Marginal fit of polyetheretherketone single crown copings obtained using different fabrication techniques

Statement of problem. Demand is increasing for polyetheretherketone (PEEK) as a fixed dental prosthesis core material. However, there is a lack of information about how the accuracy of these restorations is affected by the fabrication procedures.
Purpose. The purpose of this study was to investigate the effect of different fabrication techniques on the marginal accuracy of polyetheretherketone single crown copings.
Material and methods. A stainless steel master die was designed to simulate a prepared second lower molar to receive all-ceramic crowns. Thirty PEEK copings were produced and divided into three groups (n=10) according to the fabrication technique, as follows: (PC): milled from a pre-fabricated PEEK blank using a CAD/CAM system; (PP): pressed from pre-fabricated PEEK pellets; and (PG): pressed from PEEK granules, in addition; ten zirconia copings were produced using the same CAD/CAM system and served as control. Marginal accuracy measurements (in micrometers) were recorded at 4 reference points on each coping with a digital microscope. Data were statistically analyzed using One-way Analysis of Variance (ANOVA) followed by pair-wise Tukey Honestly Significant (HSD) test to study the difference between groups mean values
(P ≤ 0.05).
Results. The overall mean (SD) marginal gap at the marginal opening for the copings was (78.69±10.7µm) for Peek granules copings, (72.38±9.75µm) for Peek pellets copings, (45.22±6.09µm) for Peek CAD/CAM copings, and (45.22±1.3µm) for zirconia CAD/CAM copings (control). There was a statistically significant difference between the (milled and pressed) copings as indicated by ANOVA-test (P=<0.0001<0.05). Pair-wise Tukey Honestly Significant (HSD) test showed non-significant difference (P>0.05) between milled zirconia and milled PEEK copings; moreover, there was no significant difference (P>0.05) between PEEK copings pressed from pellets or granules.
Conclusions. The marginal accuracy of PEEK CAD/CAM fabricated copings showed significantly lower mean marginal gap values than PEEK pressed copings. The marginal discrepancy mean values recorded were all within the clinically acceptable range (120 μm).
Clinical implications. PEEK reinforced with ceramic fillers can be considered a promising alternative material in single restorations.