Accuracy of Dynamic Virtual Articulation: Trueness and Precision

Abstract

Purpose: To study the effects of altering condylar settings and pin openings on the trueness and precision of virtual articulators versus mechanical articulators. Materials and Methods: Maxillary and mandibular typodonts with fiducial markers were mounted on a mechanical Artex-CR articulator and the mandibular teeth were prepared to allow guidance solely by the posterior determinants of the articulator and the incisal table. The relationship of the mounted typodonts was preserved digitally by scanning using manufacturer transfer plate adaptors. On the mechanical articulator, pattern resin was allowed to set between the maxillary and mandibular occlusal surfaces (area #25-30) at the endpoints of dynamic movements at three different condylar inclinations (SCI): 10°, 30°, and 45°, n=12/inclination, or at three different incisal pin openings (2, 5, and 10 mm, n=12/opening). All other articulator settings were kept constant. Resin specimens attached to the typodonts were scanned within five minutes of setting, then removed and the articulated typodonts rescanned. FDPs #25-30 were designed on the virtual articulator using identical parameters to the mechanical articulator. Dynamic virtual movements were used to sculpt the design and a file of the design was saved. The files of both types of samples were aligned and overlaid. Interocclusal separation was measured in triplicate at the indentation created by the mesiolabioincisal point angle on the incisal edge of #8 and the mesiobucco-occlusal point angle of #3. Trueness and precision of both types of articulators were calculated and compared using one-way ANOVA, followed by the Tukey HSD test (α=.05). Results: There was no statistically significant difference at altered pin openings in either trueness (F<.202, p>.37) or precision (F<3.134, p>.09) for the majority of measurements.

The only significant difference was in the precision between the two types of articulators at 5mm incisal opening, and only at the anterior measurement point (F=15.134, p=.0008). However, these differences were less than 100 μm. When the SCI was altered, there was no statistically significant difference (F< 3.624, p>.05) between the virtual and mechanical articulators in trueness for 5 of the 6 measurements obtained (F<3.624, p>.07) or for all of the precision measurements (F<3.529, p>.07). The one trueness measurement that was significantly different (F=9.237, p=.006 ) occurs at SCI of 10º, and it was less than 100 μm. Conclusions: Dynamic movements on the virtual articulator were shown to be as true and precise as to the mechanical articulator. When there were deviations, these deviations were less than 100 μm and thus, these deviations may not be clinically relevant.