Mucosal thickening in the maxillary sinus can be caused by various factors, including:

• Dental pathology or intervention: The inferior aspect of the maxillary sinus is commonly affected by mucosal thickening due to dental pathology or intervention.

• Chronic inflammation: Chronic inflammation of the maxillary sinus can cause irregular mucosal folds and lead to the development of nasal polyps.

• Periodontal disease: Periodontitis can stimulate thickening of the maxillary sinus mucosa, and there is a positive association between periodontal status and the degree of maxillary sinus mucosal thickening.

• Infection: Maxillary sinusitis, which can arise from bacterial, fungal, or viral infections, is often attributed to periodontal disease.

• Anatomical abnormalities: Anatomical abnormalities can frequently present with obstruction, with rhinorrhea as a less prominent symptom. Septal deviation can cause unilateral or bilateral congestion and recurrent sinusitis.

• Viscous mucus: Mucus build-up in the maxillary sinus can permit bacterial infections with Pseudomonas and/or Staph Aureus most often.

In summary, mucosal thickening in the maxillary sinus can be caused by various factors, including dental pathology, chronic inflammation, periodontal disease, infection, anatomical abnormalities, and viscous mucus.