title: Limited mouth opening in oral submucous fibrosis: reasons, ramifications, and remedies.
abstract: Limited mouth opening (LMO) in oral submucous fibrosis (OSF) has been attributed to both the submucosal and muscle fibrosis (MF). While reflectory trismus was proposed before as an auxiliary mechanism by another group, the stretch-mediated muscle damage (MSD), histopathological changes in blood vessels (such as endothelial dysfunction, endothelial hypertrophy, and endarteritis obliterans), and upregulated anaerobic isoforms of lactate dehydrogenase (LDH) have been proposed by us as complementary events leading to MF. Additionally, the amount of hypoxia-mediated upregulation of anaerobic isoforms of LDH determines the extent of MF. Radiotherapy (RT)-mediated release of reactive oxygen species causes vascular damage thereby worsening hypoxia. While the alteration in LDH levels secondary to hypoxia enhances fibrosis, RT worsens it. Oral squamous cell carcinoma occurring in the background of OSF is an absolute contraindication for RT as it augurs unfavorable prognosis. An algorithm to demonstrate this with evidence is clearly depicted. The role of HIF-1α in the progression of OSF and its malignant transformation, and the consideration of hyperbaric oxygen therapy as a therapeutic remedy in OSF are underscored.
authors.affiliation: Department Of Oral Pathology, ITS Dental College, Hospital and Research Center, Greater Noida, India.
authors.forename: Mohit
authors.identifier: http://orcid.org/0000-0002-9235-0176
authors.initials: M
authors.lastname: Sharma
authors.affiliation: Department of Oral Pathology, Manipal College of Dental Sciences, Manipal University, Manipal, India.
authors.forename: Raghu
authors.initials: R
authors.lastname: Radhakrishnan
mesh_terms: D001114:Areca / Q000009:adverse effects; D002294:Carcinoma, Squamous Cell / Q000209:etiology / Q000503:physiopathology*; D002471:Cell Transformation, Neoplastic; D006801:Humans; D009062:Mouth Neoplasms / Q000209:etiology / Q000503:physiopathology*; D009914:Oral Submucous Fibrosis / Q000150:complications / Q000503:physiopathology*; D014313:Trismus / Q000209:etiology / Q000503:physiopathology*
keywords: hyperbaric oxygen therapy; hypoxia; lactate dehydrogenase; oral squamous cell carcinoma; oral submucous fibrosis; radiotherapy