| Author (Year) – Nail group | Proportion (%) | Chi-square (p-value) |
| Shah et al. (2004) - Solid | 8.3 | 7.333 (0.395) |
| Nambiar et al. (2018) - Hollow | 5.7 | |
| Maharjan et al. (2021) - Solid - Hollow | 3.3 0 | |
| Acharya et al. (2019) - Solid | 2.9 | |
| Deleanu et al. (2014) - Solid - Hollow | 0 0 | |
| Mathur et al. (2020) - Hollow | 20.0 | |
| Sathis (2017) - Solid - Hollow | 5.6 4.2 |