Development of occlusion/ dental crown & bridge courses

Development of Occlusion
INDIAN DENTAL ACADEMY
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Contents
 Introduction
 Development of concepts of occlusion
 Evolutionary changes
 Stages of Occlusion Development
 Prenatal Dental development
 Mouth of Neonate
 Dev of Dentition from birth to Complete deciduous Dentition
 Complete deciduous dentition
 The first Transitional Period
 The intertransitional period
 The 2nd
Transitional period
 Permanent Dentition

 Disorders of development of Dentition
 Development of Class II/1
 Development of Class II div/2
 Development of class III
 Development of Open bite
 Development of cross bite

Introduction to Occlusion
 Oc = up Clusion = closing ; closing up
 Occlusion - Relationship of dental arches
when tooth contacts are made.
 Ideal occlusion in broad functional term is –
 Teeth alignment is such that masticatory loads are
within physiological range and act through long axis
of as many teeth in arch as possible.
 Lateral jaw movement without mechanical
interference.
 When in rest position – freeway space is present
 Tooth alignment is aesthetically pleasing.

The Anatomical alignment of teeth
 The Dental Arches –
 Size and shape vary
 follow Catenary curve
 The Neutral Zone

The curvatures of teeth and arches
 Curve of Spee.
 Curve of Wilson
 Curve of Monson

The anatomical occlusion of teeth
Centric occlusion
B-L relation
Centric contacts
relation b/w teeth of both jaws
Arrangement of teeth in centric occ

Eccentric occlusion
Tooth contacts in lateral and protrusive occlusal
position

Andrew’s six keys of normal Occlusion
1. Molar inter arch relationship
2. Mesio- distal crown angulation
3. Labio – lingual crown inclination
4. Absence of rotation
5. Tight contacts
6. Curve of Spee.

Development of Concept of
Occlusion

Development of Concepts of
occlusion
 It can be divided into
 Fictional Period (prior to 1900)
 Hypothetical Period (1900 to 1930)
 Factual Period (1930 to present)

Fictional Period
 Fuller Clark & Imrie talked of ‘antagonism’,
‘meeting’ or ‘gliding’ of teeth.
 Talbot said it’s a historical event long since passed
in the decline of species, and possible only with an
atavism ‘throwback’ to our primitive ancestors.
 The creation of a normal standard of occlusion , a
basis on which to compare departure from normal
was lacking.

Hypothetical Period
 According to
 Edward H. Angel
 Mathew Cryer and Calvin Case
 Lischer and Paul Simon
 Milo Hellman

Edward .H. Angle
 In 1907 Angle put a hypothesis that:
“Occlusion is the basis of the science of orthodontia. The shapes of
the cusps, crowns and roots , and even the very structural material of the
teeth and attachments are all designed for the purpose of making occlusion
the one grand object…. we shall define occlusion as being normal relations
of the occlusal inclined planes of the teeth when the jaws are closed.”
 He described the illustration “Old glory”…. which
according to him was ideal occlusion.
 Angle stated Apollo Belverdo’s straight profile as ideal
 The best eg. of his hypothesis was ‘key of Occlusion’
 His hypothesis was suggestive of static occlusion

Old Glory Skull
Apollo Belverdo

Mathew Cryer and Calvin case
He opposed Angle
 How could one mix prognathic denture and orthognathic
profile?
 How bimaxillary protrusion considered normal and
individual variation was not considered?
 Then they were proved right by Turner’s illustrations
 Case’s concept of occlusion was static
Normal occlusion
( it suits Apollo’s face better)

Wheeler’s illustrations for normal occlusion
PrognathicRetrognathic

Lischer And Paul Simon
 They tried to relate concept of occlusion by
relating teeth with rest of the face and cranium.
 Lischer introduced mastication as requisite of
occlusion
 Simon outlined the anthropometric approach
Milo Hellman
 He showed racial variation in normal occlusion
 His study was also confined to static occlusion

Factual Period
 Dividing line b/w static and dynamic occlusion.
 1931 Broadbent introduced Cephalometry.
 With this advanced study tech the factual period
become functional period.
 By now 3 components of occlusion are set up
 1. Interdigitation of teeth
 2. Status of controlling musculature
 3. TMJ integrity

Evolution of dentition

Evolution of Dentition
 The mammalian dentition is 100, 000 million yrs old
 The theories behind mammalian dentition are
 Theory of Concrescence – derived by fusion of 2 or more
primitive conical teeth.
 Theory of trituberculy – each tooth derived from single
reptilian tooth by secondary differentiation of tubercule
and root.
 Theory of multituberculy – derived from reduction and
condensation of primitive multituberculate teeth.

 Non mammalian vertebrates – Polyphyodonty
(many dentitions)
 In mammals –Diphyodonty (2 dentitions )
 During growth of the animal – increase in the jaw
size is associated with tooth size
Evolution of Dentition

Dentition of fishes ( Agnatha)
Eg - Sea lamprey & hag fishes
 No true calcified teeth
 Arranged circumferentially
 Horny teeth are also seen on the tongue

Chondrichthyes (carrtilagenous fishes)
 Large no. of teeth are present
 Homodont & polyphyodont
 Teeth are covered by enameloid
lower jaw of shark

Osteichthyes
(bony fishes)
 Haplodont – conical shape
 prehension
 Polyphyodont
 Teeth- vomer, palatine bones roof of the mouth &
tongue

Amphibia
 Small, homodont, polyphyodont
 prehension
 In the frog – small teeth on the upper jaw
& no teeth on the lower jaw

Reptiles
 Homodont & polyphyodont
 Tend to be tricuspid or cone shaped
 Egg teeth – in embryos of lizards & snakes
- used to break the shell

Dentition of mammals
 Heterodont ( 4 types )
 Restricted to 2 rows
 Ability to masticate – improves digestive
efficiency for high rate of metabolism

Other features
 TMJ articulation
 Salivary glands
 Prismatic enamel
 Diphyodonty
 Secondary palate
 Significant muscle development

Dentition of protheria
 Spiny ant eater – edentulous
 Duck billed platypus – 3 functional
posterior teeth in each jaw quadrant
 No. of additional teeth develop but do not
erupt but rapidly resorb

Metatheria
(Marsupials)
 Eg. Red Kangroo
 Dental formula – 3/1, 0/0, 1/1, 4/4 .
 Feed on various plant.
 Anterior teeth allow the food to be firmly
grasped.
 Marsupials have no. of dental features
which distinguish them from placental
animals.

Eutheria
Eg - hedge hog
 Insectivoral
 Incisors form a forcep like mechanism to pick
preys.
 Molars – primitive tritubercular with sharp cusps
 Suitable for crushing the shells of insects

Rodentia
Eg - rat
 Heterogenous , Monophyodont
 Continuously growing incisors
 DF 1/1, 0/0, 0/0, 3/3
 Rat & mice are widely used as experimental
animals in Dental sciences

Carnivora
 Incisors are small and arranged in line.
 Enlarged canines – offensive weapons
 Incisors and canine – tearing flesh

Primates
 Classified in to –
 Prosimii or Lemur type
 Anthropoidea
 Mainly herbivorous sometimes
insectivorous

Prosimii or Lemur type
 DF – 2/2, 1/1, 3/3, 3/3
 incisors & canines are procumbent and
form dental comb.
 mid line diastema .
 Upper canine is blade like
 Upper molar tritubercular

Anthropoidea
(monkey, apes & Man)
 Eg -Macaca monkey
 DF – 2/2, 1/1, 2/2, 3/3
 Canines are long & prominent ( esp. in male )
 Lateral diastema

Chimpanze
 Resembles permanent teeth of man

Homosapiens
 Modern man – existed 100,000 yrs. ago

Stages of
Occlusal development

Stages of occlusal development
from clinical view ( Barnett)

According to Vander Linden
 Dev of Dentition from birth to Complete
deciduous Dentition
 Complete deciduous dentition
 The 1st Transitional Period
 The intertransitional period Mixed Dentition
 The 2nd
Transitional period
 Permanent Dentition

Prenatal Dental development

Prenatal Dental development
 Prenatal beginning of the dentition
 Initiation of odontogenesis
 bud stage
 cap stage
 bell stage
 Spatial patterns
 Arch shape
 Spacing

Initiation of odontogenesis
 3rd
week of IUL - first sign of tooth dev.
 Epithelial thickening seen
 6 wk IUL Dental lamina is formed.
IL border of maxilla
SL border of mandible

 Morphologic changes - 6wks IUL till 4-5 yrs.
 Occurs in 3 main phases-
 Initiation of entire deciduous dentition at 2nd
month IUL
 Initiation of permanent teeth in successional
lamina from 5th
month IUL
 The dental lamina elongates distal to 2nd
decid.
Molar and give rise to permanent molar tooth
germs

Bud Stage
 Seen at 7th wk IUL
 Increased mitotic activity at specific sites in DL
produces 10 knob like tooth buds
 Stage of proliferation with no
morphodifferentiation of cells

Bud Stage
Early bud stage
Late bud stage
Dental lamina
Enamel organ
Mesenchymal condensation

Cap Stage
 At end of 8th
wk concavity appears on deep surface of
bud – cap shape
 Epithelium enlarges and proliferates in to
deeper ectomesenchyme
 Its stage of morphodifferentiation

Cap Stage
Early cap stage
Late cap stage
External dental epith.
Dental follicle
Inner enamel epith.
Dental papilla
Enamel cord
Enamel knot
Dental
papilla

Bell stage
 Enlargement of tooth germ and deepening of its undersurface
 Germ looses connection with oral epith.
 Stage of Histodifferentiation
 Determine crown shape initate dentin
and enamel formation

Bell stage
outer enamel epith.
Stellate reticulum
Dental follicle
Stratum intermedium
Inner enamel epithelium
Dental papilla
Ameloblasts
Enamel matrix
Dentin
Predentin
Odontoblasts
Bell stage
Advanced Bell stage

Advanced Bell stage
 Inner dental epithelium – Ameloblasts – Enamel
 Outer dental epith. – dental cuticle
 Transition zone b/w IDE & ODE – cervical loop
 Neighboring cells of IDE in dental papilla –
Dentinoblasts/odontoblasts – Dentin
.
 Hertwig’s rootsheath proliferate from CL which
initiates radicular odontoblasts.

Arch Shape
 At 6 to 8 weeks it’s A-P flattened.
 By bell stage or 4mth IUL – Catenary pattern.
 Cleft lip and palate arrest this development.
 Lateral shift of deciduous lat. incisor is seen.
 4 diff arrangements of deciduous teeth in both jaws before
birth

Graphic Reconstruction of prenatal
Dental arch quadrant

Frontal sec through face of 24 wk fetus showing linear
distance from midline to points on tooth germs

Spacing
 Decid. anterior teeth appear crowded.
 Lateral incisor is seen out of alignment
before birth but usually erupt in good
alignment.
 Summed crown size increases eight
fold but summed interdental spacing
shows little correlatin with it.

The mouth of the Neonate

The mouth of the Neonate
 The gum pads
 Neonatal jaw relationship
 Status of dentition

Gum Pads
 At birth alveolar processes are covered by firm and pink
gum pads
 Divided in to 10 segments by transverse
grooves.
 Groove b/w canine and dm1 crypt –
lateral sulcus – assessing relation of jaws.
 Maxillary arch is horse shoe shape and
extend buccally and labially
 Mandibular arch is posterior to max. arch

Neonatal jaw relationship
 Anterior openbite is seen.
 Contact mainly occur at dm1 region.
 Infantile open bite is normal as it helps in
suckling.

The status of dentition
 Neonates are without teeth for 6mths.
 Occasionally teeth seen in this period –
 Natal
 Neonatal
 Pre-erupted
 These teeth are always mandibular incisors.
 Familial tendencies.

Tooth Eruption
 Two types -
 Preemergent eruption
 Eruption before emergence of tooth in oral cavity.
 Two processes involved –
 Resorption of the overlying bone (and primary tooth root).
 Eruption mechanism itself then move the tooth in cleared
path.
 Failure of tooth eruption –
 Failure of bone resorption (Cleidocranial dysplasia)
 Primary failure of eruption.

 Postemergent eruption
 Eruption after emergence of tooth in oral cavity.
 Postemergent spurt
 Rapid eruption from a time tooth penetrates the
gingiva till tooth reaches occlusal level.
 Eruption - During critical period b/w 8 PM to 1 AM.
 After it attain occlusal contact ,occlusal forces
opposes further eruption

 Juvenile Occlusal equilibrium
 Slow phase
 Teeth erupt to fill the space created by vertical
growth of mandibular ramus.
 Adult occlusal equilibrium
 Compensate for occlusal and proximal wear

Mechanism of tooth movement
 Bone remodelling of crypt wall
 Root formation
 Vascular pressure
 Periodontal ligament traction

Development of the Dentition from
Birth to complete Deciduous
dentition

Development of the Dentition from
Birth to complete Deciduous dentition
 After birth jaws grow considerably for 6-8 mths.
 Lower jaw more dorsally placed irt upper.
 Ventral dev takes place during 1st
yr – A-P relation
 Transverse dev –
 median suture in maxilla
 Synchondrosis in mandible (till 6 mths.)
 Eruption sequence is A B D C E

Dev of dental arches and dev of deciduous teeth
A. At birth
B. Mand. Central
incisor- 6 to 8 mths
C. Max. central incisor
7-9 months
D. U & L lateral
incisors – 1 yr.

E. 1st
molar – 16 mth.
F. Canine – 20 mth.
G. 2nd
molar – b/w 24 &
30 mths.
H. Complete deciduous
dentition with
successors within the
jaws.

Displacement of U & L Dm1 to establish
occlusion : Cone-funnel mechanism
 Palatal cusp of
max. 1st
molar –
cone
 Crater in mand.
1st
molar –funnel

The Complete Deciduous
Dentition
A B C D E
A B C D E

The Complete Deciduous Dentition
 Competed at 2.5 yrs of age after dm2 erupts and
lasts till 5 yr of age
 Physiological spaces in primary
dentition-
 Primate spaces
 Developmental spaces

Spacing in Deciduous dentition
 Gap toothed smile - normal
 Hollywood smile with teeth in contact - not normal

Occlusal relationship of U & L Dm2
 3 types of terminal planes –
 Flush terminal plane
 Mesial step
 distal step

Normal situation of the Deciduous dentition
in occlusal, anterior and lateral view

The first Transition period

The First transition period
 The emergence of 1st
permanent
molar A B C D E 6
A B C D E 6
 Transition of the incisors

The emergence of 1st
permanent molar
 1st
teeth to emerge in permanent dentition.
 In mand. 6 –7 yr In maxillary arch 7- 8 yr
 The A-P relation b/w two opposing permanent
molars depend upon –
 Their previous position within the jaw
 Sagittal relation b/w maxilla and mandible
 Terminal planes of 2nd
decid molars.

Influence of terminal plane on the
position of 1st
permanent molar

Exchange of Incisors
 After eruption of Pm1 , primary incisors exchange
with permanent incisors.
 Incisal Liability
 7 mm in maxilla
 5 mm in mandible
 The factors controlling the arrangement of
permanent incisors are -

 Interdental spaces in deciduous dentition
 physiological & primate spaces are utilized
 If closed space – crowding occur
 Increase of inter-canine width
 Increases 3 mm in both jaws at time of eruption
 Increases1.5 mm when canine erupts
 So the clasps on canine attached as space maintainer
should be cut off at this time
 Increase of anterior length
 Increase in length of arch in A-P dimension

 Change of tooth axis of incisor
 Permanent incisor erupt labially by 2 – 3 mm, attain
overjet and over bite
 Pressure by tongue , lip and perioral musculature
 Interincisal angle -
 150 degree in decid. Incisors.
 123 degree in perm. Incisor
 It increases arch circumference

 Ugly duckling stage
 Child look unusual due to
 Too large permanent incisor compared to primary.
 Flared incisors with midline diastema.
 Transitional malocclusion – called ugly duckling
stage - broadbent

Sequence of normal transition of incisors
At 5 yr. At 6 –7 yr.
At 7 –8 yr.
At 8 – 9 yr

Transition of incisors
 Loss of decid. tooth is caused by-
 Resorption of its root
 By reduction of bone cervically
 Several week passes b/w shedding of decid and eruption
of successor.
 In the interval reconstruction of alveolar process and
healing of gingival defect occur
 A perm. teeth starts eruption after ¼ of its root formed
 Perm .teeth emerge in oral cavity when ¾ root is formed.

The inter transitional Period
1 2 C D E 6
1 2 C D E 6

The inter transitional period
 Consist of both decid. & perm. teeth
 Teeth present are 1 2 C D E 6
1 2 C D E 6
 Ugly duckling stage persists in upper incisors.
 Under influence of tongue mand incisor attain
proper sites from their lingual position.
 The decid teeth present are worn out at this stage.
 It is a stable phase with little changes in dentition.

The inter transitional period

The Second Transition Period

The Second transitional period
 Transition of Lateral teeth
 Eruption of Second permanent molar

Transition of lateral teeth
 Transition of C D E with 3 4 5 .
 For smooth exchange following are
conditions–
 Leeway space of Nance
 Sum M-D width of 3, 4 & 5 < C D & E
 Space available is
 22.3 – 21.5 = 0.8 (U)
 23.5 – 21.1 = 2.4 (L)

 Order of exchange of lateral teeth
 It takes 1 ½ yrs. to complete exchange of
lateral teeth.
 Sequence of eruption is –
 4 5 3 in maxillary and 3 4 5 in mand.

Eruption of second Permanent teeth
 After exchange of lateral teeth 2nd
permanent
molar erupts. i.e after loss of all deciduous teeth.
 Sometimes it erupts before E sheds – leads to
crowding

Transition of lateral teeth and
eruption of 2nd
perm molar
At 9- 10 yrs
At 10 – 11 yrs. At 10 – 12 yrs.
At 11 – 12 yrs At 12 – 13 yrs.

The Permanent Dentition
1 2 3 4 5 6 7
1 2 3 4 5 6 7

The Permanent Dentition
 At around 13 yr of age all permanent teeth
(except 3rd
molar) are erupted.
Situation in normal
permanent dentition

Normal bucco-lingual inclination of
perm teeth in both jaws

Disorders in development of
Dentition

Disorders in development of
Dentition
 At time of eruption of Deciduous dentition –
 Teething disorder - most of infants exhibit fever,
diarrohea, vomiting , irritability etc before tooth
eruption.
 Anomolies
 Its rare for primary teeth to be congenitally missing.
 Primary tooth resorption
 Hastened by inflammation and occlusal trauma
 Delayed by splinting and absence of successor

 Ankylosis of primary teeth
 In Primary molars, esp during physiologic
resorption
 Disorders of primary Occlusion –
 Its less compared to permanent occlusion.
 Thumb sucking and other oral habits
 Posterior crossbite
 Open bites
 Class II malocclusion
 Excessive overjet
 Bruxism – functional malocclusion

 Factors affecting transition of teeth
 Dental caries in primary teeth
 Disturbance in root resorption due to pulpal or
periodontal disturbances
 A periapical lesion
 Premature loss of primary molar

 Anomolies in Permanent dentition
 Microdontia, macrodontia
 Gemination ,Fusion, Dilaceration, Talon
cusp, Dens evaginatus
 Supernumerary roots
 Dentinogenesis & Amelogenesis imperfecta
 Enamel Hypoplasia

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 Descrepancy

Deviation in individual teeth position

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

Angle’s classification of Malocclusion
 Class I
 ClassII
 Class II div 1
 Class II div 1 subdivison
 Class II div 2
 Class II div 2 subdivison
 Class III
 Class III subdivison

Development of dentition in Class II/ 1
malocclusion

In Deciduous dentition
Mand dental arch
dorsally placed irt
maxillary
Limited increase in
overbite
Distal step

In Intertransitional period
Mand dental arch dorsally
placed, large overjet
Mand 1st
perm molar
occludes dorsally to max
Increased overbite

In Permanent Dentition
Mand dental arch dorsally
placed, large overjet
Class II molar relation
Increased overbite

Change in Incisor and Molar region in Class
II /1 , from deciduous to permanent
•Distal step
•Decid incisor labially
inclined.
•Lower lip dorsally
placed.
•Mand incisor erupts
normally
•Class II molar relation
•Max incisor erupts
labially.
•Mand incisor
continue to erupt .
• lower lip supports
max incisor.
• Mand incisor touches
the palate.
• Max incisor situated
infront of lower lip
• Secondary covering
of protruding max
incisors by lips.
Adult
child

Development of dentition in Class II/2
malocclusion

Change in Incisor and Molar region in Class
II /2 , from deciduous to permanent
Mand incisor erupt
normally ,Max erupts
slightly upright
Lower lip – lingual tipping
of U. Incisor
In adult, U. C.
incisor tipped
severely palatally
Lower lip – lingual
tipping of L. Incisor
Continued eruption
– till vertical contact
In decid dentition
Less overjet
high lip line

Class II /2 with more space in anterior
segment
Palatal tipping ( By L Lip)
U C P incisor - Continuous
arch with B & C
U L P incisor erupt in
normal orientation as
sufficient space available
•Palatal tipping of U L P
incisor by L lip.
•Lingual tipping of lower
incisors.
•Rectangular arch form

Class II /2 with less space in anterior
segment
•Palatal tipping ( By L Lip)
•U C P incisor - Continous
Arch with B & C
• Lateral erupts labially
• L lip placed lingual to laterals
•Max. laterals rest on the L lip.
•Max Central and Mand incisors
are perpendicular to Occ plane

Development of dentition in
Class III malocclusion

In Deciduous dentition
Mand dental arch ventrally
placed, reverse overjet
Lower ant placed ventrally to
max. less overbite
Large mesial step

In Intertransitional period
Incisal surface of
U incisor contact ligual
surface of lower
Mand perm !st molar
occludes too far
mesially to max

In Permanent dentition
Incisal surface of U incisor
contact lingual surface
of lower
Mand perm !st molar
occludes too far
mesially to max

Development of Open bite

Anterior open bite
Asymmetrical open bite
due to thumb sucking
in Deciduous dentition
Open bite due to abnormal
Tongue position
(symmetrical)

Posterior open bite
Open bite due to incomplete
eruption of teeth.
Resulting in
interpositioning of tongue
Open bite combined with
inadequate contacts.

ClassII /1 Subdivison
• Class I on right side, class II on left
• Overjet overbite too large
• Midline shift.

ClassIII Subdivison
• Class I on right side, class III on left
• Anterior crossbite exists
• Midline shift.

Unilateral Crossbite
Maxillary dental arch crosses the mandibular
arch, distal to maxillary left canine

Bilateral Crossbite
On both sides maxillary molars occlude with their
buccal cusps instead of their palatal ones

Total exo-occlusion in ClassII/1
 All maxillary teeth positioned exteriorly to mandibular
 Brodie Syndrome or Telescope bite

Total endo-occlusion in Class III
All maxillary teeth positioned interiorly to mandibular
ones

References :
 Oral Anatomy - Berkovitz
 Development of Dentition – Van der Linden
 Transition of human Dentition – Van der Linden
 Handbook of orthodontics – Moyers
 Contemporary orthodontics –Proffit
 Orthodontics - T. M. Graber
 Oral histology – Tencate
 Dental Anatomy – Wheelers
 Dentistry for child – Mc Donald

Development of occlusion/ dental crown & bridge courses

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Development of occlusion/ dental crown & bridge courses