Remineralisation of enamel erosive lesions by daily-use fluoride treatments: network meta-analysis of an in situ study set

Objectives Daily-use fluoride products are first-line protection against enamel wear from dietary-acid exposure (DAE). This study aimed to understand effects of fluoride concentration, fluoride salt, product form and ingredients in daily-use products on remineralisation and demineralisation, via network meta-analysis (NMA) of 14 studies using one well-established in-situ model. Remineralisation (surface-microhardness recovery, SHMR) after treatment, and protection against subsequent demineralisation (acid-resistance ratio, ARR) were measured. Materials and methods Healthy participants, wearing intra-oral palatal appliances holding enamel specimens eroded with standardised DAE, used test products once. Enamel hardness was assessed (Knoop microhardness probe) pre-DAE; post-DAE; after 4 h intra-oral remineralisation; and after post-remineralisation DAE. NMA was performed using a mixed-models approach on subject-level data to estimate and compare means. Results There was a dose-response for fluoride ion in toothpastes (0-1426ppm F; p < 0.001 for SMHR and ARR). One toothpaste (silica-based, 1150ppm F as NaF) showed a benefit for SMHR versus placebo [mean(standard error)]: 8.8%(0.6%) (33.0% vs. 24.2%; p < 0.001); for ARR: 0.27(0.03) (0.43 vs. 0.15; p < 0.001; 9 mutual studies). Use of fluoride mouthwash after fluoride toothpaste increased SMHR [2.4%(1.1%); p = 0.043; 3 studies]; the effect on ARR [0.08(0.05)] was not significant (p = 0.164). Negative effects of polyvalent metal ions and polyphosphates on SMHR (p < 0.05) were observed. Conclusions NMA proved effective in discriminating between fluoride-based treatments in this in-situ study, highlighting the importance of fluoride ion to enamel protection and showing formulation ingredients can affect its performance. Clinical Relevance Daily-use fluoride products can protect enamel against dietary acids, but careful formulation is required for optimal performance.