The influence of different plasma treatment conditions on the shear bond strength of three different Polyaryletherketones (PAEKs) and veneering composites

Abstract

In this study, the influence of different gaseous plasma surface treatments on shear bond strength of three different types of PAEKs (unfilled PEEK, ceramic filled, PEKK) to veneering composites was studied. 180 samples of each type of PAEK were milled and allocated in 9 different surface treatment groups; untreated (control), adhesive, acetylene, argon, nitrogen, oxygen air, ammonia, and a gas mixture of tetrafluoromethane and oxygen. Surface roughness measurements were made to ceramic PEEK to determine the suitable polishing protocol for standardization of surface roughness of all specimens before starting any surface treatment. In the control group, the bonding protocol started directly without any surface treatment. Opaquer was added and cured followed by addition of veneering composite resins then curing. In the adhesive group, the surface of PAEK specimens was conditioned with Visiolink primer followed by opaquer application then veneering composite in the same way as the control group. In plasma-treated group, the surfaces of PAEK specimens were treated with cold low-pressure plasma using various gases at constant parameters. This followed by the bonding of opaquer and veneering composite in the same way as the control group. After bonding, surface area measurements of composite resins were made. Thermocycling test was then done through repeated cycling between two temperatures (5 and 55 °C) and in between an adequate dwell time for 20 seconds to ensure the thermal adjustment of the specimens before exposure to another extreme thermal stress. After thermal cycling, macro shear bond strength testing was done to all specimens using a universal testing machine. The results showed that plasma generally improved the shear bond strength of PAEK to veneering composite regardless of the type of PEEK used. Acetylene was the most effective gas and showed a statistically significant increase in shear bond strength within each type of PEEK. Ammonia and gas mixture of tetrafluoromethane and oxygen showed severe adverse effects on the bond strength within each material. Unfilled PEEK was the most sensitive material to plasma surface reactions while PEKK was the most resistive one.