## 4 Discussion
No previous studies were found comparing different manufacturing techniques on cantilever frameworks regarding the marginal adaptation. Therefore, it was not possible to compare the results of the study with previous studies. In the study, no differences in marginal adaptation were observed when comparing both frameworks design fabricated with the same technology. Likewise, no previous studies were found to compare the results of the study. Previous studies indicated that cantilevered metal-ceramic FPDs can be used effectively in posterior sectors [62], using non-noble alloys, and to replace a tooth with at least two abutment teeth [63; 64]. The evidence on the risk of failure of cantilevered FPDs is controversial when compared with the conventional FPDs with an intermediate pontic. Some authors demonstrated that the survival rates of cantilevered prostheses were lower and with more complications [62; 64], while others showed a comparable acceptable survival [65; 66; 67; 68], although it may vary according to the variables analyzed. Despite the fact that studies on the behavior of cantilevered FPDs are limited, it is important to evaluate this type of prosthesis because it is a treatment option as an alternative to implants or removable partial dentures in daily clinical practice. The different results among the studies may be due to the different methodology used and the absence of standardization. Several methods have been proposed for measuring the marginal fit, such as silicone replica [51; 69; 70], direct-view techniques [28; 39], profilometry [71; 72], or microcomputed tomography [60; 73]. In the study, the marginal fit was evaluated by direct viewing with external measurements on an SEM, based on a previous study that demonstrated that destructive methods are not required to assess the marginal fit [28]. There are other aspects that may also directly influence the marginal fit, such as the finish line, the cementation, and the porcelain veneering [26]. In the study, the finish line design was a chamfer, being the most used finish line in recent studies [16; 18; 20; 28; 29; 50; 53; 57]. The marginal fit measurements were performed on cemented frameworks to replicate the clinical practice. Previous studies have found higher misfit values after cementation [30; 31; 43; 50], probably due to the hydraulic pressure or the excess of cement [26]. In the study, glass-ionomer cement was used due to its reduced layer thickness [24], and the predetermined internal space for the luting agent was 50 um in all the frameworks, allowing an adequate cement flow as previously reported [29]. In addition, the luting procedure was carried out in a standardized way, under a seating force of 50 N, following previous studies that used as reference the 5 Kgf (49 N) [13; 24; 53; 69]. Regarding the veneering porcelain, there is no consensus on whether it affects the marginal fit [18; 43; 51; 74], and in the study, it has not been assessed because the purpose was to analyze only the behavior of the alloy by itself regardless of the veneering ceramic. Furthermore, the marginal adaptation can also be affected by the manufacturing technique and the Co-Cr alloy selected [60]. Although traditional techniques are handmade processes susceptible to error in any of its phases, and CAD-CAM technologies are automated processes, several factors can affect the marginal fit of the CAD-CAM restorations, such as the accuracy of the scanner, the data scanned transformation to three-dimensional models, and the machine precision [51; 75]. In the study, it was analyzed the same Co-Cr alloy with four manufacturing techniques, and it has demonstrated that it provided high precision (below 50 \(\upmu\)m) regarding the marginal adaptation, although it may also be due to the precision of the digital technologies employed, including the design and manufacturing of the wax patterns in the casting group. The study had some limitations.