Melbourne Dental School - Theses
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ItemA longitudinal cephalometric study of the polar growth phenomenon and craniofacial proportions( 1990)Throughout the orthodontic and anthropological literature, craniofacial growth, in the absence of criminal intervention, has been the subject of numerous longitudinal and cross-sectional investigations. Historically, the assessment of craniofacial growth using longitudinal cephalometric data was initiated by Broadbent (1931), who instigated the first major longitudinal growth study, the Bolton study. Since this development, some investigators have measured the craniofacial growth rates and increments (Brodie, 1941; Nanda, 1955; Bishara, Peterson and Bishara, 1984), while others have focused upon growth accelerations (Bambha and Van Natta 1963; Hunter, 1966; Bjork, 1967; Pileski, Woodside and James 1973; Houston, 1977; Lewis, Roche and Wagner, 1982; Ekstrom, 1982; Lewis et al., 1985; Kreig, 1987). The direction of growth of various craniofacial landmarks, relative to a basal reference area has also been the subject of research (Hellman, 1935; Downs 1948; Bergensen, 1961; Ricketts, 1971a, b). Similarly, the dimensions of various craniofacial proportions with growth have been investigated by different workers (Steiner, 1953; Ricketts, 1971a, b; 1981; Anderson and Popovich, 1983; Kerr and Hirst, 1987). All of the above studies have relied upon the use of various references, both anatomical and constructed, in the vicinity of the cranial base, to show entire facial changes with growth, presuming a stability of this reference area. The present study will be directed towards the method adopted by Ricketts (1971a, b) who has advocated the use of the Pterygoid Root Vertical (PtV) and Frankfort Horizontal (FH) reference planes, in conjunction with the reference point, CF (the point of intersection of these planes) to study the craniofacial pattern of the individual, presupposing a constancy in growth direction of various facial landmarks radiating outward from CF Point (the Polar Growth Phenomenon). Ricketts (1971a, b; 1981), in keeping with the concept of constancy with growth, has also suggested that various craniofacial proportions exhibit gnomonic growth, implying maintenance of angular dimensions with growth. To date, the Polar Growth Phenomenon and the concept of gnomonic growth of craniofacial proportions have not been investigated in the literature, yet these form part of the basis of growth forecasting methods of Ricketts as these relate to growth and treatment changes in the individual (Ricketts, 1972a; 1975a, b).