A case like Gilbert’s would benefit from dental expansion. However, when you prescribe dental expansion you have to think about how the teeth are expanding. With Invisalign treatment, the default movement when prescribing posterior expansion is buccal tipping. In a case like Gilbert’s, tipping works out well because his teeth begin palatally in- clined. The palatally inclined teeth are being uprighted — and that is perfectly fine.
In Gilbert’s case we don’t need any posterior buccal root torque (BRT) because the teeth started out palatally inclined, but you have to watch for that condition. In other patients with upright posterior teeth with expansion using Invisalign, there can be a tendency to tip the teeth out toward the buccal, relatively extruding the palatal cusps and intruding the buccal cusps. Most of the time that is not something that we want. In cases where you see unwanted tipping of the posterior teeth, ask your technician to give you posterior buccal root torque to maintain bodily movement.
Similarly, a patient like Emma (from chapter 6) who presents with constriction of the arches and palatal inclination may also benefit from transverse expansion to help resolve her crowding (images 7-3 and 7-4). She sets up well for expansion in the transverse dimension to gain arch length to resolve her crowding, without the need to program any poste- rior buccal root torque.
These movements are predictable tipping movements with Invisalign clear aligners. Tipping movements are predictable and typically don’t require any ClinCheck modifications.
Posterior cross bite — what about patients who require posterior expansion to resolve a posterior cross bite? With patients who present with posterior cross bite, it is critically important to consider wheth- er the patient presents with a dental cross bite or skeletal cross bite. For example, the patient in image 7-5, and his ClinCheck in image 7-6 presented with a dental cross bite on the upper-right side. His arch is constricted so we can set him up for dental expansion using Invisalign.