OBJECTIVE: The objective of this randomized controlled prospective clinical trial was to evaluate the short time clinical behaviour of an altered resin modified glass-ionomer cement (RMGIC), which is claimed to possess bioactivity, in posterior restorations and to compare it intraindividually with a nanofilled resin composite.

METHODS: Totally 78 pairs Class II and 4 pairs Class I restorations were placed in 29 female and 38 male participants with a mean age of 58.3 years (range 37-86). Each patient received at random at least one pair of, as similar as possible, Class II or Class I restorations. In the first cavity of each pair, the modified flowable RMGIC (ACTIVA Bioactive; AB) was placed after phosphoric acid etching of the cavity and without adhesive, according to the instructions of the manufacturer. In the other cavity a well established nanofilled resin composite (CeramX; RC) with a single step self-etch adhesive (Xeno Select) was placed. The restorations were evaluated using slightly modified USPHS criteria at baseline, 6 and 12 months. Caries risk and parafunctional habits of the participants were estimated.

RESULTS: 158 restorations, 8 Class I and 150 Class II, were evaluated at the one year recalls. At baseline two failed restorations were observed (2AB), at 6 months six failures (5AB, 1RC) and at 12 months another thirteen failed restorations were observed (12AB, 1RC). This resulted in annual failure rates of 24.1% for the AB and 2.5% for RC (p<0.0001). The main reasons for failure for AB were lost restorations (5), postoperative symptoms (4) and secondary caries (3). Do to the unacceptable very high one-year failure frequency, the clinical study was stopped and no further evaluation will be performed.

SIGNIFICANCE: The use of the AB restorative in Class II cavities, applied as instructed by the manufacturer after a short phosphoric acid pretreatment but without adhesive system, resulted in a non-acceptable very high failure frequency after a one year period. Further studies should be conducted using a bonding agent.