In this study, we compared the healing process of bone defects treated with a trephine bur with those treated with an ultrasonic knife using a critical-sized bone defect model on rat calvaria. Nine-millimeter critical-size bone defects were prepared using both instruments in the calvaria of adult Sprague-Dawley rats. One and four weeks after the osteotomy, we performed a histomorphometric analysis to evaluate bone regeneration around the cutting surface. Quantitative micro-computed tomography analyses of the bone volume in both groups suggested that ultrasonic knife surgery resulted in superior bone formation compared to that in trephine bur surgery. Furthermore, at the cutting surface, the ultrasonic knife treatment retained the alkaline phosphatase activity and new bone formation, which was identified using calcein staining, even one week after surgery. Considering the speed and volume of bone regeneration, the ultrasonic knife is likely to be the preferred over the trephine bur to perform osteotomies in implant surgery.
This study aimed to analyze the effect of emodin on alveolar bone resorption in rats with periodontitis through the interleukin-23 (IL-23)/T helper 17 (Th17) cells inflammatory axis. Twenty-four male Sprague Dawley rats were randomly divided into the following three groups of eight rats each: the control group (group N), periodontitis group (group P), and periodontitis + emodin intervention group (group E). After 2 weeks of continuous emodin intervention, alveolar bone loss (ABL) was evaluated by morphological analysis. Tartrate-resistant acid phosphatase staining was performed to determine the number of osteoclasts (OCs) in periodontal tissue. The ABL and trabecular separation were greater and the number of OCs and the G1/G0 and G2/M phase ratios were higher in group P than those in groups N and E (P < 0.05). In contrast, the trabecular number and thickness were decreased and the S and G2+S phase ratios were lower in group P than those in groups N and E (P < 0.05). However, these indices did not differ significantly between groups E and N. The IL-23, IL-17, RANKL, RANK, RANKL/OPG, IL-2, IL-6, IL-1β, and TNF-α levels across the three groups were in the order of group P > group E > group N and the OPG levels were in the order of group P < group E < group N (P < 0.05). Emodin may decrease the expression of RANKL and RANK proteins and levels of inflammatory factors; increase OPG, PPAR-γ, and NF-κB protein expression levels; and decrease the number of OCs through the IL-23/Th17 inflammatory axis, thus inhibiting ABL and bone resorption in rats with periodontitis and promoting the proliferation of periodontal ligament cells and alveolar bone repair.
The objective of this study was to carry out quantitative evaluations of the microstructural characteristics of bone surrounding anchor screws placed under a horizontal load and the microstructural characteristics of bone on the compressed and non-compressed sides of anchor screws by investigating the orientation of biological apatite (BAp) crystals and collagen fiber anisotropy. Anchor screws were implanted in the femurs of adult rats. They were divided into those placed under a horizontal load (horizontal loading group, n = 4), those not placed under a horizontal load (unloaded group, n = 4), and a sham group of rats that did not undergo femoral anchor screw implantation. In addition to histological observations, BAp crystal orientation and collagen fiber anisotropy were also analyzed. Osteocytes adjacent to anchor screws on the compressed side in the horizontal loading group were rounder in shape than those in normal femurs, the unloaded group, and on the non-compressed side in the horizontal loading group. Collagen fibers showed anisotropy on the non-compressed side in the horizontal loading group. BAp crystals also showed a uniaxial preferential orientation in the direction of traction on the compressed side in the horizontal loading group. These results demonstrated that the osteogenesis of bone around anchor screws placed under a sustained horizontal load gave this bone structural characteristics that differed in some respects from those of normal bone. They also showed that this bone acquired micro/nanostructural characteristics adapted to its new mechanical environment.
Calcitonin gene-related peptide (CGRP), a neuropeptide derived from sensory nerves, suppresses osteoclast differentiation; however, the detailed mechanism is unknown. Therefore, in this study, we investigated the mechanism underlying the CGRP-mediated suppression of osteoclast differentiation using a model in which mouse monocyte/macrophage RAW264.7 cells were induced to differentiate into osteoclasts with recombinant mouse soluble receptor activator of nuclear factor-kappa B ligand (s-RANKL). RAW264.7 cells were cultured with s-RANKL in the presence or absence of CGRP for 24–72 h and then quantitative real-time PCR was performed. The mRNA expression of the positive regulators of osteoclast differentiation [i.e., nuclear factor of activated T-cells 1 (Nfatc1) and B lymphocyte-induced maturation protein-1 (Blimp1)], as well as that of the negative regulators of osteoclast differentiation [i.e., MAF bZIP transcription factor B (MafB), B-cell lymphoma 6 (Bcl6), and interferon regulatory factor-8 (Irf8)], was analyzed. In RAW264.7 cells treated with s-RANKL, CGRP significantly suppressed Nfatc1 and Blimp1 mRNA expression at 24 and 48 h. On the contrary, CGRP significantly increased the mRNA expression of MafB at 24 and 48 h of culture and of Bcl6 at 48 and 72 h of culture. However, CGRP did not affect Irf8 mRNA expression. In s-RANKL-untreated RAW264.7 cells, MafB mRNA expression significantly increased from 2 to 8 h, whereas Bcl6 mRNA expression significantly increased from 4 to 24 h of culture. These results suggest that CGRP inhibits osteoclast differentiation by increasing the mRNA expression of MafB and Bcl6, which are negative regulators of osteoclast differentiation.
The automatic extraction of landmarks from three-dimensional tooth models using artificial intelligence is crucial to advance dental anatomy studies. However, collecting sufficient data for artificial intelligence training hinders progress in this field. To automatically identify anatomical landmarks on tooth models, this paper proposes a method for generating substantial amount of training data from the digital data of a single human maxillary canine. Human maxillary canine data were loaded into Blender, and the landmark was defined as the cusp of the canine. Sequentially, the coordinate values of the centroid of the landmark were used as correct answer labels. A total of 22,896 training images were generated using Python scripts, and they were split into train and validation datasets. Pairs of images and label data were fed into the artificial intelligence network, which comprises four convolutional layers and one max pooling layer. The accuracy of the trained artificial intelligence was evaluated on 915 200 × 200 pixel images, which were different from the training images. The average Euclidean distance error of the artificial intelligence-predicted coordinate values of the landmark was 6.1 pixels. Our approach, based on the training data generated in Blender using Python scripts, provides a powerful solution when it is challenging to obtain sufficient amount of medical field data for artificial intelligence-assisted procedures.
DOT1-like histone lysine methyltransferase (DOT1L) has been revealed to be highly correlated with progression of diverse types of cancer, while its role in head and neck squamous cell carcinoma (HNSCC) has still remained elusive. In this study, it was found that DOT1L was highly expressed in HNSCC tissues and cell lines, and its high expression level was closely associated with poor prognosis, tumor differentiation, T stage, and pathological stage of HNSCC patients. With the introduction of DOT1L inhibitors, SGC 0946, DOT1L inhibition significantly suppressed proliferation, migration, and invasion of HNSCC cells, while increased their apoptosis rate. To investigate the fundamental mechanism, we predicted that the expression level of Forkhead Box M1 (FoxM1) was positively correlated with DOT1L, and it was found that the expression level of FoxM1 was upregulated in HNSCC tissues and cell lines. Importantly, DOT1L activated FoxM1 through H3K79me2, and inhibition of DOT1L repressed the malignant behaviors of HNSC cells, which could be rescued by FoxM1 overexpression. Taken together, the results suggested that DOT1L could epigenetically induce the expression level of FoxM1 through H3K79me2 and affected the malignant behaviors of HNSCC cells, which could provide novel outcomes for the therapy of HNSC.
The present study used ultra-high-resolution micro-computed tomography (CT) to clarify the classification of root canal morphologies and the incidence of accessory canals in the maxillary first molar mesiobuccal (MB) root. Aspects of the relationship with root canal reinfection during or after molar endodontic treatment were also investigated. Molar three-dimensional structure, pulp cavity, and accessory canals were examined on micro-CT images of 100 Japanese maxillary first molars from the collection at the Department of Anatomy, Tokyo Dental College. The most common Vertucci’s classification of the main root canal of the Japanese maxillary first molar mesial root canal was Type I, followed by Type V. Accessory canal incidence was 75.0%, which was higher than previously reported; however, the majority of such canals were within the apical 3 mm. Many accessory canals were observed even with the single canals of Type I, suggesting that the existence of accessory canals should always be considered even if diagnostic imaging clearly shows a Type I classification.
Porous titanium (porous Ti) possesses excellent mechanical strength and three-dimensional structure. Therefore, it enables bone formation due to its good osteoconduction abilities. Osseointegration can be achieved at the implant site after bone reconstruction with porous Ti. This study aimed to assess implant stability following osseointegration at sites reconstructed with porous Ti. Hollow-shaped porous Ti were placed in the tibiae of six New Zealand white rabbits. Ti dental implants were placed 4 weeks later. Implant placed at the parent bone sites, without porous Ti, served as the controls. Histological and histomorphometric assessments of the porous Ti and control sites were performed 4 weeks later. There was no significant difference in the insertion torque between the porous Ti and control groups. The primary and secondary implant stability quotient value was higher in the porous Ti group than that in the control group. Histologically, bone reconstruction was achieved with porous Ti through osteoconduction into the original bone region and bone marrow region, as osseointegration of implants was achieved even in the bone marrow region. The bone-implant contact ratio was similar in both the groups; however, the bone-implant contact was mainly in the cortical region in the control group. In the present study, the reconstructed bone site with porous Ti showed favorable osseointegration ability when the dental implant was placed. Porous Ti is expected to be a suitable material for bone material before implant placement.
To explore the effects of vasoactive intestinal polypeptide (VIP) on the proliferation and migration of human buccal mucosal fibroblasts (HBMFs). HBMFs were primarily cultured and pretreated with lipopolysaccharide (LPS) as an inflammatory stimulant. The cells in experimental group and control group were transfected with overexpressed pcDNA3.1-VIP and its control pcDNA3.1-VIP-NC, and LPS group was also set. All cells were routinely cultured. Then the cell proliferative activity and migration capacity were detected by MTT assay and wound healing assay, respectively. The mRNA expressions of N-cadherin and proliferating cell nuclear antigen (PCNA) were determined using qRT-PCR, and the expression levels of VIP and macrophage metalloelastase (MME) were detected by Western blotting. Compared with LPS group, the cell proliferative activity and migration capacity, the mRNA expressions of N-cadherin and PCNA, and the expressions of VIP and MME were significantly increased in experimental group (P<0.05). Overexpression of VIP can enhance the proliferation and migration of HBMFs, probably by regulating the expression of MME.
To investigate the association of the interaction between peroxisome proliferator-activated receptor gamma 2 (PPAR-γ2) gene polymorphism and glycosylated hemoglobin (HbAlc) level with susceptibility to diabetic periodontitis (DP). A total of 259 DP patients and 257 patients with type 2 diabetes mellitus (T2DM) treated from August 2017 to April 2020 were enrolled, and another 180 healthy subjects were selected as control group. The HbA1c level of T2DM patients was determined using automatic biochemical analyzer. PPAR-γ2 gene Pro12Ala polymorphism was detected by the dideoxy chain termination method. The risk factors for DP were analyzed by multivariate logistic regression model. The adjusted odds ratio (OR) and 95% confidence interval of PPAR-γ2 gene Pro12Ala polymorphism and HbA1c level for the risk of DP were estimated, and the interaction between Pro12Ala polymorphism and HbA1c level was analyzed. The risk of DP increased in T2DM patients with genotypes Pro12Ala (PA) and Pro12Ala (AA) (OR=2.529, OR=2.594, P<0.01). T2DM patients with 6%≤ HbA1c <8% or HbA1c ≥8.0% had significantly elevated risk of DP (OR=2.046, OR=3.105), and T2DM patients with HbA1c ≥8.0% had higher risk of DP than those with 6%≤ HbA1c <8% (P<0.01). There was a positive interaction between HbA1c level and Pro12Ala (PA) and Pro12Ala (AA) (γ>1). Individuals with genotypes Pro12Ala (PA) or Pro12Ala (AA) are high risk population of DP. The interaction between these genotypes and HbA1c level facilitates the occurrence and development of DP. Measures should be taken to control HbA1c level or to regulate gene expression, so as to prevent DP.