Fatigue Loading Test on Screw-Retained Lithium Disilicate Crowns Adhesively Cemented on Titanium Abutment

Abstract

The aim of this study was to assess the mechanical behavior and the microleakage of crown abutments made of lithium disilicate (LDS), adhesively bonded to preconditioned titanium bonding base under dynamic loading considering the type of teeth incisors, premolars, and molars. Thirty-three monolithic LDS implant supra-structures, representing a copy of natural tooth morphology (central incisor, second premolar, or first molar) were fabricated and bonded to titanium bases, screw-retained on the implant, and subjected to dynamic loading of 250,000 loading cycles at 2 Hz. After mechanical cycling, specimens were immersed in 5% methylene blue solution for 24 h at 37 °C. Microleakage was evaluated under magnification. The presence or absence of the following parameters were also evaluated: abutment screw deformation, abutment deformation, crack or craze line on the ceramic structure, adhesive failure between titanium base and ceramic superstructure, failures in ceramic superstructure or titanium base, and remaining cement around titanium base and ceramic superstructure. Considering the type of teeth, there are eight defects in relation to the group of central incisors, whereas the group of first molars accounts for seven defects. The second premolar is the worst performer with eleven defects. Significant accumulation of dye was registered in all teeth groups, i.e., grade 2 (staining around hexagonal area of the connection), according to the applied scale. Failure of hybrid abutments could be related to the correct seal between the titanium base and the ceramic restorations. The type of teeth could also be related to the presence of failures.