1. There is ill-defined unilocular shaped radiolucence without a corticated margin on periapcial area of tooth 14, and with a periodontal pocket on the distal side. This maybe a combination syndrome of both endo. and perio. with progression, the abscess may extend through the medullary spaces away from the apical area resulting in osteomyelitis, or it may perforate the cortex and spread diffusely through the overlying soft tissue.

2. Apical absess arise as the initial periapical pathosis or from an acute exacerbation (phoenix abscess) of a chronic periapical inflammatory lesion. In the early stage, the periapical periodontal ligament fibers may exhibit acute inflammation but no frank abscess formation. best termed acute apical periodontitis.

3. Clinical Features painful tender swelling of varying size and position tenderness to pressure in buccal sulcus fever and malaise erythema and possibly draining sinus, intraoral or extra- oral unresponsive to thermal and electrical stimuli positive percussion test

4. Differential diagnosis Periapical granuloma: 根尖處牙周膜肥厚 (raiolucency) Well-defined with a corticated radiopaque line or zone of sclerotic bone. Radicular cyst: 與 periapical granuloma 類似，無法以 radiolucency 區別。 Osteomyelitis: poor-defined “moth-eaten” radiolucency