이은석, 박찬진, 조리라(강릉원주대학교 치과대학 치과보철학교실)
Introduction
Internal-connection implants have been introduced to lower mechanical failures such as loosening or fracture of abutment screw, prosthetic screws or abutments related to the type of the implant-abutment connection. It was known that this system decreases stress transferring to the cortical bone.
**Incorporation of internal connection between implant and abutment dramatically enhanced the ability of the system to resist bending forces. Representative internal connection implant system have shown high success and survival rates and stably maintained marginal bone.
**The aim of study is to investigate stress distribution in 5 kinds of the internal-tapered connection implant system using a 3-dimensional finite element model that include simulated the preload.
Material and methods
3-dimensinoal FEA modeling
**Internal connection design with 11-degree taper interface (Luna, Shinhung Co. Ltd., Seoul, Korea)
- Four different types of implant diameters (3.5, 4.0, 4.5, 5.0 mm)
- Two types of implant-abutment connections (hexagonal, conical)
**Four types of implant-abutment interface models were evaluated.
Loading and boundary conditions
** 200 N static axial force applied as the vector sum top of the abutment.
**To simulate an oblique loading condition, a 200 N static oblique with a 45 degree angulation from the abutment perpendicular axis was applied.
FEA processing
PAM-MEDYSA V2012 (ESI group, Paris, France) and Hyper-View V10.0 (Altair Engineering Inc., Troy, USA).
The Von Mises stress was measured in two interface regions (screw-abutment and abutment-implant) and at the bone of peri-implant area.
Result
Implant wall thickness(Model I)
**Under the axial loading, the wall thickness increased, the stress distribution of the implant-abutment interface was decreased.
**Under the oblique loading, asymmetrical stress distribution was presented.
Mating surface length(Model II)
**As the mating surface length increased, the maximum Von Mises stress decreased at the implant-abutment interface.
**The highest stress distribution under both loading conditions occurred at the vertical stops.
Distance to the vertical stop(Model III)
** When the distance between the lowest abutment segment and the implant vertical stop was 0 μm, the Von Mises stress at the implant vertical stop was extremely high (approximately 1500 Mpa).
**At 30 μm and 60 μm distances, the stress distributions were nearly identical at the implant-abutment interface.
**The stress distribution under oblique loading showed a similar tendency and was dependent on contact to the vertical stop.
Abutment type(Model IV)
**The Von Mises stress distributions were similar in both abutment connection shapes.
**The maximum Von Mises stress was higher in the conical connection than the hexagonal connection, particularly at the contralateral loading position.
**The maximum Von Mises stress was higher in the hexagonal connection than the conical connection at the vertical stop loading site.
Conclusion
** Increasing the implant wall thickness decreased the stress distribution at the implant-abutment interface.
** Increasing the implant-abutment contact length caused a downward moving trend in the stress distribution.
** When the abutment contacted the implant vertical stop, the stress distribution at the vertical stop area and abutment screw was extremely high.
**There were no significant findings based on different implant and abutment connecting shapes, however, the hexagonal shape generated a more favorable stress distribution than the conical shape under oblique loading.
수상 소감
이번 연구는 지대주 파절과 관련된 실패의 원인을 분석하기 위해 3차원 유한요소 분석을 이용, 임플란트 복합체에 가해지는 수직 및 경사 하중에 대한 응력분포를 평가하였습니다. 신흥 Luna 시스템을 이용하여 실험 설계를 하여 좋은 결과를 얻었습니다.
임플란트-지대주 연결부의 접촉면 유형에 따라 적절한 지대주를 선택하고 지대주 및 임플란트의 기계적 실패를 유발할 수 있는 협측 경사하중을 방지하도록 교합을 설계해야 할 것으로 사료됩니다.
