Background: Implant-supported dentures have become an essential means of restoring occlusal function after jaw reconstruction. Bone mineral density (BMD) may influence the success rate of implant denture restorations. This study aimed to explore whether the Hounsfield unit (HU) value can be used to monitor the changing trend of fibular BMD after jaw reconstruction. Results: A total of 54 patients who underwent maxillar/mandibular reconstruction with a fibula flap were included in this study. There was a significant correlation between the HU value and BMD at 1 week, 3 months, and 6 months after surgery, and both were significantly correlated with follow-up time. The difference between each pair of absorption rates (DAR) was less than 10% in 66.7% and 75.9% of patients at 3 and 6 months; however, the DAR was more than 20% in 12% and 13.8% of patients at 3 and 6 months, respectively. Conclusions There is a significant correlation between HU value and BMD. The HU value can be used to roughly reflect the fibular BMD changing trend in a group of patients as opposed to an individual, and the HU value is not equivalent to BMD.

Objective:To discuss the effect and prognostic factors of immediate facial nerve rehabilitation in malignant parotid gland tumor surgery.Methods:The patients with malignant parotid gland tumor who underwent facial nerve rehabilitation surgery in Peking University School and Hospital of Stomatology from January 2004 to July 2020 were retrospectively analyzed. Their demographic characteristics, preoperative and postoperative facial nerve function according to the House-Brackmann (HB) facial nerve grading system from HB grade Ⅰ to HB grade Ⅵ, injury sites of facial nerve including the trunks injury and branches injury, surgical timing including immediate rehabilitation and elective rehabilitation and rehabilitation methods such as facial nerve anastomosis, nerve transplantation, nerve transfer and muscle flap suspension were recorded. Patients were divided into two groups: satisfactory outcomes with HB grades Ⅰ-Ⅲ and unsatisfactory outcomes with HB grades Ⅳ-Ⅵ, and the factors that may affect the prognosis of facial nerve function were statistically analyzed. T-test was used to compare measurement data, chi-square test or Fisher’s precision probability test was used to compare count data. P<0.05 was considered statistically significant. Results:Eighty-nine patients were included in the study, including 50 males and 39 females, aged 9-82 years, the median age was 49.0 years. Preoperative facial nerve function outcomes were HB Ⅰ ( n=57), HB Ⅱ ( n=5), HB Ⅲ ( n=8), HB Ⅳ ( n=2), HB Ⅴ ( n=15) and HB Ⅵ ( n=2). Fifty-seven patients underwent immediate rehabilitation and 32 patients received elective rehabilitation. In 53 cases, the main trunk and/or the temporal and cervical trunk were injured, and 36 cases were branches injury. Facial nerve anastomosis was performed in 35 cases, 39 cases required nerve transplantation, 12 cases underwent nerve transfer, and 3 cases underwent muscle flap suspension. The follow-up time was 6-72 months. Postoperative facial nerve function outcomes were HB Ⅰ ( n=6), HB Ⅱ ( n=17), HB Ⅲ ( n=26), HB Ⅳ ( n=27), and HB Ⅴ ( n=13). Forty-nine cases were classified as group with postoperative HB grades Ⅰ-Ⅲ, and 40 cases were classified as group with postoperative HB grades Ⅳ-Ⅵ. Statistical analysis showed that there was no significant difference in terms of age and gender between two groups ( P>0.05). Among the patients with postoperative HB grades Ⅰ-Ⅲ, 73.5% (36/49) of the patients had immediate rehabilitation, 36.7% (18/49) of the patients had injury of the nerve trunks, 89.8% (44/49) of the patients had preoperative HB grades Ⅰ-Ⅲ, and 59.2% (29/49) of the patients had nerve anastomosis. Among the patients with postoperative HB grades Ⅳ-Ⅵ, 52.5% (21/40) of the patients had immediate rehabilitation, 87.5% (35/40) of the patients had injury of the nerve trunks, 65.0% (26/40) of the patients had preoperative HB gradesⅠ-Ⅲ, and 15.0% (6/40) of the patients had nerve anastomosis were in the group. There were statistically significant differences between the two groups ( P<0.05 or <0.01). Conclusions:Immediate reconstruction of the facial nerve defect during the operation of malignant parotid gland tumor can obtain better result. Furthermore, injury sites of facial nerve may affect the prognosis of facial nerve function as well.

Objective:To discuss the effect and prognostic factors of immediate facial nerve rehabilitation in malignant parotid gland tumor surgery.Methods:The patients with malignant parotid gland tumor who underwent facial nerve rehabilitation surgery in Peking University School and Hospital of Stomatology from January 2004 to July 2020 were retrospectively analyzed. Their demographic characteristics, preoperative and postoperative facial nerve function according to the House-Brackmann (HB) facial nerve grading system from HB grade Ⅰ to HB grade Ⅵ, injury sites of facial nerve including the trunks injury and branches injury, surgical timing including immediate rehabilitation and elective rehabilitation and rehabilitation methods such as facial nerve anastomosis, nerve transplantation, nerve transfer and muscle flap suspension were recorded. Patients were divided into two groups: satisfactory outcomes with HB grades Ⅰ-Ⅲ and unsatisfactory outcomes with HB grades Ⅳ-Ⅵ, and the factors that may affect the prognosis of facial nerve function were statistically analyzed. T-test was used to compare measurement data, chi-square test or Fisher’s precision probability test was used to compare count data. P<0.05 was considered statistically significant. Results:Eighty-nine patients were included in the study, including 50 males and 39 females, aged 9-82 years, the median age was 49.0 years. Preoperative facial nerve function outcomes were HB Ⅰ ( n=57), HB Ⅱ ( n=5), HB Ⅲ ( n=8), HB Ⅳ ( n=2), HB Ⅴ ( n=15) and HB Ⅵ ( n=2). Fifty-seven patients underwent immediate rehabilitation and 32 patients received elective rehabilitation. In 53 cases, the main trunk and/or the temporal and cervical trunk were injured, and 36 cases were branches injury. Facial nerve anastomosis was performed in 35 cases, 39 cases required nerve transplantation, 12 cases underwent nerve transfer, and 3 cases underwent muscle flap suspension. The follow-up time was 6-72 months. Postoperative facial nerve function outcomes were HB Ⅰ ( n=6), HB Ⅱ ( n=17), HB Ⅲ ( n=26), HB Ⅳ ( n=27), and HB Ⅴ ( n=13). Forty-nine cases were classified as group with postoperative HB grades Ⅰ-Ⅲ, and 40 cases were classified as group with postoperative HB grades Ⅳ-Ⅵ. Statistical analysis showed that there was no significant difference in terms of age and gender between two groups ( P>0.05). Among the patients with postoperative HB grades Ⅰ-Ⅲ, 73.5% (36/49) of the patients had immediate rehabilitation, 36.7% (18/49) of the patients had injury of the nerve trunks, 89.8% (44/49) of the patients had preoperative HB grades Ⅰ-Ⅲ, and 59.2% (29/49) of the patients had nerve anastomosis. Among the patients with postoperative HB grades Ⅳ-Ⅵ, 52.5% (21/40) of the patients had immediate rehabilitation, 87.5% (35/40) of the patients had injury of the nerve trunks, 65.0% (26/40) of the patients had preoperative HB gradesⅠ-Ⅲ, and 15.0% (6/40) of the patients had nerve anastomosis were in the group. There were statistically significant differences between the two groups ( P<0.05 or <0.01). Conclusions:Immediate reconstruction of the facial nerve defect during the operation of malignant parotid gland tumor can obtain better result. Furthermore, injury sites of facial nerve may affect the prognosis of facial nerve function as well.