Periapical disease refers to the disease of the root tip and its surrounding tissues. Its X-ray examination is very necessary to determine the nature, extent and scope of the disease and help to formulate the treatment plan.

1、 Apical abscess

1. Root tip abscess: divided into acute and chronic. Acute apical abscess is usually caused by acute serous inflammation. It can also be caused by acute attack of chronic periapical inflammation. Chronic apical abscess can form pus cavity due to necrosis and liquefaction of the central part of apical granuloma; Or transformed from acute periapical abscess.

2. Imaging performance:

(1) Acute stage: early X-ray examination generally does not show changes in periapical bone, sometimes the periodontal ligament space is slightly widened; With the development of the disease, it can be seen that with the pathogenic tooth as the center, the degree of bone destruction is relatively serious, showing diffuse destruction, and the boundary is unclear.

(2) Chronic stage: a low-density area with clear boundary and unsmooth edge and small bone destruction appears in the apical region, the bone plate disappears, the lesion is generally limited, and there may be hyperosteogeny reaction in the periphery.

2、 Periapical granuloma

1. Periapical granuloma: Inflammatory granulation tissue produced by mild and slow infection stimulation of periapical tissue, which is a major type of chronic periapical inflammation.

2. Imaging findings: There are round or oval hypodense areas at the root tip, lateral root or root bifurcation of the pathogenic tooth, with small lesion range, diameter generally not exceeding lcm, clear perimeter, and no dense bone plate. The bone around the lesion is normal or slightly changed compact.

3、 Periapical cyst

1. Periapical cyst is often transformed from periapical granuloma. Due to some reasons, the nutrition source of granuloma is limited, and the lesion center is denatured, necrotic, and liquefied to form a cyst. With the continuous secretion of cyst fluid, the cyst cavity also gradually expanded. Microscopically, the cyst wall is lined with stratified squamous epithelium, with epithelial nail process formation, cholesterol crystals in the cyst, and sometimes transparent bodies in the cyst wall.

2. Imaging findings: there are many pathogenic teeth such as decayed teeth and deformed teeth. Take the root tip of the pathogenic tooth as the center, form a round or oval bone with regular shape and different size to destroy the low-density lesion area, and the edge is clear and sharp. Because the cyst develops very slowly, the surrounding bone is stimulated for a long time, forming a dense line shadow at the edge of the cyst.