An epidemiologic study of oral cancer in a statewide network

Oral Cavity Cancer Secondary to Dental Trauma: A Scoping Review

(1) Background: Oral cavity cancer represents the most common site of origin of head and neck mucosal malignancies. A few limited studies have suggested that chronic irritation, particularly in non-healing ulcers, and fibrotic tissue from poor dentition or ill-fitting dentures had a role in developing mouth cancer. This scoping review aims to evaluate the existing evidence concerning Oral Cavicty Cancer (OCC) in non-smokers/non-drinkers and the relationship with dental trauma. (2) Methods: A scoping review of the PubMed, Embase, and Web of Science databases was completed in adherence with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews checklist. (3) Results: Of the 33 articles that met inclusion, in 6 of them authors discussed the role of topography in dental trauma, in 11 articles authors discussed the carcinogenesis mechanism involved in chronic mucosal trauma, in 17 articles data on ill-fitting dentures was included, 4 studies dealt with the effect of broken/sharp teeth on mucosal damage, and in 7 studies the role of oral hygiene was covered. Less frequently discussed topics included gender, risk of neck nodes, and the role of potentially malignant oral disorders. (4) Conclusions: The available literature suggests a potential connection between chronic dental trauma and the development of OCC. Studies have highlighted factors such as denture use and ill-fitting dental appliances as contributors to an increased risk of oral cancer. Interestingly, we still miss data to support the hypothesis that women, particularly those without toxic habits like smoking or alcohol consumption, appear to be disproportionately affected by oral cancer related to chronic dental trauma.

Modifiable risk factors for oral cavity cancer in non-smokers: A systematic review and meta-analysis

BACKGROUND

Oral cavity cancer (OCC) is traditionally associated with smoking, but there is an increasing prevalence of the disease among non-smokers. This review investigates possible modifiable risk factors in the development of OCC in non-smokers (OCCNS).

METHODS

PubMed, EMBASE, Web of Science, and Scopus were searched for publications prior to June 2021. Comparative studies investigating modifiable OCCNS risk factors were identified following PRISMA guidelines. Publication date, population size, and results were indexed. Study quality was assessed using MINORS (Methodological Index for Non-Randomized Studies). Factors examined by multiple studies were analyzed using random-effect meta-analysis framework.

RESULTS

Literature search resulted in 1,625 unique publications. 52 records met inclusion criterion, investigating alcohol (n = 22), chewing products (n = 18), diet (n = 7), dental health (n = 11), and medical comorbidities (n = 6).

CONCLUSION

This review demonstrates the paucity of large studies investigating OCCNS risk factors. Further investigation is warranted to help clinicians risk-stratify patients without traditional risk factors.

Occupational exposure and risk of oral and oropharyngeal squamous cell carcinoma: systematic review and 25-year retrospective cohort study of patients

Social habits such as smoking and drinking alcohol are well-known causative agents for oral and oropharyngeal squamous cell carcinoma (OSCC/OPSCC). Human papillomavirus (HPV) is a known causative agent for OPSCC. However, we often encounter patients with no identifiable risk factors. There is growing evidence of the role of occupational carcinogens in the pathogenesis of oral cancer. The aim of this study therefore was to identify any occupational carcinogens linked to oral cancer. We carried out a systematic review of the literature using PubMed, EMBASE, and Medline, along with a retrospective review of patients treated in a regional unit over 25 years. Occupations were classified based on the UK Standard of Classification 2020. Data analysis was completed using the chi-squared test. A total of 17 papers met the inclusion criteria for review. In our retrospective study a total of 874 patients were identified of whom 31% were blue-collar workers, 32.8% were white-collar workers, 20.2% were unemployed/housewives, and 16% workers in other occupations. The majority of blue-collar workers were in the construction industry and had maximum exposure to hydrocarbons and exhaust fumes. The aetiology of oral and oropharyngeal SCC is multifactorial and there is no consensus on the role of occupational carcinogens. We showcase our patient cohort and discuss the occupational exposures that appear to make them susceptible to OSCC and OPSCC. Further multicentre studies are required to enable us to understand fully the pathogenesis of oral cancer and help us to inform relevant organisations, the aim being to reduce the incidence of occupation-related cancer.

Mouthwash Use and the Risk of Oral, Pharyngeal, and Laryngeal Cancer. A Meta-Analysis

Objective: The main aim of this study was to test whether the use of mouthwash is associated with subtypes of squamous cell carcinoma of the head and neck (SCCHN) and to test the potential risk of SCCHN depending on the mouthwash use duration, frequency, or alcoholic content. Materials and methods: We performed a meta-analysis using Web of Science and Scopus databases to detect the risk change associated with mouthwash use depending on the alcohol content, duration and frequency of use, and anatomical location. We used a random-effects model with the Sidik–Jonkman estimator for effect size model measures. Results: We included 17 studies in the meta-analysis containing 17,085 cases and 20,032 controls. The risk difference for SCCHN between mouthwash users and non-users was minimal, with a value of −0.02 [−0.05, 0.01]. Alcoholic mouthwash use was associated with a minimal decrease in risk (of −0.01 [−0.07, 0.05]). Frequent usage of mouthwash was associated with a statistically significant risk increase for SCCHN but the risk increase was marginal (0.04, [0.01, 0.06]). Conclusions: Overall, our study failed to show a statistically significant correlation between mouthwash use and the risk of SCCHN. The only statistically significant correlation that we could identify was between frequent usage and SCCHN, potentially caused by prolonged contact between some constituents of mouthwash (possibly alcohol) and the oral epithelium.

Mouth Cancer Awareness in General Population: Results from Grampian Region of Scotland, United Kingdom

Objectives

The purpose of this project was to determine the level of mouth cancer awareness and to investigate the associated factors in a United Kingdom (UK) general population sample.

Material and Methods

Adult Dental Health Survey (2010) was conducted in a sample of 3,353 adult residents in the Grampian region of the UK (adjusted participation rate 58%). Participants completed a questionnaire consisting of questions on oral health, health behaviour, quality of life and cancer awareness.

Results

Overall, 81% of participants were aware of mouth cancer. This was associated with younger age, higher levels of education and better general health. Current smokers and alcohol drinkers were more aware of mouth cancer. When asked about risk factors for mouth cancer, the following were identified by the respondents: smoking (84%), poor oral hygiene (60%), drinking alcohol heavily (59%), poor diet (37%), stress (15%), being overweight (6%), drinking hot liquids (5%), eating spicy food (3%), using mouthwash (2%) and kissing someone (1%). Smokers were more likely to identify smoking as a risk factor for mouth cancer. Similarly, those who consumed alcohol almost daily were more likely to identify heavy alcohol drinking as a risk factor.

Conclusions

Awareness of mouth cancer is high in respondents from the general population, and participants were able to identify the most important risk factors. Knowledge of tobacco and alcohol as risk factors was highest amongst those exposed to them. The study proposed that the prevention strategies should focus not only on increasing knowledge, but also on changing health behaviour.

Role of Poor Oral Hygiene in Causation of Oral Cancer-a Review of Literature

Oral squamous cell carcinomas (OSCC) are among the commonest cancers in South East Asia and more so in the Indian subcontinent. The role of tobacco and alcohol in the causation of these cancers is well-documented. Poor oral hygiene (POH) is often seen to co-exist in patients with OSCC. However, the role of poor oral hygiene in the etio-pathogenesis of these cancers is controversial. We decided to evaluate the available literature for evaluating the association of POH with OSCC. A thorough literature search of English-language articles in MEDLINE, PubMed, Cochrane Database of Systematic Reviews, and Web of Science databases was conducted, and 93 relevant articles were short-listed. We found that POH was strongly associated with oral cancers. It aids the carcinogenic potential of other known carcinogens like tobacco and alcohol. Even on adjusting for known confounding factors like tobacco, alcohol use, education, and socio-economic strata, presence of POH exhibits higher odds of developing oral cancer.

Impact of oral hygiene on head and neck cancer risk in a Chinese population

BACKGROUND

Although the impact of oral hygiene on head and neck cancer risk has been investigated, few studies have been conducted among the Asian population.

METHODS

We conducted a multicenter case-control study to investigate this potential association. We performed unconditional multiple logistic regression models adjusted by potential confounders.

RESULTS

We observed an inverse association of frequency of dental visits with head and neck cancer risk, with an adjusted odds ratio (OR) of 3.70 (95% CI 2.51-5.45) for never dental visits compared with ≥1 time/year (Ptrend < .001). We also observed a positive association between the number of missing teeth and head and neck cancer risk, with an adjusted OR for ≥5 missing teeth compared with <5 missing teeth of 1.49 (95% CI 1.08-2.04). Combining multiple oral hygiene indicators, poor oral hygiene scores increased head and neck cancer risk.

CONCLUSION

Poor oral hygiene may increase head and neck cancer risk in the Chinese population. Therefore, improving oral hygiene may contribute to reducing the head and neck cancer risk in the Chinese population.

The Role of Chronic Mucosal Trauma in Oral Cancer: A Review of Literature

Chronic mucosal trauma resulting from sharp teeth, dentures, faulty restoration, or implants has frequently been associated with the development of oral cancer. The definitive evidence for the same is lacking. We undertook a search using the terms – dental trauma, mucosal trauma, oral cancer, squamous cell carcinoma, risk factor, potentially malignant lesion, dental factor, mechanical irritation, dental irritation, and cancer in the following electronic databases: MEDLINE, PubMed, ScienceDirect, Cochrane Database of Systematic Reviews, and Wiley InterScience. The search yielded 788 articles. Of these articles, only 22 articles described chronic mucosal trauma as risk factors for oral cancers and were considered in this review. The review shows that chronic mucosal irritation resulting from ill-fitting dentures may be considered a risk factor for the development of oral cancer, such cancers occur commonly over the lateral border of the tongue. However, no association has been proven between the duration of denture use and cancer formation. In patients without any addiction, such cancers occur more frequently in females. These cancers may present with an early nodal disease but their prognosis and outcomes have not been studied separately till now.

Smokeless Tobacco Use and the Risk of Head and Neck Cancer: Pooled Analysis of US Studies in the INHANCE Consortium

Previous studies on smokeless tobacco use and head and neck cancer (HNC) have found inconsistent and often imprecise estimates, with limited control for cigarette smoking. Using pooled data from 11 US case-control studies (1981-2006) of oral, pharyngeal, and laryngeal cancers (6,772 cases and 8,375 controls) in the International Head and Neck Cancer Epidemiology (INHANCE) Consortium, we applied hierarchical logistic regression to estimate odds ratios and 95% confidence intervals for ever use, frequency of use, and duration of use of snuff and chewing tobacco separately for never and ever cigarette smokers. Ever use (versus never use) of snuff was strongly associated with HNC among never cigarette smokers (odds ratio (OR) = 1.71, 95% confidence interval (CI): 1.08, 2.70), particularly for oral cavity cancers (OR = 3.01, 95% CI: 1.63, 5.55). Although ever (versus never) tobacco chewing was weakly associated with HNC among never cigarette smokers (OR = 1.20, 95% CI: 0.81, 1.77), analyses restricted to cancers of the oral cavity showed a stronger association (OR = 1.81, 95% CI: 1.04, 3.17). Few or no associations between each type of smokeless tobacco and HNC were observed among ever cigarette smokers, possibly reflecting residual confounding by smoking. Smokeless tobacco use appears to be associated with HNC, especially oral cancers, with snuff being more strongly associated than chewing tobacco.

Reappraisal of the glycerol test in patients with suspected Menière's disease

BACKGROUND

Recent advances in magnetic resonance imaging make it possible to visualize the presumed pathophysiologic correlate of Menière's disease: endolymphatic hydrops. As traditional diagnostic tests can provide only indirect evidence, they are hardly competitive in this respect and need to be rethought. This is done here for the glycerol test.

METHODS

The data of a previous retrospective analysis of the glycerol test in patients with suspected Menière's disease are reinterpreted using a simple model. The mean threshold reduction (MTR) in the frequency range from 125 to 1500 Hz (calculated from audiograms obtained immediately before and four hours after the glycerol intake) is used as the test statistic. The proposed model explains the frequency distribution of the observed MTR by the convolution of a Gaussian probability density function (representing measurement errors) with a template representing the frequency distribution of the true MTR. The latter is defined in terms of two adjustable parameters. After fitting the model to the data, the performance of the test is evaluated using receiver operating characteristic (ROC) analysis.

RESULTS

The cumulative frequency distribution of the observed MTR can be explained almost perfectly by the model. According to the ROC analysis performed, the capability of the currently used audiometric procedure to detect a glycerol-induced threshold reduction corresponds to a diagnostic test of rather high accuracy (area under the ROC curve greater than 0.9). Simulations show that methodological improvements could further enhance the performance.

CONCLUSIONS

Owing to their ability to reveal functional aspects without an obvious morphological correlate, traditional test for Menière's disease could be decisive for defining the stage of the disease. A distinctive feature of the glycerol test is that it is capable of determining, with high accuracy, whether the pathophysiologic condition of the inner ear is partially reversible. Prospectively, this could help to estimate the chances of specific therapies.

Ill-fitting dentures and oral cancer: a meta-analysis

OBJECTIVES

Several studies have investigated the relationship between the use of dentures and the duration of denture use and cancer development. Of particular interest is whether ill-fitting dentures increase the likelihood of the development of oral cancer. We conducted a meta-analysis to determine the relationship between dentures and the development of cancer.

MATERIALS AND METHODS

We searched several databases (PubMed, Medline, EMBASE, Web of Science, and the Cochrane Database of Systematic Reviews) to find published papers on the topic. In particular, the duration of denture use and the comfort and fit of the dentures were investigated.

RESULTS

The use of dentures by itself is associated with an increased risk of developing cancer (OR: 1.42, 95% CI: 1.01-1.99). In addition, ill-fitting dentures appears to substantially increase the risk of developing cancer (OR: 3.90, 95% CI: 2.48-6.13). In addition, there was no link between the duration of denture use and cancer development. This might be due to the arbitrary nature of what we defined as short and long term denture use and may have been affected by the inconsistency in time categorization between different studies.

CONCLUSION

Ill-fitting dentures are a risk factor for the development of oral cancer, greater patient education and regular checking of dentures by dentists should be undertaken as a prevention measure.

Tobacco smoking, alcohol drinking and risk of oral cavity cancer by subsite: results of a French population-based case-control study, the ICARE study

The objective was to examine the role of tobacco smoking and alcohol drinking in the incidence of oral cavity cancer by subsite in France, a high-incidence area. We analysed detailed data on lifelong tobacco smoking and alcohol drinking from 772 oral cavity cancer cases and 3555 controls included in a population-based case-control study, the ICARE study. Tobacco smoking increased the risk of oral cavity cancer even for the smaller quantities and durations, whereas alcohol drinking increased this risk only in heavy drinkers who were also ever smokers. The combined effect of smoking and drinking was greater than multiplicative. The floor of the mouth was the subsite that was the most affected by the harmful effects of tobacco and alcohol, whereas the gums were less susceptible. The risk associated with tobacco and alcohol consumption did not differ between intraoral cavity and subsites usually included in the oropharynx (soft palate and base of the tongue). Population-attributable risks for oral cavity cancer were 78.6% for tobacco smoking, 7.3% for alcohol drinking and 80.7% for tobacco and/or alcohol consumption. These results indicate that regular oral check-ups should be targeted at smokers and heavy drinkers, and that prevention efforts should be focused on smoking cessation.

A review of risk factors for oral cavity cancer: the importance of a standardized case definition

The aim of this work is to review the literature on risk factors of oral cavity cancer with a special attention to the definition of the cases, in order to highlight special features of these cancers and of their subsites. PubMed database was systematically searched to access relevant articles published between 1980 and 2010. Reference lists of selected papers were examined to identify further articles. One hundred and two studies met the inclusion criteria. Their results were difficult to compare because of the lack of uniformity in defining oral cavity. In addition, few studies examined risk factors other than alcohol and tobacco, and studies differentiating between subsites were rare. Despite these limitations, some characteristics of oral cavity cancers may be emphasized: smoked tobacco seems to be a stronger risk factor for oral cavity cancer than alcohol, and the floor of the mouth seems to be more sensitive to the harmful effects of alcohol and smoked tobacco. Studies limited strictly to oral cavity cancers and distinguishing between subsites are needed to better understand the aetiology of these cancers, and better define risk groups to target prevention efforts and screening.

Oral health and risk for head and neck squamous cell carcinoma: the Carolina Head and Neck Cancer Study

OBJECTIVE

Recent reports have linked oral health and periodontal disease indicators with increased risk of squamous cell carcinoma of head and neck (SCCHN). Thus far, evidence has been inconclusive; our objective was to study the association between oral health and SCCHN risk in the context of a large population-based study.

METHODS

A population-based case-control study of incident SCCHN, the Carolina Head and Neck Cancer Study was carried out in 2002-2006 in 46 counties in North Carolina. Controls (n = 1,361) were frequency matched with cases (n = 1,289) on age, race, and gender. Oral health was assessed using interview data on tooth loss and mobility, mouthwash use, and frequency of dental visits.

RESULTS

Subjects were 26-80 years old (median age = 61). The distribution of tooth loss among controls was 0-5 teeth = 60%; 5-14 = 15%; and 16-28 = 25%. After controlling for covariates, tooth loss did not yield any notable association with SCCHN (16-28 vs. 0-5 lost teeth: OR: 1.21, 95% CI: 0.94, 1.56). Self-reported history of tooth mobility was moderately associated with increased SCCHN risk (OR: 1.33, 95% CI: 1.07, 1.65); however, the association did not persist among never smokers. Routine dental visits were associated with 30% risk reduction (OR: 0.68, 95% CI: 0.53, 0.87).

CONCLUSIONS

These data provide support for a possible modest association of periodontal disease, as measured by self-reported tooth loss indicators, but not tooth loss per se, with SCCHN risk.

Causes of oral cancer--an appraisal of controversies

Major risk factors for oral cancer are cigarette smoking and alcohol misuse. Among Asian populations, regular use of betel quid (with or without added tobacco) increases oral cancer risks. Dentists should be aware of some emerging risk factors for oral, and particularly oropharyngeal cancer such as the role of the human papillomavirus infection (HPV). Decreases in risk could be achieved by encouraging high fruit and vegetable consumption. Some controversies related to the aetiology of this disease also need clarification. The objective of this paper is to provide an opinion on these debated controversies.

Reviewed evidence about the safety of the daily use of alcohol-based mouthrinses

Current scientific knowledge provides clear evidence that alcohol-based mouthwashes can be beneficial in a daily oral health routine, including dental hygiene and plaque control. Several issues are worth discussing, in spite of the wealth of supporting evidence. Despite some undesirable effects to some people, like burning sensation, and some contraindications, like the use by infants, alcohol addicts and patients with mucosal injuries, there is no reason to avoid the use of alcohol-containing mouthwashes as long as they are used following proper guidance by dental professionals and the manufacturers' instructions. The alleged correlation between oral cancer and alcohol-based mouthrinses presents so little, weak, inconsistent and even contradictory evidence in the literature that any kind of risk warning to patients would be uncalled for. Antimicrobial mouthrinses are safe and effective in reducing plaque and gingivitis, and should be part of a comprehensive oral health care regimen that includes brushing, flossing and rinsing to prevent or minimize periodontal disease.

Systematic review of the relation between smokeless tobacco and cancer in Europe and North America

BACKGROUND

Interest is rising in smokeless tobacco as a safer alternative to smoking, but published reviews on smokeless tobacco and cancer are limited. We review North American and European studies and compare effects of smokeless tobacco and smoking.

METHODS

We obtained papers from MEDLINE searches, published reviews and secondary references describing epidemiological cohort and case-control studies relating any form of cancer to smokeless tobacco use. For each study, details were abstracted on design, smokeless tobacco exposure, cancers studied, analysis methods and adjustment for smoking and other factors. For each cancer, relative risks or odds ratios with 95% confidence intervals were tabulated. Overall, and also for USA and Scandinavia separately, meta-analyses were conducted using all available estimates, smoking-adjusted estimates, or estimates for never smokers. For seven cancers, smoking-attributable deaths in US men in 2005 were compared with deaths attributable to introducing smokeless tobacco into a population of never-smoking men.

RESULTS

Eighty-nine studies were identified; 62 US and 18 Scandinavian. Forty-six (52%) controlled for smoking. Random-effects meta-analysis estimates for most sites showed little association. Smoking-adjusted estimates were only significant for oropharyngeal cancer (1.36, CI 1.04-1.77, n = 19) and prostate cancer (1.29, 1.07-1.55, n = 4). The oropharyngeal association disappeared for estimates published since 1990 (1.00, 0.83-1.20, n = 14), for Scandinavia (0.97, 0.68-1.37, n = 7), and for alcohol-adjusted estimates (1.07, 0.84-1.37, n = 10). Any effect of current US products or Scandinavian snuff seems very limited. The prostate cancer data are inadequate for a clear conclusion.Some meta-analyses suggest a possible effect for oesophagus, pancreas, larynx and kidney cancer, but other cancers show no effect of smokeless tobacco. Any possible effects are not evident in Scandinavia. Of 142,205 smoking-related male US cancer deaths in 2005, 104,737 are smoking-attributable. Smokeless tobacco-attributable deaths would be 1,102 (1.1%) if as many used smokeless tobacco as had smoked, and 2,081 (2.0%) if everyone used smokeless tobacco.

CONCLUSION

An increased risk of oropharyngeal cancer is evident most clearly for past smokeless tobacco use in the USA, but not for Scandinavian snuff. Effects of smokeless tobacco use on other cancers are not clearly demonstrated. Risk from modern products is much less than for smoking.

Mechanical factors activate beta-catenin-dependent oncogene expression in APC mouse colon

beta-catenin acts as a critical regulator of gastrointestinal homeostasis through its control of the Wnt signaling pathway, and genetic or epigenetic lesions which activate Wnt signaling are the primary feature of colon cancer. beta-catenin is also a key element of mechanotranscription pathways, leading to upregulation of master developmental gene expression during Drosophila gastrulation, or regulating mammalian bone development and maintenance. Here we investigate the impact of mechanical stimulation on the initiation of colon cancer. Myc and Twist1, two oncogenes regulated through beta-catenin, are expressed in response to transient compression in APC deficient (APC(1638N+)) colon tissue explants, but not in wild-type colon explants. Mechanical stimulation of APC(1638N+) tissue leads to the phosphorylation of beta-catenin at tyrosine 654, the site of interaction with E-cadherin, as well as to increased nuclear localization of beta-catenin. The mechanical activation of Myc and Twist1 expression in APC(1638N+) colon can be prevented by blocking beta-catenin phosphorylation using Src kinase inhibitors. Microenvironmental signals are known to cooperate with genetic lesions to promote the nuclear beta-catenin accumulation which drives colon cancer. Here we demonstrate that when APC is limiting, mechanical strain, such as that associated with intestinal transit or tumor growth, can be interpreted by cells of preneoplastic colon tissue as a signal to initiate a beta-catenin dependent transcriptional program characteristic of cancer.

Treatment outcome of combined modalities for buccal cancers: unilateral or bilateral neck radiation?

PURPOSE

To evaluate the outcome of treatment for buccal cancers and assess the impact of unilateral vs. bilateral adjuvant neck radiation.

METHODS AND MATERIALS

We retrospectively reviewed the course of 145 patients newly diagnosed with buccal squamous cell carcinoma without distant metastases who completed definitive treatment between January 1994 and December 2000. Of 145 patients, 112 (77%) had Stage III or IV disease. All underwent radical surgery with postoperative radiotherapy (median dose, 64 Gy), including unilateral neck treatment in most (n = 120, 82.8%). After 1997, cisplatin-based concomitant chemoradiotherapy was given for high-risk patients with more than two involved lymph nodes, extracapsular spread, and/or positive margins.

RESULTS

The 5-year disease-specific survival rate for Stages I-IV was 87%, 83%, 61%, and 60%, respectively (p = 0.01). The most significant prognostic factor was N stage, with the 5-year disease-specific survival rate for N0, N1, and N2 being 79%, 65%, and 54%, respectively (p = 0.001). For patients with more than two lymph nodes or positive extracapsular spread, cisplatin-based concomitant chemoradiotherapy improved locoregional control (p = 0.02). Locoregional control did not differ between patients undergoing unilateral or bilateral neck treatments (p = 0.95). Contralateral neck failure occurred in only 2.1%.

CONCLUSIONS

In patients with buccal carcinoma after radical resection, ipsilateral neck radiation is adequate. Bilateral prophylactic neck treatment does not confer an added benefit.

Meta-analysis of the relation between European and American smokeless tobacco and oral cancer

BACKGROUND

Smokeless tobacco is often referred to as a major contributor to oral cancer. In some regions, especially Southeast Asia, the risk is difficult to quantify due to the variety of products, compositions (including non-tobacco ingredients) and usage practices involved. In Western populations, the evidence of an increased risk in smokeless tobacco users seems unclear, previous reviews having reached somewhat differing conclusions. We report a detailed quantitative review of the evidence in American and European smokeless tobacco users, and compare our findings with previous reviews and meta-analyses.

METHODS

Following literature review a meta-analysis was conducted of 32 epidemiological studies published between 1920 and 2005 including tests for homogeneity and publication bias.

RESULTS

Based on 38 heterogeneous study-specific estimates of the odds ratio or relative risk for smokeless tobacco use, the random-effects estimate was 1.87 (95% confidence interval 1.40-2.48). The increase was mainly evident in studies conducted before 1980. No increase was seen in studies in Scandinavia. Restricting attention to the seven estimates adjusted for smoking and alcohol eliminated both heterogeneity and excess risk (1.02; 0.82-1.28). Estimates also varied by sex (higher in females) and by study design (higher in case-control studies with hospital controls) but more clearly in studies where estimates were unadjusted, even for age. The pattern of estimates suggests some publication bias. Based on limited data specific to never smokers, the random-effects estimate was 1.94 (0.88-4.28), the eight individual estimates being heterogeneous and based on few exposed cases.

CONCLUSION

Smokeless tobacco, as used in America or Europe, carries at most a minor increased risk of oral cancer. However, elevated risks in specific populations or from specific products cannot definitely be excluded.

Mouthrinses containing alcohol and oral cancer: revision of epidemiological studies

The strong association between alcohol usage and the development of oral cancer (OC) has been reported in numerous papers. As some mouthrinses contain significant amounts of ethanol, a possible relationship to this pathology has been considered. The purpose of the present paper is to analyze several epidemiological studies which evaluated the association between commercial mouthrinses and the etiology of OC. Although some authors report an association, most of the studies are unclear and sometimes contradictory. The controversial aspects regarding the role of alcohol in OC may also make difficult to find a clear relationship between the use of mouthrinses containing alcohol and OC.

Cancer incidence among a cohort of smokeless tobacco users (United States)

OBJECTIVE

Smokeless tobacco (ST) use remains a prevalent form of tobacco use among certain US populations. The purpose of this paper is to clarify its role in cancer development.

METHODS

Using data from a prospective cohort of the US population, we categorized 6,779 subjects 45-75 years of age as ST users or non-ST users. Subjects were further stratified by cigarette smoking status in order to differentiate 'exclusive' ST users (n=414) from never tobacco users (n=2,979).

RESULTS

In this cohort, exclusive ST use was not associated with increased incidence of all cancer in males (hazard ratio=0.8, 95% CI: 0.4, 1.6) or females (HR=1.2, 95% CI: 0.7-2.1) or oral cancer (standardized incidence ratio=30, 95% CI: 3, 95). No synergistic effect was observed between ST and cigarette smoking among male combined users (females were not analyzed for combined use) for the major cancers.

CONCLUSIONS

In contrast to the well-known deleterious effects of cigarette smoking, ST use did not substantially increase the risk for cancer incidence above that of non-tobacco users, particularly among males. Although the use of tobacco in any form is to be discouraged, our data suggests that cancer risks are much lower from ST use than from cigarette smoking.

Influence of alcohol in mouthwashes containing triclosan and zinc: an experimental gingivitis study

OBJECTIVES

An experimental gingivitis model was used to analyse the influence of alcohol in mouthwashes containing 0.15% triclosan and zinc chloride on the formation of supragingival plaque, the development of gingivitis and the appearance of adverse events.

MATERIAL AND METHODS

Using a double-blind crossover design, 30 subjects underwent two consecutive experimental phases with two 0.15% triclosan and zinc chloride mouthwashes, differentiated mainly by their excipient (hydroalcoholic or aqueous). In each phase, the subjects discontinued all oral hygiene measures and were treated solely with the randomly assigned experimental mouthwash for 21 days. Each experimental phase was preceded by a 14-day washout period in which, after receiving a complete oral prophylaxis, the subjects were instructed to perform thorough oral hygiene procedures. Gingivitis and plaque levels were assessed at the start and end of both the experimental phases.

RESULTS

The evolution of the gingivitis and plaque indices showed no statistically significant differences between both treatments. The mean gingival index increased from 0.30 to 0.38 with the non-alcoholic mouthwash and from 0.32 to 0.42 with the hydroalcoholic mouthwash. The respective changes in plaque index were from 0.88 to 1.93 and from 0.94 to 1.92. The hydroalcoholic mouthwash produced a larger number of fresh symptoms (p=0.033), oral itching being the most reported.

CONCLUSIONS

Alcohol does not influence the effectiveness of a 0.15% triclosan and zinc chloride mouthwash against gingivitis development and supragingival plaque formation. The absence of alcohol significantly decreases the incidence of adverse events produced by the mouthwash.

Overview of smoking and all cancers

Tobacco consumption has been clearly implicated in the causation of many cancer types, with irrefutable evidence to support the association in multiple organ systems. Tobacco cessation leads to reduced cancer risk and improved survival of those under treatment for their already established cancers. As understanding of the mechanisms by which tobacco products cause cancer increases, clinicians may be able to identify those at highest risk for tobacco-related malignancies and allow for more focused interventions toward risk reduction among current tobacco users. This article reviews the carcinogens present in tobacco products, the mechanisms by which tobacco causes cancer, and the various tumor types causally related to tobacco use.

Alcohol-containing mouthwash and oropharyngeal cancer: a review of the epidemiology

BACKGROUND

There has been concern that the use of alcohol-containing mouthwash may increase the risk of developing oropharyngeal cancer, or OPC. The authors examine the epidemiologic literature relating to this issue.

TYPES OF STUDIES REVIEWED

The authors identified all nine English-language epidemiologic studies of OPC that made reference to mouthwash. The findings and major strengths and limitations of each study are described. In addition, the authors reanalyzed data from one of the studies.

RESULTS

The results of six of the studies reviewed are negative and provide no support for the hypothesis that use of alcohol-containing mouthwash increases the risk of OPC. One of the three studies with positive results was a case series and included a follow-up case-control study, the results of which were negative. The authors reanalyzed the study with the most positive results. This analysis found that the study results were just as positive for nonmucosal cancers developing in the mouth as they were for the usual type of OPC. The authors concluded that this study's positive finding resulted from recall bias.

CLINICAL IMPLICATIONS

It is unlikely that the use of mouthwashes that contain alcohol increases the risk of developing OPC.

Mutation induction by mechanical irritation caused by uracil-induced urolithiasis in Big Blue rats

Some chronic mechanical irritations induce cancers, and it is speculated that mutations are induced by increased rate of cell proliferation caused by the irritation. In this study, it was investigated using chronic mechanical irritation to urothelium caused by urolithiasis, whether mutations are really induced by such cell proliferation or not. Male rats transgenic for lacI (Big Blue(R) rats), in which lacI mutations accumulated in tissue can be measured, were fed 3% uracil, a component of RNA, to induce urolithiasis associated with papillomatosis, and eventually with bladder cancers. The frequency of independent mutations in the bladders of the treated rats showed 3-5 fold increases at weeks 10, 20, and 51 (P=0.01 at week 51) while the frequency was not elevated at week 2. The mutation frequencies in the control bladders ranged from 3 to 9x10(-6). In both groups, G to A transitions at CpG sites, indicative of spontaneous mutations, constituted the most prevalent mutations. Mechanical irritation caused by uracil was shown to induce a 3-5 fold increase of mutations, possibly through an elevation of spontaneous mutations by vigorous cell proliferation.

Dental factors in the genesis of squamous cell carcinoma of the oral cavity

This study investigated the role of dental factors in the genesis of squamous cell carcinomas of the oral cavity. 99 newly diagnosed patients with advanced head and neck cancer were evaluated for potential demographic, dental and prosthetic risk factors. Patients with extra-oral malignancies were used as controls in the analysis of dental factors in patients with intra-oral cancers. We performed multiple comparisons of these factors against the primary tumour sites. An analysis of dental and prosthetic factors and patients with intra-oral versus extra-oral tumours revealed no significant differences. However, all 28 intra-oral malignancies arose in areas in contact with teeth and/or appliances. For example, all 10 oral tongue lesions arose on the lateral borders and all six floor of (drop) mouth primary tumours developed at the flange extension of a lower denture. Patients with partial or full dentures had significantly lower node (N) scores than patients without a prosthesis. Although this paper suggests a relationship between dental factors and the genesis of oral squamous cell malignancies, a larger prospective study would be required to achieve definitive data. Patients at risk should be followed carefully for the development of chronic irritation from teeth and appliances.

Electrocochleographic evaluation of the guinea pig model of endolymphatic hydrops

Electrocochleography (ECochG) was used to evaluate cochlear function in guinea pigs with experimentally induced endolymphatic hydrops (ELH) before and after osmotic dehydration with either glycerol or urea. We surgically induced ELH in the right ears of 9 guinea pigs, while the right ears of 6 guinea pigs received a sham operation. The left ears of the 15 animals constituted the normal group. Eight weeks after surgery, summating potential (SP) and action potential (AP) amplitudes were measured prior to and following the administration of glycerol or urea. The SPs and SP/AP ratios were reduced in all groups, with no significant differences among groups or between dehydrating agents. Some of the hydropic ears, however, did show an increased AP threshold and a recruitment effect. In measurements from 6 additional animals, serum osmolarity increased more with urea than with glycerol. The guinea pig model remains valuable for investigation of ELH, even though it differs in significant respects from ELH in humans.

Mouthwash use and dentures in relation to oral epithelial dysplasia

This case-control study investigated the potential association between oral epithelial dysplasia (OED) and both mouthwash and denture use. Incident OED cases aged 20-79 years were identified through two oral pathology laboratories. Controls were pair-matched (1:1) to cases on age (+/- 5 years), gender, appointment date and surgeon. A telephone interview was used to obtain exposure information. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were generated using conditional logistic regression. Based upon 127 case-control pairs and after adjusting for smoking, drinking, education and either denture or mouthwash use, the OR for OED and regular mouthwash use (1+ uses/week for 6+ months) was 0.8 (95% CI, 0.4-1.5) while the OR for OED and wearing a denture was 0.7 (95% CI, 0.4-1.3). There were no clear trends of increased OED risk with increased mouthwash use or years of denture wearing. Our findings suggest that neither mouthwash nor denture use are associated positively with OED risk.

Oral cancer and mouthwash use: evaluation of the epidemiologic evidence

BACKGROUND

An association between mouthwash use and cancer of the oropharynx has been the focus of many epidemiologic studies.

PURPOSE

To critically review the methodology of studies of this association.

METHODS

Studies were identified through a computerized MEDLINE search of English-language publications from 1976 to 1994. Eligible studies were independently reviewed, and specific criteria were applied to assess issues in the design, analysis, and results of the studies. Methodologic criteria were used that define a case-control study of acceptable epidemiologic quality: (1) histologic confirmation of cancer; (2) use of incident cases; (3) population-based cases; (4) equal exclusions of controls; (5) population-based controls; (6) exposure to mouthwash use before the cancer diagnosis; and (7) adjustments or restrictions for tobacco, alcohol, or both.

RESULTS

Seven case-control studies were identified. The odds ratios for these studies ranged from a protective effect (0.82 for any use of mouthwash) to an elevation in risk (2.5 at the highest exposure). Two studies had significant unadjusted odds ratios for the risk of oral cancer. Of the three studies with data on women adjusted for tobacco and alcohol use, one was statistically significant, and none of the three similar studies in men was significant (although one was close). The five studies with data on female nonsmokers, nondrinkers, or both had odds ratios ranging from 1.1 to 3.16 (only one study was significant at the p = 0.05 level), and the four studies with similar data on men were not significant. Two studies met only two of the methodologic criteria, three studies met three, one met four, and one met all seven.

CONCLUSIONS

Few of the available studies on mouthwash use and risk of subsequent oropharynx cancer adhere to basic methodologic principles of case-control design. Neither the data for the overall association nor the analysis in patients without other clinical risk factors support a link between mouthwash use and oral cancer.

A preliminary investigation of an association between dental restorations and carcinoma of the tongue

The potential association of dental restorations and tongue carcinoma was studied. We reviewed the available pretreatment dental records of 133 patients with carcinoma of the tongue seen at the British Columbia Cancer Agency between 1958 and 1992. 75 patients had teeth adjacent to the ipsilateral side of the cancer (involved side) and the contralateral (control) side of the tongue, resulting in 150 tongue/teeth pairings. Overall there was no significant association between the presence of dental fillings and tongue carcinoma, as the prevalence of bilateral dental restorations was high. Dental restorations were found in 6 patients on the involved side only. Only 1 patient developed a cancer adjacent to normal teeth with contralateral restorations. We feel that this observation merits more study. Meanwhile, careful assessment of dentition and aggressive treatment of dysplastic lesions are warranted.

Mutagenicity of ethanolic extracts of used acrylic dentures

The in vivo physicochemical sorption of mutagenic substances onto acrylic polymers was investigated in worn acrylic dentures. Thus, ethanolic extracts of acrylic dentures from 41 of a total of 69 human donors (60%), were found mutagenic in the standard plate incorporation Salmonella mutagenicity test against either TA98 or TA100 strains. Denture extracts from smokers produced mutagenicity more often than the ones from non-smokers (75% vs. 45%, P 0.01). Mutagenicity was preferentially directed against TA98 (TA98:TA100 = 2.9:1, P < 0.0005). Predilection for TA98 was more pronounced in denture extracts from non-smokers (4.7:1) than from smokers (2.0:1). When direct mutagenicity was observed, it was reduced by the rat-liver S9. Induced mutant yields were 6.1 +/- 3.9 and 7.0 +/- 8.9 times higher than the spontaneous for TA98 and TA100 respectively (smokers, 50-cm2 denture surface area eq./plate+S9). Denture extracts from smokers induced higher levels of mutation than the ones from non-smokers (TA98 + S9, smoker:non-smoker = 2:1, P < 0.01). Mutagenicity was associated with longer periods of denture usage (P 0.007). Thus, denture poly(methyl methacrylate) base material can adsorb mutagenic substances, possibly from diet and tobacco, which are extractable by ethanol. Theoretically, the in situ alcoholic desorption and recirculation of carcinogenic mutagens may have a contributory role in certain cases of intra-oral and upper alimentary tract carcinogenesis.

Analysis of the relationship between smokeless tobacco and cancer based on data from the National Mortality Followback Survey

This study investigates the potential link between the use of smokeless tobacco and oral cancer and cancer of digestive organs. The combined data of the National Mortality Followback Survey (NMFS), a probability sample of the U.S. deaths, and the coincident National Health Interview Survey (NHIS), a probability sample of the living, non-institutionalized U.S. population, are used to compute risk estimates for cancer, oral cancer, and cancer of the digestive organs associated with use of smokeless tobacco based on a cross sectional study design, simultaneously controlled for potential confounding from active smoking, alcohol consumption, and occupational exposure. Use of smokeless tobacco (either as snuff or chewing tobacco) does not increase the risk of oral cancer or cancer of the digestive organs. Alcohol emerges as a major risk factor for oral cancer with a strong dose-response relationship between the amount of drinking and risk. The same is true to a lesser extent for cancer of the digestive organs. Smoking is associated with increased risk of oral cancer but not of cancer of the digestive organs. Blue collar, technical, and service workers have significantly increased risk of cancer of the digestive organs relative to professional, managerial, and clerical workers, but not of oral cancer. Differences between findings based on the NMFS/NHIS and those obtained from other data very likely are due to inadequate control for confounding. Other reasons for differences between the NMFS/NHIS data and other studies are discussed.

Risk factors for oral cancer in Brazil: a case-control study

A case-control study of risk factors for carcinomas of the tongue, gum, floor, and other specified parts of the mouth was conducted in 3 metropolitan areas in Brazil: São Paulo (southeast), Curitiba (south), and Goiânia (central-west). We analyzed information on demographics, occupational history, environmental exposures, tobacco smoking and alcohol drinking habits, as well as diet, oral and other health characteristics obtained from interviews with 232 cases and 464 hospital non-cancer controls matched for 5-year age-group, sex, hospital catchment area and trimester of admission. Tobacco and alcohol consumption were the strongest risk factors irrespective of the anatomical site. The adjusted relative risks (RR) for ever vs. never smokers were: 6.3, 13.9, and 7.0, for industrial-brand cigarettes, pipe, and hand-rolled cigarettes, respectively. A strong correlation was seen between number of pack-years and risk. The RR for the heaviest vs. the lowest consumption categories (greater than 100 vs. less than 1 pack-years) was 14.8. Risk levels generally decreased to those of never smokers after 10 years had elapsed since stopping smoking. The risk associated with alcohol was mostly evident for wine (cancer of the tongue) and "cachaça" (all sites), a hard liquor distilled from sugar cane. Other important risk factors were drinking "chimarrão" (a type of maté), use of a wood stove for cooking, and frequent consumption of charcoal-grilled meat and manioc. Oral hygiene characteristics represented correlates of disease risk. A significant protective effect was observed for consumption of carotene-rich vegetables and citric fruits, but not for green vegetables in general.

Morphologic effects of glycerol and urea on cochlear tissues of the chinchilla

Glycerol and urea are used as test agents in confirming the diagnosis of endolymphatic hydrops. Although both substances act as osmotic diuretics, recent evidence suggests that they may have differing physiologic effects on the inner ear. This study was designed to compare the morphologic effects of urea and glycerol on cochlear tissues, using the chinchilla as an experimental model. Animals were given subcutaneous injections of glycerol (2 g/kg) or urea (1.2 g/kg) over periods of 3 hours, 4 days, or 1 week. Both agents were found to produce ultrastructural changes, including spiral ligament vacuolization, intracellular alterations of the stria vascularis, and increased numbers of Hensen's bodies in outer hair cells. These alterations appeared indicative of metabolic stress, but not toxicity. The morphologic findings provided no evidence that glycerol and urea affect the inner ear by fundamentally different mechanisms of action.