## 4 Discussion
Specifically, when applying a temperature of 1430 \({}^{\circ}\)C, values of 9.18 GPa MH and 6.28 KIC FT were obtained [42]. However, they are consistent with the observations of [PERSON] et al. [68], who, when studying 3Y-TZP zirconia-based materials at 1450 \({}^{\circ}\)C for 1 h, found values varying between 4.8 \(\pm\) 0.5 KIC and 7.4 \(\pm\) 0.6 KIC for FT and between 11 \(\pm\) 0.9 GPa and 13 \(\pm\) 0.3 GPa. These data reaffirm the relevance of considering multiple factors, including material specifications, when evaluating mechanical properties in dental ceramics. Ultimately, Incoris TZI excelled with short sintering cycles of 15 min at elevated temperatures without compromising the mechanical properties of the material. However, although U&C International's Razor Zirconia showed higher MH and FT, it used longer cycles. It is important to highlight that the analysis of the mechanical properties of ceramic materials is also directly related to the design of the dental preparation and crown preparation, milling of the block, type of cementation, and mechanical forces that occur during mastication that can lead to catastrophic failure in the short term. For this reason, they are variables that cannot be isolated and should be evaluated [69; 70; 71]. For example, it has been reported that the occlusal force will depend on age, gender, and the strategic position of the teeth in the dental arch [72], marking a great difference in values [73]; however, a dental restoration should support 2000 N, considering the occlusal force in parafunction [74]. Several studies have shown that the chemical interaction that occurs in the cement strategy significantly increases the mechanical behavior of ceramic restorations [75; 76; 77]. Occlusional morphology also has a significant relevance in the FR of CAD/CAM ceramics. A study by [PERSON] et al. investigated the RF of ceramic crowns in the posterior sector with and without manual enhancement of occlusal morphology (MEOM). The results indicated that performing MEOM resulted in a significant decrease in the RF of ceramics and is, therefore, considered detrimental and should be avoided [78]. Time optimization and energy savings are crucial factors in CAD/CAM technology, which is why furnace manufacturing companies have developed equipment that followsthis philosophy. However, despite the diversity of heat treatment protocols available, our systematic review revealed that there are specific protocols for sintering and crystallization of CAD/CAM ceramic materials that can significantly improve mechanical properties. It is important to consider the microstructure of these materials, and it is essential to follow the manufacturer's indications to avoid alterations, optimizing the biomechanical behavior of the restorations with clinical longevity as the oral cavity is influenced by various factors [79]. As outlined in the methodology, QUIN tools, tools specifically designed for assessing quality and the risk of bias in in vitro dental studies, were employed [31]. These tools constitute a fundamental basis for clinical decision making in evidence-based dental practice [80,81]. It is relevant to note that question 10 could not be considered as it was not applicable to the studies included in our SR. This may be attributed to the awareness among researchers in in vitro studies examining the effects of AHT on the mechanical properties of CAD/CAM ceramics. They understand the importance of adhering to the protocols recommended by the material's manufacturer to avoid alterations in microstructure or optical properties [44,82,83]. Finally, it is important to highlight the limitations inherent to this SR. A notable heterogeneity was observed in the selected studies, attributable to the diversity of furnaces, commercial brands, times, and heat units used. This variability was also reflected in the mechanical properties analyzed, preventing the performance of a consolidated meta-analysis. Additionally, some excluded studies had discrepancies in the sample or in the presentation of data.