Retention behavior and surface alterations of ball and TRI raptor unsplinted overdenture attachments after thermomechanical aging: an in vitro study

Abstract Background To compare the time-dependent retentive-force behavior and wear-related surface alterations of two unsplinted overdenture attachment systems, a ball attachment system and a TRI Raptor Smart Box system, after standardized thermomechanical aging. Methods In this in vitro study, a ball attachment system (clear and gray matrix inserts) and a TRI Raptor Smart Box system (purple, clear and pink inserts) were evaluated (n = 10 per subgroup). Custom specimen holders were fabricated to simulate attachment–matrix engagement. Artificial aging was performed in a thermocycling chewing simulator between 5°C and 55°C with simultaneous cyclic loading. Retentive-force measurements were obtained after 120, 720, 1440 and 2160 cycles, corresponding approximately to 1, 6, 12 and 18 months of clinical use. Pull-off force was measured using a microtensile testing device. Representative components were examined by scanning electron microscopy after the final aging interval. Results Retentive force decreased significantly over time in all subgroups. In the ball attachment system, the gray insert consistently showed higher retentive-force values than the clear insert. In the TRI Raptor Smart Box system, the purple insert showed the highest retentive-force values at 1, 6 and 18 months, with a transient crossover at 12 months, when the clear insert showed the highest mean value. The pink Raptor insert showed the lowest values overall. SEM demonstrated subgroup-specific wear-related surface alterations after cyclic aging. Conclusions Retentive-force loss was not uniform across the tested unsplinted overdenture attachment subgroups. Insert-specific material and design characteristics influenced retention behavior and may be relevant to attachment selection and maintenance planning in implant overdenture therapy.