Resumo BACKGROUND: Fear of dental pain is a major barrier to treatment for children who need dental care. The use of preoperative analgesics has the potential to reduce postoperative discomfort and intraoperative pain. We reviewed the available evidence to determine whether further research is warranted and to inform the development of prescribing guidelines. This is an update of a Cochrane review published in 2012. OBJECTIVES: To assess the effects of preoperative analgesics for intraoperative or postoperative pain relief (or both) in children and adolescents undergoing dental treatment without general anaesthesia or sedation. SEARCH METHODS: We searched the following electronic databases: Cochrane Oral Health's Trials Register (to 5 January 2016), the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2015, Issue 12), MEDLINE via OVID (1946 to 5 January 2016), EMBASE via OVID (1980 to 5 January 2016), LILACS via BIREME (1982 to 5 January 2016) and the ISI Web of Science (1945 to 5 January 2016). We searched ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform for ongoing trials to 5 January 2016. There were no restrictions regarding language or date of publication in the searches of the electronic databases. We handsearched several specialist journals dating from 2000 to 2011.We checked the reference lists of all eligible trials for additional studies. We contacted specialists in the field for any unpublished data. SELECTION CRITERIA: Randomised controlled clinical trials of analgesics given before dental treatment versus placebo or no analgesics in children and adolescents up to 17 years of age. We excluded children and adolescents having dental treatment under sedation (including nitrous oxide/oxygen) or general anaesthesia. DATA COLLECTION AND ANALYSIS: Two review authors assessed titles and abstracts of the articles obtained from the searches for eligibility, undertook data extraction and assessed the risk of bias in the included studies. We assessed the quality of the evidence using GRADE criteria. MAIN RESULTS: 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). AUTHORS' CONCLUSIONS: 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.