Abstract: We included five trials in the review, with 190 participants in total. We did not identify any new studies for inclusion from the updated search in January 2016. Three trials were related to dental treatment, i.e. restorative and extraction treatments; two trials related to orthodontic treatment. We did not judge any of the included trials to be at low risk of bias. Three of the included trials compared paracetamol with placebo, only two of which provided data for analysis (presence or absence of parent-reported postoperative pain behaviour). Meta-analysis of the two trials gave arisk ratio (RR) for postoperative pain of 0.81 (95% confidence interval (CI) 0.53 to 1.22; two trials, 100 participants; P = 0.31), which showed no evidence of a benefit in taking paracetamol preoperatively (52% reporting pain in the placebo group versus 42% in the paracetamol group). One of these trials was at unclear risk of bias, and the other was at high risk. The quality of the evidence is low. One study did not have any adverse events; the other two trials did not mention adverse events. Four of the included trials compared ibuprofen with placebo. Three of these trials provided useable data. One trial reported no statistical difference in postoperative pain experienced by the ibuprofen group and the control group for children undergoing dental treatment. We pooled the data from the other two trials, which included participants who were having orthodontic separator replacement without a general anaesthetic, to determine the effect of preoperative ibuprofen on the severity of postoperative pain. There was a statistically significant mean difference in severity of postoperative pain of -13.44 (95% CI -23.01 to -3.88; two trials, 85 participants; P = 0.006) on a visual analogue scale (0 to 100), which indicated a probable benefit for preoperative ibuprofen before this orthodontic procedure. However, both trials were at high risk of bias. The quality of the evidence is low. Only one of the trials reported adverse events (one participant from the ibuprofen group and one from the placebo group reporting a lip or cheek biting injury). From the available evidence, we cannot determine whether or not preoperative analgesics are of benefit in paediatric dentistry for procedures under local anaesthetic. There is probably a benefit in using preoperative analgesics prior to orthodontic separator placement. The quality of the evidence is low. Further randomised clinical trials should be completed with appropriate sample sizes and well defined outcome measures.

Plain-language summary: We searched several electronic databases to 5 January 2016, as well as doing some searching by hand. We included five studies in the review, which had 190 participants in total. We did not find any new studies between the previous Cochrane review in 2012 and our updated search in January 2016. Three included studies related to dental treatment (fillings and tooth extractions) and two related to orthodontic treatment (braces). Three of the five included studies compared paracetamol to a placebo (sugar tablet) and four of them compared ibuprofen to a placebo. From the available evidence, we could not determine whether or not painkillers before treatment are of benefit for children and adolescents having dental procedures under local anaesthetic. There is probably a benefit in giving painkillers before braces are fitted. Only one study reported an adverse event (one participant in each group had a lip or cheek biting injury). More research is needed. None of the included studies were at low risk of bias. The quality of the evidence is low.