Abstract: Nineteen studies met the criteria for inclusion in the review with data available for a total of 4232 participants. The included studies reported a wide variety of interventions, study populations, clinical outcomes and outcome measures. There was substantial clinical heterogeneity amongst the studies and it was not deemed appropriate to pool data in a meta-analysis. We summarised data by categorising similar interventions into comparison groups. Comparison 1: Any form of one-to-one OHA versus no OHA Four studies compared any form of one-to-one OHA versus no OHA. Two studies reported the outcome of gingivitis. Although one small study had contradictory results at 3 months and 6 months, the other study showed very low-quality evidence of a benefit for OHA at all time points (very low-quality evidence). The same two studies reported the outcome of plaque. There was low-quality evidence that these interventions showed a benefit for OHA in plaque reduction at all time points. Two studies reported the outcome of dental caries at 6 months and 12 months respectively. There was very low-quality evidence of a benefit for OHA at 12 months. Comparison 2: Personalised one-to-one OHA versus routine one-to-one OHA Four studies compared personalised OHA versus routine OHA. There was little evidence available that any of these interventions demonstrated a difference on the outcomes of gingivitis, plaque or dental caries (very low quality). Comparison 3: Self-management versus professional OHA Five trials compared some form of self-management with some form of professional OHA. There was little evidence available that any of these interventions demonstrated a difference on the outcomes of gingivitis or plaque (very low quality). None of the studies measured dental caries. Comparison 4: Enhanced one-to-one OHA versus one-to-one OHA Seven trials compared some form of enhanced OHA with some form of routine OHA. There was little evidence available that any of these interventions demonstrated a difference on the outcomes of gingivitis, plaque or dental caries (very low quality). There was insufficient high-quality evidence to recommend any specific one-to-one OHA method as being effective in improving oral health or being more effective than any other method. Further high-quality randomised controlled trials are required to determine the most effective, efficient method of one-to-one OHA for oral health maintenance and improvement. The design of such trials should be cognisant of the limitations of the available evidence presented in this Cochrane Review.

Plain-language summary: Authors from Cochrane Oral Health carried out this review and the evidence is up to date to 10 November 2017. We included research where individual patients received oral hygiene advice from a dental care professional on a one-to-one basis in a dental clinic setting with a minimum of 8 weeks follow-up. In total, within the identified 19 studies, oral hygiene advice was provided by a hygienist in eight studies, dentist in four studies, dental nurse in one study, dentist or hygienist in one study, dental nurse and hygienist in one study, and dental nurse oral hygiene advice to the control group with further self-administration of the intervention in one study. It was unclear in three of the studies which member of the dental team carried out the intervention. Over half of the studies (10 of the 19) were conducted in a hospital setting, with only five studies conducted in a general dental practice setting (where oral hygiene advice is largely delivered). Overall we found insufficient evidence to recommend any specific method of one- to-one oral hygiene advice as being more effective than another in maintaining or improving oral health. The studies we found varied considerably in how the oral hygiene advice was delivered, by whom and what outcomes were looked at. Due to this it was difficult to readily compare these studies and further well designed studies should be conducted to give a more accurate conclusion as to the most effective method of maintaining or improving oral health through one-to-one oral hygiene advice delivered by a dental care professional in a dental setting. We judged the quality of the evidence to be very low due to problems with the design of the studies.