Development of occlusion

Development ofDevelopment of
OcclusionOcclusion

What is occlusion ?What is occlusion ?
 The way maxillary and mandibular teeth articulateThe way maxillary and mandibular teeth articulate
 Much more complexMuch more complex
 Study of teeth , their morphologyStudy of teeth , their morphology
 AngulationsAngulations
 Muscles of masticationMuscles of mastication
 TMJTMJ
 Functional jaw movementsFunctional jaw movements
 Relationship of teeth in centric occlusion centricRelationship of teeth in centric occlusion centric
relation and in functionrelation and in function
 Neuromuscular controlNeuromuscular control

Changes in occlusion with ageChanges in occlusion with age
 From birth till adulthood and beyondFrom birth till adulthood and beyond
occlusion undergoes significant changesocclusion undergoes significant changes
 Sometimes drastic changes and sometimesSometimes drastic changes and sometimes
more subtlemore subtle
 Differentiate normal from abnormalDifferentiate normal from abnormal

Stages of dental developmentStages of dental development
 Gum pad stageGum pad stage
 From birth till eruption of first primary toothFrom birth till eruption of first primary tooth
 Pink firm with dense layer of fibrous periosteumPink firm with dense layer of fibrous periosteum
 Horse shoe shapedHorse shoe shaped
 Show elevations and groovesShow elevations and grooves
 Labiobuccal portion and lingual portionLabiobuccal portion and lingual portion
 Dental grooveDental groove

Stages of dental developmentStages of dental development
 Gum pad stageGum pad stage
 Divided into ten segments by ten grooves, theDivided into ten segments by ten grooves, the
transverse groovestransverse grooves
 Transverse groove between canine and first deciduousTransverse groove between canine and first deciduous
molar segment is lateral sulcusmolar segment is lateral sulcus
 Anterior open bite relation ( infantile tongue thrust)Anterior open bite relation ( infantile tongue thrust)
 Posterior segments touchingPosterior segments touching
 Maxillary gum pads slightly overlaps mandibular gumMaxillary gum pads slightly overlaps mandibular gum
pads horizontally and vertically i.e. complete overjetpads horizontally and vertically i.e. complete overjet

Primary dentition stagePrimary dentition stage
 Extends from time of eruption of firstExtends from time of eruption of first
primary teeth to time of eruption of firstprimary teeth to time of eruption of first
permanent molar around 6 yrs of agepermanent molar around 6 yrs of age

Sequence of Calcification of PrimarySequence of Calcification of Primary
TeethTeeth
 Central incisorCentral incisor 14 weeks in utero14 weeks in utero
 First molarFirst molar 15 weeks in utero15 weeks in utero
 Lateral incisorLateral incisor 16 weeks in utero16 weeks in utero
 CupidCupid 17 weeks in utero17 weeks in utero
 Second molarSecond molar 18 weeks in utero18 weeks in utero

Sequence of Eruption of PrimarySequence of Eruption of Primary
TeethTeeth
 a - b - d - c - ea - b - d - c - e
 Eruption faster in girlsEruption faster in girls
 6 month variation = normal6 month variation = normal
 no significant left/right differencesno significant left/right differences

Timing of Eruption of Primary TeethTiming of Eruption of Primary Teeth
 MANDIBULARMANDIBULAR
 Central incisorCentral incisor 661/2 month1/2 month
 Lateral incisorLateral incisor 7 months7 months
 CanineCanine 16-20 months16-20 months
 First molarFirst molar 14-16 months14-16 months
 Second molarSecond molar 20-30 months20-30 months

Timing of Eruption of Primary TeethTiming of Eruption of Primary Teeth
 MAXILLARYMAXILLARY
 Central incisorCentral incisor 771/2 month1/2 month
 Lateral incisorLateral incisor 8 months8 months
 CanineCanine 16-20 months16-20 months
 First molarFirst molar 12-16 months12-16 months
 Second molarSecond molar 20-30 months20-30 months

 OverbiteOverbite
 OverjetOverjet
 SpacingSpacing
 Molar relationshipsMolar relationships

 OverbiteOverbite
 Amount of vertical overlap between maxillaryAmount of vertical overlap between maxillary
and mandibular central incisorsand mandibular central incisors
 Described either in mm or as percentageDescribed either in mm or as percentage
 Normally varies between 10-40%Normally varies between 10-40%
 Edge to edge or zero overbiteEdge to edge or zero overbite
 Lack of overlap ------------- open bite quantifiedLack of overlap ------------- open bite quantified
in mmin mm
 May be due to presence of oral habitsMay be due to presence of oral habits

 OverjetOverjet
 Amount of horizontal overlap betweenAmount of horizontal overlap between
most protruded maxillary CI andmost protruded maxillary CI and
corresponding mandibular central incisorscorresponding mandibular central incisors
 Described in mmDescribed in mm
 Normally varies between 0-4mmNormally varies between 0-4mm
 Excessive overjet may be due to presenceExcessive overjet may be due to presence
of oral habitsof oral habits

Spacing in deciduous dentitionSpacing in deciduous dentition
 Generalized spacing (Baume’s space)Generalized spacing (Baume’s space)
 Localized spacingLocalized spacing
 No spacingNo spacing
 CrowdingCrowding
 Generalized spacing is a common occurrenceGeneralized spacing is a common occurrence
 Tooth size arch length discrepancy in the formTooth size arch length discrepancy in the form
of crowding less common ( 3% of individualsof crowding less common ( 3% of individuals
with primary dentition )with primary dentition )

Spacing in deciduous dentitionSpacing in deciduous dentition
 Localized spacing ( primate spaces )Localized spacing ( primate spaces )
 Maxillary arch between lateral incisor and canineMaxillary arch between lateral incisor and canine
 Mandibular arch between canine and first molarMandibular arch between canine and first molar
 Also known as simian and anthropoid spacesAlso known as simian and anthropoid spaces
 Helps in placement of canine cusps in oppositeHelps in placement of canine cusps in opposite
archesarches

Occlusion of the Primary SecondOcclusion of the Primary Second
MolarMolar
 In primary dentition A-P molar relationship isIn primary dentition A-P molar relationship is
described in terms of relationship betweendescribed in terms of relationship between
terminal planesterminal planes
 Look at the distal aspect of the 2nd molarLook at the distal aspect of the 2nd molar
 Flush terminal plane – most commonFlush terminal plane – most common
 Mesial stepMesial step
 Distal stepDistal step

Flush Terminal PlaneFlush Terminal Plane
 In the flush terminal plane both theIn the flush terminal plane both the
maxillary and the mandibular planemaxillary and the mandibular plane
are at the same level anterioare at the same level anterio
posteriorlyposteriorly

Flush Terminal PlaneFlush Terminal Plane

Mesial stepMesial step
 In the mesial step relationshipIn the mesial step relationship
mandibular terminal plane is relativelymandibular terminal plane is relatively
more mesial ( anteriorly) than themore mesial ( anteriorly) than the
maxillary terminal planemaxillary terminal plane

Distal stepDistal step
 In the distal step relationshipIn the distal step relationship
mandibular terminal plane is relativelymandibular terminal plane is relatively
more distal (posterior) than themore distal (posterior) than the
maxillary terminal planemaxillary terminal plane

Distribution of terminal planeDistribution of terminal plane
relationshipsrelationships
 In one study involving 121 children atIn one study involving 121 children at
age 5 yrs it was foundage 5 yrs it was found
 Distal stepDistal step 10%10%
 Flush terminal planeFlush terminal plane 29%29%
 Mesial step 1mmMesial step 1mm 42%42%
 Mesial step >1mmMesial step >1mm 19%19%

Importance of terminal planeImportance of terminal plane
 Erupting first permanent molarsErupting first permanent molars
are guided by distal surface ofare guided by distal surface of
second primary molars as theysecond primary molars as they
erupt into occlusionerupt into occlusion

Primary Cuspid OcclusionPrimary Cuspid Occlusion
 Look at long axis of the maxillaryLook at long axis of the maxillary
cuspidcuspid
 Neutro cuspid (Class I)Neutro cuspid (Class I)
 Disto cuspid (Class II)Disto cuspid (Class II)
 Mesio cuspid (Class III)Mesio cuspid (Class III)

 Neutro cuspid (Class I)Neutro cuspid (Class I)

 Disto cuspid (Class II)Disto cuspid (Class II)

 Mesio cuspid (Class III)Mesio cuspid (Class III)

The Ideal Primary OcclusionThe Ideal Primary Occlusion
 Ovoid archesOvoid arches
 Good interdental or primaryGood interdental or primary
spacingspacing
 Flush terminal plane or mesial stepFlush terminal plane or mesial step
molarsmolars
 Neutro cuspidsNeutro cuspids

The Ideal Primary OcclusionThe Ideal Primary Occlusion
 Deep biteDeep bite
 Flat curve of speeFlat curve of spee
 Shallow cuspal interdigitationShallow cuspal interdigitation
 Incisors are more vertically placedIncisors are more vertically placed

Mixed DentitionMixed Dentition
OcclusionOcclusion

Mixed dentition stageMixed dentition stage
 Starts with the eruption of firstStarts with the eruption of first
permanent toothpermanent tooth
 Completed at the time last primaryCompleted at the time last primary
tooth is shedtooth is shed
 Significant changes in dentitionSignificant changes in dentition

 Temporary open biteTemporary open bite
 Antimere should erupt with in sixAntimere should erupt with in six
monthsmonths
 Sequence of eruption of permanentSequence of eruption of permanent
teethteeth

 During mixed dentition stage presenceDuring mixed dentition stage presence
of midline diastema between centralof midline diastema between central
incisors is a normal occurrenceincisors is a normal occurrence

 Size may vary from 1mm-3mmSize may vary from 1mm-3mm
 Usually closes by the time maxillaryUsually closes by the time maxillary
canine fully eruptcanine fully erupt

Molar relatitionshipMolar relatitionship
 Class IClass I
 Class IIClass II
 Class IIIClass III

Molar relationshipMolar relationship
 Flush terminal plane may lead to:Flush terminal plane may lead to:
 End to endEnd to end (end on)(end on)
 Class I (Early or late mesial shift)Class I (Early or late mesial shift)
 Mesial step may lead to:Mesial step may lead to:
 Class I (normally)Class I (normally)
 Class IIIClass III
 Distal step leads to:Distal step leads to:

Class II
Class I
(desirable)
ETE
End to End Permanent Molar

Mesial
Step
Class III
Class I
(desirable)
Mesial Step

Disto
Step
Class II
Always
Disto Step

Causes of changes in molarCauses of changes in molar
relationshiprelationship
 Early mesial shiftEarly mesial shift
 Late mesial shiftLate mesial shift
 Mandibular growthMandibular growth

Early mesial shiftEarly mesial shift
 Occurs during early mixed dentitionOccurs during early mixed dentition
 The eruptive forces of 1The eruptive forces of 1stst
permanent molarpermanent molar
push deciduous 1push deciduous 1stst
and 2and 2ndnd
molarsmolars
 Occurs when primate spaces are presentOccurs when primate spaces are present

Leeway spaceLeeway space
 Sum of (c-d-e) > (3-4-5) This allows moreSum of (c-d-e) > (3-4-5) This allows more
space for 3-4-5 This "leeway space"space for 3-4-5 This "leeway space"
averages 1.7 mm. in the mandibularaverages 1.7 mm. in the mandibular
segment; 0.9 in the maxillary segmentsegment; 0.9 in the maxillary segment

Late mesial shiftLate mesial shift
 Refers to mandibular permanent molarRefers to mandibular permanent molar
moving mesiallymoving mesially
 If permanent molars are ETE, late mesialIf permanent molars are ETE, late mesial
shift allows mandibular molar to moveshift allows mandibular molar to move
into a Class I occlusioninto a Class I occlusion

Late mesial shiftLate mesial shift
FTP Class I
Molar moves into
this space...

Incisor LiabilityIncisor Liability
 Permanent incisors are larger thanPermanent incisors are larger than
primary incisorsprimary incisors
 This difference in size is termedThis difference in size is termed
"incisor liability""incisor liability"
 How does the body create enoughHow does the body create enough
room for the larger, permanentroom for the larger, permanent
incisors?incisors?

Overcoming Incisor LiabilityOvercoming Incisor Liability
 Interdental spacing of primary incisorsInterdental spacing of primary incisors
 Intercanine arch width growthIntercanine arch width growth
 Labial positioning of the permanentLabial positioning of the permanent
incisorsincisors
 Favorable size ratio between theFavorable size ratio between the
primary and permanent incisorsprimary and permanent incisors

 Interdental spacing of primary incisorsInterdental spacing of primary incisors
 Good interdental spacing of primary incisorsGood interdental spacing of primary incisors
allows for better alignment of the largerallows for better alignment of the larger
permanent incisors.permanent incisors.

Primary SpacingPrimary Spacing

 Intercanine arch width growthIntercanine arch width growth
 Width growth creates more room for theWidth growth creates more room for the
permanent incisorspermanent incisors
 Mandibular intercanine growth occursMandibular intercanine growth occurs
mostly during permanent incisor eruptionmostly during permanent incisor eruption
 Maxillary intercanine growth occursMaxillary intercanine growth occurs
during incisor eruptionduring incisor eruption
 UnpredictableUnpredictable

Intercanine growthIntercanine growth

 Labial positioning of the permanentLabial positioning of the permanent
incisorsincisors
 Permanent incisors erupt to a morePermanent incisors erupt to a more
labial positionlabial position
 Permanent incisors are angled morePermanent incisors are angled more
labiallylabially
 The above creates more arch lengthThe above creates more arch length

Labial positioningLabial positioning

 Favorable size ratio between the primaryFavorable size ratio between the primary
and permanent incisorsand permanent incisors
 Size ratio between the primary andSize ratio between the primary and
permanent incisors may be favorable orpermanent incisors may be favorable or
unfavorableunfavorable
 Favorable: large primary, small permanentFavorable: large primary, small permanent
 Unfavorable: small primary, largeUnfavorable: small primary, large
permanentpermanent

Mixed dentitionMixed dentition
 First transitional periodFirst transitional period
 Inter transitional periodInter transitional period
 Second transitional periodSecond transitional period

Second transitional periodSecond transitional period
 Characterized by replacement of deciduousCharacterized by replacement of deciduous
molars and canines by premolars and permanentmolars and canines by premolars and permanent
canines respectivelycanines respectively
 Ugly duckling stageUgly duckling stage

Ugly duckling stageUgly duckling stage
 Transient malocclusion seen in maxillary incisor regionTransient malocclusion seen in maxillary incisor region
between 8-9 years of agebetween 8-9 years of age
 Eruption of permanent caninesEruption of permanent canines
 As canines erupt they put pressure on roots ofAs canines erupt they put pressure on roots of
permanent lateral incisorspermanent lateral incisors
 Pressure on permanent central incisorsPressure on permanent central incisors
 Midline spacingMidline spacing
 Described by Broadbent as ugly duckling stageDescribed by Broadbent as ugly duckling stage
 Usually self correcting as the pressure is transferredUsually self correcting as the pressure is transferred
from roots to crownsfrom roots to crowns

Predicting FuturePredicting Future
Crowding –Crowding –
Mixed dentition analysisMixed dentition analysis

Mixed Dentition AnalysisMixed Dentition Analysis
 Why: predict amount of crowding afterWhy: predict amount of crowding after
permanent teeth come inpermanent teeth come in
 When: during mixed dentitionWhen: during mixed dentition
 What: boley gauge, models, predictionWhat: boley gauge, models, prediction
tabletable

MDA MethodologyMDA Methodology
 Measure mesial-distal diameter of theMeasure mesial-distal diameter of the
mandibular incisors and record the valuemandibular incisors and record the value
 Determine the space required forDetermine the space required for
alignment of incisorsalignment of incisors
 Determine the amount of space availableDetermine the amount of space available
for permanent canines and premolars afterfor permanent canines and premolars after
incisor alignmentincisor alignment

MDA MethodologyMDA Methodology
 Predict the combined width ofPredict the combined width of
mandibular canines and premolarsmandibular canines and premolars
with the aid of probability chartwith the aid of probability chart
 This estimated canine and premolarThis estimated canine and premolar
size value is subtracted from measuredsize value is subtracted from measured
spacespace

Moyer's Prediction ChartMoyer's Prediction Chart
19.519.5 20.020.0 20.520.5 21.021.0 21.521.5 22.022.0 22.522.5 23.023.0 23.523.5 24.024.0
Max.Max.
75%75%
20.620.6 20.920.9 21.221.2 21.521.5 21.821.8 22.022.0 22.322.3 22.622.6 22.922.9 23.123.1
mandmand
75%75%
20.120.1 20.420.4 20.720.7 21.021.0 21.321.3 21.621.6 21.921.9 22.222.2 22.522.5 22.822.8

Allowance for Late Mesial ShiftAllowance for Late Mesial Shift
 If permanent molars are end to end,If permanent molars are end to end,
mandibular molar should move mesially tomandibular molar should move mesially to
obtain Class I interdigitation.obtain Class I interdigitation.
 This will decrease the arch length availableThis will decrease the arch length available
for 3-4-5.for 3-4-5.
 Reduce 1.7 mm. per side with ETEReduce 1.7 mm. per side with ETE
relationship.relationship.

Johnson and Tanaka analysisJohnson and Tanaka analysis
 Variation of moyer’s analysisVariation of moyer’s analysis
 Table is not neededTable is not needed
 Sum of widths of mandibular incisors is dividedSum of widths of mandibular incisors is divided
by 2by 2
 For the mandibular arch add add 10.5 to get theFor the mandibular arch add add 10.5 to get the
resultresult
 For the maxillary arch add 11.0 to get the resultFor the maxillary arch add 11.0 to get the result
 Corresponds to 75% probability of moyers tableCorresponds to 75% probability of moyers table

Hixon and oldfather methodHixon and oldfather method
 Maximum MD daimeter of CI and LI of oneMaximum MD daimeter of CI and LI of one
side + MD Diameter of unerupted first andside + MD Diameter of unerupted first and
second premolars on radigraphs taken bysecond premolars on radigraphs taken by
paralleling technique.paralleling technique.
 Use this sum to estimate size of 3+4+5 usingUse this sum to estimate size of 3+4+5 using
the prediction chartthe prediction chart

Hixon and oldfather methodHixon and oldfather method
Measured value Estimated tooth size
23 18.4
24 19.0
25 19.7
26 20.3
27 21.0
28 21.6
29 22.3
30 22.9

Radiographic methodRadiographic method
 IOPA of the unerupted teeth and of overlyingIOPA of the unerupted teeth and of overlying
primary teeth are takenprimary teeth are taken
 The enlargement ratio for each uneruptedThe enlargement ratio for each unerupted
permanent tooth is computed by measuring thepermanent tooth is computed by measuring the
nearest erupted tooth in the mouth and then innearest erupted tooth in the mouth and then in
the radiograph.the radiograph.

Radiographic methodRadiographic method
Erupted tooth size in the mouth X unerupted tooth size in X ray
Erupted tooth size in x ray
= correct tooth size

Eruption and Occlusion of theEruption and Occlusion of the
Permanent DentitionPermanent Dentition

Permanent dentition stagePermanent dentition stage
 First molar calcification at birthFirst molar calcification at birth
 Rest calcification after birthRest calcification after birth
 Sequence of eruptionSequence of eruption
 Timing of eruptionTiming of eruption
 Permanent incisor erupt lingual and palatal toPermanent incisor erupt lingual and palatal to
deciduous incisorsdeciduous incisors
 Move labially as they eruptMove labially as they erupt
 Premolars develop below the diverging roots of thePremolars develop below the diverging roots of the
deciduous molarsdeciduous molars

 Overlap : in a normally occluding dentition, theOverlap : in a normally occluding dentition, the
maxillary teeth are labial/buccal to mandibular teethmaxillary teeth are labial/buccal to mandibular teeth
 Angulations : primary dentition teeth are verticallyAngulations : primary dentition teeth are vertically
positioned, permanent dentition buccolingual andpositioned, permanent dentition buccolingual and
mesiodistal angulationsmesiodistal angulations
 Occlusion : with the exception of mandibular centralOcclusion : with the exception of mandibular central
incisors and maxillary second molars, each permanentincisors and maxillary second molars, each permanent
teeth occludes with two teeth from the opposite archteeth occludes with two teeth from the opposite arch
 Overbite and overjet : 10-50% and 1-3 mm res.Overbite and overjet : 10-50% and 1-3 mm res.

 Posterior relationships :Posterior relationships :
 Maxillary and mandibular molars are in class IMaxillary and mandibular molars are in class I
relationshiprelationship
 Posterior segment well interdigitatedPosterior segment well interdigitated
 Maxillary canine should be occluding in the embrasureMaxillary canine should be occluding in the embrasure
between the mandibular canine and first premolar.between the mandibular canine and first premolar.

Nolla's 10 Stages of CalcificationNolla's 10 Stages of Calcification
 Stage 1 – absence of cryptStage 1 – absence of crypt
 Stage 2 - initial calcificationStage 2 - initial calcification
 Stage 3 - 1/3Stage 3 - 1/3rdrd
of crown completedof crown completed
 Stage 4 - 2/3Stage 4 - 2/3rdrd
of crown completedof crown completed
 Stage 5 - crown almost completedStage 5 - crown almost completed
 Stage 6 - crown formation completeStage 6 - crown formation complete
 stage 7 – 1/3stage 7 – 1/3rdrd
of root completedof root completed
 Stage 8 - alveolar crest pierced (2/3 root development)Stage 8 - alveolar crest pierced (2/3 root development)
 Stage 9 - gingival margin pierced (3/4 root development)Stage 9 - gingival margin pierced (3/4 root development)
 Stage 10 – apical end of root development completedStage 10 – apical end of root development completed
 Interval between Stage 6 and full interdigitation is about 5 yearsInterval between Stage 6 and full interdigitation is about 5 years

SequenceSequence
 Girls 5 months faster than boysGirls 5 months faster than boys
 6-1-2-4-3-5-7 and 6-1-2-4-5-3-7 most6-1-2-4-3-5-7 and 6-1-2-4-5-3-7 most
common in maxillacommon in maxilla
 (6-1)-2-3-4-5-7 and (6-1)-2-4-3-5-7 most(6-1)-2-3-4-5-7 and (6-1)-2-4-3-5-7 most
common in mandiblecommon in mandible

Sequence is Important!Sequence is Important!
 Alteration of sequence of eruption alertsAlteration of sequence of eruption alerts
the practitioner to potential problemsthe practitioner to potential problems
 SupernumerarySupernumerary
 Neoplasm or cystNeoplasm or cyst
 ALWAYS COUNT THE TEETH!ALWAYS COUNT THE TEETH!

Calcification times (Max. and mand.Calcification times (Max. and mand.
res.)res.)
 Central incisorCentral incisor 3-4 m3-4 m 3-4 m3-4 m
 Lateral incisorLateral incisor 10-12 m10-12 m 3-4 m3-4 m
 CuspidCuspid 4-5 m4-5 m 4-5 m4-5 m
 1st bicuspid1st bicuspid 1 1/2 y1 1/2 y 1 3/4 y1 3/4 y
 2nd bicuspid2nd bicuspid 2 y2 y 2 1/4 y2 1/4 y
 Second molarSecond molar 2 1/2 y2 1/2 y 2 3/4 y2 3/4 y

How To Remember ThisHow To Remember This
 A group of teeth beginA group of teeth begin
calcification every sixcalcification every six
monthsmonths
 Not exact, but closeNot exact, but close
enoughenough
BirthBirth 1st molars1st molars
6m6m Anterior teeth, exceptAnterior teeth, except
maxillary lateralsmaxillary laterals
12m12m Maxillary lateralsMaxillary laterals
18m18m 1st bicuspids1st bicuspids
24m24m 2nd bicuspids2nd bicuspids
30m30m 2nd molars2nd molars

Average Times to RememberAverage Times to Remember
 Hard tissue begins to enamel completedHard tissue begins to enamel completed
4-5 years4-5 years
Except for 1st molar (3) and cuspid (6)Except for 1st molar (3) and cuspid (6)
 Hard tissue begins to Root CompletionHard tissue begins to Root Completion
10 years, except for cuspids (13)10 years, except for cuspids (13)
 Eruption to Root CompletionEruption to Root Completion
3 years3 years

Why Know Calcification Times?Why Know Calcification Times?
Enamel hypoplasiaEnamel hypoplasia

Mesial Drift and AnteriorMesial Drift and Anterior
Component of ForceComponent of Force
• Axial inclinationAxial inclination
produces mesial forceproduces mesial force
• Mesial driftMesial drift
• Ectopic eruptionEctopic eruption
• Space maintenanceSpace maintenance

Ectopic EruptionEctopic Eruption

Absence of Permanent TeethAbsence of Permanent Teeth
 4-6% congenital absence4-6% congenital absence
 Females more frequently missing teethFemales more frequently missing teeth
 Most common congenitally absent teeth:Most common congenitally absent teeth:
 mandibular 2nd premolarmandibular 2nd premolar
 maxillary lateral incisormaxillary lateral incisor
 maxillary 2nd premolarmaxillary 2nd premolar

Extra Permanent TeethExtra Permanent Teeth
 Supernumerary teeth found mostSupernumerary teeth found most
frequently in the maxillary incisor regionfrequently in the maxillary incisor region
(mesiodens), and occasionally in the(mesiodens), and occasionally in the
premolar areapremolar area
 2-3% supernumerary teeth2-3% supernumerary teeth
 Males more commonMales more common

Terms: Mixed DentitionTerms: Mixed Dentition
 Classic mixed dentitionClassic mixed dentition
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 Early mixed dentitionEarly mixed dentition
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 Late mixed dentitionLate mixed dentition
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Terms - Arch LengthTerms - Arch Length
 Arch length is the distance inArch length is the distance in
millimeters from the mesial of the 1stmillimeters from the mesial of the 1st
permanent molar around the arch overpermanent molar around the arch over
the contact points to the mesial of thethe contact points to the mesial of the
1st permanent molar on the opposite1st permanent molar on the opposite
side.side.

Terms - Overbite/OverjetTerms - Overbite/Overjet
 OverbiteOverbite is a vertical measurement of theis a vertical measurement of the
amount of overlap of the incisors.amount of overlap of the incisors.
 OverjetOverjet is the millimeter horizontalis the millimeter horizontal
measurement from the labial of the maxillarymeasurement from the labial of the maxillary
central incisor to the labial of the mandibularcentral incisor to the labial of the mandibular
central incisor.central incisor.

Straight ProfileStraight Profile

Protrusive ProfileProtrusive Profile

Retrusive ProfileRetrusive Profile

Typical Child ProfileTypical Child Profile

Types of FacesTypes of Faces
 Brachycephalic - broad & shortBrachycephalic - broad & short
 Dolichocephalic - long & narrowDolichocephalic - long & narrow
 Mesocephalic - normalMesocephalic - normal

Dimensional changes in theDimensional changes in the
dental archesdental arches

Dimensional changes in theDimensional changes in the
dental archesdental arches
 The transition from primary dentition stage toThe transition from primary dentition stage to
the permanent dentition stage has an impact onthe permanent dentition stage has an impact on
dental arch length and intermolar anddental arch length and intermolar and
intercanine widthintercanine width

Changes in the maxillary archChanges in the maxillary arch
 The intercanine width increases by an average of 6.0 mm in aThe intercanine width increases by an average of 6.0 mm in a
child between 3-13 years of agechild between 3-13 years of age
 It continues to increase between 13-45 years of age by 1.7 mmIt continues to increase between 13-45 years of age by 1.7 mm
 In primary dentition stage there is an increase of intermolarIn primary dentition stage there is an increase of intermolar
width of 2.0 mm between 3-5 yearswidth of 2.0 mm between 3-5 years
 The first permanent intermolar width increases by 2.2 mmThe first permanent intermolar width increases by 2.2 mm
between 8-13 years of age and decreases by 1.0 mm by 45 yearsbetween 8-13 years of age and decreases by 1.0 mm by 45 years
of ageof age
 There is a slight decrease in arch length with age because ofThere is a slight decrease in arch length with age because of
uprighting of incisorsuprighting of incisors
( Bishara S E : arch width changes from 6weeks to 45 years of age,( Bishara S E : arch width changes from 6weeks to 45 years of age,
Am J of Orthod Dentofacial Ortop )Am J of Orthod Dentofacial Ortop )

Changes in the mandibular archChanges in the mandibular arch
 The intercanine width increases by an average of 3.7 mm in aThe intercanine width increases by an average of 3.7 mm in a
child between 3-13 years of agechild between 3-13 years of age
 It decreases between 13-45 years of age by 1.2 mmIt decreases between 13-45 years of age by 1.2 mm
 In primary dentition stage there is an increase of intermolarIn primary dentition stage there is an increase of intermolar
width of 1.5 mm between 3-5 yearswidth of 1.5 mm between 3-5 years
 The first permanent intermolar width increases by 1.0 mmThe first permanent intermolar width increases by 1.0 mm
between 8-13 years of age and decreases by 1.0 mm by 45 yearsbetween 8-13 years of age and decreases by 1.0 mm by 45 years
of ageof age
 The arch length decreases in mixed and permanent dentitionThe arch length decreases in mixed and permanent dentition
stages as a result of uprighting of incisors and the loss of leewaystages as a result of uprighting of incisors and the loss of leeway
space by mesial movement of first permanent molarsspace by mesial movement of first permanent molars
( Bishara S E : arch width changes from 6weeks to 45 years of age,( Bishara S E : arch width changes from 6weeks to 45 years of age,
Am J of Orthod Dentofacial Ortop )Am J of Orthod Dentofacial Ortop )

Development of occlusion

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