Introduction

Before starting myofunctional appliance therapy, it is important to have a clear understanding of the patient’s underlying skeletal and dental relationships. A proper diagnosis forms the foundation of successful treatment and involves a combination of clinical examination, cast analysis, and cephalometric evaluation. In his book Dentofacial Orthopedics with Functional Appliances, Rakosi described a number of cephalometric measurements that can be useful when assessing a patient before functional appliance therapy. 

In this blog, we will take a closer look at the key cephalometric landmarks, linear measurements, and angular measurements described by Rakosi, and understand how they can be used in the clinical assessment of patients planned for myofunctional appliance therapy.

Landmarks for functional cephalometric analysis

1 - Nasion

1’ - Soft tissue nasion

2 - Sella

3 - midpoint of entrance of sella turcica

4 - subnasale

5 - point A

6 - APMax - perpendicular of point A in palatal plane

7 - Pr - Prosthion

8 - Is - incisal edge of 1

9 - Ap 1 apex of 1

10 - Ii - incisal edge of mand. CI

11 - Apex of mand. CI 

12 - Infradentale

13 - Point B

14 - Pogonion

15 -Gnathion

16 - Gonion

17 - Menton

18 - Pog perpendicular to MP

19 - Articulare

20 - Condylion

21 - Orbitale

22 - Point at bisect of Pn vertical (dropped from Se-N at N’)

23 - intersection of FH plane and posterior margin of ascending ramus

24 - ANS

25 - PNS

26 - intersection of perpendicular line from Se to the palatal plane

27 - middle of incisor overbite in occlusion

28 - most distal contact between most posterior molars in occlusion

29 - Basion

30 - Ptm point

Functional Cephalometric Analysis

• Analysis for Facial Skeleton

• Analysis of the Jaw Bases

• Analysis of Dentoalveolar Relationships

Normal values

Analysis for Facial Skeleton

• Saddle angle

• Articular angle

• Gonial angle

• Jarabak’s ratio

• Anterior cranial base length

• Posterior cranial base length

Saddle Angle:

The angle formed between nasion, sella and articulare points is the saddle angle.

N: 123+5°

 It is for the assessment of the relationship between anterior and posterolateral cranial bases.

Larger saddle angle indicates the posterior positioning of the mandible indicating myofunctional therapy.

Articular angle:

The angle formed between sella, articulare and gonion.

N: 143+6°

It forms the angle between upper and lower parts of the posterior contours of the facial skeleton.

Larger angle indicates the posterior positioning of mandible or retrognathic mandible.

Smaller angle indicates prognathic mandible.

It is influenced by orthodontic or orthopedic therapy.

Gonial angle:

The angle formed between articulare, gonion and menton.

N: 128+7°

It expresses the form of mandible and also growth rotations.

It is divided into Upper gonial angle (Ar-Go-N) and Lower gonial angle (N-Go-Me).

Acute or small lower gonial angle suggests horizontal growth. It is favourable for myofunctional therapy.

Jarabak’s sum:

Saddle angle + articular angle + gonial angle = 394°

Jarabak ratio:

jarabak ratio = (posterior facial height/anterior facial height) x 100

<62% = vertical growth pattern

62 - 65% = average growth pattern

>65% = horizontal growth pattern

Anterior cranial base length (Se-N) N: 71mm

Posterior cranial base length (Se-Ar) N: 32-35mm

Analysis of the Jaw Bases

• SNA

• SNB

• Base Plane angle

• Inclination angle

• Mandibular base length

• Maxillary base length

• Length of ascending ramus

SNA:

Sagittal relationship of anterior limit of maxillary apical base( Acc. to Lundstrom: Junction of alveolar and basal bone) to the anterior cranial base.

N: 81 - 82° 

SNB:

Sagittal relationship of anterior limit of mandibular apical base to the anterior cranial base.

N: 79-80°

Base plane angle:

Angle between palatal plane and mandibular plane.

N: 25°

It is between maxillary and mandibular jaw bases.

It determines the inclination of mandibular base plane.

Small: horizontal growth pattern

Large: vertical growth pattern

It is further divided into upper base plane angle(N: 11°) and lower base plane angle (N: 14°) by the occlusal plane.

Inclination angle:

It is an angle formed between the Pn line(perpendicular line from SN at N’) to the palatal plane.

N:85°

It gives the inclination of the maxillary base.

Large angle: upward and forward inclination

Small angle: down and back tipping of anterior end of palatal plane and maxillary base.

Mandibular base length:

Distance between Gonion and Pogonion(projected onto the mandibular plane).

N: 3mm longer than SeN until 12 years; 3.5mm longer than SeN after 12 years

Maxillary base length: 

Distance between PNS and Point A(projected onto the palatal plane)

Length of ascending ramus:

Distance between gonion and condylion.

Long: horizontal; short: vertical growth pattern.

SeN:mandibular base = 20:21

Ascending ramus: mandibular base = 5:7

Maxillary base: mandibular base = 2:3

Analysis of Dentoalveolar Relationships

• Upper incisor to SN

• Lower incisor to MP

• Upper incisor to facial plane

• Lower incisor to facial plane

Upper incisor to SN:

Angle between the Long axis of upper central incisor to the SN plane.

The posterior angle is measured.

N: 102°

Large: incisor procumbency or labial crown tipping

Lower incisor to MP:

Angle between the Long axis of the lower incisor to the mandibular plane.

Posterior angle is measured.

N: 90°

Small: lingual tipping of lower incisor crown.

Upper incisor to facial plane:

Distance between the incisal edge of the upper incisor to the NPog line.

N: - 2 to - 4 mm.

Lower incisor to facial plane:

Distance between the incisal edge of the lower incisor to the NPog line.

N: -2 to +2mm.