Building upon prior research developing trigger tools for identifying preventable errors in dentistry, this study reviewed 1,885 electronic health records (EHR) across four dental practices and found that 16% contained an adverse event. The most common events were pain (27.5%), hard tissue (14.8%) or soft tissue injuries (14.8%) and nerve injuries (13.3%). An EHR-based trigger tool can be an effective approach to identifying safety incidents and measuring the quality of care.