Objective: To evaluate the perception of esthetic orthodontic appliances by means of eye-tracking measurements and survey investigation. Materials and Methods: En face and close-up images with different orthodontic appliances (aligner appliance [a], aligner appliance and attachments [b], lingual appliance [c], ceramic brackets [d], no appliance [e; control]) were shown to 140 participants. Eye movement and gaze direction was recorded by eye-tracking system. For different anatomical areas and areas of the appliances, time to first fixation and total fixation time were recorded. The questions included in a visual analog scale regarding individual sentiency were answered by the participants. Results: For all groups, the anatomical landmarks were inspected in the following order: (1) eyes, (2) mouth, (3) nose, (4) hair, and (5) ears. Only in group d, first fixation was on the mouth region (1.10 ± 1.05 seconds). All appliances except the lingual appliance (1.87 ± 1.31 seconds) resulted in a longer fixation on the mouth area (a, 2.97 ± 1.32 seconds; b, 3.35 ± 1.38 seconds; d, 3.29 ± 1.36 seconds). For close-up pictures, the fastest (0.58 seconds) and longest (3.14 seconds) fixation was found for group d, followed by group b (1.02 seconds/2.3 seconds), group a (2.57 seconds/0.83 seconds), and group c (3.28 seconds/0.05 seconds). Visual analog scale scoring of questions on visibility were consistent with eye-tracking measurements. With increasing visibility, the feeling of esthetic impairment was considered higher. Conclusions: Lingual orthodontic appliances do not change how the face is perceived. Other esthetic orthodontic appliances may change the pattern of facial inspection and are different in subjective perception.

The developmental stages of the first and second dentition, combined with abrasive wear of the dental hard tissue can be used for age determination in many mammal species and in humans. Concerning dental age determination, one has to distinguish between invasive techniques, which are mainly applied in dead individuals, and non-invasive methods suitable for living individuals. In contrast to in adults, where only few parameters are available for orientation, age determination in children and adolescents is in general fairly easy, and is facilitated by stereotypical biological growth patterns. In the present article, different methods for dental age determination are introduced, with a special focus on the fields of application, and on the limits of age determination. With increasing age, the number of valid and meaningful dental characteristics diminishes, and therefore the accuracy of dental age assessment decreases.