## 3 Results
### Scanning Electron Microscopy Results  
SEM analysis confirmed the results highlighted by optical microscopy investigation: a good overall peripheral adhesion of the restorations (Figures 3d,f and 6b) and occasional infiltrations mostly in the cervical areas of the restorations (Figures 3a and 5c) but also randomly located at the level of adhesive interface (Figure 4c,d). An intact adhesive layer in the occlusal part of the restorations was mostly found (Figures 3d,f, 4c, 5c and 6b,d). However, fissures in occlusal enamel without leakage of the adhesive interface were observed (Figures 3d,f, 4c, 5c,d and 6b,d). Figure 3: Beautiful II LS® restorations. Cervical microleakage of a cementum-located restoration (\(25\times\)) continuous with a dark-colored intact adhesive layer. Inset, resinous rete tags of about \(5\upmu\)m (\(500\times\)) (**a**). Detail of the cervical cracked adhesive layer; dentin tubuli almost perpendicular to the surface (upper-left) (\(100\times\)) (**b**). Infiltrated cementum-located restoration (right) corresponding to picture (a) and well-adapted enamel-located restoration (left) corresponding to picture d (**c**). Good cervical adhesion of an enamel-located restoration (lower right) and cracked occlusal enamel (upper left) not affecting the adhesive interface (\(25\times\)). Inset, detailed fissures in occlusal enamel, green-colored dentin due to increased Ca, O, and P content, and purple-colored restoration due to Si, Al, and Sr content (\(50\times\)) (**d**). Good cervical adhesion of a cementum-located restoration on tooth section (right) (**e**) and SEM (\(25\times\)). Inset, detailed cervical intact adhesive layer (\(100\times\)) (**f**). Black arrow, asterisk = microleakage; white arrow = resin tags, arrowhead = dentin tubuli. For the majority of restorations, a relative continuous adhesive layer was observed. This thin layer revealed good homogeneity and was composed of uniformly thick (\(\approx\)2 \(\upmu\)m) (Figure 3f) electron-dense structures (Figures 3d,f, 5c, and 6b) that virtually conformed to the tooth surface. Areas displaying increased thickness of the adhesive layer ranging between 2 and 10 \(\upmu\)m were also found (Figures 4f, 5d,e, and 6d). Well-formed resinous tags penetrating into the dentin ranging from 5 to 10 \(\upmu\)m (Figure 3a inset, Figures 5f and 6b) depending on the angulation of the section related to the tooth surface were observed. Normal dentin structure with dentin tubuli of about 2 \(\upmu\)m diameter (Figures 3a,b and 4d,e), and mosaic-like aspects of the restorations associated with filler load (Figures 3a,b, 4f, 5e and 6b) could also been described. Figure 4: Beautiful Flow II Plus® restoration. Good cervical adhesion of the cement-located restoration on the tooth section (right) (**a**) and on optical microscopy (**b**). SEM overview of the same restoration with good cervical adhesion and some white fissures in the occlusal enamel (upper-left) (25\(\times\)) (**c**). Random microleakage of the adhesive layer (250\(\times\)) (**d**). Detailed fissures in occlusal enamel (upper left) (100\(\times\)) (**e**). Continuous 5 \(\upmu\)m thick adhesive layer (500\(\times\)) (**f**). black arrow = enamel fissures, asterisk = microleakage, arrowhead = dentin tubuli. Figure 5: Dynamic Plus® restoration. Infiltrated cervical area of the cementum-located restoration on the tooth section (left) **(a)**, optical microscopy (**b**), and SEM image (upper-right) (25\(\times\)) (**c**). Cracked occlusal enamel on energy-dispersive X-ray analysis (EDX) image (500\(\times\)) (**d**) not interfering the adhesive layer of 2–6 μm (2000\(\times\)) (**e**). Well-designed resinous rete-tags of about 2 μm and adhesive layer of 6–8 μm (2000\(\times\)) (**f**). Black arrow = cracked enamel; white arrow = resin tag. Figure 6: Dynamic Flow® restorations. Good adhesion (**a**). Intact adhesive interface of the enamel-located restoration on SEM image (20\(\times\)). Inset, perfect visible 20 μm long rete tags (500\(\times\)) (**b**). Optical microscopy of restoration b (**c**).