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BACKGROUND:Due to the lack of mechanical stimulation generated by functional loading,alveolar bone atrophy and bone loss in the missing area prevents the effective embedding of dental implants.Therefore,it is necessary to implant bone meal during implantation to compensate for the lack of alveolar bone height on the stability of the implant. OBJECTIVE:To derive the optimal time point for second-stage restorations from a biomechanical perspective by means of finite element analysis,thereby providing a biomechanical basis for selecting the correct time point for second-stage restoration to shorten the clinical course of dental implantation. METHODS:Three-dimensional finite element models of the maxilla were developed for normal,16-deficient with conventional implant surgery(model B)and 16-deficient with internal maxillary sinus lift(model A).Model A was filled with hydroxyapatite bone powder between the mucosa and the maxillary sinus floor,and Model B and the normal maxillary bone model did not require bone grafting.The healing time of bone grafting was set at 3-9 months postoperatively,and a force of 200 N was applied to the adjacent teeth at 3-5 months postoperatively,and directly to the implant at 6-9 months,simulating the load applied to the implant in the second stage of restoration.Biomechanical analysis of the three models was performed with the aid of the implants and the surrounding hard and soft tissues. RESULTS AND CONCLUSION:The stress on Model A and Model B was around 103 MPa and 95 MPa respectively when the force was directly loaded onto the implant.Bone grafting increased the stress values on the implant,while not doing bone grafting reduced the stress on the implant and the whole system.As the strength of the bone powder increased,the stress values on the alveolar bone decreased.When the healing time was up to 6-9 months postoperatively,the stress values were ranked as follows:normal model<Model B<Model A,when the force was loaded in the implant or the corresponding first molar sites.The stress on the maxilla after dental implantation was higher than that on the normal maxilla.There was a slight downward trend in cancellous bone stress in Model A and significantly lower stress levels in Model B than in the normal mandible model at 6-9 months.To conclude,the use of the original alveolar bone for restoration can improve the survival rate of the implant;the second-stage restoration can be considered after 6 months when sufficient alveolar bone height is obtained after implantation.In clinical application,the timing of second-stage restoration can be adjusted appropriately on the basis of the patient's bone quality,lifestyle,age and other factors after comprehensive determination.
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Objective:To compare safety and efficacy of one-stage laparoscopic common bile duct exploration plus laparoscopic cholecystectomy (LCBDE+ LC) with endoscopic retrodrade cholangiopancreatography plus laparoscopic cholecystectomy (ERCP+ LC) in elderly patients with concomitant gallbladder and common bile duct (CBD) stones.Methods:This is a two-center retrospective study with clinical data on 492 patients aged over 80 years diagnosed with concomitant gallbladder and CBD stones treated between January, 2014 and December, 2020 at The First Affiliated Hospital of Wenzhou Medical University and Quzhou Hospital Affiliated to Wenzhou Medical University. There were 254 males and 238 females, aged (83.9±3.0) years. These patients were divided into two groups based on their operative methods: the one-stage group (LCBDE+ LC, n=186) and the two-stage group (ERCP+ LC, n=306). Differences in surgery, stones and hospitalization costs were compared between the two groups. Results:When compared with the ERCP+ LC group, the LCBDE+ LC group had significantly higher incidences of previous gastrectomy [21.5%(40/186) vs 4.2%(13/306)], multiple stones [77.4%(144/186) vs 49.3%(151/306)], larger stone diameter [13.7(6.4, 18.6)mm vs 10.9(5.7, 16.1) mm], and increased hospitalization expenditure [(2.37±0.31) Wanyuan vs (3.26±0.44) Wanyuan] (all P<0.05). However, the rates of residual stone [2.7%(5/186) vs 1.3%(4/306)], stone recurrence [2.2%(4/186) vs 5.2%(16/306)], postoperatively overall complications [3.2%(6/186) vs 1.3%(4/306)], and total hospital stay [(10.7±6.2) d vs (11.3±5.4) d] were not significantly different between the two groups (all P>0.05). Conclusions:Allowing for the similar safety and effectiveness, and lower hospitalization expenditure, LCBDE+ LC was a preferred choice for patients aged over 80 year, especially in patients who had previous gastrectomy, multiple large CBD stones, or who could not accept endoscopic procedures for treatment of CBD stones.
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Femoral neck fractures in pediatric fractures account for less than 1% which is very rare, and its mechanism is commonly caused by high-energy trauma. If children with femoral neck fracture cannot receive timely and effective treatment, they are at high risk of avascular necrosis of the femoral head (AVN), coxa vara, bone nonunion, premature physeal closure, leg length discrepancy and other complications. Surgical treatment is currently preferred over conservative treatment, which has a higher complication rate. Among them, AVN is one of the most common and the most difficult complications to manage. So far, no effective treatment measures and reliable predictors have been reported, and the related factors affecting the occurrence of AVN have also been controversial. Once femoral head necrosis occurs in children, the prognosis is not ideal due to the lack of appropriate treatment methods. Therefore, this paper reviews the research progress on the related factors of AVN after femoral neck fracture in children based on the literature reports in the past decade.