The assessment of craniofacial dimension is not a new skill in orthodontics. Cephalometry is used to assess craniofacial growth and determine treatment responses. Cephalometric radiology was introduced in orthodontics during the 1930’s but the method really gained wider acceptance for practical application during the last 20 years [1]. Over the years, whole range of analysis has been developed by number of authors. The analysis will only supply answers to a particular set of questions and these answers will depend on correct application of the method and interpretation of results.

The successful treatment of orthodontics of orthognathic surgical treatment is dependent on careful diagnosis. It is important for the clinician to be able to predict the soft tissue changes resulting from alterations of the hard tissue. Many studies have attempted to evaluate the relationship between hard tissue surgery and the effects it has on the overlying soft tissue [2]. Though cephalometric analysis has its limitations, it is a tool which will guide us in planning orthodontic treatment.

The various cephalometric analysis given by many authors such as Cephalometric Analysis for Orthognathic Surgery (COGS) [3], Quadrilateral Analysis [4], Arnett Analysis [5], Burstone and Legan Soft Tissue Cephalometric Analysis [6], etc., were used for surgical patients for interpretation of results. All these analyses were based on hard tissue references with the paradigm shift to soft tissue. Arnett and Bergman [5], presented the facial keys to orthodontic diagnosis and treatment planning.

Widely used cephalometric analysis for surgical analysis of an orthognathic surgery case are

• Burstone’s Cephalometric Analysis for Orthognathic Surgery (COGS)

• DiPaolo’s Quadrilateral Analysis

• Arnett’s Soft Tissue Cephalometric Analysis (STCA

Though each analysis has its own merits and demerits, there are many overlapping parameters studied by these three authors. Hence, the aim of the present study is to identify the significant parameters and overlapping parameters from the above analyses and to arrive at a CCAOS.

Obtaining The Lateral Cephalometric Radiograph            

Lundstrom and Lundstrom [7] findings indicate that a horizontal line, related to natural head position, adjusted to natural head orientation when indicated, presents the most reliable basis for cephalometric analysis. Some patients assume an “Unnatural head position”. Accordingly, these patients need adjustment to “natural head orientation” [5].

Anatomical Landmarks Used for the Analysis

The landmarks used in the cephalometric analysis are the following (Figure 1).

Hard Tissues

Sella (S), Nasion (N), Pterygomaxillary fissure (PTM), Subspinale (A), Supramentale (B), Pogonion (Pog), Anterior nasal spine (ANS), Posterior Nasal Spine (PNS), Gnathion (Gn), Gonion (Go) [3], J point, Nasal floor [4].

Soft Tissues

Glabella (G’), Nasal Tip (NT), Subnasale (Sn), Subspinale (A’), Submentale (B’), Upper Lip Anterior (ULA), Lower Lip Anterior (LLA), Pogonion (Pog’) [5].

Reference Planes

COGS [3]- Hard tissue-horizontal plane (H-P) [Surrogate Frankfurt Horizontal plane].

STCA [5] - Soft tissue –True vertical line.

Other Planes

Palatal plane- ANS-PNS [4], Mandibular Plane (MP)- GoGn [3,4] and Functional Occlusal Plane [3].

Cephalogram of an adult patient with skeletal malocclusion case is taken. Lateral Cephalogram is traced using 4H lead pencil on Acetate tracing paper.

Linear Measurements

Hard Tissue: In this most of the measurements are made either parallel or perpendicular to HP plane.

Figure 1: Anatomic Land Marks and Reference Planes

Chin Prominence

Perpendicular line from H-P plane is dropped from point N. Distance from Pog to this line indicates the prominence of chin. These measurement help determine if there is horizontal genial hyperplasia or hypoplasia.

Vertical Skeletal and Dental Discrepancy

Posterior Maxillary Height: Posterior maxillary height is the length of perpendicular line dropped from HP intersecting the PNS

Vertical Dental Dysplasia

It is divided into Anterior and Posterior Components:

Anterior Maxillary Dental Height and Mandibular 

Dental Height

• Perpendicular from Upper incisor (U1) to nasal floor (ANS-PNS).

• The tip of the Lower incisor (L1) to Mandibular plane (Go-Gn).

Posterior Dental Measurement

• Perpendicular length of a line through the maxillary first molar mesiobuccal cusp tip to MP

• It is a similar line through the mandibular first molar mesiobuccal tip of the cusp constructed to MP

Skeletal Assessment

Maxillary Base Length: Horizontal linear measurement along the palatal plane between the two points. The anterior limit is determined by projecting a perpendicular from point A upward to palatal plane (ANS-PNS), while the posterior limit is determined by projecting a perpendicular from the most inferior portion of Pterygomaxillary Fissure (PTM) downward to palatal plane (Figure 2).

Mandibular Base Length

Mandibular Base Length is measured horizontally along the Go-Gn plane between the two points. 

Figure 2: Maxillary Base Length

Figure 3: Mandibular Base Length

Figure 4: Assessment of Proportionality

The anterior limit is determined by projecting a perpendicular from point B downward to the mandibular plane (Go Gn), while the posterior limit is determined by projecting a perpendicular from point J downward to the mandibular plane (Go Gn) (Figure 3).

Proportionality

The quadrilateral analysis indicates that in a balanced facial pattern a 1:1 ratio exists between the maxillary and mandibular bony base lengths.

Maxillary length = Mandibular length = ALFH+PLFH

Dental Assessment

• Maxillary Incisor Position: determined by drawing line through point A parallel to the anterior lower facial height (ALFH). A perpendicular from this line to the most anterior point on the maxillary incisor (Figure 5)

• Mandibular Incisor Position: determined by drawing line through point A parallel to the anterior lower facial height (ALFH). A perpendicular from this line to the most anterior point on the mandibular incisor

• Chin Position: determined by drawing line tangent to the Pog parallel to the anterior lower facial height (ALFS). A perpendicular from this line to most anterior point on the mandibular incisor. This measurement will indicate if the chin is excessive or deficient in size

Saggittal Ratio

Extend the Quadrilateral to meet at a point. It forms an isosceles triangle. It is divided into anterior and posterior legs. The anterior legs are formed by maxillary and mandibular base and posterior legs formed extending the anterior legs to meet at a common point. This helps in pinpointing the area of deformity whether or not surgical procedure is indicated.

• Posterior Divergence of the Mandible: It is shown by MP angle. It is the angle formed between a line from Go-Gn (MP) and HP as it intersects at Gn. Posterior maxillary height and MP angle defines the vertical dysplasia of the posterior components

• Angle Of Facial Convexity: is the angle formed between N, projection of point A onto the palatal plane and projection of point B onto mandibular plane (Go-Gn)

Soft Tissue

Most of the measurements were made either parallel or perpendicular TVL. The factors considered and measured in this analysis for SCCA are:

Dentofacial Factors

• Overjet: parallel lines are drawn from incisal edge of upper and lower incisors to True vertical line (TVL) and distance between these 2 parallel lines are measured

• Overbite: Perpendicular lines are drawn from incisal edge of upper and lower incisors to True Vertical Distance Line (TVL) and the distance between these two perpendicular lines are measured

Soft Tissue Thickness

• Upper Lip (ULT): Measured from inside of upper lip to upper lip anterior

• Lower Lip (LLT): Measured from inside of lower lip to lower lip anterior or vermilion-cutaneous junction

• Pogonion–Chin (PCT): Measured from hard tissue pogonion (Pog) to soft tissue pogonion (Pog’)

Soft Tissue Lengths

•  Upper Lip Length: Distance between the projection of subscale to TVL and projection of upper lip inferior to TVL

Figure 5: Dental Assessment

Figure 6: Soft Tissue Assessment

• Lower Lip Length: distance between the projection of lower lip inferior to TVL and projection of soft tissue Menton (Me’) to TVL

True Vertical Line Projection

this gives thickness of overlying soft tissue in relation to TVL.

High Midface

• Glabella(G’) to TVL

Figure 7: Composite Cephalometric Analysis for Orthognathic Surgery

Maxillary Projections

• Nasal tip (NT)to TVL
• Soft tissue points A (A’) to TVL

Mandibular Projections

• Lower lip anterior (LLA) to TVL
• Soft tissue points B (B’) to TVL  
• Soft tissue pogonion (Pog’) to TVL
• Throat length: neck throat point (NTP) to soft tissue pogonion (Pog’)

Upper Lip Angle

Angle formed between tangent to upper lip anterior to TVL.

Nasolabial Angle

Angle formed between tangent to upper lip anterior, sub nasale and columella.

COGS do not offer a complete diagnostic assessment of both anteroposterior and vertical skeletal dysplasia. Diagnostic methods that are currently used are unable to “pinpoint” where the skeletal discrepancy exists or the magnitude of that discrepancy. The quadrilateral analysis shows that this is a vertical problem only and not an anteroposterior disharmony in jaw size4. Arnett’s Soft tissue cephalometric analysis is a method for quantifying facial disharmony and identifying its underlying cause. This is important because, as a rule, improved facial aesthetics are achieved if the underlying problems are identified and treated5. Hence, an attempt is made to study the advantages and disadvantages of these three widely used analysis and present it in a compact manner for better diagnosis. The standardized values for the Composite Cephalometric Analysis for Orthognathic Surgery (CCAOS) are being listed in Table 1.

The orthognathic surgical cases require proper planning and implementation of the treatment strategies. One cephalometric analysis cannot yield the proper inference for planning the surgical procedures hence these three analysis tracings which are widely used were simplified henceforth, saving a lot of time for the clinician, patient as well as for the proper outcome of the treatment.

Table 1: The Standard Values for the Composite Cephalometric Analysis for Orthognathic Surgery

1. R, Thomas and T.M, Graber. "Colour atlas of dental medicine - orthodontic diagnosis." Thieme Publications, 1993.

2. M.T, Chew. "Soft and hard tissue changes after bimaxillary surgery in Chinese class III patients." Angle Orthod, vol. 75, 2005, pp. 959–963.

3. C.J, Burstone et al. "Cephalometrics for orthognathic surgery." J Oral Surg, vol. 36, no. 4, 1978, pp. 269–277.

4. R.J, Di Paolo et al. "The quadrilateral analysis: an individualized skeletal assessment." Am J Orthod Dentofacial Orthop, vol. 83, no. 1, 1983, pp. 19–32.

5. G.W, Arnett et al. "Soft tissue cephalometric analysis: diagnosis and treatment planning of dentofacial deformity." Am J Orthod Dentofacial Orthop, vol. 116, 1999, pp. 239–253.

6. H.L, Legan and C.J, Burstone. "Soft tissue cephalometric analysis for orthognathic surgery." J Oral Surg, vol. 38, no. 10, 1980, pp. 744–751.

7. A, Lundstrom and F, Lundstrom. "Frankfort horizontal basis for cephalometric analysis." Am J Orthod Dentofacial Orthop, vol. 107, 1995, pp. 537–540.