Bonding strength between PEEK and C&B composite

Objective: PEEK (Polyetheretherketone) is one of most promising polymers for crowns and bridges due to its outstanding mechanical properties. As an individual modification of its colour is not possible to be acceptable for dental applications, especially in the anterior regions of the mouth, veneering is necessary. The aim of this work was to assess the shear bonding stress between PEEK classixs and conventional C&B composites depending on a special pre-treatment of the PEEK surface prior to veneering. Method: 60 specimens were cut from an extruded block of PEEK Classix (INVIBIO). The bonding strength was tested according to ISO 10477 after storage in water for 24h at 37°C. Different surface treatments were tested. In a first step the specimens were weather cleaned or not with acetone. Afterwards they were sandblasted with either 50µm or 250µm Al₂O₃-grit (corundum) at 3bar pressure. Additionally half of the specimens were treated with heat from infrared (IR) radiation prior to veneering. Basing on these pre-treatment-steps, 6 different groups of samples resulted, each group including n=10 PEEK-specimens (Table 1). The specimens were then veneered, whereas VITA LC served as veneering composite. The Student´s t-test was applied to evaluate significant differences, with p=0,05.   Result:

Table 1 shows the results of the shear-bond-strengths of the veneering composite to PEEK depending on the different surface pre-treatments

	Blasting 50µm Corundum 3 bar		Blasting 250µm Corundum 3 bar
pre-treatment	Hot	Cold	Hot	cold
Acetone yes	ni	ni	11,2±3,7* MPa	13,4±3,5 MPa
Acetone no	11,1±2,7* MPa	15,4±4,0* MPa	10,7±4,2* MPa	11,9±5,5 MPa

*significant differences, ni = not investigated

Significant differences could be observed between the bonding strength after treatment with 50µm corundum and all other specimens treated with IR radiation. Conclusion: The cleaning with acetone is advisable, as well as the use of corundum with a grit size of 50µm for sandblasting. The application of heat (IR radiation) before putting the C&B composite onto the treated PEEK surface is not beneficial. In all cases a reasonable bonding strength (> 5MPa) related to ISO 10477 was reached.