Abutment Impression Research Articles

The effect of marginal thickness on the distortion of different impression materials

An impression of the margins of a prepared tooth and adjacent gingival sulcus must be of sufficient thickness to withstand distortion and tearing when the impression is removed from the mouth. The purpose of this study was to compare the dimensional accuracy of Elite, Examix, and Express polyvinyl siloxanes; Permadyne polyether; and Permlastic polysulfide elastomeric impression materials. These materials were used to make impressions of a metal model that simulated prepared abutments with gingival sulci of various widths. A traveling microscope was used to measure the abutments and impression widths, and the number of defects in each impression was recorded. Between 70% and 100% of the abutment impressions with sulcular widths of 0.05 mm exhibited defects, which prevented accurate measurements in this group. Express material demonstrated a high number of defects in the 0.10 and 0.16 mm sulcular width groups. No great difference in average maximum distortion values or coefficients of variation (CV) were detected among the materials used to make impressions of abutments with sulcular width groups of 0.2 to 0.4 mm. For the sulci of 0.16 mm and less, Examix and Permlastic materials exhibited distortion and a CV comparable to the impressions of the wider sulcular groups, whereas Elite and Permadyne showed greater distortions and CVs. The differences were not statistically significant (analysis of variance) because of the larger CV among the groups. The larger coefficient of variation in the 0.1 and 0.16 mm sulcular width groups demonstrated inconsistencies in obtaining good impressions of abutments with such narrow sulcular widths.

Multiple abutment impressions using vacuum adapted temporary splints

The construction of a tray former from temporary splint material and the re-resulting cold-curing acrylic resin tray produce a closely adapted preliminary tray. This preliminary tray deflects the gingival tissue away from the cervical margins of the preparations, thus permitting the viscous rubber base material of the final impression to flow into contact with the cervical margins of the preparation. The end result is an accurate final impression of multiple abutments developed as part of a complete dental arch impression.