1. ORIGINAL ARTICLE
Gingival changes and secondary tooth eruption in
adolescents and adults: A longitudinal
retrospective study
Georges Andre Theytaz,a Panagiotis Christou,a and Stavros Kiliaridisb
Geneva, Switzerland
Introduction: Our aim was to investigate 8 years of vertical changes of the gingival margin and tooth displace-
ment of maxillary molars and incisors in adolescents and adults. Methods: Twenty-five adolescents and 10
adults were included in this study, with dental casts taken 2 and 10 years after orthodontic treatment. The gin-
gival contour of the teeth was traced digitally using calibrated photographs of the 2 dental casts, and gingival
changes were measured on crown superimposition. Eruption of the central incisors and first molar were mea-
sured on dental casts after scanning and superimposition on the palatal vault. Results: Adults and adolescents
presented a mean molar eruption of 0.27 and 0.34 mm and a mean incisor eruption of 0.39 and 0.73 mm, respec-
tively. Adults and adolescents presented a mean molar gingival displacement of respectively 0.34 and 0.77 mm,
and the adolescents a mean incisor gingival displacement of 0.44 mm. Correlation between secondary tooth
eruption and gingival displacement was obtained only for the incisors in the adolescent group. Conclusions:
Adolescents and adults presented apical displacement of the gingival contour of the maxillary first molars, as
was the case for maxillary incisors in adolescents. Secondary eruption of maxillary first molars and central inci-
sors continues in adolescents and adults. (Am J Orthod Dentofacial Orthop 2011;139:S129-32)
F
rom childhood to adulthood, clinical crown A relation between tooth eruption and gingival
heights in the maxilla increase differently accord- displacement has been shown for the maxillary central
ing to the type of tooth.1 However, information incisors,3 but no information exists regarding if this is
about gingival displacement in healthy adults is lacking, the case for posterior teeth.
particularly for posterior teeth, and we still do not know The aim of this retrospective longitudinal study was
if gingival movements under healthy conditions stop to monitor, on dental casts, 8 years of changes of the
during life. gingival contour of maxillary central incisors and first
Secondary tooth eruption (eruption after the teeth molars in adolescents and adults. We also measured
have reached the occlusal level) may play a role in the es- secondary tooth eruption to determine if it is correlated
tablishment of gingival position. In adults, the incisal to the gingival displacement.
edge of maxillary incisors is displaced in an occlusal di- The null hypothesis is: “no difference exists in gingi-
rection by 0.95 mm in relation to the nasion over 20 val displacement and tooth eruption between maxillary
years.2 Nevertheless, molar eruption has been measured central incisors and maxillary molars in either growing
rarely, and we do not know if and when molar eruption individuals or young adults.”
stops.
MATERIAL AND METHODS
From the Department of Orthodontics, School of Dentistry, University of Geneva,
Geneva, Switzerland. Subjects
a
Lecturer.
b
Professor and chairman. Cases were selected among patients who finished
The authors report no commercial, proprietary, or financial interest in the prod- orthodontic treatment at the Department of Orthodon-
ucts or companies described in this article. tics, University of Geneva, between 1984 and 1996
Reprint requests to: Georges Andr Theytaz, Department of Orthodontics, School
e
of Dentistry, University of Geneva, 19 rue Barthlmy-Menn, 1205 Geneva,
ee and who had dental casts taken approximately 2 and
Switzerland; e-mail, Georges-Andre.Theytaz@unige.ch. 10 years after the end of orthodontic treatment. Exclu-
Submitted, December 2009; revised and accepted, May 2010. sion criteria comprised restoration of the maxillary cen-
0889-5406/$36.00
Copyright Ó 2011 by the American Association of Orthodontists. tral incisors and maxillary first molars performed or
doi:10.1016/j.ajodo.2010.05.017 replaced during the follow-up period, poor quality of
S129

2. S130 Theytaz, Christou, and Kiliaridis
dental casts, and periodontal problems noticed by the
practitioners at or between the 2 documentations.
Forty-two patients presented the necessary docu-
mentation. Seven were excluded, 3 because of
inadequate quality of dental casts and 4 because of
restorations.
According to the age of the patients at the first doc-
umentation used in the study (2 years after debonding
and the end of orthodontic treatment), 2 groups were
defined. The adolescent group comprised 25 subjects
(7 boys, 18 girls), with a mean age of 15.9 years (range:
14.1 to 17.8). The adult group comprised 10 subjects
(6 men, 4 women), with a mean age of 31.2 years (range:
21.4 to 46.4).
Measurements of gingival margin and displacement
On the first and second dental casts, teeth 15 and 16,
teeth 25 and 26, and teeth 11 and 21 were photographed
together in a standardized way. The occlusal plane was
horizontal, and the contact point between both pair of
teeth was centered in the photographs. The distance
between the camera and the models was always the
same to keep a constant and easily calculated magnifica-
tion. This magnification has been calculated by photo-
graphing a ruler placed on the dental cast holder.
On the digital images, all teeth photographed were
traced with drawing software (FreeHand 8.0, Macrome-
dia Inc., San Francisco, Calif), and the line passing
through the surface of contact of both teeth and perpen-
dicular to the occlusal surface was also traced. Both
drawings from each case were then superimposed, fit-
ting the vertical placement of the drawing on the angles
of the teeth. The measurements were done on the image
with both drawings superimposed (Viewbox, version
3.1.1.12, dHAL Sofware, Kifissia, Greece) after magnifi-
cation adjustment. The most mesial and the most distal Fig 1. Method. A, First photograph 2 years after the end
points of each tooth were defined, and each tooth was of orthodontic treatment with drawings of teeth 11 and 21,
divided into 8 equal parts, with lines parallel to the prin- the central line passing through the surface of contact of
both teeth and perpendicular to the occlusal plane in
cipal line. The intersections of these lines with the two
black. B, Final photograph 8 years after the initial
tracings of the gingival contour were then recorded
photograph with the same drawings as in a but in red.
(Fig 1). The gingival displacement on each line was C, Tracings of initial and final photographs superimposed
calculated by the computer, and we calculated gingival by fitting the angles of the incisors. The parallel lines to the
displacement for each tooth by averaging the 3 gingival central axis divide the maxillary central incisors in 8 equal
values in the center of the tooth. parts. Arrows show the lines used for measurements.
Secondary eruption measurements
All the casts were scanned with the Laserscan 3D On the 3D model, we compared the position of the
(Willytec, GmbH, Gr€felfing, Germany). The models
a central incisors and the first molar at the first and second
were put on the articulated base with their occlusal plane documentation. The structure of reference was the
parallel to the ground, and the image was then trans- palatal vault, distal of the third rugae. All the points of
ferred to a computer (Siemens Expert, Siemens AG, reference were localized on easily reproducible areas of
Munich, Germany). each tooth and were the same on both sets of casts.
April 2011 Vol 139 Issue 4 Supplement 1 American Journal of Orthodontics and Dentofacial Orthopedics

3. Theytaz, Christou, and Kiliaridis S131
Table. Results
Adolescents Adults
Mean SD CI Mean SD CI p
Gingival displacement (mm)
Maxillary incisors 0.44** 0.50 0.28 to 0.59 0.03* 0.32 À0.13 to 0.18 ***
Maxillary molars 0.77** 0.58 0.60 to 0.93 0.34* 0.61 0.05 to 0.62 **
Secondary eruption (mm)
Maxillary incisors 0.73*** 0.38 0.62 to 0.85 0.39 0.20 0.23 to 0.56 **
Maxillary molars 0.34*** 0.22 0.28 to 0.41 0.27 0.26 0.11 to 0.43
Means, standard deviations, and confidence intervals of gingival displacement and secondary eruption measured on maxillary incisors and maxillary
first molars in adolescents and adults.
*P 0.05; **P 0.01; ***P 0.001
Statistics measurements were found that corresponds to a previous
All the statistics were conducted using SPSS 13.0 for published study.5
Windows (SPSS Inc., Chicago, Ill). Statistical significance
was set to 0.05. The results of the adolescent and the RESULTS
adult group were compared by using an unpaired t test. Gingival displacement
The same test was used to compare measurements on in- In adolescents, we observed gingival displacement of
cisors and molars. Pearson correlation coefficient was both incisors and molars, being more pronounced for
calculated to relate gingival displacement to secondary molars. In adults, we observed gingival displacement
tooth eruption, molar-to incisor secondary eruption, of maxillary molars but not of maxillary incisors. Gingi-
and molar-to-incisor gingival displacement. Tooth and val displacement of incisors and first molars was more
gingival displacement were evaluated using confidence pronounced in adolescents than in adults (Table).
intervals.
Secondary tooth eruption
Error of the method
In adolescents, we observed eruption of both incisors
The error of the method for the gingival displacement and molars, being more pronounced for incisors. In
was tested by measuring the photographs on 2 different adults, both incisors and molars showed eruption,
occasions on 15 studied cases. The error of the measure- though no statistically significant difference was found
ments was calculated by using the Dahlberg’s formula
P 2 between them. Eruption of maxillary incisors was more
(Se2 5 d =2n)4 and ranged from 0.05 to 0.1 mm. pronounced in adolescents than in adults. No statisti-
In order to compare our method with a method cally significant difference was found for molar eruption
already described in the literature3, the gingival displace- between the 2 groups (Table).
ment measured on the casts was compared with the 1
using intraoral photographs taken on the same day as Correlation
the dental casts in 20 cases. The frontal intraoral photo-
graphs should have been taken symmetrically from There is a fair correlation between secondary erup-
a centric position parallel to the occlusal plane with tion of molars and incisors (r 5 0.48 and P 0.001)
the central incisors centered in the photograph. High and between molar and incisor gingival displacement
correlation (Pearson correlation) was found between (r 5 0.36, P 0.01) when both groups are studied
the 2 methods (r 5 0.802; P 0.01). together.
The method used for the measurements of tooth Correlation between secondary tooth eruption and
eruption was evaluated by double localization of the gingival displacement was found only for the incisors
same points of reference with a difference of 10 weeks in the adolescent group (r 5 0.47 and P 0.01).
between the 2 measurements and calculated by Dahl-
berg’s formula.4 Standard error (SE) was found to be DISCUSSION
low (17.1 mm). The differences in the coordinates were The present study shows that gingival contour of
assessed and compared using paired t test. A high re- maxillary first molars and maxillary central incisors in ad-
peatability of the localization of points of reference olescents are apically displaced, which is also the case for
and a high correlation between the 2 sets of maxillary molars in adults, leading to an increase in
American Journal of Orthodontics and Dentofacial Orthopedics April 2011 Vol 139 Issue 4 Supplement 1

4. S132 Theytaz, Christou, and Kiliaridis
crown height. These results are in line with previous in- explaining the rest of the displacement may be tooth
vestigations on crown height changes. A 7-year longitu- cleaning, since gingival recession was positively
dinal study,6 showed that crown length of maxillary correlated with the frequency of toothbrushing.9
central incisors increases by about 0.85 mm between As gingival displacement continues during adoles-
11.5 and 18.5 years of age, which is half of what we cence and young adulthood, we should act with caution
found between 16 and 24 years. In the maxillary first mo- when gingival surgery is advocated for esthetic reasons
lars, the crown height increases by 1 mm between 10 and in adolescents in the maxillary anterior region.
18 years of age,1 while we found 0.58 mm in our older
adolescent group. In our investigation, the subjects CONCLUSION
studied had healthy tooth support and good oral The null hypothesis can be rejected. Tooth positions
hygiene. Therefore, pathologic gingival recessions due and gingival margins are not stable on reaching adult-
to periodontal problems, aberrant frenal attachment, or hood. Apical displacement of the gingival margin can
operative procedures cannot explain the gingival be observed on anterior and posterior teeth in adoles-
displacement we observed. Interindividual differences cents. This phenomenon seems to decline with increas-
regarding facial type, incisor inclinations, overbite, ing age but does not stop in adulthood, particularly in
overjet, incisor procumbency relative to the cranial the posterior regions. Secondary tooth eruption taking
base, and crowding can explain the variation of the place during adolescence in the anterior region explains
results we obtained. part of this gingival displacement. After this period,
Measurements concerning secondary tooth eruption tooth eruption does not stop but these displacements
suggest that maxillary central incisors and first molars are no longer correlated to gingival movements.
continue to erupt during adolescence and, though to
a lesser extent, during adulthood. These results are in
REFERENCES
agreement with a previous study in which secondary in-
cisor eruptions of 0.81 mm in an adolescent group and 1. Volchansky A, Cleaton-Jones P, Fatti LP. A technique for computer
0.19 mm in an adult group were measured.3 Molar erup- plotting of clinical crown height derived from orthodontic study
models. J Dent 1981;9:150-6.
tion of 0.4 mm in an adult group followed over 10 years
2. Forsberg CM, Eliasson S, Westergren H. Face height and tooth erup-
has been observed.5 The difference with the 0.27 mm of tion in adults—a 20-year follow-up investigation. Eur J Orthod
secondary molar eruption we found may be explained by 1991;13:249-54.
the fact that our follow-up period was shorter. It would 3. Theytaz GA, Kiliaridis S. Gingival and dentofacial changes in adoles-
have been interesting to measure molar eruption on cents and adults 2 to 10 years after orthodontic treatment. J Clin
Periodontol 2008;35:825-30.
lateral cephalograms, but the superimpositions in the
4. Houston WJB. The analysis of errors in orthodontic measurements.
molar region do not allow clear identification of molar Am J Orthod 1983;83:382-90.
position. 5. Christou P, Kiliaridis S. Three-dimensional changes in the position
Secondary eruption of the incisors in the adolescent of unopposed molars in adults. Eur J Orthod 2007;29:543-9.
group was found to be related to gingival displacement, 6. Morrow LA, Robbins JW, Jones DL, Wilson NHF. Clinical crown
length changes from 12–19 years: a longitudinal study. J Dent
explaining about 22% of the gingival movement. A pos-
2000;28:469-73.
sible explanation is that the sulcus depth is deeper in 7. Smith RG. A longitudinal study into the depth of the clinical gingival
younger individuals and decreases with increasing sulcus of human canine teeth during and after eruption. J Periodon-
age.7,8 Therefore, it can be hypothesized that during tal Res 1982;17:427-33.
adolescence, cervical gingival displacement is not due 8. Bimstein E, Eidelman E. Morphological changes in the attached and
keratinized gingiva and gingival sulcus in the mixed dentition
to attachment loss but rather to a decrease of sulcus
period. A 5-year longitudinal study. J Clin Periodontol 1988;15:
depth that coincides with secondary tooth eruption. 175-9.
After this time, gingival displacement is less correlated 9. Vehkalahti M. Occurrence of gingival recession in adults. J Perio-
to secondary tooth eruption, and the most likely factor dontol 1989;60:599-603.
April 2011 Vol 139 Issue 4 Supplement 1 American Journal of Orthodontics and Dentofacial Orthopedics