Archs oral Bid. Vol. 18, pp. 543-553, 1973. Pergamon Press. Printed in Great Britain.

A PROPOSED CLASSIFICATION FOR HERITABLE HUMAN DENTINE DEFECTS WITH A DESCRIPTION OF

A NEW ENTITY

E. D. SHIELDS, D. BIXLER and A. M. EL-KAFRAWY

Department of Oral-Facial Genetics, School of Dentistry, Indiana University-Purdue University, Indianapolis, Indiana 46102, U.S.A.

Summary-A newly recognized heritable dentine defect is described which is manifested as an amber, translucent colouration and total pulpal obliteration in all primary teeth. Permanent teeth have a thistle-tube pulp configuration with ubiquitous pulp stones and normal colouration.

The unusual finding of true denticles in these heritable dentine defects may represent the induction of odontoblastic differentiation by aberrant epigenetic factors produced in the abnormally developing dentine.

A classification for the heritable dentine defects is proposed which consists of two distinguishable groups; the dentine dysplasias and the dentinogenesis imperfectas.

INTRODUCTION

THE primary purpose of this report is to characterize a newly recognized type of dentine effect which is inherited as an autosomal dominant trait. This genetic defect is phenotypically manifested as: (1) an amber, translucent colouration in the deciduous dentition with obliteration of the pulp chamber by hypertrophy of an amorphous dentine; and (2) a normal colouration to the permanent dentition in which a circum- pulpal dentine hypertrophy produces a thistle-tube like pulp configuration with ubiquitous pulp stones.

In an attempt to relate this anomaly to previously reported cases of dentine defects, we found the literature often ‘confusing, incomplete and even contradictory. Such descriptive terms as “anomalous”, “atypical”, and “unusual” often provided a barrier to a legitimate attempt to delineate the spectrum of dentine defects. The ultimate purpose of this paper, then, is to construct and discuss a more meaningful and usable nomenclature for these heritable defects.

MATERIALS AND METHODS

Clinical and radiographic examination was initially made on four individuals in a family, all of whom had a developmental defect of dentine. A family pedigree was constructed to show genetic relationships, including 12 persons reported by the family to be affected. Subsequently, 6 of these persons had radiographic studies which confirmed the presence of this dentine defect.

Histopathologic studies were made on the deciduous teeth of the proband and permanent teeth of the proband’s mother. Serial sections were made at 7 pm and the following staining techniques employed: haematoxylin and eosin, Masson’s trichrome, periodic acid-Schiff and Alcian blue.

RESULP

A pedigree of the affected family is shown in Fig. 1. The proband (111-2) was a 14-yr-old caucasoid female in good systemic and oral health, who was referred to the

543

544 E. D. SHIELDS, D. BIXLER AND A. M. EL-KAFRAWY

I

U . . . . . . . . . . . . .

&g&75 0

FIG. I. Pedigree of family number 3608, dentine dysplasia type II. ? -affected male,

v -normal male, l -affected female, 0 -unaffected female, @ -3 un-

affecteds, sex unknown. The black dot beneath a circle or square signifies the individual was examined by the authors.

Department of Oral-Facial Genetics for evaluation of dental radiographs suggesting an aberrant form of dentinogenesis imperfecta.

She presented with a complete complement of erupted, permanent teeth, except for the developing third molars. Clinically, the teeth were of normal colour, enamel consistency and crown form, except for a mild hypoplasia of the mesial- in&al enamel lobes of the maxillary canines and talon cusps on the maxillary lateral incisors. She had no signs of attrition and had several occlusal carious lesions.

A previous radiographic survey at the age of 5 yr (Fig. 2a) showed deciduous teeth of normal shape and opacity, but the pulp chambers were totally obliterated. The patient described her deciduous teeth as having a “brown” colouration. Subsequent radiographs (Fig. 2b) of her developing permanent dentition (age 11 yr) showed a marked hypertrophy of the circumpulpal dentine and faintly outlined pulp stones.

Radiographs at 14 yr of age (Fig. 2c) revealed permanent teeth with normal root size and shape and with a thistle-tube pulp configuration, and pulp stones in every pulp chamber. The anterior maxillary teeth were the most severely affected (Fig. 2d), with nearly total obliteration of the pulps.

Histologic sections were obtained from a deciduous molar which had been salvaged by the patient’s mother. Decalcified sections revealed a very thin layer of normal coronal dentine with a sudden radicular transition into a very dense amorphous dentine with few tubules. The tubules were haphazardly arranged with irregular foci of decreased calcification staining with haematoxylin.

The mother (II-l) of the proband also had a history of “brown” deciduous teeth. Clinically, her permanent teeth were of normal form and consistency with no signs of attrition, but they did display an extremely faint, dull amber colouration. Her radio- graphic findings were essentially identical to those of her daughter. She had a peri-

HERITABLE DENTINE DEFECl’S: DENTINE DYSPLASIA TYPE II 545

apically involved, carious, maxillary left second premolar which was obtained for histopathologic examination. In this tooth (Fig. 3), the dentine of the crown was relatively normal, but dentine in the pulpal one-third showed numerous interglobular areas. Radicular dentine, on the other hand, was atubular and amorphous and even showed occasional empty lacunae. Furthermore, there was an uneven staining pattern evident with basophilic islands amidst pale staining areas. The root canals were reduced in dimension and contained a thin strip of pulp tissue.

Two false denticles with the typical, concentric, lamellated pattern were present within the pulp chamber. The floor of the pulp chamber seemed to be formed of a single large denticle, the peripheral part of which was tubular and blended impercept- ibly with the atubular, amorphous dentine. This, we felt, was a true denticle. Resorp- tion had apparently occurred in that “stone”, since there was a reversal line over which appeared apposition of the amorphous, atubular dentine. This large stone was surrounded on all sides by a narrow strip of pulp tissue.

Case 3 (III-3), a 2%yr-old male, is the proband’s first cousin on the mother’s side. He has a very mild, amber, translucent colouration of his permanent dentition. Radiographically, he manifested the same findings as III-2 and 11-l but there was somewhat more pulpal constriction.

Case 4 (IV-l) is a 2-yr-old female who is the daughter of case 111-3. Clinically, her deciduous teeth displayed an amber-bluish translucent colouration characteristic of that seen in hereditary opalescent dentine. Radiographically, there was still some pulp chamber present but a pronounced dentine hypertrophy was evident.

The other affected subjects who were examined (I-4,11-4, -5, -9 and -11 and 1114) showed radiographic findings that are nearly identical to those of the proband. Specifically searched for was a positive family history for any signs and symptoms of osteogenesis imperfecta. None was found, nor was any other disease of genetic origin apparent.

Segregation .analysis performed on affected subjects carefully examined in six of the eight sibships showed an affected to normal ratio of: males, 4: 5; females, 5 : 4. These data, plus instances of male-to-male transmission and no example of an affected person with both parents unaffected strongly, suggest an autosomal dominant trait with essentially 100 per cent penetrance. We have designated this defect as dentine dysplasia type II for reasons discussed below.

DISCUSSION

In reviewing the literature, it became evident that heritable dentine defects can be viewed as a continuum with the basic, unifying denominator for them all being that both deciduous and permanent teeth are affected and there appears to be a common time for their initiation. The latter stems from the fact that all the affected teeth have normal mantle dentine. Accordingly, an attempt has been made to create a meaningful classification of these dentine anomalies into which the various cases described in the literature, both typical and atypical, can be readily fitted. Two broad categories are identifiable, dentine dysplasia and dentinogenesis imperfecta, with subtypes of each. This nomenclature has the advantage of preserving terminology already in wide usage.

546 E. D. SHIELDS, D. BIXLER AND A. M. EL-KAFRAWY

WITKOP and RAO (1971~) have reviewed inherited defects of tooth structures. Defects of the primary tissues of teeth involve enamel, dentine, cementum and pulp; to be placed in the proposed classification the aberration must be a primary dentine defect. Table 1 summarizes the salient features of each of the primary dentine defects in this classification.

Clinical (1) Primary teeth amber, translucent (2) Secondary teeth discoloured (3) Discoloration in both dentitions (4) Loose teeth (5) Rapid attrition of crowns (6) Fragile roots

Roentgenograpbic (1) Ovoid crowns (2) Short, tapering roots (3) Obliteration of pulp cavities:

(a) Before eruption (b) After eruption

(4) Horizontal line at DE3 (crescent-shaped pulp chamber) (5) Apical extension of pulp chamber (6) Multiple apical radiolucencies (7) Thistle-tube shape to pulp chamber (8) Reduced X-ray contrast of dwtinc (9) Pulp stones in pulp chamber

Histopathologic (1) True denticles (2) False ~enticles,

Fe($E$xr;ss&d&tme remodeling

(1) Primary teeth more severely affected (2) “Normal” mantle dentine (3) “Abnormal” radicular dentine (4) Normal enamel (5) Interglobular dentine (6) Scalloping of DEJ

* -

++ I

+-+ ++ ++ L+ +-+ - ++ - -

:: +++ +++

++ _ - - - _ - -

I T 7

++ ++ +++ ++ z +i z

+ ++

i ++ +

: - _ +

++ -

z - ++ E : +

:z +i+ +-t+ +++

+

* = Unreported. + + = Typically evident in all teeth.

+ = Variable in frequency or severity. - = Absent.

Type I (dentine dysplasia)

A. Dentine dysplasia

Clinical_findings. The permanent and deciduous teeth are of normal shape, form, and consistency (NOYES, 1935; LOGAN et al., 1962; ELZAY and ROBINSON, 1967). In some cases the colour of the teeth may vary somewhat from normal and display a slight, amber transluency (WITKOP and SAUK, 1971b).

Radiographic jindings. The teeth have short roots, typically with sharp, conical, apical constrictions (WEGNER and MANNKOPF, 1958; BERNARD, 1960; STAFNEY, 1969). Pre-eruptive pulpal obliteration results in a crescent-shaped pulpal remnant parallel to the cemento-enamel junction in the permanent dentition and a total pulpal obliteration in the deciduous dentition (WITKOP and SAUK, 1971b). There are usually numerous periapical radiolucencies in non-carious teeth (RUSHTON, 1939a) which are essentially diagnostic of this disorder.

Pathologicjndings. The initial layer of “mantle” dentine and most of the coronal dentine is normal (RUSHTON, 1939a; BROOKER~~N and MILLER, 1968; BRUSZT, 1969)

HERITABLE DlXTIlNB DEFECTS: DENTINE DYSPLASIA TYPE II 547

although there are areas (especially in deciduous teeth) of atubular dentine (LOGAN et al., 1962). The dentinal tubules are blocked and shunted from their usual paths by numerous and sometimes massive true denticles (ZELLNER, 1957 ; LOGAN et al., 1962) which permeate the root and fill the pulp space.

Genetics. This is apparently an autosomal dominant trait, although only a few cases have been reported (RUSHTON, 1939a; HIGGINS and MARSLAND, 1952; ZELLNER, 1957).

Type II (anomalous dysplasia of dentine)

This is the designation for our family. The clinical, radiographic, pathologic and genetic aspects are described under “Results”. There have been three previous reports in the literature (GRIMER, 1956; RICHARDSON and FANTIN, 1970; RAO, WITKOP and YAMANE, 1970) with findings nearly identical to our case and all of which we believe represent a similar type of dentine dysplasia. GRIMER (1956) presented a case show- ing a thistle-tube deformity of the pulp cavity and pulp stones, typical of this type of dentine dysplasia. Grimer’s findings of a brown-grey colouration in the permanent dentition and a family history of severe attrition were not observed in our kindred.

RICHARDSON and FANTIN (1970) reported a dominantly inherited dentine defect in which they made no mention of tooth colouration. However, histologic sections of deciduous canines from the proband and radiographs of the permanent teeth of the proband’s mother were identical to those in our family. The proband manifested large pulp chambers, with a thistle-tube type deformity and pulp stones.

RAO et al. (1970) presented a case which showed thistle-tube pulp configurations, pulp stones and a brownish, opaque colouration of the permanent teeth. The family history was that of a dominantly inherited trait, but there were insufficient data to rule out X-linkage. Although named pulpal dysplasia by them, we feel this case has findings typical of dentine dysplasia type II. Unfortunately, no histologic sections were presented.

A fourth report by RUSHTON (1955) may also represent this same entity. He observed two individuals with abnormal colouration in their anterior teeth and first molars. The teeth that had normal colouration showed only constricted root canals as evidence of abnormality. There was no family history presented in either case but the two individuals had the same surname.

The above four reports, together with our kindred, constitute the new subgroup, dentine dysplasia type II. There are two unreported cases (C. J. WITKOP, personal communication) of familial “thistle tube” pulp chambers in deciduous teeth without pulpal obliteration. These cases may represent either heterogeneity within dentine dysplasia type II or variable gene expression.

B. Dentinogenesis imperfecta

Dentinogenesis imperfecta of the type which is seen in patients with osteogenesis imperfecta and isolated dentinogenesis imperfecta (hereditary opalescent dentine) may someday be proven to be the same genetic entity. However, until specific biochemical

548 E. D. SHIELDS, D. BIXLER AM) A. M. EL-KAFRAWY

evidence supports one thesis or another (BIXLER, CONNEALLY and CHRISTEN, 1969), the available clinical and family data force the recognition of two entities.

Type I (dentinogenesis imperfecta)

Clinical features. Typically, a striking amber translucency of both the deciduous and permanent dentition. The enamel often chips and fractures away (TOTO, 1953), allowing speedy attrition of the remaining softer dentine.

Radiographic features. Both dentitions show short, constricted roots (LISTGARDEN, 1960) and marked dentine hypertrophy. The deciduous and earlier permanent teeth have an accelerated pulpal obliteration, i.e. they are the most severely affected of all the teeth (FAIRBANK-quoted in RUSHTON, 1939; WITKOP and SAUK, 1971b). Pulpal obliteration occurs soon after eruption and sometimes even before eruption (WITKOP and RAO, 1971~).

Pathologic features. The dentino-enamel junction shows scalloping but, typically, a normal peripheral layer of dentine (HODGE and FINN, 1938; IVANCIE, 1954; LIST- GARDEN, 1960). Teeth have been observed with no normal dentine within the root (BECKS, 1931; RUSHTON, 1955). The normal “mantle” dentine merges with a dysplastic form which eventually hypertrophies to totally obliterate the pulp chamber and pulp canal.

The abnormal dentine is typically atubular (PINDBORG, 1947) while those tubules which are discernible show considerable variation in size and direction, Often inter- posed in this dentine are true denticles (PFLUGEX, 1929; RUSHTON, 1939b; MUNCH, 1956) and an interglobular type of calcification (BURSTONE, 1953; RUSHTON, 1955).

Genetics. The degree of expressivity of this trait is variable, even within an individual patient. The defect ranges from total pulpal obliteration (typically posteruptive), to teeth with generally normal dentine, to the most minimal sign of “vascular canals” (RUSHTON, 1955 ; WITKOP and SAUK, 1971b) and normal dentine.

Dentinogenesis imperfecta type I segregates as an autosomal dominant trait, with variable expressivity, within families having osteogenesis imperfecta (BLATTNER, HEYS and ROBINSON, 1942). BIXLER et al. (1969) hypothesized that the metabolic pathways involved in dentine and bone matrix formation probably come together at some point distal to the specific metabolic defects in dentinogenesis imperfecta and osteogenesis imperfecta. This could explain why one never finds dentinogenesis imperfecta type I segregating as a separate entity in families with osteogenesis imperfecta while osteogene- sis imperfecta may occur without dentinogenesis imperfecta (HEYS, BLATTNER and ROBINSON, 1960).

Type II (hereditary opalescent dentine)

This developmental defect, which is often referred to as opalescent dentine, has many clinical, radiographic, pathologic and even hereditary similarities to dentino- genesis imperfecta type I (WILSON and STEINBRECKER, 1929; HODGE et al., 1936; ROBERTS and SHOUR, 1939; LYONS, 1940; BERGMAN, ENGFELDT and SUNDVALL- HAGLAND, 1956; JOHNSON et al., 1959).

HERITABLE DENTINE DEFECTS: DENTINE DYSPLASIA TYPE II 549

The reasons for recognizing type II as a separate entity are the following: (1) Families which demonstrate dentinogenesis imperfecta type II never have

osteogenesis imperfecta (SKILLEN, 1937; PINDBORG, 1948; WINTER and MAIOCCQ 1949 ; BIXLER et al., 1969; WITKOP and SAUK, 1971b). The possible single exception (RUSHTON, 1955) is probably a chance association of two individual traits.

(2) The within-family correlation of severity, coloration and attrition is high in dentinogenesis imperfecta type II (BIXLER et al., 1969), whereas it is considerably more variable in type I.

(3) In dentinogenesis imperfecta type II, both dentitions are equally affected in clinical and radiographic appearance (SCLARE, 1948), and one never finds completely normal teeth (BIXLER et al., 1969), whereas in type I the deciduous teeth are always more severely affected than the permanent and it is not uncommon to find normal- appearing teeth in the permanent dentition.

A number of atypical cases of dentinogenesis imperfecta type II have been reported (CHAPUT, 1952; GOLDWEBER, 1957; PULVER, 1962; RUSHTON, 1955; SOBEL and DOYKOS, 1969) which seem to defy any genetic classification and, because of our present lack of knowledge concerning these isolated occurrences, they are omitted from this formal classification.

Type III (brandywine isolate hereditary opalescent dentine)

HURSEY et al. (1956) and WITKOP et al. (1966) reported unusual dental findings in a triracial isolate from southern Maryland and Washington DC.

Clinical features. In coloration and shape, the teeth in affecteds appeared some- what variable as in either dentinogenesis imperfecta type I and II. Unlike the latter two traits, multiple pulp exposures were observed in the deciduous teeth in dentino- genesis imperfecta type III.

Roentgenogruphic features. The deciduous teeth, even within a single individual, showed considerable variation in appearance, ranging from normal to dentinogenesis imperfecta type II teeth, and even to “shell” teeth. The latter, as seen in eight subjects (WITKOP et al., 1966), were characterized as teeth in which dentine formation ceased after the mantle layer was formed. Hence, the term “shell” teeth was coined to describe their hollow appearance. There are two other reports of shell teeth, a single case (RUSHTON, 1954) and one family which also had enamel aplasia (SCHIMMELPFENNIG and MCDONALD, 1953). The latter family was later found to be related to the brandy- wine isolate (WITKOP, 1971a). It must be emphasized that in all the cases reported to have dentinogenesis imperfecta type II, there are no reported instances of shell teeth.

Further radiographic variation was observed (WITKOP et al., 1966) in three cases in which the primary teeth showed normal pulp chambers and canals, and yet the clinical and histologic appearance was typical of dentinogenesis imperfecta type II. This report also described a fourth person who had similar findings in the permanent teeth.

Pathologic features. The information available is not adequate to permit a descrip- tion of the histologic features of this trait.

Genetics. The pedigree presented by HURSEY et al. (1956) is that of an autosomal

550 E. D. SHIELDS, D. BIXLER AND A. M. EL-KAFRAWY

dominant trait. Our interpretation of this dentine defect is that it represents a distinct type of dentinogenesis imperfecta, perhaps genetically allelic to type II. Differentiation of types II and III will probably be established only with the elucidation of the primary chemical defect or by linkage studies once a linkage group has been proven.

Several other entities involving abnormal dentine have been omitted from our classification either because only one case was reported, without apparent heritable components (MILLER, 1969; RAO ef al., 1970; RUSHTON, 1954) or because they were not clearly primary dentine defects (BERNICK, 1970; HAUNFELDER, 1967; MENA, 1971; WITKOP and SAUK, 1971b; BERGMAN, LYSELL and PINDBORG, 1963; RUSHTON, 1965).

It appears that primary dentine defects have four salient features: (1) a monogenic mode of inheritance; (2) various degrees of dentine tubular disorganization; (3) a normal layer of mantle dentine; and (4) true denticles, an apparently unrelated develop- mental defect. We have been impressed that the latter is a routine occurrence in this series of developmental defects.

Denticles or pulp stones are of two types: (1) True denticles, which are disorganized structures of tubular dentine, and are rare findings in normal teeth (PROVENZA, 1964; TIECKE, 1965; STENVIK and MJOR, 1970; SIGHER and BHASKAR, 1972); and (2) False denticles, which are atubular, lamellated calcifications and are relatively common. Thus, the occurrence of a relatively rare structure, the true denticle, in all these dentine defects demands some attempt at explanation. Although there is a great need for better documentation of the occurrence of true dentides, it is clear that the various single genes producing these dentine defects have a common “pleiotropic” effect in producing true denticles. We have found it conceptually more useful to consider this phenotypic pleitropism as an epigenetic effect.

We postulate that abnormal dentine produces abnormal epigenetic factors, as for example, the demonstrable altered pyroelectric and piezoelectric dentine potentials in pathologically involved teeth (ATHENSTAEDT, 1971) which may induce odontoblastic differentiation of the pluripotent mesenchymal cells within the pulp. Undifferentiated mesenchymal cells could thereby be induced to function as odontoblasts producing tubular but irregular dentine (true denticles). At this stage of our knowledge, one may only speculate on the many epigenetic factors emanating from these dentine defects that may induce odontoblastic differentiation. Possibly, different functional cell types may be produced from such epigenetic factors since in the dentine dysplasia type II cases described in this report, a very rare and unusual finding of massive internal remodeling of the true denticles was noted.

Acknowledgements-We would like to express our gratitude to Dr. CARL WITLOP for the valuable information and very useful suggestions offered in the preparation of this manuscript.

This study was supported by the National Institute of Dental Research; the senior author is a research fellow, fellowship number 1 F02 DE 52103-01, and the second author is a career development awardee, DE 05945-05.

HERITABLE DENTINE DEFWXS : DENTINE DYSPLASIA TYPE II 551

R&m&-On d&it un ddfaut hereditaire de la dentine, recemment admis, qui se mani- feste comme une coloration ambre, transparente et une obliteration totale de la pulpe dam toutes les dents primaims. Les dents primaires ont une configuration de la pulpe d’aspect tubulaire, en forme de chardon, ayant partout des pierres pulpeuses et une coloration normale.

Les decouvertes peu communes de veritables denticules dam ces defauts hCr&litaires pourraient rep&enter l’installation dune diff6renciation odontoblastique par des facteurs epig&siques abet-rants produits dans la dentine se developpant anormalement.

On propose une classification des defauts he&ditaires de la dentine, qui consiste en deux groupes distincts: les dysplasies de la dentine et lcs imperfections de la dentino- g&&se.

Zusammeafassung-Ein neu erkannter, erblicher Dentinfehler wird beschrieben, der sich in gelbbrauner, lichtdurchlassiger Verfarbung und voller Zerstorung der Pulpa bei allen Milchzahnen bemerkbar macht. Dauerzahne haben eine Tropftrichteranordnung der Pulpa mit uibiquitben Pulpasteinen und normaler F&bung.

Das unnewijhnliche Finden wahrer Dentikel in diesen erblichen Dentinfehlem kann die Induktion von odontoblastischer Ditferenzierung durch anormale epigenetische Faktoren darstellen, welche sich in dem abnormal entwickelnden Dentin bildeten.

Es wird eine Klassifizierung der erblichen Dentinfehler vorgeschlagen, die aus zwei unterscheidbaren Gruppen besteht: Die Dentindysplasie und die Dentinogenesis imperfecta.

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PLATE 1 OVERLEAF

HERITABLE DENTINE DEFECTS: DENTINE DYSPLASIA TYPE11

FIG. 2 A-D. Proband radiographs at (A) 5 yr of age demonstrating pulpal obliteration; (B) 11 yr of age, showing developmental hypertrophy of the circumpulpal dentine and developing pulp stones; (C) 14 yr of age-note thistle-tube pulp configuration; (D) also

14 yr of age with nearly total pulpal obliteration of incisors evident. Fro. 3. A longitudinal section of a maxillary second premolar (magnification x I). Note

true denticle surrounded by pulpal tissue (arrow). PLATE I

A.O.B. f.p. 554