Periodontal disease is the most common oral disease affecting adults. Effective self-care (tooth brushing and interdental aids) for plaque control and removal of risk factors such as calculus, by periodontal instrumentation (PI), commonly known as a "scale and polish", are considered necessary to prevent and treat periodontal disease.  Despite evidence of an association between sustained good oral hygiene and a low incidence of periodontal disease there is a lack of reliable evidence to inform clinicians of the relative effectiveness of different types of Oral Hygiene Advice (OHA).

This multi-centre trial, funded by the NIHR HTA Programme, aims to compare the effectiveness and cost effectiveness of theoretically based, personalised OHA or PI at different time intervals (no PI, 6 monthly PI or 12 monthly PI) or their combination to routine OHA, for improving periodontal health in dentate adults attending general dental practice.

Participating dentists will be cluster randomised to provide routine (current practice) or theory-based personalised (to the needs of the patient) OHA. A total of 1860 individual eligible patients will be randomised to no PI, 6 monthly PI or 12 monthly PI (310 to each group within each cluster of routine or personalised OHA randomised dentists). Clinical outcomes will be measured at baseline and at 3 years follow-up by trained outcome assessors and participants will also be followed-up by postal questionnaires sent annually.

The primary clinical outcome is gingival inflammation/bleeding on probing at the gingival margin measured by the Gingival Index of Loe.

The IQuaD trial is led by Professor Jan Clarkson based in the University of Dundee.

IQuaD closed to recruitment in August 2013 with 1877 participants recruited.    

For more information please see the IQuaD Study Website 


Anne Duncan;




Goulao, et al. Three behavior change theory- informed randomized studies within a trial to improve response rates to trial postal questionnaires. Journal of Clinical Epidemiology (2020) 122:35 

Duncan A, Bonetti, D, Clarkson J, Ramsay C on behalf of IQuaD Trial. Theory based response rate letter Intervention

Ramsay CR, Clarkson JE, Duncan A, Lamont TJ, Heasman PA, Boyers D, et al. Improving the Quality of Dentistry (IQuaD): A cluster factorial randomised controlled trial comparing the effectiveness and cost-benefit of oral hygiene advice and/or periodontal instrumentation with routine care for the prevention and management of periodontal disease in dentate adults attending dental primary care. Health Technol Assess 2018;22(38)

Jan E Clarkson, Craig R Ramsay, Paul Averley, Debbie Bonetti, Dwayne Boyers, Louise Campbell, Graham R Chadwick, Anne Duncan, Andrew Elders, Jill Gouick, Andrew F Hall, Lynne Heasman, Peter A Heasman, Penny J Hodge, Clare Jones, Marilyn Laird, Thomas J Lamont, Laura A Lovelock, Isobel Madden, Wendy McCombes, Giles I McCracken, Alison M McDonald, Gladys McPherson, Lorna E Macpherson, Fiona E Mitchell, John DT Norrie, Nigel B Pitts, Marjon van der Pol, David NJ Ricketts, Margaret K Ross, James G Steele, Moira Swan, Martin Tickle, Pauline D Watt, Helen V Worthington and Linda Young.  IQuaD dental trial; improving the quality of dentistry: a multicentre randomised controlled trial comparing oral hygiene advice and periodontal instrumentation for the prevention and management of periodontal disease in dentate adults attending dental primary careBMC Oral Health 2013, 13:58