Mechanical stress is an important regulatory factor in bone homeostasis. Mechanical stimulation of osteoblasts has been shown to elicit an increase in the concentration of intracellular free Ca²⁺ ([Ca²⁺]_i). The pattern of functional expression of mechanosensitive ion channels remains unclear, however. Therefore, the purpose of this study was to investigate the pharmacological characteristics of [Ca²⁺]_i in response to direct mechanical stimulation in osteoblasts. The morphological expression of mechanosensitive ion channels was also examined. Mouse osteoblast-like cells (MC3T3-E1 cells) were loaded with fura-2-acetoxymethyl ester, after which [Ca²⁺]_i was measured. Increased levels of [Ca²⁺]_i were observed in MC3T3-E1 cells in response to direct mechanical stimulation by means of a glass micropipette, but no desensitization. Application of a hypotonic solution also induced an increase in [Ca²⁺]_i but was accompanied by a desensitizing effect. Extracellular Gd³⁺, GsMTx4, or RN-1734 reversibly inhibited this mechanical stimulation-induced increase in [Ca²⁺]_i, whereas no inhibitory effect was observed with HC030031 or clemizole. When osteoblasts were stimulated with Yoda1, an increase was observed in [Ca²⁺]_i together with a significant desensitizing effect. Immunoreactivity against Piezo1 and TRPV4 channel antibodies was detected in MC3T3-E1 cells. These results suggest that osteoblasts express Piezo1 and TRPV4 channels, which are involved in mechanosensitive processes during mechanical stress.

Dental anterior fractures are common injuries, especially in those who practice extreme sports. This report describes a 25-year-old Bolivian patient who attended our private dental clinic in La Paz, Bolivia after experiencing an accident during downhill mountain biking. An intraoral examination revealed a fracture line on the buccal side in the middle third of the coronal portion of the right central maxillary incisor which extended towards the proximal and lingual sides. Multidisciplinary treatment, including crown lengthening, osteotomy, root canal treatment, fiberglass post insertion, and reattachment of the fracture segment was performed. A follow-up examination at 10 months later revealed that the tooth was completely reestablished both functionally and esthetically and that there was no periapical pathosis or discomfort. This outcome suggests that if a patient seeks a dental consultation soon after a complex crown-root fracture has occurred, and if the broken tooth segment is available, then reattachment offers an economical and simple treatment option which will allow immediate restoration of functionality and esthetic standards. Continued follow-up should form part of such a treatment plan to allow long-term pulp vitality and periodontal health status to be monitored.

The incidence of oral cancer in Japan is increasing. Interestingly, the number of young patients with oral cancer is also rising. A 19-year-old man with no history of smoking or drinking alcohol presented with a 20×15-mm elastic, hard, protruding mass with a white surface on the right-hand margin of the tongue. A biopsy resulted in a diagnosis of a well-differentiated squamous cell carcinoma of the tongue, for which a partial resection was subsequently performed. During regular follow-up, the patient demonstrated no clinical or imaging abnormalities until 4 years and 9 months later, when erosion was observed at the right palatoglossal arch. A malignant tumor of the right palatoglossal arch was diagnosed based on cytology and imaging findings, and total resection of the lesion performed. Histopathological examination of the resected lesion revealed a moderately differentiated squamous cell carcinoma. Epithelial dysplasia on the right-hand margin of the tongue was diagnosed 4 years and 9 months after the second surgery and was subsequently resected. The patient’s condition has been favorable for 7 years since the diagnosis of the second cancer, with no noted recurrence. This case emphasizes the importance of follow-up after initial treatment, as even young people, who are likely to have to endure long-lasting consequences from treatment, can develop metachronous cancer in the oral cavity.

This report describes the case of a 68-year-old man who visited our department complaining of poor denture retention and difficulty masticating due to damage to the retainer of a maxillary obturator. The patient had never been satisfied with the fit of this prosthesis, which had been placed two years earlier. The obturator and the mucosal surface of the denture base were incompatible, which had caused the retainer to detach. The maxillary defect was categorized as H3S0D0T0 according to the HS classification. The diagnosis was a masticatory disorder due to a damaged retainer and an incompatible denture base. Optical impressions and occlusal records were taken and a maxillary obturator fabricated using a CAD/CAM system. Dental CAD software was used to design and complete the tooth arrangement. The CAM system was used to mill a polyetherketoneketone disc based on the obtained data and composite resin used to face the teeth and gingiva. The maxillary obturator was placed after only three visits, spanning from impression taking to denture completion. The use of digital data allowed the time to denture completion to be shortened in addition to the number of hospital visits to be reduced. Compared to conventional impression taking, optical impressions also prevent discomfort, decreasing stress for the patient.