Cephalometric Superimposition

Summerized by : Dr. Hani Alhebshi

Cephalometric superimposition is a way to aid in monitioring the progress of skeletal and dental changes that occur over time.It  is helpful in craniofacial growth studies as well as in evaluation of treatment outcomes.

Two cephalometric tracings ( before and after for example )  are superimposed on each other and aligned on stable landmarks. There are stable landmarks that were widely accepted.  Each landmark is used to detect changes in particular part of the craniofacial complex.

Progress of changes can be recorded and evaluated by aligning the following landmarks of both tracings  :

1- Overall Changes in face & maxillomandibular complex :

A:  Anterior wall of Sella  of both tracings.

Sella-Nasion can be used to align on but less reliable.

B: De coster’s Line : The floor of the anterior cranial base , from ethmoid bone (cribriform plate) to sella turcica. ( more reliable ).

The cribriform plats stops growing anterioposteriorly after 2 years of age.

C: Cerebral Part of the frontal bone.

2- Maxillary Changes by :

A: Anterior border of the Key Ridge :  it is lowest point on the outline of the zygoma. (Best).

Note : In the vertical dimention , 2/3 of  growth occur in the orbital floor while 1/3 in the palatal plane. Therefore , superimposition of the 2 tracings is done according to that ratio when growth is evaluated. So the 2nd tracing is aligned exactly on the ridge then moved 1/3 the distance downward and fixed on that position. Assessment of growth can be done afterwards.

B:Best Fit of Palatal surface of maxilla ( Hard palate) parallel to ( ANS-PNS).

3- Mandibular Changes by :

A:   Inner wall of the symphysis. AND inferior dental canal  if it is clearly visible ( best ).

Using the lower border of the mandibl as a landmark for superimposition is not good because it is an area of growth.

B: Tooth bud of Lower 2nd or 3rd molars before their roots are developed. ( I.e : only the crown has developed.  ).

Most reliable superimposition landmarks

The following is a list of links containing valuable information on Cephalmetric Superimposition. The page will be continually updated with more links as we get more on the topic.

1. Superimposition of cephalometric radiographs advocated by American board of Orthodontics (ABO). 

2. Cephalometric Superimpositions : A Comparison of Anatomical and Metallic Implant Methods [pdf].

 

3.  Arat ZM, Türkkahraman H, English JD, Gallerano RL, Boley JC. Longitudinal growth changes of the cranial base from puberty to adulthood. Angle Orthod 80: 725-732, 2010.

 

 

References :

1.Radiographic Cephalometry , Chapter 13 by Jacobson.

2. Seminars with Dr. Nayef Felemban and Dr. Hashem Alzahrani.

3. Different web sites.

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