[Evaluation of Lateral Pterygoid Muscle Contraction in Patients with Temporomandibular Disorders Based on 3D-T2 Weighted Imaging].

Objective To evaluate lateral pterygoid muscle(LPM)contraction in the patients with temporomandibular disorders(TMD)based on 3D-T2 weighted imaging(3D-T2WI).Multiplanar reconstruction(MPR)was employed to measure the length of LPM in the images taken in closed-and open-mouth positions. Methods Seventeen TMD patients [age of(29.82±10.70)years,males/females=8/9] and 13 normal volunteers [control,age of(23.54±3.31)years,males/females=6/7] received 3D-T2WI of the temporomandibular joints in closed-and open-mouth positions from November 2019 to April 2020 in Department of Radiology,Hainan Hospital of Chinese PLA General Hospital.According to the position of the discs,the subjects were classified into the following groups:TMD with disc displacement without reduction(TMD-DDwoR),TMD with disc displacement with reduction(TMD-DDwR),TMD without disc displacement(TMDwoDD),and normal control without disc displacement(NCwoDD).MPR was employed to measure the maximal length of the superior belly of LPM.One-way analysis of variance,receiver operating characteristic curve,and permutation test were employed for the statistical analyses. Results The contraction of LPM was significantly shorter in TMD-DDwoR group [(3.36±1.96)mm] than in TMDwoDD group [(7.90±3.95)mm],NCwoDD group [(8.77±3.13)mm](F=12.891,P=0.000),and TMD-DDwR group[(7.12±3.69)mm](χ2=5.314,P=0.031). Conclusion This study confirmed that the contraction of LPM decreased in patients with TMD-DDwoR,which provided imaging evidence for the study of disc displacement mechanism in TMD patients.

Orthodontic-surgical treatment for severe skeletal class II malocclusion with vertical maxillary excess and four premolars extraction: A case report.

BACKGROUND: Patient satisfaction with facial appearance at the end of orthodontic camouflage treatment is very important, especially for skeletal malocclusion. This case report highlights the importance of the treatment plan for a patient initially treated with four-premolar-extraction camouflage, despite indications for orthognathic surgery. CASE SUMMARY: A 23-year-old male sought treatment complaining about his unsatisfactory facial appearance. His maxillary first premolars and mandibular second premolars had been extracted, and a fixed appliance had been used to retract his anterior teeth for two years without improvement. He had a convex profile, a gummy smile, lip incompetence, inadequate maxillary incisor inclination, and almost a class I molar relationship. Cephalometric analysis showed severe skeletal class II malocclusion (A point-nasion-B point = 11.5°) with a retrognathic mandible (sella-nasion-B point = 75.9°), a protruded maxilla (sella-nasion-A point = 87.4°), and vertical maxillary excess (upper incisor to palatal plane = 33.2 mm). The excessive lingual inclination of the maxillary incisors (upper incisor to nasion-A point line = -5.5°) was due to previous treatment attempts to compensate for the skeletal class II malocclusion. The patient was successfully retreated with decompensating orthodontic treatment combined with orthognathic surgery. The maxillary incisors were repositioned and proclined in the alveolar bone, the overjet was increased, and a space was created for orthognathic surgery, including maxillary impaction, anterior maxillary back-setting, and bilateral sagittal split ramus osteotomy to correct his skeletal anteroposterior discrepancy. Gingival display was reduced, and lip competence was restored. In addition, the results remained stable after 2 years. The patient was satisfied with his new profile as well as with the functional malocclusion at the end of treatment. CONCLUSION: This case report provides orthodontists a good example of how to treat an adult with severe skeletal class II malocclusion with vertical maxillary excess after an unsatisfactory orthodontic camouflage treatment. Orthodontic and orthognathic treatment can significantly correct a patient's facial appearance.

Brain activation patterns during unilateral premolar occlusion.

OBJECTIVE: To observe the characteristics of brain activation during unilateral premolar occlusion. METHODS: Functional magnetic resonance imaging was collected from 10 healthy volunteers during occlusion of the left first premolar (L1), left second premolar (L2), and right first premolar (R1). The brain activation patterns were analyzed, and the primary sensorimotor cortex, supplementary motor area, insula, thalamus, and prefrontal cortex were chosen as regions of interest. RESULTS: Single premolar occlusion activated the precentral gyrus, postcentral gyrus, cerebellum, thalamus, frontal lobe, hippocampus, cingulate gyrus, and parietal lobe. The brain areas showing activation during single premolar occlusion were similar to those activated by chewing. The activation pattern of L1 was more similar to that of L2 than R1. No significant left and right hemisphere differences in signal intensity were detected within the regions of interest. CONCLUSION: Brain activation patterns from two ipsilateral premolars were more similar than the pattern from a contralateral premolar.

[Investigation of the prevalence of temporomandibular disorders in 352 aged edentulous individuals].

OBJECTIVE: To study the prevalence of temporomandibular disorders (TMD) in 352 aged edentulous individuals in Beijing area and to analyze the correlative risk factors. METHODS: Three hundred and fifty-two aged edentulous subjects were included in the study (198 males and 154 females). The adopted questionnaire was designed according to Helkimo index, and the subjects were examined by the same examiner who would record every result as well. RESULTS: The prevalence of TMD's clinical positive signs in the edentulous subjects was 43.2% (152/352), among which temporomandibular joint (TMJ) noise [34.1% (120/352)] was the highest prevalent sign while TMJ pain on movemert was the lowest. The prevalence of mandibular movement deviation [18.2% (64/352)] fitted in between. The prevalence of TMD's clinical positive signs of male individuals was 36.9% (73/198), and the female was 51.3% (79/154). There was a significant difference in prevalence of TMD's clinical positive signs between males and females (P = 0.0067 < 0.01). The prevalence of TMD's clinical positive signs in denture wearing group was 38.6% (91/236) and that in no denture group was 52.6% (61/116). There was a significant correlation between the prevalence of TMD's clinical positive signs and wearing denture [P = 0.0125 < 0.05, OR = 1.767 (1.130 ∼ 2.763)]. CONCLUSIONS: Gender and malocclusion may be the risk factors of TMD in edentulous individuals.

[Shielding property of different prosthetic materials to shield radiation of (125)I seed].

OBJECTIVE: To investigation the shielding property to (125)I of several different prosthetic materials used in clinical when prostheses are used as carriers of (125)I seed in tumor treatment. METHODS: (125)I seeds were taken as the radiation sources to establish a model in vitro and the radiation doses were measured by thermoluminescent dosemeters (TLD). The shielding property of titanium plate, cochrome plate, and poly methyl methacrylate (PMMA) plate were detected, calculated and compared with that of plumbum plate in the control group. RESULTS: The radiation doses of the radiation source at 10 mm distance through the following materials were measured, and the results are 2.805 mGy (0.09 mm thick titanium plate), 1.082 mGy (0.48 thick titanium plate), 0.390 mGy (0.41 mm thick cochrome plate), and 0.261 mGy (0.67 mm's cochrome plate), and 2.885 mGy (1.685 mm thick PMMA plate). CONCLUSIONS: The shield property of cochrome is optimal. The poly methyl methacrylate behaves to some extend as a shield to the (125)I seed which can shield the radiation as the effects of plumbum when adopted together with the 0.557 mm's (or more) titanium plate.

[Using TiNi-SMA distractor for mandibular alveolar ridge augmentation by distraction osteogenesis: a preliminary study].

OBJECTIVE: To study the possibility of mandibular alveolar ridge augmentation by distraction osteogenesis using TiNi-SMA (shape memory alloy) distractor. METHODS: All of the mandibular premolars and the first molar were extracted from ten adult mongrel canines. One month later, box-shaped osteotomies of the alveolar bone were performed out and TiNi-SMA distractors were buried in experimental group. The bone height was measured before and 1, 5, 13 weeks after the operation. The radiographs were taken on the day of, and 1, 5, 13 weeks after operation. The animals were killed at one or three months after distraction and examined histologically. RESULTS: The bone segments were lifted up immediately after the insertion of distractors and the height achieved 7.5 - 11.5 mm one week after the operation. One month after distraction, the radiographs showed there was regeneration of bone in distraction gap. The new bone and the normal bone could not be differentiated clearly three months after distraction. No bone resorption was found during this period. In histological sections, there were collagen bundles in early distraction, then these bundles were calcified and became traeculaes. CONCLUSION: It suggests that the canine mandibular posterior alveolar ridge can be augmented by distraction osteogenesis using TiNi-SMA distractor, and the new bone is formed by intramembranous ossification.