Mandibular remodeling measured on cephalograms. 1. Osseous changes relative to superimposition on metallic implants Sheldon Baumrind, DDS, MS," Yocheved Ben-Bassat, DMD, b Edward L. Korn, PhD, c Luis Alberto Bravo, DDS, MS, PhD, a and Sean Curry, MS, PhD" San Francisco and Berkeley, Calif., Bethesda, Md., Jerusalem, Israel, and Murcia, Spain We report the results of a study aimed at quantifying remodeling of mandibular surfaces in a sample of growing children who represent those usually treated by orthodontists in the mixed and early adult dentition. The sample, 31 patients with metallic implants of the Bj5rk-type, was monitored at annual intervals between 81/2 and 151/2years of age. (Maxillary remodeling changes for the sample have been reported earlier.) The present article reports findings concerning changes at condyle, gonion, menton, pogonion, and point B as identified on lateral cephalograms. Data are reported in the Frankfort plane frame of reference with the cephalograms from different time points superimposed on the metallic implants. Mean displacement at condyle was larger than that at any other landmark and was similar in magnitude and direction to the observations of BjOrk when the difference in orientation of the vertical axis in the two studies is taken into account. The mean displacement of gonion was in an upward and backward direction at an angle of approximately 45~ to the Frankfort plane. Mean displacements at menton and pogonion were in a downward and backward direction but were very small. Mean displacement at point B was somewhat greater than that of menton and 9onion, oriented in an upward and backward direction. Individual variation for most of the parameters measured was sufficiently large to warrant the inference that caution should be used when mean values are applied to the analysis of individual cases. (AM J ORTHOODENTOFAC ORTHOP 1992;102:134-42.) This article presents quantitative data on di- mensional changes at condyle, gonion, and mandibular symphysis in a sample of growing children with me- tallic implants. Its purpose is to provide previously un- available information on the normal variability of such changes in a group of subjects typical of those com- monly seen for orthodontic treatment in the mixed or. early adult dentition. The fact that our currently available standards for craniofacial growth through time are based on such limited samples and data is evidence of how difficult it is to make accurate measurements of growing chil- dren. If the jaws merely expanded uniformly in all From the Craniofacial Research Instrumentation Laboratory, Department of Grov,'th and D~'elopment, School of Dentistry, University of California, San Francisco. This study was supported by NItI-NIDR grants nos. DE03598 and DE07332. *Professor of Grov,'th and Development/Radiology/Orthopedic Surgery, Uni- versity of California, San Francisco. bLecturer, Department of Orthodontics, ttebrew University Hadassah School of Dental Medicine, Jerusalem, Israel. "Mathematical Statistician, Biometric Research Branch. National Cancer In- stitute NIH, Bethesda, Md. '=Professor of Orthodontics, School of Stomatology, Faculty of Medicine, Uni- versity of Murcia, Spain. dPhotogrammettic Scientist, Trimble Navigation Ltd., Sunni'ale, Calif. 811/27744 directions during growth (as was once thought), the measurement of osseous changes on cephalograms and other standardized x-ray images would be relatively easy. However, the situation is more complex. It has long since been demonstrated that the changes in jaw size and shape that take place during development are the result of differential apposition of bone on some surfaces and resorption on other surfaces rather than the consequence of simple enlargement with respect to one or more fixed "growth centers." The absence of truly stable natural reference mark- ers within the jaws complicates the task of investigators who wish to quantify growth changes or to measure the effects of therapeutic intervention in growing children. For this reason, biologists have sought for many years to incorporate extrinsic markers within the growing jaws. ~3 Thus far the most successful solution has been the metallic implant method developed by Bjrrk and coworkers. 47 Indeed, it would be difficult to overstate BjSrk's contribution to our modem understanding of craniofacial development. Unfortunately for orthodon- tic and craniofacial research, however, the number of treated and untreated subjects with metallic implants is small, making it particularly important that the available records be studied with great care. One useful research 134