Restoration of Post-Bleach Enamel Gloss Using a Non-Abrasive, Nano-Hydroxyapatite Conditioner

1670

R.TAKIKAWA, K.FUJITA, T.ISHIZAKI, and R.HAYMANSANGI Co.,Ltd.Tokyo,Japan

1. Aim of Study
In recent years, vital tooth bleaching has become widespread in esthetic dentistry, as a convenient means ofimproving tooth color with only minimal invasive impact. However bleaching can result in postoperativechanges such as roughness, white turbidity or lack of gloss, giving a matt appearance to the enaml surface.
We developed a nano-hydroxyapatite conditioning agent, Renamel AfterBleach, designed to restore tooth
enamel after bleaching, and examined its effect on the gloss post-bleach enamel. We also considered a new
method of gloss measurement potentially more applicable to irregular surfaces such as tooth enamel than
traditional methods.

2-3. Application & Evaluation of Post-Bleach Enamel Surface Treatment
Two groups of mirror polished enamel specimens were prepared as described in 2-2, and polished to a standard surface gloss of (G) = 200±10. Surface roughness (Ra) for each sample was measured by scanning probe microscope (SPM) (SPI4000, SEIKO INSTRUMENTS.)(scanning area : 50×50μm, dynamic force mode). Specimens from each group were then bleached with Hi-Lite (SHOFU) (35% H2O2) according to the maker's instructions, and immersed at 37℃ overnight in a solution of either Renamel AfterBleach (SANGI) or a standard
commercially available fluoride gel. After each treatment, all specimens were washed for 1 minute in an ultrasonic bath (BRANSONIC Ultrasonic Cleaner, 60watts), and surface gloss (G) was measured by SGA and surface roughness (Ra) by SPM.
RR3. Observation and Data

4. Results

Digital camera image

UF1200 / Gloss 282

Fig.3. Comparison of shade guide* seen by digital camera and SGA*VITAPAN classical Shade Guide A3400

＊

＊

＊

UF1200300
Gloss

2Surface Gloss Analysis (SGA) System

R ＝0.9956

UF800

200

100

Computer
COM 14-1. Surface Gloss Analysis (SGA)
Comparison of the same shade guide image (Fig.3), as seen by digital camera and SGA,
showed that using SGA, high gloss points take on a white, bright image while low gloss points
take on a dark image similar to the gloss images of the shade guide, which are visible to thenaked eye. In additon, SGA allows quantification of the gloss values for irregular or arch-shaped bodies such as the teeth.
4-2. Correlation Between Surface Abrasion and Gloss
A statistical correlation was observed between surface gloss (G) and the level of abrasive, i.e.
grit size (μm), used for surface polishing of standard specimens (Fig.4), and a similartendency was observed in both SGA and digital camera images of the same (Fig.5).

4-3. Effect of Post-Bleach Enamel Treatment
Observation of the enamel surface by SPM and SGA respectively showed a significant increasein surface roughness (Ra) and decrease in surface gloss (G) after bleaching, but a significant
decrease in surface roughness and increase in surface gloss after post-bleaching treatment withboth of the agents tested (Fig.6 & 7). However the reduction in surface roughness and increasein surface gloss were significantly greater after treatment with Renamel AfterBleach thanwith the fluoride gel.
R

#600

00W1P2

MonitorDate Monitor＃600 / Gloss 67

UF800 / Gloss 192

Digital camera image2-1. Gloss Measurement Apparatus
To measure gloss (G), we used a materials surface analysis system, the Model 806H Hand-Held Surface
Gloss Analyzer (SGA) (TRICOR SYSTEMS) which comprises a configured light source (four 24-wattfluorescent lights, 4100ﾟK), CCD camera (240,000 sample points, 256 gradation sequence) and analysis
computer fitted with the maker's Wgloss Ver3.52 gloss calculation software (Fig.1). In addition, tomaintain the sample surface constantly at a regular height, a miniature high-precision ZF-axis motorizedstage, the SGSP80-20ZF(SIGMA KOKI) (a), was fitted to the sample platform, the sample was illuminatedby laser from the side, using an Easy Laser Leveler BDL210S (BLACK&DECKER) (b), and the height ofthe sample adjusted by a two-axis stage controller, the Mark-102(SIGMA KOKI) (c) (Fig.2). The SGA wascalibrated at (G) 274, using the black calibration reference plate provided, and to demonstrate its
characteristics, a standard VITAPAN classical Shade Guide was used as the object for measurement, andthe result compared with an image of the same shade guide taken by digital camera (EOS Kiss Digital)(CANON) (Fig.3).

SGA image

SGA image

2. Materials and Methods

Statistical analysis was performed using Student's t-test.

Model 806H
CCD Camera

Input

10
Grit size(μm)

1520( ＊: P<0.0001, t-test )5. Conclusion

Fig.5. Comparison between gloss and grit size (μm) of abrasive paper
used for polishing as seen by digital camera and SGA

Fig.4. Correlation between gloss and grit size(μm) ofabrasive papers* used to polish enamel surface (n=10)

cKeyboard

5Light Source*BUEHLER Grit No. UF1200, UF800, #600
Measurement Sample

115/220
VacKeyboard

12V P.S.

b115/220
Vac

・SGA is an effective method for evaluating tooth surface gloss, allowing it to be quantitatively
expressed, despite the tooth's irregular form.

a115/220
Vac

Mouse

・Our results demonstrated that Renamel AfterBleach showed greater ability to restore
smoothness and gloss to tooth enamel after bleaching than a standard commerciallyavailable fluoride gel.
R＊＊＊

Fig.2. Dedicated sample stage

＊

240

＊

＊

210
Gloss (G)2-2. Preparation & Gloss Evaluation of Standard Specimens
Sound extracted human teeth were cut into approximately 4×5×3mm blocks with a dental hand engine(EX, Royal) fitted with a diamond disk (SHOFU). The enamel surface was then polished with abrasive
papers #600 (grit size 14.5μm), UF800 (8.4μm), or UF1200(5μm) (BUEHLER) respectively under
running water, to provide three groups of standard specimens (n=10 each) : mirror polished (UF1200),regular polished (UF800), and rough polished (#600).
(G) was then measured for each group by SGA , and the relation between gloss and condition of the enamelsurface examined. In addition, specimens in each group were photographed with a digital camera (EOSKiss Digital, CANON), fitted with a polarizing filter (58mm Circular Polarizing Filter PL-C, CANON),
to allow comparison and visual assessment of the polishing standard specimens.

＊＊

100.00mean of surface roughness : Ra(nm)Fig.1. Tricor Model 806H surface analysis system

212
199
180
181
171

We concluded that Renamel AfterBleach and SGA could contribute to esthetic dentistry, byrespectively enhancing the benefit of bleaching to the patient and providing a more accurateevaluation of such benefit.
R80.00

60.00
74.73

40.00

53.50

50.43
36.07

20.00

0.00

150
Control

After bleaching

After bleaching and treatment After bleaching and treatment
with fluoride gelwith Renamel conditionerR( ＊: P<0.0001 )Fig.6. Change in enamel surface gloss after each treatment

Control

After bleaching

After bleaching and treatment After bleaching and treatment
with fluoride gelwith Renamel conditionerR( ＊: P<0.0001 )Fig.7. Mean of surface roughness:Ra(nm)change in enamel surface after each treatment

84th General Session & Exhibition of the IADR/ June, 2006
E-mail : taki@sangi-j.co.jp