IADR Abstract Archives
CAD/CAM-Milled and 3D-Printed Monolithic Zirconia Crown Retention
Objectives: To determine retention of monolithic zirconia crowns adhesively luted onto different tooth-preparation configurations with varying levels of macro-retention and to test retention of an experimentally developed micro-retentive design at the inner restoration side of 3D-printed monolithic zirconia crowns.
Methods: Sixty recently extracted human maxillary molars were prepared following three tooth-prep designs with different macro-retention level: (1) no macro-retention (flat surface); (2) prep with a 2-mm abutment height; (3) prep with a 4-mm abutment height. The preps were digitally scanned to design the crowns, enabling also to measure the whole prep area and the axial wall friction area. Thirty-six crowns (n=12) were milled using a chairside Cerec MC XL milling unit (Dentsply Sirona) and 24 crowns were 3D-printed using an inkjet XJet Carmel 1400C (XJet) 3D-printer. Twelve of the printed crowns received an inner surface micro-retention design. Crowns were adhesively luted using the self-etch adhesive-assisted composite cement Panavia V5 (Kuraray Noritake) and were pulled off from the tooth abutment using a material tester (5848 MicroTester, Instron). The pull-off force was recorded with crown retention determined by dividing it by the total surface area (N/mm2). Statistical significance was assessed with the independent-samples Kruskal-Wallis test (α=.05) with Bonferroni correction for multiple tests.
Results: The pull-off force significantly increased with increasing prep-surface area, while no difference was found by increasing friction area. No significant difference in crown retention was found between the milled and XJet-printed full crowns, while the 3D-printed micro-retentive inner surface design significantly increased crown retention when compared to the milling group.
Conclusions: Although a larger surface area increased crown retention, a larger friction area did not increase crown retention. Incorporating a micro-retentive inner surface design within the walls of 3D-printed crowns effectively increased crown retention.
Methods: Sixty recently extracted human maxillary molars were prepared following three tooth-prep designs with different macro-retention level: (1) no macro-retention (flat surface); (2) prep with a 2-mm abutment height; (3) prep with a 4-mm abutment height. The preps were digitally scanned to design the crowns, enabling also to measure the whole prep area and the axial wall friction area. Thirty-six crowns (n=12) were milled using a chairside Cerec MC XL milling unit (Dentsply Sirona) and 24 crowns were 3D-printed using an inkjet XJet Carmel 1400C (XJet) 3D-printer. Twelve of the printed crowns received an inner surface micro-retention design. Crowns were adhesively luted using the self-etch adhesive-assisted composite cement Panavia V5 (Kuraray Noritake) and were pulled off from the tooth abutment using a material tester (5848 MicroTester, Instron). The pull-off force was recorded with crown retention determined by dividing it by the total surface area (N/mm2). Statistical significance was assessed with the independent-samples Kruskal-Wallis test (α=.05) with Bonferroni correction for multiple tests.
Results: The pull-off force significantly increased with increasing prep-surface area, while no difference was found by increasing friction area. No significant difference in crown retention was found between the milled and XJet-printed full crowns, while the 3D-printed micro-retentive inner surface design significantly increased crown retention when compared to the milling group.
Conclusions: Although a larger surface area increased crown retention, a larger friction area did not increase crown retention. Incorporating a micro-retentive inner surface design within the walls of 3D-printed crowns effectively increased crown retention.