Objective      To compare the abilities of different adhesive materials to prevent bacteria and microleakage in silver-mercury bonded amalgam restorations of the root surface caries.       Methods      One hundred isolated teeth with cavity preparation were randomly divided into 5 groups

with 20 teeth in each group filled with 5 different materials (Amalgam

Amalgam ＆resin-modified glass-ionomer cement

glass-ionomer cement

Amalgam ＆total-etch adhesive cement

and Amalgam ＆self-etch adhesive cement). Each tooth was then evaluated the bacteria and microleakage by colony counting and staining.       Results      There were significant differences in the results of bacteria and microleakage among the 5 groups (P0.05). The Amalgam ＆ resin-modified glass-ionomer cement showed the lowest amount of bacteria and incident of microleakage

the highest occurrence was Amalgam

followed by Amalgam total-etch adhesive cement

Amalgam self-etch adhesive cement and glass-ionomer cement.       Conclusion      Resin-modified glass-ionomer cement can well prevent secondary caries and filling material from being broken off．