**5. Conclusion**

88 Contemporary Approach to Dental Caries

offers a higher number of possible retention sites for the fluoride. The application of highly concentrated fluoride favors the formation of the calcium-fluoride like layer (Attin et al., 1977). This deposit is later dissolved, allowing fluoride diffuse into the underlying enamel, the saliva, or a plaque layer covering the tooth. It is assumed that some of the fluoride is supporting the remineralization of the enamel. The results of a previous study confirmed that the calcium fluoride layer on the enamel was coated by phosphates and proteins from saliva as a pH-controlling reservoir that acts to decrease demineralization and promote

Fig. 8. Cumulative calcium (Ca2+) release from the bleached specimens in the buffer solution after treatment with 1% TiF4 and 1.1% NaF on the 4th, 8 th, 12 th and 16 th days (µg/ml).

**Material**

HP+NaF

Control 38% HP 38%

0

38% HP+TiF4 5

10

15

20

25

4th Day 8th Day 12th Day 16th Day

VanRijkom *et al* (VanRijkom et al., 2003) compared the erosion-inhibiting effect of the topical fluoride treatment based on the deposition of CaF2-like material using 1% NaF and 4% TiF4. It was concluded that the reduction of Ca2+ loss was more stable for TiF4 than the NaF group and the reduction appeared to be smaller for the longer acid exposure times. Recently, Magalhães *et al* (Magalhães et al., 2008) have stated that a TiF4 varnish showed better results than 2 commercial NaF varnishes in reducing enamel erosion. Based on the results of Tezel

remineralization (Rolla&Saxegaard, 1990).

4th Day

8th Day

12th Day

**Day**

16th Day

As a conclusion, considering the conditions tested, the changes in enamel were directly proportional to the treatment time and peroxide concentration. According to the methodologies used in these studies, higher concentrations of HP caused more Ca2+ loss than lower concentrations. The contact time of high concentrated bleaching agents may also be an important factor for Ca2+ loss. A recommendation to use activation methods which shorten the contact time of the highly concentrated bleaching agents can be used in the dental office. But it must still be mentioned that 10% CP would be the safest method. In addition, to avoid the unfavorable effects of bleaching treatments, it is recommended to use topical fluoride agents incorporation with bleaching agents to take advantage of remineralization process.

The findings of these *in vitro* studies may not be representative of the *in vivo* condition; in which the oral cavity is continually bathed with saliva that contains various minerals (*i.e.* fluoride, calcium phosphate), lipids, carbohydrates and proteins. They also do not represent unfavorable conditions where the deficiency of saliva or poor oral hygiene that might increase the caries risks. Further studies are needed to clarify the effects of these materials on Ca2+ loss of enamel and caries susceptibility.
