Background and Objectives:

Flowable composites were marketed for bonding of brackets during early 21st century. Flowable composite merit special attention because of their clinical handling characters of non–stickiness, fluid injectability and shear bond strength comparable to that of traditional composite adhesives.The purpose of this invitro study was to evaluate and compare the shear bond strength of a conventional composite and four different flowable composites with and without prior adhesive primer application used for bracket bonding in orthodontic treatment.

Methods:

The present invitro study was designed 100 pre adjusted edgewise stainless steel premolar brackets (Gemini, 3M Unitek) and 100 freshely extracted premolar teeth were divided into 5 groups and 2 Subgroups to be bonded with the above mentioned five adhesives. The brackets were bonded with Transbond XT, Transbond supreme LV, G–aenial Universal flow, Admira flow, Tetric Flow and cured using LED from the occlusal, gingival, mesial and distal aspects for 15 seconds each. The bonded teeth were then stored in distilled water for 24 hours before evaluation of bond strength.The shear debonding force was applied with Instron testing machine at cross head speed of 0.5mm/min. A custom made wire was used to apply the shear bond load with occluso–gingival direction. The exact force at which the bracket was debonded was noted from the electronic console attached to INSTRON Universal testing machine (33R 4467). Chi–square analysis was used to compare the mode of bond failure (ARI score).

However the result showed with prior adhesive primer application, Transbond XT showed the highest SBS and without prior adhesive primer application, Transbond supreme LV showed the highest SBS among all the flowable composites, whereas, SBS of conventional composite i.e. Transbond XT showed a significant reduction.

Interpretation and conclusion:

Though Transbond XT is a clinically efficient material as again confirmed from this study, flowable composites, (mainly Transbond supreme LV) if their flow and viscosity are balanced to improve handling property can definetly be considered as a time saving and alternative bonding system due to its comparable bond strength without bonding agent.