The maxillary antra

Published on 12/06/2015 by admin

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Last modified 22/04/2025

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The maxillary antra

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 31.231.4. In addition, a suggested systematic approach to viewing the antra on the 0° OM is shown in Fig. 31.4.

Table 31.1

Summary of the different parts of the antra shown on conventional dental and skull radiographs

Area of antrum shown Radiographic projection
Floor Periapical
  Upper oblique occlusal
  Panoramic
Main antral cavity 0° OM
  True lateral skull
Lower aspect of antral cavity Periapical
  Upper oblique occlusal
  Panoramic
Posterior wall Panoramic
  True lateral skull
Anteromedial wall Panoramic
  True lateral skull
Lateral wall 0° OM
Roof 0° OM
Relationship with upper posterior teeth PeriapicalUpper oblique occlusalPanoramic
 

image

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 31.531.23.

Infection/inflammation

Acute sinusitis

Acute sinusitis is most commonly caused by an upper respiratory tract infection, particularly the common cold. The effects on the antrum include:

Acute sinusitis can be diagnosed and treated clinically. As a result, the Royal College of Radiologists in the UK in their 2011 publication iRefer: Making the Best Use of Clinical Radiology recommend that radiological imaging is not necessary.

Chronic sinusitis (Figs 31.531.9)

Trauma

Oro-antral communication

Fractures of the maxillofacial skeleton

Fractures are discussed in detail in Chapter 29 and only a brief summary is shown below.

Cysts

The more important cysts that can affect the antra include:

image

Odontogenic cysts

These cysts are extrinsic to the antra developing in the alveolar bone beneath the antral floor.

Tumours

Benign intrinsic tumours

These are all rare but can include:

Malignant intrinsic tumours

Squamous cell carcinoma and adenocarcinoma – these uncommon but important tumours produce a rapidly growing, aggressive soft tissue mass within the antrum causing destruction of one or more of the antral walls.

Main radiographic features of a large well-established lesion

• Total opacity of the antral cavity (see Fig. 31.19) – in the absence of symptoms suggesting infection, or a history of trauma, a totally opaque antrum is a cause for serious concern and further investigation is necessary.

• Destruction of one or more of the antral walls (see Fig. 31.20) and invasion of surrounding hard and soft tissues – hence the need for CT

• Occasional displacement or resorption of teeth.

Other paranasal air sinuses

As mentioned earlier, the frontal, ethmoidal and sphenoidal air sinuses are of limited importance in routine dentistry. Many of the conditions described in relation to the maxillary antra can affect these paranasal sinuses and produce similar effects. Occasionally routine skull radiography reveals unusual abnormalities, such as the ivory osteoma in the frontal sinus (see Fig. 31.23). But generally the investigation of choice for the paranasal air sinuses is computed tomography (CT), as shown in Fig. 31.24.

To access the self assessment questions for this chapter please go to www.whaitesessentialsdentalradiography.com