Differential diagnosis

Differential DiagnosisDifferential Diagnosis
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Differential diagnosis analysisDifferential diagnosis analysis
systemsystem
 Merrifield ,in his effort to establish a sound diagnostic basis for hisMerrifield ,in his effort to establish a sound diagnostic basis for his
directional force treatment using multibanded mechanotherpydirectional force treatment using multibanded mechanotherpy
,introduced diagnostic analyses that allow clinician to determine,introduced diagnostic analyses that allow clinician to determine
 1)Whether & when are extractions necessary and1)Whether & when are extractions necessary and
 2)which teeth should be removed2)which teeth should be removed
 Attainment of previously stated objectives require a through andAttainment of previously stated objectives require a through and
accurate diagnosis that specifically identifies the major areas ofaccurate diagnosis that specifically identifies the major areas of
disharmony.disharmony.

 Thus, Weber definesThus, Weber defines diagnosisdiagnosis asas
 ““ a determination of a disease from symptoms, data or tests,a determination of a disease from symptoms, data or tests,
and the decisions and judgment made prior to treatment”.and the decisions and judgment made prior to treatment”.
 Merrifield’s diagnostic philosophy can be outlined as follows:Merrifield’s diagnostic philosophy can be outlined as follows:
 1.recognise and treat within the dimensions of the dentition1.recognise and treat within the dimensions of the dentition
(non-expansion, when normal muscular balance exist.)(non-expansion, when normal muscular balance exist.)
 2 recognize the dimension of the lower face and treat for the2 recognize the dimension of the lower face and treat for the
maximal facial harmony & balance.maximal facial harmony & balance.
 3.recognise and understand the skeletal pattern. Diagnose and3.recognise and understand the skeletal pattern. Diagnose and
treat in harmony with normal growth and developmentaltreat in harmony with normal growth and developmental
patterns.patterns.

 Any valid identification and classification of orthodontic &Any valid identification and classification of orthodontic &
orthognatic disharmony should be based on the four majororthognatic disharmony should be based on the four major
areas of the orthodontist responsibilityareas of the orthodontist responsibility
 1.Facial1.Facial
 2.Dental2.Dental
 3.Cranial3.Cranial

4.Environmental4.Environmental..

Facial disharmonyFacial disharmony
 A study of the face & its balance or lack of it must be the firstA study of the face & its balance or lack of it must be the first
concern during a differential diagnosis. The clinician must haveconcern during a differential diagnosis. The clinician must have
intuitive concept of a balanced face .intuitive concept of a balanced face .
 There are 3 factors that influences the balanced face or lack of itThere are 3 factors that influences the balanced face or lack of it
 1.the positions of teeth,1.the positions of teeth,
 2.the skeletal pattern,2.the skeletal pattern,
 3.the soft tissue thickness.3.the soft tissue thickness.

The facial balance is affected by the marked protrusion/ retrusion/The facial balance is affected by the marked protrusion/ retrusion/
crowding of teeth. the lips are supported by the max. incisor teeth. Thuscrowding of teeth. the lips are supported by the max. incisor teeth. Thus
lip protrusion is the reflection of the amt. of max. incisor protrusion.lip protrusion is the reflection of the amt. of max. incisor protrusion.
Protruded teeth thus cause facial imbalance.Protruded teeth thus cause facial imbalance.
Facial disharmonies are oftenFacial disharmonies are often
the result of abnormal skeletalthe result of abnormal skeletal
relationships.relationships.
The clinician must understandThe clinician must understand
the skeletal pattern & have thethe skeletal pattern & have the
ability to compensate forability to compensate for
abnormal skeletal relationshipsabnormal skeletal relationships
by changing the position of theby changing the position of the
teeth.teeth.
(The(The FMA,FMA, is a skeletal angularis a skeletal angular
value that is crucial in diff/dia.value that is crucial in diff/dia.
lower facial balance can belower facial balance can be
dramatically improved by usingdramatically improved by using
this knowledge).this knowledge).

 Total chin thicknessTotal chin thickness
=upper lip thickness.=upper lip thickness.
 (if it is,< ult ,the(if it is,< ult ,the
anterior teeth must beanterior teeth must be
positioned uprightpositioned upright
further to facilitate afurther to facilitate a
more balanced facialmore balanced facial
profile, because lipprofile, because lip
retraction followsretraction follows
tooth retraction.)tooth retraction.)
Facial disharmony that are not the result of skeletal or dentalFacial disharmony that are not the result of skeletal or dental
distortion are generally the result of poor soft tissuedistortion are generally the result of poor soft tissue
distribution. this problem needs to identified during diff/dia.distribution. this problem needs to identified during diff/dia.
so that crucial dental compensations can be planned.so that crucial dental compensations can be planned.

 Thus careful consideration of the positions of teeth, skeletalThus careful consideration of the positions of teeth, skeletal
pattern, & soft tissue overlay will give crucial informationpattern, & soft tissue overlay will give crucial information
about face & enable the clinician to determine whether dentalabout face & enable the clinician to determine whether dental
compensations will improve facial balance. before initiatingcompensations will improve facial balance. before initiating
tooth movement.tooth movement.
 Its impact on the overlying soft tissue must be clearlyIts impact on the overlying soft tissue must be clearly
understood.understood.

Whenever facial balance is present ,the ideal relationship ofWhenever facial balance is present ,the ideal relationship of
profile line is to be tangent to the chin & the vermilion borderprofile line is to be tangent to the chin & the vermilion border
of both lips and should bisect the nose. This results in aof both lips and should bisect the nose. This results in a
pleasing & balanced profile.pleasing & balanced profile.

 Similarly, on frontal view,Similarly, on frontal view,
the vermilion border ofthe vermilion border of
lower lip should bisect thelower lip should bisect the
distance between bottomdistance between bottom
of the chin & ala of nose.of the chin & ala of nose.
 The vermilion border ofThe vermilion border of
upper lip should alsoupper lip should also
bisect the distancebisect the distance
between from thebetween from the
vermilion border of lowervermilion border of lower
lip to ala of nose.lip to ala of nose.
 These are universallyThese are universally
accepted orthodonticaccepted orthodontic
standards for facialstandards for facial
balance & harmony.balance & harmony.

Several cephalometeric standards quantify facial balance. Two thatSeveral cephalometeric standards quantify facial balance. Two that
have been found to be very useful are the-have been found to be very useful are the-
1.1. Z angleZ angle
2.FMIA2.FMIA
Z angle:Z angle:
This Angle was developedThis Angle was developed
to further define facialto further define facial
esthetics & is an adjunctesthetics & is an adjunct
to the FMIA.to the FMIA.
It is the angle b/n the FHIt is the angle b/n the FH
plane and soft tissueplane and soft tissue
profile which quantifiesprofile which quantifies
Facial balance.Facial balance.
NORMAL RANGE- 70NORMAL RANGE- 70o-o-
8080oo
..
(ideal value- 75(ideal value- 75oo
– 78– 78oo
.).)

 Z angle is more indicated of the soft tissue profile than FMIAZ angle is more indicated of the soft tissue profile than FMIA
and is responsive to the maxillary incisor position.and is responsive to the maxillary incisor position.
 Maxillary incisor retraction of 4 mm allows 4 mm of lower lipMaxillary incisor retraction of 4 mm allows 4 mm of lower lip
retraction & apprx. 3 mm of upper lip response.retraction & apprx. 3 mm of upper lip response.
 It quantifies the combined abnormalities in the values of FMA,It quantifies the combined abnormalities in the values of FMA,
FMIA & soft tissue thickness and all have a direct bearing onFMIA & soft tissue thickness and all have a direct bearing on
facial balance.facial balance.
 If any of the 3 above component is not within the optimalIf any of the 3 above component is not within the optimal
range, differentiation can be made to determine which valuesrange, differentiation can be made to determine which values
are not optimum & whyare not optimum & why
 It gives immediate guidance to anterior tooth reposition.It gives immediate guidance to anterior tooth reposition.

FMIA:FMIA:
 Tweed believed that thisTweed believed that this
value was significant invalue was significant in
establishing the harmony ofestablishing the harmony of
the face.the face.
 Tweed established aTweed established a
standard of 68standard of 68oo
forfor
individual with an FMIA ofindividual with an FMIA of
2222oo
– 28– 28oo
..
 Standard should be 65Standard should be 65oo
ifif
the FMA is 30the FMA is 30oo
or more,or more,
and the FMIA will increaseand the FMIA will increase
if FMA is lower.if FMA is lower.

Cranial Disharmony:Cranial Disharmony:
 A careful cranial analysis must include but if not be limited toA careful cranial analysis must include but if not be limited to
study and understanding of the following information.study and understanding of the following information.
Skeletal Analysis FactorsSkeletal Analysis Factors::
FMAFMA –– It is the most significant value for skeletal analysisIt is the most significant value for skeletal analysis
because it defines the direction of lower facial growth in bothbecause it defines the direction of lower facial growth in both
the horizontal and vertical dimensions.the horizontal and vertical dimensions.
Normal Range- 22Normal Range- 22oo
– 28– 28oo
..
<<FMAFMA Deficient vertical growth.Deficient vertical growth.
>FMA Excessive vertical growth.>FMA Excessive vertical growth.

IMPA:IMPA:
 Defines axial inclination ofDefines axial inclination of
mandibular incisors w.r.t.mandibular incisors w.r.t.
mandibular plane.mandibular plane.
 It is a good guide to use inIt is a good guide to use in
maintaining or positioningmaintaining or positioning
of the mandibular incisors inof the mandibular incisors in
relation to the basal bone.relation to the basal bone.
 Standard value – 88Standard value – 88oo
..
(indicates an upright(indicates an upright
incisors, with a normalincisors, with a normal
FMA reflects optimalFMA reflects optimal
balance and harmony ofbalance and harmony of
lower facial profile)lower facial profile)

SNA:SNA:
 Indicates relativeIndicates relative
horizontal position ofhorizontal position of
the maxilla to thethe maxilla to the
cranial base.cranial base.
 Normal Range: 80Normal Range: 80oo
––
8484oo
..

SNB:SNB:
 Indicates horizontalIndicates horizontal
relationship of mandible torelationship of mandible to
the cranial base.the cranial base.
–82–82oo
..
 <74<74oo
/ >84/ >84oo
– Large maxillo-– Large maxillo-
mandibular discrepancy.mandibular discrepancy.
(orthognathic surgery(orthognathic surgery
indicated)indicated)

ANB:ANB:
 It indicates horizontalIt indicates horizontal
relationship of maxilla torelationship of maxilla to
the mandible.the mandible.
 Normal Range- 1Normal Range- 1oo
- 5- 5oo
..
 >10>10oo
/>-3/>-3oo
indicative ofindicative of
facial disproportion.facial disproportion.
(possibility of surgical(possibility of surgical
assistance)assistance)

AO-BO:AO-BO:
 This indicates relationshipThis indicates relationship
of maxilla to mandible.of maxilla to mandible.
 More sensitive than ANBMore sensitive than ANB
because it is measured atbecause it is measured at
the occlusal plane.the occlusal plane.
 Normal Range: 0–4 mm.Normal Range: 0–4 mm.

Occlusal Plane:Occlusal Plane:
 Occlusal plane valueOcclusal plane value
expresses a dentoskeletalexpresses a dentoskeletal
relationship of OP to FHrelationship of OP to FH
plane.plane.
– 12– 12oo
..
 Values < or > normal rangeValues < or > normal range
indicates more difficulty inindicates more difficulty in
treatment.treatment.
 In most orthodonticIn most orthodontic
corrections, the originalcorrections, the original
values should be maintainedvalues should be maintained
or decreased.or decreased.
 An > indicated loss of controlAn > indicated loss of control
& instability.& instability. www.indiandentalacademy.comwww.indiandentalacademy.com

Facial Height Index:Facial Height Index:
 Andre Horn studied the relationship of AFH to PFH,Andre Horn studied the relationship of AFH to PFH,
developed Facial Height Index.developed Facial Height Index.
 He found that Normal PFH isHe found that Normal PFH is 0.69 or 69%0.69 or 69% of AFH.of AFH.
 Normal Range:Normal Range: 0.65 – 0.750.65 – 0.75..
 If the value is < or > this range, the malocclusion is difficultIf the value is < or > this range, the malocclusion is difficult
to correct.to correct.

Facial Height Ratio:Facial Height Ratio:
 Facial height change ratio is valuable in the evaluation ofFacial height change ratio is valuable in the evaluation of
treatment interval changes.treatment interval changes.
 Ratio of two times as much of PFH as AFH duringRatio of two times as much of PFH as AFH during
treatment is ideal for correction of class II div 1.treatment is ideal for correction of class II div 1.
 However, even more important is the volume of the change.However, even more important is the volume of the change.
 Merrifield and Gebeck reported 2 to 1 increase in PFH to AFHMerrifield and Gebeck reported 2 to 1 increase in PFH to AFH
in the sample of successfully treated malocclusion.in the sample of successfully treated malocclusion.

Jim Gramling of Jonesboro, Arkansas, research director ofJim Gramling of Jonesboro, Arkansas, research director of
Tweed foundation compiled a large sample of successful &Tweed foundation compiled a large sample of successful &
unsuccessfully treated Class II malocclusion by theunsuccessfully treated Class II malocclusion by the
foundation and compared the results.foundation and compared the results.

 In theIn the successfulsuccessful sample, FMA was controlled, FMIA , IMPAsample, FMA was controlled, FMIA , IMPA
 In theIn the unsuccessfulunsuccessful sample, FMA , FMIA remained same orsample, FMA , FMIA remained same or
decreased, IMPA or remained the same.decreased, IMPA or remained the same.
 There was not as much Z angle increased in unsuccessfulThere was not as much Z angle increased in unsuccessful
sample.sample.
 SNA reduction was similar.SNA reduction was similar.
 AO-BO reduction was unsatisfactory.AO-BO reduction was unsatisfactory.
 Y axis & SNB remained the same for both samples.Y axis & SNB remained the same for both samples.
 By studying the data from two samples, it can be concludedBy studying the data from two samples, it can be concluded
that in unsuccessful Class II treatment, the mandibular incisorthat in unsuccessful Class II treatment, the mandibular incisor
position was not corrected or if corrected, the correction wasposition was not corrected or if corrected, the correction was
subsequently compromised by excessive, unreciprocated usesubsequently compromised by excessive, unreciprocated use
of Class II elastics in an attempt to estb proper AP maxilloof Class II elastics in an attempt to estb proper AP maxillo
mandibular dental relationships.mandibular dental relationships.

Thank You.Thank You.

Differential diagnosis

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Differential diagnosis