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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.
Subject(s)
Ceramics , Dental Bonding , Materials Testing , Microscopy, Electron, Scanning , Shear Strength , Surface PropertiesABSTRACT
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℃ 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±1.99MPa 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.
ABSTRACT
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℃ 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±1.99MPa 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.
ABSTRACT
<p><b>UNLABELLED</b>OBJECTIVE This study aims to construct a chitosan (CS)-polycaprolactone (PCL)-hydroxyapatite (HA) composite biomimetic scaffold to replace condyle and to explore the tissue engineering applications of condylar.</p><p><b>METHODS</b>A resin mold of the mandibular condyle was prepared by using rapid prototyping techniques. A mandibular condylar integrated biomimetic scaffold model was prepared by solution casting-ice Lek. PCL and CS were mixed at a ratio of 4:1. HA at quality ratios of 40%, 50%, 60%, and 70% was added to groups a, b, c, and d, respectively. The microscopic morphology, porosity, infrared spectra, X-ray diffraction pattern, and mechanical properties of the scaffold were observed.</p><p><b>RESULTS</b>The scaffold that includes both upper and lower parts displayed the same features (i.e., shape, yellow-white appearance, and hard texture) as the mandibular condyle. Scanning electron microscopy showed that the composite scaffold had a 3D network spatial structure, 70%-85% porosity, and 10-200 µm pore size. Infrared spectra showed that the peak intensity reduced with decreasing HA content. X-ray diffraction showed that the diffraction peak decreased with increasing HA content. Suitable tensile and compressive and flexural strength were discovered in the presence of 50% HA.</p><p><b>CONCLUSION</b>The scaffold prepared by solution casting-ice Lek shows favorable comprehensive features and is expected to replace human condylar.</p>
Subject(s)
Humans , Chitosan , Durapatite , Hardness , Mandible , Microscopy, Electron, Scanning , Polyesters , Porosity , Tissue Engineering , Tissue Scaffolds , X-Ray DiffractionABSTRACT
<p><b>OBJECTIVE</b>To study the retentive force and deformation of acetal resin clasp.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSION</b>The retentive force and deformation of the resin clasp are significantly lower than those of Co-Cr clasp.</p>
Subject(s)
Humans , Bicuspid , Chromium Alloys , Dental Clasps , Denture Retention , In Vitro TechniquesABSTRACT
<p><b>OBJECTIVE</b>To research the influence of gilt to the retention of the complete metal crown.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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).</p><p><b>CONCLUSION</b>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.</p>
Subject(s)
Animals , Female , Humans , Chromium Alloys , Crowns , Gold , SwineABSTRACT
<p><b>OBJECTIVE</b>To evaluate wear resistance and hardness of three kinds of new composite resins.</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>Nanofilled composite was superior to the hybrid composite in wear resistance and hardness.</p>
Subject(s)
Composite Resins , Dental Enamel , Dental Materials , Dental Restoration Wear , Hardness , In Vitro Techniques , Materials Testing , Surface PropertiesABSTRACT
<p><b>OBJECTIVE</b>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.</p><p><b>METHODS</b>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).</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>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.</p>