Development of dentition & occlusion / /certified fixed orthodontic courses by Indian dental academy

DEVELOPMENT OF DENTITION
&
OCCLUSION

INDIAN DENTAL ACADEMY
Leader in continuing dental education

www.indiandentalacademy.com

DEVELOPMENT OF TEETH:

•The embryonic oral cavity is lined by
stratified squamous epithelium- ORAL
ECTODERM

•Around 6th week of intra uterine life, the
infero-lateral border of the maxillary arch
& the supero-lateral border of the
mandibular arch show localized
proliferation of the oral ectoderm resulting
in the formation of a HORSE SHOE
SHAPED BAND of tissue called DENTAL
LAMINA.

•Deciduous teeth are formed by direct
proliferation of the dental lamina.
•The permanent teeth that replace the
primary teeth develop from its lingual
extension while the others develop from
its posterior extension called
SUCCESSIONAL LAMINA.


Stages of tooth development

•BUD STAGE
•CAP STAGE
•EARLY BELL STAGE
•LATE BELL STAGE
•ROOT FORMATION
•APICAL CLOSURE &
FORMATION OF
APICAL FORAMEN


The ectoderm in certain areas undergo proliferation to
form knob like projection that grow into the underlying
mesenchyme

which form the future ENAMAL ORGAN.
Ten such swellings are seen in each arch representing the
20 deciduous teeth


Development of OCCLUSION

STAGES:
•GUM PAD STAGE
•DECIDIOUS DENTITION STAGE
•MIXED DENTATION STAGE
FIRST TRANSITIONAL PERIOD
INTER TRANSITIONAL PERIOD
SECOND TRANSITIONAL PERIOD

•PERMANENT DENTATION STAGE

GUM PAD STAGE
•THIS IS THE PERIOD
AFTER BIRTH DURING
WHICH THE NEONATE
DOES NOT HAVE
ANY TEETH.
•IT USUALLY LASTS FOR 6
MONTHS AFTER BIRTH
•THE ALVEOLAR
PROCESSES AT THE TIME
OF BIRTH ARE KNOWN AS
GUM PADS.
•THEY ARE PINK, FIRM &
ARE COVERED BY A DENSE
LAYER OF FIBROUS
PERIOSTEUM.

• THEY ARE HORSE SHOE
SHAPED AND DEVELOP INTO 2
PARTS:
LABIO BUCCAL PORTION
LINGUAL PORTION
• THESE ARE SEPERATED FROM
EACH OTER BY A GROOVE CALLED
DENTAL GROOVE.
•THE GUM PADS ARE DIVIDED INTO 10 SEGMENTS BY
CERTAIN GROOVES CALLED TRANSVERSE
GROOVES.EACH OF THESE CONSISTS OF 1 DEVELOPING
DECIDIOUS TOOTH SAC.

•THE GINGIVAL GROOVE SEPERATES THE GUM PADS FROM
THE PALATE AND THE FLOOR OF THE MOUTH.

•THE TRANSVERSE GROOVE BETWEEN THE CANINE & 1ST
DECIDIOUS MOLAR SEGMENT IS CALLED THE LATERAL
SULCUS. www.indiandentalacademy.com

•The upper & lower gum pads are
almost similar to each other .
•The upper gum pad is both wider
as well as longer than the
mandibular gum pad.

•When the upper and lower gum pads are
approximated there is a complete over jet all
around.
•Contact occurs between the upper and lower gum
pads in the 1st molar region & a space exists
between the anterior region.
•This infantile open bite is considered normal & it
helps in suckling.

DECIDIOUS DENTATION
STAGE
THE PRIMARY DENTATION STAGE EXTENDS FROM
ERUPTION OF THE PRIMARY TEETH UNTIL THE
ERUPTION OF 1ST PERMANENT TOOTH AROUND 6
YEARS OF AGE.

CHARACTERSTICS OF
PRIMARY DENTATION:
•OVER BITE
•SPACING
•MOLAR RELATION


OVER BITE
• IT IS THE AMOUNT OF VERTICAL OVER LAP BETWEEN
MAXILLARY AND MANDIBULAR CENTRAL INCISORS.
• DEEP BITE MAY BE SEEN IN THE INITIAL STAGES OF
DEVELOPMENT.
• IT IS ASSENTUATED BY THE FACT THAT DECIDIOUS
INCISORS ARE MORE UPRIGHT WITH THE LOWER
INCISOR EDGES ALMOST CONTACTING THE UPPER
CINGULUM.
• THIS DEEP BITE REDUCES LATER DUE TO:
1. ERUPTION OF DECIDIOUS MOLARS
2. ATTRITIION OF INCISORS
3. FORWAD GROWTH OF MANDIBLE
• In about 24% of the children open bite is noted due to
various HABITS.

SPACING

 IN A PRIMARY DENTATION STAGE A CHILD
MAY HAVE GENERALISED SPACING; NO
SPACING; LOCALISED SPACING OR CROWED
DENTATION.

 GENERALISED SPACING OCCURS IN ALMOST
2/3RD OF THE CHILDREN REFERED TO AS
PHYSIOLOGICAL SPACES OR DEVELOPMENTAL
SPACES

 LOCALISED SPACES LIKE PRIMATE SPACE ARE
ALSO SEEN


PRIMATE SPACE
 ALSO CALLED SIMIAN SPACE
OR ANTHROPOID SPACE
 SEEN IN ABOUT 87% CASES
 IN THE MAXILLARY ARCH IT IS
PRESENT BETWEEN LATERAL
AND CANINE.
 IN THE MANDIBULAR ARCH
SEEN BETWEEN CANINE AND 1ST
DECIDIOUS MOLAR.
 THIS SPACE IS USED UP BY THE
DEVELOPING LARGER
PERMANENT TEETH.


NO SPACE

•NO SPACING BETWEEN THE PRIMARY
INCISORS GUARANTEES INSUFFICIEN ROOM
FOR THE PERMANENT INCISORS TO ERUPT
THUS RESULTING IN SEVERE CROWDING
REFERED TO AS HOLLYWOOD SMILE.


Molar Relation
• In the primary dentition the molar relation is
described in terms of TERMINAL PLANES.
• THE TERMINAL PLANES ARE THE DISTAL SURFACES
OF THE 2ND PRIMARY MOLARS. THESE TWO
TERMINAL PLANES CAN BE RELATED IN 3 WAYS:

1. FLUSH TERMINAL PLANE
2. MESIAL TERMINAL PLANE
3. DISTAL TERMINAL PLANE


FLUSH TERMINAL PLANE:
BOTH MAXILLARY & MANDIBULAR PLANES ARE
AT THE SAME LEVEL ANTERIO-POSTERIORLY.

MESIAL STEP TERMINAL PLANE:
MAXILLARY TERMINAL PLANE IS RELATIVELY
MORE POSTERIOR THAN THE MANDIBULAR
TERMINAL PLANE FORMING A MESIAL STEP

DISTAL STEP TERMINAL PLANE:
THE MAXILLARY TERMINAL PLANE IS
RELATIVELY MORE ANTERIOR THAN THE
MANDIBULAR TERMINAL PLANE.

ERUPTION SEQUENCE OF PRIMARY TEETH


MIXED DENTITION PERIOD
THIS STAGE STARTS WITH THE ERUPTION OF
THE PERMANENT 1ST MOLAR BY THE AGE OF 6
YEARS TO THE COMPLETION OF EXFOLIATION OF
ALL DECIDIOUS TEETH AT THE AGE OF 12-13
YEARS.

IN THE EARLY PART OF MIXED DENTITION
THERE MAY BE A TEMPORARY OPEN BITE USUALLY
DUE TO INCOMPLETE ERUPTION OF INCISORS OR
A PERSISTENT HABIT.


PHASES OF MIXED DENTITION
 FIRST TRANSITION PERIOD:
 EMERGENCE OF 1ST PERMANENT MOLAR
 INCISORS TRANSITION
 ESTABLISHMENT OF OCCLUSION
 INTER TRANSITION PERIOD
 BOTH SETS OF TEETH PRESENT
 4 PERMANENT INCISORS & 1ST PERMANENT MOLARS
PRESENT
 DECIDIOUS CANINES AND 1ST & 2ND MOLARS
 SECOND TRANSITION PERIOD
 EMERGENCE OF BICUSPIDS, CUSPIDS,& SECOND
PERMANENT MOLAR.
 www.indiandentalacademy.com
ESTABLISHMENT OF OCCLUSION

FIRST TRANSITIONAL PERIOD
Emergence of 1st permanent molar:
ERUPTS BY AROUND 6TH YEAR OF LIFE
ITS LOCATION & RELATIONSHIP DEPENDS UPON THE
DISTAL SURFACE RELATIONSHIP BETWEEN UPPER AND
LOWER SECOND DECIDIOUS MOLARS.
THE DISTAL SURFACE OF THESE DECIDIOUS 2ND
MOLARS GUIDE THE ERUPTING PERMANENT MOLAR
INTO 3 RELATIONS:


10%

29%

42%


INCISAL LIABILITY
•THE UNERUPTED PERMANENT INCISORS ARE
LARGER THAN THE DECIDIOUS INCISORS.
•THIS IS REFERED TO AS INCISAL LIABILITY.

ARCH INCISAL
LIABILITY
MAXILLA 7 mm
MANDIBLE 5 mm


INCISAL LIABILITY IS OVERCOME BY THE
FOLLOWING FACTORS:

1. UTILIZATION OF INTERDENTAL SPACES
SEEN IN PRIMARY DENTITION.
2. INCREASE IN INTER-CANINE WIDTH
3. CHANGE IN INCISOR INCLINATION


INTER-TRANSITIONAL PERIOD

 THIS IS A LATENT PERIOD WITH NO
EXCHANGE OF TEETH TAKING PLACE.
 PERMANENT INCISORS AND 1ST MOLAR
ARE PRESENT.
 DECIDIOUS CANINE, 1ST & 2ND MOLARS
ARE PRESENT
 BY THE END OF THIS STAGE ALL THE
TEETH ARE IN PROPER OCCLUSION.


SECOND TRANSITION PERIOD
 CHARACTERISED BY REPLACEMENT OF
DECIDIOUS CANINES & MOLARS BY
PREMOLARS AND PERMANENT CUSPIDS
RESPECTIVELY.

 ERUPTION OF THE NON SUCCEDENOUS
TEETH i.e., 2ND MOLARS.

 ESTABLISHMENT OF PROPER OCCLUSION


LEEWAY SPACE OF NANCE
THE COMBINED MESIO DISTAL
WIDTH OF THE PERMANENT CANINES
AND PREMOLARS IS USUALLY LESS
THAN THAT OF THE DECIDIOUS
CANINES & MOLARS.

THIS SURPLUS SPACE IS CALLED AS
LEEWAY SPACE OF NANCE.
ARCH LEEWAY SPACE
MAXILLARY 1.8 mm
(0.9 mm in each arch)

MANDIBULAR 3.4 mm
(1.7 mm in each arch)

UGLY DUCKLING STAGE
AS THE DEVELOPING PERMANENT CANINES ERUPT, THEY
DISPLACE THE ROOTS OF THE LATERAL INCISORS MESIALLY AND
INTURN ON TO THE CENTRAL INCISORS.
THIS CAUSES THE FLARING UP OF THE INCISOR CROWNS.
THUS CAUSING A MIDLINE DIASTEMA
THIS SITUATION IS BEING DESCRIBED BY BROADBENT AS UGLY
DUCKLING STAGE.
THIS OCCURS AROUND THE AGE OF 8-9 YEARS
THIS CORRECTS BY ITSELF WHEN THE PERMANENT CANINE
ERUPTS COMPLETELY.


PERMANENT DENTITION STAGE
 ALL THE PERMANENT TEETH ARE FORMED
AROUND BIRTH.

 THIS STAGE BEGINS WITH THE EXFOLIATION
OF LAST PRIMARY TEETH AND ERUPTION OF
ALL PERMANENT TEETH EXCEPT 3RD MOLAR.

 THE IMPORTANT CHARACTERSTICS OF NORMAL
OCCLUSION IN PERMANENT DENTITION WERE:

 DESCRIBED BY ANDREW’S IN 1972 AS 6 KEYS OF
OCCLUSION.


ERUPTION SEQUENCE OF PERMANENT TEETH


ANDREW’S 6 KEYS OF OCCLUSION

KEY 1: MOLAR INTER ARCH
RELATIONSHIP

KEY 2: MESIO DISTAL CROWN
ANGULATION

KEY 3: LABIO LINGUAL CROWN INCLINATION


KEY 4: ABSENCE OF ROTATION

KEY 5: TIGHT CONTACTS

KEY 6: CURVE OF SPEE


MOLAR RELATIONS
• PROPOSED BY E H ANGLE IN 1899
DEPENDING ON 1ST MOLAR
RELATIONSHIP FOR PERMANENT
DENTITION

 CLASS 1
 CLASS 2 DIV 1
DIV 2
 CLASS 3 TRUE
PSEUDO

COMPENSATORY CURVES
CURVE OF SPEE: ANTERIO POSTERIOR
CURVE PASSING THROUGH THE BUCCAL
CUSPS OF PREMOLARS AND MOLARS ON
TO THE ANTERIOR BORDER OF RAMUS TO
END ON THE CENTER OF CONDYLE.
CURVE OF WILSON: IT IS A MEDIO
LATERAL CURVE PASSING THROUGH
BUCCAL TO PALATAL AND THEN PALATAL
TO BACCAL OF THE OTHER SIDE.
CURVE OF MONSON: IT IS A
COMBINATION OF BOTH MEDIO LATERAL
AND ANTERIOPOSTERIOR CURVE TO
FORM A 8 INCH SPHERE WITH CENTER ON
GLABELLA.

"Live as if you were to die
tomorrow.
Learn as if you were to live
forever."
-Mahatma Gandhi

THANK YOU

INDIAN DENTAL ACADEMY
Leader in continuing dental education

Development of dentition & occlusion / /certified fixed orthodontic courses by Indian dental academy

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