The evaluation of dual cement resins in orthodontic bonding

Dual-cement resins are composite resins that are both light activated and chemically cured. They can be cured completely with a visible light source or by the catalyst and base reaction of the material. With the control of setting time, dual cements appear to offer clinicians advantages in orthodontic bonding. The purposes of the present research are to compare various dual cements in regard to orthodontic bonding and to evaluate them in relation to currently used chemically cured and light-cured composite resins for bonding stainless steel mesh-backed orthodontic brackets. Seven currently available orthodontic bonding systems (three light cured and four chemically cured) and three dual cements were evaluated. Each of the 10 groups contained 15 noncarious mandibular incisors. Mandibular incisor brackets were bonded to the teeth in accordance with the manufacturer's recommendation. After bonding, the teeth were stored for 5 days in water at 37 degrees C. An Instron machine (Instron Corp., Canton, Mass.) was used to test samples. All samples were compared with Concise orthodontic bonding composite (3M, St. Paul, Minn.). The results of this investigation show that it is possible to bond solid, mesh-backed metal orthodontic brackets to teeth with a dual cement. The shear bond strengths of the dual cements, as tested in the laboratory, should be adequate to withstand normal orthodontic forces. Increased control of the setting time of the dual cements will allow the clinician more time to correctly position brackets and to remove excess resin before curing. In addition, the clinician can be assured of complete polymerization with the chemical properties of the dual cement resins.