Background/Objectives: Impacted teeth are a common phenomenon, in both young and adult populations, as extensively documented in the literature. This study aims to systematically assess the global prevalence of impacted third molars and to analyze their demographic predictors. Methods: The present review adheres to PRISMA guidelines and includes studies published until December 2023. Three databases (MEDLINE, LILACS, Cochrane) were searched, and studies reporting prevalence rates and demographic predictors of impacted third molars were selected for analysis. A meta-analysis was conducted using a random-effects model to calculate pooled prevalence and assess demographic variations. Results: This review yielded 98 studies involving 183,828 subjects. The pooled prevalence of impacted third molars was 36.9% [95% CI: 33.1–40.7%] per subject and 46.4% [95% CI: 36.7–56.1%] per tooth, with the highest rates in Asia (43.1% [95% CI: 34.6–51.7%]) and the lowest in Europe (24.5% [95% CI: 16.1–33.9%]). An odds ratio of 1.173 [95% CI: 1.021–1.347%] indicated a slightly higher likelihood of third molar impaction among women compared to men, and mandibular third molar impaction was more frequent than maxillary impaction. The meta-regression indicated insufficient consistency for the geographic area to be considered a source of heterogeneity in the prevalence of impacted third molars. Conclusions: The present meta-analysis highlights the substantial prevalence of impacted third molars worldwide and underscores the influence of demographic predictors. These findings may inform region-specific clinical guidelines and preventive approaches for managing impacted third molars.

Background/Objectives: Impacted third molars are frequent and may increase surgical complexity, particularly when the mandibular third molar is in close proximity to the inferior alveolar canal (IAC). This study aimed to estimate the prevalence and impaction patterns of third molars in a Portuguese population and to characterize, using a nested CBCT subsample, the three-dimensional relationship between mandibular third molars and the IAC, including cortical integrity and lingual plate thickness. Methods: A retrospective observational analysis of 1062 orthopantomograms (OPGs) was performed to determine the prevalence and panoramic patterns using Winter, Pell and Gregory classifications and Rood–Shehab signs. A consecutive CBCT subsample (n = 205) was assessed for IAC position, contact status (no contact; contact with cortical bone; contact without cortical bone), cortical integrity, and lingual plate thickness. Descriptive statistics were complemented by effect sizes to support clinical interpretability. Results: The prevalence of impacted third molars was 34.9%, occurring predominantly in the mandible. Vertical angulation was the most prevalent pattern in both jaws. In the CBCT subsample, IAC position and contact patterns varied widely, and loss of cortical integrity was more often observed when panoramic high-risk signs were present. No clinically meaningful left–right asymmetry was identified across key anatomical risk indicators. Conclusions: In this Portuguese cohort, impacted third molars showed consistent panoramic patterns, while CBCT provided clinically relevant three-dimensional risk descriptors—particularly IAC contact type and cortical integrity—supporting selective CBCT use based on anatomical risk indicators rather than routine imaging.