The periodontal ligament is a ligament-like tissue located between the alveolar bone and cementum. Ascorbic acid (AA) is a water-soluble vitamin that plays an important role in this tissue. This study aimed to investigate the effect of AA on the proliferation of periodontal ligament fibroblasts (PDLFs). Cell proliferation was examined using the WST-8 assay. Real-time PCR was used to examine gene expression in PDLF. In some experiments, siRNA was used for the knockdown of gene expression. The WST-8 assay showed that AA promotes PDLF proliferation. Gene expression levels of cycline E1 and CDK2 were increased by AA. The cell proliferation-promoting effect of AA was abolished by the knockdown of SVCT2. Furthermore, cell proliferation was inhibited by adding an ERK inhibitor, UO128. The present study showed that AA is taken up into PDLFs via SVCT2, which contributes to rotating the cell cycle and enhancing cell proliferation. Furthermore, ERK signaling plays an important role in this process. Our results demonstrated that AA has an important role in periodontal ligament proliferation.

We aimed to explore the risk factors for denture-related oral mucosal lesions (DML). A total of 134 fixed denture wearers visiting from February 2018 to January 2023 were selected and assigned into a DML group and a non-DML group according to whether DML occurred. The denture-related factors possibly leading to DML were recorded. A binary logistic regression model was employed to analyze the correlations of different denture-related factors with the occurrence of DML. Gender, denture type, inflammatory fibrous hyperplasia, restoration method, cusp inclination, occlusal force distribution, presence of mechanical complications, implant location, and denture manufacturing time were factors affecting the occurrence of DML (P<0.05). The results of logistic regression analysis revealed that restoration method, denture type, cusp inclination, implant location, occlusal force distribution, and presence of mechanical complications were independent risk factors affecting DML (P<0.05). Restoration method, denture type, cusp inclination, implant location, occlusal force distribution, and presence of mechanical complications affect the occurrence of DML. Rational precautionary measures targeting these influencing factors should be taken to decrease the incidence rate of DML.

Osteoclasts are associated with normal bone remodeling in healthy tissues and excess bone resorption in bone-destructive diseases. Bidens pilosa is a plant belonging to the Asteraceae family and is well known for its antioxidative stress effect. In the present study, RAW264.7 cells were treated with receptor activator of the NF-kappaB ligand (RANKL), which is predominant in the foci of pathological bone resorption, with or without extracts of B. pilosa harvested in Miyako Island, Japan (MBP) to examine the effects of MBP on osteoclastogenesis. Osteoclast differentiation was evaluated based on tartrate-resistant acid phosphatase (TRAP) activity. The expression of bone resorption-related enzymes and superoxide dismutase (SOD)-2 was examined using real-time polymerase chain reaction or enzyme-linked immunosorbent assays. The oxidative stress level was evaluated using fluorescent staining. Pit-formation assays with calcium phosphate disks were used to assess the mineral resorption activity. MBP suppressed the expression of carbonic anhydrase II, matrix metalloproteinase-9, and cathepsin K and decreased the size of TRAP-positive multinuclear osteoclast-like cells in the presence of RANKL. However, these small cells expressed bone resorption-related enzymes described above. MBP reduced the formation of large-sized resorption pits but not that of small-sized pits. Additionally, SOD-2 expression was increased, whereas RANKL-induced oxidative stress was decreased after the addition of MBP. In conclusion, MBP suppressed RANKL-induced osteoclastic bone resorption via an alleviation of oxidative stress. This inhibitory effect is thought to be exerted on the formation of large osteoclasts.

Propofol affects the central nervous system rapidly and works as an anesthetic. After intravenous administration, cells resident in bone tissues are also exposed to propofol. Osteoclasts can form actin rings on bone surfaces and express carbonic anhydrase II (Car2), cathepsin K (Ctsk), and matrix metalloproteinase-9 (Mmp9), which are enzymes associated with bone decomposition and play a central role in bone resorption. This study examined the expression of enzymes involved in bone resorption and actin ring formation in cells stimulated by propofol to elucidate the difference in the effects of continuous and temporary propofol stimulation on osteoclast resorption ability. RAW264.7 cells were stimulated with propofol emulsified injection solution or 2,6-diisopropylphenol (non-emulsified propofol) for 5 h, 1.5 days, or 4 days in the presence of the receptor activator of nuclear factor kappa B ligand (RANKL). Osteoclast-like cells were confirmed by staining with tartrate-resistant acid phosphatase (TRAP). Actin rings were detected using fluorescent staining. The bone resorp­tion enzymes were detected using real-time PCR and Western blotting. The mineral resorption activity was assessed using the pit formation assay. Continuous propofol stimulation for more than 1.5 days suppressed actin ring formation and Car2, Ctsk, and Mmp9 expression. Propofol stimulation for 5 h had no suppressive effects, whereas prolonged stimulation (> 1.5 days) decreased the area of resorption pits. There was no marked difference in the suppressive effects of emulsified versus non-emulsified propofol on TRAP-positive multinuclear cell formation. Our in vitro study indicated that exposure of RAW264.7 cells to propofol for several hours did not affect their subsequent RANKL-induced differentiation into osteoclast-like cells, thus maintaining their bone resorption function. However, continuing propofol exposure suppressed the formation and activity of osteoclast-like cells.

Dental calculus is one of the risk factors of periodontal diseases and tooth loss in humans and some animals. However, present authors noticed that calculus adhering to the canine surfaces, which naturally came off the jaws due to periodontal diseases, could be removed easily by hand with little breakage. Few studies on differences in physicochemical properties of calculus between humans and animals are available. Thus, the purpose of this study was to investigate calculus interface with the tooth surface in canine and its mineral characteristics for seeking the ease when removing canine calculus. Calculus specimens involving longitudinally cut surface of the calculus and tooth, and its back surface of the naturally detached from the tooth were observed using SEM. Elemental analysis of calcium (Ca) and phosphorus (P) was performed by EPMA on the cut surface from the top surface toward the bottom. Then the molar ratios of Ca/P were measured to estimate the mineral composition. Moreover, TEM observation was performed to characterize the morphology of calculus minerals. SEM observation showed that the naturally detached back surface was smooth, indicating no apparent breakage. In addition, an apparent gap without breakage of calculus at the interface was observed, which is rarely reported in human calculus. EPMA analysis provided various Ca/P molar ratios with a lower (1.0) to higher values (3.2-3.4). Ca and P contents observed in EPMA color images showed that the mineral content of the calculus near the bottom seemed to be lower than that in the inner body of the calculus. TEM observation revealed morphologically different types of the minerals; aggregated cubic substances, rod-like and spherical substances. A stronger radio-opacity was noted in rod-like and spherical substances compared to the cubic substances, suggesting the former was non-apatitic and the latter apatitic minerals.

Resorption time is essential for bone substitution composite materials. In the best case, it has to coincide with the time of new bone formation. In this work, biphasic biomaterial consisting of natural hydroxyapatite (NHAp) and endodontic cement MTA Angelus (EC) is explored. In our experiment we have used three concentrations of the new composite material: first, EC40/NHAp60 volume %, second, EC50/NHAp50 volume %, and third, EC60/NHAp40 volume %. The main task was porosity exploration of each material and also determination of NHAp crystallite size in the material, both mentioned parameters are essential for the resorption process. Results indicate that the composite material EC40/NHAp60 has the highest porosity, at nearly 8%. We consider that such result is due to the higher content of NHAp in the specimens. In contrast, the lowest level of porosity is in the material EC60/NHAp40, at 5.2%. Porosity of the third material is between the two first mentioned composites. The size of NHAp crystallites in the biomaterial is approximately 20 nm. Consequently, it is possible to assert that the size of the crystallites is nearly the same as hydroxyapatite crystallites in natural bone, which is a prerequisite for biomaterial resorption. The study shows that material with the mentioned porosity and size of crystallites has potential to be used as bone substitute material.