u1-na (mm)distance from upper incisor to na line4 mm l1-nb (degree) angle between lower incisor to nb line 25 degrees l1-nb (mm) distance from lower incisor to nb line 4 mm u1-l1 (°) upper incisor to lower incisor angle 130 degrees l1-chin (mm) also known as holdaway ratio. it states that chin prominence should be as far away as the farthest point of the lower incisor should be. an ideal distance is 2mm from pogonion to nb line and l1 to nb line. 4mm soft tissue s line line formed by connecting soft tissue pogonion and middle of an s formed by lower border of the nose ideally, both lips should touch the s line 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". 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: patient's age where anb has tendency to reduce with age change in position of nasion as pubertal growth takes place rotational effect of jaws 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. 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: 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. 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. downs analysis namedescriptionnormal standard deviation skeletal facial angle (°)angle between nasion-pogonion and frankfurt horizontal line87.8 +/- 3.6 angle of convexity (°)angle between nasion – a point and a point – pogonion line0 +/- 5.1 mandibular plane angle (°)angle between frankfort horizontal line and the line intersecting gonion-menton21.9 +/- 5 y axis (°)sella gnathion to frankfurt horizontal plane59.4 +/- 3.8 a-b plane angle (°)point a-point b to nasion-pogonion angle−4.6 +/- 4.6 dental cant of occlusal plane (°)angle of cant of occlusal plane in relation to fh plane9.3 +/- 3.8 inter-incisal angle (°)135.4 +/- 5.8 incisor occlusal plane angle (°)angle between line through long axis of lower incisor and occlusal plane14.5 +/- 3.5 incisor mandibular plane angle (°) angle between line through long axis of lower incisor and mandibular plane 1.4 +/- 3.8 u1 to a-pog line (mm) 2.7 +/- 1.8 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. 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. 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. namedescriptionnormal tweed facial triangle impa (°)angle between long axis of lower incisor and mandibular plane angle90 (°) +/- 5 fmia (°)frankfort mandibular incisor angle65 (°) fma (°)frankfort mandibular plane angle25 (°) total180 (°) jarabak analysis analysis developed by joseph jarabak in 1972. 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. ricketts analysis landmark name landmark symboldescription upper molar a6point on the occlusal plane located perpendicular to the distal surface of the crown of the upper first molar lower molar b6point on the occlusal plane located perpendicular to the distal surface of the crown of the lower first molar condyle cia point on the condyle head in contact with and tangent to the ramus plane soft tissue dtpoint on the anterior curve of the soft tissue chin tangent to the esthetic plane or e line center of cranium ccpoint of intersection of the basion-nasion plane and the facial axis points from plane at pterygoid cfthe point of intersection of the pterygoid root vertical to the frankfort horizontal plane pt point ptjunction of pterygomaxillary fissure and the foramen rotundum. condyle dcpoint in the center of the condyle neck along the ba–n plane nose enpoint on the soft tissue nose tangent to the esthetic plane gnathion gnpoint of intersection between the line between pogonion and menton gonion gopoint of intersection between ramus plane and mandibular plane suprapogonion pmpoint at which shape of symphysis mentalis changes from convex to concave pogonion pogmost anterior point of the mandibular symphysis cephalometric pointersection of facial plane and corpus axis t1 point tipoint of intersection of the occlusal and facial planes xi point xi name of planes symbol frankfort horizontal fh plane this plane extends from porion to orbitale facial plane this plane extends from nasion to pogonion mandibular plane plane extending from gonion to gnathion ptv (pterygoid vertical) this line is drawn through ptm and is perpendicular to the fh plane basion-nasion plane plane extending from basion to nasion occlusal plane occlusal plane through molars and premolars contact (functional plane) a-pog line a line extending from point a to pogonion e-line this line extends from the tip of soft tissue nose to soft tissue pogonion the rickett analysis also consists of following measurements name description normal standard deviation facial axis angle between pt/gn and the line n/ba 90 +/- 3.5 facial angle angle between the line fl and fh 89 +/- 3 ml/fh angle between the line fh and the line ml 24 +/- 4.5 convexity distance between pog/n and a 0 +/- 2 li-a-pog distance between pog/a and li 1 +/- 2 ms-ptv projection on the line fh of the distance between the markers pt/ms-d 18 ili-/a-pog distance between the line pog/a and the line lia/li 22 +/- 4 li-el distance between the line el and li −2 +/- 2 sassouni analysis this analysis, developed by viken sassouni in 1955, 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: supraorbital plane (anterior clinoid to roof of orbits) palatal plane (ans-pns) occlusal plane (downs occlusal plane) 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. 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. mcnamara analysis landmark name landmark symbol description normal maxilla to cranial base nasolabial angle 14 degrees na perpendicular to point a 0-1mm maxilla to mandible ap mandibular length (co-gn) mandible to cranial base pog-na perpendicular small = -8 to −6mm medium = -4mm to 0mm large = -2mm to +2mm dentition 1 to a-po 1-3mm 1 to point a 4-6mm airway upper pharynx 15-20mm lower pharynx 11-14mm 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. this was followed by soft tissue cephalometric analysis for orthognathic surgery in 1980 by arnette et al. in this analysis, burstone et al. used a plane called horizontal plane, which was a constructed of frankfurt horizontal plane. landmark name landmark symbol description normal cranial base posterior cranial base ar-ptm anterior cranial base ptm-n vertical skeletal and dental upper anterior facial height n-ans lower anterior facial height ans-gn upper posterior facial height pns-n mandibular plane angle mp-hp upper anterior dental height u1-nf lower anterior dental height l1-mp upper posterior dental height um-nf lower posterior dental height lm-mp maxilla and mandible maxillary length pns-ans mandibular ramus length mandibular body length chin depth b-pg gonial angle ar-go-gn dental relationships occlusal plane op-hp upper incisors inclination u1-nf lower incisors inclination l1/go-me wits analysis a-b/op counterpart analysis template analysis computerised cephalometrics computerised cephalometrics is the process of entering cephalometric data in digital format into a computer for cephalometric analysis. digitization (of radiographs) is the conversion of landmarks on a radiograph or tracing to numerical values on a two- (or three-) dimensional coordinate system, usually for the purpose of computerized cephalometric analysis. the process allows for automatic measurement of landmark relationships. depending on the software and hardware available, the incorporation of data can be performed by digitizing points on a tracing, by scanning a tracing or a conventional radiograph, or by originally obtaining computerized radiographic images that are already in digital format, instead of conventional radiographs. computerized cephalometrics offers the advantages of instant analysis; readily available race-, sex- and age-related norms for comparison; as well as ease of soft tissue change and surgical predictions. computerized cephalometrics has also helped in eliminating any surgeon inadequacies as well as making the process less time-consuming. the first medically certified automated cephalometric analysis of 2d lateral cephalometric radiographs by artificial intelligence was brought to market in november 2019. digitization computer processing of cephalometric radiographs uses a digitizer. digitization refers to the process of expressing analog information in a digital form.