It is generally important to help patients understand by communicating correctly using plain language. However, communication gaps often occur between doctor and patient in daily medical treatment. It is also difficult for many medical practitioners to communicate with hearing-impaired patients who struggle to hear the doctor’s voice in comparison with general patients. A medical speech display system using voice recognition software is one solution. Key requirements of these systems are the ability to quickly process and accurately recognize speech.
This article describes the basic knowledge of speech recognition and the factors that significantly affect the probability of establishing a communication support system for hearing-impaired elderly patients. Moreover, in order to establish the system configuration for clinical application, the requirements for effective functioning of this system are explained based on our study on speech recognition.

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Tooth extraction in young patients to prevent future complications due to impacted lower third molar （M3） remains controversial. The aim of the present study was to assess the efficacy of prophylactic extraction of the impacted lower M3.
This multicenter retrospective study involved a chart review of the clinical records of patients treated with extraction of impacted lower M3 in each institution between April 2018 and March 2021. Data were collected, and the pre-, intra- and post-operative complications were analyzed between 273 elderly patients and 1,734 younger patients.
The rates of occurrence of postoperative hemorrhage, nerve sensory change, dry socket and postoperative infection were significantly higher in elderly patients than in younger patients （P＜0.001）. Epithelial, nerve sensory change, dry socket and postoperative infection were significant independent risk factors （P＜0.001）. Pre-operative cellulitis and cyst caused by impacted lower M3 were significantly more common in elderly patients, and cyst caused by impacted lower M3 was an independent risk factor for postoperative infection （P＝0.021）.
In conclusion, prophylactic extraction of the impacted lower M3 is effective for avoiding some pre- and post-operative complications. However, the current evidence is inadequate to recommend it.

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We report a case of stage Ⅰ mucoepidermoid carcinoma with late metastasis to the cervical lymph node and lung, although it was an early-stage cancer. The patient was a man in his 60s who visited our department because of an ill-fitting maxillary denture. A mass was found in the right soft palate, and CT showed a nodular lesion behind the right maxillary tuberosity. Surgery was performed on clinical diagnosis of malignant tumor of the right soft palate, and the lesion was histopathologically diagnosed as mucoepidermoid carcinoma. Since the margin was negative, the patient was regularly followed up after the surgery, but late metastasis to the cervical lymph node occurred at 1 year and 7 months after the surgery. Furthermore, lung metastasis occurred at 3 years and 8 months after the first surgery.
It is challenging to evaluate the prognostic factors in salivary gland carcinomas because of their various histological types. Clinical stage is an important prognostic factor in minor salivary gland carcinomas. However, occult nodal disease may be recognized even in the clinical diagnosis of N0. The utility of FDG-PET has also been reported in the diagnosis of cervical lymph node metastasis. Currently, there is no standard guideline for conducting elective neck dissection in minor salivary gland tumors. As metastasis may occurs after a long period of time, careful follow-up in such cases is crucial.

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We report the case of a foreign body in the maxillary sinus with unknown path of entry.
The patient, a 60-year-old man, was referred to our department with a chief complaint of a sense of strangeness in the right paranasal sinuses. Panoramic imaging and computed tomography （CT） showed a 34mm （length） ×3mm （diameter） foreign body in the right maxillary sinus, which was like metal, and the right maxillary sinus mucosa was clearly swollen. The object was removed under general anesthesia, and radical surgery of the right maxillary sinus was performed at the same time. The post-operative course was uneventful.
The foreign body looked like a dental material related to root canal treatment. However, from a clinical point of view, there was no tooth extraction socket or oral maxillary sinus fistula. We asked the patient how the foreign body may have entered and the history of dental treatment, but his memory was vague and the path of entry was not known.

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Traditionally, non-odontogenic developmental cysts arising in the maxilla were considered to originate from embryonic fissures. The etiology of such lesions, however, has been denied mainly because the occurrence sites are occasionally inconsistent with the clefts. Hence, the underlying mechanism implicated in the odontogenic process is well accepted. However, it is still controversial since several reports suggested that globulomaxillary cysts are independent from cysts of odontogenic origin. In the present study, we report a case of a developmental maxillary cyst in a patient with unilateral cleft lip. A 46-year-old woman was referred to our hospital for treatment of a cystic lesion in the maxilla. The patient had a surgical history of lip repair at the age of three months. Radiographic examination showed a well-demarcated maxillary cyst between the upper-left lateral incisor and canine. Cystectomy and apicoectomy of the lateral incisor were performed under general anesthesia. Histopathological examination showed pseudostratified ciliated columnar epithelium, and therefore the lesion was diagnosed as a non-odontogenic cyst. There has been no sign of recurrence for two years after the surgery.

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