Earticle

Purpose: The purpose of this study was to assess precision of crown prostheses that were fabricated by using 2 kinds of bur or 3 kinds of bur. Methods: The crowns were fabricated by using the first molar of the right maxillary in this study. The abutments that were prepared were scanned by using a scanner and designed by using CAD software. Based on the crown design, NC data were created with CAM software. The created NC data were used while fabricating the crown prostheses by using 5-axis milling machine. Scanning was done for the internal and external surface of the completed crown prostheses and 3-dimensional measurement was conducted for precision assessment. Results: The RMS±SD value for the external surface of the crown prostheses that was fabricated by using two burs and three burs were 28.5±4.1㎛ and 19.1±2.8㎛, respectively; and the value for two burs were bigger than that for three burs with statistical significance (p<0.001). The RMS±SD value for the internal surface of the crown prostheses that was fabricated by using two burs and three burs were 14.9±1.9㎛ and 13.3±2.5㎛, respectively;and the value for two burs were bigger than that for three burs but with no statistical significance. Conclusion: Based on this study, the prostheses that were fabricated by using 3 bur presented better stability compared to those that were fabricated by using 2 bur and statistically significant difference was found only in the external surface.

Purpose: The purpose of this study was to assess the internal fitness of the PMMA 3-unit bridge that was fabricated with 5-axis milling machine and to verify the clinically allowable values. Methods: For fabrication of the crown bridge in this study, 25-27 abutment teeth were used. The prepare abutment teeth were scanned with a scanner and 3-unit bridge was designed by using design software. Upon the completion of the design, the 3-unit bridge was fabricated by using a PMMA block with 5-axis milling machine. The internal surface of the fabricated 3-unit bridge was scanned by using a scanner and the difference between the 3-unit bridge and the abutment teeth was assessed by merging them together. Results: RMS±SD values for PRE group, MOL group, and BRI group were 51.2±18.2, 44.8±10.0, and 52.1±8.3㎛, respectively. The mean of the PRE group was bigger than that of the MOL and BRI group; however, statistically significant difference was not found (p>0.05). Conclusion: The PMMA 3-unit bridge that was fabricated with 5-axis milling machine presented stable internal values for each crown and overall internal values were within the range of clinically allowable values.

Purpose: This study was to evaluate the shear bond strength of ceramic fused to Ni-Cr alloy(Alophaloy) by heat treatment. Methods: The specimens were divided into 5 groups according to heat treatment conditions prior to porcelain application. Eighteen specimens from each group were subjected to the shear load a universal testing machine using a 0.1㎜/min cross-head speed and two specimens from each group were observed with SEM and EDX line profile. Results: The observation of the oxide film on the metal surface by SEM photograph showed a coarsening with an increasing degassing hold time. The diffusion of metal oxide was observed farther from the opaque layer in the heat treated specimen than no heat treated specimen. The shear bond strength measured highest to A5(55.23MPa) in the 10min holding group and measured lowest from A1(24.38MPa) in the no heat treated group, and there was a significant difference(p<0.05). Conclusion: The shear bond strength of Ni-Cr alloy improved in the heat treatment compared to the no heat treatment specimen.

Purpose: The aim of this study was to make nanomesh on the surface of titanium by potentiostatic technique which was done at the suitable potential level. Methods: In order to find the suitable potential level, use a 25℃ NaCl, NaOH and NH4F solution of 1 M and 5M as supporting electrolyte, working electrode(positive potential) was contact to the titanium specimen and counter electrode(negative potential) was contact to the Pt substrate. At the transpassive potential which was observed by potentiostatic technique, potentiostatic technique was done for 2hours. Results: As a result, 1 M NaOH solution was suitable as a supporting electrolyte, potentiostatic technique used a 25℃ NaOH solution of 1 M for 2hours, nanomesh was formed. Conclusion: The potentiostatic technique was used 25℃ NaOH solution of 1 M and 5 M as supporting electrolyte for 2hours. Nanomesh was built more uniform and fine in 1 M NaOH solution than 5 M NaOH solution.

Purpose: This study aims to offer fundamental data to develop a career program that helps the dental technology students find a proper and desired job position and to be satisfied with their job. To this goal, we analysed the differences found between the personality type, major satisfaction, job satisfaction, and preference in job position among the dental technology students. Method: We conducted a survey using Myers-Briggs Type Indicator among the subjects who are sophomores and juniors of the dental technology department of a university in Gangwon province. Our analysis was grounded on 130 valid questionnaires. Results: The results are summarized as follows: In personality type ESTJ turned out the highest as 20.0%, while ENTP was the lowest as 0.8%. The preference was revealed as Extraversion (66.9%), Sensing (74.6%), Feeling (50.8%), Judging (61.5%) respectively. Of the general characteristics, only the religious or non-religious state was statistically meaningful as (p<. 05) in emotional type (F). No statistical significance was found in the major satisfaction. The job satisfaction was statistically meaningful as p<. 05 in Judgemental type (J). GPA was statistically significant as p<. 05 in the sensory type of the personality type. Desired job position was statistically meaningful as p<. 05 in emotional and cognitive types. Conclusion: We found a meaningful difference in the job satisfaction and the desired job position with respect to the personality type of dental technology students. However clear explanation of the correlations among these factors requires a more comprehensive survey and various approaches from the personality and psychology tests, which is to follow.