## 4 Discussion
There was a definitive increase in bone density in all the groups from baseline to 6 months with the highest in the periosteal pedicle group (group A--219.86 HU). Even the eggshell group (group B) did show a good gain of bone density, i.e., 119.71 HU. There was a clear-cut difference between OFD and the other test groups, i.e., 92.28 HU (OFD) vs 219.86 HU (group A), 199.71 HU (group B). Therefore, these intergroup differences were statistically significant. The superiority of results in the pedicle group (group A) could probably be attributable to the undifferentiated mesenchymal cells of periosteum [28]  
The present study is a pioneer in all its aspects. To date, none of the studies have used Eggshell-derived nano Hydroxyapatite (EnHA) for regeneration of intrabony defects and quantified it with CBCT also. Using a periosteal pedicle with EnHA in an intrabony defect and comparing it to EnHA, OFD for bone density is a pathfinder for future studies. A study by [PERSON] et al. [29] to assess the effect of EnHA on bone healing after surgical removal of mandibular third molars bilaterally, the values at baseline and 6 months were 117.21 HU and 117.13 HU in control group, i.e., without EnHA, and in test group, i.e., with EnHA, it was 116.88 HU and 120.42 HU. The bone density gain was higher in the present study group B (EnHA) compared to the study by [PERSON] et al. Bone fill is not the same as regeneration and can be defined as the restoration of tissue in a treated periodontal alveolar defect. The mean bone fill for control group was 0.71 \(\pm\) 0.46 mm, 2.06 \(\pm\) 0.74 mm for group A and 1.77 \(\pm\) 1.25 mm for group B. It can be appreciated that group A (pedicle group) has the highest bone fill followed by group B (eggshell group) with the difference being statistically significant. [PERSON] et al. in 2014 [4] compared OFD to periosteal pedicle as GTR membrane. Here, the defect fill was 1.40 \(\pm\) 0.16 mm for test group and 0.90 \(\pm\) 0.18 mm in control (OFD) group. The current study had higher values due to usage of combination therapy of periosteal pedicle and EnHA, which could be due to osteoinductivity of nanocrystalline HA. A study by [PERSON] et al. [2] comparing periosteal pedicle with open flap debridement for regeneration of intrabony defects showed a mean defect fill of 0.58 \(\pm\) 0.51 mm in control group and 2.42 \(\pm\) 0.3 mm in test group at 6 months. These values coincide with the results of the current study. A study by [PERSON] et al. [4] showed a defect fill of 1.7 \(\pm\) 0.5 mm in control group (OFD), 2.3 \(\pm\) 0.1 mm in GTR group (collagen membrane) and 3.1 \(\pm\) 0.5 mm in aCPRT group (periosteal membrane and autogenous bone chips). The aCPRT group, when compared to OFD, showed statistically significant differences. The difference in values did not reach the same levels in the present study compared to the study by [PERSON] et al. due to the 'Gold Standard' quality of the autogenous bone chips. EnHA is still an alloplast and not an autograft, thereby the lower bone fill. The PPD at the baseline was 7.57 mm (control), 9.86 mm (group A) and 9.43 mm (group B). It reduced by 1.57 mm, 1.86 mm and 2.14 mm at the first month and 2.71 mm, 3.57 mm and 4 mm at 3 months in the respective groups. The best reduction of PPD was seen at 6 months and was found to be 3.86 mm (control), 5 mm (pedicle group) and 5.43 (EnHA group). In a study by [PERSON] et al. [30], PPD reduction of 4.4 \(\pm\) 0.1 mm in aCPRT group, 5.3 \(\pm\) 0.2 mm in GTR group and 3 \(\pm\) 0.1 mm in OFD group. These findings correlate with our study findings. In the study by [PERSON] et al. [2], mean reduction of PPD from baseline to 6 months was 1.58 \(\pm\) 0.49 mm in control group (OFD) and 2.67 \(\pm\) 0.40 mm in the test group (periosteal pedicle) for the treatment of intrabony. The PPD reduction is higher in present clinical trial. The mean CAL gain from baseline to 6 months in control group was 3.86 \(\pm\) 1.46 mm, 5.0 \(\pm\) 0.81 in test group A (periosteal pedicle and EnHA) and 5.43 \(\pm\) 1.51 mm in group B (EnHA).