DR ARIF ISMAIL

DEPARTMENT OF ORTHODONTICS

SOFT TISSUE CEPHALOMETRIC

ANALYSIS FOR ORTHOGNATHIC

SURGERY

CONTENTS :• INTRODUCTION

• CEPHALOMETRIC LANDMARKS USED FOR THE ANALYSIS

• HORIZONTAL ANALYSIS FOR THE SOFT TISSUE PROFILE

• VERTICAL ANALYSIS FOR THE SOFT TISSUE PROFILE

• CONCLUSION

INTRODUCTION :Treatment planning for patients who require orthognathic surgery should include both a hard tissue and soft tissue cephalometric analysis.

A good facial profile reflects harmony between many facial areas that are dependent on tooth position, bone position and soft tissue mass. Thus soft tissue areas such as the neck, nose and lilps must be considered in determining whether prognathism or retrognathism of the jaw exists.

The mean standard deviations for the measurements used in this soft tissue analysis were derived from a population of 40 white adults (20 men and 20 women) – between the ages of 20 and 30. All patients in the sample were orthodontically untreated with class I occlusions and had vertical facial proportions that were determined to be within normal limits (N. ANS/ANS. Me was between 0.75 and 0.85)

SOFT TISSUE LANDMARKS USED FOR THE ANALYSIS

•

• GLABELLA

PRONASALE

COLUMELLA POINT

SUBNASALE

LABRALE SUPERIUS

STOMION SUPERIUS

LABRALE INFERIUS

STOMION INFERIUS

LOWER LIP VERMILION

SOFT TISSUE POGONION

SOFT TISSUE MENTON

CERVICAL POINT

SOFT TISSUE GNATHION

HORIZONTAL ANALYSIS OF THE SOFT TISSUE PROFILE

ANALYSIS OF THE FACIAL CONVEXITY• G to Sn and Sn to Pog

• Mean Value is 12 degree with a standard deviation of 4 degree

• Clockwise opening of the angle shows a positive value and vice versa.

• Positive value suggests of a class 2 pattern

• Negative value suggests of a class 3 pattern

HOWEVER THE ANALYSIS OF THIS ANGLE DOES NOT TELL WHETHER THE MAXILLA OR THE MANDIBLE IS ACCOUNTABLE FOR THE POSSIBLE DISCREPANCY

SO TO DEFINE THE ANTERIOR POSTERIOR POSITION OF THE JAWS TWO SOFT TISSUE MEASURES ARE TAKEN.

Sn point to G perp : 6 +/- 3 mm

Pog’ point to G perp : 0 +/- 4 mmm

NASION CUTANEOUS ( NA’) POINT :

• Also known as Sellion, is the deepest soft tissue point of the nasofrontal curvature.

• Ideally it is located about 6mm above the canthus, between the supratarsal fold and the upper palpebral margin and approximately 9 to 13 mm anterior to the corneal projection.

• Distance from Glabella 4 to 6mm

NASOFRONTAL ANGLE

• Na’ forms the apex of the nasofrontal angle formed by the intersection of two lines, a tangent to the glabella (G - Na’) and the other tangent to pronasale (Pn – Na’).

• Normal Value of this angle : 120 to 135 degrees

• The antero-posterior and vertical position of the naso-

frontal angle apex is very important in the planning stage and is crucial for both pre-surgical planning and operative sequence.

• Marking off the ideal nasion cutaneous will allow to define the nasofacial angle which estabilishes the ideal dorsal line ( Pn – Na’) and contributes to the new projection of the tip

NASOFACIAL ANGLE

It is the angle formed by the intersection of the dorsal line with the nasion cutaneous perpendicular line.

The angle is 34 degree among Women and 36 degree among Men.

ANGLE OF TIP

• It is formed by the inttersection of the true vertical with the pronasale line – posterior alar point.

• The ideal value for the angle of the tip is 105 degree for Women and 100 degree for Men respectiively.

NASOLABIAL ANGLE• Formed by the intersection of

lines Cl-Sn and Sn-Ls.

• Mean Value is 102 degree with a standard deviation of 8 degree.

• It is divided into two components, upper and lower, by a true horizontal intersecting the Sn. In the diagnosis of surgical cases the upper nasolabial angle is analysed seperately from the lower, in search of components involved in the alteration and for an appropriate surgical solution.

LOWER CERVICOFACIAL ANGLE

• Formed by the intersection of Sn – Gn’ and Gn’ – C lines.

• Mean Value is 100 degree with a SD of 7 degree.

• A Mandibular set back cannot be carried out if the angle is more than 90 degree, suggesting instead, the use of another procedure to preserve the anteroposterior position of the chin.

VERTICAL ANALYSIS OF THE SOFT TISSUE PROFILE

1. HEIGHT OF THE MID THIRD OF THE FACE/ HEIGHT OF THE LOWER THIRD ( A / B)

• The mean value of the ratio is 1:1 , deviations of about 5% are accepted.

• Height of the lower third of the face increases in :

a) Maxillary vertical over growth

b) Class 3 patients with vertical height increase

c) Skeletal open bites

Height of the lower third of the face decreases in :

a) Maxillary Vertical undergrowth

b) Mandibular retrusion with deep bite

c) Vertical undergrowth of the chin

2. UPPER LIP LENGTH ( C )

• The length of the lip should be approximately 1/3 of the height of the mid third of the face.

• When the upper lip is less is anatomically short ( less than 18mm ) it is associated with an increase in the inter labial distance and an excessice exposure of the upper incisor even though the lower third has a normal height.

• Norm : Male - 22 +/- 2mm

Female - 20 +/- 2mm

3. INTERLABIAL DISTANCE ( STS – STI)

• It is the distance between the upper lip stomion and the

lower lip stomion.

• Normal value is 0 to 3 mm

• High values indicate that there is labial incompetence.

4. EXPOSURE OF THE UPPER INCISOR (STS-UI B)

• It is the distance between the stomion superioris and the border

of the upper incisor.

• The Mean Distance is 1 – 3 mm.

• At rest , 2 t0 2.5 mm of crown exposure is desirable for a harmonious smile.

• In men , exposure of the upper incisor is lesser than women.

• In patients with anterior maxillary vertical over growth – excessive exposure of the upper incisors at rest – “Gummy Smile”

• Excessive exposure of lips can also occur because of short lip. In these patients orthodontic treatment might be of help to intrude the upper anterior sector.

5. SN – STS / G – SN , MEASURE C / MEASURE A

• It is the relationship of the length of the upper lip to the

mid third of the face.

• In a harmonius face , the normal ratio is approximately 1:3.

• It allows to check whether the upper lip length is in tune with the face under study.

6. SN – STS / STI – ME’ , MEASURE C / MEASURE D

• The length of the upper lip equals half the length of the

lower lip.( Ideal Ratio – 1 : 2 )

• The average length of the lower lip ranges from 38 to 44 cm.

• Anatomically short lower lip is related to Class II , and conversely , anatomically long lower lip is related to Class III.

• Anatomically Short lower lip is corrected by advancement genioplasties.

CONCLUSION :

• Treatment using hard tissue cephalometric standards may not lead to the desired improvement in facial form.

• The soft tissue analysis evaluates both vertical and horizontal aspects of the face, including lip length and posture.

• The prime objective of orthognathic surgery is facial improvement, therefore soft tissue analysis becomes paramount in treatment planning.

REFERENCE :

• ORTHODONTICS AND ORTHODONTIC SURGERY – DIAGNOSIS AND PLANNING , JORGE GREGORET