Objectives: One aim of this in vitro study was to evaluate the influence of saliva on the formation of CaF₂ during application of a fluoride gel. The second aim was to study dissolution behaviour of the produced CaF₂ precipitate.

Methods: 160 bovine enamel specimens were divided among two experimental groups. 80 specimens (group I) were treated with a mixture of saliva and Elmex gelée (1:1, 6250 ppm F^-, pH: 5.0) and 80 specimens (group II) were treated with a mixture of Elmex gelée and distilled water (1:1, 6250 ppm F^-, pH: 5.0) for 5 minutes, respectively. Subsequently the samples were cleaned. Each 40 specimens of the two experimental groups were stored in saliva or in distilled water for 5 days. Saliva and distilled water were replaced daily. After 1h, 24h, 48h, and 120h each 10 samples were removed from the respective storing media and KOH-soluble fluoride (µm/cm²) was determined.

Results: 1h after application of the different mixtures a significant amount of KOH-soluble fluoride could be detected. During the five day period a significant loss of KOH-soluble fluoride could be observed in all groups (p<0.01, ANOVA). Specimens stored in saliva experienced a retarded decrease of KOH-soluble fluoride.

 

Group	Group I		Group II
Time / storing solution	Saliva	Distilled water	Saliva	Distilled water
1h	16.4 ± 6.6	18.0 ± 15.7	14.4 ± 3.2	9.1 ± 5.6
24h	11.8 ± 4.1	1.7 ± 1.2	19.2 ± 8.0	2.3 ± 1.4
48h	7.4 ± 4.4	1.9 ± 1.1	9.6 ± 5.8	1.8 ± 0.9
120h	4.8 ± 3.4	2.0 ± 0.8	5.1 ± 3.0	2.8 ± 3.9

 

Conclusions: The presence of salivary constituents during application of the fluoride gel has a minor influence on the subsequent dissolution behaviour. However, saliva exerts a certain protection function on dissolution of a previously formed CaF₂ layer.