Effect of application time of silver diamine fluoride on caries arrest : a randomised clinical trial

Abstract

Silver diamine fluoride (SDF) therapy is simple and straightforward. The recommended application protocols were primarily based on experts' opinions suggesting application time for SDF ranges from 10 seconds to 240 seconds, which may be too long for young children, older adults, and people with special needs. This PhD thesis presents a 6-month stratified-randomized, double-blind, active-controlled, parallel-group clinical trial, which includes nine treatment arms, focusing on the carious lesion activity response to topical 38% SDF therapy as treatment application times increase. Before the clinical trial, we performed laboratory studies and found differences between the claimed and measured fluoride and silver ion concentrations in commercially available 38% SDF solutions from four different manufacturers. The alkalinity of the four brands of SDF solutions was similar, with a pH value of approximately 10 over 180 days. We also found that the amount of fluoride delivered through the topical application of a 38% SDF solution was significantly less than that of a 5% sodium fluoride varnish. The brand and size of the micro-applicator determined the amount of the SDF solution applied to a tooth. Not all micro-applicators are compatible with SDF, and clinicians should choose suitable micro-applicators for topical SDF therapy. The randomized clinical trial aims to determine the carious lesion activity response to topical 38% SDF therapy with increasing treatment application time. The design of this 6-month stratified-randomised, double-blind, active-controlled, parallel-group clinical trial include nine treatment arms. We studied 2,106 carious teeth (234 teeth per group) from 665 3- to 4-year-old children. We block randomised the carious teeth to nine groups for SDF therapy with application times of 3, 5, 10, 15, 30, 45, 60, 120, and 180 seconds. The outcome measure is caries lesion activity (active/arrest) at the tooth-surface level at 6 months post-initial treatment. We analysed the relationship between the exposure to SDF (the SDF application time) and the response (proportion of lesions arrested) using generalized estimating equations with adjustment for the correlation effect because the children had different number of carious teeth. At the 6-month examination, we examined 642 children with 2,038 SDF-treated carious teeth and 2,939 SDF-treated carious tooth-surfaces. We found emax (maximum effect) was the best fitted model among the multiple dose-response models. The estimated proportion of arrested lesions (%) increased over time from 76.7 % at 3 s, to 86.0 % at 60 s and 87.2 % at 180 s. However, the estimated rate (increment per second) of the proportion of arrested lesions reduced over time from 0.5 %/s at 8 s and 0.05 %/s at 41 s. An 8-second application time was required to arrest 80% of caries lesions. This clinical trial revealed an increase in the proportion of lesions arrested with increasing treatment application time of SDF. A higher proportion of lesions arrested is expected if SDF is applied to single tooth-surface lesion on an anterior tooth of a child is cared for by a mother with tertiary education. This study helps clinicians make informed decisions regarding application time of 38% SDF in clinical care.