In vitro study of retention forces in traditional and PEEK milled ball attachments with two retentive caps

This in-vitro study evaluated the retention forces of traditional metal ball attachments compared with PEEK-milled ball attachments, combined with either nylon or PEEK retentive caps. A total of 40 samples were equally divided into four groups: Group I (metal ball with nylon cap), Group II (metal ball with PEEK cap), Group III (PEEK ball with nylon cap), and Group IV (PEEK ball with PEEK cap). Retention was measured using a Testometric machine at five intervals: initial removal (T0), and after 1 (T1), 6 (T2), 12 (T3), and 24 (T4) months of simulated aging. Statistical analysis was performed using one-way ANOVA and Bonferroni tests (α = 0.05). Results showed that groups with PEEK caps (Groups II and IV) demonstrated significantly higher retention values compared with nylon-cap groups (Groups I and III) at most time points, although all groups exhibited a progressive reduction over time. The use of PEEK as both ball attachment and retentive cap may provide improved long-term retention compared with conventional metal/nylon systems; however, further clinical studies are required to validate these in-vitro findings.