Influence of the Crystallization Firing Process on Marginal and Internal Adaptation of Silicate-based Glass-ceramic Inlays Fabricated With a CAD/CAM Chairside System

OBJECTIVE

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used in dental treatment. Clinicians can use chairside CAD/CAM technology, which has the advantage of being able to fabricate inlays on the same day. We aimed to evaluate the effects of crystallization firing processes, fabrication methods (one-step and two-step), and materials on marginal and internal adaptations of silicate-based glass-ceramic all-ceramic inlays fabricated with CAD/CAM chairside systems.

METHODS

Ten artificial mandibular left first molars were prepared with standardized ceramic class II mesialocclusal (MO) inlay cavities. Optical impressions were obtained using CEREC Omnicam Ban. IPS e-max CAD (IE), (Ivoclar Vivadent, Schaan, Liechtenstein), Initial LiSi Block (LS) (Hongo, Bunkyoku, Tokyo, Japan), VITA Suprinity (SP), (Vita Zahnfabrick, Bad Säckingen, Germany), and Celtra Duo (CD) (Ivoclar Vivadent, Schaan, Liechtenstein) (n=10) were milled using CEREC MC XL (Bensheim, Germany). IE and SP were crystallization-fired using CEREC Speed Fire. The silicone replica technique was used for the measurement of internal (axial and pulpal walls) and marginal (cervical and occlusal edge) adaptations. The adaptations were measured using a thin layer of light-body polyvinyl siloxane impression material placed between the master tooth inlay preparation and restoration. Marginal and internal adaptations of IE, LS, SP, and CD were measured using a stereomicroscope (500×). For IE and SP, marginal and internal adaptations were measured before and after the crystallization firing process. Data analyses were conducted using one-way ANOVA and the Tukey test. For IE and SP, marginal and internal adaptations before and after the crystallization firing process were analyzed using the t-test. The significance level was set at α=0.05.

RESULTS

One-way ANOVA revealed statistically significant differences in occlusal and cervical edge marginal adaptations among the material groups (p<0.001). The Tukey HSD test revealed a significant difference in marginal occlusal and cervical edge adaptations between LS and CD groups and IE and SP groups (p≤0.05). For IE and SP inlays, the t-test revealed a significant difference between occlusal and cervical edge adaptations before the crystallization firing process and those after the crystallization firing process, with the latter group showing a more significant discrepancy in adaptation than the former group (p≤0.05).

CONCLUSIONS

Fabrication methods (one- and two-step) affected the marginal adaptation compatibility but not internal compatibility of MO inlays. The crystallization firing process affected the marginal adaptation of inlays using lithium silicate or lithium disilicate glass-ceramics. However, adaptation to the cavity was considered clinically acceptable for all materials.

Buoyancy and maximal diving depth in penguins

Using a newly developed data logger to measure acceleration, we demonstrate that free-ranging king and Adélie penguins only beat their flippers substantially during the first part of descent or when they were presumed to be chasing prey at the bottom of dives. Flipper beating stopped during the latter part of ascent: at 29±9 % (mean ± S.D.) of dive depth(mean dive depth=136.8±145.1 m, N=425 dives) in king penguins,and at 52±20 % of dive depth (mean dive depth=72.9±70.5 m, N=664 dives) in Adélie penguins. Propulsive swim speeds of both species were approximately 2 m s-1 during dives; however, a marked increase in speed, up to approximately 2.9 m s-1, sometimes occurred in king penguins during the passive ascending periods. During the prolonged ascending, oblique ascent angle and slowdown near the surface may represent one way to avoid the potential risk of decompression sickness. Biomechanical calculations for data from free-ranging king and Adélie penguins indicate that the air volume of the birds (respiratory system and plumage) can provide enough buoyancy for the passive ascent. When comparing the passive ascents for shallow and deep dives, there is a positive correlation between air volume and the depth of the dive. This suggests that penguins regulate their air volume to optimize the costs and benefits of buoyancy.

Combined grafting of thoracic aortic aneurysm and cardiac repair using continuous cold-blood coronary perfusion

OBJECTIVE

For patients diagnosed with combined thoracic aortic aneurysms and cardiac lesions, we conduct a 1-stage operation for ascending and aortic arch grafting. We studied surgical outcome comparatively with patients undergoing aortic grafting alone. For descending and thoracoabdominal aortic grafting, we choose a 2-stage operation.

SUBJECTS AND METHODS

Subjects were 80 patients undergoing ascending and aortic arch aneurysm repair between June 1994 and March 1999. Group 1 consisted of 30 undergoing simultaneous cardiac repair. Concomitant cardiac procedures involved 21 valvular, 5 coronary arterial, and 4 valvular and coronary arterial surgeries. Group 2 consisted of 50 undergoing aortic grafting alone. We used crystalloid cardioplegia and additional antegrade continuous cold-blood coronary perfusion in Group 1, and crystalloid cardioplegia alone in Group 2.

RESULTS

Hospital mortality was 10% in Group 1 and 2% in Group 2. Surgery length, cardiopulmonary bypass time, and aortic cross-clamping time in Group 1 were significantly longer than Group 2. Myocardial ischemic time did not differ significantly. Postoperative ICU stay, mechanical ventilation time and catecholamine support time did not differ significantly. Actuarial survival was 66.9 +/- 13.1% at 52 months in Group 1 and 87.2 +/- 4.8% at 57 months in Group 2 (p = 0.2918).

CONCLUSION

Simultaneous cardiac repair and ascending and aortic arch aneurysm repair were conducted using continuous cold-blood coronary perfusion. Hospital mortality and mid-term survival did not differ significantly between groups.

[Aortic valve reconstruction of aortic root repair]

We report the choice of aortic valve reconstruction, surgical results and postoperative results in 22 patients who underwent aortic root replacement between June 1996 and October 1999. We chose the replacement using bio-prosthesis in six patients over 65 years of age and valve preservation or replacement using mechanical prosthesis in sixteen patients under 65 years of age. Ten patients underwent valve replacement using mechanical prosthesis. There was one hospital death and one late death. Six patients underwent valve replacement using bio-prosthesis. There was no hospital death and no late death. Six patients underwent valve preservation. There was one hospital death. There was no event among five patients in the mid-term follow-up, although a longer follow-up must be necessary.

Precise monitoring of porpoising behaviour of Adelie penguins determined using acceleration data loggers

A new method using acceleration data loggers enabled us to measure the porpoising behaviour of Adelie penguins (Pygoscelis adeliae), defined as a continuous rapid swimming with rhythmic serial leaps. Previous hydrodynamic models suggested that leaping would be energetically cheaper when an animal swims continuously at depths of less than three maximum body diameters below the water surface. In the present study, free-ranging Adelie penguins leapt at a mean speed of 2.8 m s(−)(1) above the predicted threshold speed (0.18-1. 88 m s(−)(1)). Wild penguins reduced drag by swimming deeper (0.91 m) and did not swim continuously within the high-drag layer while submerged. This indicates that previous calculations may be incomplete. Moreover, leaps represented an average of only 3.8 % of the total distance travelled during the porpoising cycle, which would make energy savings marginal. Among the six penguins used in our study, two did not porpoise and three porpoised for less than 7 min, also indicating that this behaviour was not important during travel to and from foraging sites, as has been previously suggested. Birds mainly porpoised at the start and end of a trip. One explanation of porpoising might be an escape behaviour from predators.