New telescopic crown design for removable partial dentures

Statement of problem. Special technical skills and experiences are required to fabricate a telescopic crown to provide adequate retention with precise frictional retention ("conus friction force") between coping and telescope . It is also difficult to control clinically alterations of retentive force s after prolonged usage. Purpose. This study examined an innovative telescopic crown system for remo vable partial dentures that can be fabricated without special technical ski ll or experience and readily adjusted retentive forces. The retention of te lescopic crowns was investigated after repeated insertion/separation tests. Material and methods. Ten telescopic crowns were constructed to evaluate re tentive forces. Each telescopic crown was adjusted to provide a retentive f orce of approximately 9.8 N. Each telescopic crown was then subjected to 10 ,000 insertion/separation cycles, and retentive force of each telescopic cr own was recorded initially and after every 1,000 cycles. The retentive forc e of each telescopic crown was re-adjusted after these measurements to prov ide a retentive force of approximately 9.8 N. The retentive force was recor ded a second time after each 1,000 insertion/separation cycles up: to 10,00 0 cycles. Results. Retention of the telescopic crowns gradually diminished, depending on the number of insertion/separation cycles. The mean retentive force aft er 10,000 insertion/separation cycles was over 2 N. All 10 telescopic crown s were re-adjusted to exert a retentive force of 9.8 N after the initial 10 ,000 cycles, and the retentive force also diminished on the second 10,000 c ycles. Conclusions. Reduction of retention was dependent on insertion/separation c ycles. This new telescopic crown with reduced retention could be easily rea djusted. Readjusted retentive forces were at least equivalent to the initia l retention.