Clinical performance of posterior compomer restorations over 4 years

To clinically evaluate two polyacid-modified resin composites (Hytac and Dyract AP) for the restoration of posterior teeth over a 4-year period and to investigate accessible margins by light microscopy.

In a controlled prospective clinical study, 71 cavities (21 occlusal, 41 MO/OD, 9 MOD) in 30 patients were restored with compomers by three dentists. Thirty-eight restorations were placed with the combination OSB/Hytac, the same patients received 33 restorations with Prime&Bond 2.1/Dyract AP. Enamel margins of the cavities were etched with phosphoric acid. At baseline, after 12, 24, and 48 months, the restorations were examined by two independent investigators according to modified USPHS-criteria. Focusing on the 40 restorations available at all recalls, a semi-quantitative margin analysis was carried out at each recall using replicas and light microscopy at x130 magnification.

Twenty restorations were not investigated at the 4-year recall (drop-out). After 48 months, 11 restorations (Hytac: n = 8, Dyract AP: n = 3) had to be replaced due to tooth fracture (n = 4), gap formation (n = 5), and adhesive failure (n = 2). Forty restorations were still in function after 4 years (overall failure rate 16%; Hytac: 21%; Dyract: 9%). Between the recalls, statistically significant differences were detected for the criteria marginal integrity (Alpha dropping from 76% at baseline to 32% after 4 years), restoration integrity (Alpha ratings at baseline 99% vs. 40% after 4 years), and occlusion (100% vs. 24%). For the criteria surface roughness (from the 6-month recall) and anatomical shape (after 4 years), a significant difference between the materials was evident in favor of Dyract AP. Except gap-free margins, the predominant criterion in the microscopic analysis at baseline was marginal overhang (24%) and 30% negative step formation after 4 years.