“…The number of articles is given within brackets region-wise and research topic-wise. Note 1: Mallampati et al (Mallampati et al, 2016) Singh, Yang, et al (2016c), Singh, Yang, et al (2016b), and Singh, Chang, et al (2016a). Studies focusing on the estimation of recovery potential: (Reuter et al, 1999), (Péra et al, 2004), (Bareel et al, 2006), (Allen and Kolb, 2009), (Konetschnik and Schneeberger, 2009), (Edo et al, 2013), (Ahmed et al, 2014), (Johansson et al, 2017).…”