They are usually present near the premolars and above the location of the mylohyoid muscle’s attachment to the mandible. Mandibular tori are usually bilateral. For the most part they occur below the root apices and are not commonly found in alveolar bone.
A similar phenomenon occurs in the maxilla, known as palatal tori. These are typically located in a mid-palatal location near the posterior hard palate. Since they do not extend toward the teeth, they are usually of no consequence for clear aligner treatment.
Mandibular tori, palatal tori and exostosis have no clear cause, although some have speculated that these are reactive phenomenon in response to local stresses in situations such as heavy occlusion or clenching and bruxism.
As the clinician you should be on the alert for heavy occlusion and bruxism as these situations tend to impair tooth movement and produce excessive wear on the occlusal surface of the aligner.
These phenomena do not pose as a limit for orthodontic tooth movement.