Suitability of the new Aryl-Ketone-Polymer indicated for removable partial dentures: Analysis of elastic properties and bond strength to denture resin

Enhancing Dental Cement Bond Strength with Autofocus-Laser-Cutter-Generated Grooves on Polyetheretherketone Surfaces

Polyetheretherketone (PEEK) is widely used in dentistry owing to its exceptional properties, including its natural appearance; however, existing surface treatment methods for bonding PEEK have limitations. Autofocus laser cutters, known for their precise engraving and cutting capabilities, offer potential for surface treatment of PEEK; thus, the objective of this study was to investigate the creation of laser groove structures on PEEK to enhance its bonding capability with dental resin cement. A dental computer-aided design and manufacturing system was used to fabricate PEEK samples, and three groove patterns (circle, line, and grid) were generated on PEEK surfaces, with air-abrasion used as the control group. The surface characteristics, cell viability, and bond strength were evaluated, and the data were statistically analyzed using one-way analysis of variance and post hoc Tukey's tests (α = 0.05). Laser-treated PEEK exhibited a uniform texture with a groove depth of approximately 39.4 µm, hydrophobic properties with a contact angle exceeding 90°, a surface roughness of 7.3-12.4 µm, consistent topography, and comparable cell viability compared with untreated PEEK. Despite a decrease in bond strength after thermal cycling, no significant intergroup differences were observed, except for the line-shaped laser pattern. These findings indicate that the autofocus laser cutter effectively enhances the surface characteristics of PEEK by creating a uniform texture and grooves, showing promise in improving bonding properties, even considering the impact of thermal cycling effects.

Effect of Various Airborne Particle Abrasion Conditions on Bonding between Polyether-Ether-Ketone (PEEK) and Dental Resin Cement

The effects of alumina particle size and jet pressure on the bond strength of polyetheretherketone (PEEK) were examined to determine the airborne particle abrasion parameters with minimal effects on PEEK and to achieve optimal bond strength, as a reference for future clinical use. An alumina particle with four particle sizes and three jet pressures was used to air-abrade PEEK. Surface roughness (R_a), morphology, chemical structure, and wettability were analyzed using a stylus profilometer, scanning electron microscope, X-ray diffractometer, and contact angle analyzer, respectively. The shear bond strength (SBS) of PEEK and dental resin cement was analyzed using a universal testing machine (n = 10). The failure modes and debonded fracture surfaces were observed using optical microscopy. Airborne particle abrasion increased the R_a and hydrophobicity of PEEK and deposited alumina residues. The SBS generally decreased after thermal cycling. A large particle size damaged the PEEK surface. The effects of different particle sizes and jet pressures on the SBS were only significant in certain groups. Adhesive failure was the main mode for all groups. Within the limitations of this study, 110 μm grain-sized alumina particles combined with a jet pressure of 2 bar prevented damage to PEEK, providing sufficient SBS and bonding durability between PEEK and dental resin cement.

Impact of material combinations and removal and insertion cycles on the retention force of telescopic systems

OBJECTIVES

A variety of dental materials are available for the fabrication of telescopic crowns. The aim was to investigate the impact of material combinations and removal and insertion cycles on their retention forces.

MATERIALS AND METHODS

CAD/CAM-fabricated cobalt-chromium-molybdenum (CoCr) and zirconia (ZrO₂) primary crowns were combined with polyetheretherketone (PEEK), polyetherketoneketone (PEKK), CoCr, and ZrO₂ secondary crowns (four combinations included PEEK/PEKK secondary crowns in a thickness of 0.5 mm bonded to the CoCr tertiary construction), resulting in 12 different material combinations: CoCr-PEEK; CoCr-PEKK; CoCr-ZrO₂; CoCr-CoCr; CoCr-PEEK 0.5; CoCr-PEKK 0.5; ZrO₂-PEEK; ZrO₂-PEKK; ZrO₂-ZrO₂, ZrO₂-CoCr; ZrO₂-PEEK 0.5; and ZrO₂-PEKK 0.5 (n = 15 pairings per material combination). Pull-off tests were performed with a universal testing machine initially and after 500, 5000, and 10,000 removal and insertion cycles in a mastication simulator. Descriptive statistics with the Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests were computed (α = 0.05).

RESULTS

The tested parameters, material combination, and removal and insertion cycles had significant impact on the retention force values (p < 0.001). An increase in removal and insertion cycles was associated with a decrease in retention forces within CoCr and ZrO₂ secondary crowns, regardless of the primary crown material. In contrast, PEEK and PEKK secondary crowns presented higher retention load values after 10,000 cycles than initially.

CONCLUSION

Different material combinations behaved differently after simulated removal and insertion regimens. This difference should be considered during treatment planning.

CLINICAL RELEVANCE

Telescopic crown systems should be made of materials with predictable retention forces that do not deteriorate with time. The implementation of new materials and technologies facilitates reproducibility and time-saving fabrication.

Bacterial Adhesion on Dental Polymers as a Function of Manufacturing Techniques

The microbiological behavior of dental polymer materials is crucial to secure the clinical success of dental restorations. Here, the manufacturing process and the machining can play a decisive role. This study investigated the bacterial adhesion on dental polymers as a function of manufacturing techniques (additive/subtractive) and different polishing protocols. Specimens were made from polyaryletherketone (PEEK, PEKK, and AKP), resin-based CAD/CAM materials (composite and PMMA), and printed methacrylate (MA)-based materials. Surface roughness (R_z; R_a) was determined using a laser scanning microscope, and SFE/contact angles were measured using the sessile drop method. After salivary pellicle formation, in vitro biofilm formation was initiated by exposing the specimens to suspensions of Streptococcus mutans (S. mutans) and Streptococcus sanguinis (S. sanguinis). Adherent bacteria were quantified using a fluorometric assay. One-way ANOVA analysis found significant influences (p < 0.001) for the individual parameters (treatment and material) and their combinations for both types of bacteria. Stronger polishing led to significantly (p < 0.001) less adhesion of S. sanguinis (Pearson correlation PC = -0.240) and S. mutans (PC = -0.206). A highly significant (p = 0.010, PC = 0.135) correlation between S. sanguinis adhesion and R_z was identified. Post hoc analysis revealed significant higher bacterial adhesion for vertically printed MA specimens compared to horizontally printed specimens. Furthermore, significant higher adhesion of S. sanguinis on pressed PEEK was revealed comparing to the other manufacturing methods (milling, injection molding, and 3D printing). The milled PAEK samples showed similar bacterial adhesion. In general, the resin-based materials, composites, and PAEKs showed different bacterial adhesion. Fabrication methods were shown to play a critical role; the pressed PEEK showed the highest initial accumulations. Horizontal DLP fabrication reduced bacterial adhesion. Roughness < 10 µm or polishing appear to be essential for reducing bacterial adhesion.

Methodology investigation: Impact of crown geometry, crown, abutment and antagonist material and thermal loading on the two-body wear of dental materials

OBJECTIVES

To investigate the impact of crown geometry, crown/abutment/antagonist material and thermal loading on the two-body wear of dental materials caused by chewing simulation.

MATERIALS AND METHODS

For the crown geometry, crowns (polymethylmethacrylate (PMMA), polyetheretherketone (PEEK) and silicate ceramic (SiO₂)) were milled with a flat, steep, or medium cusp inclination (CINC). For the crown/abutment material, crowns (PMMA, PEEK and SiO₂) were combined with PMMA, polymer-infiltrated-ceramic-network (PICN), cobalt-chrome alloy (CoCr) and natural teeth (ENAM) abutments. For the antagonist material, antagonists were fabricated from PICN, CAD/CAM resin composite (RECO), steatite (STEA), steel (STL) and ENAM and tested against flat specimens (substrates) made of veneering ceramic (VC). For thermal loading, the duration (30 s, 60 s, 120 s) and presence of temperature changes (37 °C versus 5 °C/55 °C) was varied. Material losses were determined by matching scanned specimens before and after aging (400,000 chewing cycles, 50 N, 1.3 Hz). Martens parameters were determined for the antagonists/substrates. Data were analyzed using Kolmogorov-Smirnov-test, Kruskal-Wallis H, Scheffé-Post-Hoc-tests, pairwise comparisons, Bonferroni correction, one-way ANOVA, Mann-Whitney-U and Spearman rho.

RESULTS

PMMA crowns presented the highest and PEEK the lowest material losses. Flat CINC showed the lowest material losses for PEEK and SiO₂ crowns. CoCr and ENAM abutments presented material losses in the same range. Antagonist and cumulative material losses for RECO and ENAM were similar. Thermal loading did not influence material losses.

SIGNIFICANCE

Crown geometry influences the crown and antagonists wear, with an increased cusp inclination entailing increased wear. For in vitro set-ups, CoCr abutments and RECO antagonists present valid alternatives to natural teeth. For polymers, in vitro chewing simulations may be performed at a constant temperature (37 °C).

Bonding and Thermal Cycling Performances of Two (Poly)Aryl-Ether-Ketone (PAEKs) Materials to an Acrylic Denture Base Resin

Poly(aryl–ether–ketone) materials (PAEKs) are gaining interest in everyday dental practices because of their natural properties. This study aims to analyze the bonding performance of PAEKs to a denture acrylic. Testing materials were pretreated by grinding, sandblasting, and priming prior to polymerization with the denture acrylic. The surface morphologies were observed using a scanning electron microscope and the surface roughness was measured using atomic force microscopy. The shear bond strength (SBS) values were determined after 0 and 2500 thermal cycles. The obtained data were analyzed using a paired samples t-test and Tukey’s honestly significant difference (HSD) test (α = 0.05). The surface characteristics of testing materials after different surface pretreatments showed obvious differences. PAEKs showed lower surface roughness values (0.02–0.03 MPa) than Co-Cr (0.16 MPa) and zirconia (0.22 MPa) after priming and sandblasting treatments (p < 0.05). The SBS values of PAEKs (7.60–8.38 MPa) met the clinical requirements suggested by ISO 10477 (5 MPa). Moreover, PAEKs showed significantly lower SBS reductions (p < 0.05) after thermal cycling fatigue testing compared to Co-Cr and zirconia. Bonding performance is essential for denture materials, and our results demonstrated that PAEKs possess good resistance to thermal cycling fatigue, which is an advantage in clinical applications. The results imply that PAEKs are potential alternative materials for the removable of prosthetic frameworks.