Survival rate of approximal-ART restorations using a two-layer technique for glass ionomer insertion

Good survival rates (SR) have been reported for occlusal-atraumatic restorative treatment (ART) restorations but not for approximal-ART restorations. The high-viscosity consistency of the glass ionomer cement (GIC) may lead to its incorrect adaptation into the cavity and thus to failure of the restoration. Because the use of a flowable GIC layer seemed to improve its adaptation in approximal restorations in vitro, we evaluated whether the use of an intermediate flowable GIC layer would improve the SR of approximal-ART restorations. A total of 208 children (6-7 years old) with at least one occluso-proximal carious lesion in a primary molar were selected and randomly allocated to two groups: G1, conventional technique, one-layer GIC (powder/liquid ratio 1:1); and G2, two-layer technique, consisting of a first layer of GIC with a flowable consistency (powder/liquid ratio 1:2) and a second layer of a regular consistency. Restorations were made by final-year students and evaluated after 1, 6, 12 and 18 months. Restoration survival was evaluated using Kaplan-Meier survival and logrank test. Poisson regression analyses (alpha = 5) were used to verify the influence of factors such as insertion technique, restoration surface and operators. The overall SR of the restorations after 18 months was 68 %. There was no difference in SR between the techniques, neither did the other factors influence the SR. Over 18 months, the use of an intermediate flowable GIC layer in approximal-ART restorations does not improve the restoration survival. This study suggests that the two-layer technique is not the answer for increasing approximal-ART restoration longevity.