# Assessment of Negative Gingival Recession: A Critical Component of Periodontal Diagnosis
## 3 Altered Passive Eruption  
Altered passive eruption (APE) is defined as a clinical entity that occurs in adults when a tooth has reached the occlusal plane and the gingival margin is located on the anatomic crown excessively occlusal to the CEJ in the absence of inflammation and gingival overgrowth [28,29]. \"Altered\" or \"delayed\" passive eruption is referred to as a morphological variant from a normal passive eruption process that exposes tooth structure secondary to apical migration of the gingival margin to a location at or slightly coronal to the CEJ by 20 years of age [11]. The passive eruption phase occurs in concert with the active phase of eruption (movement of tooth from its germinative position to its functional contact position with the opposing arch). Together, these two processes determine the position of the DGJ [10]. Clinically, APE is associated with excessive gingival display (gummy smile), short clinical crowns, and predisposition to gingival inflammation [30,31]. The prevalence of APE ranged from 12.1% to 29.5% and was found to be more common in patients with a thick periodontal phenotype [32,33]. However, there is a lack of clear diagnostic criteria to assess the magnitude of the amount of gingiva overlapping the anatomical crown leading to variations in the reported estimates of APE prevalence. The following are some of the criteria proposed to clinically define APE: 20% of overlapping of gingiva [34], 5-10 mm coronal extension of gingiva with respect to CEJ [35], approximation of the gingiva to the \begin{table}
\begin{tabular}{c c c c c} \hline
**Passive Eruption Phase** & **I** & **II** & **III** & **IV** \\ Mean age in years & 24.5 & 31.4 & 32.3 & 39.7 \\ Negative gingival recession (mm) & 2.15 & 1.29 & 0.6 & - \\ Total detongigival junction (mm) & 3.23 & 2.78 & 2.41 & 2.53 \\ Supracestal tissue attachment (mm) & 2.43 & 2.17 & 1.8 & 1.77 \\ \hline \end{tabular}
\end{table} 
Table 1: Dimensions of detongigival junction in 4 different stages of passive eruption. maximum buccal convexity of a tooth [32], or >2 mm of a normal detongigival dimension coronal to the CEJ [33]. [PERSON] et al. classified APE into two types (types 1 and 2) based on the width of existing keratinized gingiva in relation to the anatomic crown [36]. Type 1 is characterized by a noticeably wider gingival dimension from the gingival margin to the mucogingival junction (MGJ), and the mucogingival junction is usually located apical to the bone crest [13; 37]. Conversely, in Type 2, the keratinized gingival width falls within the normal width and the mucogingival junction is usually at the level of CEJ. The normal width of keratinized gingiva was not clearly defined in the original paper by [PERSON] et al. ; however, according to [PERSON], [PERSON], and [PERSON], this generally accepted width is 1 mm of sulcus depth in addition to the width of attached gingiva of 3.0-4.2 mm in the maxilla and 2.5-2.6 mm in the mandible [13; 37]. [PERSON] et al. further subclassified the two types based on the relationship between the alveolar bone crest and CEJ. In subgroup A, the distance from the alveolar bone crest to the CEJ will be 1.5 to 2 mm while in subgroup B, the bone crest level approximates the level of the CEJ. Recently, a proposal to rename subgroup B to \"altered active eruption\" was made, with the hypothesis that it is the failure of the active eruption phase leaving the CEJ positioned in close proximity to the alveolar bone crest [38]. Clinically, several commonly accepted criteria may suggest APE, including excessive gingival display (\(\geq\)4 mm of gingiva-to-lip distance) [39], short clinical crowns (width/length ratio \(\geq\)0.85 in the absence of wear) [40], excessively flattened papilla base [34], and inability to detect the CEJ in a deep (>3 mm) gingival sulcus without concomitant pathological signs [11; 41]. It is important to note that other conditions can contribute to excessive gingival display, including vertical maxillary excess, hypermobility of the upper lip, and anterior dentoalveolar extrusion [42; 43].