Age-related changes of bone mineral density in mandible by quantitative computed tomography.

Quantitative Computed Tomography (QCT) was used to investigate age-related changes in trabecular bones of the mandible. The volumetric Bone Mineral Density (vBMD) of mandibles was found to be increasing with aging in the 20-29, 30-39, 40-49 age groups, while resulted decreasing in the 50~ years age group in a Chinese population. The aim of this study was to validate QCT as a reliable method to measure the vBMD of the mandible and to assess vBMD of the mandible in a Chinese population. A total of seven hundred and eighteen volunteers (299 males, 419 females), ranging from 20 to 63 years of age, previously enrolled in another study, were included for vBMD measurements by QCT. A total of 50 subjects were enrolled for the validation of QCT measurement. Basic information (age, height and weight), and vBMD of the mandible (middle, body and angle) were recorded. Comparisons among age and sex groups were analyzed using the Mann-Whitney test. Linear correlation analysis between vBMD and age was performed. The mandibular vBMD was twice measured with QCT by one operator and resulted highly repeatable (ICC 0. 97, P 0. 05). The vBMD in the middle of the mandible was the highest, followed by that in the body and at the angle of mandible. In each age group, the mean vBMD increased with aging except for the 50~ years age group (P less than 0.05) in which it decreased. The mean mandibular vBMD was higher in females than males in each age group (P less than 0.05). Correlation between vBMD and age was statistically significant (r=0.15, P less than 0.01). QCT shows high precision for the measurement of BMD in the mandible. The present study provides normative data of the mandible in an age- and sex-stratified manner, which can be helpful in clinical practice.

Evaluation of the in vitro biocompatibility of a new fast-setting ready-to-use root filling and repair material.

AIM: To evaluate the in vitro biocompatibility of iRoot FS (Innovative BioCeramix Inc., Vancouver, BC, Canada) and to compare its performance with those of iRoot BP Plus (Innovative BioCeramix Inc.) and ProRoot mineral trioxide aggregate (MTA; Dentsply Tulsa Dental, Tulsa, OK, USA). METHODOLOGY: MC3T3-E1 cells were cultured for 1, 2 and 3 days in various dilutions of iRoot FS, iRoot BP Plus and MTA extracts after 7 days of setting to assess cell viability using a cell counting kit-8 (Dojindo, Kumamoto, Japan). The cell apoptosis induced by the set material extracts was evaluated through annexin V-propidium iodide flow cytometry. Changes in the cytoskeletal organization and stress fibres were observed through immunofluorescence by labelling the fibrous actin and nuclei of the cells. Cell attachment was observed under a scanning electron microscope after the MC3T3-E1 cells were cultured on the surface of a material disc set for 1 day. The data were analysed using one-way anova. RESULTS: iRoot FS extracts induced higher cell viability than the control extracts (P < 0.05) at levels comparable to those of iRoot BP Plus and MTA. Compared with the control group, iRoot FS did not promote cell apoptosis. Stretched stress fibres and cytoskeletons were detected in the cells treated with iRoot FS extracts. Scanning electron microscopy revealed that the MC3T3-E1 cells attached to iRoot FS appeared flatter and exhibited better stretch than those attached to the other extracts. CONCLUSIONS: iRoot FS displayed in vitro biocompatibility with MC3T3-E1 cells by promoting cellular proliferation and attachment without causing cell apoptosis.

Bioinformatic and expression analysis of the OMT gene family in Pyrus bretschneideri cv. Dangshan Su.

With high nutritional value in its fruits, Dangshan Su pear has been widely cultivated in China. The stone cell content in fruits is a key factor affecting fruit quality in pear, and the formation of stone cells has been associated with lignin biosynthesis. O-Methyltransferase (OMT) is a key enzyme involved in lignin metabolism within the phenylpropanoid pathway. Here, we screened 26 OMT genes from the Pyrus bretschneideri cv. Dangshan Su genome using the DNATOOLs software. To characterize the OMT gene family in pear, gene structure, chromosomal localization, and conserved motifs of PbOMTs were analyzed. PbOMTs were divided into two categories, type I (designated PbCCOMTs) and type II (designated PbCOMTs), indicating the differentiation of function during evolution. Based on the analysis of multiple sequence alignment, cis-element prediction, and phylogenetic relationships, two candidate genes, PbCCOMT1 and PbCCOMT3, were selected for the analysis of temporal and spatial gene expression in pear. The promoter regions of both PbCCOMT1 and PbCCOMT3 contain regulatory motifs for lignin synthesis. Moreover, the two genes show high similarity and close phylogenetic relationships with CCOMTs in other species. Expression analysis showed that transcript levels of two PbCCOMTs were positively associated with the contents of both stone cells and lignin during the development of pear fruit. These results suggest that PbCCOMT1 and PbCCOMT3 are closely associated with lignin biosynthesis. These findings will help clarify the function of PbOMTs in lignin metabolism and to elucidate the mechanisms underlying stone cell formation in pear.

Interactions between Golli-MBP and Th1/Th2 cytokines in patients with oral lichen planus.

OBJECTIVE: Oral lichen planus (OLP) is a prevalent cell-mediated autoimmune disease of unknown etiology. Disruption in the Th1/Th2 equilibrium has been suspected to contribute to the pathogenesis of OLP. In this study, we aimed at exploring, in OLP, the interactions between Th1/Th2 cytokines and Golli-MBP, a regulator of autogenic T cells. SUBJECTS AND METHODS: Thirty-six OLP patients aged 18-79 and nineteen control subjects aged 20-69 were enrolled in the dental clinics of Nanjing Medical University. OLP was diagnosed clinically and verified by histopathological examination. All subjects were free of other autoimmune diseases. Peripheral blood mononuclear cells (PBMC) and serum were collected from all subjects. Gene expression and protein levels of Golli-MBP, IFN-γ and IL-4 were measured, respectively, by semiquantitative reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay. RESULT: When compared with control, PBMC and serum from OLP patients exhibited a significantly higher expression and concentration of Golli-MBP and IL-4 and lower levels of IFN-γ. A strong negative correlation (r = -0.838, P < 0.000) was detected between the ratio of IFN-γ/IL-4 and Golli-MBP gene expression in PBMCs of OLP patients. CONCLUSION: These data support a potential link between Golli-MBP and the dysregulation of the Th1/Th2 equilibrium in OLP.

[Research and progress in etiology, prevention and treatment strategies of secondary caries].

Secondary caries is one of the main reasons that affect the service life of the restoration. Compared with primary caries, secondary caries have some particularities in etiology, disease progression, clinical manifestation, clinical diagnosis, treatment and prevention. Starting from the above aspects, combined with the latest basic and clinical research on secondary caries, this paper summarizes and analyzes its pathogenesis and prevention strategies, which will lay a certain foundation for in-depth understanding of secondary caries and promoting its clinical prevention and treatment.

[A preliminary study on the construction and application of the common prosperity model for the oral health of the elderly in economic acceleration zone].

Objective: To evaluate preliminary application effects of a provincial-county-township-village four-level network framework which aims at promoting oral health of the elderly, and to conduct preliminary evaluations of the application of this model in the prevention and treatment of oral diseases among the elderly in economically accelerated areas. Methods: Based on the population survey in June 2022, the study focuses on the elderly (≥85 years old) veterans who fought in the Korean War and currently resided in Wuyi County, an old revolutionary base area in Zhejiang Province with accelerated economic development. A four-level network medical service model matrix was constructed, spanning from the provincial level to the county, township, and village. Digital oral health records were established, and in-home dental treatment was provided for elderly individuals who met the inclusion and exclusion criteria. Pre-treatment and 3-months follow-up visits were conducted, and the impact of oral health was recorded using a scale, along with a survey of denture satisfaction. Results: A total of 54 elderly individuals received the geriatric oral healthcare services. After a 3-months follow-up, the mean total score of the oral health impact profile-14 questionnaires was (3.27±3.00), which was significantly lower than the score (32.82±7.15) in pre-treatment ones (Z=-2.94, P=0.003). Scores in dimensions such as physical pain, functional limitations, psychological discomfort, psychological disorders, and physical disorders were all significantly lower than the pre-treatment scores (P<0.05). The visual analogue score for denture satisfaction was 48.64±1.21, indicating a satisfaction rate of 100% (11/11). Conclusions: These findings confirm the favorable preliminary application effects of the four-level network framework in improving the prevention and treatment of oral diseases among the elderly in economically accelerated areas.

[Saliva microbiota and metabolite in individuals with caries or periodontitis].

Objective: To detect and analyze the characteristics of oral microbiota in species composition, function and metabolism among caries, periodontitis and oral healthy individuals, hunting for the microbiome-derived biomarkers with specificity and sensitivity to estimate the occurrence of these two diseases. Methods: Saliva samples were collected from 10 patients with high caries risk [decayed-missing-filled teeth (DMFT)≥6, HC group] in Department of Endodontics, 10 patients with periodontitis of grade Ⅱ A-Ⅲ C (PG group) in Department of Periodontology and 10 oral healthy individuals (HH group) from School of Stomatology, The Fourth Military Medical University during from March 2022 to June 2022. A baseline examination was conducted on all participants, including their oral conditions of caries and periodontal health. Metagenomic sequencing (Illumina PE150 platform) and liquid chromatography-mass spectrometry were used to detect microorganisms and their metabolites in the samples respectively. The sequencing data were analyzed to obtain the information of microbial taxonomic composition, functional genes and metabolites in each group of samples. The basic oral conditions and saliva samples of subjects in each group were evaluated and collected by the same professional endodontist. Results: There were no significant difference in baseline characteristics such as age and sex among the subjects in each group (P>0.05). DMFT in HC group (9.0±1.7) was significantly higher than that in HH group (0) and PG group (0) (F=243.00, P<0.001). Sequencing data analysis showed that the taxonomic compositions of salivary microbiota in each group were mainly Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria and Fusobacteria at the phylum level, and Streptococcus, Neisseria, Rothia, Prevotella at the genus level. Differential analysis showed that, compared with the HH group, HC group and PG group had significant differences in taxonomic composition (P<0.05), and the most significant among them was Prevotella. At the species level, Prevotella pallens was the most significant change in HC group, and Porphyromonas gingivalis in PG group. Metabolite analysis showed that there were significant differences in metabolites between HC group and PG group. The results showed that, compared with the HH group, the most significant metabolite change was 3-hydroxy-1, 5-diphenylpentan-1-one in HC group (P=0.001) and N1 acetylspermine in PG group (P=0.002) respectively. Compared with the PG group, the metabolite of HC group with the most significant difference is D-glucosamine 6-phosphate (P=0.006). The metabolism gene function analysis showed that, the enrichment of carbohydrate metabolism related genes was highest in HC group, followed with HH group, and it was lowest in PG group. In addition, compared with the HH group, the abundance of functional genes related to glucose metabolism, such as ABC transporter and phosphotransferase system, were significantly decreased in PG group (P<0.05), but significantly increased in HC group (P<0.05). Conclusions: There is a significant correlation between the alternation of carbohydrate metabolism of salivary microbiota with the occurrence of caries and periodontitis. In the future, Prevotella pallens and 3-hydroxy-1, 5-diphenylpentan-1-one may be the potential biomarkers of caries; while Porphyromonas gingivalis and N1 acetylspermine work in the predictions of periodontitis.

[Cone-beam CT evaluation of the effect of indirect anchorage of mini-screw assisted clear aligner on molar distalization].

Objective: To evaluate the effect of indirect anchorage with mini-screw assisted clear aligner on molar distalization. Methods: Twenty-six adult patients [12 males and 14 females, aged 19 to 31 years, mean age (26.4±4.2) years], who were treated in the Department of Orthodontics, the Affiliated Stomatological Hospital of Nanchang University between January 2018 and September 2021, were included. All the patients were treated with clear aligner and mini-screw indirect anchorage to distalize maxillary molars. In the stage of molar distalization, the mini-implants were implanted between the buccal roots of the maxillary first molar and the second premolar, and rigidly connected to the maxillary second premolar as anchorage reenforcement. Until the first molar had distally moved to the designated position, the mini-implants were transferred to the buccal area between the first and the second molars and similar device was connected to the first molar. Cone-beam CT (CBCT) images were taken before the treatment (T0), at the maxillary first molar distally moved to the designated position (T1), and at the anterior teeth alignment finished (T2). The CBCT data were imported into Mimics 20.0 software for three-dimensional reconstruction. After correcting the head position, each reference point was determined in the multi-plane reconstruction view. The bilateral porion, the right orbitale, the nasion, and the anterior nasal spine were selected as reference points to construct the three-dimensional space coordinate system. The positions of the first molar, the second premolar, and the incisor were analyzed three-dimensionally. The three-dimensional position changes of maxillary first molars and maxillary second premolars during the stages of T0-T1, T1-T2, T0-T2, and the mesiodistal and vertical position changes of maxillary central incisors were analyzed. The statistical analysis was carried out using a one-way repeated measures ANOVA. Results: There was a significant difference in the sagittal position changes of the root and cusp of the maxillary central incisors among three time points (F=24.84, P<0.001; F=27.66, P=0.001), but no difference was observed between T0 and T1 (P>0.05). There was a significant difference in lingual retraction of the maxillary central incisor root [(2.17±0.42) mm] and cusp [(1.81±0.28) mm] between T1 and T2 (P<0.05). A significant difference was noted in the sagittal position changes of the root and crown of the maxillary second premolars among three time points (F=17.16, P=0.001; F=57.99, P<0.001). However, no statistical difference was detected between T0 and T1 (P>0.05) and the difference in maxillary second premolar distalization [root (1.95±0.42) mm, cusp (2.53±0.33) mm] was observed between T1 and T2 (P<0.05). There was a statistically significant difference in the sagittal position changes of the root and the crown of the maxillary first molar among three time points (F=9.37, P=0.002; F=140.26, P<0.001). The difference in the maxillary first molar distalization [crown (3.51±0.30) mm, root (1.98±0.25) mm] between T0 and T1 was significant (P<0.05). However, no significant difference in the sagittal position of the maxillary first molars was observed between T1 and T2 (P>0.05). There was a statistically significant difference in the vertical position of the center point of the root in maxillary first molar among three time points (F=59.06, P<0.001), while (2.28±0.24) mm of intrusion between T0 and T1 was exhibited (P<0.05). However, no significant difference was found in the vertical position of the maxillary first molars between T1 and T2 (P>0.05). There was no significant difference in other measurements among three time points (P>0.05). Conclusions: The effect of indirect anchorage with mini-screw-assisted clear aligner on molar distalization was positive.

Treponema denticola Induces Alzheimer-Like Tau Hyperphosphorylation by Activating Hippocampal Neuroinflammation in Mice.

Alzheimer's disease (AD) is the most common type of dementia. Tau hyperphosphorylation and amyloid ß (Aß) deposition are the key pathological hallmarks of AD. Recent studies have shown that periodontitis is a significant risk factor for AD. The periodontal pathogen Porphyromonas gingivalis and its virulence factors have been shown to initiate and promote the hallmark pathologies and behavioral symptoms of AD. A possible link between Treponema denticola, another main periodontal pathogen, and AD has been reported. However, the role of T. denticola in AD pathogenesis is still unclear, and whether T. denticola and P. gingivalis exert a synergistic effect to promote AD development needs to be further studied. In this study, we investigated whether oral infection with T. denticola caused tau hyperphosphorylation in the hippocampi of mice and explored the underlying mechanisms. Orally administered T. denticola induced alveolar bone resorption, colonized brain tissues, and increased the activity of the phosphokinase GSK3ß by activating neuroinflammation in the hippocampus, thus promoting the hyperphosphorylation of the tau protein at Ser396, Thr181, and Thr231 in mice. An in vitro study with BV2 and N2a cell models of T. denticola invasion also verified the role of this pathogen in tau phosphorylation. T. denticola and P. gingivalis were not found to exert a synergistic effect on tau phosphorylation. In summary, these findings provide new insight into the important role of T. denticola in AD pathogenesis, providing biological connections between periodontal diseases and AD.

[A 5-year retrospective study of computer aided design and computer aided manufacturing ceramic endocrowns in endodontically treated posterior teeth].

Objective: To evaluate the clinical outcomes of computer aided design and computer aided manufacturing (CAD/CAM) ceramic endocrowns in endodontically treated posterior teeth after five years by a retrospective study. Methods: Patients who received CAD/CAM ceramic endocrowns after endodontically treatment in Department of Endodontics, School of Stomatology, The Fourth Military Medical University between January 2016 and June 2017 were invited for this clinical study. Clinical performance was evaluated in the aspect of color match, anatomic form,marginal adaptation, restoration integrity and secondary caries. Survival rate of the restorations was calculated by the use of Kaplan-Meier method. Log-rank test was applied as well for the sake of analyzing the effect of tooth position, sex and materials to the survival rate of the restorations. Results: Seventy-four patients, 25 men and 49 women with age of (38.8±10.2) years, participated in this study for a total of 101 CAD/CAM ceramic endocrowns after observation period of (62.8±12.0) months. There were 8 failed cases among 101 restorations, 5 were loss of retention, 2 were ceramic fracture and 1 was secondary caries respectively. In particular, 93% (89/96) restorations got score A on anatomic form and 95% (91/96) restorations got score A on marginal adaptation, while 38% (36/96) restorations showed the good color match compared with the abutment teeth. The estimated cumulative survival rate of CAD/CAM ceramic endocrowns in endodontically treated posterior teeth after 5 years was 93.0% (95%CI: 87.9%-98.1%). The single-factor Log-rank analysis demonstrated that there was no statistically significant difference in the survival rate of CAD/CAM ceramic endocrowns among men and women, premolars and molars, position in the dental arch, or different materials (χ²<0.01, P=0.957; χ²=0.64, P=0.422; χ²=0.69, P=0.407; χ²=0.88, P=0.349). Conclusions: Based on this clinical study, the clinical performance of CAD/CAM ceramic endocrowns in endodontically treated posterior teeth after five years is reliable, which could be a general option to restore nonvital teeth.

Dual Functions of MDP Monomer with De- and Remineralizing Ability.

Methacryloyloxydecyl dihydrogen phosphate (MDP) has been speculated to induce mineralization, but there has been no convincing evidence of its ability to induce intrafibrillar mineralization. Polymers play a critical role in biomimetic mineralization as stabilizers/inducers of amorphous precursors. Hence, MDP-induced biomimetic mineralization without polymer additives has not been fully verified or elucidated. By combining 3-dimensional stochastic optical reconstruction microscopy, surface zeta potentials, contact angle measurements, inductively coupled plasma-optical emission spectroscopy, transmission electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy with circular dichroism, we show that amphiphilic MDP can not only demineralize dentin by releasing protons as an acidic functional monomer but also infiltrate collagen fibrils (including dentin collagen), unwind the triple helical structure by breaking hydrogen bonds, and finally immobilize within collagen. MDP-bound collagen functions as a huge collagenous phosphoprotein (HCPP), in contrast to chemical phosphorylation modifications. HCPP can induce biomimetic mineralization itself without polymer additives by alternatively attracting calcium and phosphate through electrostatic attraction. Therefore, we herein propose the dual functions of amphiphilic MDP monomer with de- and remineralizing ability. MDP in the free state can demineralize dentin substrates by releasing protons, whereas MDP in the collagen-bound state as HCPP can induce intrafibrillar mineralization. The dual functions of MDP monomer with de- and remineralization properties might create a new epoch in adhesive dentistry and preventive dentistry.

[Consensus of experts on the medical risk prevention for the patients with cardiovascular diseases during dental treatment (2022 edition)].

With the aging process of population in the society, the prevalence of cardiovascular diseases (CVD) in China is increasing continuously and the number of dental patients with CVD is increasing gradually too. Due to the lack of guidelines for dental patients with CVD in our country, how to implement standardized preoperative evaluation and perioperative risk prevention remains a problem to be solved for dentists at present. The present expert consensus was reached by combining the clinical experiences of the expert group of the Fifth General Dentistry Special Committee, Chinese Stomatological Association and respiratory and cardiology experts in diagnosis and treatment for CVD patients, and by systematically summarizing the relevant international guidelines and literature regarding the relationship between CVD and oral diseases and the diagnosis and treatment of dental patients with heart failure, hypertension and antithrombotic therapy. The consensus aims to provide, for the dental clinicians, the criteria on diagnosis and treatment of CVD in dental patients in China so as to reduce the risk and complications, and finally to improve the treatment levels of dental patients with CVD in China.

In vitro generation of mature human osteoclasts.

Mononuclear precursors of human osteoclasts are found in the CD14(+) monocyte fraction of circulating peripheral blood mononuclear cells (PBMCs). It is possible to generate osteoclasts in vitro from PBMCs cultured with macrophage colony-stimulating factor and receptor activator for nuclear factor κB ligand. In these cultures, however, it is not possible to distinguish the effect of a specific agent on osteoclast resorption activity as opposed to osteoclast differentiation. To produce a population of mature human osteoclasts to study osteoclast lacunar resorption specifically, we cultured CD14(+) human monocytes on hydrophobic dishes in order to generate and maintain osteoclasts in suspension prior to culturing them on coverslips and dentine slices. Multinucleated cells formed in these cultures expressed vitronectin receptor, tartrate-resistant acid phosphatase, and cathepsin K. These cells also produced F-actin rings and were capable of extensive lacunar resorption on dentine slices after 24 h in culture. Lacunar resorption was inhibited by calcitonin and zoledronate but not by osteoprotegerin. This method of generating a highly enriched population of mature human osteoclasts should provide a valuable means of specifically assessing the effect of molecular factors (e.g., cytokines, growth factors, hormones) and therapeutic agents on osteoclast resorption activity.

The regenerative effect of platelet-rich plasma on healing in large osteochondral defects.

Platelet-rich plasma (PRP), a platelet concentrate made of autogenous blood, has been used to improve bone and soft tissue defect healing in recent years. The aim of this study was to assess the effect of PRP on articular cartilage defects in a rabbit model. Forty-eight osteochondral defects created in the femoropatellar groove were (a) left untreated, (b) treated with autogenous PRP in a poly-lactic-glycolic acid (PLGA), or (c) with PLGA alone. Platelets were enriched 5.12-fold compared to normal blood in the PRP. After four and 12 weeks, the explanted tissue specimens were assessed by macroscopic examination, micro-computed tomography, and histological evaluation. Macroscopic examination, micro-computed tomography and histology of the newly formed cartilage and bone in the defect differ significantly between the PRP-treated and the untreated groups, and stimulatory effect of PRP on osteochondral formation was observed. In conclusion, PRP in PLGA improves osteochondral healing in a rabbit model.

Effects of locally applied nerve growth factor to the inferior alveolar nerve histology in a rabbit model of mandibular distraction osteogenesis.

Distraction osteogenesis (DO) is widely used in deformities and defects of the craniofacial bone. Accelerating inferior alveolar nerve (IAN) recovery would aid the process. Nerve growth factor (NGF) plays a vital role in peripheral nerve regeneration. In this study, the ability of locally applied human NGF beta (hNGFbeta) to enhance the morphological recovery of the IAN in a rabbit model of mandibular DO was studied. Rabbits underwent bilateral DO with a rate of 0.5mm per 12h. Two doses of 40 microg hNGFbeta in buffer were injected into callus at the beginning the of consolidation time. The contralateral side received injections of placebo. Rabbits were killed at 14 and 28 days. IAN specimens were subjected to histological and histomorphometric analysis. In both 14 and 28 days consolidation experiments, nerve histological analysis showed less degeneration and more regeneration in nerve fibers on the hNGFbeta treated side than the control side. Histomorphometric analysis showed that the myelinated fiber density on the hNGFbeta treated side was significantly higher than on the control side (p<0.01). The data indicate that locally applied hNGFbeta can accelerate the morphological recovery of the IAN and may play a role in reducing nerve injury in mandibular DO clinically.

Segmental bone tissue engineering by seeding osteoblast precursor cells into titanium mesh-coral composite scaffolds.

The size and specific shape of bone grafts are important for jaw reconstruction. In this experiment, segmental bone grafts were engineered in a predetermined shape via seeding osteoblast precursor cells into titanium mesh-coral composite scaffolds. Titanium meshes were moulded into the shape of a column with length 12 mm and diameter 8mm. The column was filled with natural coral granules and the complex acted as a cell-seeding scaffold. About 4 x 10(7) osteoblast precursor cells in 200 microl cell-culture medium were seeded into each of six scaffolds and incubated in vitro for 2 days. Then, the composites were implanted subcutaneously into the backs of nude mice and incubated in vivo. Two months after implantation, the animals were killed and new bone formed in the scaffolds was investigated by gross inspection, X-ray examination, histological observation and mechanical testing. The results showed that newly formed tissue was red and presented the gross appearance of bone, and kept the original shape of the column. Titanium mesh was situated on the surface of the bone graft. An X-ray blocking shadow was observed in and around the titanium scaffolds; most of the coral granules had been absorbed. Histological observation demonstrated a large amount of new bone formed and integrated well with titanium mesh. Mechanical testing showed that new bone improved the mechanical property of the graft significantly. In conclusion, a titanium mesh-coral composite scaffold with osteoblast precursor cells is an efficient means to engineer segmental bone, possessing the desired shape and mechanical strength.

The influence of recombinant human BMP-2 on bone-implant osseointegration: biomechanical testing and histomorphometric analysis.

The healing period for bone-implant osseointegration lasts 3-6 months or even longer. The aim of this study was to investigate whether osseointegration can be enhanced by the use of bone morphogenetic protein-2 (BMP-2). In the femurs of 8 Japanese white rabbits, 16 implants were applied with 1.0 mg recombinant human BMP-2 (rhBMP-2) as group A, and the other 16 implants without rhBMP-2 as group B. Calcein green 20 mg/kg and alizarin red 20 mg/kg were injected 4 and 8 weeks after implantation, respectively. At 12 weeks, the animals were killed. In 16 implant-bone blocks, binding strength was measured by pull-out test, and the extracted implants were observed under a scanning electronic microscope. The other blocks were analysed for percentage of marked bone adjacent to the implant surface by confocal laser scanning microscope. The pull-out strengths of group A were greater than that of group B (P<0.05). Scanning electronic microscopy (SEM) showed more calcified substances on the surface of the implants of group A than B. There was more marked bone around group A than B implants at 4 weeks (P<0.05) and 8 weeks (P<0.05). rhBMP-2 improves the quantity and quality of implant-bone osseointegration. Biomechanical testing and histomorphometric analysis are reliable methods to use in researching the implant-bone interface.

The use of exfoliative cell samples to map clonal genetic alterations in the oral epithelium of high-risk patients.

Although it is widely accepted that clonal genetic alterations are an essential component of tumor progression, little is known of the distribution of such changes in high-risk lesions or how such clones are altered over time. We explored the feasibility of using exfoliative cells collected by scraping the mucosal surface to detect allelic loss in oral lesions of 22 patients (14 squamous cell carcinomas, 2 carcinomas in situ, and 6 dysplasias). The data show that the patterns of allelic loss observed in these samples closely represent those observed in biopsies of the same region. Furthermore, early indications are that this approach can be used to detect recurrent outgrowth of clones of altered cells in patients after therapy.

Bactericidal effect of Er:YAG laser combined with sodium hypochlorite irrigation against Enterococcus faecalis deep inside dentinal tubules in experimentally infected root canals.

This study evaluated the bactericidal effect of Er:YAG laser radiation combined with sodium hypochlorite (NaOCl) irrigation in the treatment of Enterococcus faecalis deep inside dentinal tubules. The Er:YAG laser was activated, respectively, at 0.3, 0.5 and 1.0 W for either 20 or 30 s; 52.5 g l(-1) NaOCl and normal saline were used for the control groups. Root canals before and after treatments were examined using scanning electron microscopy (SEM). Bacterial reductions both on the root canal walls and at 100, 200, 300, 400 and 500 µm inside the dentinal tubules were analysed using a one-way analysis of variance. SEM results showed that the Er:YAG laser combined with NaOCl disinfected the dentinal tubules from 200 to over 500 µm depth as irradiation power and time increased. This combination killed significantly more bacteria than both the negative control group at each level tested and the positive control group at 300, 400 and 500 µm inside the dentinal tubules. It reached 100% in all experimental groups, both on the root canal walls and at 100 and 200 µm inside the dentinal tubules. However, at 300, 400 and 500 µm inside the dentinal tubules, only the groups treated with 0.5 and 1.0 W for 30s exhibited no bacterial growth. Of the two groups in which no bacteria were detected at all tested depths, Er:YAG laser irradiation at 0.5 W for 30 s combined with NaOCl irrigation was preferable because of the lower emission power and shorter irradiation time, and may serve as a new option for effective root canal disinfection.

Origin of ultralow Young׳s modulus in a metastable ß-type Ti-33Nb-4Sn alloy.

Although there is difficulty in growing a Ti-33Nb-4Sn single crystal due to its ultralow ß-phase stability, the single-crystal elastic constants of metastable ß-type Ti-33Nb-4Sn (wt%) alloy were extracted successfully from its polycrystal by in-situ synchrotron X-ray diffraction technique, to clarify the origin of the ultralow Young's modulus in its polycrystal. It is indicated that compared to binary TiCr, TiV and TiNb alloys, the Ti-33Nb-4Sn alloy possesses slightly lower ß-phase stability with respect to {110}<110>(-)shear (i.e., C׳) but much lower ß-phase stability regarding to {001}〈100〉 shear (i.e., C44). An analysis by the Hill approximation suggests that the ultralow isotropic polycrystalline Young׳s modulus (EH) of Ti-33Nb-4Sn alloy originates from the extremely low shear modulus C44 as well as the relatively low C׳. This indicates that in addition to C׳, C44 has a significant contribution to the Young's modulus of polycrystal, which challenges a conventional understanding that the Young's modulus of ß-type Ti alloys is predominantly determined by C׳.