A self-gelling composition for topical application, particularly in the oral cavity, which composition comprises: an aqueous solution of ethyl orthosilicate monomer or prepolymer; an active ingredient, such as a fluoride, or an antibiotic for sustained release in the area of topical application; and a gelation agent, to provide, on mixing of the composition, the in situ gelling of the composition within a predetermined time period after topical application, to provide the penetration properties of a low-viscosity solution with the sustained release of the active ingredient from the gel.