This course in dental anatomy has dealt primarily with "normal" morphological features of the primary and secondary (permanent) dentitions. This unit provides examples of some anomalies of dental hard tissues. The classification system used is an etiopathological classification system. Examples of various anomalies with a brief description will be presented in this unit. Detailed information regarding etiology, diagnosis and treatment will be presented in other courses in your curriculum.

Bilateral talon cusps on the permanent maxillary right and left central incisors

AEtalon1 (courtesy of Dr. BM Cleghorn, Dalhousie University)

This unit will concentrate on the growth and developmental disorders of teeth. Examples of anomalies in number of teeth, structure of teeth, shapes of teeth and eruption will be highlighted.

The etiology of any given anomaly can be the result of a genetic defect, environmental influences or be idiopathic.

The normal stages of development of each of the primary and secondary teeth are important. The key events for the primary dentition are listed in the table on the left. Although there is a range of normal, this knowledge can assist in determining whether your patient's dentition is developing normally or not. Parents will frequently ask about whether their child's dentition is developing normally. In addition, this knowledge is invaluable in determining whether Individual teeth are congenitally missing. Aberrations in the timing of development may also provide insight into systemic problems.

Summary

Initial calcification of all of the primary teeth occurs between 14-19 weeks in utero.

The primary dentition begins to erupt at 6 months of age.

All primary incisors are present by 12 months of age.

The primary first molars are present by 16 months of age.

The primary canines are present by 18 months of age.

The primary dentition is complete by 30 months or 2.5 years of age.

Calcification of all of the teeth in the secondary dentition occurs from birth (permanent maxillary and mandibular first molars) to approximately 10 years of age (maxillary third molar).

In this summary table of secondary (permanent) tooth development, there is a range of 3.6-6.1 years between the time of initial calcification of the crown until the crown is completed.

On average, it takes anywhere from 2-5 years from the time of crown completion until the tooth erupts into the mouth. When teeth erupt, there is approximately 1/2 to 2/3 of the root formed. After a tooth erupts, further root formation occurs.

On average, it takes 1.5-3.5 years for the root to completely form after tooth eruption. Variations among the timing of development for the permanent teeth are shown in the table above.

Hypodontia

Hypodontia means that there are fewer than the normal complement of teeth in the dentition. It may be an isolated single tooth missing with no known etiology or it could be associated with a syndrome due to an event occurring before tooth germ formation.

The incidence of hypodontia is <1% in the primary dentition incidence and is approximately 2.5-3.5% in the secondary dentition.

The secondary teeth most frequently missing are the

third molars

second premolars

maxillary lateral incisors

The image above is an example of an abnormality of numbers (congenitally missing permanent maxillary left lateral incisor) and an abnormality of shape. The permanent maxillary right lateral incisor is a peg lateral incisor (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba)

This is an example of a retained primary molar (primary mandibular right second molar) and a single congenitally missing tooth (permanent mandibular right second premolar).

The image on the left is another example of an abnormality of numbers (congenitally missing permanent maxillary right lateral incisor) and an abnormality of shape. The permanent maxillary left lateral incisor is a peg lateral incisor (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

.

The panoramic radiograph above illustrates a case of a congenitally missing permanent maxillary right lateral incisor. The permanent mandibular right third molar had been previously extracted (courtesy of Dr. BM Cleghorn, Dalhousie University).

The bitewing radiograph on the left is of the patient's posterior right and illustrates the posterior teeth in quadrants 1 and 4. The primary maxillary right second molar is retained and the permanent maxillary right second premolar is congenitally missing (courtesy of Dr. BM Cleghorn, Dalhousie University).

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The panoramic radiograph above illustrates a congenitally missing permanent maxillary right lateral incisor (arrow labeled 1.). The arrow labeled 2. is an example of an abnormality in shape as the permanent maxillary left lateral incisor is a peg lateral (courtesy of Dr. BM Cleghorn, Dalhousie University).

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This panoramic radiograph is suggestive of a patient with ectodermal dysplasia. The clinical findings were inconclusive and confirmation of the diagnosis is awaiting genetic testing. Congenitally missing teeth include the permanent maxillary right second premolar, permanent mandibular left first and second premolars and the permanent mandibular right second premolar. Ankylosed primary teeth are present as well as an anomalous permanent maxillary left first premolar. The full case report labeled Case RT is included later in this unit (courtesy of Dr. BM Cleghorn, Dalhousie University).

The periapical radiograph on the left illustrates a single congenitally missing tooth. The arrow points to the congenitally missing permanent mandibular left second premolar. Above the arrow is the retained primary mandibular left second molar with partially resorbed roots (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

The illustration on the left is an example of induced anodontia. True anodontia is rare. This patient has been rendered edentulous as a result of caries or periodontal disease (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

The patient on the left only has four permanent canines remaining. Each of these teeth has been restored with full crowns. This condition is described as partial anodontia (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Oligodontia

Oligodontia is considered a subset of hypodontia and is due to an event that occurs before tooth germ formation. 6 or more teeth are missing. Oligodontia is usually associated with a syndrome.

This panoramic radiograph is an example of oligodontia (6 missing teeth). Also present is a peg lateral incisor.

1. congenitally missing permanent maxillary right second premolar.

2. congenitally missing permanent maxillary right lateral incisor.

3. peg lateral incisor.

4. congenitally missing permanent maxillary left first premolar.

5. congenitally missing permanent maxillary left second premolar.

6. congenitally missing permanent mandibular left second premolar.

7. congenitally missing permanent mandibular left first premolar.

8. congenitally missing permanent mandibular right second premolar.

(courtesy of Dr. BM Cleghorn, Dalhousie University)

The image on the left is an example of ectodermal dysplasia. The only teeth present are anomalous permanent mandibular canines. Ectodermal dysplasia is comprised of a group of inherited conditions that affects ectodermal structures (such as skin, teeth, hair, salivary and sweat glands). This condition can result in multiple missing teeth (hypodontia or oligodontia). This is an example of oligodontia. More than six teeth are missing and the remaining ones are abnormally formed. Therefore, in addition, this is also an example of an abnormality of shape (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Hyperdontia

The panoramic radiograph above is an example of a patient with cleidocranial dysplasia. This is an autosomal dominant genetic disorder that affects the face, the skull and the clavicles. The ossification of the clavicles, cranium and other long bones is defective. The clavicular defects can result in the patient being able to touch their shoulders. The intraoral features include multiple unerupted supernumerary teeth and delayed eruption of the permanent teeth (courtesy of Dr. BM Cleghorn, Dalhousie University).

The occlusal view of the mandibular arch pictured on the left illustrates a slightly crowded arch. Close examination reveals a supernumerary mandibular central incisor. This is not a common anomaly and illustrates the importance of careful identification and charting in dentistry (courtesy of Dr. BM Cleghorn, Dalhousie University).

The periapical radiograph of the 4th quadrant to the left illustrates a supernumerary mandibular right premolar.

1. permanent mandibular right second premolar.

2. supernumerary mandibular right second premolar.

3. permanent mandibular right first premolar.

(courtesy of Dr. BM Cleghorn, Dalhousie University)

Many mesiodens remain unerupted. This is an example of a fully erupted mesiodens lingual to the permanent maxillary left central incisor (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

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The patient in the clinical photo on the left has a peg lateral incisor (permanent maxillary left lateral incisor). The maxillary arch has been banded to regain lost space due to this microdont tooth. The goal is to create enough space to restore the peg lateral to its normal size and shape and to match the permanent maxillary right lateral incisor in size, shape and colour (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

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Macrodontia

The term macrodont means "big or large tooth". It is extremely rare to have generalized dentition of macrodont teeth.

Most Common Macrodonts

Mandibular third molars

The incidence of macrodontia is approximately 1% of the population . Macrodontia must be differentiated from gemination (one tooth bud attempting to split into two teeth) and fusion (two teeth joined with separate root canal systems) . Macrodontia may be associated with a growth disorder or with syndromes such as pituitary gigantism.

The clinical photo on the right shows two permanent maxillary canines (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba). The canine on the left is of normal length (approximately 27mm). The canine on the right is a macrodont due to its abnormally length (approximately 35mm). Booth published a case report of a patient with a maxillary canine that was 41mm in length (Booth, JM, 1988). The patient reportedly was a 5'2", 31 year old female of Dutch origin.

Secondary Maxillary Canines (Facial View)

The canine on the left is of normal length (27mm). The canine on the right is a macrodont.

Proximal view of a normal mandibular right second premolar (left) and a macrodont mandibular right second premolar

The clinical photo on the left illustrates a macrodont permanent mandibular second premolar (mesial view). The average overall length of a mandibular premolar is 23.2mm (Goodacre, C, 2003) and is illustrated on the left. The macrodont on the right has normal crown dimensions and an abnormally excessive root length (courtesy of Dr. BM Cleghorn, Dalhousie University).

Shovel-shaped Incisors

These teeth are characterized by having prominent marginal ridges associated with a deep lingual fossa on the maxillary incisors. This gives the crown of the tooth a shovel-like shape, hence the name. Shovel-shaped incisors may be associated with dens invaginatus. This would be considered an anomaly in some populations such as Caucasian populations but normal in Eastern Asian populations like the Japanese and North American Native populations, where this is very common. The incidence is approximately 15% in North American Caucasians (anomaly) in contrast to close to 100% in Asians and North American Aboriginal populations (normal in these populations) . Shovel-shaped incisors may be associated with syndromes such as Klinefelter's syndrome (extra X chromosome in males) and can also be associated with taurodont teeth or can be an isolated feature in the dentition. The clinical radiograph (below) shows shovel-shaped secondary maxillary right central and lateral incisor (courtesy of Dr. BM Cleghorn, Dalhousie University).

Secondary Maxillary Right Central and Lateral Incisors

Both crowns are shovel-shaped

Cervical Enamel Extension (Enamel Spur)

This is a condition where there is enamel projecting on root surface that is continuous with the enamel of the crown. This is more commonly found in mandibular molars in the buccal furcation region. This should be differentiated from an enamel pearl because a pearl is a separate elevation of enamel on the root while the cervical enamel extension is enamel continuous with the enamel of the crown of the tooth.

Most Common Location for Cervical Enamel Extension

Mandibular first molar

Mandibular second molar

Mandibular third molar



The incidence ranges from 8.6% to 32.6% in all populations but is more common in Asian populations. Clinically, this condition may lead to periodontal pocketing due to a lack of periodontal attachment to the enamel. The image to the right illustrates an enamel spur on a secondary (permanent) maxillary first molar.

Enamel Pearls

This is a condition of ectopic enamel that is separate from the enamel of the crown. This entity can be differentiated from a cervical enamel extension because of its separation from the enamel of the crown of the tooth.

Most Common Location for Enamel Pearls

Maxillary molars

The incidence of enamel pearls is 1.1 to 9.7% in all populations but the highest incidence of enamel pearls occurs in Asian populations. If the pearl is large, an extension of the pulp may be involved.

Radiograph of extracted maxillary third molar with two enamel pearls on the root (courtesy of Dr. BM Cleghorn, Dalhousie University).

Radicular Grooves

This is defined as an invagination along the root surface of a tooth .

Highest Incidence of Radicular Grooves

Maxillary central and lateral incisors

Problems associated with radicular grooves include periodontal pocketing due to a communication with the oral cavity and if severe, communication with the pulp. The clinical photo (right) is of an extracted secondary (permanent) maxillary right central incisor (lingual view); an endodontic access opening had been attempted prior to its extraction (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Secondary Maxillary Right Central Incisor (Lingual View) Radicular groove

Talon Cusps

This is a form of dens evaginatus and presents as an extra cusp usually found on the lingual of maxillary central and lateral incisors. Talon cusps have also been reported on the labial surface of teeth but this is less frequent. Talon cusps can contain an extension of the pulp if the talon cusp is large.

Most Common Location for Talon Cusps

Maxillary central and lateral incisors

The incidence of talon cusps ranges from 0.2 to 5.2% and can be an isolated condition (more commonly) or they can be associated with syndromes such as Rubenstein-Taybi (developmental retardation, broad thumbs, big great toes).

Permanent maxillary right lateral incisor with a lingual talon cusp (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba)

This is an occlusal view of the maxillary arch of a 12 year old African Canadian patient with talon cusps on the lingual of the permanent maxillary left and right central incisors (courtesy of Dr. BM Cleghorn, Dalhousie University).

Taurodontism

Taurodontism is defined as an enlargement of the pulp chamber of multi-rooted teeth (usually molars). This is a normal condition in Neanderthal man and is a normal condition in cud-chewing animals (L. taurus bull and Gr. odous tooth). Short roots and a lack of cervical constriction characterize the teeth involved. It is more common in the secondary dentition and is caused by a later invagination of the Hertwig's root sheath. The incidence ranges from 2.5 to 3.2% in the US population and may occur as an isolated condition (more commonly) or part of a syndrome such as Klinefelter's syndrome, Down syndrome, ectodermal dysplasia or amelogenesis imperfecta.

Proximal view of an extracted permanent maxillary right second molar from an Inuit patient (courtesy of Dr. BM Cleghorn, Dalhousie University).

Periapical radiograph of mandibular molars illustrating a taurodont mandibular left second molar (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba)

Periapical radiograph of mandibular molars illustrating a taurodont mandibular left second molar (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba)

Dilaceration

This is defined as a sharp angle or bend on the root of a tooth. Trauma or some type of developmental anomaly usually is the aetiology. Aetiology may be an idiopathic or a developmental disturbance. Endodontic treatment or extraction of these teeth may be difficult, therefore, the condition is important to diagnose.

Extracted permanent maxillary left central incisor with a short dilacerated root. This was caused by a traumatic injury at the time when the root was just beginning to form. The primary central incisor had been intruded causing the permanent maxillary incisor to have a stunted, dilacerated root (courtesy of Dr. BM Cleghorn, Dalhousie University).

Multiple dilacerated roots on an extracted permanent mandibular left second molar (courtesy of Dr. BM Cleghorn, Dalhousie University).

Gemination

Gemination is defined as the attempt by a single enamel organ to divide into two. The division of the tooth, however, is incomplete. Complete division of a tooth would be called twinning. The incidence of gemination is 0.5% in the primary (deciduous) dentition and 0.1% in the secondary (permanent) dentition. Gemination needs to be differentiated from fusion by counting and identifying the teeth present. Gemination is associated with a normal complement of teeth. The tooth is a macrodont with a common root canal system.

Most Common Teeth Associated with Gemination

Maxillary central and lateral incisors

The clinical photo on the left illustrates a permanent maxillary right lateral incisor with a notch in the incisal ridge. This macrodont tooth has a single root canal system and is an example of gemination (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Radiograph of Secondary Maxillary Left Lateral Incisor

Gemination (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

The clinical photo on the left illustrates permanent maxillary right and left central incisors with notches in the incisal ridges. These macrodont teeth both have a single root canal system and are examples of gemination (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Fusion

Fusion is defined as the union of enamel and dentin between two teeth. A differential diagnosis must differentiate fusion from concrescence and gemination. The incidence of fusion is approximately 0.5 % in the primary (deciduous) dentition and 0.1% in the secondary (permanent) dentition. The tooth presents as a macrodont with a separate root canal system (compare to gemination). The total number of teeth in the dentition is reduced by one.

Teeth Most Commonly Associated with Fusion

Maxillary central and lateral incisors

The clinical photo on the left is an example of fusion between a permanent maxillary left central incisor and a supernumerary tooth. The permanent maxillary right and left lateral incisors are unerupted. The primary maxillary left lateral incisor and canine are present in this photo (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Fusion of the permanent maxillary right central and lateral incisors (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

The clinical photo on the left is an example of bilateral fusion of primary mandibular incisors. The primary mandibular right central and lateral incisors are fused as are the primary mandibular left central and lateral incisors (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

The print of the radiograph on the left illustrates fusion between the primary mandibular left lateral incisor and the primary mandibular left canine. Two separate root canal systems are visible (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Concrescence

Concrescence is defined as the joining of teeth by cementum only. It is important to differentiate concrescence from fusion and gemination. Concrescence is caused by a displacement of tooth germs toward each other or due to hypercementosis from trauma after eruption.

Teeth Most Commonly Associated with Concrescence

Maxillary second and third molars

The photo on the left is an example of concrescence between the permanent maxillary right second and third molars (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Differentiating Gemination, Fusion and Concrescence

Differentiating gemination, fusion and concrescence is not always possible due to confounding factors such as the involvement of supernumerary teeth. However, the table to the right provides some basic guidelines that can assist in diagnosis.

Accessory Roots

It is important to diagnose anomalous roots when considering extraction or endodontic treatment. This anomaly has ethnic differences and varies greatly among different ethnic groups. Eastern Asian and North American Natives have higher incidences of extra roots on mandibular molars than do Caucasian populations.

Highest Incidence of Extra Roots

Third molars

The clinical photo on the left illustrates a buccal view of an extracted mandibular third molar with accessory root (courtesy of Dr. BM Cleghorn, Dalhousie University).

Mesiolingual view of a permanent mandibular left first molar with an accessory lingual root (courtesy of Dr. BM Cleghorn, Dalhousie University).

Dens invaginatus (dens in dente)

Oehlers classification of this condition continues to be used today (Oehlers, FAC, 1957a, Oehlers, FAC, 1957b and Oehlers, FAC, 1958). Forms include coronal (most common) and radicular type. The incidence ranges from 0.04 to 10% in all populations. "Dens in dente" is a misnomer because it means "tooth within a tooth". This is not really a tooth because it is lined by enamel only appears to be like a tooth radiographically. The severity can range from a pit to a dilated odontome. Treatment can range from restorative to extraction of the tooth.

The clinical photo on the left is an example of dens invaginatus associated with the permanent mandibular left first and second premolars (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Dens invaginatus associated with the permanent maxillary right central incisor (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

The clinical photo on the left illustrates dens invaginatus associated with the permanent maxillary left lateral incisor (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Dens evaginatus

Dens evaginatus is defined as an outgrowth on the crown of a tooth. Clinically, it appears as a small tubercle on the occlusal surface of a tooth. It may contain pulp if tubercle is large, therefore removal requires careful consideration (such as reduction over multiple appointments to allow for reparative (or tertiary dentin) to form. It is usually located near the central developmental groove or the triangular ridge of a cusp. These tubercles are most commonly found in Asian populations.

Highest Incidence of Dens evaginatus

Mandibular premolars

Occlusal view of a maxillary second premolar with dens evaginatus (courtesy of Dr. BM Cleghorn, Dalhousie University).

Radiograph of a mandibular right second premolar with dens evaginatus (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Mesial view of an extracted mandibular left second premolar with dens evaginatus (courtesy of Dr. BM Cleghorn, Dalhousie University).

Hutchinson's Incisors and Mulberry Molars

This condition results from congenital syphilis. The effect on the teeth as they are developing produces screwdriver-shaped, notched incisors and molars that have constricted occlusal surface with abnormal occlusal anatomy. The incisors are called "Hutchinson's incisors" and the molars are called "mulberry molars". This condition is not common.

Mulberry molars (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Hutchinson's incisors (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Globodontia

These teeth are rounded and lack cusp ridges and tips. The posterior teeth tend to be globe-shaped.This represent the fusion of growth centres. The teeth usually have multiple root canal systems. Yellow spots on labial aspect of the canines may be present and there may be congenitally missing premolars in the otodental syndrome. Hearing loss is also present. The clinical photos on the right and below left and right are of a patient with globodontia (courtesy of Dr. Igor Pesun, formerly from the University of Minnesota, now at the University of Manitoba).

Frontal view of patient

Occlusal view of maxillary arch

Frontal view of mandibular arch

Fluorosis

Anomalies in tooth structure occur after the tooth germ has formed. Knowledge of tooth development timing is important. Review the development tables of the teeth of the primary and secondary dentitions.

Fluorosis is caused by systemic intake of fluoride in excess of 1 ppm (parts per million) for some period of time. It is called "mottled enamel". It can result in a significant aesthetic problem if it occurs during the 2nd or 3rd year of age because secondary (permanent) anterior teeth are forming at this time. The severity of fluorosis is dose-dependent and time-dependent. Teeth are caries-resistant with enamel that is discoloured (white, yellow, brown) and can result from young children swallowing toothpaste.

Generalized fluorosis (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Generalized fluorosis (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Turner's tooth

This condition is also called Turner's hypoplasia and results in an abnormally shaped secondary (permanent) tooth. Trauma is a common cause for Turner's hypoplasia in secondary (permanent) maxillary incisors. Infection (periapical abscess) of the primary (deciduous) molars is a common etiological factor in secondary (permanent) premolars with Turner's hypoplasia. The appearance of Turner's hypoplasia can vary from discoloured areas to severe hypoplasia.

Panoramic radiograph on the left illustrates a Turner's tooth in the third quadrant (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Turner's tooth permanent mandibular left first premolar

(courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Amelogenesis Imperfecta

This is an ectodermal disorder and therefore affects the enamel only. The incidence ranges from .01% to .14% depending on the population At least 18 subtypes (Witkop, CJ, 1988) have been identified based on clinical features, light microscopic appearance and the inheritance pattern. This defect affects both the primary and secondary dentitions. Multiple modes of inheritance including autosomal dominant and autosomal recessive are possible.

Features of amelogenesis imperfecta include openbite due to attrition, eruption may be normal or late and the dentinoenamel junction is scalloped. Affected teeth are discoloured (exogenous pigment) and may be pitted, rough or smooth enamel. Enamel is thin or mottled radiographically. Problems include aesthetics, abrasion, sensitivity and caries susceptibility. Pathogenesis is a progressive, functional defect of ameloblasts. Management may include crowns (full coverage) and possibly full mouth osteoplasty (recontouring of bone) to increase the length of the clinical crowns for retention of full veneer crowns.

Pitted form of amelogenesis imperfecta

(courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Snow-capped form of amelogenesis imperfecta (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

A case study of a Type IE X-linked (dominant) smooth hypoplastic amelogenesis imperfecta (Witkop's classification) is presented to illustrate the inheritance pattern of one type of amelogenesis imperfecta. This subtype of AI (amelogenesis imperfecta) was diagnosed through the use of a pedigree and examination of all the members of the M family. The father Chris M had severe, generalized hypoplastic defects of the enamel. A pedigree illustrated that this defect was only transferred to the female children (Katrina M and Maria M). Son Marcus M had a normal dentition. The defects in the teeth of the female children were somewhat less severe than in the father but resulted in vertical banding of the enamel. A diagnosis of Type IE X-linked (dominant) smooth hypoplastic amelogenesis imperfecta was made based on a pedigree and clinical examination of all family members. The pattern of enamel defects in the family are illustrated below.

Chris M

Amelogenesis Imperfecta

Father Chris M as he initially presented. Maxillary teeth had been treated with metal ceramic crowns. Mandibular teeth are virtually devoid of enamel (courtesy of Dr. BM Cleghorn, Dalhousie University).

Occlusal view of Chris M illustrating normal tooth morphology and hypoplastic enamel

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Right BW radiograph

Chris M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Left BW radiograph

Chris M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Right PA radiograph

Chris M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Left PA radiograph

Chris M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Katrina M

Pre-treatment frontal view of daughter Katrina M aged 12 years 9 months

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Maxillary left quadrant close-up of vertical banding of enamel in patient Katrina M illustrating severely hypoplastic enamel

Right BW radiograph

Katrina M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Left BW radiograph

Katrina M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Post-treatment frontal view of Katrina M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Post-treatment view of maxillary arch of Katrina M with full coverage of all teeth

Vickie M

Pre-treatment frontal view of Vickie M aged 5 years 4 months

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Pre-treatment view of maxillary left quadrant of patient Vickie M

Pre-treatment occlusal view of maxillary arch of Vickie M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Pre-treatment occlusal view of mandibular arch of Vickie M

Marcus M

Marcus and brother Chris Jr. were unaffected by this sex-linked Type IE X-linked (dominant) smooth hypoplastic amelogenesis imperfecta.

Frontal view of Marcus M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Right BW

Marcus M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Left BW

Marcus M

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Chris Jr.

Frontal view of Chris Jr. aged 3 years 5 months

(courtesy of Dr. BM Cleghorn, Dalhousie University).

Dentinogenesis imperfecta

This is a mesodermal defect that affects the dentin. The condition is also called hereditary opalescent dentin and can be seen in isolation or associated with a systemic defect (osteogenesis imperfecta). Both the primary and secondary dentitions are affected. Dentinogenesis Imperfecta (DI) is a genetic disorder with an autosomal dominant mode of inheritance. The teeth are blue or brown and translucent. The incidence is approximately 1 in 8,000 in the USA. The classification system for this entity is less than perfect.

Common Features of Dentinogenesis Imperfecta

all teeth are discoloured (types 2 and 3 more prominent)

bell-shaped crowns

attrition

obliteration of root canals in Type 1 and 2 (more marked in the permanent dentition)

enamel is lost early in Types 1 & 2 due to a defect in the DEJ (no scalloping of the DEJ)

difficult to differentiate Types 1 and 2 clinically and radiographically

Type 1 is always associated with osteogenesis imperfecta while Type 2 is never associated unless by chance

Frontal view of dentinogenesis imperfecta (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

PA radiograph of dentinogenesis imperfecta illustrating bell-shaped crown on mandibular first molar (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Occlusal view of a patient with dentinogenesis imperfecta illustrating the severe attrition of all of the maxillary teeth (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

BW radiograph of dentinogenesis imperfecta illustrating obliterated pulps (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

PA radiograph of dentinogenesis imperfecta illustrating shell teeth (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Dentin Dysplasia

There are two forms of this condition and they are Type 1 and Type 2. The radicular form or Type 1 is the most common form. Short roots are a feature due to abnormal formation of root dentin. This is a genetic disorder with an autosomal dominant inheritance. Enamel and coronal dentin are essentially normal in Type 1. The incidence is 1 in 100,000 in North America. Teeth may exfoliate prematurely. Radiographic evidence of obliterated pulps assists in the diagnosis of this condition. Treatment includes extraction of those teeth with periapical pathosis.

PA radiograph of Type 1 dentin dysplasia illustrating short roots, and crescent-shaped pulp chambers (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

PA radiograph of Type 2 dentin dysplasia illustrating pulp stones, normal root length, and "thistle tube-shaped" enlargements of the pulp chambers (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Regional Odontodysplasia

This is a localized condition, usually with a non-hereditary cause. Sometimes regional odontodysplasia is associated with syndromes or growth abnormalities.It tends to occur in segments of the dentition.

Most Common Location for Regional odontodysplasia

Maxillary anterior teeth (occurs in segments of neighbouring teeth)

Enamel is hypoplastic and hypocalcified and the teeth appear "ghost-like" in their radiographic appearance due to their thin shell of enamel. The teeth often fail to erupt. Very large pulp chambers are evident in this condition. The aetiology is thought to be a vascular or viral problem

PA radiograph of the mandibular right quadrant illustrating the "ghost-like" appearance of the affected teeth (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

PA radiograph of the mandibular right quadrant illustrating the "ghost-like" appearance of the affected teeth (courtesy of Dr. John Perry, University of Manitoba).

Periapical cemental dysplasia (cementoma)

This presents initially as multiple periapical radiolucencies usually in the mandibular anterior region. It is important to diagnose this condition correctly as no treatment is required. The pulps of the involved teeth will be vital.

Most Common Location for Periapical Cemental Dysplasia

Secondary (permanent) Mandibular incisors

Follow up of this condition radiographically will confirm the diagnosis as the radiolucency(ies) will change to a mixed radiolucency/radiopacity then to apical radiopacities associated with the affected teeth over a period of years. Differentiation from a periapical abscess or granuloma is critical, as these conditions require root canal therapy while there is no treatment required for periapical cemental dysplasia.

Periapical cemental dysplasia initially presents as periapical radiolucencies in the mandibular incisor region

(courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Periapical cemental dysplasia at a later stage; the apical lesions become radiopaque over time; teeth remain vital (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Hypercementosis

Deposits of secondary cementum on the root surface characterize this condition. The aetiology can be due to local or systemic factors.

PA radiograph illustrating hypercementosis in the apical third of both the mesial and distal roots of the permanent mandibular right first molar (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Extracted permanent maxillary left second premolar with hypercementosis on the apical half of the root (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Impacted Teeth

These are teeth that are prevented from erupting by some physical barrier. The aetiology can be due to a lack of space (crowding) or a rotated tooth germ (so that the tooth is 'aimed' in the wrong direction).

Most Common Impacted Teeth

third molars

maxillary canines

premolars

supernumerary teeth

PA of impacted permanent mandibular right third molar (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

PA of impacted permanent mandibular right canine; the crown is undergoing resorption (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Panoramic radiograph of impacted third molars; the maxillary right third molar is both impacted and inverted; both of the mandibular third molars exhibit a 90 degree horizontal rotation (courtesy of Dr. BM Cleghorn, Dalhousie University).

Panoramic radiograph of a patient with multiple impacted and supernumerary teeth (courtesy of Dr. BM Cleghorn, Dalhousie University).

Ankylosis

This is a condition where teeth are fused to bone teeth are below the plane of occlusion.They are sometimes referred to as "submerged" teeth. However, this terminology is not really correct. The ankylosed tooth has failed to erupt while the surrounding teeth have continued to erupt. Radiographically, the periodontal ligament (PDL) will not be visible in the ankylosed area.

Most Common Ankylosed Teeth

primary (deciduous) mandibular second molars

These teeth are infra-erupted (not submerged). The aetiology can be due to trauma, genetics, infection or a disturbance in local metabolism. Treatment is usually a surgical extraction of the ankylosed tooth. Otherwise eruption of the secondary (permanent) tooth may be prevented.

PA of ankylosed and infra-erupted primary mandibular right second molar (courtesy of Drs. Steve Ahing and John Perry, University of Manitoba).

Tetracycline Staining

This is a type of anomaly caused by the ingestion of tetracycline as teeth are developing. The group of tetracycline antibiotics has an affinity for calcifying tissues such as bone and teeth. Horizontal bands of yellow or brown staining occur as teeth form. Examination of the location of the banding on the affected teeth can determine the approximate age and duration that the tetracycline was given.

Horizontal banding on this mandibular third molar indicates that the drug was ingested in the early or middle teens as the root was forming at this time. Acne is a common condition at this age and is often treated by one of the tetracycline group of antibiotics. This is the most likely aetiology of the staining on the root of this third molar. Devastating aesthetic defects can occur to tooth crowns if tetracyclines are ingested as they are developing. Therefore no tetracyclines should be administered to children under 8 years old. By this age the crown of all of the permanent teeth will have developed. Only the third molars are developing at this time.

Extracted mandibular third molar with tetracycline staining on the cervical half of the root (courtesy of Dr. BM Cleghorn, Dalhousie University).

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