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anamalies include variations in normalsize, eruption, or morphology of the

teeth. In this chapter these anomalies have beendivided into developmental abnormalities and acquiredabnormalities. The term developmental indicates that aparticular anomaly occurred during the formation ofthe tooth or teeth. Given the complexities and interac-tions involved in tooth development, from initiation atabout the sixth week in utero to eruption, the smallnumber of various anomalies is surprising. Most of thedefects considered are inherited. In contrast, acquiredabnormalities result from changes to teeth after normalformation. For instance, teeth that form abnormallyshort roots represent a developmental anomaly,whereas the shortening of normal tooth roots by exter-nal resorption represents an acquired change.

spontaneous gene mutations. When the anomaly isrestricted to supernumerary teeth, it is inherited asan autosomal recessive trait. The supernumerary teeththat occur between the maxillary central incisors aremesiodens (Fig. 18-1); those occurring in the molararea are parateeth. Those that erupt distal to the thirdmolar are called distodens or distomolar teeth (Fig. 18-2).Also, supernumerary teeth that erupt ectopically eitherbuccally or lingually to the normal arch are peridens.

Clinical FeaturesSupernumerary teeth occur in 1 % to 4% of the popu-lation. Although they may develop in both dentitions,they are more common in the permanent. Supernu-merary teeth may occur anywhere in either jaw. Singleteeth are most common in the anterior maxilla (mesio-dens) and in the maxillary molar region. Multiplesupernumerary teeth occur most frequently in thepremolar regions, usually in the mandible (Fig. 18-3).The mandibular counterpart of the mesiodens is rare.Supernumerary teeth occur twice as often in males andhave a greater incidence in Asians and Native Ameri-cans. They usually do not erupt but are discoveredradiographically. Occasionally a patient may appearclinically to be missing one or more teeth; however, anappropriate radiographic examination may reveal asupernumerary tooth interfering with normal tootheruption (Fig. 18-4). When a supernumerary tooth iserupted and clinically evident, it is commonly positionedoutside the normal arch because of space restriction.

Developmen ta I Abnormalities

NUMBER OF TEETH

SUPERNUMERARY TEETH

SynonymsHyperdontia, distodens, mesiodens, parateeth, peri-dens, and supplemental teeth

DefinitionSupernumerary teeth are those that develop in addi-tion to the normal complement. The tooth form maybe normal or abnormal. When the extra teeth havenormal morphology, the term supplemental is sometimesused. Although the cause is unknown, the tendency isfamilial. Most cases are polygenetic and represent initial

Radiographic FeaturesThe radiographic features of the supernumerary toothmay vary from normal-appearing tooth structure to a

330

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331CHAPTER 18 DENTAL ANOMALIES

4 years of age, when the deciduous teeth have formed.They may be detected in the permanent dentition ofchildren older than 9 to 12 years.

Care must be taken not to miss supernumeraryteeth in the panoramic image, especially when theimage of the tooth is distorted as a result of the posi-tioll,of the tooth outside the focal trough, for instance,in the palate. Besides the periapical intraoral exam-ination, occlusal radiographs aid in determining thelocation and number of unerupted supernumeraryteeth.

Differential Diagnosis -

Multiple supernumerary teeth have been associatedwith a number of syndromes. For instance, multipleteeth, especially bicuspids, have been associated withcleidocranial dysplasia (see Chapter 29). Supernumer-ary teeth have also been reported in Gardner's syn-drome (see Chapter 21).

AFIG. 18-1 A and B, Examples of inverted mesiodens.

ManagementThe management of supernumerary teeth dependson many factors, including their potential effect onthe developing normal dentition, their position andnumber, and the complications that may result fromsurgical intervention. If they erupt, they can causemalalignment of the normal dentition. Those thatremain in the jaws may cause root resorption or inter-fere with the normal eruption sequence. Follicles ofunerupted supernumerary teeth occasionally developinto dentigerous cysts. All of the preceding factors

conical tooth form and, in extreme cases, to grosslydeformed tooth structure. The size varies but the toothusually is smaller than the surrounding normal denti-tion. The supernumerary tooth is easily identified bycounting and identifying all the teeth. The super-numerary tooth can interfere with normal eruption;therefore the radiograph often reveals an uneruptedpermanent tooth in close proximity to the supernu,-merary tooth. Radibgraphs may reveal supernumeraryteeth in the deciduous dentition (Fig. 18-5) after 3 or

FIG. 18-2 In this panoramic image distomolars or fourth molars can be seen in bothmaxillary quadrants as well as a supplemental molar in the left maxilla, bringing the total

to five molars in this quadrant.


,332 PART V RADjOGRAPHIC INTERPRETATION OF PATHOLOGY

A

FIG. 18-3 Supernumerary or supplemental lateral incisors, A, and premolars, Band C.

FIG. 18-5 A supplemental deciduous molar (arrow).

influence the decision to either remove a super-numerary tooth or keep it under observation.

MISSING TEETH

SynonymsHypodontia, oligodontia, and anodontia

FIG. 18-4 Examples of mesiodens that interfered with theeruption and caused impaction of permanent teeth.

DefinitionThe expression of developmentally missing teeth mayrange from the absence of one or a few teeth (hypa-dontia), to the absence of numerous teeth (oligodontia),to the failure of all teeth to develop (anodontia).



Developmentally missing teeth may also be the result ofnumer9us independent pathologic mechanisms thatcan affect the orderly formation of the dental lamina(e.g., orofaciodigital syndrome), failure of a tooth germto develop at the optimal time, lack of necessary spaceimposed by a malformed jaw, and a genetically det,c;;,:)'mined disproportion between tooth mass and jaw site.

and others may show evidence of development as lateas a year after the contralateral tooth.

Differential DiagnosisA tooth may be considered to be developmentallymissing when it cannot be discerned clinically orradiographically and no history exists of its extraction.Anodontia or oligodontia frequently occurs in patientswith ectodermal dysplasia (Fig. 18-7). This inheriteddisorder results in the absence of at least two ectoder-mally derived structures, such as sweat glands, hair, skin,nails, and teeth. The severity of the condition is variableand may result in multiple missing teeth and mal-formed teeth, often having a conical shape or a notabledecrease in size. Many other syndromes and conditionsmay interfere with the development of teeth.

Clinical FeaturesHypodontia in the permanent dentition, excludingthird molars, is found in 3% to 10% of the population.Hypodontia is more frequently found in Asians andNative Americans. Although missing primary teeth arerelatively uncommon, when one tooth is missing, it isusually a maxillary incisor. The most commonly missingteeth are third molars, second premolars (Fig. 18-6),and maxillary lateral and mandibular central incisors.The absence may be either unilateral or bilateral. Chil-dren who have developmentally missing teeth tend tohave more than one tooth absent and more than onemorphologic group (incisors, premolars, and molars)involved.

ManagementMissing teeth, abnormal occlusion, or altered facialappearance may cause some patients psychologic dis-tress. If the extent ofhypodontia is mild, the associatedchanges may likewise be slight and manageable byorthodontics. In more severe cases restorative, implant,and prosthetic procedures can be undertaken.Radiographic Features

Missing teeth are recognized by identifying and count-ing the existing teeth. However, it must be kept inmind that the development of teeth may vary markedlyamong patients. Eruption of some teeth may be devel-opmentally delayed by a number of years after the estab-lished time (especially mandibular second bicuspids)

SIZE OF TEETH

A positive correlation exists between tooth size(mesiodistal diameter x buccolingual diameter) andbody height. Males also have larger primary and

FIG. 18-6 Developmental absence of all maxillary premolars and both mandibularsecond premolars. Note the retention of the maxillary primary canine as a result of theposterior position of the maxillary permanent canine.


334 PART V RADIOGRAPHIC INTERPRETATION OF PATHOLOGY

BFIG. 18-7 A and B, Examples of ectodermal dysplasia displaying various degrees ofmissing and malformed teeth.

permanent teeth than females. Beyond these normalvariations, however, individuals may occasionallydevelop unusually large or small teeth.

more commonly it involves a group of teeth, individualcontralateral teeth, or a single tooth (Fig. 18-8). Thepresence of a hemangioma (either intraosseous or inthe soft tissues) can result in an increase in the size andadvanced development of adjacent teeth. Also localizedtrue macrodontia can occur in hemihypertrophy of theface. True generalized macrodontia may also occur withpituitary gigantism. The cause of macrodontia is unknown.

The large size of the teeth is apparent on clinicalexamination. Associated crowding, malocclusion, orimpaction may occur.

MACRODONTIA

DefinitionIn macrodontia the teeth are larger than normal. Whenthe teeth are of normal size but occur in smaller-than-normal jaws, .the condition is relative macrodontia.Macrodontia may rarely affect the entire dentition, but

BFIG. 18-8 Macrodontia is a condition that results in enlarged teeth. A, :The macrodontmolar shows an increased mesiodistal dimension. B, The macrodont central incisor showsenlargement of both its mesiodistal and longitudinal dimension. (A, Courtesy Dr. B. Gratt,Los Angeles, CA.)


335DENTAL ANOMALIESCHAPTER 18

Radiographic FeaturesRadiographs reveal the increased size of both eruptedand unerupted macrodont teeth. The crowding maycause impaction of other teeth. The shape of the toothis usually normal, but some cases may exhibit a mildlydistorted morphology. ,.r;:A--,

Differential DiagnosisThe macrodont may resemble gemination or fusion.When fusion occurs, there is a missing tooth. In gemi-nation all the te~th may be present al)d often evidenceexists of.a division or cleft of the coronal or rootsegment of the tooth. However, the differentiation ofthese three conditions may not influence the treatment

provided.

ManagementIn most cases macrodontia does not require treatment.Orthodontic treatment may be necessary, however, inthe case of malocclusion.

MICRODONTIA

DefinitionIn microdontia the involved teeth are smaller thannormal. As with macrodontia, microdontia may involveall the teeth or be limited to a single tooth or groupof teeth. Relative microdontia can also occur. In thiscondition normal-sized teeth develop in an individualwith large jaws. Generalized microdontia is extremelyrare, although it does occur in some patients withpituitary dwarfism. Supernumerary teeth are fre-quently microdont. Also, the lateral incisors and thirdmolars, which often are developmentally missing, maybe small.

FIG. 18-9 Microdontia of the maxillary third molars,showing reduction in both the size and number of cusps.

~

Clinical FeaturesThe involved teeth are noticeably small and may havealtered morphology. Microdont molars may havealtered shape-from five to four cusps in mandibularmolars and from four to three in upper molars (Fig.18-9). Microdont lateral incisors are also smaller andpeg-shaped (Fig. 18-10).

FIG. 18-10 Microdontia of the maxillary lateral incisorresults in a characteristic peg-shaped deformity.

Radiographic FeaturesThe shape of these small teeth may be normal, butmore frequently they are malformed.

ManagementRestorative or prosthetic treatment may be consideredto create a more normal-appearing tooth, especiallywhen considering esthetic concerns in the anteriordentition.

Differential DiagnosisThe recognition of small teeth indicates the diagnosis.The number and distribution of microdonts may alsosuggest consideration of syndromes (e.g., congenitalheart disease, progeria).



teeth~ Some authors believe that fusion results whentwo tooth germs develop so close together that asthey grow, they contact and fuse before calcification.Others contend that a physical force or pressure gen-erated during development causes contact of adjacenttooth buds. The genetic basis for the anomaly is prob-ably autosomal dominant with reduced penetrance.Males and females experience fusion in equal numbers,and the incidence is higher in Asians and NativeAmericans.

ERUPTION OF TEETH

TRANSPOSITION

DefinitionTransposition is the condition in which two teeth haveexchanged positions. , oj;?

Clinical FeaturesThe most frequently transposed teeth are the perma-nent canine and first premolar (more often than thelateral incisor). Second premolars infrequently lieb~tween "first and second molars. The transposition ofcentral and lateral incisors is rare. Transposition in theprimary dentition has not been reported. It can occurwith hypodontia, supernumerary teeth, or the persist-ence of a deciduous predecessor.

Clinical FeaturesFusion usually causes a reduced number of teeth in thearch. It occurs in deciduous and permanent dentitions,although it is more common between deciduous teeth.When a deciduous canine and lateral incisor fuses,the corresponding permanent lateral incisor may beabsent. Fusion is more common in anterior teeth ofboth the permanent and deciduous dentition (Fig.18-12). Fusion may be total or partial depending on thestage of odontogenesis and the proximity of the devel-oping teeth. The result can vary from a single tooth ofabout normal size to a tooth of nearly twice the normalsize. A bifid crown may exist, or two recognizable teethmay be joined by dentin or enamel. The crowns offused teeth usually appear to be large and single, oran incisocervical groove of varying depth or a bifidcrown occurs.

Radiographic FeaturesRadiographs reveal transposition when the teeth are notin their usual sequence in the dental arch (Fig. 18-11).

Differential DiagnosisTransposed teeth are usually easily recognized.

ManagementTransposed teeth are frequently altered prostheticallyto improve function and esthetics.

ALTERED MORPHOLOG Y OF TEETH

FUSION

SynonymSynodontia

Radiographic FeaturesRadiographs disclose the unusual shape or size of theentire tooth. The true nature and extent of the unionare frequently more evident on the radiograph thancan be determined by clinical examination. Fused teethmay show an unusual configuration of the pulpchamber, root canal, or crown.Definition

Fusion of teeth results from the combining of adjacenttooth germs, resulting in union of the developing

tiLl. I D- I ~ tuslon OT tne central ana lateral InCIsors Inboth the primary and the permanent dentition. Note thereduction in number of teeth and the increased width of thefused tooth mass.

!-IIJ. I G- I I A croppea panoramic Image aemonsuaung

bilateral transposition of the maxillary canines and first

bicuspids.



Differential DiagnosisThe differential diagnosis for fused teeth includesgemination and macrodontia. Fusion may be differ-entiated from gemination by the reduced numberof teeth, except in an unusual case, in which thefusion is between a supernumerary tooth and; ,ji~,normal tooth. The differentiation is usually acaderrocbecause little difference exists in the treatment

provided.

CONCRESCENCE

DefinitionConcrescence occurs when the roots of two or moreteeth are united by cementum. It may involve eitherprimary or secondary teeth. Although its cause isunknown, many authorities suspect that space restric-tion during development, local trauma, excessiveocclusal force, or local infection after development mayplay an important role. If the condition occurs duringdevelopment, it is called true concrescence; if later, it isacquired concrescence.

Management.The management ofa case of fusion depends on whichteeth are involved, the degree of fusion, and the mor-phologic result. If the affected teeth are deciduous, theymay be retained as they are. If the clinician contem-plates extraction, it is important first to determinewhether the succedaneous teeth are present. In the caseof fused secondary teeth, the fused crowns may bereshaped with a restoration that mimics two independ-ent crowns. The morphology of fused teeth requiresradiographic evaluation before they are reshaped.Endodontic therapy may be necessary and perhapsmay be difficult or impossible if the root canals are ofunusual shape. In some cases it is most prudent to leavethe teeth as they are.

Clinical FeaturesMaxillary molars are the teeth most frequently involved,especially a third molar and a supernumerary tooth.Involved teeth may fail to erupt or may erupt incom-pletely. The sexes are equally affected.

Radiographic FeaturesA radiographic examination may not always distinguishbetween concrescence and teeth that are in closecontact or are simply superimposed (Fig. 18-13). Whenthe condition is suspected on a radiograph and extrac-tion of one of the teeth is being considered, additional

A BFIG. 18-13 A, Concrescence occurs when two teeth are joined by a mass of cemen-tum. 8, Extraction of one tooth may result in the unintended removal of the secondbecause cementum is often not well visualized radiographically. (Courtesy Dr. R. Kienholz,Dallas, Texas.)


,jjlS 'AK I V :AUIVI.JKAI'HIL IN I tKI'Kt IAIIVN VI- I'AI HVLUCJY

>rojections

at ditterent angles may be obtamed to>etter delineate the condition.

:Iinical

Features;emination more frequently affects the primary teeth,)ut it may occur in both dentitions, usually in thencisor region. It can be detected clinically after thelllomalous

tooth erupts. The occurrence in males andemales is about equal. The enamel or dentin of gemi-lated

teeth may be hypoplastic or hypocalcified.

Jlnerentlal

uiagnosist is usually impossible to determine radiographicallyvith certainty whether the teeth whose root imag~~areuperimposed

are actually joined. Is the periodontalnembrane space continuous around each root? If the

'oots are joined, it may not be possible to tell whetherhe union is by cementum or by dentin (fusion).

{adiographic

Features~diographsreveal the altered shape of the hard tissuemd

pulp chamber of the germinated tooth. Radio->aque enamel outlines the clefts in the -crowns andnvaginations

and thus accentuates them. The pulp:hamber is usually single and enlarged and may be par-ially divided (Fig. 18-14). In the rare case of premolar~emination, the tooth image suggests a molar with an~nlarged

crown and two roots.

\t1anagement~oncrescence affects treatment only when the decision

s made to remove one or both of the involved teeth.lhis condition complicates the extraction. The clini-

:ian should warn the patient that an effort to removeme might result in the unintended and simultaneous

'emoval of the other.JITTerential uiagnosisthe

differential diagnosis of gemination includesusion. If the malformed tooth is counted as one, indi-iduals with gemination have a normal tooth count,vhereas those with fusion are seen to be missing a tooth.

.JEMINATION

iynonym['winning

JeTlrntlon

;emination is a rare anomaly that arises when the tooth)ud of a single tooth attempts to divide. The result may)e an invagination of the crown, with partial division,)r in rare cases complete division throughout the crownmd

root, producing identical structures. Completewinning results in a normal tooth plus a supernumer-

try tooth in the arch. Its cause is unknown, but some~vidence exists that it is familial.

VJanagement\. geminated tooth in the anterior region may com->romise

arch esthetics. Areas of hypoplasia and invagi-lation lines or ar~as of coronal separation represent:aries-susceptible

sites that may in time result in pulpalnfection. Affected teeth can cause malocclusion andead

to periodontal disease. Consequently the affectedooth may be removed (espe'cially if it is deciduous), the:rown(s) may be restored or reshaped, or the tooth may

~

IG. 18-14 A, Gemination of a mandibular lateral incisor showing bifurcation of therown and the pulp chamber. B, Almost complete gemination of a deciduous lateral incisor.


,339DENTAL ANOMALIESCHAPTER 18

be left untreated' and periodically examined to pre-clude the development of complications. Before treat-ment is initiated on primary teeth, the status of thesuccedaneous teeth and configuration of their rootcanals should be determined radiographically.

tooth, it is usually fully expressed in the molars and lessoften in the premolars. Single or multiple teeth mayshow taurodont features, unilaterally or bilaterally andin any combination of teeth or quadrants.

;J:i!!i",;f

Clinical FeaturesBecause the body and roots oftaurodont teeth lie belowthe alveolar margin, the distinguishing features of theseteeth are not recognizable clinically.

T AURODONTISM

DefinitionTaurodont teeth have longitudinally enlarged pulpchambers. The c.rown is of normal sh,ape and size, butthe body is elongated and the roots are short. The pulpchamber extends from a normal position in the crownthroughout the length of the extended body, leading toan increased distance between the cementoenameljunction and the furcation. Taurodontism may occur ineither the permanent or primary dentition (or both).Although some evidence of the trait can be seen in any

Radiographic FeaturesThe distinctive morphology of taurodont teeth is quiteapparent on radiographs. The peculiar feature is anextension of the rectangular pulp chamber into theelongated body of the tooth (Fig. 18-15). The short-ened roots and root canals are a function of the longbody and normal length of the tooth. The size of thecrown is normal.

FIG. 18-15 Taurodontia, revealed as an enlarged pulp chamber, in all permanent firstmolars (A), in a primary first molar (8), and in a permanent molar (C).


,340 PART V RADIOGRAPHIC INTERPRETATION OF PATHOLOGY

Differential DiagnosisThe image of the taurodont tooth is characteristic andeasily recognized radiographically. The developing molarmay appear similar; however, the identification of thewide apical foramina and incompletely formed roots helpsin the differential diagnosis. Taurodontism4~~beenreported with greater frequency in trisomy 21 sytidrome.

Radiographic FeaturesRadiographs provide the best means of detecting aradicular dilaceration. The condition occurs most oftenin permanent maxillary premolars. One or more teethmay be affected. If the roots bend mesially or distally,the condition is clearly apparent on a periapical radio-graph (Fig. 18-17). When the roots are bent buccally(labially) or lingually, the central ray passes approxi-mately parallel with the deflected portion of the root.The dilacerated portion then appears at the apical endof the unaltered root as a rounded opaque area with adark shadow in its central region cast. by the apicalforamen and root canal (an appearance like a bull's-eye). The periodontal ligament (PDL) space aroundthis dilacerated portion may be seen as a radiolucenthalo (Fig. 18-18), and the radiopacity of this segmentof root is greater than the rest of the root. In somecases, especially in the maxilla, the geometry of the pro-jections may preclude the recognition of a dilaceration.

ManagementTaurodont teeth do not require treatment.

.DILACERATION

DefinitionDilaceration is a disturbance in tooth formation thatproduces a sharp bend or curve in the tooth. One ofthe oldest concepts is that it is probably the result ofmechanical trauma to the calcified portion of a partiallyformed tooth. Although this may occur, especially tothe maxillary incisors, most cases are likely to be truedevelopmental anomalies. The angular distortion mayoccur anywhere in the crown or root.

Differential DiagnosisOccasionally dilacerated roots are difficult to differen-tiate from fused roots, condensing osteitis, or a densebone island. They can usually be identified, however, byobtaining radiographs exposed from different angles.

Clinical FeaturesMost cases of radicular dilaceration are not recognizedclinically. If the dilaceration is so pronounced that thetooth does not erupt, the only clinical indication of thedefect is a missing tooth. If the defect is in the crownof an erupted tooth, it m~y be readily recognized as anangular distortion (Fig. 18-16).

ManagementThe dilacerated rOot generally does not require treat-ment because it provides adequate support. If it mustbe extracted for some other reason, its removal can becomplicated, especially if the surgeon is not preparedwith a preoperative radiograph. In contrast, dilaceratedcrowns are frequently restored with a prosthetic crownto improve esthetics and function.

DENS IN DENTE

SynonymsDens invaginatus, dilated odontome, and gestantodontome

DefinitionDens in dente results from an infolding of the outersurface into the interior of a tooth. This can occur ineither the crown or the root during tooth developmentand may involve the pulp chamber or root canal, result-ing in deformity of either the crown or the root. Theseanomalies are seen most often in tooth crowns. Coronalinvaginations usually originate from an anomalousinfolding of the enamel organ into the dental papilla.In a mature tooth the result is a fold of hard tissuewithin the tooth characterized by enamel lining the fold(Fig. 18-19). The most extreme form of this anomaly isreferred to as the dilated odontome"

A BFIG. 18-16 A, Dilaceration of the crown may be readilyrecognized clinically. 5, Radiograph of the specimen in A.(Courtesy Dr. R. Kienholz, Dallas, Texas.)


.


AFIG. 18-17 A, Dilaceration of the root of a maxillary lateral incisor. 8, Dilaceration ofthe root of a mandibular third molar.

FIG. 18-18 Dilacerated root. The apical portion of theroot of this third molar is bent buccally or lingually into theplane of the central ray. Note the halo in the apical region,produced by the POL space giving a "bull's-eye" appearance

(arrow).

When dens in dente involves a root (radicular densinvaginatus), it appears to be the result of an invagina-tion of Hertwig's epithelial root sheath. This resultsin an accentuation of the normal longitudinal rootgroove. In contrast to the coronal type (lined withenamel), the radicular-type defect is lined with cemen-tum. If the invagination retracts and is cut off, it leavesa longitudinal structure of cementum, bone, and rem-nants of PDL within the pulp canal. The structure oftenextends for most of the root length. In other cases the

FIG. 18-19 Dens in dente is characterized by an infold-ing of enamel into the tooth. This sectioned canine with adens in dente shows enamel (arrows) folded into the tooth'sinterior.


;S4L '-Alt I V ""Ulv,-""",nIL IN I 1:"""1:1'"IVN VI" "AI HULUl.Y

the coronal detect, It IS trequently thill, otten ot poorquality, and even missing in some areas. Furthermore,the cavity is usually separated from the pulp chamber bya relatively thin wall and opens into the oral environ-ment through a narrow constriction. The pit is oftendifficult to keep clean, and consequently, it offers con-ditions favorable for the development of caries. Suchcarious lesions are difficult to detect clinically and willrapidly involve the pulp. In addition, sometimes fine canalsextend between the invagination and the pulp chamber,resulting in pulpal disease even in the absence of caries.

root sheath may bu<1 011 a saClIKe mvagmauon that pro-duces a circumscribed cementum defect in the root.Mandibular first premolars and second molars areespecially prone to develop the radicular variety of this

invagination anomaly.Little difference in the frequency of oc<:;ul;'i'ence

exists among white and Asian people. If all grades ofexpression of invagination, mild to severe, are included,the condition is found in approximately 5% of thesetwo racial groups. The condition appears to be rare inblacks. No. sexual pre;dilection exists. Although no spe-cific mode of inheritance seems to fit all the data, a highdegree of inheritability seems to exist. Kaalograpnlc t-eatures

Most cases of dens in dente are discovered radiograph-ically. The infolding of the enamel lining is moreradiopaque than the surrounding tooth structure andcan easily be identified (Fig. 18-20). Less frequentlythe .radicular invaginations appear as poorly defined,slightly radiolucent structures running longitudinallywithin the root. The defects, especially the coronalvariety, may vary in size and shape from small and super-ficial to large and deep. If a coronal invagination isextensive, the crown is almost invariably malformed;when the crown is malformed, the apical foramen isusually wide (Fig. 18-21). A frequent cause of an openapical foramen is the cessation of root developmentthat occurs as a result of death of the pulpal tissue. Inthe most severe form (dilated odontome) the tooth isseverely deformed, having a circular or oval shape witha radiolucent interior (Fig. 18-22). Dens in dente canbe identified in the radiographic image even before thetooth erupts.

\..llntcal t-ea1:uresCoronal dens in dente may be identified clinically as apit at the incisal edge or the cingulum. The pit in thecingulum may be particularly broad and deep, espe-cially when these features occur in the lateral incisor.Often the lingual marginal ridges or cingula are promi-nent. In most cases, however, the dens in dente is notlarge, and crown morphology appears normal. Dens indente occurs most frequently in the permanent maxil-lary lateral incisors, followed by (in decreasing fre-quency) the maxillary central incisors, premolars, andcanines and less often in the posterior teeth. Invagina-tion is rare in the crowns of mandibular teeth and indeciduous teeth. It occurs symmetrically in about halfthe cases. Concomitant involvement of the central andlateral incisors. may occur.

The clinical importance of dens invaginatus resultsfrom the risk of pulpal disease. Although enamel lines

D

FIG. 18-20 Dens in dente is seen radiographically as a radiopaque infolding of enamelinto the tooth's pulp chamber. A-C, Various degrees of involvement of the maxillary lateralincisors.


\343CHAPTER 18 DENTAL ANOMALIES

BFIG. 18-21 A and B, Examples of severe malformationsof dens in dente. These usually result in necrosis of the pulp,open apices, and periapical inflammatory lesions.

A

Differential DiagnosisThe appearance and usual occurrence in incisors areso characteristic that, onc~ recognized, little probabil-ity exists that the anomaly will be confused with anothercondition.

ManagementAlthough it is important to evaluate every case individu-ally, the placement of a prophylactic restoration in thedefect is typically the treatment of choice and shouldensure a normal life span for the tooth. Failure of earlyidentification and hence treatment may result in prema-ture tooth loss or the requirement for root canal therapy.

BFIG. 18-22 A, A dilated odontome is positioned justposterior to the developing mandibular third molar in thispanoramic film. B, The specimen radiographs represent twoviews of a dilated odontome.

lingual ridge of a buccal cusp. Dens evaginatus mayoccur bilaterally and usually in the mandible. Thetubercle often has a dentin core, and a very slenderpulp horn frequently extends into the evagination.Mter the tubercle is worn down by the opposing teeth,it appears as a small circular facet with a small black pitin the center (Fig. 18-24, B). Wear, fracture, or indis-criminate surgical removal of this tubercle may precip-itate a pulpal infection. In rare cases a microscopicdirect communication may occur between the pulp andthe oral cavity through this tubercle. In these instancesthe pulp may become infected shortly after eruption.

DENS EVAGINATUS

SynonymLeong's premolar

DefinitionIn contrast to the dens in dente, dens evaginatus is theresult of an outfolding of the enamel organ. The resultis an enamel-covered tubercle, usually in or nearthe middle of the occlusal surface of a premolar oroccasionally a molar (Fig. 18-23). Canines are rarelyaffected. The frequency of occurrence of dens evagi-natus is highest in Asians and Native Americans.

Clinical FeaturesClinically, dens evaginatus appears as a tubercle ofenamel on the occlusal surface of the- affected tooth. Apolyplike protuberance exists in the central groove or

Radiographic FeaturesThe radiographic image shows an extension of a dentintubercle on the occlusal surface unless the tubercle is


\


A BFIG. 18-23 A, Dens evaginatus, seen as a tubercle inthe mandibular premolar. 5, Radiograph of the specimen.(Courtesy Dr. R. Kienholz, Dallas, Texas.)

already worn down. The dentin core is usually coveredwith opaque enamel. A fine pulp horn may extend intothe tubercle, but this may not be visible radiographi-cally. If the tubercle has been worn to the point ofpulpal exposure or has fractured, pulpal necrosis mayresult (see Fig. 18-24). This is indicated by an openapical foramen and periapical radiolucency.

A

Diffe~ential DiagnosisThe clinical and radiographic appearance may be char-acteristic or may be difficult to visualize if the tuberclehas been worn down to the occlusal surface.

ManagementIf the tubercle causes any occlusal interference or showsevidence of marked abrasion, it should probably beremoved under aseptic conditions and the pulpcapped, if necessary. Such a precaution may precludepulpal exposure and infection as the result of acciden-tal fracture or advanced abrasion.

B

FIG. 18-24 A, Periapical film of mandibular first bicuspidwith a dens evaginatus and apical rarefying osteitis. B, Clin-ical photograph of another case with dens evaginatus involv-ing both mandibular second bicuspids, since the tubercleshave been worn down there is now a black pit representingcommunication with the pulp chamber.

AMELOGENESIS IMPERFECTA

DefinitionAmelogenesis imperfecta is a developmental distur-bance that interferes with normal enamel formation. Itleads to marked changes in the enamel of all or nearlyall the teeth in both dentitions. Most forms are auto-somal dominant or recessive, but two types are X-linked.Amelogenesis imperfecta is not related to any time orperiod of enamel development or any clinically demon-strable alteration (disease or dietary abnormality) in


345DENTAL ANOMALIESCHAPTER 18

other tissues. Th'e enamel may lack the normal pris-matic structure, being laminated throughout its thick-ness or at the periphery. AS a result these teeth aremore resistant to decay. The dentin and root form areusually normal. Eruption of the affected teeth is oftendelayed, and a tendency for impaction exists. Althou~at least 14 variants of the condition have beendescribed, four general types have characteristic clini-cal or radiographic appearances: a hypoplastic type,a hypomaturation type, a hypo calcified type, and ahypomaturation.-hypocalcified type associated withtaurodontism. A

Clinical FeaturesHypoplasia. As a result of some defect in ameloblasts,the enamel of the affected teeth fails to develop to itsnormal thickness. It is so thin that the dentin showsthrough and imparts a yellowish-brown color to thetooth. In the various hypoplastic forms the enamelmay be pitted, rough, or smooth and glossy. Thecrowns of the teeth may not have the usual contourof enamel but rather have a roughly square shape.The reduced enamel thickness also causes the teeth tobe undersized, with lack of contact between adjacentteeth (Fig. 18-25). The occlusal surfaces of the poste-rior teeth are relatively flat with low cusps. This is aresult of the attrition of cusp tips that were initially lowand not fully formed. An anterior open bite may benoted.

Hypomaturation. In the hypomaturation form of amel-ogenesis imperfecta, the enamel has a normal thicknessbut a mottled appearance. It is softer than normal(density comparable to dentin) and may crack awayfrom the crown. Its color may range from clear tocloudy white, yellow, or brown. In one form of hypo-maturation the teeth appear to be snow-capped (withwhite opaque enamel).

BFIG. 18-25 A, A cropped panoramic film of amelogene-sis imperfecta (generalized hypoplastic form) with absenceof enamel; note that without the normal tooth crowns thefollicular spaces appear large. B, Intraoral films of anothercase of amelogenesis imperfecta; note the very thin enamel

layer.

Hypocalcification. Hypocalcification of teeth is morecommon than the hypoplastic variety of amelogenesisimperfecta. The crowns of the teeth are normal in sizeand shape when they erupt because the enamel is ofregular thickness (Fig. 18-26). However, because theenamel is poorly mineralized (less dense than dentin),it starts to fracture away shortly after it comes into func-tion. This creates clinically recognizable defects. Thesoft enamel abrades rapidly and the softer dentin alsowears down rapidly, resulting in a grossly worn tooth,sometimes to the level of the gingiva. An explorer pointunder pressure can penetrate the soft enamel; yet cariesin these worn teeth is unusual. The hypocalcifiedenamel has increased permeability and becomesstained and darkened. The teeth of a young person with

generalized hypomineralization of the enamel are fre-quently dark brown from food stains.

Hypomaturation/hypocalcification. This classificationindicates a combination of hypo maturation andhypocalcification that involves both the permanent anddeciduous dentition. If the dominant defect is hypo-maturation, then the term hypomaturation-hypocalcifica-lion is used. The enamel is usually mottled anddiscolored (yellow and brown). The enamel has thesame radiopacity as the dentin. When the dominantdefect is hypocalcification, the term hypocalcification-hypomaturation is used. The appearance of the teeth issimilar, but the enamel is thin.


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