For high pressure applications it is common to use one or two back-up rings to prevent the O-ring from extruding out of the clearance gap on the low pressure side of a groove.
Back-up rings are typically made of a high grade engineering plastic, such as PTFE or PEEK. These higher modulus materials do not suffer the same visco-elastic extrusion mechanism as elastomers.
Backup rings can be supplied as solid rings or with scarf cuts to aid installation.