development of occlusion

DEPT. OF PEDODONTICSGOVT. COLLEGE OF DENTISRY, INDORE

SUBMITTED BY:PALLAVI TRIPATHIARVIND UIKEYBDS FINAL YEAR

Development of Occlusion

INDEX Introduction Evolution Periods of occlusal development Neo-natal period. Primary dentition period. Mixed dentition period. Permanent dentition period Conclusion References

INTRODUCTION Term occlusion is derived from the Latin

word, “occlusio” “defined as the relationship between all the

components of the masticatory system in normal function, dysfunction and parafunction.”

An ideal occlusion is the perfect interdigitation of the upper and lower teeth, which is a result of developmental process consisting of the three main events, jaw growth, tooth formation and eruption

EVOLUTION To develop a functional occlusion it became

necessary for the teeth and bones to develop synchronously. Over a period of time there was loss or fusion of cranial and facial bones, the number of bones have reduced and the dental formula has also undergone changes

PERIODS OF OCCLUSAL DEVELOPMENT Occlusal development can be divided into the

following development periods:

o Neo-natal period.o Primary dentition period.o Mixed dentition period.o Permanent dentition

period.

NEONATAL PERIOD(LASTS UPTO 6 MONTHS AFTER BIRTH)

GUM PADS

• Alveolar processes at the time of birth- gum pads. • Pink in colour, firm and are covered by a dense layer of fibrous

periosteum

Gum Pads

The gum pad soon gets segmented by a groove called transverse groove, & each segment is a developing tooth site.

The pads get divided into ‘labio-buccal’ & ‘lingual portion’, by a dental groove.

The groove between the canine and the 1st molar region is called the lateral sulcus, useful for judging the inter arch relationship at a very early stage

RELATIONSHIP OF GUM PADSoMandibular lateral sulci lies posterior to maxillary lateral sulci.

o Mandibular functional movements are mainly vertical, and to a little extent antero-posterior. Lateral movements are absent

NEONATAL JAW RELATIONSHIP A ‘precise bite’ or jaw relationship is not yet

seen. Therefore, neonatal jaw relationship cannot be used as a diagnostic criterion for reliable prediction of subsequent occlusion in the primary dentition.

STATUS OF DENTITION AT BIRTH

Natal,Neonatal & Pre-erupted Teeth

Natal Teeth (Present at Birth)Neonatal Teeth (Erupted during the 1st month)Pre-erupted (Erupting during the 2nd & 3rd month)

Clinical Significance

Difficulty to mother during breast feeding

Remove only if they are superneumeraries or if they

are loose enough that there is danger of exfoliation

One week old boy with two neonatal teeth

PRIMARY DENTITION STAGE

(From around the 6th month to 6 years)

SEQUENCE OF ERUPTION

A B D C E

Primary(upper)

First evidence of calcification(Weeks in utero)

Crown completed(months)

Eruption(months)

Root completed(years)

Central 14 (13-16) 11/2 10 11/2

Lateral 16 21/2 11 2Canine 17 9 19 31/4

1st molar 151/2 6 16 21/2

2nd molar 19 11 29 3

Chronology of Primary Dentition

Primary(Lower

First evidence of calcification(Weeks in utero)


Eruption(months)


Central 14 (13-16) 21/2 8(6-10) 11/2

Lateral 16 3 13( 10-16)

11/2

Canine 17 9 20(17-23)

31/4

1st molar

151/2 51/2 16( 14-18)

21/4

2nd molar

18 10 27 3

Some of the characteristic clinical features of deciduous dentition are:1. Both the dental arches are half round in shape

or ovoid.2. Almost no curve of Spee is present.3. Shallow cuspal interdigitation.4. Slight overjet.5. Deep bite.6. Vertical inclination of the incisors.7. Spaced dentition.8. Different maxillo-mandibular relations like

flush, mesial & distal terminal planes.

18

MIXED DENTITION PERIOD(AROUND 6 YEARS- 12 YEARS)

The mixed dentition period can be divided into three phases:o First transitional period.o Inter-transitional period.

o Second transitional period.

FIRST TRANSITIONAL PERIOD The first transitional period is characterized

by the emergence of the first permanent molars and the exchange of deciduous incisors with the permanent incisors.

Emergence of first permanent molars The mandibular first molar is the first permanent

tooth to erupt at around 6 years of age. The location and relationship of the first

permanent molars depends much upon the distal surface relationship between the upper and the lower second deciduous molars. 20

The mesio-distal relation between the distal surfaces of the upper and lower second deciduous molars can be of 3 types:

A. Flush terminal planeB. Mesial step terminal planeC. Distal step terminal plane

.

21

A. Flush terminal plane, B. Distal step terminal plane, C. mesial terminal plane

EXCHANGE OF INCISORSDuring the first transitional period the deciduous incisors are replaced by the permanent incisors. The mandibular central incisors are usually the first to erupt. The permanent incisors

are considerably larger than the deciduous teeth they replace. This difference between the amount of space needed

for the accommodation of the incisors and the amount of space available for this, is called ‘Incisal liability’.

The incisal liability is roughly about 7.6 mm in the maxillary arch & about

6 mm in the mandibular arch.

TRANSITION OF INCISORSThe incisal liability is over come by the

following factors:Interdental physiological spacing in the primary incisor

region. (4 mm in maxillary arch & 3 mm in mandibular arch)

Increase in inter-canine arch width: Significant amount of growth occurs with the eruption of

incisors and canines.

Increase in anterior length of the dental arches:

Permanent incisors erupt labial to the primary incisors to obtain an added space of around 2-3 mm.

Change in inclination of permanent

incisors:Primary teeth are upright but

permanent teeth incline to the labial surface, thus

decreasing the inter-incisal angle from about 151

degrees in the deciduous dentition to 124 degrees in

the permanent dentition. This increases the arch perimeter.

INTER-TRANSITIONAL PERIOD In this period the maxillary and mandibular

arches consist of sets of deciduous and permanent teeth.

Between the permanent incisors and the first permanent molars are the deciduous molars and canines.

This phase during the mixed dentition period is relatively stable and no change occurs.

28

Fig: OPG of mixed dentition

29

SECOND TRANSITIONAL PERIOD The second transitional period is

characterized by the replacement of the deciduous molars and canines by the premolars and permanent cuspids respectively.

The combined mesio-distal width of the permanent canines and premolars is usually less than that of the deciduous canines and molars. The surplus space is called leeway space of Nance.

30

LEEWAY SPACE OF NANCE

• Described by Nance in 1947

Maxilla: 0.9 mm/segment = 1.8 mm. Mandible: 1.7 mm/segment =

3.4mm.

UGLY DUCKLING STAGE Sometimes a transient self-correcting

malocclusion is seen in the maxillary incisor region between 8 to 9 years of age.

This is a particular situation seen during the eruption of the permanent canines.

As the developing permanent canines erupt they displace the roots of the lateral incisors mesially. This results in transmitting 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.

This condition usually corrects by itself when the canines erupt and the pressure is transferred from the roots to the coronal area of the incisors.

32

PERMANENT DENTITION PERIOD Permanent dentition forms within the jaws

soon after birth, except for the cusps of the first permanent molars, which form before birth.

Permanent incisors develop lingual or palatal to the deciduous incisors and move labially as they erupt.

Premolars develop below the diverging roots of the deciduous molars.

34

CHRONOLOGY OF HUMAN PRIMARY TEETH

36

Permanent(Upper)

First evidence of calcification ( weeks in utero)


Eruption( months)


Central 3-4 mo 4-5 yr 7-8 yr 10Lateral 10-12 mo 4-5 yr 8-9 yr 11Canine 4-5 mo 6-7 yr 11-12 yr 13-151st premolar 11/2-13/4 yr 5-6 yr 10-11 yr 12-13

2nd premolar 2-21/4 yr 6-7 yr 10-12 yr 12-14

1st molar At birth 21/3-3 yr 6-7 yr 9-10

2nd molar 21/3-3 yr 7-8 yr 12-13 yr 14-16

3rd molar 7-9 yr 12-16 yr 17-21 yr 18-25

Chronology of Permanent Dentition

ERUPTION SEQUENCE The frequently seen sequences in the

maxillary arch (permanent):6-1-2-4-3-5-7 or6-1-2-3-4-5-7

The frequently seen sequences in the mandibular arch (permanent):

6-1-2-3-4-5-7 or6-1-2-4-3-5-7

39

THE PERMANENT DENTITION

The permanent incisors develop lingual to the deciduous incisors and move labially as they

erupt.


The premolars develop below the diverging roots of the deciduous molars.


At approximately 13 years of age all

permanent teeth except third molars are fully erupted.

Vertical overbite of about one third the

clinical crown height of the mandibular central incisors. Overjet and over bite decreases

throughout the second decade of life due to

greater forward growth of the mandible.

CONCLUSIONIn its simplest of definition, occlusion is the way the maxillary and mandibular teeth articulate, but in reality dental occlusion

is a much more complex relationship, because it not only involves the study of the teeth, but also their morphology and

angulations, the muscles of mastication, the skeletal structures, the temporomandibular joint, and the functional jaw

movements. In addition to this, it also involves the relationship of the teeth in centric occlusion, in centric relation, and even during function, and because all this, requires neuromuscular

coordination, occlusion should also involve an understanding of the neuromuscular systems, it is the responsibility of we ‘pedodontists’ to have an adequate knowledge on these

subjects, to help us differentiate abnormal from normal, before initiating therapy.

REFERENCES Orthodontics The Art and Science by S. I.

Bhalajhi Textbook of Pediatric Dentistry by Nikhil

Marwah Textbook of Pedodontics by Shobha Tandon

45

Thank You.

development of occlusion

Health & Medicine