Biomechanical Evaluation and Factorial Analysis of the 3-Dimensional Printing Self-Designed Metallic Reconstruction Plate for Mandibular Segmental Defect.

PURPOSE: Reconstruction plates are frequently used to treat mandibular segmental defects. The aim of this study is to compare the biomechanical performance of a 3-dimensional-printed self-designed titanium alloy reconstruction plate with that of the traditional reconstruction plate in mandible reconstruction. The analyzed parameters of the self-designed reconstruction plate, including plate length (100 mm and 125 mm), plate thickness (2.1, 2.4, and 2.7 mm), and bone mass (100, 75, and 50%), were also evaluated. METHODS: An artificial mandible with anatomical geometry was used to develop the self-designed reconstructed plate. Both in vitro experiments and finite element simulations were performed for the biomechanical comparison of the self-designed and traditional reconstruction plates. In finite element analysis, 3 major muscle forces of mandible movement were set as the loading condition, and the displacement of the condyle was fixed in all directions as the boundary condition. RESULTS: The biomechanical performances (stresses in the plate and strains in bone) of the self-designed reconstruction plate were superior to those of the traditional plate. Factorial analysis indicated that plate length and thickness had significant effects on decreasing stresses of the plate and mandibular bone. CONCLUSIONS: The self-designed reconstruction plate might have a benefit to reduce the stresses/strains in plate itself and surrounding bone.

Biomechanical Comparison of Open and Arthroscopic Transosseous Repair of Triangular Fibrocartilage Complex Foveal Tears: A Cadaveric Study.

PURPOSE: To biomechanically compare the stability between open repair and arthroscopic transosseous repair technique for reattachment of the foveal triangular fibrocartilage complex (TFCC). We also evaluated the feasibility of a new aiming device for the creation of 2 bone tunnels simultaneously during the arthroscopic technique. METHODS: Six matched pairs of fresh-frozen forearm cadaver specimens were prepared for testing. Group I specimens were treated by open repair with suture anchor. Group II specimens were treated by arthroscopic transosseous suture with a new aiming device. Before and after disruption of the TFCC fovea and after its repair, dorsal and palmar translation of the ulna was measured in both groups in response to a load (3 kg) applied in the palmar and then in the dorsal direction. The total translation of the ulna was calculated as the sum of the mean dorsal and palmar translations. RESULTS: The mean total ulnar translation before and after TFCC disruption, and after TFCC repair was 5.94 ± 2.16 mm, 9.08 ± 2.64 mm, and 6.04 ± 2.18 mm, respectively. The specimens demonstrated a significant increase in the total translation of the ulna after disruption of the ulnar attachment of TFCC (P = .003), whereas a significant decrease was observed after TFCC foveal repair (P = .003). The median percentage of eliminated translation after TFCC repair was 64% and 172%, respectively, in groups I and II (P = .043). CONCLUSIONS: The athroscopic transosseous suture technique demonstrated superior repair efficacy to the open repair technique in terms of biomechanical strength. This cadaveric study also demonstrated the feasibility of a new aiming device. CLINICAL RELEVANCE: When making decisions about TFCC foveal repair, arthroscopic transosseous suture technique may provide better biomechanical strength than the open repair technique.

Predicting the holistic force-displacement relation of the periodontal ligament: in-vitro experiments and finite element analysis.

BACKGROUND: The biomechanical property of the periodontal ligament (PDL) is important in orthodontics and prosthodontics. The objective of this study was to evaluate the feasibility of measuring the biomechanical behavior of the periodontal ligament using micro-computed tomography (micro-CT). METHODS: A custom-made apparatus measured the force and displacement of a porcine PDL specimen within the micro-CT environment. Synchronized computed tomography (CT) images were used to obtain the deformation and displacement of the entire specimen and to reconstruct the three-dimensional mesh model. To match the experimental results, finite element analysis was then applied to simulate the biomechanical response of the PDL. The mechanical model of the PDL was assumed as the hyperelastic material in this study. RESULTS: The volume variations of the tooth and the alveolar bone were less than 1%, which implies that tooth displacement was caused mostly by displacement of the PDL. Only translational displacement was observed with each load step because the transformation matrix acquired from the CT image registration was identical. The force-displacement curve revealed the nonlinear behavior of the PDL. There was a high correlation between the experimental displacement results and the simulation displacement results. The numerical results (based on the assumption that the PDL is the hyperelastic material) showed good agreement with the experimental results. CONCLUSIONS: Nondestructive measurements by micro-CT obtained the biomechanical behavior of the PDL. Using the hyperelastic characteristic as the constitutive model can properly predict the force-displacement relation of the PDL after loading. This study provided a feasible approach for measuring the biomechanical behavior of the PDL for further dental application.

Single versus Double Plate Fixation in Condylar Neck Fractures: Clinical Results and Biomechanics Simulation.

The open reduction of mandibular condyle neck fractures is difficult due to the limited surgical field and complex facial nerve structures. The most effective fixation method for narrow fractured segments is debated as standard double four-hole plate fixation is often not feasible. This research compared bone stability and force resistance between single-long-plate and double-short-plate fixations using clinical outcomes, a Sawbones mandible model, and finite element analysis. In patients with condyle neck fractures, nine were fixed with single-long-plate and twelve with double-short-plate fixations, with no significant differences in malocclusion and facial palsy rates. In compression tests with a Sawbones model, displacements in the posterior part were similar in both fixation groups. In contrast, the anterior part had significantly higher displacements in the single-long-plate group. Finite element analysis showed higher displacements in both anterior and posterior parts in the single-plate group compared to the double-short-plate group. Maximum stresses were at the second screw hole in single-long-plate fixation and the turning point of the upper plate at the condyle neck in double-short-plate fixation. Double-short-plate fixations demonstrated better stability and force resistance than single-long-plate fixations.

Factorial analysis of variables affecting bone stress adjacent to the orthodontic anchorage mini-implant with finite element analysis.

INTRODUCTION: Mini-implants are now widely accepted as anchorage for orthodontic tooth movement because of the convenience of the placement procedure, their comparative low cost, and the fact that they can be immediately loaded after surgery. In this study, we incorporated a finite element approach and factorial analysis to determine the biomechanical effects of exposure length of the mini-implant, the insertion angle, and the direction of orthodontic force. METHODS: Twenty-seven finite element models were constructed to simulate the biomechanical response of the alveolar bone adjacent to the mini-implant. Factorial analysis was performed to investigate the comparative influence of each factor. RESULTS: The simulation results showed that the exposure length of the mini-implant had a statistically significant influence on bone stress, with a contribution of 82.35%. Increased exposure length resulted in higher bone stress adjacent to the mini-implant. Whereas all factors investigated had a statistically significant influence on cancellous bone stress, the stress values associated with cancellous bone were much less than those of cortical bone. CONCLUSIONS: Increased exposure lengths resulted in higher bone stresses adjacent to the mini-implant. The percentage of contribution of the insertion angle of the mini-implant (6.03%) was also statistically significant but much less than that of the exposure length (82.35%). The direction of orthodontic force had no significant effect on cortical bone stress.

Clinical features and outcomes of patients with chronic granulomatous disease in Taiwan.

BACKGROUND: Chronic granulomatous disease (CGD) is a rare primary immunodeficiency disease characterized by defective neutrophil killing of microbial pathogens and recurrent infections. We aimed to investigate the clinical, genetic features, treatment, and outcomes in patients with CGD. METHODS: Pediatric patients diagnosed with CGD from a medical center in Taiwan were enrolled from January 1999 to Oct 2021. RESULTS: Nine pediatric patients with CGD were enrolled: six X-linked (XL) CGD with CYBB gene mutations, three autosomal recessive (AR) CGD with two NCF1 and one CYBA gene mutations. The median age of onset and age of diagnosis was 0.92 and 2.64 years, respectively. Patients with XL-CGD had a younger age of onset (4.6 months vs. 1.83 years, P = 0.06) and age of diagnosis (1.71 vs. 8.86 years, P = 0.024) than AR-CGD patients. The most common sites of infections were skin and soft tissue abscesses. The most common pathogens were Staphylococcus, Serratia, and Salmonella spp. Prophylactic antibiotics, anti-fungal agents, and interferon-gamma (IFN-γ) were given in 9 (100%), 7 (77.8%), and 8 (88.9%) patients, respectively. The mean duration of IFN-γ usage was 5.15 years. One male patient with XL-CGD was successfully treated with hematopoietic stem cell transplantation at 2.2 years. The mortality rate was 11.1%, and the estimated overall survival at 20 years was 66.7%. CONCLUSION: Staphylococcus aureus, Serratia marcescens, and Salmonella infections are important in Taiwanese CGD patients. Patients with XL-CGD have early disease onset. IFN-γ prophylaxis and prophylactic anti-microbial agents might have an effect on alleviating the infection episodes in CGD patients.

Investigation of a Modified Novel Technique in Bilateral Sagittal Splitting Osteotomy Fixation: Finite Element Analysis and In Vitro Biomechanical Test.

PURPOSE: To evaluate the biomechanical properties of the modified novel 2-hole monocortical plate fixation (2HMCPf) and traditional 4-hole monocortical plate fixation (4HMCPf) techniques in bilateral sagittal splitting osteotomy (BSSO) synthesis using a finite element analysis (FEA) and an in vitro biomechanical test with the application of a shearing loading force on a sawbone mandible model. MATERIALS AND METHODS: A three-dimensional mandible models were generated using the geometry obtained from the computerized tomography image of a sawbone mandible. Plates and screws were generated and combined with the mandible in a CAD environment. The 2HMCPf and traditional 4HMCPf techniques for BSSO osteosynthesis were then analyzed under the occlusal load using the FEA. An in vitro biomechanical test was executed to verify the result of FEA. The force on fixation failure and pattern of failure were recorded. RESULTS: The results revealed that the von Mises Stress on the mandible cortical bone (75.98 MPa) and the screw/plate (457.19 MPa) of the 2HMCPf group was lower than that of the 4HMCPf group (987.68 MPa, 1781.59 MPa). The stress concentrated on the central region of the 4HMCPf group and the distal set of the 2HMCPf group. In vitro study using the sawbone mandible model showed mechanical failure at the region of the proximal segment near the osteotomy site with the 4HMCPf group (average 32.198 N) but no failure on the fixation sites with the 2HMCPf group. Instead, the mandible sawbone fractured on the condyle neck region (average 44.953 N). CONCLUSION: From the biomechanical perspective, we proved that the 2HMCPf method was able to withstand a higher shearing loading force than the 4HMCPf fixation method in BSSO osteosynthesis.

Metaphyseal locking plate as an external fixator for open tibial fracture: Clinical outcomes and biomechanical assessment.

OBJECTIVE: This study aimed to evaluate the outcome of using a metaphyseal locking plate as a definitive external fixator for treating open tibial fractures based on biomechanical experiments and analysis of clinical results. METHODS: A metaphyseal locking plate was used as an external fixator in 54 open tibial fractures in 52 patients. The mean follow-up was 38 months (range, 20-52 months). Moreover, static axial compression and torsional tests were performed to evaluate the strength of the fixation techniques. RESULTS: The average fracture healing time was 34.5 weeks (range, 12-78 weeks). At 4 weeks postoperatively and at the final follow-up, the average Hospital for Special Surgery knee score was 85 (range, 81-100) and 94 (range, 88-100), respectively, and the American Orthopaedic Foot and Ankle Society score was 88 (range, 80-100) and 96 (range, 90-100), respectively. Based on the static test result, the axial stiffness was significantly different among groups (p=0.002), whereas the torsional stiffness showed no significant difference (p=0.068). CONCLUSIONS: Clinical outcomes show that the use of locking plate as a definitive external fixator is an alternative choice for tibial fractures after obtaining appropriate fracture reduction. However, external locked plating constructs were not as strong as standard locked plating constructs. Therefore, the use of external locked plating constructs as a definitive treatment warrants further biomechanical study for construct strength improvement.

Effects of lining materials on microleakage and internal voids of Class II resin-based composite restorations.

PURPOSE: To evaluate the ability of various lining materials to reduce cervical marginal microleakage and internal voids within Class II resin-based composite restorations. MATERIALS AND METHODS: 168 extracted molars were prepared with both moderate and deep Class II cavities. The teeth were then randomly divided into 14 groups and restored with direct composite or sandwich techniques using various lining materials [flowable composites, compomers and resin-modified glass-ionomer cements (RMGI)]. Following restoration, the teeth were stored for 24 hours, thermocycled, and placed in fuchsin dye for 24 hours. Subsequently, the teeth were sectioned in halves and observed through a stereomicroscope. Cervical microleakage and internal voids were assessed separately as the length ratio of dye penetration to the cervical wall and the area ratio of voids to sectioned restorations. The data were analyzed with one-way ANOVA. RESULTS: Flowable composite lining groups demonstrated either similar or more cervical microleakage than did their respective direct restoration groups. Groups lined with RMGIs showed similar or better marginal sealing than did their resin restoration groups. In deep cavities, Vivaglass Liner group showed the best marginal sealing. RMGI-lined groups exhibited more internal voids in deep restorations.

Metaphyseal locking plate as a definitive external fixator for treating open tibial fractures--clinical outcome and a finite element study.

We evaluated both the outcome of using a locking plate as a definitive external fixator for treating open tibial fractures and, using finite element analysis, the biomechanical performance of external and internal metaphyseal locked plates in treating proximal tibial fractures. Eight open tibial patients were treated using a metaphyseal locked plate as a low-profile definitive external fixator. Then, finite element models of internal (IPF) as well as two different external plate fixations (EPFs) for proximal tibial fractures were reconstructed. The offset distances from the bone surface to the EPFs were 6 cm and 10 cm. Both axial stiffness and angular stiffness were calculated to evaluate the biomechanical performance of these three models. The mean follow-up period was 31 months (range, 18-43 months). All the fractures united and the mean bone healing time was 37.5 weeks (range, 20-52 weeks). All patients had excellent or good functional results and were walking freely at the final follow-up. The finite element finding revealed that axial stiffness and angular stiffness decreased as the offset distance from the bone surface increased. Compared to the IPF models, in the two EPF models, axial stiffness decreased by 84-94%, whereas the angular stiffness decreased by 12-21%. The locking plate used as a definitive external fixator provided a high rate of union. While the locking plate is not totally rigid, it is clinically stable and may be advisable for stiffness reduction of plating constructs, thus promoting fracture healing by callus formation. Our patients experienced a comfortable clinical course, excellent knee and ankle joint motion, satisfactory functional results and an acceptable complication rate.

Biomechanical comparison of axial load between cannulated locking screws and noncannulated cortical locking screws.

The goal of this study was to compare the biomechanical stability of cannulated locking screws and noncannulated cortical locking screws in a periarticular locking plate. Twelve fresh-frozen porcine tibias with a 1-cm gap created distal to the tibial plateau were used to simulate an unstable proximal tibial fracture. All specimens were fixed with a periarticular proximal lateral tibial locking plate and divided into 2 groups based on whether the proximal metaphyseal screw holes of the plate were inserted with either cannulated locking screws or noncannulated cortical locking screws. An axial compressive load was applied to cause failure in each specimen using a materials testing instrument. The axial stiffness and maximum failure strength in axial loading were recorded. Axial stiffness of the constructs using noncannulated cortical locking screw was significantly higher than that of the constructs using cannulated locking screws (P=.006). Axial failure strength of the constructs using noncannulated cortical locking screw was significantly higher than that of the constructs using cannulated locking screws (P=.002). The failure mode observed in all specimens was a permanent screw-bending deformity over the head-shaft junction of proximal metaphyseal screws, irrespective of whether they were cannulated or noncannulated cortical locking screws. Fixation with noncannulated cortical locking screws offered more stability than cannulated locking screws with regard to axial stiffness and failure strength in a porcine model with unstable proximal tibial fractures.

Biomechanical testing of spinal fusion segments enhanced by extracorporeal shock wave treatment in rabbits.

BACKGROUND: Extracorporeal shock wave treatment (ESWT) has been proven effective in enhancing spinal fusion in a preliminary animal study. However, biomechanical tests were not performed. METHODS: All 12 rabbits in this study underwent decortication at the bilateral L5 and L6 transverse processes. Bone was chipped off and placed onto the intertransverse space. The rabbits were divided into two groups, a study group (n = 6) and a control group (n = 6). In the study group, the bilateral L5 and L6 transverse processes were treated with 1000 impulses of ESWT at 14 kilovolts (KV) (equivalent to 0.18 mJ/mm(2)) at 12 and 18 weeks after surgery. The control group rabbits did not undergo ESWT. A series of radiographic examinations on each rabbit were subsequently performed. All rabbits were killed at 21 weeks, and their spines were harvested for biomechanical tests. RESULTS: Radiographic examination showed 5 of the 6 rabbits in the study group had callus formation in the fusion masses. Biomechanical tests of the fusion segments showed that the mean flexion stiffness (with internal control) in the study group was 2.11 +/- 0.46, while that in the control group was 1.17 +/- 0.19. The mean extension stiffness (with internal control) in the study group was 1.70 +/- 0.39, while that in the control group was 1.23 +/- 0.29. Statistical analysis showed that the fusion segments in the study group had significantly better flexion and extension stiffness than those in the control group (p < 0.05). CONCLUSION: In this animal study, radiographic examinations showed that ESWT stimulated new bone growth. Biomechanical tests showed that ESWT significantly increased the flexion and extension stiffness of spinal fusion segments.