By:

Piyush Verma

MDS 1st yr

Dept of Pedodontics & Preventive Dentistry

Index• Introduction

• Evolution

• Periods of occlusal development

Neo-natal period.

Primary dentition period.

Mixed dentition period.

Permanent dentition period

• Developmental disturbances

• Conclusion

• References

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

EvolutionTo 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 contd…• 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.

Gum Pads contd…

The upper gum pad is horse shoe

shaped & shows:

o Gingival groove: separates

gum pad from the palate.

o Dental groove: starts at the

incisive papilla, extends

backward to touch the

gingival groove in the

canine region & then

moves laterally to end in

the molar region.

o Lateral sulcus.

Gum Pads contd…

The lower gum pad is ‘U’

shaped and rectangular,

characterized by:

o Gingival groove: lingual

extension of the gum

pads.

o Dental groove.

o Lateral sulcus.

Relationship of Gum Padso Anterior open bite is seen at rest with

contact only at the molar region.

o Complete overjet.

o Class II pattern with maxillary gum

pad being more prominent.

o Mandible is distal to the maxilla of 2.7

mm- male and 2.5- female. ( Sillman JH

1938)

oThe range of variation of this distal

relationship is from 0 to 7 mm. .

( Sillman JH 1938)

Relationship of Gum Pads

o Mandibular 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.

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

Precociously Erupted Primary

Teeth

Natal tooth Neonatal teeth

Pre-erupted teeth’ or ‘Early Infansive teeth’ are teeth that

erupt during the 2nd or 3rd month.

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

Kates et al (1984) reported a 66% proportion for females

against a 31% proportion for males.

EtiologyIt has been related to several factors, such as:-

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 the baby’s tongue

and/or to the maternal breast

Riga-Fede disease- oral condition

found, rarely in newborns manifests

as an ulceration on the ventral surface

of the tongue or on the inner surface

of the lower lip. Caused by trauma to

the soft tissue from erupted baby

teeth.

Riga-Fede disease

Diagnosis

A radiographic verification of the relationship

between a natal and/or neonatal tooth and

adjacent structures, nearby teeth, and the

presence or absence of a germ in the primary

tooth area would determine whether or not the

tooth belongs to the normal dentition ( Almeida

CM et al 1997)

Most natal and neonatal teeth are primary teeth

of the normal dentition and are not

supernumerary teeth ( Brandt Sk et al 1983)

Correspond to teeth of the normal primary

dentition in 95% of cases, while 5% are

supernumerary (Hawkins C 1932)

Treatment If the erupted tooth is diagnosed as a tooth of the normal

dentition -- maintenance of these teeth in the mouth is the first

treatment option, unless this would cause injury to the baby

(Chow MH 1980, Roberts MW 1992)

When well implanted-- these teeth should be left in the arch

and their removal should be indicated only when they interfere

with feeding or when they are highly mobile, with the risk of

aspiration (Toledo AO 1996)

Reasons for removal -- The risk of dislocation and consequent

aspiration, traumatic injury to the baby’s tongue and/or to the

maternal breast, (Kates GA et al 1984)

Martins et al (1998) suggested smoothing of the incisal

margin to prevent wounding of the maternal breast during

breast feeding.

If the treatment option is extraction, certain precautions should

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.

(From around the 6th month to 6 years)

Sequence of Eruption

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 2

Canine 17 9 19 31/4

1st molar 151/2 6 16 21/2

2nd molar 19 11 29 3

Chronology of Primary Dentition

Wheelers…

Primary

(Lower

First evidence of

calcification

(Weeks in utero)

Crown

completed

(months)

Eruption

(months)

Root

completed

(years)

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

Wheelers…

Status of Dentition(during primary dentition period)

At around 5 – 6 YearsThere are 48 teeth/parts of teeth present in the jaw. It is at this

time that there are more teeth in the jaws than at any other time.

Features Of Primary

Dentition• Spacing- 2 types of dentition are seen:

•A) Spaced dentition - usually seen in the

deciduous dentition to accommodate the

larger permanent teeth in the jaws.

• More prominent in the anterior region,

and are called ‘physiological spacing’ or

‘developmental spacing’.

• Absence of spaces in the primary

dentition is an indication that crowding of

teeth may occur when the larger

permanent teeth erupt.

Features Of Primary

Dentition contd…

• Most subhuman primates

have it through out life and use

it for interdigitation of the

opposing canines. This space is

used for early mesial shift.

primate spaces’, ‘simian spaces’ or

‘anthropoid spaces’.

Features Of Primary Dentition

contd…

Non- spaced dentition

Teeth are present without any

spaces in between the teeth

Due to narrow dental arches or

if teeth are wider than usual

Usually indicates in developing

permanent dentition but it is not

always the case

Features Of Primary

Dentition contd…Shallow overjet & overbite. Initially a deep bite may occur due to the fact that

the deciduous incisors are more upright than their successors. The lower incisal

edges often contact the cingulum area of the maxillary incisors. This deep bite

is later reduced by:

oEruption of deciduous molars.

oAttrition of incisors.

oForward movement of the mandible due to growth.

Features Of Primary

Dentition contd…

Almost vertical

inclination of anteriors.

Features Of Primary

Dentition contd…

Ovoid arch form.

Molar RelationshipThe molar relationship in the primary dentition can be classified

into 3 types:

oStraight/flush terminal plane.

oMesial step.

oDistal 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 caninnes

is one of the most stable in

primary dentition

Classified as:

Class 1

Class 2

Class 1

Class 2

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

Eruption of 1st Permanent MolarThe 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

Early Shift

• Early shift occurs during the early mixed dentition period.

• Since this occurs early in the mixed dentition, it is called early shift.

Late Shift

This occurs in the late mixed

dentition period and is thus

called late shift.

Leeway Space of Nance

• Described by Nance in 1947

Maxilla: 0.9 mm/segment = 1.8 mm.

Mandible: 1.7 mm/segment = 3.4mm.

• Although the deciduous posterior segment of teeth is larger than

the permanent segment, converse is true of the anterior segments

• Nance did not consider large difference in mesiodistal size

between the deciduous incisor teeth & their permanent

successors– arch needs to be looked in its totality

• 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

• Moorrees -- measurements of deciduous

& permanent teeth in the mouths obtained

by longitudinal studies, there is no leeway

space

• Total no. of permanent teeth destined to

replace total no. of deciduous teeth in an

average child – slighly less than 1mm

more space in mandibular arch, 6mm

more in maxillary arch

• 1.7 mm leeway space taken up by the

larger permanent incisors, requires more

distal eruption of permanent canines

•Allows reduction of incisor crowding in

mandibular arch

• If the permanent molars were allowed or even encouraged to

drift mesially and utilize the leeway space – no enough room in

the arch for the incisor segment

• Initially – permanent incisors are forced into a crowded position

• If molars are held stable, incisors will utilize the leeway space,

ultimately the average mandibular arch will have enough room

for proper alignment

Secondary spacing

• Term was coined by Baume

• Observed in closed primary dentition

• Secondary spacing can also occur

during the eruption of permanent

central incisors

Distal Step

When the deciduous second

molars are in a distal step, the

permanent first molar will

erupt into a class II relation.

This molar configuration is not

self correcting and will cause a

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

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)

Transition of Incisors contd…

Increase in inter-canine arch width:

Significant amount of growth occurs with the eruption of

incisors and canines.

Transition of Incisors contd…

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.

Transition of Incisors contd…

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 parameter.

Inter-Transitional Period

Inter-Transitional Period contd…

Root formation of emerged

incisors, and molars

continues, along with

concomitant increase in

alveolar process height.

Inter-Transitional Period contd…

Resorption of roots of

deciduous canines and

molars.

Second Transitional Period

Ugly Duckling Stage(Broadbent’s phenomenon)

Around the age of 8 - 9 years, a

midline diastema is commonly

seen in the upper arch, which is

usually misinterpreted by the

parents as a malocclusion.

Its typical features are:

oFlaring of the lateral incisors.

oMaxillary midline diastema.

Ugly Duckling Stage contd…

Crowns of canines on young

jaws impinge on developing

lateral incisor roots, thus

driving the roots medially and

causing the crowns to flare

laterally.

Ugly Duckling Stage contd…

The roots of the central incisors are also forced

together, thus causing a maxillary midline diastema.

Ugly Duckling Stage contd…

With the 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.

Ugly Duckling Stage contd…

Hence this unaesthetic metamorphosis, eventually leads to an

aesthetic result.

Self correcting anomalies

Sequence of EruptionThe canines in the upper arch erupt only after the premolars

have replaced the deciduous molars, whereas the canine erupt

before the premolars in the lower arch.

Second Transitional Period contd…

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

The Permanent Dentition

This period is marked by the

eruption of the four permanent

second molars.

Nolla’s Stages of Tooth Development

Moyers

In 1960 Nolla studied the stages of tooth development using

panoramic & postero-anterior radiographs.

The Permanent Dentition contd…

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.

Permanent

(Upper)

First evidence

of calcification

( weeks in

utero)

Crown

completed

(months)

Eruption

( months)

Root

completed

(years)

Central 3-4 mo 4-5 yr 7-8 yr 10

Lateral 10-12 mo 4-5 yr 8-9 yr 11

Canine 4-5 mo 6-7 yr 11-12 yr 13-15

1st 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

Wheelers…

Permanent

(Lower)

First evidence of

calcification

( weeks in utero)

Crown

completed

(months)

Eruption

( months)

Root completed

( years)

Central 3-4 mo 4-5 yr 6-7 yr 9

Lateral 3-4 mo 4-5 yr 7-8 yr 10

Canine 4- 5 mo 6-7 yr 9-10 yr 12-14

1st premolar 13/4-2yr 5-6 yr 10-12 yr 12-13

2nd premolar 21/4-21/2 yr 6-7 yr 11-12 yr 13-14

1st molar At birth 21/2-3yr 6-7 yr 9-10

2nd molar 21/2-3yr 7-8 yr 11-13 yr 14-15

3rd molar 8-10 yr 12-16 yr 17-21 yr 18-25

Wheelers…

The Permanent Dentition contd…

The permanent incisors

develop lingual to the

deciduous incisors and move

labially as they erupt.

The Permanent Dentition contd…

The premolars develop below

the diverging roots of the

deciduous molars.

The Permanent Dentition contd…

At approximately 13

years of age all

permanent teeth

except third molars

are fully erupted.

Features of Permanent

DentitionCoinciding midline. Class I molar relationship.

Features of Permanent

Dentition contd…

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 and that the distal

surface of the DB cusp of the upper

first permanent molar should make

contact and occlude with mesial

surface of the MB cusp of the lower

second molar.

Andrews keys to normal

occlusion

Key II Crown angulation (Tip)

The angulation of the facial axis of

every clinical crown should be

positive

The gingival portion of the long axis

of the all crowns must be distal than

the incisal portion.

Andrews keys to normal

occlusionKey III Crown inclination

In upper incisors, the gingival

portion of the crown’s labial surface

is lingual to the incisal portion.

In all other crowns, including lower

incisors, the gingival portion of the

labial or buccal surface is labial or

buccal to the incisal or occlusal

portion.

Andrews keys to normal

occlusionKey IV – Rotations

The fourth key to normal

occlusion is that the teeth should

be free of undesirable rotations.

Andrews keys to normal

occlusionKey V – Tight contacts

contact points should be tight

(no spaces).

In absence of abnormalities

such as genuine tooth size

discrepancies, contact point

should be tight.

Andrews keys to normal

occlusionKey VI – Occlusal plane or curve

of spee

The curve of Spee should have no

more than a slight arch.

Intercuspation of teeth is best

when the plane of occlusion is

relatively flat.

A deep curve of spee results in a

more contained area for the upper

teeth, making normal occlusion

impossible.

Andrews keys to normal

occlusionKey VII – Correct tooth size or the bolton’s ratio

Bennett and McLaughlin in 1993 gave seventh key

to normal occlusion. i.e. the upper and lower tooth

size should be correct.

Roth (1981) added some functional keys to the previous six

keys to normal occlusion by Andrew:

a) Centric relationship and centric occlusion should be coincident.

b) In protrusion, the incisors should disclude the posterior teeth,

with the guidance provided by the lower incisal edges passing

along the palatal contour of the upper incisors.

c) In lateral excursions of the mandible, the canine should guide

the working side whilst all other teeth on that and the other side

are discluded.

d) When the teeth are in centric occlusion, there should be even

bilateral contacts in the buccal segments.

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

Absence of teeth ( Agenesis)

Sequece of agenesis is –

3rd molar > Mand. 2nd premolars > Max

Lateral Incisors > Max. 2nd Premolar

Absence of teeth ( Agenesis)

Supernumerary teeth

Deviation in tooth size

Its relative in nature

All teeth combined > or < relative to size of jaws or

head.

Crowding

Spacing

Deviation in size of individual teeth

Tooth size Discrepancy

Tooth size Discrepancy

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

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

temperomandibular 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, and if we need to determine an abnormal course of

development, 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

• Handbook of Orthodontics: Robert E. Moyers.

• Orthodontics the art & science: S. I. Bhalajhi.

• Textbook of Orthodontics: M.S. Rani.

• Textbook of Pediatric Dentistry: S.G. Damle.

• Dental Anatomy, Physiology & Occlusion: Wheeler.

• Textbook of Pedodontics: Shoba Tandon.

• Textbook of Orthodontics: Samir E. Bishara.

• Contemporary orthodontics –Proffit

• Textbook of Pedodontics: Koch.

• Orthodontics principles and practice: T. M. Graber.