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Transcript
Orthodontics I/9
Dr Jamal Naim
PhD in Orthodontics
Development of the oral Complex
Disturbances of Dental Development
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Developmental disturbances of teeth
Disturbances during initiation of tooth germs (tooth

number anomalies)
Disturbances during morpho-differentiation of tooth

germs (tooth shape and size anomalies)
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Disturbances during apposition of hard tissues
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Disturbances during eruption of teeth
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Disturbances during eruption of teeth
Concrescence: Cemental union of two teeth.
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Disturbances during eruption of teeth
Delayed tooth eruption is the most commonly encountered
deviation from the normal eruption due to local or systemic factors.
ETIOLOGY: Disturbances may occur in any of the phases of eruption:
1.Ectopic position of the tooth germ,
2.Obstacles in the eruption path,
3.Failures in the eruption mechanisms due to trauma, surgery,
congenital diseases or other causes.
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Disturbances during eruption of teeth
Local factors:

Mucosal Barriers-scar tissue due to trauma/surgery

presence of compact bone,

Supernumerary teeth

Odontogenic or Non Odontogenic Tumours or cysts

Ankylosis of deciduous teeth
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Premature loss of primary teeth
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Lack of resorption of deciduous tooth

Arch- Length deficiency and Lack of space
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Disturbances during eruption of teeth
Systemic factors:
Nutrition
Vitamin D deficiency
Endocrine disturbances: Hypothyroidism Hypoparathyroidism
Long term chemotherapy
Hiv Infection
Drugs: Phenytoin
Anemia
Prematurity/ Low birth weight
Genetic disorders: Amelogenesis Imperfecta, Apert syndrome,
ectodermal dysplasia, Cleidocranial dysplasia, Down syndrome
Familial/ Inherited
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Disturbances during eruption of teeth
Ankylosed teeth:
Fusion between cementum and bone
Teeth fail to erupt to the occlusal level
Most common cause of primary exfoliation
Mandible more affected than maxilla
Infraocclusion due to lack of growth
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2nd semester 2015-2016
Disturbances during eruption of teeth
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Ectopic eruption is a disturbance in which the tooth does
not follow its usual eruptive course.
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Occur most likely in the eruption of upper first molar.
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The early mesial drift of the 1st upper molar (leeway space)
with undermined resorption of the second primary molar
leads to its delayed eruption.
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Ectopic Eruption

Other Teeth could erupt ectopically due to different causes:
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Ectopic Eruption
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Undermined resorption & Ectopic Eruption
Other teeth could cause undermined resorption and stay
unerupted or erupt ectopically:
 Mandibular permanent lateral incisors initiating loss of the
primary canines.
 Maxillary permanent lateral incisor initiating loss of the
primary canine.
 Mandibular first permanent molar initiating loss of primary
second molar.
 Wisdom teeth initiating undermined resorption of the 2nd
permanent molars.
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Occlusion
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Definition
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Dental occlusion refers to the “relationship of the
maxillary and mandibular teeth when they are in
functional contact during activity of mandible
(dynamic) or in maximum intercuspation (static)”
Ricketts defined occlusion as, „the act of closure or
process of being closed.
Centric occlusion is the occlusion of opposing
teeth when the mandible is in centric relation.
Centric occlusion is the first tooth contact and may
or may not coincide with maximum intercuspation.
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Definition

Malocclusion is not a disease, but simply a variation
from the normal position.
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Ideal!
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Anatomic!
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Aesthetic!
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Normally functioning occlusion !
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Normal adult occlusion
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The dental arches vary from parabolic shape to
horse-shoe shape.
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Normal adult occlusion
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Coincident Midline
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Every tooth has contact with two opposing teeth
with the exeption of lower central incisors and lower
upper third molar.
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Normal adult occlusion

An overbite (vertical relationship) exists between
upper and lower teeth, the incisor overbite is
between ¼ to 1/3 of the crown height of the lower
Normal overbite
incisors.
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Deep bite
2nd semester 2015-2016
Normal adult occlusion

Maxillary incisors occlude on their palatal aspect with
the incisal edge of the lower incisors forming an
overjet (horizontal relationship) of 1 to 3 mm.
Normal overjet
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Increased overjet
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Negative overjet
Normal adult occlusion

Molar relationship: mesiobuccal cusp of upper 1st
molar occludes in the buccal groove of the lower 1st
molar.

Common occlusal plane

Compensatory curves: spee, wilson curve and
monson sphere
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Andrew's six keys of normal occlusion

120 patients, 1960-1964
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Without orthodontic treatment
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The dentition was attractive
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The occlusion was correct
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There is no need for orthodontic treatment
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I. Molar relationship:

The distal surface of the disto-buccal
cusp of the upper first permanent molar
occludes with the mesial surface of the
mesio-buccal cusp of the lower second
permanent molar.

The mesiolingual cusp of the upper first
molar seats in the central fossa of the
lower first molar.
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II. Crown angulation
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III. Crown inclination
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Labio-lingual, bucco-lingual torque
The crowns of the maxillary
incisors are so placed that the
incisal portion of the labial surface
is labial to the gingival portion of
the clinical crown.
In all other crowns, the occlusal
portion of the labial or buccal
surface is lingual to the gingival
portion.
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III. Crown inclination
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In the maxillary molars the
lingual crown inclination is
slightly more pronounced as
compared to the cuspids and
bicuspids.
In the mandibular posterior
teeth the lingual inclination
progressively increases.
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Andrew's six keys of normal occlusion
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IV. No rotations

V. No spaces (tight contacts)
VI. Flat occlusal planes:
Not deeper than 1,5 mm in the
mandible
excessive

flat
reversed
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Roth adding


Cusp/embrasure relationship buccally, cusp/fossa lingually
There should be 0.013 mm space between anterior teeth
in occlusion
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Malocclusion
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Definition

Malocclusion is not a disease but simply a variation
from the normal occlusion.


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
Malocclusions can be broadly divided into 3 types:
Individual tooth malpositions.
Malrelation of the dental arches or dentoalveolar
segments.
Skeletal malrelationships.
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