Diseases of the Teeth and Jaws

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Crest® Oral-B at dentalcare.com Continuing Education Course, Revised June 10, 2010

Diseases of the Teeth and Jaws

This continuing education course is intended or general dentists, hygienists, and dental assistants. This

course will help the dental auxiliary to understand the importance of high-quality radiographs and will, in

the long run, make him or her that much more valuable to the dental team.

Conflict of Interest Disclosure StatementThe author reports no conflicts of interest associated with this work.

ADA CERP

The Procter & Gamble Company is an ADA CERP Recognized Provider.

ADA CERP is a service of the American Dental Association to assist dental professionals in identifying

quality providers of continuing dental education. ADA CERP does not approve or endorse individual

courses or instructors, nor does it imply acceptance of credit hours by boards of dentistry.

Concerns or complaints about a CE provider may be directed to the

provider or to ADA CERP at:

http://www.ada.org/pro /ed/ce/cerp/index.asp

Overviewy law and by practice, the dentist is responsible or diagnosing conditions o the teeth and jaws.

Nevertheless, a dental auxiliary should have some knowledge of the basic dental disease appears

on radiographs. This knowledge will help the auxiliary to understand the importance of high-quality

adiographs and will, in the long run, make him or her that much more valuable to the dental team.

Learning ObjectivesUpon the completion of this course, the dental professional will be able to:

• ecognize the radiographic appearance o dental caries, periodontal disease, periapical pathology, and

healing of extraction wounds.

• Have a basic knowledge of the radiographic appearance of tooth and bone fractures, developmental

anomalies and regressive changes o the teeth, and developmental abnormalities o the skull and jaws.

Allan G. Farman, B.S.D., EdS, MBA, PhD;

Sandra A. Kolsom, CDA, RDA;

Members of the ADAA Council on EducationContinuing Education Units: 4 hours



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Course Contents• Glossary

• Defective Restorations and Dental CariesDefective RestorationsEnamel Caries

Dentin CariesRecurrent Caries

Cervical Burnout and Mach Banding• Periodontal Disease

Dental CalculusProliferative Gingival HyperplasiaHorizontal Bone Loss and Vertical Bone Loss

• Periapical PathologyAcute Apical Periodontitis, Acute Periapical

Abscess and Chronic Periapical AbscessPeriapical Granuloma

Apical Radicular CystOsteosclerosis and Condensing Osteitis

Osteoradionecrosis and Osteonecrosis• Healing of Extraction Wounds

Normal Healing and Fibrous HealingSocket Sclerosis and Residual RootFragments

• FracturesFractured Teeth

Fractured Bones• Developmental Abnormalities

Supernumerary Teeth

Hypodontia (Too Few Teeth)Macrodontia

MicrodontiaHutchinson’s Teeth

EvaginationInvagination (Dens in Dente)Taurodontism and Pyramidal Teeth

DilacerationSupernumerary Roots

Fusion and GeminationConcrescence

Regional OdontodysplasiaDentinogenesis Imperfecta and DentinDysplasia

Amelogenesis ImperfectaTurner’s Tooth and Environmental Hypoplasia

Talon Cusp and Enamel Pearl

• Regressive Changes in TeethAttrition and AbrasionErosionPulp Stones

HypercementosisAnkylosis

External ResorptionInternal Root Resorption

• Developmental Anomalies of the JawsMandibular Tori

Maxillary TorusStafne Bone Cavity and Clefts

• Summary

• Course Test• References

• About the Authors

GlossaryAbrasion – pathological wearing away of thesurface layers of hard or soft tissues.

Anomaly – abnormality.

Apical foramen – an opening at a tooth’s root tip

that allows the entry of nerve and blood vessels tothe pulp.

Attrition – wearing away by friction or rubbing.

Autosoma – pertaining to a chromosome otherthan a sex chromosome.

Bilateral – two sided.

Cementoenamel junction – the meeting of thenamel of the crown and the cementum of the root

at the cervix of a tooth.

Chronic – persisting over a long period of time.

Ectopic – out of place; e.g., an ectopic tootheruption is one that occurs outside the normalpath.

Embrasure – the V-shaped space between

curved adjacent surfaces of teeth.

Epithelial – type of tissue that forms the coveringof all body surfaces.

Erosion – the destruction of tooth substance bychemical or mechanical-chemical action.

Exfoliate – to shed teeth, particularly referring toprimary teeth.

Exudate – a liquid substance that oozes from

blood and lymph vessels, typically as a result ofinflammation.

Fibrous – composed of or containing fibers.



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Radiodensity – the degree of radiolucency orradiopacity of a substance or tissue.

Radiolucent – a term that describes the abilityof a substance or tissue to allow passage of

radiation with relatively little attenuation (reductionof energy) resulting in a darker image on a finished

radiograph.

Radiopaque – a term that describes the abilityof a substance or tissue to attenuate (reduce orslow) the energy of radiation that passes through it

resulting in a lighter image on a radiograph.

Sclerosis – hardening of a body tissue.

Scurvy – a condition that results from anascorbic acid (vitamin C) deficiency; common

symptoms include weakness, poor wound healing,and hemorrhage under the skin and mucous

membranes.

Suppurative – forming pus.

Taurodontism – an anatomical abnormality

in which a tooth’s pulp chamber is elongated,enlarged, and extends into the region of the roots.

Defective Restorations and Dental Caries

Defective Restorations

The junction of a restored tooth and the restorative

material should always appear sharp and distinct,though there will be some qualitative differencesfor interposed radiolucent bases. Restorations that

radiographically fail to extend to tooth preparationmargins (open margins) those that extend

beyond the preparation margins (overhangs),

Furcation – the point at which the roots of multi-rooted teeth separate.

Gonadal – pertaining to the ovaries or testes.

Granuloma – a tumor that filled with granulationtissue.

Hemihypertrophy – an excessive growth of one

half of the body, an organ, or a part (e.g., facialhemihypertrophy).

Incipient – the beginning stage; e.g., incipientcaries is the beginning stage of tooth decay when

the decay has not yet completely penetrated thenamel.

Intraosseous – within bone.

Lamina dura – the compact bone that lines the

tooth sockets.

Lobulated – divided into lobes, subdivisions.

Necrosis – the death of cells or tissues.

Opalescent – a translucent appearance.

Orifice – the entrance or outlet of any bodycavity.

Osseous – bony or of bone-like structure or

consistency.

Ossification – the formation of bone or a change

into bone.

Pathosis – a disease condition.

Periodontium – a collective term that denotesthe tissues surrounding and supporting the teeth;includes 1) the gingiva, 2) the cementum of the

tooth root, 3) the periodontal ligament, and 4) thealveolar bone.

Polyp – a general term that describes any massof tissue that bulges or projects outward orupward from the normal surface level.

Prognathic – pertaining to a forward relationshipof the jaws to the head (anterior to the skull)

resulting in a protruding lower face.Figure 1.



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demineralized and thus will appear smaller in theradiograph because the rest of the advancing edge

is not radiographically visible. Clinically the lesionwill usually be larger than its radiographic image.

Figure 2 illustrates fairly advanced enamel caries

with penetration into the dentin.

Dentin Caries

Dentin Caries extends into the tooth dentinand can be recognized by noting the focal loss

of dentinal radiopacity. Most commonly, this

darkened dentin is located beneath carious enameland, typically, the lateral dimension of the dentinalinvolvement exceeds that of the associated enamelcaries (Figure 3). Dentin caries may be discerned

interproximally, on the occlusal surface, buccally/ lingually, or on root surfaces.

and those with inappropriate contours maybe considered defective restorations. Such

restorations are usually defective at the time theyare inserted, though they may become defectiveas a result of fracture, attrition, abrasion or

erosion.

Figure 1 is a molar bitewing radiograph thatdiscloses a defective restoration on tooth #3. The

restoration ends short of the margin mesially anddistally, and illustrates both open margins andoverhangs.

Enamel Caries

While advanced dental caries may well involvethe entire tooth, early or incipient caries involves

only the enamel. Once a carious lesionpenetrates through the enamel, it is usually

considered to be dentinal caries. Clinically,enamel caries usually appears as a stained

system of occlusal grooves or as chalkywhite bands along the labial/buccal gingivalaspects of the teeth. Radiographically, enamel

caries is characterized by a focal loss of thenormal enamel radiopacity, particularly on the

interproximal surfaces.

It appears as a radiolucent cone shape, with the

base at the exterior surface and the tip of thecone toward the pulp. The lesion follows the

enamel rods. After progression into the dentinthe lesion usually takes on a radiolucent fan

shape.

To locate interproximal caries, and interproximal

or bitewing survey is usually most valuablebecause the maxillary and mandibular teeth

are simultaneously imaged on one film andthe projection geometry is most favorable for

accurate imaging. Anterior bitewing examinationrequires a change of geometry, which is notas favorable for interproximal caries detection.

These interproximal surfaces are thin and can beeasily examined clinically. Periapical examination

of the anterior region is useful for the detection of

cemental caries.

To be detectable on a radiograph there must be a30% to 50% change in the mineral content of the

enamel lesion. Less than 30% demineralizationwill not produce a detectable image. The

advancing edge of the lesion may not be 30%

Figure 3.

Figure 2.



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sharp and distinct, and, as a rule, recurrent cariesshould be suspected whenever radiolucencies are

present between the tooth and the restoration.

In Figure 4, recurrent caries appears at the

mesial of tooth #3 and #4, and the distal of tooth#28. Also, note areas of interproximal caries on

tooth #5.

Cervical Burnout and Mach Banding

Cervical burnout is an area of apparentlyincreased radiolucency in the mesial and distal

cervical (neck) regions of the tooth. Such regionsare often mistaken for interproximal caries when

in fact they only appear radiolucent because theyhave neither the radiopaque enamel of the region

immediately above nor the bone tissue below.

Figure 5 illustrates cervical burnout in apremolar bitewing radiograph. Note that the

cementoenamel junction and the crest of thealveolar bone lie respectively just above and

just below the burnout area. As a point of

comparison, note the interproximal enamel carieson the first and second premolars.

While carious lesions and areas of cervicalburnout do resemble each other, there are a

couple of tips to help differentiate between them.First, cervical burnout is found only in the cervical

region or tooth neck, which is fortunately anuncommon area for caries to develop. Second,

the cementoenamel junctions sharply limit areasof burnout incisally and occlusally, as the alveolarcrest limits the area apically. Caries would not be

so sharply defined.

Occlusal caries may be undetectable on aradiograph until the decay reaches the dentin.

Early radiographic appearance may be a thinradiolucent shadow below the enamel. An opticalillusion referred to as Mach banding can produce

the same image in healthy teeth. Detection ofincipient occlusal caries is most effective by direct

clinical examination.

Periodontal DiseaseA tooth in the intact periodontium maintains firmattachment to a collar of the gingiva through

connective tissue fibers. Beneath the gingiva,bone is attached to the root surface through the

periodontal ligament, a complex system of fibrous

Incipient occlusal dentin caries may be difficult to

identify on radiographs and root caries must becarefully distinguished from cervical burnout, as

we will discuss later.

Recurrent Caries

Recurrent caries is the condition in whichcarious lesions develop or extend along the

margins of existing restorations. A diligent searchfor recurrent caries should be made whenever

radiographs detect (1) interproximal restorationoverhangs; (2) open margins on restorations;

(3) restorations which appear to end short ofpreparation margins; (4) restorations whichappear unusually shallow as judged by the

thickness of the restorative material.

Radiographically, recurrent caries presents

as radiolucent lines that extend inward fromthe tooth surface along a restoration or asradiolucent zones, which appear to lie completelybeneath the restoration, without any observable

communication with the tooth surface. Asmentioned previously, the junction of a restored

tooth and the restorative material should appear

Figure 5.

Figure 4.



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At times, calculus deposits become so heavythat they completely surround the tooth. Not

surprisingly, such severe cases are associatedwith advance periodontal bone loss.

connective tissue. Deposits of free bacteria andbacteria-rich plaque produce inflammation in the

gingival collar, which, in turn, disrupts the fibrousgingival-tooth attachment.

The continued presence of plaque and calculusproduces inflammation in the periodontal

ligament, leading to bone loss and weakenedattachment strength between the ligament and

the tooth. In time, the inflammatory process cancause considerable bone loss – to the point thatthe tooth becomes unstable and eventually is lost.

Ongoing research is pointing towards

collaboration between certain systemic diseasesand periodontal health. As dental professionals it

is our responsibility to discuss these findings withour patients.

Clinically, the extensive bone loss and gingival

recession of advanced periodontal disease maybe easily visualized. In less advanced cases,the periodontal probe can be used to measure

the distance between the gingival crest and theperiodontal attachment. Bleeding at the point of

probing and measurement of significant distancesare strong indications of periodontal disease.Figure 6 radiographically illustrates probe depth

in a case of moderate periodontal disease withearly alveolar bone loss. Figure 7 illustrates

severe periodontal disease with extensive loss ofalveolar bone around the tooth.

Dental CalculusDental Calculus is mineralized dental plaque.

Heavy calculus deposits are most commonlyfound opposite the salivary duct orifices located

near the mandibular incisors and maxillarymolars. Calculus is usually classified assupragingival, which occurs above the gingivaon the exposed tooth surfaces and subgingival,which is found beneath the gingiva. It is well

known that the bacteria on the calculus inducesinflammation in the periodontal tissue and

contributes to the development of gingivitis and

periodontal disease.

On a dental radiograph, calculus is commonlyseen interproximally, either filling the dental

embrasures or producing distinct radiopaquespurs such as that seen on the distal of the

maxillary molar in Figure 8. Figure 8.

Figure 7.

Figure 6.



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defects whose height varies markedly comparedto the adjacent tooth crowns. This defect

is known as vertical bone loss and can berecognized on a radiograph by noting that a line

representing the residual bone crest sharplyintersects another line between the tooth necks.

Vertical loss is sharply apparent distal to themaxillary first molar and between the premolars(Figure 11).

Vertical bone loss may extend to the root apex,

and prominent calculus deposits are often noted.

Care must be taken to assess the degree ofbone loss, especially around molars wherespecial attention should be directed to thefurcational periodontal ligament space.

Vertical bone loss extending into this area may

appear as a focally widened ligament space.

Proliferative Gingival HyperplasiaGingival enlargements arise from a variety of

local and systemic factors, and may be localized(Figure 9) or may involve the entire gingival

area. Localized gingival enlargements mostcommonly result when a discrete area of the

gingiva is irritated by plaque, calculus or extrinsicfactors such as popcorn hulls or hard candy.Less frequently, local conditions represent an

extension of underlying bone disease.

Generalized gingival enlargement may result fromlongstanding, chronic inflammation such as thatnoted in chronic gingivitis or periodontitis. It has

also been associated with the hormonal changesthat occur with puberty and pregnancy, with

certain drug therapy (i.e., Cyclosporins, Dilantin,Nifedipine), with systemic disorders such as

scurvy and leukemia, and with genetic disorderssuch as fibromatosis gingiva.

In nearly all cases, generalized gingivalenlargements produce only minimal osseous

change; and, thus, if they are definable onradiographs at all, it is only on the basis of their

increased gingival soft tissue outline.

Horizontal Bone Loss

Generalized, extensive periodontal bone loss, inwhich the crest of the residual bone is parallel

to the cementoenamel junction, is referred to as

horizontal bone loss (Figure 10).

Vertical Bone LossWith periodontal disease, bone loss may be

relatively severe around some teeth, whileleaving the immediately adjacent teeth firmly

anchored. Such focal loss creates osseous

Figure 10.

Figure 11.

Figure 9.



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periodontium. These remnants can proliferatewithin an apical granuloma to form an apical

radicular cyst, which can grow to severalcentimeters if left untreated. Apical radiolucenciesgreater than about six millimeters usually contain

epithelial cyst material. Figure 14 illustratesa clearly defined apical periodontal cyst in a

pulpless tooth following acute trauma.

A cyst can continue to grow even after theirritation has ceased or the source has beenremoved. Such continuing growths are termed

residual cysts.

If the process starts from a lateral, rather than anapical canal, a lateral radicular cyst can occur.

Periapical Pathology

Acute Apical Periodontitis

Following the necrosis of the dental pulp throughany cause, irritants drain and can cause a

reaction in the periodontal tissues adjacent tothe apical foramen. There is usually little, if any,

immediate bone resorption, so apical periodontitisis often difficult to detect with radiographs except

that the tooth may appear slightly elevated in thetooth socket due to the collection of inflammatoryxudate.

Acute Periapical Abscess

Acute, by definition, means short term. Acuteabscesses often show little radiographic change

because over the short run, the body has not hadufficient time to resorb bone.

Chronic Periapical Abscess

The chronic periapical abscess represents asuppurative process that has been present longenough to cause the body to resorb bone. It is

not possible to absolutely differentiate betweena chronic abscess, dental granuloma, or small

radicular cyst solely by using a dental radiograph.However, a radiographic image of multipleforaminae (many openings or passages) within

the pathological area is strongly suggestive ofsinus tract formation and drainage of pus. Notice

the four prominently radiolucent foraminae in theresorbed periapical area (Figure 12).

Periapical GranulomaThe periapical granuloma represents the body’s

defense mechanism attempepresents the body’sdefense mechanism attempting to wall off irritants

draining from a non-vital dental pulp. Whilethey cannot be radiologically differentiated from

abscesses or cysts, they can be differentiatedfrom normal anatomical landmarks such as theincisive fossa because the periodontal ligament

space is widened and the lamina dura is notcontinuously intact.

Figure 13 illustrates apical periodontal pathosis inthe area of the right central incisor. Note the lossof continuity of the lamina dura and the widenedperiodontal ligament space on the affected side.

Apical Radicular Cyst

Epithelial remnants from tooth formation arealways present as builder’s debris within the

Figure 12.

Figure 13.



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Notice how the cystic formation in Figure 15follows the lateral aspect of the tooth root, thus

differentiating it from an apical cyst.

A cyst can continue to grow even after the

irritation has ceased or the source has beenremoved. Such continuing growths are termed

residual cysts.

Osteosclerosis and Condensing Osteitis

Increased bone deposition may be secondary toa variety of local irritants, most notable infection.

Such increased bone deposits are termedosteosclerosis, or alternatively, condensing

osteitis. Figure 16 illustrates the radiographicappearance of condensing osteitis surrounding

the apices of a deeply carious first molar.

Although osteosclerosis is commonly associatedwith carious, frequently non-vital teeth, it may also

be found at the apices of entirely normal teeth,most commonly the mandibular first permanentmolar. It should be pointed out that involved

teeth usually show fully formed roots without asignificant degree of root resorption. (Other terms

used to indicate condensing osteitis are rarefyingor sclerosing osteitis.)

Osteoradionecrosis and OsteonecrosisOsteoradionecrosis (ORN) also known as

postradiation osteonecrosis (PRON), is a serious,debilitating and deforming potential complication

of radiation therapy for the treatment of cancer.It is known to occur following radiation treatmentwhen the maxilla or mandible is directly in the

field of radiation.

Bisphosphonate-associated osteonecrosis of the jaw (ONJ) is uncommon but has been associated

with intravenous bisphosphonate cancer therapy.Any needed dental procedures should becompleted before intravenous bisphosphonate

cancer treatment is started. More research isneeded for patients receiving oral bisphosphonate

for the treatment of osteoporosis. At this time, it

does not seem to be a serious risk and normaldental services are recommended.

Diagnosis depends primarily on clinical and

radiographic changes in the bone. These signsand symptoms typically include ulceration of the

mucosa, loosening of the teeth and exposure ofnecrotic bone.

Figure 16.

Figure 14.

Figure 15.



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Socket Sclerosis

If healing is accompanied by excessive bonedeposition, socket sclerosis results, leading to

radiodense areas within the socket as illustrated(Figure 19).

Residual Root FragmentsIf the tooth is not completely removed, e.g., If the

tooth is not completely removed, e.g., because ofa root fracture or residual deciduous tooth root,

a residual tooth fragment may persist. Thesefragments can be distinguished from socketsclerosis by the presence of a root canal and

an intact periodontal ligament space. Figure 20illustrates the appearance of a residual root and

intact ligament space following the extraction of a

mandibular first molar.

Fractures

Fractured TeethTraumatic injuries, extensive caries and oral

neglect can lead to fracturing of the dental tissues.

Healing of Extraction Wounds

Normal Healing

Following normal tooth extraction, the extractionsocket is clearly demarcated by the radiopaquebundle bone into which the periodontal ligaments

had anchored the tooth. A radiograph of a recentfirst mandibular molar extraction site is illustrated

(Figure 17). Note the clear outline of the rootocket.

With healing, new bone is deposited into thesocket, and, with time, the bundle bone slowly

fades. After about 18 months, it can no longer bedistinguished from the surrounding tissue.

Fibrous HealingOccasionally dental extraction sites lay down afOccasionally dental extraction sites lay down afibrous tissue healing. Such tissues appear as

radiolucent areas such as that in Figure 18 andsometimes last for periods well in excess of the

normal healing time.

Figure 19.

Figure 20.

Figure 17.

Figure 18.



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retained intraosseous wiring is visible at the healed

fracture site (Figure 25).

Developmental Abnormalities

Supernumerary Teeth

The relatively common abnormality of teethnumbering in excess of the standard 32 permanentor 20 deciduous is known as supernumerary

dentition. Areas of the jaws most frequentlyaffected with supernumeraries include the

maxillary central and lateral incisor and molarregions, and the mandibular premolar region.

The most common supernumerary tooth is themesiodens, occurring between the maxillary

central incisors (Figures 26 & 27). This tooth isusually small and cone-shaped and may be either

erupted or impacted.

Supernumerary teeth of the maxillary molar regionoccur either distal to the third molar, thus calledfourth molars, or between or adjacent to the third

and second molars, becoming paramolars.

Multiple-impacted supernumerary teeth are

classically associated with Gardner’s Syndrome,a hereditary condition marked by multiple polypsof the colon, and cleidocranial dysplasia, a rarehereditary condition in which there is defective

ossification of the cranial bones and completeor partial absence of the clavicles. Given the

serious ramifications of these diseases, it is vitally

Maxillary incisors are particularly prone to

traumatic injuries. The fracture often leads tolosing portions of the tooth crown such as thetraumatic loss of the incisal edges (Figure 21).

Fracture can also affect the tooth root, appearing

as a radiolucent line across or with the tooth’slong axis. Be careful not to mistake the artifactof a fingernail crimp as a fracture! Figure 22 is a

radiograph of a fractured tooth. A fingernail crimpwould be very similar, though possibly somewhat

more broad and radiolucent (Figure 23).

Fractured Bones

Even though bone is usually strong and resilient,Even though bone is usually strong and resilient,

a forceful blow can cause it to break. Therefore,patients with a history of traumatic injury and a

clinical picture of bruising and tenderness shouldbe radiographed to detect a fracture. Depending

on the nature of the injury, a fracture can bea straight or jagged line, which may penetratepartially or completely through the bone and leave

the bones normally aligned or displaced. Figure24 illustrates a non-displaced mandibular fracture

in the canine region.

If the fracture site is unstable, or displaced,intraosseous wiring is used to maintain positionduring healing.

During healing, the body often lays down excess

bone or callus in the injured area. This callus and

Figure 23.Figure 21. Figure 22.



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first permanent molar, and retention and ankylosis

of the mandibular second deciduous molars.

More severe forms of congenital hypodontia are

associated with hereditary anhidrotic ectodermaldysplasia, a disease characterized by theabsence of eyebrows and eye lashes, a depressednasal bridge, prominent supraorbital ridges,

light, scanty hair and wrinkled palms secondaryto hyperkeratosis. In such patients, it is not

uncommon for only three or four teeth to develop.

important to consider them whenever multiplesupernumerary teeth are encountered.

Hypodontia (Too Few Teeth)

Missing teeth is an exceedingly common finding,which can usually be attributed to extraction ortraumatic evulsion. Such acquired hypodontia

must be contrasted with congenital hypodontia,which arises because of a developmental error.

Congenital hypodontia most commonly affectsthe third molars, the permanent maxillary lateralincisors and the maxillary and mandibularpremolars. Frequently, hypodontia is bilateral.

Figure 28 is an example of a patient withcongenital hypodontia, affecting the mandibular

second premolars bilaterally, the left mandibular

Figure 27.

Figure 28.

Figure 24.

Figure 25.

Figure 26.



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MicrodontiaMicrodontia is a condition characterized by

unusually small teeth. Again, it commonly affectsonly one tooth, most often the maxillary lateral

incisor or peg lateral and the third molar. It mayalso manifest as a feature of other anomalies suchas supernumerary teeth. Figure 31 is a maxillary

third molar microdont.

Generalized microdontia is very uncommon. It hasbeen associated with pituitary dwarfism, hypoplastic

type amelogenesis imperfecta and anhidroticectodermal dysplasia.

Hutchinson’s TeethHutchinson’s teeth result from a highly distinctive

form of enamel hypoplasia, occurring only in

congenital syphilis. Affected incisors demonstrateconvergence of mesial-distal dimension approachingthe incisal edge. Typically, there is a distinctivenotch on the mid-incisal edge, which has been

likened to the appearance of a screwdriver (Figure2). All maxillary and mandibular incisors may show

the defect, although the maxillary lateral incisor mayappear normal while the others are defective.

Macrodontia

Macrodontia is the formation of unusually largeteeth. Most commonly, this developmental

anomaly presents as a single enlarged tooth, and,less frequently, as multiple macrodonts. Figure 29

is a right maxillary lateral incisor macrodont witha small hypoelastic enamel defect on the labial

tooth surface.

The patient’s radiograph, shown in Figure 30

clearly outlines the macrodont and additionallyreveals an impacted maxillary canine.

As noted earlier, macrodontia usually resultsin a single large tooth. Much less frequently,multiple macrodonts are encountered with suchconditions as facial hemihypertrophy and pituitary

giantism. Tooth fusion, which will be discussedlater, produces teeth that are virtually identical

to macrodonts; and, indeed, it may well beimpossible to distinguish between the two.

Figure 30.

Figure 32.

Figure 31.Figure 29.



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a pattern of large pulp chambers and short roots.

Clinically, the teeth appear normal, but on aradiograph, they demonstrate a distinct rectangularoutline, such as seen in tooth #19 (Figure 36).

Taurodontism may affect multiple teeth, but it

is limited almost entirely to the molars. It is

associated with Kleinfelter’s Syndrome, asyndrome of gonadal defects, appearing in males,with an extra X chromosome, which should besuspected whenever taurodontism is encountered

in patients with unexplained mental retardation, atall, thin appearance, long legs and arms, and a

distinctly prognathic jaw.

Evagination

Evaginationrepresents a somewhat rare dentaldevelopmental malformation in which thereappears to be a small accessory cusp arising

from the occlusal surface of a tooth. Figure 33illustrates a maxillary premolar with evagination

occupying the space between the buccal andlingual cusps.

Although it may occur on any tooth, it is mostcommonly observed on the premolars. The

malformation is composed of enamel and dentinand may extend into the pulp; and thus, attrition

on caries involving the evagination may lead topulp necrosis and periapical disease.

Invagination (Dens in Dente)Invagination represents a deep infolding of the

tooth with extension of the enamel down throughthe dentin into the pulp. Such teeth can be

severely deformed, appearing with an enlargedpulp chamber that has been likened to a toothwithin a tooth (dens in dente).

The most commonly affected tooth is the

permanent maxillary lateral incisor (Figures 34 &

35). Single dens in dente are most common, butdouble varieties also occur.

Taurodontism and Pyramidal Teeth

Taurodontism is a fairly common developmentaldefect in which the affected multi-rooted teeth

display apically displaced furcation, producing

Figure 34.

Figure 35.

Figure 33.



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The curvature is more visible if it occurs in a

plane perpendicular to the central X-ray beam. Ifit occurs parallel to the beam, it casts a shadowsimilar to a radiopaque cyst or bone deposit

because the axis is oriented toward or away fromthe beam.

Supernumerary Roots

Teeth having a greater number of roots than isanatomically typical have supernumerary roots.The canines, mandibular premolars and maxillary

second premolars are usually single rooted, and aradiographic appearance such as that in Figure 39

would be diagnostic of supernumerary roots.

Fusion and Gemination

FusionFusion is defined as the joining of twooriginally separate teeth through the dentin, or

through the dentin and enamel. In contrast,gemination represents incomplete division of what

should have been two separate teeth. Fusionmay involve supernumerary teeth, and gemination

Pyramidal teeth are morphologically similar totaurodontism. They exhibit enlarged, elongated

pulp chambers but only single roots as illustratedin tooth #18 (Figure 36). In effect, the condition

appears to represent extreme apical displacementof the furcation, resulting in a single broad root,

which, in actuality, is the body of the tooth.The clinician will sometimes encounter bothtaurodontism and pyramidal teeth in the same

patient.

Dilaceration

Dilaceration is an unusual bend in the toothroot(s). The curvature usually results from traumaand can occur anywhere along the root. Sincethe tooth crown is clinically normal, the degree of

dilacerations can only be detected radiographically.

Dilaceration may range from mild curvature(Figure 37) to severe bending (Figure 38).

Figure 39.

Figure 36.

Figure 37.

Figure 38.



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Regional OdontodysplasiaRegional odontodysplasiarepresents adevelopmental disorder in which one or severalteeth in a contiguous group fail to properly form.

The condition occurs sporadically without adistinct familial pattern and most commonly affects

the anterior maxillary quadrants. The involvedteeth often fail to erupt, or if they do erupt, they

are misshapen with irregular crowns and defectivemineralization. Unerupted teeth are characterizedby soft tissue swelling and painful symptoms.

adiographic features typically consist of one

tooth, or segment of teeth, demonstrating

incomplete formation and reduced radiopacity.Because of their radiolucency, they are sometimesknown as ghost teeth. In Figure 43, the posteriormaxillary segment demonstrates an unerupted

and incompletely mineralized second premolarand second molar. The first molar is absent and

swelling of the overlying soft tissue is noted.

may occur in quadrants also affected by partial

anodontia; thus, counting the teeth in the affectedarea is of limited diagnostic value. Regardless ofwhich process initiated the error, it is practically

impossible to distinguish between fusion andgermination, and in either case, the tooth will

appear much like that in Figure 40.

The distinction between fusion and germinationis primarily of academic interest and thus, theetiology is of less clinical concern than is the

presence of the condition and the potentialramifications involved.

ConcrescenceConcrescence represents the joining of adjacentteeth via the cementum with obliteration of theintervening periodontal ligaments. Concrescence

is usually found in two teeth, rarely in three ormore. The clinical appearance of the condition

is shown in Figure 41 and the appearance on aradiograph in Figure 42.

Figure 43.

Figure 40.

Figure 41.

Figure 42.



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The second type is coronal dentin dysplasia

and is characterized by the thistle-funnel pulp

chamber enlargement in the permanent teeth(Figure 46).

Amelogenesis ImperfectaAmelogenesis Imperfecta constitutes a diverse

group of distinct, genetic disorders which sharegeneralized defective enamel formation. As

distinct conditions, varieties of amelogenesisimperfecta have been linked to autosomal,X-linked, dominant, and recessive genes.

Clinically, the enamel may be partially missing(hypoelastic); very soft (hypocalcified); or

firm but chippable (hypomaturation). Varyingdegrees of yellow to brown tooth discolorationmay be present. On the radiograph, theteeth may show hypoplasia from failure of

enamel formation or a chipped and worn-awayappearance from partial formation (Figure 47).

Dentinogenesis Imperfecta and DentinDysplasiaDentinogenesis Imperfecta is an inheriteddisorder, usually showing a dominant autosomal

pattern. Clinically, the teeth have a peculiartranslucent appearance with discoloration rangingfrom brown to yellow to gray. Such teeth are

termed opalescent.

Radiographically, all teeth in the deciduous andpermanent dentitions show early and frequently

complete obliteration of the pulp chambers andcanals with short, blunted roots (Figure 44).

Dentin dysplasia is another autosomal dominantcondition in which there is markedly disturbed

dentin formation. This extremely rare condition

occurs in two distinct patterns. The first,referred to as radicular dentin dysplasia, ischaracterized by partial or complete obliterationof the pulp chamber and extremely short, blunted

roots (Figure 45). When persistent, the pulpchamber displays a characteristic crescent.

Figure 44.

Figure 45.

Figure 46.

Figure 47.



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Mild opacification and focal surface pitting may

not be visible on radiographs.

Talon Cusp and Enamel Pearl

The talon cusp represents a developmentalanomaly in which a peculiar lingual cusp forms

on the maxillary or mandibular incisors. Whensmall, the cusp cannot be distinguished from anaccentuated cingulum. When well-developed,

the cusp appears clinically (Figure 50) and, on aradiograph (Figure 51).

The enamel pearl is a misplaced (ectopic)

globule of enamel, occurring most commonly inthe furcation areas or near the cementoenamelroot surfaces of the molar teeth. Affecting the

maxillary more often than the mandibular areas,the relatively rare enamel pearls may contain a

dentin core, occasionally with pulpal extension.

adiographically, the pearl appears as a roundor semi-spherical area of increased radiodensity.When occurring on the mesial or distal aspects,

the pearl produces an obvious convex profile.On the buccal or palatal/lingual aspects, it is less

easily seen and may resemble pulp stones.

Regressive Changes in Teeth

Attrition

Attrition represents the physiologic wearingaway of tooth structure through such causes

as normal mastication. The incisal, occlusal

In cases of hypocalcification, the radiodensity

of the enamel and the dentin are very close and,thus, delineating between them is difficult.

Turner’s Tooth and Environmental Hypoplasia

Enamel hypoplasia, limited to a single tooth,is known as urner’s Hypoplasia and theaffected tooth is termed Turner’s tooth. The

most frequently affected teeth are the permanentmaxillary incisors and the maxillary and

mandibular premolars. Common causes forthe condition include local trauma or infectionderived from an overlying deciduous tooth.

Clinical appearance can range from mild, opaquechalkiness or brown discoloration or frank enamel

pitting (Figure 48).

In contrast to the genetic nature of Turner’sHypoplasia, environmentally-induceddevelopmental failure of enamel formation

affecting multiple teeth is termed generalizedenvironmental enamel hypoplasia.

Environmental factors can include nutritionaldeficiencies, excessive fluoride ingestion, and

severe, fever-producing childhood diseases.

Clinically, the affected teeth show localized

enamel deficiency ranging from focal opacificationto severe pitting. The distribution of enamel

defects reflects the chronology of enamel

formation with most severely affected areasrepresenting the area that were forming at thetime of the environmental influence.

The radiographic features of generalizedenvironmental enamel hypoplasia consist of linear

bands of relatively radiolucent enamel (Figure 49).

Figure 48.

Figure 49.



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acidic and the process does not involve bacterial

action. Clinically, erosion is usually described inconnection with the gingival one-third of the labialaspect of the anterior teeth, although any tooth

surface can be affected. Erosion may arise dueto environmental factors such as personal diet

and occupations that involve working with acids.

Chronic vomiting may produce extensive erosionof the lingual tooth surfaces due to the acidnature of stomach contents (Figure 53).

Pulp Stones

Pulpal calcification is an extremely commonfinding and is considered by many to be a

and interproximal surfaces are typically affected,and often the enamel is worn away so that theexposed dentin is clearly visible. Although attrition

rarely results in serious disease, advance casescan lead to pulp necrosis and periapical disease.

Abrasion

The pathologic wearing away of tooth structuresecondary to friction is abrasion. Agents, whichcontribute, include abrasive toothpaste, improper

use of toothbrush, flosses and toothpicks, andpersonal habits such as excessive brushing, and

holding pins, nails and tacks between the teeth.

A common form of abrasion involves the cervicalareas, producing a sharply defined V-shapeddefect such as that crossing the buccal aspect ofthe premolar (Figure 52).

ErosionErosion represents loss of tooth structure causedby chemical action. Usually these chemicals are

Figure 51.

Figure 52.

Figure 53.

Figure 50.



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Hypercementosis

Excessive deposition of cementum along the

root surface is termed hypercementosis.The precise cause of this condition is not wellunderstood, although the loss of tooth antagonism

and local inflammation is often associated withit. A special exception is osteitis deformans or

Padget’s disease, in which teeth in an affected jaw typically demonstrate a remarkable degree of

hypercementosis.

adiographically, the condition is characterized

by a bulbous, opaque expansion of root contours,usually involving much of the root length, while

preserving the periodontal ligament space andlamina dura (Figure 55). Less commonly, the

overgrowth is limited to the root apex.

Ankylosis

Tooth ankylosis represents a direct union of tooth

to bone, eliminating the normally interposedperiodontal ligament. Ankylosis is uncommon,usually encountered with deciduous teeth and

often, though not exclusively, associated with localtrauma and/or infection.

Clinically, deciduous ankylosis typically presentsa retained tooth positioned below the level of the

occlusal plane and is termed a submerged tooth.adiographically, the ankylosed tooth typically

exhibits signs of partial root resorption, obliterationof portions of the periodontal ligament, mild

osseous sclerosis and apparent direct attachmentof root and bone (Figure 56). On occasion,impacted teeth will become ankylosed in the jaw.

External Resorption

Mild external resorption of permanent teeth is arelatively common finding. Its specific causes can

often be attributed to trauma, orthodontic therapy,reimplantation, cysts, tumors and infection. Inother cases, no specific cause can be identified.

oot resorption most commonly is limited to the

apical portion of the root and lacks any clinical

manifestations. However, the condition canadvance to the point that teeth become mobileand exfoliate.

adiographic appearances include blunting ofroot apices with shortening of root length. In

variation of normal pulpal development.Calcifications presenting as distinct intra-chamber

(or less often intra-canal) radiopacities are known

as pulp stones. Figure 54 illustrates a prominentstone in the pulp chamber of the second maxillarymolar. It must be noted that it is often difficultto differentiate the radiographic appearance of

a pulp stone from the simple superimposition offurcation contours.

Figure 54.

Figure 56.

Figure 55.



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chamber or canal (Figure 58). If the canal is

involved, it is virtually impossible to distinguishbetween internal and external resorption.

Developmental Anomalies of the Jaws

Mandibular Tori

Mandibular tori epresent benign overgrowthsof mature, lamellar bone, occurring on the

lingual mandibular cortex. Typically attached tothe mandible opposite the premolar region and

superior to the mylohyoid line, they are mostcommonly bilateral. There is some variation in

incidence among races with a higher incidenceamong Orientals than in Caucasians. Apparently,genetic factors also influence tori development, as

the offspring of parents with mandibular tori havea much higher incidence of development.

Radiographically, tori appear as well-defined

areas of radiopacity overlying the tooth roots(Figure 59), particularly extending from thecanine to the molar regions. If tori are seen on

radiographs, they should be clinically confirmedin order to rule out other conditions, which lead to

osseous radiopacity.

Maxillary Torus

The maxillary torus presents as a hard,frequently lobulated, benign overgrowth of

mature lamellar bone. It is frequently located inthe midline of the hard palate (Figure 60) and

attached by a broad, bony base.

some cases, abrupt loss may be noted, and, with

advancing disease, the entire root may appearlost. Figure 57 illustrates a marked blunting androot loss following orthodontic therapy.

It is critically important to examine the tissues

immediately surrounding the resorbing root.While, in most cases, the resorption is mild andrelatively inconsequential, it can be severe and

may be secondary to a number of significanttumors, including odontogenic neoplasms and

metastatic cancer. Care must be taken to avoidsimply identifying the condition without making

a thorough investigation for signs of a far moreerious disease.

Internal Root ResorptionInternal resorption represents a peculiar internal

dissolution of dentin, which can extend eventuallyinto the enamel and/or cementum by the tooth

root. Usually, only a single tooth is involved, andalthough the cause is not clearly understood, it isoften linked to inflammation.

Clinically, internal resorption in the pulp

chamber may lead to the ooth of Mummery

with a developing pink hue in the tooth crown.Resorption in the root canal is not clinicallyvisible; however, perforation of the root usuallyrequires that the tooth be extracted.

Radiographic evidence of internal resorption

consists of an unusual widening of the pulp

Figure 57. Figure 58.



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well-defined radiolucency found at the angle of themandible below the mandibular canal that has no

significance except in its differentiation from otherconditions (Figure 62).

Clefts

Developmental clefts of the palate are notuncommon. They result from a smooth defectand are often associated with marked tooth

displacement.

SummaryMany conditions of the hard and soft tissues of the

oral cavity and surrounding area can be diagnosedand treated through the use of quality dentalradiographs. The importance of quality dental

radiographs cannot be overstated and is coveredin other continuing education courses offered by

the American Dental Assistants Association.

The condition is more common in Native

Americans, American Indians and Eskimos thanin Caucasians or Blacks and has a population-

wide frequency of occurrence of about 25percent. Hereditary factors have been implicated.Radiographically, the maxillary torus appears as

a well-defined radiopacity situated at, or superiorto, the apices of the maxillary teeth (Figure 61).

On panoramic radiographs, it may be visualizedin the midline and over the roots of the canines,

premolars and molars.

Stafne Bone Cavity

The Stafne cavity is an osseous defect causedby pressure of the submandibular salivary gland

on the mandible during its development. It is a

Figure 59. Figure 61.

Figure 62.

Figure 60.



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Course Test PreviewTo receive Continuing Education credit for this course, you must complete the online test. Please go to

www.dentalcare.com and find this course in the Continuing Education section.

1. The carious lesion on the canine tooth in the below image involves which dental structures?

a. Enamel onlyb. Dentin only

c. Pulpd. Enamel and dentin

2. What type of bone loss affects the molar tooth in the below image?

a. Horizontal bone loss

b. Vertical bone lossc. Osteosclerotic

d. Attrition

3. The radiolucency at the upper left associated with the apex of tooth #8 in the below image

could be:a. An abscess

b. A cystc. A granuloma

d. All of the above

4. The radiopacity to the right of the molar in the below image is:

a. A root fragmentb. Condensing osteitisc. Calculus

d. A maxillary torus



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5. The radiolucency across the lateral incisor in the below image is:

a. A fracture of the tooth root

b. A transverse carious lesionc. A fingernail crimp artifactd. Horizontal bone loss

6. The radiopacity above the maxillary premolar in the below image is:a. Calculus

b. An enamel pearlc. An impacted supernumerary tooth

d. Osteosclerosis

7. The tooth in the below image probably resulted from:

a. Fusion or geminationb. Evaginationc. Invagination

d. Fracture

8. What regressive change is illustrated in the below image?

a. Internal resorptionb. External resorption

c. Ankylosisd. Hypercementosis



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9. The radiolucency in the patient’s left mandible in the below panoramic radiograph is most

likely a:

a. Circular fractureb. Talon cuspc. Mandibular tori

d. Stafne bone cavity

10. The apical radiopacity at the base of the premolar in the below image is:a. Condensing osteitis

b. External resorptionc. A root fragment

d. Cervical burnout

11. A diligent search for recurrent caries should be made when radiographs detect __________.

a. open margins on restorationsb. interproximal restoration overhangs

c. restorations which appear to end short of the preparation marginsd. All of the above.

12. A normal anomaly of the X-ray process which sometimes causes an image that lookssuspiciously like interproximal caries is:

a. Proliferative gingival hyperplasiab. Dental calculus

c. vertical bone lossd. Cervical burnout

13. Disorders that may clinically show a peculiar translucent appearance with discolorationranging from brown to yellow to gray is/are ____________.

a. dentinogenesis imperfectab. amelogenesis imperfecta

c. Turner’s hypoplasiad. All of the above.

14. ____________ is an anatomical abnormality in which a tooth’s pulp chamber is elongated,enlarged, and extends into the region of the roots.

a. Taurodontism

b. Hemihypertrophyc. Lobulatedd. Ossification



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15. Dilaceration is a ____________.

a. unusual bend in the tooth crown

b. unusual bend in the tooth root(s)c. v-shaped space between curved adjacent surfaces of teethd. disease condition

16. Epithelial remnants (builder’s debris) can proliferate within an apical granuloma to form

____________.a. an apical or lateral radicular cyst

b. a macrodontc. a pulp stone

17. Which of the following is associated with the Tooth of Mummery?a. Pulp stones

b. Impacted supernumerary molarsc. Internal root resorption

d. Periapical granulomae. Pyramidal teeth

18. Teeth numbering in excess of the standard 32 permanent or 20 deciduous teeth are known as:

a. Macrodontsb. Microdontsc. Hypodonts

d. Supernumeraries

19. Mineralized plaque seen opposite the salivary ducts is ____________.

a. proliferative gingival hyperplasiab. dental calculus

c. an enamel pearld. a talon cusp

e. early concrescence

20. A congenital disease characterized by the presence of only three or four teeth, the absence of

eyebrows and eye lashes, and wrinkled palms is ____________.a. ectodermal dysplasia

b. Hutchinson’s syndromec. Kleinfelter’s syndrome

d. facial hemihypertrophye. Turner’s syndrome

21. The approximate population-wide incidence of the maxillary torus is _____.a. 66%

b. 33%c. 15-18%

d. 10%

e. 25%

22. Gingival enlargements can occur as a result of ____________.a. plaque

b. calculusc. extrinsic factors

d. All of the above.



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23. Bone loss which demonstrates remarkable variation in height relative to the adjacent tooth

crowns is:

a. Internal resorptionb. Vertical bone lossc. Socket sclerosis

d. Bundle bone

24. The laying down of excess bone in an extraction socket is known as:a. Incomplete healing

b. Socket fibrosisc. Socket sclerosisd. Bundle bone

25. A tooth with the notched appearance of a screwdriver is known as:

a. Hutchinson’s toothb. Turner’s tooth

c. Tooth of Mummeryd. Kleinfelter’s tooth

e. Talon’s tooth



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ReferencesNo references cited.

About the Authors

Original Manuscript:Allan G. Farman, B.S.D., EdS, MBA, PhD

Dr. Farman is a Diplomate of the Board of Oral and Maxillofacial Radiology, andProfessor of Oral and Maxillofacial Radiology in the Department of Primary Patient

Care at the University of Louisville School of Dentistry.

Revised 2004 and 2009:

Members of the Council on Education of the ADAA

Members of the Council on Education of the American Dental Assistants Association helped with therevision of this course. All members of the Council on Education are ADAA Active or Life Members with

an interest in dental assisting education. Each one volunteers their time to the lifelong learning of dentalassistants.

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Diseases of the Teeth and Jaws

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