Evaluation of stability of interface between CCM (Co-Cr-Mo) UCLA abutment and external hex implant

PURPOSE: The purpose of this study is to evaluate the stability of interface between Co-Cr-Mo (CCM) UCLA abutment and external hex implant. MATERIALS AND METHODS: Sixteen external hex implant fixtures were assigned to two groups (CCM and Gold group) and were embedded in molds using clear acrylic resin. Screw-retained prostheses were constructed using CCM UCLA abutment and Gold UCLA abutment. The external implant fixture and screw-retained prostheses were connected using abutment screws. After the abutments were tightened to 30 Ncm torque, 5 kg thermocyclic functional loading was applied by chewing simulator. A target of 1.0 × 10⁶ cycles was applied. After cyclic loading, removal torque values were recorded using a driving torque tester, and the interface between implant fixture and abutment was evaluated by scanning electronic microscope (SEM). The means and standard deviations (SD) between the CCM and Gold groups were analyzed with independent t-test at the significance level of 0.05. RESULTS: Fractures of crowns, abutments, abutment screws, and fixtures and loosening of abutment screws were not observed after thermocyclic loading. There were no statistically significant differences at the recorded removal torque values between CCM and Gold groups (P>.05). SEM analysis revealed that remarkable wear patterns were observed at the abutment interface only for Gold UCLA abutments. Those patterns were not observed for other specimens. CONCLUSION: Within the limit of this study, CCM UCLA abutment has no statistically significant difference in the stability of interface with external hex implant, compared with Gold UCLA abutment.

Study on Cognitive Reserve in Korea Using Korean Version of Cognitive Reserve Index Questionnaire / 신경정신의학

OBJECTIVES: To evaluate cognitive reserve in Korea using Korean version of Cognitive Reserve Index questionnaire (K-CRIq) and to investigate the effects of gender and age on cognitive reserve. METHODS: Three hundred and fifty-eight healthy subjects aged 25–85 years old in one community participated in the study. K-CRIq was developed and administered to all subjects to assess the effects of gender and age on cognitive reserve. Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were administered to subjects over 65 years old to test concurrent validity. RESULTS: Age and gender as well as their interaction significantly affected Cognitive Reserve Index (CRI) score. Men had higher cognitive reserve than women over 45 years old, but at younger ages there was no gender difference in cognitive reserve. CRI score and sub-scores were strongly associated with the MMSE and MoCA. CONCLUSION: The results indicate that the gender effect on cognitive reserve is disappearing in the young generation in Korea. Scores in neuropsychological tests are predicted well by the CRI score.