Evaluation of stable retentive properties of overdenture attachments.

OBJECTIVES To evaluate fatigue of stud (ERA Overdenture (orange and white), Locator Root (pink) and OP anchor # 4) and magnetic (Magfit EX600W) attachments by measuring maximum retentive force. To compare retentive force of overdenture attachments after their reach stable retention. To determine minimum number of cycles required to reach stable retention. MATERIAL AND METHODS Three specimens of each type of attachment were used. Micromaterial testing machine (MMT-250NB-10, Shimadzu Co., Tokyo, Japan) with a sensor interface PCD-320 and software package PCD-30A (Kyowa Electronic Instruments Co., Tokyo, Japan) was used to performe 2000 insertion-removal cycles with 50 mm/min cross head speed. Maximum retentive force was measured initially and after each 40 cycles. STATISTICAL ANALYSIS paired-samples t-test, one-way ANOVA and Scheffe post-hoc tests (P<0.05). RESULTS Before and after fatigue simulation statistically significant differences existed among the five types of attachments. Decrease of retention was characteristic for all attachments except OP. After fatigue LRP was most retentive. Magnetic attachments preserved maximum amount of retention measured at the baseline (98%). EO and EW attachments have preserved only 25% and 37% of initial retention respectively. CONCLUSIONS Due to fatigue overdenture attachments gradually loose their retention. Stud attachments are more susceptible to fatigue than magnets. Eight hundred cycles are required to achieve relatively stable retention of overdenture attachments.