RESULTS No statistical significant difference in bond strength between both categories was observed in caries-affected dentin at immediate evaluation and in sound dentin after ageing .
Etch- and -rinse adhesives , however , performed better in sound enamel and dentin substrates considering immediate bond strength .
None study assessed the long-term adhesive effectiveness to sound or demineralized enamel .
Although the articles included in this meta- analysis showed high heterogeneity and high risk of bias , the in vitro literature suggests superior performance of etch- and -rinse adhesives in primary teeth in comparison with self-etch systems
AIM To systematic ally review the literature for in vitro studies that evaluated the immediate or after ageing bond strength of  etch- and -rinse and self-etch adhesive systems to enamel and dentin of primary teeth .
Influence of substrate, shape, and thickness on microtensile specimens' structural integrity and their measured bond strengths.
OBJECTIVES To verify whether substrate , shape , or thickness of microtensile specimens have a significant influence on their measured bond strength . METHODS Sixty-four extracted molars provided microtensile specimens  , which were prepared on enamel and dentin , in different shapes and thicknesses . The teeth were r and omly divided into 16 groups ( n = 4 ) . Groups 1 - 8 included hourglass-shaped specimens . In Groups 1 - 4 specimens were prepared from enamel and in a thickness at the bonding interface of 0.5 mm x 0.5 mm , 1 mm x 1 mm , 1.5 mm x 1.5 mm , and 2 mm x 2 mm , respectively . In these same thicknesses , hourglasses were trimmed in Groups 5 - 8 , but the specimens were prepared from dentin . Groups 9 - 16 included specimens obtained following the non-trimming technique . Groups 9 - 12 provided enamel sticks in the four evaluated thicknesses . In these same thicknesses and shape but from dentin were cut the specimens of Groups 13 - 16 . Two specimens from each group were viewed using a scanning electron microscope . On the other ones , microtensile bond strength was measured and the values were statistically analyzed . RESULTS Substrate , shape , and thickness of the specimens had a significant effect on their recorded bond strength ( p < 0.05 ) . Higher bond strength values were recorded by dentin versus enamel specimens and by sticks versus hourglasses . Also , bond strength decreased as specimen thickness increased . SEM analysis revealed that the trimmed specimens , especially if from enamel , often exhibited lines of fracture in the area of action of the bur . SIGNIFICANCE It seems advisable to avoid the trimming action particularly on enamel specimens . If the hourglass shape is preferred , the cross-sectional area should not exceed 1 mm x 1 mm
RESULTS No statistical significant difference in bond strength between both categories was observed in caries-affected dentin at immediate evaluation and in sound dentin after ageing .
Etch- and -rinse adhesives , however , performed better in sound enamel and dentin substrates considering immediate bond strength .
None study assessed the long-term adhesive effectiveness to sound or demineralized enamel .
Although the articles included in this meta- analysis showed high heterogeneity and high risk of bias , the in vitro literature suggests superior performance of etch- and -rinse adhesives in primary teeth in comparison with self-etch systems
AIM To systematic ally review the literature for in vitro studies that evaluated the immediate or after ageing bond strength of  etch- and -rinse and self-etch adhesive systems to enamel and dentin of primary teeth .