2010 Volume 44 Issue 1 Pages 1-7
This study was conducted to improve protection of the abutment tooth by modifying the inner crown form in an electroformed telescope crown. Inner crowns with a 0°, 2° and a combination taper (0° taper for the cervical 1.5mm and 2° taper above that) were made of gold alloy, and five outer crowns were made by electroforming on the inner crowns. We measured the retentive force and the negative pressure generated between the inner and outer crowns with 60% glycerin solution substituted for saliva. The peak retentive forces for the inner crowns with the 0° taper and for the combination crowns were greater than those for the 2° tapered crowns. There was no difference between the 0° taper crowns and the combination taper crowns. There were also no differences among the three types for the maximum negative pressure. The distances before the generation of peak retentive force and maximum negative pressure were significantly greater for 0° than for the other tapers. The retentive force generating distance at 0° was significantly greater for the 2° and combination tapers. A 0° electroformed telescope required significantly greater retentive energy for removal than either the 2° or combination taper. We concluded that the combination taper, which had an improved inner crown, helped reduce the retentive energy imparted on the abutment tooth without reducing the retentive force, and could be used as an effective retainer for protection of the abutment teeth.
