3. CHARLESJ.BURSTONE
Charles J. Burstone (April 4,
1928 February 11, 2015)
He was an American orthodontist
who was notable for his
contributions to biomechanics and
force-systems in the field of
orthodontics.
He wrote more than 200 articles in
scientific fields.
4. HarryL.LeganDr. Legan is an internationally recognized orthodontic expert on diagnosis
and treatment planning, obstructive sleep apnea, orthognathic surgery,
biomechanics, and distraction osteogenesis.
5. Horizontal plane 7º to SN plane
Burstone CJ et al Cephalometrics for orthognathic
surgery, J Oral Surg . 1978 Apr ; 36(4):269-77.
HORIZONTAL PLANE SUBSTITUTED S-N
PLANE:
ARTICLE FOR HARD TISSUE
6. Although the hard tissue analysis will show the
nature of existing skeletal discrepancy, it is
incomplete in providing information concerning
the facial form and proportions of patients in
many circumstances for orthognathic surgery.
Because the soft tissue covering the teeth and
bone is highly variable in its thickness, and this
variation may be greater than the variation found
in the position and size of the teeth and bones.
7. Hard tissue measurements can deviate considerably
from the facial form the patient expresses with the
soft tissue.
Patient may appear either more or less convex in their
profiles than is indicated by their hard tissue because
of differences in thickness of soft tissue.
By considering these factors Burstone and Legan gave
soft tissue analysis for orthognathic surgery.
8. SAMPLE SIZE-
The mean and standard deviations for the
measurements used in this soft tissue analysis
were derived from a population of 40 patients.
20 MEN
20 WOMEN
Between the age group of 20-30 yrs.
Patient in the sample were orthodontically
untreated class 1 occlusions and had vertical
proportions A-ANS , ANS-Me, within limits.
23. Facial Convexity Angle
G-Sn-Pg
Drop a line form Glabella ‘G’ to
Subnasale ‘Sn’ and a line Sn to soft tissue
pogonion ‘Pg’.
Mean value : 12 ± 4⁰
increased +ve value - convex profile
Increased -ve value - concave profile
(class3 skeletal and dental relationship)
24. MAXILLARY PROGNATHISM
G-Sn
Drop line perpendicular to horizontal
plane from Glabella. Measure the distance
from perpendicular line to Sn ( parallel to
HP)
Mean value: 6 ± 3 mm
Describes the amount of maxillary
excess/deficiency in anteroposterior
dimension.
+ve=maxillary prognathism.
–ve=maxillary retrognathism.
25. This measurement and other related
measurements are important in planning treatment
for anterior maxillary advancement and
reduction.
And
For total alveolar or Le Fort Ⅰ maxillary
advancement or reduction.
26. MANDIBULAR PROGNATHISM
G-Pg
Drop a perpendicular line to HP from
Glabella. Measure the position of the
pogonion from this line parallel to HP.
Mean value: 0 +/- 4
Increased –ve or +ve value is indicative
of retrognathic or prognathic mandible.
27. If pogonion is positioned posteriorly, further
examination is necessary to determine whether the
small hard tissue chin,
mandible average body positioned posteriorly
small body of mandible
or the thin soft tissue over this chin
or combination
are at fault.
28. VERTICAL HEIGHT RATIO
G-Sn/Sn-M
Drop a perpendicular line to HP from
Glabella, to this line drop a perpendicular
line to Sn and M. Measure the distance
from G-Sn and Sn – Me ( all perpendicular
to HP )
The ratio of middle 3rd to lower 3rd
facial height measured perpendicular to
HP.
Ratio less than 1 = denotes
disproportionality and there is large lower
3rd face and vice versa.
Disadvantages - Further evaluation of
lower 3rd of face is needed.
29. LOWER FACE THROAT ANGLE
Sn-Gn-C Angle
Formed by the intersection of lines Sn-
Gn & Gn-C
.
Mean value:100⁰ ± 7⁰
INFERENCE
Obtuse lower face neck angle indicates
that any procedures that reduce the
prominence of chin should not be done.
30. LOWER VERTICAL HEIGHT DEPTH RATIO
Sn-Gn/C-Gn
Drop a line from Sn to Gn and C to Gn .
Measure the distance from Sn – Gn and C
–Gn .
Mean value : 1.2 : 1
If the ratio is more than 1 = short neck.
In that case anterior projection of the
chin probably should not be reduced.
Useful in determining the feasibility of
reducing / increasing the chin prominence.
32. NASOLABIAL ANGLE
Cm-Sn-Ls Angle
Cm – Sn - Ls - NASOLABIAL ANGLE
Draw a line from Sn to Cm and drop a
line from Sn to Ls. Measure the angle
formed.
Mean value : 102⁰ ± 8⁰
Important measurement in assessing the
anteroposterior maxillary dysplasias
ACUTE nasolabial angle = treated by
surgically retracting the maxilla / maxillary
incisors / both.
OBTUSE nasolabial angle = suggests the
degree of maxillary hypoplasia and indicates
for maxillary advancement or orthodontic
proclination of maxillary incisors.
33. UPPER LIP PROTUSION
Ls to Sn-Pg (Linear)
Draw a line from Sn to soft tissue Pg,
the amount of lip Protrusion / Retrusion is
measured with perpendicular linear
distance from this line to the prominent
point of the lip.
Standard value - 3±1mm
The abnormal values can be treated by
retracting or protracting the incisors ,
surgically or orthodontically advancing or
retracting the maxilla accordingly.
34. LOWER LIP PROTUSION
Li to Sn-Pg linear
Drop a line from Sn to Pg and the
amount of lip protrusion / retrusion is
measured with perpendicular linear
distance from this line to the most
prominent point of both lips .
standard value - 2±1mm
By retracting / protracting the incisors
surgically / orthodontically advancing or
reducing the chin prominence , possible to
achieve desired lower lip.
35. MENTOLABIAL SULCUS DEPTH
Si to Sn-Pg
It is perpendicular distance
between deepest point on the
mentolabial sulcus to Li-Pg’ line.
Standard Value 4 ± 2 mm
A sulcus of about 4mm is
average in providing a lower lip
to chin contour.
36.
37. VERTICAL LIP CHIN RATIO
Sn-StmS/Sn-StmI
To assess lower third of face
Mean values : ( 1 : 2 )
Lower 3rd of the face ( Sn-Me ) can be
divided into three parts : length of the
upper lip ( distance from Sn to Stms )
should be approximately 1/3rd the total
and distance from Stmi to Me should be
2/3rd.
If the ratio becomes less than the normal
( ½ ) -- vertical reduction genioplasty is
recommended.
38. MAXILLARY INCISOR EXPOSURE
StmS- U1
It is obtained by measuring the distance
between tip of upper central incisor and
Stms.
Standard Value -2 ± 2 mm
Increased incisor exposure may be due
to vertical maxillary excess or short upper
lip .
Decreased incisor exposure may be due
to vertical maxillary deficiency or larger
upper lip.
39. INTER-LABIAL GAP
It is the distance between Stms and Stmi
Standard Value - 2 ±2 mm
Patients with vertical maxillary excess
tend to have large interlabial gap and lip
incompetence .
Patients with vertical maxillary
deficiency tend to have no Inter labial gap
and Lip redundancy.
40. REFERENCES :
Radiographic Cephalometry – Alexander Jacobson
Charles J. Burstone, H. Legan et al –Cephalometrics for
orthognathic surgery, J Oral Surgery, 1978, vol 36; 269-277
Charles J. Burstone, H. Legan- Soft tissue cephalometric
analysis for orthognathic surgery 1980, J Oral Surgery, 1980,
vol 38;744-750
