to use high-performance liquid chromatography to assess the bisphenol A (BPA) released from an orthodontic adhesive (Transbond XT; 3M Unitek, Monrovia, Calif) with various light-curing tip distances and to correlate the release to the degree of conversion.

Methods

One hundred thirty-eight premolar brackets were divided into 3 groups of 40 each for the high-performance liquid chromatography analysis and 3 groups of 6 each for assessing the degree of conversion. Fourier transform infrared spectroscopy was used for this purpose. Each group was studied at light-curing tip distances of 0, 5, and 10 mm. Statistical analyses were performed by using 2-way analysis of variance (ANOVA), post-hoc multiple comparisons Tukey HSD tests, and paired t tests. Pearson correlation was used to assess the correlation between the degree of conversion and BPA release.

Results

BPA release was greater in specimens cured with a greater light-curing tip distance. The degree of conversion decreased with increased light-curing tip distances. A negative correlation was found between BPA release and degree of conversion.

Conclusions

Clinicians should ensure that the adhesive is completely cured by keeping the light-curing tip as close to the adhesive as clinically possible.

Section snippets

Material and methods

A visible light-cured adhesive, Transbond XT, was used. From 138 premolar stainless steel brackets (3M Unitek), 120 were used to assess BPA release with HPLC, and 18 were used for estimating the DC with the FTIR spectrometer (Perkin-Elmer, Norwalk, Conn). BPA released and the DC values were assessed at 3 light-curing tip distances from the bracket: 0, 5, and 10 mm.

The varying distances of the curing tip were standardized by using a specially fabricated wooden box on which a yellow tile was

Results

Table I shows the mean concentrations of BPA released on days 1, 7, 21, and 35 at the 3 light-curing tip distances of 0, 5, and 10 mm. Table II, Table III, Table IV, Table V, Table VI, Table VII show the BPA release from days 1 to day 35 in the 3 groups and between the 3 groups. Greater amounts of BPA were observed at the 10-mm light-curing tip distance. There was a statistically significant increase in the mean release of BPA as the light-curing tip distance was increased (P <0.05). A

Discussion

Leaching of BPA was observed on day 1 even at the 0-mm light-curing tip distance; this substantiates the observation of Thompson et al14 that cured orthodontic adhesives are far from inert. Tip distances of 0 and 5 mm showed increases of BPA released up to day 21, after which the concentration showed a marginal decrease. At 10 mm, the day 1 release was not only greater, but this increased release remained more or less constant until day 35. This could be because of the depletions in the

Conclusions

Release of BPA was detected from Transbond XT with light-curing tip distances of 0, 5, and 10 mm, thus indicating that the cured composite is not inert. Increasing the light-curing tip distance caused a decrease in the DC, and this led to greater BPA release. The clinician should keep the light-curing tip as close to the adhesive as clinically possible.

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The authors report no commercial, proprietary, or financial interest in the products or companies described in this article.

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