New nano-sized Al2O3-BN coating 3Y-TZP ceramic composites for CAD/CAM-produced all-ceramic dental restorations. Part I. Fabrication of powders.

Partially sintered 3 mol % yttria-stabilized tetragonal zirconium dioxide (ZrO(2), zirconia) polycrystal (3Y-TZP) ceramics are used in dental posterior restorations with computer-aided design-computer-aided manufacturing (CAD/CAM) techniques. High strength is acquired after sintering, but shape distortion of preshaped compacts during their sintering is inevitable. The aim of this study is to fabricate new machinable ceramic composites with strong mechanical properties that are fit for all-ceramic dental restorations. Aluminum oxide (Al(2)O(3))-coated 3Y-TZP powders were first prepared by the heterogeneous precipitation method starting with 3Y-TZP, Al(NO(3))(3) . 9H(2)O, and ammonia, then amorphous boron nitride (BN) was produced and the as-received composite powders were coated via in situ reaction with boric acid and urea. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to analyze the status of Al(2)O(3)-BN on the surface of the 3Y-TZP particles. TEM micrographs show an abundance of Al(2)O(3) particles and amorphous BN appearing uniformly on the surface of the 3Y-TZP particles after the coating process. The size of the Al(2)O(3) particles is about 20 nm. The XRD pattern shows clearly the peak of amorphous BN among the peaks of ZrO(2).

[Summary of 61 cases of removable denture restoration in children with congenital tooth deficiency].

PURPOSE: To explore the methods and characteristics of removable denture restoration in children with congenital missing teeth. METHODS: From 1998 to 2018, 61 children aging 3 to 12 years old with congenital dental deficiency were treated with removable dentures. There were 59 males and 2 females. Removable denture prostheses were designed according to the characteristics of the children and the residual teeth in the mouth. There were 42 complete dentures in 21 cases, 40 single jaw complete dentures and maxillary removable partial dentures in 20 cases and 40 removable partial dentures in upper and lower jaw, totally 61 cases and 122 dentures. RESULTS: After wearing the removable denture, the appearance, chewing and pronunciation of the children were improved significantly. CONCLUSIONS: Although the etiology of congenital tooth defect is not completely clear, children can have early denture restoration. It solves the difficulty of eating, improves appearance and pronunciation, and promotes growth and physical and mental health of children.

[Research on physical and mechanical properties, crown accuracy by using self- made FUS-invest dental investment].

PURPOSE: To evaluate the physical and mechanical properties of pure titanium castings cast by self- made FUS-invest dental investment, and evaluate casting accuracy. METHODS: Seven pure titanium castings were cast by self-made FUS-invest zirconium investment and analyzed using servo hydraulic dynamic experiment system (JJG139-83 standard), scanning electron microscope and energy spectrum analysis. Thirty-eight crowns of pure titanium were cast by two different methods. One cast by FUS-invest zirconium embedding material was used for experiment and the other cast by phosphate embedding material was used as control. Casting accuracy was assessed through measuring the difference value d at the marginal marker points and distance between casting pieces of wall and working modes of casting were examined under microscope. Scanning electron microscope with energy-dispersive spectrum (EDS) was used to analyze the status of composition of the casting surface. SPSS 17.0 software package was used to investigate the difference of two groups. RESULTS: ①Qualitative analysis of servo hydraulic dynamic experiment system showed various mechanical properties: elastic modulus (123.5±14.2) GPa, yield strength (569.3±16.5) MPa, tensile strength (668.4±16.1) MPa, elongation (4.5±0.2)%. EDS analysis of the fracture was observed at different depth (13, 25, 50, 350 µm) under the surface of pollution layer, a little Si and Fe with different atomic percentage was found but no Zr. ②No significant difference (P>0.05) was found between each group of four markers on the marginal fit, and internal fit, whereas significant difference (P<0.01) was found at different marker point. CONCLUSIONS: The mechanical properties of commercially pure titanium casting by self-made FUS-invest zirconium-based investment can meet the qualification of dental metal materials, although elongation was a little lower. Both the marginal adaptation and internal fit between the two groups had no significant difference. The mean marginal difference was 46 µm, the mean internal difference at axial angle was 56 µm and approximately 0 at axial wall.

[Common errors and mistakes seen in Chinese prosthodontic articles].

As an editor of dental journals, the author found that some inappropriate writing and mistakes existed in many articles, which reduced the quality of the published papers. The problems can be divided into three categories: irregular terminology; not concise, inaccurate description; improper use of punctuation and title code. They were illustrated respectively in this article for readers to avoid these mistakes in the future.

[Corrosion resistance of casted titanium by compound treatments in the artificial saliva with different fluoride concentrations].

OBJECTIVE: To study the corrosion resistance of casted titanium by plasma nitriding and TiN-coated compound treatments in the artificial saliva with different fluoride concentrations and to investigate whether compound treatments can increase the corrosion resistance of casted titanium. METHODS: Potentiodynamic polarization technique was used to depict polarization curve and to measured the current density of corrosion (Icorr) and the electric potential of corrosion (Ecorr) of casted titanium (Group A) and casted titanium by compound treatments (Group B) in the artificial saliva with different fluoride concentrations. After electrochemical experiment, the microstructure was observed by scanning electron microscope (SEM). RESULTS: The Icorrs of Group A and B in the artificial saliva of different fluoride concentrations were (1530.23 ± 340.12), (2290.36 ± 320.10), (4130.52 ± 230.17) nA and (2.62 ± 0.64), (7.37 ± 3.59), (10.76 ± 6.05) nA, respectively. The Ecorrs were (-0.93 ± 0.10), (-0.89 ± 0.21), (-0.57 ± 0.09) V and (-0.21 ± 0.04), (-0.17 ± 0.03), (-0.22 ± 0.03) V, respectively.The Icorrs of Group B were significantly lower (P < 0.01)than that of Group A. The Icorrs increased significantly with the increasing of fluoride concentrations (P < 0.01). The Ecorrs of Group B were significantly higher than that of Group A (P < 0.01). The SEM confirmed the microstructure in the casted titanium was much severely than that in Group B, the microstructure in Group A and B corroded more and more heavily with increasing of fluoride concentrations. CONCLUSIONS: The increase of fluoride concentrations influence the corrosion resistance of both treated and untreated casted titanium negatively, but plasma nitriding and TiN-coated compound treatments can significantly increase the corrosion resistance of casted titanium.

[Experimental study on the bonding strength between FCVA film and titanium].

PURPOSE: To study the bonding strength between the FCVA (filtered cathode vacuum arc) film and the titanium substrate. METHODS: According to the Engineer Manual of Germany (VDI3198), the indentation test was applied to evaluate the bonding strength between the FCVA film and the titanium substrate. The structure of the FCVA film and the interface between the film and the substrate were observed by means of scanning electron microscope(SEM). RESULTS: The fracture pattern of the film was classified as HF3 at the load of 400N, the bonding strength was enough between the FCVA film and the titanium substrate. SEM photograph showed the thickness of the FCVA film was about 1.2µm equably and the film bonded to the substrate well. CONCLSION: The bonding strength between the FCVA film and the titanium substrate was enough to meet clinical demand.

[Effect of investment composition ratio for pure titanium crown and bridge on some mechanical properties of mould].

OBJECTIVE: To determine the optimal composition of a self-developing investment material by measuring physical and mechanical properties of mould. METHODS: L(9) (3(4)) orthogonal design was adopted. One hundred and fifty specimens with the size of 80 mm × 20 mm × 20 mm were prepared to measure the atmospheric temperature bending strength, high temperature bending strength and residual bending strength. Nine specimens with the size of 5 mm diameter 25 mm heigh were prepared to survey the thermal expansion curve from ambient temperature to 1150°C. RESULTS: Strengths were greatly affected by fine powder proportion in refractory and water/powder ratio. When the content of fine powder was 35% and water/powder ratio was 1:7.5, adequate atmospheric temperature strength and high temperature strength could be achieved. Moreover, the residual strength was moderate. The thermal extension curves of specimens in experiment group were almost similar. And the average linear expansion coefficient was (4 ∼ 5) × 10(-6)/°C. CONCLUSIONS: The three kinds of bending strength of self-developing investment material are compared with commercialized investment material for titanium casting when water/powder ratio and the content of fine powder are carefully controlled.

[Research progress on the treatment of obstructive sleep apnea and hypopnea syndrome with mandibular advancement device].

Obstructive sleep apnea and hypopnea syndrome (OSAHS) is characterized by obstruction of upper airway and respiratory disturbance, excessive daytime sleepiness and tiredness.The possible causes are obesity, hypertension, and upper airway malformations,etc. The location and degree of upper airway structure narrowing in patients have been investigated in many ways, such as X-ray, multi-slices spiral computed tomography, etc. With multi-planar reconstruction technique,3-dimensional construction of upper airway can be established which shows the delicate changes of the upper airway structure. Mandibular advancement device is known as an effective treatment on mild and moderate OSAHS. By advancing the mandible forward, it can increase the space of upper airway, especially the oropharyngeal space. This paper reviewed the methods of investigating on OSAHS and the change of upper airway structure in OSAHS patients treated with mandibular advancement device. Supported by Combined Research Fund of Bureau of Health, Yunan Province and Kunming Medical College(Grant No.2009CD205).

[Effect of investment for titanium crown and bridge on reactive layer of castings].

OBJECTIVE: To investigate the effect of self-developing investment (FUS-invest) on the reactive layer of titanium castings. METHODS: Three 10 mm x 10 mm x 1 mm pure titanium castings were founded using FUS-invest. Metallographical structure of reactive layer was observed. X-ray diffraction (XRD) and scanning electron microscope with energy-dispersive spectrum (EDS) were used to analyze the status of composition of the casting surface. Micro-Vickers hardness was measured. RESULTS: The metallograph indicated that the reactive layer was composed of coarse flake-shaped alpha phase of grains. The value of micro-Vickers hardness with the range 243 to 314 MPa had not significantly difference under the depth of 105 microm beneath the surface. The XRD pattern clearly showed the peaks of ZrO2, SiO2, Mg2TiO4 and TiO2. EDS analysis demonstrated that the main elements were Al, Si, Zr and Cl. CONCLUSION: FUS-invest is suited for pure titanium casting because of the thin reactive layer and less change to metallographical structure.

[Clinical evaluation of bovine colostrum containing oral hyaloplasmic gel on satisfaction of complete denture in xerostomia patients].

PURPOSE: The purpose of this study is to investigate the effect of bovine colostrum-containing gel on the satisfaction of wearing complete denture in xerostomia patients. METHODS: 23 edentulous patients with xerostomia and complete denture were employed to assess the differences of satisfaction after the gel was used in their dry oral cavity one week,one month and three months by using satisfaction questionnaire. The statistical analysis was carried out with SPSS11.0 software package. RESULTS: Three months after the use of gel, the satisfaction of complete denture was statistically improved in respects of general satisfaction, speech, retention of mandible denture, comfort and mastication improved than that before treatment (P<0.05). There was no significant difference about retention of maxillary denture (P>0.05). CONCLUSION: Bovine colostrum-containing gel can be used to improve the satisfaction of xerostomia patients treated with complete denture. After 3 months of treatment, the xerostomia is alleviated in most patients.

[Study of the bonding strength of pure titanium and light-cured hard crown and bridge composite after filming by TiSiN].

OBJECTIVE: To evaluated the bonding strength between pure titanium and Solidex after deposition by magnetron sputtering TiSiN with different content of Si (9%, 19%) and analyzed the surface component by electron probe micro-analysis (EPMA). METHODS: All pure titanium samples divided into 3 groups according to different surface treatment, then bonded with Solidex light-cured composite. Material test machine was used to measure bonding strength and the surface was analyzed by EPMA. RESULTS: The bonding strength of deposition with TiSiN groups were higher than unfilming group, increasing the content of Si could enhance the bonding strength between pure titanium and Solidex in TiSiN groups (P < 0.05). EPMA showed amorphous materials like TiN, SiN gathered on the surface in TiSiN groups. There were obvious interspaces between unfilming pure titanium and Solidex, contrary no interspaces was observed in TiSiN groups. CONCLUSION: The bonding strength of filming groups was higher than unfilming group, amorphous material like TiN, SiN gathering on the surface may prevent the microleakage and stop metal ion leaking.

[Effects of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge on the reaction layer].

OBJECTIVE: To investigate the effects of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge on the reaction layer. METHODS: 10 mm x 10 mm x 1 mm titanium castings were invested. Spectrum analysis was done to its reaction layer, the metallographic examination was observed and Vickers hardness was measured. RESULTS: The reaction layer was not obvious by the metallographic examination. The layer with plenty of Si was hardly detectable. The needle crystal layer diffused distribution on the surface of the titanium matrix. The depth was about 55 microm. Spectrum analysis showed that the contents of Si and Zr decreased as the depth increased. The microhardness, which obviously decreased from the surface to the matrix, tended to be equal with the hardness of the matrix after the depth reached 75 microm from the surface. CONCLUSION: The thickness of the reaction layer of the improved FUS-invest investment for zirconium-oxide titanium crown and bridge was decreased to 55 microm from 85 microm, which was the thickness before improvement.

[Study of TiN plating coat on increasing shear bond strength].

PURPOSE: To investigate the feasibility of increasing bond strength of polymer ceramic to titanium using TiN coating. METHODS: Twelve pure titanium specimens were casted and divided into two groups randomly. In one group,the surface was processed with conventional handling,in the other group,the surface was coated with TiN. Then the specimens in each group was bonded with polymer ceramic material (Ceramage). The shear bond strength was measured using parallel interface shearing. The interface between polymer ceramic and titanium was observed under SEM. Two samples t test was conducted with SPSS11.0 software package. RESULTS: The shear bond strength of TiN plating coat group was (29.78+/-0.78)MPa, larger than that of the conventional handling group (25.73+/-0.37)MPa, the difference was significant (P<0.01) between the two groups, and both of them exceeded ISO9693:1999(P<0.01). CONCLUSION: TiN plating coat can effectively improve the shear bond strength.

[Exploration and classification in the amount of die stone of working cast model of denture restoration].

PURPOSE: The objective of this study was to survey the amount of working cast model of denture restoration, and to calculate the amount of die stone powder of each working cast model, then to classify the working cast model, with the expectation to perfuse the working cast model in clinic according to this classification, and to achieve the goal of increasing quality of working cast model and saving materials. METHODS: 311 working cast models were selected to perfuse with three kinds of tray including small size, middle size and large size randomly in clinic. The amount of die stone powder of working cast model was calculated, and the data were analyzed using SPSS 13.0 software package. The mean values of the die stone powder was used to establish a classification, which was verified clinically. RESULTS: The results showed that the working cast model of denture restoration could be divided into three kinds: small group (< or = 45 g), middle group (46-55 g) and large group (56-65 g). The samples for verification were all in the size of this classification of the amount of die stone powder. CONCLUSIONS: There is a close relationship between the amount of die stone powder of working cast model and the size of the tray, the dental arch. By clinical application of the classification, quantitative control of standard water powder ratio, improvement of model qualities and saving of materials can be achieved.

[Cr-Ti-Al-N complex coating on titanium to strengthen Ti/porcelain bonding].

OBJECTIVE: To study the feasibility of magnetron sputtering Cr-Ti-Al-N complex coating as an interlayer on titanium to enhance the titanium-ceramic binding strength. METHODS: With a three-point bending test according to ISO 9693, the binding strength of Duceratin (Degussa) to titanium substrate prepared with 4 different surface treatments (polishing, polishing and megnetron sputtering Cr, Ti, Al, and N complex coating, sandblasting, sandblasting and coating) was evaluated. Ti/porcelain interface and fractured Ti surface were examined using scanning electron microscopy with energy-dispersive spectrometry (EDS). RESULTS: The binding strength of polished and coated titanium/Duceratin was significantly higher than polished titanium group (P<0.05). The binding strength of sandblasted and coated titanium/Duceratin did not differ significantly from that of sandblasted titanium group (P>0.05), and the strength in the two sandblasted titanium groups was significantly higher than that in polished and coated titanium group (P<0.05). CONCLUSION: Megnetron sputtering Cr-Ti-Al-N complex on polished titanium can increase the titanium/porcelain binding strength. Megnetron sputtering coating is a promising Ti/porcelain interlayer.

[A study of mandible chewing movement in patients with developmental lateral jaw deformity].

OBJECTIVE: The purpose of the present study was to investigate effects of developmental lateral jaw deformity (DLJD) on masticatory movement. METHODS: Three coordinates of mandibular movement signals were recorded in 35 young healthy adults with normal occlusion and 28 patients with DLJD by means of a Sirognathography System during gum chewing movement. Paired and unpaired t-tests were used to compare significant difference of intra-group and inter-groups in displacement and speed. P < 0.05 was chosen as significance level. RESULTS: (1) The rhythm and directional sequence of chewing trajectory in both frontal and sagittal planes were normal in control group, while anomalies of rhythm and distribution (n = 9) and reversed sequencing (n = 7) were found in DLJD group. (2) The maximum magnitude of jaw retrusion and average speed were significant higher in DLJD group than those in control group (P < 0.01). The spatial displacement and average speed in horizontal plane and in chewing phase were also higher in DLJD group compared with control group (P < 0.05). CONCLUSIONS: DLJD patients showed anomalies in chewing pattern as well as chewing speed and displacement in horizontal plane.

[The effect of casting techniques on the accuracy of titanium crown and bridge].

OBJECTIVE: To investigate the method of enhancing the accuracy of titanium crowns by improving the casting method. METHODS: A self-assembled die was used to fabricate 48 standardized wax crowns. The dies were averagely divided into two groups. 21 crowns were successfully fabricated from one group according to the improved techniques. 18 crowns were fabricated by traditional method. A reference mark was scribed 90 degrees apart at four sites on the margin of each wax pattern and respective die. The distance between the margins of the wax pattern and the die was measured under a stereomicroscope. Similar method was also applied to measure the margin of castings. The castings were longitudinally split through midline. The distance between the 4 points(B',C',D',E') selected in the inner part of the crown and the die was respectively examined. RESULTS: Castings acquired by the improved method were more complete and had smoother surface. Marginal discrepancy value had significant difference between the two groups. Value in experimental group was smaller. Distance from B',E' to die between the two groups had no significant difference, but the distance from C',D' to the die was significantly different. The experimental group was smaller. CONCLUSION: Standardized crowns fabricated by the improved titanium casting technique were more accurate, but special investment for titanium crowns and bridges should be developed to compensate the casting shrinkage of metal.

[Effect of mold temperature on mechanical properties of Ti-Zr alloy castings].

OBJECTIVE: To investigate the influence of mold temperature on the mechanical properties of Ti-Zr alloy castings. METHODS: Ti-Zr alloy was cast into a mold which was made of a zircon (ZrO2.SiO2) investment with a casting machine (China) designed as vacuum, pressure and centrifuge. At three mold temperatures (room temperature, 300 degrees C, 600 degrees C) the Ti-Zr alloy was cast separately. The ultimate tensile strength (sigmab), 0.2% offset yield point strength (sigma0.2), and elongation to fracture (delta) were determined by a universal testing machine with 15 mm pre-marked gauge interval. The surface micro-structures of Ti-Zr alloy castings at three mold temperatures were observed by optical microscope. RESULTS: At a higher mold temperature during casting, the tensile strength and yield strength of Ti-Zr alloy were significantly increased, while the elongations were significantly decreased. The micro-structure of the surface was different from the inner part. There was a reacted layer in the outermost surface. The thickness of reacted layers at the three mold temperatures was about 35.5 man (room temperature), 55.0 microm (300 degrees C) and 65.5 microm (600 degrees C), respectively. The inner part of microstructure composed of main a phases within the prior alpha grain boundaries. CONCLUSION: The mold temperature is one of the major factors influencing Ti-Zr alloy mechanical properties. Comparing with Ti6Al4V alloy and Co-Cr alloy castings, Ti-Zr alloy is more suitable for denture frame.

[The bonding characteristic of titanium and RG experiment porcelain].

OBJECTIVE: To study the bonding characteristic of Titanium and RG experiment porcelain. METHODS: 5 specimens with a size of 10 mm x 5 mm x 1.4 mm were cast from pure titanium. Then 1 mm of RG experiment opaque and body porcelain were fused on the surface of the titanium specimens. The interface of titanium and porcelain was analyzed with a scanning electron microscope with energy-despersive spectrometry; 6 metal specimens with the size of 25 mm x 3 mm x 0.5 mm were cast from Ni-Cr alloy and a uniform thickness of 1 mm of VMK 99 porcelain was veneered on the central area of 8 mm x 3 mm 18 metal specimens as the same size were cast from pure titanium. The uniform thickness of 1 mm of VITA TITANKERAMIK porcelain, of Noritake super porcelain Ti-22 and of RG experiment porcelain were veneered on every 6 specimens respectively in the central area of 8 mm x 3 mm. The specimens were subjected to a three-point bending test on a load-test machine with a span of 20 mm, then the failure loads were recorded and statistically analysised. The RG porcelain/titanium crown was fabricated by fusing RG opaque porcelain and body porcelain to cast titanium substrate crown. RESULTS: The SEM results show no porosity and crackle were found in the interface. The energy-dispersive spectrometry show that there are Si, Ti and O in the 1 micro m layer between porcelain and titanium, which suggesting titanium and experiment porcelain bonding well. The three point test showed the fracture force for the combinations of titanium/VITA TITANKERAMIK porcelain, titanium/Noritake super porcelain Ti-22 and titanium/RG experiment porcelain were (7.233 +/- 2.539) N, (5.533 +/- 1.199) N and (6.316 +/- 1.433) N respectively. There were not statistically significant differences among them (t test, P < 0.01). The fracture force for the Ni-Cr alloy/VMK99 porcelain combination (12.733 +/- 3.297) N was significantly greater than those of the cast titanium/porcelain (t test, P > 0.05). The crown was translucent with no crack. CONCLUSION: RG porcelain is well compatible with titanium.