The aim of this systematic review was to determine the patient, radiological, and operative variables associated with surgical difficulty in the extraction of third molars, according to a visual ...analogue scale completed by the surgeon, operative time, or surgical technique. Searches of the PubMed (MEDLINE), Scopus, and Cochrane Library databases were conducted by two independent reviewers. Randomized and non-randomized clinical trials and prospective cohort studies evaluating surgical difficulty in the extraction of impacted mandibular or maxillary third molars according to patient, radiological, and operative variables were included. The full texts of 21 of the 859 articles initially retrieved were analysed, and 15 articles were included in the final systematic review. All 15 reported prospective cohort studies. The following variables were found to be on the spectrum of highly difficult or complex cases: older patient age and being overweight (patient variables), surgeons with little experience and the use of complex surgical techniques requiring tooth sectioning linked to hard tissue impaction (operative variables), and adverse radiological factors such as deep impaction, unfavourable angulation and root morphology, and a close relationship with the second molar, maxillary sinus, or the inferior alveolar nerve canal (radiological variables).
