Relationships Between the Gonial Angle and Mandibular Ramus Morphology in Dentate Subjects: A Panoramic Radiophotometric Study
Analysis of dental panoramic radiographs (DPRs) is an indispensable diagnostic tool for dental implants both pre and post operation. Many studies on linear and angular morphometry of the mandibular body have been conducted, but those on the mandibular ramus have not yet been reported. The purpose of this study was to investigate the differences in the morphometric parameters of the mandibular ramus between high and low gonial angles (GAs) on DPRs as well as between genders, and to determine the relationships between GA and variables of the mandibular ramus morphometry. The DPRs of 156 dentate subjects (78 for each gender) with more than 15 teeth present, a mean age of 49.54 years, and a mean number of teeth of 26.20 were examined. The films were divided into the following 2 groups of GA: less than 120° (low gonial angle, LGA) and more than 125° (high gonial angle, HGA) in both the right and left sides. The parameters for Ar′-Go, MaF-Go, RW, and RD in the LGA group were significantly larger than those in the HGA group in both men and women, but that for the ramus angle (RA) was significantly smaller in the LGA group than in the HGA group. Significant gender differences in the 2 GA groups were recognized with respect to the Ar′-Go, MaF-Go, RW, and RD parameters. Significant negative low and moderate correlations were found between GA and the Ar′-Go, MaF-Go, RW, and RD variables, whereas significant positive low correlation was found between GA and the RA variable. Within the limits of this study, the analysis of the mandibular ramus morphometry on DPRs in terms of GA size and gender was found to be useful for devising a highly predictive and strategic plan for implant-supported oral rehabilitation.
Anatomic landmarks and reference lines, and parameters of linear and angular measurements on the dental panoramic radiographs.
Anatomic landmarks and reference lines: MP: Mandibular plane; RL: Ramus line; Go: Gonion; GA: Gonial angle; Ar′: Point where the RL contacts with the posterior margin of mandibular condyle; Co: Condylion; Co′: Point where the perpendicular line to RL passes through Co; MaF: Point where the perpendicular line to RL passes through the middle of the inferior border of the mandibular foramen; MN: Point where the perpendicular line to RL contacts with the deepest point of the mandibular notch. Linear and angular measurements: Ar′-Go: Line distance from Ar′ to Go; MaF-Go: Line distance from MaF to Go; MN-MaF: Line distance from MN to MaF; CH: Line distance from Co′ to Ar′; RW: Ramus width (distance between anterior and posterior margins of the ramus on the perpendicular line to RL through the point MaF); RCW: Ramus cortical width (width of the cortex at the posterior margin on the line RW); RI: Ramus index (width of the cortex at the deepest point of the ramus notch); RD: Ramus depth (distance of the perpendicular line from the deepest point of the ramus notch to RL); RA: Ramus angle (angle at the posterior ramus notch); PRI: RCW/p (p: posterior distance from MaF to posterior margin on the line of RW)
Classification of the 3 categories of the ramus cortical index (RCI) on the dental panoramic radiographs. RCI 1: Endosteal margin of the cortex (EMC) appears to be clear, even, and sharp on single or both sides. RCI 2: EMC is obscure and uneven, or shows to form semilunar defects or layers of cortical residues (1 to 3) on single or both sides. RCI 3: EMC is discontinuous, unclear, or porous in the cortex and has heavy cortical residues (>3) on single or both sides.
Scattergram showing the linear relationship between the gonial angle size and the variables for the ramus height and width. R indicates correlation coefficients; N, number of the right and left sides of subjects.
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