Minimally invasive evaluation of chronic maxillary sinusitis with CBCT

INTRODUCTION

CBCT (Cone Beam Computed Tomography) is a radiographic imaging technique used for medical assessment of the hard tissue structures of the face. Although its main use is for dental pathology, it has a specific role in rhinology for the evaluation of chronic sinonasal pathology, mainly in the maxillary sinus. A wide range of chronic sinus lesions may be detected on the CBCT: mucosal thickening, fluid or air-fluid levels, retention cysts, pseudocysts, polyps, tumors, foreign bodies within the maxillary sinus, and bone pathology (like fibrous dysplasia) [1]. Anatomic variation of the maxillary sinus can also be assessed on the CBCT, providing valuable details prior to surgery.

In most cases, the pathology described on the CBCT within the maxillary sinus is incidental, but thorough information can be obtained due to the 3D acquisition of the images. The most frequent maxillary lesions are mucosal thickening (polypoid/non-polypoid) and retention cysts [2, 3, 4]. The entire volume of the maxillary sinus is described, including the natural ostium, accessory ostia (if present), the ostiomeatal complex, the floor and roof of the maxillary sinus, and the relation with the roots of the teeth. The relation between dental (periapical lesions, root contact with the floor of the maxillary sinus, periodontal bone loss) and sinus pathology can be determined on the CBCT. The root contact with the sinus was the only dental pathology associated with lesions within the maxillary sinus [3]. Odontogenic maxillary sinusitis is the most common pathology diagnosed with CBCT; it can be related to specific tooth injuries, especially the upper molars and the first and second premolars, which are in close vicinity to the floor of the sinus [1]. Periapical lesions and periodontal pathology can determine alteration of the respiratory epithelium within the maxillary sinus, but maxillary sinus lesions can appear in the absence of dental pathology [5, 6, 7]. The relation between the sinus lesions and dental lesions has to be assessed from a clinical, endoscopic, and imaging point of view. When maxillary sinus pathology is described on the CBCT, the ENT specialist has to evaluate the predisposing factors of obstruction within the nasal fossa (nasal septum deviation, septal spurs, concha bullosa, inferior turbinate hypertrophy, polyps in the nasal fossa or middle meatus). The best way to obtain thorough information is nasal endoscopy, either rigid or flexible.

The incidence of maxillary sinus pathology findings on CBCT is around 50% [1, 5], but there are studies showing 76% incidental sinus pathology findings [6].

Although CT (computed tomography) is the gold standard for imagistic assessment of the paranasal sinuses, and in complicated cases, CT associated with MRI is necessary to assess the site of the disease, the extent of the lesions, and the orbital and cerebral involvement. CBCT has certain benefits for defining uncomplicated sinusitis. One of the advantages of CBCT is the low dose of radiation compared to classic CT [1]. Although there are other low-dose imaging acquisition techniques available, like extremity CBCT and clinical multidetector computed tomography (MDCT), CBCT proved its superiority when addressing maxillary sinus pathology [8]. Another advantage of CBCT is the quality of the images obtained – a 3D assessment of the entire maxillary sinus cavity.

The relation between periodontal disease and mucosal thickening of the maxillary sinus can be investigated with CBCT. There is a direct and significant correlation between the severity of alveolar bone loss and mucosal thickening: the more severe the alveolar bone loss, the thicker the mucosa within the maxillary sinus [9,10]. It must be noted that a thickening of the mucosa less than 2 mm is considered normal [10,11]. The distance between the root apex and the floor of the maxillary sinus is another factor that influences mucosal thickening: the greater the distance, the lower the mucosal thickening [10]. The periodontal disease is considered among the most common causative factors of odontogenic sinusitis [10].

In particular situations, dental implants may contribute to odontogenic sinusitis, especially in cases of migration of the implant to the sinus when maxillary ostium obstruction develops. If alveolar bone resorption is present, then maxillary sinus lifting or bone grafting is recommended [12]. The bone architecture and dimensions prior to implantation are assessed with CBCT. Low bone mass identified on imagistic acquisitions should be taken into consideration when planning implant treatments, especially in patients with endocrine and metabolic disease (osteoporosis, postmenopausal state, diabetes mellitus, Cushing’s disease) [13, 14, 15].

Another use of CBCT is the possibility to distinguish odontogenic from non-odontogenic sinusitis, taking into account the dimension of the mucosal thickening (over 2 mm), the location of the sinus pathology (floor of the sinus/ entire sinus), the relation between sinus teeth and floor of the sinus, and the presence/absence of periodontal pathology. Texture analysis using specific contrast and correlation parameters of the CBCT acquisition images can enhance the differentiation between odontogenic and non-odontogenic sinusitis, offering a more precise diagnosis and allowing a better management plan [11].

Anatomic variations of the maxillary sinus can be described on CBCT: from intrasinus septa to accessory ostium and hyper/hypo pneumatization of the maxillary sinus. The presence of an accessory ostium is a favorable factor of chronic maxillary rhinosinusitis due to alteration of mucociliary clearance, and it has to be assessed preoperatively either by CT or CBCT [16,17]. During functional endoscopic sinus surgery, the accessory ostium should be eliminated to restore the clearance of the sinus. Septation within the maxillary sinus can contribute to non-odontogenic maxillary sinusitis and should be addressed surgically if the situation requires [18].

MATERIALS AND METHODS

We performed a systematic search on PubMed on the use of CBCT in detecting maxillary sinus pathology and the relation between dental lesions and maxillary sinusitis. An interrogation was made on specific terms: “cone-beam computed tomography” , “odontogenic sinusitis”, “maxillary sinusitis”, “anatomic variations”, “endoscopic sinus surgery”, “dental lesions”. We included: original comparative studies relevant to CBCT in rhinosinusitis, and studies relevant to the relation between dental and sinus pathology. We excluded papers/studies with non-sinonasal applications of CBCT.

RESULTS

The available literature and studies indicate that CBCT has become a reliable tool in the evaluation of sinonasal pathology. It can be used in cases that are suspected of acute or chronic sinus pathology, or it can reveal incidental findings of chronic asymptomatic conditions. Due to the fact that this type of investigation is routinely used in patients with dental problems, conditions of the maxillary sinus are most often found. However, its use encompasses all sinus pathology, and there is a large variety of alterations that will be revealed.

A thickening of the sinus membrane is one of the most often encountered alterations, and it can be discovered in any sinus, but again, it is more often associated with the maxillary sinus in patients with endodontic conditions. The average thickness in a normal healthy maxillary sinus is about 1.18–1.21 mm [19], while in patients with associated apical conditions, the thickness was about 2.56–2.74 mm [19-22]. Another study emphasized the connection between apical periodontitis and membrane thickening in the maxillary sinus, this condition becoming a rule in patients with severe apical periodontitis, with a percentage as high as 100% [20]. Further studies are consistent with these findings, revealing a likelihood of membrane thickening three times more often in patients with periapical lesions than in healthy patients [22]. A very interesting aspect is the fact that membrane thickening appeared more often, even in

patients that did not have contact between the periapical lesions and the sinus floor, and the presence of root canal treatments did not alter these percentages [21].

Another condition that was associated with membrane thickening on CBCT was periodontal bone loss; in patients with a severe condition, the risk was 4.6 times higher than in those with mild bone loss [23]. Vertical intrabone pockets were also present in association with this imagistic finding, thus showing another risk factor that we have to keep in mind. A very interesting result from the literature showed that in 4 months from extraction, the thickened membrane will reverse to normal.

Mucous retention cysts are also more often related to the maxillary sinus, with a percentage as high as 28.6% [24, 25]. The symptoms, if present, will vary according to the size of the cyst, and the exact location may differ as well, with up to 53.6% in the sinus walls [24, 25]. Due to the fact that CBCT is routinely used in patients with dental problems, these findings may influence the course of treatment. The studies also revealed that patients with periapical lesions, endodontal treatment, or significant bone loss [26] are prone to this pathology.

Antroliths are calcified masses of the maxillary sinus. They can have various shapes and sizes, with a reported maximum of 91 mm [27]. Although the reflex is to remove the antrolith, the studies revealed that its presence does not increase the risk of membrane perforation during dental implant procedures [28].

The reviewed literature also emphasized the role of CBCT in diagnosing intramaxillary foreign bodies. The nature of these foreign bodies is varied, ranging from tooth fragments to implants or complete teeth [29]. Of course, one of the most often encountered foreign bodies is root filling material that reached the maxillary sinus via a perforated root [30]. The studies emphasized a very important aspect, and that is that most patients who developed this condition did not have a CBCT prior to surgery [30]. Screws that are used in dental practice could also migrate into the maxillary sinus, especially if the sinus membrane is thin. Due to its high resolution in assessing bone and structures of similar consistency, CBCT is a valuable tool in evaluating these patients.

DISCUSSION

There is a wide range of problems that may affect the maxillary sinus. In patients requiring dental treatments, we have to thoroughly evaluate the local problems in order to avoid complications. The cases of dental implant failure are often associated with undiagnosed sinonasal problems that will lead to complications and secondary implant problems.

The high cost of such complications and the morbidity of the patient justify the routine use of imaging investigations in order to exclude any state that might lead to such complications. CBCT represents another tool to serve the same purpose, and that of ensuring a complete evaluation of our patients.

However, there are certain advantages of the technology that make it stand out. Aspects such as low exposure to radiation, availability, and cost-efficiency are just some of the advantages provided by this technology. An overweight or claustrophobic patient can also safely undergo the investigation.

Another aspect that must be taken into account is the legal problems that might surface in case of complications. The scan results not only help us provide the best standard of care for our patients with minimum complications, but also provide a reliable evaluation that can be reviewed at any moment.

CONCLUSION

Experience and the available literature indicate that the proper assessment of patients requiring more extensive dental treatment should include an imagistic evaluation prior to treatment initiation. This aspect is even more important for patients requiring dental implants, as they are prone to sinus infection and implant failure if proper drainage is not ensured. CBCT has proven its value in assessing these patients, providing high-quality images with a low-dose exposure to radiation. It is suitable for claustrophobic patients; it is a fast and reliable diagnostic tool.

Its limitations, such as the not-so-large target area and the less-than-average, limited pictures when compared to conventional CT scans, do not alter the accuracy in diagnosing maxillary sinus problems. As shown by the numerous articles describing its use and advantages, this method has become a standard of care, especially for patients undergoing significant dental treatments, allowing an evaluation of the site requiring intervention and revealing any silent conditions that could translate into future complications.

Conflicts of interest and sources of funding

The authors declare no conflict of interest. This research received no external funding.

Authors’ contribution

Conceptualization, CV, IGI, VZ, AR, ROP, IAS, LG, RH, ROA.; methodology, CV, ROA.; software, CV, ROA validation, CV, IGI, VZ, AR, ROP, IAS, LG, RH, ROA; formal analysis, CV, IGI, VZ, AR, ROP, IAS, LG, RH, ROA; investigation, CV, IGI, RH, ROA.; resources, CV, IGI, VZ, AR, ROP, IAS, LG, RH, ROA.; data curation, CV.; writing—original draft preparation,

CV, ROA.; writing—review and editing, CV, IGI, VZ, AR, ROP, IAS, LG, RH, ROA; visualization, CV, IGI, VZ, AR, ROP, IAS, LG, RH, ROA; supervision, CV. All authors have read and agreed to the published version of the manuscript.

Ethics approval and consent to participate

Not applicable.

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