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Objective To evaluate the potential influence of muscular capacity and facial morphology on facial expressions in children. Materials and methods A cross‐sectional study was carried out on 40 healthy children (ages 9–13), without previous orthodontic treatment. Masseter muscle thickness and anthropometric facial proportions were measured using ultrasound and digital calipers respectively. A three‐dimensional infrared face‐tracking system was used to register facial expressions. The maximal amplitude of smile and lip pucker (representing maximal lateral and medial commissure movement) were used for analysis. Stepwise regression was used to investigate whether muscle thickness or anthropometric facial proportions were associated with the quantity of commissure movement. Results When performing maximal smile, children with thicker masseter muscles were found to have more limited displacement of the commissures (R = 0.39; p = 0.036). When performing lip pucker, children with thicker masseter muscles were found to have greater commissure movement (R = 0.40; p = 0.030). No significant associations were found between anthropometric facial proportions and facial expressions. Conclusion Masseter muscle thickness seems to be associated with facial expressions in children. Those with thicker muscles show more limited commissure movement when smiling, but greater movement with lip pucker. This indicates that masticatory muscles may serve as a surrogate for mimic muscle activity. Facial morphology of the subjects does not seem to be associated with facial expression.

Mesiodens is the most common type of supernumerary tooth, located between the maxillary central incisors. A young man was referred by his orthodontist for management of a supernumerary tooth located in quadrant I, superposed to the bottom of the right maxillary sinus, distally orientated with the crown in contact with the apex of the palatal root of the maxillary first molar. The tooth was found on a panoramic radiography before starting his orthodontic treatment. To remove it and in order to study, its relationship to the anatomical structures a cone-beam CT examination was performed. This revealed the presence of a mesiodens located on the right paramedian maxillary area. Pericoronal tissue submitted for histopathological examination showed an uninflamed dental follicle. Healing was uneventful. This case shows that mesiodens outside the arch, located in the posterior palate, may be not discovered in a panoramic radiograph.