MATERIALE PLASTICE ♦ 50♦ No. 3 ♦ 2013 http://www.revmaterialeplastice.ro 208 Comparative in vitro Study of the Tensile Bond Strength of Three Orthodontic Bonding Materials KRISZTINA MÁRTHA 1 , ALEXANDRU OGODESCU 2* , IRINA ZETU 3 , EMILIA OGODESCU 2* , RÉKA GYERGYAY 4 , MARIANA PACURAR 1 1 University of Medicine and Pharmacy of Târgu Mure’, Faculty of Dental Medicine, Department of Orthodontics and Pediatric Dentistry, 38 Gheorghe Marinescu Str., 540141, Târgu Mureº, Romania 2 ”Victor Babeº” University of Medicine and Pharmacy, Faculty of Dental Medicine, 2 nd Department, Discipline of Paedodontics- Orthodontics, 9 Revolutiei 1989 Blv., Timisoara, Romania 3 „Gr.T.Popa” University of Medicine and Pharmacy, Faculty of Dental Medicine, Discipline of Orthodontics, 16 Universitatii Str., Iasi, Romania 4 University of Medicine and Pharmacy of Târgu Mures, Faculty of Dental Medicine, 38 Gheorghe Marinescu Str., 540141, Târgu Mureº, Romania The bonding materials used in orthodontics must resist to masticatory and active orthodontic forces. The aim of this study is to evaluate and compare the tensile bond strength of three orthodontic bonding procedures: acid etching and chemically cured macrofilled composite (Evicrol, SpofaDental, Jièin, Cehia), glass ionomer cement Ketac Cem (3M ESPE AG, Seefeld, Germany) and self-etching primer with light cure adhesive bond material (Transbond Plus Self Etching Primer + Transbond Plus Color Changer Adhesive, 3M Unitek, Monrovia, California). Moreover, after removing the brackets, the Adhesive Remnant Index (ARI) has also been measured. For this purpose 30 recently extracted human premolars were used, grouped randomly in three groups, 10 teeth for each tested material. After bonding the brackets, these were torn off from the teeth surfaces with a tensile testing machine (Instron 1195). The ultimate tensile strenght (UTS) and the ARI has been measured. Our conclusion was that glass ionomer cement fails first to the tractioning forces, while light cured composite has proven to resist best to streching and traction. Although light-cured composite has failed to lower forces than the chemically cured one, the frequency of ARI score 3 has been the highest, which means that its adhesion is the best. Key words: tensile bond strength, bonding material, adhesive remnant index The properties of an adhesive agent used in orthodontics must be understood from the adhesion structural and molecular mechanisms point of view. One of the basic questions of physico-chemistry is: why do materials cohere? The molecular theory affirms that due to the attractive forces in and between different molecules. These forces produce bindings with different resistances (resistance = the energy needed to dissolve the binding) from covalent and ionic to hydrogen and other weaker intermolecular bonds. The majority of solid materials, including dental tissues and the metallic base of brackets, do not cohere due to the simple touching of their surfaces. A liquid agent has to be introduced between the two solid surfaces facing each other. The fluid waters equally the two surfaces and enters the porosities of the solid material. Therefore, the most important properties of the liquid from this viewpoint are the angel of contact and viscosity [1, 2]. To resist in time all the possible disrupting forces, the fluid has to be transformed into solid phase. This convertion can be phisical (ex: cooling process) or chemical. In case of adhesive materials used in dentistry, chemical convertion takes place: polimerization of monomers for composites and neutralization for cements [2, 3]. Bonding is the most suitable expression to characterize and classify the binding mechanisms. Bonding means adhesion and attachment. These two terms reflect the nature of the binding mechanisms that take place: adhesion, the chemical and attachment [5], the mechanical * email: ogodescu@yahoo.com, 0723330890 mechanism. Adhesion is realized by hydrogenic bindings, London forces and other Van der Waals type bondings. Under attachment is understood when a solid substance which is rigid but porous - the conditioned enamel - makes possible the penetration of the adhesive and the solidification of this „in situ”. The bonding between the sole of the bracket and the adhesive is based merely on the mechanical component because of the high retentivity of the bracket base [3-5]. Wetting capacity, penetration and tixotropy are the most important and desired properties of adhesive materials used in orthodontics. It is preferred the bonding time to be short, volumetric contraction small and water absorbtion minimal [6]. The brackets bonded with the adhesive should resist masticatory and orthodontic forces. Therefore durability is a key question, but in the same time after finishing the treatment, the components of the fixed orthodontic appliance should be removed together with the adhesive [7]. At this phase the risk of enamel lesion grows. The aim of this experimental study is to evaluate and compare the resistance to traction of three adhesive materials: autopolimerising composite (Evicrol), glass ionomer cement (Ketac-Cem) and self-etching primer with fotopolimerising composite (Transbond Plus Self Etching Primer + Transbond Plus Color Changer Adhesive). Moreover, after removing the brackets, we have also measured the Adhesive Remnant Index (ARI).