Burstone Analysis

INTRODUCTION
The introduction of radiographic cephalometrics in
1934 by Hofrath in Germany and Broadbent in the United
states provided both a research and a clinical tool for the
study of malocclusion and underlying skeletal
disproportions. Cephalometric films could be used to
evaluate dentofacial proportions and clarify the anatomic
basis for a malocclusion. The orthodontist needs to know
how the major functional components of the face (cranial
base, jaws, teeth) are related to each other. Any
malocclusion is the result of an interaction between jaw
position and the position the teeth assume as they erupt,
which is affected by the jaw relationship.
www.indiandentalacademy.com

A cephalometric analysis especially designed for
the patient who requires maxillofacial surgery was
developed to use landmarks and measurements that can
be altered by common surgical procedures. Because
measurements are primarily linear, they may be readily
applied to prediction overlays and study cast mountings
and may serve as a basis for the evaluation of post
treatment stability.

The successful treatment of the orthognathic
surgical patient is dependant on careful diagnosis.
Cephalometric analysis can be an aid in the diagnosis of
skeletal and dental problems and a tool for stimulating
surgery and orthodontics by the use of acetate overlays.
The first step in the diagnosis of the orthognathic
surgical patient is to determine the nature of dental and
skeletal defects.

Patients who require orthognathic surgery usually
have facial bones as well as tooth positions that must be
modified by a combined orthodontic and surgical
treatment. For this reason, a specialized cephalometric
appraisal system, called CEPHALOMETRICS FOR
ORTHOGNATHIC SURGERY (COGS) was developed at
The University of Connecticut.

The COGS system describes the horizontal and
vertical position of facial bones by use of a constant co -
ordinate system . The sizes of bones are represented by
direct linear dimensions and their shapes, by angular
measurements. The standards are based on a sample
obtained from the child research council of The University
of Colorado school of medicine through 16 females and 14
males. www.indiandentalacademy.com

ADVANTAGES
 The chosen landmarks and measurements can be
altered by various surgical procedures.
 The comprehensive appraisal includes all the facial
bones and a cranial base reference.
 Rectilinear measurements can be readily transferred
to a study cast for mock surgery.
 Standards and statistics are available for variations
in age and sex from ages 5 to 20 on the basis of
developmental age.
 Critical facial skeletal components are examined.
 A systematized approach to measurement that can
be computerized is used.

The COGS appraisal describes
 Dental,
 Skeletal
 Soft tissue variations.
Today we will discuss about the dental and skeletal
assessment.

Diagram
ANATOMIC LANDMARKS

SELLA (S) : Centre of pituitary fossa.
NASION (N) : Most anterior point of nasofrontal
suture in the midsagittal plane.
ARTICULARE (Ar): Intersection of basisphenoid and
posterior border of the condyle.
PTERYGOMAXILLARY : Most posterior point on the
FISURE (PTM) anterior contour of maxillary
tuberosity.
SUB SPINALE (A) : Deepest point in midsagital plane
between ANS and Prosthion.

POGONION (Pg) : Most anterior point in
midsagittal plane of the
contour of the chin.
SUPRAMENTALE (B) :Deepest point in the
midsagittal plane between
Infradentale and Pg.
ANS : Most anterior point of nasal
floor.
MENTON (Me) : Lowest point of the contour
of mandibular symphysis.

GNATHION (Gn) : Mid point between Pg and
Me.
MANDIBULAR PLANE : Plane constructed
(MP) from Me to the angle
of Mandible (Go)
NASAL FLOOR (NF) : Plane constructed from PNS
to ANS
GONION (Go) : Located by bisecting
posterior ramal plane and
MPA

I. CRANIAL BASE
The baseline for comparison of most of the data in this
analysis is a constructed plane called HORIZONTAL
PLANE (HP), which is a surrogate Frankfort plane,
constructed by drawing a line 7 o from the line S to N.www.indiandentalacademy.com

Cranial base is measured as the length from Ar to N,
parallel to HP. Ar –N is a relatively stable anatomical
plane, however it can be changed by cranial surgery
that affects N, such as Le fort II and III osteotomies.
Ar –N is also slightly altered with auto correctional
rotations of mandible, where Ar moves closer to N.

Ar- PTM
Measured parallel to HP to determine horizontal
distance between posterior aspects of mandible and
maxilla. The greater the distance between Ar-PTM,
the more the mandible will lie posterior to the maxilla,
assuming that all other facial dimensions are normal.
Therefore, one factor for prognathism or
retrognathism can be evaluated by this measurement
of cranial base.

II. HORIZONTAL SKELETAL PROFILE
Here all the measurements are made parallel
to HP, since most surgical corrections are primarily
done in anteroposterior direction. These include:

A. Degree of Skeletal Convexity
The N-A –Pg (Angle)
gives an indication of the
overall facial convexity. A
positive (+) angle of
convexity denotes a convex
face; a negative (-) angle
denotes a concave face. A
perpendicular from HP is
dropped through N. The
horizontal position of A is
measured to this
perpendicular line ( N-A).

This measurement describes the apical base of maxilla in
relation to N and enables the clinician to determine if
the anterior part of maxilla is protrusive or retrusive.
Useful in planning treatment of anterior maxillary
horizontal advancement or reduction, and of total
maxillary horizontal advancement or reductions.
B. N-B
Also measured in a plane parallel to HP from the
perpendicular line dropped from N. This
measurement describes the horizontal position of the
apical base of mandible in relation to N.
Useful in planning the treatment of anterior
mandibular horizontal advancement or reduction and
the total mandibular horizontal advancement or
reduction.

C. N- PG
Measured in the same manner as N-A and N-B and
indicates the prominence of the chin. This
measurement helps to determine if there is a
horizontal genial hyperplasia or hypoplasia.
Useful in the planning of treatment augmentation or
reduction genioplasty, of anterior mandibular
horizontal advancement or reduction, and of total
mandibular horizontal advancement or reduction.
Thus we can see that the measurements of the
horizontal skeletal profile represents
 Facial convexity
 Horizontal relationship of apical base A and B
points
 And the chin positions related to N.

III. VERTICAL SKELETAL AND DENTAL
A. SKELETAL
A vertical skeletal discrepancy may reflect an anterior,
posterior or complex dysplasias of face. Vertical
skeletal cephalometric measurements are divided into
 Anterior components
 Posterior components

Anterior components is
subdivided into
Middle third
facial
height :
Distance
from N to
ANS is
measured
perpendicul
ar to HP.
Lower third
facial
height :
ANS – GN,
measured
perpendicul
ar to HP

Posterior components is subdivided into :
a. Posterior maxillary height : Length of
perpendicular line dropped from HP intersecting
PNS
b. Divergence of mandible posteriorly : Shown
by MP – HP Angle.
Vertical skeletal measurements of the anterior
and posterior components of the face will help in
the diagnosis of anterior, posterior, or total
vertical maxillary hyperplasia or hypoplasia, and
clockwise or counter - clockwise rotations of the
maxilla and mandible.www.indiandentalacademy.com

The typical surgical correction of these problems
include total maxillary vertical advancement or
reduction, anterior maxillary vertical augmentation or
reduction, posterior maxillary vertical augmentation
or reduction, combinations of the above two and
mandibular ramus rotation and ramus height
reduction.

B. Dental
Assessment of vertical dental dysplasia is also divided
into
 Anterior component
 Posterior component

a. Anterior maxillary dental height ( 1-NF ):
Perpendicular line dropped from incisal edge of
maxillary central incisor to NF.
b. Anterior mandibular dental height (1 - MP) :
Perpendicular line dropped from incisal edge of
mandible central incisor to MP.
These two measurements define how far the incisors
have erupted in relation to NF and MP respectively.
Anterior component is subdivided into

Posterior component
Posterior maxillary dental height : Perpendicular line
through maxillary 1st molar mesiobuccal cusp tip to
NF
Post mandibular dental height : Perpendicular line
through mandibular 1st molar mesiobuccal cusp tip to
MP.

IV. MAXILLARY LENGTH
Distance from PNS
– ANS that is projected on
a line parallel to the HP.
This measurement along
with the N-ANS and PNS
– N gives a quantitative
description of the maxilla
in the skull complex.

V. MANDIBULAR LENGTH
Ar - Go : Length of
Mandibular ramus
Go - Pg : Length of
Mandibular body
Ar - Go - Gn Angle : Gonial
angle that represents the
relationship between
ramal plane and MP.
B - Pg : Distance from B
point to line perpendicular to
MP through Pg describes chin
prominence.

These measurements are helpful in the diagnosis of
variations in ramus height, that effect open bite or
deep bite problems, increased or diminished
mandibular body length, acute or obtuse Go angles
that also contribute to skeletal open or closed bite, and
finally, as an assessment of chin prominence.

VI. DENTAL
Here, the teeth has
to relate to each other
through a common
plane, such as occlusal
plane (OP) or to a plane
in each jaw , the MP, or
the NF plane.

OP
Line drawn from the buccal groove of both 1 st
permanent molars through a point 1 mm apical of the
incisal edge of the central incisor in each respective
arch.
OP ANGLE
Is the angle formed between this plane and HP. If the
teeth over lap anteriorly to produce an overbite, the
OP can be drawn as a single line.www.indiandentalacademy.com

INCREASED OP- HP
 Skeletal open bite
 Lip incompetence
 Increased facial height
 Retrognathia
 Increased MP angle
DECREASED OP- HP
 Deep bite
 Decreased facial height
 Lip redundancy

AB – OP
Constructed by dropping a perpendicular line to OP
from points A and B, respectively, and than
measuring the distance between these two linear
intersections. If A- B distance is large with point B
projected posteriorly to A, mandibular denture – base
discrepancy that predisposes to a class II occlusion is
present.

ANGULATION
1 – NF (angle) : Line drawn from incisal edge of
central incisor through the tip of the root to the point
of inter section with NF
1 – MP (angle) : Line drawn from incisal edge of
central incisor through the tip of the root to the point
of intersection with MP.
These angulations determine the procumbency or
recumbency of the incisors and are vital in assessing
long term stability of the dentition.

NORMAL VALUES

CONCLUSION
A thorough knowledge about Burstone analysis will
definitely help the orthodontist and the maxillofacial
surgeon in successfully treating orthognathic surgery
patients and in establishing an esthetic, harmonious
and stable relationship of the cranial base, jaws and
teeth.

Thank You

Burstone Analysis

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