Peel Bond Strength between 3D-printing Tray Materials and Elastomeric Impression/Adhesive Systems: A Laboratory Study

Abstract

The present study aimed to evaluate the bonding between three 3D-printing custom tray materials and three elastomeric impression/adhesive systems by peel test. The peel bond strength of the 3D-printed custom tray materials was compared with that of a conventional light-curing resin.

CAD-designed test blocks were printed by stereolithography (SLA), digital light processing (DLP), and fused filament fabrication (FFF) using the corresponding tray materials Dental LT, FREEPRINT tray, and polylactide (PLA), and the reference test blocks were conventionally fabricated with a light-curing resin (n = 12). Through SEM analyses and roughness measurements, the surface topographies of the four tray materials were investigated qualitatively and quantitatively. The force at failure in the peel test was recorded to calculate the bond strength between each tray material and impression/adhesive system. The failure mode and rupture site were identified by comparatively examining the peeled surfaces of tray and impression material using a microscope.

The result showed that Dental LT had a smooth surface with the best surface finish. Surface textures could be found on both surfaces of FREEPRINT tray and PLA, but the texture orientations of the two were opposite and perpendicular to each other. The reference light-curing resin exhibited a porous surface with numerous valleys and few peaks. The four tray materials did not statistically differ in peel bond strength with VSXE and PE, but PLA and reference showed higher peel bond strength with VPS than Dental LT and FREEPRINT tray. For bonding with Dental LT, FREEPRINT tray and reference, the peel bond strength of VSXE and VPS showed no significant difference, but both were higher than that of PE. For bonding with PLA, VPS showed the highest peel bond strength, followed by that of VSXE, and the peel bond strength of PE was the lowest. For peeling from VSXE and VPS, the mixed failure ratios of PLA and reference were higher than those of Dental LT and FREEPRINT tray. For peeling from PE, the failure modes of the four tray materials were all mostly adhesive failure. Cohesive failures could only be found in the VSXE groups. The rupture site of adhesive failure in all groups was partly at the adhesive-impression material interface and partly within the adhesive, but never at the adhesive-tray material interface.

In summary, a good chemical compatibility between the 3D-printed tray materials and the adhesives was achieved. The surface topographies of the tray materials influenced the peel bond strength, but only the roughness parameter dales void volume (Vvv) could be partly related to the peel bond strength. The 3D-printed tray materials could be good alternatives to the conventional light-curing resin when the VSXE or PE impression/adhesive system is used. For bonding with VPS impression/adhesive system, PLA seems an ideal tray material, whereas Dental LT and FREEPRINT tray may need further surface roughening.