This study was performed to investigate the changes of head posture according to natural standing or sitting posture. Twenty seven healthy dental students without any signs and symptoms of temporomandibular disorders participated in this study. Cervical resting posture (CRP) of the head in sagittal plane was measured by Cervical-Range of-MotionR(CROM, USA) and lateral cephalograph was taken in natural posture. The items related to angle in cephalograph were the angles of cranial and cervical inclination to true vertical line(VER/NSL, VER/AML), the angles of cervical inclination to nasion-sella line(CVT/NSL, OPT/NSL), the angles of cervical inclination to horizontal line(CVT/HOR, OPT/HOR), the angle of cervical lordosis(CVT/OPT). The items related to line measurement were the distance from subocciput to C1(D1), Cl´to C2(D2), C2 to C3(D3), C3:fo C4(D4), the.upper(PNS to posterior pharyngeal wall) and the lower(tongue base to posterior pharyngeal´ wall) pharyngeal space, the distance from nasion to menton(Na -Me), and the radius of cervical curvature from the first cervical vertebra(Cl). to the. fifth cervical vertebra(C5).´ The data were analyzed with SAS/STAT program
The obtained results were as follows
I. Most items related to angular measurement showed significant difference between in standing and sitting posture. The angles of CRP, CVT/NSL, OPT/NSL, CVT/HOR, OPT/HOR, and CVT/OPT were high in sitting posture, but the angles of VER/NSL, VER/AML were low in sitting posture.
2. In vertebral distance, only the distance between C3 and C4 was differed by the posture, which decreased in sitting posture. In sitting posture, the distance from nasion to menton(Na-Me) was longer, but the radius was shorter than in standing posture.
3. Correlationship in angular measurement was almost same in both postures. Cervical resting posture(CRP) was correlated with VER/NTSL. VER/NSL was correlated with CRP, CVT/NSL, and OPT/NSL, VER/AML was correlated with CVT/IiOR, OPT/HOR, CVT/OPT, and the angle of cervical lordosis(CVT/OPT) was correlated with the radius.
4. CorTelationship in linear measurement was observed only in among D3, D4, and radius. And the Na-Me was not correlated with any other items.
From this results, The author concluded that the head posture in sitting was more backward extended than in standing.
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