logo 49 | The Camlog Partner Magazine Science| 9 Methods for improving bonding strength by pretreating the bonding surfaces of titanium bases Corundum blasting of the bonding surfaces [4] The surfaces of the titanium bases CAD/CAM intended for bonding to the meso- and suprastructure are usually corundum blasted first. This abrasive surface treatment, which is also recommended by the manufacturer, inevitably leads to a rougher surface and thus to improved bonding strength during cementing. Different grit sizes from various manufacturers are available on the market for this abrasion method. To determine the stability of the bond and the bonding strength between titanium bases CAD/CAM and lithium disilicate crowns after applying different methods, a total of 60 samples were divided into four groups: prior to bonding with Multilink Hybrid Abutment (Ivoclar Vivadent), the titanium bases were blasted with either 30-µm, 50-µm or 110-µm aluminum oxide (Al2O3) particles. The control group received no pretreatment. Finally, the prepared restorations were screw-retained to the embedded implants. After artificial aging, a number of bonds already failed. In the control group, 73% of the crowns loosened, and in the 30-µm and 110-µm groups respectively, micromovement was observed in 40% of the samples. Significantly better results were obtained with 50-µm blasting. Only 7% in this group failed the load test. In comparison, the highest pull-off forces (420 ± 139.5N; pull-off test) were measured in this group at the same time, due to the highest measured surface roughness across all groups. Conclusion: In conjunction with lithium disilicate crowns, pretreatment with 50-µm Al2O3 particles (in the test: Cobra Aluoxyd; Renfert GmbH) can be recommended in particular. Cleaning of blasted titanium bases [5] During a try-in of the abutment, for example when using a chairside workflow or when taking a digital impression at abutment level, the previously blasted abutments are contaminated with saliva. The manufacturer specifies that the parts should be cleaned and disinfected before and after each use on the patient without naming specific agents. This study tested which cleaning steps are necessary after contamination with saliva to restore ideal adhesion levels of the surfaces. Again, the titanium bases were bonded to lithium disilicate crowns for the load test. After 1.2 million cycles, all samples treated prior to cementation with the cleaning methods a) water spray, b) alcohol bath, c) suspension of zirconium particles, or d) repeated blasting exhibited significantly increased bonding failures at a micro level compared to uncontaminated titanium bases. However, the retention strength of the abutment-lithium disilicate-crown connection was comparable in all but one case. Only the group cleaned with ultrasound in an alcohol bath exhibited a significantly reduced retention strength and therefore appears to be less suitable when compared with the other cleaning agents. Conclusion: After contamination of the pre-treated bonding surfaces with saliva, the cleaning method with water (spray), treatment with a suspension of zirconium particles or repeated blasting are suitable for re-establishing a good bonding effect. Mechanical stability of various material compounds under load Modern ceramics for the fabrication of dental restorations should address characteristics such as time efficiency in fabrication (CAD/CAM), low chipping risk, but also protection of the implant-abutment connection against overloading. When bonding with titanium
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