Disturbances of dental development Copyright by Ortho Department, Yangon

1. Disturbances of dental development.

2. ▪ Occur as isolated disturbances in dental development or accompany major
congenital defects and syndromes. These are most common contributors to
class I malocclusion and also called local factors due to its localized
effects on occlusion.
Significant disturbances include –
Congenital missing teeth.
Malformed and supernumerary teeth.
Interference with eruption.
Ectopic eruption.
Early loss of primary teeth.
Traumatic displacement of teeth.

3. Congenital missing teeth.
▪ It results from disturbances in an initial stages of tooth formation- initiation
and proliferation. Termed anodontia, oligodontia, hypodontia depending upon
the severity of missing teeth.
Hypodontia - refers to a lack of one to six teeth, excluding third
molars;
Oligodontia - refers to a lack of more than six teeth, excluding third
molars; and
Anodontia - refers to a complete absence of teeth in one or both
dentitions.
Anodontia and oligodontia are usually associated with systemic abnormality
or syndromes. (ectodermal dysplasia)
▪ Hypodontia is a relatively common in permanent dentition and affecting the
most distal tooth of any given type.
Eg. Lateral incisor, lower central , second premolar and last molar.
▪ Very rarely canine is the missing tooth.

4. Missing lateral incisor.
▪ The effects depend upon the space conditions in the arch.
In crowded arch, the space available from the missing laterals is used
up to align the adjacent teeth. Usually the canines erupted mesially into the
space of missing laterals. There will be no clinically evident crowding but
aesthetic will be compromised.
In spaced arch, the extra-spaces will be left between the central
incisors and canines causing aesthetic disability.
▪ The tooth size between the upper and lower anterior teeth must be
proportionate to achieve class I canine relation with normal overjet and
overbite.
▪ Normal occlusion will not be achieved if laterals were missing in either arch.

6. Ectodermal dysplasia have thin, sparse hair and an absence of sweat
glands in addition to their characteristically missing teeth.

11. Missing second premolar.
▪ The mandibular second premolar is the most commonly missing teeth.
▪ If lower second premolar is missing, the primary second molar is usually
overretained resulting postnormal or class II molar relation.
▪ The long term prognosis of retained second deciduous molar is usually not
very good.
▪ Thus decision has to be made whether to retain the deciduous molar,
extraction and replace it with prosthesis or extraction and close the space
orhtodontically.
▪ In crowded arch the space resulting from extraction of second primary molar
may be used to correct crowding.
Missing last molar.
▪ No significant effects on the occlusion and alignment.

13. Malformed teeth.
▪ Results from disturbances during morphodifferentiation stages of tooth
development.
▪ Variation in size particularly of maxillary lateral incisors called peg laterals
are most common. Normal occlusion will not be possible with mismatched
upper and lower anterior tooth sizes.
▪ Germination or fusion of teeth occasionally occurs and normal occlusion is
impossible in the presence of fused or germinated teeth.
▪ Fusion results in teeth with separate pulp chambers joined at the dentin ,
whereas gemination results in teeth with a common pulp chamber.

14. Small size maxillary lateral incisor.

16. Disproportionate small all (A) or large( B) maxillary lateral incisors are
relatively common.
This creates a tooth size discrepancyt hat makes normal alignment and
occlusion almost impossible .
It is easier to build up small laterals than reduce the size of large ones,
because dentin is likely to be exposed interproximally after more than
1 – 2 mm in width reduction.

18. Gemination of the upper left permanent central incisor

20. Supernumerary teeth.
▪ Results from disturbances during the initiation and proliferation stages of
dental development.
▪ Most commonly appear in mid-lines called mesiodens. Also occur as
supernumerary lateral incisors, extra premolars and paramolars.
▪ Single supernumerary usually appear as isolated incident but multiple
supernumerary may appear as part of syndromes. (cleidocranial dysplasia )
▪ It has great potential to disrupt normal tooth eruption and cause malposition
of teeth.

23. The maxillary midline is the most common location for a
supernumerary tooth, often called a mesiodens because of
its location.
It can be of almost any shape.
The supernumerary may block the eruption of one or
both the central incisors or, as in this girl, may separate them
widely and also displace the lateral incisors.

27. Maxillary mid-line supernumerary.

28. Maxillary mid-line supernumerary.

29. Interference with eruption.
▪ The eruption of permanent teeth may be prevented or delayed by the
failure of resorption of the overlying bone and primary tooth root
(Ankylosed primary molar ) , the presence of thick fibrotic gingiva, retained
primary tooth, supernumerary teeth, sclerotic bone overlying the crown of
the permanent tooth.
▪ Delayed eruption of some permanent teeth contribute to malocclusion due to
drift of other teeth into improper position in the arch. Usually the affected teeth
may be impacted or deflected from its normal path.
▪ Multiple unerupted teeth are usually associated with syndromic condition as in
cleidocranial dysplasia.

30. Interference of tooth eruption due to retained primary canine.

31. Ectopic eruption.
▪ Eruption of teeth in the wrong place due to malposition of a permanent tooth
bud. A tooth is said to be malposed if it resorbed the root of the other primary
tooth rather than the tooth that it has to replace.
▪ The maxillary first molar is most commonly affected. The permanent molar
may be ectopic if it erupts too far mesially and impacted against the distal
surface of second primary molar. This result in shortening of the arch length
and crowding.
▪ The transposition of teeth or bizarre eruption positions usually occurs between
the canine and lateral incisor or first premolar. The eruption of first premolar
in place of canine create esthetic problem and occlusal interference during
lateral movement of jaw because of the palatal cusp of premolar.

32. Ectopic eruption of maxillary first permanent molar

36. Ectopic eruption of the permanent maxillary first molar , apparently results
from mesial position or inclination of the tooth bud .
The result is a delay eruption of first molar and root resorption of the 2nd
primary molar.

37. Transposition of premolar with canine
Ectopic eruption of the permanent
maxillary canine

40. A, Mandibular 2nd premolars tend to erupt tipped distally and are prone to horizontal
impaction , especially if the first molar is lost prematurely but orthodontic correction is
possible
B , lf the first molar is lost prematurely and the unerupted 2nd premolars are tipped
distally ,the 2nd premolar can migrate back against the second molar, and may erupt in
tight contact with it.
C, Rarely the premolars migrate distally beneath the permanent molars, and
D, extreme migration into the mandibular ramus, even to the point that a premolar
is found at the top of the coronoid process, is possible.( D, CourtesyD r. K. Mitchell.)

41. Early loss of primary teeth.
▪ Most common clinical presentation in children. When a unit within the dental
arch is lost, the arch tends to contract and the space close due to drifting of
adjacent teeth.
▪ If the primary 2nd molar is lost prematurely, the first permanent molar drift
mesially. The first molar drifts mesially more rapidly and bodily in the absence
of occlusal contacts.
▪ Early loss of primary 2nd molar therefore significantly contribute to the
development of crowding in the posterior part of the dental arch.
▪ When the primary first molar or canine is lost prematurely, the space tends to
close by the distal drifting of the incisors. This cause crowding in the premolar
and canine region.
▪ If the loss is unilateral, the permanent teeth drift only on that side leading to
and asymmetry in the occlusion in addition to crowding.

42. Early loss of primary canine with distal drifting of incisors.

43. Early loss of primary canine with distal drifting of incisors.

44. Early loss of second primary molar with mesial drift of first permanent molar.

45. Early loss of the left second primary molar
led to marked mesial drift of the permanent
first molar .
Note the space closure on the patient's left
side ( the right side of this mirror image
photo ) , where almost no room for the
second premolar remains.
Mandibular arch , early loss of the left
primary canine led to a shift of the
permanent incisors linguallay and to the
left.

46. Secondary crowding in the lower arch following the early
loss of primary molars.
Note the crowding localised to the premolar region.

47. Traumatic displacement of teeth.
▪ Can occur in children as well as in adults with serious consequences
on the alignment and occlusion of teeth.
▪ Trauma to teeth can cause –
- Damage to permanent tooth buds from an injury to primary teeth.
- Drift of permanent teeth after premature loss of primary teeth.
- Direct injury to permanent teeth.
.

48. Traumatic displacement of lateral incisor.

49. ▪ Damage to permanent tooth bud would cause defects in the enamel if
injury occurs during the stage of crown formation.
Dilaceration – a bend or angle along the length of a root or disturbances in
root formation would occur if an injury occurs after the completion of crown
formation.
▪ If primary tooth is lost prematurely, the adjacent permanent tooth will be
drifted into the space causing localized crowding .
Permanent teeth may be displaced labially, palataly or intruded into the
socket after an injury. If treatment is not given immediately, the injured tooth
may remain in the displaced position. Ankylosis usually follows after an
injury so that treatment will be difficult or even impossible.

51. Dilacerated tooth.
Distortion of the root (dilaceration) of
the lateral incisor resulted from trauma
at an earlier age than displaced the
crown relative to the forming root.