QUADRILATERAL ANALYSIS

by Tony Pious

History

The quadrilateral analysis was developed by Rocco J.Di.Paolo in 1983

Initially a clinical verification of lower facial proportion was accomplished using 32 untreated orthodontic cases later along with Chinnapi, Di paolo and Langley expanded it to include 180 untreated cases.

The quadrilateral analysis concerns primarily with the skeletal configurations of the individual dentofacial complex in both the horizontal and the vertical dimensions regardless of dentoalveolar relationships.

The standard method of anteroposterior jaw measurement

was the ANB angle. But this proved to be varied as the

positions of the anatomical landmarks greatly influenced the

readings. eg-The horizontal and vertical shift of the nasion

affected the readings and also the rotation of the jaws.

The WITS appraisal was a more effective means to measure

this relationship as it was un affected by the shift in the

position of the nasion or the rotation of the jaws.

But the problem with the wits appraisal was that it was

unable to determine which jaw was affected or the extent of

the variation

Comparison with standard methods of measurement

The concept of lower facial proportionality states that in a balanced

facial pattern there is a 1:1 proportionality that exists between the

maxillary base length and the mandibular base length, also the

average of the anterior lower facial height and posterior lower facial

height equals these denture base lengths.

Therefore max length =mandibular length=ALFH+PLFH 2 The standard deviation between the measurement is + or -1.5 mm

Skeletal Assesment :

The two horizontal facial planes used in the construction of the quadrilateral are the palatal plane(ANS-PNS) and the mandibular plane(GoGN) A measure of anterior upper facial height is established and related to the cranial base(S-N)

Maxillary base length :The maxillary base length is determined horizontally

between two points projected on the palatal plane. The anterior limit of Maxillary base length is determined by projecting a perpendicular from point A upward to the palatal plane while posterior limit is determined by

projecting a perpendicular from the most inferior portion of the pterygomaxillary fissure down to the palatal plane.

Mandibular base length:The mandibular base length is measured horizontally between two points projected on the mandibular plane. The anterior limit of the mandibular base length is determined by projecting a perpendicular from point B downward to the mandibular plane while posterior limit is determined by projecting a perpendicular from pont j downward to the mandibular plane.

Point J is located at the deepest point of the curvature formed at a junction of the anterior portion of the ramus and corpus of the mandible. This point can also be located by drawing a tangent through the most posterior point of the arc on the anterior border of the ramus. A second line is drawn parallel to the mandibular plane along the alveolar crest of the molar teeth, Angle formed by two lines is bisected. The intersection of this bisector to the inner curvature of the mandible is point J

Anterior lower facial height is measured from the projection of point A onto the palatal plane to the projection of point B onto the mandibular plane. Posterior lower facial height is measured from the projection of PTM onto the palatal plane to the projection of point J onto the mandibular plane.

Anterior upper facial height is measured from the projection of point A onto the palatal plane to the nasion on the cranial base plane a proportional relationship exists between the anterior upper facial height and anterior lower facial height 45:55

Anterior lower facial height and anterior upper facial height intersect at a point A on the palatal plane. The intersection forms an angle of facial convexity(165-178) This angle relates the quadrilateral to the cranial base and upper face and is a means of establishing a skeletal profile assessment .

Pt.A line: maxillary incisor position is determined by drawing a line through Point A parallel to the anterior lower facial height. A measurement is then made by drawing a perpendicular from this line to the most anterior point on the maxillary central incisor.The average measurement is 5 mm. Plus or minus 1 mm.

Pt B line: mandibular incisor position is determined by drawing a line through point B .This line is parallel to the anterior lower facial height.From this line measurement is made by drawing a perpendicular from this line to the most anterior point on the mandible central incisor.The average measurement is 2 mm (+ or -) 1 mm

Dental Assessment:

Pogonion Line: It is constructed by joining a line tangent to pogonion and parallel to anterior facial height.The most anterior point of mandibular central incisor is then related perpendicular to the pogonion line.This measurement will indicate whether the chin is excessive or deficient in size.The average is 2 mm anterior or posterior to the pogonion.

The sagittal ratio is important in assesing the relative anteroposterior position of the maxillary and the mandibular bony bases. Skeletal malformations of the jaws may be either in the bony bases or located posteriorly. Therefore pinpointing the area of the deformity will have a significant impact on whether or not a certain surgical procedures are indicated. for eg-In a case of mandibular prognathism it would be necessary to determine whether the reduction of the bony base length is required or the mandibular surgery posterior to the bony base area.

Sagittal Ratio:

Method: The lines that are used to measure the bony

base lengths in the quadrilateral pattern are extended posteriorly to a point X. This forms the sagittal angle.

When the anterior and posterior lower facial heights are parallel and the maxillary and mandibular bony bases are equal a proportional relation exists with the sides A B C D of the similar isoceles triangle. The ratio of A to B and C to D is called the sagittal ratio.

Any forward or retroposition of the bony base will cause unequal lengths of the posterior legs(linesA and C).In balanced skeletal patterns the sagittal ratio in adoloscents is 1.0:1.50 + or – 0.05In adults it is 1.0:1.45 + or – 0.05

Angle of facial convexity is measurement of the skeletal profile: This angle is formed by the intersection of anterior lower facial height with anterior upper facial height and relates the quad to the upper face. The degree of convexity will vary depending upon the skeletal type and the position of the quad pattern as it relates to the upper face.It shows possible areas of cranial facial deflections and bony base discrepancies.

The sagittal angle is 23 + or - 1

Type 1 :This face has a normodivergent pattern showing a favorable vertical growth.

In majority of the cases Type 1 cases the maxillary and mandibular basal arch lengths are equal and the average vertical height is equal to the arch length.

Malocclusion in this group are dentoalveolar in origin

Facial types:

Type 2:This face is hypodivergent showing a

predominant horizontal growth pattern. There is

a reduction in lower facial height with an

undesirable growth pattern resulting in a

skeletal deep bite. The average vertical height is

deficient compared to the denture base length.

A deficient average vertical height is associated with any of

the followin

1)maxillary and mandibular base lengths are comparable in

size.

2)maxillary base length is longer than the mandibular base

length.

3) mandibular base length longer than the maxillary base

length.

Type 3 :

This face is hyper divergent showing a predominantly

vertical growth pattern.Increase in lower facial height

with an undesirable vertical growth pattern , resulting in

an skeletal open bite.Average vertical height is excessive

when compared to the denture base lengths . Posterior

alveolar compensation may prevent a dental open bite

in some cases. These cases usually present with a deep

curve of spee and lack of posterior alveolar development.

Hence the quadrilateral analysis helps not only in

determining the skeletal discrepancy but it also

helps in locating the defect and determining the

extent of the defect. Therefore helps in determining

weather the particular case requires orthodontic

treatment or a surgical treatment or a combination

of both.

CONCLUSION

  NORMAL PATIENT VALUE INFERENCE

DENTAL

Point A line 5 mm + 1 mm 13 mm Proclined upper incisor

Point B line 2mm + 1mm 5 mm Proclined lower incisor

Pogline 2 mm 8mm Retruded chin

SKELETAL

Max base length - 56 -

Mandibular base length - 56 -

Anterior lower facial height - 66 -

Posterior lower facial height - 38 -

RATIO 1:1:1 1:1:0.9 Near balanced ratio

Anterior upper facial height - 62 -

AUFH:ALFH 45:55 62:66 Increased AUFH

Angle of convexity 165° - 175° 169° Normal

Sagittal angle 23° + 1° 29° Convex angle

A:B:C:D 1.0:1.45 1:1.02 Unequal proportion

(mild skeletal

disturbances)

THANK YOU