Efficiency of light-emitting diode and halogen units in reducing residual monomers.
BACKGROUND
In this in-vitro study, we aimed to compare the residual monomers in composites beneath brackets bonded to enamel, using a light-emitting diode (LED) or a halogen unit, and to compare the residual monomers in the central to the peripheral areas of the composite.


METHODS
Twenty bovine teeth preserved in 0.1% thymol were used in this study. Ten teeth were used to standardize the thickness of the composite film, since different thicknesses would cause different absorbance of light. Brackets were bonded to 10 bovine incisors, with the halogen light (n = 5) and the LED (n = 5). The brackets were debonded, and the remaining composite on the enamel surface was sectioned in 2 regions: peripheral (0.8 mm) and central, resulting in 2 subgroups per group: central halogen (n = 5), peripheral halogen (n = 5), central LED (n = 5), and peripheral LED (n = 5). The spectrometric analysis in the infrared region was used to measure the free monomers with the attenuated total reflectance method.


RESULTS
Normal distribution was tested by using the Kolmogorov-Smirnov test. Data were compared by 2-way analysis of variance (ANOVA) at P <0.05. The LED group showed fewer residual monomers than did the halogen group (P = 0.014). No differences were found among the regions (P = 0.354), and there were no interactions between light type and region (P = 0.368).


CONCLUSIONS
LED leaves less residual monomer than does the halogen light, even with half of the irradiation time; there were no differences between the central and peripheral regions, and no interaction between light type and region.
Department of Orthodontics, School of Dentistry, State University of Rio de Janeiro, Rio de Janeiro, Brazil. carvalhofar@gmail.com
Felipe de Assis Ribeiro
Fde A
Carvalho
Rhita C
RC
Almeida
Marco Antonio
MA
Almeida
Lucia H S
LH
Cevidanes
Marcia C Amorim M
MC
Leite
D000134:Acid Etching, Dental; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D055117:Curing Lights, Dental / Q000145:classification*; D017005:Dental Debonding / Q000295:instrumentation; D003743:Dental Enamel / Q000648:ultrastructure; D008422:Materials Testing; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D019279:Resin Cements / Q000737:chemistry / Q000528:radiation effects*; D013055:Spectrophotometry, Infrared; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors
D003188:Composite Resins; D010756:Phosphoric Acids; D011109:Polymethacrylic Acids; D019279:Resin Cements; C477790:Transbond XT; C516047:Transbond XT Light Cure Adhesive Primer; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C030242:phosphoric acid