Student Theses, Dissertations and Capstones

Document Type

Thesis - NSU Access Only

Degree Name

Master of Science (M.S.) in Dentistry

Copyright Statement

All rights reserved. This publication is intended for use solely by faculty, students, and staff of Nova Southeastern University. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, now known or later developed, including but not limited to photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author or the publisher.

Department

College of Dental Medicine

First Advisor

Xiaozhe Han

Date of original Performance / Presentation

January 2026

Publication Date / Copyright Date

1-1-2026

Abstract

Clear aligners have become a popular treatment modality in Orthodontics and involve wearing plastic aligners to facilitate tooth movement. Several patients have reported discomfort indicative of an allergic reaction with the use of these aligners and the resolution of these issues with discontinued use. Objective: The objective of this study was to determine whether Invisalign® SmartTrackTM aligner material is cytotoxic to the THP-1 monocyte cell line and to observe any changes in the expression patterns of inflammatory cytokines produced by these monocytes upon exposure to the aligner elute. Methods: This study evaluates the effect of the Invisalign® aligner elute on THP-1 monocytes. This cell type was chosen for these experiments because they are robust immune cells that are known to produce numerous inflammatory cytokines during an innate immune response and play an important role in hypersensitivity reactions. 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay was performed to determine cellular cytotoxicity over a time period (24, 48, and 72 hours) at different concentrations of artificial saliva (negative control), methylene diphenyl diisocyanate (positive control), 1-week and 4-week aligner elutes. Quantitative Polymerase Chain Reaction (qPCR) and Enzyme-Linked Immunosorbent Assay (ELISA) were done to evaluate changes at 24 and 72 hours in mRNA and protein expression levels, respectively. Results: The MTT assay results show that the aligner elute decreases the viability of THP-1 cells; the 4-week elute expressed a decrease in proliferation of the cells over time, with the cells having the least viability at 72 hours, while the 1-week elute showed the cells had decreased viability at 48 hours, but increased viability at 72 hours. The qPCR results depicted TNF-α, IL-8, and IL-10 having reduced mRNA expression levels at 24 hours in the 4-week elute group. The ELISA results demonstrated that TNF-α, a prominent pro-inflammatory cytokine, is upregulated in THP-1 cells after exposure to the aligner elute, with the 1-week elute being upregulated at 24 hours and the 4-week elute being increased at 72 hours. Conclusions: The outcome of this study confirms that the Invisalign® aligner elute is cytotoxic to THP-1 cells and that the elute with a longer incubation time (i.e., 4-week elute) appeared to be more toxic than the elute with a shorter incubation time (i.e., 1-week elute). TNF-α, IL-8, and IL-10 displayed reduced mRNA expression levels in the 4-week elute group at 24 hours, which can mean that the elute is too toxic to the cells, resulting in not enough cells being left to produce mRNA. It is also important to note that mRNA expression is not always correlated to protein expression, especially when looking at a time range within hours. This study showed that TNF-α, a robust pro-inflammatory cytokine, was upregulated at the protein level in THP-1 cells upon exposure to the aligner elute. Overall, this study suggested that an imbalanced monocyte inflammatory response is elicited by aligner elute, which could be potentially associated with the hypersensitivity reactions observed clinically.

Disciplines

Dentistry

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