Developmental defects of teeth

           Developmental defects of teeth:-

DEVELOPMENTAL DISORDERS OF TEETH :

·        Size of teeth: Microdontia & Macrodontia.

·        Shape of teeth: Gemination, Fusion, Concrescence, Dilaceration, Talon cusp, Dense in dent, Dens evaginatus & taurodontism.

·        Number of teeth: Anodontia, Supernumerary teeth, Predecidious dentition & Post permanent dentition.

·        Structure of teeth: Amelogenesis Imperfecta, Environmental enamel hypoplasia, Dentinogenesis Imperfecta & Dentin Dysplasia.

Developmental alteration of teeth:-

            The factors that affect the size of the developing teeth include

1. heredity
2. genetic
3. environmental

Deciduous dentition appears to be more affected by maternal intrauterine influences; the permanent teeth seem to be more affected by environment.

1} Microdontia:-

            This term is used to describe teeth which are smaller than normal i.e. outside the usual limits of variation. It should be applied only when the teeth are physically smaller than usual.

            Microdontia is associated strongly with hypodontia and females demonstrate a higher frequency of microdontia.

Types:-

      True generalized microdontia: -

 In this all the teeth are smaller than normal. The teeth are reportedly well formed, merely small. It is uncommon, but may occur as an isolated finding in Down syndrome, in pituitary dwarfism etc.

      Relative generalized microdontia: -

In this the teeth are normal in size or slightly smaller and are present in jaws that are larger than normal giving an illusion of true microdontia. Since it is recognized that a person may inherit the jaw size and tooth size from each parent, the hereditary factor may have an obvious role in such a condition.

      Isolated microdontia/microdontia involving only a single tooth:-

Rather a common condition. Affects most often the maxillary lateral incisor and third molar, which are also the most often congenitally missing teeth. Microdontia of lateral incisor is called “Peg laterals”. In such teeth, the root is of normal length. The mesiodistal diameter is reduced and the proximal surfaces converge toward the incisal edge. It is an autosomal dominant with incomplete penetrance. Prevalence varies from 0.8 to 8.4% of population. When a peg shaped tooth is present, the remaining permanent teeth often exhibit a slightly smaller mesiodistal length. Supernumarary teeth when present also exhibit microdontia.

Treatment – treatment of the dentition is not necessary unless desired for aesthetic considerations. Maxillary peg laterals often are restored to full size by porcelain crowns.

                                       Peg laterals

A peg lateral is defined as ‘‘an undersized, tapered, maxillary lateral incisor’’6 that may be associated with other dental anomalies, such as canine transposition and overretained deciduous teeth. Individuals with malformed lateral incisors often display a diastema in the midline region caused by the distal movement of the central incisor.7 Due to their reduced size, the malformed lateral incisors may also allow the formation of other diastemata in the anterior region. These patients may exhibit otherwise normal dentitions unless other congenital etiologic factors or habits are present.

In the restoration of peg lateral incisors, there are many factors to be considered that depend on the patient’s expectations and the expertise of the clinician. The type of treatment should be selected based on functional and esthetic requirements, need for extractions, the position of the canines, and the potential for coordinating restorative and orthodontic treatment.

Treatment options vary but include the following:

(1) Extraction of the peg-shaped tooth and orthodontic movement of the canine into the space of the lateral incisor; the canines can then be recontoured to resemble lateral incisors;

(2) Extraction and replacement with a single-tooth implant-supported restoration or a fixed partial denture (FPD); or

(3) Direct or indirect restoration of the peg lateral incisors to develop normal tooth morphology. All of these treatment approaches may produce acceptable results.

Treatment options include procedures such as porcelain laminate veneers, metal-ceramic restorations, and all-ceramic crowns, as well as minimally invasive procedures such as direct resin composite bonding. Porcelain laminate veneers have high abrasion resistance and color stability. Also, the properties of porcelain laminate veneer such as color, form, surface, individual characterization through internal and external staining, and the fact that these restorations can be further colorcorrected during cementation with special cement colors, make them an attractive treatment option. However, porcelain laminate veneers are relatively expensive.

A conservative veneer technique is the application of the resin composite without tooth reduction. Resin composite veneers can be altered and repolished in situ, and this feature is very useful when subtle changes to the emergence angles are desirable. Also, resin composite veneers are not as expensive as porcelain laminate veneers.

The treatment includes 2 primary objectives: to restore or replace the hypoplastic dental crowns and to close the diastema. If the patient does not smoke or drink dark-colored liquids that can alter the color of the teeth, esthetic bonding with resin composite may be the most conservative approach for several reasons: sound tooth structure will not be removed, the procedure may not require administration of local anesthetic, the procedure may be accomplished in 1 appointment, and the treatment is relatively inexpensive

2} Macrodontia:- (Megalodontia, Megadontia)

            It refers to teeth that are larger than normal. It should be applied only when the teeth are physically larger than usual. It should be used to describe teeth that have been altered by fusion or germination.

            Macrodontia is often seen with hyperdontia and males have a greater prevalence of macrodontia.

Types:-

1. True generalized Macrodontia: -

       Condition in which all teeth is larger than normal. Usually associated with pituitary gigantism and pineal  hyperplasia with hyperinsulinism.

2. Relative generalized Macrodontia: -

A rather more common condition. Seen when normal or slightly larger than normal teeth are present in small jaws resulting in crowding which gives the illusion of macrodontia. As in microdontia, the importance of heredity must be considered.

3. Macrodontia of a single tooth:-

Relatively uncommon and is of unknown etiology. True macrodontia of a single tooth should not be confused with fusion of teeth in which, early in odontogenesis, the union of two or more teeth results in a single large tooth.

Development alterations in number of teeth:-

            Variations in the number of teeth that develop are common. Anodontia refers to a total lack of tooth development. Hypodontia denotes the lack of development of one or more teeth; Oligodontia (a subdivision of hypodontia) indicates the lack of development of six or more teeth. Hyperdontia is the development of an increased number of teeth and the additional teeth are termed Supernumerary.

           

1.      Anodontia:-

  Failure of teeth to develop (same as agenesis of teeth)

  True total absence of teeth which may involve both deciduous and permanent teeth is a very rare condition, when it occurs it is frequently associated with more generalized disturbance, hereditary ectodermal dysplasia.

            Induced or false anodontia occurs as a result of extraction of all teeth, while the term pseudoanodontia is sometimes applied to multiple unerupted teeth.

            Pseudo anodontia is the clinical presentation of having no teeth when teeth have either been removed or obscured from view by hyperplastic gingiva.

 

2.      Hypodontia:- (Oligodontia)

            A rather common condition involves absence of one or more teeth. 

Hypodontia: having less than 6 congenitally missing teeth. (Partial anodontia)

Oligodontia: having 6 or more congenitally missing teeth.

Pathogenesis:-

Hypodontia correlates with the absence of appropriate dental lamina. Genetic control appears to exert a strong influence on the development of teeth. Numerous hereditary syndromes are associated with both hypodontia and hyperdontia. Many cases of primary hypodontia and hyperdontia appear to be autosomal dominant with incomplete penetrance and variable expressivity. The environment is not without its influence, with occasional examples supporting multifactorial inheritance.

            Some investigators have implied that hypodontia is a normal variant, suggesting that humans are in an intermediate stage of dentitional evolution. A proposed future dentition would contain one incisor, one canine, one premolar and two molars per quadrant.

            Both genetic and environmental factors may be responsible for the absence of the developing tooth bud. The dental lamina is extremely sensitive to external stimuli, and damage before tooth formation can result in hypodontia. Trauma, infection, radiation, and severe intrauterine disturbances have been associated with missing teeth.

Ectodermal dysplasia

Clinical features:-

1.      Dentition affected: - It affects both deciduous and permanent teeth, though it is uncommon in deciduous teeth (less than 1% of the population).

2.      Teeth involved:-  when present in deciduous dentition, it most frequently involves the mandibular incisors. Congenitally missing teeth in permanent dentition are not rare with the third molar being the most commonly missing (20 to 23% of the population). After the molars the maxillary lateral incisors and second premolars are absent most frequently. Grabber in his report showed that the overall frequency of patients with congenitally missing teeth (excluding third molars) has ranged from 1.6-9.6% in various series of studies in different countries.

3.      Gender:- A female predominance of approximately 1.5:1 is reported.

4.      Other features:-

Hypodontia is associated positively with microdontia, reduced alveolar development, increased freeway space and retained primary teeth. In severe cases of hypodontia, the bilateral absence of corresponding teeth may be striking.

Treatment:-

            Sequelae associated with hypodontia include abnormal spacing of teeth, delayed tooth formation, delayed deciduous tooth exfoliation, and late permanent tooth eruption. Single missing tooth may be replaced by removable or fixed prosthetics. When multiple teeth are missing, prosthetic replacement with fixed prosthodontics, resin-bonded bridges or osseointegrated implants with associated crowns. For children and young adults, a resin-bonded bridge often is appropriate while waiting for full dental maturation.

3.      Hyperdontia:-

Hyperdontia is the development of an increased number of teeth, and the additional teeth are called “Supernumerary teeth”.

Pathogenesis:-

      As with hypodontia, the influence of genetic and environmental factors should be considered in its pathogenesis. The pathogenesis of hyperdontia has been postulated to be caused by the development of excess dental lamina, which presumably leads to the formation of additional tooth germs. Many theories have been postulated for the formation of supernumerary teeth –

      It develops from the third tooth bud arising from the dental lamina near the permanent tooth bud.

      It may also possibly develop from splitting of the permanent tooth bud itself

      Conversely others have suggested that hyperdontia represents Atavism, the reappearance of an ancestral condition. But this hypothesis is not accepted.

      Hyperactivity theory – well supported in the literature, which suggests that supernumeraries are formed as a result of local, independent, conditioned hyperactivity of the dental lamina.

      Another theory proposes the hereditary tendency for the development of supernumerary teeth.

Prevalence:-

            The prevalence of supernumerary teeth in caucasianns is between 1% and 3%, with a slightly higher rate seen in Asian populations. Approximately 76% to 86% of cases represent single tooth hyperdontia, with two supernumerary teeth noted in 12-23% and three or more supernumerary teeth noted in less than 1% of cases.

Classification:-

1.      According to morphology:-

It can be classified as Conical, Tuberculate, Supplemental, Odontome.

      Conical – resembles a small peg-shaped conical tooth. It develops with the root formation ahead of or at an equivalent stage to that of permanent incisors and usually presents as mesiodens. This conical supernumerary can result in rotation or displacement of the permanent incisors but rarely delays eruption.

      Tuberculate – this type possess more than one cusp or tubercle. It is frequently described as barrel-shaped and may be invaginated. They are often paired and are commonly located on the palatal aspect of central incisors. They rarely erupt and are frequently associated with delayed eruption of the incisors.

      Supplemental – it refers to a duplication of teeth in the normal series and is found at the end of the tooth series. The most common supplemental tooth is the permanent maxillary lateral incisors, but supplemental premolars and molars also occur. Supernumerary teeth in deciduous dentition are most often are of supplemental type.

      Odontome – Howard included this category in supplementary teeth, however this is not universally accepted. The term Odontoma refers to any tumor of odontogenic origin.

2.      According to location:-

      Mesiodens – a supernumerary tooth in the maxillary anterior incisal region

      Distomolar or distodens – an accessory fourth molar

      Paramolar – a posterior supernumerary tooth situated lingually or bucally to a molar tooth

 Clinical features:-

            A supernumerary tooth may closely resemble the teeth of the group to which it belongs, i.e. molars, premolars, or anterior teeth, or it may bear little resemblance in size or shape to the teeth with which it is associated. Occurrence may be single or multiple, unilateral or bilateral, erupted or impacted and in one or both jaws.

1. Dentition affected: - most frequently it is the permanent dentition more affected than primary dentition.
2. Jaws:- 90% of supernumerary teeth occurs in the maxilla, with the strong predilection  for the anterior region. Non-syndromic multiple supernumerary teeth occur most frequently in the mandible.
3. Site:- most commonly in maxillary anterior region followed by maxillary and mandibular fourth molars, premolars, canines and lateral incisors. In Non-syndromic cases, it occurs most commonly in the premolar region, followed by molar and anterior regions respectively.
4. gender:- most commonly seen in males in ratio of 2:1
5. Age of occurrence: - most supernumerary teeth develop during the first two decades of life.
6. Associated syndromes:- The conditions commonly associated with an increased prevalence of supernumerary teeth include cleft lip and palate, cleidocranial dysplasia, and Garden syndrome. Supernumerary teeth associated with cleft lip and cleft palate result from fragmentation of the dental lamina during cleft formation. Gardner’s syndrome is characterized by the occurrence of multiple impacted supernumerary teeth. This syndrome consists of

1.      multiple polyposis of the large intestine

2.      osteomas of the bones

3.      multiple epidermoid or sebaceous cysts of the skin

4.      occasional occurrence of desmoid tumors

5.      impacted supernumerary  and permanent teeth.

Although most supernumerary teeth occurs in the jaws, examples have been reported in the gingiva, maxillary tuberosity, soft palate, maxillary sinus, spenomaxillary fissure, ansal cavity and between the orbit and the brain. 75% of the supernumerary tooth anterior maxilla fails to erupt.

Transposition – normal teeth may erupt into an inappropriate position (e.g. a canine present between two premolars). This pattern of abnormal eruption is called transposition and should not be confused as supernumerary tooth.

Treatment:-

            The presence of supernumerary teeth should be suspected if there is a significant delay in the eruption of a localized portion of the dentition. Early dianosis and treatment often are crucial in minimizing the aesthetic and functional problems of the adjacent teeth. Complication created by anterior supernumerary teeth tends to be more significant than those associated with extra teeth in the posterior regions. The standard care is early removal of the accessory tooth. This results in spontaneous eruption of the adjacent dentition in 75% of the cases within 11/2 to 3 years for full eruption.

            A consequence to late therapy may include the delayed eruption or resorption of the adjacent teeth or the displacement of the teeth with associated crowding, malocclusion, or diastema formation. Supernumerary teeth also predispose the area to subacute periodontitis, gingivitis, periodontitis, abscess formation and the development of odontogenic cysts and tumors.

3.      Predeciduous dentition:- ( premature eruption, natal teeth, neonatal teeth )

            Accessory teeth may be present at or shortly after birth. Historically, teeth present in newborns have been called Natal teeth ( Massler); those arising within the first 30 days of life are designated neonatal teeth. Although some authors have suggested that these teeth may represent predeciduous supernumerary teeth, most are prematurely erupted deciduous teeth (not supernumerary teeth). Approximately 85% of natal teeth are mandibular incisors, 11% are maxillary incisors and 4% are posterior teeth.

            Some authors suggested these predeciduous teeth as hornified epithelial structures without roots, occurring over the crest of the alveolar ridge, which may be easily removed. They undoubtedly represent dental lamina cyst of the newborn, is white in color and is packed with keratin so that it appears hornified.

Treatment – the erupted teeth in most cases represent the deciduous dentition and removal should not be performed. If the teeth are mobile and are at risk for aspiration, removal is indicated. Traumatic ulceations of the adjacent soft tissues (Riga –Fede disease) may occur during breast feeding but often can be resolved with appropriate measures.   

4.  Post permanent dentition:-

            In some persons after extraction of all the permanent teeth, have been reported of eruption of subsequent teeth after the insertion of the full denture. The majority of such cases are the result of delayed eruption of retained or embedded teeth or presence of multiple unerupted supernumerary teeth.

Developmental disturbance in shape of teeth:-

1.      Gemination:-

      Definition:-

Historically, geminated teeth are defined as anomalies which arise from an attempt at division of a single tooth germ by an invagination, with resultant incomplete formation of two teeth.

   It is defined as a single enlarged tooth or joined (i.e. double) tooth in which the tooth counts is normal when the anomalous tooth is counted as one.

        The term Twinning has sometimes been used to designate the production of equivalent structures by division resulting in one normal and one supernumerary tooth. Some authors suggested that this term led to confusion. They told that extra teeth are termed supernumerary teeth and another name is not necessary.

      Clinical features:-

Gemination occurs in both primary and permanent dentition, with a higher frequency in the anterior maxillary regions. The overall prevalence appears to be approximately 0.5% in the deciduous teeth and 0.1% in the permanent dentition. It is usually unilateral but occasionally bilateral (0.02% in both dentitions).

The structure is usually one with two completely or incompletely separated crowns that have a single root and root canal.

      Treatment:-

The presence of double teeth in decidupus dentition can result in

crowding, abnormal spacing, and delayed or ectopic eruption of the underlying permanent teeth. Several approaches are available for the treatment of the joined teeth in the permanent dentition. These include –

1.      Surgical division with accompanying endodontic therapy in most of the cases

2.      Selected reshaping with or without placement of full crowns

3.      In some cases pulpal or coronal anatomic features that are resistant to reshaping require surgical removal with prosthetic replacement.

2.      Fusion:-

      Definition:-

Fusion has been defined as the union of two normally separated tooth buds with the resultant formation of a joined tooth with confluence of dentin.

Fusion is defined as a single enlarged tooth or joined (i.e. double) tooth in which       the tooth counts reveals a missing tooth when the anomalous tooth is counted as one.

      Pathogenesis:-

It has been thought that some physical force or pressure produces contact of the developing teeth and their subsequent fusion. If this contact occurs early, atleast before calcification begins, the two teeth may be completely united to form a single large tooth. If the contact of teeth occurs later, when a portion of the tooth crown has completed its formation, there may be union of the roots only. The dentin, however, is always confluent in cases of true fusion.

      Clinical features:-

       Occurs in both primary and permanent dentition, with a higher frequency in the anterior maxillary regions. The overall prevalence appears to be approximately 0.5% in the deciduous teeth and 0.1% in the permanent dentition. It is usually unilateral but occasionally bilateral (0.02% in both dentitions). Depending on the stage of development of the teeth at the time of the union, fusion may be complete or incomplete. The tooth may have separate or fused root canals. There may be possible clinical problems related to appearance, spacing, and periodontal conditions.

      Treatment:- same as that for gemination.

3.      Concrescence:-

      Definition:-

It is the union of two adjacent teeth by cementum alone without confluence of the underlying dentin.

Concrescence of teeth is actually a form of fusion which occurs after root formation has been completed. In this condition, teeth are united by cementum only.

      Pathogenesis:-

Several hypothesis have been postulated –

1.      Developmental – when two teeth develop in close proximity, developmental union by cementum is possible.

2.      Post-inflammatory – in case of inflammatory damage of the interdental bone and to the roots of teeth, the repair is by deposition of cementum once the inciting process resolves.

3.      Traumatic injury – with traumatic injury or resulting crowding may result in resorption of the interdental bone so that the two roots are in approximate contact and become fused by the deposition of cementum between them.

      Clinical features:-

                        Concrescence can occur before or after the teeth have erupted, and although it usually involves two teeth it may involve more than two teeth. This process is noted most frequently in the posterior maxillary region. The developmental pattern often involves a 2^nd molar tooth in which its roots closely approximate the adjacent impacted third molar. The post inflammatory pattern frequently involves carious tooth that exhibits large coronal tooth loss.

      Treatment:-

Often requires no therapy unless the union interferes with the eruption, then surgical removal may be needed. Postinflammatory concrescence should be kept in mind whenever extraction is planned for nonvital teeth with apices that overlie the roots of an adjacent tooth. Significant extraction difficulties have been encountered while extracting the concrescence tooth, surgical separation is often required to complete the procedure without loss of significant portion of the surrounding bone.

4. Accessory cusps:-

The cuspal morphology of teeth exhibits minor variations among different populations. Some of these include –

1)      Cusp of carabelli – it is an accessory cusp located on the palatal surface of the mesiolingual cusp of a maxillary molar. The cusp may be seen in the permanent or deciduous dentitions and varies from a definite cusp to a small indented pit or fissure. When present, the cusp is most pronounced on the first molar and is increasingly less obvious on the second and third molars. When cusp of carabelli is present, the remaining permanent teeth often are larger than normal mesiodistally. A significant variation exists among different populations, with the prevalence reported to be as high as 90% in whites and rare in Asians.  An accessory cusp seen occasionally on the mesiobuccal cusp of mandibular molar is termed a Protostylid.

2)      Talon cusp – (dens evaginatus of anterior tooth)

Definition - It is a well-delineated additional cusp that is located on the surface of an anterior tooth and extends at least half the distance from the cementoenamel junction to the incisal edge.

Pathogenesis – it is commonly associated with the syndromes. In isolated cases, genetic influences appear to have a effect because identical talon cusps occasionally have been documented in twins.

      Clinical features:-

      Dentition affected – the occurrence is more in permanent dentition than deciduous.

      Teeth commonly involved – more commonly seen with permanent maxillary lateral incisors (55%) or central incisors (33%) but have been seen less frequently on mandibular incisors (6%) and maxillary canines (4%). In deciduous dentition maxillary central incisors is commonly involved. 

      Site – in all cases the talon cusp projects from lingual surface of the affected tooth and forms a three-pronged pattern that resembles an eagle’s talon. On rare occasion the cusp may project from the facial surface or from the both surface of a single tooth.

      Prevalence – the frequency of talon cusp in population ranges from less than 1% to 8%

      Gender – both have equal predilection

      Radiographic features – radiographically the cusp is seen overlying the central portion of the crown and includes enamel and dentin. Only few cases demonstrate visible pulpal extensions on dental radiographs.

       A deep developmental groove may be present where the cusp fuses with underlying surface of the affected tooth. Most, but not all, the talon cusp contain a pulpal extension.

      Syndromes associated with talon cusp – Sturge – Weber syndrome and Rubinstein – Taybi syndrome. The features in Rubinstein – Taybi syndrome include developmental retardation, broad thumbs and great toes, characteristics facial features, delayed or incomplete descent of testes in males, stature, head circumference and bone age below the fiftieth percentile.

      The talon cusps possess problems with regard to esthetics, caries control and occlusal accommodation.

    Treatment:-

            Cusp of carrabelli does not need any treatment unless there is a deep groove which can be prophylactically sealed to prevent the occurrence of caries.

            Talon cusp on the mandibualr teeth requires no treatment. In maxillary teeth the talon cusp interferes with the occlusion and should be removed. Other complications include compromised aesthetics, displacement of teeth, caries, periodontal problems, and irritation of the adjacent soft tissue. Because many of these cusps contain pulp, rapid removal results in loss of vitality, therefore periodic grinding can be accomplished, with time allowed for tertiary dentin deposition and pulpal recession. At the end of grinding, the exposed dentin is coated with a desensitizing agent. After successful removal, the exposed dentin is covered by calcium hydroxide, the peripheral enamel is etched and a composite resin is placed.

4.      Dens evaginatus:- (occlusal tuberculated premolar, Leong’s premolar, evaginated odontome, occlusal enamel pearl, central tubercle)

         Definition – is a cusp like elevation of enamel located in the central grove or lingual ridge of the buccal cusp of permanent premolar or molar teeth.

Pathogenesis – it is due to proliferation and evagination of an area of the inner enamel epithelium and subjacent odontogenic mesenchyme into the dental organ during early tooth development.

Clinical features –

 The dens evaginatus frequently occurs on premolar teeth but it is also been reported to occur on molars, cuspids, and incisors. It is usually bilateral and demonstrates a marked mandibular predominance.

It has been thought to develop only in persons of mongoloid ancestry: Chinese, Japanese, Filipinos, Eskimos, and American Indians.

Radiographically, the occlusal surface exhibits a tuberculated appearance and often a pulpal extension is seen in the cusps.

Shovel – shaped incisors: dens evaginatus which is seen in association with maxillary incisors. Affected incisors demonstrate prominent lateral margins creating a hollowed lingual surface that resembles the scoop of a shovel. Typically the thickened margins converge at the cingulum, not uncommonly there is deep pit, fissure,at this junction. Maxillary lateral and central incisors most frequently affected, with mandibular incisors and canines less commonly reported.

The dens evaginatus may contribute to incomplete eruption, displacement of teeth and/or pulp exposure with subsequent infection following occlusal wear or fracture.

Treatment:-

            Dens evaginatus often results in occlusal problems and is more prone to fracture, frequently resulting in pulpal exposure. Pulpal necrosis results in cessation of root development. In such case, apexification should be carried out. The removal of cusp is often indicated but the preservation of vitality is met with partial success. The elimination of opposing occlusal interferences, combined with gradual grinding of the tubercle and direct capping with calcium hydroxide has been suggested as the best approach. Other investigators have protected the cusp from fracture by the placement of composite reinforcement around the projection until root formation is complete.

5. Dens invaginatus:- (Dens in Dente, dilated composite odontome)

Definition – the ‘dens in dente’ is a developmental variation which is thought to arise as a result of an invagination in the surface of tooth crown before calcification has occurred.

The term ‘dens in dente’ originally applied to a severe invagination that gave the appearance of a tooth within a tooth, is actually a misnomer.

In other cases the invagination may be dilated and disturb the formation of the tooth, resulting in anomalous tooth development termed ‘Dilated odontome’.

Etiology – Several causes of this condition have been proposed. These include an increased localized external pressure, focal growth retardation, and focal growth stimulation in certain areas of tooth bud.

The radicular variety of dens in dente results from an infolding of hertwig’s sheath and takes its origin within the root after development is complete.

Types – Coronal and Radicular

Clinical features –

      Dentition affected – permanent more than deciduous dentition

      Jaw – maxillary predominance is seen  

      Teeth affected – in order of decreasing frequency, the teeth affected most often include the permanent lateral incisors, central incisors, premolars, canines, and molars.

      Prevalence – coronal dens invaginatus is seen more frequently; the reported prevalence varies from 0.04% to 10% of all patients.

      The depth of invagination varies from a slight enlargement of cingulum pit to a deep infolding that extends to the apex. Before eruption the lumen is filled with soft tissue similar to the dental follicle. On eruption this soft tissue loses its vascular supply and becomes necrotic.

      Coronal dens invaginatus – is a deep invagination of the crown. Historically it has been classified into three types

1.      Type 1 exhibits an invagination that is confined to the crown

2.      Type 2 an invagination that extends below the CEJ and ends in a blind sac that may or may not communicate with the adjacent pulp.

3.      Type 3 extends through the root and perforates in the apical or lateral radicular area without any immediate communication with the pulp. In this type near the apical area the enamel is replaced by cementum and there is direct communication between the oral cavity and the periapical tissue and often produces inflammatory lesions in presence of vital pulp.

      Radicular dens invaginatus – a rare condition where there is surface invagination in the roots of the teeth that has been lined by enamel. Cementum lined invagination have also been reported.

      Radiographically – the affected tooth demonstrates an enlargement of the root. On close examination one can see pear shaped invagination of enamel and dentin with a narrow constriction at the opening on the surface of the tooth and closely approximating the pulp as in its depth.

Treatment -

            On eruption the invagination communicates with the oral environment resulting in necrosis. In small type I invagination, the opening of the invagination is restored upon eruption in an attempt to prevent carious involvement and subsequent pulpal inflammation. With larger invagination, the contents of the lumen and any carious dentin must be removed; then calcium hydroxide base may be placed to help treat any possible microcommunications with the adjacent pulp. In case of obvious communication or pulpal pathosis, both the invagination and the pulp canal require endodontic therapy. In teeth with open apices, apexification is carried out. Dens invaginatus with periapical inflammatory lesion require endodntic therapy and in some cases periapical surgery, if the lesion does not subside.

            If the invagination does not significantly disrupt the tooth’s morphology, complications are rare in radicular invaginatus unless there is communication with the oral cavity. If the communication occurs and the opening is close to neck of the tooth, then it can be exposed and restored to minimize the damage to the tooth and surrounding structures.

6. Taurodontism:-

Definition - it is an enlargement of the body and pulp chamber of a multirooted tooth with apical displacement of the pulpal floor and bifurcation of the roots.

The term taurodontism was given by Sir Arthur Keith in 1913. The term bull-like teeth and its usage is derived from the similarity of these teeth to those of ungulate or cud-chewing animals.

Etiology – a variety of causes have been enumerated by Mangion as follows

1. A specialized or retrograde character \
2. A primitive pattern
3. A mendelian recessive trait
4. An atavistic feature
5. Mutation resulting from odontoblastic deficiency during dentinogenesis of roots.

Hammer and his associates believe that taurodontism is caused by failure of hertwig’s epithelial sheath to invaginate at the proper horizontal level.

This condition is of anthropological interest in as much as it has been found in fossil hominids, especially in the Neanderthal man, with a very high prevalence during the Neolithic period.

Clinical features –

      Dentition affected – may affect either primary or permanent dentition, although permanent tooth involvement is more common.

      Teeth affected – the teeth involved are almost invariably molars, sometimes only a single tooth, at other times several molars in the same quadrant

      Jaw affected – exclusively seen in mandibular jaw.

      Prevalence – the reported prevalence is highly variable (0.5 to 46%) and most likely is related to different diagnostic criteria and racial variation.

      The condition may be unilateral or bilateral.

      Types – the classification is given by Shaw according to the degree of  apical displacement of the pulpal floor into

a.       Hypotaurodontism – mild

b.      Mesotaurodontism – moderate

c.       Hypertaurodontism – severe in which bifurcation or trifurcation occurs near the apices of the root.

      Syndrome associated – taurodontism may occur as an isolated trait or as a component of a specific syndrome. An increased frequency of taurodontism has been reported in patients with cleft lip or palate and also in Klinefelter syndrome. Other syndrome associated include Amelogenesis imperfects, type IE, and type IV, Cranioectodermal dysplasia, ectodermal dysplasia, Microdontia-taurodontism-dens invaginatus, oral-facial-digital type II, Down syndrome etc.

      The teeth themselves have no remarkable or unusual morphological clinical characteristics.

      Radiographically – the diagnosis is made only by radiographically. Affected tooth tend to be rectangular in shape rather than taper towards the roots. The pulp chamber is extremely large with a much greater apico-occlusal height than normal. In addition, the pulp lacks the usual constriction at the cervical of the tooth and the roots are exceedingly short. The bifurcation or trifurcation may be only few millimeters above the apices of the root.

Treatment –

            No specific therapy required. Coronal extension of the pulp is not seen so no complication occur while restoration. Some investigators have suggested the taurodontic shape may exhibit decreased strength and stability as an abutment tooth for prosthetic procedures. If endodontic therapy is required, the shape of the pulp chamber frequently increases the difficulty of locating, instrumenting and obturating the pulp canals. For the furcation involvement considerable periodontal destruction has to occur.

7.  Dilacerations:-

           

Definition – Dilacerations is in the root or, less frequently, the crown of a tooth.

 Etiology –

1. The condition is thought to be due to trauma during the period in which the tooth is forming, with the result that the position of the calcified portion of the tooth is formed at an angle. The damage frequently follows avulsion or intrusion of the overlying primary predecessor, an event that normally occurs before 4 yrs of age.
2. The bend may also develop secondary to the presence of an adjacent cyst, tumor or odontogenic hamartoma (e.g. odontoma, supernumerary tooth).
3. Some cases are idiopathic developmental disturbances and there is no local injury related.

Clinical features –

      Dentition affected – permanent more than deciduous

      Teeth affected – permanent maxillary anteriors followed by mandibular anterior dentition.

      The age of the patient and the direction and degree of force appear to determine the extend of the tooth’s malformation. The abnormal angulations may be present anywhere along the length of the root.

      Altered maxillary anterior tooth demonstrate the bend in the crown or coronal half of the root; failure of eruption is often seen. The same is seen in mandibular anteriors but usually they erupt into full occlusion.

      Those teeth that demonstrate dilacerations and erupt into full occlusion often follow an altered path and present in a labial or lingual position.

      When dilacerations are seen in posterior teeth the bend is usually present in  the apical third and frequently do not exhibit delayed eruption.

Treatment –

            Dilacerations in deciduous teeth often demonstrate inappropriate resorption and result in delayed eruption of permanent teeth. Extraction is indicated when normal eruption or]f permanent teeth is indicated. Patients with dilacerations of permanent teeth require no therapy. In case of failure of eruption, such tooth can be exposed and orthodontically moved into position. Orthodontic treatment is difficult as the affected tooth on reposition may result in perforation of the buccal alveolar ridge by the malpositioned root. The extraction of the dilacerated tooth is difficult with frequent fracture of the root while extraction. Great care has to be taken while performing endodontic therapy, to avoid root perforation.

Root Dilaceration concentrates stress if the affected tooth is used as abutment. This increased stress may affect the stability and longevity of the abutment tooth. Splinting the affected tooth results in multirooted abutment and overcomes the stress related problems.

8. Supernumerary roots:-

Definition – the term supernumerary root refers to the development of an increased number of roots on a tooth compared with that classically described in dental anatomy.

For e.g. teeth that are normally single rooted, particularly the mandibular bicuspids and cuspids, often have two roots. Both maxillary and mandibular molars, particularly 3^rd molar, also may exhibit one or more supernumerary roots.

The most frequently affected teeth are the permanent molars from either arch and mandibular cuspids and premolars.

Radiographically – sometimes the roots are divergent and are seen easily on the radiographically. In other instances the additional root is small, superimposed over other roots and difficult to ascertain.

Treatment –

            Requires no specific treatment. Extracted teeth should be examined closely to ensure that all roots have been removed. During endodontic treatment the extra canal should be searched and treated accordingly otherwise may lead to endodontic failure.

The radix endomolaris and radix paramolaris:-

These are the supernumerary roots present in the Mandibular molars. The supernumerary root located distolingually in Mandibular molars is called Radix endomolarix. The supernumerary root located on the mesiobuccal side is called the radix paramolaris. The additional roots were first mentioned in the literature by Carabelli. Bolk reported the occurrence of a buccally located additional root.

Etiology –

            The etiology behind the formation of the additional root is still unclear. Several reasons have been proposed

1. it could be related to external factors during odontogenesis
2. Penetrance of an atavistic gene or polygenetic system.
3. racial genetic factors

Prevalence – the presence of a first separate RE in the first molar is associated with certain ethnic groups. In African population a maximum of frequency 3% is found, while in mongoloid traits a prevalence ranging from 5% to more than 30% has been reported. In Caucasians, the RE is considered to be a normal morphological variant and frequency is about 3.4 to 4.2%. RP – 0% in mand.first molar, 0.5% in II molar, 2% in man III molars.

Teeth affected – manibular first molars are affected most commonly and less frequently on the second molar.

Morphology of Radix entomolaris and paramolaris –

 The RE is located distolingually. With its coronal third completely or partially fixed to the distal root. The dimension of the RE can vary from a short conical extension to a mature root with normal length and root canal. In general, the RE is smaller than the distobuccal and mesial roots and can be separate or partially fused with the other roots.

Classification – by Carlsen and Alexandersen – describes four types of RE according to the location of the cervical part of the RE into type A, B, C and AC.  Types A and B refer to a distally located cervical part of the RE with two normal mesial na done normal distal root components. Type C refers to a mesially located cervical part, while type AC refers to a central location, between the distal and mesial root components.

9. Ectopic enamel:-

Definition – ectopic enamel refers to the presence of enamel in unusual locations mainly in the tooth root

Types –

1.      Enamel pearls – these are hemispheric structures that may consists entirely of enamel or contain underlying dentin and pulp tissue.

Pathogenesis – they are thought to arise from localized bulging of the odontoblastic layer. This bulge may provide prolonged contact between Hertwig’s root sheath and the developing dentin, triggering the induction of enamel formation.

Clinical features – enamel pearls are found most frequently on the roots of maxillary molars with the second most frequent site being mandibular molars. It is highest in Asians and prevalence is 1.1 to 9.7%. The majority occurs on the roots at the furcations area or near the cementoenamel junction. The enamel pearl occasionally contains vital pulp tissue. Radiographically, pearls appear as well-defined, radiopaque nodules along the root’s surface.

Clinical significance – the enamel surface precludes normal periodontal attachment with connective tissue. The attachment with the connective tissue is less resistant to breakdown; once separation occurs; rapid loss of attachment is likely. In addition this ectopic enamel is conducive to plaque retention and inadequate cleaning.

Treatment – when the enamel pearl is detected radiographically, patient should be advised to follow a meticulous oral hygiene in an effort to prevent localized loss of periodontal attachment.

2. Cervical enamel extensions –

These extensions represent a dipping of the enamel from the cementoenamel junction toward the bifurcation of the molar teeth. This extension typically forms a triangle form with the base towards the cervical area and the tip towards the bifurcation.

Pathogenesis – same as enamel pearl

Clinical features –

      Location- located  on the buccal surface of the root overlying the bifurcation

      Teeth commonly affected- in descending order; the first, second, third molars respectively. More common in mandibular than maxillary.

      These apical extensions have been correlated positively to localized loss of periodontal attachment with furcations involvement. It is also associated with the development of inflammatory cysts that are identical to inflammatory periapical cysts and are called buccal bifurcation cysts.

         Treatment –

               Treatment directed to provide access for cleaning and achieving a more durable attachment. This can be achieved by flattening or removing the enamel in combination with an excisional new attachment procedure and furcations plasty.

                   Developmental alterations in the structure of teeth:-

These includes

1.      Amelogenesis imperfecta

2.      Dentinogenesis imperfecta

3.      Dentin dysplasia

4.      Regional odontodysplasia

Amelogenesis imperfecta:-

(Hereditary enamel dysplasia, Hereditary brown enamel, Hereditary brown opalescent teeth)

Amelogenesis imperfecta encompasses a complicated group of conditions that demonstrate developmental alterations in the structure of the enamel in the absence of any systemic disorder. It is ectodermal disturbance, since the mesodermal components of the teeth are normal.

At least 14 different hereditary subtypes of Amelogenesis imperfects exist, with numerous patterns of inheritance and a wide variety of clinical manifestations.

The formation of enamel is a multistep process, and problems may arise in any one of the steps. In general, the development of enamel can be divided into three major stages

1. Elaboration of the organic matrix
2. Mineralization of the matrix
3. Maturation of the enamel.

The hereditary defects of the formation of enamel also are divided along these lines: hypoplastic, hypocalcified, and hypomaturation.

Classification –

Clinical and radiographic features:-

Prevalence – varies between 1:718 and 1:14,000. both deciduous and permanent dentitions are diffusely involved.

Hypoplastic Amelogenesis imperfecta – in this type the basic alteration centers on inadequate deposition of enamel matrix. Any matrix present is mineralized appropriately and radiographically contrasts well with the underlying dentin.

Types-

      In generalized type pinpoint to pinhead sized pits are scattered across the surface of the teeth. The buccal surfaces of the teeth are affected more severely, and the pits may be arranged in rows or columns. Staining of these pits may occur.

      In the localized pattern, the affected teeth demonstrate horizontal roes of pits, a linear depression, or one large area of hypoplastic enamel surrounded by a zone of hypocalcification. Typically the altered area is located in the middle third of the buccal surfaces of the teeth.

      In autosomal dominant smooth pattern, the enamel of all teeth exhibits a smooth surface and is thin, hard and glossy. The absence of appropriate enamel thickness results in teeth that are shaped like crown preparations and demonstrate open contact points. The color of teeth varies from opaque white to translucent brown. Radiographically, the teeth exhibit a thin peripheral outline of radiopaque enamel.

      The X-linked dominant smooth pattern represents lyonization effect. Males with this disease exhibits diffuse thin, smooth, and shiny enamel in both dentitions. The color varies from brown- to yellow-brown. Radiographs shows peripheral outline of radiopaque enamel. Females with this disease exhibit vertical furrows of thin hypoplastic enamel, alternating between bands of normal thickness.

      In the rough pattern, the enamel is thin, hard and rough surfaced. The teeth taper toward the inciso-occlusal surface and demonstrate pen contact points. The color varies from yellow to white. The teeth are less vulnerable to attrition.

      In enamel agenesis, there is total lack of enamel formation. The teeth are the shape and color of the dentin, with a yellow-brown hue, open contact points. Crowns taper toward the inciso-occlusal surface. Anterior open bite is commonly seen. A lack of eruption of many teeth with significant resorption frequently occurs. Radiographs demonstrate no peripheral enamel overlying the dentin.

Hypomaturation amelogenesis imperfecta – in this type the enamel matrix is laid down and mineralization begins. However there is defect in the maturation of the enamel’s crystal structure. Affected teeth are normal in shape but exhibit a mottled, opaque white-brown discoloration. The enamel is softer than normal and tends to chip from the underlying dentin. Radiographically the enamel demonstrates radiodensity similar to the underlying dentin.

      In the pigmented pattern the surface enamel is mottled and agar-brown. The enamel often fractures from the underlying dentin and is soft enough to be punctured by a dental explorer.

      The snow-capped pattern exhibits a zone of white opaque enamel on the incisal or occlusal one quarter to one third of the crown. The affected teeth often demonstrate an anterior to posterior distribution and have been compared with a denture dipped in white paint. Both deciduous and permanent dentition are affected.

Hypocalcified amelogenesis imperfecta –

In this type, the enamel matrix is laid down appropriately but no significant mineralization occurs. The teeth are appropriately shaped on eruption, but the enamel is very soft and easily lost. On eruption the enamel is yellow-brown or orange, but it often becomes stained brown to black and exhibits rapid calculus apposition. With the years of function much of the enamel is removed, except for the cervical portion that is occasionally calcified better.

Hypomaturation/hypoplastic amelogenesis imperfecta –

This type exhibits enamel hypoplasia in combination with Hypomaturation. Both the deciduous and permanent dentition is involved diffusely. Two patterns are recognized that are similar but differentiated by the thickness of enamel and the overall tooth size.

      In the Hypomaturation-hypoplastic type, the predominant effect is one of enamel Hypomaturation in which the enamel appears as mottled yellowish white to yellow-brown. Pits are frequently seen on the buccal surface of the teeth. Radiographically, the enamel appears similar to dentin in density and large pulp chambers may be seen in addition to varying degrees of taurodontism.

      In the hypoplastic and Hypomaturation pattern, the predominant defect is one of enamel hypoplasia in which the enamel is thin; the enamel that is present demonstrate Hypomaturation. Radiographs shows decrease in thickness of enamel.

Tricho-dento-osseous syndrome - it is an autosomal dominant defect which includes hypoplastic/Hypomaturation or Hypomaturation/hypoplastic type of amelogenesis imperfecta as dental findings. Other systemic changes are present- kinky hair, osteosclerosis, and brittle nails. The kinky hair is present at birth but may straighten with age. The osteosclerosis primarily affects the base of the skull and the mastoid process. The mandible often exhibits a shortened ramus and an obtuse angle.

Treatment and prognosis –

The main problems encountered are aesthetics, dental sensitivity, and loss of vertical dimension. In addition, in some type of amelogenesis imperfecta there is an increased prevalence of caries, anterior open bite, delayed eruption, tooth impaction, or associated gingival inflammation.

In cases where there will be rapid attrition, the full coverage should be done as soon as possible otherwise a loss of usable crown length occurs. When sufficient crown length is not present, full dentures or overdentures in some cases often become the satisfactory approach.

In cases where there is less rapid tooth loss, aesthetic appearance is the prime consideration. The aesthetic can be improved by placement of full crowns or facial veneers. In some cases a lack of good enamel bonding of veneers occurs and does not result in a durable restoration. The use of GIC with dentinal adhesives often overcomes this weakness.

Dentinogenesis imperfecta:-

This is an autosomal dominant condition affecting both deciduous and permanent dentition. Affected teeth are yellowish – brown and have broad crowns with the constriction of the cervical area resulting in a Tulip shape. Radiographically, the teeth appear solid, lacking pulp chambers and root canals. Enamel is easily broken leading to exposure of dentin that undergoes accelerated attrition. The gene maps to chromosome #4. It encodes a protein called dentin sialophosphoprotein (DSPP).

 Dentinogenesis imperfecta is a hereditary developmental disturbance of the dentin in the absence of any systemic disorder. Similar dental changes may be seen in conjunction with the systemic hereditary disorder of bone, Osteogenesis imperfecta.

Classification –

Two systems, one by Witkop and the other by Shields, are well accepted but not totally satisfactory. It is evident that the third type of dentinogenesis (Shields type III or Witkop’s Brandywine isolate) is not a separate disease and merely represents a variation of expression of the Shields type II.

Shields	Clinical presentation	Witkop
Dentinogenesis imperfecta I	Osteogeneis imperfecta with opalescent dentin	Dentinogenesis imperfecta
Dentinogenesis imperfecta II	Isolated opalescent teeth	Hereditary opalescent teeth
Dentinogenesis imperfecta III	Isolated opalescent teeth	Bradywine isolate

 Levin suggested that the diagnosis of dentinogenesis imperfecta should be reserved for defective dentin formation with opalescent teeth in the absence of systemic disease. Appropriately, dentin defects associated with the systemic bone disease are termed Osteogenesis imperfecta with opalescent teeth.

Clinical features –

 The dental alterations in dentinogenesis imperfecta and Osteogenesis imperfecta with opalescent dentin are similar clinically, histologically and radiographically.

      Race – more common in whites

      Prevalence – 1:8000. It is randomly distributed in united states and Europe.

      Dentition – both dentitions are equally affected. Deciduous teeth are affected severely, followed by the permanent incisors and first molars, with second and third molars being least altered.

      The dentitions have a blue-to-brown discoloration, often with a distinctive translucence. The enamel frequently separates easily from the underlying defective dentin. Once exposed, the dentin often demonstrate significantly accelerated attrition

      Significant clinically obvious enamel hypoplasia is noted in some patients. The enamel abnormality is thought to be a secondary defect and not a direct expression of the dentinogenesis imperfecta gene.

Radiographic features –

      The teeth have bulbous crowns, cervical constriction, thin roots and early obliteration of the root canals and pulp chambers.

      Although pulp is obliterated, some teeth may show normal-sized pulps or pulpal enlargement (shell teeth)

      Shell teeth demonstrate normal-thickness enamel in association with extremely thin dentin and dramatically enlarged pulps. The thin dentin may involve the entire tooth or be isolated to the root. This rare abnormality has been seen most frequently in deciduous teeth in the presence of dentinogenesis imperfecta.

Initially this pulpal enlargement was discovered in the large Maryland Brandywine isolate and thought to be a new variant of dentinogenesis imperfecta (type III or Brandywine isolate). Current evidence strongly supports Brandywine isolate representing nothing more than variable expressivity of the gene for dentinogenesis imperfecta.

Histological features –

            It demonstrates altered dentin. The dentin adjacent to the enamel junction appears to normal dentin, but the remainder is distinctly abnormal. Short misshapen dentin tubules course through an atypical granular dentin matrix, which often demonstrates interglobular calcification. Scanty atypical odontoblasts line the pulp surface and cells can be seen entrapped within the defective dentin.

Treatment –

            Because of dentin deposition it is difficult to perform RCT. In spite of the risk of early enamel loss and significant attrition, the teeth are not good candidates for full crowns because of cervical fracture. Overlay dentures placed on teeth that are covered with fluoride releasing GIC have been used with success in some cases. In patients with excessive attrition, the vertical dimension has been rebuilt by placing nonprecious metal casting with adhesive luting agents on teeth that have received no preparation and are not subjected to occlusal wear. On long term many are the candidates for full dentures or implants.

Dentin dysplasia:-

(Rootless teeth)

Definition – it is a rare disturbance of dentin formation characterized by normal enamel but atypical dentin formation with abnormal pulpal morphology.

Dentin dysplasia should have no correlation with systemic disease or dentinogenesis imperfecta. 

The first description of this disease  was made by Ballschmiede in 1920.

Classification –

1. By shields and associates                                                                                                                                            

      Type I – dentin dysplasia

      Type II – anomalous dysplasia of dentin

2.   By witkop

      Radicular dentin dysplasia (type I)

      Coronal dentin dysplasia (type II)

Etiology-

            Dentin dysplasia, both type 1 and type 2 appears to be a hereditary disease, transmitted as an autosomal dominant characteristics.

Clinical features –

1. Dentin dysplasia type I – dentin dysplasia type I (radicular dentin dysplasia or rootless teeth) has been referred to as rootless teeth because the loss of organization of the root dentin often leads to a shortened root length. The approximate prevalence is 1:100,000. The enamel and coronal dentin are normal clinically and well formed, but the radicular dentin loses all organization and subsequently shortened dramatically. Because of shortened roots, the initial clinical signs are extreme tooth mobility, and premature exfoliation, spontaneously or secondary to trauma. The radicular strength of the dentin is reduced, with the teeth being predisposed to fracture during extraction. Both dentition are affected

2. Dentin dysplasia II (coronal dentin dysplasia) – exhibits numerous features of dentinogenesis imperfecta. In contrast to type I, the root length is normal in both dentitions. The involvement of each dentition is different clinically. Deciduous teeth closely resemble those of dentinogenesis imperfecta. Clinically, the teeth demonstrate a blue–to–amber -to-brown translucence. The permanent dentition demonstrates normal clinical coloration.

Radiographic features –

1. Dentin dysplasia type I – the deciduous teeth are affected severely, with little or no detectable pulp and roots that are markedly short or absent. The permanent teeth vary according to the proportion of organized versus disorganized dentin. With early disorganization, no pulp can be detected and the roots are extremely short or absent. With somewhat later disorganization, crescent or chevron-shaped pulp chamber can be detected overlying shortened roots that exhibit no pulp canals. Late disorganization results in a normal pulp chambers overlying roots, each of which exhibits a large pulp stone. The root is flared at the site of the stone, and the canal is constricted apical to the stone.
2. Dentin dysplasia types II – in deciduous dentition, the dental changes include bulbous crowns, cervical constriction, thin roots, and early obliteration of the pulp. In permanent dentition, the pulp chambers exhibit significant enlargement and apical extension. This altered pulpal anatomy has been described as Thistle tube-shaped or Flame-shaped. Pulp stones develop in enlarged pulp chambers.

Histological features –

1. In dentin dysplasia type I – the coronal enamel and dentin are normal. Apical to the point of disorganization, the central portion of root forms whorls of tubular dentin and atypical osteodentin which are surrounded by a peripheral layer of normal dentin, giving the root the appearance of a “Stream flowing around boulders”.
2. in dentin dysplasia type II – the deciduous teeth demonstrate the pattern described in dentinogenesis imperfecta. The permanent teeth exhibit normal enamel and dentin. Adjacent to the pulp, numerous areas of intergobular dentin are seen. The radicular dentin is atubular, amorphous, and hypertrophic. Pulp stones develop in any portion of the chamber.

Treatment and prognosis –

1. In type I dentin dysplasia –

      Preventive care is of foremost importance. Because of shortened roots, early loss from periodontitis is common.

      Pulp vascular channels extend close to the DEJ, so even shallow occlusal restorations can result in pulpal necrosis.

      If periapical inflammatory lesion develops, the treatment is guided by the length of the root. If adequate length is present which is necessary for the root canal therapy then, the treatment can be carried out, otherwise the that particular tooth has to be sacrificed.

2.  In type II dentin dysplasia –

      The deciduous teeth are managed in similar manner to dentinogenesis imperfecta. Because the pulp canals are not usually obliterated completely in permanent dentition, endodontic treatment can be accomplished readily.

Regional odontodysplasia:-

(Odontodysplasia, odontogenic dysplasia, odontogenesis imperfecta, Ghost teeth)

Definition – it is a localized, nonhereditary developmental abnormality of teeth with extensive adverse effects on the formation of enamel, dentin, and pulp.

This is an unusual anomaly in which one or more several teeth in a localized area are affected in an unusual manner.

Etiology – most cases are idiopathic, but a number have been related to various syndromes, growth abnormalities, neural disorders and vascular malformation. Most popular theory revolves around the vascular abnormalities. A number of causes have been proposed –

1. Abnormal migration of neural crest cells
2. Latent virus
3. Local circulatory deficiency
4. Local trauma
5. Hyperpyrexia
6. Malnutrition
7. Medication used during pregnancy
8. Radiation therapy
9. Somatic mutation

Clinical features –

It is an uncommon finding that occurs in both dentition and shows no racial predilection.

      Gender – shows slight female predominance

      Age – shows bimodal peak that correlates with the normal time of eruption of deciduous (2 to 4 yrs) and permanent (7 to 11yrs) dentitions.

      Jaws affected – the maxillary teeth are involved more frequently than the mandibular, the most frequently affected teeth being the maxillary permanent central incisors, lateral incisors and canines.

      Typically the process affects a focal area of dentition. Involvement of deciduous dentition is followed by similarly affected permanent teeth. In the area of altered teeth, the surrounding bone often exhibits a lower density.

      Many of the affected teeth fail to erupt. Erupted teeth demonstrate small irregular crows that are yellow to brown, often with a very rough surface.

      Caries and associated periapical inflammatory lesions are fairly common. Because of dentinal clefts and very long pulp horns, pulpal necrosis is common.

      The most common presenting signs and symptoms include delayed or failure of eruption, early exfoliation, abscess formation, malformed teeth, and noninflammatory gingival enlargement.

Radiographic features –

            The altered teeth demonstrate extremely thin enamel and dentin surrounding an enlarged radiolucent pulp, resulting in a pale wispy image of the tooth; hence the term Ghost teeth. There is lack of contrast between the dentin and the enamel with a fuzzy appearance of the coronal silhouette. Short roots and open apices can be seen.

Histopathological features –

The most characteristics features of the disease are the marked reduction in the amount of dentin, the widening of the predentin layer, the presence of large layers of interglobular dentin and an irregular tubular pattern of dentin. The follicular tissue surrounding the crown may be enlarged and typically exhibits focal collections of basophilic enamel-like calcification called Enameloid conglomerates.

Treatment –

      The therapy is directed towards retention of the altered teeth, whenever possible, to allow for appropriate development and preservation of the surrounding alveolar ridge.

      Endodontic therapy on nonvital tooth that has sufficient hard tissue to allow restoration has been performed.

      Because fragile nature of the coronal hard tissue and the ease of pulp exposure, tooth preparation is contraindicated.

      Unerupted teeth should remain untouched, restoring function with a removable partial prosthesis until the skeletal growth period has passed.

      Severely affected and infected teeth need to be removed

      Retention of the abnormal dentition is often difficult. But some investigators have shown continued development of teeth affected by this disease. The teeth lost their ghostly appearance and revealed a decrease in pulp size, a significant increase in dentin thickness and development of normal radicular anatomy. In contrast, the enamel remained hypoplastic. The surrounding bone became well developed and lost its diminished density.