A low-density shadow in the left lower molar area of the mandible may be an apical granuloma, a jaw cyst, or an apical abscess. Specific need to go to the hospital for further examination to confirm. 1. Apical granuloma. When the apical part of the tooth is inflamed, the inflammation can stimulate the apical part of the root to form granulation tissue, X-ray film shows that there is a low-density dark shadow in the apical part of the root, the border is clear, and the diameter is usually less than one centimeter. 2. Apical abscess. When a tooth has periapical inflammation, an abscess may also form in the apical region. X-rays show a cloudy marginal translucent shadow with indistinct surrounding borders. 3. Jaw cyst. Jaw cysts may be caused by chronic inflammatory stimulation or congenital development. Chronic inflammatory stimulation may result in the formation of root-end cysts with a dense white line of bone around the translucent area, often larger than one centimeter in diameter. Dental cysts are caused by congenital developmental anomalies and can be seen encircling the crown within the transillumination zone with clear borders. Low-density shadow of the left mandible is recommended to go to the hospital for timely examination and surgical treatment to avoid affecting the health of teeth and jaws.