Volume 85 • Number 11

Prevalence of Altered Passive Eruption

in Orthodontically Treated and
Untreated Patients
Jose Nart,* Neus Carrió,* Cristina Valles,* Carols Solı́s-Moreno,* Maria Nart,† Ramon Reñé,‡
Cristina Esquinas,§ and Andreu Puigdollersi

Background: Some authors have reported that after ortho-

dontic treatment (OT), a ‘‘gummy smile’’ might develop.
Nevertheless, there are no studies in the literature that inves-
tigate whether OT increases the presence of altered passive
eruption (APE). The primary aim of this cross-sectional
study is to evaluate the prevalence of APE after OT (OT

I
group) and compare it with patients who never received n dentistry, esthetics is one of the
OT (control group). A secondary aim is to identify which var- major concerns for both practitioners
iables are related to APE. and patients. An esthetically pleasing
Methods: The study population consisted of 190 patients smile is defined as one in which the size,
(95 patients each in the control and OT groups), providing shape, position, and color of the teeth
1,140 anterior teeth for the clinical examination. The follow- are in harmony with surrounding gingi-
ing clinical parameters were assessed: presence or absence val soft tissue, the lips, and finally, the
of APE, clinical crown length, and gingival biotype, which face.1 As classically described, the ideal
was divided into three categories: thin-scalloped, thick-flat, smile includes a gingival display of ap-
and thick-scalloped. proximately 1 to 2 mm.2 However, some
Results: Twenty-eight patients (29.5%) were diagnosed patients show >2 mm of gingival tissue.
with APE in the control group and 40 (42.1%) in the OT Although this situation is not pathologic,
group, although this difference was not statistically signifi- it can produce a poor esthetic effect
cant (P = 0.07). Furthermore, 34 (75.6%) patients with thick- known as a ‘‘gummy smile.’’3 Excessive
flat biotype were diagnosed with APE, whereas 30 (31.3%) gingival display or gummy smile may
and four (8.2%) with thick-scalloped and thin-scalloped bio- be the result of a short upper lip, hyper-
types, respectively, had APE. These differences were statisti- mobile lip, vertical maxillary excess,
cally significant (P <0.001). anterior overeruption, wear and com-
Conclusions: It was concluded that: 1) the prevalence of pensatory eruption, altered active erup-
APE is higher after OT but not to a statistically significant de- tion, and altered passive eruption (APE).4
gree and 2) APE is more common in individuals with a thick- APE is a clinical condition wherein
flat gingival biotype. J Periodontol 2014;85:e348-e353. ‘‘the gingiva in the adult is located incisal
to the cervical convexity of the crown
KEY WORDS
and removed from the cemento-enamel
Cemento-enamel junction; crown lengthening; orthodontics; junction (CEJ) of the tooth.’’5 APE has
periodontics; surgery, plastic; tooth eruption. also been referred to as retarded passive
eruption,6 incomplete passive eruption,7
* Department of Periodontology, School of Dentistry, International University of Catalunya, and delayed passive eruption.8,9 Regard-
Barcelona, Spain.
† Department of Periodontology, University of Granada, Granada, Spain. less of its name, APE can lead to clinical
‡ Private practice, Mollerussa, Lleida, Spain. crowns that appear square in shape and
§ Department of Research, School of Dentistry, International University of Catalunya.
i Department of Orthodontics, School of Dentistry, International University of Catalunya. can be perceived as unesthetic.6
Gottlieb and Orban10 described two
phases of tooth eruption. The active
phase of eruption is defined by emerging
motion of the tooth on the occlusal di-
rection until the tooth reaches the occlusal

doi: 10.1902/jop.2014.140264

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J Periodontol • November 2014 Nart, Carrió, Valles, et al.

plane of its antagonist. This process is accompanied consent. The UIC’s Ethics Committee approved the
by passive eruption, which is the apical migration study. Individuals were selected according to the
of the soft tissues, with gradual exposure of the following inclusion criteria: 1) systemically healthy;
crown of the tooth. Classically, the passive phase 2) non-smoking; 3) all maxillary front teeth present
has been divided into four stages according to the from canine to canine; 4) no evidence of attachment
location of the dentogingival junction (DGJ) with loss, gingival overgrowth/hyperplasia, or inflamma-
respect to the CEJ.11 In Phase I, the DGJ is located tion; 5) no history of periodontal surgery; 6) not
on the enamel; in Phase II, the DGJ is located on pregnant or lactating; 7) CEJ detectable with peri-
enamel and cementum; in Phase III, the DGJ is odontal probe; and 8) no alterations of the incisal
located entirely on the cementum; and in Phase IV, edge tooth such as restorations, traumatic injury, or
the DGJ is on cementum, and the root surface is attrition. Because the length of the clinical crown has
exposed. At present, only the first stage is consid- shown statistically significant changes up to 19
ered to be physiologic, while the remaining three are years,14 only individuals aged ‡20 years were in-
a consequence of pathologic periodontal breakdown cluded in the study. Patients were excluded from the
processes. study if they were taking drugs causing gingival
Evidence to date fails to clarify the causes and enlargement, received OT after the age of 20, or
mechanisms that may lead to APE, although a few received interceptive OT. Because of the limited
studies have related such mechanisms to the mor- ethnic diversity, only data from whites were analyzed.
phology adopted by the coronal periodontium.12
Data Collection and Clinical Measurements
Kokich3 suggested that there are three unesthetic
An interview was conducted to obtain demographic
situations that may develop during orthodontic treat-
characteristics of the study population (age and sex).
ment (OT): 1) the gummy smile; 2) gingival margin
In addition, data of other variables were collected
discrepancies; and 3) the ‘‘missing papilla.’’ Further-
such as OT, being the main independent variable,
more, Keim13 reported that, ‘‘the resulting gummy
duration of OT, clinical crown length, and gingival
smile in these cases is most recognizable by the fact
biotype. The primary outcome variable was the
that the patient presents with shortened clinical
presence of APE.
crowns and gingival tissue that is obviously thicker
Clinical parameters (presence or absence of APE,
than normal in the labiolingual dimension.’’
clinical crown length, and gingival biotype) were
Nevertheless, to the best of the present authors’
assessed by the same calibrated examiner (JN) at
knowledge, there are no studies in the literature that
the mid-buccal site of the six maxillary anterior teeth.
investigate whether OT increases the presence of APE.
The examiner was masked to whether patients re-
Therefore, the primary aim of this cross-sectional study
ceived OT.
is to evaluate the prevalence of APE after OT and
Absence of APE was determined with a periodontal
compare it with patients who never received OT. A
probe¶ to the nearest 0.5 mm if the distance from the
secondary aim is to identify which variables are related
gingival margin to the CEJ was 0.5 to 2 mm.15 A
to APE.
diagnosis of APE was established if the distance
MATERIALS AND METHODS from the gingival margin to the CEJ was >2 mm in ‡2
of the six maxillary anterior teeth because of
Study Design and Patient Selection
esthetic relevance. Local anesthesia was delivered
A total of 190 consecutive patients (71 males and 119
if the patient felt uncomfortable.
females, aged 22 to 38 years; mean age: 26.41 + 3.67
Clinical crown length was defined as the distance
years) referred to the Department of Periodontology at
from the gingival margin to the incisal edge of the
International University of Catalunya (UIC), Barcelona,
crown for each study tooth. Measurements were
Spain, from February 2011 to December 2013 were
made on stone casts to the nearest 0.1 mm by using
included in this cross-sectional study. Patients were
a caliper.# Results obtained from both central incisors
classified in two groups: those who finished OT (full fixed
were averaged, as well as for lateral incisors and
appliances) at the Department of Orthodontics (UIC,
canines.
Barcelona, Spain) before age 20 (OT group) and those
Gingival biotype was divided into three categories:
who never received OT (control group).
thin-scalloped, thick-flat, and thick-scalloped.16 The
In the control group, the mean age of 95 patients
determination of the gingival thickness was based
(36 males and 59 females) was 26.47 – 3.83 years
on the transparency of the same periodontal probe
(range: 22 to 38 years), and in the OT group the
through the gingival margin.16,17
mean age of 95 patients (35 males and 60 females)
was 26.34 – 3.51 years (range: 22 to 36 years).
Patients were informed about the nature of the ¶ PCP-UNC 15, Hu-Friedy, Chicago, IL.
study and were required to provide signed informed # BG, Hu-Friedy.

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Altered Passive Eruption in Orthodontically Treated Patients Volume 85 • Number 11

Intra-Examiner Repeatability
The intra-examiner repeatability of the clinician was
conducted by measuring the distance from the gin-
gival margin to the CEJ in 10 volunteers, not involved
in the study, on two occasions 24 hours apart. Cal-
ibration was accepted if 90% of the recordings could
be reproduced within a difference of 0.5 mm.
Sample Size Calculation
According to Volchansky and Cleaton-Jones,9 the
prevalence of APE is 12%. The hypothesis was that
the prevalence of APE in orthodontic patients is
greater, !25% to 30%. Accepting an a error of 5%
and a statistical power of 90% in a bilateral contrast,
190 individuals (95 patients in each group) were
needed to detect a minimum difference of 15% be-
tween groups for statistical significance. The arcsin
approximation was used.
Figure 1.
Statistical Analyses APE versus normal eruption. A) APE. B) Normal eruption.
A patient-level analysis was performed for presence
or absence of APE and gingival biotype, whereas a
Table 1.
cluster-level analysis was carried out for the clinical
crown length. Descriptive statistics were expressed Prevalence of APE (n [%]) in Control and
as mean – SD and percentage for continuous and OT Groups
categorical data, respectively. The comparisons
between groups were performed using the x2 test Control OT Group
(exact Fisher test with observed frequencies <5) for Group (n = 95) (n = 95) P
categorical variables or Kendall t-c for trend analysis,
whereas continuous variables were tested using t test APE 28 (29.5) 40 (42.1)
0.07*
(Mann–Whitney U test if the variables were not nor- Non-APE 67 (70.5) 55 (57.9)
mally distributed). Crude odds ratios (ORs) were
* No statistically significant difference (P >0.05).
calculated in some relationships. Finally, a stepwise
multivariate logistic regression model was performed
to identify which variables were related to APE. not increase the probability of APE (crude OR = 1.740;
Relevant clinical variables were included in the final 95% confidence interval [CI] 0.955 to 3.172).
model (study group, age, sex, duration of OT, and The mean starting age of the OT was 13.80 – 2.55
gingival biotype) as independent variables with a sig- years and the mean finishing age was 16.15 – 2.45
nificant univariate association (P <0.3).18 P <0.05 was years. The mean duration of OT was 2.4 – 1.0 years
considered to be statistically significant. All statistical (range 1 to 7). No relationship was observed between
analyses were performed using a statistical software the presence of APE and duration of OT (P = 0.78).
package.** In the control group, the mean length of the clinical
crowns was 9.85 – 1.21 mm for canines, 8.67 – 1.00
RESULTS mm for lateral incisors, and 10.29 – 1.03 mm for
A total of 190 patients were enrolled in the study (95 central incisors. The corresponding results for the
patients in each group) providing 1,140 anterior OT group were 9.69 – 1.00, 8.52 – 0.91, and 10.20 –
teeth for the clinical examination (Fig. 1). No sta- 0.76 mm. No statistically significant differences were
tistically significant differences were found between found between the groups for canines (P = 0.34),
the groups for age (P = 0.80) or sex (P = 0.88). lateral incisors (P = 0.28), and central incisors (P =
Twenty-eight patients (29.5%) were diagnosed 0.50) (Table 2).
with APE in the control group and 40 (42.1%) in the Finally, thick-flat, thick-scalloped, and thin-scalloped
OT group, although this difference was not statisti- gingival biotype was present in 45, 96, and 49 pa-
cally significant (P = 0.07) (Table 1). When com- tients. Results from the bivariate analysis only
parisons were made between males and females, no showed a statistically significant association between
statistically significant differences in the prevalence APE and gingival biotype (age, sex, and duration of
of APE were observed (38.0% and 34.5%, respectively;
P = 0.62). Furthermore, it was observed that OT did ** SPSS v.17.0, IBM, Chicago, IL.

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J Periodontol • November 2014 Nart, Carrió, Valles, et al.

OT were not related to APE). Thirty-four (75.6%) CI 0.011 to 0.247; and 0.015; 0.002 to 0.100, re-
individuals who had thick-flat biotype were di- spectively).
agnosed with APE, whereas 30 (31.3%) and four
(8.2%) with thick-scalloped and thin-scalloped bio- DISCUSSION
types, respectively, had APE. These differences were The results reported in this study demonstrate that
statistically significant (P <0.001) (Table 3). More- after OT, the prevalence of APE is higher than in
over, a linear trend was observed toward lower individuals who never received OT. Twenty-eight
prevalence of APE in patients with a thin-scalloped patients (29.5%) were diagnosed with APE in the
gingival biotype (P < 0.001). Comparing control and control group and 40 (42.1%) in the OT group;
OT groups, similar results were obtained. In the however, these differences were not statistically
control group, the percentage of patients with thick- significant (P = 0.07). These results are in agreement
flat biotype with APE was significantly greater than with the clinical impressions of some authors,3,13
with thick-scalloped and thin-scalloped biotypes who reported that after OT patients often develop
(60.9%, 28.3%, and 3.8%, respectively; P <0.001). a gummy smile.
The corresponding results for the OT group were Data regarding prevalence are helpful because
90.9%, 34.0%, and 13.0% (P <0.001). they allow practitioners to know how often they
To further investigate which variables were related should be observing a given condition. In this study,
to APE, a stepwise multivariate logistic regression the prevalence of APE was 35.8% (29.5% for the
model was constructed (Table 4). The independent control group and 42.1% for the OT group). However,
variables were study group, age, sex, duration of OT, based on a series of 1,025 patients with a mean age
and gingival biotype (the reference category was of 24.2 – 6.2 years, Volchansky and Cleaton-Jones9
thick-flat biotype), whereas APE was considered as recorded a 12.1% prevalence of APE. One possible
a dependent variable. Only gingival biotype was explanation for this could be the different diagnostic
related to APE, and patients with a thick-scalloped or criteria used for APE. Volchansky and Cleaton-
thin gingival biotype were less likely to have APE Jones9 diagnosed APE ‘‘when the gingival margin
than those with thick-flat biotype (OR = 0.052; 95% was coronal to the CEJ at a level approximating the
maximum convexity of the buccal or labial aspect
of the tooth and associated with pseudo-pocketing.’’
Table 2. It has been described that the curvature of the
cervical line in a maxillary central incisor is 3 to
Comparison of Clinical Crown Length (mm) 4 mm.19 Thus, the prevalence of APE observed by
of Central Incisors, Lateral Incisors, and Volchansky and Cleaton-Jones9 included only those
Canines in OT and Control Groups teeth with a gingival margin positioned 3 to 4 mm
(mean 6 SD) over the CEJ. In the present study, a diagnosis of
APE was established if the distance from the gingival
Teeth OT Group Control Group P
margin to the CEJ was >2 mm in ‡2 of the six
anterior teeth.
Central incisors 10.20 – 0.76 10.29 – 1.03 0.50* It should be noted that the prevalence of APE in
Lateral incisors 8.52 – 0.91 8.67 – 1.00 0.28*
the adult population has been little studied to date,
possibly because of the lack of clear diagnostic cri-
Canines 9.69 – 1.00 9.85 – 1.21 0.34* teria. There are some clinical criteria such as short
* No statistically significant difference (P >0.05). clinical crown and flat gingival architecture that are
commonly used for the diagnosis of APE. However,
these criteria are subjective and may be related
Table 3. to anatomic structures.20 Therefore, to carry out
Comparison of Gingival Biotype (n [%]) for a clinical diagnosis, it is necessary to search for the
Individuals With and Without APE in position of the CEJ with a probe. If the distance from
the gingival margin to the CEJ is 0.5 to 2 mm,15
Control and OT Groups a greater distance of 2 mm could be used as a di-
agnostic criterion of APE. On the other hand, Alpiste-
Thick-Flat Thick-Scalloped Thin-Scalloped Illueca21 showed that when the left maxillary central
(n = 45) (n = 96) (n = 49) P incisor had APE, the lengths of the clinical crowns of
APE 34 (75.6) 30 (31.3) 4 (8.2) all teeth in the upper anterior sextant were signifi-
<0.001* cantly smaller than in the rest of the series. These
Non-APE 11 (24.4) 66 (68.7) 45 (91.8) results suggest that APE usually affects all second
* Statistically significant difference (P <0.05). sextant teeth.

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Table 4.
Univariate and Stepwise Logistic Regression Model of APE

Variable Crude OR (95% CI) P OR (95% CI)* P

OT group versus control 1.740 (0.955 to 3.172) 0.07 — —

Age (years) 0.975 (0.898 to 1.058) 0.19 — —
Sex (female) 0.857 (0.465 to 1.577) 0.24 — —

Biotype
Thick-flat† 1 1
Thick-scalloped 0.147 (0.066 to 0.329) <0.001 0.052 (0.011 to 0.247) <0.001
Thin-scalloped 0.029 (0.008 to 0.098) <0.001 0.015 (0.002 to 0.100) <0.001

Duration of OT (years) 1.057 (0.715 to 1.563) 0.78 — —

* Stepwise multivariate logistic regression model.
† Reference category.

According to Sterrett et al.,6 the ideal crown length tendency in families with individuals presenting
for maxillary anterior teeth was defined as 9.79 mm APE, and the presence of thick and fibrotic gingival
for centrals, 8.24 mm for laterals, and 9.47 mm for biotype that tends to migrate more slowly during the
canines. When comparing mean observed values of passive phase than thin gingival tissue.12,13
the maxillary anterior clinical crowns to those pre- In this study, 75.6% of patients that had thick-flat
sented by Sterrett et al., lengths were similar.6 biotype (short and wide teeth, a broad zone of ker-
Despite no statistically significant differences be- atinized tissue, and a flat, slightly scalloped gingival
ing seen for clinical crown lengths between control margin) were diagnosed with APE, whereas only
and OT groups, it should be noted that there was 8.2% with thin-scalloped biotype had APE. The
a tendency toward higher clinical crown lengths for separate analysis of the two groups showed similar
teeth in the control group. If one considers that a results. It is important to note that gingival biotype
short clinical crown is one of the clinical criteria of was, independently of age, sex, study group, and
APE, these results could probably explain the clinical duration of OT, associated with APE.
impressions of some authors,3,13 who reported that Batista et al.23 used cone-beam computed to-
after OT a gummy smile may develop. mography to diagnose and characterize the hard and
Konikoff et al. 22 evaluated the clinical crown soft tissue anatomic features of APE-affected teeth.
length of the maxillary anterior teeth pre- and post- The mean soft tissue thickness (measured 2 mm
orthodontics (the day of bracket removal and 5 years apical to the gingival margin) was ‡1 mm for canines,
after orthodontic completion). Immediately after lateral incisors, and central incisors, and all in-
OT, clinical crown length in maxillary central incisors dividuals with APE presented features of a thick
did not change from pre- to postorthodontic values, biotype with a flat gingival architecture. In the
whereas that in lateral incisors and canines in- present study, the gingival biotype was determined
creased. By the clinical examination ‡5 years later, based on the visibility of a periodontal probe through
all maxillary anterior clinical crowns increased sig- the gingival margin. Some studies17,24 have re-
nificantly in length. However, most patients included ported that transgingival probing is an adequately
in their study were <20 years old (34.5% of partici- reliable and objective method to evaluate gingival
pants aged 8 to 15 years and 28.5% of volunteers biotype.
aged 16 to 20 years), and the literature demonstrated The major limitations of this study are the lack of
that there is an increase in the clinical crown length evidence for the criteria used to diagnose APE at
of individuals up to 19 years.14 Clearly, passive erup- a patient-level analysis and the difficulty in the de-
tion most likely occurred from the completion of tection of the CEJ with a periodontal probe. However,
orthodontics to the clinical examination 5 years later. this is the first study that evaluates which factors are
In contrast, in the present study, all patients were related to APE. Further investigations are needed to
20 years or older. confirm these findings.
Few studies have evaluated the possible causes of
APE. A number of factors have been proposed, such CONCLUSIONS
as interocclusal interference on the part of soft tis- It was concluded that: 1) the prevalence of APE is
sues during the eruptive phase, a certain hereditary higher after OT but not to a statistically significant

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J Periodontol • November 2014 Nart, Carrió, Valles, et al.

degree and 2) APE is more common in individuals 14. Volchansky A, Cleaton-Jones P. Clinical crown height
with thick-flat gingival biotype. (length) — A review of published measurements. J Clin
Periodontol 2001;28:1085-1090.
ACKNOWLEDGMENT 15. Ainamo J, Löe H. Anatomical characteristics of gin-
giva. A clinical and microscopic study of the free and
The authors report no conflicts of interest related to attached gingiva. J Periodontol 1966;37:5-13.
this study. 16. De Rouck T, Eghbali R, Collys K, De Bruyn H, Cosyn J.
The gingival biotype revisited: Transparency of the
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