Lateral cephalometric radiographs

Lateral cephalometric radiograph is a radiograph of the head taken with the x-ray beam perpendicular to the patient's sagittal plane. Natural head position is a standardized orientation of the head that is reproducible for each individual and is used as a means of standardization during analysis of dentofacial morphology both for photos and radiographs. The concept of natural head position was introduced by Coenraad Moorrees and M. R Kean in 1958^[9][10] and now is a common method of head orientation for cephalometric radiography.^[11][12]

Registration of the head in its natural position while obtaining a cephalogram has the advantage that an extracranial line (the true vertical or a line perpendicular to that) can be used as a reference line for cephalometric analysis, thus bypassing the difficulties imposed by the biologic variation of intracranial reference lines. True vertical is an external reference line, commonly provided by the image of a free-hanging metal chain on the cephalostat registering on the film or digital cassette during exposure. The true vertical line offers the advantage of no variation (since it is generated by gravity) and is used with radiographs obtained in natural head position.

Posteroanterior (P-A) cephalometric radiograph

A radiograph of the head taken with the x-ray beam perpendicular to the patient's coronal plane with the x-ray source behind the head and the film cassette in front of the patient's face.^[13] PA ceph can be evaluated by following analyses that have been developed through the years:

• Grummon analysis
• MSR
• Hewitt analysis
• Svanholt-Solow analysis
• Grayson analysis

Steiner analysis

Cecil C. Steiner developed Steiner Analysis in 1953. He used S–N plane as his reference line in comparison to FH plane due to difficulty in identifying the orbitale and porion. Some of the drawbacks of the Steiner analysis includes its reliability on the point nasion. Nasion as a point is known not to be stable due to its growth early in life. Therefore, a posteriorly positioned nasion will increase ANB and more anterior positioned nasion can decrease ANB. In addition, short S–N plane or steeper S–N plane can also lead to greater numbers of SNA, SNB and ANB which may not reflect the true position of the jaws compare to the cranial base. In addition, clockwise rotation of both jaws can increase ANB and counter-clockwise rotation of jaws can decrease ANB.

Wits analysis

The name Wits is short for Witwatersrand, which is a University in South Africa. Jacobsen in 1975 published an article called "The Wits appraisal of jaw disharmony".^[16] This analysis was created as a diagnostic aid to measure the disharmony between the AP degree. The ANB angle can be affected by multitude of environmental factors such as:

1. Patient's age where ANB has tendency to reduce with age
2. Change in position of nasion as pubertal growth takes place
3. Rotational effect of jaws
4. Degree of facial Prognathism

Therefore, it measured the AP positions of the jaw to each other. This analysis calls for 1. Drawing an Occlusal Plane through the overlapping cusps of Molars and Premolars. 2. Draw perpendicular lines connecting A point and B Point to the Occlusal Plane 3. Label the points as AO and BO.^[17]

In his study, Jacobsen mentioned that average jaw relationship is -1mm in Males (AO is behind BO by 1mm) and 0mm in Females (AO and BO coincide). Its clinical significance is that in a Class 2 skeletal patient, AO is located ahead of BO. In skeletal Class 3 patient, BO is located ahead of AO. Therefore, the greater the wits reading, the greater the jaw discrepancy.

Drawbacks to Wits analysis includes:^[18]

• Left and Right molar outlines may not always coincide
• Occlusal plane may differ in mixed vs permanent dentition
• If curve of spee is deep then it may be difficult to create a straight occlusal plane
• Angulation of functional occlusal plane to pterygomaxillary vertical plane was shown to decrease from age 4 to 24.

Delaire Analysis

Prof. Jean Delaire started developing his analysis along with Dr M. Salagnac back in the 70's. ^{[citation needed]} This analysis is still developed and improved by his pupils. This analysis is based on reciprocal proportion and balance and doesn't use standard deviation. It gives the ideal architecture the patient should have, based on his skull shape, posture and functions.^[19]

Downs analysis

Bjork analysis

This analysis by Arne Bjork was developed in 1947 based on 322 Swedish boys and 281 conscripts. He introduced a facial polygon which was based on 5 angles and is listed below. Bjork also developed the 7 structural signs which indicates the mandibular rotator type.^[20]

• Nasion Angle - Formed by line connecting ANS to Nasion to Sella
• Saddle or Cranial Base Angle - Formed by line connecting Nasion to Sella to Articulare
• Articular Angle - Formed by line connecting Sella to Articulare to Gonion
• Gonial Angle – Formed by line connecting Articulare to Gonion to Gnathion
• Chin Angle – Formed by line connecting Infradentale to Pogonion to the Mandibular Plane.

Tweed analysis (triangle)

Charles H. Tweed developed his analysis in the year 1966.^[21] In this analysis, he tried describing the lower incisor position in relation to the basal bone and the face. This is described by 3 planes. He used Frankfurt Horizontal plane as a reference line.^[22][23]

Jarabak analysis

Analysis developed by Joseph Jarabak in 1972.^[24] The analysis interprets how the craniofacial growth may affect the pre and post treatment dentition. The analysis is based on 5 points: Nasion (Na), Sella (S), Menton (Me), Go (Gonion) and Articulare (Ar). They together make a Polygon on a face when connected with lines. These points are used to study the anterior/posterior facial height relationships and predict the growth pattern in the lower half of the face. Three important angles used in his analysis are: 1. Saddle Angle - Na, S, Ar 2. Articular Angle - S-Ar-Go, 3. Gonial Angle - Ar-Go-Me.

In a patient who has a clockwise growth pattern, the sum of 3 angles will be higher than 396 degrees. The ratio of posterior height (S-Go) to Anterior Height (N-Me) is 56% to 44%. Therefore, a tendency to open bite will occur and a downward, backward growth of mandible will be observed.^[25]

Ricketts analysis

The Rickett analysis also consists of following measurements

Sassouni analysis

This analysis, developed by Viken Sassouni in 1955,^[26][27] states that in a well proportioned face, the following four planes meet at the point O. The point O is located in the posterior cranial base. This method categorized the vertical and the horizontal relationship and the interaction between the vertical proportions of the face. The planes he created are:

1. Supraorbital plane (anterior clinoid to roof of orbits)
2. Palatal plane (ANS-PNS)
3. Occlusal plane (Downs occlusal plane)
4. Mandibular plane (Go-Me)

The more parallel the planes, the greater the tendency for deep bite and the more non-parallel they are the greater the tendency for open bite. Using the O as the centre, Sassouni created the following arcs

• Anterior Arc – Arc of a circle between the anterior cranial base and the mandibular plane, with O as the center and O-ANS as the radius.
• Posterior Arc – Arc of a circle between anterior cranial base and mandibular base with O as centre and OSp as radius.
• Basal Arc – From A point should pass through B point
• Midfacial Arc – From Te and should pass tangent to the mesial surface of the maxillary first molar

Harvold analysis

This analysis was developed by Egil Peter Harvold in 1974.^[28] This analysis developed standards for the unit length of the maxilla and mandible. The difference between the unit length describes the disharmony between the jaws. It is important to know that location of teeth is not taken into account in this analysis.

The maxillary unit length is measured from posterior border of mandibular condyle (Co) to ANS. The mandibular unit length is measured from posterior border of mandibular condyle (Co) to Pogonion. This analysis also looks at the lower facial height which is from upper ANS to Menton.^[29]

McNamara analysis

COGS analysis (cephalometrics for orthognathic surgery)

This analysis was developed by Charles J. Burstone when it was presented in 1978 in an issue of AJODO.^[30] This was followed by Soft Tissue Cephalometric Analysis for Orthognathic Surgery in 1980 by Arnette et al.^[31] In this analysis, Burstone et al. used a plane called horizontal plane, which was a constructed of Frankfurt Horizontal Plane.

• Counterpart Analysis
• Template Analysis

Structural method

According to American Board of Orthodontics, this method is based on series of study performed by Arne Bjork,^[33][34] Birte Melsen^[35] and Donald Enlow.^[36] This method divides superimposition in three categories: Cranial base superimposition, maxillary superimposition and mandibular superimposition. Some of the important landmarks in each category is listed below as per the structural method.