Retention force of differently fabricated telescopic PEEK crowns with different tapers.

To assess the retention force between primary and secondary PEEK crowns made by different fabrication methods. Primary crowns with different tapers (0 degrees , 1 degrees , and 2 degrees ) were fabricated and secondary crowns that were either milled from breCam BioHPP blanks, pressed from pellets (BioHPP Pellet) or granules (BioHPP Granulat) were produced. Each specimen was measured 20 times in a pulloff-test and results were analyzed using 2-/1-way ANOVA and linear regression analyses (p<0.05). Within 0 degrees tapered crowns milled secondary crowns showed lower retention forces compared to pressed pellet crowns. Crowns with a 1 degrees taper, however, showed no impact of the fabrication method on retention force. At a 2 degrees taper, granular pressed crowns displayed lower values than their milled counterparts. Within the milled group, a 0 degrees taper showed lower retention values than the higher tapers, whereas in the pressed groups, no impact of taper angle on retention force was found.