POSTERIO-ANTERIOR CEPHALOMETRIC ANALYSIS
POSTERIO-ANTERIOR CEPHALOMETRIC ANALYSISBy:Dr Jasmine Arneja
Precepted by:Dr ShalajDr vishal
IntroductionSetupGeneral landmarksMSRRicketts analysisGrummons analysisHewitts analysisSvanholt and Solow analysisGrayson analysisconclusion
In orthodontics, the primary indication for obtaining a posteroanterior cephalometric film is the presence of facial asymmetry. it is also important in cases of dentoalveolar asymmetries, dental and skeletal crossbites, and functional mandibular displacements. (transverse discrepancies)The posteroanterior cephalometric projection, also called as the Caldwell projection. Introduction
A headholder or a cephalostat that can be rotated 90 is used, so that the central X-ray beam penetrates the skull of the patient in a posteroanterior direction and bisects the transmeatal axis perpendicularly. The standard distance from X-ray source to patient is 5 feet (152.4 cm)The tip of the nose and forehead should lightly touch the cassette and the FHP should be parallel to the floor Cephalometric set-up
No double shadows The top of the petrous portion of the temporal bone should lie near the center of the orbitSign of a good PA cephalogram
Being a more reproducible position, NHP is now frequently used. Natural head position is a standardized orientation of the head, which is readily assumed by focusing on a distant point at eye level (Moorrees, 1985). Reproducibility of natural head position, assessed as the error of a single observation, has been found to be close to 2, which supports its use in cephalometry (Lundstrom and Lundstrom, 1992).
ag - antegonion - the highest point in the antegonia/ notch (left and right) ans anterior nasal spine cd - condylar - the most superior point of the condylar head (left and right)cor - coronoid the most superior point of the coronoid process (left and right) iif- incision inferior frontale - the midpoint between the mandibular central incisors at the level of the incisal edges isf - incision superior frontale - the midpoint between the maxillary central incisors at the level of the incisal edges m - mandibular midpoint - located by projecting the mental spine on the lower mandibular border, perpendicular to the line ag-ag
Ipa - lateral piriform aperture - the most lateral aspect of the piriform aperture (left and right) lo - latero-orbitale - the intersection of the lateral orbital contour with the innominate line (left and right) Im - mandibular molar - the most prominent lateral point on the buccal surface of the second deciduous or first permanent mandibular molar (left and right) mo - medio-orbitale - the point on the medial orbital margin that is closest to the median plane (left and right) mf - mental foramen - the centre of the mental foramen (left and right)
tns - top nasal septum - the highest point on the superior aspect of the nasal septum ma - mastoid - the lowest point of the mastoid process (left and right) mx - maxillare - the intersection of the lateral contour of the maxillary alveolar process and the lower contour of the maxillozygomatic process of the maxilla (left and right) . Aka JUGAL POINTum - maxillary molar - the most prominent lateral point on the buccal surface of the second deciduous or first permanent maxillary molar (left and right)
za - point zygomatic arch - point at the most lateral border of the centre of the zygomatic arch (left and right) mzmf - zygomatic ofrontal medial suture point-in - point at the medial margin of the zygomaticofrontal suture (left and right) Izmf - zygomaticofrontal lateral suture point-out - point at the lateral margin of the zygomaticofrontal suture (left and right)A1 point- point selected at the interdental papilla of the upper incisors at the junction of crown and gingivaB1 point- point selected at the interdental papilla of the lower incisors at the junction of crown and gingiva
B1- most reliable skeletal landmarkMandibular canine- most reliable dental landmark
Mandibular 6 and maxillary 3- least reliable dental landmarksZF suture- least reliable skeletal landmark
(Gravely JF, Benzies PM. The clinical significance of tracing error in cephalometry. Br J Orthod 1974)Most and least reliable landmarks
The MSR normally runs vertically from crista galli to the through the anterior nasal spine to the chin area and typically nearly perpendicular to the Z planeIf the location of Cg is in question: midpoint of the Z plane an be connected to the ANSIf there is upper facial asymmetry, midpoint of the Z plane can be connected to the midpoint of the Fr- Fr lineMEDIAN SAGGITAL REFERENCE PLANCE in PA Ceph
Most of the posteroanterior cephalomctric analyses described in the literature are quantitative, and they evaluate the craniofacial skeleton by means of linear absolute measurements of: width or height (Solow, 1966; Ricketts et al, 1972; Ingerslev and Solow, 1975; Movers et al, 1988; Nakasima and Ichinose, 1984; Grummons and Kappeyne van de Coppello, 1987; Athanasiou et al, 1992); angles (Ricketts et al, 1972; Svanholt and Solow, 1977; Droschl, 1984; Grummons and Kappeyne vande Coppello, 1987; Athanasiou et al, 1992); ratios (Costaras et al, 1982; Grummons and Kappeyne van de Coppello, 1987; Athanasiou et al, 1992); and volumetric comparison (Grummons and Kappeyne van de Coppello, 1987).
The different structures of the craniofacial complex can also be analysed using qualitative methods (Sollar, 1947; Grayson et al, 1983; Proffit, 1991). The analysis proposed by Grummons and Kappeyne van de Coppello (1987) contains quantitative assessment of vertical dimensions and proportions. PA ceph analysis
Ricketts gave a normative data of parameters measured, which is helpful in determining the vertical transverse skeletal and dental problemsIt has the following components:Dental realtionsSkeletal relationsDental to skeletalJaw to craniumInternal structures
Dental relations:Molar relations (a6-b6): difference in width between the upper and lower molars measured at the most prominent buccal contour of each tooth. Used to describe bucco-lingual relation of molars
Dental relations:Intermolar width (b6-b6): from buccal surface of mandibular left to right molar. Helpful in determining the eitiology of crossbite.
Dental relations:Intercanine width (b3-b3) : from tip of mandibular right to left canine.Normal value: 22.7 mm at age 7 (non erupted teeth). The distance widens 0.8 mm per year until age 13 when it reaches the adult value of 27.5 mm
Denture midline: midline of upper arch to lower arch
Skeletal relations:Maxillomandibular width right: from the Jugal process to the frontofacial plane (Ag to MZF- j). Useful in determining the skeletal crossbite.Maxillomandibular width left
Skeletal relations:Maxillomandibular midline: angle formed by the ANS- Me plane to a plane perpendicular to ZA-AZInterpretation: Determines the mandibular midline deviation with respect to the midsagittal plane. This asymmetry might be the consequence of functional or skeletal problems
Skeletal relations:Maxillary width : J-JIndicates transverse maxillary growth and should be taken into account for planning and evaluation of palatal disjunction
Mandibular width: Ag-Ag
Dental to Skeletal relations:Lower molar to jaw left: B6 to J-Ag lineLower molar to jaw right: B6 to J- Ag rightInterpretation: An increased measure indicates the likelihood of a buccal mandibular expansion
Dental to Skeletal relations:Denture- jaw midline: midline of denture to ANS-Me
Dental to Skeletal relations:Occlusal plane tilt: difference of the height of the occlusal plane to the ZFL-ZFR plane
Jaw to cranium relations:Postural symmetry : Difference between angles ZAG-ZA on left and Z-AG-ZA on right side. Normal value: 0.Standard deviation : 2. Interpretation: Used for the diagnosis of asymmetry.
Inner structural problems Nasal width : The maximum width of the nasal cavity.Normal value: 25 mm at age 8. It increases 0.7 mm per year. Standard deviation: 2 mm.Interpretation: Used for the analysis of the airways. Sometimes mouth breathing might be due to a narrow nasal cavity or to insufficient transverse growth of the maxilla.
Nasal height :The distance between the anterior nasal spine (ANS) and the Z - Z plane. Normal value: 44.5 mm at age 9, increases 1 mm per year. Standard deviation : 3mm
Facial width :The distance between points ZA and ZA. Normal value: 116 mm at age 9. It increases 2.4 mm per year. Standard deviation: 3 mm.
This is a comparative and quantitative posteroanterior cephalometric analysis. It is not related to normative data. The analysis is presented in two forms: the comprehensive frontal asymmetry analysis summary frontal asymmetry analysis. The analyses consist of different components, including horizontal planes, mandibular morphology, volumetric comparison, maxillomandibular comparison of asymmetry, linear asymmetry assessment, maxillomandibular relation, and frontal vertical proportionsGRUMMONS ANALYSIS(Grummons and Kappeyne van de Coppello, 1987)
1. Construction of horizontal planes one connecting the medial aspects of the zygomaticofrontal sutures (Z);one connecting the centres of the zygomatic arches (ZA); one connecting the medial aspects of the jugal processes (J); and one parallel to the Z-plane through menton.
2. A midsagittal reference line (MSR) is constructed from crista galli (Cg) through the anterior nasal spine (ANS) to the chin area An alternative way of constructing the MSR line, if anatomical variations in the upper and middle facial regions exist, is to draw a line from the midpoint of Z-plane either through ANS or through the midpoint of