and 50% in another. the cause of this situation is usually a periapical or periodontal infection of a maxillary posterior tooth, where the inflammatory exudate has eroded through the bone superiorly to drain into the maxillary sinus. an estimated 0.5 to 2.0% of viral rhinosinusitis (vrs) will develop into bacterial infections in adults and 5 to 10% in children. pathophysiology biofilm bacterial infections may account for many cases of antibiotic-refractory chronic sinusitis. biofilms are complex aggregates of extracellular matrix and interdependent microorganisms from multiple species, many of which may be difficult or impossible to isolate using standard clinical laboratory techniques. bacteria found in biofilms have their antibiotic resistance increased up to 1000 times when compared to free-living bacteria of the same species. a recent study found that biofilms were present on the mucosa of 75% of people undergoing surgery for chronic sinusitis. diagnosis classification illustration depicting sinusitis sinusitis (or rhinosinusitis) is defined as an inflammation of the mucous membrane that lines the paranasal sinuses and is classified chronologically into several categories: acute sinusitis – a new infection that may last up to four weeks and can be subdivided symptomatically into severe and nonsevere. some use definitions up to 12 weeks. recurrent acute sinusitis – four or more full episodes of acute sinusitis that occur within one year subacute sinusitis – an infection that lasts between four and 12 weeks, and represents a transition between acute and chronic infection. chronic sinusitis – when the signs and symptoms last for more than 12 weeks. acute exacerbation of chronic sinusitis – when the signs and symptoms of chronic sinusitis exacerbate, but return to baseline after treatment. roughly 90% of adults have had sinusitis at some point in their lives. acute health care providers distinguish bacterial and viral sinusitis by watchful waiting. if a person has had sinusitis for fewer than 10 days without the symptoms becoming worse, then the infection is presumed to be viral. when symptoms last more than 10 days or get worse in that time, then the infection is considered bacterial sinusitis. pain in the teeth and bad breath are also more indicative of bacterial disease. imaging by either x-ray, ct or mri is generally not recommended unless complications develop. pain caused by sinusitis is sometimes confused for pain caused by pulpitis (toothache) of the maxillary teeth, and vice versa. classically, the increased pain when tilting the head forwards separates sinusitis from pulpitis. for cases of maxillary sinusitis, limited field cbct imaging, as compared to periapical radiographs, improves the ability to detect the teeth as the sources for sinusitis. a coronal ct picture may also be useful. chronic for sinusitis lasting more than 12 weeks, a ct scan is recommended. on a ct scan, acute sinus secretions have a radiodensity of 10 to 25 hounsfield units (hu), but in a more chronic state they become more viscous, with a radiodensity of 30 to 60 hu. nasal endoscopy and clinical symptoms are also used to make a positive diagnosis. a tissue sample for histology and cultures can also be collected and tested. nasal endoscopy involves inserting a flexible fiber-optic tube with a light and camera at its tip into the nose to examine the nasal passages and sinuses. sinus infections, if they result in tooth pain, usually present with pain involving more than one of the upper teeth, whereas a toothache usually involves a single tooth. dental examination and appropriate radiography aid in ruling out pain arises from a tooth. ct of chronic sinusitis ct scan of chronic sinusitis, showing a filled right maxillary sinus with sclerotic thickened bone. mri image showing sinusitis. edema and mucosal thickening appears in both maxillary sinuses. maxillary sinusitis caused by a dental infection associated with periorbital cellulitis frontal sinusitis x-ray of left-sided maxillary sinusitis marked by an arrow. there is lack of the air transparency indicating fluid in contrast to the other side. treatment treatments treatment indication rationale time viral and some bacterial sinusitis sinusitis is usually caused by a virus which is not affected by antibiotics. antibiotics bacterial sinusitis cases accompanied by extreme pain, skin infection, or which last a long time may be caused by bacteria. nasal irrigation nasal congestion can provide relief by helping decongest. drink liquids thick phlegm remaining hydrated loosens mucus. antihistamines concern with allergies antihistamines do not relieve typical sinusitis or cold symptoms much; this treatment is not needed in most cases. nasal spray desire for temporary relief tentative evidence that it helps symptoms. does not treat cause. not recommended for more than three days' use. recommended treatments for most cases of sinusitis include rest and drinking enough water to thin the mucus. antibiotics are not recommended for most cases. breathing low-temperature steam such as from a hot shower or gargling can relieve symptoms. there is tentative evidence for nasal irrigation in acute sinusitis, for example during upper respiratory infections. decongestant nasal sprays containing oxymetazoline may provide relief, but these medications should not be used for more than the recommended period. longer use may cause rebound sinusitis. it is unclear if nasal irrigation, antihistamines, or decongestants work in children with acute sinusitis. there is no clear evidence that plant extracts such as cyclamen europaeum are effective as an intranasal wash to treat acute sinusitis. evidence is inconclusive on whether anti-fungal treatments improve symptoms or quality of life. antibiotics most sinusitis cases are caused by viruses and resolve without antibiotics. however, if symptoms do not resolve within 10 days, either amoxicillin or amoxicillin/clavulanate are reasonable antibiotics for first treatment with amoxicillin/clavulanate being slighlty superior to amoxicillin alone but with more side effects. a 2018 cochrane review, however, found no evidence that people with symptoms lasting seven days or more before consulting their physician are more likely to have bacterial sinusitis as one study found that about 80% of patients have symptoms lasting more than 7 days and another about 70%. antibiotics are specifically not recommended in those with mild / moderate disease during the first week of infection due to risk of adverse effects, antibiotic resistance, and cost. fluoroquinolones, and a newer macrolide antibiotic such as clarithromycin or a tetracycline like doxycycline, are used in those who have severe allergies to penicillins. because of increasing resistance to amoxicillin the 2012 guideline of the infectious diseases society of america recommends amoxicillin-clavulanate as the initial treatment of choice for bacterial sinusitis. the guidelines also recommend against other commonly used antibiotics, including azithromycin, clarithromycin, and trimethoprim/sulfamethoxazole, because of growing antibiotic resistance. the fda recommends against the use of fluoroquinolones when other options are available due to higher risks of serious side effects. a short-course (3–7 days) of antibiotics seems to be just as effective as the typical longer-course (10–14 days) of antibiotics for those with clinically diagnosed acute bacterial sinusitis without any other severe disease or complicating factors. the idsa guideline suggest five to seven days of antibiotics is long enough to treat a bacterial infection without encouraging resistance. the guidelines still recommend children receive antibiotic treatment for ten days to two weeks. corticosteroids for unconfirmed acute sinusitis, nasal sprays using corticosteroids have not been found to be better than a placebo either alone or in combination with antibiotics. for cases confirmed by radiology or nasal endoscopy, treatment with intranasal corticosteroids alone or in combination with antibiotics is supported. the benefit, however, is small. for confirmed chronic rhinosinusitis, there is limited evidence that intranasal steroids improve symptoms and insufficient evidence that one type of steroid is more effective. there is only limited evidence to support short treatment with corticosteroids by mouth for chronic rhinosinusitis with nasal polyps. there is limited evidence to support corticosteroids by mouth in combination with antibiotics for acute sinusitis; it has only short-term effect improving the symptoms. surgery for sinusitis of dental origin, treatment focuses on removing the infection and preventing reinfection, by removal of the microorganisms, their byproducts, and pulpal debris from the infected root canal. systemic antibiotics are ineffective as a definitive solution, but may afford temporary relief of symptoms by improving sinus clearing, and may be appropriate for rapidly spreading infections, but debridement and disinfection of the root canal system at the same time is necessary. treatment options include non-surgical root canal treatment, periradicular surgery, tooth replantation, or extraction of the infected tooth. for chronic or recurring sinusitis, referral to an otolaryngologist may be indicated, and treatment options may include nasal surgery. surgery should only be considered for those people who do not benefit with medication or have non-invasive fungal sinusitis. it is unclear how benefits of surgery compare to medical treatments in those with nasal polyps as this has been poorly studied. a number of surgical approaches can be used to access the sinuses and these have generally shifted from external/extranasal approaches to intranasal endoscopic ones. the benefit of functional endoscopic sinus surgery (fess) is its ability to allow for a more targeted approach to the affected sinuses, reducing tissue disruption, and minimizing post-operative complications. however, if a traditional fess with messerklinger technique is followed the success rate will be as low as 30%, 70% of the patients tend to have recurrence within 3 years. on the other hand with use of tfse technique along with navigation system, debriders and balloon sinuplasty or ebs can give a success rate of over 99.9%. the use of drug eluting stents such as propel mometasone furoate implant may help in recovery after surgery. another recently developed treatment is balloon sinuplasty. this method, similar to balloon angioplasty used to "unclog" arteries of the heart, utilizes balloons in an attempt to expand the openings of the sinuses in a less invasive manner. the effectiveness of the functional endoscopic balloon dilation approach compared to conventional fess is not known. treatments directed to rhinovirus infection a study has shown that patients given spray formulation of 0.73 mg of tremacamra (a soluble intercellular adhesion molecule 1 receptor) reduced the severity of illness. prognosis a 2018 review has found that without the use of antibiotics, about 46% were cured after one week and 64% after two weeks. epidemiology sinusitis is a common condition, with between 24 and 31 million cases occurring in the united states annually. chronic sinusitis affects approximately 12.5% of people. research based on recent theories on the role that fungi may play in the development of chronic sinusitis, antifungal treatments have been used, on a trial basis. these trials have had mixed results.