How can Sinusitis occur? 

In physiological conditions, the sinuses are sterile. Sinusitis can occur if the sinus secretion clearance is reduced or Ostia Sinus becomes blocked, which causes secretion retention, negative sinus pressure, and reduced oxygen partial pressure. This environment is suitable for the growth of pathogenic organisms. If an infection occurs due to a virus, bacteria, or fungus in the sinus that contains these secretions, sinusitis occurs.

Phatophysiology of Sinusitis
Image Source:

Pathophysiology of Sinusitis involved by the following factors:

1. Obstruction in the sinus drainage pathway (sinus ostium),
2. Impaired Cilia Function,
3. impaired accumulation and quality of mucus.

1. Obstruction of the sinus ostium

Normally, sinus mucus flow as clearance is one-way from the sinus through the sinus ostium into the nasal cavity. Upper respiratory tract infections (due to viruses, bacteria, or allergen exposure) will cause swollen sinus mucosa or edema. Swelling leads to the facing mucosa will meet each other, causing the sinus ostium to narrow. This causes the cilia can not move and also causes ostium clogging. The narrowing of the ostium gradually creates a blockage that disrupts the sinus mucus flow.

When there is a blockage, the air in the sinus cavity begins to decrease, so the air pressure in the sinus cavity changes to be more negative than the atmospheric pressure. This negative pressure allows bacteria in the nasal cavity to enter the sinus cavity, especially when inhaling or removing nasal secretions. Apart from infection and allergens, sinus ostium obstruction can also occur due to polyps, foreign bodies, septal deviation, or tumors.

2. Impaired Cilia Function

As with the nasal mucosa, there is also a ciliated mucosa in the sinus. Cilia play a role in mucous flow from the sinus cavity to the nasal cavity. Disruption of ciliary function will have an impact on the accumulation of mucus in the sinus cavity. The impaired ciliary function can be caused due to viral, bacterial infections, high airflow, chemicals that are toxic to cilia, inflammatory mediators, scarring, and Kartagener's syndrome (primary ciliary dyskinesia). 

3. Impaired accumulation and quality of mucus

When sinus ostium obstruction occurs, the sinus cavity mucosa will continue to produce mucus, resulting in excessive mucus accumulation. Cilia can only work if there is a suitable composition of the mucous fluid.

Mucus in the respiratory tract consists of two layers. The first layer is a thinner, thinner serosa (sol phase) that surrounds the ciliary shaft and helps cilia work. The second layer (gel phase) has a thicker consistency and is above the first layer.

The movement of cilia transports the mucous layer of this gel phase into the sinus ostium. If the composition of the mucus layer becomes thickness, mucus transport will be slower so that the gel phase layer will increasingly accumulate in the sinus cavity. Changes in mucous quality due to inflammation debris will also increasingly impair the movement of cilia.

Combination of ostium obstruction and impaired ciliary function

The combination of the two factors above creates a negative pressure in the sinus cavity that causes transudation or blockage of sinus drainage. The initial effect is serous fluid secretion (considered as non-bacterial sinusitis), which can heal without treatment. If it does not heal, the secretions accumulate in the sinuses, which is a suitable medium for growth and multiplication of bacteria. The secretions will turn into purulent called acute bacterial sinusitis that require antibiotic therapy. If treatment is adequate, then this situation can continue, hypoxia will occur, and anaerobic bacteria will multiply.

The Relation between Dental Diseases and Sinusitis

Can infected tooth cause sinusitis?
Maxillary anterior has associations that are very close to the roots of the premolar and upper molar teeth. This association can cause clinical problems such as infections originating from teeth, and oroantral fistulas can rise to the top and cause sinus infections.

Maxillary sinusitis begins by sinus ostium obstruction due to inflammatory processes in the nasal mucosa. This inflammatory process will cause sinus and drainage interferences. 

Unilateral antrum involvement is often an indication of dental involvement as a cause. If this happens, the organism responsible is likely to be the gram-negative group. These organisms are more common in dental infections than gram-positive bacteria, which are typical in the sinuses.

Dental diseases such as apical and periodontal abscesses can produce radiological features that are dominated by gram-negative bacteria. In odontogenic sinusitis cases, thick secretions will worsen and interfere with the drainage, especially if the meatus medius is impaired by edema or purulent or other anatomical abnormalities such as deviation and hypertrophic conchae/turbinate. The roots of the second premolar and first molars are closely related to the maxillary sinus floor and, in some individuals, are directly related to the maxillary sinus mucosa so that the spread of bacteria is directly from the tooth root to the sinuses can occur.