Trueness and intaglio fit of custom-made polyetheretherketone post-and-cores fabricated using different techniques

Statement of problem

Applications of polyetheretherketone (PEEK) as a promising alternative to ceramic materials have extended to include post-and-cores. However, information regarding the available fabrication techniques for producing custom-made PEEK post-and-cores and their effect on accuracy is still scarce.

Purpose

The purpose of this in vitro study was to evaluate the trueness and intaglio fit of custom-made PEEK post-and-cores fabricated using different techniques.

Material and methods

Ten mandibular second premolars were collected, decoronated, and endodontically treated. For the fabrication of custom-made post-and-cores, each post space was prepared, scanned, and designed by using the exocad software program. Each reference design was used to fabricate PEEK post-and-cores with 3 different techniques (N=30): group P, heat pressing; group S, subtractive manufacturing, and group A, additive manufacturing. All the fabricated restorations were scanned, providing the test data as standard tessellation language (STL) files, which were imported with the reference data into a reverse engineering software program to evaluate the 3D trueness of each fabrication technique. To evaluate the intaglio fit, restorations coated with silicone material were scanned to provide the test data as STL files, which were superimposed on the STL files of the scanned restorations. One-way analysis of variance (ANOVA) and 2-way mixed model ANOVA tests were used to analyze the data (α=.05).

Results

For 3D trueness, root mean square (RMS) values representing the deviations between the scans of the fabricated restorations and the reference designs varied significantly among different groups (P<.001), with the highest mean deviation found in group A (102.8 ±31 µm), while the lowest mean deviation was found in group S (42.2 ±11 µm). For the intaglio fit, the deviations between the scans of the fabricated restorations and the scans of the coated restorations varied significantly among different groups (P<.001), with the highest mean deviation found in group A (228.4 ±47 µm), while the lowest mean deviation was found in group S (96.2 ±14 µm). Simple effects comparisons showed the highest value of deviation in the apical area in group A (P<.001).

Conclusions

Custom-made PEEK post-and-cores fabricated by using subtractive manufacturing and heat pressing techniques showed better trueness and intaglio fit compared with additively manufactured restorations. Before printed PEEK restorations can be considered a suitable alternative to pressed or milled ones, improvements are required to confirm their reliability.