Introduction

The maxillary antra, because of their close proximity to the upper teeth, are the most important of the paranasal sinuses in dentistry. Nowadays the imaging modalities of choice to investigate possible disease within the antra are computed tomography (CT), cone beam CT (CBCT) and magnetic resonance (MR) (see Chapters 16 and 18). However, as the antra are often imaged on conventional dental radiographs, as well as on certain skull views, clinicians still need to know:

Similar radiographic changes can be seen in the other paranasal sinuses – frontal, ethmoidal and sphenoidal. They are of less clinical relevance in dentistry and are discussed only briefly.

Normal anatomy

The maxillary antrum or sinus is an approximately pyramidal cavity. It contains air, is lined by mucoperiosteum with a pseudostratified ciliated columnar epithelium and occupies most of the body of the maxillary bone. It is present at birth, but at that stage it is little more than a slit-like out-pouching of the nasal cavity. It grows rapidly by a process known as pneumatization during the eruption of the deciduous teeth and reaches about half its adult size by three years of age. The final size of the antra (like the other air sinuses) is very variable.

Pneumatization in adulthood causes further changes in antral shape and size. The cavity often enlarges downwards into the alveolar process or laterally into the body of the zygoma. The internal surface can be smooth or ridged with prominent bony septa. The lateral wall contains canals or grooves for the nerves and blood vessels supplying the upper posterior teeth.

The main anatomical parts of the antra (see Fig. 31.1) can be divided into:

Normal appearance of the antra on conventional radiographs

An antrum appears radiographically as a radiolucent cavity in the maxilla, with well-defined, dense, corticated radiopaque margins or walls. In general, the larger the cavity the more radiolucent it will appear. The internal bony septa and blood vessel canals in the walls all produce their own shadows. The thin epithelial lining is not normally seen. The different parts of the antra shown on conventional dental and skull radiographs are summarized in Table 31.1. Typical normal radiographic appearances are shown in Figs 31.2–31.4. In addition, a suggested systematic approach to viewing the antra on the 0° OM is shown in Fig. 31.4.

Antral disease

The major pathological conditions that can affect the antra, directly or indirectly, include:

These various disease entities can result in the following radiological changes:

Investigation and appearance of disease within the antra

Various imaging modalities can be used to investigate possible disease within the antra, depending on their availability. These include:

Appearances of antral diseases using various imaging modalities are shown in Figs 31.5–31.23.