TFF2 and periodontitis: The proportions of FG+/SP+ neurons, FG+/TRPV1+ neurons, or FG+/SP+/TRPV1+ neurons were not significantly different between the control and the ligature group (Figure 2G), suggesting that altered expressions of SP or TRPV1 in gingival afferents are not major contributors to the nociceptor regulation of periodontitis.