The utility of toluidine blue application as a diagnostic aid in patients previously treated for upper oropharyngeal carcinoma

The Use of Fluorescent Markers to Detect and Delineate Head and Neck Cancer: A Scoping Review

OBJECTIVES

The aim of surgery for head and neck squamous cell carcinoma (HNSCC) is to achieve clear resection margins, whilst preserving function and cosmesis. Fluorescent markers have demonstrated potential in the intraoperative visualisation and delineation of tumours, such as glioma, with consequent improvements in resection. The purpose of this scoping review was to identify and compare the fluorescent markers that have been used to detect and delineate HNSCC to date.

METHODS

A literature search was performed using the Ovid MEDLINE, Ovid Embase, Cochrane CENTRAL, ClinicalTrials.gov and ICTRP databases. Primary human studies published through September 2023 demonstrating the use of fluorescent markers to visualise HNSCC were selected and reviewed independently by two authors.

RESULTS

The search strategy identified 5776 records. Two hundred and forty-four full texts were reviewed, and sixty-five eligible reports were included. The most used fluorescent markers in the included studies were indocyanine green (ICG) (n = 14), toluidine blue (n = 11), antibodies labelled with IRDye800CW (n = 10) and 5-aminolevulinic acid (5-ALA) (n = 8). Toluidine blue and ICG both have limited specificity, although novel targeted options derived from ICG may be more effective. 5-ALA has been demonstrated as a topical marker and, recently, via enteral administration but it is associated with photosensitivity reactions. The fluorescently labelled antibodies cetuximab-IRDye800CW and panitumumab-IRDye800CW are promising options being investigated by ongoing trials.

CONCLUSION

Multiple safe fluorescent markers have emerged which may aid the surgical resection of HNSCC. Further research in larger cohorts is required to identify which marker should be considered gold standard.

Diagnostic Accuracy of Toluidine Blue Electrospun in Detecting Oral Potentially Malignant Disorders

OBJECTIVE

Oral potentially malignant disorders (OPMDs) with epithelial dysplasia can progress to oral squamous cell carcinoma (OSCC). Toluidine blue (TB) has been used in oral screening with various methods. This study aimed to evaluate the sensitivity and specificity of TB-containing electrospun fibers in detecting OPMDs with epithelial dysplasia compared to histopathology.

METHODS

The concentrations of polyvinylpyrrolidone (PVP) and TB were optimized for fiber diameter and puncture strength using the design of experiments method with a central composite design. These optimized fibers were tested on 36 suspected OPMD lesions in 30 patients, followed by a biopsy for histopathological examination.

RESULTS

The quadratic and two-factor interaction models described the relationship between TB and PVP concentrations and fiber characteristics. The TB-containing electrospun fibers had 77.3% sensitivity and 35.7% specificity in detecting OPMDs with epithelial dysplasia.

CONCLUSION

The TB-containing electrospun fibers offer advantages such as easy application, cost-effectiveness, and enhanced sensitivity in identifying OPMDs with epithelial dysplasia. However, their diagnostic accuracy is insufficient as a standalone diagnostic method, and they should be considered an adjunctive tool for detecting dysplastic changes in the oral epithelium.

TRIAL REGISTRATION

Thailand Clinical Trials Registry: TCTR20240429002.

Toluidine blue O demethylated photoproducts as type II photosensitizers

Toluidine blue O (TBO) is a type I-type II photosensitizer that has shown good efficacy and selectivity in antimicrobial and anticancer photodynamic therapy applications. However, its complex photochemistry with multiple photoproducts hinders its application as a photosensitizer. We have previously described the mechanism for photooxidative demethylation of TBO which in acetonitrile yields two main products: demethylated-TBO (d-TBO) and double-demethylated-TBO (dd-TBO). In the current work, we describe the photophysical properties of these two photoproducts. In acetonitrile and phosphate buffer, demethylation induces an hypsochromic shift in the absorption and fluorescence emission maxima. Fluorescence quantum yields increase slightly for the demethylated photoproducts, in agreement with the lengthening of the fluorescence lifetimes. Triplet excited states lifetimes in the presence of oxygen decreased slightly upon demethylation. However, the singlet oxygen quantum yield increased significantly reaching unity for the dd-TBO photoproduct. These results are interpreted in terms of the competing pathways of TBO photochemistry. For TBO, demethylation is the main pathway for deactivation of the excited state, while for d-TBO, demethylation and singlet oxygen generation are significant. For dd-TBO, singlet oxygen generation is the main deactivation pathway. Overall, TBO demethylated photoproducts demonstrate good potential as candidates for photodynamic therapy applications.

Toluidine Blue Stain as a Rapid Onsite Tool for Preliminary Diagnosis in Imprint Smears of Bronchoscopic Biopsy: A Cytohistopathological Correlation

Introduction  Lung cancer is currently the most common cause of cancer-related mortality, with 11.4% of cancers and 18% of cancer-related deaths worldwide whereas Indian figures are 6.9 and 9.3%, respectively. Hence, the need for early diagnosis. Bronchial biopsy has the highest sensitivity among all the samples that can be obtained by bronchoscopic techniques in case of endobronchial lesions. Imprint cytology has emerged as an important cytological method. Toluidine blue has been studied for its use as rapid onsite stain for cytological evaluation on various samples of cytology in different anatomic sites. This has helped in quick and less expensive, preliminary reporting. Objectives  This article aims to assess the efficacy of onsite toluidine blue stain on imprint smears of bronchoscopic biopsies to diagnose malignancy in suspected cases of lung carcinoma. Study Type  Prospective study on accuracy of a diagnostic test. Materials and Methods  A total of 100 cases of bronchoscopy were included in the study. The patients were clinico-radiologically suspected to have brochogenic carcinoma and all of them were subjected to biopsy. Imprint smears were prepared from the bronchoscopy biopsy specimens. Smears were stained onsite with toluidine blue stain, and histopathology sections were stained with hematoxylin and eosin, also confirmed by immunohistochemistry. Results  Sensitivity and specificity of onsite toluidine blue stain for malignancy reporting were 97.9 and 80%, respectively, when compared to histopathology as standard. Conclusion  Toluidine blue can be used as an onsite staining method on imprint smears of bronchoscopic biopsy for preliminary detection of lung malignancy.

An innovative fluorometric bioanalysis strategy towards recognition of DNA methylation using opto-active polymer: A new platform for DNA damage studies by genosensor technology

Efficient pharmacotherapy of cancer is related to accurate recognition of genetic mutations and epigenetic alterations in the early-stage diagnosis. In the present study, a novel optical genosensor based on toluidine blue as photonic probe was developed to detection of DNA methylation using hybridization of pDNA with cDNA. Biomedical analysis was performed using UV-vis and fluorometric methods. For the first time, this strategy was applied for the distinction of methylated DNA from unmethylated-DNA-based on the interaction of optical probe with methylated-DNA and unmethylated DNA. Fluorescence spectroscopic data showed that poly-toluidine blue could be bind to DNA sequences and lead to different fluorescence patterns and could be used as an efficient geno-platform for the sensitive bioassay of mutation. The excitation and emission wavelengths were 580 and 630 nm, respectively. Non-binding of mismatch sequences with the optical probe was used as negative control. Under optimal conditions, linear range was 1 zM to 0.2 pm and the lower limit of quantitation was obtained as target concentrations ranging 1 zM. The designed genosensor showed high capability to distinct methylation from un-methylated. Therefore, the designed DNA-based bioassay could detect DNA methylation significantly. Finally, bioanalysis of real samples showed that the designed genosensor could use to detect DNA methylation which is a new platform for point of care analysis.

Evaluation of the Role of Toluidine Blue Paint as an Adjunctive Method to Biopsy in Suspicious Oral Lesion: A Hospital Based Study

Early detection is a major step in the success of cancer therapy. Histopathology report is considered as the gold standard in the formulation of management protocol of any malignancy worldwide. But unfortunately, there is a delay in the detection of oral cancer very often due to inconclusive histopathology reports. The main reason behind it is obtaining a biopsy specimen from the non-representative area of the lesion. A hospital-based evaluation of the role of Toluidine Blue dye, used as an adjunctive method prior to biopsy was conducted in a tertiary care hospital on 200 patients presenting with oral lesions persistent for more than 3 weeks. The participants were divided into two equal groups by alternate sampling. In one group biopsy was taken by clinical judgment and in others, Toluidine Blue was used prior to obtaining a biopsy to decide the area to be biopsied. Data was collected using a predesigned proforma and was analyzed with the help of SPSS version 20. Results in two groups were compared with respect to sensitivity, specificity, positive and negative predictive values, false positive and false negative percentages. The Sensitivity, Specificity, Positive Predictive Value and Negative Predictive Value of wedge biopsy without staining were 73.68, 58.14, 70.00, and 62.50% respectively. These values were 95.08, 82.05, 89.23, and 91.43% respectively when Toluidine Blue staining was done as an adjunctive before the biopsy procedure. These results indicate the promising role of Toluidine blue staining before the biopsy to diagnose oral malignancy more efficiently than obtaining biopsy specimens on clinical assessment only and in avoiding the delay in initiating the treatment in case of oral malignant lesions.

A Prospective Study to Evaluate the Role of Narrow Band Imaging and Toludine Blue in the Screening of Premalignant and Malignant Lesions of the Oral Cavity in a Tertiary Referral Centre

In India cancer patients come at a very advanced stage with many of them being crossed the stage of resection. A wide range of non invasive techniques like toludine blue staining, methylene blue staining, Narrow band imaging have been developed for the early detection of malignant and premalignant lesions in the mucosa including oral cavity and gastrointestinal tract. However it is difficult for the clinicians to decide which diagnostic tool is most appropriate and useful for screening, resulting in failure to pick up the lesions at an early stage. Various online journals have been reviewed and no journal was found to support this point. This study here by describes Toludine blue and narrow-band imaging (NBI), diagnostic tools already proven independently as a useful screening method in many fields, and demonstrate its usefulness in the early detection of premalignant and malignant lesions of the oral cavity, as reported by previous studies in the otolaryngologic literature and compare both screening tools which has not been done till now. This study was done in a tertiary referral centre in middle India from March 2018 to August 2019 in order to evaluate the role of different screening tools (NBI and Toludine blue).44 patients with suspicious oral cavity lesions (premalignant and malignant) who had given consent for both NBI and toludine blue screening techniques were selected from the suspected (premalignant and malignant lesions) who had visited the OPD during the study period. Patients with proven malignancy were excluded from the study. A detailed history of the patient taken and standard Ear, nose, throat, oral cavity and neck examination of patient carried out. After subjecting the patients to screening tools like NBI and toludine blue, the efficacy of these techniques in helping us to take a representative biopsy was evaluated. In present study the sensitivity (to correctly identify all patients with disease), specificity (to correctly reject healthy patients without disease) of older technique toludine blue in detecting premalignant lesion was 66.6%, 87.8% while for NBI was 66.6%, 95%. For malignant lesion sensitivity and specificity of toludine blue was 94.3%, 100%, while the same for NBI was 100%, 88.8% respectively. Both NBI and toludine blue staining can be adopted for screening and the accurate detection of biopsy site and in the follow up of premalignant lesions to look for malignant transformation. Time tested is Toludine blue which is cheap and easily available. But being a better tool and having an upper hand in evaluating the lesions, NBI should be made available in all the secondary and tertiary care centres as a screening method.

A Systematic Review of Oral Biopsies, Sample Types, and Detection Techniques Applied in Relation to Oral Cancer Detection

Background: Early identification of the stage of oral cancer development can lead to better treatment outcomes and avoid malignant transformation. Therefore, this review aims to provide a comprehensive overview that describes the development of standardized procedures for oral sample collection, characterization, and molecular risk assessment. This can help investigators to choose the appropriate sampling method and downstream analyses for different purposes. Methods: This systematic review was conducted according to the PRISMA guidelines. Using both PubMed and Web of Science databases, four independent authors conducted a literature search between 15 and 21 June 2021. We used key search terms to broaden the search for studies. Non-conforming articles were removed using an EndNote-based and manual approach. Reviewers used a designed form to extract data. Results: This review included a total of 3574 records, after eliminating duplicate articles and excluding papers that did not meet the inclusion criteria. Finally, 202 articles were included in this review. We summarized the sampling methods, biopsy samples, and downstream analysis. The biopsy techniques were classified into tissue and liquid biopsy. The common sequential analysis of tissue biopsy includes histopathological examination such as H&E or IHC to identify various pathogenic features. Meanwhile, liquid samples such as saliva, blood, and urine are analyzed for the purpose of screening to detect mutations in cancer. Commonly used technologies are PCR, RT-PCR, high-throughput sequencing, and metabolomic analysis. Conclusions: Currently, tissue biopsies provide increased diagnostic value compared to liquid biopsy. However, the minimal invasiveness and convenience of liquid biopsy make it a suitable method for mass screening and eventual clinical adoption. The analysis of samples includes histological and molecular analysis. Metabolite analysis is rising but remains scarce.

Photodynamic therapy for treatment of bacterial keratitis

Microbial keratitis is the main cause of corneal opacification and the fourth leading cause of blindness worldwide, with bacteria the major infectious agent. Recently, bacterial keratitis has become a serious threat due to routine use of antibiotics leading to selection of resistant and multidrug-resistant bacteria strains. New approaches for treatment of bacterial keratitis are necessary to outcome the increasing antibiotic resistance. Antimicrobial photodynamic therapy is based on three agents: photosensitizer, oxygen, and light radiation. This therapy has been successful for treatment of infections in different tissues and organs as well as against different type of infectious agents and no resistance development. Also, new photosensitizers are being developed that has increased the spectrum of therapeutic protocols for treatment of a number of infectious diseases. Thus, antimicrobial photodynamic therapy has an extraordinary potential for treatment of those bacterial keratitis cases that actually are not solved by traditional antibiotic therapy.

Validity of Toluidine Blue test as a diagnostic tool for high risk oral potentially malignant disorders- a multicentre study in Sri Lanka

Introduction

- Early detection plays a major role to reduce the mortality of oral squamous cell carcinoma (OSCC). Many adjunctive techniques have emerged with claims of differentiating high risk oral potentially malignant disorders (OPMDs) from benign lesions. Toluidine blue (TB) test has been established as a diagnostic adjunct in detecting high risk OPMDs and early asymptomatic OSCCs. As majority of OSCC are preceded by OPMDs, recognition of them at an early stage is important in the management of this devastating disease.

Methods

-This study was conducted as a multi-center study prospectively for a period of 2 years. Sixty five patients presented with OPMDs were selected and TB test was performed followed by a biopsy for histopathological confirmation. Criterion validity was assessed with histological diagnosis of the incisional biopsy of the OPMD as a gold standard test verses TB test results.

Results

The sensitivity of the TB test was 68.3% and the specificity 63.1% with a false positive rate of 36.8% and false negative rate of 31.7%. However, the predictive value of the positive test was 80%.

Conclusion

- TB testing might be a potential adjunct diagnostic aid in identifying high risk OPMDs. Further studies with extensive sample size and different demographics are needed to validate our findings.

Fatty Acid Conjugates of Toluidine Blue O as Amphiphilic Photosensitizers: Synthesis, Solubility, Photophysics and Photochemical Properties†

Toluidine blue O (TBO) is a water-soluble photosensitizer that has been used in photodynamic antimicrobial and anticancer treatments, but suffers from limited solubility in hydrophobic media. In an effort to incrementally increase TBO's hydrophobicity, we describe the synthesis of hexanoic (TBOC6) and myristic (TBOC14) fatty acid derivatives of TBO formed in low to moderate percent yields by condensation with the free amine site. Covalently linking 6 and 14 carbon chains led to modifications of not only TBO's solubility, but also its photophysical and photochemical properties. TBOC6 and TBOC14 derivatives were more soluble in organic solvents and showed hypsochromic shifts in their absorption and emission bands. The solubility in phosphate buffer solution was low for both TBOC6 and TBOC14, but unexpectedly slightly greater in the latter. Both TBOC6 and TBOC14 showed decreased triplet excited-state lifetimes and singlet oxygen quantum yields in acetonitrile, which was attributed to heightened aggregation of these conjugates particularly at high concentrations due to the hydrophobic "tails." While in diluted aqueous buffer solution, indirect measurements showed similar efficiency in singlet oxygen generation for TBOC14 compared to TBO. This work demonstrates a facile synthesis of fatty acid TBO derivatives leading to amphiphilic compounds with a delocalized cationic "head" group and hydrophobic "tails" for potential to accumulate into biological membranes or membrane/aqueous interfaces in PDT applications.

Early Glottic Cancer Treated by Transoral Laser Surgery Using Toluidine Blue for the Definition of the Surgical Margins: A Pilot Study

Background and objectives: Transoral laser microsurgery (TLM) is widely accepted for its advantages, which consist of a brief hospital stay, rapid functional recovery, low management costs and the fact that it can be easily repeated in cases of recurrence. However, a high incidence of positive or narrow surgical margins has been reported in the literature, even if controversy still exists on the prognostic significance of positive resection margins. The aim of the study was to evaluate the utility of toluidine blue staining in defining the resection margins of early glottic cancer (T1a–T2) treated with TLM. Materials and Methods: This retrospective study was conducted on patients with early glottic cancer (T1a–T2) managed by TLM. A group of patients treated between 2010 and 2014 underwent toluidine blue staining (TB group) of the lesions before starting the cordectomy by TLM, and a group of patients treated by TLM between 2006 and 2009 was considered the control group. Results: A total of 44 subjects were included in this study: 41 were men, and 3 were women. The mean age was 58 ± 9.0 years (median 59.0, range 41–77). Twenty-three of the 44 patients were included in the TB group and 21 in the case control group. In the TB group, only the positivity of the deep margin was a predictor of local recurrence (p = 0.037), while in the control group, positive or close margins and the type of cordectomy were predictive factors of local recurrence (p = 0.049). Considering the TB group and control cases, the 5-year local recurrence-free survival was 95.6% and 80.9%, respectively (p = 0.14). Conclusions: From this first study, toluidine blue staining seems to be a useful modality to improve the rate of the negative resection margins of early glottic cancer (T1a–T2) treated by TLM.

Lugol Chromoscopy in the Follow-up of Head and Neck Carcinoma

Introduction:

Lugol is helpful in identifying early second primary tumors (SPTs) during oroscopy and pharyngoscopy, but this technique has not been assessed during follow-up visits with these patients.

Aim:

The aim of this study is to describe the use of Lugol (a low-cost method) to diagnose SPTs in the oral cavity and oropharynx.

Methods:

Patients treated for squamous cell carcinoma of the head and neck were randomly assigned to two groups. Group A was examined with routine oroscopy and pharyngoscopy without Lugol, and Group B was examined with routine oroscopy and pharyngoscopy without stain and with Lugol. A total of 211 patients were included during 4 years.

Results:

Six oral and oropharynx carcinomas were detected in Group A. Eighteen oral and oropharynx carcinomas were detected in Group B, twelve of which were not seen without chromoscopy but were detected with Lugol.

Conclusion:

Lugol increases the detection of malignant lesions compared to routine examination alone.

Methylene Blue as a Diagnostic Aid in the Early Detection of Potentially Malignant and Malignant Lesions of Oral Mucosa

BACKGROUND

In vivo stains are the prompt resources, which have emerged in recent years to aid as clinical diagnostic tools in detecting early potentially malignant and malignant lesions. Toluidine blue, by its property of retaining in the increased DNA and RNA cellular activity areas, aids in delineating the suspicious areas. However, it is hazardous if swallowed, and has been shown to have toxicity to fibroblasts. Methylene blue has a similar chemical structure and exhibits similar physicochemical properties as toluidine blue. It is less toxic to the human body and has recently been proposed for screening some gastrointestinal or prostate tumors. The application of this material in detecting oral lesions has so far not been addressed. The objective of this study was to evaluate the sensitivity and reliability of in vivo staining with methylene blue as a diagnostic adjunct in screening for oral malignant or potentially malignant lesions.

METHODS

The present study involved the examination of 75 patients suspected of having oral malignant or potentially malignant lesions by methylene blue staining. The results of methylene blue uptake were compared with a simultaneous biopsy of these lesions.

RESULTS

The overall sensitivity was 95% (100% for malignancy and 92% for potentially malignant lesions) and specificity was 70%. The positive predictive value was 91% and negative predictive value of 80% was observed in the study.

CONCLUSION

We consider that methylene blue staining is a useful diagnostic adjunct in a large, community-based oral cancer screening program for high-risk individuals.

The impact of antimicrobial photodynamic therapy on peri-implant disease: What mechanisms are involved in this novel treatment?

According to the American Academy of Implant Dentistry, 3 million Americans have dental implants, and this number is growing by 500,000 each year. Proportionally, the number of biological complications is also increasing. Among them, peri-implant disease is considered the most common cause of implant loss after osseointegration. In this context, microorganisms residing on the surfaces of implants and their prosthetic components are considered to be the primary etiologic factor for peri-implantitis. Some research groups have proposed combining surgical and non-surgical therapies with systemic antibiotics. The major problem associated with the use of antibiotics to treat peri-implantitis is that microorganisms replicate very quickly. Moreover, inappropriate prescription of antibiotics is not only associated with potential resistance but also and most importantly with the development of superinfections that are difficult to eradicate. Although antimicrobial photodynamic therapy (aPDT) was discovered several years ago, aPDT has only recently emerged as a possible alternative therapy against different oral pathogens causing peri-implantitis. The mechanism of action of aPDT is based on a combination of a photosensitizer drug and light of a specific wavelength in the presence of oxygen. The reaction between light and oxygen produces toxic forms of oxygen species that can kill microbial cells. This mechanism is crucial to the efficacy of aPDT. To help us understand conflicting data, it is necessary to know all the particularities of the etiology of peri-implantitis and the aPDT compounds. We believe that this review will draw attention to new insights regarding the impact of aPDT on peri-implant disease.

Future Imaging Alternatives: The Clinical Non-invasive Modalities in Diagnosis of Oral Squamous Cell Carcinoma (OSCC)

Background : Oral squamous cell carcinoma (OSCC) has a remarkably high incidence worldwide, and a fairly serious prognosis. This is encouraging further research into advanced technologies for non-invasive methods of making early diagnoses, ideally in primary care settings. Method : In this article, the available objective Non-imaging methods for diagnosing OSCC have been reviewed. MEDLINE, EMBASE, the Cochrane Library, and CINAHL have been searched for advanced technologies of non-invasive methods in diagnosis of OSCC, including oral brush biopsy, optical biopsy, saliva-based oral cancer diagnosis and others. Results : Toluidine blue, one of the oldest non-invasive methods for diagnosing OSCC, is unreliable because of its subjectivity, as it is dependent on the experience of the examiner. The diagnosis of Oral carcinoma by Oral brush biopsy with exfoliative cytology based on nano-bio-chip sensor platform shows 97–100% sensitivity and 86% specificity. Another promising non-invasive technique for OSCC diagnosis is saliva-based oral cancer diagnosis, which is an alternative to serum testing. Optical biopsy, which uses the technology of spectroscopy, can be used to detect changes at a sub-cellular level; thus, it provides information that may not be available with conventional histology with reliable sensitivity and specificity. Conclusion : It is clearly evident that screening and early effective detection of cancer and pre-cancerous lesions have the potential to reduce the morbidity and mortality of this disease. The imaging technologies are subjective procedures since all of them require interpretation and significantly affected by the examiner experience. These make further research for advanced objective procedures. Saliva-based oral cancer diagnosis and optical biopsy are promising objective non-invasive methods for diagnosing OSCC. They are easy to perform clinically at primary care set. They show promising pathways for future development of more effective method for the diagnosis of OSCC.

Assessing the accuracy of autofluorescence, chemiluminescence and toluidine blue as diagnostic tools for oral potentially malignant disorders--a clinicopathological evaluation

OBJECTIVES

Early detection of oral cancer and their precursors is the key to reducing the high mortality rate attributable to oral cancer. A variety of new chair-side diagnostic tools are currently available that may enhance oral mucosal examination and facilitate the detection of benign and malignant disorders. The aim of this study was to investigate the accuracy of autofluorescence, chemiluminescence and toluidine blue (TBlue) when used in combination against conventional oral examination and surgical biopsy for the detection and assessing risk status of oral potentially malignant disorders.

MATERIALS AND METHODS

A total of 126 patients, with white, red and mixed white and red patches were included. Following a comprehensive oral examination, all patients underwent a standard protocol of autofluorescence, chemiluminescence and TBlue examination. A surgical biopsy was performed to assess oral epithelial dysplasia.

RESULTS

Seventy patients had leukoplakia/erythroplakia and 44 had epithelial dysplasia. In relation to leukoplakia/erythroplakia, autofluorescence, chemiluminescence and TBlue showed a sensitivity of 87.1, 77.1 and 52.9 % and a specificity of 21.4, 26.8 and 67.9 %, respectively. For dysplasia cases, autofluorescence, chemiluminescence and TBlue showed sensitivity and specificity of 84.1, 77.3 and 56.8 % and 15.3, 27.8 and 65.8 %, respectively.

CONCLUSION

While all the three tests were useful in detecting oral mucosal changes, their accuracy in identifying oral potentially malignant disorders (OPMD) is questionable. However, in combination, the tests yielded better results, with improved specificity.

CLINICAL RELEVANCE

These research tools are helpful in specialist clinics but further studies are necessary to examine their role in screening in primary care settings.

Current concepts and future of noninvasive procedures for diagnosing oral squamous cell carcinoma--a systematic review

Background

Oral squamous cell carcinoma (OSCC) has a remarkably high incidence worldwide, and a fairly serious prognosis, encouraging further research into advanced technologies for noninvasive methods of making early diagnoses, ideally in primary care settings.

Objectives

Our purpose was to examine the validity of using advanced noninvasive technologies in diagnosis of OSCC by identifying and evaluating relevant published reports.

Data source

MEDLINE, EMBASE, and CINAHL were searched to identify clinical trials and other information published between 1990 and 10 June 2014; the searches of MEDLINE and EMBASE were updated to November 2014. Study selection: Studies of noninvasive methods of diagnosing OSCC, including oral brush biopsy, optical biopsy, saliva-based oral cancer diagnosis, and others were included.

Data extraction

Data were abstracted and evaluated in duplicate for possible relevance on two occasions at an interval of 2 months before being included or excluded.

Data synthesis

This study identified 163 studies of noninvasive methods for diagnosing OSCC that met the inclusion criteria. These included six studies of oral brush biopsy, 42 of saliva-based oral diagnosis, and 115 of optical biopsy. Sixty nine of these studies were assessed by the modified version of the QUADAS instrument. Saliva-based oral cancer diagnosis and optical biopsy were found to be promising noninvasive methods for diagnosing OSCC.

Limitation

The strength of evidence was rated low for accuracy outcomes because the studies did not report important details required to assess the risk for bias.

Conclusions

It is clear that screening for and early detection of cancer and pre-cancerous lesions have the potential to reduce the morbidity and mortality of this disease. Advances in technologies for saliva-based oral diagnosis and optical biopsy are promising pathways for the future development of more effective noninvasive methods for diagnosing OSCC that are easy to perform clinically in primary care settings.

Diagnostic modalities for squamous cell carcinoma: an extensive review of literature-considering toluidine blue as a useful adjunct

INTRODUCTION

Oral Squamous Cell Carcinomas have been considered as the most prevalent malignancies in the head and neck region and are frequently undiagnosed until symptomatic with an advanced stage of disease. So there is an urgent need to device methods for the detection of oral premalignant lesions and oral cancer at an early stage in order to improve the survival rate for patients. A number of tests have been done for the detection of oral cancer which include oral brush biopsy, the Vizilite, oral autofluorescence including chemiluscence, photodynamic detection, toluidine blue staining, methylene blue staining, incisional biopsy and many more.

MATERIAL

The article reviews various diagnostic modalities available at present for detection of squamous cell carcinomas and oral epithelial dysplasias based on advanced PUBMED search of the English language literature from the year 1972 to present in order to help us select the most suitable among them fulfilling the desired criteria of being non-invasive, highly specific and sensitive, economically viable, having a scope to be used for mass screening, easy to process, having low inter examiner variability and possibly not requiring high expertise to conduct and interpret the results.

CONCLUSION

After reviewing various diagnostic modalities, we conclude that toluidine blue staining emerges as a clear winner among all these and it can act as a valuable adjunct to incisional biopsy in detection of oral cancer and may not substitute it except in certain circumstances when its results are carefully correlated with the patient history and clinical characteristics of the mucosal disorder, considering the fact that incisional biopsy has been reported to cause dissemination of cancer cells in the circulation there by increasing the possibility of metastasis. We must emphasize that toludine blue is a screening modality and not a diagnostic procedure like biopsy and hence cannot replace a confirmatory biopsy as a whole.

A chemiluminescent light system in combination with toluidine blue to assess suspicious oral lesions-clinical evaluation and review of the literature

OBJECTIVES

The aim of the study was an evaluation of an acetic acid wash and chemiluminescent light system in combination with toluidine blue in order to detect visual identified, potentially malignant lesions.

MATERIALS AND METHODS

Forty-four patients with 50 oral lesions of primary uncertain visible dignity were included. Next to a clinical examination, a screening with ViziLite® (VL) as well as toluidine blue (TB; together ViziLite® Plus (VLP)) was conducted. Histopathology served as gold standard and sensitivity (SE), specificity (SP), positive as well as negative predictive value (PPV, NPV) was calculated descriptively. Additionally, a PubMed literature search using the key words "ViziLite" and "chemiluminescence oral cancer" was conducted.

RESULTS

Histological diagnosis showed 40 lesions of reactive/inflammatory nature, moderate dysplasia (n = 3) and oral squamous cell carcinoma (OSCC n = 7). All OSCCs and one dysplasia were identified correct via clinical diagnosis (SE 90 %, SP 100 %, PPV 100 %, NPV 97.5 %). VL examination could show all malignancies with low specificity (SE 100 %, SP 30 %, PPV 26 %, NPV 100 %). TB and VLP were positive in all cases of cancer and in one case of inflammation (SE 80 %, SP 97.5 %, PPV 89 %, NPV 95 %). In the review, eight clinical trials with similar results were included.

CONCLUSIONS

The adjunct of TB to VL reduces the number of false positives without increasing the rate of false negatives.

CLINICAL RELEVANCE

Clinical evidence to justify the additional cost of the system for diagnosis of suspicious lesions is weak. However, for the potential role of VLP in detection of lesions not otherwise identified in the visual exam in general dental practice further studies are required.

Chemiluminescence and Toluidine Blue as Diagnostic Tools for Detecting Early Stages of Oral Cancer: An invivo Study

BACKGROUND

There is a need for development and use of diagnostic aids that help the dental specialist more readily identify and assess Potentially Malignant Epithelial Lesions (PMELs) and Oral Squamous Cell Carcinoma (OSCC). This study was done to assess the value of two such commercially available tools: chemiluminescent light kit or ViziLite and 1% toluidine blue.

AIMS AND OBJECTIVES

a) To detect epithelial dysplastic changes using chemiluminescene (commercially available as ViziLite) and toluidine blue staining in PMELs and OSCC patients and compare the results obtained with histopathological examination. b) To determine whether these techniques can be used to detect early epithelial dysplastic changes in clinically normal appearing oral mucosa of high risk (with habits) patients.

MATERIALS AND METHODS

A total of 60 patients- 25 patients with PMELs, specifically oral leukoplakia, 10 patients with clinically diagnosed OSCC and 25 high risk patients with no clinically visible lesion, were screened with ViziLite and toluidine blue staining; followed by incisional biopsy.

RESULTS

Sensitivity and specificity of ViziLite were calculated to be 95.45% and 84.6% respectively. ViziLite detected early epithelial dysplastic changes in one high risk patient with clinically normal appearing oral mucosa. Sensitivity and specificity of toluidine blue were calculated to be 86.36% and 76.9% respectively.

CONCLUSION

ViziLite was relatively reliable in screening PMELs compared to toluidine blue, and was a useful chair side diagnostic aid.

Laser in dentistry: An innovative tool in modern dental practice

The term LASER is an acronym for ‘Light Amplification by the Stimulated Emission of Radiation’. As its first application in dentistry by Miaman, in 1960, the laser has seen various hard and soft tissue applications. In the last two decades, there has been an explosion of research studies in laser application. In hard tissue application, the laser is used for caries prevention, bleaching, restorative removal and curing, cavity preparation, dentinal hypersensitivity, growth modulation and for diagnostic purposes, whereas soft tissue application includes wound healing, removal of hyperplastic tissue to uncovering of impacted or partially erupted tooth, photodynamic therapy for malignancies, photostimulation of herpetic lesion. Use of the laser proved to be an effective tool to increase efficiency, specificity, ease, and cost and comfort of the dental treatment.

Methylene blue as an early diagnostic marker for oral precancer and cancer

Oral cancer is one of the most common neoplasm's and is ranked eighth in the cancer incidence worldwide. Early detection is of critical importance because survival rates markedly improve. In vivo staining is a simple, inexpensive, and fairly sensitive method. Involved 120 patients (50 with Premalignant Lesion, 50 with OSCC and 20 controls) stained by Methylene Blue (MB). The results of MB uptake were compared with a simultaneous biopsy of these lesions. Pathologically confirmed precancers and cancers were the positive targets of this screening, while hyperkeratosis without dysplasia and no evidence of malignancy were sorted as negative subjects of screening. The results revealed sensitivity of 91.4%, specificity of 66.6%, positive predictive value 97.7% and negative predictive value 33% leading to diagnostic accuracy of MB stain to 90%. We state that MB staining is useful diagnostic tool in community oral cancer screening programmes for high-risk individuals.

Assessment of oral mucosa in normal, precancer and cancer using chemiluminescent illumination, toluidine blue supravital staining and oral exfoliative cytology

Context:

Carcinoma in an early stage of development is hard to detect clinically because the lesion may not be palpable and color of the lesional tissue is not necessarily different from the color of the surrounding mucosa. In order to improve the efficacy of the diagnosis, techniques are being developed to complement clinical examination and to facilitate the identification of initial carcinomas.

Aims:

To find out the efficacy of chemiluminescent illumination (ViziLite™) for the diagnosis in precancer and cancer patients and compare this result to toluidine blue staining and oral exfoliative cytology.

Materials and Methods:

This study was done in 3 groups. Each group consists of 10 cases. Group I consists of normal appearing mucosa. Group II and III consist of clinically diagnosed pre-cancer and clinically suggestive of cancer respectively. Chemiluminescent illumination, toluidine blue supravital staining, oral exfoliative cytology and biopsy were performed in all cases.

Statistical analysis used:

SPSS version 10.05 was used to calculate positive and negative predictive values.

Results:

In Group I, all 10 patients showed negative result to ViziLite™. 8 patients showed positivity and 2 patients showed negativity to ViziLite™ test in Group II. 9 patients were positive and one patient was negative for ViziLite™.

Conclusions:

Chemiluminescent illumination test was sensitive for precancerous and cancerous lesions, which presented as keratotic lesions and red-white lesions. It showed negative result to erosive lesions. Toluidine blue staining test was reliable in precancerous and cancerous lesions, which present as erosive and red-white lesions. It showed negative result to keratotic lesions. Oral exfoliative cytology has diagnostic value in cancer patients than in precancer patients. These Results indicate that chemiluminescent illumination test is relatively reliable and accurate than toluidine blue staining test and useful chair side diagnostic test.

Toluidine blue: A review of its chemistry and clinical utility

Toluidine blue is a basic thiazine metachromatic dye with high affinity for acidic tissue components, thereby staining tissues rich in DNA and RNA. It has found wide applications both as vital staining in living tissues and as a special stain owing to its metachromatic property. Toluidine blue has been used in vivo to identify dysplasia and carcinoma of the oral cavity. Use of toluidine blue in tissue sections is done with the aim to highlight components, such as mast cells granules, mucins, and cartilage. This article provides an overview on chemistry, technique, and the various applications of toluidine blue.

Relevance of tumor angiogenesis patterns as a diagnostic value and prognostic indicator in oral precancer and cancer

Tumor angiogenesis occurs by recruitment of endothelial cell precursors or by sprouting of existing capillaries, which differ from the normal vasculature by having an altered morphology that can be exploited for diagnosis and as a prognostic indicator. Improved technologies have propelled diagnosis into a new era. These technologies have to be used with great precision. The diagnosis of a dysplastic premalignant lesion of the oral mucosa cannot be based solely on clinical findings. Therefore histologic evaluation of a representative biopsy specimen is necessary. Accurate judgment of the proper site for biopsy is essential for reaching a correct diagnosis. The aim of this report is to analyze the vascular patterns with the help of direct oral microscopy and the technique of stereo-optical microscopy in the oral cavity to select biopsy sites, and compare the outcome of a directed biopsy with that of biopsy specimens obtained from sites selected solely on the basis of clinical criteria. The study sample comprised 50 oral mucosal lesions. A statistically significant difference was noted between samples judged to be microscopically representative sites. We conclude that this method would aid in early and better diagnosis and treatment planning of oral premalignant and malignant lesions by assessing the various vascular patterns in the mucosa.

The utility of toluidine blue staining and brush cytology as adjuncts in clinical examination of suspicious oral mucosal lesions

The objective of this study was to investigate the utility of toluidine blue and brush cytology in patients with clinically detected oral mucosal lesions. Clinical examination of 35 patients was completed before toluidine blue application, oral brush cytology and scalpel biopsy. Lesions were photographed before and after stain application; followed by brush cytology. All findings were compared with histopathologic results. Severe dysplasia and carcinoma-in-situ were determined as 'positive'; no dysplasia and mild to moderate dysplasia were defined as 'negative'. The sensitivity, specificity, positive and negative predictive values of clinical examination and toluidine blue were the same: 0.923, 0.433, 0.414, and 0.929, respectively. Those of brush cytology were 0.923, 0.517, 0.462, and 0.938. The concordance of all methods was 30% for benign and 61% for malignant lesions. Adjuncts identified 92% of carcinoma-in-situ and squamous cell carcinoma as confirmed by histopathology, in contrast to clinical findings alone in which 62% of these lesions were identified (p=0.046). In conclusion, adjunct diagnostic methods decreased the level of uncertainty for the diagnosis of oral malignancies and lichenoid dysplasias when applied as adjuncts to clinical examination.

Oral mucosal malignancy and potentially malignant lesions: an update on the epidemiology, risk factors, diagnosis and management

An oral examination for the assessment for malignant and potentially malignant oral mucosal lesions is routine in general dental practice. It may be uncommon for general dental practitioners to encounter oral cancer, with anecdotal reports suggesting that this occurs about once every 10 years in a busy general dental practice. However, potentially malignant oral mucosal lesions are relatively common, occurring in about 2.5% of the population. This update highlights the epidemiology, risk factors, diagnosis and management of these oral mucosal lesions.

Toluidine blue color perception in identification of oral mucosal lesions

The objective of this study is to examine observer agreement on the rank of the color tones after toluidine blue staining of a mucosal lesion. Cohort study with repeated measures is the design of the study. Twenty observers ranked and scored 8 specified areas on the color images of a lesion before and after toluidine blue application in two sessions. Inter and intra-observer variations were analyzed with Cohen's kappa. The L* (the black-white axis), a* (red-green axis), and b* (yellow-blue axis) values were measured and set as the gold standards. Intra and inter-observer agreements were к = 0.86 and к = 0.854. All color parameters were effective on the color ranking order (pL* = 0.00, pa* = 0.007, pb* = 0.00), although L* and b* were more effective on the ranking of the samples than a*. Areas that appeared pale blue visually had a significant blue component, but the observers were confused with the effect of whiteness of the area in clinical decision making.

The adjunctive role of toluidine blue in detection of oral premalignant and malignant lesions

PURPOSE OF REVIEW

To review the literature on toluidine blue (TBlue) and to discuss the utility of TBlue in assessing and in clinical management of patients with oral mucosal lesions. The literature search was conducted using key word search including oral cancer, oral premalignant lesions, and TBlue and by selecting references from the articles reviewed.

RECENT FINDINGS

The findings of this review show that TBlue has utility as an adjunct in the detection of premalignant and malignant oral mucosal lesions and in identifying high-risk areas of lesions for biopsy in patients at increased risk of cancer when evaluated by experienced healthcare workers.

SUMMARY

TBlue positive lesions, whether histologically benign or with dysplasia, predict molecular change and behavior of oral premalignant lesions. TBlue may provide information regarding lesion margins, accelerate the decision to biopsy, guide biopsy site selection and treatment of oral premalignant and malignant lesions. These findings support the utility of TBlue as a clinical adjunct in assessment of oral mucosal lesions.

Porphyrin and nonporphyrin photosensitizers in oncology: preclinical and clinical advances in photodynamic therapy

Photodynamic therapy (PDT) is now a well-recognized modality for the treatment of cancer. While PDT has developed progressively over the last century, great advances have been observed in the field in recent years. The concept of dual selectivity of PDT agents is now widely accepted due to the relative specificity and selectivity of PDT along with the absence of harmful side effects often encountered with chemotherapy or radiotherapy. Traditionally, porphyrin-based photosensitizers have dominated the PDT field but these first generation photosensitizers have several disadvantages, with poor light absorption and cutaneous photosensitivity being the predominant side effects. As a result, the requirement for new photosensitizers, including second generation porphyrins and porphyrin derivatives as well as third generation photosensitizers has arisen, with the aim of alleviating the problems encountered with first generation porphyrins and improving the efficacy of PDT. The investigation of nonporphyrin photosensitizers for the development of novel PDT agents has been considerably less extensive than porphyrin-based compounds; however, structural modification of nonporphyrin photosensitizers has allowed for manipulation of the photochemotherapeutic properties. The aim of this review is to provide an insight into PDT photosensitizers clinically approved for application in oncology, as well as those which show significant potential in ongoing preclinical studies.

Adjunctive techniques for oral cancer examination and lesion diagnosis: a systematic review of the literature

BACKGROUND

Adjunctive techniques that may facilitate the early detection of oral premalignant and malignant lesions (OPML) have emerged in the past decades.

METHODS

The authors undertook a systematic review of the English-language literature to evaluate the effectiveness of toluidine blue (TB), ViziLite Plus with TBlue (Zila Pharmaceuticals, Phoenix), ViziLite (Zila Pharmaceuticals), Microlux DL (AdDent, Danbury, Conn.), Orascoptic DK (Orascoptic, a Kerr Company, Middleton, Wis.), VELscope (LED Dental, White Rock, British Columbia, Canada) and OralCDx (Oral CDx Laboratories, Suffern, N.Y.) brush biopsy. They abstracted data relating to study design, sampling and characteristics of the study group, interventions, reported outcomes and diagnostic accuracy of adjunctive aids from 23 articles meeting inclusion and exclusion criteria, including availability of histologic outcomes.

RESULTS

The largest evidence base was for TB. A limited number of studies was available for ViziLite, ViziLite Plus with TBlue and OralCDx. Studies of VELscope have been conducted primarily to assess the margins of lesions in known OPML. The authors identified no studies of Microlux DL or Orascoptic DK. Study designs had various limitations in applicability to the general practice setting, including use of higher-risk populations and expert examiners.

CONCLUSIONS

There is evidence that TB is effective as a diagnostic adjunct for use in high-risk populations and suspicious mucosal lesions. OralCDx is useful in assessment of dysplastic changes in clinically suspicious lesions; however, there are insufficient data meeting the inclusion criteria to assess usefulness in innocuous mucosal lesions. Overall, there is insufficient evidence to support or refute the use of visually based examination adjuncts. Practical Implications. Given the lack of data on the effectiveness of adjunctive cancer detection techniques in general dental practice settings, clinicians must rely on a thorough oral mucosal examination supported by specialty referral and/or tissue biopsy for OPML diagnosis.

Detection of LINE-1s hypomethylation in oral rinses of oral squamous cell carcinoma patients

This study aimed to (i) investigate long interspersed nuclear element-1 (LINE-1) methylation levels of oral squamous cell carcinomas (OSCCs), the major type of oral malignancies; and (ii) investigate whether the hypomethylation of LINE-1s can be detected in oral rinses of OSCC patients. The combined bisulfite restriction analysis polymerase chain reaction (PCR) of LINE-1s (COBRALINE-1) was used. We found that tissues from OSCC specimens had lower methylation levels of LINE-1s than cells collected from the oral rinses of normal volunteers. Interestingly, cells collected from oral rinses of OSCC patients also revealed hypomethylated LINE-1s at the same level as OSCC tissues. There was no difference in the level of hypomethylation due to stages, locations, histological grades, and history of betel chewing, smoking and/or alcohol consumption. In conclusion, OSCCs possessed global hypomethylation and this alteration could be detected from oral rinses of OSCC patients by a simple PCR technique, COBRALINE-1. Therefore, COBRALINE-1 of oral rinses may be applied for non-invasive detection of oral malignancies.

A survey of the current approaches to diagnosis and management of oral premalignant lesions

BACKGROUND

Early diagnosis of oral premalignant lesions (OPLs) and oral squamous cell carcinoma facilitates treatment with less aggressive approaches and results in a better prognosis. The authors conducted a study to identify current practices in the diagnosis and management of these oral lesions by oral medicine professionals.

METHODS

The authors sent a questionnaire to 176 diplomates of the American Board of Oral Medicine and asked them to complete the questionnaires and return them by mail.

RESULTS

The initial clinical approach taken by most of the responders included visual examination, elimination of possible local causes and two-week follow-up. Adjuvant clinical tests included toluidine blue, oral brush biopsy and exfoliative cytology. If there was no clinical improvement after two weeks, most responders recommended that a biopsy be performed. Induration, red component, nonhomogeneous surface and ulceration were characteristics of lesions that increased the responders' decisions to perform a biopsy. Lesion symptoms and location also contributed to their decisions to perform a biopsy. Follow-up more frequently than twice a year was recommended for red lesions, lesions with histologically confirmed dysplasia or both. Most clinicians recommend a biopsy during follow-up of an OPL whenever the lesion changes in appearance.

CONCLUSIONS

The findings of this survey may provide background for initial guidelines to be used by oral practitioners to diagnose and manage OPL. Clinicians' awareness of the complexity of OPL diagnosis and management is important, and referral to an experienced provider is recommended.

Application of in vivo stain of methylene blue as a diagnostic aid in the early detection and screening of oral squamous cell carcinoma and precancer lesions

BACKGROUND

Early detection of oral malignant or precancerous lesion by screening individuals with high-risk factors may identify candidates who should receive treatment to prevent cancer progression and reduce patient mortality. Among the diagnostic tools, in vivo staining is advocated as a simple, inexpensive, and fairly sensitive method.

METHODS

The present study involved the examination of 58 patients suspected of having oral malignant or precancerous lesions by methylene blue staining. The results of methylene blue uptake were compared with a simultaneous biopsy of these lesions. The pathologically confirmed precancers and cancers were the positive targets of this screening, while benign epithelial lesions were sorted as negative subjects of screening.

RESULTS

The results revealed sensitivity of 90%, specificity of 69%, positive predictive value of 74%, and negative predictive value of 87%.

CONCLUSION

We consider that methylene blue staining is a useful diagnostic adjunct in a large, community-based oral cancer screening program for high-risk individuals.

Utility of toluidine blue in oral premalignant lesions and squamous cell carcinoma: Continuing research and implications for clinical practice

Toluidine blue (TB) has been shown to aid in the detection and diagnosis of oropharyngeal squamous cell carcinoma (OSCC) and oral premalignant lesions (OPLs). TB has been shown to enhance visualization of oral lesions and assist in identifying sites of increased risk of dysplastic/malignant change and promote biopsy. TB has been shown to identify lesions with molecular changes associated with risk of progression of OPLs to OSCC. A recent prospective longitudinal study showed TB retention in histologic benign lesions and lesions with mild dysplasia that are at increased risk of progression to cancer. Clinical trials show that TB is useful in identifying asymptomatic OSCC and premalignant lesions at risk of progressing to SCC, which might otherwise be undetected until lesions become more advanced. The data supports TB use in oral examination of patients at risk of OSCC.

Rose bengal staining in detection of oral precancerous and malignant lesions with colorimetric evaluation: a pilot study

Early detection of oral precancerous and malignant lesions is still a diagnostic challenge for most of clinicians, and ideal adjuncts for detection of these lesions are currently unavailable. Our preliminary study has indicated that rose bengal (RB) staining might have the potency as a diagnostic aid; however, its clinical significance and reliability in hospital-based population are still not clear. In the present study, we investigated the efficacy of RB staining in detection of oral precancerous and malignant lesions. RB staining was conducted in 132 patients, and staining results were determined by a 4-graded shade guide, which had been quantitatively measured in the 1976 CIEL*a*b* space by instrumental colorimetry. Histological examination was performed in 128 of 132 patients after RB staining. The sensitivity and specificity to detect epithelial dysplasia (DP) and oral squamous cell carcinoma were 93.9 and 73.7%, respectively. The positive and negative likelihood ratios were 3.570 and 0.082, respectively. Moreover, RB staining seemed promising to detect DP in oral leukoplakia, lichen planus and leukokeratosis. In this study, 5 of 6 DP or oral squamous cell carcinoma were identified by RB staining before histological examination. In conclusion, RB staining may be a valuable diagnostic test in detection of oral precancerous and malignant lesions.

Use of methylene blue as a diagnostic aid in early detection of oral cancer and precancerous lesions

We assessed the sensitivity, specificity, and positive and negative predictive value of methylene blue staining in the diagnosis of oral cancer in 58 patients. The sensitivity was 90%, the specificity 69%, positive predictive value 74%, and negative predictive value 87%. Because of the number of false negatives and false positives we recommend that the diagnosis should always be confirmed by histopathological examination of a biopsy specimen. Methylene blue staining may, however, be useful as a screening tool for oral cancer in large, high-risk groups in a similar way to the more expensive toluidine blue.