STUDY OF SALIVARY FILMS ON HYDROXYAPATITE 167 film was too _small and no visible adsorbed material was observed. The IR spectra were recorded for the 800-2000 cm- 1 spectral region, as shown in Figure 2. The spectra showed the existence of amide I and II in the regions around 1,650 and 1,550 cm-1, respectively, besides the large background from HAP. The band at_around 1250 cm- 1 , probably due to the sulphate groups, was also observed. The film formation was found to depend on each individual and the collecting time. The signals of amides gradually increased with time for individual A, but no remarkable changes were observed for individual B. The results have shown that the proteins secreted from salivary glands adsorb on the HAP surface to form the pellicle-like film, and these observations mostly coincide with the results by the previous researchers (16,30-34). The adsorbed materials on the HAP disks for individual A were also analyzed using XPS. Table I summarizes the results, showing atomic concentrations of the detected elements at each collecting time. The elements of Ca, P, and O drastically decreased for the treated HAP samples, whereas -rhe other elements increased, suggesting that almost the entire area of the analyzed HAP surface was covered with pellicle-like film. The composition of HAP just soaked in distilled water for 120 minutes, though not shown here, was almost identical to that of the original HAP (O minute). The formation of the pellicle­ like film was found to be a fairly rapid process as compared with previous reports (10,16,30-34), reaching an apparent saturation level within 0.2 minutes. There was only a little difference among the samples treated for different periods, and no significant differences among three individuals, though the data are not shown here. These phe­ nomena are in contrast with the IR results in Figure 2, and are largely a result of the difference in analysis depths of these two techniques, that is, the thickness of the film must be beyond the XPS analysis depth. The surface compositions of treated HAP samples were different from that of dried saliva, that is, more N, Si, and S and less Ca, HAP {A} 2000 1600 1200 800 W avenumbers(cm· 1) Figure 2. ATR-FT-IR spectra of HAP surfaces exposed to the saliva in the mouth, obtained from two individuals (A,B) at different periods, and untreated HAP (C). a: 30 b: 60 c: 120 minutes.

168 JOURNAL OF COSMETIC SCIENCE Table I Chemical Constituents of HAP Disk Surfaces Obtained from XPS Analysis (atomic%) Time (min) Ca p 0 C N Si s Na Cl 0 10.2 7.9 30.9 50.1 0.7 0.2 0 0 0 0.2 0.5 0.6 15.7 74.4 7.3 0.6 0.5 0.2 0.2 5 0.8 0.9 18 69 10.7 0.5 0.2 0.1 0 30 0.5 0.4 18.7 69.3 9.4 1.6 0.2 0.1 0.2 60 0.2 0.2 14.5 74.1 8.8 1.5 0.3 0.2 0.2 120 0.3 0.3 15.6 72.4 9 1.8 0.5 0.1 0 Dried saliva 0.8 0.9 16.2 75.1 5.3 0.5 0.1 0.4 0.8 Samples are the same as in Figure 3. P, Na, and Cl for the treated HAP samples, indicating the preferential adsorption of saliva in the early stage. Elements like N and S can be attributed to the protein of human oral origin, though the contribution of non-protein nitrogen such as urea, uric acid, and amino acids to nitrogen content should also be considered. The narrow scan spectra of Ols, Nls, Cls, and Si2p for the films formed during periods of 0.2 to 120 minutes are shown in Figure 3. The Cls line at 284.6 eV, attributed to hydrocarbon, was used for charge correction. The numbers attached to each spectral curve indicate the values of binding energies at the top of the spectral peaks. The Ols spectrum at O minute came from HAP itself. The large spectral shift of Ols for treated HAP has suggested that the analyzed HAP surface area was almost totally covered with pellicle-like film. In accordance with the previous study (17), the increase in the Nls Ols Nls Cls Si2p 535 531 527 404 400 396 290 286 282 107 103 99 Binding energy(e V) Figure 3. XPS narrow scan spectra (Ols, Nls, Cls, Si2p) of HAP surfaces exposed to the saliva in the mouth at different exposure times. a: O b: 0.2 c: 30 d: 120 minutes. Samples are the same as in Table I.