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 (T 1 ), 120 000 cycles of chewing simulation plus 540 cyclic dislodgements (T 2 ), and 240 000 cycles of chewing simulation plus 1080 cyclic dislodgements (T 3 ). 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 T 1 , T 2 , and T 3 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 T 2 and T 3 ; 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.