A review discussion of the use of acyl phosphine oxides in dental materials and to compare this class of compounds with the most commonly used initiator system, which is the camphorquinone/amine-system.The completely different initiation reactions are shown and a general synthesis for acyl phosphine oxides is presented.The comparison of a monoacyl phosphine oxide with a bisacyl phosphine oxide and a camphorquinone/amine-system in a testing composition covers curing depth, inhibition layer, residual monomer, mech. properties and adhesion of the testing composition to the tooth, proving that the acyl phosphine oxides are initiators mostly topping the "classical" system.The adhesion to a tooth depends on factors, such as salt and complex formation of acidic monomers with calcium, hydrogen bridge building to collagen fibers of the tooth, entanglement of the adhesive with this collagen, hydrophobia and hydrophilia of the monomers , use of solvents, viscosity, acidity, and mainly, the used initiator.