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Main Instructor 高嘉澤
Department / Institution Chung Shan Medical University Hospital
Classification Case report
The second molar alignment in the orthodontic treatment is necessary. Sometime the second molar may be sacrificed or extracted by the treatment plan. Third molar substituted the second molar might be a good option. The objective of this case is to show how a patient was treated by the third molar replace extracted upper second molar.
This individual is a 25-years-old male whose chief complaint was upper bilateral second molars buccally flared out. Via clinical examination, facial symmetry, straight profile and upper second molars buccally tipping without occlusal function were noted. Cephalometric analysis showed SNA=77o, SNB=75 o, U1-PP=122 o, IMPA=72 o, ODI=72. The diagnosis was Angle’s class I malocclusion with bilateral upper second molars buccally tipping. The treatment plan was to extract bilateral upper second molars and closed space with third molars substitution. The final treatment result was acceptable with a harmonious profile and stable occlusion.
The second molar substitution may be indicated as follows: excessive crowding in both arches, normal or open growth direction, steep mandibular plane angle with an open bite tendency, the patient has an obtuse nasal-labial angle. How to achieve functional occlusion by third molar replaced second molar, it is crucial to control degree of the rotation, extrusion and torque of maxillary third molar. The present case report is to show the biomechanism of third molar protraction. 
The third molar morphology and size is important in replacing the second molar. How to achieve the normal occlusion should be carefully evaluated.
The Third Molar Replacement the Extracted Second Molar- Case Report