Bisphenol A Release from Orthodontic Clear Aligners: An In-Vitro Study

Abstract

Bisphenol A (BPA) is a widely used synthetic compound that has been identified as an endocrine disruptor. It has been linked to adverse health effects such as developmental defects, infertility in both men and women, cardiovascular disease, and obesity. There has been increased interest in BPA’s effects on the developing fetus and data has revealed that doses below the presumed safe dose can produce harmful effects. Orthodontic clear aligner therapy is a popular treatment modality that involves the patient wearing sets of plastic aligners up to 22 hours per day for the duration of treatment. The BPA release from these aligners was rarely investigated. The objective of this study was to detect, quantify, and compare the amount of BPA released by 3 popular brands of orthodontic aligners in artificial saliva, artificial gastric fluid, and ethanol. Equal amounts of SmileDirectClub®, Invisalign®, and Essix Ace® aligners were placed in sterile glass vials and submerged in 5.5mL artificial saliva, artificial gastric fluid, and ethanol. Samples were incubated at 37°C and 1 mL aliquots were removed at various time points. Samples were prepared and analyzed using high performance liquid chromatography tandem mass spectrometry. BPA was released from all three brands of aligners with great variability. Peak BPA concentrations were detected in artificial saliva; Smile Direct Club® produced 5.0 ng/mL after 20 days, Invisalign® released 3.5ng/mL after 24 hours, and Essix Ace® released 6.3ng/mL after 10 days of incubation in artificial saliva. There was no significant difference in BPA concentration between the 3 types of aligners in the 3 media. When comparing time points, there was a significant increase of BPA release in the first 24 hours after incubation compared to the baseline (p<0.001). There is potential BPA release from orthodontic aligners. There was no significant difference in the amount of BPA released between the three types of aligners at any time point. The majority of BPA release occurred during the first 24 hours.

Bisphenol-A release from thermoplastic clear aligner materials: A systematic review

“…However, the BPA concentration at T 0 was significantly lower in the VFR group comparatively. Katras et al (2021) reported a well-documented release of BPA at all time intervals from all the CA materials tested. It was found that the concentrations reached the peak at different time points for the different materials.…”

“…None of the included studies provided information on sample size determination, random sequence generation and concealment mechanism, and where the full trial protocol can be accessed (Table 2). Only one study (Katras et al, 2021) reported blinding of the investigators and two (Katras et al, 2021; Schuster et al, 2004) on the inherent limitations of the study.…”

“…Out of the included studies, one was a clinical trial (RCT) (Raghavan et al, 2017), while others were in vitro studies (Alhendi et al, 2022; El Idrissi et al, 2020; Katras et al, 2021; Kotyk and Wiltshire, 2014; Schuster et al, 2004). BPA release from CAs was the sole objective in three studies (Alhendi et al, 2022; El Idrissi et al, 2020; Katras et al, 2021), while the clinical trial also assessed the leaching from heat-cured and self-cured Hawley retainers (Raghavan et al, 2017). One of the in vitro studies evaluated the BPA release from different orthodontic materials including CA (Kotyk and Wiltshire, 2014), while another investigated the structural changes in aligners after intra-oral exposure, in addition to the leaching of substances (Schuster et al, 2004).…”

“…The reasons for exclusion after full-text evaluation are listed in Supplementary Table 2. Thus, six studies were finally included for the qualitative synthesis (Alhendi et al, 2022; El Idrissi et al, 2020; Katras et al, 2021; Kotyk and Wiltshire, 2014; Raghavan et al, 2017; Schuster et al, 2004), out of which one was in French (El Idrissi et al, 2020), which was professionally translated to English and then assessed. The PRISMA flow chart is provided in Figure 1.…”

“…Considering the long duration of orthodontic treatment, the use of such polymer-based materials in the oral cavity has become a matter of public health concern (Freitas, 2022; Peter et al, 2022). Though claimed to be BPA-free, studies on the same are contradictory (Alhendi et al, 2022; Katras et al, 2021; Schuster et al, 2004).…”