[Accuracy evaluation of recording maxillomandibular relation with the mandibular kinesiography].

PURPOSE: To evaluate the accuracy of recording maxillomandibular position relationship with the mandibular kinesiography by surface electromyography analysis of the masticatory muscles and MRI of temporomandibular joint (TMJ). METHODS: Eight edentulous patients were selected randomly, and the maxillomandibular position relationship was determined by mandibular kinesiography and traditional method respectively. Then the corresponding bite plates were made to wear. Surface electromyography test of left and right anterior temporal and masseter muscle and magnetic resonance scan of the temporomandibular joint were performed on closed mouth position to record peak potentials, calculate asymmetric indexes, analyze the position relationship between the joint disc and the condyle, measure TMJ joint space. SPSS 18.0 software package was used for data analysis. RESULTS: There was no significant difference in the amplitude of the anterior temporal or masseter muscle, the asymmetry index of total, asymmetry index of masseter, asymmetry index of temporalis, the anterior, upper and posterior spaces of TMJ between the mandibular kinesiography group and the traditional group (P＞0.05). The temporomandibular articular disc process relationship of the two groups were conformed to the normal physiological position relationship. CONCLUSIONS: Mandibular kinesiography could accurately record the maxillomandibular position relationship in patients with edentulous jaws.

[Fracture resistance of endodontically treated maxillary premolars restored with different CAD/CAM all-ceramic restorations].

PURPOSE: This study was to evaluate the fracture resistance of endodontically treated maxillary premolars restored with different CAD/CAM all-ceramic restorations in vitro. METHODS: Mesio-occluso-function tip(MOF) cavities were prepared in 21 extracted human maxillary premolars due to endodontic treatment. The teeth were divided into 3 groups. G1:conventional composite resin; G2: cavities；G3: conventional composite resin with a horizontal glass fiber post inserted palatal walls. Restorations were fabricated from a pressable lithium disilicate glass-ceramic and adhesively cemented (Rely X U200). Then, the specimens were subjected to a compressive load at a crosshead speed of 0.5 mm/min until fracture. The fractured specimens were analyzed to determine the fracture pattern using a stereomicroscope. SPSS 15.0 software package was used to analyse the data. RESULTS: G3（1570.7±108.7） had higher failure load than G1(1214.6±95.8) and G2(1285.9±87.6)(P<0.05). G1 was similar to G2.The crown was lost in G1 and G2. There was a fracture of the crown and tooth in G3. CONCLUSIONS: CAD/CAM all-ceramic crown with fiberglass posts might be an effective method for restoration of endodontically treated premolars with MOF cavity defect.

[Effect of ball attachments with different materials on retention of mandibular implant supported overdenture].

PURPOSE: To investigate the effect of ball attachments with different materials on retention of mandibular implant supported overdenture. METHODS: The experimental groups were divided into group A (titanium ball / titanium cap group) and group B (titanium ball / golden cap group), each group had 3 samples. A standard mandibular edentulous model was made, and the implants (4.8*10 RN SP) were embedded in the bilateral canine region. Mandibular complete dentures were made routinely and the attachments were attached. Five thousand times of insertion-separation cycles were carried out. After 200 times of cycles, the retention force was tested. The difference between 2 groups was compared by using SPSS 13.0 software package. The change of positive structure surface morphology was observed under scanning electron microscope at the beginning and the end of the experiment. RESULTS: The retention force of group A decreased from （27.00±0.16） N to （4.18±0.03） N, and the retention force of group B decreased from （21.58±0.06） N to （19.15±0.06）N. Decay of retention of group A was significantly greater than that of group B. At the end of the experiment, the globular structure of group A was severely broken, while a smooth and clear spherical structure was displayed in group B. CONCLUSIONS: The retention of mandibular implant supported overdenture decreases with the increase of insertion-separation times. The decay of retention force is related to destruction of positive structure surface. The fatigue resistance of the precious metal material is better.

Magnesium ion implantation on a micro/nanostructured titanium surface promotes its bioactivity and osteogenic differentiation function.

As one of the important ions associated with bone osseointegration, magnesium was incorporated into a micro/nanostructured titanium surface using a magnesium plasma immersion ion-implantation method. Hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 30 minutes (Mg30) and hierarchical hybrid micro/nanostructured titanium surfaces followed by magnesium ion implantation for 60 minutes (Mg60) were used as test groups. The surface morphology, chemical properties, and amount of magnesium ions released were evaluated by field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, field-emission transmission electron microscopy, and inductively coupled plasma-optical emission spectrometry. Rat bone marrow mesenchymal stem cells (rBMMSCs) were used to evaluate cell responses, including proliferation, spreading, and osteogenic differentiation on the surface of the material or in their medium extraction. Greater increases in the spreading and proliferation ability of rBMMSCs were observed on the surfaces of magnesium-implanted micro/nanostructures compared with the control plates. Furthermore, the osteocalcin (OCN), osteopontin (OPN), and alkaline phosphatase (ALP) genes were upregulated on both surfaces and in their medium extractions. The enhanced cell responses were correlated with increasing concentrations of magnesium ions, indicating that the osteoblastic differentiation of rBMMSCs was stimulated through the magnesium ion function. The magnesium ion-implanted micro/nanostructured titanium surfaces could enhance the proliferation, spreading, and osteogenic differentiation activity of rBMMSCs, suggesting they have potential application in improving bone-titanium integration.

[Comparison of the antibacterial activity on oral pathogens among six types of nano-silver base inorganic antibacterial agents].

OBJECTIVE: To Compare the antibacterial activity on oral pathogens among six types of nano-silver base inorganic antibacterial agents. METHODS: The oral pathogens selected were Streptococcus mutans(ATCC6715),Lactobacillus (ATCC4356),Actinomyces viscosus (ATCC19246), Candida Albicans (ATCC76615), Staphylococcus aureus (ATCC25923), Escherichia coli (ATCCC25922). Minimal bactericidal concentration (MBC) was determined by Liquid dilution method. RESULTS: Nano-silver base inorganic antibacterial agents had fine bactericidal activity against oral pathogens. The general antibacterial activity of six types were nearly equal. CONCLUSION: It is possible that nano-silver base inorganic antibacterial agents can be used in dental antibacterial materials.

[The influence of cerebral blood flow of volunteers with magnetic attachment measured by transcranial Doppler].

PURPOSE: To investigate the influence of cerebral blood flow of volunteers with magnetic attachment. METHOD: The mean flow velocity of the middle cerebral arteries (MCA) of 24 volunteers with magnetic attachment denture were measured by transcranial Doppler (TCD). All data were analyzed by SPSS10.0. RESULTS: The results showed the mean flow velocity of MCA of 24 volunteers with magnetic attachment was not significantly different from those without magnetic attachment (P>0.05). CONCLUSION: The magnetic attachment had little effect on cerebral blood flow.