Clinical Evaluation of Implant Suprastructures Depending on the Biomechanical Characteristics of the Materials Used
Authors: Stoeva Daniela , Filtchev Dimitar , Nikolova Neli , Pavlova Zhanina , Slavkov Svetoslav , Iliev Georgi 
Published: August 2022

The choice of an appropriate implant suprastructure, which should be made according to the individual characteristics of each patient, is a leading factor in achieving good aesthetic results. The aim of this study was to assess the clinical behavior of implant suprastructures according to functional, biological, and aesthetic criteria. Methods: The study enrolled 23 patients with a total of 27 implants in different areas of the oral cavity. The following groups were studied for a period of 1 year: Group A, the control group (monolithic implant crowns made of zirconium dioxide on a titanium base); Group B (monolithic implant crowns made of lithium disilicate with individualized (custom) titanium alloy abutment); and Group C (implant crowns made of zirconium dioxide with individualized titanium alloy abutment). The functional criteria included suprastructure fracture, crown fracture or chipping, screw fracture or loosening, faceting or wearing of the occlusal surface of the crown, articulation relations, and suprastructure fracture. The biological indicators included the probing pocket depth (PPD) and Mombelli et al.’s plaque index and bleeding on probing. The bone loss level was measured radiographically. Digital measurements of the bone loss level were performed when definitive prosthetics were placed and 1 year after. The platform of the implant was taken as a reference point. Two parallel lines ran distally and medially to the implant and descended to the level of the first thread, which was in contact with the bone. The aesthetic evaluation was based on Jempt’s papilla index and considered differences in the color of the peri-implant mucosa. The suprastructures were examined at 2 weeks and 1 year after the initiation of prosthetic treatment. Results: Regarding the functional criteria, no deviations from the reference range were registered in any of the study groups for both measurements. Radiography showed no bone loss in any of the study groups. Group B showed the best behavior regarding biological complications, followed by Group C. There was no plaque accumulation in Group B, but statistically significant amounts were found in Groups A (p = 0.08) and C (p = 0.01). Group B had the lowest bleeding index, but the differences between the groups were found to be insignificant during the observations at the one-year mark. On the vestibular side of the papillae, p = 0.39, while on the oral side, p = 0.35. The PPD measurements showed that there were statistically significant differences between the three groups when they were compared after the second week and after one year (p = 0.00). Jempt’s papilla height index showed the highest values in Group B, which increased by two times throughout the study period. The increase was statistically significant in Groups B and C, while the growth in Group A remained statistically insignificant (p = 0.10). The aesthetic indicator “Gingiva color around the restoration” showed mild margo gingivalis graying in Groups B and C. Conclusions: Individualized implant abutments made of titanium alloy and monolithic restorations made of lithium disilicate or zirconium dioxide have stable biomechanical behavior and may be the optimal choice for the prosthetic treatment of partial edentulousness. Because this study took place within a limited period of time, clinical trials with a longer follow-up period need to be carried out.