Statement of problem
Studies that have analyzed the bond strength of resilient denture liners to milled
denture bases are sparse, and the authors are unaware of research that has investigated
the tensile bond strength of denture relining materials to 3D-printed denture bases.
The purpose of this in vitro study was to evaluate the tensile bond strength of both
hard and soft denture reline materials on denture bases fabricated by 3D printing
and computer-aided design and computer-aided manufacture (CAD-CAM) milling technology.
Material and methods
Injected, milled, and printed denture base specimens were fabricated (n=30) and bonded
to 5 different denture reline materials: soft chairside reline (Coe Soft and PermaSoft),
hard chairside reline (Tokuyama Rebase ii and Kooliner), and hard laboratory reline
(ProBase Cold). Specimens of each reline material were divided into 5 groups (n=10)
and were placed in distilled water for 24 hours before tensile testing. Maximum tensile
stress values before failure were recorded, and the failure mode was also determined.
The type of failure was analyzed by a scanning electron microscope. Statistics were
analyzed with 2-way ANOVA and multiple comparison tests (α=.05).
Overall, no statistically significant difference in tensile bond strength was found
in the injected, milled, and printed denture groups. However, the printed denture
base group demonstrated significantly lower values of tensile bond strength (P<.05) with PermaSoft, Tokuyama Rebase ii, and ProBase Cold groups than other denture
base groups (milled and injected). The milled denture bases had the highest mean value
of tensile bond strength with 4 of the 5 denture relining materials tested (Coe Soft,
PermaSoft, Tokuyama Rebase ii, and Kooliner). No statistically significant difference
(P>.05) was found among the injected, milled, and printed denture bases when relined
with Kooliner. When comparing the denture reline type, the lowest values were seen
with the soft chairside relining materials, and highest values with the hard laboratory
reline material. Among the modes of failure, adhesive failures were observed predominantly
with the printed denture base materials relined with soft chairside relining materials,
while cohesive and mixed modes of failure were found in the milled and injected denture
The printed denture bases had significantly lower tensile bond strength values than
the injection and milled denture bases with the PermaSoft, Tokuyama Rebase ii, and
ProBase Cold denture relines, while milled denture bases demonstrated the highest
values of tensile bond strength for all chairside relining groups. In addition, the
soft chairside relining materials showed the lowest tensile bond strength values regardless
of the denture processing method with respect to the denture base type (injected,
printed, and milled) compared with the hard relining materials.