Precise description of study methodology.
For each group, a sample of +- 15 patients with class 2 malocclusion aged between 9 and 15
years will be collected for this prospective study who presented for an initial orthodontic
consultation between October 2022 and july 20262 at ULB's Erasme Hospital. Each patient will
be treated with Invisalign MA or the Herbst appliance by residents of the orthodontic program
directed by P. Maria Orellana
Inclusion criteria included a Class II skeletal malocclusion with an ANB greater than 4°; (In
the case of a Class 2 Division 2 malocclusion, the retroclined upper incisors will be
proclined to obtain an overjet allowing mandibular advancement. If the patient has a
transverse deficit, palatal expansion will be performed before treatment with aligners and
during treatment in herbst cases.) Class II molar and canine relationship and CVM2/CVM3
cervical vertebral maturation.
Informed consent forms in the patient's native language will be submitted before the start of
each treatment.
Only a profile cephalometry will be taken in the patients considered for this study at the
time of the initial consultation.
This will avoid unnecessary radiographic exposure, and a panoramic view of each patient will
be extracted from a CBCT using the FDA-approved BlueskyBio program.
Aligners or Herbst appliance for orthodontic treatment will be fabricated on the basis of a
3D optical scan (Itero), after which patients will begin treatment.
Levelling of the Spee curve, derotation of (pre)molars and palatal incisors in the case of
class 2 division 2 malocclusion will be carried out before the mandibular advancement stage
if necessary in the Aligner group.
A full-face ultra-low dose CBCT scan will be performed on all included subjects before the
mandibular advancement stage according to a strict protocol by a certified physician. Active
mandibular advancement will be continued till a KLass I molar relationship is obtained and
will be followed by 2 months without mandibular advancement to allow the mandibular condyles
to take a central position in the condylar fossae. After this 2-month period, a second CBCT
scan will be performed (T2), with a minimal time interval of one year between the two CBCT
scans, using the same protocol.
CBCTs will be acquired using a Promax Mid 90 Kv with settings of 90 kV and 8.9 mAS, and tube
current modulation will be used to enable patient-specific dose reduction.
After the second CBCT, orthodontic treatment will be continued until completion, and
retention and regular post-treatment follow-up will be scheduled for each patient.
The superposition of CBCT (T1) and (T2) images on the anterior cranial base will be used to
determine exact mandibular lengthening, condylar displacement, mandibular rotation and chin
displacement using the following methodology described and developed by Hugo. De Clerck in
2009.