Interchangeability of semiadjustable articulators after 2 to 7 years of use

Purpose: The purpose of this study was to test the interchangeability of articulators that had been in use from 2 to 7 years and compare these results with the interchangeability of the same articulators 1 year earlier. Materials and Methods: Forty-six Whip Mix model #2240 articulators (Whip Mix Corporation, Louisville, KY) that were in clinical use from 2 to 7 years were checked for interchangeability using the Whip Mix #2245 check system. The horizontal tolerance of the check system was 94 μm. Articulators were also evaluated in the vertical dimension at 4 predetermined locations around the check system cylinders using 26-μm-thick shimstock. Vertical discrepancies between the cylinders were recorded as the thickness of 0, 1, 2, or more than 2 pieces of shimstock. Interchangeability results were compared with those determined 1 year previously using the same evaluation methods using the Exact McNemar's Test of Agreement (α = 0.05). Results: Using the Whip Mix 2245 check system, 35 (76%) articulators were interchangeable after 2 to 7 years of use. This compares to 38 (83%) that were interchangeable upon evaluation 1 year earlier. The decrease in interchangeability was not significant (p = .4531). Forty-three (94%) of the articulators had vertical discrepancies of 52 μm or less at the initial evaluation. One year later, 45 (98%) of the articulators had vertical discrepancies of 52 μm or less. After 1 year, there were significant differences in the amount of vertical space between the cylinders only at the right side (p = .014). Conclusion: The Whip Mix model #2240 articulator can remain interchangeable during clinical use for 7 years, but should be routinely checked for calibration. J Prosthod 2000;9:142-147.