• Journal of Audiology & Otology
• /
• 제24권2호
• /
• pp.71-78
• /
• 2020

Background and Objectives: Currently limited information is available on speech stimuli processing at the subcortical level in the recipients of cochlear implant (CI). Speech processing in the brainstem level is measured using speech-auditory brainstem response (S-ABR). The purpose of the present study was to measure the S-ABR components in the sound-field presentation in CI recipients, and compare with normal hearing (NH) children. Subjects and Methods: In this descriptive-analytical study, participants were divided in two groups: patients with CIs; and NH group. The CI group consisted of 20 prelingual hearing impairment children (mean age=8.90±0.79 years), with ipsilateral CIs (right side). The control group consisted of 20 healthy NH children, with comparable age and sex distribution. The S-ABR was evoked by the 40-ms synthesized /da/ syllable stimulus that was indicated in the sound-field presentation. Results: Sound-field S-ABR measured in the CI recipients indicated statistically significant delayed latencies, than in the NH group. In addition, these results demonstrated that the frequency following response peak amplitude was significantly higher in CI recipients, than in the NH counterparts (p<0.05). Finally, the neural phase locking were significantly lower in CI recipients (p<0.05). Conclusions: The findings of sound-field S-ABR demonstrated that CI recipients have neural encoding deficits in temporal and spectral domains at the brainstem level; therefore, the sound-field S-ABR can be considered an efficient clinical procedure to assess the speech process in CI recipients.

• 한국정밀공학회지
• /
• 제23권11호
• /
• pp.126-134
• /
• 2006

In this study, the effect of stem-end design on contact pressure and stress distribution in revision TKR was investigated using finite element method. The finite element model of tibia, including the cortical bone, the cancellous bone and canal, was developed based on CT images. The implant models with various stem lengths, diameters, friction coefficients, and press-fit effects were considered. The results showed that the longer stem length, the stronger press-fit, the bigger stem diameter, and the higher friction coefficient increased both peak contact pressure and Von-Mises stress distributions. The results supported the clinical hypothesis that peak contact pressure and stress are related to the stem end pain. The results of this study will be useful to design the stem and reduce the end-of-stem pain in revision TKR.

• 대한치과기공학회지
• /
• 제38권1호
• /
• pp.1-6
• /
• 2016

Purpose: The present study was to determine the stress distribution of an abutment screw according to implant abutment material. Methods: This study was a tightening torque 10 Ncm, 20 Ncm, set to 30 Ncm, and a titanium alloy (Ti-6Al-4V), PEEK (polyetheretherketone), Endoligns (60% Carbon Fiber Reinforced PEEK) material of the custom abutment titanium alloy (Ti-6Al-4V) the stress distribution in the material of the abutment screw will be evaluated by the finite element analysis. Results: Abutment screw most stress has been concentrated on the interface between the fixture and the abutment was also part of the interface that the threads are started. Depending on the abutment of the abutment screw Material von Mises stress values are shown differently. 10Ncm T10 under the tightening torque of 294.2 MPa, P10 is 562.8 MPa, appeared to E10 is 295.8 MPa, 20Ncm tightening torque under T20 is 581.1 MPa, P20 is 1125 MPa, E20 was shown to 585.1 MPa, 30Ncm tightening torque under T30 is 918.2 MPa, P30 is 1795 MPa, E30 has appeared 925.1 MPa. Conclusion: If the abutment is used as Endoligns, it was confirmed that the abutment screw exhibits of von Mises stress value is similar to the titanium alloy abutment.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.128-131
• /
• 2002

Several FE models were developed based on micro-CT images of a mandibular specimen. A new dental implant model was suggested from parameter study for the relation between shape and interfacial stress of dental implants. It is found that the proposed model is highly beneficial.

• 대한치주과학회:학술대회논문집
• /
• 대한치주과학회 2007년도 제47회 종합학술대회 연제초록
• /
• pp.173-174
• /
• 2007

• 대한두경부종양학회지
• /
• 제4권1호
• /
• pp.13-19
• /
• 1988

Brachytherapy is known to be a good modality to achieve local control as a boost treatment following limited external irradiation, which may reduce the external beam related acute radiation sickness, particularly in head and neck cancer. The authors developed iridium-192 ribbons recently to replace the radium needles. Total of 13 head and neck cancer patients had been treated with Ir-192 ribbons during last one year from October 1986 to September 1987, and the results were analysed to assess the applicability of the fabricated sources. The conclusion is as follows; 1) Iridium implant achieved 54% (7/13) of complete response and 69% (9/13) of overall response rate in head and neck cancer. 2) Iridium is superior to radium and cecium in brachytherapy because of easier to use and lesser exposure to the personnel. 3) Afterloading technique is useful to modify dose distribution, to expand treatment site and method, and to develop interstitial hyperthermia.

• 전기학회논문지
• /
• 제64권3호
• /
• pp.429-432
• /
• 2015

Radio Frequency (RF) coils in Magnetic Resonance Imaging (MRI) systems interact with a patient's tissues, resulting in the absorption of RF energy by the tissues. The presence of an electrically conducting medical implant may concentrate the RF energy and causes tissue heating near the implant devices. Here we present a novel design for a medical lead to reduce this undesired heating. Specific Absorption Rate (SAR), an indicator of heating, was calculated. Remcom XFdtd software was used to calculate the peak SAR distribution (1g and 10 g) in a realistic model of the human body. The model contained a medical lead that was exposed to RF magnetic fields at 64 MHz (1.5 T MRI), 128 MHz (3 T MRI) and 300 MHz (7 T MRI) using a model of an MR birdcage body coil. Our results demonstrate that, our proposed design of adding nails to the medical lead can significantly reduce the SAR for different MRI systems.

• 구강회복응용과학지
• /
• 제27권3호
• /
• pp.293-304
• /
• 2011

구치부 가위교합을 개선하기 위한 여러 방법 중, 교정용 미니임플란트(OMI)와 조합된 Dragon helix를 이용한 방법이 이전에 소개된 바 있으며 이는 간접 골성고정원의 역할이 중요하다. 이에 본 연구에서는 간접골성고정원으로 사용된 OMI의 식립각도에 따라 나타나는 구치부의 치근에 나타나는 응력분포와 OMI의 표면에서의 응력 분포 및 변위를 유한요소 해석으로 비교하고자 하였다. 상악 제1대구치와 상악 제2소구치의 치근 사이에 OMI의 식립 각도를 골 표면에 대하여, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$으로 변화시키면서 최대응력분포와 변위를 관찰하였다. OMI의 식립 각도가 $90^{\circ}$일 때 상악 제1대구치와 상악 제2대구치의 구개 치근첨에 최대응력분포가 나타났고, 상악 제1대구치에서는 협측으로 변위의 양이 가장 적게 나타났으며, 상악 제2대구치에서는 함입 및 구개측으로의 변위량이 가장 크게 나타났다. OMI에서는 식립각도가 감소됨에 따라 최대 응력분포가 나사첨 부분으로 이동되었으며, 그에 따라 OMI의 변위량은 증가하였다. 이상의 결과로 OMI의 식립각도가 $90^{\circ}$일 때 고정원의 역할이 최대가 되었으며, 구치부 가위교합의 개선 효과가 가장 크게 나타남을 알 수 있었다.

• 대한치과보철학회지
• /
• 제54권2호
• /
• pp.110-119
• /
• 2016

목적: 본 연구는 임플란트 지대주의 체결부 길이와 골정에 대한 고정체 상단의 위치에 따라서, 하중 적용 시 고정체, 지대주, 나사 및 골에서의 응력 분포에 어떤 변화가 나타나는지 평가해 보고자 하였다. 재료 및 방법: 원추형 사면과 육각 기둥 형태의 회전저항구조를 갖는 내측 연결형 임플란트에서 지대주의 체결부 길이가 2.5 mm, 3.5 mm, 4.5 mm인 경우와 각 경우에서 고정체 상단이 골정과 같거나 골정보다 2 mm 상방에 위치할 때를 상정하여, 유한요소분석을 위한 모델을 총 6개 형성하였다. 각 경우에서 170 N의 30도 경사하중을 적용하였다. 결과: 6개의 유한요소분석 모델 모두에서, 임플란트는 고정체와 지대주의 체결 상단 부위에서, 주위 골에서는 골정 부근에서 최대 응력 값을 나타냈다. 지대주의 체결부 길이가 길어질수록, 주어진 하중에서 발생되는 고정체, 지대주, 나사 및 골에서의 최대 응력 값은 줄어들었다. 고정체 상단이 골정과 동일한 높이에 있는 경우보다 골정 2 mm 상방에 위치하는 경우에서 지대주의 체결부 길이가 길어질수록 모든 부위에서 더 큰 비율로 최대 응력 값의 감소를 나타내었다. 결론: 지대주의 체결부 길이가 길어질수록 모든 부위에서 주어진 하중에 따른 최대 응력 값이 줄어드는 것을 알 수 있었고, 임플란트의 기계적 및 생물학적 합병증 예방에 도움이 될 수 있을 것으로 판단된다.

• 대한치과교정학회지
• /
• 제41권6호
• /
• pp.423-430
• /
• 2011

Objective: To evaluate the extent and aspect of stress to the cortical bone after application of a lateral force to a two-component orthodontic mini-implant (OMI, mini-implant) by using three-dimensional finite element analysis (FEA). Methods: The 3D-finite element models consisted of the maxilla, maxillary first molars, second premolars, and OMIs. The screw part of the OMI had a diameter of 1.8 mm and length of 8.5 mm and was placed between the roots of the upper second premolar and the first molar. The cortical bone thickness was set to 1 mm. The head part of the OMI was available in 3 sizes: 1 mm, 2 mm, and 3 mm. After a 2 N lateral force was applied to the center of the head part, the stress distribution and magnitude were analyzed using FEA. Results: When the head part of the OMI was friction fitted (tapped into place) into the inserted screw part, the stress was uniformly distributed over the surface where the head part was inserted. The extent of the minimum principal stress suggested that the length of the head part was proportionate with the amount of stress to the cortical bone; the stress varied between 10.84 and 15.33 MPa. Conclusions: These results suggest that the stress level at the cortical bone around the OMI does not have a detrimental influence on physiologic bone remodeling.