Model-Based Cost-Effectiveness of Direct Restorations: Amalgam Dominates

A phase-down of dental amalgam use has been mandated and the feasibility of its phase-out in England by 2030 is being explored. Amalgam use in English National Health Service (NHS) care still predominates for posterior restorations, though access to this care is increasingly limited. The objective of this study was to quantify the relative long-term costs and consequences of amalgam versus composite direct posterior restorations in adult permanent teeth in the English NHS setting.

A microsimulation model of restoration failure and reintervention was constructed and parameterised in TreeAge Pro, based on a review of the literature. It extrapolated costs and outcomes of directly restoring cariously-cavitated lower premolar teeth in 10 000 18-year-old English NHS patients with amalgam and composite restorations over a lifetime-horizon. Discounting of 3.5% was applied to costs and outcomes. An extended medical-sector perspective with societal considerations was taken. Deterministic and probabilistic sensitivity analyses were performed.

Amalgam robustly dominated conventional and bulk-fill composite restorations, being less costly over a lifetime from patient (£70) and funder perspectives (£34), with the restoration and tooth surviving significantly longer (4-years; 12-years non-discounted). Amalgam also incurred reduced numbers of visits (1), treatment time (43-min), and laboratory costs (£8) for fixed and removable prosthodontics over a lifetime. Time until a direct restoration was no longer possible was significantly higher for amalgam than composite (6-years; 17-years non-discounted).

The model showed good internal and external validity, accurately predicting tooth survival following restoration in relation to long-term NHS claims data. Without considerable educational change to upskill clinicians and health service change, an amalgam phase-out in England will likely have significant lifelong impacts on restoration and tooth survival and costs for all stakeholders, whilst reducing societal productivity and exacerbating already existing issues of limited access to care and socio-economic inequalities.