Effects of different treatments of the ridge surface on the shear bondstrength between acrylic teeth and thermal polymer resin.

PURPOSE: To evaluate the shear bond strength between denture base and artificial teeth subjected to five different modifications on the ridge surface. METHODS: 30 acrylic central anterior teeth were randomly divided into five groups (n= 6). The ridge surface of these teeth were treated with different methods: (1) No treatment applied; (2) Monomer wetting; (3) Grinding; (4) Grinding followed by sandblasting; (5) Grinding followed by monomer wetting. After the ridge surface of the teeth were treated, they were packed with denture base resin. The shear bond strength between acrylic teeth and denture base resin was performed using a universal testing machine. The data was statistically analyzed using one-way ANOVA (P< 0.05). RESULTS: The monomer wetting group showed the highest shear bond strength values, and the grinding followed by sandblasting group was the lowest, both were statistically significant compared to each other. There were no statistical differences between the other groups. CLINICAL SIGNIFICANCE: Treating the surface of the denture ridge with a monomer provided the highest shear bond strength values, and the grinding followed by sandblasting group was the lowest, statistically significant compared to each other.

[The microscopic characteristic of the dentinal tubule obstructed by desensitizer and the effect of desensitizer on the shear strength of resin cements].

OBJECTIVE: To observe the microscopic characteristic of the dentinal surface and cross section after using dental desensitizer, and evaluate the effect of the dental desensitizer on the shear strength of resin cements. METHODS: To use the dental desensitizer (Gluma, Single Bond 2, BisBlock) individually on the prepared human bicuspid teeth which were extracted for orthopaedics. The microscopic characteristic of the dentinal surface and cross section were observed with scanning electron microscope (SEM). The adhered posts to the teeth pretreated with desensitizer were bonded with resin cements. The shear strength was measured and data was analyzed by SPSS 13.0 statistics software. RESULTS: The orifices of dentinal tubule were mostly occluded in Gluma samples and partly occluded in BisBlock samples. Resin layer was observed in Single Bond 2 samples. BisBlock group gathered the best shear strength, the shear strength value was (13.04+/-2.76) MPa. Marked statistic difference were found when compared with control group. CONCLUSION: Gluma, Single Bond 2 and BisBlock can block the orifices of dentinal tubule. BisBlock enhanced the bonding strength of the resin cements.

[Effect of different dental polishing methods on cobalt-chromium casts surface roughness and accuracy].

PURPOSE: To evaluate the effect of different polishing methods on surface roughness and accuracy of cobalt-chromium castings. METHODS: Five polishing methods were compared: centrifugal barrel polishing, electrical brightening, grinding, grinding+centrifugal barrel polishing and grinding+electrical brightening. 30 specimens (30 mmx 10 mm x l.5 mm) were divided into 6 groups which were cast and polished for surface roughness test.30 upper complete denture bases were cast and divided into 6 groups. The dimensional accuracy between the posterior border of the upper complete denture and model at five different positions were determined by traveling microscope measuring method respectively before and after polishing. One-way ANOVA with SPSS13.0 was used for statistical analysis. RESULTS: Specimens polished by grinding+centrifugal barrel got the smoothest surface (P < 0.01) with Ra0.19 microm, compared with Ra3.38 microm before polishing. No significant difference of the posterior border gaps between the cast base and model was found (P > 0.05). CONCLUSIONS: Bases polished by grinding + centrifugal barrel had the smoothest surface. There is no influence of centrifugal barrel polishing on dimensional accuracy of cast upper base.