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Salivary Levels of Eluents Released During Invisalign Treatment With Attachments
TAKE-HOME MESSAGE
- This in vivo study evaluated the salivary levels of eluents released from polyester urethane (Invisalign™) aligners and resin composite attachments. Elevated levels of bisphenol-A (BPA) were found in patients' oral rinse samples at the end of clear aligner therapy in conjunction with bonded resin attachments. After attachment removal, there were still detectable traces of BPA in oral rinse samples, albeit at a significantly reduced level. This suggests a link between the presence of composite attachments and BPA release.
- Considering the feasible estrogenicity and cytotoxicity of the released factors, practitioners should apply appropriate risk management measures, reduce the number of attachments to the absolutely necessary level, and consider the utilization of alternative materials for attachments, such as BPA-free resin-bonded buttons made of medical-grade polymers with improved biological properties.
abstract
This abstract is available on the publisher's site.
Access this abstract nowBACKGROUND
The aim of the present study was to investigate qualitatively and quantitatively the elution of substances from polyester-urethane (Invisalign™) aligners and resin composite attachments (Tetric EvoFlow) in vivo.
METHODS
Patients (n = 11) treated with the aligners and attachments (16 per patient, without other composite restorations) for an average of 20 months, who were planned for attachment removed were enrolled in the study. Patients were instructed to rinse with 50 mL of distilled water upon entry and the rinsing solution was collected (before removal). Then, the attachments were removed with low-speed tungsten carbide burs for adhesive residue removal, a thorough water rinsing was performed immediately after the grinding process to discard grinding particle residues, and subsequently, after a second water-rinsing the solution was collected for analysis (after removal). The rinsing solutions were analyzed for targeted (LC-MS/MS: Bis-GMA, DCDMA, UDMA, BPA) and untargeted (LC-HRMS: screening of leached species and their degradation products) compounds.
RESULTS
Targeted analysis revealed a significant reduction in BPA after attachment removal (4 times lower). Bis-GMA, DCDMA, UDMA were below the detection limit before removal but were all detectable after removal with Bis-GMA and UDMA at quantifiable levels. Untargeted analysis reviled the presence of mono-methacrylate transformation products of Bis-GMA (Bis-GMA-M1) and UDMA (UDMA-M1), UDMA without methacrylate moieties (UDMA-M2), and 4-(dimethylamino) benzoic acid (DMAB), the degradation product of the photo-initiator ethyl-4-(dimethylamino) benzoate (EDMAB), all after attachment removal. Several amino acids and endogenous metabolites were also found both before and after removal.
CONCLUSIONS
Elevated levels of BPA were traced instantaneously in patients treated with Invisalign™ and flowable resin composite attachments for the testing period. BPA was reduced after attachment removal, but residual monomers and resin degradation products were found after removal. Alternative resin formulations and attachment materials may be utilized to reduce eluents.
Additional Info
Salivary levels of eluents during Invisalign™ treatment with attachments: an in vivo investigation
Prog Orthod 2024 Jun 03;25(1)22, L Stocker, SK Zervou, SN Papageorgiou, S Karakousoglou, T Triantis, A Hiskia, G Eliades, T EliadesFrom MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
In the past decade, there has been an increased acceptance of clear aligner–based orthodontic therapy. The use of composite attachments has helped overcome some inherent limitations of clear aligners. The authors of this study attempted to investigate, both qualitatively and quantitatively, the elution of bisphenol A (BPA), resin monomers, and degradation monomer compounds from polyester urethane aligners as well as resin composite attachments.
The big question is why it is important to study the elution of these substances. The answer relies on the fact that there is an increasing body of evidence showing an association between BPA and negative health effects, ranging from precocious puberty to prostate cancer in male patients and an increased risk of mammary gland tumors in female patients. Additionally, the bioavailability of resin monomers has been linked to adverse oral tissue reactions.
The study comprised 7 female and 4 male participants (mean age, 24.2 years) who underwent clear aligner therapy for an average duration of 20.3 months and had an average of 16 attachments per patient. All attachments were fabricated using the same flowable composite resin and following the same curing protocol. At the time of enrollment, all patients underwent a planned attachment removal, most likely due to the completion of treatment. The authors used sophisticated techniques to detect the substances leaching from the plastic aligners and composite resins. As part of the study protocol, the authors collected oral rinse samples before and after attachment removal.
The authors reported that the levels of BPA were quite high in oral rinse samples collected before attachment removal; however, these levels were significantly reduced (four times) after attachment removal. This would imply that the cumulative levels of BPA in the oral milieu during clear aligner therapy for a duration of approximately 20 months must have been quite high and that the amounts found in this study must be an under representation
The levels of resin monomers — bisphenol A-glycidyl methacrylate and urethane dimethacrylate — were below the “limit of detection” in samples collected before attachment removal; however, they were all elevated to detectable levels in samples after attachment removal. The authors also reported that the levels of degradation monomer compounds were below the “limit of detection” in samples before attachment removal and elevated to detectable levels in samples after attachment removal.
This study clearly sheds light on the fact that these substances leaching from plastic aligners and composite resins are indeed present in the oral samples, warranting further investigation. This study also highlights the importance of finding suitable alternatives for resin formulations and attachment materials.