Evaluation of Bisphenol-A Release from Vacuum formed Retainers after Immersion in Distilled Water using High Performance Liquid Chromatography: A Randomised Clinical Trial

Abstract

Introduction: With the increasing demand for aesthetics, the popularity of Vacuum-formed Retainers (VFRs) has been on the rise. Bisphenol-A (BPA) is added to the polymers to make them clear and tough. BPA is identified as an endocrine disruptor linked to developmental defects, infertility, cardiovascular disease and cancer. The release of BPA from various orthodontic materials, including VFRs, has been reported infrequently and with variable results. Aim: To assess the effect of immersing VFRs in distilled water on BPA release in the saliva of patients wearing VFRs. Materials and Methods: This was a single-centre prospective randomised clinical trial. A total of 28 patients aged between 15 and 25 years, who had completed their fixed orthodontic treatment in 2021 at Bharati Vidyapeeth Deemed to be University (BVDU), Dental College and Hospital, Sangli, Maharashtra, India, were selected for this in-vivo study. Patients were randomly divided into two groups. Group I patients received VFRs without immersion in water before delivery, while Group II patients received VFRs that were immersed in distilled water at 37˚C for 24 hours before delivery. Four samples of unstimulated whole saliva were collected across four different time intervals: T0 (before VFR delivery), T1 (after one hour of wearing retainers), T2 (after one week of wearing retainers) and T3 (after three weeks of wearing retainers). These samples were tested for BPA release using HPLC analysis. For numerical continuous data following a normal distribution, intergroup comparison was conducted using a one-way Analysis of Variance (ANOVA) test and intra-group comparisons were performed using a paired t-test. An alpha error of 5% and a power of 80% were maintained, with p<0.05 considered statistically significant. Results: The mean age of patients selected for the study was 20±5 years. Statistical analysis revealed that the mean release of BPA (0.33 ppm) in saliva was highest in patients from Group I at T1, decreasing to 0.177 ppm at T2 and further reducing to 0.013 ppm at T3. In comparison, the mean values of BPA release in the saliva of patients in Group II were significantly lower at all time intervals: T1 (0.07 ppm), T2 (0.009 ppm) and T3 (0.001 ppm). Intergroup comparison using a one-way ANOVA test showed that the difference in BPA release between the two groups was statistically significant (p-value=0.05). Tukey’s post-hoc test revealed statistically significant differences in BPA release between T1-T2, T2-T3 and T1-T3. Conclusion: Prior immersion of VFRs in distilled water for 24 hours at 37°C before delivery to patients can be a simple solution to reduce BPA release in saliva.

Keywords

• polyethylene
• polymer
• saliva
• toxicit