## 4 Discussion  
According to our results, the 3D-printed standardized orbital implant has a more efficient outcome than the conventional manual-bending implant. The volume of the postoperative lesion side was not statistically different from the volume of the normal side in Group A, while those volumes were significantly different in Group B (\(p\)-value \(<\) 0.05). Considering that the normal, preoperative, and postoperative side orbital volumes of both groups were not statistically different, as shown in Table 2, the surgical result of group A is superior. The precise restoration of the fractured orbital structure is important. The restoration requires not only accurate deformation of the orbit but also the appropriate spatial positioning of the globe [16]. However, restoration of the premorbid bony contour [3,16] is challenging and can result in enophthalmos, dystopia, diplopia, and blindness [4, 5, 6, 7, 8]. Even a small change in orbital volume can cause significant enophthalmos [28, 29, 30, 31]. While the 3D-printed implant is made of PCL, the manual-bending implant is made of polyethylene. PCL, which is approved by the US Food and Drug Administration for use as a medical implant, is a non-toxic, biocompatible, and bio-degradable polymer [27,32]. Polyethylene is a highly stable and flexible material for facial implants and exhibits rapid ingrowth of tissue with collagen deposition and resistance to infection [33]. The most obvious difference between the two materials is that PCL is absorbable and polyethylene is non-absorbable. However, absorbable and non-absorbable implants in orbital wall reconstruction produce similar results in long-term follow-up [34,35]. Therefore, the disparity in results according to the absorbable characteristics of implant materials was excluded in the present study. Historically, organic autologous implants made of calvarium or cartilage have been introduced in reconstruction of orbital fracture [36]. In addition, inorganic implants including those of titanium, polyethylene, and poly lactic acid have been used [11, 12, 13, 14, 15]. Inorganic implants can be manipulated easily but can lead to complications including diplopia, exophthalmos, enophthalmos, or limited ocular movement due to inaccuracy [8]. Additionally possible is atrogenic injury to the surrounding tissue due to repeated insertion and withdrawal of the implant to obtain the suitable contour [3]. Recently, the PSI using 3D-printing technology has been introduced. This implant can be elaborately shaped to restore normal orbital anatomy at the fracture site [2, 3, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25]. Rapid prototyping (RP) has high applicability because it creates a complex model similar to a normal orbit. RP is used as a template to bend a customized implant made of a polymer such as titanium, [2, 3, 24, 25] because differences between both orbital volumes and contours are clinically minor. [37] PSI is created by computer-aided design and milled by computer-numerical-control from a titanium alloy block [23,38]. However, considering that orbital fracture is a common facial injury, RP and PSI are high-cost and time-consuming. Additional engineers are required to apply the software necessary to produce a customized product for each procedure. In a previous study, [26] the authors described the creation of a standardized 3D-printed implant. Orbital data obtained by 3D CT at an interval 1 mm from 100 adult cadavers, 50 males with a mean age of 50.4 years (range: 21-60) and 50 females with a mean age of 54.3 years (range: 27-60). The cadavers were limited to those presumed not to cause bone abnormalities due to the cause of death and its complications. In addition, when a metal component by dental treatment was present in the tooth, it was extracted. Then,orbital data were averaged and used to create 3D-printed implants. The implant design was suitable for a simulation test on 10 adult patients. The 3D-printed implant, which was initially 1.15 mm, now is being fabricated using 0.8-mm-thick polycaprolactone.