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References

What is the purpose of chewies when using Invisalign?. 2021. https://tinyurl.com/mvxbdhap (accessed July 2022)
Movemints. Are Invisalign Chewies actually effective?. 2020. https://tinyurl.com/4afk3saj (accessed July 2022)
Bowman SJ, Celenza F, Sparaga J Creative adjuncts for clear aligners, part 2: Intrusion, rotation, and extrusion. J Clin Orthod. 2015; 49:162-72
Tabrizi R, Karagah T, Aliabadi E, Hoseini SA. Does gum chewing increase the prevalence of temporomandibular disorders in individuals with gum chewing habits?. J Craniofac Surg. 2014; 25:1818-1821 https://doi.org/10.1097/SCS.0000000000000993
Tyneside Integrated Musculoskeletal Service. Temporomandibular disorders (TMD). 2021. https://tinyurl.com/2p9dfy76 (accessed July 2022)
Commisso MS, Martínez-Reina J, Mayo J. A study of the temporomandibular joint during bruxism. Int J Oral Sci. 2014; 6:116-123 https://doi.org/10.1038/ijos.2014.4
Dalmedo VH. Management of masseter hypertrophy and bruxism with Botulinum Toxin A. PMFA J. 2021; 8:(6)

Letters to the editor

From Volume 49, Issue 7, July 2022 | Page 603

Authors

Shoukat Ashiti

Senior House Officer, Department of Oral and Maxillofacial Surgery James Cook University Hospital

Articles by Shoukat Ashiti

Article

Invisalign Chewies and potential temporomandibular disorder

Chewies (Invisalign, Align Technology, Birmingham) are small soft plastic, silicone-like material, cylindrical in shape, not edible, and reusable devices. They are made of a material called styrene copolymer. They are used to remove the air bubbles between the Invisalign and teeth to make sure that the aligner is seating perfectly, and providing balanced forces on all teeth. Chewies are available in different colours and some of them have favourable scents.1,2 Many companies now sell similar items with different features, for example some are edible.

Patients are instructed to use them every time they take out the aligners, and before bedtime. Different manufacturers have different instructions. One website recommends using them for 5 minutes twice a day, while others recommend using them each time the aligner is put on.1,2 Several websites claim that these accessories can somehow speed up the treatment, by enhancing the fit of the aligner and removing air gaps, which results in moving teeth more effectively.1,2 Chewies are used to ‘overcome poor tracking or aligner lag’. All this might encourage patients to use these devices excessively and induce their misuse because patients may think that they will achieve aesthetic results sooner with more use of Chewies; however, there are no clinical studies or scientific evidence to support this practice.

Several websites mention that there are few or no side effects for the use of these Chewies. However, we report here the case of a patient who was seen at the consultation clinic of the oral and maxillofacial department at James Cook University Hospital. After history taking and examination, it was found that her complaint of myofascial pain and disk displacement with reduction began after she started using Chewies, with the patient reporting an improvement in symptoms after she stopped using them. We have also seen another patient who was also experiencing TMD, who after undergoing a full medical history and clinical examination, reported that the discomfort had started after using Chewies, but stopped after discontinuation. Could this consistant non-functional practice of chewing plastics during the day be a potential cause and trigger for temporomandibular disorder (TMD) and could there be an association between Chewies and TMD/myofascial pain?

The mechanism of chewing these soft plastics is similar to chewing gum. It has been reported that patients with Class II skeletal patterns were more prone to have TMD symptoms due to chewing gum.4 It has also been suggested that any constant and repetitive oral habits, such as clenching, bruxism, lip or pencil or nail-biting, or any activity that causes an imbalance of the masticatory system, could potentially contribute to TMD.5 Thus, if we consider the use of these Chewies is a para/non-functional activity, especially when they are used excessively, this could explain the complaints of our patients

Furthermore, TMD has been associated with the overload of masticatory muscles,5 which can produce shear stresses that can result in degenerative changes within the disk over time.6 Although Chewies are required to fit Invisalign, their excessive use could contribute to overload on muscles resulting in TMD. Equally important, oral parafunctional habits can be associated with acquired masseteric hypertrophy, which also can result in trismus, TMD and myofascial pain.7

Unfortunately, there are no studies or articles that address the benefits of using Chewies for Invisalign treatment. Also, there are no clinical trials to support the instructions on how to use them. Marketing strategies appear to encourage their overuse by suggesting that the aesthetics results will be achieved sooner by more use. Proper instructions and side effects should be explained to patients when these devices are given. Observational cohort studies, either retrospective or prospective, would be of benefit to find out whether patients have, or are developing, TMD/myofascial symptoms after using Chewies.