Color stability of bleached tooth enamel brushed with different stain-removing toothpastes

OBJECTIVE

The effects of four toothpastes on the color stability of in-office bleached tooth specimens were determined.

MATERIALS AND METHODS

We evaluated an experimental toothpaste (EXP) and three commercially available toothpastes: Colgate Optic White (OPW), Aquafresh White & Protect (AWP), and Crest 3D White (CDW). OPW, AWP, and CDW contained inorganic abrasives, whereas EXP and AWP contained sodium polyphosphate. Forty-eight randomly selected human-extracted maxillary central incisors were bleached and brushed twice daily over 30 days. We analyzed the final color difference (ΔE*ab, ΔE00 , ΔWID ), arithmetic average surface roughness (Ra) of the enamel measured on days 0 and 30, and scanning electron microscopy images of enamel surfaces and toothpastes. ΔE*ab, ΔE00 , ΔWID , and Ra were analyzed using one-way analysis of variance and Tukey's test (α = 0.05).

RESULTS

ΔE*ab and ΔE00 values were significantly lower after toothbrushing with EXP, OPW, and CDW than with AWP. OPW induced the greatest positive ΔWID . Ra was significantly increased by OPW and CDW, but slightly increased by AWP, with cube-like particles, and EXP, with no particle-like structures.

CONCLUSIONS

Only EXP stabilized the color of bleached teeth without increasing the enamel surface roughness. Sodium polyphosphate with approximately 10 phosphate groups was effective at removing stains.

CLINICAL SIGNIFICANCE

The effect of toothpaste on the color stability of bleached teeth depends on the constituting abrasives and chemical components. Polyphosphoric acid has different stain-removal effects depending on its degree of polymerization. Additionally, although certain types of abrasives may be effective for color stability, they also increase the surface roughness of the enamel.

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.

Effect of chemical surface treatment of contaminated CAD-CAM resin composite blocks on surface free energy and bond strength

PURPOSE

To evaluate the effects of four chemical treatment methods on the contaminated surfaces of VITA ENAMIC (EN) and CERASMART (CS) resin composite computer-aided design-computer-aided manufacturing blocks (RCBs).

METHODS

Each RCB was contaminated with a handpiece oil for 1 minute. These contaminated surfaces were then chemically treated by Gel Etchant (PA), Ivoclean (IC), Monobond Etch & Prime (MB), or Ceramics Etch (HF) reagents (n= 12), after which their shear bond strengths, morphologies, failure modes, and surface free energies were examined.

RESULTS

The shear bond strengths of the HF-treated surfaces significantly exceeded those of the specimens treated with the other reagents. Adhesive fractures were observed for both the EN and CS blocks after 24 hours of treatment with lubricating oil, PA, and IC. The largest numbers of mixed and cohesive fractures were detected for the MB- and HA-treated specimens. The HF-treated EN and CS blocks possessed the highest surface free energies. The bonding strengths of the resin composites decreased after the contamination of their surfaces; however, the adhesion properties of both blocks were considerably improved by chemical treatment.

CLINICAL SIGNIFICANCE

The lubricating oil contamination of dental handpieces significantly reduces the adhesion between the CAD-CAM resin composite block and the resin composite. Therefore, it is necessary to remove contamination and improve the adhesiveness using an optimal chemical surface treatment.

Effect of various resin cements and immediate dentin sealing on tooth fracture resistance of zirconia inlay restorations

PURPOSE

To compare the effect of the immediate dentin sealing (IDS) and resin cement type on fracture resistance of Class II mesio-occluso-distal (MOD) zirconia inlay restorations.

METHODS

90 Class II MOD cavities on freshly extracted human mandibular third molars, prepared with a high-speed handpiece, were divided into two groups: those with IDS (CR+) and without IDS (CR-). The CEREC system was used to prepare zirconia inlays from Katana super translucent multi-layered blocks. The inlays were cemented with one of three resin cements: RelyX Unicem 2 (RU), Multilink Automix (MA), or Super-Bond (SB). These specimens were stored in water at 37°C for 24 hours and exposed to 5,000 thermal cycles. A vertical load was applied with a metal sphere (Φ 6-mm) on a material testing system, with a crosshead speed of 0.5 mm/minute, until the specimen fractured. Fracture resistance was measured for each tooth, and the fractures were categorized according to Burke's classification. Statistical analyses were conducted using two-way ANOVA and Tukey's honest significant difference tests (P< 0.05).

RESULTS

No significant differences in tooth fracture resistance were identified between the CR+ and CR- groups. The SB group had a significantly higher fracture resistance compared to that of the MA group. Fracture morphology showed many mode IV fractures in all groups. IDS did not affect tooth fracture resistance, although there was a significant difference in tooth fracture resistance for different resin cement types used with Class II MOD zirconia inlay restorations.

CLINICAL SIGNIFICANCE

Zirconia inlay restorations provide excellent mechanical performance, morphology, and esthetic appearance. In vitro, zirconia inlays cemented with any luting resin cement restored tooth fracture resistance to levels similar to that of intact teeth. Fracture resistance varied among the different resin cements.

Effect of etching with low concentration hydrofluoric acid on the bond strength of CAD/CAM resin block

The effect of etching for 90 s with low concentrations (0.5, 1.0, 2.0, 3.0, 3.5, and 4.0%) of hydrofluoric acid (HF) on the adhesiveness of computer-aided design/computer-aided manufacturing (CAD/CAM) resin blocks [CERASMART (CS), SHOFU BLOCK HC (HC), KATANA AVENCIA Block(KA), and VITA ENAMIC (EN)] was investigated. Energy dispersive spectroscopy revealed that the silicon content of HC, KA, and EN groups remained almost constant with HF etching of ≤4%. HF etching increased the surface roughness of all blocks. The HF concentration resulting in the highest shear bond strength in each group was as follows: CS (2.0%), HC (3.0%), KA (3.5%) and EN (0.5%). Scanning electron microscopy revealed that the bonding interface of etched surfaces differed significantly from that of airborne-particle abrasion surfaces. Thus, low concentration HF etching is effective for surface treatment of CAD/CAM resin blocks. The etching effect and optimum HF concentration differ with the block composition and structure.

Effect of kinematic viscosity on the staining performance of caries detector dyes

The relationship between performance of caries detector dyes and solvent molecular weight has been reported, but viscosity has not yet been investigated. Therefore, using extracted human teeth, we compared 6 experimental caries detector dyes with different viscosities to clarify the relationship between dye viscosity and staining performance in sclerotic dentin. Carious dentin started showing dentin staining when stained with caries detector dyes with kinematic viscosity≥263 mm²/s, showed no immunoreactivity for Streptococcus mutans on immunohistochemistry, and contained dentinal tubules free of debris on scanning electron microscopy. Samples stained using a caries detector dye with kinematic viscosity of 332 mm²/s contained calcification product-like debris in the dentinal tubules. These findings suggest that the caries detector dye has a threshold kinematic viscosity between 263 and 332 mm²/s at which sclerotic dentin and tissues beyond are not stained. The caries detector dye appears to control tooth dyeability based on solvent viscosity.

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.