The 7 patients were divided into 3 groups according to whether taste buds were regenerated and whether or not the taste function completely recovered. Group 1 consisted of Nos. 2 and 7 with regenerated taste buds and complete recovery of the EGM threshold (Table 1). Figure 1A shows pre- and postoperative distributions of the number of taste buds per papilla in No. 2. The preoperative mean number of taste buds was 4.2, and the taste buds completely disappeared 13 days after surgery. Regenerated taste buds were first detected 6 months after surgery, and then the number of taste buds gradually increased. In the GLM of No. 2 under a binomial distribution, the fit was estimated as y = 5/[1 + exp(2.6827 – 0.1395x)] (a curved line in Figure 1A). In the
model, AIC and residual deviance were 106.04 and 26.546, respectively. The linear and constant models fit poorly: the AIC and residual deviance were 321.85 and 104.96 for the linear model, while those for the null model were 384.81 and 184.64, respectively. The lowest AIC of the GLM model among all models tested suggests that the logistic fit describes the change of taste buds after surgery better. Figure 1B shows the relationship between the fitting curve of the number of regenerated taste buds and the change of EGM thresholds. The EGM showed no response 13 days after surgery and began to recover 10 months after surgery. It reached the normal range (–4 dB) 21 months after surgery. Figure 1C shows regenerated taste buds in 2 FP of this case 24 months after surgery, as indicated in Figure 1A. Similar tendencies in taste bud regeneration and recovery of the EGM threshold were observed in No. 7. Taste buds had completely disappeared 42 days after surgery, and regenerated taste buds were first detected 5 months after surgery. Group 2 consisted of Nos. 3, 4, and 5 with regenerated taste buds and no recovery of the EGM threshold (Table 1). All taste buds had disappeared 17, 21, and 71 days after surgery, respectively. Figure 2A shows the distribution of the number of taste buds per papilla of No. 3. The mean number of taste buds was 2.1 preoperatively, and regenerated taste buds were first detected 8 months after surgery. However, regenerated taste buds were not found on the dorsal surface of the tongue and only on the tongue’s lateral border throughout the observation period. In the GLM of