A knowledge of the clinical histoanatomy of the teeth, maxilla and maxillary sinus is very important for a clear understanding of the pathophysiology of odontogenic maxillary sinusitis.

In order to maintain the normal functions of the maxillary sinus, ventilation and drainage of the maxillary sinus via the natural ostium and ostiomeatal complex need to be preserved. The maxillary sinus is ventilated via the natural ostium, which is approximately 5 mm in diameter, and drained by the mucociliary transport system of the maxillary sinus epithelium. Consequently, lesions around the natural ostium and ostiomeatal complex disrupt the ventilation and drainage of the maxillary sinus, potentially resulting in maxillary sinusitis.

In regard to factors that could interfere with the treatment of maxillary sinusitis, impaired mucociliary function, bacterial and virus infections, occlusion of the ostiomeatal complex, or a combination of these three factors can perpetuate an inflammatory vicious cycle in the closed maxillary sinus, which could result in intractable maxillary sinusitis.

The ciliated columnar epithelium in cases of intractable odontogenic maxillary sinusitis is neither severely damaged nor irreversibly injured. As a result, the mucociliary function of the epithelium is almost certain to recover once the ventilation and drainage of the maxillary sinus are successfully restored. Consequently, out of the three aforementioned factors that potentially interfere with the treatment of odontogenic maxillary sinusitis, the treatment strategy is focused on the two remaining factors: infections and occlusion of the ostiomeatal complex.

The treatment goal of paranasal sinusitis, including maxillary sinusitis, is to sufficiently restore and improve the ventilation and drainage function of each sinus and to normalize the sinus epithelium, and thereby achieve cure of the sinusitis. Control of the aforementioned factors that could interfere with the treatment should be undertaken simultaneously.

The etiopathophysiology of odontogenic maxillary sinusitis has changed over time. Untreated dental diseases (e.g., dental caries) causing odontogenic maxillary sinusitis has become rare recently. In fact, most teeth identified as being associated with odontogenic maxillary sinusitis have already received dental treatment, especially root canal treatment, that is, endodontics.

Inadequate root canal treatment, for example, when the root canals of the teeth are incompletely filled with a filling material during endodontics can cause pulpitis and pulp necrosis at the root apex. Pulp inflammation causes apical lesions (apical periodontitis), resulting in odontogenic infection, such as alveolar ostitis. When odontogenic inflammation is constantly present at the floor of the maxillary sinus, the maxillary sinus is exposed to the potential danger of inflammation.

The inflammatory vicious cycle formed among dental lesions, odontogenic infection and factors that can disrupt the treatment of sinusitis can influence the outcomes of odontogenic maxillary sinusitis. A vicious cycle of inflammation in the closed maxillary sinus can result in intractable maxillary sinusitis. Impaired mucociliary function, bacterial and virus infections, occlusion of the ostiomeatal complex, or a combination of these three factors can perpetuate an inflammatory vicious cycle in the closed maxillary sinus and interfere with the treatment of sinusitis, potentially resulting in intractable odontogenic maxillary sinusitis.

The maxillary sinus mucosa in cases of odontogenic maxillary sinusitis is characteristic. From the histopathological point of view, the ciliated columnar epithelium in these cases is neither severely damaged nor irreversibly injured. As a result, the mucociliary function of the epithelium is almost certain to recover once the ventilation and drainage of the maxillary sinus is successfully restored. Out of the three aforementioned factors that potentially interfere with the treatment of odontogenic maxillary sinusitis, the treatment strategy is focused on how to manage the two remaining factors: infections and occlusion of the ostiomeatal complex.

The etiopathophysiology of odontogenic maxillary sinusitis has changed over time. Untreated dental diseases (e.g., dental caries) causing odontogenic maxillary sinusitis have become rare. Instead, most teeth which cause odontogenic maxillary sinusitis have already received dental treatment, especially root canal treatment, that is, endodontics. Consequently, it is very important that the teeth always be suspected as the cause of odontogenic maxillary sinusitis, even if a dental procedure has already been performed.

In the diagnosis of odontogenic maxillary sinusitis, it is important to detect the relationship between endodontic and periodontic lesions, including evidence of periapical lesions and the maxillary sinus.

Cone-beam CT, in addition to physical examination, is extremely accurate and useful for the diagnosis of odontogenic maxillary sinusitis. Plain dental radiography frequently fails to detect maxillary dental infections that could cause odontogenic maxillary sinusitis. The relationship between the causative teeth (endodontic and periodontic lesions, including evidence of periapical lucencies) and the maxillary sinus can be accurately observed and odontogenic maxillary sinusitis can be accurately diagnosed using cone-beam CT. In addition to accurate diagnosis of apical lesions, the maxilla, maxillary sinus, periodontal ligament space, lamina dura, pulp cavity, root canal and canal-treated roots, as well as apical periodontitis, alveolar ostitis and marginal periodontitis of the causative teeth can be observed. Metal artifacts are minimized, making cone-beam CT useful for diagnosis of the periodontal tissue condition and identification of the causative teeth, including root-canal-treated and crown-restored teeth.

The management of odontogenic maxillary sinusitis (OMS) involves a combination of medical treatment with dental surgery and/or endoscopic sinus surgery. Intractable OMS resulting from a vicious cycle of inflammation in the closed maxillary sinus is difficult to cure using only conservative therapies, such as antibiotic administration and dental treatment.

The inflammatory vicious cycle formed among dental lesions, odontogenic infection and factors that can disrupt the treatment of sinusitis can influence the outcomes of OMS, and a vicious cycle of inflammation in the closed maxillary sinus can result in intractable maxillary sinusitis. Impaired mucociliary function, bacterial and virus infections, occlusion of the ostiomeatal complex, or a combination of these three factors can perpetuate an inflammatory vicious cycle in the closed maxillary sinus and interfere with the treatment of sinusitis, potentially resulting in intractable OMS. Consequently, the treatment strategies for OMS are focused on how to manage the inflammatory vicious cycle in the closed maxillary sinus.

The ciliated columnar epithelium in cases of intractable OMS is neither severely damaged nor irreversibly injured. As a result, the mucociliary function of the epithelium is almost certain to recover once the ventilation and drainage of the maxillary sinus are successfully restored; therefore, of the three aforementioned factors that could interfere with the treatment of OMS, the treatment strategy is focused on how to manage the two remaining factors: infections and occlusion of the ostiomeatal complex.

The treatment results of intractable OMS are exceptionally good, once the ventilation and drainage of the maxillary sinus are successfully restored after endoscopic sinus surgery. The causative teeth (endodontic treated teeth with periapical lesions) can be preserved with antibiotic treatment alone, without dental retreatment. Consequently, endoscopic sinus surgery can be considered as the first-line therapy for intractable OMS caused by root canal treatment (endodontics), followed by close dental follow-up and dental treatment where necessary.

The pathophysiology of odontogenic maxillary sinusitis caused by odontogenic infections precipitated by maxillary lesions is not yet clear.

The maxillary lesions include acute maxillary sinusitis, retention cysts of the maxillary sinus, postoperative maxillary cysts and odontogenic cysts. The main clinical symptom is persistent cheek pain, even after the maxillary lesions have improved and there are no lesions in the tooth crown or periodontal tissue. All teeth with odontogenic infections precipitated by maxillary lesions respond with pain to percussion.

The pathological findings of the odontogenic infections are ascending pulpitis and pulpal necrosis precipitated by maxillary lesions, after which, ascending pulpitis and pulpal necrosis cause odontogenic maxillary sinusitis.

When patients complain of persistent cheek pain even after maxillary lesions have improved and there are no lesions of the tooth crown or periodontal tissue, odontogenic infections (i.e. ascending pulpitis and pulpal necrosis) precipitated by maxillary lesions should be suspected.

In cases of odontogenic maxillary sinusitis caused by odontogenic infections precipitated by maxillary lesions, the management of odontogenic maxillary sinusitis involves a combination of medical treatment with dental surgery (endodontics) and/or endoscopic sinus surgery.

The inflammatory vicious cycle formed among dental lesions, odontogenic infection and factors that can disrupt the treatment of sinusitis can influence the outcomes of odontogenic maxillary sinusitis. A vicious cycle of inflammation in the closed maxillary sinus can result in intractable maxillary sinusitis. Impaired mucociliary function, bacterial and virus infections, occlusion of the ostiomeatal complex, or a combination of these three factors can perpetuate an inflammatory vicious cycle in the closed maxillary sinus and interfere with the treatment of sinusitis, potentially resulting in intractable odontogenic maxillary sinusitis.

Consequently, the treatment strategies for odontogenic maxillary sinusitis are focused on how to manage the inflammatory vicious cycle in the closed maxillary sinus.

Recently, dental implantation has been routinely performed in many dental hospitals and institutions. Inevitably, complications associated with dental implants have also increased.

Two hypotheses have been proposed for the pathogenesis of odontogenic maxillary sinusitis caused by dental implant placement and/or maxillary sinus augmentation surgery.

According to the first, odontogenic infections, such as odontogenic maxillary sinusitis, are caused by the surgical procedure in which dental implants are placed. The cycle of inflammation involving odontogenic infection and factors that interfere with successful treatment of sinusitis influences the outcomes of maxillary sinusitis.

The other hypothesis is that odontogenic infections, such as odontogenic maxillary sinusitis, are caused by chronic infection of neighboring teeth, such as apical periodontitis during dental implantation. According to this hypothesis, the inflammatory vicious cycle formed among dental lesions, odontogenic infection and factors that can disrupt the treatment of sinusitis can influence the outcomes of odontogenic maxillary sinusitis.

Both the hypotheses suggest that a vicious cycle of inflammation in the closed maxillary sinus results in intractable maxillary sinusitis.

Impaired mucociliary function, bacterial and virus infections, occlusion of the ostiomeatal complex, or a combination of these three factors can perpetuate an inflammatory vicious cycle in the closed maxillary sinus and result in intractable maxillary sinusitis caused by dental implantation.

The maxillary sinus mucosa in cases of maxillary sinusitis caused by dental implantation is characteristic. From the histopathological point of view, the ciliated columnar epithelium in cases of intractable odontogenic maxillary sinusitis is neither severely damaged nor irreversibly injured. As a result, the mucociliary function of the epithelium is almost certain to recover once the ventilation and drainage of the maxillary sinus are successfully restored. The three aforementioned factors that potentially interfere with the treatment of odontogenic maxillary sinusitis, the treatment strategy is focused on how to manage the two remaining factors: infections and occlusion of the ostiomeatal complex.

Two hypotheses have been proposed for the pathogenesis of maxillary sinusitis caused by dental implant placement and/or maxillary sinus augmentation surgery.

According to the first, odontogenic infections, such as odontogenic maxillary sinusitis, are caused by the surgical procedure in which dental implants are placed. The cycle of inflammation involving odontogenic infection and factors that interfere with successful treatment of sinusitis influences the outcomes of maxillary sinusitis caused by dental implantation.

The other hypothesis is that odontogenic infections, such as maxillary sinusitis, are caused by chronic infection of neighboring teeth, such as apical periodontitis, which occurs during dental implantation.

Both the hypotheses suggest that a vicious cycle of inflammation in the closed maxillary sinus results in intractable maxillary sinusitis.

Impaired mucociliary function, bacterial and virus infections, occlusion of the ostiomeatal complex, or a combination of these three factors can perpetuate an inflammatory vicious cycle in the closed maxillary sinus and result in intractable maxillary sinusitis caused by dental implantation.

From the histopathological point of view, the pseudostratified ciliated columnar epithelium in cases of refractory maxillary sinusitis caused by dental implantation is neither severely damaged nor irreversibly injured. As a result, the mucociliary function of the epithelium is almost certain to recover once the ventilation and drainage of the maxillary sinus are successfully restored. Consequently, the pathophysiology of refractory maxillary sinusitis caused by dental implantation is one of the reasons why transnasal endoscopic sinus surgery (ESS) is indicated in cases of refractory sinusitis requiring surgery.

The treatment results are good once the ventilation and drainage of the maxillary sinus is successfully restored after transnasal ESS and support the concept that ESS can be considered as the first-line therapy for refractory sinusitis caused by dental implantation, followed by treatment of the dental implant (extraction of the implant body and/or removal of bone substitute), where necessary.

The pathogenesis of maxillary sinusitis caused by maxillary sinus floor elevation (maxillary sinus augmentation surgery: MSAS) is that the surgical procedure causes odontogenic infections and triggers an inflammatory cycle between odontogenic infections and the factors that interfere with the treatment of sinusitis. Impaired mucociliary function, bacterial and virus infections, occlusion of the ostiomeatal complex, or a combination of these three factors can perpetuate an inflammatory vicious cycle in the closed maxillary sinus and result in intractable maxillary sinusitis caused by MSAS.

There is no consensus on the management of bone prosthetic materials displaced into the maxillary sinus following MSAS. When the displacement of bone prosthetic material into the maxillary sinus occurs, first of all, closure of the perforation between the oral cavity and maxillary sinus should be performed to prevent infection. Next, antibacterial therapy should be initiated in conjunction with ventilation and drainage of the maxillary sinus. After this procedure, bone prosthetic materials displaced into the maxillary sinus will in most cases be drained out of the maxillary sinus via the natural ostium.

From the histopathological point of view, the pseudostratified ciliated columnar epithelium in cases of refractory maxillary sinusitis caused by MSAS is neither severely damaged nor irreversibly injured. As a result, the mucociliary function of the epithelium is almost certain to recover once the ventilation and drainage of the maxillary sinus are successfully restored. Consequently, the pathophysiology of refractory maxillary sinusitis caused by MSAS is one of the reasons why endoscopic sinus surgery (ESS) is indicated in cases of refractory sinusitis requiring surgery.

The treatment results are good once the ventilation and drainage of the maxillary sinus are successfully restored after ESS, and support the concept that ESS can be considered as the first-line therapy for refractory maxillary sinusitis caused by MSAS, followed by removal of the bone substitute, where necessary.

When a dental implant is displaced into the maxillary sinus following dental implant placement and/or maxillary sinus augmentation surgery, the exact procedures for dental implant extraction should be selected based on the pathophysiological condition of the nose and paranasal sinuses.

In the case of displacement of a dental implant alone, endoscopic transnasal extraction of the dental implant using maxillary sinus fenestration (via the middle meatus and/or via inferior meatus) is indicated. When it is accompanied by nasal septal deviation and/or inferior turbinate hypertrophy, endoscopic transnasal septoplasty and/or inferior turbinotomy are also indicated for obtaining working space. When it is accompanied by sinusitis, endoscopic transnasal sinus surgery is also indicated.

Endoscopic sinus surgery is indicated and is the procedure of first choice for the extraction of a displaced dental implant in the maxillary sinus in patients with any pathophysiological conditions of the nose and paranasal sinuses.