Abstract: We included nine randomised trials, published between 1998 and 2014, involving 662 participants. The population consisted of both children and adolescents in four trials, only adults in four trials, and both children/adolescents and adults in one trial. Four studies examined only permanent teeth, and five studies evaluated both deciduous and permanent teeth. Six trials used Er:YAG (erbium-doped yttrium aluminium garnet) lasers, two trials employed Er,Cr:YSGG (erbium, chromium: yttrium-scandium-gallium-garnet) lasers, and one trial used Nd:YAG (neodymium-doped yttrium aluminium garnet) laser. Overall, the trials had small sample sizes, and the majority were at unclear or high risk of bias. The primary outcomes were evaluated in a limited number of trials (removal of caries (four trials (but only two reported quantitative data)); episodes of pain (five studies)). There was insufficient evidence to suggest that either lasers or drill were better at caries removal (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.99 to 1.01; 2 studies; 256 treated caries; P = 0.75; I2 = 0%; low-quality evidence). The incidence of moderate or high pain was greater in the drill group compared to the laser group (RR 0.40, 95% CI 0.28 to 0.57; 2 studies; 143 participants; P < 0.001; I2 = 50%). Similarly, the need for anaesthesia was significantly higher in the drill group than in the laser group (RR 0.25, 95% CI 0.10 to 0.65; 3 studies; 217 children/adolescents; P = 0.004; I2 = 0%). In terms of marginal integrity of restoration, there was no evidence of a difference between laser and drill comparisons evaluated at 6 months (RR 1.00, 95% CI 0.21 to 4.78; 3 studies), 1 year (RR 1.59, 95% CI 0.34 to 7.38; 2 studies), or 2 years (RR 1.00, 95% CI 0.21 to 4.74; 1 study). There was no evidence of a difference for durability of restoration between laser therapy or drill at 6 months' follow-up (RR 2.40, 95% CI 0.65 to 8.77; 4 studies), at 1 year (RR 1.40, 95% CI 0.29 to 6.78; 2 studies) or at 2 years' follow-up (RR 0.50, 95% CI 0.02 to 14.60; 1 study). Only two trials investigated the recurrence of caries, but no events occurred during 6 months' follow-up. There was insufficient evidence of a difference between laser or drill in terms of pulpal inflammation or necrosis at 1 week (RR 1.51, 95% CI 0.26 to 8.75; 3 studies) and at 6 months (RR 0.99, 95% CI 0.10 to 9.41; 2 studies). Given the low quality of the body of evidence, we concluded that evidence was insufficient to support the use of laser as an alternative to traditional drill therapy for caries removal. We found some evidence in favour of laser therapy for pain control, need of anaesthesia and patient discomfort, but, again, the body of evidence was of low quality. Additional well-designed, randomised trials investigating the most relevant outcomes are needed.

Plain-language summary: Cochrane Oral Health provided the search strategies and carried out the search in several electronic databases. We selected nine randomised trials for inclusion in this review that were conducted between 1998 and 2014. The evidence in the review is up to date as of 22 June 2016. The trials involved a total of 662 participants, with 1498 teeth treated. Three studies were conducted in the USA, one in Taiwan, one in China, one in Bulgaria, one in Germany, one in Turkey and one in the UK. The population consisted of both children and adolescents in four trials, only adults in four trials, and both children/adolescents and adults in one trial. Despite the number of included studies, only a few trials adequately and completely reported information on the primary outcomes. Two trials reported on removal of decay, and there was not enough evidence to conclude that either lasers or drills were better at decay removal. Only five trials reported on episodes of pain, which was significantly reduced in people treated with lasers. There was no difference in terms of side effects, such as inflammation or death of dental pulp, between the two interventions. The overall quality of the evidence for the nine studies was low. Only one study adequately randomised participants, and none of the included studies was at low risk of bias. This review highlights the need for high-quality studies comparing laser therapy and mechanical drills in the treatment of dental decay.