A Study on Bracket-Adhesive Combinations in Aspect of Shear Bond Strength and Bond Failure

전단접착강도와 탈락양상을 고려한 브라켓-접착제의 선택

The purpose of the present study was to seek bracket-adhesive combinations which have adequate bond strength with no enamel and bracket fracture. The shear bond strengths were measured, the sites of failure and the enamel damage were investigated and the peripheral sealing and adaptation between enamel surface, bonding adhesive and bracket were evaluated. 240 noncarious human premolars were divided into twenty four groups of ten teeth. Shear bond strengths of each group were determined in an universal testing machine after two days passed and the debonded specimens were inspected to determine the predominant bond failure sites. To evaluate peripheral sealing and adaption between enamel surface, adhesive and bracket, each specimen was cut longitudinally into two halves which included the midsection of the bracket, adhesive and enamel and exmined in scanning electron microscope. Six different types of brackets were bonded to the tooth with four different type of adhesives. Six different types of brackets were Image, Plastic, Crystaline, Fascination, Transcend 2000 and metal bracket and four different adhesives were No-mix, Light-Bond, OrthoLC and Superbond C&B. From this study, it may be concluded that (1) The mean shear bond strength varied from a high of 36.58 Kg (410.07 Kg/$cm^2$) with the Fascination-Light Bond combination group to a low of 8.93 Kg (75.51 Kg/$cm^2$) with theImage-OrthoLC combination group. When using OrthoLC as adhesive, the mean shear bond strength was significantly lower than that of other combination groups, (2) Regardless of adhesives, the mean shear bond strength of Fascination brackets was relatively high whereas Plastic and Image brackets had low shear bonding strength. The shear bond strength of Crystaline bracket and Transcend 2m was relatively equal to or lower than that of metal bracket, (3) There was a correlation between bond strength, enamel damage and bracket fracture. As the shear bond strength was increased, the rate of enamel damage and bracket fracture were increased, (4) The combination groups that use OrthoLC as adhesive were debonded in shear stress without enamel fracture and bracket fracture, whereas the combination groups that use Superbond C&B as adhesive experienced a relative high enamel fracture rate and bracket fracture rate, (5) Peripheral sealing and adaptation between enamel-adhesive-bracket were relatively good when using Light-Bond or No-mix as adhesive. Regardless of adhesives, adaptation between bracket-adhesive were relatively good in Ceramic brackets, (6) The combination groups which had adequate bonding strength with no enamel and bracket fracture were Crystaline-No mix, Crystaline-Light Bond, Crystaline-OrthoLC, metal-No mix, metal-Light Bond and metal-OrthoLC combination groups.

적절한 전단접착강도를 가지면서 법랑질손상과 브라켓파절을 적게 일으키는 브라켓-접착제의 그룹을 찾아내기 위하여 전단접착강도, 법랑질손상, 브라켓탈락양상, 브라켓 주위의 밀봉과 법랑질-접착제-브라켓 사이의 긴밀도를 연구하였다. 교정치료 목적으로 발치한 240개의 치아를 각각 10개씩 24개의 군으로 나누어서 브라켓을 접착한 후 48시간 후에 전단접착강도를 측정하고 브라켓 탈락 양상을 조사하였다. 또한 브라켓 주위의 밀봉과 법랑질-접착제-브라켓 사이의 긴밀도를 평가하기 위하여 브라켓이 접착된 치아를 반으로 자른 후 주사전자현미경상에서 관찰하였다. 6종류의 브라켓과 4종류의 접착제가 사용되었으며 브라켓은 Image, Plastic, Crystaline, Fascination, Transcend, metal bracket을 사용하였으며 접착제로는 No-mix, Light-Bond, OrthoLC, Superbond C&B가 사용되었다. 이와같은 연구로부터 다음과 같은 결론을 내렸다. 1. 전단접착강도는 Fascination-Light Bond 군에서 36.58 Kg(410.07 Kg/$cm^2$)으로 가장 높았으며 Image-OrthoLC 군에 서 8.93 B◎ (75.51 Kg/$cm^2$)으로 가장 낮았다. OrthoLC를 접착제로 사용하였을 때 전단접착강도는 다른 접착제를 사용하였을 때 보다 비교적 낮았다. 2. 접착제의 종류에 관계없이 Fascination bracket의 전단접착강도는 비교적 높았으며 Image, Plastic bracket의 전단접착강도는 비교적 낮았다. Crystaline, Transcend bracket의 전단접착강도는 metal bracket의 전단접착강도와 비슷하거나 낮았다. 3. 전단접착강도와 법랑질 파절, 브라켓 파절은 상관관계가 있었으며, 접착강도가 증가할수록 법랑질 파절과 브라켓 파절은 증가하였다. 4. OrthoLC를 접착제로 사용하였을 때 법랑질 파절과 브라켓 파절은 일어나지 않았으나 Superbond C&B를 접착제로 사용하였을 때는 법랑질 파절과 브라켓 파절의 빈도가 높았다. 5. No-mix, Light-Bond를 접착제로 사용하였을 때 브라켓 주위의 밀봉과 법랑질-접착제-브라켓의 긴밀도는 양호하였다. 접착제의 종류에 관계없이 Ceramic bracket에서 접착제-브라켓의 긴밀도는 양호하였다. 6. 적절한 전단접착강도를 가지면서 법랑질 파절과 브라켓 파절을 일으키지 않는 군은 Crystaline-No mix, Crystaline Light Bond, Crystaline-OrthoLC, metal-No mix, metal-Light Bond, metal-OrthoLC군이였다.