Switch to Dark theme

References

Przystańska A, Kulczyk T, Rewekant A Introducing a simple method of maxillary sinus volume assessment based on linear dimensions. Ann Anat. 2018; 215:47-51 https://doi.org/10.1016/j.aanat.2017.09.010
Bolger WE, Woodruff WW, Morehead J, Parsons DS Maxillary sinus hypoplasia: classification and description of associated uncinate process hypoplasia. Otolaryngol Head Neck Surg. 1990; 103:759-765 https://doi.org/10.1177/019459989010300516
Whyte A, Boeddinghaus R Imaging of odontogenic sinusitis. Clin Radiol. 2019; 74:503-516 https://doi.org/10.1016/j.crad.2019.02.012
Chronic maxillary rhinosinusitis of dental origin: a systematic review of 674 patient cases. 2014. 10.1155/2014/465173
Royal College of Radiologists. iRefer. 2025. https://www.irefer.org.uk/(accessedApril2025
Evaluation of mucous retention cyst prevalence on digital panoramic radiographs in the local population of Iran. 2022. 10.1155/2022/8650027
Evaluation of anatomical variations of the maxillary sinus in patients with and without mucous retention cyst. 2023. 10.1177/01455613231206284
Yeung AWK, Tanaka R, Khong PL, von Arx T, Bornstein MM Frequency, location, and association with dental pathology of mucous retention cysts in the maxillary sinus. A radiographic study using cone beam computed tomography (CBCT). Clin Oral Investig. 2018; 22:1175-1183 https://doi.org/10.1007/s00784-017-2206-z
Dogan ME, Uluısık N, Yuvarlakbaş SD Retrospective analysis of pathological changes in the maxillary sinus with CBCT. Sci Rep. 2024; 14 https://doi.org/10.1038/s41598-024-66527-7

Radiographic appearance of the maxillary sinuses in health and disease

From Volume 52, Issue 5, May 2025 | Pages 304-310

Authors

Nicholas Drage

BDS, FDS RCS(Eng), FDS RCPS(Glas), DDR RCR

BDS, FDSRCS, FDSRCPS, DDR RCR, Consultant in Dental and Maxillofacial Radiology, University Dental Hospital, Cardiff and Vale University Health Board, Cardiff.

Articles by Nicholas Drage

Email Nicholas Drage

Simon Haworth

BDS, PhD, MFDS RCS (Ed), DDMFR RCR, Consultant/Senior Lecturer in Dental and Maxillofacial Radiology, Bristol Dental School, University of Bristol.

Articles by Simon Haworth

Abstract

The maxillary sinuses are frequently seen on intra-oral and panoramic radiographs taken in general dental practice. Variation in normal appearances of the maxillary sinuses can be mistaken for disease and a wide range of odontogenic and non-odontogenic diseases can change sinus appearance. This means that a systematic approach is needed when interpreting radiographs, including those of the sinuses. The article provides examples of normal anatomy and illustrations of some of the more common abnormal findings, as well as suggestions for management in these cases.

CPD/Clinical Relevance:

The maxillary sinuses are visible on radiographs in general dental practice, meaning that practitioners need to be able to recognize features of health and disease in them.

Article

The maxillary sinuses are air-filled cavities located in the body of the maxilla. They are the largest of the paranasal sinuses and, in adulthood, each contains around 15 ml of air.1 There are right and left maxillary sinuses, which develop separately and are not connected. They are pyramidal in shape, with the geometric base on the lateral wall of the nose and the apex projecting into the zygomatic process.

The margins, which are visible on dental radiographs, are:

  • The floor, consistently seen on peri-apical radiographs and panoramic radiographs;
  • The medial wall, consistently identified on panoramic radiographs; and
  • The posterior wall (anterior margin of the pterygomaxillary fissure), consistently identified on panoramic radiographs.

    • The sinuses are lined by pseudostratified columnar ciliated epithelium with goblet cells and they drain into the nasal cavity through the ostium, which is located high up on the medial wall of the sinuses. The sinuses vary in size. Hypoplasia is quite common with a prevalence reported of approximately 10% (Figure 1).2

    Figure 1. Peri-apical radiograph of the right posterior maxilla demonstrating the floor of the right maxillary sinus (large white arrows), zygomatic buttress (small black arrows) and the floor of the nose (hard palate) (small white arrows)..

    On panoramic and peri-apical radiographs, the bony margins of the sinuses appear as thin, white (corticated) lines and the sinuses themselves appear radiolucent because they are filled with air. The normal appearance of the sinuses on radiographs commonly obtained in general dental practice is shown in Figures 1–5. Note that only some of the bony margins are visible on these radiographs.

    Figure 2. Peri-apical radiograph of the right posterior maxilla demonstrating normal neurovascular channels within the right maxillary sinus (arrowed). Note that the margins of the neurovascular channels are lightly corticated and therefore should not be mistaken for fracture lines. The floor of the sinus appears low-lying due to atrophic bone loss of the alveolar process in the edentulous ridge.
    Figure 3. Cropped panoramic radiograph showing the left maxillary sinus and the associated normal anatomical features. (a) With the important landmarks outlined: yellow: visible margins of the left maxillary sinus (f: floor; p: posterior margin (anterior margin of the pterygomaxillary fissure); m: medial wall); blue: left zygomatic buttress and lower margin of the zygomatic arch; red: shadow of floor of nose (hard palate); green line: ghost shadow of the floor of nose (hard palate); pink: infraorbital canal; orange: medial margin of the left inferior concha. (b) Without outlines for comparison.
    Figure 4. Cropped panoramic radiograph showing prominent but normal shadows of the inferior conchae. These shadows can make the sinuses appear radiopaque but should not be mistaken for disease, since the shadows extend outside the sinus space. The shadow of the inferior concha can become more pronounced if the patient is positioned too far back in the panoramic unit. The right inferior concha shadow has been outlined in orange.
    Figure 5. Cropped panoramic radiograph showing severe hypoplasia of the left maxillary sinus. The right maxillary sinus is normal. The absence of the normal aerated left maxillary sinus is developmental in this case and should not be mistaken for bony disease.

    Disease affecting the maxillary sinuses

    Diseases affecting the maxillary sinuses can be extrinsic and intrinsic. Extrinsic conditions include infection of odontogenic origin, and benign odontogenic cysts and tumours arising in the maxillary alveolus. Intrinsic conditions include infection/inflammation arising within the maxillary sinuses, benign cysts and tumours arising with the maxillary sinus, and malignant tumours arising within the maxillary sinus.

    Extrinsic conditions

    Infection of odontogenic origin

    Peri-apical infection arising from the maxillary premolar and molar teeth may cause inflammatory changes in the mucosal lining of the maxillary sinuses (Figure 6). Long-standing chronic inflammation may lead to the formation of antroliths which may occasionally be identified on dental radiographs (Figure 7). It is estimated that 25–40% of cases of maxillary sinusitis may be of odontogenic origin.3 A systematic review demonstrated that the commonest odontogenic causes are of iatrogenic origin.4

    Figure 6. Peri-apical radiograph showing extensive caries in the upper right second premolar. There is marked widening of the apical periodontal ligament space consistent with peri-apical inflammation. There is localised thickening of the mucosal lining in the floor of the maxillary sinus in the second premolar region (arrowed), which is likely secondary to the peri-apical infection. Note there is also extensive caries in the upper right first molar and upper right second molar.
    Figure 7. (a) Peri-apical radiograph showing an endodontic–periodontal lesion on the upper left second molar. This has raised the sinus floor slightly. There is mucosal thickening, although it is difficult to appreciate on the radiograph. However, there is an antrolith (arrowed) in the posterior aspect of the sinus, suggesting the infection/inflammation has been present for some time. (b) Coronal cone beam computed tomography slice through the upper left second molar showing the mucosal thickening in the floor of the sinus and the antrolith (arrowed).

    Examples include oro-antral fistula and the displacement of roots and foreign bodies into the sinus (Figures 7 and 8). Displaced root fragments may move over time since the wafting action of the cilia in the mucosal lining tends to move objects towards the ostium.

    Figure 8. Cropped panoramic radiograph of the right maxilla showing two radiopaque foreign bodies in the right maxillary sinus consistent with endodontic sealer (arrowed).

    Chronic peri-apical infection leads to the formation of a peri-apical granuloma, which typically has well-defined and corticated margins. As the granuloma enlarges, it will tend to cause superior expansion of the floor of the maxillary sinus (Figure 9).

    Figure 9. Sagittal cone beam computed tomography slice showing a displaced root in the left maxillary sinus (black arrow) with an associated mucosal inflammatory change (white arrows).
    Figure 10. Peri-apical radiograph showing extensive caries in the upper left second premolar. There is a well-defined corticated radiolucency consistent with a peri-apical granuloma. Note the mild superior expansion of the floor of the left maxillary sinus (arrowed).

    In all cases where the sinus inflammation is thought to be a result of dental infection, the initial management involves treating the source of infection. This may involve treating the affected tooth or, in more complex cases, referral to secondary care (e.g. for removal of displaced root fragments and closure of an oro-antral fistula).

    Benign odontogenic cysts and tumours in the maxillary alveolus

    Odontogenic cysts or tumours that arise in the maxillary alveolus can expand to occupy part of the space of the maxillary sinus.

    Cysts with a predisposition to expand into the sinus include the radicular cyst, dentigerous cyst and the odontogenic keratocyst. Although rare, odontogenic tumours, such as ameloblastoma, may expand into the maxillary sinus.

    All these conditions are benign and relatively slow growing, so the margins are well defined and corticated even as the cyst/tumour expands into the maxillary sinus. The corticated margin of the sinus remains intact. This significant feature confirms the cyst/tumour is arising outside the maxillary sinus. Examples are shown in Figures 11 and 12.

    Figure 11. Peri-apical radiograph of the upper right first molar showing a small radicular cyst. Note the cyst has well-defined corticated margins with expansion of the floor of the right maxillary sinus (arrowed). Radicular cysts and peri-apical granulomas have similar radiographic features but, if the radiolucency measures more than 15 mm in diameter, it is more likely to be a radicular cyst.
    Figure 12. (a) Cropped panoramic radiograph showing a large odontogenic keratocyst occupying part of the right maxillary sinus. The corticated margins are arrowed. Note that the presence of corticated margins suggests the lesion is arising outside the maxillary sinus. (b) Coronal CBCT slice through the maxillary sinuses confirming the odontogenic keratocyst is occupying the majority of the right sinus (arrowed).

    If the cyst/tumour is very large, cone beam computed tomography (CBCT) may be required to determine the full extent of the lesion before surgical intervention (Figure 12). Patients should be referred to secondary care when an odontogenic cyst or tumour is suspected.

    Intrinsic conditions

    Infection/inflammation in the maxillary antra

    Patients who present with maxillary sinusitis that is not of odontogenic origin should be treated medically. The patient's GP will generally manage simple sinusitis in the first instance and often patients do not require any further imaging.

    In cases of refractory or recurrent sinusitis, cross-sectional imaging is required (CT, CBCT or MRI).5 This will generally be arranged after assessment by an ear, nose and throat surgeon.

    In these cases, panoramic radiographs and peri-apical radiographs are not required. In addition, plain radiographs, such as occipitomental radiographs, are no longer indicated as they provide non-specific findings.5

    Benign cysts and tumours

    These lesions arise within the maxillary sinus itself. The most common cyst seen on dental imaging is the mucous retention cyst. This is caused by a blockage of the mucous-producing cells in the lining of the maxillary sinus. They are benign, rarely cause symptoms and are a common incidental finding on panoramic radiographs. One study found that mucous retention cysts were detected on 5% of panoramic radiographs.6 They are reported to be present on 5.6–12.9% of CBCT scans.7,8,9

    The mucous retention cyst appears as a round/domed shaped soft tissue radiopacity within the sinus. There is no corticated margin, which confirms the cyst is arising within the maxillary sinus. In the absence of any clinical signs or symptoms, mucous retention cysts require no radiographic follow-up. Examples of mucous retention cysts are shown in Figure 13.

    Figure 13. Examples of typical mucous retention cysts. Note the margins are well defined and smooth but are not corticated. The lack of cortication suggests the origin is from within the maxillary sinus. (a) Cropped panoramic radiograph showing a mucous retention cyst in the floor of the right maxillary sinus. (b) Cropped peri-apical radiograph showing part of a mucous retention cyst in the right maxillary sinus.

    Osteomas are benign, slow-growing tumours often located in the paranasal sinuses, most commonly in the frontal sinus. Most are asymptomatic and may be detected as an incidental finding on radiographs. They typically present as a well-defined, rounded/lobular radiopacity with the density of bone within the maxillary sinus (Figure 14). If asymptomatic, surgical removal is not necessarily needed but, if they start to cause sinus obstruction, surgical invention will generally be required.

    Figure 14. An example of an osteoma in the right maxillary sinus. (a) Cropped panoramic radiograph showing a very radiopaque bony mass in the right maxillary antrum (arrowed). (b) Coronal cone beam computed tomography slice through the right maxillary sinus of the same patient showing the bony mass is attached to the wall of the maxillary sinus (arrowed). The findings on panoramic radiography and cone beam computed tomography are consistent with a surface (periosteal) osteoma.

    Malignant tumours

    Malignancy arising with the maxillary sinus is rare. The commonest malignancies are squamous cell carcinoma and adenocarcinoma.

    Symptoms include sinus pain, paraesthesia, loosening of the teeth and epistaxis. Patients with these symptoms require urgent referral to secondary care, even if no abnormality is seen on the dental radiographs because not all walls of the maxillary sinus are visible.

    Typical findings seen on panoramic radiographs include destruction of the bony walls of the sinus and destruction of the maxillary alveolus. An example is shown in Figure 15.

    Figure 15. Panoramic radiograph of the maxilla of a patient with advanced squamous cell carcinoma arising from the left maxillary sinus. Note the total loss of the corticated margin of posterior floor of the sinus and complete destruction of the posterior alveolus. The normal sinus floor (white arrows) and the posterior alveolus (black arrows) on the right side are arrowed for comparison.

    Conclusion

    Sound knowledge of the normal anatomy and appearance of the maxillary sinuses is key to detecting abnormalities. The presence or absence of a bony margin around a lesion is useful in determining whether it arose from the maxillary alveolus or within the sinus itself.

    The management of patients with abnormal sinus appearances on a radiograph will depend strongly on the patient's history and clinical presentation.