Maxillary lateral incisors are the second most commonly congenitally missing teeth. When they are missing, orthodontic treatment can either open space to replace the tooth with an implant later, or close the space and substitute the canine. Selecting the best option depends on factors like malocclusion and tooth sizes. For opening space, implants are usually placed after growth is complete, so it is important to monitor eruption and implant site development early. Ankylosed primary molars can also affect future implant placement if not addressed. The orthodontist must consider various factors like age, gender, and tooth development when deciding how to manage congenitally missing teeth and ankylosed primary molars in adolescent patients.

1. EARLY TREATMENT SYMPOSIUM
Congenitally missing teeth:
Orthodontic management in
the adolescent patient
Vincent O. Kokich, Jr, DMD, MSD
Tacoma, Wash
M
axillary lateral
incisors are the
second most
common congenitally ab-
sent teeth. Two treatment
options exist for treating
patients with this prob-
lem. One option is to
open space to replace the
missing tooth; the other
is to close the space and
substitute the canine for
the missing lateral inci-
sor. Selecting the appropriate treatment plan depends
on the malocclusion, the tooth-size relationship, and the
size and esthetics of the canine.
Implants have become the restoration of choice for
most patients when the treatment option is to open
space. Unfortunately, implants cannot be placed until
facial growth is complete. Therefore, it is important to
monitor eruption and implant site development from an
early age. This raises many interesting questions such
as: How much space is necessary? What can be done in
the mixed dentition to appropriately develop a future
implant site? How will the gingival architecture be
affected in the area of the missing tooth? The orthodon-
tist must answer these questions when planning treat-
ment for patients in the mixed dentition.
In opening space, the main concern is alveolar ridge
width in the area of the missing lateral incisor. Alveolar
ridge width may be influenced in the mixed dentition
during the eruption of the permanent canine. The ideal
situation is to encourage the canine to erupt adjacent to
the permanent central incisor. After the canine has
erupted, it can be moved distally into its normal
position. By moving the tooth distally, bone is laid
down, forming an alveolar ridge with adequate bucco-
lingual width to facilitate proper implant placement.1
Occasionally, the canine does not erupt adjacent to the
central incisor. When this occurs, a future bone graft
might be necessary to establish the appropriate width in
the edentulous area to place an implant.
What if the patient is in the mixed dentition and has
a large diastema between the permanent central inci-
sors? In this instance, the centrals occupy over half of
the natural lateral incisor position, and when they are
moved mesially and the diastema is closed, there will
probably be good alveolar width for a future implant.
However, this type of movement in an adult will affect
papilla heights on the distal of the central incisors as the
teeth are moved toward each other. According to
Atherton,2
the distal sulcus will be everted as the space
is closed, leaving the papilla behind. As the nonkera-
tinized gingiva is exposed, the tissue looks red. Over
time, this tissue will keratinize, but the location of the
papilla will not change. In an adult patient, this can be
an esthetic dilemma for the periodontist and the restor-
ative dentist when placing the implant and replacing the
missing tooth. Fortunately, in the mixed dentition, as
the child continues to grow and the teeth erupt, the bone
and the gingiva constantly change. As a result, the
future esthetics of the implant site do not seem to be
affected.
The mandibular second premolar is another com-
mon congenitally missing tooth. Maintaining this space
is often important, especially when an implant is
planned for the future; the primary second molar can be
an ideal space maintainer. However, this tooth will
occasionally become ankylosed. Fortunately, this is a
relatively uncommon occurrence, and it is often diag-
nosable in the mixed dentition as these teeth begin to
submerge below the level of the occlusal plane. Unfor-
tunately, this may result in a bony defect between the
primary molar and the adjacent permanent teeth, which
may ultimately affect future implant placement. How
Affiliate assistant professor, Department of Orthodontics, School of Dentistry,
University of Washington, Tacoma.
Presented at the International Symposium on Early Orthodontic Treatment,
February 8-10, 2002; Phoenix, Ariz.
Am J Orthod Dentofacial Orthop 2002;121:594-5
Copyright © 2002 by the American Association of Orthodontists.
0889-5406/2002/$35.00 ϩ 0 8/1/124174
doi:10.1067/mod.2002.124174
594

2. can this problem be detected early, and what should be
done in the mixed dentition to facilitate future peri-
odontal and restorative treatment?
The orthodontist must remember that the crowns of
the primary molars are naturally shorter than those of
the adjacent permanent first molar. Therefore, a step in
the occlusal plane does not indicate that a primary
molar is ankylosed. Certain methods of detection, such
as tapping the tooth to determine a difference in sound,
generally do not predict ankylosis. The best method to
determine true ankylosis of the primary molar is by
evaluating the interproximal bone level on a bitewing
radiograph. If the interproximal bone level is flat, the
tooth is probably erupting at the same rate as the
adjacent permanent tooth. If the radiograph shows a
developing vertical defect between the primary and the
permanent teeth, then the tooth is ankylosed and may
need to be extracted before the defect worsens. Unfor-
tunately, extracting an ankylosed primary molar is
often a difficult procedure that might require a flap as
well as bone removal. The ultimate result could be a
narrow ridge buccolingually that requires future bone
grafting to achieve successful implant placement.
Age, gender, and presence of a permanent successor
ultimately influence the decision to extract an ankylo-
sed primary molar. What if a 14-year-old girl has a
submerged primary second molar, and the succedane-
ous second premolar is congenitally absent? Should the
primary tooth be extracted? This decision should be
based on the patient’s remaining facial growth. As a
child grows, the rami lengthen; this causes the posterior
teeth to erupt to maintain occlusion.1
This affects a
14-year-old boy more than a girl, because boys gener-
ally continue to grow until they are 18 years or older.
Therefore, ankylosis in a 14-year-old girl with little
remaining facial growth will have minimal effect on the
occlusion. The primary tooth can be maintained but
will most likely need to be reduced mesiodistally and
temporarily restored into a more ideal occlusion.
A 14-year-old boy with an ankylosed primary
second molar and no permanent second premolar will
require extraction of the primary tooth because he will
continue to grow throughout adolescence. This will
allow the edentulous alveolar ridge to move occlusally
as the adjacent teeth erupt.3
Donnelly and Swoope4
showed that as the periosteum is stretched over the
edentulous ridge, osteoblastic activity is stimulated to
lay down bone and promote alveolar ridge develop-
ment.
What if the succedaneous second premolar is
present? Should an ankylosed primary molar be ex-
tracted? This depends on age as well as location and
stage of root development of the premolar. A-9-year-
old with an ankylosed and submerged primary second
molar and a premolar with one-third root formation
might eventually experience a significant effect on the
occlusion because of the ankylosed tooth. Therefore, it
might be better to extract the tooth and maintain the
space until the premolar root development is complete
and the tooth erupts naturally. An 11-year-old with
initial radiographic evidence of ankylosis will exhibit
further root formation and significant root resorption of
the primary tooth. In this instance, the orthodontist
might choose to wait until the ankylosed tooth exfoli-
ates by normal eruption of the premolar.5
Orthodontists commonly encounter patients with
congenitally missing maxillary lateral incisors and
ankylosed mandibular primary second molars. Treat-
ment decisions must be based on eruption pattern, age,
gender, and presence of a permanent tooth. If the
patient is missing the maxillary lateral incisors, guided
eruption and ridge development are critical. Early
diagnosis and treatment of ankylosed primary second
molars also might be important to the future periodontal
and restorative treatment of the adolescent. Therefore,
monitoring these patients in the mixed dentition is
essential to preserve various treatment options in the
future.
REFERENCES
1. Kokich VG. Managing orthodontic–restorative treatment for the
adolescent patient. In: McNamara JA, Brudon WL, editors.
Orthodontics and dentofacial orthopedics. Ann Arbor (Mich):
Needham Press; 2001. p. 423-52.
2. Atherton JD. The gingival response to orthodontic tooth move-
ment. Am J Orthod 1970;58:179-86.
3. Ostler MS, Kokich VG. Alveolar ridge changes in patients
congenitally missing mandibular second premolars. J Prosthet
Dent 1994;71:144-9.
4. Donnelly MW, Swoope CC. Periosteal tension in the stimulation
of bone growth in the mandible [thesis]. Seattle: University of
Washington; 1973.
5. Kurol J, Olson L. Ankylosis of primary molars: a future periodon-
tal threat to the first permanent molars? Eur J Orthod 1991;13:
404-9.
American Journal of Orthodontics and Dentofacial Orthopedics
Volume 121, Number 6
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