Shear bond strength of orthodontic brackets bonded using halogen light and light-emitting diode at different debond times

Abstract

The aim of this in vitro study was to compare the photoactivation effects of QTH (Quartz-Tungsten-Halogen) and LED (Light-Emitting Diode) on the SBS (Shear Bond Strength) of orthodontic brackets at different debond times. Seventy-two bovine lower incisors were randomly divided into two groups according to the photoactivation system used (QTH or LED). The enamel surfaces were conditioned with Transbond self-etching primer, and APC (Adhesive Pre-Coated) brackets were used in all specimens. Group I was cured with QTH for 20 s and Group II with LED for 10 s. Both groups were subdivided according to the different experimental times after bonding (immediately, 24 h and 7 days). The specimens were tested for SBS and the enamel surfaces were analyzed according to the Adhesive Remnant Index (ARI). The statistical analysis included the Tukey's test to evaluate the main effects of photoactivation and debond time on SBS. The Chi-square test was used to compare the ARI values found for each group, and no statistically significant difference was observed. The debond time of 7 days for QTH photoactivation showed statistically greater values of SBS when compared to the immediate and 24 h periods. There was no statistically significant difference between the QTH and LED groups immediately and after the 24 h period. In conclusion, bonding orthodontic brackets with LED photoactivation for 10 s is suggested because it requires a reduced clinical chair time.

Shear Bond Strength of Brackets Bonded With Different Led Units & Curing Times and at Different Debond Times in an In-Vitro Study

“…This indicates a sign of bond failure at the enamel & adhesive interface [3]. Similarly other studies also found that the ARI frequencies did not disclose significant differences between the study groups [12,20,21].…”

“…The adequate bond strengths to enamel surface for metal orthodontic brackets ought to be ranged between 8 and 9 shear bond strengths (MPa), as these values are sufficient to resist standard orthodontic forces [12]. Hence, many researches have been accomplished to assess the correlation between adhesive bond strength and post-bonding time.…”

“…LED curing units have also shown advanced mean scores of shear bond strengths (SBS) when the cure time was raised from 10 seconds to 40 seconds [10][11][12].…”

“…In recent times, fresh LED curing light units (VALO Ortho; Ultradent Products, South Jordan, Utah) and (Elipar S10; 3M Unitek, Monrovia, Calif), hve been commercially available for bonding the brackets [12]. As it has a high-intensity light waves, so it might cure the adhesive materials within 3 seconds.…”

Comparison of shear bond strength of orthodontic bracket bonding to teeth using light-curing units between halogen and LED: An in vitro study

“…Where as in 2010 Di Nicoló Ret al also found no significant difference in bond strength, but bond strength of halogen group (20.01±5.24 MPa) was higher than LED Group (17.35±5.07 MPa). 13 Atmadja and Bryant carried out a study evaluating the micro-hardness of four resins (P30, Prisma-Fil, Heliomolar and Durafil). 14 They concluded that: a) the micro-hardness values decreased with the increasing depth of polymerization, b) the most effective exposure time was 40 seconds, c) reducing the thickness is better than to increase the exposure time d) polymerization reaction continues even after the light source is removed.…”