• Journal of Korean Neurosurgical Society
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• v.64 no.4
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• pp.575-584
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• 2021

Objective : Cervical expansive laminoplasty is an effective surgical method to address multilevel cervical spinal stenosis. During surgery, the spinous processes of C2 and C7 are usually preserved to keep the insertion points of the cervical musculature and nuchal ligament intact. In this regard, dome-like laminectomy (undercutting of C7 lamina) instead of laminoplasty is performed on C7 in selected cases. However, resection of the lamina can weaken the C7 lamina, and stress fractures may occur, but this complication has not been characterized in the literature. The objective of the present study was to investigate the incidence and risk factors for C7 laminar fracture after C7 dome-like laminectomy and its impact on clinical and radiological outcomes. Methods : Patients who underwent cervical open-door laminoplasty combined with C7 dome-like laminectomy (n=123) were classified according to the presence of C7 laminar fracture. Clinical parameters (neck/arm pain score and neck disability index) and radiologic parameters (C2-7 angle, C2-7 sagittal vertical axis, and C7-T1 angle) were compared between the groups preoperatively and at postoperatively at 3, 6, 12, and 24 months. Risk factors for complications were evaluated, and a formula estimating C7 fracture risk was suggested. Results : C7 lamina fracture occurred in 32/123 (26%) patients and occurred at the bilateral isthmus in 29 patients and at the spinolaminar junction in three patients. All fractures appeared on X-ray within 3 months postoperatively, but patients did not present any neurological deterioration. The fracture spontaneously healed in 27/32 (84%) patients at 1 year and in 29/32 (91%) at 2 years. During follow-up, clinical outcomes were not significantly different between the groups. However, patients with C7 fractures showed a more lordotic C2-7 angle and kyphotic C7-T1 angle than patients without C7 fractures. C7 fracture was significantly associated with the extent of bone removal. By incorporating significant factors, the probability of C7 laminar fracture could be assessed with the formula 'Risk score = 1.08 × depth (%) + 1.03 × length (%, of the posterior height of C7 vertebral body)', and a cut-off value of 167.9% demonstrated a sensitivity of 90.3% and a specificity of 65.1% (area under the curve, 0.81). Conclusion : C7 laminar fracture can occur after C7 dome-like laminectomy when a substantial amount of lamina is resected. Although C7 fractures may not cause deleterious clinical outcomes, they can lead to an unharmonized cervical curvature. The chance of C7 fracture should be discussed in the shared decision-making process.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.3
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• pp.224-231
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• 2010

Purpose: This study was to investigate how the crestal module design could affect the level of marginal bone stress around dental implant. Materials and methods: A submerged implant of 4.1 mm in diameter and 10 mm in length was selected as baseline model (Dentis Co., Daegu,Korea).A total of 5 experimental implants of different crestal modules were designed (Type I model : with microthread at the cervical 3 mm, Type II model : the same thread pattern as Type I but with a trans-gingival module, Type III model: the same thread pattern as the control model but with a trans-gingival module, Type IV model: one piece system with concave transgingival part, Type V model: equipped with beveled platform). Stress analysis was conducted with the use of axisy mmetric finite element modeling scheme. A force of 100 N was applied at 30 degrees from the implant axis. Results: Stress analysis has shown no stress concentration around the marginal bone for the control model. As compared to the control model, the stress levels of 0.2 mm areas away from the recorded implant were slightly lower in Type I and Type IV models, but higher in Type II, Type III and Type V models. As compared to 15.09 MPa around for the control model, the stress levels were 14.78 MPa, 18.39 MPa, 21.11 MPa, 14.63 MPa, 17.88 MPa in the cases of Type I, II, III, IV and V models. Conclusion: From these results, the conclusion was drawn that the microthread and the concavity with either crestal or trans-gingival modules maybe used in standard size dental implants to reduce marginal bone stress.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.2
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• pp.179-195
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• 2010

In the internal connection system, the loading transfer mechanism within the inner surface of the implant and also the stress distribution occuring to the mandible can be changed according to the abutment form. Therefore it is thought to be imperative to study the difference of the stress distribution occuring at the mandible according to the abutment form. The purpose of this study was to assess the loading distributing characteristics of three different abutments for GS II$^{(R)}$ implant fixture(Osstem, Korea) under vertical and inclined loading using finite element analysis. Three finite element models were designed according to three abutments; 2-piece Transfer$^{TM}$ abutment made of pure titanium(GST), 2-piece GoldCast$^{TM}$ abutment made of gold alloy(GSG), 3-piece Convertible$^{TM}$ abutment with external connection(GSC). This study simulated loads of 100N in a vertical direction on the central pit(load 1), on the buccal cusp tip(load 2) and $30^{\circ}$ inward inclined direction on the central pit(load 3), and on the buccal cusp tip(load 4). The following results were obtained. 1. Without regard to the loading condition, greater stress was concentrated at the cortical bone contacting the upper part of the implant fixture and lower stress was taken at the cancellous bone. 2. When off-axis loading was applied, high stress concentration observed in cervical area. 3. GSG showed even stress distribution in crown, abutment and fixture. GST showed high stress concentration in fixture and abutment screw. GSC showed high stress concentration in fixture and abutment. 4. Maximum von Mises stress in the surrounding bone had no difference among three abutment type. In GS II$^{(R)}$ conical implant system, different stress distribution pattern was showed according to the abutment type and the stress-induced pattern at the supporting bone according to the abutment type had no difference among them.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.2
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• pp.271-300
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• 1993

The purpose of this study was to analyze the stress distribution at supporting bone according to the types of connection modality between implant and tooth in the superstrcture. This investigation evaluated the stress patterns in a photoelastic model produced by three different types of dental implants such as Branemark, Steri-Oss, IMZ and resin tooth using the techniques of quasi three dimensional photoelasticity. The teeth-supported bridge had a first molar pontic supported by second premolar and second molar as a control group. The implant and toothsupported bridge had a first molar pontic supported by second premolar and implant posterior retainer as an experimental group. Prostheses were mechanically connected to an adjacent second premolar by the rigid of nonrigid connection, Nonrigid connection used an attachment placed between the tooth-supported and fixture-supported component. The female(keyway) of attachment was placed on the distal end of the retainer supported by the tooth ; the male(Key) of attachment connected to the osseointegrated bridge was engaged into the keyway. All prostheses were casted in the same nonprecious alloy and were cemented and screwed on their respective abutments and implants. 16㎏ of vertical loads on central fossae of second premolar, first molar pontic, implant of second molar were applied respectively and 6.5㎏ of inclined load on middle buccal surface of first molar pontic was applied. The results were as follows : 1. Under the vertical load on the central fossa of first mloar pontic, the stress developed at the apex of tooth of implat was more uniformly distributed in the case of nonrigid connection than in the case of rigid connection. 2. Under the vertical load on the central fossa of first molar pontic, the stress developed around the cervical area of tooth of implant was larger in the case of rigid connection than in the case of nonrigid connection because the bending moment was more occured in the case of rigid connection than in the case of nonrigid connection. 3. Stress was more restricted to the loaded side of nonrigid connection than to that of rigid connection 4. Under the inclined load. The set screw loosening of implant was more easily occured in the case of nonrigid connection than in the case of rigid connection due to torque moment. 5. In the case of Branemark implant, the stress concentration in second premolar was larger and the stress developed around the cervical area of implant was lower than any other cases under the vertical load, because Branemark implant with the flexible gold screw was showed in incline toward second premolar by a bending moment. 6. The stress developed around the apex of tooth or implant was more uniformly distributed in the case of Steri-Oss implant with stiff screw than in the case of Branemark implant under the vertical load. But, the stress developed around the cervical area of the Steri-Oss implant was larger than that of any other implants because bending moment was occured by vertical migration of second premolar. 7. The stress distribution in the case of IMZ implant was similar to the case of natural teeth under small vertical load. But, the residual stress around the implant was showed to occurdue to deformation of IMC and sinking of screw under larger vertical load.

• Journal of Dental Rehabilitation and Applied Science
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• v.26 no.1
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• pp.39-46
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• 2010

To assess the stress distribution of implant prosthesis induced by intentional misfit using photoelastic model. Stress was measured at the surrounding bone after applying vertical load to the implant. Three implants were placed in each of three photoelastic resin blocks. No misfits were used for the control group, while for the experimental group $100{\mu}m$ misfit after cutting the crown was used. The photoelastic stress analysis was performed. In control group, stress concentration was not shown when the load was not applied, whereas stress concentration was shown only in the loaded part even when load was applied and the stress was distributed in anterior-posterior direction when applying a load in the middle. When intentional misfits were given, stress around the fixture was incurred when tightening the screw even if load was not applied. If the load was applied, stress was concentrated around the implants including areas where the load was applied. In particular, the prosthesis made of UCLA showed more stress concentration as compared with a conical abutment. In the UCLA case, concentration was shown from the apex following through the axis to the cervical area. Prosthesis with misfit makes the stress concentrated though the load was not applied and it induces even more severe stress concentration when the load was applied. This founding demonstrates the importance of the correct prosthesis production.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.1
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• pp.233-248
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• 1991

The purpose of this study was to qunatatively analyze the stress patterns induced in the abutment, superstructure, supporting bone and to determine the deflection of abutment and superstructure by appling occlusal force to natural teeth supported fixed prostheses and implant-supported fixed prostheses. The analysis has been conducted by using the two dimensional finite element method. The implant and natural tooth-supported bridge has a first molar pontic supported by mandibular second bicuspid and implant posterior retainer, which were rigidly(Model A) or flexible(Model B). The natural teeth-supported bridge has a first molar pontic supported by mandibular second bicuspid and second molar, which were rigidly splinted together(Model C). 63.5kg(Load P1) of localized load on central fossa of first molar pontic and 24kg(Load P2) of distributed load on each occlusal surface were applied respectively. 1. The coronal portion of premolar pontic and posterior abutment in fixed partial denture deflected inferiorly in order of Model B, Model C and Model A under Load P1 and Load P2. 2. Mesial displacement of the coronal portion of premolar showed in Model A, Model B and Model C under Load P1, but mesial displacement of that in Model B and distal displacement of that in Model A and Model C showed under Load P2. 3. Mesial displacement of the coronal portion of the pontic and distal displacement of the coronal portion of posterior abutment showed in Model A, Model B and Model C under Load P1 and Load P2. Displacement in the case of Model B was greater than that of Model A and Model C. 4. In the case Model A under Load P1 and Load P2, high stress apically was concentrated in the mesiocervical portion of the posterior abutment than in the disto-cervical portion of the premolar. 5. In the case of Model B under Load P1 and Load P2 high stress was concentrated in the case of the premolar than in that of posterior abutment and high stress especially was concentrated in the connected portion of pontic and posterior abutment. 6. In the case of Model C under Load P1 and Load P2, high stress was concentrated in the distal area of the cornal portion of premolar and the mesial area of the coronal portion of posterior abutment, and stress pattern was anteroposterially symmetric around the pontic. 7. Load P1 and Load P2 compared, stress magnitude was different but stress pattern was similar in Model A, Model B and Model C. 8. Under Load P1 and P2, stress magnitude in the mesial distal portion and the portion of root apex of the posterior abutment was in order of Model B, Model A and Model C.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.324-332
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• 2009

The purpose of this study was to investigate the effect of rigidity of post core systems on stress distribution by the theoretical technique, finite element stress-analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with a zirconia ceramic crown were prepared and 1.5 mm ferrule height was provided. Each model contained cortical bone, trabecular bone, periodontal ligament, 4 mm apical root canal filling, and post-and-core. Six combinations of three parallel type post (zirconia ceramic, glass fiber, and stainless steel) and two core (Paracore and Tetric ceram) materials were evaluated, respectively. A 50 N static occlusal load was applied to the palatal surface of the crown with a $60^{\circ}$angle to the long axis of the tooth. The differences in stress transfer characteristics of the models were analyzed. von Mises stresses were chosen for presentation of results and maximum displacement and hydrostatic pressure were also calculated. An increase of the elastic modulus of the post material increased the stress, but shifted the maximum stress location from the dentin surface to the post material. Buccal side of cervical region (junction of core and crown) of the glass fiber post restored tooth was subjected to the highest stress concentration. Maximum von Mises stress in the remaining radicular tooth structure for low elastic modulus resin core (29.21 MPa) was slightly higher than that for high elastic modulus resin core (29.14 MPa) in case of glass fiber post. Maximum displacement of glass fiber post restored tooth was higher than that of zirconia ceramic or stainless steel post restored tooth.

• Journal of Korean Medical Ki-Gong Academy
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• v.11 no.1
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• pp.236-261
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• 2009

'Jeom-hyeol-gigong(點穴氣功)' gives a drill, Gi(氣) as a place to jam. This pathogen(邪氣) is removed. Given the low places and supplement it energy to flow up the well is the cure. This is an internal organ and muscular Gi allows a natural flow. Blood, one that moves and guides Gi is Gi I still feel that it makes any blood, making you feel good in life is flowing with vitality. Gi driving our whole body, while supplying vital energy and blood circulation, helping to defend the body is functioning. 'Jeom-hyeol-gigong' principle of Gi where the blockages to flow naturally energy is to let the flow. Aura of the voluntary and proactive action will be to have healthy bodies. Gi as a whole-body blood circulation leading to the cells in each tissue to supply energy and nutrients to every cell as the original principles of free activities that will maximize your life. Gi to prevent the three causes Internal causes: 5 greed and 7 emotions External causes: climate, food, pathogens, stress, etc. The internal nor the external causes: internal and external factors that cause the complex elements, incorrect position of the bone caused by an imbalance Heart disease will be police officers and raise their resistance to disease than the body, what jung-gi(正氣) have to develop. Beneficial to human body's resistance to raise the jung-gi people young-gi(營氣) and wi-gi(衛氣) should be enhanced. If the form is perfectly possible, Gi cycle itself should not have to breathe. Abdominal diagnosis 'bok-su-ap-an-beop(伏手壓按法)', 'sam-ji-tam-an-beop(三指探按法)' hands are like this, which outlined five viscera in order to understand the problem, the lower side of the clavicle (lung), the pit of stomach (Heart), both the lower ribs (liver), navel below (kidney) can be diagnosed at such areas. In each area of the skin, abdominal muscle tension, aching, or pressing a fuss about, beating the ruling of the state and the problem is a clue. And mo-hyeol(募穴) and certain Acupressure group, the chest, back, belly, so that scattered around each' book 'of the problem can be found. This is also the target of such a diagnosis, such as shape, color of skin, muscle Mostly the scope of the pitch in the cervical spine is broad across the hips. sugi(手氣) method that 'an method(按法) and 'ma method(摩法), bak method(拍法) is.