NATURAL HEAD POSITION AND NATURAL HEAD ORIENTATION - BASIC CONSIDERATIONS IN CEPHALOMETRIC ANALYSIS AND RESEARCH

Natural head position (NHP) provides the key for meaningful cephalomet ric analysis because an extracranial reference line is used instead of intracranial reference lines, known to be subject to considerable bio logical variation in their inclination. Although the principle of natu ral head position is being recognized in the orthodontic literature, i ts registration may contain an element of unavoidable error that requi res correction. A new concept of natural head orientation (NHO) has be en introduced to maximize the contribution of NHP to cephalometrics. I t is defined as the head orientation of the subject perceived by the c linician, based on general experience, as the natural head position in a standing, relaxed body and head posture, when the subject is lookin g at a distant point at eye level. The present study was designed to d etermine the accuracy and validity of NHO, using lateral profile photo graphs cut in a circular shape, obtained from 27 orthodontic patients, 10-14 years old. Findings among four investigators showed a high corr elation (r= 0.82-0.96), in orientating these profile photographs in es timated natural head position (NHP). Moreover, investigators showed go od correlation (r= 0.57-0.84) in head orientation after a 3-week inter val. Mean differences for the same period varied between 0.1 and 2.9 d egrees. The validity of NHO was supported also by a panel investigatio n. Clinicians as well as auxiliary personnel can be trained to make a critical judgement of the recorded natural head position and correct h ead orientation, whenever indicated, to enhance the reliability of cep halometric analysis in clinical practice and research.