The Denture Frame Analysis: an additional diagnostic tool.

The purpose of this study was to evaluate the Denture Frame Analysis. This adjunctive cephalometric analysis of the lateral headfilm was introduced in Japan, but no data exist for the Caucasian population at present. One-hundred-and-six Caucasians were randomly selected and assigned to one of four groups, according to their malocclusion: Angle Classes I, II, and III, and anterior open bite. Statistical testing showed significant differences among the four groups for most of the measurements investigated. The Denture Frame Analysis distinguished the different types of malocclusion, and evaluated skeletal and dental relationships. The occlusal plane aids in the determination of the objectives and limits of orthodontic therapy.

An analysis of hinge axis translation and rotation during opening and closing in dentulous and edentulous subjects.

In order to evaluate the influence of interocclusal environment, condylar movement was investigated by computerized axiography. The sample consisted of 50 dentulous and 50 edentulous Caucasians. The mean length of translation at maximum opening in dentulous subjects was 16 mm, while edentulous subjects showed an average of 11 mm. The mean angle of hinge axis rotation at maximum opening was 30 degrees in dentulous subjects and 17 degrees in edentulous subjects. The mean length of translation and the rotation of hinge axis in opening and closing movements was smaller in edentulous subjects than in dentulous ones. In opening and closing movement of edentulous subjects, the length of translation and the rotation value revealed no significant correlation with age or duration of upper and lower prosthesis. No significant difference was shown between edentulous and dentulous subjects on translative quantity in protrusive movement.

Orthopedic jaw movement observations. Part V: Transversal condylar shift in protrusive and retrusive movement.

Unguided protrusive and retrusive mandibular movement was investigated in 76 asymptomatic volunteers and temporomandibular joint (TMJ) patients using computerized axiography. In 38 of these subjects, guided pro-/retrusion was also recorded. Measurements were performed in a three-dimensional Cartesian coordinate system (x = anteroposterior; y = transversal, toward the hinge axis; z = craniocaudal). Transversal shift (y) was measured and evaluated as well as the distance "s" and horizontal condylar inclination (HCl) at the point of maximum transversal deviation. The patterns of the tracings were analyzed with a view to diagnostic improvements. The objective of this study was to evaluate transversal shift and to examine the postulate of symmetrical behavior of the TMJs in pro-/retrusion. The mean mandibular shift was 0.15 mm to the left. This maximum deviation was seen in a mean distance "s" of 7.42 mm in relation to the Cartesian coordinate system in reference position. These results suggest a functional dominance of the right part of the mandible in protrusive and retrusive movement.

Recording orthopedic jaw movements. Part IV: The rotational component during mastication.

The recording and analysis of mastication provides information on neuromuscular engrams, and hence avoidance mechanisms. Avoidance mechanisms are pathologic movement patterns which are developed to avoid occlusal interferences during functional movements. Evaluation of hinge-axis rotation permits selective quantitative analysis of a complex movement pattern. The objective of this study was to determine the amount of hinge axis rotation in mastication using computerized axiography. Furthermore, the distance of the condyles from reference position (RP) at maximum rotation was evaluated and the chronological sequence of translation and rotation was investigated. The mean value for the rotational angle of the mandible (gamma) during mastication was 14.1 degrees in the volunteers and 13.44 degrees in the patients. The linear spatial distance from RP amounted to a mean of 6.57 mm on the right side and 6.21 mm on the left in the volunteers. In the patients, the measurements were 6.33 mm on the right side and 6.7 mm on the left. In most cases, maximum rotation did not correspond with maximum translation. The chronological sequence of maximum excursion was not constant.

The reproducibility of condylar hinge axis positions in patients, by different operators, using the electronic mandibular position indicator.

Three operators each made five recordings from 15 symptomatic patients using the electronic mandibular position indicator. The method consisted of measuring bilateral spatial changes of the hinge axis recalculated by the computer to an intercondylar distance of 110 mm and a third position, calculated from the rotation of the hinge axis, at the incisal guidance table. All individual patient recordings were related to the origin of the same coordinate system. This origin is designated and defined as the reference position, with purposeful elimination of any stated joint position for this definition. The measurements were in all planes of space at 10-millimicron increments, including the rotation of the transverse hinge axis in hundredths of degrees. These data showed that the reproducibility of hinge axis positions, ie, reference positions, to hinge axis condylar positions dictated by the maximum intercuspation of teeth was in average less than 0.2 mm for each record from all operators and patients.

Orthopedic jaw movement observations. Part II: The rotational capacity of the mandible.

Using computerized axiography, particularly the electronic mandibular position indicator (EMPI), the mandibular opening movement was measured in 86 asymptomatic volunteers and temporomandibular joint (TMJ) patients. Terminal hinge-axis movement and hinge-axis rotation at maximum-guided mouth opening were recorded. The angle of hinge-axis rotation was used as a parameter for both movements, in accordance with the neutral-zero method. This is a well-established technique in orthopedics and is the standard tool for quantitative functional analysis of joints. An average group was defined, 50% being volunteers. The interquartile range for terminal hinge-axis movement in this study was 5.42 degrees-7.41 degrees in the volunteers and 4.73 degrees-7.25 degrees in the patients. The interquartile range for hinge-axis rotation at maximum opening was from 29.09 degrees-34.87 degrees in the volunteers and from 26.7 degrees-35 degrees in the patients. Computerized axiography is a refined tool for analyzing rotational and translational capacities of the mandible. It is a valid and practical method for orthopedic-diagnostic evaluation of mandibular movements and gives objective criteria for diagnosis in accident victims.

Computerized axiography: principles and methods.

This paper reviews earlier methods for the analysis of mandibular movement and gives a detailed account of state-of-the-art procedures. Special emphasis is given to computerized axiography and the application of this method to the diagnostics of the temporomandibular joint (TMJ). The article discusses the advantages of computerized axiography over the mechanical device and points out the limitations of the axiographic method. One major advantage of the computerized system is having the enlarged diagram of tracings on the computer screen. This means that small changes such as initial disk displacements can be diagnosed more readily than with the mechanical device.