Effect of Crown Height Space and Abutment Configuration on the Maximum Recorded Load of Implant-Supported Monolithic Zirconia Crown Assemblies

This in vitro study evaluated the effects of crown height space (CHS) and abutment configuration on maximum recorded load and described post-test damage in implant-supported monolithic zirconia crown assemblies. Sixty specimens were assigned to six groups (n = 10) combining Ti-base or multi-unit configurations with nominal CHS levels of approximately 13.5, 15.5, or 17.5 mm. After 200,000 thermomechanical aging cycles at 50 N with thermal cycling between 5 °C and 55 °C, specimens underwent eccentric vertical loading on the buccal incline of the functional cusp using a 4 mm spherical tip at 1 mm/min. The primary outcome was maximum recorded load (global peak load), not the onset of irreversible damage. Two-way ANOVA indicated a CHS effect (p = 0.012), but no significant effect of abutment configuration (p = 0.128) or interaction (p = 0.627). The CHS effect persisted in the HC3 analysis (p = 0.043). The lowest versus highest CHS comparison remained significant in heteroscedasticity-sensitive analyses; the lowest-versus-intermediate comparison depended on analytical approach. Four zirconia crown fractures occurred in the lowest-CHS Ti-base group; other post-test damage predominantly involved prosthetic connection components. Within these laboratory conditions, CHS influenced assembly-level maximum recorded load without establishing a continuous or linear relationship.