## 2 Materials and Methods  
The Tel-Aviv University local institutional review board (IRB) approved the research. The retrospective study analyzed 50 consecutive cephalometric radiographs from a single private surgical practice (DMA) of skeletal Class-III deformity (prognathic) patients aged 20-35. Inclusion criteria were a pre-operation cephalometric radiograph performed after completion of orthodontic preparation (de-compensation) and 1-2 weeks prior to surgery; all of the patients underwent non-extraction orthodontic treatment. Exclusion criteria were syndromic patients, including cleft lip/palate.  
The cephalometric analysis serves as the gold standard in evaluating soft and hard tissue prior to orthodontic treatment, as well as for the evaluation and planning of orthognathic surgery using a list of standard-specific structures and measurements [16; 17]. Part of the points (landmarks) on the cephalometric radiograph includes [4]: A point (subnasal)--the most concave point of the maxilla; B point (supramental)--the most concave point on mandibular symphysis; N point (nasion)--the most anterior point on frontonasal suture; Or (orbitalae)--the most inferior point on the margin of orbit; Po (portion)--the most superior point of outline of external auditory meatus; anterior nasal spine (ANS)--the anterior point on maxillary bone; posterior nasal spine (PNS)--posterior limit of bony palate or maxilla; condylion (Co)--the most posterior/superior point on the condyle of mandible; gnathon (Gn)--point located perpendicular on mandibular symphysis; gonion (Go)--the most posterior inferior point on the angle of the mandible.  
Based on the anatomical landmarks, there are a few planes addressed on the radiograph: Frankfort horizontal plane (FH: Or-Fo)--represents the habitual postural position of the head; the palatal plane (PP: ANS-PNS)--represents the plane of the maxilla; mandibular plane (MP: Go-Gn)--represents the lower border of the mandible; U1--upper incisor tooth plane, from the incisal edge to the root apex of the upper incisor tooth; L1--lower incisor tooth plane, from the incisal edge to the root apex of the lower incisor tooth.  
Figure 1 shows the measurements performed on the cephalometric radiograph. The following lines were drawn and measured: Frankfort horizontal plane (FH), inferior mandibular plane (MP), palatal plane (PP), the upper incisal longitudinal axis (U1), lower incisor longitudinal axis (L1), overjet (OJ), mandibular length (CO-A), and maxillary length (CO-Gn). Measurements included the upper incisal to the Frankfort horizontal plane angle (U1 to FH), the upper incisal to palatal plane angle (U1 to PP), the lower incisal to the mandibular plane angle (L1 to MP), the maxilla--mandibular difference (subtraction of maxillary length from the mandibular length in millimeters, Diff).  
The Cephninja(r) Pro Version 5.02 (WA, UNITED STATES) application performed all angles and plane length measurements by calibrating the application ruler to the cephalometric radiograph and appointing the anatomical landmarks accordingly. The same examiner performed two independent measurements at two different times to check the measurements consistency.  
The statistical analysis was performed using SPSS software version 25.0 (IBM, Armonk, NY, USA). Descriptive statistics were performed, followed by the Pearson correlation coefficient test in order to check for possible correlation between the maxilla-mandibular difference and the U1 to FH angle, U1 to PP angle, L1 to MP angle, and the OJ.