[PPS-O-4] Effect of different surface treatments on the bond strength between light-cure hard chairside relining material and CAD/CAM milled denture base material
[Abstract]
[Objective]
Novel light-cure hard chairside relining material overcoming previous limitations such as restricted working time and difficulty in removal from undercut areas has been developed. However, its bond strength to denture base materials fabricated by CAD/CAM remains uncertain. This study aimed to compare the bond strength between milled and auto-polymerized denture base material to a light-cure hard chairside relining material, under different surface treatments.
[Method]
PMMA disk (Ivotion Base, Ivoclar Vivadent) was used in the experiments, while autopolymerizing resin (Fit Resin, Shofu) poured into disk-shaped silicone moulds served as control. Surface of each disk specimen, milled into dimension of 15 x 15 x 10 mm, was wet-polished with 500-grits abrasive paper and divided into 3 groups (n=8): no treatment (NT), sandblasting (SB) with 50 μm Al2O3 and bur roughening (BR) with flame-shaped crosscut carbide bur (7NF, Shofu). Relining procedure was performed with light-cure hard chairside reliner (HIKARELINER, Tokuyama Dental) and light-curing device (Portalite, Tokuyama Dental). After water storage at 37°C for 24 hours, tensile test with universal test machine (AG-Xplus, Shimadzu) and fracture mode analysis at 100x magnification (VHX-1000, Keyence) were performed for 48 specimens. Bond strength was analyzed using two-way ANOVA with post-hoc Tukey tests, considering surface treatment and material as factors (α = 0.05).
[Results and Discussion]
Experimental groups showed significantly lower bond strength than controls (p<0.05). Sandblasted groups exhibited significantly higher bond strength than nontreated and bur-roughened groups (p<0.05). While adhesive failure was predominantly observed, control groups with surface treatments primarily displayed cohesive failure. The adhesion process initiates as adhesive dissolves the outer layer of denture base, facilitating deeper penetration for the reliner. Because this process is also influenced by the cross-linking degree of polymers, reduced bond strength observed in milled PMMA disks might stem from its cross-linked polymer chains, in contrast to linear chains in auto-polymerized resin(1). Under the limited conditions, it is concluded that the bond strength of CAD/CAM material is clinically acceptable and can be improved by sandblasting.
[References]
1) Koseoglu M, Tugut F, Akin H. Tensile bond strength of soft and hard relining materials to conventional and additively manufactured denture-base materials. J Prosthodont 2023; 32
[Objective]
Novel light-cure hard chairside relining material overcoming previous limitations such as restricted working time and difficulty in removal from undercut areas has been developed. However, its bond strength to denture base materials fabricated by CAD/CAM remains uncertain. This study aimed to compare the bond strength between milled and auto-polymerized denture base material to a light-cure hard chairside relining material, under different surface treatments.
[Method]
PMMA disk (Ivotion Base, Ivoclar Vivadent) was used in the experiments, while autopolymerizing resin (Fit Resin, Shofu) poured into disk-shaped silicone moulds served as control. Surface of each disk specimen, milled into dimension of 15 x 15 x 10 mm, was wet-polished with 500-grits abrasive paper and divided into 3 groups (n=8): no treatment (NT), sandblasting (SB) with 50 μm Al2O3 and bur roughening (BR) with flame-shaped crosscut carbide bur (7NF, Shofu). Relining procedure was performed with light-cure hard chairside reliner (HIKARELINER, Tokuyama Dental) and light-curing device (Portalite, Tokuyama Dental). After water storage at 37°C for 24 hours, tensile test with universal test machine (AG-Xplus, Shimadzu) and fracture mode analysis at 100x magnification (VHX-1000, Keyence) were performed for 48 specimens. Bond strength was analyzed using two-way ANOVA with post-hoc Tukey tests, considering surface treatment and material as factors (α = 0.05).
[Results and Discussion]
Experimental groups showed significantly lower bond strength than controls (p<0.05). Sandblasted groups exhibited significantly higher bond strength than nontreated and bur-roughened groups (p<0.05). While adhesive failure was predominantly observed, control groups with surface treatments primarily displayed cohesive failure. The adhesion process initiates as adhesive dissolves the outer layer of denture base, facilitating deeper penetration for the reliner. Because this process is also influenced by the cross-linking degree of polymers, reduced bond strength observed in milled PMMA disks might stem from its cross-linked polymer chains, in contrast to linear chains in auto-polymerized resin(1). Under the limited conditions, it is concluded that the bond strength of CAD/CAM material is clinically acceptable and can be improved by sandblasting.
[References]
1) Koseoglu M, Tugut F, Akin H. Tensile bond strength of soft and hard relining materials to conventional and additively manufactured denture-base materials. J Prosthodont 2023; 32