A. HUGGER*, S. VOGT, U. BERNTIEN, U. STÜTTGEN (Dept. of Prosthodontics, Westdeutsche Kieferklinik, Heinrich-Heine-University Düsseldorf)
Some electronic jaw registration systems offer the possibility of recording and determination of the individual hinge axis. With the help of mathematical procedures individual hinge axis points can be detected and can be used for transferring the correct orientation of the jaws in the skull into the articulator. With only a gentle manipulation of the mandible we recorded and deter- mined the position of individual hinge axis points in relation to arbitrary hinge axis points by the electronic registration system String-Condylocomp LR3 and with individual paraocclusal appliances. 14 persons (8 males, 6 females) without signs of temporomandibular disorders were examined on three different days and the coordinates of the individual hinge axis points in dorsal(-)/ventral(+)- and caudal(-)/cranial(+)-direction were compared. In relation to the position of arbitrary hinge axis points on the skin (12 mm before tragus and 3 mm under the line tragus-canthus) the individual hinge axis points were detected in mean on the right side 9.34 mm dorsal (std.dev. 0.78, min. -26.00, max. 4.00) and 1.98 mm caudal (std.dev. 0.68, min. -13.00, max. 10.00), on the left side 4.70 mm dorsal (std.dev. 1.02, min. -16.00, max. 14.00) and 0.51 mm cranial (std.dev. 0.77, min. -13.00, max. 13.00). Per person and per day the range of distances from the arbitrary hinge axis point could vary from 0 to 15 mm in the corresponding directions. In conclusion using the arbitrary hinge axis point mentioned above the position of this point should be placed more dorsally, but it must be considered that under the condition of only a gentle manipulation with recording several times the sensitive electronic method determines the individual hinge axis points more often in a variable range of values.