Retention force of overdenture retained with telescopic crowns: A comparison of polyether ether ketone and zirconia ceramic telescopic crowns

Abstract

Introduction/Objective. Recently, new materials for double crowns have been introduced, such as zirconia and polyether ether ketone (PEEK). However, some characteristics of these materials, such as retentive force and duration of ?settling in phase,? have not been investigated sufficiently. During the ?settling in phase,? telescopic overdenture has not yet achieved its definitive retention force, and it can be harmful for periodontal tissue if the value is above optimal for a long period of time. The objective was to measure the in vitro overall pull-off force of telescopic crowns where primary crowns were made from zirconia ceramics and a survey of the ?settling in phase? duration. Methods. Forty zirconia primary telescopic crowns were produced on prepared canine teeth. Twenty secondary crowns were of PEEK and other 20 of zirconia with electroplated gold copings. The pull-off force measurements were conducted utilizing a dynamometer until a constant value was obtained. Results. The specimens of the PEEK group showed higher initial retentive force values. Settling in phase was finished between 800 and 900 cycles of separation for both groups. Comparing the value of the pull-off force between individual different cycles, a statistically significant reduction was recorded up to the 800th cycle, while between the 800th and the 900th cycle there was no difference. Conclusions. The settling in phase was finished between 800 and 900 cycles of separation in both groups. Final retentive force values for both tested telescopic groups were in the optimal range which is 5?9 N per one telescopic crown.