The study of the colorimetric characteristics of the cobalt-chrome alloys abutments covered by four different all-ceramic crowns by using dental spectrophotometer / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aims to evaluate the optical data of the different sites of the cobalt-chrome (Co-Cr) alloy abutments covered by four different all-ceramic crowns and the color difference between the crowns and target tab using a digital dental spectrophotometer.</p><p><b>METHODS</b>Ten Co-Cr alloy abutments were made and tried in four different groups of all-ceramic crowns, namely, Procera aluminia, Procera zirconia, Lava zirconia (Lava-Zir), and IPS E.max glass-ceramic lithium disilicate-reinforced monolithic. The color data of the cervical, body, and incisal sites of the samples were recorded and analyzed by dental spectrophotometer. The CIE L*, a*, b* values were again measured after veneering. The color difference between the abutments covered by all-ceramic crowns and A2 dentine shade tab was evaluated.</p><p><b>RESULTS</b>The L* and b* values of the abutments can be increased by all of the four groups of all-ceramic copings, but a* values were decreased in most groups. A statistical difference was observed among four groups. After being veneered, the L* values of all the copings declined slightly, and the values of a*, b* increased significantly. When compared with A2 dentine shade tab, the ΔE of the crowns was below 4.</p><p><b>CONCLUSION</b>Four ceramic copings were demonstrated to promote the lightness and hue of the alloy abutments effecttively. Though the colorimetric baseline of these copings was uneven, veneer porcelain can efficiently decrease the color difference between the samples and thee target.</p>

A study of the osteoblasts adhesion, growth and proliferation on the surface of pure titanium immobilized by RGD peptide / 实用口腔医学杂志

Objective: To evaluate the effect of pure titanium modified by bioadhesive RGD peptide on the early attachment, growth and proliferation of osteoblasts. Methods: The titanium samples were hydroxylated by alkali/hot water aging and sol-gel layer-by-layer deposition technique. Afterwards, the terminal -NH_2 group was introduced to the titanium surface by organosilane APTMS self-assembled monolayers and the functional group -NH_2 was further reacted with EDC/NHS by which RGD peptides was covalently immobilized to titanium. The efficiency of this bioreactive surface in promoting cell attachment and the competitive inhibition effect of RGD peptide with different concentrations were observed by calculating the amount of osteoblasts attached on the modified titanium. The growth and proliferation were observed by MTT method and scanning electronic microscopy. Results: The cell adhesion percentage of the RGD modified titanium group was much higher than that of the other groups. The RGD peptide solutions with higher concentration had stronger inhibitory impact on the cell adhesion onto the titanium surface. The cell growth, morphology and proliferation on the RGD peptide modified titanium were better than other groups. Conclusion: Bioadhesive peptide can be chemically grafted onto the titanium surface by means of self-assembled monolayers technique. The cells′ biological behaviors on the surface of RGD immobilized titanium are greatly improved in vitro.

A static magnetic field loading system for in vitro cultured cells / 生物医学工程学杂志

Magnetic attachments have flux leakages, thus they will exert certain magnetic fields on the adjacent tissues when used in the patients' oral cavities. There are few research reports on the biological effects of the magnetic fields generated by magnetic attachments on human body. A cellular static magnetic field (SMF) loading system was developed in this study. By using this system, in vitro cultured human periodontal ligament cells (HPDLCs) were loaded with SMF simulating those of magnetic attachments. The cellular SMF loading system could produce constant SMF and the strength of the SMF is adjustable. The system is small and is able to exert SMF to cells cultured in different culture vessels such as culture dishes and culture plates, thus is suitable to researches in multiple biological items of cells. The results of the SMF loading experiment on HPDLCs showed that this cellular SMF loading system could effectively load cells with SMF of different strengths for different time in vitro. The development of this system has provided a useful tool for the researches on the cellular hiologioal effects of SMF.

Reproducibility of centric relation of the patient with severe dental attrition for oral rehabilitation / 华西口腔医学杂志

<p><b>OBJECTIVE</b>Standards for determining mandibular position, especially the centric relation (CR), are in controversy because of anatomical, neurophysiological factors and research methods or instrument. The purpose of this study was to reevaluate the reproducibility of centric relation of the patients with severe dental attrition for oral rehabilitation.</p><p><b>METHODS</b>Reproducibility of the centric relation of 6 patients with severe occlusal attrition was investigated by using D5A Denar fully adjustable articulator and the Pantronic recording system.</p><p><b>RESULTS</b>1. In supine position, anterior-posterior(AP) displacement of centric relation (CR) was 0.14 mm and superior-inferior(SI) displacements of CR were between 0.11 mm-0.12 mm. 2. In upright position, anterior-posterior displacement of CR was 0.35 mm and superior-inferior changes of CR were between 0.13 mm-0.20 mm.</p><p><b>CONCLUSION</b>The CR is the most stable and reproducible position of mandibule in normal stomatological system and is useful as a reference position in occlusal treatment and functional rehabilitation.</p>

The measurement of retentive forces in mandibular complete overdenture with Magfit magnetic attachments / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the in vivo retentive forces of mandibular complete overdenture with Magfit attachments, as well as the relation between the location of magnetic attachments and the retentive forces of the denture.</p><p><b>METHODS</b>5 patients were selected and treated with mandibular complete overdentures retained by Magfit EX600 and MD800 attachments. A strainometer was used to measure the retentive forces in anterior, central and posterior parts of the overdenture before and after magnets were set. The vertical and anterior-upper 60 degrees retentive forces of the overdenture were measured one month later.</p><p><b>RESULTS</b>The retentive forces of the overdentures after setting magnets were significantly greater than that before magnets were set (P < 0.05). There was no significant difference in retentive forces between the different parts (P > 0.05). The retentive force in vertical direction was greater than that in anterior-upper 60 degrees direction (P < 0.025).</p><p><b>CONCLUSION</b>Magnetic attachments can significantly improve the retention of mandibular complete overdenture. The location of magnetic attachments greatly influences the retentive force of the overdenture.</p>

Relationship between maxillofacial complexion and age-sex in Han nationality / 中华医学美学美容杂志

Objective To explore the relationship between the maxi ll ofacial complexion and age-sex in Han nationality. Methods The maxillofacial skin chroma L*, a* and b* were measured a nd compared in 1462 people aged from 18 to 85 years old in Han nationality, incl uding 682 men and 780 women, by means of Minolta Chroma Meter CR-100. Results Male had the lower L* and b* value and the hig her a* value than those in female. The maxillofacial chroma L* and a* were related to age negatively, and b* was related to age positiv ely. Conclusion The effect of sex and age on color of the maxillofacial skin should be considered while matching colors in construction o f maxillofacial defect.

Interface bond and compatibility between GI-II glass/alumina composite and Vitadur alpha veneering porcelain / 中华口腔医学杂志

<p><b>OBJECTIVE</b>Multiple layer techniques were commonly employed in fabricating all-ceramic restorations. Bond and compatibility between layers were vitally important for the clinical success of the restorations. The purposes of this study were to investigate the bond of the interface between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and to study the thermal compatibility between them.</p><p><b>METHODS</b>Prepared a bar shaped specimen of GI-II glass/alumina composite 25 mm x 5 mm x 1 mm in size, with bottom surface pre-notched. The upper surface was veneered with Vitadur alpha veneering porcelain (0.2 mm opaque dentin and 0.6 mm dentin porcelain), then fractured and the fracture surface were examined under scanning electron microscope (SEM) and electron microprobe analyzer (EMPA) with electron beam of 10 micrometer in diameter; ten all-ceramic single crowns for an upper right central incisor were fabricated and the temperatures of thermal shock resistance were tested.</p><p><b>RESULTS</b>SEM observation showed tight bond between the composite and the porcelain; The results of EMPA showed that penetration of Na, Al elements from glass/alumina into veneering porcelain and Si, K, Ca elements from veneering porcelain into glass/alumina occurred after sintering baking; The temperature of thermal shock resistance for anterior crowns in this study was 158 +/- 10.3 degrees C, cracks were mainly distributed in veneering porcelain with thicker layer.</p><p><b>CONCLUSIONS</b>Chemical bond exists between the GI-II glass/alumina composite and Vitadur alpha veneering porcelain, and there is good thermal compatibility between them.</p>

Development of GI-II tinted infiltration glass and determination of its properties / 华西口腔医学杂志

<p><b>OBJECTIVE</b>Glass is the weak phase in the glass-alumina composite, and it plays a key role in determining the physical, mechanical and optical properties. The purpose of this study was to explore the fabrication arts of GI-II tinted infiltration glass and determine its properties.</p><p><b>METHODS</b>The thermal properties of the glass were tested on a TMA2940 thermal analyzer with heating rate of 5 degrees C/min and temperature range of 25-750 degrees C. The bar-shaped specimens were prepared with the size of 25 mm x 5 mm x 2 mm and their flexural strengths and elastic modulus with 3-point bending test were measured. The Vicker's hardness and indentation fracture toughness were also determined. The refractive index and changes of chemical constituents were tested by means of V prismatic refractometer and 2910 DTA analyzer.</p><p><b>RESULTS</b>The results showed that the thermal expansion coefficient, Tg and Tf, refractive index, 3-point bending flexural strength, bending elastic modulus, Vicker's hardness, indentation fracture toughness and density were 6.997 x 10(-6) degrees C-1 (25-500 degrees C), 635 degrees C and 650 degrees C, 1.64 MPa, 96.27 MPa, 31.16 GPa, 5.534 GPa, 1.05 MN.m1/2, and 3.214 g/cm3 respectively. Though certain heat processing conditions did result in micro-crystalline in the glass, it remained stable under routine glass infiltration firing cycles.</p><p><b>CONCLUSION</b>GI-II tinted infiltration glass had favorable physical, mechanical properties and good thermal stability.</p>

Preparation of nanometer powders of dental alumina ceramics / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to explore the preparation method of nanometer powders of dental alumina ceramics.</p><p><b>METHODS</b>The effects of concentration of inorganic precursors, pH value, calcination temperature and ageing time on the synthesizing process, phase composition and microstructure of the materials were studied. Aluminium nitrate with concentrations of 0.03 mol/L, 0.05 mol/L, 0.1 mol/L and 0.2 mol/L were used as inorganic precursors to prepare alumina powders via sol-gel method. Ammonia water was added into the solutions to adjust the pH values to 5, 9 and 11. The dried gel was then calcined under different temperatures, from 950 degrees C to 1200 degrees C. The prepared alumina powders were studied by using X-ray diffraction (XRD), and scanning electron microscope (SEM).</p><p><b>RESULTS</b>The alumina powder which was prepared with 0.1 mol/L aluminium nitrate, pH 9, and calcined at 1200 degrees C for 10 min showed good physical characteristics. The diameter of final powder was about 70 nm.</p><p><b>CONCLUSION</b>With the proper preparation condition, weakly agglomerated powders of alumina in nanometer particle size could be obtained.</p>

A study of alumina powder used in fabrication of GI-II infiltrated ceramic / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This investigation was to analyze the mechanism of formation of porous structure by studying some characteristics of the alumina powder used for GI-II Infiltrate Ceramic.</p><p><b>METHODS</b>The alumina powder crystal type was analyzed with X-diffractometer, and its size distribution was obtained by powder size analysis device, and fracture surface of alumina adobe was observed under scanning electronic microscope.</p><p><b>RESULTS</b>Alumina crystals were purely alpha type, with firmest structure and best stability. Fine powder whose size was smaller than 0.5 micron occupied 9 wt% (mass) and, coarse powder with sizes between 1 to 3.5 microns occupied 75 wt% (mass). The SEM graphs of adobe showed that fine powders were attached to the surface of coarse powders, dispersed evenly, and alumina powders contacted each other firmly.</p><p><b>CONCLUSION</b>The crystal type, size distribution and even dispersion of the studied alumina powder contributed to the formation of porous structure of alumina sintered body (preform), which was the material prerequisite in forming porous preform and one of the key factors to the rise of strength of GI-II Infiltrated Ceramic.</p>

Properties of GI-II glass/alumina composite infiltrated with GI-II tinted infiltration glass / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to determine the thermal, mechanical properties and density of the composite infiltrated with GI-II tinted infiltration glass.</p><p><b>METHODS</b>The bar-shaped aluminum oxide and glass/alumina composite specimens with the size of 20 mm x 5 mm x 5 mm were prepared, with two free-end surfaces perpendicular to the long axis of the specimens and parallel to each other. The thermal expansion curves were obtained on a TMA2940 thermal analyzer with heating rate of 5 degrees C/min and temperature range of 25 degrees C to 1000 degrees C. The bar-shaped specimens with the size of 25 mm x 5 mm x 2 mm were fabricated and employed to test the density using Archmede's method. The flexural strength, elastic modulus were measured by means of 3-point bending test with the same specimens. The fractured specimens were indented with Vicker's diamond pyramid under load of 49 N for 15 seconds to determine the hardness and indentation fracture toughness.</p><p><b>RESULTS</b>The thermal expansion coefficient of the glass/alumina composite was 7.620 x 10(-6) degrees C-1 (25-500 degrees C), which was higher than that of Vitadur alpha veneering porcelain. The 3-poit flexural strength, elastic modulus, Vicker's hardness, indentation fracture toughness and density were 389.6 MPa, 92 GPa, 9.409 GPa, 3.2425 MNm-3/2 and 3.662 g/cm3 respectively.</p><p><b>CONCLUSION</b>The thermal expansion of the GI-II glass/alumina composite is compatible with that of Vitadur alpha veneering porcelain, and the material could meet the strength demands for clinical use.</p>

Spectral transmittance of GI-II glass/alumina composite / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purposes of this study were to determine the spectral transmittance of GI-II glass/alumina composites and to explore the effects of different specimen thickness and fining arts of glass infiltration on the transmittance. Data were compared with those of Vita In-Ceram Alumina materials.</p><p><b>METHODS</b>Plate-shaped specimens 12.5 mm in diameter, with 3 thickness (0.5, 1.0, 1.5 mm), 6 color groups for GI-II and 4 color groups for Vita In-Ceram Alumina were fabricated. Specimens of color AL2 for In-Ceram and IG2 for GI-II were selected in the study of relationship between different infiltration arts and transmittance. Five infiltration time duration and three temperatures were studied. A spectrophotometer with standard A light source paralleled light beam 5 mm in diameter and spectra range 380-780 nm was employed to measure the spectral transmittance.</p><p><b>RESULTS</b>The range of spectral transmittance were 2.7%-4.5% for GI-II and 2.4%-5.2% for Vita In-Ceram Alumina. Transmittance decreased with specimen thickness, but they were not linearly related. Transmittance of GI-II tended to increase and that of Vita In-Ceram Alumina decreased as the infiltration temperature elevated. The transmittance increased with infiltration time less than 4 hours and reduced with prolonged time over 6 hours for both materials.</p><p><b>CONCLUSION</b>GI-II glass/alumina composite has comparatively lower translucency. Influences of factors as color, thickness and infiltration arts on translucency of restorations should be considered in the clinical selection of the all-ceramic materials.</p>

Retentive force of modified RPI clasp / 实用口腔医学杂志

0.05).Conclusion: Modified RPI clasp with clinically acceptable retentive force and better cosmetic effcts is feasible for clinical application.

A study of mutagenic effects of simulating static magnetic field produced by magnetic attachment on human periodontal ligament fibroblasts / 实用口腔医学杂志

0.05).Conclusion:It suggests that HPDLFs exposured to static magnetic field produced by magnetic attachment have little mutagenic effects on chromosomes and DNA.

Condylar path of the patients with severe dental attrition / 实用口腔医学杂志

Objective:To study the characteristics of condylar path in the patients with severe dental attrition.Methods:Using D5A De nar fully adjustable articulator and the Pantronic recording system, the kinemat ic character of condylar paths of 15 patients with severe occlusal attrition was investigated. In addition, the effects of posterior condylar determinants on oc clusal rehabilitation were studied in 5 cases. Results: The mean intercondylar distance of the patients was (60.72?4.40) mm, and the immediate side shift (ISS) was 1.35 mm(right)and 1.24 mm(left),the progressive si de shift (PSS) were 14.65 degrees (right) and 17.11 degrees (left),respectively. The Pantronic protrusive condylar guidance (PRO) were 23.45 degrees (right) and 26.85 degrees (left); The Pantronic nonworking path (ORB) was 26.50 degrees and the Fisher angle was present between protrusive path and nonworking path. In th e 5 cases of occlusal rehabilitation ISS, PSS and Panotronic reproducibility ind ex (PRI) were decreased.Conclusion: Occlusal rehabilitation main ly affect ISS, PSS and PRI.

The influences of repeated firing cycle on the color of the glass/alumina composite -veneering porcelain structure / 实用口腔医学杂志

0.05). The maximum color differences ( ?E) in the selected firing cycles were 2.279 8 and 1.389 4 for GI Ⅱand Vita In Ceram Alumina groups respectively, the maximum ?E between the two groups was 2.295 6, which fell into the clinically acceptable threshold for color differences. Conclusion: Color stability of all ceramic restorations with GI Ⅱand Vita In Ceram Alumina as substructure can be guaranteed after repeated firing of veneering porcelain up to 10 times.

Preparation of nanometer powder of dental zirconia ceramics / 实用口腔医学杂志

?Objective: To study the preparation method of nanometer powder of zirconia, which was used to toughen dental alumina ceramics. Methods: The inorganic precursors at the concentrations of 0.0155 , 0.03, 0.05, 0.1 and 0.28 mol/L were used to prepare zirconia powder via precipitation method. Ammonia water was added into the said solutions to control the pH value at 7.0, 8.5 and 9. The dried precipitation product was then calcined. The prepared zirconia powder were studied by using X ray diffraction (XRD) and scanning electron microscope (SEM). Results: The zirconia powder prepared under the condition of 0.03 0.05 mol/L concentration of inorganic precursors, pH = 8.5, and calcined at 700 ℃ for 2 h was even in size,well dispersed and well micronized. The diameter of the final powder was about 100 nm. Conclusion: With proper preparation condition, weakly agglomerated powder of zirconia in nanometer size can be obtained.

Study of crown and framework fitness of DA9-4 alloys / 实用口腔医学杂志

0.05 ). And the fitness values(?m) of the crown of DA9-4 alloy were:the margin gap of the crown 71.3 ?8.34, the shoulder gap 53.4?4.83, the axial wall gap 41.85?8.08, the occlusal lift amount 55.2?9.21.Conclusion:DA9-4 alloy has good fitness and can meet the require of clinic.