Upon a comprehensive literature search, there are articles reported to place implants at maxillary first molar area. However, for variant reasons, these models are not clinical comparable. First, animal sizes are too small to have enough bone to support implant, i.e., Koutouzis et al. reported their experiment on rat model [31]. They placed diameter 1.5 mm × 2 mm length implants in approximately 9-week-old male Wistar rats in which maxillary first molars were extracted at week 5. It is just showed by figures in their article that the interradicular bone at the maxillary first molar obviously less than 2 mm, and the 2-mm length implant is projected into the sinus. And even in sham control rat (as showed in the article Fig. 5e, f), almost half of the implant was exposed in oral cavity without bone support, indicating body size of the rat is a crucial issue to take in consideration. Second, implant placement in clinically irrelevant position. Du et al. presented their research about place implant in 3-month female Sprague-Dawley rats [32]. Body weight is between 245 g and 279 g. They extracted the maxillary first molar and placed implant at mesial dental root socket. However, immediate implant placement at maxillary molar roots sockets in clinic should avoid for easily penetrating the floor of maxillary sinus and even dislocating the implant into the sinus due to the maxillary first, and second molar roots are close to the floor of sinus, particularly, in pneumatized sinus, so that interradicular bone in socket is the option to place implant. Therefore, the model reported by Du et al. is not clinically comparable. Third, bone of extract sockets has not appropriately formed. Inouye et al. [33] and Lin et al. [34] reported their experiments. They extracted the maxillary first molar from rats and placed implant at the socket area 4 weeks after the extraction. Histologically, bone formation starts at 4 weeks and complete around 24 weeks after the dental extraction; therefore, the socket has only soft tissue and immature bone at 4 weeks post extraction [35]. Clinically delayed implant placement must be in 12 weeks or more post extraction to wait for completion of alveolar bone formation [35, 36]. Thus, this model is not clinically relevant. Consequently, the maxillary first molar socket as an implantation site remains to be improved.