Nano-hydroxyapatite Toothpaste With Hydrolyzed Conchiolin Increases Tooth Enamel Gloss
Objectives: Hydrolyzed conchiolin (HC), derived from proteins promoting biomineralization in shells, is used in cosmetics and shampoos for moisturization, repair and gloss improvement. We tested its ability in toothpaste, in combination with nano-hydroxyapatite (nHAP), to increase enamel gloss.
Methods: Enamel sections from extracted human teeth were examined with a surface gloss analyzer (806H, TRICOR Systems Inc.). To equalize differences, sections were treated with a diluted phosphoric acid etchant (Clearfil, Kuraray-Noritake Dental), adjusting gloss to the same value for each. Test dentifrices of different nHAP concentration were used: control groups A, B, C, without HC (nHAP content ratio A: B: C = 1: 1.4: 2, n=5), and experimental groups A+, B+, C+, containing HC (Promois PEARL-P, Seiwa Kasei) (nHAP concentration as for controls, n=6). Teeth immersed in a slurry (25g/40ml) of the respective dentifrice were brushed 9min/day for 6 days (load 100g, amplitude 2cm, speed 100 rpm/min), and surface gloss measured daily after brushing. The difference between the obtained value and adjusted gloss value (⊿G) for each tooth was calculated, and the difference in daily ⊿G values between experimental and control groups compared. Samples sent to Tokyo Metropolitan Industrial Technology Research Institute were tested for the presence of HC in the post-brushing enamel surface layer, using a Time-of-Flight Secondary Ion Mass Spectrometer (TOF-SIMS, ULVAC-PHI).
Results: Gloss values increased for all teeth throughout the study, but the increase in ⊿G was higher for experimental groups than controls. Average daily ⊿G increase per nHAP concentration group was 14% (A→A+), 19% (B→B+) and 22% (C→C+) over the 6 days, suggesting synergy between HC and nHAP concentration.
Conclusions: HC, in conjunction with nHAP, promotes increased enamel gloss. Though not detected in the post-treatment enamel surface, it is postulated to support mineral deposition by nHAP.