Cephalometry

Cephalometry

Introduction :

         Cephalometry includes the measurement, description, assessment of the morphology as well as the study of the growth phenomena of the craniofacial skeleton on a profile teleradiographic image.

This study is carried out by means of points, lines, angles and planes. First described by anthropologists and selected by

orthodontists.

1. Definition of lateral teleradiography (Normalateralis):

      Profile teleradiography is an integral part of the systematic complementary examinations of the orthodontic file.
The examination is carried out with the patient’s head immobilized in a rigorously determined position with a significant foetus-object distance.
This radiographic examination allows:
• to examine the architecture of the skull, face, jaws and dental occlusion with precision thanks to graphic analyses called cephalometric analyses.
• to estimate the effect that growth will have on the evolution of the case and then monitor the growth of the face and jaws,
• to verify the results of the treatment concerning the correction of the shift of the bony bases and the modification of the dental axes.

2. Aims of cephalometry:

The purpose of cephalometric analysis is:

* Provide elements representing assistance in establishing the diagnosis, prognosis and therapeutic strategy.

* Make the diagnosis as complete as possible.

* Assess the subject’s skeletal type.

* Evaluate the elements of the Dg:

_ The bone bases

_ Alveolar processes

     _ The teeth

     _ The profile

3. Cephalometric anatomy:

3.1. Definition:

It is the recognition on a profile teleradiography of the image of the cutaneous, skeletal, alveolar and dental structures. 

3.2. Drawing technique:

The film is placed on a negatoscope, the skin profile on the right, the tracing is made on tracing paper, allows the determination of the anatomical structures as well as the different points, lines and planes necessary for the cephalometric analysis.

3.3. Structures to be studied:

3.3.1. The base of the skull:

The structures are identified from the base of the skull:

• The frontal bone in front is visible by its external and internal cortices and pneumatized by the frontal sinus between them.
• The nasal bones are visible anteriorly in a tile shape with the frontonasal suture 
• The tracing continues through the ceiling of the orbit which flexes at the level of the frontal sinus and then forms the orbital rim (orbital cavities).
• The ethmoid is visible in front by its cribriform plate.  
• The image of the Turkish seal continues with the clenoid processes, anterior in front and posterior in back.
• The basi-sphenoidal extends backwards and downwards by the bas-occipital which forms the anterior edge of the occipital hole, this oblique line is called the clivus.
• The keyridge is a radiological image born from the enfilade by the X-ray beams of the anterior wall of the temporal fossa, the inferior border of the maxillary pyramid and the anterior face of the maxillary pyramid. 

 Cephalometry

3.3.2. The maxilla:

     – It is visible at the level of the hard palate.

     – The anterior alveolar contour of the maxilla presents a concavity and joins the contour of the hard palate at the level of the anterior nasal spine (ENA).

    – the posterior nasal spine (PNS) is located at the posterior end of the hard palate.

    – The pterygomaxillary cleft has the shape of an inverted oil drop, the posterior wall of which is formed by the anterior edge of the pterygoid process and the anterior wall formed by the posterior face of the maxillary tuberosity.

3.3.3. The mandible:

– The image of the symphysis continues with the lower border of the mandible, the goniac angle and the outline of the posterior border of the ramus (rising branch of the mandible).

– The neck of the condyle continues with the condylar head, which is difficult to locate, the sigmoid notch and the coronoid process which is less developed than the condyle.

– The external auditory canal is located immediately behind the condyle, presents an oval image inclined upwards and forwards.

3.3.4. Cervical vertebrae:

– The tracing of the structures of the base of the skull and the face is completed by the tracing of two vertebrae: Atlas and Axis.

– The vertical bony finger-shaped odontoid process is always visible and easy to spot, the magnum opus is located about 5 to 6 mm high and in front of its apex.

3.3.5. The teeth:

– Outline of the most vestibular upper and lower central incisors.

– The upper and lower first molars.

– The germs of the wisdom teeth in pointer.

3.3.6. Skin structures: 

Trace the skin profile including: the forehead, nose, nasolabial angle, both lips and chin.

4. Cephalometric points and lines: 

From the previously recognized structures, it is possible to identify different points which will allow the determination of the lines and planes necessary for the different cephalometric analyses.

     We differentiate between bone points and skin points, median points and bilateral points and constructed points which result from a geometric construction.

1. .The points:
   1. Median bony points:

• S (Sellion): located in the center of the image of the sella turcica.
• Na (Nasion): Most anterior and superior point of the nasofrontal suture.
• ENA (anterior nasal spine): most anterior point of the premaxilla.
• ENP (posterior nasal spine): most posterior point of the bony palate.
• A of “Downs”: most posterior point of the image of the anterior concavity of the premaxilla
• Pr (prosthion): most anterior point of the image of the upper alveolar processes, between the two central incisors 
• Id (infradental point or lower alveolar point): most anterior point of the image of the lower alveolar processes between the lower central incisors 
• B (from DOWNS): most posterior point of the image of the anterior concavity of the mental symphysis 
• Pog (pogonion): most anterior point of the image of the mental symphysis 
• Me (chin): lowest point of the image of the mental symphysis 
• Gn (gnathion): point located halfway between point Me and Pog, it is a constructed point.
• Ba (basion): most inferior point of the basioccipital image (or most anterior point of the foramen magnum) 
•  Op (Opisthion): most posterior point of the occipital hole.

 Cephalometry

4.1.2. Bilateral bone points: These points are double. 

– S/Or (Suborbital): lowest point of the image of the external rim of the orbit 

– Pt (pterygoid point): point midway between the most superior point and the most posterior point of the image of the pterygomaxillary fissure 

– Co (condylar): most superior point of the image of the mandibular condyle 

– Go (gonion): point located midway between the posterior part and the lower part of the mandibular angle.

– Po (porion): most superior point of the image of the external auditory canal

– Ar (articular): this is the point of intersection between the external face of the base of the skull and the posterior face of the condyle image. 

– Xi: Center of the mandibular ascending branch.

 Cephalometry

 Cephalometry

4.1.3. Skin points:

– Cutaneous nasion (Nasion cutaneous): Most posterior point of the nasal saddle, opposite the bony nasion.

– S/N (subnasal): junction point between the upper lip and the nose

– St (Stomion): junction point between the upper and lower lip

– Cutaneous Pog: most anterior point of the image of the cutaneous mental symphysis

– Cutaneous me: lowest point of the image of the cutaneous mental symphysis.

4.2. PLANS: 

4.2.1 Horizontal planes:

1/ PHF (Frankfurt Horizontal Plane): plane passing through the forearm and the suborbital

2/ Bispinal (Palatin): connects ENA to ENP; this plane is roughly parallel to the PHF 

3/ Mandibular (from DOWNS): passes through Me and tangent in the region of the mandibular angle 

4/ Occlusal: plane bisecting the molar and incisor overlaps – 

5/Line S-Na: line joining S to Na 

6/ Skull base line: line joining Ba to Na

4.2.2. Vertical planes:

1/ Facial: goes through Pog and Na 

2/ Ramal: tangent to the posterior edge of the ramus (rising branch of the mandible) 

3/ Ptv (vertical pterygoid axis): perpendicular to the PHF and passing through the most posterior point of the image of the pterygomaxillary fissure 

4/ Y (BRODIE Y axis): joint S to Gn 

5/ Facial axis (RICKETTS): joins Pt to Gn-/CC; this line represents, like the Y axis, the general axis of facial growth

4.2.3. Aesthetic lines:

1/ E (aesthetic line): joins the tip of the cutaneous nose to the cutaneous pogonion

2/ S (Steiner line): joins the skin pog and the middle of S formed by the lower contour of the nose and the bottom of the concavity of the upper lip, the two lips must be flush with this line.

3/Merifield’s line: joins the cutaneous pog and the most protrusive lip, the intersection of this line with the Frankfurt plane forms the angle Z (value: 78°) expressing the degree of labial protrusion.

 Cephalometry

  Wisdom teeth can be painful if they are misplaced.
Composite fillings are aesthetic and durable.
Bleeding gums can be a sign of gingivitis.
Orthodontic treatments correct misaligned teeth.
Dental implants provide a permanent solution for missing teeth.
Scaling removes tartar and prevents gum disease.
Good dental hygiene starts with brushing twice a day.
 

Cephalometry