Is toombak a risk factor for oral leukoplakia and oral squamous cell carcinoma ? A systematic review.

INTRODUCTION: Toombak is a form of smokeless tobacco that is not well known in Western Society but is widely used by the Sudanese population and many others in the sub-Sahara region. However, unlike other smokeless tobacco products, information on the carcinogenic potential of toombak is scarce. The present review explored any potential epidemiological association between the use of toombak and oral leukoplakia and oral squamous cell carcinoma (OSCC). METHODS: Databases including the Web of Science, SCOPUS, EMBASE and PubMed were searched for literature on the potential association between toombak and oral leukoplakia and OSCC. The search also included grey literature. The search period extended from 1990 to 2018. Following data mining, the study selection was conducted by two reviewers independently. RESULTS: Eight studies that satisfied the inclusion criteria were included. Based on these results, there was a threefoldto sevenfold increased risk of developing the oral leukoplakia and oral squamous cell carcinoma among toombak users compared with non-users. CONCLUSION: Based on the results of the systematic review, there is a strong epidemiological evidence to suggest toombak to be a major risk factor for both oral leukoplakia and OSCC. Further studies are necessary to evaluate the molecular pathway of toombak-induced oral carcinogenesis.

Are electronic nicotine delivery systems (ENDs) helping cigarette smokers quit?-Current evidence.

BACKGROUND: Electronic cigarettes (e-cigarettes) and other electronic vaping devices are commonly used as a method to help tobacco smoking cessation. However, the data on their safety and efficacy are currently scarce. The aim of this review was to explore the role of e-cigarettes in tobacco cessation among tobacco users. TYPES OF STUDIES REVIEWED: PubMed, EMBASE, Scopus, Web of Science, and grey literature from January 1990 were searched up to and including September 2018. Two independent reviewers performed the study selection according to eligibility criteria. RESULTS: A total of 13 studies that met the eligibility criteria were included. The majority of studies were done in the USA, and all studies were longitudinal cohort studies. The odds of increased smoking cessation in association with e-cigarette use ranged from onefold to sixfolds. No significant increase in smoking cessation was found among e-cigarette users compared with non-e-cigarette users. Pattern of e-cigarette had positive influence on smoking cessation among users. CONCLUSIONS AND PRACTICAL IMPLICATIONS: E-cigarette use was not significantly associated with increased smoking cessation among cigarette smokers. We also found that pattern of e-cigarette may have significant effect on smoking cessation capability of e-cigarettes. Well-designed randomized controlled clinical trials are needed to assess the clinical efficacy of e-cigarettes in comparison with approved smoking cessation therapies.

Animal Models--Decoding the Molecular Biology of Oral Cancer.

Animal models have long been used to understand the initiation and progression of carcinogenesis, including that of oral mucosa.(1) One of the earliest models used was the chemical-induced oral cancer model, among which the Syrian Hamster check pouch was preferred for its ideal anatomical location and physiological features.(2) Salley et al(3) demonstrated that the cheek pouch mucosa underwent gradual changes from hyperplasia, carcinoma in situ to squamous cell carcinoma when exposed to polycyclic hydrocarbon 9, 10 dimethyl-1,2, benzanthracene (DMBA). Morris(4) standardized the dosage of carcinogen to 0.5% solution of DMBA in acetone and established that 5-week old animals were ideal to induce tumor with minimum time lag and maximum yield. Lin et al(5) demonstrated the synergistic effect of arecaidine with DMBA.

Potential role of tumor microenvironment in the progression of oral cancer.

The stromal cells adjacent to the tumor including the fibroblasts, infammatory cells, lymphatic and vascular endothelial cells constitute the 'tumor microenvironment' (TM).(1) Recent in vivo and invitro studies have emphasized the role of stromal components on the growth, differentiation and invasiveness of the tumor cells. In addition, vascular, lymphatic or perineural invasion have proven to have independent prognostic value.(2) Despite the compelling evidence correlating the TM with the initiation and progression of cancer, our knowledge on the role of the genes mediating the various cellular interactions in the tumour stroma is limited.(2,3).

Chronic mechanical irritation and oral squamous cell carcinoma: A systematic review and meta-analysis.

The objective of the present article was to qualitatively and quantitatively review the association between chronic mechanical irritation and oral squamous cell carcinoma (OSCC). PubMed, SCOPUS, and Web of Science databases were searched using the keyword combinations "chronic trauma and oral squamous cell carcinoma; chronic irritation and oral squamous cell carcinoma; chronic irritation and oral cancer; and chronic trauma and oral cancer." Duplicates and irrelevant articles were excluded after the title and abstract screening. The full texts of the remaining articles were assessed using selection criteria. A total of 375 (PubMed-126; SCOPUS-152; WOS-97) articles were screened, and 343 duplicates and irrelevant articles were excluded from the study. Only 9 of the remaining 32 articles met the selection criteria and were included in the qualitative analysis. Buccal mucosa and tongue, being highly prone to chronic irritation through the dental prosthesis, were the common sites for OSCC. Edentulous subjects with ill-fitting dentures were at a high risk of developing chronic irritation associated-OSCC. According to the Joanna Briggs Institute of risk assessment, eight of the nine included studies had a low risk of bias. The quantitative analysis showed a significant association (p < 0.00001) between the chronic oral mucosal irritation and OSCC with an overall risk ratio of 2.56 at a confidence interval of 1.96-3.35. Chronic oral mucosa irritation has a significant association with OSCC, and the nature of association could be that of a potential co-factor (dependent risk factor) rather than an independent risk factor.

Exophytic oral verrucous hyperplasia: a new entity.

OBJECTIVE: Exophytic oral verrucous hyperplasia (OVH) is a new entity described by an expert working group from South Asia. First reported in Taiwan, there are no reports so far from an Indian population. The aim was to use the microscopic features described by the expert group to differentiate OVH from other oral verruco-papillary lesions in an Indian archive. MATERIALS AND METHODS: In a retrospective multicentre study, using pathology archives, 188 verruco-papillary lesions were retrieved from pathology archives. A proforma listing histopathological criteria for OVH based on published guidelines (Annals of Dentistry, University of Malaya, 2013) was used. Patients' demographic and clinical data were transcribed from patient charts. The Pearson chi-square test was used to determine associations between clinical and histopathological features. RESULTS: Of 188 oral verruco-papillary lesions that were evaluated, based on microscopic features the cases were reclassified as OVH (57), verrucous carcinoma (VC) (84), oral squamous cell carcinoma (16), and other verruco-papillary lesions (31). Both OVH (70%) and VC (60%) showed male predominance and commonly affected buccal mucosa (OVH 74% and VC 57%). Absence of downward growth of the hyperplastic epithelium into lamina propria when compared with the level of the basement membrane of the adjacent normal epithelium was a distinct feature in OVH. Keratin plugging, epithelial dysplasia and subepithelial lymphocytic infiltration were found to be significantly different (P < 0.05) in OVH versus VC. The sample size of other verruco-papillary lesions was insufficient for statistical comparison. CONCLUSION: Apart from the absence of an endophytic growth pattern in OVH, we noted the presence of dysplasia in OVH. This significant observation does institute a debate as to whether this enigmatic lesion could possibly be a precedent of oral squamous or verrucous carcinoma. We propose OVH is a distinct entity in our Indian population and should be considered in the classification of oral potentially malignant disorders.