Table 2. Failure pattern for tested specimens (in percentage).

Group	Failure Model
	Cohesive	Adhesive	Mixed
Group 1: drying with spray + sandblast with Al2O3	88	9	3
Group 2: washed with water and dried with spray + sandblast with Al2O3	40	50	10
Group 3: washed with distilled water and dried with spray + sandblast with Al2O3 + zirconium oxide (Ivoclean)	100	0	0
Group 4: washed with distilled water and dried with spray + sandblast with Al2O3 + potassium hydroxide (Zirclean)	100	0	0
Group 5: washed with distilled water and dried with spray + sandblast with Al2O3 + 1% NaClO	98	2	0