DEVELOPMENT OF

OCCLUSION

INTRODUCTION

• Latin word, “occlusio” means relationship between all

components of the masticatory system.

• Ideal occlusion is perfect interdigitation of the upper

and lower teeth.

• The occlusion is regarded as a ‘dynamic’ rather than

‘static’ interrelation between the facial structures.

Periods of Occlusal Development

Occlusal development can be divided into the following

development periods:

• Neo-natal period.

• Primary dentition period.

• Mixed dentition period.

• Permanent dentition period.

NEONATAL PERIOD

➢Lasts upto 6 months after birth.

GUM PADS- alveolar processes at time of birth

➢Pink in color, firm. Covered by dense layer of fibrous

periosteum.

➢Segmented by groove- transverse groove & each segment is

a developing tooth site.

➢Pads get divided into labiobuccal & lingual portion by dental

groove.

➢Groove between canine & 1st molar region- lateral sulcus,

useful for judging inter-arch relationship at early stage.

Upper gum pad- horse

shoe shaped & shows:

• Gingival groove: separates

gum pad from the palate.

• Dental groove: starts at the

incisive papilla, backward till

gingival groove in canine

region & then moves laterally

to end in the molar region.

• Lateral sulcus

Lower gum pad- U‟

shaped and rectangular,

characterized by:

• Gingival groove: lingual

extension of the gum pads.

• Dental groove

• Lateral sulcus

Relationship of Gum

Pads

• Anterior open bite is seen at rest

with contact only at the molar

region.

• Complete overjet.

• Class II pattern with maxillary

gum pad being more prominent.

• Mandible is distal to the maxilla

by 2.7 mm- males & 2.5- females.

(Sillman JH 1938)

• The range of variation of this distal relationship is from

0 - 7 mm. (Sillman JH 1938)

• Mandibular lateral sulci lies posterior to maxillary lateral

sulci.

• 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.

Precociously Erupted Primary Teeth

• Pre-erupted teeth or Early Infansive teeth are teeth that

erupt during the 2nd or 3rd month.

Natal tooth Neonatal teeth

Natal/neonatal teeth Classification

Hebling (1997) classified natal teeth into 4 clinical

categories:

1) Shell-shaped crown poorly fixed to the alveolus by

gingival tissue and absence of a root;

2) Solid crown poorly fixed to the alveolus by gingival

tissue and little or no root;

3) Eruption of the incisal margin of the crown through

gingival tissue

4) Edema of gingival tissue with an unerupted but palpable

tooth.

Gender - Predilection for females 66% to males 31%

(Kates)

Etiology- several factors are there-

• Superficial position of the germ

• Infection or malnutrition

• Eruption accelerated by febrile incidents or hormonal

stimulation

• Hereditary transmission of a dominant autosomal gene

• Osteoblastic activity inside the germ area related to the

remodeling phenomenon and hypovitaminosis

Natal/neonatal teeth Associated

syndromes

• Hallerman-Streiff

• Ellis-Van Creveld

• Craniofacial dysostosis

• Multiple steatocystoma

• Congenital pachyonychia

• Sotos Syndrome.

Natal/neonatal teeth Complications

• Interfere with feeding

• Risk of aspiration

• Traumatic injury to baby’s tongue or maternal breast

• Riga-Fede disease- oral condition, found rarely in

newborns manifests as ulceration on ventral surface of

tongue or inner surface of the lower lip. Caused by trauma

to the soft tissue from erupted baby teeth.

Diagnosis-

• Radiographic verification of relationship between natal or

neonatal tooth and adjacent structures, presence or absence of

a germ in primary tooth area- determines tooth belongs to the

normal dentition or not (Almeida CM)

• Mostly natal & neonatal teeth - primary teeth of normal

dentition (95%) & not supernumerary teeth (Brandt)

Treatment-

• If diagnosed as tooth of normal dentition - maintenance of teeth

in mouth - first treatment option (Chow MH, Roberts MW)

• Reasons for removal -- Risk of dislocation, aspiration,

traumatic injury to baby’s tongue, maternal breast (Kates GA)

If the treatment option is extraction, certain

precautions to be taken -

• Avoiding extraction up to the 10th day of life to prevent

hemorrhage.

• Assessing the need to administer vitamin K before

extraction (0.5-1.0 mg IM)

• Considering the general health condition of the baby

• Avoiding unnecessary injury to the gingiva

• Being alert to the risk of aspiration during removal.

• Around 6 months to 6 yrs

• Features Of Primary Dentition

• Spacing- 2 types of dentition are seen:

• A) Spaced dentition - seen in

deciduous dentition to accommodate

the larger permanent teeth in the jaws.

• More in anterior region-‘physiological

spacing’ or ‘developmental spacing’.

• Absence of spaces in primary dentition-

crowding of permanent teeth.

PRIMARY DENTITION PERIOD

Non- spaced dentition

• Teeth without any spaces, due to

narrow dental arches or if teeth are

wider than usual.

• Most sub-human primates have it

throughout life and use it for

interdigitation of the opposing canines

called primate spaces’, ‘simian

spaces’ or ‘anthropoid spaces’.

• Space is used for early mesial shift.

Molar Relationship-

In the primary dentition classified into 3 types:

1. Straight/flush terminal plane.

2. Mesial step.

3. Distal step.

Flush Terminal Plane

• If the distal surface of maxillary and mandibular deciduous

second molars are in the same vertical plane; then it is

called a flush terminal plane

• Normal molar relationship in the primary dentition,

because the mesiodistal width of the mandibular molar is

greater than the mesiodistal width of the maxillary molar.

Mesial Step

• Distal surface of mandibular

deciduous second molar is

mesial to the distal surface of

maxillary deciduous second

molar.

Distal Step• Distal surface of mandibular

second deciduous molar is

more distal to the distal

surface of the maxillary

second deciduous molar

Canine relationship

• Relationship of maxillary & mandibular deciduous canines

is one of the most stable in primary dentition

• Classified as:

Class 1 Class 2

MIXED DENTITION PERIOD

Around 6 years- 12 years

• The mixed dentition period can be divided into three

phases:

1. First transitional period.

2. Inter-transitional period.

3. Second transitional period.

First transitional period

• Eruption of 1st Permanent Molar

• The location & relation of the 1st permanent molar

depends much upon the distal surface of the upper &

lower 2nd deciduous molar.

Transition to Class I Molar Relation• The shift in lower molar from a flush terminal plane to a

class I relation can occur in two ways:

• Early Shift- occurs during the early mixed dentition

period. Since this occurs early-early shift.

• Late Shift- occurs in the late mixed dentition period and is

thus called late shift.

Early shift Late shift

Leeway Space of Nance

• Nance (1947)

• Maxilla: 0.9 mm/segment = 1.8 mm.

• Mandible: 1.7 mm/segment = 3.4mm.

• Maxillary incisors, as a group in one

quadrant– 3.2to 3.5 mm larger

• Mandibular incisors, as a group in

one quadrant – 2.4 to 2.5 mm larger

• The latter figures balance out or

cancel the 1.7 mm of so called

leeway space

Distal Step

• When deciduous second molars are in distal

step, permanent first molar will erupt into

class II relation.

• This molar configuration is not self correcting

and will cause class II malocclusion despite

Leeway space and differential growth.

Mesial Step

• Primary second molars in mesial

step relationship lead to a class I

molar relation in mixed dentition.

• This may remain or progress to a

half or full cusp class III with

continued mandibular growth

• Influence of terminal

plane on the position of

1st permanent molar

• Distal Step – 23.3% incidence,

abnormal, Class II- 38.6%

• Straight terminal plane –

49.2% incidence, Class I or II

• Mesial Step - <2mm 26.7%,

class I 58.9% >2mm 0.8%.

Class III- 2.5%

Exchange of Incisors-

• During the first transitional period the deciduous incisors

are replaced by the permanent incisors..

• This difference between the amount of space needed for

the accommodation of the incisors and the amount of

space available for this, is called ‘Incisor liability’.

• It is roughly about 7.6 mm in the maxillary arch and

about 6mm in the mandibular arch. (Wayne)

Transition of Incisors

• Incisal liability is overcome :

• Interdental physiological

spacing in the primary incisor

region. (4mm, maxilla & 3mm,

mandibula)

• Increase in inter-canine arch

width.

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.

Inter-Transitional Period

• This is a stable phase where little changes take place in

the dentition.

• Root formation of emerged incisors, and molars

continues, along with concomitant increase in alveolar

process height.

• Resorption of roots of deciduous canines and molars.

Second Transitional Period

• Characterized by replacement of deciduous molars &

canines by premolars and permanent canines.

• At around 10 years of age the deciduous canine shed, but

just before the shedding a transient or self correcting

malocclusion is seen between the age of 8-9 years.

Ugly Duckling Stage (Broadbent’s

phenomenon)

• Around the age of 8 - 9 years, a midline diastema is

commonly seen in the upper arch, looks as malocclusion.

• Flaring of the lateral incisors.

• Maxillary midline diastema.

• Crowns of canines impinge on developing lateral incisor

roots.

• With eruption of the canines, the impingement from the

roots shift incisally thus driving the incisor crowns

medially, resulting in closure of the diastema as well as

the correction of the flared lateral incisors.

• Hence this unaesthetic metamorphosis, eventually leads

to an aesthetic result.

Second Transitional Period contd…

Eruption of permanent second molars

• Before emergence- second molars, oriented in a mesial &

lingual direction

• Teeth- formed palatally, guided into occlusion by Cone

Funnel mechanism , upper palatal cusps (cone) slides

into the lower occlusal fossa (funnel)

• Arch length is reduced by mesial eruptive forces

• Thereby, crowding if present is accentuated

SELF CORRECTING ANOMALIES

• 1. PREDENTATE

PERIOD:

• A) Retrognathic mandible

• B) Anterior open bite

• C) Infantile swallowing

pattern

• CORRECTION

• Corrects with differential

and forward growth of the

mandible

• Eruption of primary

incisors

• During the first year of life

with introduction of solid

foods

• PRIMARY DENTITION

• A) Anterior deep bite

• B) Flush terminal plane

• C) Spacing

• D) Edge to edge

• CORRECTION

• Eruption of deciduous molars

• Attrition of incisal edges

• Forward and downward growth of mandible (early shift)

• Eruption of first permanent molar

• Late shift (Leeway space)

• Eruption of first permanent molars

• Eruption of permanent incisors

• MIXED DENTITION

• A) Anterior deep bite

• B) Mandibular anterior crowding

• C) Ugly duckling stage

• D) End-on relation

• CORRECTION

• Proprioceptive response condition of patient (with the eruption of 1st permanent molars and premature contact of the pad of tissue overlying them as natural bite opener)

• Tongue pressure

• Increase in intercanine width

• Maxillary canine eruption

• With eruption of first permanent molars

• Late mesial shift in non-spaced dentition

• PERMANENT DENTITION

• A) Overjet and overbite

• CORRECTION

• Decreases with eruption of

all permanent molars

• Differential growth of

mandible

PERMANENT DENTITION PERIOD

• Marked by eruption of the four permanent second molars.

• Calcification begins at birth with the calcification of the

cusps of the first permanent molar and extends as late as

the 25th year of life.

• Complete calcification of incisor crowns take place by 4 –

5 years and of the other permanent teeth by 6 – 8 years

except for third molars.

Features of Permanent

Dentition• Coinciding midline.

• Class I molar relationship

• 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.

ANDREWS KEYS TO

NORMAL OCCLUSION• Key I – Molar relationship- MB cusp

of the max 1st molar falls into the

mesiobuccal groove of the mand 1st

molar.

• Key II Crown angulation (Tip)

Angulation of facial axis should be

positive

• Key III Crown inclination- upper

incisors the gingival portion of the

crown’s labial surface is lingual to the

incisal portion.

• Lower incisors and other crowns,

gingival portion of the labial or buccal

surface is labial or buccal to the

incisal or occlusal portion

• Key IV – Rotations- teeth should

be free of undesirable rotations

• Key V – Tight contacts- Contact

points should be tight (no spaces).

Key VI – Occlusal plane or curve

of spee - should have no more

than a slight arch.

Key VII – Correct tooth size or the

bolton’s ratio

(Bennett and McLaughlin, 1993).

Abnormalities in dental arch

1. Arch Length Discrepancy

1. Crowding

2. Spacing

2. Deviation in no. of teeth-

1. Absence of teeth (Agenesis)

2. Supernumerary teeth

Sequence of agenesis is –

• 3rd molar > Mand. 2nd premolars >

Max Lateral Incisors > Max. 2nd

Premolar

Supernumerary teeth

3. Deviation in tooth size

• Its relative in nature

• All teeth combined > or < relative to size of jaws or head.

• Crowding

• Spacing

4. Ankylosis

• Frequent in mand deciduous molars.

• In permanent 2 types-

• Due to abnormal position within jaw, Max perm. Canine

• Due to lack of space, Mand 3rd molar

Centric relation

• Definition: Relationship of mandible to maxilla when properly

aligned condyle–disk assemblies are in most superior

position against the eminentiae.

• The centric relation refers to the fully seated condylar

position.

• It is the universally accepted jaw position because it is

physiologically and biomechanically correct and is the only

jaw position that permits an interference-free occlusion.

Maximum intercuspation position

• The tooth-to-tooth relationship in maximum contact is called

as maximum intercuspation position (MIP).

Neutral zone

• Definition: The potential space between the lips and cheeks on

one side and the tongue on the other.

• Any part of the dentition out of harmony with the neutral zone

will result in instability, interference with function, or some

degree of discomfort.

CONCLUSION

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

temperomandibular joint, and the functional jaw

movements.