Under anesthesia, two implants were placed in maxillary diastemata in each rat (Fig. 2a). After implantation before the animal awakened, an X-ray was taken extraorally with a digital perioapical digital film. The X-ray indicates two implants were successfully placed in maxillary diastemata in one rat (Fig. 2b).

When rats arrived at animal facility, animals were stabilized for synchronizing. At day 50, rats were undergone implantation. One week after the implantation (day 57), a slight body weight loss of 2 g was observed. The body weight increase trend is recovered in 2 weeks after the implantation. As compared to the body weight continuing increase before the implantation, it indicates the procedure of implantation will have a slight effect on systemic condition (Table 1 and Fig. 1b).

Seven weeks after implantation, day 99 of the experiment, the rats were examined under anesthesia. Only one implant was survived and in a sounding condition without movement and sign of inflammation. X-ray indicates implant is located in maxillary diastema and surrounded by bone-like tissue (Fig. 2c). Implant success and failure rate is analyzed by using Clopper-Pearson’s exact method at 95% confidence interval. Our experiment data indicate that the true success rate of implantation in maxillary natural diastema in rat is less than 38.4% at a confident level of 95%. Since there is not enough data to construct a baseline of osseointegration with statistical significance (Fig. 1c), we ended the experiment at this time point and obtained samples for analysis.

Micro-CT was used to examine the location and osseointegration of the implant, indicating the implant is located in the maxillary diastema without dislocation (Fig. 3a–g). Micro-CT 3D constructed image indicates osseointegration around the implant fixture (Fig. 3 h).

Micro-CT images indicate maxillary fist molar site will be able to provide substantial cancellous bone to support a dental implant (Fig. 4).