Definition:
Resin-modified glass-ionomer luting cements (RMGICs) are hybrid cements that combine the acid–base setting reaction of conventional glass-ionomer cements with an additional resin polymerisation reaction. They are designed to:
chemically bond to enamel and dentine
release fluoride
have improved early strength and lower early solubility compared to conventional GICs
provide thin-film luting for indirect restorations.
Clinical case:
A 62-year-old patient requires multiple metal–ceramic crowns on posterior teeth. Preparations are adequate but one tooth has a short clinical crown, and the patient has moderate caries risk. You choose an RMGIC luting cement to:
gain chemical adhesion to enamel and dentine
benefit from fluoride release
take advantage of higher early strength and easier clinical handling compared with conventional GIC, while still using a broadly “conventional” cementation technique.
You avoid its use for a thin, feldspathic all-ceramic crown on an upper lateral incisor because of concerns about hygroscopic expansion and ceramic fracture.
Uses:
Luting metal and metal–ceramic crowns and bridges
Luting reinforced core all-ceramic restorations (e.g. zirconia or alumina cores) where wall thickness is adequate
Luting prefabricated and cast metal posts, particularly in teeth with limited mechanical retention
Luting orthodontic bands, especially where fluoride release is desired
Alternative to conventional GIC where improved early strength, lower early solubility and easier handling are required.
Use with caution or avoid for:
Very thin feldspathic or glass-ceramic shells and veneers
All-ceramic restorations at risk of fracture from cement expansion, especially when RMGIC is also used as a core material.
How to use them in clinical practice?
A typical chairside flow:
Try-in and adjust
Check fit, contacts and occlusion of the restoration.
Clean restoration according to manufacturer’s guidance.
Tooth preparation
Clean preparation (pumice/slurry), rinse and gently dry.
Do not desiccate dentine; a slightly moist surface is desirable.
Conditioning (if recommended)
Some RMGIC systems recommend a polyacrylic acid conditioner; others rely on the inherent self-conditioning of the resin–acid mix.
Follow manufacturer instructions.
Activation and mixing
Many RMGICs are supplied in capsules: activate and triturate according to manufacturer.
For powder–liquid systems, mix briskly to a smooth consistency within the stated mixing time.
Application
Apply cement to the internal surface of the restoration (thin, uniform layer).
Avoid air entrapment.
Seating
Seat the restoration promptly within the working time.
Maintain steady pressure; stabilise whilst the cement sets.
Light-curing and cleanup
Light-cure accessible margins if recommended (improves early set and allows quicker cleanup).
At gel stage, remove excess cement from margins and interproximal areas.
Final set and checks
Allow the chemical cure to proceed in deeper areas not reached by light.
Check occlusion and finish margins as required.
Constituents:
Glass-ionomer component
Fluoro-alumino-silicate glass powder
Polyacrylic acid (often incorporated in powder)
Tartaric acid
Resin component
Hydrophilic monomers (commonly HEMA)
Other dimethacrylates (UDMA, Bis-GMA derivatives, depending on product)
Photo-initiators and/or redox initiators for light and chemical cure
Fillers and additives
Radiopaque fillers
Pigments and stabilisers
Chemistry:
Two overlapping setting mechanisms:
Acid–base reaction
Identical in principle to conventional GIC: polyacid attacks glass, releasing Ca²⁺, Al³⁺ and F⁻, forming a polysalt matrix with fluoro-alumino-silicate cores.
Resin polymerisation
Photo-initiated and/or chemically initiated free-radical polymerisation of HEMA and other dimethacrylates.
Produces an interpenetrating network of inorganic polysalt matrix and organic resin phase.
This dual-cure nature:
accelerates development of early strength
reduces early solubility and water sensitivity
introduces water sorption and potential hygroscopic expansion as the resin phase absorbs moisture over time.