Development of dentition and
occlusion
Dr. Zuber Ahamed Naqvi
OBJECTIVES
 Stages of tooth development
 Pre – dental period
 The deciduous dentition period
 The mixed dentition period
 The permanent dentition
 The permanent dentition
 period
 The mixed dentition period
• Stages of tooth development (based on shape
of enamel organ):
• Bud stage
• Cap stage
• Bell stage
Tooth formation
Primary epithelial bands: Horseshoeshaped bands.
Two subdivisions:
vestibular lamina and dental lamina
vestibule
dental arches
BUD STAGE
1. Tooth bud
2. Oral epithelium
3. Mesenchyme
Cap Stage
• Histodifferentiation (differentiation
of tissues)
• Morph differentiation
• Dental papilla
dentin and pulp
tissue (mesenchymal origin)
• Basement membrane separating the
dental organ and the dental papilla
becomes the future site for the
dentinoenamel junction (DEJ)
• Remaining mesenchyme surrounds
the dental/enamel organ and
condenses to form the dental sac or
the dental follicle
Bell Stage
Early bell stage
Advanced bell stage
• Bell-like shape
•
differentiation produces four types of cells within the enamel/dental organ
–
–
–
–
1. inner enamel epithelium
2. outer enamel epithelium
3. stellate reticulum
4. stratum intermedium
The dental papilla undergoes differentiation and produces two types of cells
– 1. outer cells of the DP – forms the dentin-secreting cells (odontoblasts)
– 2. central cells of the DP – forms the primordium of the pulp
ROOT FORMATION
• Takes place as the crown is
completely shaped and the
tooth begins to erupt
• Root formation is through
the formation of a cervical
loop (CL)
• Two layers consisting of Iner
enamel epithelium and
outer enamel epithelium
• The CL begins to grow down
into the dental sac
• It forms a Hertwig's root
sheath
Periodontal ligament
• The mesenchyme of the
dental sac condenses to
form the periodontal
ligament
• The cells of the
disintegrating Hertwig root
sheath develop into discrete
islands of epithelial cells
– become epithelial rests
of Malassez
Development of occlusion
Occlusion is the relationship of the mandibular and maxillary
teeth when closed or during excursive movements of the
mandible; when the teeth of the mandibular arch come into
contact with the teeth of the maxillary arch in any functional
relationship.
Periods of occlusal development
• 1. Pre – dental period
• 2. The deciduous dentition
• period
• 3. The mixed dentition period
• 4. The permanent dentition
• period
GUM PADS
• The alveolar processes at the time
of birth are known as gum pads
• The gum pads are pink, firm &
covered by a dense layer of
fibrous periosteum
• They are HORSE-SHOE shaped &
develop in two parts:
(1) the labio-buccal portion &
(2) the lingual portion
• The two portions of the gum pads
are separated from each other by a
groove called the dental groove
dental groove
GUM PADS
• Lateral sulcus-The transverse
groove b/w canine & first deciduous
molar segment .
• The lateral sulcus of the mandibular
arch is normally more DISTAL to
that of the maxillary arch
• The gum pads are divided into TEN
SEGMENTS by certain grooves
called TRANSVERSE GROOVES
• • Each of these segments consist of
one developing deciduous tooth sac
• • The gingival groove separates the
gum pads from the palate & floor of
the mouth
• There is a complete overjet all around
• (1) Contact occurs b/w the upper & lower gum pads in the
first molar region
• (2) A space exist b/w them in the anterior region
• This infantile open bite is Open bite considered normal & it
helps in suckling
NATAL TEETH
Neonatal teeth
• Teeth that are present
at the time of birth are
called NATAL TEETH
Teeth that are erupt during the
first month of age are called
Neonatal teeth
The natal & neonatal teeth are mostly located in the mandibular incisor
region & Show a familial tendency.
The deciduous dentition period
• Primary teeth begin to erupt at the age of 6 months.
• The eruption of all primary teeth is completed by 2.5 to 3.5
years of age when second deciduous molars come into
occlusion.
The mixed dentition period
• The mixed dentition period begins at
approximately 6 years of age with the
eruption of the first permanent molars.
primary + permanent teeth (6 Y – 12 Y)
Classified into three phases:
• 1. First transitional period
• 2. Inter-transitional period
• 3. Second transitional period
First transitional period
The first transitional period is characterized by :
(1) the emergence of the first permanent molars &
(2) the exchange of the deciduous incisors with the permanent
incisors
The mesio-distal relation b/w the Distal
Surfaces of the upper & lower second
deciduous molars can be of three types :
• FLUSH PLANE
• MESIAL STEP
• DISTAL STEP
•
Flush to Class I molar relation
This occurs by(1) utilization of the physiological
spaces and primate spaces( early
shift)
(2) & leeway space in the lower arch (
late shift)
(3) by differential forward growth of
the mandible
Inter – transitional period
• In this period the maxillary & mandibular
arches consist of Sets of deciduous &
permanent teeth
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Second transitional period
• Leeway space of Nance - The combined mesio-distal width of the
permanent canines & premolars is usually less than that of the deciduous
canines & molars
Maxillary arch - 1.8mm (0.9 mm in each quadrant of the arch)
Mandibular arch- 3.4mm (1.7 mm in each quadrant of the arch)
The normal leeway space according to Moyers is 2.6 mm in the maxilla
and 6.2 mm in the mandible.
• The ugly duckling stage:
• As the developing permanent canines erupt, they displace the
roots of the lateral incisors mesially.
• This result in transmitting of the force on to the roots of the
central incisors which also get displaced mesially
• A resultant distal divergence of the crowns of the two central
incisors causes a midline spacing
• This situation has been described by Broadbent as the ugly
duckling stage.
The permanent dentition period
• The eruption sequence of the permanent dentition may exhibit variation
• The frequently seen sequences in the maxillary arch are: – 6 – 1 – 2 – 4 – 5 –
3 – 7 or – 6–1–2––4 -3–5–7
In case of the mandibular arch the sequence is –
6 – 1 – 2 – 3 – 4 – 5 – 7 or – 6–1–2–4–3–5–7
• References:
Contemporary orthodontics. 5th edition.
William R Proffit
Orthodontics : the art and science. 4th edition.
S I Bhalaji
Dentistry for the child and adolescent. 8th
edition. Ralph E. McDonald, David R. Avery,
Jeffrey A. Dean