[Accuracy of 6D computed-derived implant guides made in China for dental implant surgery in edentulous patients].

PURPOSE: To evaluate the accuracy of 6D computed-derived implant guides made in China, in order to provide methods and basis for reducing deviation. METHODS: 3D rapid prototyping technique was used to fabricate implant guides for auxiliary surgical implantation in edentulous patients, and the position deviation between the preoperative design and the actual implant was measured. Sixteen edentulous patients with 172 implantation sites were measured. In 10 patients, six implants were implanted in the maxilla, 4 implants in the mandible, and 6 implants were implanted both in the maxilla and mandible of 6 patients. A total of 28 implants were tilted implant in 14 patients. Preoperative cone-beam CT(CBCT) data were imported into the 6D Dental Planning Software to design and make the implant guides. Digital guides were used to assist implant placement. Preoperative design and postoperative CBCT were imported into the software for 3D reconstruction and registration, and then exported to Geomagic Studio software for analysis to obtain the deviation between the preoperative design and the implantation, so as to analyze the accuracy of the guides. The differences were analyzed by SPSS 25.0 software package with paired t-test and single factor analysis of variance. RESULTS: The distance deviation of implant neck center point was (0.83±0.27) mm and the horizontal deviation was (0.60±0.21) mm. The distance deviation of implant bottom center point was (1.11±0.35) mm, and the vertical deviation was (0.45±0.19) mm. The angle deviation was (3.16±1.73)°. CONCLUSIONS: The 6D computed-derived implant guides made in China can improve the accuracy and efficiency of implant surgery for edentulous patients and obtain a better long-term clinical effect to meet clinical requirements well. Since the deviation is similar to other implant guide plate systems that reported aborad, it must be taken into account in the process of clinical design, in order to avoid risks and unnecessary complications. This method is worthy of wide clinical application.

[Clinical study of titanium mesh in conjunction with concentrate growth factors to rebuild severe bone defect of anterior maxilla].

PURPOSE: To evaluate the effect of overlaying titanium mesh with concentrate growth factors(CGF) for rebuilding severe buccal bone defect of anterior maxilla when used in association with dental implantation. METHODS: Twenty patients with severe buccal bone defect of maxilla were selected. A total of 25 dental implants were placed, including 5 cases in bilateral central incisor area and 15 cases in unilateral central incisor area. After implantation, the defects were treated with Bio-oss and Bio-guid in conjunction with fixation of titanium mesh and then CGF technology was used. Two-stage surgery was carried out after 6 months of submerged healing, and permanent prosthesis was used 3 months after temporary restoration. The repairs of the defect were observed at the second stage surgery. The height of margin bone around implants and the thickness of bone at implants lingual side were measured, at the time of the second stage operation, and 3, 6, 12, 18 months after permanent restoration. The differences were analyzed by SPSS 19.0 software package with multi-sample nonparametric test and Fierdman test. RESULTS: At the time of second operation, the bone plate at lingual side was completely reconstructed, and new bone was formed at the top of implants. Clinical measurements showed that the averaged thickness of bone at lingual side was (2.69±0.154) mm at that time. Three, 6, 12, 18 months after restoration, the values were (2.67±0.152) mm, (2.66±0.153) mm, (2.65±0.153) mm, (2.65±0.151) mm, respectively. Implant-abutment junction was used as a base line to assess vertical bone absorption, the marginal bone of implant neck at lingual side was all inferior to the base line, the distance was (0.02±0.048) mm, (0.69±0.085) mm，(0.87±0.019) mm, (0.87±0.013) mm, respectively. Statistical analysis showed the thickness of bone of labial side decreased significantly over time after permanent restoration (P<0.01). Likewise, the height of marginal bone was also decreased significantly (P<0.01). However, the difference between them at 12 months and 18 months was not statistically significant (P>0.05). CONCLUSIONS: The results indicate that bone augmentation at maxilla can be achieved using titanium mesh in conjunction with CGF. The height and thickness of newly formed bone at the implant neck margin will be stabilized after 1 year. This method is worthy of wide clinical application.

Leafy head2, which encodes a putative RNA-binding protein, regulates shoot development of rice.

During vegetative development, higher plants continuously form new leaves in regular spatial and temporal patterns. Mutants with abnormal leaf developmental patterns not only provide a great insight into understanding the regulatory mechanism of plant architecture, but also enrich the ways to its modification by which crop yield could be improved. Here, we reported the characterization of the rice leafy-head2 (lhd2) mutant that exhibits shortened plastochron, dwarfism, reduced tiller number, and failure of phase transition from vegetative to reproductive growth. Anatomical and histological study revealed that the rapid emergence of leaves in lhd2 was resulted from the rapid initiation of leaf primordia whereas the reduced tiller number was a consequence of the suppression of the tiller bud outgrowth. The molecular and genetic analysis showed that LHD2 encodes a putative RNA binding protein with 67% similarity to maize TE1. Comparison of genome-scale expression profiles between wild-type and lhd2 plants suggested that LHD2 may regulate rice shoot development through KNOX and hormone-related genes. The similar phenotypes caused by LHD2 mutation and the conserved expression pattern of LHD2 indicated a conserved mechanism in controlling the temporal leaf initiation in grass.

Study of the factors affecting the forward and back extraction of yeast-lipase and its activity by reverse micelles.

The experimental results of yeast-lipase extracted by AOT-reverse-micelles in isooctane are reported. The effects of pH values and ionic strength in the aqueous phase, surfactant concentration, phase volume ratio, temperature, stirring time, and cosolvent concentration on the phase transfer of the lipase by the reverse micelles are studied. One hundred percent of forward extraction yield, 68% of back extraction yield, and 45% of activity recovery yield for the lipase are obtained. The phase transfer of the lipase is controlled by electrostatic and hydrophobic interactions.

[Cotransformation of rice by bar and cecropin B gene expression cassettes lacking vector backbone sequences].

Whole plasmids are used in both Agrobacterium-mediated transformation and direct DNA transfer, generally leading to the integration of vector backbone sequences into the host genome along with the transgene(s). The undesirable vector backbone sequences may not only promote transgene rearrangements and affect transgene or endogenous gene expression negatively, but have disadvantage on the safe assessment of the transformants as "desert DNA". The direct DNA transforming systems can transfer minimal gene expression cassettes (promoter, open reading frame, terminator) into plant genome and generate "safer" transformants, also it can delivery multiple genes of agronomic relevance to economically-important crop plants. But there is seldom researching reports on the topic till now. The present paper studied some factors that affecting the transforming efficiency of liner gene expression cassettes to rice varieties by particle bombardment, and the integration patterns of the gene expression cassettes in rice genome were compared with that of the whole plasmids. The results showed: (1) The transforming frequency of gene expression cassettes to rice via particle bombardment is 0.1%-0.5%, the cotransforming frequency of non-selectable gene is about 50%-60% when two separate gene expression cassettes were used for transformation. Increasing the DNA mole content can increase the transforming frequency and the beside sequences of gene constructs may play an important role on the variation of transforming efficiency between different rice varieties. (2) It's reported that the selectable and non-selectable transgene expression cassettes generated low-copy-number transgenic plants with simple integration patterns. While our results showed that the non-selectable cecropin B gene cassette generated simple integration patterns with 1-3 copies in the rice genome, but the selectable bar gene cassette which got 4-14 copies had much more complex integration patterns than that of the whole plasmids which got 1-3 copies only. As the bar gene is promoted by the CaMV35 promoter, in which there is a 19 bp palindromic sequence could act as recombination hot spot and lead to DNA rearrangement, we presumed that the transgene recombination events happened during the integration course have generated the complex Southern patterns of bar gene expression cassette. The recombination character, the heredity behavior and the expression law of gene expression cassettes in the rice genomes will be reported in our future papers.

[The new safe strategy on the marker genes in transgenic plant].

The presence in transgenic plants of antibiotic and herbicide resistant selective marker genes might be an unpredictable hazard to the ecosystem as well as to human health. There are two applicable strategies can be used to resolve this problem. One is to remove the resistant marker genes before the transgenic plants are released to field. The other is to develop and use safe marker genes to produce transgenic plants. The present paper reviewed three technique systems employed to remove resistant marker genes in transgenic plants and several safe marker genes used in plant transformation.