The efficacy of mesenchymal stem cells to regenerate and repair dental structures

OBJECTIVES: Identification, characterization, and potential application of mesenchymal stem cells (MSC) derived from human dental tissues. METHODS: Dental pulp and periodontal ligament were obtained from normal human impacted third molars. The tissues were digested in collagenase/dispase to generate single cell suspensions. Cells were cultured in alpha-MEM supplemented with 20% fetal bovine serum, 2 mM l-glutamine, 100 microM l-ascorbate-2-phosphate. Magnetic and fluorescence activated cell sorting were employed to characterize the phenotype of freshly isolated and ex vivo expanded cell populations. The developmental potential of cultured cells was assessed following co-transplantation with hydroxyapetite/tricalcium phosphate (HA/TCP) particles into immunocompromised mice for 8 weeks. RESULTS: MSC were identified in adult human dental pulp (dental pulp stem cells, DPSC), human primary teeth (stem cells from human exfoliated deciduous teeth, SHED), and periodontal ligament (periodontal ligament stem cells, PDLSC) by their capacity to generate clongenic cell clusters in culture. Ex vivo expanded DPSC, SHED, and PDLSC populations expressed a heterogeneous assortment of makers associated with MSC, dentin, bone, smooth muscle, neural tissue, and endothelium. PDLSC were also found to express the tendon specific marker, Scleraxis. Xenogeneic transplants containing HA/TCP with either DPSC or SHED generated donor-derived dentin-pulp-like tissues with distinct odontoblast layers lining the mineralized dentin-matrix. In parallel studies, PDLSC generated cementum-like structures associated with PDL-like connective tissue when transplanted with HA/TCP into immunocompromised mice. CONCLUSION: Collectively, these data revealed the presence of distinct MSC populations associated with dental structures with the potential of stem cells to regenerate living human dental tissues in vivo.     

三种丙烯酸树脂牙和丙烯酸牙托粉的结合强度实验研究

为了探求人造牙从基托上脱落下来的原因,本文作者对三种丙烯酸树脂牙和三种丙烯酸牙托粉的拉伸结合强度和剪切结合强度进行了测试,结果表明,材料和不同品牌材料的匹配都会影响人造牙与基托的结合强度;塑料牙盖嵴面打磨粗糙后,可显著增强塑料牙与基托树脂的结合强度。     

应用"摇椅形"弓丝矫治前牙开牙合的临床研究

目的　研究“摇椅形”弓丝对前牙开牙合畸形的矫治效果。方法　对 14例前牙开牙合的患者应用“摇椅形”弓丝同时配合前牙区垂直牵引进行矫治 ,通过分析矫治前后X线头颅定位侧位片 ,评价其矫治效果。结果　矫治后上下颌切牙伸长、内收 ,下颌磨牙直立 ,牙合平面改建 ;同时控制了开牙合患者垂直方向的生长。结论　应用“摇椅形”弓丝同时配合前牙区垂直牵引矫治开牙合畸形符合利用固定矫治器治疗开牙合的机理 ,能获得良好的矫治效果。     

咬合板治疗磨牙症的磨牙信息监测研究

目的　应用自行研制的磨牙症监测仪客观评价稳定型咬合板与尖牙高型咬合板治疗磨牙症的临床效果。方法　将 2 0名磨牙症患者随机分为两组 ,在受试条件基本一致的情况下 ,于低于息止颌位 0 5mm的高度分别制作稳定型咬合板与尖牙高型咬合板。应用自行研制的磨牙症监测仪监测每名患者治疗前后的磨牙时间与磨牙次数。结果　尖牙高型咬合板组患者磨牙时间与磨牙次数明显减少 ,治疗前后差异有极显著性 ;稳定型咬合板组患者治疗前后的监测数据差异无显著性。结论　磨牙症监测仪能自动测量和记录戴咬合板的磨牙症患者的磨牙数据 ,有一定的临床应用价值 ;尖牙高型咬合板治疗磨牙症的临床效果明显优于稳定型咬合板。     

犬恒牙牙根正常发育过程中细胞凋亡的研究

目的：探讨细胞凋亡在牙根发育过程中的生理作用。方法：采用原位末端标记技术(TuNEL)，观测犬恒牙牙根发育过程中各组织中凋亡细胞的分布情况：结果：牙根发育时期在成牙本质细胞、牙髓组织、牙乳头组织、上皮根鞘、牙槽骨组织中有特异性细胞凋亡发生。结论：细胞凋亡在牙根发育过程中的发生具有时空特异性，提示其在牙根形态形成过程中发挥重要的生理作用。     

Use of separate single-tooth implant restorations to replace two or more consecutive posterior teeth: a prospective cohort study for up to 1 year

PURPOSE

The aim of this study was to evaluate the periodontal and prosthodontic complications of multiple freestanding implants in the posterior jaws for up to 1 year of function.

MATERIALS AND METHODS

Eight patients received 20 implants posterior to canines. Two or more implants were consecutively inserted to each patient. Single crowns were delivered onto the implants. Marginal bone loss, implant mobility, probing depth, and screw loosening were examined to evaluate the clinical success of such restorations for maximum 1 year of functional loading.

RESULTS

All the implants performed well during the observation period. Neither periodontal nor prosthodontic complications were found except a slight porcelain chipping. While the marginal bone level was on average 0.09 mm lower around the implant after 6 months of loading, it was 0.15 mm higher after 1 year.

CONCLUSION

Within the limits of this investigation, separate single-tooth implant restorations to replace consecutive missing teeth may clinically function well in the posterior jaw.     

Evaluation of selective caries removal in deciduous teeth by a fluorescence feedback-controlled Er:YAG laser in vivo

This study investigated the ability and efficacy of an Er:YAG laser with a fluorescence feedback system for caries removal in deciduous teeth. Seventy-nine carious lesions were excavated using a fluorescence-controlled Er:YAG laser. Endpoint of treatment was defined by emission of fluorescence from the dentine surface below the pre-selected threshold level of 7 units and the subsequent termination of Er:YAG laser radiation. Dentine samples were obtained from the cavity floor, and viable counts of both Streptococcus mutans and Lactobacilli, expressed as colony forming units (log CFU), were evaluated. Preparation time was recorded to assess efficacy of the treatment procedure. S. mutans and/or Lactobacilli were found in 25 out of 79 lesions. Regarding the counts for S. mutans and Lactobacilli, the median log CFU was 0 (min, 0; max, 5.5) and 0 (min, 0; max, 6), respectively, with 2.4% of all samples yielding more than 100 CFU S. mutans and 4.8% yielding more than 100 CFU Lactobacilli. In 8 out of 79 cases, laser excavated cavities were not judged being caries-free using the conventional tactile criterion for assessing caries tissue. Focussing on these teeth, the median log CFU was 0 (min, 0; max, 0.5) for S. mutans and 0 (min, 0; max, 1.6) for Lactobacilli. The mean time for treatment was 2.3 +/- 1.2 min. Of the children, 93.8% rated the laser treatment to be comfortable. The study indicates that the fluorescence feedback-controlled Er:YAG laser might be an appropriate device for caries removal in children using the suggested threshold level of 7 units.     

模型转化法建立磨牙及其牙周组织的三维有限元模型

目的建立下颌第二恒磨牙及其牙周膜、牙槽骨的分析用模型。方法应用CAE软件3D MAX6.0及CATIA4.0生成磨牙及其牙周组织的三维有限元模型,利用HYPERMESH划分网格,生成可分析的三维有限元实体模型。结果建立了下颌第二恒磨牙及其牙周膜、牙槽骨的三维有限元模型,可以分别进行受力状态下应力、应变的分析。结论该模型可供口腔正畸矫治中磨牙的受力分析应用。