Consequences of employment self–etching primer adhesive in orthodontic practice

The purposes of this study were to evaluate the shear bonding strength of stainless steel brackets bonded with selfetching primer adhesive system (Trans-bondTM 3M Uniteck, Monrovia, California, USA), compared with same system which employ 35% phosphoric acid gel, separated primer and adhesive. Also to assess and compare clinically the brackets bonding failure rate after using the 2 different techniques in orthodontic patients and to examine bracket / adhesive failure mode by using modified adhesive remnant index (MARI). Fifty six extracted human premolars used in the laboratory part, they were divided into 2 groups (I and II), each one subdivided into upper first and second, lower first and second premolars; 7 for each subgroup. In the first group bonding was carried out by using the conventional technique (phosphoric acid / adhesive) wh-ile in the second one, the selfetching primer was used. In the clinical part 15 pat-ients with upper and lower fixed appliances (central, lateral incisors, canines and premolars) with 1316 years old. The fol-low up period extended into 1215 months. The statistical analyses in the laboratory (in vitro) part reported significantly lower but acceptable shear bond strength (8.69 and 8.42 MPa) for the upper first and second premolars, and 8.13 and 8.99 MPa for lower first and second premolars in comparison with the conventional groups (11.61 and 11.63 MPa) for upper first and second premolars, and 11.48 and 11.59 MPa for the lower first and second pre-molars as tvalues were significant (2.69, 3.05 for the upper first and second pre-molars; 2.68, 2.45 for the lower first and second premolars) at p < 0.05 between study groups, but in the clinical trial no significant difference between the groups wererecorded in relation to bonding failure rateas values of Z test of two proportions wereranged between 0.98 and 1.94, 0.00 and1.94 for the upper and lower arches respectively,in spite of the higher percentagesof failure rate for the selfetching primeradhesive group. The MARI reported higherfrequencies at score 2, and score 3 forthe control and experimental (selfetching primer) groups respectively.It can be concluded that in spite of thelower bondin strength values for the selfetching primer adhesive, but the resultsappear to be acceptable and this adhesive is recommended to be used in orthodonticpractice. In accompanied to that the residualadhesive amount were smaller thanthose of the conventional one so that lessdamage happened to enamel surface duringdebonding procedures.