Compatibility of mechanical and computerized axiographs: a pilot study

There is little known information comparing axiographic data obtained with a mechanical device and data obtained with a computerized device. However, long-term follow-up of patients may necessitate comparison of previously made mechanical axiographic data with records obtained through computer-aided axiography.

The purpose of this study was to compare measurements between mechanical and computerized axiographs in recording the rotational and translation movements of the mandible.

The study enrolled 31 subjects with no detectable clinical signs of temporomandibular disorders. A single operator obtained 3 separate axiographic tracings of right and left condylar paths for each subject, using repeated opening, closing, protrusive, and retrusive movements. Data were collected for both the mechanical (SAM Axiograph Axo 200), and the computerized axiographs (SAM Axiotron and Axo 500). Angular (degrees) and linear measurements (mm) for the mechanical axiograph were made from the tracings obtained on grid paper using a compass, ruler, and protractor. The computer performed the measurements for the computerized axiograph tracings. All parameters were compared statistically with a Wilcoxon signed rank test (alpha = .05). The same operator remeasured all mechanical axiographic tracings for 20 subjects 1 week later to evaluate measurement error. Chronbach's alpha was used as a measure of consistency between the 2 measurements.

Mean opening and closing angles varied between 52.4 and 54.2 degrees, and mean protrusive, and retrusive angles varied between 50.1 and 54.9 degrees. Mean opening and closing distances varied between 11.4 and 12.3 mm, and mean protrusive and retrusive distances varied between 8.2 and 8.7 mm. Comparison with the Wilcoxon signed rank test showed no significant differences for any parameter tested. There were high and medium inter-item correlations between repeated measurements of the manual device when Chronbach's alpha was applied, but these results were not sufficient to prove consistency between 2 consecutive measurements.

The results showed nonsignificant differences between the recordings of the mechanical and computerized axiographs tested. The authors hypothesize that minor differences may be attributed to hand-measuring errors for the tracings generated by the mechanical axiograph. This study is limited due to the impact of poor precision of the manual device on the study results when these recordings are compared to another instrument. Therefore, it is not possible to conclude that data from the manual and the computerized axiographs are compatible with each other.