145 Three-Dimensional Bolton–Brush Growth Study Landmark Data: Ontogeny and Sexual Dimorphism of the Bolton Standards Cohort DAVID DEAN,PH.D. MARK G. HANS, M.S.D., D.D.S. FRED L. BOOKSTEIN,PH.D. KRISHNA SUBRAMANYAN, B.ENG., M.ENG., PH.D. Objective: The treatment of craniofacial reconstructive surgery patients may benefit from comparison to average referent three-dimensional landmark data. These data may be useful for diagnosis, treatment planning, prosthetic design, or outcomes assessment. With regard to subadult patients, we hypothesize that the pattern of ontogenetic shape change of same sex, same ethnicity, referent populations will show gross uniformity. We present a preliminary shape analysis of 50 three-dimensional landmarks derived from 317 Bolton– Brush Growth Study biorthogonal image pairs. We determine which landmarks can be collected from scanned radiographs reliably by four operators for the precisely locatable points, ontogenetic trends in landmark configuration shape change, and patterns of sexual dimorphism. Participants: Participants were Bolton standards individuals (16 male and 16 female) who contributed biplane cephalograms seven or more times with an- nual or greater spacing between ages 3 and 18 years. Design: After removing outliers, we searched for ontogenetic heterogeneity, including sexual dimorphism and within sex-specific Procrustes coordinate shape spaces. Results: A cut-off of 4.3-mm interoperator error left 32 landmarks in our anal- ysis. Three different approaches (principal component analysis, age-trend analysis, and principal components of age residuals) all found no patterns of individual variation around sex-specific average trends of shape change. Male shape change peaks at age 15, a correlate of the growth spurt. Conclusions: Simultaneous frontal and lateral anatomic landmark identifi- cation improves three-dimensional localization reliability. Three-dimensional craniodental shape change from ages 8 to 18 within the Bolton standards pre- sents little heterogeneity. Considerations of ethnicity aside, these may be ini- tial grounds for use of these data as a normative referent. KEY WORDS: cephalometry, craniofacial, cranium, dentition, morphometrics, normative, Procrustes, referent, relative warp, shape, skull, X-ray The goal of several craniofacial growth studies undertaken since the 1920s has been to describe patterns of normative Dr. Dean is an Assistant Professor in the Department of Neurological Surgery, School of Medicine, Case Western Reserve University, and University Hospitals of Cleveland, Cleveland, Ohio. Dr. Hans is Associate Professor and Chair of the De- partment of Orthodontics, Case Western Reserve University. Dr. Bookstein is a Dis- tinguished Scientist at the Institute of Gerontology, University of Michigan, Ann Arbor, Michigan. Mr. Subramanyan was a Ph.D. candidate in the Department of Biomedical Engineering, Case Western Reserve University while this work was being done. This project was partially supported by a Whitaker Foundation Research Grant to D.D., NIH grants GM37251 and DA09009 to F.L.B., and an American Association of Orthodontists Foundation research grant to M.H. Partial support was also provided by a grant from Leibinger-Howmedica (Pfizer) to D.D. The results of this paper were presented at the Whitaker Foundation Bio- medical Engineering Conference, August 1998, La Jolla, California. Submitted June 1998; accepted June 1999. Reprint requests: David Dean, Department of Neurological Surgery, Bolton DO3080, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-4905. E-mail dxd35@po.cwru.edu. variation. Cephalometric comparisons of patient craniodental measurements to a well-characterized referent has been found helpful for diagnosis by many craniofacial practitioners (Gray- son, 1989). However, there has been criticism of various tra- ditional cephalometric methods, such as linear distance or an- gle comparisons of patient to normative (Moyers and Book- stein, 1979), the selection criteria for normative samples (Hunter et al., 1993; Kowalski, 1993; Dean et al., 1998a), or the clinical need for cephalometric diagnosis (Atchison et al., 1991). Diagnosis, however, is only the first of four stages of patient care where referent data, especially in the form of land- mark coordinates, may be useful. The other three stages are treatment planning, stereotactic treatment, and outcomes as- sessment. Two dimensional, longitudinal, and serial average data, such as the published Bolton standards (Broadbent et al., 1975), are commonly compared to subadults and adults undergoing max-