T. Morneburg et Pa. Proschel, DIFFERENCES BETWEEN TRACES OF ADJACENT CONDYLAR POINTS AND THEIR IMPACT ON CLINICAL-EVALUATION OF CONDYLE MOTION, The International journal of prosthodontics, 11(4), 1998, pp. 317-324
Purpose: Recent research revealed that traces of single posterior refe
rence points can depend on the location of the monitored point. The ai
m of this study was to quantify this dependence and to point out its c
onsequences for clinical application of condylar path registrations. M
aterials and Methods: In 60 asymptomatic volunteers, mandibular motion
was recorded during protrusion, lateral excursion, and opening-closin
g of the jaw. Simultaneous trace-patterns of 10 condylar points includ
ing the hinge-axis point and the kinematic-axis point were compared wi
th respect to length, inclination angles, coordination, and shape. Res
ults: in protrusion, traces of the different condylar points were equa
l and independent of the location of the monitored point. Bennett angl
es depended on the sagittal position of the reference point and varied
by 0.8 degrees per 1 mm change of location. Opening-closing traces di
ffered considerably. Their lengths varied by up to 9 mm and inclinatio
n angles varied by 40 degrees. Opening-closing patterns also showed ir
regularities like those observed in temporomandibular disorders. Irreg
ularities were minor for the hinge-axis point and least for the kinema
tic-axis point. Conclusion: In tooth-guided movements ''condyle motion
'' is represented by the traces of any point near the condyle. In open
ing-closing, however, the trajectory of a single condylar point will n
ot reliably represent condylar motion. For articulator adjustment, con
dylar angles must not be taken from opening-closing, but only from pro
trusion. In diagnostic applications, one has to be aware that irregula
r traces may not only result from dysfunction, but may as well be a re
sult of the choice of reference point.