Traumatic dental injuries are one of the most prevalent diseases globally, impacting people of different ages and socio-economic statuses. As disease prevention is preferable to management, understanding when an individual's overjet is prone to dental trauma helps identify at-risk patients, so to institute preventive strategies. The aim of this study was to identify the different overjet sizes that present an increased risk for developing dental trauma across different ages and dentition stages. The title and protocol were registered and published a priori with the Joanna Briggs Institute (JBI) and PROSPERO (CRD42017060907) and followed the JBI methodology of systematic reviews of association (etiology). A three-step search strategy was performed, including electronic searches of gray literature and four databases. Studies of healthy human participants of any age and in any dental dentition stage were considered for inclusion. Only high methodological quality studies with low risk of bias were included. Where possible, meta-analyses were performed using the random-effects model, supplemented with the fixed-effects model in situations where statistical heterogeneity was ≤50%, assessed using the I2 statistic. The study identified 3718 articles, 41 were included. An increased overjet was significantly associated with higher odds of developing trauma in all dentition stages and age groups. Children 0-6 years with an overjet ≥3mm have an odds of 3.37 (95%CI, 1.36-8.38, P = 0.009) for trauma. Children in the mixed and secondary dentition with an overjet >5mm have an odds of 2.43 (95%CI, 1.34-4.42, P = 0.004). Twelve-year-old children with an overjet >5mm have an odds of 1.81 (95%CI, 1.44-2.27, P < 0.0001). The results confirm the association between increased overjet and dental trauma. A child in the primary dentition could be considered as having an overjet at risk for trauma when it is ≥3mm. In the early secondary dentition, the threshold for trauma is an overjet ≥5mm. © 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.