Effect of different acids surface treatments and thermocycling on shear bond strength of composite resin to feldspathic ceramic


Background: the aim of this study was to evaluate the effect of different surface acids treatments (37%phospjoricacid, 5%hydrofluoric acid, 1.23 acidulated phosphate fluoride) of feldspathic ceramic VITA 3D MASTER , and theeffect of thermocycling on shear bond strength using a ceramic repair kit (ivoclar/vivadent).Material and Methods: sixty Nickel-Chromium metal base plates were prepared(9mm diameter,3mm depth) usinglost wax technique, 2mm thick layer of ceramic(VITA 3D MASTER) fused to metal plates, all specimens wereembedded in acrylic resin blocks except their examined surfaces and divided into 3 main groups 20 specimenseach, Grp A: treatment with 37%phosphoric acid for 2 mins, Grp B: etching with 5% hydrofluoric acid for 2mins, GrpC: etching with 1.23% acidulated phosphate fluoride for 10 mins; monobond-plus, heliobond, resin composite(TetricEvoCeram) were applied to each specimen according to manufacturer's instruction using transparent splitmold(5mm diameter, 4 mm height); specimens were stored in 37OC distilled water for 12 weeks, 10 specimens ofeach group were subjected to thermocycling between 5 oC and 55 o C for 800 cycles with 30s dwell time; shearbond strength was determined by a universal testing machine (instron 1122) at a cross head speed 0.5mm/min; Oneway ANOVA test, LSD test and student-t test were used to analyze shear bond strength.Results: Mean shear bond strength values for the tested groups were: A1= 11.65±0.68 Mpa, A2=10.88±0.58 Mpa,B1=17.93±0.41 Mpa, B2=17.42±0.35 Mpa, C1=15.17±0.61 Mpa, C2=14.51±0.48 Mpa ; one way ANOVA test showedhighly significant difference among groups; LSD test revealed that the use of 5% HF for ceramic surfacetreatment(GB) was highly significant than the treatment with 37%PA(GA) or 1.23%APF(GC) respectively and the useof 1.23%APF(GC) was highly significant than the use of 37%PA(GA); Student t- test showed a significant differencebetween subgroups of the same group with and without thermocycling.Conclusion: ceramic surface treated with 5% HF acid for 2 mins recorded the highest shear bond strength, followedby surface treatment with 1.23% APF for 10 mins, most specimens treated with 5%HF showed cohesive failure with inceramic while specimens treated with 1.23%AFP showed more (adhesive/cohesive) failure than adhesive orcohesive alone, and specimens treated with 37% PA showed nearly 50:50 adhesive and combination failure,thermocycling reduced the bond strength of each group significantly.