• The Journal of Advanced Prosthodontics
• /
• v.1 no.1
• /
• pp.10-18
• /
• 2009

STATEMENT OF PROBLEM. Despite an improved bone reactions of Mg-incorporated implants in the animals, little yet has been carried out by the experimental investigations in functional loading conditions. PURPOSE. This study investigated the clinical and histologic parameters of osseointegrated Mg-incorporated implants in early loading conditions. MATERIAL AND METHODS. A total of 36 solid screw implants(diameter 3.75 mm, length 10 mm) were placed in the mandibles of 6 beagle dogs. Test groups included 18 Mg-incorporated implants. Turned titanium implants served as control. Gold crowns were inserted 4 weeks after implant placement and the dogs were immediately put on a food diet. Implants were observed for 10 weeks after loading. Radiographic assessments and stability tests were performed at the time of fixture installation, $2^{nd}$ stage surgery, 4 weeks after loading, and 10 weeks after loading. Histological observations and morphometrical measurements were also performed. RESULTS. Of 36 implants, 33 displayed no discernible mobility, corresponding to successful clinical function. There was no statistically significant difference between test implants and controls in marginal bone levels(P=.46) and RFA values. The mean BIC % in the Mg-implants was $54.5{\pm}8.4%$. The mean BIC % in the turned implant was $45.3{\pm}12.2%$. These differences between the Mg-implant and control implant were statistically significant(P=.005). CONCLUSIONS. The anodized, Mg-incorporated implant demonstrated significantly more bone-to-implant contact(BIC) in early loading conditions. CLINICAL IMPLICATIONS. The results of this study in beagle dogs suggest the possibility of achieving predictable stability of early loaded free-standing dental implants with Mg-incorporated surface.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.49 no.6
• /
• pp.332-338
• /
• 2023

Objectives: This study aimed to compare the effectiveness of a hybrid arch bar (hAB) with the conventional Erich arch bar (EAB) for the management of jaw fractures, focusing on their use for temporary fixation in patients undergoing open reduction and internal fixation (ORIF). Materials and Methods: Patients presenting with maxillary and mandibular fractures at our institution were included in this prospective, comparative study. Placement time and ease of occlusal reproducibility were recorded intraoperatively for Group A (hAB patients) and Group B (EAB patients). The primary outcome was comparison of the postoperative stability of the two arch bars. Postoperative measurements also included mucosal overgrowth, screw loosening or wire retightening, and replacement rates. The data were tabulated and computed with a P<0.05 considered statistically significant. Results: The study included 41 patients. A statistically significant difference was observed in postoperative stability scores (3) between Group A and Group B (85.0% vs 9.5%, P=0.001). The mean placement time in Group A (23.3 minutes) significantly differed from that in Group B (86.4 minutes) (P<0.001). The ease of intraoperative occlusion was not different between the two groups (P=0.413). Mucosal overgrowth was observed in 75.0% of patients (15 of 20) in Group A. Conclusion: The hAB was superior to EAB in clinical efficiency, maxillomandibular fixation time reduction, stability, versatility, and safety. Despite temporary mucosal overgrowth, the benefits of hAB outweigh the disadvantages. The choice between hAB and EAB should be based on specific clinical requirements.

• Journal of Veterinary Science
• /
• v.25 no.1
• /
• pp.2.1-2.14
• /
• 2024

Background: Sufficient surgical resection is necessary for effective tumor control, but is usually limited for vertebral tumors, especially in the cervical spine in small animal neurosurgery. Objective: To evaluate the primary stability and safety of customized three-dimensional (3D)-printed implants for cervical spine reconstruction after total vertebrectomy. Methods: Customized guides and implants were designed based on computed tomography (CT) imaging of five beagle cadavers and were 3D-printed. They were used to reconstruct C5 after total vertebrectomy. Postoperative CT images were obtained to evaluate the safety and accuracy of screw positioning. After harvesting 10 vertebral specimens (C3-C7) from intact (group A) and implanted spines (group B), implant stability was analyzed using a 4-point bending test comparing with groups A and C (reconstituted with plate and pins/polymethylmethacrylate after testing in Group A). Results: All customized implants were applied without gross neurovascular damage. In addition, 90% of the screws were in a safe area, with 7.5% in grade 1 (< 1.3 mm) and 2.5% in grade 2 (> 1.3 mm). The mean entry point and angular deviations were 0.81 ± 0.43 mm and 6.50 ± 5.11°, respectively. Groups B and C significantly decreased the range of motion (ROM) in C3-C7 compared with intact spines (p = 0.033, and 0.018). Both groups reduced overall ROM and neutral zone in C4-C6, but only group B showed significance (p = 0.005, and 0.027). Conclusion: Customized 3D-printed implants could safely and accurately replace a cervical vertebra in dog cadavers while providing primary stability.

• Elastomers and Composites
• /
• v.46 no.3
• /
• pp.211-217
• /
• 2011

Wood Polymer Composite (WPC) has attracted a great deal of attention in environmental industries due to renewable resources, processability, excellent physical properties and logging regulations for application to housing units and engineering construction materials. In this study, commercial WPCs were prepared by using a modular intermeshing co-rotating twin screw extruder. The effect of three main factors such as wood flour contents, coupling agent concentrations and pre-treatment of wood flour on the properties of WPCs was extensively investigated. It was found that tensile strength and thermal stability were decreased with increasing wood flour contents whereas the water absorption was increased. Addition of maleic anhydride grafted polypropylene (PP-g-MA) into WPC exhibited better physical properties. On the contrary, the water absorption was slightly decreased with PP-g-MA. Finally the sample, which was prepared with pre-treated wood flour, represented the highest tensile strength. However, the water absorption of the sample was increased due to the transition of crystalline structure of cellulose.

• Journal of Korean Neurosurgical Society
• /
• v.62 no.4
• /
• pp.422-431
• /
• 2019

Objective : In an aging society, the number of patients with symptomatic degenerative spondylolisthesis (DS) is increasing and there is an emerging need for fusion surgery. However, few studies have compared transforaminal lumbar interbody fusion (TLIF) and lateral lumbar interbody fusion (LLIF) for the treatment of patients with DS. The purpose of this study was to investigate the clinical and radiological outcomes between TLIF and LLIF in DS. Methods : We enrolled patients with symptomatic DS at L4-5 who underwent TLIF with open pedicle screw fixation (TLIF group, n=41) or minimally invasive LLIF with percutaneous pedicle screw fixation (LLIF group, n=39) and were followed-up for more than one year. Clinical (visual analog scale and Oswestry disability index) and radiological outcomes (spondylolisthesis rate, segmental sagittal angle [SSA], mean disc height [MDH], intervertebral foramen height [FH], cage subsidence, and fusion rate) were assessed. And we assessed the changes in radiological parameters between the postoperative and the last follow-up periods. Results : Preoperative radiological parameters were not significantly different between the two groups. LLIF was significantly superior to TLIF in immediate postoperative radiological results, including reduction of spondylolisthesis rate (3.8% and 7.2%), increase in MDH (13.9 mm and 10.3 mm) and FH (21.9 mm and 19.4 mm), and correction of SSA ($18.9^{\circ}$ and $15.6^{\circ}$) (p<0.01), and the changes were more stable from the postoperative period to the last follow-up (p<0.01). Cage subsidence was observed significantly less in LLIF (n=6) than TLIF (n=21). Fusion rate was not different between the two groups. The clinical outcomes did not differ significantly at any time point between the two groups. Complications were not statistically significant. However, TLIF showed chronic mechanical problems with screw loosening in four patients and LLIF showed temporary symptoms associated with the surgical approach, such as psoas and ileus muscle symptoms in three and two cases, respectively. Conclusion : LLIF was more effective than TLIF for spondylolisthesis reduction, likely due to the higher profile cage and ligamentotactic effect. In addition, LLIF showed mechanical stability of the reduction level by using a cage with a larger footprint. Therefore, LLIF should be considered a surgical option before TLIF for patients with unstable DS.

• Journal of Korean Foot and Ankle Society
• /
• v.17 no.2
• /
• pp.130-135
• /
• 2013

Purpose: Preshaped Locking compression plate(LCP) has holes with fixed angle between screw and plate and have advantage firm fixation because it has stability of angular and axial deformity. We evaluated usefulness of LCP after open reduction and internal fixation in distal fibular fracture. Materials and Methods: Between December 2011 and May 2012, 23 patients with fracture of distal fibula were followed up at least 12 months underwent open reduction and internal fixation with LCP. There were 15 males and 8 females with a mean age 39.8(20~69) years. According to Danis-Weber classification, there were 20 cases of type B and 3 cases of type C. There were 13 cases of isolated lateral malleolus fractures, 1 case of bimalleolar fracture, 6 cases of trimalleolar fractures and 3 cases of distal tibia fractures with proximal fibula fracture. Intraoperatively, we assessed whether preshaped LCP fit lateral margin of distal fibula or not and evaluated quality of reduction and postoperative complications. The cases were analyzed by radiological bone union time and clinical results according to the criteria of Meyer Results: Of all cases, complete bone union was achieved and average radiological bone union time was 7.3(6~12) weeks. The clinical results were excellent in 18 cases(78%), good in 5 cases(22%). There were 5 cases of plate with 3 holes, 13 cases of plate with 4 holes, 2 cases of plate with 5 holes, 1 case of plate with 6 holes and 2 cases of plate with 7 holes. The average number of screws at proximal fragement was 2.5 and at distal fragment was 3.5. In 14 cases (60.8 %), we needed re-bending of plate because the distance between plate and lateral cortical margin of distal fibula was more than 5 mm at anteroposterior X-ray after reduction. All cases have anatomical reduction and there were no complications of wound infections. There were no complaint about hardware irritation. Conclusion: At fractures of distal fibula,preshaped LCP had a excellent stability although far cortex was not fixed with screw and bending of plate. And there are less complications of hardware irritation and wound problems. But, Some complement would be needed because there were no complete fitting between precontour of LCP and lateral cortical margin of distal fibula.

• Analytical Science and Technology
• /
• v.25 no.5
• /
• pp.273-283
• /
• 2012

Phthalate plasticizers are regulated by RoHS, REACH and CPSC as hazardous substances. Responding to these international environmental restrictions, we developed ABS certified reference material (CRM) for determination of phthalate plasticizers such as DMP, DEP, DBP, BBP, DEHP and DnOP. The candidate material has been made with ABS resin widely used in electric and electronic products and 6 kinds of phthalate plasticizers. The making of the material involved a series of processes like extruding, cooling, pelletizing, and drying using twin screw extruder. Then it has been certified according to ISO Guide 35. Using isotope dilution-gas chromatography/mass spectrometry (ID-GC/MS), homogeneity, short-term stability, and long-term stability were evaluated. The certified values were determined by using primary reference material (PRM) of KRISS for traceability. From now on, we will provide ABS CRM to national and international companies and research institutes after certification as certified reference material and registering on COMAR (code of reference material).

• The Journal of Korean Academy of Prosthodontics
• /
• v.48 no.4
• /
• pp.280-286
• /
• 2010

Purpose: This study evaluated the detorque values of screws in a multiple implant-supported superstructure using stone casts made with 2 different impression techniques. Material and methods: A fully edentulous mandibular master model and a metal framework directly connected to four implants (Br${\aa}$nemark $System^{(R)}$; Nobel Biocare AB) with a passive fit to each other were fabricated. Six experimental stone casts (Group 1) were made with 6 non-splinted impressions on a master cast and another 6 experimental casts (Group 2) were made with 6 acrylic resin splinted impressions. The detorque values of screws ($TorqTite^{(R)}$ GoldAdapt Abutment Screw; Nobel Biocare AB) were measured twice after the metal framework was fastened onto each experimental stone cast with 20 Ncm torque. Detorque values were analyzed using the mixed model with the fixed effect of screw and reading and the random effect of model for the repeated measured data at a .05 level of ignificance. Results: The mean detorque values were 7.9 Ncm (Group 1) and 8.1 Ncm (Group 2), and the mean of minimum detorque values were 6.1 Ncm (Group 1) and 6.5 Ncm (Group 2). No statistically significant differences between 2 groups were found and no statistically significant differences among 4 screws were found for detorque values. No statistically significant differences between 2 groups were also found for minimum detorque values. Conclusion: In a multiple external hexagon implant-supported prosthesis, no significant differences between 2 groups were found for detorque values and for minimum detorque values. There seems to be no significant differences in screw joint stability between 2 stone cast groups made with 2 different impression techniques.

• Journal of the Korean Arthroscopy Society
• /
• v.7 no.2
• /
• pp.189-195
• /
• 2003

Purpose : To evaluate the clinical results after anterior cruciate ligament (ACL) reconstruction with hamstring tendon and Ligament Anchor (LA) screw Materials and Methods : 103 patients (104 cases) who were followed up at least more than 2 years after ACL reconstruction were included in this study. The average period of follow-up was 36 months. The clinical results such as physical examination and Lysholm knee score and instrumented anterior laxity test with Telos were evaluated. Results : The Lysholm knee score was 57.9 in average preoeratively and improved to 95.2 in average at follow up. On the Lachman test, there were mild (+) instability in 46 cases $(45\%)$, moderate (++) in 33 $(31\%)$, severe (+++) in 25 $(24\%)$ preoperatively. 90 cases $(87\%)$ were converted to negative and 14 $(13\%)$ to mild at follow up. On Pivot-shift test, there were negative (-) instability in 22 cases $(22\%)$, mild (+) in 62 $(59\%)$, moderate (++) in 12 $(11\%)$ and severe in 8 $(8\%)$ preoperatively. 87 cases $(84\%)$ were converted to negative and 17 $(16\%)$ to mild at follow up. On instrumented anterior laxity test with $Telos^{\circledR}$, side to side difference on 20 lb was $13.4{\pm}5.6$ (7-25) mm in average preoperatively, and was decreased to $3.6{\pm}1.5$ (1-6) mm in average at follow-up. Complications were quadriceps muscle atrophy in 27 $(30.0\%)$, saphenous nerve paresthesia in 19 $(18.3\%)$, anterior knee crepitus in 13 $(12.5\%)$ and over-penetration of screw through lateral femoral cortex in 5 cases $(4.8\%)$. Conclusion : ACL reconstruction with hamstring tendon and LA screw was one of the choice of graft and fixatives in restoring knee stability and in improving clinical results with little complications such as anterior knee pain.

• The korean journal of orthodontics
• /
• v.41 no.4
• /
• pp.280-287
• /
• 2011

Objective: This study compared the stability of cylindrical miniscrews (Cy, 7 mm in length) with that of tapered miniscrews (Ta, 5 mm in length), using torque values to determine if the healing time before loading affects the stability of the miniscrew and if the insertion torque is associated with the removal torque measured after a few weeks of healing. Methods: Ta and Cy with different thread lengths were placed in the tibias of 12 female New Zealand white rabbits (body weight: 3.0 - 3.5 kg), and the maximum insertion torque values (ITV) were measured. No orthodontic forces were applied so as to allow us to determine the pure effects of the different shapes. After 3 different healing periods (2, 4, and 6 weeks), maximum removal torque values (RTV) were measured immediately before the rabbits were sacrificed. Results: No miniscrews were loosened. There were no significant differences in ITV or RTV between the Ta and Cy nor were there any significant differences in the ITV and RTV between the 3 groups, which had different healing periods. There was a correlation between the ITV and RTV. Conclusions: Shorter Ta showed similar stability as Cy, as determined by torque values. This result strongly suggests that the tapered shape is more advantageous than the cylindrical shape. The RTV did not increase significantly over time. It is recommended that a miniscrew be loaded immediately; waiting a few weeks before loading should be avoided. The correlation between the ITV and RTV suggests that the ITV can be used to estimate a screw's future stability.