Evaluation of shear bond strength of orthodontic brackets using trans-illumination technique with different curing profiles of LED light-curing unit in posterior teeth

Abstract

BackgroundAlthough using light-cured composites for bonding orthodontic brackets has become increasingly popular, curing light cannot penetrate the metallic bulk of brackets and polymerization of composites is limited to the edges. Limited access and poor direct sight may be a problem in the posterior teeth. Meanwhile, effectiveness of the trans-illumination technique is questionable due to increased bucco-lingual thickness of the posterior teeth. Light-emitting diode (LED) light-curing units cause less temperature rise and lower risk to the pulpal tissue. The purpose of this study was to evaluate the clinical effectiveness of trans-illumination technique in bonding metallic brackets to premolars, using different light intensities and curing times of an LED light-curing unit.MethodsSixty premolars were randomly divided into six groups. Bonding of brackets was done with 40- and 80-s light curing from the buccal or lingual aspect with different intensities. Shear bond strengths of brackets were measured using a universal testing machine. Data were analyzed by one-way analysis of variance test and Duncan's post hoc test.ResultsThe highest shear bond belonged to group 2 (high intensity, 40 s, buccal) and the lowest belonged to group 3 (low intensity, 40 s, lingual). Bond strength means in control groups were significantly higher than those in experimental groups.ConclusionsIn all experimental groups except group 6 (80 s, high intensity, lingual), shear bond strength was below the clinically accepted values. In clinical limitations where light curing from the same side of the bracket is not possible, doubling the curing time and increasing the light intensity during trans-illumination are recommended for achieving acceptable bond strengths.

Light-curing of orthodontic bracket adhesive by transillumination through dentine and enamel

“…However, scattering cannot be considered as an independent phenomenon since light propagation is composed of absorbed, transmitted and reflected light [14]. Our results are thus in line with the earlier conclusions that transillumination seems to be clinically viable curing method for bonding brackets to incisors but not to premolars [9,10]. The present in vitro study design does not allow analysis of the light scattering effects of the pulpal tissues that has been shown to exceed that of enamel and dentin [15].…”

“…As an alternative method to increase the degree of cure, light curing through the tooth has been suggested [7,8]. However, there are only a few studies that have investigated the viability of this curing method [9,10]. The results of Oesterle and Shellhart [9] showed that transillumination through extracted maxillary incisors resulted in sufficiently high bond strengths of brackets, particularly when the curing time was 50 s. From the clinical point of view, the optimal bond strength has been considered to be at least 5.9 MPa [11], whereas the risk for enamel fractures increases when the bond strength is higher than 9.7 MPa [12].…”

“…The results of Oesterle and Shellhart [9] showed that transillumination through extracted maxillary incisors resulted in sufficiently high bond strengths of brackets, particularly when the curing time was 50 s. From the clinical point of view, the optimal bond strength has been considered to be at least 5.9 MPa [11], whereas the risk for enamel fractures increases when the bond strength is higher than 9.7 MPa [12]. Heravi et al [10] on the other hand, found that light curing through premolars resulted in bond strengths below clinically acceptable values even if curing time was increased to 80 s. In a previous study we studied the light propagation through the dental hard tissues and showed that light penetrates enamel better than dentin, and that penetration of light is enhanced if enamel and dentin are moisturized [6].…”

Effectiveness of high irradiance for short-time exposures on polymerization of composite under metal brackets

“…1,2 Bracket rebonding requires additional appointments, delaying the treatment and potentially compromising the results. 3 Orthodontic brackets are often bonded using resin-based, light-cured composites due to greater control of working time relative to chemically cured composites.…”

Reliability of Adhesive Remnant Index Score System Determined with Naked Eyed and Different Magnifications

“…34 Ayrıca LED ışık cihazlarının dişlerde ısı artışına neden olmadığı, diş çevresindeki yumuşak dokulara zarar vermediği, ergonomik olduğu ve transillüminasyonda (lingual yönden ışınlama) kullanılabildiği belirtilmektedir. 35,36 Oesterle ve ark. da yapmış oldukları araş-tırmada 100 adet insan üst santral kesici dişinde geleneksel tungsten-quartz halojen ışık kaynağı kullanarak transillüminasyon şeklindeki ışınlama-nın bağlanma dayanımına etkisini değerlendirmiş-lerdir.…”