JUVORA LIMITED

To optimize the gypsum mold temperatures for pressed PEEK, and to estimate the impact, tensile strength and flexural properties of pressed and milled PEEK. Where appropriate, these properties were compared with those of PMMA.

Since the mold temperature could affect the properties of the injected parts, the temperature of 20 gypsum specimens was monitored using the multi-thermocouple system (n = 5). A total of 210 specimens were prepared for mechanical tests according to the ISO standard for denture base polymer (n = 10). The Izod impact, tensile strength, and flexural behavior were assessed. PEEK-OptimaNI1 (PEEK-pressed) was tested after processing via the pressing method at4 different mold temperatures. Machining PEEK-Juvora (PEEK-milled) specimens were prepared using the CAD-CAM production method. Data were analyzed via one-way ANOVA performed at a confidence level of 95% and a significant P-value of (P ≤ 0.05).

In comparison to the furnace temperature more heat was required to preheat the gypsum mold up to 100, 150, 175 and 200 °C for pressing purposes. The highest impact strength was 5.7 kJ/m² for PEEK-pressed at 100 °C mold temperature and 4 kJ/m² for PEEK-milled. The latter had a higher tensile strength of 118 MPa. The best result for PEEK-pressed was 97 MPa at 200 °C mold temperature. Under a 4-point bending test, Young's modulus of PEEK-milled was 5591 MPa, while the highest for PEEK-pressed was 4936 MPa at 200 °C mold temperature.

Compared to PMMA, given the superior mechanical properties of PEEK, it may become the material of choice for future use. Dentures constructed from PEEK polymer could well be routinely constructed in the near future.

This study aims to test the influence of different surface treatments and conditioning on the shear bond strength between polyetherketone (PEEK) and composite.

Surfaces (570 plates) were used untreated, etched, air-particle abraded or activated with silica-modified alumina oxide. Surface roughness was determined after different treatments. Cylinders of composite were polymerized onto the surfaces. Eighteen different pre-treatment combinations were applied, partly combined with opaque application. Shear bond strength (SBS) was determined following ISO TR 11405. Baseline tests were performed 24 h after composite polymerization. For investigating the influence of storage and aging, the specimens were either stored in distilled water (37 °C, 90 days) or thermally cycled (12,000 cycles 5 °C/55 °C, distilled water). Means and standard deviations were calculated (statistics: one-way ANOVA/Bonferroni (α = 0.05)).

Surface roughness varied between 0.04 ± 0.01 and 6.76 ± 1.11 μm. Only etching caused a significant (p < 0.001) increase. SBS strongly varied between 0.0 ± 0.0 and 23.2 ± 2.1 MPa. After thermal cycling (TC), nine of the investigated systems showed SBS higher than 5 MPa, varying from 8.8 ± 2.7 MPa (#7) to 19.4 ± 2.5 MPa (#4). After water storage, nine systems provided SBS higher than 5 MPa, seven even values higher than 10 MPa. Maximum SBS was 27.1 ± 3.1 MPa (#2) and lowest value was 5.4 ± 2.6 MPa (#4). Significant (p < 0.001) differences were found between the individual systems after 24 h, TC and after 90 days storage.

For good bonding between PEEK and composite, cleaning and roughening is recommended. Surface conditioning prior to bonding seems essential. Combination with opaque revealed an increase in SBS.

Successful bonding on PEEK surfaces can be achieved by surface roughening and subsequent surface activation with acetone- or phosphate-based methacrylate primers or tribochemical treatment.