Robert Ricketts was born into a poor farmer family in Illinois, but with his wit, determination and unparalleled contributions, he rose to international eminence in orthodontia. Dr. Ricketts attended Dental School in Indiana and was a determined scholar in orthodontics at the University of Illinois. He was a student of Dr. Allan G. Brodie and a follower of Dr. W.B. Downs.

He was an expert and authority in the science of human craniofacial development and has done extensive research on cephalometrics, prediction of growth and computer-aided diagnosis. He emphasised that changes occurring in the face of growth should be integrated into treatment planning.

Ricketts’ approach to selecting landmarks and parameters on a cephalogram was primarily based on the facial growth pattern. Two types of landmarks were used ( Fig. 25.1 ). The first type was skeletal landmarks and the second was dental landmarks. His 11-factor analysis of the skeleton and dental relationship later added the 12th factor, which encompasses the evaluation of the soft tissue profile. The skeletal and dental landmarks are tabulated in Table 25.1 . Of these, Xi point is a unique geometric point which represents the centre of the ramus. The steps in location are given in the following.

Landmarks used in Ricketts’ summary analysis.

The location of the Xi point ( Fig. 25.2 ) can be found geometrically by drawing a line through the Porion-Orbitale (FH) and perpendicularly through the pterygoid vertical (PTV). This can be done by:

• 1.

  Constructing planes perpendicular to the F.H. and PTV.

• 2.

  The planes are tangent to points (R1, R2, R3 and R4) on the borders of the ramus.

• 3.

  Ensuring such planes form a rectangle enclosing the ramus.

• 4.

  The Xi point is located at the centre of the rectangle at the intersection of the diagonals.

  • R1 point is a geometrically constructed point on the vertical ramus of the mandible. The R1 point is the deepest point on the curve of the anterior border of the ramus, one-half the distance between the inferior and superior curves.

  • R2 point of the mandible is located opposite to R1 on the posterior border of the ramus.

  • R3 point of the mandible is located at the centre and most inferior aspect of the sigmoid notch of the ramus.

  • R4 point of the mandible is on the border of the mandible directly inferior to the centre of the sigmoid notch of the ramus.

Construction of the Xi point according to Ricketts.

(A) Reference planes FH and PTV are used to draw R1, R2, R3 and R4 on the borders of the ramus. (B) The Xi point is in the centre of the rectangle where the diagonals intersect. FH , Frankfort horizontal; PTV , pterygoid vertical.

Reference planes ( Fig. 25.3 )

Dr. Ricketts’ analysis used the following reference planes:

• 1.

  Horizontal reference plane:

  • Frankfort horizontal (FH) plane is constructed by connecting the porion and the orbitale.

• 2.

  Vertical reference plane:

  • PTV is constructed by drawing a line perpendicular to the Frankfort plane at the posterior margin of the pterygopalatine fossa.

  • The intersection of the FH and PTV has been found to be stable (i.e. change in the location of this point because the patient’s facial growth is minimal). Therefore, serial cephalometric tracings of a patient superimposed at this point are recommended.

• 3.

  Facial axis:

  • The facial axis is a line from the Pt point through the cephalometric gnathion, which normally intersects the Ba-N plane at a right angle.

• 4.

  Cranial base: Basion-nasion line.

  • The Ba-N line defines the border between the face and the cranium. The angle between the Ba-N line and the Frankfort plane is 30 degrees in a normal Caucasian adult.

• 5.

  Occlusal plane:

  • The occlusal plane can be constructed by a line bisecting the overbite of the molars and passing through the overbite of the first bicuspids. In an adult Caucasian, the plane passes just inferior to the Xi point, nearly bisecting the angle of lower facial height. It is almost parallel to the FH and palatal plane.

Planes used in Ricketts’ summary analysis.

D.C. , A point selected in the centre of the neck of the condyle, where the Basion Nasion plane crosses it; O , orbitale; A , subspinale; S , sella; N , nasion; P , porion.

Ricketts’ 12-factor summary analysis is a simplified version of his detailed and comprehensive cephalometric analysis. It provides an overview of the patient’s craniofacial and dental growth direction. Cephalometric norms are based on research studies of normally growing individuals and may not truly reflect growth in a patient with malocclusion and abnormal growth ( Table 25.1 ).