Objective: Alveolar bone loss is a common adverse effect of intrusion treatment.Mandibular incisors are prone to dehiscence and fenestrations as they suffer from thinner alveolar bone thickness. Methods: Thirty skeletal class II patients treated with mandibular intrusion arch therapy were included in this study. Lateral cephalograms and cone-beam computed tomography images were taken before treatment (T1) and immediately after intrusion arch removal (T2) to evaluate the tooth displacement and the alveolar bone changes. Pearson’s and Spearman’s correlation was used to identify risk factors of alveolar bone loss during the intrusion treatment. Results: Deep overbite was successfully corrected (P < 0.05), accompanied by mandibular incisor proclination (P < 0.05). There were no statistically significant change in the true incisor intrusion (P > 0.05). The labial and lingual vertical alveolar bone levels showed a significant decrease (P < 0.05). The alveolar bone is thinning in the labial crestal area and lingual apical area (P < 0.05); accompanied by thickening in the labial apical area (P < 0.05). Proclined incisors, non-extraction treatment, and increased A point-nasion-B point (ANB) degree were positively correlated with alveolar bone loss. Conclusions While the mandibular intrusion arch effectively corrected the deep overbite, it did cause some unwanted incisor labial tipping/flaring. During the intrusion treatment, the alveolar bone underwent corresponding changes, which was thinning in the labial crestal area and thickening in the labial apical area vice versa. And increased axis change of incisors, non-extraction treatment, and increased ANB were identified as risk factors for alveolar bone loss in patients with mandibular intrusion therapy.

Background The current oil production determines oil workers’ occupational noise exposure. Without effective protection, noise will affect various aspects of worker’s body functions, including acting on the adrenal cortex system and resulting in renal function damage. Objective To evaluate the associations of noise exposure and its cumulative exposure level with renal function impairment of oil workers. Methods Oil workers from a collective medical examination in a hospital were selected as the study subjects. In accordance with the national standard Measurement of Physical Agents in the Workplace Part 8: Noise (GBZ/T 189.8—2007), noise exposure was measured three times at the oil workers' work site, and their average value was calculated to obtain the cumulative noise exposure (CNE). A questionnaire survey was conducted to collect general information such as socio-demographic characteristics, family history, lifestyles, and occupational history. All blood biochemical indicators were measured in the fasting state. Renal function impairment was judged based on the glomerular filtration rate. The relationship between CNE and renal function was analyzed using receiver operating characteristic curve (ROC) for workers with noise exposure. Results A total of 2 917 subjects were included in the study and their prevalence of renal function impairment was 14.2%. The univariate analysis results suggested statistically significant differences in the prevalence of renal function impairment among the oil workers grouped by having hypertension or not, gender, age, marital status, marital status, smoking, and alcohol consumption (P＜0.05); the prevalence of renal impairment was significantly higher in those with abnormal values of uric acid, total cholesterol, triglycerides, high-density lipoprotein, and fasting glucose than in those with normal values (P＜0.05); the oil workers with noise exposure [n=1565, 53.7%, equivalent sound level ≥80 dB(A)] showed a higher prevalence of renal function impairment than those without (P＜0.05). The results of multiple logistic regression analysis showed that being female (OR=2.811, 95%CI: 1.960-4.030), age at 31 years and above (OR_31-40=3.502, 95%CI: 1.402-8.751; OR_41-50=4.255, 95%CI: 1.759-10.291; OR_≥51=7.179, 95%CI: 2.864-17.996), showing abnormal uric acid (OR=5.932, 95%CI: 4.486-7.843), having hypertension (OR=1.593, 95%CI: 1.230-2.063), alcohol consumption (OR=2.648, 95%CI: 1.346-5.212), and smoking (OR=1.816, 95%CI: 1.133-2.911) had higher risks of developing renal function impairment; besides, those exposed to noise had 1.351 times (95%CI: 1.073-1.702) higher risks of developing renal function impairment than non-exposed individuals. Noise-exposed oil workers in the renal impairment group had higher noise exposure intensity and CNE compared to the noise-exposed oil workers in the normal renal function group (P＜0.05), and the workers had an increased risk of renal function impairment when the CNE was >95.85 dB(A)·year versus CNE ≤ 95.85 dB(A)·year (OR=2.583, 95%CI: 1.956-3.411). Conclusion Exposure to noise, higher noise exposure intensity, and higher level of CNE may be associated with developing renal function impairment in oil workers. Oil workers with CNE above 95.85 dB(A)·year are at an increased risk of renal impairment.