Conversion assemblies enable a disposable tip to connect to an existing air/water dental syringe configured to receive a non-disposable tip. A conversion kit enabling an air/water syringe body to receive a disposable tip includes a retainer body having a distal opening into which the proximal end of the elongated disposable tip is inserted, and one or more internal components with cut-outs, grooves or channels to direct air and water from the syringe body to the air-carrying channels and water-carrying tube of the disposable tip. All of the components internal to the retainer are installed through the proximal opening in the retainer, enabling the proximal end of the retainer to be adjacent to the syringe body, such that there are no seams in the outer surface of the retainer from the syringe body to the distal end of the retainer that might collect pathogens or dirt.
