It has been hypothesized that biofilm bacterial infections may account for many cases of antibiotic-refractory chronic sinusitis. Biofilms are complex aggregates of extracellular matrix and inter-dependent 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.

By definition chronic sinusitis lasts longer than 12 weeks and can be caused by many different diseases that share chronic inflammation of the sinuses as a common symptom. Symptoms of chronic sinusitis may include any combination of the following: nasal congestion, facial pain, headache, night-time coughing, an increase in previously minor or controlled asthma symptoms, general malaise, thick green or yellow discharge, feeling of facial 'fullness' or 'tightness' that may worsen when bending over, dizziness, aching teeth, and/or bad breath. Each of these symptoms has multiple other possible causes, which should be considered and investigated as well. Often chronic sinusitis can lead to anosmia, the inability to smell objects. In a small number of cases, acute or chronic maxillary sinusitis is associated with a dental infection. Vertigo, lightheadedness, and blurred vision are not typical in chronic sinusitis and other causes should be investigated.

Chronic sinusitis cases are subdivided into cases with polyps and cases without polyps. When polyps are present, the condition is called chronic hyperplastic sinusitis; however, the causes are poorly understood and may include allergy, environmental factors such as dust or pollution, bacterial infection, or fungus (either allergic, infective, or reactive).

Chronic rhinosinusitis represents a multifactorial inflammatory disorder, rather than simply a persistent bacterial infection. The medical management of chronic rhinosinusitis is now focused upon controlling the inflammation that predisposes patients to obstruction, reducing the incidence of infections. However, all forms of chronic rhinosinusitis are associated with impaired sinus drainage and secondary bacterial infections. Most individuals require initial antibiotics to clear any infection and intermittently afterwards to treat acute exacerbations of chronic rhinosinusitis.

A combination of anaerobic and aerobic bacteria are detected in conjunction with chronic sinusitis. Also isolated are "Staphylococcus aureus" (including methicilin resistant "S.aureus" ) and coagulase-negative "Staphylococci" and Gram negative enteric organisms can be isolated.

Attempts have been made to provide a more consistent nomenclature for subtypes of chronic sinusitis. The presence of eosinophils in the mucous lining of the nose and paranasal sinuses has been demonstrated for many patients, and this has been termed eosinophilic mucin rhinosinusitis (EMRS). Cases of EMRS may be related to an allergic response, but allergy is not often documented, resulting in further subcategorization into allergic and non-allergic EMRS.

A more recent, and still debated, development in chronic sinusitis is the role that fungi play in this disease. It remains unclear if fungi are a definite factor in the development of chronic sinusitis and if they are, what the difference may be between those who develop the disease and those who remain free of symptoms. Trials of antifungal treatments have had mixed results.

Recent theories of sinusitis indicate that it often occurs as part of a spectrum of diseases that affect the respiratory tract ("i.e.", the "one airway" theory) and is often linked to asthma. All forms of sinusitis may either result in, or be a part of, a generalized inflammation of the airway, so other airway symptoms, such as cough, may be associated with it.

Both smoking and secondhand smoke are associated with chronic rhinosinusitis.

Adenoiditis occurs mainly in childhood, often associated with acute tonsillitis. Incidence decreases with age, with adenoiditis being rare in children over 15 years due to physiological atrophy of the adenoid tissue.

It is currently believed that bacterial biofilms play an integral role in the harboring of chronic infection by tonsil and adenoid tissue so contributing to recurrent sinusitis and recurrent or persistent ear disease. Also, enlarged adenoids and tonsils may lead to the obstruction of the breathing patterns in children, causing apnea during sleep.

The most common bacteria isolated are Haemophilus influenzae, group A beta-hemolytic Streptococcus, Staphylococcus aureus, Moraxella catarrhalis, and Streptococcus pneumoniea. Heamophilus influenza, Moraxella catarrhalis and Streptococcus pneumonia are the three most resistant pathogens of otitis and rhinosinisitis in children suffering from these diseases.

Rhinorrhea can also occur when individuals with allergies to certain substances, such as pollen, dust, latex, soy, shellfish, or animal dander, are exposed to these allergens. In people with sensitized immune systems, the inhalation of one of these substances triggers the production of the antibody immunoglobulin E (IgE), which binds to mast cells and basophils. IgE bound to mast cells are stimulated by pollen and dust, causing the release of inflammatory mediators such as histamine. In turn, this causes, among other things, inflammation and swelling of the tissue of the nasal cavities as well as increased mucus production. Particulate matter in polluted air and chemicals such as chlorine and detergents, which can normally be tolerated, can make the condition considerably worse.

If caused by a head injury, rhinorrhea can be a much more serious condition. A basilar skull fracture can result in a rupture of the barrier between the sinonasal cavity and the anterior cranial fossae or the middle cranial fossae. This rupture can cause the nasal cavity to fill with cerebrospinal fluid. This condition, known as cerebrospinal fluid rhinorrhoea or CSF rhinorrhea, can lead to a number of serious complications and possibly death if not addressed properly.

There is low or very-low quality evidence that probiotics may be better than placebo in preventing acute URTIs. Vaccination against influenza viruses, adenoviruses, measles, rubella, "Streptococcus pneumoniae", "Haemophilus influenzae", diphtheria, "Bacillus anthracis", and "Bordetella pertussis" may prevent them from infecting the URT or reduce the severity of the infection.

Causes can be remembered by mnemonic HERNIA:

- Hereditary factors: the disease runs in families

- Endocrine imbalance: the disease tends to start at puberty and mostly involves females

- Racial factors: whites are more susceptible than natives of equatorial Africa

- Nutritional deficiency: vitamins A or D, or iron

- Infection: "Klebsiella ozaenae", diphtheroids, "Proteus vulgaris", "E. coli", etc.

- Autoimmune factors: viral infection or some other unidentified insult may trigger antigenicity of the nasal mucosa.

Children have 2-9 viral respiratory illnesses per year. In 2013 18.8 billion cases of upper respiratory infections were reported. As of 2014, upper respiratory infections caused about 3,000 deaths down from 4,000 in 1990. In the United States, URIs are the most common infectious illness in the general population. URIs are the leading reasons for people missing work and school.

Though it is widely held that fungal infections of the nose and paranasal sinuses are not common, most agree that their frequency has been increasing over past decades.

Specific infections, such as syphilis, lupus, leprosy and rhinoscleroma, may cause destruction of the nasal structures leading to atrophic changes. Atrophic rhinitis can also result from long-standing purulent sinusitis or radiotherapy of the nose, or as a complication of surgery of the turbinates. The United Kingdom National Health Service has stated that "Most cases of atrophic rhinitis in the UK occur when the turbinates are damaged or removed during surgery". Some authors refer to as Atrophic rhinitis secondary to sinus surgery as the empty nose syndrome.

Due to the human ear's function of regulating the pressure within the head region, catarrh blockage may cause discomfort during changes in atmospheric pressure.

Sinusitis is inflammation of the paranasal air sinuses. Infections associated with teeth may be responsible for approximately 20% of cases of maxillary sinusitis. 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. Once an odontogenic infection involves the maxillary sinus, it is possible that it may then spread to the orbit or to the ethmoid sinus.

Catarrh , or catarrhal inflammation, is inflammation of the mucous membranes in one of the airways or cavities of the body, usually with reference to the throat and paranasal sinuses. It can result in a thick exudate of mucus and white blood cells caused by the swelling of the mucous membranes in the head in response to an infection. It is a symptom usually associated with the common cold, pharyngitis, and chesty coughs, but it can also be found in patients with adenoiditis, otitis media, sinusitis or tonsillitis. The phlegm produced by catarrh may either discharge or cause a blockage that may become chronic.

The word "catarrh" was widely used in medicine since before the era of medical science, which explains why it has various senses and in older texts may be synonymous with, or vaguely indistinguishable from, common cold, nasopharyngitis, pharyngitis, rhinitis, or sinusitis. The word is no longer as widely used in American medical practice, mostly because more precise words are available for any particular pathosis. Indeed, to the extent that it is still used, it is no longer viewed nosologically as a disease entity but instead as a symptom, a sign, or a syndrome of both. The term "catarrh" is found in medical sources from the United Kingdom. The word has also been common in the folk medicine of Appalachia, where medicinal plants have been used to treat the inflammation and drainage associated with the condition.

Bacterial infections of the orbit have long been associated with a risk of catastrophic local

sequelae and intracranial spread.

The natural course of the disease, as documented by Gamble (1933), in the pre-antibiotic era,

resulted in death in 17% of patients and permanent blindness in 20%.

Barodontalgia, commonly known as tooth squeeze and previously known as aerodontalgia, is a pain in tooth caused by a change in ambient pressure. The pain usually ceases at ground level. Dental barotrauma is a condition in which such changes in barometric pressure changes cause damage to the dentition.

The most common victims are underwater divers because in deep dives pressures can increase by several atmospheres, and military pilots because of rapid changes.

In pilots, barodontalgia may be severe enough to cause premature cessation of flights.

Most of the available data regarding barodontalgia is derived from high-altitude chamber simulations rather than actual flights. Barodontalgia prevalence was between 0.7% and 2% in the 1940s, and 0.3% in the 1960s.

Similarly, cases of barodontalgia were reported in 0.3% of high altitude-chamber simulations in the Luftwaffe.

The rate of barodontalgia was about 1 case per 100 flight-years in the Israeli Air Force. During World War II, about one-tenth of American aircrews had one or more episodes of barodontalgia. In a recent study, 8.2% of 331 Israeli Air Force aircrews, reported at least one episode of barodontalgia.

Barodontalgia is a symptom of dental disease, for example inflammatory cyst in the mandible.

Indeed, most of the common oral pathologies have been reported as possible sources of barodontalgia: dental caries, defective tooth restoration, pulpitis, pulp necrosis, apical periodontitis, periodontal pockets, impacted teeth, and mucous retention cysts. One exception is barodontalgia manifested as referred pain from barosinusitis or barotitis-media. The latter two conditions are generated from pressure changes rather than pressure-related flare-up of pre-existing conditions.

A meta-analysis of studies conducted between 2001 and 2010 revealed a rate of 5 episodes/1,000 flight-years. Maxillary and mandibular dentitions were affected equally in flight, but in diving, maxillary dentition was affected more than the mandibular dentition, which can indicate a greater role for maxillary sinus pathology in diving barodontalgia. Surprisingly, despite cabin pressurization, the current in-flight barodontalgia incidence is similar to the incidence in the first half of the 20th century. Also, despite the greater fluctuation in divers' pressures, the weighted incidence of barodontalgia among aircrews is similar to the weighted incidence among divers. Furthermore, contrary to common belief, and in contrast to diving conditions, the role of facial barotrauma in the cause of in-flight barodontalgia is only minor (about one-tenth of cases).

Treatment for fungal sinusitis can include surgical debridement; helps by slowing progression of disease thus allowing time for recovery additionally we see the options below:

- In the case of invasive fungal sinusitis, echinocandins, voriconazole, and amphoterecin (via IV) may be used

- For allergic fungal sinusitis, systemic corticosteroids like prednisolone, methylprednisolone are added for their anti-inflammatory effect, bronchodilators and expectorants help to clear secretions in the sinuses.

Antibiotics are aimed at gram positive bacteria. Medical attention should be sought if symptoms persist beyond 2–3 days.

Aetiology of CTS is multifactorial, the causative factors include:

- previous restorative procedures.

- occlusal factors

- developmental conditions/anatomical considerations.

- trauma

- others, e.g, aging dentition or presence of lingual tongue studs.

Most commonly involved teeth are mandibular molars followed by maxillary premolars, maxillary molars and maxillary premolars. in a recent audit, mandibular first molar thought to be most affected by CTS possibly due to the wedging effect of opposing pointy, protruding maxillary mesio-palatal cusp onto the mandibular molar central fissure.

Nasal polyps resulting from chronic rhinosinusitis affect approximately 4.3% of the population. Nasal polyps occur more frequently in men than women and are more common as people get older, increasing drastically after the age of 40.

Of people with chronic rhinosinusitis, 10% to 54% also have allergies. An estimated 40% to 80% of people with sensitivity to aspirin will develop nasal polyposis. In people with cystic fibrosis, nasal polyps are noted in 37% to 48%.

Complications include hearing loss, blood infection, meningitis, cavernous sinus thrombosis, and optic nerve damage (which could lead to blindness).

An odontogenic infection is an infection that originates within a tooth or in the closely surrounding tissues. The term is derived from "" (from ancient Greek "odous" - "tooth") and "" (from Greek "genos" - "birth"). Odontogenic infections may remain localized to the region where they started, or spread into adjacent or distant areas.

It is estimated that 90-95% of all orofacial infections originate from the teeth or their supporting structures. Furthermore, about 70% of odontogenic infections occur as periapical inflammation, i.e. acute periapical periodontitis or a periapical abscess. The next most common form of odontogenic infection is the periodontal abscess.

In general, chronic periodontal conditions do not cause any pain. Rather, it is acute inflammation which is responsible for the pain.

Common marginal gingivitis in response to subgingival plaque is usually a painless condition. However, an acute form of gingivitis/periodontitis, termed acute necrotizing ulcerative gingivitis (ANUG), can develop, often suddenly. It is associated with severe periodontal pain, bleeding gums, "punched out" ulceration, loss of the interdental papillae, and possibly also halitosis (bad breath) and a bad taste. Predisposing factors include poor oral hygiene, smoking, malnutrition, psychological stress, and immunosuppression. This condition is not contagious, but multiple cases may simultaneously occur in populations who share the same risk factors (such as students in a dormitory during a period of examination). ANUG is treated over several visits, first with debridement of the necrotic gingiva, homecare with hydrogen peroxide mouthwash, analgesics and, when the pain has subsided sufficiently, cleaning below the gumline, both professionally and at home. Antibiotics are not indicated in ANUG management unless there is underlying systemic disease.

OAF is a complication of oroantral communication. Other complications may arise if left untreated. For example:

- Candidal infection

- Chronic maxillary sinus infection of bacterial origin

- Osteomyelitis

- Rhinosinusitis

- Sinus pathology

Therefore, OAF should be dealt with first, before treating the complications.