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Le fort I = 3 : 1 Le fort II = 3 : 2 Le fort III = 1 : 1 Aug Genioplasty = 1 : 1(+/-) Slid. Genioplasty = 1 : 1(consistent)
Quantitative CriteriaQuantitative Criteria
The Rule of Fifths The Rule of Fifths
Mandibular DeficiencyMandibular Deficiency
I. Microgenia = I. Microgenia = Simple retrusion of chin
II. Retrogenia = Retrogenia = Deficient chin profileStevens(1968)
I Degree = < 10 mm II Degree = 10 – 20 mm
III Degree = > 20 mm
III . Sagittal Mandibular Deficiencies
IV. Mandibular deficiencyLow Angle typeHigh Angle type
Cont…
Mandibular ExcessMandibular Excess I. Asymmetric Mand Protrusion
With Open biteWithout Open bite
II . Unilateral Condylar HyperplasiaElongation of condylar neckDeviation of chin to normal sideLip line slopes to affected side & cross bite on unaffected side
Mandibular ExcessMandibular Excess
III . Mandibular HemihypertrophyLower border at lower level than affected sideMarked Convexity or BowingLittle or no displacement of chinNo midline deviation
GENERAL PRINCIPLESGENERAL PRINCIPLES
Access ( Primarily Intra-oral).Adequate Exposure.Good Postoperative Cosmesis.Good Postoperative Function.Preservation of essential structures.Maintenance of adequate nutrition and waste elimination.
Mandibular OsteotomiesMandibular Osteotomies
Body osteotomy (ostectomy)Body osteotomy (ostectomy) Sowray-Haskell Sowray-Haskell
Bilateral Sagittal Split OsteotomyBilateral Sagittal Split Osteotomy Introduced by Trauner & Obwegeser(1957) Obwegeser ( 1964) Modified by Dal Pont(1961) &
Hunsuck(1968) Use of natural plane of cleavage between
buccal and lingual plates Movements possible: Ant, Post & Rotations.
TechniqueTechniqueIncision & ExposureCorticotomyCorticotomy checkDivision by osteotome ( Wedge action)Nerve identification & preservationRelease of musculatureControl of bleedingFixationClosure Post-op care