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Evaluation of defects in surface detail for monophase, 2-phase, and 3-phase impression techniques: an in vitro study
Giuseppe Varvara1, Giovanna Murmura2, Bruna Sinjari3
1Assistant Professor, Department of Medical, Oral and Biotechnological Sciences, Dental School, 'G. D'Annunzio' University of Chieti-Pescara, Chieti-Pescara, Italy.
Statement Of The Problem:
Polyvinyl siloxane materials of various consistencies have been tested to reduce defects commonly associated with different definitive impression techniques.
Purpose:
The purpose of this in vitro study was to compare the number of visible defects within the surface of a new 3-phase, 2-step impression injection technique with the number found in the monophase and in the conventional 2-phase, 1-step and 2-phase, 2-step impression techniques.
Material And Methods:
Two complete crown abutment preparations were impressed 10 times for each of these 4 techniques, which gave 20 abutment impressions for each group. The 3-phase, 2-step impression--injection technique included extra-light--body impression material added for the impression and injected after reinsertion. After the removal of all of these impressions, an examiner counted the number of open voids and bubble-like enclosed voids visible to the naked eye at a working distance of approximately 150 mm. Only the defects in the area of the prepared abutments were included in the assessment.
Results:
The frequency of defects ranged from 100% of the impressions in the monophase group to 5% with the new 3-phase, 2-step impression injection technique. No statistical differences were seen between the two 2-phase (1-step and 2-step) impression techniques, although there were numerically fewer impressions with defects with 2 steps (45%) than with 1 step (55%). The 3-phase, 2-step impression injection technique had the greatest accuracy, with fewer specimens with defects (5%) than with either of the 2-phase techniques, although these differences did not reach statistical significance.
Conclusions:
The 3-phase, 2-step impression injection technique provides improved defect-free reproduction of detail, showing fewer defects than other impression techniques.
