Research on skull trauma biomechanical stress distribution in case of dental implants existence.

BACKGROUND: When the jaw bone is subjected to an external force, the stress is transmitted from the force point along the alveolar bone to the skull and skull base. In the case of a dental implant, the stress distribution is mainly dependent on the implant position, type, and mechanical properties. OBJECTIVE: To investigate the dental implant position influence on the stress distribution and transmission in case of facial frontal trauma. Furthermore, the correlation between facial trauma and skull trauma in the case of a dental implant exists. METHODS: In this study, a Finite Element Method (FEM) model was constructed based on a real skull shape, size, and anatomy. Dental implants were modeled based on imported CAD Data. Five cases were investigated including no dental implant and the replacement of teeth no. 18, 19 20 and 21. Facial trauma was mimicked by applying an external load on the lower frontal jaw. Finally, the stress distribution based on the bone geometry and implant position were evaluated and compared. RESULTS: Results suggested that a dental implant could significantly influence the stress distribution in the skull in case of facial trauma. In addition, the dental position greatly affects stress transmission from the mandible to the skull bones through the zygomatic arch. CONCLUSION: The position of the dental implant could have a significant role in stress transmission and distribution in case of facial or even brain trauma. Thus, increasing the possibility of a correlation between facial and brain trauma.

Numerical simulation and analysis of midfacial impacts and traumatic brain injuries.

BACKGROUNDS: The maxillofacial region is the exposed part of the human body and is susceptible to injury due to the limited protective equipment. Due to anatomic proximity of the maxillofacial skeleton and cranium, the force can be transmitted directly to the brain in case of maxillofacial impact, maxillofacial injuries are often accompanied with craniocerebral trauma. Therefore, it is necessary to study the biomechanical response mechanism of trauma to improve prevention of traumatic brain injury (TBI). METHODS: To investigate the biomechanical mechanism between the two injuries, a finite element (FE) head model including skull, midfacial bones and detailed anatomical intracranial features was successfully developed based on CT/MRI data. The model was validated by comparing it with one classical cadaver experiment. During the simulations, three different load forces were used to simulate common causes of injury seen in the clinic including boxing-type impact injury and car accident-type impact injury, and four locations on the model were considered as common injury sites in the midface. RESULTS: Twelve common impact scenarios were reproduced by FE simulation successfully. Simulations showed that there was a linear relationship between the severity of TBI and the collision energy. The location of TBI was directly related to the location of the impact site, and a lateral impact was more injurious to the brain than an anterior-posterior impact. The relative movement between the skull and brain could cause physical damage to the brain. The study indicated that the midfacial bones acted as a structure capable of absorbing energy and protecting the brain from impact. CONCLUSIONS: This biomechanical information may assist surgeons better understand and diagnose brain injuries accompanied by midfacial fractures.

Clinical application and accuracy analysis of 3D printing guide plate based on polylactic acid in mandible reconstruction with fibula flap.

BACKGROUND: Due to the special anatomy morphology and physiological function of the mandible, it has always become a challenge to accurately reconstruct the mandibular defect in maxillofacial surgery. Digital three dimensions (3D) printing surgical guide, as the effective method for individual and accurate surgery, is a hotspot of clinical research at present. In this study, 3D printing PLA surgical guide plate was applied to reconstruct the mandibular defect with fibula flap, its clinical effect and accuracy were evaluated, which aimed to improve the accurate reconstruction of mandibular defects. METHODS: After sterilization, the dimension deformation of the PLA standard specimen were measured. Eighteen patients diagnose with mandibular tumor were collected as observation objects. Then partial mandible resection and simultaneous mandible reconstruction with fibula graft were implemented according to the computer-aided design plan. The clinical effects of 3D printing PLA guide plates application were evaluated by facial contours, occlusal stability and chewing function. Through registering the postoperative computed images reconstruction with preoperative designed shape, the reconstruction accuracy was evaluated by detecting the maximum difference including the distance between lateral convex point of the condyles, the distance between medial convex point of the condyles and the horizontal contained angle between long axis of the condyles. RESULTS: After high temperature steam sterilization, the curvature of the PLA specimen with 100% filling rate and 4.8 mm thickness were the smallest and their dimension deformation had no statistical significance (P>0.05). The minimally deformed 3D printing PLA guide plate were smoothly placed in the right place during the operation. After surgery, the face was symmetrical, the occlusal relationship was restored well and no deviation of the mandibular movement were found. The spiral computed tomography (SCT) scanning showed that the distance between lateral/medial convex points of the condyle and the horizontal contained angle were 128.34±8.68 mm, 88.69±6.75 mm and 145.87°±12.01°. Compared with preoperative design, the maximum deviation of the actual postoperative registration was 1.67±0.63, and the difference was not statistically significant (P>0.05). CONCLUSIONS: The application of 3D printing PLA guide plate in the segmental section and reconstruction of the mandible can effectively simplify the operation, and better reconstruct the continuity of the mandible. The surgical accuracy can fully meet clinical needs with relatively low prices.

[Clinical application of midpiece facial nerve dissection in regional parotidectomy].

OBJECTIVE: To propose and evaluate the clinical effect of midpiece facial nerve dissection through transparotid approach in regional parotidectomy. METHODS: A total of 136 patients with benign parotid tumors were categorized into three groups according to the way of facial nerve dissection: anterograde dissection from main trunk (anterograde, n=70), retrograde dissection from distal branches (retrograde, n=34), and midpiece dissection through transparotid approach (middle dissection, n=32). Surgery duration, facial nerve injury, salivary fistula, earlobe sensation, Frey's syndrome, and aesthetic evaluation were compared. RESULTS: The surgery duration in the middle dissection group was significantly shorter than that in the other two groups. The proportion of salivary fistula was higher in the anterograde group (9 cases, 12.9%; P<0.05) compared with that in the other groups. Postoperative facial nerve injury was similar between the middle dissection (1 case, 3.1%) and anterograde groups (3 cases, 4.3%) with lower injury rate compared with the retrograde group (7 cases, 20.6%). The anterograde group had more cases of hypoesthesia of the earlobe (12 cases, 17.1%; P<0.05) than the other two groups. Aesthetic score was higher in the anterograde and middle dissection groups compared with that in the retrograde group (P<0.05). CONCLUSIONS: Midpiece facial nerve dissection is technically feasible and clinically viable in regional parotidectomy.

Positron Emission Tomographic Imaging Elucidates the Complex Relationship Between Glucose Uptake and Tissue Blood Flow Mechanism in Squamous Cell Oral Cancer Patients.

BACKGROUND Through the clinical use of positron emission tomography, we aimed to elucidate the complex relationship between glucose uptake and squamous cell oral cancer (ScOC) growth, along with its mechanism with respect to tissue blood flow (tBF). MATERIAL AND METHODS We retrospectively reviewed a total of 69 newly diagnosed ScOC patients by Fluorine-18 fluorodeoxyglucose (18F-FDG) positron emission tomography (PET). Maximum and mean standard uptake values (SUV↑ and SUV) were recorded to assess glucose uptake. Multi-shot spin-echo echo-planar imaging-based pseudo-continuous arterial spin labeling (pcASL) technique at 3.0 T MRI was used to obtain tBF values in ScOC (tBF-ScOC). Patients were divided according to T-stage and location. Pearson's correlation coefficients were calculated between both SUV and tBF-ScOC for significant correlations. RESULTS Forty-one (59.4%) patients had oropharynx and the other 28 (40.6%) patients had laryngopharynx. Significant positive correlations were detected between SUV↑, SUV, tBF-ScOC and non-advanced T-stage (T1a, T1b, T2 and T3), while a negative correlation was observed in the advanced T-stage (T4a and T4b). CONCLUSIONS Using PET imaging, we established the relationship between glucose uptake and ScOC growth on the basis of the division of T-stage and tumor location of ScOC, thereby elucidating the underlying mechanism. Our findings provide insights important to the diagnosis, treatment, and care of ScOC patients.

Elevated Matrix Metalloproteinase-9 Expression Correlates With Advanced Stages of Oral Cancer and Is Linked to Poor Clinical Outcomes.

PURPOSE: Using a meta-analytic approach, the relation between increased matrix metalloproteinase-9 (MMP-9) expression, tumor stage, and clinical outcomes in oral cancers was investigated. MATERIALS AND METHODS: Multiple English- and Chinese-language electronic databases were searched to identify high-quality case-and-control studies relevant to this meta-analysis. Methodologic quality of the included trials was assessed using the Strengthening the Reporting of Observational Studies in Epidemiology statement to ensure consistency in reviewing and reporting the results. Statistical analyses were carried out with STATA 12.0 statistical software. RESULTS: Nine case-and-control studies containing a combined total of 419 patients with oral cancer were included in the present meta-analysis. Results showed that patients who were positive for MMP-9 expression had a significantly poorer overall survival compared with those negative for MMP-9 (effect size = 2.10; 95% confidence interval, 0.98 to 3.22; P < .001). MMP-9 expression also positively correlated with lymph node metastasis and advanced T-stage groups (P < .05 for all comparisons). Further, high MMP-9 expression level correlated with increased oral cancer risk in Asians (P < .05 for all comparisons) as shown by method-stratified subgroup analysis. CONCLUSION: The present results strongly suggest that MMP-9 expression level influences tumor invasion and metastasis in oral cancers. Based on these results, MMP-9 can be an excellent therapeutic target in patients with oral cancer.

Micro-ribonucleic acid 143 (MiR-143) inhibits oral squamous cell carcinoma (OSCC) cell migration and invasion by downregulation of phospho-c-Met through targeting CD44 v3.

OBJECTIVE: The aim of this study was to investigate the roles and mechanisms of Micro-ribonucleic acid 143 (miR-143) in oral squamous cell carcinoma cells. STUDY DESIGN: Following the detection of miR-143 expression, cell proliferation, migration, and invasion assays and Western blot analysis were conducted in the oral squamous cell carcinoma (OSCC) cell lines. RESULTS: We found that the expression of miR-143 was significantly decreased in the OSCC cell lines (SCC-4, Tca-8113, CAL-27) and tumor tissues. Meanwhile, miR-143 was significantly correlated with the migration and invasion in OSCC cell lines. Further investigation revealed that the expression level of miR-143 was opposite to that of its potential target gene-CD44 v3 and was also related to phospho-c-Met activation. CONCLUSIONS: miR-143 could exert significantly suppressive effects on the ability of migration and invasion in OSCC cell lines, and the mechanism of this might be related to the activity of phospho-c-met though the CD44 v3/HGF signal. miR-143 could thus provide new applications for the treatment of OSCC.

Repair of critical bone defects with injectable platelet rich plasma/bone marrow-derived stromal cells composite: experimental study in rabbits.

BACKGROUND: Platelet-rich plasma (PRP) has been applied to promote bone healing and developed as a novel material for bone regeneration. This study aimed to investigate the feasibility of PRP carrier to deliver bone marrow derived stromal cells (BMSCs) and regenerate bone tissues to reconstruct critical bone defects in rabbits. METHODS: Critical sized defect were made on eighteen rabbits' crania and treated by different composites: BMSCs/PRP (n=6); Autogenous particulate cancellous bone group (n=6) and PRP alone group (n=6). The defects were evaluated by gross observation, radiographic examination, histological examination, and mechanical examination at 12 weeks postoperatively. RESULTS: The results showed that repair of bone defect was the least in PRP alone group, and significant new bone formation could be observed in BMSCs/PRP group and particulate cancellous bone group, radiopacity area in BMSCs/PRP group attained 76.5%, which was in the same range of that in autogenous particulate cancellous bone group (82.4% in radiopacity area), compressive strength of engineered bone in BMSCs/PRP group attained 71% of that in autogenous particulate cancellous bone group (p<0.05). CONCLUSION: These data implicated that BMSCs delivered from PRP gel can repair bony defect in immunocompetent animals, and the tissue engineered bone in BMSCs/PRP group is comparable to autogenous particulate cancellous bone group for the repair of critical-sized bone defect.