3.4.3. Micro Computed Tomography (μCT)

Mean bone volume (%) in the control group was 18.19 ± 4.39% and in the Hepa/Ti, PDGF/Hepa/Ti, BMP/Hepa/Ti, and PDGF/BMP/Hepa/Ti groups mean bone volumes were 13.05 ± 5.15, 21.29 ± 9.56, 40.95 ± 9.07, and 43.73 ± 6.75%, respectively (Figure 7; *n* = 8). Bone volumes in the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups were significantly higher than in the other groups (*p* < 0.05). But, there was no significant difference between the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups (*p* > 0.05).

**Figure 7.** μCT 3D images of the five study groups. (**a**) Ti group; (**b**) Hepa/Ti group; (**c**) PDGF/Hepa/Ti group; (**d**) BMP/Hepa/Ti group; and (**e**) PDGF/BMP/Hepa/Ti group (×12.5 magnification). Note pronounced re-modeling of peri-implant bone and vertical bone growth in the BMP/Hepa/Ti and PDGF/Hepa/Ti groups. No bone growth was observed in defect areas in the Ti, Hepa/Ti, and PDGF/Hepa/Ti groups.

#### 3.4.4. Histomorphometric Analysis

Jaw quadrants in the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups exhibited bone formation approaching microthreads and bone remodeling around implants (Figure 8). There was about 1.1 mm more bone gain in the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups than in the control group (*p* < 0.05). In the control and heparin groups, vertical bone loss was observed in buccal defect areas. The control, heparin, and PDGF groups showed failure of osseointegration in lingual regions observed a 1 mm gap between fixture and bone (Figure 9). The microBIC values of the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups were significantly greater than those of the other groups (*p* < 0.05), but no significant difference was observed between the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups (*p* > 0.05). The BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups showed successful osseointegration in lingual portions (Figure 10). Mean group percentages (±SD) of BIC and ITBD within macrothreads eight weeks after surgery were not significantly different (*p* > 0.05) (Table 3).

**Figure 8.** Histological specimens of the five groups. (**a**) Ti group; (**b**) Hepa/Ti group; (**c**) PDGF/Hepa/Ti group; (**d**) BMP/Hepa/Ti group; and (**e**) PDGF/BMP/Hepa/Ti group (×12.5 magnification). Note pronounced peri-implant bone re-modeling and vertical bone growth in the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups. Red lines indicate defect levels.

**Figure 9.** Microthread defect areas in the control (Ti), Hepa/Ti and PDGF/Hepa/Ti groups. Group BIC and ITBD within macrothreads at 8 weeks after surgery were not significantly different. In the control and heparin groups, vertical bone loss was detected in buccal defect areas. Failure of osseointegration in the lingual portion observed as a 1 mm gap between fixture and bone was present in the control, heparin, and PDGF groups. (**a**–**c**) Ti group; (**d**–**f**) Hepa/Ti group; (**g**–**i**) PDGF/Hepa/Ti group; (**a**,**d**,**g**) lingual portion of microthread; and (**c**,**f**,**i**) buccal portion of microthread. (**a**,**c**,**d**,**f**,**g**,**i**) ×40 magnification, (**b**,**e**,**h**) ×12.5 magnification.

**Figure 10.** Microthread defect area in the BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti groups. The BMP/Hepa/Ti and PDGF/BMP/Hepa/Ti group exhibited successful osseointegration in lingual portions. (**a**,**d**) lingual microthread portion; (**c**,**f**) buccal microthread portion; (**a**–**c**) BMP/Hepa/Ti group; (**d**–**f**) PDGF/BMP/Hepa/Ti group. (**a**,**c**,**d**,**f**) ×40 magnification, (**b**,**e**) ×12.5 magnification.

**Table 3.** Results of histometric analysis performed at 8 weeks after surgery. (Buccal bone level, BIC on macrothreads, and bone density on macrothreads; *n* = 8).


Notes: BG: Bone growth height in buccal defect area (mm); microBIC: Bone to implant contact in the microthreads (%); macroBIC: Bone to implant contact in macrothreads (existing bone area around implant, %); ITBD: Intra-thread bone density in macrothreads (existing bone area around implant, %); a,b: Means with the same superscripts in same columns were not significantly different; *p* values were obtained by ANOVA; \**p* < 0.05.
