Introduction
This model enables a forecast of favorable/unfavorable craniofacial growth in patients with Class III malocclusion. The predictive model is the result of the cooperation of a team of expert orthodontists
and data scientists (1). It has been elaborated, implemented, and validated on a database of cephalometric values from 728 untreated Class III Caucasian patients (6 to 14 years of age), and from 91 untreated Class III Caucasian
patients followed longitudinally during the growth process.
Inclusion criteria
For each subject, the inclusion criteria to enter in the diagnosis of Class III malocclusion must be as follows:
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No orthopedic/orthodontic treatment prior to cephalogram
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No congenitally missing or extracted teeth
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No craniofacial syndromes
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Anterior crossbite, accentuated mesial step relationships of the primary second molars, permanent first molar relationship of at least one-half cusp Class III, a negative Wits appraisal (less than -2mm), and ANB angle less than 0
Cephalometric variables The 11 cephalometric variables to be detected concern the following values:
ANGULAR MEASUREMENTS (degrees):
- SNA : Sella-Nasion-point A, antero-posterior position of the maxilla to the anterior cranial plane
- SNB: Sella-Nasion-point B, antero-posterior position of the mandible to the anterior cranial plane
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NSAr: Nasion-Sella-Articulare, saddle angle
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ArGoMe: Articulare-Gonion-Menton, gonial angle
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PP-SN: Palatal Plane to Sella-Nasion, inclination of the palatal plane to the anterior cranial plane
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PP-MP: Palatal Plane to Mandibular Plane, inclination of the palatal plane to the mandibularplane
LINEAR MEASUREMENTS (mm, all linear measurements should be reported in life size, 0% enlargement):
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S-N: Sella-Nasion, length of the anterior cranial base antero-posterior length of the cranial base
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S-Ar: Sella-Articulare, height of the middle cranial base
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N-Me: Nasio-Menton, total anterior facial height
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Co-Go: Condylion-Gonion, mandibular ramus height
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Go-Gn: Gonion-Gnation, mandibular corpus length
Guide
The clinician has to enter the 11 cephalometric values of the patient in the model, together with the patient’s age. The prognostic evaluation of the craniofacial growth is reported as an outcome of 0= favorable
growth, (“good grower”), or 1= unfavorable growth, (“bad grower”).
The prognostic criterion of growth is based on the predicted evolution of sagittal skeletal imbalance of each subject, derived from the difference between patient’s
CoGn-CoA values compared with the standard CoGn-CoA values of a normal population, reported in the Atlas of cephalometric values of Bhatia and Leighton (2).
Subjects that exhibit during the growth process a spontaneous reduction
of the difference between the starting values and the standard values are defined good growers, and the opposite for bad growers. In the database, 31% of longitudinally followed subjects are good growers, i.e., they exhibited a
progressive reduction of the distance from the reference values, while 69% exhibited a worsening of the Class III maxillomandibular differential and were classified as bad growers.
References
(1) Auconi P et al. Understanding interactions among cephalometric variables during growth in untreated Class III subjects. Eur J Orth 39, 395-401, 2017
(2) Bhatia SN, Leighton BC A manual of facial
growth 1993, Oxford Univ Press, Oxford UK