Objetives: This study define altered passive eruption (APE) and evaluate the morphology of the dentogingival unit. Material and Methods: 123 individuals subjected to clinical examination and parallel profile radiography of the upper central incisor. An evaluation was made of the correlation between the clinical diagnosis of APE and the degree of gingival overlap; by using a 19% overlap to define APE (Kappa concordance index = 0.7). The Mann- Whitney / Wilcoxon test was used to identify the variables influencing APE. Results: Statistically significant differences were observed between the teeth with and without APE: gingival width (p = 0.0073), clinical crown length (p = 0.0000), smiling exposed gums (p = 0.0000), bone crest thickness (p = 0.0030), connective tissue attachment thickness (p = 0.0003) and biological width (p = 0.0015). Conclusions: The APE is characterized by: a gingival overlapping of over 19% of the length of the anatomical crown, increased gingival width and gingival smile; furthermore is associated to a thick bone crest and connective tissue attachment. Statistical analysis confirms two morphological patterns of APE.