ABSTRACT
The purpose of this study was to investigate the effect of glazing treatment of multi-colored zirconia disc and lithium disilicate block on the optical properties. From an Ultra Translucent Multi-Layered (UTML) disc containing 50% cubic crystal and a lithium disilicate-based Amber Mill Direct (AMD) block, the 1.2 mm thick specimens of the upper layer (T), the center (M), and the lower layer (B) were prepared. Three types of paste glaze of InSync Glaze Paste, IPS E.max Ceram Glaze Paste, and Amber Ceram G7 Glaze Paste were applied and fired to a uniform thickness on the surface of the specimen. CIE L * , a * , b * values were measured using a spectrophotometer and contrast and translucency were calculated. The bonding interface with the glaze layer was observed using HR FE-SEM. In the glazed groups, L * value increased, but a * value and b * value decreased. The translucency value measured in the untreated group was statically higher in the AMD groups than in UTML groups (P0.05), but significantly decreased compared to the untreated group after glazing treatment in the AMD group (P<0.05). The contrast ratios generally increased after glaze treatment compared to the untreated group. Since the glaze treatment can affect the optical properties of ceramic restorations, the choice of glaze should be considered important for the desired color by the dental technician.
ABSTRACT
The purpose of this study was to evaluate the structural characteristics of the thread length of orthodontic mini-screws and the effects of insertion and removal torques according to the formation of the cutting flute. Two types of mini-screws were made, with a thread length of 6.0 mm and a thread length of 3.3 mm. In order to examine the effect of flute formation, the experiment group was divided into a miniscrew test group with flute formation and an experiment group without flute formation. To evaluate the effect of flute formation, two flutes were formed at 180°on the circumference, and at the tip of the mini screw, up to 4 mm for thread length of 6.0 mm and 2.4 mm for thread length of 3.3 mm. A biomechanical test block formed of 2 mm cortical bone and 10 mm cancellous bone was used to eliminate the influence of the difference in cortical bone thickness and bone density according to the insertion site. 1 mm diameter guide hole was drilled on the test block and the mini-screw was placed vertically. Using a 0.1 N·cm precision digital torque gauge, the maximum torque value was recorded at this time by embedding it to the top of the screw under a static load of 1.2 kg and the value when it was removed in the opposite direction. The insertion torque values for the 6.0 mm and 3.3 mm length mini screws were (29.53±1.84) N·cm and (26.84±2.15) N·cm, and the removal torque values are (14.50±1.37) N·cm and (13.15±2.89) N·cm, respectively.There were no statistically significant differences (P>0.05). The flute of 6.0 mm mini-screws had no statistically significant difference in both insertion and removal torque values and increased to (30.13±1.97) N·cm and (18.65±1.10) N·cm (P>0.05). In experiments with 3.3 mm mini-screws, the insertion and removal torque values decreased to (20.99±3.94) N·cm and (11.32±2.03) N·cm, respectively, showing a statistically significant decrease only in the insertion torque values (P<0.05). The insertion and removal torque values of the mini-screw were not significantly increased even when the screw length was doubled, and the flute formation effect was different with the screw length.
ABSTRACT
The purpose of this study was to investigate the effect of glazing treatment of multi-colored zirconia disc and lithium disilicate block on the optical properties. From an Ultra Translucent Multi-Layered (UTML) disc containing 50% cubic crystal and a lithium disilicate-based Amber Mill Direct (AMD) block, the 1.2 mm thick specimens of the upper layer (T), the center (M), and the lower layer (B) were prepared. Three types of paste glaze of InSync Glaze Paste, IPS E.max Ceram Glaze Paste, and Amber Ceram G7 Glaze Paste were applied and fired to a uniform thickness on the surface of the specimen. CIE L * , a * , b * values were measured using a spectrophotometer and contrast and translucency were calculated. The bonding interface with the glaze layer was observed using HR FE-SEM. In the glazed groups, L * value increased, but a * value and b * value decreased. The translucency value measured in the untreated group was statically higher in the AMD groups than in UTML groups (P0.05), but significantly decreased compared to the untreated group after glazing treatment in the AMD group (P<0.05). The contrast ratios generally increased after glaze treatment compared to the untreated group. Since the glaze treatment can affect the optical properties of ceramic restorations, the choice of glaze should be considered important for the desired color by the dental technician.
ABSTRACT
The purpose of this study was to evaluate the structural characteristics of the thread length of orthodontic mini-screws and the effects of insertion and removal torques according to the formation of the cutting flute. Two types of mini-screws were made, with a thread length of 6.0 mm and a thread length of 3.3 mm. In order to examine the effect of flute formation, the experiment group was divided into a miniscrew test group with flute formation and an experiment group without flute formation. To evaluate the effect of flute formation, two flutes were formed at 180°on the circumference, and at the tip of the mini screw, up to 4 mm for thread length of 6.0 mm and 2.4 mm for thread length of 3.3 mm. A biomechanical test block formed of 2 mm cortical bone and 10 mm cancellous bone was used to eliminate the influence of the difference in cortical bone thickness and bone density according to the insertion site. 1 mm diameter guide hole was drilled on the test block and the mini-screw was placed vertically. Using a 0.1 N·cm precision digital torque gauge, the maximum torque value was recorded at this time by embedding it to the top of the screw under a static load of 1.2 kg and the value when it was removed in the opposite direction. The insertion torque values for the 6.0 mm and 3.3 mm length mini screws were (29.53±1.84) N·cm and (26.84±2.15) N·cm, and the removal torque values are (14.50±1.37) N·cm and (13.15±2.89) N·cm, respectively.There were no statistically significant differences (P>0.05). The flute of 6.0 mm mini-screws had no statistically significant difference in both insertion and removal torque values and increased to (30.13±1.97) N·cm and (18.65±1.10) N·cm (P>0.05). In experiments with 3.3 mm mini-screws, the insertion and removal torque values decreased to (20.99±3.94) N·cm and (11.32±2.03) N·cm, respectively, showing a statistically significant decrease only in the insertion torque values (P<0.05). The insertion and removal torque values of the mini-screw were not significantly increased even when the screw length was doubled, and the flute formation effect was different with the screw length.