Bond strength of denture teeth to denture bases in CAD/CAM-milled, printed, and conventional fabrication techniques

This in-vitro study examined the bond between denture teeth (milled, printed, and prefabricated) and milled, printed, and autopolymerized denture bases.

In total, 88 specimens (11 groups, n = 8 per group) of denture teeth and denture base resins were fabricated using systems of three different manufacturers (Vita Zahnfabrik, Ivoclar Vivadent, and Formlabs). The groups consisted of combinations of six different teeth, five different denture base materials, and four different adhesive bonding options. Teeth were either printed, milled, or prefabricated, while denture bases were either conventionally polymerized, milled, or printed. In addition, two dentures were milled from industrially prepolymerized blocks. After 24 hours of storage in distilled water, all specimens were loaded to failure to determine fracture forces. The fracture pattern was classified according to adhesive, cohesive, and mixed failures. Statistical analysis was performed using one-way analysis of variance and the Bonferroni test for post-hoc analysis. The level of significance (α) was set to .05.

Mean fracture forces ranged between 34.6 N and 649.3 N. The monobloc dentures Formlabs (459.0 ± 82.5 N) and Ivoclar (649.3 ± 32.3 N) featured the significantly highest fracture forces (P .001). For adhesively luted teeth, the conventional base-conventional tooth group showed the highest bond strength (289.5 ± 44.3 N), while the printed base-printed tooth group had the lowest (34.6 ± 12.7 N). The milled base group showed intermediate values (236.5 ± 56.4 N).

Bond strength between denture teeth and denture base depends on the fabrication process. Monolithic systems demonstrated optimal bond strength. Among all other combinations, the conventionally polymerized denture base combined with prefabricated teeth showed the best results. Prefabricated teeth and milled teeth in combination with milled denture bases showed similarly good results. Printed denture bases in combination with prefabricated, milled, and printed teeth showed reduced and variable bond strength. A precise bonding protocol is recommended to ensure optimal bonding of different systems.