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WHAT IS‌‌ Cephalometrics is the interpretation of lateral skull radiographs taken under standardized conditions. A collection of numbers intended to summarize information from a cephalogram.
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Purpose of Cephalometrics Virtually indispensable to orthodontics. Study craniofacial growth (comparing to the same individual) Diagnosis (comparing to standards) Planning orthodontic treatment Evaluation of treated cases
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TWENTY CENTURIES OF CEPHALOMETRY THE SCIENTIFIC APPROACH TO SCRUTINY THE HUMAN CRANIOFACIAL PATTERNS WAS DONE FIRST BY ANTHROPOLOGISTS AND ANATOMISTS ON DRY SKULLS. THE MEASUREMENT OF DRY SKULL FROM OSTEOLOGICAL LANDMARKS IS CALLED CRANIOMETRY. THE MEASUREMENT OF HEAD OF LIVING SUBJECTS FROM BONY LANDMARKS LOCATED BY PALPATION AND PRESSING THROUGH SUPRAADJASCENT STRUCTURES IS CALLED CEPHALOMETRY
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TWENTY CENTURIES OF CEPHALOMETRY(CONTD..)
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HUMAN FORM HAS BEEN STUDIED FOR MANY REASONS, HISTORICALLY AS AN AID IN SELF PORTRAYAL IN SCULPTURES,DRAWING,AND PAINTING TO TEST THE RELATION OF PHYSIQUE TO HEALTH, TEMPERAMENT, AND BEHAVIOUR TRAITS. HIPPOCRATES(500BC) DESIGNATED TWO FORMS HABITUS PHTHISICUS(LONG THIN BODY) HABITUS APOPLETICUS(SHORT THICK BODY) ARISTOTLE(400BC),GALEN(200AD), ROSTAN(1828) CARRIED ON WITH THE RESEARCH www.indiandentalacademy.com
TWENTY CENTURIES OF CEPHALOMETRY(CONTD..) KRETSCHMER(1921) ADHERED TO THREE GREEK FORMS 1. PYKNIC(COMPACT) 2. ASTHENIC( WITHOUT STRENGTH) 3. ATHLETIC LATER HE INCLUDED DYSPLASTIC PHYSIQUE
MEASUREMENT AND PROPORTION EGYPTIANS DEVELOPED A PROPORTIONATE SYSTEM OF HUMAN BODY, KNOWN AS CANONS. IT WAS ENCLOSED INTO A GRID WITH 18 HORIZONTAL LINES,LATER CHANGED INTO 22 LINE GRID SYSTEM.THE TOP THREE SQUARES WERE DIVIDED INTO FIVE PARTS TO DRAW FACE INTO ACCURATE DETAIL. www.indiandentalacademy.com
TWENTY CENTURIES OF CEPHALOMETRY(CONTD..) GREEK SYSTEM WAS NOT AS RIGID AS EGYPTIAN. INDIAN ICONOMETRY – TWO PROPORTIONAL SYSTEM WERE USED 1. SARIPUTRA 2.ALEKHYALAKSANA FACE HEIGHT WAS USED AS MODULE FOR BOTH. UNITS USED TO MEASURE WERE ANGULA. 1 ANGULA =8mm IN BYZANTINE EMPIRE, RECTANGULAR GRID WAS REPLACED BY SCHEME OF THREE CONCENTRIC CIRCLES,WITH NOSE LENGTH AS RADIUS OF CIRCLES. LEONARDO DA VINCI,DRAWINGS SHOWED STUDY www.indiandentalacademy.com OF PROPORTIONAL SYSTEM AND COORDINATE
TWENTY CENTURIES OF CEPHALOMETRY(CONTD..)
DURER WAS MOST OUTSTANDING, PROVIDED A PROPORTIONATE ANALYSIS OF THE LEPTOPROSOPIC AND EURYPROSOPIC FACE IN A COORDINATE SYSTEM. HE ALSO MADE USE OF TWO LINES TO GIVE FACIAL ANGLE, SHOWED ABOUT THE VARIATION IN FACIAL MORPHOLOGY. PETRUS CAMPER GAVE REFERENCE PLANRE CALLED CAMPERS HORIZONTAL LINE VAN LOON 1915 ADVOCATED PROPER ORIENTATION OF CAST ACCORDING TO FACE PACINI1922 INTRODUCED A METHOD STANDARDISED HEAD RADIOGRAPHY IN 1931 CEPHALOMETRY RADIOGRAPHY CAME TO FULL VERSION WHEN BROADBENT IN US AND HOFRATH IN GERMANY SIMULTANEOUSLY PUBLISHED METHOD OF STANDARDISED HEAD RADIOGRAPHY. www.indiandentalacademy.com
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RADIOGRAPHIC CEPHALOMETRIC TECHNIQUE BASIC EQUIPMENT FOR PRODUCING A LATERAL CEPHALOGRAM ARE AN X-RAY APPARATUS COMPRISES OF AN X-RAY TUBE, A VACUUM TUBE SERVES AS SOURCE OF X RAYS. HAS 1. CATHODE, TUNGSTEN FILAMENT SORROUNDED BY MOLYBDENUM FOCUSING CUP, ACTS AS SOURCE OF ELECTRONS. 2. ANODE, SMALL TUNGSTEN BLOCK EMBEDDED IN COPPER STEM, WHICH STOPS THE ACCELERATED ELECTRONS AND TRANSFER LESS THAN 1% INTO X RAY PHOTONS.
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TRANSFORMERS, STEP DOWN PROVIDE LOW VOLTAGE,10V AND HIGH CURRENT TO CATHODE AND STEP UP, TO PROVIDE HIGH POTENTIAL DIFFERENCE FOR GENERATION AND ACCELARATION OF ELECTRON CLOUD. FILTERS, MADE OF ALUMINIUM, FILTERS OUT THE LOW ENERGY X RAYS. COLLIMATORS,MADE OF LEAD, GIVES SHAPE TO THE BEAM,SO THAT ONLY HIGH ENERGY BEAM REACHES PATIENT COOLANT SYSTEM, TO COOL THE ANODE BY DISSIPATING ENERGY INTO OIL SORROUNDING TUBE 2. IMAGE RECEPTOR SYSTEM, RECORDS THE FINAL PRODUCT OF X RAYS AFTER THEY PASS THROUGH SUBJECT. CONSISTS OF AN EXTRA ORAL FILM,EITHER 8 INCHES INTO 10 INCHES OR 10 INTO 12 INCHES, SENSITIVE TO FLOUROSCENT LIGHT RADIATED FROM INTENSIFYING SCREENS. www.indiandentalacademy.com
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CEPHALOSTAT
TWO EAR RODS PATIENT HEAD IS FIXED BY INSERTED THEM INTO EAR HOLES. HAS INFRAORBITAL POINTER TO STANDARDIZE THE POSITION FORE HEAD CLAMP TO SUPPORT THE FACE,POSITIONED AT NASION PROPER ALLIGNMENT IS CHECKED IF RADIOPAQUE CIRCLE OF FILM SIDE EAR ROD IS REASONABLY CENTERED IN BEAM SIDE ROD. www.indiandentalacademy.com
PATIENT POSITIONING IN LATERAL CEPHALOGRAM
F-H PLANE IS KEPT PARALLEL TO THE FLOOR AND MID SAGITTAL PLANE PARALLEL TO CASSETTE AND PERPENDICULAR TO THE FLOOR. SOME PREFER CANTHOMEATEL LINE AT 10DEGREE TO www.indiandentalacademy.com FLOOR
•THE STANDARDISED F-H PLANE IS ACHIEVED BY PLACING THE ORBITAL POINTER BELOW THE ORBIT TILL POINTER AND EAR RODS ARE PARALLEL •NASAL POSITIONER IS PLACED. •USUALLY LEFT SIDE FACES CASSETTE. •THE PATIENT CLOSES IN CENTRIC OCCLUSION WITH TONGUE PLACED IN POSTERIOR AREA OF SOFT www.indiandentalacademy.com PALATE.
NATURAL HEAD POSITION..WHY? •NATURAL HEAD POSITION IS A STANDARDISED AND REPRODUCIBLE POSITION OF THE HEAD IN AN UPRIGHT POSTURE WHEN PERSON IS FOCUSSING ON DISTANT OBJECT AT EYE LEVEL.(MOORREES) •IN 1884 FRANKFORT AGREEMENT. FH PLANE WAS CONSIDERED AS STANDARD PLANE FOR ALL CRANIOMETRIC RESEARCH. •BUT DOWNS SHOWED THE VARIATION IN CANT OF F-H PLANE(1956) •BJORK(1951) ALSO SHOWED IN TWO ADULT BANTU MEN THE VARIATION IN S-N PLANE WHEN BOTH WERE SHOWN TO HAVE SAME PROFILE WHEN ALLIGNED IN IN NATURAL HEAD POSITION •VERY FREQUENTLY LEFT AND RIGHT EARS ARE ASSYMETRICALIN HORIZONTAL AND VERTICAL DIRECTION www.indiandentalacademy.com
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ORIENTATION OF NATURAL HEAD POSITION VARIOUS METHODS •SOME ACCEPT MOST RELAXED POSITION OF THE HEAD (SELF BALANCE POSITION) •ORHAN PROPOSED “TARGET ON THE MIRROR TECHNIQUE” •SERDAR USUMEZ(2001) DEVICED AN INCLINOMETER WHICH WAS VERY USE FUL IN REPRODUCING THE NATURAL HEAD POSITION •NATURAL HEAD POSTURE IT’S THE ORTHOPOSITION OF THE SUBJECTS NAMELY MOMENTARY INTERIM POSITION WHEN TAKING THE FIRST STEP FROM STANDING TO WALKING POSTURE. www.indiandentalacademy.com
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NATURAL HEAD POSITION VS NATURAL HEAD POSTURE NOT INTERCHANGEABLE AS POSTURE IS RECORDED IN DYNAMIC MOTION AND MORE PHYSIOLOGIC IN CHARACTER AND CHARCTERISTIC OF AN INDIVIDUAL WHERE AS POSITION IS A STATIC AND IS MEASURED BY STANDARDISED PROCEDURE APPLIED TO ALL INDIVIDUALS. MOORREES PROPOSES LATERAL CEPH TO BE TAKEN IN STANDARDISED NATURAL HEAD POSITION. NATURAL HEAD POSTURE IS THE ONE IN WHICH PATIENT PRESENTS HIMSELF TO THE WORLD SO WHY NOT TO USE IT.
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TRACING OF CEPHALOGRAM ITEMS REQUIRED 1.A 1.LATERAL CEPHALOGRAM 2.ACETATE MATTE TRACING PAPER 3.SHARP 3H PENCIL 4.MASKING TAPE 5. A PROTRACTOR 6.SHEETS OF CARD BOARD 7. VIEW BOX
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TRACING TECHNIQUE Cephalogram is placed on the view box and taped and fixed Place the matte acetate film over the radiograph and tape it securely. The shining slide is placed down. Trace the three registration crosses.
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Now the bilateral structures are first traced independently and average is drawn by visual approximation, represented by broken line.
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Stepwise Tracing Technique Section 1; Soft tissue profile, external cranium and vertebra
1. Draw three registration crosses 2Trace Soft Tissue Profile 3.Trace external contour of cranium 4. Trace outline of atlas and axis vertebra
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Section 2; Cranial base internal border of cranium, frontal sinus than ear rods 5.Trace internal border of cranium
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6.Trace orbital roof
7.Trace outline of pituitary fossa or sella turcica
. 8. Trace planum sphenoidale . 9 .Trace frontal sinus 10 Trace dorsum sella 11 Trace occipital bone 12 Trace outline of floor of middle cranial fossa www.indiandentalacademy.com
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Section 3: Maxilla 14 Trace outline of nasal bone 15 Trace piriform aperture 16 Trace lateral orbital margins and infra orbital ridges 17. Trace outline of key ridges 18. Trace Pterygomaxillary fissure 19. Trace anterior nasal spine 20. Trace superior outline of nasal floor separating oral and nasal cavity www.indiandentalacademy.com
21. Trace posterior nasal spine 22. Trace outline of maxillary first molars 23. Trace anterior outline of maxilla from ANS inferiorly, overlying roots of maxillary incisors. 24Trace outline of maxillary incisors
Section 4;
Mandible
25 Trace anterior border of symphysis of mandible 26 Trace internal marrow space of symphysis 27 Trace inferior border of mandible 28 www.indiandentalacademy.com
29. Trace mandibular condyles 30. Trace mandibular notches 31. Trace anterior aspect of RAMI interiorly 32. Trace mandibular first molars. 33. Trace most anteriorly placed lower incisors
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Landmarks and reference points CEPHALOMATRIC LANDMARKS TYPES ANATOMIC REPRESENT ANATOMIC STRUCTURES OF SKULL (ANTHROPOLOGICAL ) DERIVED LAND MARKS THAT HAVE BEEN OBTAIN SECONDARILY FROM ANATOMIC STRUCTURES (CONSTRUCTED)
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PROPERTIES OF REFERENCE POINTS EASE OF LOCATION ACCORDING TO MOYERS : IT DEPENDS UPON, QUALITY OF THE RADIOGRAPHS OVERLAPPING ANATOMICAL CONTOURS OBSERVER EXPERIENCE CONSTANCY OF CONTOURS THIS STRUCTURES OF SKULL SHOWS DEPENDENCE ON AGE, SEX, RACE, GROWTH ETC. THUS CONSTANCY IS NOT RELIABLE IN CONTRA DISTINCTION TO THE POINTS LOCATED CLOSE TO THE BASE OF SKULL, WHERE VARIATION IS MINIMAL.
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REQUIREMENTS OF REFERENCE POINTS EASILY SEEN UNIFORM IN OUTLINE AND SHOULD BE REPRODUCIBLE LAND MARKS SHOULD PERMIT VALID QUANTITATIVES MEASUREMENT OF LINE AND ANGLE PROJECTED FROM THEM
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No. Code Definition 1 N Nasion. The most anterior point of the nasofrontal suture in the median plane. The skin nasion (N1) is located at the point of maximum convexity between nose and forehead. 2 S Sella. The sella point (S) is defined as the midpoint of the hypohysial fossa. It is a constructed (radiological) point in the median plane.
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3 Se Midpoint of the entrance to the sella, according to A.M.Schwarz at the same level as the jugum sphenoidale,independent of the depth of the sella. This point represents the midpoint of the line connecting the posterior clinoid process and the anterior opening of the sella turcica. 4 Sn Subnasale, A skin point; the point at which the nasalseptum merges mesially with the integument of the upper lip • 5 A Point A, subspinale. The deepest midline point in the curved bony outline from the base to the alveolar process of the maxilla, i.e. at the deepest point between the anterior nasal spine and prosthion. In anthropology, it is known as subspinale • www.indiandentalacademy.com
6 APMax The anterior landmark for determining the length of the maxilla. It is constructed by dropping a perpendicular from point A to the palatal plane.  7 Pr Prosthion. Alveolar rim of the maxilla; the lowest most anterior point on the alveolar portion of the premaxilla, in the median plane, between the upper central incisors. 8 Is (or Is⊼) Incisor superius. Tip of the crown of the most anterior maxillary centrals.
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9 AP⊥ Apicale ⊥. Root apex of the most anterior maxillary central incisor. 10 Ii (or IsT) Incisor inferius. Tip of the crown of the most anterior mandibular central incisor. 11 AP T Apicale T. Root apex of the most anterior mandibular central incisor. 12 Id Infradentale. Alveolar ridge of the mandible; the highest, most anterior point on the alveolar process, in the median plane, between the mandibular central incisors. www.indiandentalacademy.com
13 B PointB, supramentale. Most anterior part of the mandibular base. It is the most posterior point in the outer contour of the mondibular alveolar process, in the median plane. In anthropology, it is known as supramentale, between infradentale and pogonion. 14 Pog Pogonion, Most anterior point of the bony chin, in the median plane. Â
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15 Gn Gnathion. This point is defined in a number of ways. According to Martin and Saller (1956), it is located in the median plane of the mandible, where the anterior curve in the outline of he chin merges into the body of the mandible. Many authors have located gnathion between the most anterior and the most inferior point of the chin. Graig defines it with the aid of the facial and the mondibular plane; according to Graig, gnathion is the point of intesectin of these two planes. Muzi and May give it as the lowest point of the chin (A.M.Schwarz uses the same definition) and therefore synonymous with Menton www.indiandentalacademy.com
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16 Go Gonion. A constructed point, the intersection of the lines tangent to the posterior margin of the ascending ramus and the mandibular base. •
17 Me Menton. According to Krogman and Sassouni, Menton is the most caudal point in the outline of the symphysis; it is regarded as the lowest point of the mandible and corresponds to the anthropological gnation.
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18 APMan The anterior landmark for determining the length of the mandible. It is defined as the perpendicular dropped from Pog to the mandibular plane.
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19 Ar Articulare. This point was introduced by Bjork (1947). It provides radiological orientation, being the point of intersection of the posterior margin of the ascending ramus and the outer margin of the cranial base. 20 Cd Condylion. Most superior point on the head of the condyle 21 Or Orbitale. Lowermost point of the orbit in the radiograph 22 Pn/2 A constructed point. It is obtained by bisecting the Pn vertical, between its intersectin with the palatal plane and point N’.  www.indiandentalacademy.com
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23 Int.FH/ Intersection of the ideal Frankfurt horizontal and the R.asc. posterior margin of the ascending ramus. Â 24 ANS Anterior nasal spine. Point ANS is the tip of the bony anterior nasal spine, in the median plane. It corresponds to the anthropological acanthion. 25 PNS Posterior nasal spine. This is a constructed radiological point, the intersection of a continuation of the anterior wall of the pterygopalatine fossa and the floor of the nose. It marks the dorsal limit of the maxilla. Â
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26 S’ Landmark for assessing the length of the maxillary base, in the posterior section. It is defined as a perpendicular dropped from point S to a line extending the palatal plane. 27 APOcc Anterior point for the occlusal plane. A constructed point, the midpoint in the incisor overbite in occlusion. 28 PPOcc Posterior point for the occlusal plane. The most distal point of contact between the most posterior molars in occlusion. 29 Ba
Basion.
Lowest point on the anterior
margin of the foramen magnum in the median plane. www.indiandentalacademy.com
3 30 Ptm Pterygomaxillary fissure. The contour of the fissure projected onto the palatal plane. The anterior wall represents the maxillary tuberosity outline, the posterior wall the anterior curve of the pterygoid process. This point corresponds to PN
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SOFT TISSUE PROFILE ANATOMY The visible surface of the soft tissue facial profile extends from the hairline (trichion) (1) to the superior cervical crease (2) The three superposed level may be differentiated: The upper, frontal level, which belongs to the cranium and is located between the hairline (1) and the supraorbital ridge(3); The middle, maxillary level, which is situated between the supraorbital ridge (3) and the occlusal plane; and · The inferior, mandibular level, which is located between the occlusal plane and the superior cervical crease. www.indiandentalacademy.com
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Cephalometric landmarks G – glabella – the most prominent point in the midsagittal plane of forehead; • Ils- inferior labial sulcus-the point of greatest than cavity in the midline of the low lip between labrale inferius and mention; • Li – Labrale inferius –the median point in the lower margin of he lower membranous lip; • Ls – labrale superius – the median point in the lower margin of the upper margin of the upper membranous lip; • Ms – menton soft tissue – the constructed point of intersection of a vertical co-ordinate from menton and the inferior soft tissue contour of the chin; •
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Ns- nasion soft tissue-the point of deepest con-cavity of the soft tissue contour of the root of the root of the nose; · Pn – pronasale – the most prominent point of the nose; · Pos – pogonion soft tissue – the most prominent point o n the soft tissue contour of the chin; Ns- nasion soft tissue-the point of deepest concavity of the soft tissue contour of the root of the root of the nose; · Pn – pronasale – the most prominent point of the nose; · Pos – pogonion soft tissue – the most prominent point o n the soft tissue contour of the www.indiandentalacademy.com chin;
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Sls – superior labial sulcus – the point of greatest concavity in the midline of the upper lip between subnasale and labrale superius; · Sn –subnasale – the point where the lower border of the nose meets the out contour of the upper lip; · St – stomion – the midpoint between stomion superius and stomion inferius; · Sti – stomion inferius – the highest point of the lower lip; · Sts – stomion superius – the lowest point of the upper lip www.indiandentalacademy.com
DENTITION (Cephalometric landmarks) APOcc – anterior point for the occlusal plane – a constructed point, the midpoint of the incisor overbite in occlusion; · Iia – incision inferius apicalis – the root apex of the most anterior mondibular central incisor; if this point is needed only for defining the long axis of the tooth, the midpoint on the bisection of the apical root width can be used; · Iii – incision inferius incisalis – the incisal edge of the most prominent mandibular central incisior; Isa – incision superius apicalis – the root apex of themost anterior maxillary central incisor; if this point is needed only for defining the long axis of the tooth, the midpoint on the bisection of the apical root width www.indiandentalacademy.com can be used;
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• Isi – incision superrius incisalis –the incisal edge of the maxillary central incisor; · L1 – mandibular central incisor – the most labial point on the crown of the mandibular central incisor; · L6 – mondibular first molar – the tip of the mesiobuccal cusp of the mandibular first permanent molar; · PPOcc – posterior point for the occlusal plane – the most distal point of contact between the most posterior molars in occlusion (Rakosi); · U1 – maxillary central incisor – the most labial point on the crown of the maxillary central incisor; U6 – maxillary first molar – the tip of the mesiobuccal cusp of the maxillary first www.indiandentalacademy.com
PHARYNX Cephalometric landmarks • ans – anterior nasal spine; · apw – anterior pharyngeal wall; · hy – hyoid; · pns – posterior nasal spine; · ppw – posterior pharyngeal wall; · pt – posterior point of tongue · ptm – pterygomaxillary fissure; · spw – superior pharyngeal wall; · U – tip of uvula; · Uo- point on the oral side of the soft palate; · Up – point on the pharyngeal side of the soft palate; · Ut – upperwww.indiandentalacademy.com point of tongue.
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cervical vertebrae
The cervical vertebrae make up the upper part of the vertebral column. There are seven cervical vertebrae. A typical cervical vertebra consists of a body and a vertebral arch. Cephalometric landmarks · cv2ap – the apex of the odontoid process of the second cervical vertebra; · cv2ip – the most inferoposterior point on the body of the second cervical vertebra; · cv2ia – the most inferoanterior point on the body of the second;d vertical vertebra; www.indiandentalacademy.com
· cv3sp - the most superopostrior point on the body of the third cervical vertebra; · cv3ip – the most inferoposterior point on the body of the third cervical vertebra; · cv3sa – the most superoanterior point on the body of the third cervical vertebra; · cv3ia – the most inferoanterior point on the body of the third cervical vertebra; · cv4sp – the most suproposterior point on the body of the fourth cervical vertebra; · cv4ip – the moswt inferoposterior point on the body of the fourth cervical vertebra; · cv4sa – the most superoanterior poijnt on the body of the fourth cervical vertebra; www.indiandentalacademy.com
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cv4ia – the most inferoanterior point on the body of the fourth cervical·
cv5sp – the most suproposterior point on the body of the fifth cervical vertebra cv5ip - the most inferoposterior point on the body of the fifth cervical vertebra; · cv5sa – the most superoanterior point on the body of the fifth cervical vertebra; · cv5ia – the most inferoanterior point on the body of the fifth cervical vertebra; www.indiandentalacademy.com
• cv6sp – the most superoposterior point on the body of the sixth cervical vertebra; · cv6ip – the most inferoposterior point on the body of the sixth cervical vertebra; · cv6sa – the most superoanterior poijnt on the body of the sixth cervical vertebra; · cv6ia – the most inferoanterior point on the body of the sixth cervical vertebra;
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LINES AND PLANES IN CEPHALOMETRICS CAN BE OBTAINED BY CONNECTING TWO LAND MARKS BASED ON ORIENTATION, THEY CAN BE VERTICAL HORIZONTAL
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HORIZONTAL PLANES S.N. PLANE IT IS THE CRANIAL LINE BETWEEN THE CENTER OF SELLA TURSICA (SELLA) AND THE ANTERIOR POINT OF THE FRONTO-NASAL SUTURE (NASION). IT REPRESENTS THE ANTERIOR CRANIAL BASE. FRANKFORT HORIZONTAL PLANE THIS PLANE CONNECTS THE LOWEST POINT OF TE ORBIT (ORBITALE) AND THE SUPERIOR POINT OF THE EXTERNAL AUDITORY MEATUS (PORTION).
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PALATAL PLANE IT IS A LINE LINKING THE ANTERIOR NASAL SPINE OF THE MAXILLA AND THE POSTERIOR NASAL SPINE OF THE PALATINE BONE. OCCLUSAL PLANE IT IS A DENTURE PLANE BISECTING THE POSTERIOR OCLUSION OF THE PERMANENT MOLARS AND PREMOLARS (OR DECIDUOUS MOLARS IN MIXED DENTITION) AND EXTENDS ANTERIORLY. www.indiandentalacademy.com
MANDIBULAR PLANE SEVERAL MANDIBULAR PLANES ARE USED IN CEPHALOMETRICS, BASED ON THE ANALYSIS BEING DONE. THE MOST COMMONLY USED ONES ARE: TANGENT TO THE LOWER BORER OF THE MANDIBLE (TWEED). A LINE CONNECTING GONION AND GNATHION (STEINER) A LINE CONNECTING GONION AND MENTON (DOWNS)
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REFERNCE PLANES
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REFERENCE PLANES
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BASION – NASION PLANE IT IS A LINE CONNECTING THE BASION AND NASION. IT REPRESENTS THE CRANIAL BASE. BOLTON’S PLANE THIS IS A PLANE THAT CONNECTS THE BOLTON’S POINTS POSTERIOR TO THE OCCIPITAL CONDYLES AND NASION. VERTICAL PLANES A. POG LINE IT IS A LINE FROM POINT A ON THE MAXILLA TO POGONION ON THE MANDIBLE. FACIAL PLANE IT IS A LINE FROM THE ANTERIOR POINT OF THE FRONTO-NASAL SUTURE (NASION) TO THE MOST ANTERIOR POINT OF THE MANDIBLE (POGONION). FACIAL AXIS A LINE FROM PTM POINT TO CEPHALOMETRIC GNATHION. www.indiandentalacademy.com
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ERRORS OF CEPHALOMETRIC MEASUREMENTS RADIOGRAPHIC PROJECTION ERRORS ERRORS WITHIN THE MEASRUING SYSEM ERRORS IN LANDMARK IDENTIFIATION
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RADIOGRAPHIC PROJECTION ERRORS MAGNIFICATION OCCURS BECAUSE THE X-RAY BEAMS ARE NOT PARALLLEL WITH ALL THE POINTS IN THE OBJECT THE MAGNITUDE OF ENLARGEMENT IS RELATED TO THE DISTANCES BETWEEN THE FOCUS THE OBJECT AND THE FILM LONG FOCUS-FILM DISTANCES ARE FAVOURABLE USE OF ANGULAR RATHER THAN LINEAR MEASUREMENTS IS A CONSISTENT WAY TO ELIMINATE THE IMPACT OF MANGIFICATION www.indiandentalacademy.com
DISTORTION OCCURS BECAUSE OF DIFFERENT MAGNIFICATION BETWEEN DIFFERENT PLANES. SOME LANDMARK ARE USEFUL FOR SUPERIMPOSING RADIOGRAPHS ARE AFFECTED BY DISTORTION, OWING TO THEIR LOCATION IN A DIFFFERENT DEPTH OF FIELD. BOTH LINEAR AND ANGULAR MEASUREMENTS WILL BE VARIOUSLY AFFECTED. A COMBINATION OF INFORMATION FROM LATERAL AND FRONTAL FILMS HAS BEEN PROPOSED. MISALIGNMENT OR TILTING OF THE CEPHALOMETRIC COMPONENTS (E.G. THE FOCAL SPOT), THE CEPHALOSTAT, AND THE FILM WITH RESPECT TOEACH OTHER, AS WELL AS ROTATIONS OF THE PATIENTS’S HEAD IN ANY PLANE OF SPACE, WILL INTRODUCE ANOTHER FACTOR OF DISTORATION www.indiandentalacademy.com
ERRORS WITHIN THE MEASURING SYSTEM BECAUSE OF PARALLAX AND MECHANICAL ERRORS. ERRORS RELATED TO THE RECORDING PROCEDURE HAVE TWO COMPONENTS. 1. PRECISION WITH A MARKED POINT ON THE FILM OR TRACING CAN BE IDEENTIFIED BY THE CROSS-HAIR OF THE RECORDING DEVICE AND 2. THE ERRORS OF THE DIGITZING SYSTEM. AN ACCURACY OF 0.1MM IS DESIRABLE, WITHOUT ANY DISTORTION OVER THE SURFACE OF THE DIGITIZER (HOUSTON, 1979). www.indiandentalacademy.com
ERRORS IN LANDMARK IDENTIFICATION LANDMARK IDENTIFICATION ERRORS ARE CONSIDERED THE MAJOR SOURCE OF CEPHALOMETRIC ERROR. FACTORS INCLUDE 1.THE QUALITY OF THE RADIOGRAPHIC IMAGE 2.THE PRECISION OF LANDMARK DEFINTION AND THE REPRODUCIBILITY OF LANDMARK LOCATIONS; AND 3. THE OPERATOR AND THE REGISTRATION PROCEDURE. www.indiandentalacademy.com
QUALITY OF RADIOGRAPHIC IMAGE EXPRESSED IN TERMS OF SHARPNESS – BLUR AND CONTRAST – AND NOISE. SHARPNESS IS THE SUBJECTIVBE PRECEPTION OF THE DISTINCTNESS OF THE BOUNDARIES OF A STRUCTURE IT IS RELATED TO BLUR AND CONTRAST. BLUR IS THE DISTANCE OF THE OPTICAL DENSITY CAHNGE BETWEEN THE BOUNDARIES OF A STRUCTURE AND ITS SURROUNDINGS . RESULTS FROM THREE FACORS GEOMETRIC UNSHARPNESS,RECEPTOR UNSHARRPNESS MOTION UNSHARPNESS www.indiandentalacademy.com
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CONTRAST IS THE MAGNITUTDE OF THE OPTICAL DESNITY DIFFERENCES BETWEEN A STRUCTURE AND ITS SURROUNDINGS. INCREASED CONTRAST ENHANCES THE SUBJECTIVE PERCEPTION OF SHARPNESS. CONTRAST IS DETERMINED BY 1.THE TISSUE BEING EXAMINED 2.THE RECEPTOR AND 3.THE LEVEL OF Kv USED. MOST IMPORTANT BEING THE FILM-CASSETTE SYSTEM AND THE KV LEVEL USED. www.indiandentalacademy.com
NOISE REFERS TO ALL FACTORS THAT DISTURB THE SIGNAL IN A RADIOGRAPH. RELATED TO 1. THE RADIOGRAPHIC COMPLEXITY OF THE REGION 2. RECEPTOR MOTTLE OR QUANTUM NOISE. THESE TYPES OF ERRORS CAN BE MINIMIZED BY FILMS OF HIGH QUALITY.
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PRECISION OF LANDMARK DEFINITION AND REPRODUCIBILITY OF LANDMARK LOCATION. BAUMRIND AND FRANTZ POINTED OUT THAT ERRORS IN LANDMARK LOCATIONS ARE FUNCTION OF THREE VARIABLES 1. THE ABSOLUTE MAGNITUDE OF THE ERROR IN LANDMARK LOCATION. 2. THE RELATIVE MAGNITUDE OF THE LINEAR DISTANCE ANGULAR OR LINEAR MEASUREMENT. 3. THE DIRECTION FROM WHICH THE LINE CONNECTING THE LANDMARKS INTERCEPTS THEIR ENVELOPE OF ERRORS. ENVELOP IS THE PATTERN OF THE TOTAL ERROR DISTRIBUTION. www.indiandentalacademy.com
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ADVANTAGES OF THE CEPHALOMETRY 1. ONLY AVAILABLE METHOD THAT PERMITS THE INVESTIGATION OF THE SPATIAL RELATIONSHIPS BETWEEN CFRANIAL STRUCTURES AND BETWEEN DENTAL AND SURFACE STRUCTURES 2. MODER ECONOMICAL22 IN COMPARISON TO COMPUTED TOMOGRAPHY AND MRI. 3. NON-INVASIVE AND NON-DESTRUCTUVE THUS PRODUCING A RELATIVELY HIGH INFORMATION YELD AT RELATIVELY LOW PHYSIOLOGIC COST. 4. STANDARDIZED CAN BE USED FOR SERIOAL ASSEMENTS OF GROWTH AND ONGOING PRCOESSES OF TREATMENT 5. CEPHALMETRICS PRODUCES TANGIBLE PHYSICAL RECORDS THAT ARE RLEATIVELY PERMANENT. 6. THE SAM SETS OF CEPHALOGRAMS CAN BE USED FOR TESTING DIFFERENT THEORIES AND HYPOTHESES. 7. THEY ARE RELATIVELY EASY TO STORE REPRODEUCE AND www.indiandentalacademy.com TRANSPORT
LIMITATIONS OF CEPHALOMETRY RADIATION EXPOSURE ARE REAL CEPHALOMETRICS IS CHARACTERIZED BY A NUMBER OF TECHNICAL LIMITATIONS. THE ABSENCE OF ANATOMICAL REFERENCES WHOSE SHAPE AND LOCATION REMAIN CONSTANT THROUGH TIME INHERENT AMBIGUITY IN LOCATING ANATOMICAL LANDMARKS AND SURFACES ON X-RAY IMAGES SINCE THE IMAGES LACK HARD EDGES, SHADOWS, AND WELL DEFINED OUTLINES. THEY ARE TWO DIMENSIONAL IMAGES OF THREE DIMENSIONAL . THIS CONTRADICTION LEAD TO DIFFERENTIAL PROJECTIVE DISPLACEMENT OF ANATOMICAL STRUCTURES LYING AT DIFFERENT PLANES WITHIN THE HEAD. www.indiandentalacademy.com
CONCLUSION
Indispensable diagnostic aid but requires proper skill and technique and an eye of an expert to interpret ate.
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