Abstract: We included eight trials, which randomised 365 participants. The trials all used a split-mouth design, some with more than one pair of lesions treated within the same participant. Studies took place in university or dental public health clinics in Brazil, Colombia, Denmark, Germany, Thailand, Greenland and Chile. Six studies evaluated the effects of micro-invasive treatments in the permanent dentition and two studies on the primary dentition, with caries risk ranging from low to high. Investigators measured caries risk in different studies either by caries experience alone or by using the Cariogram programme, which combines eight contributing factors, including caries experience, diet, saliva and other factors related to caries. The follow-up period in the trials ranged from one to three years. All studies used lesion progression as the primary outcome, evaluating it by different methods of reading radiographs. Four studies received industry support to carry out the research, with one of them being carried out by inventors of the intervention. We judged seven studies to be at high overall risk of bias, primarily due to lack of blinding of participants and personnel. We evaluated intervention effects for all micro-invasive therapies and analysed subgroups according to the different treatment methods reported in the included studies. Our meta-analysis, which pooled the most sensitive set of data (in terms of measurement method) from studies presenting data in a format suitable for meta-analysis, showed that micro-invasive treatment significantly reduced the odds of lesion progression compared with non-invasive treatment (e.g fluoride varnish) or oral hygiene advice (e.g to floss) (OR 0.24, 95% CI 0.14 to 0.41; 602 lesions; seven studies; I2 = 32%). There was no evidence of subgroup differences (P = 0.36). The four studies that measured adverse events reported no adverse events after micro-invasive treatment. Most studies did not report on any further outcomes. We assessed the quality of evidence for micro-invasive treatments as moderate. It remains unclear which micro-invasive treatment is more advantageous, or if certain clinical conditions or patient characteristics are better suited for micro-invasive treatments than others. The available evidence shows that micro-invasive treatment of proximal caries lesions arrests non-cavitated enamel and initial dentinal lesions (limited to outer third of dentine, based on radiograph) and is significantly more effective than non-invasive professional treatment (e.g. fluoride varnish) or advice (e.g. to floss). We can be moderately confident that further research is unlikely to substantially change the estimate of effect. Due to the small number of studies, it does remain unclear which micro-invasive technique offers the greatest benefit, or whether the effects of micro-invasive treatment confer greater or lesser benefit according to different clinical or patient considerations.

Plain-language summary: This review ​considered evidence that was up to date at 31 December 2014. We found eight relevant trials with 365 participants. These trials involved children and adults whose decay lesions (tooth decay) were randomly assigned to different micro-invasive and non-invasive treatments. There were no studies comparing micro-invasive interventions with invasive treatment (fillings). Four studies received financial support from intervention inventors or manufacturers to carry out the research. The current evidence shows that micro-invasive treatments can significantly reduce the likelihood of dental decay progression compared with the described non-invasive methods. There are too few studies to decide which micro-invasive treatment technique is best or the impact of different clinical and patient considerations. No negative side effects were reported; however, only half of the studies measured this outcome and the follow-up time of some of the studies was relatively short. Although further research could possibly change our findings, the available evidence gives us moderate confidence that micro-invasive treatments are much more effective than non-invasive treatments for stopping tooth decay.