Abstract: We included three randomised controlled trials (RCTs) involving 1358 participants. None of the studies provided useable data for the key outcomes of not having seen a dentist in the past year, not brushing teeth twice a day, chronic pain, clinically important adverse events, and service use. Data for leaving the study early and change in plaque index scores were provided. Oral health education compared with standard care When 'oral health education' was compared with 'standard care', there was no clear difference between the groups for numbers leaving the study early (1 RCT, n = 50, RR 1.67, 95% CI 0.45 to 6.24, moderate-quality evidence), while for dental state: no clinically important change in plaque index, an effect was found. Although this was statistically significant and favoured the intervention group, it is unclear if it was clinically important (1 RCT, n = 40, MD - 0.50 95% CI - 0.62 to - 0.38, very low quality evidence).These limited data may have implications regarding improvement in oral hygiene. Motivational interview + oral health education compared with oral health education Similarly, when 'motivational interview + oral health education' was compared with 'oral health education', there was no clear difference for the outcome of leaving the study early (1 RCT, n = 60 RR 3.00, 95% CI 0.33 to 27.23, moderate-quality evidence), while for dental state: no clinically important change in plaque index, an effect favouring the intervention group was found (1 RCT, n = 56, MD - 0.60 95% CI - 1.02 to - 0.18 very low-quality evidence). These limited, clinically opaque data may or may not have implications regarding improvement in oral hygiene. Monitoring compared with no monitoring For this comparison, only data for leaving the study early were available. We found a difference in numbers leaving early, favouring the 'no monitoring' group (1 RCT, n = 1682, RR 1.07, 95% CI 1.00 to 1.14, moderate-quality evidence). However, these data are problematic. The control denominator is implied and not clear, and follow-up did not depend only on individual participants, but also on professional caregivers and organisations - the latter changing frequently resulting in poor follow-up, but not a good reflection of the acceptability of the monitoring to patients. For this comparison, no data were available for 'no clinically important change in plaque index'. We found no evidence from trials that oral health advice helps people with serious mental illness in terms of clinically meaningful outcomes. It makes sense to follow guidelines and recommendations such as those put forward by the British Society for Disability and Oral Health working group until better evidence is generated. Pioneering trialists have shown that evaluative studies relevant to oral health advice for people with serious mental illness are possible.

Plain-language summary: We ran an electronic search in November 2015 for trials that randomised people with serious mental illness to receive either oral health advice, monitoring, or standard care. Three studies meeting the required standards were found and are included in this review. Key results The data available in the included trials suggests that participants receiving oral health education had statistically better plaque index scores than those not receiving oral heath education, but what this actually means clinically is unclear. The trials provided no information about such important issues as number of visits made to dentists or how many times teeth were brushed each day and if there were any potential adverse effects of oral health education. The review authors suggest that although there is currently no real evidence available from trials, it would make sense to follow the guidelines and recommendations put forward by the British Society for Disability and Oral Health working group regarding oral health care for people with mental health problems. Quality of the evidence The quality of evidence in the small number of trials available was low to moderate. There is currently a lack of good-quality evidence available from trials to aid in decision-making about the overall effectiveness of oral health advice for people with serious mental illness. More good-quality trials are required to gather better and more concrete evidence. Ben Gray, Senior Peer Researcher, McPin Foundation. http://mcpin.org/