The INTERVAL trial, funded by NIHR HTA, is a UK multi-centre randomised controlled trial evaluating the effectiveness and cost effectiveness of three dental recall strategies, including one advocated by the recent NICE guidance, on maintaining oral health.

An NIHR-HTA funded feasibility phase started in June 2009 and recruited across 10 dental practices in the UK. After the initial 18 month feasibility study, the trial continued to full recruitment of 2372 participants across 50 dental practices.

The primary outcome is the mean proportion of site bleeding on probing at 4 years follow-up.

The INTERVAL trial is led jointly by Professor Jan Clarkson and Professor Nigel Pitts from the University of Dundee.

For more information please see the INTERVAL study website

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Craig Ramsay;




Jan E. Clarkson, Nigel B. Pitts, Debbie Bonetti, Dwayne Boyers, Hazel Braid, Robert Elford, Patrick A. Fee, Ruth Floate, Beatriz Goulão, Gerry Humphris, Ian Needleman, John D. T. Norrie, Fiona Ord, Marjon van der Pol, Craig R. Ramsay, David N. J. Ricketts, Helen V. Worthington, Linda Young and INTERVAL Trial Collaboration.  INTERVAL (investigation of NICE technologies for enabling risk-variable-adjusted-length) dental recalls trial: a multicentre randomised controlled trial investigating the best dental recall interval for optimum, cost-effective maintenance of oral health in dentate adults attending dental primary care. BMC Oral Health 2018, 18:135