Journal of Craniomandibular Function, 03/2009

The following paper shows the identification of the terminal hinge axis using two different electronic axiography systems. The terminal hinge axis points were determined and compared in 26 subjects (5 male, 21 female, average age 38 ± 10.8 years) who had been selected from a patient population receiving occlusal splint therapy. This was done using a juxta-articular hinge axis tracing appliance (CADIAX® diagnostic) and an abarticular tracing appliance (Jaw Motion Analyzer®). For the statistical evaluation of the consistency between the different methods to determine the terminal hinge axis points, Pearson's correlation coefficient was determined. On average, the mean terminal hinge axis point values of both systems showed a good to very good correlation. The correlation coefficient determined for the respective coordinates indicates an average (x coordinate left: 0.53) to good (y coordinate left: 0.9) correlation of results. The hinge axis points established by the CADIAX diagnostic showed a higher reproducibility than the points determined by the Jaw Motion Analyzer system. The range of dispersion seems to depend upon the scale of the translational movement and upon the ability to control translational movements in hinge axis movement. The CADIAX diagnostic provides such rotation control during dynamic axis localization. The Jaw Motion Analyzer should have this type of control system added. Not all temporomandibular joints are able to perform translation-free hinge axis movements. Keywords: CADIAX diagnostic, hinge axis movements, Jaw Motion Analyzer, terminal hinge axis

The function of articulator analysis is to provide a detailed visual presentation of functional occlusion. The mechanical situation using a cast can only approximately reflect the actual biological situation. This article will present a new computer-based system and will illustrate its mode of operation with examples. In this study, the occlusal surfaces of mandibular and maxillary dental arches were first digitized using a 3D scanner and real mandibular movements were then recorded using an ultrasonic measuring system (Jaw Motion Analyser [JMA]). A coupling component of the JMA system that was used clinically provided a precise record of the spatial position of the mandible and was used for referencing both sets of data. A feature of the method presented here was the option to visualize the results "live" and simultaneously with the movement of the patient's mandible. This allowed a 3D view of the arch positions during mastication from any perspective. To analyze the intercuspidation, dynamic images were generated in which the proximity areas and contact areas were marked. It was then possible to visualize the tooth contact relationships with the help of tomograms. This allowed the authors to display the size, position and number of dynamic contact areas, and the frequency with which the contact areas of the occlusal surfaces occluded. Keywords: virtual articulator, virtual occlusion, dynamic occlusion, occlusal contacts, occlusion

Three-dimensional scans and measurements were taken of casts of the maxillary arches of 18 subjects with naturally healthy tooth structures. The cusp angles of the premolars and molars and the palatal inclines of the canines were determined. The functional measurements in relation to the joints were taken using the Cadiax Compact. The results of the measured tooth angles showed a sequential decrease in the palatal incline of the buccal cusps from the canines towards the second molars, whereas the buccal angles of the palatal cusps increased from mesial to distal. The inner angle between the two cusp angles at the flanks sloping towards the fissure widened from mesial to distal in all casts. In principle, this confirmed the occlusal scheme of sequential guidance, with canine dominance through the general distribution of cusp angles. A direct relationship between the cusp angles and the measurements of condylar function (as it exists between the horizontal condylar guidance inclination and Bennett's angle) could not be verified (r < 0.6 and P > 0 according to Spearman's rank correlation coefficient). However, evidence of other complex relationships became apparent. A steep condylar path and canine guidance indicated that the lateral cusps were just as steep. A wide Bennett angle resulted in flat cusp angles. Considering the fact that it is not the individual cusp angles, but the three-dimensional torsion curve of sequential cusp angles that is influenced, there are clear dependencies with bilateral symmetry (with r >= 0.6 and P < 0.05). This interdependence is found between two indices: one is derived from the quotient of the sums of the buccal divided by the palatal cusp angles and the other index is derived from the addition of the canine inclination angle with the contralateral condylar path and the subtraction of the respective Bennett angle. Keywords: Bennett angle, condylar path, cusp angle

In the case of mechanical or electronic axiography, mandibular excursions are recorded using a tracing bow, which is attached to the lower teeth. This attachment is carried out either paraocclusally or periocclusally. Traditionally, the paraocclusal attachment required dental technical preparation using laboratory acrylic. After that, the paraocclusal tray adapter could be fixed using suitable cements. The procedure described in this report requires no dental technical preparation and guarantees more flexible implementation of paraocclusal axiography. Keywords: attachment, axiography, paraocclusal, periocclusal, tray adapter