Improving the Quality of Dentistry

A randomised controlled trial comparing oral hygiene advice and periodontal instrumentation for the prevention and management of periodontal disease in dentate adults attending dental primary care. 


Gum disease is the most common oral disease affecting adults and can lead to tooth loss.  It is largely a preventable disease, however, there is uncertainty on how best to maintain good oral health and prevent this disease in adults.  Effective home plaque control by tooth brushing and flossing and removal of risk factors such as calculus by the dentist are considered necessary for good periodontal health and prevention of disease. Currently oral health hygiene advice (OHA) is provided in an ad hoc way and there is some evidence that a more personalised approach might be more effective.  Periodontal instrumentation (commonly called ‘scale and polish’) is usually performed as part of routine 6 month check-up.  However there is conflicting evidence that the 6-monthly periodontal instrumentation (PI) has the desired effect.  The estimated cost to the NHS and patients is at least £220M and for the NHS it represents approximately 10% of annual dental treatment expenditure and it is included in 45% of all course of NHS dental treatment.  This trial looks at the effectiveness and frequency required of OHA and PI.  Participants will be randomly allocated to one of three different PI groups (no PI; 6 monthly PI; 12 monthly PI).  It also looks at whether these interventions are worthwhile uses of resources for both the NHS and patients.  Each participant will also have a 50% chance of receiving either routine or personalised OHA dependent upon the training their dentist received.  Evidence for policy makers, healthcare workers and patients on the type of OHA and frequency of PI could be associated with an improvement in periodontal health and reduction in cost to society.

This is a UK Collaborative Study funded by the NIHR HTA Programme.

Status Update:

The IQuaD study has now closed and the results were published in 2018 in the NIHR HTA Journal (link here): (

The trial recruited 1877 participants from 63 dental practices in England and Scotland. Many thanks to all who took part and helped us answer this important research question.




Trial staff login · Public information

School of Dentistry, University of Dundee

Health Services Research Unit, University of Aberdeen