Effectiveness and Predictability of Skeletally Anchored Maxillary Protraction in Adolescent Class III Patients: A Retrospective Study Using CBCT

Objectives: This study’s primary aims are to evaluate the treatment effects of skeletally anchored maxillary protraction (SAMP) treatment compared to conventional treatment. This study’s secondary aim is to determine SAMP treatment effects on a patient’s airway minimal axial area compared to conventional treatment. Methods: CBCTs were collected from three time points: Initial (before treatment), Progress (after expansion, only for SAMP group), and Final (after treatment). This retrospective study consisted of twenty-three patients who received SAMP treatment (n=23, avg age at initial = 13.5) and twenty-five patients who received conventional treatment (n=25, avg age at initial = 14.5). Cervical vertebral maturation (CVM) and spheno-occipital synchondrosis maturation (SOS) were evaluated. Airway minimal axial area was measured from three dimensional (3D) CBCTs. To evaluate treatment changes, CBCTs were 3D superimposed on the anterior cranial base. Stepwise multiple linear regression was used to evaluate the variables that affect, as well as the magnitude of their effect on, the anterior movement of the maxilla. Results: SAMP group showed significantly more A point movement of 1.98mm compared to 0.65mm seen with conventional treatment (P<0.01). When the patient is 1 year older, A point forward movement decreases by approximately 0.3mm. Pogonion downward movement and condylion to pogonion length were also significantly larger for the SAMP group. The greatest contributing factor for class III correction in the SAMP group was increase in mandibular plane angle (R2 = 0.6; P = 0.0131). SAMP experienced more maxillary molar downward movement and more soft tissue A point forward movement compared to conventional treatment. There is no difference in airway minimal axial area between SAMP and Conventional Groups. Conclusions: SAMP had significantly more ANS and A point forward movement. The most significant dental change was more downward movement of the maxillary molar in the SAMP group. The most significant soft tissue change was from soft tissue A point forward movement in the SAMP group. Age can be used as a predictive factor for magnitude of maxillary protraction in the SAMP group. A majority of the change in ANB correction was due to change in FMA. There is no difference in airway minimal axial area between SAMP and Conventional Groups.