Dental College : Various oral mucosal diseases such as oral potentially malignant disorders(OPMD)and squamous cell carcinoma (SCC)may develop in the oral cavity and are difficult to differentiate. Optical instruments are not invasive and can be repeatedly used. Since 2010, we have used optical instruments effectively to improve diagnosis and treatment. In this study, we conducted subjective and objective evaluations using optical instruments for distinguishing between leukoplakia and SCC.Eighty-two patients diagnosed with SCC and leukoplakia at the Department of Oral and Maxillofacial Surgery, Tokyo Dental College, between April 2017 and March 2018 were selected and evaluated using optical instruments. Also, an oral cancer screening model that used AI(AI oral cancer screening system：AIOS)was prepared and its effectiveness was evaluated.In the subjective evaluation by optical instruments, Fluorescence Visualization Loss(FVL)was confirmed in all SCC cases. In the objective evaluation, SCC was lower than leukoplakia in luminance(SCC 52.6 vs Leukoplakia 74.5cd/m 2 ) . In the coefficient of variation of luminance, SCC was higher than leukoplakia in luminance(SCC 0.22 vs Leukoplakia 0.12) . Regarding luminance ra-

Oral cancer screening is important for early detection and early treatment, which help improve survival rates. Biopsy is invasive and painful, while fluorescence visualization using optical instruments is non-invasive, convenient, and provides results in real time, and examinations can be repeated. The purpose of this study was to determine the usefulness of optical instruments in oral screening. A total of 314 patients who were examined using optical instruments at Tokyo Dental College between 2014 and 2018 were enrolled in this study. Fluorescence visualization images were analyzed using subjective and objective evaluations. Subjective evaluation for detecting oral cancer offered 98.0% sensitivity and 43.2% specificity. Regarding the objective evaluations for detecting oral cancer, sensitivity and specificity were 61.9% and 62.7% for mean luminance, 90.3% and 55.7% for luminance ratio, 56.5% and 67.7% for standard deviation of luminance, and 72.5% and 85.4% for coefficient of variation of luminance. Fluorescence visualization with subjective and objective evaluation using optical instruments is useful for oral cancer screening.

Objectives: We aimed to investigate the relationship between MR imaging detectability and its pathological depth of invasion (DOI) of oral tongue cancer, as well as its usefulness to assess the necessity of elective neck dissection. Methods: We retrospectively reviewed early stage oral tongue cancer patients treated with radical surgery with clinically N0, between May 2009 and February 2016. Collected data include age, sex, pathological DOI, DOI on MRI, locoregional control rate, disease-free survival rate, and overall survival rate. These data were statistically compared between the detectable lesion (DL) group and undetectable lesion (UL) group on MRI. Interobserver agreement in evaluation of detectability of the oral tongue cancer was assessed by k statistics. Results: Total of 53 patients were studied, and 28 were DLs and 25 ULs. Pathological DOI in UL was significantly smaller than that of DL (average 1.7 vs 4.6 mm, p < 0.001). Cutoff value between UL group and DL group was 3.5 mm (sensitivity 96 %, specificity 75 %). 96 % of ULs had pathological DOI smaller than 4 mm, the recommended cutoff value for neck dissection. There was no significant difference in locoregional control rate (p = 0.24), disease-free survival rate (p = 0.24) or overall survival rate (p = 0.92). Interobserver agreement in evaluation of detectability on MRI was very good (k-value = 0.89, p < 0.001). conclusions: When oral tongue cancer is not detected on MRI, it indicates pathological DOI being smaller than 4 mm, which may imply that elective neck dissection is unnecessary.

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The World Health Organization defines primary intraosseous squamous cell carcinoma (PIOSCC) as a squamous cell carcinoma (SCC) arising primarily within the jaws and having no connection with the oral mucosa. Here, we report a case of PIOSCC in which it was difficult to differentiate the condition from pericoronitis of an impacted maxillary wisdom tooth. The patient was a 27-year-old pregnant woman with a pain in the right maxillary wisdom tooth. The pain was diagnosed as pericoronitis of the right maxillary wisdom tooth, and the tooth was extracted under local anesthesia. During extraction, soft tissue was observed in the coronal part of the tooth, and it was diagnosed as SCC arising in a dentigerous cyst. Because the tumor may still be present, surgical resection was performed under general anesthesia. There has been no recurrence or metastasis at the 1-year follow-up. This case was histopathologically considered from being a benign odontogenic tumor to a malignant tumor. However, it revealed an extensive aberrant type and invasion equivalent to SCC. Thus, the histopathological diagnosis was PIOSCC arising from a dentigerous cyst. Although advanced cases of PIOSCC have been published, diagnosis of PIOSCC in the early stages is rare. In this case, we diagnosed pericoronitis of an impacted maxillary wisdom tooth and extracted the tooth. Therefore, we discovered it accidentally. In the early stages, diagnosis can be difficult both clinically and histopathologically.

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