The effect of different height titanium base abutments on the internal fit of a zirconia crown

Background and objectives. This in vitro study aimed to evaluate the effect of titanium base abutment height on the internal fit of CAD/CAM-fabricated zirconia crowns. Achieving a precise internal fit is critical to the long-term success of implant-supported restorations, yet limited data exist regarding how abutment height may influence this parameter. Materials and methods. Twenty implant analogues made of Grade 4 titanium (diameters: 4.5 mm and 3.75 mm; lengths: 12 mm and 13 mm) and twenty titanium base abutments (diameter: 3 mm) with two different sulcular heights (6 mm and 4 mm), along with their corresponding scan bodies, were selected. The specimens were divided into two groups of 10 each. Group A employed Dentium® scan bodies and analogues with 6 mm abutment height, while Group B used SGS® scan bodies and analogues with 4 mm abutment height. Crown design and milling were performed using a standardized CAD/CAM workflow. Internal fit was assessed using the digital silicone replica technique and 3D analysis with Geomagic Control X software, both before and after thermocycling. Mechanical performance was evaluated by measuring removal torque values (RTVs) before and after cyclic loading. Results. There were no statistically significant differences in internal fit between the two groups, both before (p = 0.605) and after thermocycling (p = 0.800). Similarly, no significant differences were found in pre- and post-loading RTVs between groups (p > 0.05). Conclusion. The findings of this research suggest, with certain caveats, that titanium base abutments may serve as a viable alternative to standard dental implant restoration procedures. Careful selection and customization of the abutment height should be tailored to the specific clinical case, taking into account various factors such as crown dimensions, patient-specific anatomical considerations, and the functional demands of the restoration.