## 4 Discussion
Temporary cements must provide sufficient retention to the prostheses and provide an efficient seal between the tooth and restoration. Our study indicated that the retention was superior with Kerr Temp-Bond clear cement than with Kerr Temp-Bond NE conventional cement. The result in the present study for the retentive force in group 1, i.e., milled crowns with 10-degree taper and cemented with non-eugenol cement (43.01 N), was slightly less than that in group 2, i.e., milled crowns with 10-degree taper and cemented with clear cement (43.57 N). However, the outcome pertaining to group 3, i.e., milled crowns with 20-degree taper and cemented with non-eugenol cement (49.25 N) was lower than that of group 4, i.e., milled crowns with 20-degree taper and cemented with clear cement (60.77 N). Significantly higher outcomes were achieved when clear cement was used along with 3D-printed crowns, as shown in the comparison of group 5, i.e., 3D-printed crowns with 10-degree taper and cemented with non-eugenol cement (49.47 N), and group 6, i.e., 3D-printed crowns with 10-degree taper and cemented with clear cement (158.38 N). The highest retentive pull-off force was recorded in group 8, i.e., 3D-printed crowns with 20-degree taper and cemented with clear cement (178.74 N). Temp-Bond clear cement is a dual-cure, eugenol-free, transparent, non-adhesive, resin-based cement for temporary and provisional restorations. It offers dual-curing, ease of handling, excellent bond strength, and easy retrievability when desired. Kerr Temp-Bond NE conventional cement is a non-eugenol, zinc-oxide-based temporary cement that may be used in patients allergic to eugenol [42]. A vigilant selection of temporary cement is as significant as the fabrication of the provisional prostheses, since the cement must retain the prostheses during function, provide an efficient seal at the margins, and decrease post-operative sensitivity [43]. [PERSON] et al. found that temporary crowns cemented with zinc oxide-based eugenol and non-eugenol cements had better retention than those cemented with resin-based temporary cement [44]. [PERSON] et al. found that the non-eugenol, resin-based temporary cement had the highest tensile strength, followed by the non-eugenol zinc oxide-based cement, and the least retentive strength was observed in the resin-based acrylic urethane cement [45]. In the present study, the samples were thermocycled for 5000 cycles between baths held at 5\({}^{\circ}\) and 55\({}^{\circ}\) with a dwell time of 60 s and a transfer time of 5 s using a thermocycling machine to represent 6 months in the oral environment. The clinical selection of long-term provisional crowns fabricated with 3D printing technology, prepared with 10\({}^{\circ}\) or 20\({}^{\circ}\) tapers, and cemented with clear cement would be most favorable in terms of the retention of crowns. 3D-printed provisional crowns can be used as an alternative to conventional and CAD/CAM-milled crowns for long-term provisionalization. However, the present study had some limitations. Occlusal forces acting on cemented restorations in the mouth are dynamic in nature, in contrast to the monotonic static loading used in this in vitro study. Experimental conditions can be carried out with cyclic loading for closer simulations of the oral environment in clinical situations. Further studies can also be conducted with different preparation designs to assess their influence on the mechanical properties of milled and 3D-printed provisional restorations, such as wear resistance, flexural strength, fracture toughness, and color stability [46]. Lastly, to standardize the tooth preparation, 3D-printed resin dies were used to cement the provisional crowns instead of natural teeth. The data obtained may overestimate the pull-off retentive force, because in clinical situations, the dentine cement interface may be weaker than the interface between the 3D-printed resin and the cement. Further in vivo studies should be conducted to confirm the results of this study.