Objective  To investigate the regulation of P2X3 protein expression in the trigeminal ganglion sensory neurons after the nociceptive stimulation by orthodontic tooth movement force. Methods  Male Sprague-Dawley rats weighing 200-250 g were used. The mimic tooth movement appliance was used in experimental group rats. The animals were sacrificed after 4 h, 1 d, 2 d, 3 d, 5 d, 7 d and 14 d. The semi－quality of P2X3 protein was measured by Western blot. The expression place and strength of P2X3 was detected by in situ hybridization with an oligonucleotide probe in the same time. Results  A major specific protein of 4.5×104 was found by Western blot in trigeminal ganglion of rats. The expression strength of P2X3 receptor increased after given force to the teeth of rats from 1 day of experiment, 3 day group rats showed peak change. 14 day group had returned to control values. The level change of P2X3 mRNA expression showed the same result. Conclusion  The results suggest that the P2X3 receptor expression is transiently upregulated and anterogradely transported in trigeminal primary sensory neurons after orthodontic tooth movement and that P2X3 receptor may play role in the pathomechanism of nociceptive in primary sensory neurons during orthodontic clinic treatment.

Objective  To develop a functional biomechanical mandibular model, and to observe the stress distribution of angle-fractured mandible under different rigid internal fixation（RIF） methods. Methods  A biomechanical model of mandible was built which include the simulative temporal-mandibular joint（TMJ） and was under mechanical loads of masseter, temporalis, medial pterygoid and lateral pterygoid. The different stress pattern was measured by strain gauges. Under the standard mandibular angle fracture, bilateral molar biting and four pairs of muscles loading, the strains were compared to evaluate the stability of one-or two-miniplate fixation. Results  The fixation of miniplate in the lateral oblique line can recover the main stress on the non-fracture side, but it was broken in the fracture side. The tension increased in the lower border of mandibular angle. Conclusion  Through the biomechanical study based on the functional mandibular model, only one miniplate fixation in lateral oblique line for mandible angle fracture was insufficient buttressing of the segments, while the additional miniplate in the lower margin can recover the stress pattern and provide more stability.

Objective  To investigate the effects of time varied stress on the shape-alteration of myoblast in rats and to provide a theoretic base to determine the mechanics of myoblast in orthodontic therapy. Methods  Based on the pulsatile mechanical system our group founded, this study loaded different strain（2.5 kPa、5.0 kPa and 10.0 kPa） to the myoblast of lateral pterygoid muscle. The alterations in shape under time varied stress of 6 h and 12 h were assessed by phase-contrast microscopy, scanning electron microscope. Results  The orientation of myoblast seemed no obvious orderliness before loading. But after loading the lower time varied strain（2.5 kPa, 5.0 kPa）, they were changed their orientation to paralel with the direction of strain along with the membrane. Meanwhile, there had one trend to set the shape of myoblast more upright along with the membrane after loading the higher time varied stress（10.0 kPa）. Conclusion  It was proved that the different time varied stress in vitro expressed the different influence on the remolding of myoblast.

Objective  To clone the catalytic domain gene sequence of RgpAcd of Porphyromonas gingivalis（P.gingivalis） and to induce its fusion expression in E. coli. Methods  The desired DNA fragment RgpAcd was obtained by PCR and was separately sequenced and identified by inserting into inter-vector pMD18-T vector. The correctly fragment was linked with and cloned into a prokaryotic expression vector pET-15b. The recombinant expression plasmid which had been confirmed by enzymes digestion was transformed to E. coli competent cells BL21（DE3） and expression of fusion protein was induced by IPTG. Results  A 1 476 bp specific fragment was obtained and DNA sequencing showed that the fragment was consistent with those of the published. After induction with IPTG, a fusion protein of 5×104 was visualized on SDS-PAGE gel. Conclusion  The protein of RgpAcd will be obtained for further study and its protein was correctly expressed in E. coli BL21 cells.

Objective  To investigate the mechanical properties and microstructure of nano-zirconia toughened alumina ceramics with variety of nano-zirconia content  in centrifugal infiltrate casting processing of dental all-ceramic. Methods  Composite powder with different ethanol-water ratio, obtained serosity from ball milling and centrifugal infiltrate cast processing of green, then sintered at 1 450 ℃ for 8 h. The physical and mechanical properties of the sintered sample after milling and polishing were tested. Microstructures of the surface and fracture of the sintered sample were investigated by SEM. Results  The experimental results showed that there had statistical significience （P＜0.01） on static three-point flexure strength and Vickers Hardness in three kinds of different nano-zirconia content sintered sample. Fracture toughness of 20% group was different from other two groups, while 10% group had not difference from 30% group（P＜0.05）. The mechanical properties of this ceramic with 20% nano-zirconia was the best of the three, the static three-point flexure strength was（433±19） MPa and fracture toughness was（7.50±0.56） MPa·m1/2. The intra/inter structure, fracture of intragranular and intergranular on the surface and fracture of sintered sample in microstrucre was also found. Conclusion  Intra/inter structure has strengthen toughness in ceramics. It has better toughness with 20% nano-zirconia, is suitable dental all-ceramic restoratives.

Objective  To evaluate the effect of K2O addition on the crystallization property of dental glass-ceram-ics in the Li2O-SiO2-Al2O3-P2O5-ZnO system.  Methods  Different content of K2O was added into Li2O-SiO2-Al2O3-P2O5-ZnO glass system. The heat-treated system of the glass-ceramics was determined by differential thermal analyses（DTA）, then the crystallization components and the microstructure of the glass-ceramics with different content of K2O were investigated from X-ray diffraction（XRD） analyses and scanning electron microscopy（SEM）. Results  Addition of K2O helped to reduce the viscosity of the glass system and improved crystallization. More lithium disilicate crystals appeared after heated-treatment of the glass system which contained 5.3wt% addition of K2O, and the homogeneously lath-shaped crystals were 4 μm in length.  Conclusion  Certain content of K2O can improve the crystallization property of dental glass-ceramics in the Li2O-SiO2-Al2O3-P2O5-ZnO system.

Objective  To observe the influence of different investing methods and mold cooling methods on pure titanium castings invested in the self-made investment, and to provide theoretic base for the development for the investment. Methods  The influence of investing methods（one-step investing method and two-step investing method） on castability and crown fit of titanium castings were investigated, and the influence of cooling methods on reaction layers, mechanical properties and crown fit of titanium castings were investigated. Results  Both the investing methods exhibited good castability, but only the titanium full crowns by one-step investing method showed clinically acceptable fit. Although the quenching group showed thinner reaction layer（100 μm）, lower strength and similar elongation rate, the titanium castings by bench cooling showed clinically acceptable full crown fit with 115 μm thick reaction layer as cast. Conclusion  The one-step investing method and the bench cooling are recommended for the self-made investment.

Objective  To compare the impacts of different beverages on plaque pH of caries-sensitive and caries-free children and to evaluate the applicability of in situ pH measurements in human dental plaque using Beetrode microelectrode. Methods  The subjective population consisted of 20 children（aged 3-5 years）. Ten of them were caries-free（dmft=0）; the other were caries-active（dmft>4）. The dental plaque pH were measured in situ with a pH microelectrode within 1 h after drinking three different beverages respectively. Then the resting pH value（pHrest）, minimum pH value（pHmin）, the range of the pH（△pH） was analyzed by ANOVA. Results  There was a significant difference in pHrest between caries-free and caries-sensitive children. All the pH responses in the plaque following drinking three different beverages showed a classic Stephan-type response. The differences of the pHmin, △pH in sound sites were no statistic significance（P>0.05） after drinking beverages in caries-free children. However the changes in the caries-sensitive group were more pronounced than the non-caries group. There were significant differences on the pHmin, △pH among different beverages（P<0.05）. Conclusion  The cariogenicity of plaque in caries-active children was stronger than that of the caries-free group. Different beverages have different potential cariogenicity.

Objective  To find out the characteristic topographic distribution of the muscle spindles in human masseter and temporal muscle, and to clarify the neurobiology roles of masticatory muscles during chew and adjusting mandibular position. Methods  The muscle spindles of masseter and temporal muscle on both sides of 5 human corpses fixed in formalin for more than 1 year were observed and quantitatively analyzed by picture analysis equipment. Results  The muscle spindles were maldistributed and spindles were commonly clustered in some individual portions, and the muscle spindle figures were diversiform, which were predominantly composed of the spindle simple and spindle complexes. the masseter spindles of the deep portion were obviously more than that of the superficial. Spindles of temporal muscle were concentrated in the anterior approach to the coracoid. Conclusion  The distribution of muscle spindles in the masseter and temporal muscle is heterogeneous, spindle density in the deep portion of masseter and the anterior of temporolismuscle is greater than others. The deep of masseter and the anterior of temporal muscle play an important part in maintaining mandibular position and balance.

 Objective  To evaluate the probability of repairing the severe cleft lip and nose in one time. Methods  35 patients were included. A revised method was presented based on the popular methods used. Results  Among 35 patients, the length of lip in two sides was equal in 33 patients, and the appearance of the nose shape was satisfactory in 31 patients evaluated by third expert group. Conclusion  The method presented in this paper could repair the abnormalities of the lip and nose effectively in severe cleft lip patients in one time and was adapted in the patients who could not be treated with serial methods because of a bad economic state.