三种类型骨内牙种植体的临床修复设计

作者将三种类型国产骨内牙种植体——羟基磷灰石涂层钛合金二段式种植体（HA-Ti)，纯钛叶状种植体（Ti-Blade)，纯钛螺旋状种植体（Ti-Screw)共35枚植入21例患者上下颌骨内，均已作永久性修复，临床观察19-48个月，除4枚已取出外，其余尚留于口中行使功能。作者认为，适当选择适应证，合理设计上部修复体对3种类型国产牙种植体的成败至关重要。     

Non-viral-mediated gene therapy approaches for bone repair

OBJECTIVES: Bone repair strategies continue to be developed for alternatives to autografting, allogeneic implants of banked bone, and other bone substitutes. Efforts have included the delivery of potent growth and/or differentiation factors and the use of gene therapy. For bone regeneration, gene therapy is the delivery, uptake and expression of DNA that has been localized to a wound bed. The objective of the current study is to investigate methods to enhance non-viral-mediated means of gene uptake and expression for use in bone regeneration. METHODS: Several types of DNA-polymer complexes, either applied directly to baby hamster kidney (BHK) cells, or released from a porous, resorbable gene-activated matrix (GAM), were evaluated in vitro for their ability to transfect cells with a circular plasmid DNA construct expressing green fluorescent protein. Complexes included conjugates containing a lipophilic reagent, liposomes, poly-ethyl-oxazoline, and poly-ethyleneimine (PEI). Data were subjected to analysis of variance and Fisher's protected least significant difference for multiple comparisons with significance established at p < 0.05. RESULTS: Transfection efficiencies of the liposome and PEI complexes improved in vitro when released from resorbable GAMs. The lipophilic reagent FuGene 6 demonstrated abundant uptake and expression in the initial 1- and 2-day evaluation periods. In contrast, the DNA-liposome and PEI GAM complexes demonstrated a sustained release, uptake and expression by the BHK cells at the 2-, 4-, and 7-day, and 4- and 7-day evaluation intervals, respectively. CONCLUSION: GAM technology appears to improve the functional stability and release duration of incorporated DNA-polymer complexes in the present in vitro studies. The ongoing objective of our research is to develop a localized treatment to improve the uptake and expression of plasmid DNA by non-viral-mediated gene therapy.     

A simple method of making an implant-level impression when presented with limited space,unfavorable implant positions,or problematic implant angulations

Making an implant-level impression for the purpose of abutment selection when implants are placed in limited space, unfavorable positions, or compromising angulations can be a time-consuming procedure. An impression procedure is presented that makes use of either prefabricated screw-retained titanium implant index copings or plastic snap-on implant index copings to help resolve problematic implant placement. Both the titanium and plastic implant index copings are easy to modify and therefore make impression procedures more predictable.     

Human periodontal ligament cell responses to recombinant human bone morphogenetic protein-2 with and without bone allografts

BACKGROUND: Recombinant human bone morphogenetic protein-2 (rhBMP-2) has been found to promote the osteoblastic differentiation of human periodontal ligament cells. Its effect depends on the delivery system used. In this study we examined the effect of rhBMP-2 on the proliferation and osteoblastic differentiation of human periodontal ligament cells cultured alone or with 3 different bone allografts. METHODS: The rhBMP-2 effect on cell proliferation and osteoblastic differentiation was examined by measuring [3H] thymidine incorporation and ALPase activity, respectively, on human periodontal ligament (hPDL) cells. Two human demineralized freeze-dried allografts of cortical (DFDBAco) and cancellous (DFBDAca) bone origin and 1 non-demineralized freeze-dried allograft (FDBA) of cancellous bone origin, derived from different tissue banks, were used to evaluate the rhBMP-2 effect on cell osteoblastic differentiation. The measurements were taken on various days. RESULTS: rhBMP-2 decreased hPDL cell proliferation. rhBMP-2 acted on the third day of the process of cell differentiation, had a specific time of action, achieved its peak effect on the fourth and fifth days, and then did not provoke any further effects. The 3 bone allografts were efficiently combined with rhBMP-2. The combination of rhBMP-2 and DFDBAco showed the effect with the longest duration. rhBMP-2, on day 4, made the inactive bone allograft more active while, on the other days, its effect was dependent on the allograft alone. CONCLUSIONS: rhBMP-2 promotes the osteoblastic differentiation of human periodontal ligament cells and decreases cell proliferation. In this study rhBMP-2 in the presence of the bone allografts tested resulted in hPDL cell differentiation.     

FGF signalling in craniofacial development and developmental disorders

The Fgf signalling pathway is highly conserved in evolution and plays crucial roles in development. In the craniofacial region, it is involved in almost all structure development from early patterning to growth regulation. In craniofacial skeletogenesis, the Fgf signal pathway plays important roles in suture and synchondrosis regulation. Mutations of FGF receptors relate to syndromatic and non-syndromatic craniosynostosis. The Fgf10/Fgfr2b signal loop is critical for palatogenesis and submandibular gland formation. Perturbation of the Fgf signal is a possible mechanism of palatal cleft. Fgf10 haploinsufficiency has been identified as the cause of autosomal dominant aplasia of lacrimal and salivary glands. The Fgf signal is also a key regulator of tooth formation: in the absence of Fgfr2b tooth development is arrested at the bud stage. Fgfr4 has recently been identified as the key signal mediator in myogenesis. In this review, these aspects are discussed in detail with a focus on the most recent advances.     

Shaping ability of progressive versus constant taper instruments in curved root canals of extracted teeth

AIM: To compare the shaping ability of progressive versus constant taper shaft instruments in curved root canals of extracted human teeth. METHODOLOGY: A total of 40 root canals of mandibular molars with curvatures ranging between 20 degrees and 40 degrees were divided into two groups of 20 canals each and embedded in a muffle system. The root canals sectioned horizontally at three levels before preparation and then remounted into the mould. All root canals were prepared with ProTaper (progressive taper) or Hero Shaper (constant taper) instruments. Pre- and post-instrumentation radiographs and cross-sectional images were obtained. The parameters evaluated were: working safety (instrument failure, apical blockage and loss of working length) and shaping ability (straightening, cross-sectional area, transportation and centring ability). The data were analysed statistically using Student's t-test. RESULTS: No instrument fractured during preparation. One Hero Shaper instrument permanently deformed. Both instrument systems maintained working length well. The canals prepared with Hero Shaper instruments were straightened to a lesser degree (P < 0.05). ProTaper instruments removed more dentine in the coronal and the middle sections of the canals. Canals prepared with Hero Shaper instruments had less transportation (P < 0.01) and better centring ability (P < 0.05) in the apical section. CONCLUSIONS: Both instrument systems were safe to use and maintained working length well. The canals prepared with Hero Shaper had less transportation and were better centred in the apical region, possibly because their smaller taper reduced instrument stiffness.     

常用根管充填材料生物相容性研究

通过细胞附着实验和扫描电镜技术对四种常用根管封闭剂以及三种牙胶尖的生物相容性研究发现：所有充填材料甚至一直被 认为细胞毒性最小的牙胶尖均有明显的细胞毒性。因此，在临床上，为了避免材料对根尖周细胞产生机械刺激和减少细胞毒性作用，应尽量避免根管充填材料超填。本文还就氯仿是否可用于根管治疗进行了讨论。     

Validation of DIAGNOdent for quantification of smooth-surface caries: an in vitro study

The aims were 1) to validate a laser-based device, KaVo DIAGNOdent, for quantification of caries lesions on smooth surfaces, using histopathologic and microradiographic analyses as the gold standard, and 2) to test inter- and intra-observer agreements. We also investigated the influence on DIAGNOdent readings of the storage medium used for extracted teeth. Two observers measured independently the tooth surfaces of 40 extracted premolars that had been stored in thymol-saturated saline. After subsequent storage in neutral-buffered formalin for 14 days they were re-measured. The teeth were then sectioned for histopathologic and microradiographic analysis. The Spearman rank correlation coefficients between lesion depth and DIAGNOdent readings were 0.78-0.83 and 0.85 for teeth stored in thymol-saturated saline and formalin, respectively. Inter- and intra-observer agreements were 0.94 and 0.95 when the teeth were stored in thymol-saturated saline. The DIAGNOdent reading was almost 1.5 times higher for teeth stored in formalin than for those stored in thymol saline. The Spearman rank correlation coefficient between mineral loss in enamel (deltaZ) and DIAGNOdent readings ranged from 0.64 to 0.68. It was concluded that DIAGNOdent may be helpful for assessing smooth-surface caries, but the cut-off points need to be assessed under clinical conditions. The increase in fluorescence associated with storage of teeth in formalin warrants further investigation.