Bond Strength of Orthodontic Cement at Different Time Intervals

Objectives: To determine bond strength to enamel of self-etch bonding system Transbond Plus SE Primer (TBSEP) applied at different time intervals after mixing its components, and before bonding the orthodontic brackets.

Methods: 30 recently extracted premolars, caries and restoration free, were placed over acrylic resin for support. The they were divided into three groups: CG: brackets were bonded over the enamel surface using Transbond Plus Self-etching Primer (3M ESPE, St Paul, MN) as recommended by manufacturer. Group EG1: waited 4 minutes after mixing the bonding agent components before bonding the brackets to enamel. Group EG2 waited 4 hours after mixing TBSEP components, before bonding the brackets to enamel. Specimens were stored in water at 37¼ C for 30 days before being tested in in shear at an unversal testing machine (Tinius Olsen H10KS) at a 0.1 cm/min crosshead speed. Data were recorded in MPa and analyzed using a one-way ANOVA calculated at a 0.05 significance level.

Results: Bond strength means and standard deviation (in parenthesis) are shown in table. No statistical difference were found among groups. Bond strength of EG2 was less than 1 MPa different from the control group. The hoghest bond strength was from group EG1 which used the bonding system to bond the brackets 4 minutes after it was mixed.

	CG	EG1	EG2
Bond Strnegth, MPa	13.0(7.0)	14.8 (5.9)	12.0(3.5)

Conclusions: Waitting  up to 4 hours after mixing TBSEP components does not affects the bond strength of the orthodontic bracket to enamel.