# Review of Professionally Applied Fluorides for Preventing Dental Caries in Children and Adolescents
## 3 Results and Discussions  
### Fluoride Gels  
The most widely used fluoride gels are: acidulated phosphate fluoride (APF) with 1.23% (12,300 ppm) fluoride ion and 2% sodium fluoride (NaF) with 0.90% (9050 ppm) fluoride ion [16; 17]. An early study conducted by [PERSON] et al. [21] showed that an acidic environment increases the fluoride intake by enamel, justifying the highly acidic formulation (pH of approximately 3.0) of fluoride gels [22]. Regular use of professionally applied fluoride gel is likely beneficial only for persons at high caries risk, especially those who do not live in areas with fluoridated water or do not brush their teeth daily with fluoride toothpaste [17]. Typically, fluoride gel application consists of using a gel loaded tray held in the mouth for 4 min. There is a 30 min restriction for rinsing, eating, and drinking after the treatment to allow the teeth to absorb the fluoride and help repair the existing lesion with less soluble minerals [16; 17]. The most common adverse effect of fluoride gel application is over ingestion manifested by nausea and vomiting. This can be prevented by seating the patient upright,not overfilling trays (no more than 2-2.5 g per tray or 40% of tray's volume), by using well-fitted or custom trays, by the use of a suction device, and by separate insertion of upper and lower trays. Moreover, gagging may occur in young children, or they may find the experience unpleasant [23]. Studies showed that the use of professionally applied fluoride gel has a low risk for dental fluorosis, even among children under the age of 6, because it is applied by a dental professional relatively infrequently, from once a year to four times a year [17; 22]. [PERSON] et al. (2015) performed a meta-analysis on self-applied and professionally applied fluoride gel: 25 trials (8479 participants) on permanent teeth and 3 trials (1254 participants) on primary teeth. The D(M)FS preventive fraction on average was 17% (95% CI 3% to 31%; \(p=0.018\)) greater in non-placebo-controlled trials (the decline in caries was 38% (95% CI 24% to 52%; \(p<0.0001\), 2808 participants) for the 10 trials with no treatment as a control group, and 21% (95% CI 15% to 28%; \(p<0.0001\), 5671 participants) for the 15 placebo-controlled trials. The d(e/m)fs pooled prevented fraction was 20% (95% CI 1% to 38%; \(p=0.04\)), with low quality evidence [24]. [PERSON] et al. (2019) performed a network meta-analysis and concluded that 1.23% APF gel presented a double chance of arresting or reversing non-cavitated carious lesions on any coronal surfaces versus no treatment (moderate certainty) [2]. Studies conducted on professionally applied fluoride gel showed that caries-preventive fractions ranged between 23% and 60% (Table 1). Some studies reported non-significant differences between the test and control group, regarding professionally applied fluoride gel [28; 29; 30]. The European Academy of Paediatric Dentistry (EAPD) does not recommend the use of fluoride gels under the age of 6 years due to the danger of swallowing. In permanent dentition, EAPD moderately recommends 2 to 4 applications per year in appropriately sized trays, in an upright position, associated with suction devices during and after application to reduce swallowing, and interdiction to eat or drink 20-30 min after fluoride gel application [31]. The Australian Research Center for Population Oral Health (ARCPOH) recommended the use of high concentration fluoride gels (more than 1.5 mg/g fluoride ion) to be used for people aged 10 years or more who are at an elevated risk of developing caries [32]. Recently, atmospheric plasma activation of a hydroxyapatite enamel-like model proved to be almost twice as effective regarding fluoride incorporation from a 1450 ppm fluoride gel (Fluor Protector, Ivoclar Vivadent, Schaan, Liechtenstein) than usual gel application. Furthermore, a certain antimicrobial and biofilm modulation was observed [33].