Bonding strength and fatigue survival of conventional, additive and subtractive complete dentures

This study evaluated the bonding strength, fatigue survival, and fracture modes of dentures fabricated through conventional, additive (SLA/DLP), and subtractive CAD/CAM workflows to test their clinical durability after simulated oral ageing. Eight denture base-tooth combinations (n = 8 per group) were produced using either heat-polymerised PMMA, additively manufactured resins (Formlabs Denture Base LP or Voco V-Print Dentbase) or subtractively milled PMMA (Voco CediTec DB). Prefabricated (VITA Vionic) or CAD/CAM-fabricated denture teeth were then bonded. Surface roughness was quantified using laser scanning microscopy and the degree of conversion using Raman spectroscopy. The specimens underwent hydrothermal ageing with dynamic loading (1.2 million cycles at 5 °C/55 °C) followed by quasi-static shear fracture testing and fracture mode analysis. The conventional fabricated cast-on samples achieved the highest mean fracture load both before (445.7 ± 49.2 N) and after aging (411.7 ± 45.7 N) with 100% survival. Additive workflows (SLA/DLP) groups showed cohesive failures pre-aging; however, the DLP workflow demonstrated a 57% strength reduction post-aging (p = 0.0057) and 87.5% survival. Subtractive groups had the lowest survival rates (50–62.5%), significant strength losses (p < 0.05), and predominantly adhesive failures at the tooth-base interface. Ageing significantly affected bond strength in selected additive and subtractive groups (p < 0.05), whereas the conventional cast-on group remained unaffected. Conventional heat-polymerized PMMA bonded to prefabricated teeth remains the benchmark for denture fabrication. Additive CAD/CAM workflows approach similar performance, whereas subtractive methods require further optimization to improve bond stability under hydrothermal fatigue.