Chen Yx

Oral bacterial adhesion forces to biomaterial surfaces constituting the bracket–adhesive–enamel junction in orthodontic treatment

Bacterial adhesion to biomaterial surfaces constituting the bracket-adhesive-enamel junction represents a growing problem in orthodontics, because bacteria can adversely affect treatment by causing demineralization of the enamel surface around the brackets. It is important to know the forces with which bacteria adhere to the surfaces of these junction materials, as the strength of these forces will determine how easy it will be to remove the bacteria. We compared the adhesion forces of five initially colonizing and four cariogenic strains of bacteria to an orthodontic adhesive, stainless steel, and enamel, with and without a salivary conditioning film. Adhesion forces were determined using atomic force microscopy and a bacterial probe. In the absence of a salivary conditioning film, the strongest bacterial adhesion forces occurred to the adhesive surface (-2.9 to -6.9 nN), while adhesion forces to the enamel surfaces were lowest (-0.8 to -2.7 nN). In the presence of a salivary conditioning film, adhesion forces were reduced strongly, to less than 1 nN, and the differences between the various materials were reduced. Generally, however, initial colonizers of dental hard surfaces presented stronger adhesion forces to the different materials (-4.7 and -0.6 nN in the absence and presence of a salivary conditioning film, respectively) than cariogenic strains (-1.8 and -0.5 nN).

Biologic response of rapid tooth movement with periodontal ligament distraction

INTRODUCTION Length of treatment is a complaint of many orthodontic patients. The purpose of this study was to evaluate the security and feasibility of rapid tooth movement with periodontal ligament distraction. METHODS Eight male beagles, aged 13 to 16 months, were used in this study. Extraction of the mandibular second premolar and alveolar surgery to reduce the osteal resistance on the mesial side of the extraction socket were performed on the experimental side. Then a device was placed to distract the first premolars distally on the experimental side; on the control side, the first premolars were distalized with nickel-titanium coil springs. The beagles were killed in the first, second, fourth, and eighth weeks after orthodontic force application. RESULTS The first premolar on the experimental side moved more rapidly than that on the control side (P <0.05). Histologic data indicated that more new bone was deposited on tension area of the experimental side than on the control side. Active and extensive bone resorption in the compressive area and bone deposition in the tension area were observed on the experimental side. CONCLUSIONS These results suggest that the periodontal ligament can be rapidly distracted without complications. The rapid orthodontic tooth movement by distracting the periodontal ligament cannot be emulated by current conventional orthodontic concepts and methods.

Effects of Hypoxia on the Immunomodulatory Properties of Human Gingiva–Derived Mesenchymal Stem Cells

The environment of bone marrow mesenchymal stem cells (MSCs) is hypoxic, which plays an important role in maintaining their self-renewal potential and undifferentiated state. MSCs have been proven to possess immunomodulatory properties and have been used clinically to treat autoimmune diseases. Here, we tested the effects of hypoxia on the immunomodulatory properties of MSCs and examined its possible underlying mechanisms. We found that hypoxic stimulation promoted the immunomodulatory properties of human gingiva–derived mesenchymal stem cells (hGMSCs) by enhancing the suppressive effects of hGMSCs on peripheral blood mononuclear cells (PBMCs). The proliferation of PBMCs was significantly inhibited, while the apoptosis of PBMCs was increased, which was associated with the Fas ligand (FasL) expression of hGMSCs. The in vivo study showed that systemically infused hGMSCs could enhance skin wound repair, and 24-h hypoxic stimulation significantly promoted the reparative capacity of hGMSCs. For mechanism, hGMSC treatment inhibited the local inflammation of injured skin by suppressing the inflammatory cells, reducing the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), and increasing anti-inflammatory cytokine interleukin-10 (IL-10), which was promoted by hypoxia. Hypoxia preconditioning may be a good optimizing method to promote the potential of MSCs for the future cell-based therapy.

Poisson Analysis of Streptococcal Bond-strengthening on Saliva-coated Enamel

The forces responsible for bond-strengthening in initial oral bacterial adhesion are unknown. Since Lifshitz-Van der Waals and electrostatic forces work instantaneously upon approach, it is hypothesized that bond-strengthening is governed by hydrogen bonding. Poisson analysis of adhesion forces observed during the retraction of bacterial probes from surfaces in atomic force microscopy can be used to analyze the nature of the adhesion forces. Streptococcal adhesion forces increased from about −0.7 to −10.3 nN when the contact time between cell surfaces and salivary films on enamel was increased from 0 to 120 sec. Initial and final adhesion forces were stronger for initial colonizers of tooth surfaces (S. mitis, S. sanguinis) than for later, more cariogenic, strains (S. sobrinus, S. mutans). Retraction curves after increased contact times showed minor peaks, representative of hydrogen bonds, and Poisson analyses indicated repulsive non-specific forces of around +0.3 nN and slightly more attractive hydrogen-bonding forces (−1.0 nN) for initial than for late colonizers (−0.8 nN).

Effects of Class III magnetic orthopedic forces on the craniofacial sutures of rhesus monkeys

INTRODUCTION The objectives of this study were to develop an intraoral intermaxillary Class III magnetic orthopedic appliance (MOA-III), to investigate the influence of Class III orthopedic forces on the craniofacial sutures of rhesus monkeys, and to elucidate the mechanism of Class III malocclusion orthopedic treatment. METHODS Six male rhesus monkeys in the mixed-dentition stage were divided into 3 groups of 2 each: a 90-day experimental group, a 45-day experimental group, and a control group. Six craniofacial sutures were observed. The experimental monkeys received heavy forces (300 g) per side initially, created by opposing Nd(2)Fe(14)B magnetic units in a cast MOA-III. The control groups received no treatment. Before the appliances were inserted, metal implants were placed in each animal as bone markers for direct measurement. To determine the rate of bone apposition, each animal was injected with fluorescent dyes intravenously before and during the experimental period. Intraoral photographs, dental casts, and cephalometric radiographs of each animal were obtained at the beginning and end of the experiment. RESULTS Distances between metal implants on both sides of the sutures were enlarged in the experimental groups. Cephalometric analysis showed that the treatment effects of MOA-III are a combination of skeletal and dental changes in the maxilla and the mandible. Distinct changes from physiologic growth remodeling were observed in some sutures but not in the control groups. No inflammation was noted in either experimental or control monkeys. CONCLUSIONS The MOA-III can be an efficient intraoral appliance to treat Class III malocclusion that is caused by a deficient maxilla; heavy orthopedic forces (300 g per side) are safe and effective in the rhesus monkey.

Osteoimmunology in orthodontic tooth movement

The skeletal and immune systems share a multitude of regulatory molecules, including cytokines, receptors, signaling molecules, and signaling transducers, thereby mutually influencing each other. In recent years, several novel insights have been attained that have enhanced our current understanding of the detailed mechanisms of osteoimmunology. In orthodontic tooth movement, immune responses mediated by periodontal tissue under mechanical force induce the generation of inflammatory responses with consequent alveolar bone resorption, and many regulators are involved in this process. In this review, we take a closer look at the cellular/molecular mechanisms and signaling involved in osteoimmunology and at relevant research progress in the context of the field of orthodontic tooth movement.

Influence of fixed orthodontic treatment on the menstrual cycle of adult females: A prospective longitudinal study

OBJECTIVE To investigate the influence of fixed orthodontic treatment on the menstrual cycle, including menstrual cycle length (MCL) and duration of menstrual bleeding (DMB), in adult female patients. MATERIALS AND METHODS This was a prospective longitudinal study conducted in Chengdu, China. A total of 164 adult women with normal menstrual cycles were recruited in the study, with 79 patients undergoing orthodontic treatment and 85 serving as controls. Data of MCL, DMB, and accompanying symptoms were collected over six consecutive menstrual cycles in each participant. Students t test, Chi-square test, Moses extreme reaction test, and repeated measures analysis of variance were used for statistical analysis. RESULTS The MCL of the first menstrual cycle (T1) was significantly elongated by 2.1 ± 0.5 days compared with baseline (P  =  .003, 95% CI [-3.7, -0.5]). Variability of MCL of the orthodontic group at T1 was also significantly greater (range, 15-46 days) than that of the control group (range, 24-36 days) (P < .05). No significant difference in MCL was found in the subsequent five menstrual cycles (T2-T6) compared with baseline, and no significant differences in DMB or other accompanying symptoms were observed throughout the study. CONCLUSION Fixed orthodontic treatment may influence the MCL of adult females in the first month after bonding, but showed no effect on DMB or subsequent MCL through the follow-ups.