Durability of extensive Class II open-sandwich restorations with a resin-modified glass ionomer cement after 6 years

To evaluate the durability of a modified open-sandwich restoration utilizing a resin-modified glass ionomer cement (RMGIC) in large cavities.

268, mostly extensive, Class II Vitremer/Z100 restorations were placed in 151 patients. 47% of the restorations were placed in patients considered as caries-risk patients. Six experimental groups, differing from each other in thickness of RMGIC layer and preconditioning, were evaluated at baseline and annually during 6-7 years according to modified USPHS criteria.

After 6 years, 220 restorations were evaluated. 42 failures (19%) were observed. The most frequent reasons for failure were material fracture (n = 11), tooth fractures (n = 9) and secondary caries (n = 10). Non-acceptable proximal dissolution of the RMGIC was seen in six restorations. Significantly more failures, but similar dissolution of the RMGIC, were recorded in high caries risk patients. No differences were seen between the experimental groups or between restorations with thick or thin RMGIC layer. 160 restorations were also evaluated at 7 years. Another 13 failures were observed, eight with non-acceptable dissolution, three secondary caries and two fractures. It can be concluded that the modified open sandwich restoration showed an acceptable durability for the extensive restorations evaluated. An accelerating dissolution of the RMGIC was observed at the end of the study.