Radiopaque dental composition

A dental composition comprising:

• a resin matrix comprising:
• cross-linkable component(s) as Component A characterized by the Formula (I):
• wherein:
• a is an integer selected from 0 and 1,
• A is selected from:
• B is selected from:
• *—(CH2)b—*, *—(CH2—CH2—O—CH2—CH2)—*, *—(CH2—CH2—O—CH2—CH2—CH2)—*, *—(CH2—CH2—CH2—O—CH2—CH2—CH2)—*,
• b is an integer selected from 2 to 6,
• B′ being selected from *—(CH2)b′—*, *—(CH2—CH2—O—CH2—CH2)—*,
• b′ is an integer selected from 2 to 6,
• R is H or methyl,
• X is selected from H, methyl, ethyl, hexyl, tert-butyl, and Br,
• Y is H and Br,
• “*” representing those site(s) of a moiety of the monomer, where that moiety is bonded to another moiety of the monomer;
• ethylenically unsaturated component(s) with acidic moiety as Component B;
• and
• an initiator system comprising:
• photoinitiator(s) as Component C, and
• reducing agent(s) as Component D.