Effect of Different Mechanical Properties of Core Build-up Materials on the Root Furcation of A Severely damaged Primary Molar: A Finite Element Analysis

Objectives: To assess the von Mises stress and stress distribution pattern on the root furcation of a severely damaged primary molar restored with different core build-up materials and stainlesssteel crown (SSC). Materials and Methods: The finite element analysis was used to investigate stresses induced in the tooth structures included a sound primary molar and severely damaged primary molars restored with four different core-build up materials, including flowable composite core build-up, bulkfill resin composite, RMGIC and nano-RMGIC. The maximum von Mises stress was used to representthe internal load induced in the model. Results: Overall maximum von Mises stresses was the highest in the sound tooth. However, when focusing on apico-cervical aspect, all restored primary molars showed higher maximum von Mises stress than the sound tooth. The stress distribution pattern of each group was similar, except for the nano-RMGIC group that showed high stress concentrated at the tooth furcation and the buccal aspect of the root furcation. From the ratio of its tensile strength and the maximum von Mises stress, the nano-RMGIC possessed the highest fracture resistance, followed by bulk-fill composite, RMGIC and flowable composite core group, respectively. Discussion: Although nano-RMGIC possessed the highest fracture resistance, it showed an unfavorable stress distribution pattern, which caused high stress at the root furcation. The bulk-fill composite possessed not only high fracture resistance but also favorable stress distribution. Conclusion: The present study introduces crucial information that could lead to an alternative treatment for severely damaged primary molar. Our findings recommend bulk-fill composite as a potential core build-up material. > ว.ทันต.มศว ปีที่ 16 ฉบับที่ 1 พ.ศ. 2566 หน้า 62-77. > SWU Dent J. 2023;16(1): 62-77

Expression and Regulation of bone moephogenetic protein receptors in human alveolar bone cells

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ICAM-1-mediated osteoblast-T lymphocyte direct interaction increases mineralization through TGF-β1 suppression

Modulation of osteoblast functions by T lymphocytes is important in inflammation-associated mineralized tissue diseases. The study aimed to determine whether direct interaction between these two cell types affects osteoblast functions and mineralization. The results showed that direct contact between the two cell types was evident by scanning electron microscopy and transmission electron microscopy. Under osteogenic induction, higher hydroxyapatite precipitation was observed in cocultures with direct contact with T lymphocytes compared with that by osteoblasts cultured alone. Cocultures without direct cell contact caused a decrease in mineralization. Direct cell contact also upregulated intercellular adhesion molecule (ICAM)-1 and simultaneously downregulated transforming growth factor (TGF)-β1 in osteoblasts. However, the downregulation of TGF-β1 was reversed by ICAM-1 blocking. Exogenously added TGF-β1 in cocultures with direct cell contact suppressed mineralization. In conclusion, studies are consistent with ICAM-1-mediated direct contact between osteoblasts and T lymphocytes increasing mineralization via downregulation of TGF-β1 in osteoblasts in vitro. This suggests a possible unexpected, but crucial, role of T lymphocytes in enhancing matrix mineralization during the repair process in vivo. The study identifies ICAM-1/TGF-β1 as possible novel therapeutic targets for the treatment and prevention of inflammation-associated mineralized tissue diseases

Geranylgeraniol prevents zoledronic acid-mediated reduction of viable mesenchymal stem cells via induction of Rho-dependent YAP activation

Long-term use of zoledronic acid (ZA) increases the risk of medication-related osteonecrosis of the jaw (MRONJ). This may be attributed to ZA-mediated reduction of viable mesenchymal stem cells (MSCs). ZA inhibits protein geranylgeranylation, thus suppressing cell viability and proliferation. Geranylgeraniol (GGOH), which is a naturally found intermediate compound in the mevalonate pathway, has positive effects against ZA. However, precise mechanisms by which GGOH may help preserve stem cell viability against ZA are not fully understood. The objective of this study was to investigate the cytoprotective mechanisms of GGOH against ZA. The results showed that while ZA dramatically decreased the number of viable MSCs, GGOH prevented this negative effect. GGOH-rescued ZA-exposed MSCs formed mineralization comparable to that produced by normal MSCs. Mechanistically, GGOH preserved the number of viable MSCs by its reversal of ZA-mediated Ki67+ MSC number reduction, cell cycle arrest and apoptosis. Moreover, GGOH prevented ZA-suppressed RhoA activity and YAP activation. The results also established the involvement of Rho-dependent YAP and YAP-mediated CDK6 in the cytoprotective ability of GGOH against ZA. In conclusion, GGOH preserves a pool of viable MSCs with osteogenic potency against ZA by rescuing the activity of Rho-dependent YAP activation, suggesting GGOH as a promising agent and YAP as a potential therapeutic target for MRONJ