Effect of Surface Polishing on Physical Properties of an Occlusal Splint Material for Additive Manufacturing under Protection Gas Post-Curing Condition

Abstract

The aim of this study was to evaluate the effect of surface polishing as well as the post-curing atmospheres (air and nitrogen gas) on the physical properties of an occlusal splint material for additive manufacturing. Flexural strength, flexural modulus, Vickers hardness number (VHN), degree of carbon double bond conversion (DC), water sorption (WSP), and water solubility (WSL) were evaluated. Surface polishing significantly affected the evaluated properties. Regardless of the post-curing atmosphere, flexural strength, flexural modulus, VHN, and DC showed significantly higher values for the polished specimens when compared with the unpolished ones, while WSP and WSL were significantly lower for the polished specimens. Unpolished specimens post-cured at nitrogen gas showed significantly higher VHN and DC values. However, the effect of the post-curing at a nitrogen gas atmosphere was non-significant in polished specimens. The current results suggested that surface polishing plays a role in the physical properties of the evaluated occlusal splint material and can enhance all the evaluated properties regardless of the post-curing atmosphere. Meanwhile, the post-curing at a nitrogen gas atmosphere can enhance the VHN and DC but its effect is confined only to the surface layers, which can be removed during surface polishing.

Effect of ethylene oxide unit number in bis-EMA on the physical properties of additive-manufactured occlusal splint material

“…Although the superficial layer of the inner surface of the occlusal splint is rarely removed, that of the outer surface is occasionally removed by adjusting the occlusal contact and/or surface polishing. A previous study indicated that superficial layer removal enhanced the mechanical properties, including DC and water solubility, of the PMMA-based materials used in additive-manufactured occlusal splints [38].…”

Influence of Post-Curing in Nitrogen-Saturated Condition on the Degree of Conversion and Color Stability of 3D-Printed Resin Crowns

“…Although most studies of nitrogen-saturated post-curing modes suggest improved physical properties on surfaces, it is suggested that these advantageous effects are only restricted to the surface. If the post-cured surface was removed by a polishing procedure, there was no significant difference in microhardness or degree of conversion rate [ 21 ]. This might be obvious, since the nitrogen-saturated atmosphere is only in contact with the surface of the prosthesis.…”

“…Recently developed post-curing machines decrease the concentration of oxygen in the air by filling the curing chamber with nitrogen, and it has been reported that post-curing in a nitrogen-saturated condition can reduce the contact of oxygen radicals with the surface of 3D-printed resins and therefore improve their mechanical properties [ 14 , 16 , 17 , 18 ]. Also, many studies have demonstrated improvements in the surface characteristics of 3D-printed resins that are post-cured in nitrogen-saturated conditions [ 19 , 20 , 21 ]. However, no studies regarding the optical properties of 3D-printed resins post-cured under nitrogen-saturated conditions, such as color and translucency, have been reported so far.…”

Efficacy of Nitrogen Saturated Post-curing on Color Stability of Three-dimensional Printed Resin Crowns

“…Recently developed post-curing machines decrease the concentration of oxygen in the air by filling the curing chamber with nitrogen, and it has been reported that post-curing in a nitrogensaturated condition can reduce the contact of oxygen radicals with the surface of 3D-printed resins and therefore improve their mechanical properties [14,[16][17][18]. Also, many studies have demonstrated improvements in the surface characteristics of 3D-printed resins that are post-cured in nitrogen-saturated conditions [19][20][21]. However, no studies regarding the optical properties of 3D-printed resins post-cured under nitrogen-saturated conditions, such as color and translucency, have been reported so far.…”