Thread Depth Effects on Stability and Positional Accuracy in Guided Immediate Implants: A Randomized Controlled Trial

Abstract

Objectives To evaluate the influence of implant thread depth on implant stability and positional accuracy in fully guided immediate implant placement.Materials and Methods Fifty-four patients received a reference tapered (BLT), a standard-thread (MST), or a deep-thread implant (MDT). Fifty-four implants were placed using fully guided surgery and evaluated over 1-year follow-up. Primary outcomes were implant stability (insertion torque, ISQ, ISV). Secondary outcomes included positional accuracy and marginal bone level (MBL) at 12 months.Results Primary and longitudinal stability were comparable across groups. Insertion torque was highest for MDT implants, followed by MST and BLT implants (BLT: 35.28 +/- 11.18; MST: 40.00 +/- 11.88; MDT: 43.89 +/- 10.92 Ncm; p = 0.062). A higher proportion of MDT implants achieved insertion torque >= 40 Ncm (MDT: 14/18; MST: 12/18; BLT: 8/18). Angular deviation differed among implant groups (MDT: 5.57 degrees +/- 3.71 degrees; BLT: 4.73 degrees +/- 2.46 degrees; MST: 3.58 degrees +/- 1.81 degrees; p = 0.062). In subgroup analysis comparing implants differing only in thread depth (MST vs. MDT), angular deviation was significantly greater for MDT (p = 0.029), particularly in molar sites. At 12 months, MBL did not differ significantly among groups.Conclusions In fully guided immediate implant placement, deeper-thread implants showed higher insertion torque values but were associated with greater angular deviation, while longitudinal stability and marginal bone levels remained comparable. Deeper-thread designs may be beneficial when enhanced primary stability is required, provided careful angulation control is ensured.Trial Registration cris.nih.go.kr Identifier: KCT0009402; This clinical trial was not registered prior to participant recruitment and randomization