Abstract: A plug and method of its use are disclosed for forming a removable closure in openings of dental appliances or other physiological appliances, the plug including an elongated shaft portion having a diameter mating with the opening, and an inner or gingival end of the plug which is enlarged by up to about 5%, more preferably about 1-5% and most preferably about 1-2% relative to the elongated shaft portion, the enlarged gingival plug end being an annulus having a radial thickness of up to about 20% and more preferably about 11% of the diameter of the enlarged plug end, the enlarged plug and the thickness of the annulus being selected together with the shaft material, preferably a resilient elastomer, to produce a cork type or press-fit engagement of the enlarged plug end in the appliance opening to retain the plug firmly in place.