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(9+10) Eruption & Development of dentin after birth (Importance of…
(9+10)
Eruption
&
Development of dentin
after birth
Erruption:
Process which tooth emerge through the soft tissue of jaws and the olying mucosa to enter into the oral cavity
(Multi-factorial)
Phase 1: Pre-erruptive
Form, Move
Tooth germ grows (Calcification)
Jaw becomes crowded
Lengthening of jaw posteriorly
Permanent second molar tooth germs move backwards
Anterior tooth germs move forward
*Posterior teeth: from side by side to under baby teeth between divergent roots
*Anterior teeth move lingually of the roots of their deciduous teeth
Phase 2: Erruptive Phase:
Root form, Occlusal plane
Initiation of root formation
Permanent teeth do not erupt until crown is formed
Gubernacular cord and canal. & Dental follicle. It is like a pathway for the tooth to erupt. Strand of epithelium (Dental Follicle), causes thinning of mucosa and resorption of bone.
Dental follicle release factors that cause osteoclastic activity . Remodling of bone wall of crypt by esteoblasta and clasts
Gubernacular cord, CT overlaying toth connect with lamina propri. Deegeneration of CT (dec. in blood vessels and degerate nerves) by macrophages. Macr[hages destory cells and thin mucosa.
PDL Form
Phase 3:Post erruptive phase
Accomodation for growth
Compensation of occlusal wear
Accomodation for interproximal wear
Mesial Drift:
After crown comes up
Formation of PDL
Initial fibre deevelopment
Secondary fibre development
FUrther fibre development
Formation of Bone
Intraosseous phase: 1-10um/day, Extraosseous phase: 75um/day
Shedding/exfoliation:
process which baby teeth drop out of mouth by gradual resorption by roots of baby teeth, PDL also becomes removed. - Why? Change over dentition from primary to adult dentition
Osteoclast/bone remodelling
Ondotoclast (Cementoclast; dentinoclast)
Resorption of soft tissue
Soft tissue makes primary teeth appear pink
Clinical
Hypodontia
Overretained primary teeth
Clinical Implication
Thumbsuck (Upward force of palate)
Muscular Force (Cancrum oris)
Supra-eruption and tilting of teeth
Theories
Myth: Teeth errupt because root formation occurs (X) because teeth can errupt without roots (radiotheraphy) may assist but not prerequsite
Vascular pressure: Difficult to prove
Periodontal ligament helps push teeth into occlusion: Rich in fibroblast causes contractions. There are instances where teeth have PDL but dont errupt. (Primary failure of erruption)
Bone remodelling and effect of dental follicle causes erruption: cause changes --> Signalling processes --> osteoclast resorpt bone macrophage break down soft tissue. (Found animal, removed tooth, kept dental folicle intact replace tooth with metal object) dental follicle errupted into the mouth. Proves that follicle is the intitiative body for erruption
Implications
Osteopetrosis
Sequence and chronology of tooth calcification and eruption
Chronological enamel hypoplasia
Green teeth - Severe neonatal hyperbilirubinemia
Post-natal development
Birth to
Full Primary
(0 - 3 years)
1st ITP
: (3 - 6 years)
Tooth buds of premolars begin to form
Spacing
Shift
Early Molar Shift
Primate
/
Anthropoid
/
Simian
Space
Interdigitation of opposing canines
Mesial to maxillary canine (Between Incisor & Canine)
Distal to mandibular canine (Between Canine & First Molar)
Seen in primates
Early Mesial Shift
When
: Early mixed dentition
Spacing
: Flushed terminal (5's)
Eruption of 6
Pushes primary molars
forward
Closes existing space
Closes
Primate space
(btwn primary molars)
Decreases arch length
Late Mesial Shift
When
: Late mixed dentition
Spacing
: No spacing
Eruption of 6
:
After primary molars exfoliate
,
permanent shift
Unable to close space
Migrate mesially
Use up
Leeway space
Leeway space
:
Primary molars + Primary canine
Permanent Premolar + Permanent canine
Sum of primary > permanent
1.8mm Maxilla
3.4mm Mandible
Terminal Plane
(Impt for
Occlusion
)
Flushed Terminal / Vertical plane
Aligned occlusion
End-End or Class 1
Distal Step
Distal occlusion space between Primary 4s
Class II or End-End
Mesial Step
Mesial occlusion space between Primary 4s
Class 1 or 3
Relevance
: Permanent 6s depends on Primary 5s
Reason
: Mandible grows more than Maxilla
Space for 6's
Maxilla Tuberosity Aposition
Posteriorly
Buccally
Alveolar
Mandible Ramal
Resorption
: Anterior
Apposition
: Posterior
Mixed Dentition
2nd ITP
(8 - 10years)
Maxillary canines lateral to nose
Mandibular canines border of the mandible
Space for 6's
Maxilla Tuberosity Aposition
Posteriorly
Buccally
Alveolar
Mandible Ramal
Resorption
: Anterior
Apposition
: Posterior
Role of tongue & lip:
Mandibular incisor move into position
Mesial drift
2nd TP
(10-12 years)
Replacement of primary molars & canines
Ugly duckling stage is corrected
1st TP
(6 - 8 years)
Characterized by Permanent 6s
Incisal Liability
Permanent larger than primary
Maxillary
need
7mm
more space
Mandibular
need
6mm
more space
Incisal Liability overcome by
:
1)
Interdental spacing
between primary incisors
2)
Intercanine width
growth
3)
Labial positioning
of erupted incisors (arc length)
4)
Favourable
Size Ratio: Large primary; Small permanent
Tooth Classifications
Successional Teeth
Permanent teeth replace primary teeth
Anterior + Premolars
Accessional Teeth
Permanent teeth that erupt posterior to primary teeth
Molars
Adult Dentition
(12 years)
Ugly Duckling Stage
(7 - 12year)
Usually self-correcting by (10 -11 years)
Erupting canine guides erupted central incisors
Calcification
: Neonatal Lines
Hypomineralized
Darker than striae of retzius (weekly)
Identify enamel before and after birth
Forensic
Child death before/after birth
Child life after birth
Infanticide/Stillbirth
High Fever
Enamel hypoplasia
Tetracycline (Antibiotics) staining
Intrinsic staining
Not for pregnant women
Not for children
under 8
Importance of Primary Teeth
3) Digestion
1) Succession space
5) Growth of jaw
4) Speech
2) Aesthetic
S-A-D-S-G
Factors affecting occlusion
General factors
Skeletal
Musclar
Dental
Hypodontia: Affect occlusion
Local factors
Trauma
Mallposed crown
Dilacerated root
Obstruction (Superumerary Teeth)
Shedding
Resorption of
roots
Loss of
PDL
Pre-eruptive Phase
Types of movement
Total bodily movement
Growth in one part of tooth germ remains fixed while the rest continues to grow leading to change in the centre of tooth germ
Develop on lingual aspect of deciduous
Muscle Function Determines
PDL Bone and Other parts
Mechanism of Tooth Movement
Root
Vascular
Bone
Consequence Mesial Drift, Dental Tipping, Mastication on gap
