• Archives of Craniofacial Surgery
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• v.23 no.1
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• pp.23-28
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• 2022

Background: Intermaxillary fixation (IMF) is a technique that allows for the reduction and stabilization of mandibular fractures. Several methods of IMF, such as self-tapping screws or arch bars, have been developed. This study aimed to validate the usefulness of IMF with a self-tapping screw compared to IMF with arch bars with focus on the patients' perspective. Methods: We retrospectively reviewed the medical records of all patients who were treated for mandibular fractures at our hospital between August 2014 and February 2021. A total of 57 patients were enrolled in this study. Thirteen patients were excluded from the analysis: three patients were lost to follow-up, and 10 patients did not undergo IMF. Finally, 44 patients were analyzed, of which 31 belonged to the arch bar group, and 13 belonged to the screw group. Patient discomfort and pain during IMF application and removal were analyzed using a patient self-assessment questionnaire. The surgeon also assessed oral hygiene, IMF stability, and occlusion. Results: We applied IMF to 34 men (77%) and 10 women (23%). The mean age of the patients was 37.3 years. The most common fracture site was the angle (30%), followed by the parasymphysis (25%), the body (23%), the condyle (11%), and the ramus (11%). Patient discomfort and oral hygiene were statistically favorable in the screw group. The IMF application time was statistically shorter in the screw group (p< 0.001). IMF stability was not statistically different between the two groups. The pain score during IMF removal was lower in the screw group (p< 0.001). Conclusion: Compared to arch bars, IMF screws provide more comfort during the IMF period, help maintain favorable oral hygiene, and have a shorter application time. From the patient's perspective, IMF screws are an excellent alternative to conventional arch bars when applicable.

• 대한치과보철학회:학술대회논문집
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• 2002.11a
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• pp.86-86
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• 2002

• Elastomers and Composites
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• v.54 no.1
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• pp.7-13
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• 2019

Recycling of waste polyvinyl chloride plastics has attracted much attention due to environmental problems, but the poor mechanical properties, low thermal stability, frequent breakage of strands, and melt cracking of the waste plastics have limited their widespread use. To overcome these disadvantages of waste PVC (W-PVC), recycled PVC powder blend was prepared by adding high-density polyethylene (HDPE) and ethylene vinyl acetate (EVA) as a heat stabilizer and compatibilizer, respectively. An intermeshing co-rotating twin screw extruder was used to prepare the blend, and the characteristics of the blend were analyzed by SEM and TGA, and by using a UTM and Izod impact tester. The impact strength was improved as the EVA content increased for the W-PVC/HDPE (80/20 wt%) blend. As the HDPE and EVA contents increased in the W-PVC/HDPE/EVA blend, the impact strength increased. SEM observations also revealed the improved interfacial adhesion for the EVA-containing blend.

• Journal of Korean Neurosurgical Society
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• v.61 no.2
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• pp.180-185
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• 2018

Objective : Many lumbosacral fixation techniques have been described to offer a more screw-bone purchase. The forward anatomical fixation parallel to the endplate is still the most preferred method. Literature revealed little knowledge regarding the mechanical stability of lumbosacral trans-endplate fixation compared to the traditional trans-pedicular screw fixation method. The aim of this study is to assess the pull-out strength of lumbosacral screws penetrating the end plate and comparing it to the conventional trans-pedicular screw insertion method. Methods : Eight lumbar and eight sacral vertebrae, with average age 69.4 years, Left pedicles of the 5th lumbar vertebrae were used for trans-endplate screw fixation, group 1A, right pedicles were used for anatomical trans-pedicular screw fixation, group 1B. In the sacral vertebrae, the right side S1 pedicles were used for trans-endplate fixation, group 2A, left side pedicles were used for anatomical trans-pedicular screw fixation, group 2B. The biomechanical tests were performed using the axial compression testing machine. All tests were applied using 2 mm/min traction speed. Results : The average pull-out strength values of groups 1A and 1B were $403.78{\pm}11.71N$ and $306.26{\pm}17.55N$, respectively. A statistical significance was detected with p=0.012. The average pull-out strength values of groups 2A and 2B were $388.73{\pm}17.03N$ and $299.84{\pm}17.52N$, respectively. A statistical significance was detected with p=0.012. Conclusion : The trans-endplate lumbosacral fixation method is a trustable fixation method with a stronger screw-bone purchase and offer a good alternative for surgeons specially in patients with osteoporosis.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.653-664
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• 2007

Statement of problem: The screw detorque value is a measure of the preload remaining in the screw just before detorquing. Purpose: This study evaluated the effect of different screw tightening sequences and tightening methods on detorque values for a well-fitting implant superstructure. Material and method: An implant superstructure that connected directly to four implants (Astra Tech) was fabricated on a fully edentulous mandibular acrylic resin model. Six well-fitting dental stone casts were made with a pickup impression of the superstructure from the acrylic resin model. To evaluate the effect of three screw tightening sequences (1-2-3-4, 2-4-3-1, and 2-3-1-4) and two tightening methods (2-step and 1-step) on the stability of screw joint, the detorque values for a well-fitting implant superstructure were measured twice after screw tightening using 20 Ncm. Detorque values were analyzed using multi-way analysis of variance and two-way analysis of variance at a .05 level of significance. Results: 1. The mean detorque values for three screw tightening sequences were 12.3 Ncm, 12.6 Ncm, and 12.0 Ncm, respectively. 2. The mean detorque values for two screw tightening methods were 12.0 Ncm, and 12.2 Ncm, respectively. 3. The mean of mimimum detorque values for three screw tightening sequences and for two tightening methods were 10.6 Ncm, 11.1 Ncm, 10.5 Ncm, and 9.8 Ncm, respectively. 4. No statistically significant differences among the variables of screw tightening sequence and tightening method were found (p>.05) for detorque values and for mimimum detorque values. Conclusion: Within the limitations of this study, the screw tightening sequence and tightening method did not have a significant effect on the detorque values for a well-fitting implant superstructure.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.893-898
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• 2003

Coulomb friction is an important factor for precise position tracking control systems. The control systems with friction causes the steady state error because of being sensitive to the change of system condition and highly nonlinear characteristics. To overcome these problems, we use an estimation scheme of Coulomb friction to experiment for it's compensating. The estimated factor for Coulomb friction is used as a feed-forward compensator to improve the tracking performance of ball-screw systems. The tracking performance was improved by compensating the estimated friction torque in the feed-forward term. And, the sliding mode control which is derived from the Lyapunov stability theorem is applied for robust stability and reducing chattering. The experimental results show that the sliding mode controller with adaptive friction compensator has a good tracking performance compared with the friction uncompensated controller.

• Journal of the Korean Arthroscopy Society
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• v.2 no.1
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• pp.85-92
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• 1998

Various methods for fixation of graft have been widely used for reconstruction of anterior cruciate ligament. However, the biomechanical strength of each fixation techniques are not fully understood. The purpose of this study is to compare the pull out strength of different fixation techniques which is probably the most important factor for the success at the initial stage of healing. Biomechanical test was carried out to measure and compare the pull out tensile strength of five different fixation techniques in 35 pig(Yorkshire) knees. ANOVA and Duncan multiple comparison test was applied for statistical analysis. In the two fixation techniques with bone patellar tendon bone graft, the mean maximum tensile strength was $1333.4{\pm}148.5N$ with titanium interference screw, while it was $1310.1{\pm}168.9N$ with biodegradable interference screw. The failure mode were pulled out of bone plugs from the femoral tunnel in majority cases. In the fixations with hamstring tendon, the mean maximum tensile strength were $1405.9{\pm}135.1N$ with SemiFix screw, $820.3{\pm}104.5N$ with biodegradable interference screw, and $682.1{\pm}54.2N$ with Endobutton. The mode of failure was variable in each technique. The tendon was pulled out from the tunnel in biodegradable interference screw fixation, the screw was bent in the SemiFix system, and the polyester tape were ruptured or the buttons were pulled into tunnel in Endobutton fixation. The mean maximum tensile strength of two interference screws with bone patellar tendon bone was statistically comparable to that of SemiFix with hamstring tendon. However biodegradable interference screw and Endobutton with hamstring tendon showed weaker maximum tensile strength than above three fixation techniques (P<0.05).

• The Journal of the Korean dental association
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• v.55 no.7
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• pp.457-466
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• 2017

In the case of failed fixed implant prosthesis accompanied by abutment screw fracture, fractured screw fragment must be removed to use the existing implant fixtures. A 61-year-old male patient, who had a failed maxillary fixed implant prosthesis accompanied by three abutment screw fracture, hoped to reconstruct the maxillary implant prosthesis, while maintaining the existing implant fixtures. To use the existing implant fixtures, fractured screw fragments were removed. A maxillary implant overdenture using available existing implants was planned. Bar-attachment with Locator was used for implant splinting, denture stability, and retention. Final impression was taken after treatment of peri-implantitis. Jaw relation registration was taken to evaluate available interarch space for bar-attachment. After fabricating bar-attachment, centric relation was taken. Implant overdenture using bar-attachment with Locator was delivered after wax-denture evaluation. This case report showed that a satisfactory clinical result was achieved by implant overdenture using existing implant fixtures in a maxillary edentulous patient.

• Journal of Korean Neurosurgical Society
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• v.53 no.6
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• pp.331-336
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• 2013

Objective : The offset connector can allow medial and lateral variability and facilitate intralaminar screw incorporation into the construct. The aim of this study was to compare the biomechanical characteristics of C7 intralaminar screw constructs with and without offset connector using a three dimensional finite element model of a C6-7 cervical spine segment. Methods : Finite element models representing C7 intralaminar screw constructs with and without the offset connector were developed. Range of motion (ROM) and maximum von Mises stresses in the vertebra for the two techniques were compared under pure moments in flexion, extension, lateral bending and axial rotation. Results : ROM for intralaminar screw construct with offset connector was less than the construct without the offset connector in the three principal directions. The maximum von Misses stress was observed in the C7 vertebra around the pedicle in both constructs. Maximum von Mises stress in the construct without offset connector was found to be 12-30% higher than the corresponding stresses in the construct with offset connector in the three principal directions. Conclusion : This study demonstrated that the intralaminar screw fixation with offset connector is better than the construct without offset connector in terms of biomechanical stability. Construct with the offset connector reduces the ROM of C6-7 segment more significantly compared to the construct without the offset connector and causes lower stresses around the C7 pedicle-vertebral body complex.

• Journal of Trauma and Injury
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• v.35 no.1
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• pp.34-42
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• 2022

Purpose: Percutaneous iliosacral (IS) screw fixation for pelvic ring injuries is a minimally invasive technique that reduces the amount of blood loss and shortens the procedure time. Moreover, two unilateral IS S1 screws exhibit superior stability to a single IS screw and are also safer for neurological injuries than an S2 screw. Therefore, this study aimed to evaluate fixation using percutaneous two unilateral IS S1 screws for pelvic ring injuries and its subsequent clinical outcomes. Methods: We retrospectively reviewed 38 patients who underwent percutaneous two unilateral IS S1 screw fixation for pelvic ring injuries. The procedure time, blood loss, achievement of bone union, radiological outcomes (Matta and Tornetta grade), and postoperative complications were evaluated. Results: The mean procedure time, hemoglobin loss, bone union rate, and time to union were 40.1 minutes (range, 18-102 minutes), 0.6 g/dL (range, 0.3-1.0 g/dL), 100%, and 153.2 days (range, 61-327 days), respectively. The Matta and Tornetta grades were excellent, good, and fair in 24 (63.1%), 11 (28.9%), and three patients (7.9%), respectively, and the postoperative complications were S1 screw loosening, widening of the symphysis pubis (2.3 and 2.5 mm), lumbosacral plexopathy, and S1 radiculopathy in one (2.6%), two (5.3%), one (2.6%), and one patient (2.6%), respectively. However, all neurological complications recovered spontaneously. Conclusions: Percutaneous two unilateral IS S1 screw fixation was useful for treating pelvic ring injuries. In particular, it involved a short procedure time with little blood loss and also led to 100% bone union and good radiological outcomes.