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Study design: Light microscope (polarized light microscopy), scanning electron microscope, x-ray (contact micro radiography) and microsensor study of artificial caries lesions on enamel before and after treatment with artificial salvia and a hydroxyapatite suspension.
Results: Remineralisation of the enamel surface (A) and the subsurface areas (B) was increased by application of an aqueous hydroxyapatite suspension.
I Ref.: Okashi T, Kani T, Isozaki A, Nishida A, Shintani H, Tokumoto T, Ishizu E, Kuwahara Y, Kani, M: Remineralization of artificial caries lesions by Hydroxyapatite. I Dent Health 41, 214 – 223 (1991).
II Ref.: Kani T, Kani M, Isozaki A, Kato H, Fukuoka Y, Ohashi T, Tokumoto T: The effect of apatitecontaining dentifrices on artificial caries lesions. I Dent Health 38, 364–366 (1988).
(A) Scanning electron microscope analysis of the examined enamel samples
(B) Light microscope analysis of the periferal surface zonae
Periferal zone of an artificial enamel caries after storage in distilled water (control) compared with a sample treated with hydroxyapatite in a toothpaste. The black ribbon shows the occurrence of a demineralised layer in each case.
Hydroxyapatite suspensions reduce caries incidence
Study design: Randomised study with 181 children (92 boys, 89 girls) from different japanese schools over a period of 3 years. After lunch the children brushed their teeth under supervision with a toothpaste containing 5 % hydroxyapatite and a control group with a paste without hydroxyapatite. Yearly controls of the DMFT index were diagnosed as well as the caries incidence on newly erupted teeth.
Results: 1. The DMFT index were significantly deeper in the apatite group. 2. The incidence for caries in newly erupted teeth was significantly lower compared to control.
Ref.: Kani T, Kani M, Isozaki A, Shintani H, Ohashi T, Tokumoto T: Effect to apatite-containing dentifrices on dental caries in school children. I Dent Health 39, 104 – 109 (1989).
Hydroxyapatite suspensions lead to smoother teeth surfaces and reduce bacterial plaque formation
Study design: Under standardised conditions samples of enamel from freshly extracted human teeth were flat polished and treated with 3 polishing pastes with increasing RDA numbers (120/170/250) followed by remineralisation with a hydroxyapatite containing tooth cream. Examination of the surface was done by SEM (scanning electron microscope) for colonisation with streptococcus mutans bacteria.
- Roughness of the sample increased with the increased RDA numbers.
- Treatment with a hydroxyapatite paste formed a surface roughness lower than before polishing.
- After polishing, the speed of colonisation with SM germs increased significantly, and could be reduced successfully with the hydroxyapatite suspension.
Ref.: Nishio M, Kawamata H, Fujita K, Ishizaki T, Hayman R, Ikemi T: A new enamel restoring agent for use after PMTC. Posterpresentation 82nd General Session & Exhibition of the IADR / March 2004.
Hydroxyapatite seals bleached enamel
Study design: Cleaned samples of enamel from freshly extracted human teeth were sealed with nail varish leaving a window and were treated with a bleaching cream containing 35 % hydrogen preroxide. After the bleaching a part of the samples were polished with a hydroxyapatite containing suspension for 20 seconds. The surfaces were examined and compared with a scanning electron microscope with a colour penetration test.
- The »cleaned« samples showed some signs from tootbrushing.
- The bleached surfaces were rougher than the nonbleached.
- The bleached samples treated with hydroxyapatite were smoother then without.
- The bleached as well as the hydroxyapatite treated samples showed some colour penetration whereas the penetration was deeper in the non hydroxyapatite treated group.
Ref.: Kawamata H, Nishio M, Fujita K, Ishizaki T, Hayman R, Ikemi T: Posterpresentation 82nd General Session & Exhibition of the IADR / March 2004.
Hydroxyapatite in toothpaste leads to brightening and higher gloss
Study design 1: Interactions with polishing properties The study was done with extracted teeth which were treated with toothpastes containing different amounts of hydroxyapatite (15 %, 3 % and 0 %) and special pastes (20 and 60 %). The pastes were mixed with water 1:1 delution and the teeth were polished every 15 minutes over a 5 hour period.
Study design 2: Influence on brightnes and gloss 12 Volunteers between 20 and 50 who had never used hydroxyapatite toothpaste before brushed their teeth for two weeks with a toothpaste without hydroxyapatite. The brightness and gloss were measured both before und after the two weeks. This group was then separated in two groups, the first used a toothpaste containing 3 % and the other the same paste but with 15 %. After 2, 4 and 6 weeks the development of brightness and gloss was measured.
- The variation of the hydroxyapatite content did not influence the polishing properties.
- Toothpastes containing hydroxyapatite lead to brigther teeth.
- Interactions between polishing properties and brightening properties could not be found.
Ref.: Niwa M, Sato T, Li W, Aoki H: Polishing and Whitening Properties of Toothpaste, J Mater Sci, Mater Med 12, 277 – 81 (2001).