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Volume 30 , Issue 6
November/December 2015

Pages 1256–1261

Torque Loss of Different Abutment Sizes Before and After Cyclic Loading

Izabela Cristina Maurício Moris, DDS, MS/Adriana Cláudia Lapria Faria, DDS, MS, PhD/Ricardo Faria Ribeiro, DDS, MS, PhD/Renata Cristina Silveira Rodrigues, DDS, MS, PhD

PMID: 26574850
DOI: 10.11607/jomi.3868

Purpose: The aim of this study was to compare 3.8- and 4.8-mm abutments submitted to simulations of masticatory cycles to examine whether abutment diameter and cemented vs screw-retained crowns affect torque loss of the abutments and crowns. Materials and Methods: Forty implant/abutment sets were divided into the following groups (n = 10 in each group): (1) G4.8S included 4.8-mm abutment with screw-retained crown; (2) G4.8C included 4.8-mm abutment with cemented crown; (3) G3.8S included 3.8-mm abutment with screw-retained crown; and (4) G3.8C included 3.8-mm abutment with cemented crown. All abutments were tightened with torque values of 20 Ncm, and 10 Ncm for screw-retained crowns. Torque loss was measured before and after cycling loading (300,000 cycles). Results: Torque loss of screw-retained crowns significantly increased after cycling in abutments of groups G3.8S (P ≤ .05) and G4.8S (P = .001). No difference was noted between the abutments before cycling (P = .735), but G3.8S abutments presented greater torque loss than the other groups after cycling (P = .008). Significant differences were noted in the abutment torque loss before and after cycling loading only for the G3.8C group (P ≤ .05). Conclusion: The abutment diameter affects torque loss of screw-retained crowns and leads to failure during the test; mechanical cycling increases torque loss of abutment screw and screw-retained crowns.

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