Impression material consistency and peripheral tissues

The behaviour of three alginate impression materials was tested in vivo by sectioning the peripheries of a series of impressions in a standard manner and measuring the extension in three directions: buccal, lingual and into the depth of the sulcus. The three materials used reacted in accordance with their various consistencies. There were statistically significant differences between all the materials in the inferior measurement, but very few differences in the buccal dimension. Lingually however, one extended significantly further than the other two. It is concluded that the facial tissues, probably muscles, play a restraining role in buccal impression material extension but that the inferior and lingual extensions are more susceptible to the consistency of the material rather than the tissues. This should be carefully considered before selecting a suitable material for impressions.