1964 Effect of hydroxyapatite toothpaste on vital tooth color
112 12C.GAO , H.LIU , and I.KATAYAMA , Peking University, China, Meikai University School of Dentistry, JapanOBJECTIVE
Hydroxyapatite(HAP), a registered anticaries agent in Japan, is reported to remineralize areas ofsurface and sub-surface demineralized tooth enamel.
We set out to examine the effect of such remineralization on the structure and color of human
tooth enamel, which reportedly changes up to 2 Lumin shades in color when treated with bleaches
such as hydrogen peroxide.

SEM OBSERVATION

CLINICAL TESTMATERIAL and METHODIN VITRO TESTTEST TOOTHPASTES
A commercial toothpaste containing medical grade HAP ('Apagard,' Sangi Co., Ltd., Japan)(Toothpaste A) and an identically prepared control toothpaste containing no HAP(Toothpaste B), were used in the present study. (Table 1)
CLINICAL TEST
Two groups of 6 persons each from Peking University, aged between 22 and 36 and confirmed
to have healthy teeth, participated in the study. Each group brushed their teeth 5 minutes 3 times
daily for about 30 days, one group using Toothpaste A (Group A) and the other Toothpaste B (Group B).
The color of each subject's central incisors was recorded initially, then every 2-3 days, taking
3 measurements each at the center of the labial surface using a Photoresearch Spectra-Scan PR-650
photocolorimeter (standard light source D55 , brightness 1500 Lux) to obtain CIE L*a*b* readings.
IN VITRO TEST
To evaluate results, the difference between initial and final average CIE L*a*b* values (delta E) on theVITA Lumin shade guide was calculated for each subject. This was then compared with the averagedelta E for reddish brown tabs (A1 through A4) and reddish yellow tabs (B1 through B4) on the VITA
Lumin shade guide, calculated from measurements obtained with a MURAKAMI COLOR RESEARCHLABORATORY CMS-35FS spectrophotometer.
SEM OBSERVATION
Two groups of decay-free, extracted human teeth (crown portion only) were subjected to surface
etching by 5 minutes immersion in a hydrochloric acid solution adjusted to pH 2.0. The teeth werethen brushed 5 minutes 3 times daily for 7 days (100 strokes per mintue, brushing pressure 150g),
one group with Toothpaste A and the other with Toothpaste B. Teeth were stored at 37゜C, 100% relative
humidity, between brushings. The teeth were then examined by field emission scanning electron
microscope (FE-SEM S-4500, Hitachi), using standard observation procedures.

Containing Hydroxyapatite

SEM Observation
Toothpaste A
L*

Toothpaste B

a*

b*

L*

a*

b*

Control

69.74(1.03)

7.00(1.01)

18.25(1.94)

Control

73.90(3.35)

7.33(1.01)

21.49(1.54)

2nd day

71.57(1.24)

7.26(0.65)

18.09(1.44)

3rd day

71.60(3.57)

6.77(1.23)

20.00(1.44)

6th day

71.77(2.39)

7.43(0.68)

18.15(1.57)

7th day

71.50(2.72)

6.48(0.86)

19.91(1.57)

9th day

72.28(2.23)

7.47(0.65)

18.41(1.17)

10th day71.86(2.17)

6.73(1.10)

20.34(1.36)

13th day72.05(2.28)

7.38(0.77)

18.41(3.70)

14th day

73.67(3.10)

6.71(0.93)

20.55(1.17)

16th day

72.39(1.86)

7.10(0.81)

18.41(3.70)

17th day

74.01(1.18)

6.81(1.09)

19.74(3.70)

20th day72.18(1.67)

7.14(0.96)

18.74(1.89)

21th day

72.96(3.32)

6.59(1.28)

20.09(1.96)

23th day

72.84(2.40)

6.98(1.05)

18.59(1.59)

24th day

74.24(4.18)

6.74(1.06)

20.04(1.79)

27th day73.08(2.15)

6.95(0.91)

18.38(1.76)

28th day

73.52(2.37)

6.77(0.77)

20.21(1.63)

29th day

73.21(1.38)

6.98(0.88)

18.54(1.87)

Toothpaste B

INGREDIENTS OF TEST TOOTHPASTE

70

aptho
To

Test Toothpaste

65

est

A
aphtoo
Test

After

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Before

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After

Toothpaste B

BeforeWATER
GLYCERIN
DICALCIUM PHOSPHATEDICALCIUM PHOSPHATE DIHYDRATE
MEDICAL GRADE HYDROXYAPATITESODIUM LAURYL SULFATESODIUM LAURYL SARCOSINATEFLAVORCARBOXYMETHYL CELLULOSETOCOPHEROL ACETATESODIUM SACCHARINZEOLITEPOLYETHYLENE GLYCOL
ALKYLDIAMINOETHYLGLYCINE HYDROCHLORIDE SOLUTION

Toothpaste A

Toothpaste A

RESULTS

Shade Guide

75

Ingredient

Toothpaste B

Toothpaste A

L*

Table 1

Non‑Hydroxyapatite

B

L*a*

b*

A154.09(0.01)-1.16(0.02)

4.18(0.02)

A2

53.52(0.01)-0.62(0.01)

6.34(0.01)

A3

51.75(0.02)-0.28(0.01)

7.06(0.02)

A3.5

50.00(0.02)

0.49(0.04)

10.32(0.02)

A4

48.34(0.01)

1.10(0.03)

12.12(0.04)

B154.75(0.01)-1.22(0.02)

2.31(0.02)

B2

53.92(0.01)-1.35(0.03)

5.68(0.04)

B3

50.91(0.01)-0.37(0.05)

9.39(0.03)

B4

48.91(0.01)-0.08(0.04)

11.15(0.05)

CLINICAL
Teeth of subjects in Group A showed a distinct increase in brightness (L*) in the first weekof the study, followed by a small but steady increase thereafter. Almost no change in the otherparameters recorded was seen. Teeth of subjects in Group B showed decreased brightness (L*)
in the first week, but steadily returned to their initial level of brightness. No change in the otherparameters recorded was seen.
Average delta E values were calculated at 3.48 for Group A, 1.45 for Group B and 2.52 for A tabs
and 3.55 for B tabs on the Lumin scale. Expressed in terms of Lumin equivalent, the increase inbrightness in the teeth of subjects in Group A corresponded to almost 1.4 tabs (1.38) on the reddish
brown scale and almost 1 tab (0.98) on the reddish yellow scale.
IN VITRO
FE-SEM observation showed a fine particle coating on the etched surface of extracted teeth brushedwith Toothpaste A, and a relatively smooth tooth surface. Teeth brushed with Toothpaste B showed
an uneven surface and areas of damage to the surface crystals.

CONCLUSION
Though less powerful than bleaches, the results suggest HAP-containing toothpaste can alter toothcolor by at least one shade with daily brushing, and this effect may be related to its enamelrecrystallization properties.