The investigator proposes a multi-centre study to investigate tipping of teeth, bringing into consideration the height of the osteotomy line and the height and placement of the transpalatal distractor as possible factors. If tipping occurs depending on these factors, the investigator could identify the situations that cannot be straightened by the orthodontist and provide another course of action for these specific patients.

Surgically Assisted Rapid Maxillary Expansion (SARME) is widely accepted for the treatment of maxillary hypoplasia. The differences between SARME with a tooth-borne or a bone-borne distractor have already been extensively investigated, bringing to light that a bone-borne distractor has less negative side effects. One of the major concerns with the tooth-borne distractor is the tipping of the anchor teeth, which is bypassed by the bone-borne distractor which applies its force directly on the bone. One study investigated the tipping of teeth with a bone-borne distractor in 10 patients, showing that there was a minor change in the tooth axis. The investigator proposes a multi-center study to investigate this tipping further, bringing into consideration the height of the osteotomy line and the height and placement of the transpalatal distractor as possible factors. If tipping occurs depending on these factors, the investigator could identify the situations that cannot be straightened by the orthodontist and provide another course of action for these specific patients.

Inclusion Criteria:

• Undergoing a surgically assisted rapid maxillary expansion with a bone borne transpalatal distractor.
• Cone beam CT pre op and 3 weeks post op is available

Exclusion Criteria:

• Complication of the process by e.g. surgical site infection
• Asymmetrical expansion of more than 3.0 mm measured at the central incisivae occurred