Application of "cusp writer" findings to practical and theoretical occlusal problems. Part II

Occlusal consequence of using average condylar guidance settings: An in vitro study

STATEMENT OF PROBLEM

A simplified mounting technique that adopts an average condylar guidance has been advocated. Despite this, the experimental explanation of how average settings differ from individual condylar guidance remains unclear.

PURPOSE

The purpose of this in vitro study was to examine potential occlusal error by using average condylar guidance settings during nonworking side movement of the articulator.

MATERIAL AND METHODS

Three-dimensional positions of the nonworking side maxillary first molar at various condylar and incisal settings were traced using a laser displacement sensor attached to the motorized stages with biaxial freedom of movement. To examine clinically relevant occlusal consequences of condylar guidance setting errors, the vertical occlusal error was defined as the vertical-axis positional difference between the average setting trace and the other condylar guidance setting trace. In addition, the respective contribution of the condylar and incisal guidance to the position of the maxillary first molar area was analyzed by multiple regression analysis using the resultant coordinate data.

RESULTS

Alteration from individual to average settings led to a positional difference in the maxillary first molar nonworking side movement. When the individual setting was lower than average, vertical occlusal error occurred, which might cause occlusal interference. The vertical occlusal error ranged from -2964 to 1711 μm. In addition, the occlusal effect of incisal guidance was measured as a partial regression coefficient of 0.882, which exceeded the effect of condylar guidance, 0.431.

CONCLUSIONS

Potential occlusal error as a result of adopting an average condylar guidance setting was observed. The occlusal effect of incisal guidance doubled the effect of condylar guidance.

The effect of the articulator settings on the cusp inclines as measured by a coordinate measuring machine

PURPOSE

The purpose of the study was to learn the effect of changes in the articulator settings on the cusp angles during working, nonworking, and protrusive movements; the purpose was also to determine the ability of the coordinate measuring machine to measure the movements.

MATERIALS AND METHODS

The condylar angles and the anterior guide angles on a Hanau 96H2 articulator (Teledyne Hanau Corp, Buffalo, NY) were varied; 432 working, nonworking, and protrusive cusp angles were measured at the first molar by a coordinate measuring machine.

RESULTS

The data from the coordinate measuring machine was used to produce formulas. The formulas were used to calculate the working, nonworking, and protrusive cusp angles that will occur as a result of 72 different articulator settings.

CONCLUSIONS

The coordinate measuring machine is useful for making measurements of articulator movements. Additional research may measure the movements of other articulators or compare articulators (such as the arcon and nonarcon).

Occlusal adjustment under the control of intra-oral recording with the aid of the functiograph

Objective diagnosis of occlusal relationships is possible with the aid of a new instrument called the 'Functiograph'. It enables recordings of both the free and tooth-guided mandibular movements to be made intra-orally on the same tracing plate. A series of twenty cases has been undertaken and a number of selected examples are illustrated. Occlusal equilibration under the control of tooth-guided movement records enables the estimation of the results of occlusal correction in an objective and methodical way.

Computer-graphic representation of mandibular movements in three dimensions. Part II: the sagittal and frontal planes

Mandibular movements can be represented and viewed graphically in three planes--occlusal (approximately horizontal but variable), sagittoid (approximately sagittal), and frontal. The student of occlusion can vary the settings of the mathematical articulator and observe the three-dimensional changes produced in the interocclusal movement patterns.

Computer-graphic representation of mandibular movements in three dimensions. Part I. The horizontal plane

A computer-graphics simulation was developed to display the effects of mandibular movement patterns of both the maxillary and mandibular teeth in the occlusal plane. The many parameters affecting mandibular movement patterns may be varied selectively. The effects of these parameters on the pathways of movement described by the supporting cusps during occlusion can be graphically observed in the horizontal plane.