Expression of RUNX2/LAPTM5 in the Induction of MC3T3-e1 Mineralization and Its Possible Relationship with Autophagy.

BACKGROUND: The study aims to correlate osteogenesis with autophagy during the mineralization induction of MC3T3-e1 through exploring the expression of runt-related transcription factor 2 (RUNX2)/lysosomal-associated transmembrane protein 5 (LAMPT5). METHODS: The induction of mineralization in MC3T3-e1 was followed by detecting the expressions of osteogenesis-related indexes such as RUNX2, alkaline phosphatase (ALP), osteocalcin (OCN), and LAPTM5 using RT-qPCR and Western blot from 0 to 14 days. Transmission electron microscope was utilised in visualizing the alterations of autophagosomes, which was followed by immunofluorescence detecting the subcellular localization of autophagy-related index sequestosome 1 (P62) and microtubule-associated protein 1 light 3 (LC3) protein and scrutinising the expression of P62 mRNA and P62 and LC3 proteins. RESULTS: Induction of MC3T3-e1 mineralization demonstrated an increased expression of osteogenesis-related indicators such as RUNX2, ALP, OCN, and LAPTM5 (p < 0.05), as evident from the results of RT-qPCR and Western blot. Meanwhile, the expression of autophagosomes increased one day after mineralization induction and then experienced a gradual decline, and enhanced expression of LC3 protein was noted on days 1-2 of mineralization induction but was then followed by a corresponding reduce. In contrast, a continuous increase was reported in the expression of P62 mRNA and protein, respectively (p < 0.05). Up- and down-regulating RUNX2/LAPTM5 expression alone confirmed the aforementioned results. CONCLUSION: It was therefore proposed that RUNX2 may be responsible for an early increase and then a gradual decrease in LAPTM5-mediated autophagy through the regulation of its high expression. Meanwhile, increased LAPTM5 expression in osteogenic mineralization presumed that RUNX2/LAPTM5 promoted autophagy and osteogenic expression, which may play a bridging role in the regulation of autophagy and osteogenesis.

Effect of a dentifrice containing different particle sizes of hydroxyapatite on dentin tubule occlusion and aqueous Cr (VI) sorption.

BACKGROUND: Dentin hypersensitivity is a common negative oral condition that can be treated with dentifrice containing hydroxyapatite (HA). The study evaluated the effect of nano-HA dentifrice on plugging the dentinal tubules for an anti-sensitivity reaction compared to a dentifrice containing common-sized particles. Also, the adsorption capacity of different particle sizes of HA mixed in a dentifrice and which is the optimal particle size was considered. METHODS: Fourty premolar dentine discs and fourty molar dentine discs were randomly divided into 4 groups: distilled water group, ordinary dentifrice group and 80, 300 nm HA dentifrice group. Each dentin disc was brushed with a dentifrice twice daily at 7600 rpm under 100 g force for 2 mins for 7 consecutive days and divided into two parts, half of the dentin disc was detected by the scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), the other half was brushed with distilled water and observed by SEM. One milliliter dentifrice solution (80 nm HA dentifrice, 300 nm HA dentifrice, ordinary dentifrice) was added to 50 ml potassium dichromate solution for 1, 14, and 28 d. The residual Chromium (Cr6+) concentration in the supernatant was measured by the diphenylcarbon phthalocyanine hydrazine method. The elemental constitution in the precipitate was detected by EDS. The Kruskal-Wallis test was used to analyze surface mineralization and different plugging rates of dentinal tubules. The absorption capacity of dentifrices were also evaluated by the Kruskal-Wallis test. RESULTS: The plugging rate in the HA dentifrice group was higher than that in the ordinary dentifrice group, and the 80 nm HA dentifrice group showed the best result. The atomic percentages of Ca and P of 80 nm dentifrice group on the surface of dentinal tubules were the highest. The 80 nm HA dentifrice group showed the best adsorption and stable effect of Cr6+, followed by the 300 nm HA dentifrice group. The 300 nm HA dentifrice and the ordinary dentifrice showed desorption phenomenon. CONCLUSIONS: The dentifrice containing HA, especially the 80 nm HA dentifrice, exerts good dentinal tubule occlusion and surface mineralization effect. This dentifrice was also a good adsorbent of Cr6+.

Healing of root and surrounding periodontium after root damage with miniscrew implants: a histomorphologic study in dogs.

OBJECTIVES: The main purpose of this study was to investigate the detailed healing process of the roots and surrounding periodontium [cementum, periodontal ligament (PDL), and bone] at different time points after intentional root damage with miniscrew implants (MSIs). MATERIALS AND METHODS: After cone-beam computed tomography examination and measurement, a total of 78 premolar and molar roots from five beagle dogs were intentionally damaged by implanting miniscrews in the interradicular region. MSIs were immediately removed, and the histological morphology was observed at days 0 and 3 and at weeks 1, 2, 3, 4, 6, 8, and 12 after root injury using haematoxylin and eosin and fluorescence stainings (fluorescence staining was performed at days 28 and 56). RESULTS: An early new attachment of PDL adhering on to the damaged root surface was found at week 2 after root injury. Tissue differentiation of newly formed bone tissue, PDL, and cementum began at week 3. Moreover, the newly formed cementum and bone were constantly forming and mineralising at weeks 4, 6, 8, and 12, and the width of PDL gradually narrowed until close to the normal width at week 12. CONCLUSIONS: This study demonstrated the complete healing process of the roots and surrounding periodontium after root damage with MSIs in dogs when the damage was limited to the cementum or dentin. CLINICAL RELEVANCE: The findings of this study may help provide a better understanding of the detailed healing process in roots and PDLs damaged by MSIs.

Construction of the animal model of mandibular severe alveolar bone atrophy in Beagle dogs / 口腔疾病防治

Objective @#To establish an animal model that clinically conforms to the characteristics of severe alveolar ridge atrophy. @*Methods @#Beagle dogs were used as experimental subjects. Bilateral fourth premolars and first molars in mandible were extracted. A horizontal groove was made on alveolar ridge which was 8 mm from the cemento-enamal junction of mandible third premolar and second molar. Rongeur was used to remove the alveolar bone above this groove and bone chisel was used to level the bone-free area. A box-shaped defect cavity of the size 25 mm × 8 mm was formed with sterile silicone prosthesis implanted. After careful suture we waited for the subjects to heal naturally. Eight weeks after operation, CBCT examination was performed.@*Results @#Eight weeks after bone remodeling the top of alveolar ridge of operation area appeared to be a circular arc. The average distance from the bottom of the ridge to inferior alveolar nerve canal was 2.5 mm. @*Conclusion @#This study successfully established the Beagle dog animal model for severe alveolar ridge atrophy and laid the foundation for experiments on vertical bone augmentation.