Tear strength of new elastomeric impression materials

Adequate tear strength is a critical requirement of elastomeric impression materials for accurate recording of the margin area. Newer impression materials claim superior tear strength compared to older formulations. Objective: To evaluate the tear strength of contemporary elastomeric impression materials. Methods: Thirteen impression materials from 5 manufacturers were evaluated. A metal mold for axial notch specimens with 2mm thickness (ASTM D614) was used to make tear strength specimens (n=10 per Material).  Each of the impression materials were mixed according to instructions, inserted into the mold and held until setting.  After the recommended setting time, specimens were removed and placed into an Instron testing machine. Specimens were loaded in tension to failure using a .5mm/min crosshead speed.  The tear strength of each impression material was calculated.  A one-factor ANOVA and Tukey post-hoc analysis evaluated the data for differences. Significance was set at p=.05 . Results: Tear strength values (N/mm) for all materials tested are presented below: (Ts = Tear Strength; SD = Standard deviation; HB = Heavy Body; RB = Regular Body; LB = Light Body; XLB = Extra Light Body). Letters on right identify subsets of insignificant difference.

Conclusions: There is a significant difference in tear strength among the elastomeric impression materials tested. Newer light body VPS impression materials exhibited higher tear strength than reported for conventional materials.