Tweed’s Philosophy
Write short note on Tweed diagnostic triangle.
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Write short note on Tweed’s triangle.
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Write short answer on Tweed’s diagnostic triangle.
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Write briefly on Tweed’s analysis.
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Write short note on Tweed’s analysis.
Answer.
Tweed’s Analysis
It is a type of cephalometric analysis.
- It is given by Charles Tweed.
- Cephalometric points used are:
- Porion: Superiomost point of orbitale.
- Orbital: Inferiomost point of lower border of orbit.
- Tweed’s analysis makes use of three planes.
- The planes used are:
- Frankfort horizontal plane (FH plane): Join porion and orbitale.
- Mandibular plane: A tangent is drawn to lower border of mandible.
- Long axis of lower incisor: A line is drawn along the long axis of incisors.
Objectives of Analysis
- Determination of the position of lower incisor.
- Evaluation of prognosis.
Angle’s Formed
- Angle’s formed by these three planes are:
- Frankfort mandibular plane angle (FMA)—It is formed by intersection of the FH plane with the mandibular plane.
- The mean value is 25° in well balanced cases.
- Incisors mandibular plane angle (IMPA)—It is the angle formed by the intersection of the long axis of the lower incisor with the mandibular plane.
- It indicates the inclination of the lower incisor.
- The mean value is 90° in well balanced cases.
- Frankfort mandibular incisor angle (FMIA)—It is the angle formed by the intersection of the long axis of the lower incisor with the FH plane.
- The mean value is 65° in well balanced cases.
- Frankfort mandibular plane angle (FMA)—It is formed by intersection of the FH plane with the mandibular plane.
Interpretation
- FMA>28°: This indicates that patient has high angle and growth of mandible is clockwise.
- FMA<23°: This indicates that patient has low angle and growth of mandible is counterclockwise.
- IMPA>110°: Lower incisors are proclined.
- IMPA<85°: Lower incisors are retroclined.
Summary of Tweed’s Triangle
Clinical Importance
- It is used in orthodontics for classification, diagnosis, treatment planning as well as prognosis.
- Tweed had also mentioned about extraction of teeth for correcting the alveolodental prognathism and also the positioning of mandibular incisors upright over the basal bone.
- If FMA is 20° to 30° the prognosis of orthodontic treatment along with extraction is excellent to good.
- If FMA is 30° to 35° the prognosis of orthodontic treatment along with extraction is excellent lies in the range of good to fair.
- If FMA is 35° to 40° the prognosis of orthodontic treatment along with extraction is unfavorable.
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