Apart from complete failures, the important criterion for clinical success of crowns is the absence of complications.
The most frequent complication of polymer crowns seems to be delamination and fracture of non-reinforced crowns. For metal–ceramic crowns of the control group also, however, the number of delaminations was comparable with other data for chipping or facing of metal–ceramic restorations.
Regarding the effect of fibre reinforcement, this study revealed no clinically relevant effect of fibre reinforcement on the survival of posterior single crowns. Thus, the results of this study are in accordance with the conclusion of Behr et al.that single molar composite crowns do not benefit from fibre reinforcement.