In our retrospective study, the autotransplantation teeth, using 3D replica, was an efficient method with a 100% success rate during one-year follow-up, according the success criteria previously mentional. Verweij et al[14] reported that high success rates were reported when using donor tooth replicas, success and survival rates of 80.0 - 91.1 % and 95.5 - 100 %, respectively. Healthy periodontal ligament and the good tissue adaptation are considered the most important factors in successful tooth transplantation[12]. Meanwhile, the extraoral time, number of fitting attempts of the donor teeth, skill of surgeon, and the trauma of the recipient socket may influence the periodontal ligament.
We used a 3D replica of donor tooth to preserve the periodontal ligament of the donor tooth. Firstly, the 3D replica of donor tooth can replace the real one to determine whether the recipient socket is ideally suited for the donor tooth; the process will damage the periodontal ligament seriously. Second, the use of the 3D replica of donor tooth shorten the extraoral time to 0-4 mins in our surgery. Meanwhile the use of minimally invasive technique reduced the damage of the periodontal ligament during the extraction of the donor tooth. Andreasen et al reported that the normal periodontal healing would proceed if the extraoral time of the donor tooth was less than 18 min[19]. The extraoral time in our cases were much less than 18 min and were consistent with other clinical studies. As Jang et al reported that there were immediate autotransplantation in four of five teeth and one with 2 min extraoral time[6].
In our cases, there are two cases cost 3.5 and 4 minutes due to the error range of the 3D replica, that is the inaccuracy of the model. So the accuracy of the 3D replica model is important to the produce of the surgery. The accuracy of the 3D replica model also effected the fitness of the donor teeth to the recipient socket. Many factors may affect the accuracy of the replica model, such as the data from the CBCT, the material shrinkage during the building or postcuring and the minimal thickness of the layers[20]. So far there is no standard definition of the clinically acceptable differences between the replica model and the donor teeth, although several studies reported that the differences of less than 0.25 mm are clinically acceptable[21]. And Lee et al reported that the mean deviations of the replica model manufactured by 3D printer were 0.038-0.047 mm[22], which is much less than the clinically acceptable value. Also Lee and Kim reported that the 3D replica models were, on an average, 0.149 mm smaller in size than the real teeth[23]. And Khalil et al proved that the dimensional differences between the 3D replica models made by 3D printing technologies and the real teeth were below 0.25 mm, which is accepted by the clinical demand[24]. Therefore, the 3D printing technologies, used for 3D replica models of the donor teeth, is accuracy enough for the autotransplantation of the teeth. The fitness of the donor teeth to the recipient socket was well in our clinical operation, expect the two cases due to the date of the CBCT was incomplete during the date transmission.
The use of a 3D replica model of a donor tooth can not only reduce the damage to the periodontal ligament but also increase the ease of the autotransplantation and lower the requirement for the experience of the surgeon. Verweij et al demonstrated that the surgery time of the autotransplantation when using replica model can be shorten to less than 30 minutes even if the surgery was done by a less experienced surgeon[25]. Shahbazian et al compared the traditional technique to 3D autotransplantation and found that the time of the surgery proceduce were 40-90 min and 30-45 min, respectively[26].
Many other factors affect the success of the autotransplantation tooth. Yoshino et al analyzed the influence of age on the tooth autotransplantation and found that the younger the patient is, the higher success rate of the tooth autotransplantation, the success rate was lower in the 55-69 years old group[27]. Sugai et al and Yoshino et al also reported that patients under 40 years old showed a higher success rate than the older one group[28, 29] Yoshino et al also analyzed the influence of gender on the tooth autotransplantation and found that compared with female the survival rate of the tooth autotransplantation of males was low at 5-years, 10-years and 15-years follow-ups and need more attention during the autotransplantation process[30]. Therefore, the use of donor tooth replicas are more needed in male patients so that the surgery process can be handle well.
The third molars slated for autotransplantation in all cases in the present study is mature teeth with developed roots, so the revascularization of the pulp is not likely to happen after transplantation and needed root canal therapy[28, 31]. Some cases in the present study use the GBR to regeneration the bone defect. Yu. HJ et al reported that using GBR during autotransplantation in recipient site where buccolingual alveolar bone atrophy had occurred could also result in a good long-term outcome[17]. Other studies also proved that the usefulness of GBR in the autotransplantation at recipient sites with bone defects[16]. The autogenous bone that was collected from extraction socket was used for the GBR in the present study. Compared with xenogenic bone, autogenous bone has the capable of osteogenesis, osteoinduction, and osteoconduction, and may reduce the forgein-body reaction. The success rate of using GBR in autotransplantation is consistent with the non GBR one.
The success rate of the autotransplantation, using 3D replica, is high, but the long-term survival rate still need to be observed, and the precise of the autotransplantation need not only a 3D replica as a guide but also a preparation guide of the recipient site and a guide for occlusion, all of which still need more research.