An evaluation of the ability of a dentin plug to control extrusion of thermoplasticized gutta-percha

Overextension of gutta-percha when using any of the thermoplasticized obturation techniques has often been mentioned as a possible deleterious yet common sequela. The purpose of this study was to test a means of controlling the extrusion of material at the apical seat of the preparation when thermoplasticized gutta-percha techniques are used. Eighty human maxillary central incisors were prepared via step-back technique, in vitro, with apical stops placed 1 mm short of the actual apical foramen and the foramen was checked for patency. Teeth were divided into 10 groups, embedded in special "tooth trays," and four groups had intentional dentin plugs of 1-mm thickness placed to enhance the apical stop. A tooth tray of patent teeth and one of dentin-plugged teeth were than obturated by (a) the Obtura technique, (b) the Ultrafil technique, (c) the Touch 'n Heat technique, and (d) the Thermafil technique. Teeth were removed from the trays, extruded material carefully excised and weighed, and the weights evaluated by statistical analysis to determine results. When foramen patency was maintained, the Thermafil technique demonstrated significantly greater problems with overextension of material than did other techniques. The dentin plug served as an effective means of preventing extrusion.