J Korean Acad Prosthodont.  2003 Aug;41(4):519-531.

A study of screw loosening after dynamic continous fatigue test of several abutment screw

• Kim JM
• Han JS
• Lee SH
• Yang JH
• Lee JB
• Kim YS

Abstract

STATEMENT OF PROBLEM: Chronic implant screw loosening remains a problem in restorative practices. Some implant manufactureres have introduced abutment screws with treated material, surfaces and macrostructures in an effort to reduce potential loosening. PURPOSE: This study evaluated the materials and loading cycles on detorque value after dynamic continous fatigue test in the sinulated conditions of posterior single restoration. MATERIAL AND METHOD: Fourteen of each of the following abutment screws - titanium alloy, gold alloy, gold-tite, and titanium alloy modified - were used in test. SEM is used to verify macrostructures of each screws. ZrO2/Al2O3 composite abutment was tightened on 4x10.0mm titanium external implant at 30 Ncm. Cyclic loading machine delivered dynamic loading forces between 20 and 320N for 100,000, 200,000, 300,000, 500,000, and 1,000,000 cycles at frequencies 14Hz. Torque and detorque value after loading was measured. RESULTS: All measued screws had different screw length and thread form. Titanium modified screw had greater detorque value than others before and after cyclic loadings(p<0.05). All abutment screws had no significant change in mean percentage of detorque value after loading to initial value after less than 500,000 cyclic loadings, but significant lower value after 1,000,000 cycles(p<0.05). CONCLUSION: Within limintations of this study, all abutment screws may be loosend after about1 year use. Annual check-up is nessasary to prevent screw loosening.

Keyword

Dental implant; Dynamic fatigue test; Detorque value