Papers by Author: Yong Duk Park

Abstract: Hydroxyapatite has high affinity rate with organic substance in an oral cavity, therefore lately nano-sized hydroxyapatite is extensively researched to increase affinity to tooth and remineralization. The objective of this research is indirectly to investigate the effect of nanohydroxyapatite on remineralization using valuation about whiteness and bacterial contamination of the bovine tooth. We have designed in vitro test for this purpose. The bovine teeth are sliced into human teeth size then the baseline whiteness of total 60 teeth is measured and assigned into 3 groups by cross-matching according to the whiteness. These samples were embedded into resin mold and underwent mechanical brushing during fixed schedule. The whiteness and bacterial contamination of teeth are measured and compared among 3 groups. Each dentifrice used in the experiment is composed of B.S.I group (30% Calcium Carbonate, precipitated-CaCo3) with abrasion rate of 100, Test Ⅰgroup (15% Sodium Metaphosphate, insoluble-NaPo3), Test Ⅱ group (15% Nano-hydroxyapate-Ca10(PO4)6(OH)2. After 20,000 strokes of mechanical brushing with each group sample teeth whiteness is measured for 2nd time and then the sample teeth were submerged into the same solution with oral bacteria for 10 days. The teeth whiteness is measured again for 3rd time and the bacteria from the surface of teeth are cultivated on agar badge for 3 days. We have compared with average of whiteness before and after test in group and each other 3 group. The whiteness of teeth was maintained in test group II, however in other group the whiteness achieved through brushing was lost. Also, Group II had the smallest area of bacterial colony on agar badge (p<0.01). It is concluded that the dentifrice including the nano-hydroxyapatite is replaced with the organic substance in enamel resulting the increase in whiteness and the resistance to bacterial colonization, which leads to the increase the enamel remineralization in teeth and result to decrease in caries susceptibility.

Abstract: The aim of this in vitro study was to evaluate the tooth whitening effect of toothpaste containing nano-sized hydroxyapatite (HA). There were 3 types of dentifrices, which had a different level of abrasive components. For group 1, a newly developed toothpaste containing Nano-sized hydroxyapatite (Nano-HA) was used. Commercially available toothpastes were used in groups 2 and 3. Group 2 used toothpastes containing silica and multi phosphate. Group 3 used toothpastes containing abrasives with silica and micro-sized HA. In order to simulate 6-months of tooth brushing, the tooth specimens in all 3 groups were placed on a V8 Cross Brushing Machine (Sabri Co. U.S.A.) and brushed 10,000 times with the toothpaste slurries. The tooth specimens were then soaked in artificial saliva for 24 hours to create conditions similar to those encountered in vivo. The whitening efficacy was assessed before and after tooth brushing using the VITA shade scores of Shadeeye-EX NCC Dental Chroma meter (Shofu Co. Japan). All toothpastes produced significant differences in the mean shade change in the teeth before and after tooth brushing (p<0.05). However, there were no significant differences in the change in the shade between each group (p>0.05). Although the new Nano-HA toothpaste did not have superior whitening effects to the commercially available whitening toothpastes, they had a similar whitening efficacy to commercially available whitening toothpastes. These effects might come from the physical properties of Nano HA, which increase the surface dimension more than the Micro-sized HA and have the potential of remineralization.

Abstract: Hydroxyapatite is the main component of enamel that gives the tooth a bright white appearance and eliminates the diffused reflection of light by filling up the fine pores of the tooth surface. Accordingly, remineralization of the teeth can be expected to some extent if hydroxyapatite is used to treat an incipient caries lesion (early white spot lesion). In addition, the remineralization effect will be increased if the particle size of hydroxyapatite can be reduced to less than that of the micron-size in existing toothpaste preparations. The aim of this in vitro study was to evaluate the effect of nano-hydroxyapatite toothpaste, which was produced by nano-technology, on the remineralization of human enamel. A tooth specimen, on which artificial incipient caries had been induced, was immersed into two toothpaste slurries for remineralization. One contains nano-sized hydroxyapatite and fluoride, and the other contains nano-sized hydroxyapatite excluding fluoride. In order to evaluate the remineralization effect, the Vickers Hardness Number & SEM image of the enamel surface was evaluated at each step. There were significant differences in VHN values between those obtained before and after the remineralization steps. The results showed that the remineralization effect increased with increasing immersing time (P<0.05). However, there were no significant differences in VHN values between the two groups (P>0.05). SEM also demonstrated differences the in micro surface at each step. In conclusion, a toothpaste containing nano-sized hydroxyapatite has the potential to remineralize an incipient caries lesion. In addition, the addition of fluoride had no synergistic effect on remineralization.