Submucosal Thickness in Oral Submucous Fibrosis Patients

Published Date: 20 Sep 2017

Discussion

DISCUSSION

OSMF is a potentially malignant condition which is of multifactorial etiology with areca nut chewing being the commonest cause.⁷²This condition has a significant mortality rate because it can transform into oral cancer, particularly squamous cell carcinoma as seen in 3-7.6% of the cases.⁷³The geographical distribution of OSMF shows confinement to tropical areas primarily in South Asia. ⁷²

The initial pathology of OSMF is characterized by juxta-epithelial inflammation including edema. Later, collagen bundles with early hyalinization are seen and inflammatory infiltrate becomes more chronic consisting of lymphocytes and plasma cells. Epithelium may show atrophic changes and dysplastic features and in advanced stages, OSMF is characterized by formation of thick bands of collagen fibers and hyalinization extending deep into the submucosal tissues and decreased vascularity.74

Management of OSMF includes cessation of habit and the preferred medical treatment is use of steroids in oral and systemic form, injections of placental extract, and hualuronidase, IV interferon, antioxidants like lycopene and physiotherapy.9

Diagnostsic ultrasonography has gained more importance in dentistry in the last few decades . This is a real time imaging modality which is based on the sound waves. Echogenicity is the ability to bounce an echo. The echogenicity primarily depends on the collagen content within the tissue.⁷⁵ Tissuesthat have higher echogenicity are called "hyperechogenic" and are typically represented with lighter colors on images inultrasonography. In contrast, tissues with lower echogenicity are called "hypoechogenic" and are usually represented with darker colors. Areas that lack echogenicity are called "anechogenic" and are usually displayed as completely dark. Ultrasonography has been used in few studies to detect fibrosis like scleroderma where ultrasonography could detect decreased blood flow, increased echogenicity and loss of subcutaneous fat and reduction in the size of the lesion after treatment.⁷⁶ Recently ultrasonography was used as non-invasive investigative tool for evaluation of OSMF.² Evaluation of OSMF using ultrasonography demonstrates number, length and thickness of the fibrotic bands and colour Doppler and spectral Doppler shows decreased vascularity color Doppler shows vascularity in lesional area.

Taking this in to consideration the present study compared pre and post treatment submucosal thickness in patients with OSMF using ultrasonography. Fifty OSMF patients were selected for the study and ultrasonographic measurement of oral submucosa was done before and after the treatment. Treatment schedule for the patient included intralesional injection of dexamethasone and hyaluronidase biweekly for 8 weeks. Later the ultrasonographic measurements were correlated with the mouth opening. Majority of the patients in the study were males (47) as compared to females (3).It can be due to higher prevalence of tobacco and betel nut chewing habits in male population. The age range of the patients was 18-55 yr with a mean age of 33.7yrs. 39 patients had gutkha chewing habit. 9 patients chewed pan and betel nut and 2 patients chewed pan, betel nut and tobacco.

P Rangaiah et al (2010) measured the thickness of submucosa with the application of ultrasonography (USG) in patients with OSMF and controls and correlated clinical and histological stages of the disease with the USG measurements. The mean submucosal thickness of Anterior Buccal Mucosa (ABM) for cases was 0.209 cm and for controls was 0.056 cm, Posterior Buccal Mucosa (PBM) for cases was 0.218 cm and for controls was 0.057 cm, Upper Labial Mucosa (ULM) for cases was 0.149 cm and for controls was 0.055 cm, and for Lower Labial Mucosa (LLM) for cases was 0.162 cm and for the controls was 0.060 cm. The study group had a increased submucosal thickness when compared to control group in all the measured sites. A significant positive association was obtained in relation of submucosal thickness with frequency of chewing habits.⁶⁰

Manjunath K et al (2011) evaluated the prognosis of treatment given to the OSMF patient by assessing the Peak Systolic Volume (PSV).Cases with good prognosis had statistically significant reduction in the PSV where as cases with poor prognosis did not have any significant difference between pre and post treatment values of PSV.²

Devathambi JR (2013) showed that the range of the normal submucosal thickness was between 0.045 and 0.056 cm.The submucosal thickness in OSMF patients ranged between 0.090 cm to 0.258. As the stages of OSMF advanced there was an increase in submucosal thickness of the buccal mucosa. In stage III OSMF patients (Khanna and Andrade) the anterior buccal mucosa measurement was 0.169cm which was consistent with our study.⁶¹

In our study submucosal thickness decreased over four sites after the treatment and there was a significant correlation between pre and post treatment mouth opening and submucosal thickness. Hence it proves that mouth opening depends on the fibrosis of submucosal layer. This is in accordance with the study done by Shivakumar SC et al (2010) where mouth opening was correlated with the fibrosis histopathologicaly, ⁷⁸ while in our study correlated mouth opening with ultrasonographic thickness of submucosa. Literature does not reveal any other study which assessed the submucosal thickness before and after the treatment in OSMF patients. Hence the present study is the first of its kind where USG is used as a diagnostic and prognostic tool in the treatment of OSMF by assessing the change in thickness of submucosa.

Though USG has not been used to evaluate fibrosis of oral mucosa, it has been regularly used as a diagnostic tool in other fields like fibrosis of liver. Jian an zhu et al (2003) compared ultrasound findings with histopathology in liver cirrhosis and concluded that ultrasound was diagnostically accurate and reliable in diagnosing liver cirrhosis.⁷⁹

In the present study pretreatment submucosal thickness of right and left buccal mucosa was 0.168cm and 0.164cm respectively which reduced to 0.133cm after the treatment. Similarly upper and lower labial submucosal thickness decreased to 0.210 cm to 0.170cm after the treatment. Both the results were statistically significant (p value <0.00).Due to paucity of studies in this regard, the present study cannot be compared with previous studies.

The most striking changes occur in the submucosal connective tissue where there is a marked increase in echogenicity. Ultrasound diagnosis is based on the transformation of sound waves into visible light waves. Clinicians use the images obtained to identify differences in anatomical structures examined. The most important parameters describing the interactions between ultrasound and tissue through which it is transmitted are attenuation, velocity and impedance.⁶⁴ The attenuation and velocity are directly proportional to the amount of collagen present in the tissue and inversely proportional to the water content.⁸⁰ Collagen has greater modulus of elasticity as compared to other tissue which results in higher velocity and impedance and ultimately leads to more echogenicity.⁸¹

Anjum Aara et al (2012) had reported 3.7 mm increase in mouth opening at the end 20 patients after giving biweekly intralesional injections of Dexamethasone (4mg/ml), Hyaluronidase 1500 IU and 0.5 ml of Lignocaine 2% for a period of 12 weeks.⁷¹

Panigrahi R et al (2014) evaluated combination of 1ml triamcinolone accetonide (10mg/ml) and hyaluronidase (1500) injected submucosally at 14 days interval, for a total of 8 doses and mean mouth opening was found to be improved by 11.47 mm.⁷⁶

In our study the mean pretreatment mouth opening was 29.92 mm.After the treatment the mean mouth opening increased to 34.98 mm which was statistically significant.(p value <0.00).The mean increase in the mouth opening was 5.06. Better results in the present study compared to Anjum Aara et al could be attributed due to adjunctive antioxidants and physiotherapy advised to the patient. Increased mouth opening seen in the study done by Panigrahi R et al could be because of local potency of triamcinolone acetonide injection.

The most effective treatment for OSMF is intralesional injection of a combination of corticosteroids and and a hydrolyzing agent. Dexamethasone is a potent steroidwhich reduces the inflammation of juxta epithelial surface. Hyaluronidase is an enzyme which hydrolyzes the hyaluronic acid component or the ground substance of connective tissue. It temporary decreases the viscosity of the intercellular cement substance and promotes diffusion of injected fluids thus facilitating their action.⁷⁷

Thus advantages of using ultrasonography in evaluating OSMF include noninvasive procedure, non ionizing radiation is used, less time is required, repeatable, cost effective, extend of the lesion and vascularity can be assessed, larger area can be studied as compared to biopsy and prognosis of the treatment can be evaluated.

Even then the most important drawback with ultrasound in comparison with histopathology is failure to detect mild fibrosis and microscopic changes in the tissues.⁸³ It is operator sensitive as ultrasound scanning reading depends on operator’s experience. Ultrasound is operator dependent and reading of the scan is dependent on the radiologist's experience.

Limitation of our study was that the muscle layer was not assessed as fibrosis in OSMF can involve muscle fibers and cause reduced mouth opening. Thickness of anterior and posterior buccal mucosa was not assessed separately in this study.

FUTURE PROSPECTIVES

Studies should be done to assess the thickness of submucosa as well as muscle layer in OSMF patients.

Further studies can be undertaken to correlate submucosal thickness with chewing habits, clinical staging and histological staging.

Evaluation of OSMF using intra oral probe is advised which may yield more accurate and reliable results.

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