Which treatment aim can be achieved using either a functional or fixed orthodontic appliance, but not by a removable appliance?

The treatment aim that can be achieved using either a functional or fixed orthodontic appliance, but not by a removable appliance, is the correction of jaw relationship.

Functional orthodontic appliances are specifically designed to modify the position of the jaw and to encourage growth in favorable directions. They can actively change the relationship between the upper and lower jaws, which is essential for correcting skeletal discrepancies. Similarly, fixed appliances, such as braces, can also adjust the relationship of the jaws through the application of continuous pressure over time.

Removable appliances, while effective for certain types of tooth movement and minor adjustments, do not provide the same degree of control or force needed to modify the skeletal relationships of the jaws. They are primarily limited to dental movements rather than significant changes in the jaw alignment itself.

The other treatment aims focus more on the positioning of the teeth rather than the relationship between the jaws, making them more achievable with removable appliances.