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