RELIABILITY OF PANORAMIC RADIOGRAPHS TO DETERMINE GONIAL AND FRANKFURT MANDIBULAR HORIZONTAL ANGLES IN DIFFERENT SKELETAL PATTERNS
Figure 1. Gonial and Frankfurt mandibular plane angles shown on lateral cephalogram
cephalogram. However, panoramic images have got the advantage of reduced superimposition of anatomical structures. Mattila et al. 2 reported that gonial angle can be determined from panoramic radiography with the same degree of accuracy as from lateral cephalogram; while, Fischer-Brandies et al. 3 stated that in determining the gonial angle, the lateral cephalometric radiograph should be preferred. The aim of the present study is to check the possible application of panoramic radiograph to determine gonial and Frankfurt Mandibular plane angles.
2. Material and Methods
A total of 90 patients with the mean age range of 18.9 ± 5.9 years who attended our orthodontic clinic were retrospectively selected for the current study. The radiographic data of the patients included lateral cephalometric and panoramic radiographs taken with the same digital machines.( Cranex D, Sordex Dental Imaging, Germany). The samples were allocated into three equal groups of 30 subjects based on the measurement of their Go angle on lateral cephalogram: 1. Horizontal growers: Go < 120 ° 2. Normal growers: 120 ° ≤ Go < 130 ° 3. Vertical growers: 130 ° ≤ Go The criteria for the selection of the patients radiographs had to be high quality and sharpness, and all radiographs had to be taken by the same apparatus and same technician, with patients in the natural head position. In lateral cephalograms, the gonial angle was determined in the intersection of the ramal plane( Ar-Go) and mandibular plane( Go-Gn) using a protractor with 1 degree accuracy. FMA was also determined as the angle formed by the intersection of Frankfurt Horizontal plane( FH) and the Mandibular Plane( Go-Gn).( Fig. 1) In panoramic radiographs, the gonial angle was determined from two tangents which were drawn from the inferior border of the mandible and posterior borders of condyle and ramus of both sides. And FMA was determined as the intersection of the porion-orbitale line and mandibular plane( Go-Gn).( Fig. 2) One week after the first measurements, the tracings and measurements were repeated by the same investigator. Intraclass correlation coefficients( ICC) were used to measure the reliability of the results. ICC coefficients ranged from 0.813 to 0.92 indicating excellent reliability of the measurements.
3. Results
In this cross-sectional study, the agreement between Go and FMA measured in panoramic and lateral cephalometric radiographs was analyzed.
82 STOMA. EDUJ( 2016) 3( 1)