Proceedings of the International scientific and practical conference ―Science at the Frontier of Civilizations‖ (March 16-18, 2026) / Publisher website: www.naukainfo.com. – Helsinki, Finland, 2026. - 145 p.

50 implantation. An analysis of dental arch defects was performed in 110 patients included in the study groups: 60 individuals in Group 1 who had undergone radiotherapy, and 50 individuals in Group 2 with no history of radiotherapy. For the clinical characterization of partial secondary edentulism, the Kennedy classification was used, as it is one of the most widely applied classifications in prosthodontic dentistry and allows assessment of the anatomical structure of partial edentulism for further planning of prosthetic and implant treatment. Kennedy Class I includes bilateral distal extension defects in which posterior teeth are missing on both sides of the dental arch. Such defects are considered clinically complex because they lack distal support and create less favorable conditions for conventional prosthetic treatment. Kennedy Class II includes unilateral distal extension defects, in which posterior teeth are missing on one side of the dental arch. This type is also regarded as clinically complex, particularly when the defect is extensive. Kennedy Class III represents bounded edentulous spaces limited by natural teeth on both sides, which generally provide more favorable conditions for prosthetic rehabilitation. Kennedy Class IV includes a single anterior bounded edentulous area crossing the midline. Such defects have particular functional and aesthetic significance and require careful planning of restoration. In Group 1, bilateral distal extension defects (Kennedy Class I) were identified in 18 patients (30.00%), unilateral distal extension defects (Class II) in 20 patients (33.33%), bounded edentulous spaces (Class III) in 14 patients (23.33%), and anterior defects crossing the midline (Class IV) in 8 patients (13.33%). In Group 2, Kennedy Class I defects were detected in 11 patients (22.00%), Class II in 13 patients (26.00%), Class III in 18 patients (36.00%), and Class IV in 8 patients (16.00%). Thus, clinically more complex distal extension defects predominated in the group of patients after radiotherapy: the combined proportion of Kennedy Class I and II defects in Group 1 reached 63.33%, whereas in Group 2 it was 48.00%. In contrast, patients without a history of radiotherapy more frequently exhibited Kennedy Class III defects – 36.00% compared with 23.33% in Group 1.