Comparison On Shear Bond Strength Of Edgewise Brackets Bonding With Three Orthodontic Adhensives Under Different Adhensive Conditions

Objective: To compare the shear bond strength(SBS) and adhensive remnant index(ARI) score of Edgewise brackets bonding with three adhensive under moist and dry conditions.Try to find which adhensive can either produce the best clinical adhensive strength or prevent enamel lesion and save chair time.Methods:Sixty extracted fresh human premolars were randomly and equally divided into 6 groups.Edegwise brackets were bonded directly with composite resin,Unite bonding adhensive and resin modified glass ionomer cement(RMGIC) under moist and dry conditions,the tooth specimen was stored in salivary of 37℃for 24 hours and MTS New 810 100KN testing machine was used to apply shear force.Shear bond strength was measured with t test and analysis of variance and adhensive remnant index was measured by steromicrograph.Results:1)The results suggest no difference in shear bond strength whether composite resin(9.93±2.40MPa) and Unite bonding adhensive (9.97±3.01MPa) or Resin-modified glass ionomer cement(9.78±3.33MPa) under dry conditions.2)Singificant differences were observed between groups tested under dry conditions and groups tested composite resin(5.3±1.91MPa) and Unite bonding adhensive(5.09±1.29MPa) under moist conditions,no significant differences were found between the group tested RMGIC under moist conditions and the groups tested under dry conditions,although the SBS of RMGIC were lower than the groups tested under dry conditions.3)The comparisons of the ARI scores revealed nosignificant difference among the groups of composite resin and Unite bonding adhensive under dry conditions,the adhensives failed at braket /adhensive interface. Under moist conditions composite resin and Unite bonding adhensive exhibited failure at the enamel/adhensive interface. RMGIC exhibited cohensive failure of the adhensive under dry and moist conditions.It is concluded that RMGIC can meet the clinical adhensive requirement under moist and dry conditions.It may avoid lesion to enamel ,and saves chair-time.It is a better adhensive in orthodontic clinic.