## 4 Discussion
The two connected retainers were also designed with the 3D software Exocad (DentalCAD 3.1 Rijeka, Exocad, Darmstadt, Germany), which was used to select the measurements of the connector area during the design process. Testing using the Instron machine (Instron 5969, Norwood, MA, USA) utilized a 2.5-mm three-dimensional generated rod that simulates the loading of a cusp area directly on the connector. The loading was configured at a 0-degree angle from the connector's vertical axis. In the literature, the connector area is commonly tested on three-unit, four-unit, or long-span FDPs, regardless of the type of materials [18; 19; 25; 26]. Although the pontic design of FDPs is more critical with connector area testing in the literature, the fabrication of two-unit FDPs in this study aids in minimizing the factors that could influence the results. If there is a pontic design, the force distribution in the three-point universal testing may affect the fracture resistance load and the mode of fracture readings. Additionally, the retainers (crowns) were designed with exact tooth dimensions that follow the abutment preparation to ensure the connector area is in the middle of the metal model. To resemble a clinical scenario with triangular connector designs, avoiding an unequal force distribution on the connector area that could influence the fracture properties of 3D-printed resin material is our priority in this study. A study by [PERSON] et al. in 2013 [34] tested the stress distribution using finite element analysis. The study found that the maximum [PERSON] stresses are concentrated at the connector area, especially in the cervical region [34]. The cylindrical connector design was less stressed than the triangular design [34]. All-ceramic FDPs framework strength depends on the connector dimension [3]. Hence, it is necessary to enhance the strength of 3D-printed resin FDPs by manufacturing an adequate connector dimension. In addition, [PERSON] et al. in 2014 found the failure probability decreased with the high width of the connector [25]. For all ceramic prostheses, the connector dimension is more important than the abutment core thickness, as found by [PERSON] et al. in 2013 [16]. In another study, [PERSON] et al. found that nonrigid connectors produced less stress than rigid ones [33]. In this study, evaluating the connector dimension on fracture properties for a ridge connector is essential. According to [PERSON] et al., the nonrigid connector transfers the stress to the supporting structure rather than concentrating it in the connector area [22]. In addition, [PERSON] et al. (2019) recommended that minimum connector dimensions prove crucial for the load-bearing capability of monolithic e.max CAD FPDs [24]. Significantly, the reduction of connector dimension increased the strength of 3D-printed resin FDPs. According to the results, the mean of Modulus, Yield Strength, and Compressive Strength of 2 \(\times\) 3 mm connectors were significantly larger among the other groups. In triangular connector shape design, the cross-sectional connector area decreases as the connector dimensions decrease, Table 1, which is the denominator that the fracture load will be divided on to produce the stress values in megapascals. We should remember that usually, in three-point bends of specimens that have relatively comparable cross-sections, stress can be compared easily since the denominator is almost equal. However, in this current study, we are comparing loads, moduli, and strengths that are different in cross-section, which makes it look odd that the fracture strengths were reduced as the cross-section decreased. Another way to look at it is to normalize those loads and strengths by unifying the denominators across the tested groups. Then, the results may look more relevant and comparable. [PERSON] et al. tested all ceramic zirconia-based FDP connector diameters [26]. The authors evaluated the fracture strength properties of varied materials.