Dental anomalies

Dental Anomalies

1. Dental anomalies

2. Prepared by: Romissaa Ali Demonstrator of Oral medicine,Periodontology , Diagnosis and Radiology Al-Azhar Univerisity

3. Disturbances in size . DISTURBANCES IN SHAPE. Disturbances in number Disturbances in Eruption Disturbances in structure of Enamel. Disturbances in structure of dentin. Disturbances in Enamel and dentin Disturbances in cementum

4. Microdontia involving one or two teeth is far more common than the generalized types. Individual teeth most frequently affected by microdontia are the maxillary lateral incisors (peg laterals) and the maxillary third molars .

5. The crowns often exhibit a conical shape . Supernumerary teeth are commonly smaller than normal, and their crowns are often conical.

6. When all teeth in both arches are measurably larger than normal, the condition is termed true generalized macrodontia (seen in rare conditions such as pituitary gigantism).

7. The term relative generalized macrodontia is used to describe a condition in which the mandible, the maxilla, or both are somewhat smaller than normal but the teeth are normal in size. Rhizomegaly , also termed radiculomegaly , is an uncommon type of macrodontia in which the root or roots of a tooth are considerably longer than normal.

8. Total anodontia is a rare condition in which the patient has no deciduous and no permanent teeth. It usually occurs in association with a generalized disorder such as hereditary ectodermal dysplasia . it is inherited disase in some families as an X-linked recessive disorder affecting essentially males , and in other families as an autosomal recessive disorder affecting males and females.

9. The gene for the X-linked variety has been mapped to the long arm of the X chromosome (Xq12- q13.1). A gene from this region has been found to encode a transmembrane protein that is expressed in keratinocytes , hair follicles, and sweat glands . All features are basic to defects in the development of the ectodermally derived structures (hair, sweat glands, teeth).

10. The more common form of anodontia is partial anodontia , hypodontia or oligodontia , and involves one or more teeth . The most common congenitally absent teeth are the third molars, followed by the maxillary lateral incisors and the second premolars . A close correlation exists between congenital absence of a deciduous tooth and congenital absence of the permanent successor , suggesting some genetic influence .

11. They are far more common in the maxilla (90%) than in the mandible (10%). A supernumerary tooth located between the maxillary central incisors, termed a mesiodens is the most common, followed by maxillary fourth molars ( paramolars ) and maxillary lateral incisors.

12. In the mandible the most common supernumerary teeth are premolars. A supernumerary tooth may resemble the corresponding normal tooth or it may be rudimentary and bear little or no resemblance to its normal counterpart.

13. Supernumerary teeth may be single or multiple and erupted or impacted. Multiple supernumerary teeth, which are generally impacted, are characteristically seen in cleidocranial dysplasia and Gardner syndrome.

14. DISTURBANCES IN ERUPTION: Premature Eruption Delayed Eruption Impacted Teeth Eruption Sequestrum

15. Premature Eruption : Erupted deciduous teeth present at birth are termed natal teeth . Deciduous teeth that erupt during the first 30 days of life are termed neonatal teeth . Premature eruption usually involves only one or two teeth, most commonly the deciduous mandibular central incisors.

16. Natal teeth and neonatal teeth are usually part of the normal complement of deciduous teeth; they are not supernumerary teeth and should therefore be retained if possible. Premature eruption of permanent teeth is usually a consequence of premature loss of the preceding deciduous teeth.

17. In the event that the entire permanent dentition is obviously erupting prematurely, the possibility of an endocrine dysfunction such as hyperthyroidism should be considered.

18. Delayed Eruption: This occurrence is relatively uncommon and is usually idiopathic or associated with certain systemic conditions such as rickets, cleidocranial dysplasia, or cretinism .

19. Local factors such as gingival fibromatosis , in which dense fibrous connective tissue impedes tooth eruption, can result in delayed eruption of the deciduous dentition. Treatment of the systemic condition or the causative local factors may alleviate the eruption.

20. In conditions such as cleidocranial dysplasia , the pathophysiologic basis for non eruption is unclear and no known treatment exists. Delayed eruption of permanent teeth may result from the same local and systemic conditions that give rise to the delayed eruption of deciduous teeth.

21. Examples of physical barriers that impair tooth eruption and result in impaction include dental crowding, supernumerary teeth, some odontogenic cysts, and odontogenic tumors (particularly odontomas ).

22. The most common impacted teeth are the mandibular and maxillary third molars and maxillarycuspids , mandibular second premolars and supernumerary teeth. Mesioangular impactions of third molar are the most common type. An impacted tooth that is totally surrounded by bone is completely impacted , whereas one that is partly in bone and partly in soft tissue is partially impacted.

23. Partially impacted teeth, particularly mandibular third molars, may communicate with the oral cavity via an inconspicuous periodontal pocket on the distal aspect of the adjacent second molar , thus predisposing the impacted tooth to pericoronal infection and dental caries. Individual teeth that fail to erupt for no apparent reason have sometimes been termed embedded teeth ; however, this term is rarely used

24. The common complications of impacted teeth are root resorption of adjacent normal teeth, infection and associated pain, a predisposition to dentigerous cyst formation, and external resorption of the impacted tooth. External resorption in an impacted tooth usually begins in the occlusal area of the crown and radiographically resembles dental caries.

25. It may arise from the small area of slightly thickened cortical bone that occupies the area of the central occlusal fossa of molars or may rep- resent a miniature complex odontoma present in the follicular soft tissue overlying the tooth

26. Although most eruption sequestra are spontaneously exfoliated and therefore require no treatment , they may occasionally remain in the alveolar mucosa for several days and may be brought to the attention of a dentist. In this event, they can be easily removed.

27. DISTURBANCES IN SHAPE: DILACERATION Taurodontism   DENS INVAGINATUS Supernumerary CuspsS Supernumerary Roots Gemination Fusion Concrescence Hypercementosis Cervical Enamel Projection

28. Although occasional examples of dilaceration result from trauma during tooth development , most cases are the result of continued root formation during a curved or tortuous path of eruption . In some instances the cause of the bent or curved root is idiopathic .

29. Taurodontism , meaning bull-like teeth, is a developmental disturbance that primarily affects molars. Both the permanent and deciduous teeth may be affected, although involvement of the permanent teeth appears to be more common .

30. It recognized radiographically and characterized by teeth that exhibit an overall rectangular shape, minimal constriction and definition of the cervical margin, and an apically displaced furcation that results in an extremely large pulpal chamber that exhibits an exaggerated apical- occlusal height and short pulpal canals

31. The unusual root shape probably results from late invagination of Hertwig’s root sheath, the mechanism that determines the shape of the tooth roots. Taurodontism may also occur in patients with amelogenesis imperfecta , and Down syndrome. Taurodontism requires no treatment but can be a complicating factor during root canal treatment procedures.

32. Dens invaginatus , also termed dens in dente , is a developmental abnormality that primarily affects the permanent maxillary lateral incisors.

33. Mild cases is characterized by the presence of an invaginated lingual pit that extends for varying distances into the substance of the tooth. The extent of the invagination is not always clinically visible. The external pit on the lingual surface is often inconspicuous on clinical examination but may be visible in a periapical radiograph .

34. In its most extreme form the deep invagination results in a bulbous expansion of the affected root, a form termed a dilated odontoma . As a result, most teeth with deep invaginations quickly develop pulpitis , pulpal necrosis, and inflammatory periapical disease in what clinically appears to be an intact tooth.

35. Early radiologic diagnosis and prophylactic restorative treatment of the abnormality are essential if pulpal and periapical diseases are to be prevented. Treatment of the more severe forms of dens invaginatus is usually extraction.

36. Occasionally, teeth exhibit supernumerary cusps. The most common example of this phenomenon is the Carabelli cusp , which develops on the mesiolingual surface of permanent maxillary first molars. This particular supernumerary cusp usually presents no clinical problems and is therefore represent a normal anatomic variation. Supernumerary Cusps :

37. however, certain teeth exhibit supernumerary cusps that result in clinical problems that may require treatment . Examples of such supernumerary cusps are dens evaginatus and talon cusps

38. Dens evaginatus is a developmental abnormality that primarily affects premolar teeth. It is characterized by the development of an abnormal globe-shaped projection of enamel in the region of the central groove , between the buccal and lingual cusps of premolars,

39. The clinical significance of dens evaginatus is that it can interfere with tooth eruption and result in incomplete eruption or tooth displacement. Because this extra cusp contains a pulp horn, attrition or fracture can result in pulp exposure leading to pulpal inflammation and its sequelae .

40. Talon cusp: It is seen on the lingual aspect of maxillary central incisors, is called a talon cusp, because its unusual shape resembles an eagle’s talon. This is abnormal cusp arises from the cingulum portion of the tooth and usually extends to the incisal edge a s a prominent projection of enamel .

41. If the cusp interferes with normal occlusion, preventive care that includes endodontic and restorative treatment of the affected tooth may be required to achieve normal tooth form . Simple reduction of the cusp should not be attempted, because the cusp contains a prominent pulp horn .

42. Supernumerary Roots : It is common occure in mandibular premolars cuspids,and maxillary and mandibular third molars.

43. Gemination is characterized by the partial division or twinning of a single tooth germ , resulting in a tooth that exhibits two separate or partly separated crowns and a single root and root canal . Gemination can affect the deciduous and permanent dentitions .

44. Fusion can be complete or incomplete . If fusion begins before calcification, then the union will involve all components of the tooth , including enamel, dentin, cementum , and pulp.

45. If the union begins at a later stage of tooth development , the affected teeth may have separate crowns and the fusion may be limited to the roots. Fusion can be differentiated from gemination by counting the teeth in the area. The clinical implications of fusion include esthetic considerations, crowding when fused to a supernumerary tooth , and periodontal disease.

46. FIGURE 1-18 Gemination and fusion. B, Gemination

47. Concrescence is a type of fusion that occurs after root formation is complete . The condition is thought to occur as a result of traumatic injury to the area or crowding with interseptal bone loss, resulting in close approximation of the tooth roots.

48. Concrescence can occur before or after tooth eruption and primarily involves the permanent maxillary molars. The clinical implications of concrescence relate primarily to the importance of its radiographic diagnosis before attempting tooth extraction .

49. Hypercementosis Teeth with these shapes are difficult to extract without surgically removing significant amounts of the surrounding bone . Hypercementosis is more common in teeth that are subjected to either increased or decreased occlusal forces , on the teeth of patients with Paget disease or hyperpituitarism , and on adjacent teeth in areas of chronic inflammation .

50. Cervical Enamel Projection : Focal apical extensions of the coronal enamel beyond the normally smooth cervical margin ( cementoenamel junction) and onto the root of the tooth.

51. This occur primarily on maxillary and mandibular molars. Their clinical significance relates to the fact that they could contribute to periodontal pocket formation, which might progress to periodontal disease. The cervical enamel projection is also thought to play a role in the development of the paradental cyst

52. Cervical enamel projections differ from the ectopic droplets of enamel that primarily occur in the bifurcation or tri- furcation areas on the roots of molars . These are termed enamel pearls. Treatment is not recommended, because it often leads to the development of root caries, external resorption , or pulpitis .

53. DISTURBANCES IN STRUCTURE OF ENAMEL Acquired Disturbances Amelogenesis Imperfecta

54. Acquired Disturbances: Focal enamel hypoplasia Generalized enamel hypoplasia

55. The environmental factors are bacterial and viral infections (e.g., syphilis, scarlet fever), inflammation, nutritional deficiencies (e.g., vitamins A, C, D; calcium), chemical injuries (e.g., fluoride), and trauma . Enamel defects resulting from environmental factors usually affect either the deciduous or the permanent dentition . Environmental factors often damage both types of hardtissues .

56. Focal enamel hypoplasia : A common form of focal enamel hy poplasia of known cause is Turner tooth, which results from localized inflammation or trauma during tooth development . Typical examples of this phenomenon occur when a deciduous tooth develops a caries- or trauma-related abscess that damages the underlying developing permanent successor .

57. Generalized enamel hypoplasia they are manifested clinically as a horizontal line of small pits or grooves on the enamel surface that correspond to the time of development and the duration of the insult .

58. congenital syphilis affects the incisal edges of the permanent incisors and the occlusal surfaces of the permanent first molars . The notched, screwdriver-shaped incisors are termed Hutchinson incisors, whereas the globular occlusal surfaces of the first molars are termed mulberry molars.

59. Enamel hypoplasia that results from hypocalcemia secondary to vitamin D deficiency is usually of the pitted type. A well-recognized example of chemically induced generalized enamel hypoplasia results from the ingestion of fluoride .

60. Although total fluoride intake will vary with total water consumption, fluoride -induced enamel hypoplasia ( fluoride mottling ) Increased fluoride levels interfere with ameloblastic function, which adversely affects both enamel matrix formation and enamel matrix calcification . Regardless of the degree of fluoride mottling, affected teeth are largely resistant to dental caries .  

61. It affect both the primary and permanent dentitions. These disorders are confined to the enamel; the other components of the teeth are normal.

62. Three basic types of amelogenesis imperfecta : (1) The hypoplastic type (focal or generalized), which exhibits decreased enamel matrix formation caused by a disturbance in the functioning of the ameloblasts ; (2) The hypocalcified type , which exhibits a severe defect in mineralization of the enamel matrix .

63. Both dentitions are commonly affected to some degree. In the X-linked subtypes the clinical appearance differs between males and females. (3) The hypo- maturation type , which exhibits a less severe alteration in mineralization with focal or generalized areas of immature enamel crystallites .

64. DISTURBANCES IN STRUCTURE OF DENTIN Generalized disturbances in dentin formation are usually hereditary and include conditions such as dentinogenesis imperfectaand (DI) dentin dysplasia (DD).

65. Dentinogenesis imperfecta Dentin Dysplasia

66. Type I: DI that occurs in patients afflicted with osteogenesis imperfecta (OI) This type is usually inherited as an autosomal dominant trait . Although the teeth have the same opalescent color as in type II . Type II: DI that is not associated with OI. the common term for this type of DI is hereditary opalescent dentin . It is the most common type and is inherited as an autosomal dominant trait .

67. Type III: DI (Brandywine type) is rare and inherited as an autosomal dominant trait ; it occurs in a racial isolate in the state of Maryland . Clinically, it is the same as type I and type II except that patients exhibit multiple pulpal exposures in the deciduous dentition.

68. In all three subtypes of DI, teeth of both dentitions are affected with variable clinical appearances . The teeth are opalescent with the color ranging from bluish-gray to brown to yellowish. The dentin is abnormally soft, providing inadequate structural support to the overlying ename l . Although the enamel is normal , it fractures or chips away easily, exposing the occlusal and incisal dentin .

69. Radiographic features : The teeth in DI subtypes I and II are similar and exhibit bulb-shaped crowns with constricted cementoenamel junctions and thin roots . Depending on the age of the patient, the teeth will exhibit varying stages of obliteration of the pulp chambers and pulp canals .

70. The cementum , periodontal ligament, and supporting alveolar bone appear normal. The teeth in DI type III may be similar to those seen in types I and II, or they may exhibit extremely large pulpal chambers surrounded by a thin shell of dentin .

71. Type I ( radicular DD): type I is far more common than type II. All teeth in both dentitions are affected . The color of the teeth is usually within the normal range . In some cases the crowns of the teeth may exhibit a slight bluish or brownish translucency in the cervical region.

72. The teeth usually exhibit a normal eruption pattern, although occasional delayed eruption has been reported. Affected teeth often exhibit increased mobility and may exfoliate prematurely .

73. RADIOGRAPHIC FEATURES : The roots of the teeth are usually short, blunt, bulged, conic, or absent. The mandibular molars commonly have characteristic W-shaped roots. In the deciduous dentition, teeth often exhibit total obliteration of the pulpal chambers and canals . The permanent teeth may also exhibit pulpal obliteration.

74. Type II (coronal DD): Both the primary and permanent dentitions are affected in this type of DD. Clinically the deciduous teeth exhibit a bluish-gray, brownish, or yellowish color and have the same translucent, opalescent appearance that is seen in DI. In contrast, the permanent teeth have a normal clinical appearance.

75. RADIOGRAPHIC FEATURES : The deciduous teeth of DD exhibit obliterated pulpal chambers and canals. The pulpal obliteration occurs after tooth eruption. The roots of the deciduous and permanent dentitions are of normal shape and length.

76. The pulp chambers in the permanent teeth are abnormally large, rather than obliterated, and exhibit a radicular extension that imparts a thistle or flame shape to the root portion of the pulp. Pulpal calcifications ( pulp stones ) are visible in most of the coronal pulp chambers and the root pulp canals are narrowed .

77. Regional odontodysplasia (ROD), or ghost teeth , is a sporadically occurring nonhereditary disturbance of tooth development characterized by the defective formation of enamel and dentin in addition to abnormal pulp and follicle calcifications teeth exhibit a delay or a total failure to erupt. The teeth are considerably deformed with a soft leathery surface and are discolored, yellowish-brown .  

78. RADIOGRAPHIC FEATURES The teeth have been described as ghost teeth because of the marked decrease in radiodensity . The enamel and dentin are very thin and indistinct; the pulpal chambers are extremely large . Pulp stones may occasionally be visible.

79. Hypophosphatasia is inherited in the majority of cases as an autosomal recessive condition. Hy pophosphatasia is a disorder of bone mineralization caused by a deficiency in alkaline phosphatase in serum and tissues .

80. The cause of hypophosphatasia is a basic defect in the gene encoding for tissue nonspecific alkaline phosphatase (TNSALP). Delayed formation and eruption of the dentition, premature loss of primary teeth, and the spontaneous loss of permanent teeth are characteristically seen in hypophosphatasia

81. Reference : CONTEMPORARY ORAL AND MAXILLOFACIAL PATHOLOGY, second edition

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