## 4 Discussion  
This study showed that the average length of hospital stay increased by 25% after the COVID-19 pandemic. This may be due to later-stage diagnoses, which result in more extensive lesions and larger surgical areas. The length of hospital stay before the COVID-19 pandemic did not vary based on the location of MRONJ, whereas after the pandemic, it increased by 25-50% among patients with MRONJ in the mandible or maxilla. This could be attributed to the extended maxillary lesions, which are more difficult for patients to detect compared to those in the mandible. Furthermore, the length of hospitalization increased by 25% after the COVID-19 pandemic for patients with underlying conditions, such as multiple myeloma, NHL, breast cancer, and prostate cancer, and by 50% for those with osteoporosis and lung cancer. During the COVID-19 pandemic, oncology patients, particularly those at higher risk owing to age, likely had limited access to treatments and care despite the healthcare system's efforts to provide appropriate therapies for high-risk groups. During the quarantine period, many older patients avoided leaving their homes, which led to the neglect of their oncological therapies. This reluctance to seek care directly contributed to later diagnoses and more advanced stages of MRONJ. Osteonecrosis cases were more frequently observed in the mandible than in the maxilla, with a more pronounced shift toward mandibular involvement before the pandemic compared to after. These findings are consistent with those of previous studies, which show that the mandible is more susceptible to MRONJ owing to its poor blood supply, making the disease more likely to develop in this region [20; 21; 22]. MRONJ typically develops in patients undergoing treatment for conditions affecting bone metabolism, including cancers such as breast cancer, prostate cancer, renal cancer, multiple myeloma, and lung cancer, for which antiresorptive therapies, such as bisphosphonates or denosumab, are used to prevent bone metastases. Additionally, MRONJ can occur in patients receiving treatment for osteoporosis and other metabolic bone diseases. MRONJ is associated with the prolonged use of these medications, which inhibit bone remodeling and increase the risk of necrosis, particularly following dental extractions or oral surgeries [4; 5; 6]. Some articles have discussed the emergence of post-COVID-19-related osteonecrosis of the jaw (PC-RONJ) as a significant complication in patients recovering from COVID-19, highlighting cases of maxillary osteonecrosis and its association with corticosteroid use and underlying health conditions [23; 24]. Before the COVID-19 pandemic, the length of hospital stay did not differ for patients who underwent surgeries with and without PRF placement (average 4 days). However, after the pandemic, the average length of hospital stay increased by 20% for patients who underwent surgeries with and without PRF placement. Previous studies have discussed the  
Figure 2: Primary diseases for which antiresorptive medication was administered in the two groups. potential effectiveness of PRF in managing and preventing MRONJ. PRF plays a significant role in preventing MRONJ, particularly in patients undergoing antiresorptive therapy, due to its growth factor content and its ability to enhance wound healing. Furthermore, PRF has been reported to promote angiogenesis and soft tissue regeneration, thereby reducing the risk of MRONJ after dental extractions or surgeries. PRF is considered an effective adjunct in the prevention and treatment of MRONJ, enhancing tissue healing and reducing complications [25, 26, 27, 28]. The average fasting blood glucose level was 0.4 mmol/L higher in the post-COVID-19 group. However, it remained within the normal range (<6 mmol/L) in both groups. The difference in fasting blood glucose levels was minor and likely of little clinical significance.