Table 4.

Characteristic details and summary of results from studies identified in the systematic review.

Author(s)	LDH Type and Ratio M2+:M3+	LDH Incorporated in:	Fluoride Release Protocol	Outcome/Analysis Technique	Summary of Results
Calarco et al. [27]	MgAl 2:1	Composite: UDMA, Bis-GMA, TEGDMA, EBPADMA, glass filler	Discs (14 × 1 mm) in artificial saliva (15 mL at 37 °C). F− release measured per h until 8 h, then daily (10 days), and then weekly (3 weeks).	F− release: ion chromatography Mechanical properties: dynamic-mechanical analysis (DMA) Cytotoxicity assay: MTT Cell migration: modified Boyden chamber method [39]. Odontogenic-related gene expression: polymerase chain reaction.	LDH-fluoride containing dental resins demonstrated: A lower release rate of fluoride compared to fluoride-glass filled dental resins (FGDR). Continuous low release of fluoride increased the migratory response of human dental pulp stem cell subpopulation (STRO-1+) and indicated a complete odontoblast-like cell differentiation. Note, this effect was not observed with FGDR.
Tammaro et al. [28]	MgAl 2:1	Composite: UDMA, Bis-GMA, TEGDMA, EBPADMA, glass filler	Discs (20 × 1 mm) in NaCl 0.9% w/v, 50 mL (37 °C). F− release measured per h (6 h), then 12 h and other intervals (160 days).	F− release: ISE Characterization: XRPD, FTIR, DMA hDPSC proliferation assay: PicoGreen dsDNA and microplate reader Alkaline phosphatase activity Extracellular matrix mineralisation: Alizarin red S staining	LDH-fluoride in dental resins (0.7, 5, 10, 20 wt.%): Improved the mechanical properties with an increase in filler concentration. Released fluoride slowly over 6 months. Increased alkaline phosphatase activity of hDPSCs cells.
Yokogawa el al [29]	MgFe 2.7:1	Analysed LDH powder alone	0.1 g immersed in H2S water (300 mL) F− release measured at 1, 2, 3, 4, 5, 6, 12 and 18 h (°C not stated).	F− release: UV-VIS spectroscopy H2S uptake: GC/FPD Characterization: XRPD, FTIR, SEM and EDX, particle size analysis	LDH-fluoride was able to uptake volatile sulphur compounds (VSC) and release fluoride (Figure 3). No iron cations were released from the LDH structure.
Perioli et al. [30]	MgAl 2:1	Muco-adhesive patches: sodium carboxy methyl cellulose, polycarbophil propylene glycol, de-ionised water	Circular films (diameter 25 mm) adhered to a Teflon cell with 100 mL of 1.2 mM NaHCO3 water (37 ± 0.1 °C) agitated at 60 rpm. F− release in vitro at predetermined times for 4 h.	F− release: ion chromatography Characterization: XRPD, ICP-OES, TGA Film morphology: 8 MP camera and SEM Water holding: weight as produced, after hydration and dehydration Ex-vivo muco-adhesion: dynamometer In-vivo tolerability: five volunteers to evaluate residence time, swelling capacity, salivary modification, fragment loss, acceptability and organoleptic properties.	LDH-fluoride (1–4% w/w) in a hydrophilic buccal mucoadhesive (2 cm2) attached to the gum of five healthy volunteers: Released fluoride at a controlled rate, which increased with an increase in LDH-fluoride. Kinetic studies demonstrated that the concentration gradient of fluoride was the driving force for release. Fluoride release followed Fickian diffusion and a zero-order mechanism

Note: Urethane di-methacrylate (UDMA); bisphenol-A glycidyl dimethacrylate (Bis-GMA); Triethylene glycol dimethacrylate (TEGDMA); ethoxylated bisphenol A dimethacrylate (EBPADMA; Ion selective electrode (ISE); X-ray Powder Diffraction (XRPD); Fourier Transform Infra-Red Spectroscopy (FTIR); Human dental pulp stem cells (hDPSC); Double stranded deoxyribonucleic acid (dsDNA); Gas Chromatography-Flame Photometric Detector (GC/FPD); Scanning Electron Microscopy (SEM); Energy Dispersive X-ray Spectroscopy (EDX); hydrogen sulphide (H₂S); Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES); Thermal Gravimetric Analysis (TGA); sodium bicarbonate (NaHCO₃).