Abstract
During the daily activity the orthodontic systems are suffering various loadings which together with saliva lead to a depreciation of bonding material which is used to fix the brackets on the dental surfaces. For this study human incisive shaped bovine bone were used to simulate mastication in a media consisting in a mixture of sesame, poppy and sunflower seeds and water. The aim is to compare the shear resistance of the bond with the one evaluated for fresh mounted brackets. Also a qualitative analysis is aimed based on micro photos took before and after bracket debonding. There are not rare the cases when patients are returning to doctor immediately after orthodontic system installation despite the medical advice because it is almost impossible to inhibit natural habits developed. In the first period after the installation of the orthodontic systems the reflex of biting the food is present in all the cases and that produces the detachment of the incisive bonded brackets. However during the mastication components of the food are interacting with the brackets generating local loads over the brackets themselves and also over the bonding material which can be a polymer or a composite. These loadings together with the ones meant by the doctor are producing in time small fractures and cracks at the bonding level with consequences on shear resistance of brackets on the tooth. Keywords: orthodontics, adhesive, bracket, shear strength