Effect of internal connection type and screw channel angle on the screw stability of anterior implant‐supported zirconia crowns

Abstract

AbstractObjectivesTo investigate the effect of implant–abutment connection and screw channel angle on screw stability by comparing a newly introduced and an established connection, before and after cyclic loading.Materials and MethodsImplants (N = 44) with Torcfit (TF) or Crossfit (CF) connection were divided to be restored with a straight (CFS and TFS) or an angled screw access channel (CFA and TFA) titanium‐base abutment (n = 11). CFA and TFA received screw‐retained crowns, whereas CFS and TFS received hybrid zirconia abutments and cement‐retained crowns. The initial torque value (ITV) of each complex (ITVI) and removal torque value (RTV) after 24 h (RTVI) were measured. Screws were replaced with new ones, ITVs were recorded again (ITVF), and crowns were cyclically loaded (2.4 million cycles, 98 N) to measure RTVs again (RTVF). Percentage torque loss was calculated. Data were analyzed (α = 0.05).ResultsITVs were similar among groups (p ≥ .089). CF led to higher RTVs (p ≤ .002), while CFS had higher RTVI than CFA (p = .023). After 24 h, CFS had lower percentage torque loss than TF, while CFA had lower percentage torque loss than TFA (p ≤ .011). After cyclic loading, CF led to lower percentage torque (p < .001).ConclusionThe implant–abutment connection affected the removal torque values. However, no screw loosening occurred during cyclic loading, which indicated a stable connection for all groups. Screw access channel angle did not affect screw stability after cyclic loading.