Three-dimensional analysis of the interchangeability of a semiadjustable articulator system in service over time

Statement of problem

Some contemporary articulator systems claim to be highly precise in their interchangeability, with tolerances below 10 μm in vertical error; however, the claims have not been independently verified.

Purpose

The purpose of this study was to investigate the interchangeability of calibrated semiadjustable articulators in service over time.

Material and methods

A calibrated mounting articulator served as the master articulator, while the test groups were used articulators with a minimum of 1-year use by predoctoral dental students (n=10); used articulators with a minimum of 1-year use by prosthodontic residents (n=10); and new articulators (n=10). One set of mounted maxillary and mandibular master models was positioned in the master and test articulators. High-precision reference markers on the master models were used to determine interarch 3D distance distortions (dR_R, dR_C, and dR_L), interocclusal 3D distance distortion (dR_M), interocclusal 2D distance distortions (dx_M, dy_M, and dz_M), and interocclusal angular distortion (dθ_M) relative to the master articulator. All measurements were conducted three times using a coordinate measuring machine and then averaged to derive the final data set.

Results

For interarch 3D distance distortion, the mean dR_R ranged from 4.6 ±21.6 μm for new articulators to 56.3 ±47.6 μm for articulators used by prosthodontic residents; mean dR_C ranged from 65 ±48.6 μm for new articulators to 119.0 ±58.8 μm for articulators used by prosthodontic residents; and mean dR_L ranged from 12.7 ±39.7 μm for articulators used by prosthodontic residents to 62.8 ±75.2 μm for new articulators. For interocclusal 3D distance distortion, the mean dR_M ranged from 21.5 ±49.8 μm for new articulators to 68.6 ±64.9 μm for articulators used by predoctoral dental students. For the 2D distance distortions, the mean dx_M ranged from −17.9 ±43.4 μm for articulators used by predoctoral dental students to −61.9 ±48.3 μm for articulators used by prosthodontic residents; mean dy_M ranged from 18.1 ±59.4 μm for new articulators to 69.3 ±115.1 μm for articulators used by prosthodontic residents; and mean dz_M ranged from 29.5 ±20.2 μm for new articulators to 70.1 ±37.8 μm for articulators used by prosthodontic residents. Mean dθ_M ranged from −0.018 ±0.289 degree for new articulators to 0.141 ±0.267 degree for articulators used by prosthodontic residents. One-way ANOVA by articulator type revealed statistically significant differences among the test groups for dR_R (P=.007) and dz_M (P=.011) only, where articulators used by prosthodontic residents fared significantly poorer than the other test groups.

Conclusions

The new and used articulators tested did not fulfill the manufacturer’s claim of accuracy of up to 10 μm in the vertical dimension. Up to 1 year of time in service, none of the investigated test groups fulfilled the criterion for articulator interchangeability, even if the more lenient threshold of 166 μm were accepted.