EARLY TREATMENT SYMPOSIUM

Congenitally missing teeth:Orthodontic management inthe adolescent patientVincent O. Kokich, Jr, DMD, MSDTacoma, Wash

Maxillary lateralincisors are thesecond most

common congenitally ab-sent teeth. Two treatmentoptions exist for treatingpatients with this prob-lem. One option is toopen space to replace themissing tooth; the otheris to close the space andsubstitute the canine forthe missing lateral inci-

sor. Selecting the appropriate treatment plan dependson the malocclusion, the tooth-size relationship, and thesize and esthetics of the canine.

Implants have become the restoration of choice formost patients when the treatment option is to openspace. Unfortunately, implants cannot be placed untilfacial growth is complete. Therefore, it is important tomonitor eruption and implant site development from anearly age. This raises many interesting questions suchas: How much space is necessary? What can be done inthe mixed dentition to appropriately develop a futureimplant site? How will the gingival architecture beaffected 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 ridgewidth in the area of the missing lateral incisor. Alveolarridge width may be influenced in the mixed dentitionduring the eruption of the permanent canine. The idealsituation is to encourage the canine to erupt adjacent tothe permanent central incisor. After the canine has

erupted, it can be moved distally into its normalposition. By moving the tooth distally, bone is laiddown, forming an alveolar ridge with adequate bucco-lingual width to facilitate proper implant placement.1

Occasionally, the canine does not erupt adjacent to thecentral incisor. When this occurs, a future bone graftmight be necessary to establish the appropriate width inthe edentulous area to place an implant.

What if the patient is in the mixed dentition and hasa large diastema between the permanent central inci-sors? In this instance, the centrals occupy over half ofthe natural lateral incisor position, and when they aremoved mesially and the diastema is closed, there willprobably be good alveolar width for a future implant.However, this type of movement in an adult will affectpapilla heights on the distal of the central incisors as theteeth are moved toward each other. According toAtherton,2 the distal sulcus will be everted as the spaceis closed, leaving the papilla behind. As the nonkera-tinized gingiva is exposed, the tissue looks red. Overtime, this tissue will keratinize, but the location of thepapilla will not change. In an adult patient, this can bean esthetic dilemma for the periodontist and the restor-ative dentist when placing the implant and replacing themissing tooth. Fortunately, in the mixed dentition, asthe child continues to grow and the teeth erupt, the boneand the gingiva constantly change. As a result, thefuture esthetics of the implant site do not seem to beaffected.

The mandibular second premolar is another com-mon congenitally missing tooth. Maintaining this spaceis often important, especially when an implant isplanned for the future; the primary second molar can bean ideal space maintainer. However, this tooth willoccasionally become ankylosed. Fortunately, this is arelatively uncommon occurrence, and it is often diag-nosable in the mixed dentition as these teeth begin tosubmerge below the level of the occlusal plane. Unfor-tunately, this may result in a bony defect between theprimary molar and the adjacent permanent teeth, whichmay 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;121:594-5Copyright © 2002 by the American Association of Orthodontists.0889-5406/2002/$35.00 � 0 8/1/124174doi:10.1067/mod.2002.124174

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can this problem be detected early, and what should bedone in the mixed dentition to facilitate future peri-odontal and restorative treatment?

The orthodontist must remember that the crowns ofthe primary molars are naturally shorter than those ofthe adjacent permanent first molar. Therefore, a step inthe occlusal plane does not indicate that a primarymolar is ankylosed. Certain methods of detection, suchas tapping the tooth to determine a difference in sound,generally do not predict ankylosis. The best method todetermine true ankylosis of the primary molar is byevaluating the interproximal bone level on a bitewingradiograph. If the interproximal bone level is flat, thetooth is probably erupting at the same rate as theadjacent permanent tooth. If the radiograph shows adeveloping vertical defect between the primary and thepermanent teeth, then the tooth is ankylosed and mayneed to be extracted before the defect worsens. Unfor-tunately, extracting an ankylosed primary molar isoften a difficult procedure that might require a flap aswell as bone removal. The ultimate result could be anarrow ridge buccolingually that requires future bonegrafting to achieve successful implant placement.

Age, gender, and presence of a permanent successorultimately influence the decision to extract an ankylo-sed primary molar. What if a 14-year-old girl has asubmerged primary second molar, and the succedane-ous second premolar is congenitally absent? Should theprimary tooth be extracted? This decision should bebased on the patient’s remaining facial growth. As achild grows, the rami lengthen; this causes the posteriorteeth to erupt to maintain occlusion.1 This affects a14-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 littleremaining facial growth will have minimal effect on theocclusion. The primary tooth can be maintained butwill most likely need to be reduced mesiodistally andtemporarily restored into a more ideal occlusion.

A 14-year-old boy with an ankylosed primarysecond molar and no permanent second premolar willrequire extraction of the primary tooth because he willcontinue to grow throughout adolescence. This willallow the edentulous alveolar ridge to move occlusallyas the adjacent teeth erupt.3 Donnelly and Swoope4

showed that as the periosteum is stretched over theedentulous ridge, osteoblastic activity is stimulated to

lay down bone and promote alveolar ridge develop-ment.

What if the succedaneous second premolar ispresent? Should an ankylosed primary molar be ex-tracted? This depends on age as well as location andstage of root development of the premolar. A-9-year-old with an ankylosed and submerged primary secondmolar and a premolar with one-third root formationmight eventually experience a significant effect on theocclusion because of the ankylosed tooth. Therefore, itmight be better to extract the tooth and maintain thespace until the premolar root development is completeand the tooth erupts naturally. An 11-year-old withinitial radiographic evidence of ankylosis will exhibitfurther root formation and significant root resorption ofthe primary tooth. In this instance, the orthodontistmight choose to wait until the ankylosed tooth exfoli-ates by normal eruption of the premolar.5

Orthodontists commonly encounter patients withcongenitally missing maxillary lateral incisors andankylosed mandibular primary second molars. Treat-ment decisions must be based on eruption pattern, age,gender, and presence of a permanent tooth. If thepatient is missing the maxillary lateral incisors, guidederuption and ridge development are critical. Earlydiagnosis and treatment of ankylosed primary secondmolars also might be important to the future periodontaland restorative treatment of the adolescent. Therefore,monitoring these patients in the mixed dentition isessential to preserve various treatment options in thefuture.

REFERENCES

1. Kokich VG. Managing orthodontic–restorative treatment for theadolescent 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 patientscongenitally missing mandibular second premolars. J ProsthetDent 1994;71:144-9.

4. Donnelly MW, Swoope CC. Periosteal tension in the stimulationof bone growth in the mandible [thesis]. Seattle: University ofWashington; 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.

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