A cross-over randomised controlled trial of selective pressure impressions for lower complete dentures and laboratory investigations into impression pressure variation

Part I of this Thesis gives a brief outline of the history and evidence for impression techniques for complete dentures. The literature review suggested there was a paucity of high quality evidence for impression techniques for complete dentures, especially in the form of randomised controlled trials (Jokstad et al 2002, Harwood 2008). The literature review from Part I suggested that selective pressure impressions for complete dentures required evidence on three levels; firstly, in-vitro evidence on the numerous factors that affect pressure, secondly evidence that within a specific impression technique the pressure is re-distributed, and thirdly evidence that the specific impression technique provides patient benefit. Part II, III and IV of this Thesis address each of these issues in turn. Part II of the Thesis uses laboratory based in-vitro impression pressure research to investigate new issues and re-address old controversies where the evidence in the literature was conflicting or deficient. Part III investigates the specific distribution of pressure within the impression technique used for the clinical trial of Part IV, concluding that the pressure was distributed in a specific and useful way, which was clinically significant. The Clinical Trial reported in Part IV of this Thesis, had the primary objective of assessing patient preference for a specific selective pressure impression for complete dentures. The cross-over, randomised, controlled, clinical trial (RCT) was performed comparing a selective pressure impression with a placebo and an alternative method of redistributing pressure. Patients who had shown a specific pressure related clinical problem were recruited for the study. The results show that the preference for the selective pressure impression was greater than that of the other two techniques. The work of this Thesis introduces dentists to a successful impression technique and provides them with clear, clinically relevant and useful evidence for that impression technique