Ricky W.K. Wong

The role of vascular endothelial growth factor in ossification

Osteogenesis and angiogenesis are two closely correlated processes during bone growth, development, remodelling and repair. Vascular endothelial growth factor (VEGF) is an essential mediator during the process of angiogenesis. Based on an extensive literature search, which was carried out using the PubMed database and the keywords of osteogenesis, VEGF, endochondral ossification and intramembranous ossification, this manuscript reviews the role of VEGF in ossification, with emphasis on its effect in endochondral and intramembranous ossification. Osteogenesis and angiogenesis are closely correlated processes. VEGF acts as an essential mediator during these processes. It not only functions in bone angiogenesis but also in various aspects of bone development.

Use of cervical vertebral maturation to determine skeletal age.

INTRODUCTION The purpose of this study was to evaluate the validity of the cervical vertebral maturation (CVM) method as an indicator of skeletal age in the circumpubertal period by correlating it to the hand-wrist method (HWM). METHODS Hand-wrist and lateral cephalometric radiographs of 400 Chinese subjects were randomly selected. Their ages were 10 to 15 years for girls and 12 to 17 years for boys, so they were within the circumpubertal period. Skeletal ages were assessed according to the CVM method and the HWM. RESULTS The CVM was significantly correlated with HWM skeletal age (Spearman r = 0.9521 [boys] and 0.9408 [girls]). All patients in cervical vertebral stage 3 of the CVM corresponded to stages MP3-FG or MP3-G (around the peak of the growth spurt) in the HWM. CONCLUSIONS The CVM is a valid indicator of skeletal growth during the circumpubertal period, providing information for timing of growth modification.

Potent anti-microbial activity of traditional Chinese medicine herbs against Candida species

Anti‐candidial activities of eight traditional Chinese medicinal (TCM) herbs were evaluated against six different Candida species. TCM preparations were screened for antifungal activity using a standard agar diffusion assay. Following identification of potential candidate herbs, their minimum inhibitory concentration (MIC) values were determined using the standardised NCCLS M‐27A broth microdilution assay. Among TCM herbs, Rhizoma Coptidis had potent antifungal activity against Candida glabrata, Candida krusei and Candida tropicalis, but not against Candida albicans, Candida dubliniensis and Candida parapsolosis. The MIC values of the Rhizoma Coptidis against C. glabrata, C. krusei and C. tropicalis were 50, 50 and 100 μg ml−1 respectively. We report here, for the first time, the potent antifungal activity of Rhizoma Coptidis and Cortex phellodendri Chinesis on three different non‐albicans Candida species, C. glabrata, C. krusei and C. tropicalis and hence their possible use as therapeutic agents.

Dentofacial characteristics of Chinese obstructive sleep apnea patients in relation to obesity and severity

OBJECTIVE To evaluate dentofacial characteristics in relation to obesity and degree of severity of obstructive sleep apnea (OSA) in male Chinese patients and to elucidate the relationship between demographic parameters (age, body weight, height, and body mass index [BMI]) cephalometric parameters and OSA in these subjects. MATERIALS AND METHODS Lateral cephalograms of 121 Chinese male patients in natural head posture were obtained. Based on BMI value, the patients were divided into three groups. Based on apnea-hypopnea index (AHI) value, the patients were divided into a mild-to-moderate and a severe group. RESULTS The hyoid position and soft palate length were significantly different among the three obesity groups. Soft palate length was significantly longer (P < .01) in the severe OSA group than in the mild-to-moderate OSA group. Tongue base was significantly more inferiorly placed (P < .05) in the severe OSA group than in the mild-to-moderate OSA group. Craniocervical extension was significantly increased (P < .05) in the severe OSA group. Statistically significant differences were found among the three obesity groups in mandibular length, mandibular body length, maxillary length, anterior cranial base length, and overbite. The multiple stepwise linear regression analysis identified body weight, lower posterior facial height, mandibular body length, craniocervical extension, and sella-hyoid distance as the significant predictive variables for AHI. CONCLUSIONS This study revealed the existence of craniofacial and upper airway soft tissue differences in relation to obesity and severity of OSA among male Chinese OSA patients. Body weight and certain cephalometric parameters were significant predictors of OSA in Chinese male subjects.

The effects of orthodontic appliances on Candida in the human mouth.

BACKGROUND Candida is an opportunistic pathogen present in about 50-60% of the healthy human population, and becomes pathogenic when the host immune defence is undermined such as in HIV infection. Adhesion and colonization of the oral cavity by Candida albicans is an initial step in candidosis, and the presence of orthodontic and other oral appliances seems to alter the oral ecological environment, hence may tip the balance to favour the candidal presence. OBJECTIVE The purpose of this paper was to review the literature with specific attention to prevalence; intra-oral density of the candidal organisms; and Candida carriage status in orthodontic patients before, during, and after treatment. CONCLUSIONS The limited amount of literature demonstrated that the density of Candida increases; the most common Candida species isolated in the orthodontic patients was C. albicans; and that there seems to be a direct relationship between the presence of a removable appliance, Candida, and low salivary pH levels. No healthy patients developed Candida infection from the orthodontic appliances. However, there seems to be a trend that some non-Candida carriers converted to Candida carriers following the insertion of the appliances by unknown mechanism. This may indicate a more cautious approach when providing orthodontic treatments to immunocompromised children concerning the possible increased risk of candidal infection.

Effect of psoralen on bone formation.

To compare the amount of new bone and bone cells produced by psoralen in collagen matrix to that produced by collagen matrix in vivo. Eighteen bone defects, 5 mm by 10 mm were created in the parietal bone of nine New Zealand White rabbits. Six defects were grafted with psoralen mixed with collagen matrix. Six defects were grafted with collagen matrix alone (negative control—collagen) and six were left empty (negative control—empty). Animals were killed on day 14 and the defects were dissected and prepared for histological assessment. Quantitative analysis of new bone formation and bone cells were made on 100 sections (50 sections for each group) using image analysis. A total of 454% more new bone was present in defects grafted with psoralen in collagen matrix than those grafted with collagen matrix. No bone was formed in the negative control—empty group. The amount of bone forming osteoblasts was also significantly greater in the psoralen group than the negative control–collagen group. Psoralen in collagen matrix has the effect of increasing new bone formation locally in vivo. Psoralen in collagen matrix can be developed as a bone graft material.

Effect of quercetin on bone formation.

Quercetin is a flavonol, also a phytoestrogen, available commonly in onions and apples. Our laboratory compared the amount of new bone produced by quercetin in a collagen matrix to that produced by bone grafts and a collagen matrix. Eighteen bone defects, 5 × 10 mm were created in the parietal bone of nine New Zealand White rabbits. In the experimental group, six defects were grafted with quercetin solution mixed with a collagen matrix. In the control groups, six defects were grafted with a collagen matrix alone (active control) and six were left empty (passive control). Animals were killed on day 14 and the defects were dissected and prepared for histological assessment. Serial sections were cut across each defect. Quantitative analysis of new bone formation was made on 100 sections (50 sections for each group) using image analysis. A total of 556% more new bone was present in defects grafted with quercetin in a collagen matrix than those grafted with a collagen matrix alone. No bone was formed in the passive control group. In conclusion, quercetin in a collagen matrix has the effect of increasing new bone formation locally, and can be used as a bone graft material.

Factors regulating endochondral ossification in the spheno-occipital synchondrosis.

OBJECTIVES To identify the temporal pattern of core-binding factor alpha1 (Cbfa1) and vascular endothelial growth factor (VEGF) expressions in the spheno-occipital synchondrosis in vitro with and without tensile stress. MATERIALS AND METHODS Sixty male BALB/c mice were randomly divided into an experimental group (with tensile stress) and a control group (without tensile stress) at each of five time points. Animals were sacrificed and the cranial base synchondroses were aseptically removed. In the experimental groups, mechanical stress was applied on the surgical explants with helical springs and incubated as organ culture for 6, 24, 48, 72, and 168 hours. In the control group, the springs were kept at zero stress. Tissue sections were subjected to immunohistochemical staining for quantitative analysis of Cbfa1 and VEGF expression. RESULTS Quantitative analysis revealed that Cbfa1 and VEGF expressions reached a peak increase at 24 and 48 hours, respectively. Compared with the control groups, both Cbfa1 and VEGF were expressed consistently higher in the experimental groups at all time points. CONCLUSION Mechanical stress applied to the spheno-occipital synchondrosis elicits Cbfa1 expression and subsequently up-regulates the expression of VEGF. Increased levels of expression of both factors could play a role in the growth of the spheno-occipital synchondrosis.

Relationships Between Cranial Base Synchondroses and Craniofacial Development: A Review

Synchondrosis is defined as the development of a union between two bones by the formation of either hyaline cartilage or fibro-cartilage. This paper reviews the relationship between cranial base synchondroses and craniofacial development. The cranial base synchondroses are important growth centers of the craniofacial skeleton. Their abnormalities lead to numerous growth and developmental conditions in the craniofacial region. In dentofacial orthopedics, mechanical forces are commonly applied to cranial bones for growth modification to treat such conditions. Molecular biology and genetics provide tools to investigate the molecular mechanisms, genes and transcription factors responsible for synchondrosis and craniofacial development.

Effect of Buguzhi (Psoralea corylifolia fruit) extract on bone formation

The objective of the study is to compare the amount of new bone produced by Buguzhi (Psoralea corylifolia fruit) extract in collagen matrix to that produced and collagen matrix in vivo. Eighteen bone defects, 5 mm by 10 mm, were created in the parietal bone of 9 New Zealand white rabbits. Six defects were grafted with Buguzhi extract mixed with collagen matrix. Six defects were grafted with collagen matrix alone (positive control) and 6 were left empty (negative control). Animals were sacrificed on day 14 and the defects were dissected and prepared for histological assessment. Quantitative analysis of new bone formation and bone cells was made on 100 sections (50 sections for each group) using image analysis. A total of 275% more new bone was present in defects grafted with Buguzhi extract in collagen matrix than those grafted with collagen matrix. No bone was formed in the negative control group. The amount of bone cells was also significantly greater in the Buguzhi group than in the positive control group. To conclude, Buguzhi extract in collagen matrix has the effect of increasing new bone formation locally in vivo. Buguzhi extract in collagen matrix can be used as a bone graft material. Copyright