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BACKGROUND: The rate of residual liver recurrence after the resection of colorectal liver metastases is high, and most cases recur within 5 years of the initial hepatectomy. Here, we report two cases of residual liver recurrence after radical resection of colorectal liver metastases after a long recurrence-free survival period. CASE PRESENTATION: Case 1 involved a 62-year-old woman treated for ascending colon cancer in April 2011 who underwent right hepatectomy for synchronous colorectal liver metastasis in April 2012. However, in September 2021, computed tomography revealed residual recurrence in the lateral segment of the liver, and a lateral segmentectomy of the liver was performed. In Case 2, a 52-year-old man treated for cecal cancer in July 2002 underwent lateral segmentectomy of the liver for metachronous colorectal liver metastasis in October 2006. Subsequently, there was no recurrence; however, computed tomography showed residual liver recurrence in the right lobe of the liver in October 2021, and an expanded posterior hepatic segmentectomy was performed. Histopathological findings in both cases were consistent with colorectal liver metastases. CONCLUSIONS: We encountered two cases in which residual liver recurrence was observed after a long period of recurrence-free survival. Although rare, there have been a few cases of late recurrence of liver metastases after radical resection of cancer liver metastases.

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The novel coronavirus pandemic has resulted in an urgent need to study the risk of infection from aerosols generated during dental care and to conduct a review of infection controls. However, existing studies on aerosol particles related to dental treatment have mainly evaluated only the scattering range. Few studies have been conducted on the specifics of the generation of aerosol particles in clinical settings, their mechanisms and patterns of distribution throughout open or enclosed spaces, the duration that they remain suspended in air, and the amount and size of particles present. To minimize the influence of background particles, laser lights, a high-sensitivity camera, and particle counters were used in a large super clean laboratory to investigate the dynamics of aerosols generated during the operation of dental micromotors. The results indicate that aerosols tend to scatter upward immediately after generation and then gradually disperse into the surroundings. Most of the particles are less than 5 µm in size (only a few are larger), and all particles are widely distributed over the long term. Our research clearly elucidates that aerosols produced in dental care are distributed over a wide area and remain suspended for a considerable time in dental clinics before settling.

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OBJECTIVES: A new computer-aided screening system for osteoporosis using panoramic radiographs was developed. The conventional system could detect porotic changes within the lower border of the mandible, but its severity could not be evaluated. Our aim was to enable the system to measure severity by implementing a linear bone resorption severity index (BRSI) based on the cortical bone shape. METHODS: The participants were 68 females (>50 years) who underwent panoramic radiography and lumbar spine bone density measurements. The new system was designed to extract the lower border of the mandible as region of interests and convert them into morphological skeleton line images. The total perimeter length of the skeleton lines was defined as the BRSI. 40 images were visually evaluated for the presence of cortical bone porosity. The correlation between visual evaluation and BRSI of the participants, and the optimal threshold value of BRSI for new system were investigated through a receiver operator characteristic analysis. The diagnostic performance of the new system was evaluated by comparing the results from new system and lumbar bone density tests using 28 participants. RESULTS: BRSI and lumbar bone density showed a strong negative correlation (p < 0.01). BRSI showed a strong correlation with visual evaluation. The new system showed high diagnostic efficacy with sensitivity of 90.9%, specificity of 64.7%, and accuracy of 75.0%. CONCLUSIONS: The new screening system is able to quantitatively evaluate mandibular cortical porosity. This allows for preventive screening for osteoporosis thereby enhancing clinical prospects.

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