• Maxillofacial Plastic and Reconstructive Surgery
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• v.31 no.3
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• pp.207-215
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• 2009

Purpose: The aim of the present study is to evaluate the long term bone healing after horizontal ridge augmentation using auto block bone graft for implant installation timing. Materials and Methods: Five Beagle dogs(which were 14 months old and weighted approximately 10kg). In surgery 1(extraction & bone defect), premolars(P2, P3,P4) were extracted and the buccal bone plate was removed to create a horizontally defected ridge. After three months healing, in surgery 2(ridge augmentation). Auto block bone grafts from the mandibular ramus were used in filling the bone defects were fixed with stabilizing screws. The following fluorochrome labels were given intravenously to the beagle dogs: oxytetracycline 1week after the surgery, alizarin red 4 weeks after the surgery, calcein blue 8 weeks after the surgery. The tissue samples were obtained from the sacrificed dogs of 1, 4, 8, 12, 16 weeks after the surgery. Non-decalcified sections were prepared by resin embedding and microsection to find thickness of $10{\mu}m$ for the histologic examination and analysis. Results: 1. We could achieve the successful reconstruction of the horizontal bone defect by auto block bone graft. The grafted bone block remained stable morohologically after 16 weeks of the surgery. 2. In the histologic view. We observed osteoid tissue from the sample $4^{th}$ week sample and active capillary reconstruction in the grafted bone from the $12^{th}$ week sample. Healing procedures of auto bone grafts were compared to that of the host bone. 3. Bone mineralization could be detected from the $8^{th}$ week sample. 4. Fluorochrome labeling showed active bony changes and formation at the interface of the host bone and the block graft mainly. Bony activation in the grafted bone could be seen from the $4^{th}$ week samples. Conclusions: Active bone formation and remodeling between the grafted bone and host bone can be seen through the revascularization. After the perfect adhesion to host bone, Timing of successful implant installation can be detected through the ideal ridge formation by horizontal ridge augmentation.

• Archives of Craniofacial Surgery
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• v.17 no.1
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• pp.1-4
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• 2016

Absorbable plates are used widely for fixation of facial bone fractures. Compared to conventional titanium plating systems, absorbable plates have many favorable traits. They are not palpable after plate absorption, which obviates the need for plate removal. Absorbable plate-related infections are relatively uncommon at less than 5% of patients undergoing fixation of facial bone fractures. The plates are made from a mixture of poly-L-lactic acid and poly-DL-lactic acid or poly-DL-lactic acid and polyglycolic acid, and the ratio of these biodegradable polymers is used to control the longevity of the plates. Degradation rate of absorbable plate is closely related to the chance of infection. Low degradation is associated with increased accumulation of plate debris, which in turn can increase the chance of infection. Predisposing factors for absorbable plate-related infection include the presence of maxillary sinusitis, plate proximity to incision site, and use of tobacco and significant amount of alcohol. Using short screws in fixating maxillary fracture accompanied maxillary sinusitis will increase the rate of infection. Avoiding fixating plates near the incision site will also minimize infection. Close observation until complete absorption of the plate is crucial, especially those who are smokers or heavy alcoholics. The management of plate infection is varied depending on the clinical situation. Severe infections require plate removal. Wound culture and radiologic exam are essential in treatment planning.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.2 no.1
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• pp.5-17
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• 2009

We developed bone-insertion pin screw that can be used for purposed treatment by combining with the external fixator which is the subsidiary tool for the healing of the fracture (open fracture of long bone, reconstruction of soft tissue and arthrodesis etc.) Furthermore, for the frist time, we succeeded in domestic-producing this screw, using specially-designed treating tool stuck on the lathe machine and abrasive blasting machine, and the post-dealing technique and process. In comparison with other foreign products, we could get more desirable results in various tests. This pin screw has 103% characteristics of the average of foreign products. Thus we'd like to introduce design techniques, post-dealing process and result of function tests.

• Journal of Trauma and Injury
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• v.25 no.4
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• pp.278-282
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• 2012

An esophageal perforation following anterior cervical fusion is rare. Early development of an esophageal perforation after anterior cervical fusion is usually due to iatrogenic injury from retraction, injury associated with the original traumatic incident, improperly placed instruments or a bone graft. A 31-year-old man had a cervical dislocation and spinal cord injury because of severe cervical trauma after a traffic accident. He was quadriplegic and had no feeling below T4 dermatome. Anterior decompression of the cervical spine and anterior fusion with mesh with autobone were performed. An esophagocutaneous fistula occurred 7 days after anterior cervical surgery. A second anterior surgery was done because of pus drainage. The mesh was changed with an iliac bone graft, and the esophagocutaneous fistula site was primary repaired, but pus continued to drain. Conservative treatment, which consisted of wound drainage and intravenous administration of antibiotics, was tried, but was unsuccessful. After all, we removed the plate and screws, but did not removed the iliac bone graft, We closed the esophageal fistula, and transposed the sternocleidomastoid muscle flap to the interspace between the esophagus and the cervical spine. The wound to the esophagus was well repaired. In conclusion, precautionary measures are needed to avoid the complication, and adequate treatment is necessary to resolve those complications when they occur.

• The Journal of Advanced Prosthodontics
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• v.14 no.6
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• pp.346-359
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• 2022

PURPOSE. Four and six implant-supported fixed full-arch prostheses with various framework materials were assessed under different loading conditions. MATERIALS AND METHODS. In the edentulous maxilla, the implants were positioned in a configuration of four to six implant modalities. CoCr, Ti, ZrO₂, and PEEK materials were used to produce the prosthetic structure. Using finite element stress analysis, the first molar was subjected to a 200 N axial and 45° oblique force. Stresses were measured on the bone, implants, abutment screw, abutment, and prosthetic screw. The Von Mises, maximum, and minimum principal stress values were calculated and compared. RESULTS. The maximum and minimum principal stresses in bone were determined as CoCr < ZrO₂ < Ti < PEEK. The Von Mises stresses on the implant, implant screw, abutment, and prosthetic screws were determined as CoCr < ZrO₂ < Ti < PEEK. The highest Von Mises stress was 9584.4 Mpa in PEEK material on the prosthetic screw under 4 implant-oblique loading. The highest maximum principal stress value in bone was found to be 120.89 Mpa, for PEEK in 4 implant-oblique loading. CONCLUSION. For four and six implant-supported structures, and depending on the loading condition, the system accumulated different stresses. The distribution of stress was reduced in materials with a high elastic modulus. When choosing materials for implant-supported fixed prostheses, it is essential to consider both the number of implants and the mechanical and physical attributes of the framework material.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.131-136
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• 2016

PURPOSE. The aim of this study was to observe stress concentration in the implant, the surrounding bone, and other components under the pull-out force during the crown removal. MATERIALS AND METHODS. Two 3-dimensional models of implant-supported conventional metal ceramic crowns were digitally constructed. One model was designed as a vertically placed implant ($3.7mm{\times}10mm$) with a straight abutment, and the other model was designed as a 30-degree inclined implant ($3.7mm{\times}10mm$) with an angled abutment. A pull-out force of 40 N was applied to the crown. The stress values were calculated within the dental implant, the abutment, the abutment screw, and the surrounding bone. RESULTS. The highest stress concentration was observed at the coronal portion of the straight implant (9.29 MPa). The stress concentrations at the cortical bone were lower than at the implants, and maximum stress concentration in bone structure was 1.73 MPa. At the abutment screws, the stress concentration levels were similiar (3.09 MPa and 3.44 MPa), but the localizations were different. The stress at the angled abutment was higher than the stress at the straight abutment. CONCLUSION. The pull-out force, applied during a crown removal, did not show an evident effect in bone structure. The higher stress concentrations were mostly observed at the implant and the abutment collar. In addition, the abutment screw, which is the weakest part of an implant system, also showed stress concentrations. Implant angulation affected the stress concentration levels and localizations. CLINICAL IMPLICATIONS. These results will help clinicians understand the mechanical behavior of cement-retained implant-supported crowns during crown retrieval.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.5
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• pp.391-399
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• 2004

Distraction osteogenesis has been thought to be promising technique for replacing bone graft in maxilla and mandible. The purpose of this study was to investigate the expression of osteonectin on distraction osteogenesis. Sixteen rabbits were used for this experiment. Osteotomy was performed between premolar and mental foramen. On the experimental group, distraction device was connected to the respective bone segments. On the control group, bone segments were fixed using plate and screws after osteotomy. Distraction was carried out at the rate of 0.7mm per day to obtain a 4.9mm elongation on the experimental group. After 3 days, 7 days, 14 days, and 28 days two rabbits of each group were sacrificed. The results obtained from this study were as follow : Experimental group was observed that the gaps between the distracted bone edges were occupied by new bone. Expression of Osteonectin were detected throughout the experiment in both groups and Expression of Osteonectin were markedly increased during distraction and consolidation period in experimental group than control group. From these results, it could be stated that distraction was shown to improve and accelerate bone formation and mechanical stress like distraction has considerable effects on osteonectin.

• Composites Research
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• v.26 no.5
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• pp.328-333
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• 2013

In this study, bone plate made of glass/polypropylene composite material which was applied to an artificial bone was tested to check the service ability under fatigue loading. To check serviceability of composite bone plates fatigue test was carried out considering changes in the moisture absorption rate, locking position of screws and loading condition. Test results showed that all the tested specimens had the fatigue life more than one million cycles which was much higher fatigue life than the expected value of 650,000 cycles. Screw position was not critical impact on the deformation of the fracture site. In this paper, the mechanical performance of the glass/polypropylene composite was verified by fatigue test under various water absorption conditions, and this result may give useful information on the design of composite bone plate.

• Archives of Craniofacial Surgery
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• v.20 no.5
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• pp.297-303
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• 2019

Background: Absorbable plates are widely used in open reduction and internal fixation surgeries for facial bone fractures. Absorbable plates are made of polyglycolic acid (PGA), polylactic acid (PLA), polydioxane (PDS), or various combinations of these polymers. The degradation patterns of absorbable plates made from different polymers and clinical courses of patients treated with such plates have not been fully identified. This study aimed to confirm the clinical courses of facial bone fracture patients using absorbable plates and compare the degradation patterns of the plates. Methods: A retrospective chart review was conducted for 47 cases in 46 patients who underwent open reduction and internal fixation surgery using absorbable plates to repair facial bone fractures. All surgeries used either PLA/PGA composite-based or poly-L-lactic acid (PLLA)/hydroxyapatite (HA) composite-based absorbable plates and screws. Clinical courses were confirmed and comparisons were conducted based on direct observation. Results: There were no naturally occurring foreign body reactions. Post-traumatic inflammatory responses occurred in eight patients (nine cases), in which six recovered naturally with conservative treatment. The absorbable plates were removed from two patients. PLA/PGA compositebased absorbable plates degraded into fragments with non-uniform, sharp surfaces whereas PLLA/HA composite-based absorbable plates degraded into a soft powder. Conclusion: PLA/PGA composite-based and PLLA/HA composite-based absorbable plates showed no naturally occurring foreign body reactions and showed different degradation patterns. The absorbable plate used for facial bone fracture surgery needs to be selected in consideration of its degradation patterns.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.28 no.3
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• pp.196-204
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• 2002

For the study of its stability when the screw has been fixed after sagittal split ramus osteotomy(SSRO) of the mandible, the methods of screw arrangement are classified into two types, triangular and straight. The angles of screws to the bone surface are classified as perpendicular arrangements, the $60^{\circ}$ anterioinferior screw, known as triangular, and the most posterior screw, called straight arrangement, thus there are four types. The finite element method model has been made by using a three dimensional calculator and a supercomputer. The load directions are to the anterior teeth, premolar region, and molar region, and the bite force is 1 Kgf to each region. The distribution of stress, the von-Mises yield strength, and safety of margin refer to the total sum of transformed energy have been studied by comparison with each other. The following conclusion has been researched : 1. When shear stress is compared, in the triangular arrangement in the form of "ㄱ", the anterosuperior screw is seen at contributing to the support of the bone fragment. In the straight arrangement, substantial stress is seen to be concentrated on the most posterior angled screw. 2. When the von-Mises yield strength is compared, it seemed that the stress concentration on the angled anteroinferior screw is higher, it shows a higher possibility of fracture than any other screw. In the straight arrangement, stress appeared to be concentrated on the most posteriorly angled screw. 3. When the safety margins of the transfomed energy are compared, the energy conduction is much greater in the case of the angled screw than in the case of the perpendicular screw. The triangular arrangement in the form of "ㄱ" shows a superior clinical sign to that of the straight arrangement. Judging from the above results, when the screw fixation is made after SSRO in practical clinical cases, two screws should be inserted in the superior border of mandibular ramus and a third screw of mandibular inferior border should be inserted in the form of triangular. All screws on the bony surface should be placed perpendicularly-$90^{\circ}$ angles apparently best promote bony support and stability.