• The Journal of Korean Academy of Prosthodontics
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• v.36 no.3
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• pp.468-482
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• 1998

Since the concept of osseointegration was introduced by Branemark of Sweden, dental implants have been used for various dental prosthetic treatments. The survival rate of dental implant is likely to be closely related to the total biomechanical role of each component of implant system. The use of interchangeable component is very attractive for dental practitioners because such an approach would save treatment cost, flexibility of prosthetic treatment options as well as conveniences. Therefore, the use of interchangeable implant system has been increasing without scientific assessment of safety and efficacy of various interchangeable implant system. The purpose of this study, therefore, were to compare the geometric characteristic of four interchangeable dental implant screws and the loosening torque of these screws. Four types of dental implant screws tested in this study were Nobelpharma, 3i, Impla-med, Restore. Four screws each of the test specimens were subjected for scanning electron microscopic examinations under the same condition and a 35x magnified standard SEM picture was objected from each test specimen using JSM-5200 scanning microscope. From each of the SEM pictures, eight parameters. i.e., diameter of screw head. screw length, thread pitch, major diameter. neck diameter, neck length, crest width and root width were determined using a caliper. The measurement for each parameters were then corrected for their magnification factor. The loosening torque were also determined by using a torque gauge. All of the measurements were statistically analyzed by ANOVA test and multiple range test. Statistical significance was set in advance at the probability level of less than 0.05. All analyses were done with SPSS software for the personal computer. The conclusion obtained from this studies were summarized as the following; 1. No statistically significances were noted in the thread pitch. and crest width in the four screws, and in the case of major diameter, the Impla-med screw was significantly smaller than the other three screws (p<0.05). Therefore, four implant bolts could be physically inserted in a abutment nuts. 2. The diameter of screw head was decreased in the order of Restore, 3i, Nobelpharma, Impla-med screws and the length of screws were decreased in the order of 3i, Restore, Nobelpharma and Impla-med. The diameter of neck was decreased in the order of Impla-med, Restore. Nobelpharma, 3i screws. The differences of each of these parameters were statistically significant (p<0.05). The width of root of screws were decreased in the order of Nobelpharma, Impla-med, Restore and 3i. The differences among Nobelpharma and Impla-med. Restore and 3i were statistically significant (p<0.05). 3. When the screws were loosening 1, 3, 4 and 5 times, the loosening torque for Impla-med and 3i screws were significantly higher than that of Nobelpharma or Restore screws (p<0.05). However, when statistically smaller than that of 3i, Restore or Nobelpharma screws(p<0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.3
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• pp.275-286
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• 2002

Statement of problem. Surface alteration of the implant screws after function may be associated with mechanical failure. Theses metal fatigue appears to be the most common cause of structural failure. Purpose. The purpose of this study was to evaluate surface alteration of the implant screws after function through the examination of used and unused implant screws in SEM(scanning electron microscope). Materials and methods. In this study, abutment screws(Steri-oss, 3i), gold retaining screw(3i) and titanium retaining screw(3i) were retrieved from patients. New, unused abutment and retaining screws were prepared for control group. Each of the old, used screws was retrieved with a screwdriver. And retrieved implant complex of Steri-oss system was prepared for this study. Then, SEM investigation and EDS analysis of abutment and retaining screws were performed. And SEM investigation of cross-sectioned sample of retrieved implant complex was performed. Results. In the case of new, unused implant screws, as maunfactured circumferential grooves are regularly examined and screw thread are sharply remained. Before ultrasonic cleansing of old, used implant screw, a lot of accumulation and corrosion products were existed. After ultrasonic cleansing of old, used implant screws, circumferential grooves as examined before function were randomly deepened and scratches increased. Also, dull screw thread was examined. More surface alterations after function were examined in titanium screw than gold screw. And more surface alteration was examined when retrieved with driver than retrieved without driver. Conclusions. These surface alteration after function may result in the screw instability. Regularly cleansing and exchange of screws was recommended. We recommend the use of gold screw rather than titanium screw, and careful manipulation of the driver.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.33 no.5
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• pp.499-503
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• 2007

Introduction: In orthognathic surgery, internal fixation has been usually done with titanium plates and screws. Recently, Biodegradable plates and screws have been frequently used but the reports of long term results of postoperative stability are rare, especially after maxillary reposition in orthognathic surgery. Objective: In order to clarify the clinical utility of self-reinforced bioresorbable poly-70L/30DL-Lactide miniplates & screws in maxillary fixation after LeFort I osteotomy, this study examined the postsurgical changes in maxilla and complications of biodegradable plates and screws. Study design: Nineteen patients who had undergone maxillary internal fixation using biodegradable plates and screws were evaluated radiographically and clinically. A comparison study of the changes in maxilla position after surgery in all 19 patients was performed with 1-week, 1-month, 3-months, 6-months and/or 1-year postoperative lateral cephalograms by tracing. Complication of the biodegradable plates and screws was evaluated by follow-up roentgenograms and clinical observation. And one-way ANOVA test was used for statistical analysis. Results: The position of the maxillary bone was stable after surgery and was not changed significantly from 1 week to 1 year after operation. And we could not find any complication of biodegradable plates and screws. Conclusions: Internal fixation of the maxilla after LeFort I osteotomy using self-reinforced biodegradable plates and screws is a reliable method for maintaining postoperative position of the maxilla after LeFort I osteotomy.

• Journal of Korean Foot and Ankle Society
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• v.24 no.2
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• pp.94-97
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• 2020

Purpose: Fatigue breakage of cortical screws sometimes occurs after syndesmosis fixation, regardless of the period of screw retention. This study compared the fatigue strength of a novel screw design to conventional cortical screws in the fixed state of syndesmosis. Materials and Methods: Twelve sawbone models were tested mechanically to determine the fatigue strength of three screw designs. The first group was composed of cortical screws, while the second and third groups were newly-designed screws. The second group was composed of screws with a 2.4-mm diameter thread-free portion of the mid-shank while the third group had a 2.0-mm diameter thread-free mid-shank. A 400 N load was applied repetitively to a fibula model and the number of cycles until screw failure was recorded. Four screws from each group were tested, giving a total of 12 fatigue tests. Results: The average cycles until screw failure for groups 1, 2, and 3 were 8,134, 63,186, and 2,581, respectively. The second group showed the highest fatigue strength (p=0.018). The other two screw designs showed similar fatigue strength (p=0.401). Conclusion: New screw designs with a thread-free portion in the mid-shank could reduce the occurrence of fatigue breakage after syndesmosis fixation.

• Journal of Korean Neurosurgical Society
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• v.52 no.5
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• pp.459-465
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• 2012

Objective : To present the accuracy and safety of cervical pedicle screw insertion using the technique with direct exposure of the pedicle by laminoforaminotomy. Methods : We retrospectively reviewed 12 consecutive patients. A total of 104 subaxial cervical pedicle screws in 12 patients had been inserted. We also assessed the clinical and radiological outcomes and analyzed the direction and grade of pedicle perforation (grade 0: no perforation, 1: <25%, 2: 20% to 50%, 3: >50% of screw diameter) on the postoperative vascular-enhanced computed tomography scans. Grade 2 and 3 were considered as incorrect position. Results : The correct position was found in 95 screws (91.3%); grade 0-75 screws, grade 1-20 screws and the incorrect position in 9 screws (8.7%); grade 2-6 screws, grade 3-3 screws. There was no neurovascular complication related with cervical pedicle screw insertion. Conclusion : This technique (technique with direct exposure of the pedicle by laminoforaminotomy) could be considered relatively safe and easy method to insert cervical pedicle screw.

• Clinics in Shoulder and Elbow
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• v.24 no.3
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• pp.141-146
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• 2021

Background: The purpose of the present study was to determine how long superior screws alone or in combination with posterior placement of metaglene screws protruding and penetrating into the scapular spine in reverse total shoulder arthroplasty affect the strength of the scapular spine in a fresh cadaveric scapular model. Methods: Seven fresh cadaver scapulas were allocated to the control group (short posterior and superior screws) and seven scapulars to the study group (spine base fixation with a four long screws, three with both long superior and long posterior screws). Results: The failure load was lower in the spine fixation group (long screw, 869 N vs. short screw, 1,123 N); however, this difference did not reach statistical significance (p>0.05). All outside-in long superior or superior plus posterior screws failed due to scapular spine base fracture; failures in the short screw group were due to acromion fracture. An additional posterior outside-in screw failed to significantly decrease the failure load of the acromion spine. Conclusions: The present study highlights the significance of preventing a cortical breach or an outside-in configuration when a superior or posterior screw is inserted into the scapular spine base.

• Journal of Biomedical Engineering Research
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• v.31 no.3
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• pp.199-209
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• 2010

The locking compression plates-distal femur(LCP-DF) are being widely used for surgical management of the extra-articular complex fractures of the distal femur. They feature locking mechanism between the screws and the screw holes of the plate to provide stronger fixation force with less number of screws than conventional compression bone plate. However, their biomechanical efficacies are not fully understood, especially regarding the number of the screws inserted and their optimal configurations. In this study, we investigated effects of various screw configurations in the shaft and the condylar regions of the femur in relation to structural stability of LCP-DF system. For this purpose, a baseline 3-D finite element (FE) model of the femur was constructed from CT-scan images of a normal healthy male and was validated. The extra-articular complex fracture of the distal femur was made with a 4-cm defect. Surgical reduction with LCP-DF and bone screws were added laterally. To simulate various cases of post-op screw configurations, screws were inserted in the shaft (3~5 screws) and the condylar (4~6 screws) regions. Particular attention was paid at the shaft region where screws were inserted either in clustered or evenly-spaced fashion. Tied-contact conditions were assigned at the bone screws-plate whereas general contact condition was assumed at the interfaces between LCP-DF and bone screws. Axial compressive load of 1,610N(2.3 BW) was applied on the femoral head to reflect joint reaction force. An average of 5% increase in stiffness was found with increase in screw numbers (from 4 to 6) in the condylar region, as compared to negligible increase (less than 1%) at the shaft regardless of the number of screws inserted or its distribution, whether clustered or evenly-spaced. At the condylar region, screw insertion at the holes near the fracture interface and posterior locations contributed greater increase in stiffness (9~13%) than any other locations. Our results suggested that the screw insertion at the condylar region can be more effective than at the shaft during surgical treatment of fracture of the distal femur with LCP-DF. In addition, screw insertion at the holes close to the fracture interface should be accompanied to ensure better fracture healing.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.2
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• pp.210-225
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• 2004

Statement of problem: Implant screw loosening has been remained problem in restorative practices. Surface treatment of screw plays a role of preventing screw from loosening in implant screw mechanism. Purpose : The purpose of this study was to investigate surface characteristics of TiN and ZrN film ion plated screw with titanium and gold alloy screw and to evaluate wear resistance, surface roughness, and film adhesion on screw surface using various instruments. Material and methods : GoldTite screws and titanium screws provided by 3i (Implant Innovation, USA) and TorqTite screws or titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, korea) were selected. Ion plating which is much superior to other surface modification techniques was carried out for gold screws and titanium screws using Ti and Zr coating materials with nitrogen gas. Ion nitrided surface of each abutment screw was observed with field emission scanning electron microscopy (FE-SEM, micro-diamond scratch tester, vickers hardness tester, and surface roughness tester. Results : 1) The surface of gold screw and GoldTite is more smooth than ones of other kinds of non coated screw. 2) The ZrN and TiN coated surface is the more smooth than ones of other kinds of screw. 3) The hardness of TiN and ZrN coated surface showed higher than that of non coated surface. 4) The TiN coated titanium screw and ZrN coated gold screw have a good wear resistance and adhesion on the surface. 5) The surface of ZrN coated screw showed low surface roughness compared with the surface of TiN coated screw. Conclusion : It is considered that the TiN and ZrN coated screw which would prevent a screw from loosening can be applicable to implant system and confirmed that TiN and ZrN film act as lubricant on surface of screw due to decrease of friction for recycled tightening and loosening.

• Journal of Korean Neurosurgical Society
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• v.61 no.5
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• pp.568-573
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• 2018

Objective : Thoracic pedicles have special and specific properties. In particular, upper thoracic pedicles are positioned in craniocaudal plane. Therefore, manipulation of thoracic pedicle screws on the left side is difficult for right-handed surgeons. We recommend a new position to insert thoracic pedicle screw that will be much comfortable for spine surgeons. Methods : We retrospectively reviewed 33 patients who underwent upper thoracic pedicle screw instrumentation. In 15 patients, a total of 110 thoracic pedicle screws were inserted to the upper thoracic spine (T1-6) with classical position (anesthesiologist and monitor were placed near to patient's head. Surgeons were standing classically near to patient's body while patients were lying in prone position). In 18 patients, a total of 88 thoracic pedicle screws were inserted to the upper thoracic spine with the new standing position-surgeons stand by the head of the patient and the anesthesia monitor laterally and under patient's belt level. All the operations performed by the same senior spine surgeons with the help of C-arm. Postoperative computed tomography scans were obtained to assess the screw placement. The screw malposition and pedicle wall violations were divided and evaluated separately. Cortical penetration were measured and graded at either : 1-2 mm penetration, 2-4 mm penetration and >4 mm penetration. Results : Total 198 screws were inserted with two different standing positions. Of 198 screws 110 were in the classical positioning group and 88 were in the new positioning group. Incorrect screw placement was found in 33 screws (16.6%). The difference between total screw malposition by both standing positions were found to be statistically significant (p=0.011). The difference between total pedicle wall violations by both standing positions were found to be statistically significant (p=0.003). Conclusion : Right-handedness is a problem during the upper thoracic pedicle screw placement on the left side. Changing the surgeon's position standing near to patient's head could provide a much comfortable position to orient the craniocaudal plane of the thoracic pedicles.

• Asian Spine Journal
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• v.12 no.6
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• pp.1053-1059
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• 2018

Study Design: Retrospective review. Purpose: To detect the effect of cannulated (poly-axial head) and solid (mono-axial head) screws on the local kyphotic angle, vertebral body height, and superior and inferior angles between the screw and the rod in the surgical management of thoracolumbar fractures. Overview of Literature: Biomechanics studies showed that the ultimate load, yield strength, and cycles to failure were significantly lower with cannulated (poly-axial head) pedicle comparing to solid core (mono-axial head). Methods: The medical charts of patients with thoracolumbar fractures who underwent pedicle screw fixation with cannulated or solid pedicle screws were retrospectively reviewed; the subjects were followed up from January 2011 to December 2015. Results: Total 178 patients (average age, $36.1{\pm}12.4years$; men, 142 [84.3%]; women, 28 [15.7%]) with thoracolumbar fractures who underwent surgery and were followed up at Hamad Medical Corporation were classified, based on the screw type as those with cannulated screws and those with solid screws. The most commonly affected level was L1, followed by L2 and D12. Surgical correction of the local kyphotic angle was significantly different in the groups; however, there was no significant difference in the loss of correction of the local kyphotic angle of the groups. Surgical correction of the reduction in the vertebral body height showed statistical significance, while the average loss of correction in the reduction of the vertebral body height was not significantly different. The measurement of the angles made by the screws on the rods was not significantly different between the cannulated (poly-axial head) and solid (mono-axial head) screw groups. Conclusions: Solid screws were superior in terms of providing increased correction of the kyphotic angle and height of the fractured vertebra than the cannulated screws; however, no difference was noted between the screws in the maintenance of the superior and inferior angles of the screw with the rod.