LED vs Halogen Light-Curing of Adhesive-Precoated Brackets

Abstract

Objective: To test the hypothesis that bonding with a blue light-emitting diode (LED) curing unit produces no more failures in adhesive-precoated (APC) orthodontic brackets than bonding carried out by a conventional halogen lamp. Materials and Methods: Sixty-five patients were selected for this randomized clinical trial, in which a total of 1152 stainless steel APC brackets were employed. In order to carry out a valid comparison of the bracket failure rate following use of each type of curing unit, each patient's mouth was divided into four quadrants. In 34 of the randomly selected patients, designated group A, the APC brackets of the right maxillary and left mandibular quadrants were bonded using a halogen light, while the remaining quadrants were treated with an LED curing unit. In the other 31 patients, designated group B, halogen light was used to cure the left maxillary and right mandibular quadrants, whereas the APC brackets in the remaining quadrants were bonded using an LED dental curing light. The bonding date, the type of light used for curing, and the date of any bracket failures over a mean period of 8.9 months were recorded for each bracket and, subsequently, the chi-square test, the Yates-corrected chi-square test, the Fisher exact test, KaplanMeier survival estimates, and the log-rank test were employed in statistical analyses of the results. Results: No statistically significant difference in bond failure rate was found between APC brackets bonded with the halogen light-curing unit and those cured with LED light. However, significantly fewer bonding failures were noted in the maxillary arch (1.67%) than in the mandibular arch (4.35%) after each light-curing technique. Conclusions: The hypothesis cannot be rejected since use of an LED curing unit produces similar APC bracket failure rates to use of conventional halogen light, with the advantage of a far shorter curing time (10 seconds).

Does a reduction of polymerization time and bonding steps affect the bond strength of brackets?

“…In vivo studies confirmed this [6,7]. When focusing at the curing time some investigations are reporting a significant difference in bond strength between 10 and 20 s LED curing [9] and for both used devices higher bond strengths with increased curing time [10].…”

“…Light-emitting diode (LED) curing devices are considered as a serious competitor for the gold standard quartztungsten-halogen (QTH) lights [6,7]. They are considered to be more reliable and to provide several other positive features such as a long life time, a minimal heat development, and a low electricity consumption [8,9].…”

Clinical effect of reducing curing times with high-intensity LED lights

“…We demonstrated that a 6-second curing time per tooth with a high-intensity curing light is sufficient to produce clinically adequate bond failure rates that are comparable to brackets cured with a standard intensity LED for 20 seconds. 15–17 This finding extends our knowledge from previous clinical studies 6–8 that compared halogen- and LED-curing-light performance. Mavropoulos et al 18 showed that sheer bond strength depends on energy density, but the relationship is nonlinear and is influenced by both power density and curing time.…”

“…3–5 Compared with the halogen curing system, LED lights can achieve clinical bonding success with shorter curing time. 6–8 Curing-light manufacturers advertise that by increasing the light intensity, also referred to as power density, even less curing time is needed to reach adequate bond strengths.…”

Survival analysis of brackets and tubes:A twelve-month assessment

“…[20][21][22][23][24] However, it is difficult to directly compare bracket failure rates between studies due to variation in operators, bonding techniques, adhesives, research designs, and observation periods.…”