Effect of different fabrication techniques on the marginal precision of polyetheretherketone single-crown copings

Demand is increasing for polyetheretherketone (PEEK) as a fixed dental prosthesis core material. However, information is lacking about how the precision of these restorations is affected by the fabrication procedures.

The purpose of this in vitro study was to evaluate the influence of different fabrication techniques on the marginal precision of PEEK single-crown copings.

A stainless-steel master die was designed to simulate a prepared mandibular second molar to receive ceramic crowns. Thirty PEEK copings were fabricated and divided into 3 groups (n=10) according to the fabrication technique: milled from a prefabricated PEEK blank by using a computer-aided design and computer-aided manufacturing (CAD-CAM) system (PC); pressed from prefabricated PEEK pellets (PP); and pressed from PEEK granules (PG); in addition, 3-mol yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) copings (n=10) were produced by using the same CAD-CAM system and served as a control. Marginal precision measurements (in μm) were recorded at 4 reference points on each coping by using a digital microscope. The data obtained were statistically analyzed by using 1-way ANOVA and the pair-wise Tukey (HSD) test to study the difference between group mean values (α=.05).

The overall mean ±standard deviation marginal gap at the marginal opening for the copings was 78 ±10 μm for PEEK granules copings, 72 ±9 μm for PEEK pellet copings, 45 ±6 μm for PEEK CAD-CAM copings, and 43 ±1 μm for the 3Y-TZP CAD-CAM control. A statistically significant difference was found between the milled and pressed copings as indicated by the ANOVA test (P<.001). The pair-wise Tukey honestly significant difference (HSD) test showed a nonsignificant difference (P>.05) between milled 3Y-TZP and milled PEEK copings; moreover, no significant difference was observed between the PEEK copings pressed from pellets or granules (P>.05).

The marginal precision of PEEK CAD-CAM-fabricated copings showed significantly lower mean marginal gap values than PEEK pressed copings. The marginal gap mean values recorded were all within a clinically acceptable range (120 μm).