Prediction of jaw opening function after mandibular reconstruction using subject-specific musculoskeletal modelling.

BACKGROUND: Mandibular reconstruction patients often suffer abnormalities in the mandibular kinematics. In silico simulations, such as musculoskeletal modelling, can be used to predict post-operative mandibular kinematics. It is important to validate the mandibular musculoskeletal model and analyse the factors influencing its accuracy. OBJECTIVES: To investigate the jaw opening-closing movements after mandibular reconstruction, as predicted by the subject-specific musculoskeletal model, and the factors influencing its accuracy. METHODS: Ten mandibular reconstruction patients were enrolled in this study. Cone-beam computed tomography images, mandibular movements, and surface electromyogram signals were recorded preoperatively. A subject-specific mandibular musculoskeletal model was established to predict surgical outcomes using patient-averaged muscle parameter changes as model inputs. Jaw bone geometry was replaced by surgical planning results, and the muscle insertion sites were registered based on the non-rigid iterative closest point method. The predicted jaw kinematic data were validated based on 6-month post-operative measurements. Correlations between the prediction accuracy and patient characteristics (age, pathology and surgical scope) were further analysed. RESULTS: The root mean square error (RMSE) for lower incisor displacement was 31.4%, and the error for peak magnitude of jaw opening was 4.9 mm. Age, post-operative infection and radiotherapy influenced the prediction accuracy. The amount of masseter detachment showed little correlation with jaw opening. CONCLUSION: The mandibular musculoskeletal model successfully predicted short-range jaw opening functions after mandibular reconstruction. It provides a novel surgical planning method to predict the risk of developing trismus.

Somatosensory and trigeminal pathway abnormalities in Chinese patients with trigeminal neuralgia.

This study aimed to evaluate somatosensory function in Chinese patients with trigeminal neuralgia (TN) using a standard quantitative sensory testing (QST) battery and electrophysiological tests consisting of contact heat-evoked potentials (CHEPs) and blink reflex (BR). Twenty patients with TN and 20 sex- and age-matched healthy controls were recruited for this study. A standard QST protocol recommended by the German Research Network on Neuropathic Pain was carried out on the patients' painful and contralateral faces, the controls' right faces, and all participants' right hands. The CHEPs and BR were recorded at the Cz electrode and bilateral lower bellies of the orbicularis oculi, respectively, with thermal stimuli applied to both sides of the patient's face and the control's right face. The cold detection threshold, heat pain threshold, and mechanical pain threshold on the painful face were lower than those of healthy controls (P < 0.05), whereas the cold pain threshold and mechanical detection threshold were higher (P < 0.05) on the painful faces than those of the contralateral faces from patients or healthy controls. Mechanical pain sensitivity was higher in both test sites than in healthy controls (P < 0.05). Significantly longer N latencies (P < 0.05) and lower N-P amplitudes (P < 0.01) were detected in the patients' painful sites than in the contralateral sites and those of healthy controls. Comprehensive somatosensory abnormalities were found in painful facial sites in patients with TN, suggesting disturbances in the processing of somatosensory stimuli. Deficiencies in electrophysiological tests further revealed unilaterally impaired function of the trigeminal pathway in TN patients.

Endoscopic visualization of the inferior alveolar nerve associated with somatosensory changes after impacted mandibular third molar extraction.

The aim of this study is to assess the relationship between somatosensory functional changes and inferior alveolar nerve (IAN) exposure after impacted mandibular third molars (M3M) removal. We recruited 35 patients who underwent impacted M3M extraction near the IAN. The M3Ms were extracted by combined endoscopy, piezosurgery, and contra-angle high-speed turbine handpiece. All IAN canal perforations and exposed regions were recorded and measured by endoscopy after extraction and on cone-beam computed tomography (CBCT) images before extraction. The patients were followed up 1, 7, and 35 days after surgery. A standardized quantitative sensory testing (QST) battery was performed on the lower lip skin. All of 35 cases had exposed IAN on CBCT images, 5 of which had no exposed IAN under endoscopy. For the other 30 cases, the endoscopy-measured IAN length and width were shorter than the CBCT measurements (P < 0.001). The warm and mechanical detection thresholds (MDT) on the operation side were significantly higher than the contralateral side after surgery (P < 0.05). Thermal sensory limen, MDT, and cold pain threshold were strongly correlated with the exposed IAN length and MDT also with the exposed IAN width one day after surgery. In conclusion, it was found that not all exposed IAN in CBCT images were real exposure after surgery. The intraoperative exposed IAN endoscopic measurements were smaller than by CBCT and strongly correlated with some QST parameters.

Digital replication and transfer of interim to definitive complete arch implant-supported fixed prostheses by using a laboratory scanner.

The present technique describes an effective digital approach for the replication and transfer of occlusion, maxillomandibular relationship, and esthetic parameters from interim to definitive complete arch implant-supported fixed prostheses by laboratory scanning with transfer plates. Monolithic zirconia complete arch implant prostheses have been fabricated with satisfactory functional and esthetic outcomes.

[Study on prediction of involvement in facial nerve in the patients with parotid tumors by using facial electroneurography].

OBJECTIVE: To investigate the possibility of predicting facial nerve involvement in the patients with parotid tumors using facial electroneurography (ENoG). METHODS: In the study, 53 patients with primary parotid tumors were included in the study, 28 were benign tumors and 25 were malignant. There was no significant difference of tumor locations and sizes between the two groups. House-Brackmann facial nerve function evaluation was grade I in all the patients who received examination of facial electroneurography, including stimulation strength, amplitude, and latent time bilaterally. The facial electroneurography results in the affected side were compared with the results of contralateral normal side, intraoperative appearance and postoperative histopathological diagnosis. The facial electroneurography results were analyzed by Wilcoxon signed rank test and receiver operator characteristic (ROC) curve. RESULTS: During the facial electroneurography examination, the mean stimulation strength in the patients with benign parotid tumor was 20.0 mA. There was significant decrease in the amplitude at the affected side compared with the normal side upon posterior auricular stimulation (P<0.05). But there was no significant difference in the latent time between the bilateral sides (P>0.05). However, in the patients with malignant parotid tumor, the mean stimulation strength was higher at 24.5 mA. There was significant decrease in the amplitude or even no response at the affected side compared to the normal side upon posterior auricular stimulation (P<0.05). No response was detected in the multiple branches of facial nerve of affected sides in 36.0% patients upon posterior auricular stimulation. The amplitude of branches III and IV was significantly lower at the affected side than that at the normal side upon anterior auricular stimulation (P<0.05). The area under the ROC curve for ENoG was 0.884. CONCLUSION: When the facial nerve was involved by the parotid tumors, the stimulation strength in the electroneurography was larger. There was significant difference in the amplitude and the latent time of the facial nerve between the affected side and the normal side upon the posterior auricular stimulation. The rate of absence of reaction wave was higher in the patients with malignant tumors. It was feasible to predict the facial nerve involvement by ENoG for the parotid gland tumor patients without clinical appearances of facial paralysis.

[Comparison of self-controlled retruded approach and bimanual manipulation method on the relationship of incisal point displacement in the mandibular retruded contact position].

OBJECTIVE: To evaluate the relationship of incisal point displacements in the mandibular retruded contact position (RCP) between the self-controlled retruded approach and bimanual manipulation method. METHODS: Twelve healthy young volunteers were selected. The RCP was guided through the self-controlled retruded approach and bimanual manipulation method. The track of the incisal point was recorded, using the mandibular movement trace recording system. The movement direction of the incisal point in horizontal plane was observed. The distance between the incisal point of the RCP and intercuspal contact position (ICP) was measured. RESULTS: Except one volunteer's incisal point movement direction of the RCP was oblique, others were straight toward posterior. The displacements of the incisal point from the ICP to RCP guided through self-controlled approach and bimanual manipulation method were (1.15 ± 0.64) mm, (0.98 ± 0.29) mm respectively. There was no statistical significance between the two methods (P > 0.05). CONCLUSION: The displacements of the incisal point from the ICP to RCP guided through self-controlled approach and bimanual manipulation method are approximately the same.

[Pilot evaluation of masticatory efficiency and patients' satisfaction in long-centric occlusal pattern complete denture wearers].

OBJECTIVE: To assess the masticatory efficiency and patient' satisfaction in long-centric occlusal pattern complete denture wearers. METHODS: The anatomic occlusal pattern and long-centric occlusal pattern complete dentures were made for each of 10 edentulous patients with severe alveolar rigde absorption simultaneously using the technique of interchangeable artificial teeth. The order of delivery of different occlusal pattern complete denture was determined according to randomized principle. For each kind of occlusal pattern complete denture, the masticatory efficiency was measured with spectrophotometer after the dentures were worn 2, 4, 6, 8, 10 and 12 weeks. A psychometric questionnaire was completed by the patients after wearing the dentures for more than three months and analyzing the patients' rating of the denture satisfaction. RESULTS: No significant differences in masticatory efficiency was found between the long-centric occlusal pattern complete denture wearers and the anatomic occlusal complete denture wearers. The patients' grade of denture satisfaction in long-centric occlusal pattern complete dentures wearers was significantly better than that in anatomic occlusal denture wearers (P<0.05). CONCLUSION: Complete denture with long-centric occlusion can be used to improve the clinical effect of edentulous patients with severe absorption of residual alveolar rigde.

[Effect of early-loaded small diameter implants retained mandibular overdentures on masticatory performance].

OBJECTIVE: To evaluate the clinical effect and masticatory efficiency of two early loaded Small Diameter Implants (SDI) retained mandibular overdentures. METHODS: Eight mandibular edentulous patients received two SDIs insertion between mental foramina. The mandibular overdentures were connected with implants for early loading in the period of 2-4 weeks following implant insertion. The data of visual analogue scale (VAS) of denture satisfaction and masticatory ability were collected at baseline, two weeks, three months and six months following overdenture loading. Masticatory efficiency was evaluated before surgery and six months after overdenture loading. RESULTS: Within the period of six months following overdenture loading, all the 16 implants remained stable. Compared with the baseline, the VAS data of denture satisfaction,stability, masticatory and poltophagy ability two weeks, three months and six months after overdenture loading were significantly improved with 30 degree (P<0.01), especially the masticatory and poltophagy ability of hard and crisp food. The value of masticatory efficiency improved considerably six months after overdenture loading (P<0.01). CONCLUSION: Mandibular overdentures retained by two SDIs can significantly improve patients' denture satisfaction and masticatory efficiency, and provide more rational diet.

[Masticatory performance and assessment of life quality of children with ectodermal dysplasia after prosthetic rehabilitation].

OBJECTIVE: To evaluate masticatory performance and life quality of children with ectodermal dysplasia (ED) after prosthetic rehabilitation. METHODS: Six children with ED received denture restoration and 18 healthy children were involved in this study. The surface electromyography (EMG) of masseter (MM) and anterior temporalis (TA) during clenching and chewing movement were recorded. The EMG amplitude, area, asymmetry index of total and activity index of MM/TA were compared at each stage. The masticatory efficiency was measured with spectrophotometer. The life quality was assessed using visual analogue scale questionnaire. RESULTS: The EMG amplitude of MM and TA during chewing in ED Group were 41.7% and 45.6% of the control group respectively, the area were 35.9% and 36.0% respectively. Significant difference in asymmetry index of total during clenching was observed between the two groups (P < 0.05) but not during chewing (P > 0.05). The differences of activity index of MM/TA during clenching and chewing between the two groups were not detected (P > 0.05). The masticatory efficiency of ED group was 67.2% of the control group. The score of chewing function in children with ED after prosthetic rehabilitation was three times higher than before, and no difference was present between the two groups (P > 0.05). CONCLUSIONS: Early prosthetic rehabilitation can significantly improve the masticatory performance and life quality of children with ED.

[Evaluation and analysis of facial somatosensory changes of chronic masticatory muscle pain patients with quantitative sensory testing].

OBJECTIVE: To evaluate and analysis facial somatosensory changes of patients with chronic masticatory muscle pain (MMP) quantitatively. METHODS: The seven parameters of standardized quantitative sensory testing (QST) protocol were used to test the pain sites, contralateral sites of masticatory muscles of 20 chronic MMP patients and the same sites of right masticatory muscles of 20 matched healthy controls. QST thresholds were compared within groups using paired t test and between groups using unpaired t test. RESULTS: Compared to the controls, all seven parameters of bilateral sides of patients had changed. Mainly cold detection thresholds [(-1.2±0.5) and (-1.7±0.9) °C] and cold pain thresholds [(27.6±2.3) and (27.0±2.0) °C] of pain and contralateral sides increased significantly, while warm detection thresholds [(2.0±1.1) and (2.1±1.2) °C], heat pain thresholds [(37.9±3.2) and (39.7±3.9) °C], and mechanical pain thresholds [(49.3±34.1) and (111.8±86.3) mN] of pain and contralateral sides decreased significantly (P<0.05). Mechanical detection thresholds of pain sites [(1.8±1.4) mN] significantly increased (P=0.01). CONCLUSIONS: Chronic MMP patients were detected thermal hyperesthesia, thermal hyperalgesia, and mechanical hyperalgesia. Mechanical hypoesthesia was found at the pain sites of masticatory muscles. Chronic MMP might influence the central modulation of trigeminal nerve system.

[Classification and clinical characteristics of masticatory myospasm].

OBJECTIVE: To determine the classification of masticatory myospasm by analyzing characteristics of clinical appearances. METHODS: Thirty-six cases of masticatory myospasm from 2000 to 2010 were included. The clinical data of these patients were analyzed, including patient information, patient history, clinical characteristics, severity and the frequency of myospasmodic movement, electromyogram (EMG), and the efficacy of botulinum toxin injection treatment. RESULTS: There were 11 males and 25 females, aged from 15 to 71. According to the clinical manifestation and EMG findings, patients could be divided into two groups: 18 cases were classified as jaw closing type which involved masseter and/or temporalis muscles presenting as trismus and acute pain, the other 18 cases were jaw opening type which involved lateral pterygoid muscles complaining difficulty in jaw closing and teeth clenching. The jaw closing type was often seen in patients of 20 to 50 years old, the jaw opening was frequently seen in patients over 50 years old. Jaw closing type was attacked intermittently and unilaterally, but jaw opening was often attacked continually and bilaterally. The rating scale of the severity of spasmodic movement was not different between the two types, but the frequency of spasmodic attack was much higher for jaw opening type (P < 0.05). The EMG of jaw closing type was classified into persistent, rhythmic and irregular type. The EMG of jaw opening type was classified into spontaneous and exercise-induced type. Twelve cases were treated by botulinum toxin injection that could significantly relieve symptoms. CONCLUSIONS: Masticatory myospasm can be classified into jaw closing and jaw opening types. Jaw closing type involves masseter and/or temporalis muscles and jaw opening type involves lateral pterygoid muscles. Botulinum toxin injection was the most effective therapy for the masticatory myospasm.