Effect of Delayed Setting Expansion of Dental Stones on Implants

Objectives: This comparative study evaluated how delayed setting expansion of 3 dental stones affected implant analogue positions in three dimensions (x, y, z axes) within implant verification casts.

Methods: A positioning jig was fabricated to reproducibly index a reference pin with 4 cylindrical fiduciary markers (6x10mm) which served as implant analogues.  This jig was used to replicate 3 groups (n=6) of casts poured in an experimental (zero expansion) and two common dental stones (Type IV, and Type V).  Three-dimensional analysis was conducted utilizing a contact probe coordinate measurement device (Faro Arm).  Measurements were made to establish the movement of the 4 markers from the reference pin and consisted of (1) Location, the movement from a vertical reference point, (2) Angle, the movement from a horizontal reference point over time, and (3) Height of the marker.  The measurements were taken at 6 time intervals; 1 (initial set), 2, 24, 48, 72, 96 hours.  The differences (absolute values) between the initial set and all other times were calculated.  Data were analyzed using 1-way Analysis of Variance and Tukey HSD post hoc tests (p<0.05)

Results: No significant differences changes of the markers were noted for Location, Angle, or Height over the time intervals measured.

Conclusions: There were no differences in the effect on the Location, Angle or Height of dental analogs when embedded in the zero expansion, Type IV, or Type V dental stones over the time of set (up to 96 hours).