pbl cephalometry dentistry

8/9/2019 PBL cephalometry Dentistry

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CEPHALOMETRICS

Defne cephalometrics• Craniometry is the measurement of the head of a living subjet from bon!

landmar"s loated b! #al#ation or #ressing through the adjaent tissues$

The dra%ba" of raniometr! is& it is a ross'setional stud!$

• (ith the advent of e#halometr!& disadvantages of raniometr! %ere

overome$

• )cephalo’ means head and )metric’ means measurement$

• The measurement of the head from the shado%s of the bon! and soft

tissue landmar" on the radiogra#hi image is "no%n as

roentgenographic cephalometry

• Aording to Mo!er& cephalometrics is a radiogra#hi tehni*ue for

abstrating the human head into a geometri sha#e$

• Ce#halometr! an be used for longitudinal studies$

Types o cephalograms• Lateral e#halogram

• +rontal or antero#osterior e#halogram

• Obli*ue e#halogram

Used o cephalogram• Ce#halogram is used in orthodonti diagnosis to eluidate the s"eletal&

dental and soft tissue relationshi#s of the raniofaial region$

• It is a valuable tool in the identi,ation and lassi,ation of s"eletal and

dental anomalies$

• It hel#s in treatment #lanning$ Res#onse to treatment an be a##raised on

subse*uent e#halogram$

• Ce#halogram are useful in estimating the faial t!#e$

• It an be used to *uantif! the hanges brought about b! the treatment$

• It hel#s to distinguish hanges #rodued b! natural gro%th and

orthodonthi treatment$

•

Assessment of gro%th of faial s"eleton is #ossible through seriale#halograms$


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• It is also used in gro%th #redition$

• It is used to #lan the s"eletal re#ositioning in surgial orthodonthis

• +untional anal!sis an be arried out %ith the hel# of e#halograms$

• Ce#halograms are tangible reords that are relativel! #ermanent unli"e

other diagnosti measurements li"e ali#er readings& #al#ation& #robing&

et$

• Ce#halograms are relativel! non'destrutive and non'invasive #roduing a

high !ield of information at relativel! lo% #h!siologi ost$

• Ce#halograms are eas! to store& trans#ort and re#rodue$

Limitation and drawbacks o cephalogram• Patient is e-#osed to ioni.ing radiation %hih is harmful$ Hene& it is used

onl! %hen it is diagnostiall! and thera#eutiall! desirable$

• The absene of anatomial referenes %hih remain onstant %ith time is

a serious disadvantage %hen liniians %ish to om#are e#halograms

ta"en at di/erent time #oints$

• The #roesses of image a*uisition as %ell as measurement #roedures

are not %ell standardi.ed$

• The di0ult! in loating landmar"s and surfaes on the 1'ra! image as the

image la"s hard edges and de,ned outlines$

• The strutures being imaged are three dimensional %hereas the

radiogra#hi image is t%o dimensional$

• Anatomial strutures l!ing at di/erent #lanes %ithin the head undergo

#rojetive dis#laement$

• Some referene landmar"s and #lanes do not agree %ith the anatomial

landmar"s$

• Patient is #ositioned %ith the ear rods in the e-ternal aousti meatus$ Theo#erator assumes that the meatuses are s!mmetrial$ It need not be so$

• Patient is made to bite in ma-imum interus#ation %hile ta"ing the

e#halogram$ There ould be a mandibular shift from entri relation$

• A e#halometri anal!sis ma"es us of means obtained from di/erent

#o#ulation sam#les$ The! have onl! limited relevane %hen a##lied to

individual #atient$

• The om#osite of lines and angles used in the e#halometri anal!sis

!ields limited information about the #atient2s dento's"eletal #atterns$


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• An orthodonti diagnosis annot be made solel! on the basis of

e#halomtri anal!sis$

CEPHAL!ET"#C "AD#$"APH% & TECH'#(UE

Cephalometric landmarksCe#halometri landmar"s an be broadl! lassi,ed into hard tissue and soft

tissue #oints$

CEPHAL!ET"#C LA'D!A")*

Hard tiss+e points

Unilateral points


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• Nasion (N) : #oint %here frontonasal and internasal sutures meet in the

midline$

• Anterior nasal spine (ANS) : Most anterior #oint of ma-illa$ 3sed for

vertial measurement$

• Point A (Subspinale): the dee#est #oint in the urvature bet%een anterior

nasal s#ine 4A5S6 and inferior most #oint in the ma-illar! alveolar #roess$

• Point B (Supramentale): the dee#est #oint in the urvature bet%een

#ogonion and su#erior most #oint in the mandibular alveolar #roess$

• Pogonion (Pog): Anterior most #oint in the ontour of the lateral shado% of

the hin$

• Gnathion (Gn): The most anterior and inferior #oint on the lateral shado%

of hin$ It is a##ro-imatel! in the mid#oint bet%een #ogonion and menton$

• Menyon (Me): The inferior most #oint in the ontour of the hin$

• Basion (Ba): The most #osterior and inferior #oint in the sagittal #lane on

the anterior rim of foramen magnum$

• Sella (S): Centre of the #ituitar! fossa or sella turia$

Bilateral points

• Orbitale (O): The lo%est #oint on the outline of the bon! orbit$ In the

lateral e#halogram& overla##ing of the t%o side is seen$ In that situation&lo%est #oint in the averaged outline is used for onstruting this #oint$

• Gonion (Go): The most #osterior and inferior #oint at the angle of

mandible$

• Articulare (Ar): Intersetion of the inferior surfae of the ranial base and

the #osterior surfaes of the ne"s of the ond!les of mandible$

• Porion (Po): Su#erior most #oint of the e-ternal auditor! meatus$ 3suall!

onl! anatomi #orion is ta"en into onsideration$ The mahine #orion

%hih is the shado% of the ar rods are not onsidered$

• Bolton point (Bo): The highest #oint in the u#%ard urvature of the

retroond!lar fossa$

*ot tiss+e points

• Sot tissue glabella (G’): The most #rominent #oint in the midline of the

forehead$

• Sot tissue nasion (Na’): Root of the nose in the midline$

• Sot tissue pogonion (S Pog): Most #rominent #oint in the soft tissueontour of hin$


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"eerence planes +sed in cephalometryMost ommonl! used referene #lanes and their e-#lanation

"eerence Planes

Plane Defniton

Sella'nsion

#lane 4S56

Line joining sella #oint and nasion

+ran"fort

hori.ontal #lane

4+H6

Line onneting orbitale and #orion


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• A58 reading less than ;@ or negative angulations suggests s"eletal

lass III #attern$

• *keletal analysis& A', angle

•

ccl+sal plane angle

• It is the angle formed b! the S'5 #lane and the olusal #lane$ Olusal

#lane is dra%n through the overla##ing us#s of ,rst molars$

• Olusal #lane angle sho%s the relation of dentition to anterior ranial

base$ The mean value is :B@$

!andib+lar plane angle

• It is the angle formed b! the S'5 #lane and the mandibular #lane$

Mandibular #lane is dra%n b! a line onneting gonion and gnathion$

• Mandibular #lane angle denotes the gro%th #attern of an individual$ The

mean value is =;@$

• High mandibular #lane angle is indiative of vertial gro%th #attern and

lo% mandibular #lane angle is indiative of hori.ontal gro%th #attern$

7ental anal!sisMaxillary #ncisor position

• 3##er inisor is related to 5'A line for determining its #osition$

• 3##er inisor to 5'A 4linear6> the distane bet%een inisal edge of u##er

inisor to the 5'A line$ Mean value is B mm$

• It inreases %ith u##er inisor #rolination and dereases %ith

retrolination$


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• 3##er inisor to 5'A 4angular6> The angle bet%een long a-is of u##er

inisor to the 5'A line$ Mean value is ;;@$

• It inreases %ith inisor #rolination

!andib+lar incisor position• Lo%er inisor is related to 5'8 line determining its #osition$

• Lo%er inisor to 5'8 4liner6> The distane bet%een inisal edges of lo%er

inisor to the 5'8 line$ Mean value is Bmm$

• It inreases %ith lo%er inisor #rolination and dereases %ith

retrolination$

• Lo%er inisor to 5'8 4angular6> The angle bet%een long a-is of lo%er

inisor to the 5'8 line$ Mean value is ;$

• It inreases %ith lo%er inisor #rolination and dereases %ith

retrolination$

#nterincisal angle• Interinisal angle is formed b! long a-is of the u##er inisor and long a-is

of the lo%er inisor$

• The mean value is :=;$

• More aute angulations are found %hen u##er and or lo%er inisors are

#rolined$

• More obtuse angulations are found %hen u##er and Jor lo%er inisor are

retrolined$

• 5oting the angulations of u##er teeth to 5'A line and lo%er inisor to 5'8

line is hel#ful in deteting inisors %ith defetive angulations$

Soft tissue anal!sis


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• Steiner2s line is dra%n from the middle of S'sha#ed urve formed b! lo%er

border of nose to the soft tissue ontour of the hin$

• The li#s in %ell balaned faes should lie along this line$

•

Li#s loated anterior to this line are labelled #rotrusive$ Orthodontitreatment ma! be underta"en to redue #rotrusion$

Drawback o *teiner-s analysis• Steiner2s A58 angle %hih is a ommonl! used measure of ja% relationshi#

is ; in normal adult$

• A58 angle is a/eted b! rotation of ja%s& and length of ranial base$

• Clo"%ise rotation of ja% bases ould lead to inrease in A58 angulations$

Counterlo"%ise rotation leads to derease in A58 angulations$

• Short ranial base results in ba"%ard #osition of nasion in relation to

ja%s$ This inreases A58 angulations$ Long ranial base leads to derease

in A58 angle$

*tener-s analysis& s+mmary

9aKable 5orma

l

Inreased 7ereased

:$ S5A ?; Prognathi

ma-illa

Retrognathi ma-illa

;$ S58 ? Prognathi

mandible

Retrognathi mandible

=$ A58 ; Class II s"eletal

#attern

Class III s"eletal #attern

B$ Olusal

#lane

:B Clo"%ise

rotation of

olusal #lane

Counterlo"%ise rotation of

olusal #lane

$ Mandibular

#lane

=; 9ertial gro%th

#attern

Hori.ontal gro%th #attern

$ 3 inisor to

5A 4angular6

;; 3##er inisor

#rolination

3##er inisor retrolination


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F$ 3 inisor to

5A 4linear6

Bmm 3##er inisor

#rolination

3##er inisor retrolination

?$ L inisor to

58 4angular6

; Lo%er inisor

#rolination

Lo%er inisor retrolination

$ L inisor to

58 4angular6

B mm Lo%er inisor

#rolination

Lo%er inisor retrolination

:

$

Interinisal

angle

:=; Retrolined

inisors

Prolined inisors

:

:$

S line mm Protrusive li#s Retrusive li#s


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• In other %ords& N'a-is indiates the do%n%ard& rear%ard or for%ard

#osition of the hin$

Ra"osi2s T'a-is

• Ra"osi2s N'a-is is the measured angle bet%een 5'S'


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Cephalometric points +sed• Porion> Su#erior most #oint of the e-ternal aousti meatus$

• Orbitale > Inferior most #oint along the lo%er border of orbit$

Planes 0 +sed:$ +ran"fort hori.ontal #lane> Obtained b! joining #orion and orbitale$

;$ Long a-is of lo%er inisor> Obtained b! dra%ing a line along the long a-is

of inisors$

=$ Mandibular #lane> Obtained b! dra%ing a tangent to lo%er border of

mandible$

Angles ormed:$ +ran"fort mandibular #lan angle 4+MA6> it is the angle formed at the

intersetion of +ran"fort hori.ontal #lane and mandibular #lane$ 9alue is

; in %ell'balaned faes$

;$ Inisor mandibular #lane angle 4IMPA6> It is the angle formed at the

intersetion of mandibular #lane and long a-is of lo%er inisor$ 9alue is

in %ell'balaned faes$

=$ +ran"fort mandibular inisor angle 4+MIA6> It is the angle formed at the

intersetion of long a-is of lo%er inisor and +ran"fort hori.ontal #lane$

9alue is in %ell'balaned faes$

• Tweed-s diagnostic triangle

•

#nterpretations• +MA ;? means high angle #atient and mandible gro%s lo"%ise$


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• +MA D ;= means lo% angle #atient and mandible gro%s ounterlo"%ise$

• IMPA :: means #rolined lo%er inisors$

• IMPA D ? means retrolined lo%er inisors$

Clinical applications• T%eed2s triangle is used in diagnosis& lassi,ation& treatment #lanning

and #rognosis$

• T%eed advoated e-tration of teeth to orret alveolodental #rognathism

and to #osition the lo%er inisors u#right over basal bone$

• (hen the +ran"fort mandibular #lane angle is in the range of ; to =&

the #rognosis for orthodonti treatment %ith e-trations is e-ellent to

good$

• (hen the +ran"for" mandibular #lane angle is in the range of = to =&

the #rognosis for orthodonti treatment %ith e-trations is good to fair$

• (hen the +ranfort mandibular #lane angle is in range of = to B& the

#rognosis for orthodonti treatment %ith e-trations is unfavourable$

pbl cephalometry dentistry

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