세라믹 브라켓의 형태에 따라 토오크가 미치는 영향에 대한 유한요소법 및 광탄성 실험법에 의한 연구

Abstract

[한글]

심미적인 장점 때문에 교정 치료시 널리 사용되고있는 세라믹 브라켓은 재질의 취성 및 부적절한 형상으로 인해 토오크를 가할 때 빈번한 파절을 일으킨다. 본 연구에서는 형태적인 차이를 나타내는 세라믹 브라켓들에서 토오크가 미치는 영향을 유한요소법과 광탄성

실험법을 통해 비교 연구하여 브라켓 형상 설계의 개선을 위한 기초자료를 모색하였다.

연구를 위해 기존 제품 중에서 형상에 독특한 차이를 보이는 세 가지의 세라믹 브라켓(A : Transcend, B : Signature, C : 20/20 M ceramic)과 치수가 다른 세 가지 각형 선재(G : .017 in ×.025 in, H : .018 in ×.025 in, I : .019 in ×.025 in)를 선정하였다. 선정된 재료들은 영상처리기법을 이용하여 치수를 측정하였으며, 측정 결과는 각 연구에 필요한 모델링에 사용되었다. 유한요소법과 광탄성 실험법을 통하여 토오크를 가하였을 때 나타나는 응력 분포 상태를 비교 연구하여 아래와 같은 결론을 얻었다.

1. 형상이 좌우 대칭인 브라켓에 각형 선재로 토오크를 가했을 때 토오크를 주는 방향에서 상대적으로 던 큰 응력이 발생하였다.

2. 동일한 브라켓에서 치수가 다른 세 가지의 각형선재를 사용하여 토오크를 가했을 때 가장 큰 최대 주응력의 값은 치수가 큰 순으로 나타났다.

3. 슬롯 모서리의 곡률 반경이 A 브라켓보다 큰 B 브라켓은 그 부위의 응력 집중이 상대적으로 작게 나타났다.

4. B 브라켓과 같이 슬롯 바닥의 중간 부분이 올라간 형태는 A 브라켓과 같은 평평한 형태에 비해 응력이 슬롯의 양 모서리에 집중되었다.

5. 브라켓의 날개 하부의 곡면 형태가 A와 B 브라켓에 비해 상대적으로 완만한 C 브라켓은 그 부위에서 상대적으로 작은 응력이 발생하였다.

6. 슬롯이 경사진 C 브라켓의 형상 설계는 토오크를 주는 방향에 따라서 응력 분포에 현격한 차이를 나타내었다.

A STUDY ON THE EFFECTS OF TORQUE ON THE DESIGN OF CERAMIC BRACKETS BY FINITE

ELEMENT METHOD AND PHOTOELASTICITY

Moon Woo Limb

Dept. of Dental Science, Graduate School, Yonsei Uni.

(Directed by Assoc. Prof. Hyoung Seon Baik, D.D.S., Ph.D.)

Esthetically pleasing ceramic 7rackets are widely used clinically. However, due

to physical characteristics of ceramic and the inadquate design of the brackets,

brittle failure of the brackets are frequently observed especially while applying

torque.

The purpose of this study was to compare and analyze the effects of torque on

ceramic brackets using finite element method and photoelasticity. For the study

three kinds of ceramic brackets(A : Transcend, B : Signature, C : 20/20 M ceramic)

with distinctively different designs and three kinds of rectangular wires(G : .017

in ×.025 in, H : .018 in x.025 in, I : .019 in ×.025 in) were selected and then

measured using image processing technique. With the measured results the modelling

was done and then the study was conducted. The resulted stress distributions of the

bracket models were compared and analyzed.

The results are as follows :

1. On brackets with symmetrical designs, the intensity of stress was greater on

the side where applied torque was directed.

2. When wires with three different size were used on a saute bracket, the value

of the maximum principal stress was greater as wire size got bigger.

3. Compare to bracket A, bracket B with greater rounding radius of the slot

corner showed much less stress concentration on that area.

4. Bracket B, which had raised middle portion of the slot base, had greater

stress concentration on both slot comers than that of the bracket A with the flat

slot base.

5. Bracket C, which had less steep curvature under the wings than that of bracket

A and 7, produced less stress than that of bracket A and B.

6. Bracket C with a slanted slot design showed stress distributions that are

distinctively different form one another depending on the direction of the applied

torque.

[영문]

Esthetically pleasing ceramic 7rackets are widely used clinically. However, due to physical characteristics of ceramic and the inadquate design of the brackets, brittle failure of the brackets are frequently observed especially while applying

torque.

The purpose of this study was to compare and analyze the effects of torque on ceramic brackets using finite element method and photoelasticity. For the study three kinds of ceramic brackets(A : Transcend, B : Signature, C : 20/20 M ceramic)

with distinctively different designs and three kinds of rectangular wires(G : .017 in ×.025 in, H : .018 in x.025 in, I : .019 in ×.025 in) were selected and then measured using image processing technique. With the measured results the modelling

was done and then the study was conducted. The resulted stress distributions of the bracket models were compared and analyzed.

The results are as follows :

1. On brackets with symmetrical designs, the intensity of stress was greater on the side where applied torque was directed.

2. When wires with three different size were used on a saute bracket, the value of the maximum principal stress was greater as wire size got bigger.

3. Compare to bracket A, bracket B with greater rounding radius of the slot corner showed much less stress concentration on that area.

4. Bracket B, which had raised middle portion of the slot base, had greater stress concentration on both slot comers than that of the bracket A with the flat slot base.

5. Bracket C, which had less steep curvature under the wings than that of bracket A and 7, produced less stress than that of bracket A and B.

6. Bracket C with a slanted slot design showed stress distributions that are distinctively different form one another depending on the direction of the applied torque.