## 3 Results and Discussion
### Material Properties
#### 3.4.2 Bond Strength Properties  
Bond strength is essential in introducing new materials that adhere to the tooth structure. The adhesion to tooth structure should provide retentive strength and marginal seal, be relatively simple to achieve, and have clinical durability, reflected in the longevity and success of the bonded restorations. Figure 6C describes the percentage distribution of studies assessing the bond strength, with microdensile (67%) and macro shear (33%) being the most applied tests.  
The micro tensile bond strength test (\(\upmu\)TBS) was the prevailing method for measuring the microscale bond strength of adhesive materials, while shear bond strength is a method for determining the bond strength by applying a shearing force parallel to the adhesive-substrate interface [37].  
Most included manuscripts investigated bonding strength using micro-tensile testing (67%) instead of shear bond strength (33%). This difference could reflect that \(\upmu\)-TBS correlates with vivo data, while shear bond tests are technique-sensitive when applied to large surface areas of testing [38; 39].  
Thirty-five percent of the studies in this review have investigated the effects of different surface treatments and adhesives on the bond strength of CAD-CAM RCBs to dentin. For example, [PERSON] et al. [39] found that using glass beads for air abrasion enhanced the bond. Some studies reported that air abrasion may damage the surface of CAD-CAM resin blocks [39]. [PERSON] et al. [40] stated that combining surface treatments improves bond strength between CAD-CAM materials and resin cement [41].  
Various surface treatments can significantly enhance the bond strength of CAD-CAM resin materials. These treatments include air abrasion, which uses aluminum oxide particles to create a rough surface for better micromechanical retention, and hydrofluoric acid (HF) etching, which etches the surface to improve bonding [40]. Silane coupling agents also increase surface wettability and chemical bonding between the resin matrix and fillers. Combining these methods, such as HF etching followed by silane application, often yields the highest bond strength.  
[PERSON] and coworkers found that grinding the surface of hybrid ceramics and applying a universal adhesive resulted in the most robust adhesion. Regarding different CAD-CAM composite materials, [PERSON] et al. [41] found that composite CAD-CAM RCBs were more receptive to bonding than resin nano-ceramic materials [42; 43].  
[PERSON] and collaborators [43] have investigated the effects of three silane primers and five adhesive agents on the bond strength of CAD-CAM RCBs to dentin. The study found that combining a tributyl borane derivative and a silane primer in the SB-Dual adhesive resulted in stronger bonding between the repairing resin composite and the composite block than other agents tested.  
Similarly, [PERSON] et al.'s work [44] examined the bond strength between a polymer-infiltrated ceramic network (PICN) and a composite for repair and the effect of several cenario surface treatments. The study found that the most effective way to repair hybrid ceramics was by first surface grinding and then applying universal adhesive, as this method resulted in the most robust adhesion.