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Clinical Outcome of the Altered Cast Impression Procedure

PI: Richard Frank, D.D.S., M.S.D., Professor, Department of Prosthodontics, School of Dentistry, University of Washington

Several studies have demonstrated the advantages of an altered cast impression procedure (ACIP) for distal extension removable partial dentures (RPD). The procedure has been taught in dental schools since the mid 1960s, but a review of RPDs provided in community practices suggested the procedure is not widely used. The question arose: Is the demonstrated benefit of the ACIP too small to be worth the time and cost and technique sensitivity imposed on the dentist?

Power calculations were done and recruitment is underway. No summary of results to date has been made because too few subjects have been complete.

Nine million Americans between the ages of 18 and 74 wear a mandibular RPD, and 80% of these are distal extension bases. Since 20-35% need relining within two to three years, the importance of a technique (ACIP) which may decrease the need for relining is apparent. On the other hand, if no practical or predictable differences in RPDs made with and without the ACIP can be demonstrated clinically, then it is difficult to justify the continued application of this technique. The original studies which suggest the superiority of the ACIP involved no more than seven subjects, and the statistical importance may have been misleading. This study, which looks at differences in clinical treatment outcomes in a large group, should clarify the recommended status of this method in teaching and practice.

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