Evaluation of retention for two different designs of digitally fabricated extracoronal attachments after 1 year of simulated aging

Abstract

Objective To assess changes in dislodging forces for the OT-Cap and OT-Cap Tecno attachment-retained partial dentures throughout 1 year of simulated aging. Patients and methods Fourteen three-dimensional-printed class II mandibular models with last premolars prepared to receive splinted crowns with computer-assisted designing/computer-assisted manufacturing extracoronal attachment were divided into two groups; group I: seven partials retained by OT-Cap attachment and group II: seven partials retained by OT-Cap Tecno attachment. Dislodging forces were measured at baseline (T0), then after; 60 000 cycles of chewing simulation plus 270 cyclic dislodgements (T1), 120 000 cycles of chewing simulation plus 540 cyclic dislodgements (T2), and 240 000 cycles of chewing simulation plus 1080 cyclic dislodgements (T3). Results The independent t test revealed a nonsignificant difference between the mean value of initial retention for each group and the manufacturer specifications. It also revealed that group II exhibited; significantly higher mean values of retention at T1, T2, and T3 with P values (P = 0.002, P < 0.001, and P = 0.016), and lower mean values of retention loss at 0–3 and 0–6 intervals with P values (P < 0.001 and P = 0.011), but, higher mean values of retention loss at the 6–12 interval (P < 0.001). As revealed by repeated-measures analysis of variance; the time-dependent loss of retention was expressed as: 0–3 months more than 3–6 months more than 6–12 months for the OT-Cap group (difference was significant between T2 and T3; P < 0.05), and as; 0–3months less than 3–6 months less than 6–12 months for Tecno group (P < 0.05). Conclusion The precision Tecno attachment offered higher and more durable retention and more uniform retention behavior than its semiprecision counterpart.