Subjects classified as bruxists based on the diagnostic criteria for sleep bruxism described by the American Academy of Sleeping Medicine, i.e. if they have at least one of the following two points:

1. The subject reports or is aware of noises of grinding or clamping during sleep.

2. One or more of the following signs are present:

   • Abnormal wear of teeth;
   • Discomfort, fatigue or pain in the muscles of the face;
   • Hypertrophy of muscles during voluntary clamping;
   • Any abnormalities in the mandibular muscle activity cannot be expressed by other sleep disorders, medical, neurological, drug use or substance abuse;
   • Bruxoff ® cut-off more than 4.

Subjects with good health, with no evidence of bruxism symptoms or signs. Bruxoff ® cut-off equal or less than 4.

Bruxoff ® is a holter that measures the masseter muscle contraction and heart rate.

The primary outcome of the study is the change in potential recorded by Bruxoff®, defined as the variation in nocturnal masseter contraction activity just in bruxism patients treated with aligners.The study aims to evaluate and compare diagnostic records measured with the Bruxoff® at three time points. Each time, the Bruxoff® is used two nights in a row. The purpose of the first night's data collection is to help the patient learn how to apply and use the device to its fullest potential; only the data collected on the second night will be used in the study to determine whether or not the patient has bruxism.

• The Bruxoff® device is initially administered for two consecutive nights before the start of aligner therapy (T0).
• 2 months after starting clear aligner therapy (T1), Bruxoff® is given for two consecutive nights.
• The last 2 records are registered 6 months after the beginning of the treatment with clear aligners (T2).

The secondary outcome consists in the mutation of signs (i.e. tooth wear) and symptoms (i.e. massetere muscles pain) of bruxism.

In order to evaluate how occlusal relationships have changed in bruxism patients treated with aligners at the three study times (T0, T1, T2), we compare their clinical condition with non-bruxism patients.

Furthermore, it's possible to measure the following characteristics during the three study times (T0, T1, and T2), both in the individual group and between patients with and without bruxism, using the Visual Analogue Scale (range 0-10):

• the mutation of the chewing muscles' pain and of the related migraines;
• the variation of the functional limitation during routine mandibular movements related to treatment with clear aligners.