[Research of implant accuracy using a digital registration method].

PURPOSE: The aim of this study was to introduce a new method to evaluate the clinical accuracy of implant position. The results were compared to traditional cone beam CT (CBCT) method. METHODS: A total of 36 implants from 24 patients with sufficient bone volume were enrolled into the study. CBCT method and digital registration method were compared to evaluate the accuracy of implant position. The measurement parameters were defined as deviations between ideal and postsurgical implant position at occlusal point(d1), apical point(d2) and axis(α). The deviations between two methods were analyzed with SPSS 19.0 software package. RESULTS: The deviations between ideal and postsurgical implant position using CBCT were (0.88±0.64) mm for occlusal point, (1.07±0.85) mm for apical point and (4.74±2.35)° for angle. In digital registration method, the deviations were (0.86±0.67) mm for occlusal point, (1.12±0.88) mm for apical point and (4.56±2.66)° for angle. No significant difference(P＞0.05) was found between the two methods. CONCLUSIONS: There was no significant difference between the two methods in evaluating the clinical accuracy of implant position. Digital registration method could be accepted in clinical application.

Design of FRM-Based Nonuniform Filter Bank With Reduced Effective Wordlength for Hearing Aids.

This paper presents a design method for frequency response masking (FRM)-based nonuniform filter bank with reduced effective wordlength. Instead of designing prototype filters separately, we propose to model the filter bank design problem as a nonlinear programming problem and jointly design the prototype filters in the FRM structure. Moreover, in this work, all the filters are designed directly in the finite wordlength space, such that they can be directly implemented using efficient fixed-point arithmetic without any quantization. By simultaneously considering all the subband constraints during optimization, the proposed method is able to guarantee the desirable stopband attenuation for all subbands and achieve optimal effective wordlength (EWL) for the coefficients, reducing the hardware complexity for very large-scale integration (VLSI) implementation. Experimental results show that the hardware complexity of filter banks can be reduced without sacrificing the audiogram compensation performance for hearing aid applications.

Influence of different base materials and thicknesses on the fracture resistance of endocrown: A three-dimensional finite element analysis.

INTRODUCTION: To analyze the stress distribution of the all-ceramic endocrown with different base materials and thicknesses using three-dimensional finite element analysis. METHODS: A endodontically treated maxillary premolar was scanned by micro-CT, a three-dimensional finite element model of the endocrown with fluid resin as the base material was divided into control (0 mm), 1 mm, 2 mm, and 3 mm groups according to base thickness. Three kinds of conventional base materials were used and divided into glass ion group (A), fluid resin group (B), and nanocomposite resin group (C), and a three-dimensional finite element model of the endocrown with 1.0 mm thickness of base was established. A static loading with axial and 45° direction was applied to each model, the stress distribution of each part of the endocrown was analyzed under different base materials and thicknesses. RESULTS: The different thickness of the base layer has an influence on the components of the restoration and the tooth. The stress in the control group was the largest. The stress was the lowest when the thickness of the base layer was 1 mm; The maximum of the equivalent stress, the first, second, and third principal stress in the endocrown, abutment, and alveolar bone, are basically the same with the different base materials. The stress on the base layer increases with the elastic modulus of base materials increases. CONCLUSIONS: The base layer played a force buffering effect on the dental body restored with endocrowns, and the effect was the best at 1 mm; The selection of base material has little influence on the whole, but in order to protect the weak tissues of the cavity bottom, the base material with lower elastic modulus can be used.

Dual-Band Dual-Mode Button Antenna for On-Body and Off-Body Communications.

A dual-band dual-mode button antenna for body centric communications is presented. At the lower band, a spiral inverted-F antenna is designed with omnidirectional radiation pattern for on-body communication. At the upper band, the high-order mode of the inverted-F antenna is utilized together with a metal reflector to realize broadside radiation for off-body communication. For demonstration, a prototype is implemented. The measured peak gains on the phantom at the lower and upper bands are -0.6 and 4.3 dBi, respectively. The antenna operating on the phantom has measured efficiencies of 46.3% at the lower band and 69.3% at the upper band. The issue of specific absorption rate (SAR) is studied. The maximum transmitted power under the SAR regulation of 1.6 W/kg is found to be 26.4 dB·m, which is high enough for body centric communications. In addition, the transmission performance between two proposed antennas mounted on the body is investigated by measuring the transmission loss. With an overall miniaturized size, the robust button antenna could be integrated in clothes and be a potential candidate for wireless body area network applications.

[Effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker].

PURPOSE: To evaluate the effect of amount of silane coupling agent on flexural strength of dental composite resins reinforced with aluminium borate whisker (ABW). METHODS: ABW was surface-treated with 0%, 1%, 2%, 3% and 4% silan coupling agent (γ-MPS), and mixed with resin matrix to synthesize 5 groups of composite resins. After heat-cured at 120 degrees centigrade for 1 h, specimens were tested in three-point flexure to measure strength according to ISO-4049. One specimen was selected randomly from each group and observed under scanning electron microscope (SEM). The data was analyzed with SAS 9.2 software package. RESULTS: The flexural strength (117.93±11.9 Mpa) of the group treated with 2% silane coupling agent was the highest, and significantly different from that of the other 4 groups (α=0.01). CONCLUSIONS: The amount of silane coupling agent has impact on the flexural strength of dental composite resins reinforced with whiskers; The flexual strength will be reduced whenever the amount is higher or lower than the threshold. Supported by Research Fund of Science and Technology Committee of Shanghai Municipality (08DZ2271100).

Hybrid effects of zirconia nanoparticles with aluminum borate whiskers on mechanical properties of denture base resin PMMA.

The aim of this study was to investigate the hybrid effects of ZrO2 nanoparticles (nano-ZrO2) and aluminum borate whiskers (ABWs) on flexural strength and surface hardness of denture base resin, polymethyl methacrylate (PMMA). Both nano-ZrO2 and ABWs were modified by silane coupling agent (Z6030) before being mixed with PMMA. Various amounts of silanized nano-ZrO2 and ABWs were mixed with PMMA to prepare ZrO2-ABW/PMMA composites. Flexural strength and surface hardness were evaluated using three- point bending test and Vickers hardness test respectively. Fractured surfaces were also observed by scanning electron microscopy (SEM). The mechanical behaviors of silanized ZrO2-ABW/PMMA composites were significantly improved. Flexural strength reached a maximum value of 108.01 ± 5.54 MPa when 2 wt% of nano-ZrO2 was mixed with ABWs at a ZrO2/ABW ratio of 1:2, amounting to an increase of 52% when compared with pure PMMA. Surface hardness achieved a maximum value of 22.50 ± 0.86 MPa when 3 wt% of nano-ZrO2 was mixed with ABWs at the same ZrO2/ABW ratio, which was an increase of 27% when compared with pure PMMA.

[Effect of nano ZrO2 on flexural strength and surface hardness of polymethylmethacrylate].

PURPOSE: To study the effect of polymethylmethacrylate(PMMA's) mechanical properties reinforced by nano ZrO(2) particles with different filling amounts. METHODS: The nano ZrO(2) particles were surface-treated by silane coupling agent(Z-6030) in 1.5wt% ratio, the untreated particles were regarded as the control group. The modified nano ZrO(2) particles were mixed with the PMMA powders in proportion of 0.5%,1%,1.5%,2%,2.5%,3% and 3.5%, respectively.Then the nano ZrO(2) /PMMA composites were synthesized. The specimens were examined by Vickers hardness test and three-point bending test, the surface of fracture was observed by SEM.All data were analyzed with ANOVA test by SAS 6.12 software package. RESULTS: Fourier transform infrared(FTIR) spectroscopy showed that the silane coupling agent linked to the nano ZrO(2) particles' surface after treating,the Vickers hardness was highest when the adding amount of nano ZrO(2) particles was 1.5% and 2%(P<0.05).The flexural strength of nano ZrO(2)/PMMA composites in the proportion of 1.5% was the highest(P<0.05). SEM indicated that the ductile fracture existed on the surface of fracture. CONCLUSIONS: The silane coupling agent can enhance the bonding strength of nano ZrO(2) particles and the PMMA matrix, the PMMA's mechanical properties could be improved by adding the nano ZrO(2) particle in an appropriate proportion. 1.5% and 2% of nano ZrO(2) particles render the nanocomposite the maximal Vickers hardness, while 1.5% ZrO(2) nanoparticles render the nanocomposite the maximal flexural strength.

[Pedigree analysis and prosthodontic treatment of patients with dentinogenesis imperfecta type II].

PURPOSE: To study the heritable character and explore the prosthodontic treatment of opalescent dentin, also known as dentinogenesis imperfecta type II(DGI-II). METHODS: Pedigree analysis was performed in the family members of patients with DGI-II found in Shanghai. The proband was treated with ceramometal restorations and investigated the treatment status of the DGI-II affected individuals in the family. RESULTS: Five sequential generations with DGI-II were found in this family. The prevalence of later generation was approximately 50%. The rate of prosthodontic treatment was 90% nearly, including ceramometal restorations in the most of the patients and removable partial dentures in the others. The esthetic and mastication functions of the patients were good after treatment. CONCLUSIONS: DGI-II showed a autosomal dominant pattern of inheritance. Ceramaometal restorations can prevent the affected teeth from abrasive and fracture, and also can help rehabilitate the esthetic and mastication functions of the teeth.

[The effect of different dispersive methods on flexural strength nano-ZrO(2) reinforced denture polymethyl methacrylate].

PURPOSE: To study the effect of different dispersive methods on flexural strength of nano-ZrO(2)/polymethl methacrylate(PMMA) composite samples. METHODS: The nanometer ZrO2 particles which were modified by coupling agent Z-6030 were mixed to PMMA as the filler materials (3%) by means of handle disperse, ball milling disperse and ultrasonic wet disperse, respectively. Pure PMMA was used as blank control .With reference to the standard of ISO-1567:1999, standard samples were made and tested by three-point bending test. Then the data of flexural strength of the four groups were analyzed statistically with SAS 6.12 software package for one-way ANOVA(Newman-Keuls test). And the optimized synthesis way of the PMMA composite materials was selected. RESULTS: The flexural strength of the ball milling group and the ultrasonic group were significantly higher than the handle group and blank group(P<0.05), with an increase of 17%,10% compared with the blank group. There was no significant difference between the ball milling group and the ultrasonic group (P>0.05). CONCLUSION: Dispersal ways have effect on the flexural strength of PMMA composite materials which are filled with ZrO(2) particles.

[Stress analysis of the all-ceramic crown with a numerical approach].

OBJECTIVE: To analyze the stress distribution in all-ceramic crowns when it was subjected to load. METHODS: A 3D numerical model of the all-ceramic crown of the right mandibular first molar was generated from scanned CT images. Finite element analysis (FEA) was used to evaluate the stress distribution in the all-ceramic crown when it was subjected to 5 load conditions. RESULTS: Stress distributions under 5 loading conditions were obtained. Stress concentrations were generally found near the loading areas at the veneer and at the lower surface of the core beneath the loading areas. In the 5 loading conditions, it was found that when the crown was loaded with vertical concentrated load, the tensile stresses around the shoulder areas were uniform, while stress concentration with maximum of 32.25 MPa was found at the shoulder areas in lingual-buccal direction when loads were applied at an angle of 10 degrees with the tooth axis on the buccal side. The masticatory load which was applied at 20 degrees with the tooth axis on the buccal side would cause stress concentration at the shoulder in mesial-distal direction. The maximum value could reach 11.29 MPa. CONCLUSIONS: The occlusal surface of the all-ceramic crown must be trimmed to increase multiple contact zones with the opposite surfaces in antagonist teeth to avoid excessive concentrated stress that may cause crown failure.

[Microleakage of various cementing agents for casting ceramics].

PURPOSE: To observe and compare the microleakage of different composite resin cement systems for IPS Empress 2 ceramics base. METHODS: Sixteen healthy non-carious human molars were selected in the study. Class V ceramic inlay was prepared by IPS Empress 2 ceramics. The samples were divided into two groups, eight in each group. RelyX Unicem and Variolink 2 were used for bonding respectively in 2 groups. All specimens were stored in water at 37 degrees centigrade for 24 hours, then the specimens were subjected to 500 thermocycles ranging from 5 degrees centigrade to 55 degrees centigrade. Eight specimens in each group were evaluated by dye penetration. The microleakage was examined with light microscope. Statistical analysis was performed with SPSS11.0 software package. RESULTS: Enamel margins exhibited lower leakage than dentin margins by using two cementing agents for casting ceramics (P<0.05). The depth of dye for Variolink 2 and RelyX Unicem at enamel and dentin was not significantly different (P>0.05). CONCLUSIONS: The microleakage of Variolink 2 and RelyX Unicem for IPS Empress 2 ceramics base has similar sealing abilities.

[Color distribution of the anterior teeth in 137 elder people].

PURPOSE: To study the color distribution of the anterior teeth in elder people. METHODS: 612 anterior teeth from 137 people aging from 60 to 81 years and 200 anterior teeth from 100 young people aging from 20 to 40 years were collected. A digital colorimeter was used to measure the value of L*,a*,b* of the teeth, and the chromatism (deltaE) was calculated according to the formula deltaE=(deltaL*(2)+deltaa*(2)+deltab*(2))1/2. All data were analyzed with SAS 6.12 software package for Student's t test. RESULTS: Totally, there were 612 vital anterior teeth from elder people, including 201 central incisors,199 lateral incisors and 212 canines, were collected. No difference was found between the teeth on the right side and the left side in terms of L*,a*,b*value(P>0.05). The mean value of L*,a*,b* of the central incisors was 71.2+/-6.22,0.97+/-1.12,15.9+/-5.04, respectively and that of the lateral incisors and the canines were 69.6+/-5.52,0.6+/-1.18,13.9+/-4.15 and 68.4+/-5.99,0.15+/-1.02,19.6+/-4.87, respectively.The mean value of L*,a*,b* of the central incisors and the canines from the youngster was 75.82,-0.11,12.68 and 72.07,1.22,17.92, respectively.There were significant differences between the central incisors and the lateral incisors as well as the canines (P<0.05) in terms of L* value. Meanwhile difference was also found among the incisors and the canines in terms of a* and b* value(P<0.05). The deltaE between the central incisors and the lateral incisors was 2.945NBS, and the value between the canines and the central incisors as well as the lateral incisors was 4.629NBS and 5.832NBS, respectively, indicating that the color difference could be perceived visually. Compared to the youngster, the teeth of the elder people demonstrated a lower L* and a* value, but a higher b* value (P<0.05). CONCLUSIONS: Among elder people, the central incisors look much brighter than the lateral incisors and canines, while the canines have more redness and yellowness than the incisors, and the color of the lateral incisors exhibits lighter than the central incisors and the canines. Compared to the teeth from younger people, the teeth from elder people look much darker and yellower but less red. Supported by Shanghai Leading Academic Discipline Project (Grant No.T0202).

[Influence of time on shear strength using resin cements].

PURPOSE: To compare the shear bond strength of different composite resin cement systems at different time intervals. METHODS: 48 healthy non-carious human molars were selected in the study. The samples were divided into two groups, 24 in each group. (1) RelyX unicem was used on bonding, (2) Variolink 2 was used on bonding. All specimens were stored in water at 37 degrees C for 2 hours, 24 hours and 1 week. 8 specimens in each group were stressed in shear until failure. Statistical analysis was performed with SPSS11.0 software package. Debonged surface was examined under light microscope. RESULTS: Shear bond strengths of two resin cements showed a significant increase as time went (P<0.05). The failure involved the adhesive/dentin interfaces. CONCLUSIONS: Time can influence the shear bond strength using different composite resin cement systems. Supported by Shanghai Leading Academic Discipline Project (Grant No.T0202).

[Influence of different amount of silane coupling agent on the flexural strength of PMMA/nanometer ZrO2 composites].

PURPOSE: To study the influence of different amount of silane coupling agent Z-6030 on the flexural strength of PMMA/nanometer ZrO(2) composites. METHODS: Nanometer ZrO(2) particles were modified by silane coupling agent Z-6030 with different percentages.In situ polymerization method was used to combine PMMA/ nanometer ZrO(2) composites of denture base plate. With reference to the standard of ISO1567:1999, standard samples of the experimental group were made. PMMA II type powder and PMMA II type liquor were used,which was not added nanometer ZrO(2) and silane coupling agent to make the standard samples of common denture base plate. PMMA II type powder and PMMA II type liquor were used,which was added nanometer ZrO(2) unmodified by silane coupling agent to make the standard samples of the control group. The data of flexural strength of the base plate materials were tested with three-point bending test. One-way ANOVA was adopted to analyze the data using SAS 6.12 software package. RESULTS: When the percentage of silane coupling agent Z-6030 was 3.5%,the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate was strongest, which was significantly higher than that of the common denture base plate group,the control group,2.0% group,4.0% group,4.5% group and 5.0% group(P<0.05). 0.5% group,1.0% group,1.5% group,2.5% group,3.0% group and 3.5% group had no significant difference with each other(P>0.05). 0.5% group,1.0% group,1.5% group,2.0% group,2.5% group,3.0% group,4.0% group,4.5% group,5.0% group,the common denture base plate group and the control group had no significant difference with each other(P>0.05). CONCLUSION: Using proper percentage of silane coupling agent Z-6030 can improve the flexural strength of PMMA/nanometer ZrO(2) composite resin material of denture base plate. This study showed that the best range of the percentage of silane coupling agent Z-6030 was 3.5%.

[The influence of the try-in pastes on the colour of all-ceramic veneers].

PURPOSE: To study the influence of the try-in pastes on the color of all-ceramic veneers made by Ips-empress II system. METHODS: 50 discolored teeth were collected and restored with all-ceramic veneers. Five try-in pastes including A1, A3, transleucent(Trt), white opaque(WOT) and B0.5 opaque(B0.5),which were different in shade, were respectively used to try in before cementing. The color was measured by the ShadeEye, a digital colorimeter, and expressed in terms of 3 coordinate values (L*,a*,b*) of the CIEL*a*b* system. Then the color differences(deltaEa*b*) of all-ceramic veneers[deltaEa*b*=(deltaL*(2)+deltaa*(2)+deltab*(2))(1/2)] as well as the value of L*deltaC(ab)[C(ab)=(a*(2)+b*(2))(1/2)] and H(ab)[H(ab)=arctan(b*/a*)]were calculated. Meanwhile,the thickness of the measurement point was measured and recorded. One-way ANOVA was used to analyze deltaEa*b* as well as L*,C(ab) and Hab. RESULTS: The average thickness of the ceramic was 1.088mm, and the colour of the veneers after try in with WOT paste and B0.5 paste performed a higher L* value than the other pastes (P<0.05).And the veneers also showed a higher C(ab) value after try in with WOT,B0.5 and A3 paste than the A1 and Trt paste (P<0.05). No significant differences were found in Hab value after these 50 veneers tried in with these five kinds of pastes. CONCLUSIONS: It's more advisable to choose the WOT or the B0.5 luting agent to cement the veneer when the abutment tooth is severely discolored, while the Trt or the A1 shade and A3 shade luting resin may be more appropriate if the abutment tooth doesn't discolor or a little compared with the adjacent tooth.

[Progress of research on fiber posts].

In the last few decades, casting metal has been the most commonly used post-core systems. But the elastic modulus of metal posts is higher than that of the dentin. Root fractures often happen because of the higher elastic modulus. The fiber posts can reduce or avoid root fractures because their elastic modulus is similar to that of the dentin. Therefore, they are widely used clinically to preserve tooth tissues and restore them after failure. This review article aims to introduce the recent research of the fiber posts.

[Clinical analysis of colour distribution in tetracycline teeth].

PURPOSE: To analyze the colour range and distribution of tetracycline teeth, and the difference from normal teeth. METHODS: 142 cases with 468 anterior tetracycline teeth and 100 cases with 200 normal anterior teeth were collected. The color was measured by a computer-aided Shade-Eye NCC colorimeter, and expressed in terms of 3 coordinate values (L,a,b) of the CIE-1976-Lab color system. Chroma (Cab)and hue (h(ab) degrees)were calculated according to the value of a and b. The data were analyzed with SAS6.12 software package for description, Student's t test and Duncan test. RESULTS: The range of L, a, b Cab, h(ab) degrees of tetracycline teeth was 42.33-77.00, -0.6-9.6, 2.67-31.5, 5.24-31.89, 38.62 degrees-95.47 degrees, respectively. Significant difference of L value and hue (h(ab) degrees) was found between tetracycline teeth and normal teeth (P < 0.01), which indicated that tetracycline teeth were darker and redder than normal teeth. There was no difference of chroma (Cab) between tetracycline teeth and normal teeth (P > 0.05). Moreover there was significant difference of L value between canine and central incisor, and of H value (h(ab) degrees) between canine and lateral incisor in tetracycline teeth, which indicated that canine was darker and redder than incisor, and redder than lateral incisor, but there was no significant difference in chroma (Cab) among all anterior teeth and no difference in L, a, b between central incisor and lateral incisor. CONCLUSIONS: The study showed the color distribution of tetracycline teeth was wider and more dispersive than normal teeth, and much darker and redder than normal teeth. Supported by Shanghai Leading Academic Discipline

[Inducement and proliferation of MSCs in vitro and preliminary study on interface between MSCs and metal materials].

OBJECTIVE: The aims of the present study were to assess the characteristics of MSCs which were induced and proliferated in vitro, then to learn the interfaces between them and metal materials. METHODS: Adult dogs were selected as experimental animals, the MSCs (marrow stem cells) were aspirated from the femur, which were induced to the phenotype of OB (osteoblast), then to proliferated in vitro with metal materials. Using biochemical tests, phase contrast microscopy, transmit electromicroscope, scanning electromicroscope to detect MSCs and the image of interface. RESULTS: MSCs had powerful osteogenic phenotype when they were induced in vitro, and they also attached to the metal materials. And there were more cells which attached on tensile stress area than other areas. CONCLUSION: The MSCs induced in vitro could be used as source of osteoblast. The affects of air--abrasion with alumina are not significant, but they have relation to the extent of strain and property of stress.

[Using moiré interferometre in the study of porcelain-fused-metal interfacial fracture mechanics].

OBJECTIVE: To evaluate the usage of moiré interferometre in porcelain-fused-metal interfacial fracture mechanics. METHODS: Raster was produced on the surface of samples with different thickness of porcelain and metal in 5 groups. The stripes of u field and v field under different load were collected. Then the rupture tenacity Jc was calculated and the extensions of flaws were observed. RESULTS: Stress concentration appeared around the flaws under load conditions. The stripe became denser under more load. The rupture tenacity Jc and the direction of flaw extension of each group were different. CONCLUSION: Moiré interferometre can be used in the study of porcelain-fused-metal interfacial fracture mechanics and to prognosticate the direction of flaw extension.