Removal torque of a two-piece zirconia abutment with a novel titanium component in an internal connection implant system after dynamic cyclic loading / 대한치과보철학회지

PURPOSE: The aim of this study was to evaluate screw removal torque of the two-piece zirconia abutment with the novel titanium component compared to the conventional onepiece titanium abutment in the internal connection implant before and after dynamic cyclic loading. MATERIALS AND METHODS: Two types of the abutment assemblies with internal connection were prepared and divided into the groups; titanium abutment-titanium abutment screw assemblies as control, and zirconia abutment-titanium socket-titanium abutment screw assemblies as experimental group. A total of 12 abutments and implants were used of six assemblies each group. Each assembly was tightened to 30 Ncm. A cyclic load of 300 N at an angle of 30 degrees in reference to the loading axis was applied until one million cycles or failure. The removal torque values (RTVs) of the abutment screws were measured with a digital torque gauge before and after cyclic loading. The RTVs of the pre load and post load were analyzed with t-test, and P-values .05). CONCLUSION: Within the limitation of this study, the two-piece zirconia abutment with the titanium component did not show a significant RTV difference of the abutment screw compared to the titanium abutment after dynamic cyclic loading.

The influence of implant elastic modulus on stress distributions in implant and peri-implant bone / 医用生物力学

Objective To investigate the effects of changes in elastic modulus of dental implants on stress distributions in implants and peri-implant bone by 3D finite element analysis, so as to supply experimental evidence for new implant system. Methods The model of the mandible with implant bone was constructed based on CT data. The elastic modulus of implants was set as 110, 90, 70, 55 and 40 GPa, respectively. The model was applied with static load of 300 N in vertical direction, 100 N in horizontal direction and 130 N in oblique direction, respectively, to stimulate occlusal state. The stresses on different parts of implants with different elastic modulus and peri-implant bone under 3 kinds of loads were calculated and analyzed. Results As the elastic modulus of implants declined, stresses in cortical bone around implants under horizontal and oblique loads decreased, and stresses in the implants showed a decreasing tendency as well. Conclusions The decrease in elastic modulus of implants can benefit the transferring of load from the implants to the surrounding bone, and reduce the risk of long-term implant failure.

Effect of various abutment systems on the removal torque and the abutment settling in the conical connection implant systems / 대한치과보철학회지

PURPOSE: The aim of this study was to evaluate the effects of different abutment materials on abutment screw loosening and settling-down effect in conical connection type implant system. MATERIALS AND METHODS: Three types of abutment, cementation, gold UCLA, and metal UCLA abutment were used. Two UCLA groups were fabricated in a similar pattern to cementation abutment. Type III gold alloy and Nickel-Chromium alloy was used for casting gold UCLA abutment and metal UCLA abutment, respectively. Fixture and abutment were tightened to 30 Ncm by using digital torque controller and re-tightening was conducted with same force after 10 minutes. Digital torque gauge was used to measure loosening torque and fixture/abutment length was measured by digital micrometer. Dynamic loads between 25 N and 250 N were applied with 0degreesangle to the abutment axis. After loading, fixture/abutment length was re-measured and amount of settlement was calculated. Loosening torque value was also measured for comparison. RESULTS: All three groups showed significant differences of length when comparing before and after loading, but there was no significant difference of settling amount in all groups. Loosening torque values were significantly decreased when comparing before and after loading in all groups(P<.05). However, there was no significant difference in loss of loosening torque values when compared to groups. CONCLUSION: In internal conical connection type implants, dynamic load affected on settlement and loosening torque of implant, but there was no differences between abutments materials. Likewise gold UCLA abutment, metal UCLA abutment might be able to withstand functional load.

Microleakage of endodontic temporary restorative materials under dynamic loading / 대한치과보존학회지

The purpose of this study was to compare the sealing abilities of four endodontic temporary restorative materials using a methylene blue dye penetration test under dynamic loading. Standardized access cavities were prepared in forty-four intact human permanent molar teeth, and the cavities were restored with Caviton, MD-Temp, IRM, or ZOE. After thermocycling, an intermittent load of 98 N at 1 Hz was applied for 1,000 cycles to the long axis of the functional cusp of each of the teeth, which were immersed in a 1% methylene blue solution. The teeth were split in half, and the linear depth of dye penetration was evaluated according to the criteria. The results were analyzed using one-way ANOVA (p = 0.05) and Duncan's multiple range test. The results demonstrated that Caviton and MD-Temp showed significantly lower microleakage than IRM and ZOE. It was concluded that Caviton and MD-Temp exhibited better sealing ability than IRM and ZOE under dynamic loading.