# Fluoride Ion Release Characteristics of Fluoride-Containing Varnishes--An In Vitro Study  
[PERSON]  
1 Department of Orthodontics, School of Dentistry, Faculty of Health, Witten/Herdecke University, 58455 Witten, Germany; [EMAIL_ADDRESS] (S.C.M.) [EMAIL_ADDRESS] (G.D.) 1  
[PERSON]  
2 Department of Orthodontics and Dentofacial Orthopedics, Friedrich-Schiller-University Jena, 07743 Jena, Germany; [EMAIL_ADDRESS] 2  
[PERSON]  
3 Department of Biological and Material Sciences in Dentistry, School of Dentistry, Faculty of Health, Witten/Herdecke University, 58455 Witten, Germany; [EMAIL_ADDRESS] (E.A.N.); [EMAIL_ADDRESS] (W.H.A.) 3  
[PERSON]  
3 Department of Biological and Material Sciences in Dentistry, School of Dentistry, Faculty of Health, Witten/Herdecke University, 58455 Witten, Germany; [EMAIL_ADDRESS] (E.A.N.); [EMAIL_ADDRESS] (W.H.A.) 3  
[PERSON]  
1 Department of Orthodontics, School of Dentistry, Faculty of Health, Witten/Herdecke University, 58455 Witten, Germany; [EMAIL_ADDRESS] (G.D.) 1  
[PERSON]  
4 Department of Operative and Preventive Dentistry, School of Dentistry, Faculty of Health, Witten/Herdecke University, 58455 Witten, Germany; [EMAIL_ADDRESS] (G.D.) 1  
[PERSON]  
1 Department of Orthodontics, School of Dentistry, Faculty of Health, Witten/Herdecke University, 58455 Witten, Germany; [EMAIL_ADDRESS] (G.D.) 1  
Footnote 1: email: [PERSON]DDRESS] (E.A.N.); [EMAIL_ADDRESS] (W.H.A.)  
Footnote 2: email: [PERSON]DDRESS] (E.A.N.); [EMAIL_ADDRESS] (W.H.A.)  
Footnote 3: email: [PERSON]DDRESS] (E.A.N.); [EMAIL_ADDRESS] (W.H.A.)  
Footnote 4: email: [PERSON]DDRESS] (E.A.N.); [EMAIL_ADDRESS] (W.H.A.)  
Footnote 5: email: [EMAIL_ADDRESS] (W.H.A.)  
Footnote 6: email: [EMAIL_ADDRESS] (  
In addition to the daily low-dose application of fluoride in the form of toothpastes and mouthwashes, the use of high-dose fluoride products on the tooth in proximity to orthodontic brackets is another treatment option. To avoid the need for patient compliance, a noncompliant approach could be advantageous. Given that the average orthodontic treatment time is around 28.6 months [8], this time should be seen as the benchmark for the durability of fluoride products.  
Investigations of fluoride release kinetics have shown that fluoride ions are released by an initial surface elution followed by a continuous diffusion of fluoride ions from the tested dental material [9]. These kinetics and the bioavailability of fluoride are influenced by the composition and buffer capacity of the fluoride-containing product; the pH value of saliva and its content of antimicrobial substances, calcium, fluoride, and inorganic phosphate; and the temperature [10; 11; 12].  
Many manufacturers promise long-term fluoride release and effective caries protection throughout the period of orthodontic therapy when using their dental care products. According to the manufacturers, Bifluorid12 (VOCO GmbH, Mannheim, Germany) applied twice a year and Protecto CaF2 nano one-step seal (Bonadent GmbH, Frankfurt am Main, Germany) applied once a year should be effective against acid attacks.  
In contrast, data from in vitro and in vivo studies suggest a reapplication of fluoride-releasing products every 3 to 3.5 months to prevent the advent of white spot lesions during orthodontic treatment [13; 14].  
The aim of the present in vitro study was to evaluate the fluoride release characteristics of the three tested fluoride-containing varnishes by investigating the fluoride concentration dynamics in the surrounding solution for a period of 60 days.