Abstract
In prosthetic dentistry, double crown systems have proved their suitability as retainers for removable partial dentures. However, investigations in this context, regarding polyetheretherketone, are scarce. Therefore, the aim of this study was to test the retention force (RF) between polyetheretherketone (PEEK) primary and cobalt-chromium (CoCr), zirconia (ZrO2) and galvanic (GAL) secondary crowns with three different tapers. Primary PEEK-crowns were milled with the tapers 0°, 1°, and 2° (n = 10/taper, respectively). Afterwards, 90 secondary crowns were fabricated: (i) 30 CoCr-crowns milled from Ceramill Sintron (AmannGirrbach, Koblach, Austria) (n = 10/taper), (ii) 30 ZrO2-crowns milled from Ceramill ZI (AmannGirrbach, Koblach, Austria) (n = 10/taper), and (iii) 30 GAL-crowns made using electroforming (n = 10/taper). RF was measured in a pull-off test (20 pull-offs/specimen) and data were analyzed using 2-/1-way Analysis of Variance (ANOVA) followed by the Tukey-Honestly Significant Difference (HSD) post hoc test and linear regression analyses (p < 0.05). The measured mean RF values ranged between 9.6 and 38.2 N. With regard to the 0°, 1°, and 2° tapered crowns, no statistically significant differences between CoCr and ZrO2 were observed (p > 0.141). At 0° taper, no differences in retention forces between GAL, CrCr, and ZrO2 crowns were found (p = 0.075). However, at 1° and 2° taper, lower RF for GAL-crowns were observed (p < 0.009, p < 0.001, respectively). According to this laboratory study, PEEK might be a suitable material for primary crowns, regardless of the taper and the material of secondary crown. Long-term results, however, are still necessary.
Highlights
Polyetheretherketone (PEEK) is a high performance thermoplastic polymer, which consists of an aromatic backbone molecular chain, interconnected by ketone and ether functional groups [1].Its structure confers outstanding chemical resistance and resistance to thermal and post-irradiation degradation [1]
This study investigated the influence of CAD/CAM fabricated CoCr, ZrO2, and electroformed GAL secondary crowns on a PEEK primary crown and the influence of three different taper angles, i.e., 0 ̋, 1 ̋, and 2 ̋, respectively
Regarding the first hypothesis, relating to the different material groups, the results showed that the GAL crowns behaved differently, compared to CoCr and ZrO2 : GAL showed significantly lower retention force values than CoCr and ZrO2 in 1 ̋ and 2 ̋ taper groups
Summary
Polyetheretherketone (PEEK) is a high performance thermoplastic polymer, which consists of an aromatic backbone molecular chain, interconnected by ketone and ether functional groups [1].Its structure confers outstanding chemical resistance and resistance to thermal and post-irradiation degradation [1]. Polyetheretherketone (PEEK) is a high performance thermoplastic polymer, which consists of an aromatic backbone molecular chain, interconnected by ketone and ether functional groups [1]. PEEK presents a lower solubility and water absorption as compared to current esthetic computer-aided-design/computer-aided-manufacturing (CAD/CAM) polymers [2] and is Materials 2016, 9, 187; doi:10.3390/ma9030187 www.mdpi.com/journal/materials. Materials 2016, 9, 187 chemically inert [1]. Biofilm formation on the surface of PEEK is equal to or even lower than on dental materials, such as titanium and zirconia [3]. Due to these promising physico-mechanical properties, PEEK shows some advantages to traditional alloys and ceramic dental materials
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