[Experimental study on the optical properties of different-translucency zirconia-ceramic restorations].

PURPOSE: The purpose of this in vitro study was to measure the color difference(△E) on titanium alloy background and translucency parameter(TP) of four kinds of zirconia-based all-ceramic specimens, providing a clinical reference for restoring grayish abutment. METHODS: Four groups with a total of 24 ceramic specimens were fabricated to a final specimen dimension of 14 mm×14 mm×1.5 mm, two kinds of zirconia with different translucency（Beitefu high-translucency, Cercon low-translucency）and their corresponding body porcelain at the shade of A2 were used as followed:high-translucency zirconia sintered dentine porcelain(Group A),low-translucency zirconia sintered dentine porcelain(Group B),high-translucency zirconia sintered opaque and dentine porcelain(Group C),low-translucency zirconia sintered opaque and dentine porcelain(Group D).The color parameters of the specimens under two backgrounds (titanium alloy and shade A3 light-activated resin-based composite) were measured by Shade Eye NCC colorimeter, then the △E value was determined by the relevant equations. The color parameters under black and white background were measured, and TP value was calculated. The experimental data were analyzed with SPSS 17.0 software package. RESULTS: There was significant difference of the TP value and the △E value among four groups specimens(P＜0.05), the TP value was arranged as follows: group D＜group C＜group B＜group A. The specimen used with opaque porcelain showed significantly reduced translucency. The △E value was arranged as follows: group D ＜ group C ＜ group B ＜ 1.5 ＜ 2 ＜group A, the △E value of group A cannot be accepted in clinic. CONCLUSIONS: The restoration of low-translucency zirconia sintered translucency veneering ceramic has better translucency, with value of △E＜1.5 when used on the grayish abutment, which has a good aesthetic performance.

Altered Intrinsic Brain Activity in Patients With Toothache Using the Percent Amplitude of a Fluctuation Method: A Resting-State fMRI Study.

Objective: The percent amplitude of fluctuation (PerAF) technique was utilized to evaluate the neural functions of specific cerebrum areas in patients with toothache (TA). Patients and Methods: An aggregation of 18 patients with TA (eight males and 10 females) were included in the study. We also recruited 18 healthy controls (HCs; eight men and 10 women) aligned for sex and age. Resting functional magnetic resonance imaging (rs-fMRI) scans were obtained. Then, we utilized the PerAF method and a support vector machine (SVM) to analyze the image data and measure neural abnormalities in related cerebrum areas. Receiver operating characteristic (ROC) curve analysis was utilized to appraise the two data sets. Results: The PerAF signals in the right dorsolateral superior frontal gyrus (RDSFG) and the right posterior central gyrus (RPCG) of TA sufferers were lower than HC signals. These results may reveal neural dysfunctions in relevant cerebrum regions. The AUC values of PerAF in the two areas were 0.979 in the RDSFG and 0.979 in the RPCG. The SVM results suggested that PerAF could be utilized to distinguish the TA group from HCs with a sensitivity of 75.00%, a specificity of 66.67%, and an accuracy of 70.83%. Conclusion: Patients with TA had marked differences in PerAF values in some regions of the cerebrum. Changes in PerAF values represented distinctions in blood oxygen level dependent semaphore intensity, which reflected the overactivity or inactivation of some cerebrum areas in those suffering from TA. At the same time, we analyzed the PerAF values of TAs with ROC curve, which can be helpful for the diagnosis of TA severity and subsequent treatment. Our results may help to elucidate the pathological mechanism of TA.

[Effect of different sandblasting conditions on the metal-ceramic bonding strength of Co-Cr alloy fabricated by selective laser melting technology].

OBJECTIVE: To investigate the effect of different sandblasting conditions on the metal-ceramic bonding strength of Co-Cr alloy fabricated by selective laser melting (SLM) technology. METHODS: A total of 63 specimens of Co-Cr alloy fabricated by SLM were prepared and randomly divided into nine groups (n=7). Each group was treated with different powder particles (A1=50 µm, A2=100 µm, and A3=150 µm) and pressures (B1=0.2 MPa, B2=0.4 MPa, and B3=0.6 MPa) in sandblasting. One sample was randomly selected from each group for microstructure observation by scanning electron microscope (SEM). Ceramic was fired at the center of the specimens. Metal-ceramic bonding strength was measured with universal testing machine. Results were statistically analyzed with SPSS 17.0 software. RESULTS: The mean bond strengths were as follows: Group A1B1: 27.22 MPa±0.95 MPa, Group A1B2: 27.58 MPa±0.47 MPa, Group A1B3: 26.80 MPa±0.71 MPa, Group A2B1: 27.54 MPa±0.78 MPa, Group A2B2: 30.75 MPa±0.43 MPa, Group A2B3: 26.93 MPa±0.88 MPa, Group A3B1: 28.18 MPa±0.93 MPa, Group A3B2: 29.55 MPa±0.57 MPa, and Group A3B3: 28.11 MPa±0.91 MPa. The particle factor of Al2O3 and the pressure factor of blasting showed statistical significance (P<0.05). An interaction was observed between the factors of particle and pressure (P<0.05). Mixed fracture mode of all specimens was observed after the shear strength test. CONCLUSIONS: In conclusion, metal-ceramic bonding strength reaches the maximum when specimens are sandblasted with 100 µm alumina oxide at 0.4 MPa pressure.

Impact of Dentinal Tubule Orientation on Dentin Bond Strength.

This study aimed to determine the impact of dentinal tubule orientation on dentin bond strength to provide a reference for clinical cavity preparation in resin-bonded restoration. Patients aged 13-16 years were selected, including 18 males and 21 females. Forty-eight human maxillary first premolars from orthodontic extractions were chosen to prepare the test models with the dentinal tubule orientations perpendicular and parallel to the bonding substrate. The test models in the vertical and parallel groups were divided into three groups: total-etching with 20% phosphoric acid, total-etching with 35% phosphoric acid and self-etching, with the dentinal tubule surfaces bonded with composite resin blocks in each group. After the standard test models of dentinal tubule-composite resin blocks were placed in distilled water and stored at 37°C for 24 h, shearing tests were performed using a universal material testing machine at a crosshead speed of 0.5 mm/min. The bond strength values in the vertical group were 19.33±1.59 MPa for the 20% phosphoric acid group, 21.39±2.34 MPa for the 35% phosphoric acid group, and 16.88±1.54 MPa for the self-etching group. The bond strength values in the parallel group were 24.53±1.99 MPa for the 20% phosphoric acid group, 25.16±2.88 MPa for the 35% phosphoric acid group, and 20.83±1.99 for the self-etching group. After using same total-etching adhesive, the shear bond strength of the parallel group was higher than that of the vertical group, and the difference was statistically significant (P<0.05). Regardless of vertical group or parallel group, the difference in the bond strength value between the total-etching groups and the self-etching group was statistically significant (P<0.05). It was concluded that the dentin bonding substrate which was parallel to the direction of the dentin tubule achieved an improved bond strength; the total-etching adhesives achieved higher bond strengths in dentin bond than the self-etching adhesives.

[Experimental research of hot alkaline solution etching treatment on zirconia/resin bonding strength].

PURPOSE: In this experiment, we applied hot alkaline solution (20%NaOH solutions) to treat the surfaces of zirconia ceramics in vitro, then evaluated the changes of bond strength of zirconia ceramics and resin cement. METHODS: Eighteen pieces of zirconia ceramic specimens were made, using the same method of grinding and polishing, and then randomly divided them into 3 groups: group A with hot alkali solution treatment (20%NaOH) (n=6), group B underwent sand blasting with a diameter of 110 ?m alumina particles (n=6), group C was as the control group. Atomic force microscope was used to measure the roughness of the surface of the specimens, and the zirconia surfaces were scanned to get topography maps, then made them into ceramic/resin-bonded specimens. After 24 h of water reservoir processing, shearing bonding strength (SBS) test was conducted and their bond interfaces were observed to investigate the lesions of different degree in these specimens. The data were analyzed with SPSS20.0 software package. RESULTS: Surface roughness was group B> group A > group C, SBS was group B>group A>group C. CONCLUSIONS: Under the condition of 180degrees centigrade, bonding strength between zirconia and resin cement after treatment with 20% NaOH solution was significantly higher than without any treatment, but lower than sand blasting treatment.

[Evaluation of the effect of modified wet particle erosion on bond strength between 3Y-TZP zirconia framework and veneering porcelain].

PURPOSE: To evaluate the effect of bond strength between 3mol% yttrium-stabilized tetragonal zirconium polycrystal (3Y-TZP) zirconia framework after modified wet particle erosion and veneering porcelain. METHODS: A total of 174 [8 mm× 8 mm× 3 mm (±0.02)] specimens were prepared and then randomly divided into different groups according to different particle size, sandblasting pressure, sandblasting time through conventional sandblasting (experimental groups); specimens in the control group were not sandblasted. The bond strength between 3Y-TZP zirconia framework and veneering porcelain was measured using a universal testing machine. Statistical analysis was performed using SPSS17.0 software package. The bond strength of specimens treated by two methods-conventional sandblasting and modified wet particle erosion under the same condition (150 µm, 0.6 MPa, 30 s) were acquired, while the surface was analyzed microscopically before the specimens were veneered with the veneering ceramic under scanning electronic microscope (SEM). RESULTS: The bond strength of conventional sandblasting group under the condition (110 µm, 0.4 MPa,30 s) was maximal, and significantly higher than the control group (P<0.05). The bond strength of modified wet particle erosion group was significantly higher than the conventional sandblasting group and control group (P<0.01); SEM showed that the surface of specimen with modified wet particle erosion was homogeneously rough; the surface specimen with conventional sandblasting was heterogeneously rough, some microcracks were seen in some areas. CONCLUSIONS: Sandblasting can slightly enhance the bond strength between 3Y-TZP zirconia framework and veneering porcelain, modified wet particle erosion is recommended for 3Y-TZP zirconia framework surface treatment.

[The influence of lower vertical dimension construction of complete denture on cerebral blood flow].

PURPOSE: To investigate the influence of lower vertical dimension construction on cerebral blood flow among patients with complete denture. METHODS: Ten edentulous patients were chosen and lower vertical dimension was constructed with complete denture. Transcranial Doppler ultrasonography was used to detect the average peak flow velocity, peak systolic velocity and end-diastolic peak flow velocity of the middle cerebral artery. The detection was performed before chewing, 10 minutes after chewing and 20 minutes after chewing, respectively. Before-after self control study was designed, and SPSS18.0 software package was used to analyze the data with independent samples t test and multiple comparisons and analysis of variance. RESULTS: There was no significant increase in cerebral blood flow before chewing, 10 minutes after chewing and 20 minutes after chewing in the experimental group, while blood flow velocity of the control group was significantly increased. The blood flow velocity of the experimental group 10 minutes after chewing was significantly lower than that of the control group, while no significant difference was found after chewing between the experimental group and control group 20 minutes. CONCLUSIONS: No significant increase of cerebral blood flow is detected in patients whose vertical dimension are lower when restored with complete denture during mastication.

[Evaluation of bond strength between low fusing porcelain with goldplated cobalt-chromium alloys].

PURPOSE: To evaluate the bond strength of Vita OMEGA 900 low fusing porcelain fused with the goldplated Wirobond cobalt-chrome metalt ceramic alloy. METHODS: Low fusing porcelain was fused with the cobalt-chromium alloy strips(group A) and the goldplated cobalt-chromium alloy strips(group B) respectively according to ISO9693 (A:8,B:10). 8 specimens of each group were submitted to three point bending test. Two more test pieces fused with gold plated cobalt-chromium alloys were made (group B'). One test piece of both group B and group B' were observed under scanning electron microscope (SEM) randomly. The data was analyzed with SPSS 16.0 software package. RESULTS: The bond strength (MPa) of group A and group B was 29.92±4.28 and 28.20±5.21, respectively (P>0.05), both higher than 25 MPa required by ISO9693. SEM showed that Vita OMEGA 900 low fusing porcelain and the goldplated Wirobond cobalt-chrome metalt ceramic alloy combined together closely without cracks. Much gold was fused to the cobalt-chrome alloy surface of breaking porcelain specimen after testing. CONCLUSIONS: Vita OMEGA 900 low fusing porcelain can match with the goldplated Wirobond cobalt-chrome metalt ceramic alloy. Supported by Foundation of Education Department of Jiangxi Province (GJJ10367).

[Finite element stress analysis of all-ceramic continuous crowns of the lower anterior teeth in differential shoulder thickness].

PURPOSE: To investigate the stress distributions under load in 3 types of all-ceramic continuous crowns of the lower anterior teeth with differential shoulder thickness. METHODS: Cone-beam CT (CBCT) was used to scan the in vitro mandibular central incisors, and achieve three-dimensional finite element model of all-ceramic continuous crowns with different shoulder width by using Mimics, Abaqus software. Different load conditions were simulated based on this model to study the effect of shoulder width variation on finite element analysis of 3 kinds of different all-ceramic materials of incisors fixed continuous crowns of the mandibular. RESULTS: Using CBCT, Mimics10.01 software and Abaqus 6.11 software, three-dimensional finite element model of all-ceramic continuous crowns of the mandibular incisor, abutment, periodontal ligament and alveolar bone was established. Different ceramic materials and various shoulder width had minor no impact on the equivalent stress peak of periodontal membrane, as well as alveolar bone. With the same shoulder width and large area of vertical loading of 120 N, the tensile stress was the largest in In-Ceram Alumina, followed by In-Ceram Zirconia and the minimum was IPS.Empress II. Under large area loading of 120 N 45° labially, when the material was IPS.Empress II, with the shoulder width increased, the porcelain plate edge of the maximum tensile stress value increased, while the other 2 materials had no obvious change. CONCLUSIONS: Finite element model has good geometric similarity. In the setting range of this study, when the elastic modulus of ceramic materials is bigger, the tensile stress of the continuous crown is larger. Supported by Research Project of Department of Education, Jiangxi Province (GJJ09130).

[The effect of H2O2 surface treatment of posts on the bond strength between glass fiber posts and the resin cement].

PURPOSE: To evaluate the effect of H2O2 on the push-out bond strength between glass fiber posts and the resin cement. METHODS: Eighteen Tenax glass fiber posts and 18 Macthpost glass fiber posts were randomly assigned to 6 groups according to the surface treatments. Group A, no surface treatment (control group); Group B, treated with silane agent; Group C, treated with 3% H2O2, then with silane agent; Group D, treated with10% H2O2, then with silane agent; Group E, treated with20% H2O2, then with silane agent; Group F, treated with 30% H2O2, then with silane agent. The posts were adhered using the resin cement to form cylindrical resin block. Each resin block was sectioned to 7 sections of 1 mm thick. A push-out test was performed on other sections of each post to measure bond strengths. The date was recorded and analyzed with SPSS13.0 software package. The failure modes were examined with stereomicroscope. RESULTS: The bond strengths of Tenax post from A1 to F1 were (22.35±3.43) MPa, (22.75±1.92) MPa, (27.21±3.60) MPa, (32.32±2.19) MPa, (36.15±2.32) MPa and (40.51±2.37) MPa, respectively. The bond strengths of Macthpost post from A2 to F2 were (17.29±3.23) MPa, (17.01±3.18) MPa, (20.48±2.11) MPa, (23.60±2.60) MPa, (27.65±3.77) MPa and (30.52±2.99) MPa, respectively. No significantly difference (P>0.05) was found between Group A and Group B, except other groups. CONCLUSIONS: Treatment with H2O2 followed with silane agent can significantly improve the bond strength between Tenax and Macthpost glass fiber posts and resin cement. The group treated with 30% H2O2 has the highest bond strength, and the treatment procedure is more useful to improve the adhesion of the glass fiber post. Supported by Science and Technology Plan Project of Department of Health of Jiangxi Province (20131084).

[An in vitro study of retentive force and deformation of resin clasp].

OBJECTIVE: To study the retentive force and deformation of acetal resin clasp. METHODS: 40 premolars and 40 molars were cast respectively. Undercut of 0.25 mm or 0.50 mm depth were measured for each with undercut gage. According to the type of abutment and the depth of undercut, the specimens were divided into 4 groups: Premolars with 0.25 mm undercut, premolars with 0.50 mm undercut, molars with 0.25 mm undercut and molars with 0.50 mm undercut, 20 specimens each group. 10 three-arm clasps with resin and Co-Cr alloy were fabricated in each group, respectively. The clasps were set into the corresponding abutments and soaked in distilled water. The retentive force of the clasps when 0, 720, 1440, 2160, 2880, 3600, 4320 consecutive times of setting in and removing out from the abutments were measured. The distance between the tips of retentive arm and resistant arm after 0 and 4320 cycles were recorded. RESULTS: 1) The mean retentive force of resin clasps (1.69 N) was significantly lower than that of Co-Cr clasps (5.87 N) (P<0.01). With the same factors, the retentive force of resin clasps were significantly less than that of Co-Cr clasps (P<0.01). The retentive force of molar clasps were significantly lower than that of premolar models (P<0.01). The retentive force of 0.25 mm undercut clasps were significantly lower than that of 0.50 mm undercut clasps (P<0.01). With increasing time of the cycles, the retentive force of Co-Cr clasps significantly reduced (P<0.01), but the retentive force of resin clasps didn't change significantly (P>0.05). 2) After 4320 times, the distance between the tips of retentive arm and resistant arm of Co-Cr clasps increased significantly (P<0.05), but the distance between the tips of resin clasps didn't change significantly (P>0.05). CONCLUSION: The retentive force and deformation of the resin clasp are significantly lower than those of Co-Cr clasp.

[The influence of gilt to the retention of the complete metal crown].

OBJECTIVE: To research the influence of gilt to the retention of the complete metal crown. METHODS: Sixty Ni-Cr alloy complete metal crown were divided into three groups, control group (common Ni-Cr alloy complete metal crown), whole gold-plating group (whole gilding on the tissue surface of the inner Ni-Cr alloy complete metal crown), partial gold-plating group (gilding on the tissue surface of 1/3 cervical inner Ni-Cr alloy complete metal crown). The retention force of complete metal crown was measured by tensile force/pressure ergograph. RESULTS: The retention force of control group, partial gold-plating group, whole gold-plating group were (657 +/- 151) N, (632 +/- 139) N, (569 +/- 103) N, respectively. There were significant differences between control group and whole gold-plating group, whole gold-plating group and partial gold-plating group (P < 0.05). There was no significant difference between control group and partial gold-plating group (P > 0.05). CONCLUSION: The force of retention would decrease after gilding on the tissue surface of the inner Ni-Cr alloy complete metal crown, but have no influence to normal retention requirement of complete crown. Although the retention of partial gold-plating complete metal crown had somewhat decrease, it could be ignored.

[Effect of different treatments of dentin surface on sheer bond strength between different bonding agents and dentin].

OBJECTIVE: To evaluate the effect of Zinc oxide-eugenol cement and Gluma desensitizer on the sheer bond strength of three kinds of dentin bonding agents. The three dentin bonding agents were Zinc phosphate cement, Glass ionomer cement and Super-Bond C&B. To find the theory depending for the using of different protective methods and the selecting of different kinds of dentin bonding agents in prepared abutment teeth. METHODS: The buccal surfaces of ninety freshly extracted human premolars were flattened to expose an adequate area of lower dentin. Followed by wet-grinding on a series of silicon carbide paper from number 320, 400, 600 grit to produce the dentin bonding surface. The teeth roots were embedded in self-curing resin with the crown out of the resin. The embedded ninety teeth were divided randomly into three groups. The group A was control and the dentin surfaces were not treated. The group B was covered with a paste of Zinc oxide-eugenol cement. The group C was covered with Gluma desensitizer. Calculating the sheer strength between three bonding agents and dentin after the two treatments of dentin surface. The results were statistically assessed with SPSS software. Dentin surfaces were observed with scanning electron microscope (SEM). RESULTS: The sheer bond strengths of Zinc phosphate cement had significant decrease (P<0.05), especially the C1 group. The sheer bond strengths of Glass ionomer cement and Super-Bond C&B had no significant difference. CONCLUSION: Zinc oxide-eugenol cement and Gluma desensitizer could reduce the sheer bond strength of Zinc phosphate cement with dentin surface. Zinc oxide-eugenol cement and the Gluma desensitizer could not effect Glass ionomer cement and the Super-Bond C&B with dentin.

[An in vitro investigation of wear resistance and hardness of three kinds of new composite resins].

OBJECTIVE: To evaluate wear resistance and hardness of three kinds of new composite resins. METHODS: Three kinds of new composite resins, Solidex, Spectrum, Filtek Z350, were tested. Enamel as control group. A refited MG-200 wear machine was used in this study. Scanning electron microscope (SEM) was used to observe the friction surface of each tested material. Hardness of each tested material was determined by Vickers indentation technique. The data of wear and hardness were analyzed by Mann-Whitney test and 1-way ANOVA. The relationship between the hardness of the composites and the amount of wear of them was determined by a regression analysis method. RESULTS: Filtek Z350 showed the lowest volumetric wear and highest Vickers hardness in the composites (P < 0.05). No significant differences in wear and hardness were observed between Solidex and Spectrum (P > 0.05). Significant relationships were observed between the hardness of the composites and the amount of wear of them (r = 0.968 6) (P < 0.05). Different wear characters of the friction surface of the tested materials were observed by SEM. CONCLUSION: Nanofilled composite was superior to the hybrid composite in wear resistance and hardness.

[Dental caries and periodontal diseases in adult Jiangxi cohort: a sample investigation].

PURPOSE: To investigate the current status of dental caries and periodontal diseases in the population aged 35-44 and 65-74 years in Jiangxi province, and to provide information for prevention of these diseases. METHODS: 1584 people (aged 35-44 and 65-74 years) were selected by equal-sized stratified multi- stage and random sampling. Their dental caries and periodontal diseases were examined in routine epidemiologic surgery manner. Student's t test and Chi-square test were applied for statistical analysis using SPSS12.0 software package. RESULTS: In the age group of 35-44 and 65-74 years, the prevalence rate of dental caries was 59.4% and 85.5%, the mean DMFT was 2.19 and 4.91, the prevalence rate of root caries was 32.7% and 79.5%, the mean DFRoot was 0.28 and 1.25,the rate of healthy periodontal tissues was 0.1% and 5.3%. CONCLUSIONS: Dental caries and periodontal diseases are quite common diseases in Jiangxi Province. We should reinforce the oral health care and the propaganda for oral care knowledge in order to treat caries and periodontal diseases better and earlier, and improve the life quality of middle-aged and elderly citizens.