PBL core skills faculty development workshop 1: An experiential exercise with the PBL process

This report describes the first in a series of foundation-building faculty development workshops focused on the instructional methodology of problem-based learning (PBL). The PBL Process workshop reported here introduced the learning theory topics supporting PBL and utilized an extended roleplay method to provide participants with personal experience with the PBL learning cycle. Overall, participants were satisfied with the methods and content of the workshop. A majority of survey respondents indicated that simulating a complete iteration of the PBL process was an effective way to learn about PBL. Participants expressed relatively greater difficulty understanding and performing activities related to qualitative assessment of learning processes. The workshop was developed to align with adult learning principles, and continued refinement of the workshop has enhanced the learning theory components underpinning PBL as well as the experiential aspects. These dual goals have resulted in blending the existing experiential workshop with an online distance-learning component addressing the learning theory topics relevant to PBL pedagogy.     

小鼠釉质发育过程中成釉器中间层细胞增殖、凋亡以及组织非特异性碱性磷酸酶的表达

目的:观察小鼠釉质发育过程中成釉器中间层细胞的增殖、凋亡和其组织非特异性碱性磷酸酶(tissue nonspecific alkaline phosphatase,TNSALP)的表达,探讨中间层在釉质形成过程中的可能作用.方法:取出生后1、3、5、7、9、11、15d的BALB/c小鼠56只,解剖分离含下颌第一磨牙区的下颌骨,脱钙,制片,HE染色进行牙釉质发育情况的组织学观察,分别采用原位末端标记法(TUNEL法)、SP免疫组织化学技术、PV二步法观察中间层细胞的凋亡及检测Bcl-2、增殖细胞核抗原(proliferating cell nuclear antigen,PCNA),并对TNSALP进行组织学定位.通过Image-pro plus 6.0图像分析软件.对图像进行半定量分析.采用SPSS13.0软件包进行t检验、单因素方差分析及SNK-q检验.结果:出生后1d.中间层细胞增殖细胞核抗原由比成釉细胞表达高的强阳性表达逐渐降低;至7d时,其表达为阴性,而且中间层细胞随釉质的发育逐渐凋亡.中间层细胞先于成釉细胞表达TNSALP,出生后5d时即呈现强阳性染色,而后其表达又逐步减弱;成釉细胞7d时开始出现阳性,且呈逐渐增强趋势.结论:中间层细胞的增殖和凋亡及其TNSALP的表达与成釉细胞具有相关性,提示中间层细胞有可能参与成釉细胞的分化及釉质形成.     

The origins of fear of occupational exposure in the clinical dental setting

Although there is a growing literature on the incidence of occurrence and reporting of occupational exposures in clinics in dental schools, the contributing factors to fear of such injuries and their dynamic evolution over time remain unstudied. It is hypothesized that fear of occupational exposures is a function of estimated likelihood of such events and their perceived importance. Individual personality factors and situational circumstances are also thought to play a role, although it is believed that these factors recede in importance as students gain direct knowledge through clinical experience. Path analysis methods are applied to longitudinal survey data in a single dental school to confirm these hypotheses.     

Neural hyperplasia in maxillary bone of multiple endocrine neoplasia type 2B patient

Multiple endocrine neoplasia (MEN) type 2B is the rarest and most aggressive form of MEN syndrome. MEN 2B patients manifest characteristic oral and facial features besides the neural crest cell-derived tumors, including medullary carcinoma, pheochromocytoma, mucosal neuroma, and ganglioneuromatosis of the gut. We report a case of MEN 2B diagnosed on the basis of the warning signs of mucosal neuroma and multiple neural hyperplasias in the maxillary bone resected during orthognathic surgery. A subsequent systemic examination under the pathologic diagnosis of neural lesions revealed medullary thyroid carcinoma, megacolon, thickened corneal nerves, and RET gene mutation, thus verifying the diagnosis of MEN 2B. An immunohistochemical study revealed an increased number of unmyelinated Schwann cells in the hyperplastic nerves. We suggest that intraosseous neural hyperplasia is a specific finding of the MEN 2B syndrome in addition to the known oral and facial manifestations.     

Gatifloxacine-loaded PLGA and β-tricalcium phosphate composite for treating osteomyelitis

Gatifloxacine (GFLX)-containing poly(lactide-co-glycolide) (PLGA) was introduced to the pores and surfaces of porous β-tricalcium phosphate (βTCP) granules by melt compounding whereby no toxic solvent was used. The granular composite of GFLX-loaded PLGA and βTCP released GFLX for 42 days in Hanks' balanced solution and exhibited sufficient in vitro bactericidal activity against Streptococcus milleri and Bacteroides fragilis for at least 21 days. For in vivo evaluation, the granular composite was implanted in the dead space created by the debridement of osteomyelitis lesion induced by S. milleri and B. fragilis in rabbit mandible. After a 4-week implantation, the inflammation area within the debrided area was markedly reduced accompanied with osteoconduction and vascularization in half of the rabbits, and even disappeared in one of the six rabbits without any systemic administration of antibiotics. Outside the debrided area, inflammation and sequestrum were observed but the largest of such affected areas amounted to only 0.125 times of the originally infected and debrided area. These findings showed that the granular composite was effective for the local treatment of osteomyelitis as well as an osteoconductive scaffold which supported and encouraged vascularization.     

Inhibition of the proliferation of human periodontal ligament fibroblasts by hyaluronidase

Hyaluronan (HA) exists in various living tissues as one of the major matrix macromolecules, and is well known to play an integral role in cell differentiation and proliferation. The present study was conducted to elucidate whether or not the proliferation of periodontal ligament (PDL) cells are affected specifically by the degradation of HA by hyaluronidasze (HAase). Human PDL fibroblasts were isolated and cultured with and without 15-150U/ml bovine testicular HAase from 1 to 11 days after seeding. The cells were also cultured with anti-CD44 antibody of 2 microg/ml. For the control against the anti-CD44 antibody treatment, 2 microg/ml IgG was used. The HA-dependent pericellular matrix was visualized by particle-exclusion assay. The number of cells was counted by MTT assay during the proliferation. The mRNA levels of HA synthases (HASs), HAases (HYALs) and CD44s were examined by a quantitative real-time PCR analysis. The cell proliferation was inhibited by the treatment with HAase and anti-CD44 antibody in cultured PDL fibroblasts. HASs mRNAs were down-regulated, whereas HYALs mRNAs were up-regulated significantly by the treatment with HAase and anti-CD44 antibody. The CD44s mRNA level exhibited no significant changes. These results suggest that HA may contribute to modulate the proliferation of cultured human PDL cells through a CD44-mediated mechanism.     

A comparative evaluation of different compensating curves in the lingual and labial techniques using 3D FEM.

Because adults dislike the visibility of orthodontic appliances, the use of the lingual orthodontic technique has increased over time. But few studies compare tooth movement of the lingual technique with that of the labial technique. In this study, human mandibular left teeth were aligned, and a 3-dimensional finite element model was made (consisting of 19382 nodes and 12150 elements). To compare the effect of compensating curves on canine retraction between the lingual and the labial orthodontic techniques, the compensating curve was increased on the.016-in stainless steel labial or lingual archwire, and a 150-g force was applied distally on the canine. The relative direction and the amount of tooth displacement of the finite element model were compared on a schematic displacement graph (magnified 10,000 times), and the compressive stress distributed on the root surface was observed. The pattern of tooth movement (with or without a compensating curve) was different between the labial and the lingual techniques. As the amount of compensating curve increased (0, 2, and 4 mm) in the archwire, the rotation and the distal tipping of the canine was reduced. The antitip and antirotation action of compensating curve on the canine retraction was greater in the labial archwire than in the lingual archwire.     

Expression and significance of stromal cell-derived factor-1alpha and its receptor CXCR4 in human dental pulp cells

OBJECTIVE: To investigate the expression of CXCR4 in cultured human dental pulp cells (HDPC) in vitro and the corresponding ligand SDF-1alpha level of HDPC supenatants stimulated by lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF-alpha), and to explore the role of SDF-1alpha on the proliferation and the migration of HDPC. METHODS: The expression of CXCR4 in HDPC was detected by immunocytochemistry technique and indirect immunofluorescence technique. The culture supernatants of HDPC were collected after HDPC had been simulated by LPS and TNF-alpha of different concentrations for 48h and then the SDF-1alpha level was assayed by quantitative sandwich ELISA. Meanwhile, the effects of recombinant human SDF-1alpha (rhSDF-1alpha) on the proliferation and the migration of HDPC at different concentrations were observed by MTT and Boyden Chamber Assay. RESULTS: CXCR4 was expressed in cytomembrane of HDPC and SDF-1alpha was secreted into their normal cell supernatants with a concentration of (4513.55 +/- 962.92) ng/L. The secretion of SDF-1alpha was both significantly decreased by stimulation with LPS and TNF-alpha (P < 0.05). In addition, rhSDF-1alpha stimulated the HDPC proliferation at the concentrations of 50, 100, 200 microg/L (P < 0.01) and increased the chemotactic migration of HDPC significantly after 9h's incubation with the concentrations of 50, 100 microg/L (P < 0.05). CONCLUSIONS: SDF-1alpha accelerated the proliferation and the migration of HDPC which expressed CXCR4. SDF-1-CXCR4 axis may play a role in repair of pulp injury.     

味觉出汗综合征的临床分析

为了观察味觉出汗综合征的发病情况,对100例行腮腺区手术的患者,作了客现的碘-淀粉试验检查。结果表明:行浅叶切除术者,其发病率(100％)明显高于包括肿瘤及其周围部分正常腺体的区域切除术者(发病率为18.18％)。放射治疗虽可降低味觉出汗综合征的发病率,但放射治疗后仍有复发可能。