In vitro bonding strength of denture teeth to denture base in CAD/CAM-milled, 3D-printed and conventional manufacturing processes

To investigate the survival rates and fracture resistance of dentures made from different teeth (milled, 3D-printed, fabricated), bases (milled, 3D-printed, pressed) and bonding combinations.

Specimens (11 groups, n = 8 per group) were fabricated from combinations with a denture tooth (anterior tooth 21) and a denture base material. The groups consisted of combinations of teeth (6x), denture base materials (5x) and adhesive bonding options (4x). The teeth were printed, milled or prefabricated. The denture base was produced conventionally or was milled or 3D-printed. Two dentures were milled from one industrially produced block. The dentures were subjected to thermal and mechanical loading (TCML) and subsequent fracture test. Statistics: ANOVA, Bonferroni-test, Kaplan-Meier survival, Pearson correlation; α = 0.05.

Mean loading cycles varied between 221,869 (8), 367,610 (11), 513,616 (6) 875,371 (3) and 9,000,030 (4). ANOVA revealed significant (p ≤ 0.001) different surviving cycles. Log Rank test showed significantly (p < 0.001) different loading cycles. Fracture force after TCML varied between 129.8 +/- 97.1 N (3) and 780.8 +/- 62.5 N (9). ANOVA comparison revealed significant (p < 0.001) different fracture loadings between the individual systems. Correlation was found between fracture force and loading cycles (0.587, p < 0.001).

Different survival rates and fracture forces were found for dentures made of different teeth (milled, 3D-printed, prefabricated), bases (milled, 3D-printed, pressed) and bonding combinations. Milled, pressed and prefabricated systems provided longer survival and fracture force than the other tested systems.

 Optimal tooth-base combinations can help to produce a denture that is stable and resistant during clinical application.