Rough hypoplastic amelogenesis imperfecta with follicular hyperplasia Edmund Peters, DDS, MSc, FRCD(c),” Mark Cohen, BDS, M Dent, FRCD(C),b and Mario Altini, BDS, M Dent,c Edmonton, Alberta, Canada, Saskatoon, Saskatchewan, Canada, and Johannesburg, South Africa

UNIVERSITY OF ALBERTA, UNIVERSITY OF SASKATCHEWAN, AND UNIVERSITY OF

WITWATERSRAND, JOHANNESBURG

This report documents a unique case of rough hypoplastic amelogenesis imperfecta with apparent anterior oligodontia and multiple anomalies of the associated mesenchymally derived tissues. Multiple unerupted teeth showed hypercementosis, distorted roots with aberrant dentin formation, and marked follicular hyperplasia. The hyperplastic follicles had a complex histopathologic appearance that recapitulated some features of the WHO-type odontogenic fibroma. The features of these teeth, the nature of the associated follicular lesions, and their relationship to the unerupted teeth are discussed. (ORAL SIJRC ORAL MED ORAL PATHOL 1992;74:87-92)

A melogenesis imperfecta (AI) encompasses a group of hereditary diseases that involves the defec- tive formation and/or calcification of enamel. Hy- poplastic, hypomature, or hypocalcified enamel oc- curring in various inheritance patterns define the different subtypes. However, the biologic potential of AI is not limited to defective enamel. Further local stigmata could include unerupted teeth, anterior open bite, pulpal calcifications, interradicular dentinal dys- plasia, root and crown resorption, cementum deposi- tion, truncated roots, and association with tauro- dontism.lM3 Some of these features could be secondary to the genetically determined defects in amelogenesis. The extent to which they can be used to determine distinct subtypes is not clear.

This article documents an unusual case of hy- poplastic AI characterized by apparent anterior oli- godontia and multiple unerupted distorted teeth as- sociated with large solid fibrous pericoronal lesions. The fibrous lesions were histologically characterized by a florid distribution of odontogenic epithelial islands and complex calcifications. The possible rela-

“Department of Oral Biology, Faculty of Dentistry, University of Alberta. bFaculty of Dentistry, University of Saskachewan. ‘Department of Oral Pathology, University of the Witwatersrand, Johannesburg. 7/14/35501

tionship of these lesions to the unerupted teeth is dis- cussed.

CASE REPORT

A 26-year-old black man was referred to us for manage- ment of a 3 cm fluctuant infectious swelling of the right cheek that had occurred after extraction of a partially erupted right upper second molar. His medical history and general physical condition were unremarkable. Intraoral examination revealed the patient was partially edentulous with eruption of small yellow premolars and first molars in each quadrant (Fig. 1, A and B). Except for the recent re- moval of the second molar, the patient reported that he had had no previous extractions. There were no further abnor- malities other than a somewhat nodular fibrotic gingiva.

A radiographic examination (Fig. 2) showed well-devel- oped roots in the erupted teeth. With the exception of the recently extracted upper right second molar, the second and third molars were unerupted in all quadrants and showed distorted and poorly developed roots. The unerupted teeth were associated with large well-defined radiolucencies that extended to involve the crest of the alveolar ridge in the mandible. Occlusal radiographs showed a radiopacity in the anterior part of the mandible that possibly represented an incisor. The lack of enamel was evident in all teeth.

After a discussion with the patient, the decision was made to remove the unerupted molars and associated radiolucent lesions while the patient was under a general anesthetic and the abscess was being drained. Solid pericoronal soft tissue masses were easily enucleated with the impacted teeth. The pathologic specimens consisted of three intact and four

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88 Peters, Cohen, and Altini ORAL SURG ORAL MED ORAL PATHOL .July 1992

Fig. 1. Upper (A) and lower (B) arches showing anterior oligodontia; posterior teeth exhibit simplified coro- nal morphology reflecting lack of enamel.

Fig. 2. Radiograph of unerupted posterior molars in association with enlarged pericoronal radiolucent spaces that extend to alveolar crest (arrows) in two areas.

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Amelogenesis imperfecta 89

Fig. 3. Intact surgically removed molars. Roots are distorted and appear disproportionately large in com- parison to crown. No enamel is evident.

fragmented molars and multiple gray-tan pieces of forma- lin-fixed solid soft tissue, the largest of which measured 25 X 15 mm. The teeth (Fig. 3) showed the same features as the erupted teeth. Ground and decalcified sections of the teeth were examined with light microscopy, and further in- tact portions were examined with scanning electron micros- copy. The soft tissue was processed routinely for light mi- croscopy.

The ground sections showed a very thin, irregular zone of granular enamel. The dentin was well formed; however, the roots were truncated and there were aberrant dentinal out- pouchings encased within extensive zones of cementum (Fig. 4). The decalcified sections showed large foci of intra- pulpal dysplastic dentin interspersed and blended with irregular and whorled calcifications (Fig. 5). Scanning electron microscopy demonstrated the scanty, poorly form- ed, rough, and friable nature of the coronal layer (Fig. 6).

The soft tissue consisted of a moderately cellular fibrous tissue characterized by the presence of numerous conglom- erates of variably sized, globular, eosinophilic, periodic ac- id-Schiff/diastase-positive hyaline material and islands of odontogenic epithelium (Fig. 7). In some areas the globules showed concentric calcifications, and in other areas the globules blended into and were replaced by a translucent nonstaining crystalline material. The translucent structures were present in large masses in localized areas. The epithe- lial islands often showed vacuolar changes and occasionally were associated with the conglomerates.

The clinical and histologic features suggested a diagno- sis of rough hypoplastic amelogenesis imperfecta with asso- ciated abnormalities of the odontogenic mesenchymal tissues that included aberrant root formation, dysplastic intrapulpal calcifications, hypercementosis, and massive follicular hyperplasia.

Fig. 4. Representative ground section of molar with very thin and inconsistent, irregular, granular layer of enamel. Malformed roots show aberrant dentin formation in bud- ding radicular outgrowth; however, dentin is qualitatively unremarkable. Enlarged zones of cementum encase inter- radicular aspects. (Original magnification ~7.)

The patient was subsequently questioned further on the presence of similar abnormalities in his family, including

parents and grandparents. He stated that no other members had a similar condition; however, it was not possible to ex- amine other family members. After an uneventful recovery from surgery, the patient was lost to further follow up.

90 Peters, Cohen, and Altini ORAL SURG ORAL MED ORAL PATH~L July 1992

Fig. 5. Representative decalcified section with pulp. Ir- regular masses of disorganized calcified material are evi- dent; supporting pulpal tissue shows artifactual reticular degeneration. (Hematoxylin-eosin stain: original magnifi- cation X200.)

DISCUSSION

This case involves two major points of interest: (1) the nature of the malformed enamel and the AI sub- type and (2) the nature of the follicular hyperplasia and its relationship to the nonerupted teeth.

The thin granular enamel layer documented in this case is described in the rough hypoplastic form (enamel agenesis). Enamel agenesis is a rare form of AI, usually with an autosomal recessive inheritance pattern.” 2 Although this inheritance pattern is con- sistent with our case, the family pedigree could not be clinically confirmed. Other cases in this category have been reported by Witkop and Sauk,’ Frank and Bo- lander,4 Catena et aL5 Chosak et al.,6 and Ooya et al7 In addition to the thin granular layer of enamel, these reports typically described multiple unerupted teeth that could undergo partial resorption. These reports do not specifically note enlarged follicles or the root anomalies evident in our case. The apparent congen- ital absence of the anterior teeth in our case is intriguing; however, this finding is based on the patient’s history, since no prior clinical documenta- tion was available. A further possible interpretation is that these teeth were resorbed; resorption of unerupted teeth is well documented in AI, although complete, region-specific resorption of multiple teeth would be unique.

In this case, the size of the follicular lesions and their complex histologic appearance suggested an in- terpretation of concomitant odontogenic fibromas (WHO-type).8 However, calcific structures and epi- thelial islands can occur within the contiguous fibrous tissue of unerupted teeth in AI’ as well as in other

conditions, such as regional odontodysplasia9 and epidermolysis bullosa, lo in which there is a disruption of odontogenesis. To a lesser extent, calcifications and islands of odontogenic epithelium are also character- istically found in normal follicles.” These observa- tions support the suggestion that such features, in the absence of a distinctive cellular stromal component made up of plump fibroblasts, are not of pathogno- manic significance in the diagnosis of odontogenic fi- broma (WHO-type). I2 Thus, we interpret these le- sions as hamartomatous follicular proliferations.

Two reports I3914 of patients without AI who had unerupted teeth and histologically similar enlarged dental follicles indicate this process occurs in condi- tions that do not involve a disruption in odontogene- sis. These reports also emphasize the similarities of these lesions to WHO-type odontogenic fibromas but favored the interpretation that they represented ham- artomatous growths. A further report by van Heerden et a1.15 described two patients with rough hypoplastic AI who were from the same region as our patient. The first case was thought to show an autosomal dominant inheritance; the inheritance pattern in the second was not established. Both patients had follicular enlarge- ments, root malformations, and hypercementosis. The authors interpreted the follicular lesions to represent WHO-type odontogenic fibromas. Of further possible interest in this report was the observation that in the second case numerous teeth were missing, which sug- gested further similarities to our case. The authors noted evidence of some previous extractions in the mandible but do not indicate whether any teeth might have been congenitally absent.

There have been suggestions that follicular enlarge- ments, such as those noted in our case, might block eruption 14, ’ 5; an alteration in collagen fibrillogenesis has been postulated as a possible mechanism.14 How- ever, eruption defects, apparently without follicular enlargements, are often found in AI. Further, in nor- mal development the follicle does not obstruct but promotes the intraosseous phase of eruption. If erup- tion is blocked experimentally, there is subsequent continued proliferation of the coronal follicular por- tion that resorbs bone and produces an unused erup- tion pathway.*6-‘8 Whether this observation is appli- cable in the pathologic context of AI is not clear. Pos- sibly a similar follicular proliferation could occur in some forms of AI that exhibit unrelated primary eruption defects. In keeping with this concept, the le- sions in our case occasionally extended to the alveolar crest and, in spite of their large size, clinical expan- sion of the bone was not a notable feature. Parenthet- ically, it is unlikely that the distorted roots and aber- rant dentin formation found only in the unerupted

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Fig. 6. Representative scanning electron micrograph of a longitudinally fractured molar with friable and granular nature of enamel demonstrated by ground section in Fig. 4. (Original magnification X60.)

Fig. 7. (A), Section of hyperplastic follicular tissue. The fibrous stroma shows numerous scattered islands of epithelium and a spectrum of complex deposits, from nonstaining refractile crystalline structures (B) to clusters of irregularly shaped eosinophilic, strongly PAS/diastase positive droplets (C); these droplets often showed concentric calcifications. (A and B, Hematoxylin-eosin stain; C, Periodic acid-Schiff stain/diastase digestion; original magnifications, A, ~63, B and C, X400.)

teeth were causally related to the eruption defect; rough hypoplastic AI with a concomitant spectrum of rootless teeth and even devitalized crown shells or ar- unusual features that involve the associated mesen- tificial crown replicas transplanted into follicles can chymally derived tissues and possibly congenital ab- erupt.i81 l9 sence of some teeth. The follicular hyperplasia, which

In summary, this article documents a rare case of was the most dramatic manifestation of the associated

92 Peters, Cohen, and Altini

mesenchymal anomalies, is clearly not unique to this condition. There does not appear to be convincing ev- idence to indicate whether these lesions are primary factors that impede eruption or occur as secondary events.

The technical assistance of Jean Crooks and Colleen Murdoch is gratefully acknowledged.

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Edmund Peters, DDS, MSc, FRCD(c) Department of Oral Biology Faculty of Dentistry University of Alberta Edmonton, Alberta, Canada T6G 2N8