Effects of cyclosporin A on dental alveolar bone: a histomorphometric study in rats

BACKGROUND: We have previously reported cyclosporin A (CA)-induced osteopenia around the dental alveoli of the mandibular incisors of rats. The drug-induced tooth displacement and the regional anatomical complexity around the mandibular incisors might complicate the local effects of CA. Therefore, the purpose of this study was to evaluate the dental alveolar bone histomorphology around maxillary secondary molars in CA-treated rats and to further elucidate the effects of CA on the dental alveolus. METHODS: Twenty Sprague-Dawley rats were assigned to a CA and a control group. Animals in the CA group received CA (15 mg/kg) daily and the control rats received only mineral oil. At the end of weeks 2 and 4, five animals in each group were sacrificed. Dental alveoli around the maxillary second molar region were frontally sectioned and stained with toluidine blue by undecalcified histological processing. Ten serial tissue sections, 80 microm apart, were selected for histometric evaluation. Bone volume, bone-specific surface, and osteoid formation were measured at buccal, apical, and palatal locations in dental alveolus. RESULTS: Overall bone mass in dental alveolus decreased more in the CA group than in the control group at both observation intervals. All histometric measurements, except the bone-specific surface, were significantly affected by the alveolar location (palatal, apical, and buccal) and CA therapy (P= 0.004 and <0.001, 0.001 and <0.001, 0.004 and <0.001 for drug therapy and location of the dental alveolus in bone volume, marrow volume, and the ratio of bone surface to volume, respectively). Decreased bone volume, but increased marrow volume, were noted in the CA group compared to the control group. Although the alveolar bone surface area did not differ between the CA group and the control group, greater alveolar surface-to-volume ratio was noted in the CA group. For osteoid, more decreased volume, seam width, and fractional formation surface were observed in the CA group compared to the control group (P <0.001, <0.001, and = 0.046 in osteoid volume, seam width volume, and formation surface, respectively). CONCLUSIONS: Because the bone mass and the osteoid formation in the dental alveolus around the maxillary molar region showed a decrease after CA exposure, we conclude that this drug has inhibitory effects on the dental alveoli.     

A comparative morphologic study of Carabelli cusp between Chinese and Japanese students.]

The study of teeth,dentition and occlusion is helpful to guide oral medical clinic and the study of anthropology.Our department of Osaka Dental University and had many items of research work about teeth,dentition and occlusion between Chinese and Japanese students.This article reports the study of Carabelli cusp.The results revealed:(1)the rate of Carabelli cusp is higher in Japanese than in Chinese and is higher in male than in female.(2)the rate of Carabelli cusp of the first maxillary molar of both side is very high.(3)The rate of Carabelli cusp is related to the height and the type of cusp numbers.These all illustrated the occurence of Carabeiil cusp were influenced by race, individual and the development of teeth.     

One germline mutation of PTCH gene in a Chinese family with non-syndromic keratocystic odontogenic tumours

Keratocystic odontogenic tumours (KOCTs) are common benign cystic tumours that arise sporadically or associated with nevoid basal cell carcinoma syndrome (NBCCS). PTCH mutation can be found in sporadically or NBCCS associated KOCTs. Few PTCH mutations in families with non-syndromic KOCTs have been reported. Through PCR and gene sequence analysis, the authors discovered one missense mutation c.3277G>C in exon 19 of PTCH gene in a Chinese family with non-syndromic KOCTs. This mutation causes one highly conserved glycine residue transit to arginine on the 10th transmembrane region of PTCH protein. This work revealed that the missense mutation of PTCH is the causative and dominant gene of KOCTs in this family.     

Epithelial cells in PDL are critical in resuming the integral relation between tooth root and supporting bone after trauma--a transplantation experiment

OBJECTIVE: The aim of this study was to determine the response of the residual epithelial network following traumatic breakdown of the periodontal ligament (PDL). METHODS: Mandibular incisor sections with PDL (experimental) and sections denuded of PDL (control) from 4- to 6-week-old Wistar-Furth rats were transplanted into the defects created in the frontal bone of the recipient syngeneic rats. At intervals, the defects with implanted teeth roots were collected and processed for histological and biochemical examination. Immunolocalization of epithelial cells was performed to monitor their phenotypic changes during transplantation healing period. RESULTS: (1) Histological observation of the experimental sample revealed the sequence of cellular response characterized by an initial degeneration of PDL followed by a proliferation of granulation tissue. There was also a marked odontoblastic reaction with extensive deposition of regular dentine within the pulp chambers. In the control group, initial signs of bony fusion with dentine led to an extensive ankylosis and bone replacement between roots and defects. (2) Immunostaining indicated that, in experimental groups, the pattern of regularly spaced epithelial cells lying in close approximation to the root surface was distinct 10 days post-transplantation but became diminished afterwards. The immunoreaction against epithelial cells was negative in the control. CONCLUSION: Residual PDL is essential to prevent ankylosis after trauma and epithelial cells may facilitate the re-establishment of root-PDL-bone complex by transforming into mesenchymal cells.     

The growth hormone receptor gene is associated with mandibular height in a Chinese population

Genetic influences are important in the determination of mandibular morphology, and growth hormone receptor (GHR) is believed to have an important influence on the growth of craniofacial bone. In this study, we used quantitative trait locus methods to evaluate the relationship between craniofacial morphology and single-nucleotide polymorphisms (SNPs) in GHR in an unselected healthy Chinese population. We systematically screened the 10 exons and nearby introns of GHR and identified 6 SNPs. Using 4 SNPs as markers, we studied the relationships between genotypes and craniofacial linear measurements. Individuals with the genotype CC of polymorphism I526L had a significantly greater mandibular ramus length (condylion-gonion/ articulare-gonion) than those with genotype AC or AA. Haplotype analysis showed that there were also significant differences between the long and short mandibular height groups in an extreme population. Our results indicate that the GHR gene polymorphism I526L is associated with mandibular height in the Chinese population.     

氯化镧对人牙釉质人工龋的影响──扫描电镜、电子探针分析

借助体外人工龋方法从形态和内部结构变化上探讨了氯化镧（Ｌａ３＋）对人牙釉质龋的影响。磨片光镜下显示Ｌａ３＋预处理阻抑龋病发展的作用不如氟化钠（Ｆ－），但Ｌａ３＋与Ｆ－先后预处理能明显减轻龋损程度。扫描电镜观察发现Ｌａ３＋及Ｆ－预处理均能在牙面形成覆盖物，但以Ｌａ３＋与Ｆ－先后预处理产生的覆盖物较致密且与牙面结合较紧密。电子探针分析显示Ｌａ３＋处理后釉质表层内钙（Ｃａ２＋）含量明显减少，而Ｌａ３＋显著增加，表明Ｌａ３＋能与Ｃａ２＋发生离子交换反应而进入釉质。这种牙面覆盖物的形成及Ｌａ３＋－Ｃａ２＋交换反应可能是Ｌａ３＋预处理能防龋的关键之一。     

The application of mini-implants for orthodontic anchorage

The aim of this study was to explore the use of mini-implants for skeletal anchorage, and to assess their stability and the causes of failure. Forty-five mini-implants were used in orthodontic treatment. The diameter of the implants was 2mm, and their lengths were 8, 10, 12 and 14mm. The drill procedure was directly through the cortical bone without any incision or flap operation. Two weeks later, a force of 100-200g was applied by an elastometric chain or NiTi coil spring. Risk factors for the failure of mini-implants were examined statistically using the Chi-square or Fisher exact test as applicable. The average placement time of a mini-implant was about 10-15min. Four mini-implants loosened after orthodontic force loading. The overall success rate was 91.1%. The location of the implant was the significant factor related to failure. In conclusion, the mini-implants are easy to insert for skeletal anchorage and could be successful in the control of tooth movement.     

本科阶段口腔正畸教学模式与质量管理初探

口腔正畸学是口腔医学中专业性极强的分支学科,因而一直是口腔医学难教难学课程。本科生阶段正畸教学时数少,内容多,教学效果难以保证,理论与实践难以结合。医学院校的办学宗旨是培养掌握临床技能的创新人才,上海交通大学口腔医学院口腔正畸教研室为了更好培养适应社会需要,具有国际国内竞争力,适应不同层次要求的口腔医务工作者,坚持教学改革,加强质量管理,经过多年的教学实践,在教学改革和教学管理方面,取得了一些成绩。本文旨在分析正畸教学现状,探讨教学改革和教学质量管理的方法,为进一步深化教学改革、提高教学质量奠定基础。     

Creating an effective PBL case in oral and maxillofacial surgery at a Chinese dental school: a dental education primer

Problem-based learning (PBL) is a widely accepted educational method centered on the discussion and learning that emerge from a clinically based problem; however, little has been reported on the details of PBL case-writing in the dental education literature. This article outlines some principles of writing a PBL case as it is practiced at a Chinese dental school and presents, as an example, an actual case based on a clinical problem (ameloblastoma of the jaw) intended to provide a learning focus for predoctoral dental students. A good PBL case should allow for progressive, interdependent actions to be taken in the evaluation and overall management of the patient in context and should trigger inquiry and discussion among students in both the basic sciences (anatomy, physiology, biochemistry, pharmacology, pathophysiology, etc.) and related clinical sciences. The epidemiological, sociological, and ethical considerations related to each problem should also be emphasized as an essential component of effective health care provision.