## 2 Materials and Methods
### Definition of the Chosen Protocol  
The exercise protocol required each participant to perform one isotonic exercise, two isometric exercises, and resting position during the study. Each exercise was to be performed for 5 min daily, totaling 15 min per day for three months. The exercises are illustrated and described in detail in Table 1 (videos are available in the Supplementary Materials). The third exercise (Exercise C in Table 1) involved using two occlusal thicknesses, which were placed into the mouth at the first molars, one on the right and one on the left. In the absence of these molars, participants were instructed to place the shims on the last available tooth. The shims were made from Anycubic Colored UV Resin using a Prusa mk3s+ 3D printer (Prusa Research a.s., Prague, Czech Republic) and were available in three sizes: 3 mm, 5 mm, and 7 mm. The thickness chosen depended on the participant's facial biotype \begin{table}
\begin{tabular}{p{14.2 pt} p{142.3 pt} p{142.3 pt}} \hline \hline
**Figure** & **Explanation of the Exercise** & **Objectives of the Exercise** \\ \hline A—CHEEK LIFT EXERCISE & & \\ - With your mouth open, bring your upper lip down and inward into your mouth, covering your upper teeth, until you feel the muscle stretch. Move your cheeks upward, lifting the corners of your mouth until your cheekbones protrude. Place your fingers on your cheekbones to feel the upward movement of the muscle. After a few seconds, relax the cheek muscle, keeping the incisors covered by the upper lip. Contract the cheek muscle again 20 times, each contraction lasting a few seconds. Repeat 5 times. & Activation of zygomatic major and minor and stretching of orbicularoris muscles. \\ \hline B—INNER CHEEK EXERCISE & & \\ - Insert the index fingers of both the right and left hands fully into your mouth and place them against the inner cheeks. Slightly move the index fingers outward. Contract the cheek muscles inward, applying a light and continuous resistance against the index fingers. Hold this position for 45 s, then relax for 15 s. Repeat 5 times. & Activation of orbicularisoris muscles and masseter muscles. \\ \hline C—SEPARATED DETAL ARCHES EXERCISE & & \\ - Insert the occlusal spacers between the dental arches, on both the right and left sides. The teeth should not press on the occlusal spacers; there should always be a space, even when swallowing. Close your lips as if giving a kiss. Place the tip of your tongue on the palate above the upper incisors. Separate the dental arches at the back ( molars) without straining the muscles. Perform the exercise progressively, gradually increasing the duration until reaching 5 min per day & Activation of buccinator muscle, masseter muscle, and orbicularis muscles. \\ \hline D—RESTING POSITION & & \\ - Close your lips without effort. Place the tip of your tongue on the palate above the upper incisors. Keep the posterior dental arches slightly separated. Maintain this position as long as possible throughout the day. & Relaxing of zygomatic major and minor, or orbicularis muscles. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Description of the exercises against facial aging. and the free space between the dental arches, with increasing thickness corresponding to increased exercise difficulty. Specifically, participants with a brachycephalic biotype were assigned 3 mm thicknesses, those with a normal biotype 5 mm, and dolichoephalic participants 7 mm. Participants were informed that they might find it challenging to perform all the exercises as required in the initial days. Common side effects included muscle pain during or after exercise and tremors. In case of difficulty, participants were advised to shorten the exercise time. The first session (T0) involved collecting anamnestic data and an analysis of the morphological characteristics of the participants' faces. Body weight was also recorded to ensure that any facial changes observed at the end of three months were not due to fat redistribution.