Long-term behavior of double crown retained dentures with metal and metal-free secondary crowns and frameworks made of Vectris^sup ©^ on all-ceramic primary crowns: a prospective, randomized clinical trial up to 14 years

Objectives This prospective randomized clinical trial aimed to evaluate the long-term behavior of metal-free double crown retained dentures with secondary crowns and dental frameworks made of the fiber-reinforced composite Vectris© on all-ceramic primary crowns (IPS Empress 2©) over a period of up to 14 years and to subsequently evaluate patient satisfaction. For the control group, electroplated gold copings and metal frameworks were used. Materials and methods A total of 29 patients were treated with a total of 37 prostheses on 165 primary crowns. Of these 37 prostheses, 27 were allotted to the control group and 10 to the test group. The mean observation time was 91±57 months; patient satisfaction surveys were conducted over 77±59 months. Results Success rates in both groups were compared using Kaplan-Meier survival curves and log-rank test. Up to about 3 years, both types of prostheses exhibited similar success rates. Afterwards, a massive decrease in the Vectris© curve could be noted, whereas the metal curve dropped only slightly. This difference was also statistically significant (p=0.032361). There was a comparable susceptibility to damages in both groups: 88.9 % (control) and 90 % (test), respectively, of the prostheses had to be repaired within the period of investigation (p=0,121). Damages of the Vectris © secondary crowns could be detected significantly more often compared to the electroformed gold copings (p