Deformation of elastomeric interocclusal registration materials of varying thickness

Objective: Error may be incorporated during the fabrication of indirect restorations. Distortion of interocclusal records during articulation of casts could result in occlusal disharmony or improper restoration design.

Two studies have evaluated the effect of interocclusal record thickness on the accuracy of transferring casts to an articulator. Adrien and Schouver (1997) attributed increased error at greater thickness to use of an arbitrary hinge axis. Breeding and Dixon (1992) found significant increases in distortion as thickness was increased. The thickness interval, however, seemed larger than one would generally use clinically. The present study evaluated the deformation under compression at more clinical thicknesses. The objective of this study was to evaluate the effect of thickness of elastomeric interocclusal registration materials on deformation.

Methods: Ten 10 mm diameter samples of each material 1, 2, 3, 4, and 5 mm thick were auto-mixed and set for three minutes. They were subjected to a compressive load of 25N on the Zwick testing apparatus. The deformation was measured directly.

Results:

            For each material except Blu-Mousse, deformation increased significantly (P<.05) with each millimeter increase in thickness (One-Way ANOVA, Tukey’s Multiple Comparison Test). Deformation increased significantly for all Blu-Mousse groups except one. Conclusion: Increasing the thickness of elastomeric interocclusal registration materials in 1 mm increments resulted in increased deformation in all but one group. Differences of up to .26 mm were found and could be clinically significant. Interocclusal registrations should be made at minimal interocclusal distance.