Incisor Mandibular plane Angle and Tweed philosophy

1. 1 Incisor mandibular plane angle Incisor mandibular plane angle And And Tweed philosophy Tweed philosophy Prepared by: Prepared by: Dr. Mohammed Alruby Dr. Mohammed Alruby هنيد ثلث بهذ دقف هانغ لجا نم ينغل عضاوت نم هعفر لله عضاوت نمو ophy Dr. Mohammed Alruby I Incisor ncisor mandibular plane Angle and mandibular plane Angle and T Tweed philos weed philosophy Dr. Mohammed Alruby

2. 2 Introduction: = Margolies was first relate the axial inclination of the mandibular incisor with the mandibular plane. = Brodie found the axial relationship of lower incisors to the mandibular plane, Class I: 90,9 degree Class II 1: 89,3 degree Class II 2: 86,6 degree He considered the axial inclination of lower incisors as a part of the general growth pattern which varies for each individual. = Charles H Tweed introduced the philosophy of uprighting the mandibular incisors to improve stability of the dentition and achieve maximum balance and harmony of facial lines. And placing the teeth uright over the basal bone improved the dental health and function. Diagnosis: The lower incisor to mandibular plane angle: reveals the inclination of lower central incisors to MP from gonion to menton (Down) and gonion to gnathion (Steiner). The diagnostic facial triangle: =The accepted values of triangle: FMA: 25 degree, FMIA: 65 degree, FMPA: 90 degree. FMIA is considered to be the most important of these angle because, this angle is most closely to profile area, where the profile within normal limits, variation in mandibular plane may affect the other two angles, and still leave the FMIA at 65 degree. = The ultimate balance and facial harmony in esthetics is achieved when the mandibular incisors are positioned over the basal bone. = The normal relationship of the mandibular incisors teeth to their basal bone is the most reliable guide in diagnosis and treatment plane of Class I and II and bi-maxillary protrusion. Classification of facial growth trends: Tweed classify the facial growth trends into 3 types: 1-Type A (25%): == the mandibular incisor remains stable and free from crowding == middle and lower face grows in forward and downward in unison with no change in size of ANB angle. == growth is approximately equal in both vertical and horizontal dimension. Subdivision: 1- Class I with ANB angle > 4.5 degree: no treatment is indicated until the full eruption of all 4 cuspid teeth following the serial extraction. 2-Class II with ANB angle < 4.5 degree: place the patients under Klohn cervical gear to restrain the maxillary growth. As the maxillary denture moves posteriorly, point B moves forward. 2-Type B: middle face grows more rapidly than the lower face Growth occur predominantly in the vertical dimension. Subdivision: ==when ANB is less than 4 degree, the prognosis is fair. == When 6 < ANB >12 degree; extraction of all 4 premolars and point A will drop down and back as a result of treatment == treatment require 36 to 42 months to complete. 3-Type C: lower face growing downward and forward more rapidly than the middle face with decrease size of ANB angle. ophy Dr. Mohammed Alruby I Incisor ncisor mandibular plane Angle and mandibular plane Angle and T Tweed philos weed philosophy Dr. Mohammed Alruby

3. 3 == growth occurs predominantly in horizontal direction. == mandibular incisors cutting edge engage in the lingual surface of maxillary incisors: -------- lingual tipping of mandibular incisor as the orbicularis oris muscle is thin and strong. --------- maxillary incisors are tipped labially if orbicularis oris is more relaxed. Subdivision: == growth is confined to horizontal dimension with little vertical growth. == growth is predominantly in horizontal direction. ** The diagnostic facial triangle: Tweed divided the patients into 2 groups: 1-Patients with balance and harmony of facial proportion: inclination of mandibular incisors was 90 degree in relation to body of the mandible. == Margolis suggested to check the inclination of incisors in relation to mandibular border. == so occlusion was normal range 90 degree to MP 2-Patients lack of these qualities: Conclusion: 1-If FMA angle >30, the occlusal plane conversed posteriorly in relation to MP 2-If FMA angle is = 25+-4 the occlusal plane does not conversed posteriorly. 3-If FMA angle <30 the occlusal plane conversed posteriorly less, sometimes it is parallel to it. ** Tweed anchorage preparation: tipping posterior segment distally Can be classified into three categories: 1-First degree anchorage preparation: Minimal anchorage preparation; ANB; 0—4 degree Facial esthetic is good Discrepancy less than 10mm Mandibular 3rd molar must be upright Direction of inter-maxillary elastic pull should not exceed 90 degree. 2-2nd degree anchorage preparation: ANB exceed 4.5: class II Mandibular 2nd molars should always be bounded, must be tipped distally so that, their distal marginal ridges are at gum level Direction of pull of inter-maxillary elastics should always be 90 3-3rd degree; total anchorage preparation: ANB not exceed 5 degree Discrepancy 14-20mm All posterior teeth (2nd molar to terminal molars) are tipped distally. Distal marginal ridge of terminal molars is below gum level. N:B: in severe cases the preparation is done in both arches. Prognosis: The prognosis is of treatment result based on the configuration of the triangle: 1-FMA: 16 to28: prognosis is good At 16: IMPA should be 90 -+5 ophy Dr. Mohammed Alruby I Incisor ncisor mandibular plane Angle and mandibular plane Angle and T Tweed philos weed philosophy Dr. Mohammed Alruby

4. 4 At 22: IMPA should be 90 At 28: IMPA should be 90-5=85 2-FMA: 28 to 35: prognosis is fair At 28; IMPA should be 90-5=85, extraction is necessary in majority of cases At 35: IMPA ranged from 80 to 85 3-FMA; above 35: prognosis is bad, extraction frequently complicate problems. N:B: Marrifield said, Z angle measurements and profile line provides an accurate critical description of lower face relationship. Angle formed by FHP and line touch chin and most prominent part of lip Patient with normal FMA, IMPA, FMIA, and ANB, has Z angle with 80 in adult and 78 in child with 11 to 15 years of age. Tweed history: = Charlis H, Tweed graduated from improvised Angle course in 1928, he was 33 years old and Angle 73 years. = Angle admired Tweed ability, he asked him to help in article, published in dental Cosmos. =at 11/8/1930 Angle at age of 75 years. = at 1932 Tweed published 1st article in Angle orthodontics, which is report of cases treated with edgewise arch mechanism = he retracted 80% of failure cases with the extraction of 1st premolars = in 1936, Tweed published his 1st article on extraction of teeth for ortho malocclusion correction. Thanks ophy Dr. Mohammed Alruby I Incisor ncisor mandibular plane Angle and mandibular plane Angle and T Tweed philos weed philosophy Dr. Mohammed Alruby