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Abstract
Ever since its inception in 1931 1 , Lateral Cephalometric
radiographs have been widely used in orthodontics and in orthognathic
surgery as an important descriptive, analytic and diagnostic technique.
It developed from the anthropologic fields of craniometry and
cephalometry, and inherited from them the use of the same landmarks
and planes that had previously been applied to dry skulls. Lateral
cephalometric radiography also inherited the same fundamental
problem of defining a reproducible reference plane for orientation
during recording procedures and analysis. Traditionally, intracranial
reference lines have been used for clinical cephalometric analysis of
malocclusion cases. However, validity of intracranial reference systems
have been questioned on several occasions because of their variability
to the horizontal plane, related to the head in natural head position
(NHP)2-7.2,3,4,5,6,7.
Natural head position (NHP) has been described as a standardized
and reproducible position of the head in an upright posture with the
eyes focused on a point in a distance at eye level8. There are various
head positions that have been advocated in the literature including the
Natural Head Posture, defined as the muscle-balanced posture arrived
at after repeated extensions and flexions, in continually decreasing
magnitudes, until a relaxed posture is achieved9, and the Natural Head
Orientation, or Estimated Natural Head Position, the position that the
examiner estimates the head would assume, if the patient were standingin the natural head position10.The concept of natural head position is not new. Leonardo da Vinci
(1452- 1519) and Albrecht Durer (1471- 1528) used scaffoldings of
horizontal and vertical lines on drawings of models positioned in
“natural pose” in order to permit more accurate artistic and scientific
replication of the human head. Artists, anatomists, and anthropologists
have used natural head position to study man’s face throughout the
ages. Moreover, NHP has been used routinely for clinical examination
in medicine and dentistry by plastic and maxillofacial surgeons, as well
as by orthodontists.
When observed in natural head position, the angulation of
conventional intracranial reference planes to the true vertical varies
widely. Different clinical cephalometric analyses will therefore provide
differing interpretations of morphology, depending upon the particular
intracranial plane adopted as the ”reference”. Conventional intracranial
reference planes also vary over time, within individuals, and relative to
each other. Therefore, conventional cephalometric interpretation may
change depending upon the age at which the analysis is completed11.
Many studies12-14 12 ,13 , 14 have found natural head position to be
remarkably reproducible in both children and adults, males andfemales, Caucasian and non-Caucasian subjects15-17.15,16,17.
Natural head posture has also been shown to be correlated to
craniofacial morphology18,19, future growth trends20 and to respiratory
needs21-24.21,22,23,24
Several researchers have argued that natural head position is the
logical orientation position and reference for the evaluation of
craniofacial morphology where the individual is presented as he/sheappear in life. Diagnostic profile assessment is considered inappropriate
if the head is not in NHP. Likewise, before treatment and after
treatment photographs are often criticized if the head is not in the same
position, because this is thought to introduce bias in the assessment of
treatment changes25. Hence, lateral cephalograms recorded routinely in
natural head position would be more meaningful clinically.
Despite the presence of this huge number of studies, none have
developed norms for a cephalometric analysis based on natural head
position in the Egyptian population. from here came the idea of our
study to help spread the use of natural head position more routinely in
diagnosing orthodontic and orthognathic Egyptian patients.