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Eight‐year study on conventional glass ionomer and amalgam restorations in primary teeth

The aim of this randomized clinical study was to compare the longevity and the cariostatic effects of conventional glass ionomer and amalgam restorations in primary teeth placed in everyday practice in the Danish Public Dental Health Service. All restorations inserted during a 7‐month period by 14 clinicians in 2 municipalities were included in the study. The sample consisted of 515 conventional glass ionomer restorations and 543 amalgam restorations in 666 children aged between 2.8 and 13.5 years. The restorations were in contact with 592 unrestored surfaces in primary and permanent teeth. The study was terminated after 8 years, with 2% of the restorations in function and 7% patient dropouts. Fifty percent of the teeth restored with glass ionomer and 63% of those with amalgam were exfoliated with the restoration in situ, while 42% of the glass ionomer and 20% of the amalgam restorations had been repaired or replaced. Fracture of restoration, endodontic complication, and loss of retention were the major reasons for failure. The 50% survival time for glass ionomer restorations in all cavity types was 42 months, while the median survival time for amalgam restorations could not be estimated but exceeded 7.8 years (P<0.001). Progression of caries lesions on tooth surfaces adjacent to amalgam restorations required operative treatment on 30% of the teeth, while only on 16% of teeth adjacent to glass ionomer restorations. The 75% survival time was 40 months for surfaces in contact with glass ionomer compared to 25 months for surfaces in contact with amalgam (P=0.005). Multivariate analyses were performed in order to assess the influence of a number of factors on the longevity of restorations, occurrence of prevalent failures, and caries treatment of surfaces in contact with the restorations. Owing to the high frequency of failures of the conventional glass ionomer restorations, it was concluded that they are not an appropriate, universal alternative to amalgam for restorations in primary teeth, although they reduce caries progression and the need for operative treatment of adjacent surfaces.