 Welcome back to a new session on dentistry and model. So today we have a cephalometric analysis, the most common analysis that is down's analysis. So basically we know, analysis we can do skeletal and dental relationship assessment or we can measure it by keeping a reference to a landmark or a plane drawn on the lateral safe. So these can be either we can do hand tracing or more commonly we can do digitalizing using specialized softwares. So down's analysis is a very common analysis used in orthodontics which was first published by Mr. Downs in 1948. His full name is Williams Downs and it is one of the most frequently used cephalometric analysis, which has basically five skeletal and five dental parameters. So total 10 parameters out of which five skeletal and five dental. And this is used between 12 to 17 years of aged patients. So according to Down, the balance of phase is determined by position of the mantable. So mantable is the key element to determine the balance. So in Down's analysis, the Frankfurt horizontal plane kept as a reference plane. Okay, that is a line from anatomic porion to orbitaly. So this is the point, porion, porion is nothing but the bony point on external auditory meanders. And the orbitaly point we have seen in our cephalometric landmarks. This is a line connecting porion to orbitaly which is known as Frankfurt horizontal plane or FH plane. So this is the FH plane which is connecting porion to orbitaly. So Down kept this plane as reference base from which the degree of retrognathism, orthognathism or prognathism is determined. So this is the reference plane he kept that is FH plane or plane which connects porion or orbitaly. The first skeletal parameters, so let's see what are the five skeletal and five dental parameters. The five skeletal parameters, the first one is facial ankle, ankle of convexity. Third one is mantibular plane ankle. The fourth one is y-axis also known as growth axis. Fifth one is AB plane ankle. This is skeletal parameters. Now let's see what are the dental parameters. The first one is cantoff occlusal plane, inter incisal ankle, incisor occlusal plane ankle, incisor mantibular plane ankle and upper incisor to A pogonian line. So these are the ten parameters, five skeletal and five dental. So let's see one by one. The first one is skeletal parameters and the facial ankle. So facial ankle, it is the inside inferior angle formed by intersection of FH plane and nasion pogonian plane. So nasion is this point, hope you can see this point, nasion and pogonian. Pogonian is this point. Pogonian is placed on the symphysis at the lower portion. Pogonian is a most anterior point on the symphysis of mantibular. So these two planes are connected, that is nasion, pogonian and FH plane. And the angle formed inside is known as facial ankle. So this is the facial ankle. So facial ankle, the common value or the mean value is 87.8 degree which ranges from 80 to 82 to 95 degree. So what are the significance of this facial ankle? The one is it indicates the anterior-posterior positioning of mantibular in relation to the upper face. So the anterior-posterior positioning of mantibular in relation to the upper face. So it increased in cases of class 3 because this mantibular when it is positioned forwardly, that is in class 3, this ankle will increase. So this line will move forward, so this ankle will increase. And it decreases in class 2. So class 2, the exact opposite happens. This line will come backwards and this ankle will decrease. So that is all about facial ankle. It is by FH plane and nasion-pogonian line, the inside ankle, mean values 87.8 degree increases in class 3, decreases in class 2. The second ankle is ankle of convexity in skeletal parameters. So ankle of convexity is basically it is very difficult to differentiate because any ankle we need two lines to intersect at one point. So you might not be able to differentiate it because it is joined by nasion point A, nasion and point A. So that is a black line, hope you can see this black line nasion to point A. Then point A to pogonian, that is a red line. So these two lines intersect and forms one ankle that is known as ankle of convexity. Why you cannot differentiate it because the ankle of convexity is zero degree. So literally there is no ankle between these two lines. It is starting from nasion to point A and point A to pogonian. So that is ankle of convexity, the normal value is zero. It ranges from minus 8.5 degree to 10 degree. So what is the significance? Significance, a positive ankle suggests a prominent maxilla in relation to mandible. Negative ankle suggests a prognathic profile. So positive ankle suggests a prominent maxilla in relation to this maxilla, this line, prominent maxilla. This will be like this. So you will get a positive ankle and negative ankle when you have a prognathic profile. So it will be negative ankle, this will be positive ankle. So this prognathic will get, sorry, when maxilla goes forward or such as glass toe relation, you get a positive ankle. And this goes right anteriorly, that is mandible when it goes anteriorly. This will change left and you get a negative ankle. So that is ankle of convexity. The third one is mandibular plane ankle. Mandibular plane angle is formed by FH plane and mandibular plane. That is a tangential line to the lower border of mandible. So this angle is, this angle is mandibular plane angle. So this is formed by FH plane and tangential line to the lower border of mandible forms a line. These two line intersect here and forms an angle. This is known as mandibular plane angle and the average value is 21.9 degree. The range is from 17 to 28 degree. So the higher mandibular plane angle occurs in both retrusive and protrusive phase and a suggestive of unfavorable hyperdivergent phase. So when there is a hyperdivergent phase, this mandibular plane angle will be increased. That is a divergent how divergent the phase is began understand by mandibular plane angle. So this is how it forms FH plane and mandibular plane. The fourth one is y-axis. This is an important question y-axis. So y-axis is nothing but an axis which connects the cellar tosica and nathion. Nathion is the most inferior point in the symphysis of the lower border of mandible. This nathion and cellar tosica which connects and the second line is FH plane. So FH plane, this is FH plane and cellar nathion plane which intersect here forms an angle. This is known as y-axis. So this average value is 59 degree. Average value is 59 degree which ranges from 53 to 66 degree. So this is important. Commonly asked, what is y-axis? Nathion to cellar tosica. Average value is 59 degree. It increases in the class 2 profile and it decreases in class 3 profile. Because this axis will move forward in class 3 when the mandible is going anterior in class 3. So this angle will be reduced because anyway this plane won't change. So this mandible moving forward in class 3, this angle will reduce and in class 2 this will increase. So that is y-axis. So the last one in skeletal parameter is AB plane angle. So AB plane angle is 2 planes which are 1 is point A to point B. So I hope you can see the green line which connects point A in the maxilla and point B in the mandible. So this line and the second one is nasion-pogonion. So nasion is here, pogonion is here. So the green line. So two green lines. And the angle formed between these two lines is the AB plane angle and it is always negative. Because the point B is always positioned behind point A. You can see point A is little ahead of point B. So this angle is always negative. And the average value is minus 4.6 degree which ranges from minus 9 to 0 degree. So it indicates the maxilla-mantibular relationship in relation to the facial plane. So the maxilla-mantibular relationship in relation to the facial plane. And the positive angles you can see in class 3 malocclusion. So class 3 malocclusion you can see the positive angle. And in class 1 malocclusion mostly this will be negative. Sorry in class 3 malocclusion this will be a positive angle with a mandibular prominence. So when mandible is going forward this angle this is already negative. So this will change and it will become a positive angle. So that's all about the skeletal parameters of Daum's analysis. Facial angle, angle of convexity, mandibular plane angle, y-axis AB plane angle. Facial angle is FH plane at nasion-pogonion line which is 87.8 degree, increases in class 3 and decreases in class 2. Angle of convexity which is nasion 0.8 to 0.8 to pogonion which is almost parallel. The angle is 0 degree, ranges from minus 8.5 to 10 degree. Mantibular plane angle is here FH plane and tangential line which is 21.9 degree, ranges from 17 to 28. Y-axis is also known as growth axis that is FH plane and cellar nation that will increase in class 2 and decrease in class 3. And the last one is AB plane angle which is this green lines A and B with nasion and pogonion which is negative always because A is ahead of B. And you can see a positive angle in class 3 malocclusion. So we completed the skeletal parameters. Now let's see the dental parameters. So next we have our first dental parameter that is cantoff occlusal plane. So cantoff occlusal plane, the two lines are occlusal plane and FH plane. So we have this occlusal plane, you can see this green line occlusal plane and the FH plane and the angle formed here is cantoff occlusal plane which is average is 9.3 degree with a range of 1.5 to 14 degree. So this is the occlusal plane, a line which goes through occlusion. We have this molars and incisors. So the line goes like this and the FH plane it intersects here. This angle is cantoff occlusal plane. It gives a measure of slope of occlusal plane relative to FH plane. So how much is this slope compared to this FH plane? That is the significance of cantoff occlusal plane which increases in class 2 pattern and decreases where there is a long ramus of multiple. It increases in class 2 facial structures and decreases whereas a long ramus is present. So that is the cantoff occlusal plane. The second one is inter incisal angle. It is very easy inter incisal angle. It means the incisors that is maxillary and manipular incisors long axis. So this is the manipular incisor long axis and this is the maxillary incisor long axis and the angle formed inside is inter incisor angle which is average 135.4 degree ranges from 130 to 150.5 degree. That angle decreased in class 1 bimaxillary protrusion. So if there is a bimaxillary protrusion this line will go anterior and this angle will reduce and it increases in class 2 division 2. So in class 2 division 2 what happens is the central incisor will be reclined. So this line will go forward and this angle will increase. So that is inter incisal angle. The lines are lower central incisor and upper central incisor and the inside angle is inter incisal angle. Average value is 135.4 degree. The third one is incisor occlusal plane angle. The simple trick is you can easily make out the lines from the title itself inter incisor incisor occlusal plane. Incisor occlusal plane is nothing but the lower central incisor the same line we used for inter incisor and with incisor occlusal plane. And the occlusal plane this is occlusal plane and the angle formed between these two lines. So I have shaded it here with red ink. So the lower central incisor and the occlusal plane. So the angle here formed is incisor occlusal plane angle. So it is average value is 14.5 degree ranges from 3.5 to 20 degree. And an increase in this angle is a suggestion of or suggestive of increased lower incisor proclamation. So if it is more proclined the angle will be more. So that is inter sorry incisor occlusal plane angle. The fourth one is incisor manipular plane angle. So instead of occlusal plane angle here we have manipular plane angle. So this is from the same axis that is lower central incisor and the manipular plane angle is here. Manipular plane angle is here. So the angle formed between these two that is incisor manipular plane angle. The basic value is 1.4 degree and ranges from minus 8.2 to 7 degree. And increasing in this angle suggestive of increased lower incisor proclination. If this lower incisor is proclined this angle will automatically increase. So this is lower incisor angle and manipular plane angle. If lower incisor is proclined this angle will increase. So that is incisor manipular plane angle. And the last one in the Dental parameters that is upper incisor to a Pogonion line. So it is not an angle. So we can see upper central incisor and the tip of upper central incisor or the incisor edge of central incisor. And the line that is a Pogonion line and the distance between tip of the central incisor to a Pogonion line. So it is a linear measurement not an angle. The only linear measurement in Down's analysis is upper incisor to a Pogonion line. So this linear measurement on average is 2.7 millimeter which is ranging from minus 1 to 5 millimeter. So the measurement is more in patience with upper incisor proclination. If this is here the distance will be more. So that is a Pogonion line to the incisor edge of upper central incisor. So that is Dental parameters. So we have covered Dental parameters that is counter for collusion plane. That is FH2, FH2 collusion plane. Then enter incisor angle. So I have removed few lines here. This is FH plane. Enter incisor angle is 135.4 degree which is ranging from 130 to 150. Whereas this scant of occlusion plane is 9.3 degree ranging from 1.5 to 14 degree. And the third one is incisor occlusion plane angle. The incisor incisor occlusion plane angle which will be here. Incisor occlusion plane angle this angle which is average value is 14.5 degree ranging from 3.5 to 20. The next one is incisor mantibular plane angle also known as IMPA incisor mantibular plane angle. That is incisor here mantibular plane angle so this angle which is 1.4 degree. And the last one is upper incisor to apogonium line that is a linear measurement. Apogonium line and the tip of central incisor that is 2.7 millimeter ranging from minus 1 to 5 millimeter. So that is all about the Amps analysis. So the Amps analysis is little complicated. We have too many parameters, 5 skeletal and 5 dental parameters. But it is the most commonly used parameter analysis in cephalometrics. And the fundamental is FH plane. It is basically check the mantibular mantibule. FH plane is a plane which connects for you into orbit lay. So in skeletal parameters we have facial angle, angle of convexity, mantibular plane angle, y axis AB plane angle, y axis is a short knot. In dental parameters we have cantoff occlusion plane, inter incisor angle, incisor occlusion plane angle, incisor mantibular plane angle, upper incisor to apogonium line. The upper incisor to apogonium line is a linear measurement not an angle. Press taller angle. So that is all about Down's analysis. I will come up with Steiner's analysis and Tweed's analysis in next session. Thank you.