devp of primary dentition / orthodontic courses by indian dental academy

DEVELOPMENT DEVELOPMENT OF DENTITIONOF DENTITION

INDIAN DENTAL ACADEMY

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1.PRE-DENTAL PERIOD(Birth- 6 months)

a. Gum padsb. Precociously erupted primary teeth

2. DECIDUOUS DENTITION PERIOD(6 months- 6 years)

3. MIXED DENTITION PERIOD(6 years- 12 years)

4. PERMANENT DENTITION PERIOD

(12 years onwards)


1. PRE-DENTAL PERIOD- Birth- 6 months

a.GUM PADS-The alveolar processes at the time of birth are known as gum pads


The gum pads are pink, firm and resilient and are covered by a dense layer of fibrous periosteum.Upper gum pad : Horse shoe shapedLower gum pad : ‘U’ shapedDevelop in 2 parts:

a. Labio-buccal portion b. Lingual portion

The 2 portions are separated by a groove called DENTAL GROOVE


a. LABIO-BUCCAL PORTION-

Differentiates first and grows more rapidly.Divided into 10 segments by grooves called TRANSVERSE GROOVES.Each segment consist of one developing tooth sac.The transverse groove between canine and 1st deciduous molar is called the LATERAL SULCUS.


b. LINGUAL PORTION

Differentiates later. Remains relatively smooth. The upper and lower gum pads are

separated from the palate and the floor of the mouth respectively by a groove called GINGIVAL GROOVE.


RELATIONSHIP OF GUM PADS.


Upper gum pad is wider and longer than the lower gum pad . Thus when approximated, complete overjet present all around.

Anterior open bite present at rest with contact only in the deciduous 1st molar region.

Tongue protrudes anteriorly through this space- helps in suckling

Permits eruption of lower incisors without impingement on upper gum pad.

Lateral sulcus of mandibular arch is normally distal to that of maxillary arch.


b. PRECOCIOUSLY ERUPTED PRIMARY TEETH-1.NATAL TEETH- Teeth that are present at the time of birth are called natal teeth. Usually mandibular incisors. Show familial tendency.


2.NEO-NATAL TEETH-

Teeth that erupt during 1st month of age are called neonatal teeth.

Mostly seen in mandibular incisor region and show familial tendency.


DEVELOPMENT OF PRIMARY DENTITION-

Initiation of primary tooth buds occurs during 6 weeks of intrauterine life.

Primary teeth begin to erupt at about 6 months of age.

Eruption of all primary teeth is completed by 24- 30 months of age


ERUPTION AGE AND SEQUENCE OF DECIDUOUS DENTITION -

SEQUENCE: A- B- D- C- E

The mandibular central incisors are the 1st to erupt at around 6-7 months of age.

- Timing of tooth eruption is highly variable.

- A variation of 3 months from the mean age has been acceptable as normal.


ERUPTION AGES OF PRIMARY TEETH

ARCH TOOTH MONTHSMAXILLARY A 10 (08-12)

B 11 (09-13)C 19 (16-22)D 16 (14-18)E 29 (25-33)

MANDIBULAR A O8 (06-10)B 13 (10-16)C 20 (17-23)D 16 (14-18)E 27 (24-30)

Source –Wheelers 8th edition.www.indiandentalacademy.com

NORMAL FEATURES OF PRIMARY DENTITION-

1. PHYSIOLOGICAL SPACES/ DEVELOPMENTAL SPACES:

Usually seen in deciduous dentition to accommodate the larger permanent teeth in the jaws.

Absence of spacing in deciduous dentition is an indication that crowding of teeth may occur in permanent dentition.


2. PRIMATE / SIMIAN / ANTHROPOID SPACES- Present mesial to deciduous maxillary canine and distal to mandibular canine.

Commonly seen in primates.

Help in interdigitation of opposing canines.

Used for EARLY MOLAR SHIFT.


3.ALMOST VERTICAL INCLINATION OF INCISORS

4.SHALLOW OVERJET AND OVERBITE


TERMINAL PLANE RELATIONSHIP-

The mesio- distal relation between the distal surfaces of the upper and lower 2nd deciduous molars is called the TERMINAL PLANE

BAUME’S CLASSIFICATIONa. FLUSH TERMINAL PLANE – (76%)

- Distal surfaces of the upper and lower 2nd deciduous molars are in the same vertical plane.

- This is regarded as normal relation in deciduous dentition.


b. MESIAL STEP- (14%)

Distal surface of mandibular deciduous 2nd molar is mesial to the distal surface of maxillary deciduous 2nd molar.


c. DISTAL STEP- (10%)Distal surface of mandibular deciduous 2nd molar is more distal than the distal surface of maxillary 2nd molar.


The primary dentition is usually established by 3 years of age.

Between 3-6 years , the dental arch is relatively stable and very few changes occur in the dentition in this period.

The deciduous dentition period lasts for 6 years of age till the eruption of permanent 1st molars which marks the beginning of the mixed dentition period.


Maturation of oral functionsNew born infants are obligatory nasal breathers, at a later period breathing through mouth becomes a physiologically possible.Once airway is established, next physiologic priority is to obtain milk.It is accomplished by 2 maneuvers- 1. Suckling. (not sucking) 2. Swallowing.

Maturation of oral function has a gradient from front to back.Suckling reflex normally disappears during 1st year of life.



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devp of primary dentition / orthodontic courses by indian dental academy

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