Characteristics and features of developmental, hereditary and congenital disorders affecting the teeth and other hard tissues. Genetic concepts of development and role of teratogens on developing tissues,

1. Developmental
Disorders
Dr. Ali Yaldrum
B.D.S, M.Sc (London)
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2. Learning Objectives
• Define and use the key terms
• Compare and contrast developmental, hereditary, and
congenital disorders
• Provide examples of teratogenic agents and describe how a
teratogenic agent may affect morphogenesis.
• Describe the characteristics of developmental, hereditary, and
congenital disorders.
• Describe the dental implications and appropriate dental care
modifications associated with the disorders discussed.

3. ‘The Basics’

4. • Developmental disorders
• Hereditary disorders
• Congenital disorders

5. Developmental disorders
• Occur when there is a disturbance in the development
of the body that results in an abnormality.
• e developmental abnormality can be very severe and
cause spontaneous abortion or miscarriage or it can
be very minor and cause few, if any, problems.

6. Hereditary disorders
• Caused by a genetic abnormality that can be passed
from generation to generation.
• Many hereditary conditions are not compatible with
life and result in a spontaneous abortion or early
infant death; others can be very mild and not even
noticed.

7. Congenital disorders
Congenital abnormalities, sometimes called birth
defects, are present at or around the time of birth and
can be caused by a variety of factors

8. A congenital abnormality could be hereditary or
developmental, as long as it is present at or around
the time of birth.

9. Hereditary and developmental conditions not obvious
at birth can become manifest later in life.

10. Concepts of developmental
anomalies
• Teratology is the study of developmental anomalies
that take place during fetal development
• e agents that cause developmental anomalies are
called teratogens

11. Teratogens
• Alcohol
• Tobacco
• Cocaine
• Heroine
• Warfarin
• Tetracycline
• Maternal diabetes
• Maternal folic acid
deficiency
• SLE

13. Overview of Genetic
Concepts
• Chromosomes
• Genes

14. Chromosomes
• e DNA molecule is packaged into thread-like
structures called chromosomes.
• Each chromosome is made up of DNA tightly coiled
many times around proteins called histones that
support its structure.

16. Genes
• Gene is a molecular unit of heredity of a living
organism
• It is a name given to some stretches of DNA and RNA
that code for a polypeptide

17. Control genes play key roles in
• organ formation and the pa erning of structures
throughout the embryo
• regulate the signaling pathway between cells & tissues

18. CHAPTER 6 • DEVEL
Figure 6.7. X Chromosome with the loci of specific genes
identified. The location of representative inherited disor-
ders on the X chromosome. Genes that are located at the
same locus on homologous chromatids are called alleles.
(From Rubin E, Farber JL. Pathology. 3rd ed. Philadelphia:
Lippincott Williams & Wilkins, 1999.)
p
q

19. Few Facts
• Teeth form from cooperative interaction of two germ
layers, ectoderm and ectomesenchyme (neural crest
derivative)
• Enamel is formed from ectodermal components
• Dentin, Pulp, Cementum, the supporting PDL and bone
are all derived from ectomesenchyme

20. Disorders of development of
teeth
e development of teeth and associated structures
are regulated by genes, but the genetic program is
very sensitive to disturbances in the environment such
as infections or toxic chemicals.

21. Disorders of development of
teeth
• Disturbance in number of teeth
• Disturbance in size of teeth
• Disturbance in form of teeth
• Disturbance in structure of teeth

22. Disturbance in number of
teeth
• Hypodontia
• Anodontia
• Hyperdontia (supernumerary)
• Hypohidrotic ectodermal dysplasia

23. Hypodontia
• congenital absence of teeth
• one or several teeth are missing
Anodontia
• when there is complete absence of one or both
dentitions

24. Hypodontia
• Genetic basis not yet understood
• several regulatory genes involved in tooth involvement,
mutations in these genes is likely to be responsible.
• more common in the permanent dentition (2-10% of
population)
• in primary dentition prevalence is less then 1%

25. Hypodontia
Symmetrically missing:
• third molars
• permanent maxillary lateral incisors
• mandibular second premolars

26. Hypodontia
• more common in females
• may be symmetrical
• unusual for deciduous teeth to be congenitally
missing > permanent dentition will also fail to form
• severe hypodontia / anodontia may be associated
with other developmental abnormalities

27. Hypodontia
• teeth additional to those of normal series
• may develop in tooth bearing areas
• frequent in anterior & molar regions of maxilla
• premolar region of the mandible
• cle palate, cleidocranial dysplasia

28. • may prevent eruption, may develop dentigerous cyst if
unerupted
• more common in females
• occur in single
• about 1-3% of population
• present in deciduous dentition

29. Mesiodens
• Supernumerary teeth occurring in certain sites may be
referred by special terms.
• Supernumerary teeth developing b/w the maxillary
central incisors
• most common form
• conical crowns & short roots

30. Mesodens

31. Paramolar
• arises alongside maxillary molars
• usually buccally placed
Distomolar
• develops distal to a third molar

32. Distomolar

33. Supplemental teeth
• morphologically resembles those of normal series
• mostly reduced in size

34. Ectodermal dysplasia
syndrome
• is not a single disorder
• a group of syndromes all deriving from abnormalities
of ectodermal structures
• more then 150 syndromes

35. • Heritable conditions in which there are abnormalities
of two or more ectodermal structures such as the hair,
teeth, nails, sweat glands, cranial-facial structure,
digits and other parts of the body.
Ectodermal Dysplasias: A Clinical And Genetic Study.

36. Abnormal structures:
• Hair
• Nails
• Skin
• Sweat Glands

37. • “Anhidrotic ectodermal dysplasia," and "Christ-
Siemens-Touraine syndrom
• have reduced ability to sweat because of fewer sweat
glands
• sparse hairs on scalp and body

38. Distinctive facial features including
• prominent forehead
• fla ened bridge of the nose

39. Additional features include
• thin, wrinkled, and dark-colored skin around the eyes
• chronic skin problems such as eczema
• bad-smelling discharge from the nose

40. Teeth
• tooth buds frequently absent
• or growth of teeth that are peg shaped or pointed
• enamel may be defective
• multi disciplinary approach is required

43. Disturbances of size of teeth
• size of both jaw & teeth influenced by genetic &
environmental factors
Microdontia
• teeth in the dentition appear smaller then normal
• or may be relatively small in comparison with a large
mandible & maxilla

44. • may involve entire dentition or one or two teeth
• Autosomal dominant inheritance pa ern

46. Macrodontia
• generalized is characterized by the appearance of
enlarged teeth throughout the dentition
• may be absolute as seen in pituitary gigantism
• or may be relative owing to a disproportionately small
maxilla and mandible would result in crowding

47. Disturbances in form of teeth
Disturbances in tooth form may involve
• Crown
• Root
• Or both
• frequent variations of the crowns affect maxillary
permanent lateral incisors

48. • Premolars or molars with an increased or decreased
number of cusps are also frequently seen

49. Dilaceration
• an extraordinary curving or angulation of tooth roots
• cause of this condition has been related to trauma
during root development
• most frequently involves maxillary incisors

50. Flexion
• is a deviation or bend restricted just to the root porion
of the tooth
• bend is less then 90 degrees
• result of trauma

51. Flexion

52. Taurodontism (bull-like tooth)
• Pulp chamber has a greater apico-occlusal height than
in normal teeth with no constriction at the level of
amelo-cemental junction
• e result is that the chamber extends apically, well
beyond the neck of the tooth

53. • affects multi rooted teeth
• caused by failure of Hertwigs sheath to invaginate at
proper level
• rare in primary dentition

54. Taurodontism

55. Dens in Dente
• Also called Dens Invaginatus
• means tooth with in a tooth
• uncommon developmental anomaly
• primarily affects maxillary lateral incisors

56. • deeply invaginated lingual pit
• susceptible to caries, if le una ended tooth will
decay very rapidly

58. Double teeth
• Descriptive term used to describe a developmental
anomaly where two teeth appear joined
• degree of union is variable may involve crown, root or
both
• Incisors canines in the primary dentition
• more common in the primary dentition

59. Fusion
• Fusion is the joining of two developing tooth germs
resulting in a single large tooth structure
• entire length of the teeth
• may involve only roots, in which cementum & dentin
are shared

61. Gemination
• is the fusion of two teeth from a single enamel organ
• result is a partial cleavage, with the appearance of two
crowns that share the same root canal

63. Concrescence
• Concrescence is an acquired disorder in which the
roots of one or more teeth are united by cementum
• may take place before or a er eruption
• most commonly seen in association with the maxillary
2nd & 3rd molars

65. Disturbances in structure of
teeth
• Defects of the teeth like pi ing or discoloration are
mostly the markers of past diseases systemic or
localized.
• It is very un-common that the disease process which
caused the defect in tooth structure is still active.

66. Amelogenesis
Enamel normally develops in two stages
• Secretory stage
• Maturation stage

67. Secretory stage
In this stage Ameloblasts perform dual function;
• Matrix production
• Initial mineralization

68. Matrix production involves synthesis and secretion of
• Enamel proteins mainly enamelin and amelogenin
• Initial mineralization occurs immediately a er the
secretion of enamel proteins

69. Maturation stage
• is stage involves withdrawal of water and proteins
from the enamel and a concomitant increase in the
mineral content.

70. Disturbances in the enamel formation can be classified
accordingly;
• Hypo plastic enamel; disturbances in the production of
enamel matrix
• Hypo mineralized enamel; disturbances in the initial
mineralization and maturation

71. Hypoplastic enamel
• In this condition ameloblasts fail to produce a normal
volume of matrix
• However, any matrix which is produced generally
becomes fully mineralized as normal enamel
• Clinical features:Pits or groves on enamel surface, or a
general reduction in the thickness of whole of the
enamel

72. Generalized pi in & Smooth Surface

73. Hypo-mineralized Enamel
• It results from a failure of ameloblasts to fully calcify
the previously formed matrix
• Clinical features: White and opaque, a er eruption it
may become pigmented buff, orange, or brown and be
quickly chipped and worn away

74. • Hypo mineralized and hypo-plastic enamel defects may
involve a single tooth, a group of teeth or all of the
teeth, and the structure of the enamel formed depends
on the severity and duration of the disturbance and its
nature

76. Disturbance in structure of
enamel
Abnormalities of the enamel can be classified as;
Local causes:
• Infection
• Trauma
• Radiotherapy
• idiopathic (enamel opacities)

77. General causes:
1.Environmental/Systemic (chronological hypo-plasias)
A.Pre-natal:
I.infections e.g. rubella, syphilis
II.maternal disease
III.excess fluoride ions

78. B.Neo-natal:
I.Haemolytic disease of the newborn
II.Hypocalcaemia
III.Premature birth/prolonged labour

79. C.Post-natal:
I.Severe child hood infections
II.Chronic diseases in child hood e.g. congenital heart
disease
III.Nutritional deficiencies, e.g. vitamin D
IV.Cancer chemotherapy
V.Excess fluoride

80. 2.Genetic:
A.Teeth only affected:
• Amelogenesis imperfecta
B.Teeth affected in association with generalized defects:
• Ectodermal dysplasia syndrome
• Down syndrome

81. Amelogenesis Imperfecta
• ‘Amelogenesis imprfecta is a genetic abnormality of
the enamel formation which only affects the
amelogenesis’
• All types of amelogenesis imperfecta affects the
deciduous and permanent dentition.

82. It is classified into 2 distinct types.
• Hypo mineralized type
• Hypo plastic type

83. Hypo mineralized type is further divided into 2 types.
• Hypo maturation type
• Hypo calcified type

84. Hypo calcified type
• Is the most common form of this disorder
• Newly erupted teeth appear normal in size and shape
and have enamel of normal thickness
• Enamel is of a so , chalky consistency and is rapidly
lost by a rition and abrasion, exposing the dentin.

85. • Gross a rition is a feature of it, and the teeth may be
worn down to gingival level.
• Enamel has a similar density to dentin in radiographs.

86. Hypo maturation type
• In this type the enamel is generally of normal on
eruption but exhibit variable opaque, mo led,
brownish-yellow to white appearance
• Enamel is so and a rition occurs but not as severely
as in hypo calcified type

87. Hypo plastic type
• In this for enamel does not reach to the normal
thickness and there is a considerable variation in the
clinical appearance.
• In some cases localized areas of hypoplasia are
randomly distributed over the surface of the enamel
producing generalized roughness and pi ing or
irregular grooving and wrinkling.

88. • In the smooth form, enamel over the whole of the
crown is affected and the teeth have sharp, needle like
cusps.
• Enamel is very thin but hard and glassy

91. Dentinogenesis Imperfecta
• Most of the clinically significant disturbances of
dentinogenesis have a genetic etiology, but some
environmental or systemic disturbances affecting
calcium metabolism or calcification may also produce
abnormal dentin.

92. Local Cause General Causes
Dentinogenesis Imperfecta
Type I - osteogenesis
imperfecta
Type II -Teeth only affected
(Shell teeth)
Type III - Brandywine Isolate
(DSPP gene)
Dentine dysplasia
Type I - radicular dentine
dysplasia
Type II - coronal dentine
dysplasia
Enviormental
Vit-D
Hypophosphotasia
Juvenile hypoparathyroidism
Other mineral
deficiencies

93. • is uncommon defect of collagen formation is
transmi ed as an autosomal dominant trait.
• e dentin is so and has an abnormally high water
content.

94. • e enamel appears normal but uniformly brownish or
purplish and abnormally translucent.
• e crowns of the molars tend to be bulbous and the
roots are usually short.
• Enamel is weakly a ached to the dentine and tends to
chip away very easily.
• In severe cases the teeth become rapidly worn down to
the gingival level.

96. • Radiological examination shows short, blunt roots with
partial or complete obliteration of the pulp chambers
and root canals by dentine.
• Histological examination shows that the dentine
contains a reduced number of tubules and areas of a-
tubular dentin may also be present. is abnormal
dentine partly or totally obliterates the pulp chamber
and root canal.

98. • Biochemical analysis shows an increased water and
decreased mineral content.
• e hardness of the of the dentine is low explaining
the rapid a rition of teeth which occurs following loss
of enamel.
• Caries is un-usual in affected teeth, presumably due to
the reduced number of invasion pathways in the
dentin.

101. Shell Teeth
• is rare anomaly is so called because only a thin
shell of hard dental tissue surrounds overlarge pulp
chamber

102. • appears to be a variant of dentinogenesis imperfecta
• normal, but thin mantle dentine which covers irregular
dentine.
• Pulp lacks a normal odontoblast layer and consist of
coarse connective tissue which becomes incorporated
into the deep surface of the dentine.

103. References
• J. V. Soames, J. C. Southam, “Disorders of development of teeth and craniofacial anomalies” in
Oral Pathology, 4th Edition, Oxford University Press, 2007 pp 1-15.
• Leslie DeLong, Nancy W. Burkhart, “Developmental, Hereditary and Congenital Disorders” in
General Oral Pathology for Hygienists, 1st Edition, Lippinco Williams and Wilkins, 2008 pp
110-146.