Pattern of permanent teeth present in individuals withectodermal dysplasia and severe hypodontia suggeststreatment with dental implantsAlbert D. Guckes, DDS, MSD Michael W. Roberts, I)DS, MScD George R. McCarthy, I)DS

Abstract

Purpose: The objective of this study was to assess thepat-tern of permanent teeth present in a self-selected sample of17female and 35 male patients with ectodermal dysplasiapresenting for treatment with dental implants.

Methods: Mean age of sample: 18.7 years, age range:5.9 to 60.9years. Panoramic radiographs were examinedindependently by two investigators to determine the perma-nent teeth present. None of the sample reported extractionsof permanent teeth prior to presenting for implants.

Results: Permanent teeth most likely to be present, re-ported as a percentage of the patient sample with that tooth,were: maxillary central incisors (42%), maxillary first mo-lars (41%), mandibular first molars (39%), maxillary nines (22%), mandibular second molars (17%), maxillarysecond premolars (15%), and mandibular premolars (12%).Comparing dentition by quadrants, mandibular anteriorteeth (canines and incisors) were least likely to be present.

Conclusions: Results support previous findings that themaxillary central incisors, maxillary first molars, mandibu-lar first molars, and maxillary canines are the most con-served teeth in hypodontia. Successful use of osseointegratedimplants in the anterior mandibles of most of these patientssuggests that habilitation of the mandible with dental im-plant-supported prostheses is a reasonable option. (PediatrDent 20:278-80, 1998)

E ctodermal dysplasia (ED) is an inherited disor-der in which at least two structures derived fromthe ectoderm are abnormal. ED may be inher-

ited by all Mendelian means of inheritance.1 Signs andsymptoms have been well described.2’ 3 Oral findingscan be significant and include multiple tooth abnor-malities including anodontia and hypodontia withassociated lack of normal alveolar ridge development.4Other physical signs may involve the sweat glands, scalphair, nails, skin pigmentation, and abnormal or under-development of craniofacial structures.5’ 6

The condition includes two major types,hypohidrotic, in which the sweat glands are absentor decreased significantly, and hidrotic, in which thesweat glands are normal. The hypohidrotic is the moresevere type and is associated with sensitivity to heat andfrequent high fevers. This type is also thought to havemore associated dental defects. Hypohidrotic ED is anX-linked recessive trait. Birth prevalence of X-linkedhypohidrotic ED has been estimated to be between1/10 000 and 1/100 000.7 The gene responsible forhypohidrotic ED has recently been identified.8

Hypodontia is the second most frequently reportedsign in ED (80% of cases).* The pattern of missingteeth in severe hypodontia has been reported in pre-vious studies.9-J J Although Schalk-van der Weide andcolleagues found no association between congenitallymissing teeth and ectodermal symptoms in a studycomparing dental findings in 167 patients witholigondontia with 135 normal controls, they sug-gested that an individual with the most stable teethmissing, or with several teeth missing, should be ex-amined carefully for signs of ED.9 In another study,individuals with hypodontia associated with a syn-drome were found to be more likely to be missingmore teeth than individuals with hypodontia not as-sociated with a syndrome.~° In a sample of patientswith X-linked hypohidrotic ED, Crawford foundmore teeth missing in males and a difference in thepattern of teeth missing between males and females. ~lThesleff has recently summarized information con-cerning the genetic control of tooth development.~2

Additional information concerning the pattern ofpermanent teeth present in severe hypodontia may con-tribute to knowledge concerning etiological factors intooth agenesis.J3 Also, this information may be helpfulin formulating a general approach to planningprosthodontic treatment of individuals with ED andsevere hypodontia. The purpose of this study was toassess the pattern of permanent teeth present in a self-selected sample of patients with ED presenting fortreatment with dental implants.

278 American Academy of Pediatric Dentistry Pediatric Dentistry - 20:4, 1998

MethodsThe self-selected patient sample consisted of 17 fe-

males and 35 males diagnosed as having a form of EDwith associated severe hypodontia, who presented tothe dental clinic at the National Institute of DentalResearch, National Institutes of Health, for treatmentwith dental implants. The participants were respond-ing to information concerning a dental implant clinicaltrial distributed by the National Foundation for Ecto-dermal Dysplasia (National Foundation for EctodermalDysplasias, 219 East Main, PO Box 114, Mascoutah,IL 62258-0114). Mean age of the sample was 18.7years, with an age range from 5.9 to 60.9 years.

Panoramic radiographs of the sample were obtainedand examined independently by two investigators us-ing a standard radiographic viewing box to determinethe permanent teeth present. None of the participantsreported extractions of permanent teeth prior to present-ing for treatment with dental implants. Disagreementsbetween investigators concerning tooth identificationwere resolved by consensus.

ResultsThe permanent teeth most likely to be present re-

ported as a percentage of the patient sample with thattooth present were: maxillary central incisors, presentin 42% of the sample, maxillary first molars (41%);mandibular f~rst molars (39%); maxillary canines(22%); mandibular second molars (17%); maxillarysecond premolars (15%); and mandibular premolars(12%) (Fig

5.00

Man~bularTeeth

Fig 1. Percent of patients with each permanent tooth present.

Comparing dentition quadrants, mandibular ante-rior teeth (canines and incisors) were least likely be present (Wilcoxon’s signed-rank test, P < 0.01).No significant differences were found between malesand females.

DiscussionThe results support those of other studies in that the

maxillary central incisors, maxillary first molars, man-dibular first molars, and maxillary canines are the mostconserved teeth in severe hypodontia.10’ 14.15

Because males with ED usually exhibit more signsthan females, a random sample of ED patients withhypodontia would be expected to demonstrate moremissing teeth in males than females.ll However, a pre-requisite for participation in the protocol was severehypodontia associated with a form of ED. Conse-quently, all patients had severe hypodontia and wereseeking treatment with dental implants. This likelyobscured gender differences in severity of hypodontia.

Considerable research supports the efficacy of reha-bilitating a completely or partially edentulous mandibleusing a prosthesis supported by implants anchored inthe anterior mandible.16’ 17 The congenital absence ofteeth can result in minimal bone support for completeor partial, removable prostheses.

The congenital absence of teeth can result in mini-mal volume of bone for the placement of endosseousimplants in locations favorable for subsequent restora-tions. However, most of the patients whose radiographscomprised this sample, were successfully treated withmandibular fixed/detachable or bar-clip prostheses sup-ported by implants.~8 Preliminary results from theimplant phase of this study, which included most ofthis sample, found that 203 of 243 cylindrical threadedimplants (92%) placed primarily in the anterior man-dibles of 52 patients aged 7 to 68 years with severehypodontia successfully osseointegrated and were stillfunctioning after 3 years. Success rates varied by agegroup, 87% in preadolescents (aged 7-11), 90% adolescents (aged 12-17), and 97% in adults (olderthan 17). We have reported previously on a child whohad implants placed in the anterior mandible at age 3.5years that successfully osseointegrated and functionedto support a bar-clip overdenture after 5 years.19

Benefits of placing implants in young patients havenot been demonstrated. Bone volume may not be suf-ficient for placing the implants in ideal positions tosupport the prosthesis. Also, craniofacial growth willnecessitate remake and redesign of the prosthesis asgrowth occurs. If implant-supported prostheses wereshown to have positive effects on craniofacial growth,social development, self-image, and food choice, theiruse in the anterior mandible might be routinely recom-mended in younger patients.

Pediatric Dentistry -20:4, 1998 American Academy of Pediatric Dentistry 279

SummaryThe results of this study support previous findings

that the maxillary central incisors, maxillary first mo-lars, mandibular first molars, and maxillary canines arethe most conserved teeth in severe hypodontia. Becauseof the frequency of missing permanent mandibular an-terior teeth, individuals with ED and severe hypodontiamay be candidates for prosthodontic management withendosseous implant-supported mandibular dentures.

Dr. Guckes is an associate professor and Director of the Gradu-ate Program in Prosthodontics, Department of Prosthodon-tics, Dr. Roberts is an associate professor and Chair, Depart-ment of Pediatric Dentistry, both at the University of NorthCarolina School of Dentistry. Dr. McCarthy is Chief, Com-missioned Officers Dental Clinic, Clinical Center, the Na-tional Institutes of Health.

References

1. Freire-Maia N, Pinheiro M: Ectodermal Dysplasia: Aclinical and genetic study. New York:Alan R. Liss Inc.1984. 187-957

2. Freire-Maia N: Ectodermal dysplasias. Hum Hered21:309-312, 1971.

3. Lowry RB, Robinson GC, Miller JR: Hereditary ectodermaldysplasia: Symptoms, inheritance patterns, differential diag-nosis, management. Clin Pediatr 5:395-402, 1966.

4. Levin LS: Dental and oral abnormalities in selected ectoder-mal dysplasia syndromes. Birth Defects Orig Artic Ser24:205-227, 1988.

5. Bixler D, Saksena SS, Ward, RE: Characterization of the facein hypohidrotic ectodermal dysplasia by cephalometric andanthropometric analysis. Birth Defects Orig Artic Ser24:197-203, 1988.

6. Anton-Lamprecht I, Schleiermacher E, Wolf M: Autosomalrecessive anhidrotic ectodermal dysplasia: report of a case anddiscrimination of diagnostic features. Birth Defects OrigAttic Ser 24:183-95, 1988.

7. Clarke A: X-linked hypohidrotic ectodermal dysplasia: clini-cal and genetic studies. DM thesis, Oxford University, 1988.

8. Kere J, Srivastava AK, Montonen O, Zonana J, Thomas N,Ferguson B, Munoz F, Morgan D, Clarke A, Baybayan P,Chen EY, Ezer S, Saarialho-Kere U, de la Chapelle A,Schlessinger D: X-linked anhidrotic (hypohidrotic) ectoder-mal dysplasia is caused by mutation in a novel transmem-brane protein. Nat Genet 13:409-416, 1996.

9. Schalk-van der Weide Y, Beemer FA, Faber JA, Bosman F:Symptomatology of patients with oligodontia. J Oral Rehabil21:247-61, 1994.

10.Schalk-van der Weide Y, Steen WH, Bosman F: Distribu-tion of missing teeth and tooth morphology in patients witholigodontia. ASDC J Dent Child 59:133-40, 1992.

11.Crawford PJ, Aldred MJ, Clarke A: Clinical and radiographicdental findings in X linked hypohidrotic ectodermal dyspla-sia. J Med Genet 28:181-85, 1991.

12.ThesleffI: Two genes for missing teeth. Nat Genet 13:379-380, 1996.

13.Kjaer I, Kocsis G, Nodal M, Christensen LR: Aetiologicalaspects of mandibular tooth agenesis--focusing on the roleof nerve, oral mucosa, and supporting tissues. Eur J Orthod16:371-75, 1994.

14.Nakata M, Koshiba H, Eto K, Nance W: A genetic study ofanodontia in X-linked hypohidrotic ectodermal dysplasia.AmJ Hum Genet 32:908-919, 1980.

15.Tso MS, Crawford PJ, Miller J: Hypodontia, ectodermaldysplasia and sweat pore counts. Br DentJ 158:56-60, 1985.

16.Adell R, Lekholm U, Rockier B, Branemark PI: A 15-yearstudy of osseointegrated implants in the treatment of theedentulous jaw. lntJ Oral Surg 10:387-416, 1981.

17.Adell R: Clinical results ofosseointegrated implants support-ing fixed prostheses in edentulous jaws. J Prosthet Dent50:251-54, 1983.

18.Guckes AD, Brahim JS, McCarthy GR, Rudy SF, CooperLF: Using endosseous dental implants for patients with ec-todermal dysplasia. J Am Dent Assoc 122:59-62, 1991.

19.Guckes AD, McCarthy GR, Brahim J: Use of endosseousimplants in a 3-year-old child with ectodermal dysplasia: casereport and 5-year follow-up. Pediatr Dent 19:282-85, 1997.

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280 American Academy of Pediatric Dentistry Pediatric Dentistry - 20:4, 1998