Stratified Randomized Controlled Trial of ∅3.3 mm Versus ∅4.1 mm Hydrophilic Titanium-Zirconium Implants Supporting...

To compare ⌀3.3 mm and ⌀4.1 mm hydrophilic titanium-zirconium implants supporting fixed dental prostheses (FDPs) in mandibular distal-extension situations among participants with varying degrees of hyperglycaemia.

Participants were stratified according to HbA1c (5.8%-< 7.0% vs. ≥ 7.0%) and subsequently randomized within each stratum to receive either ⌀3.3 mm or ⌀4.1 mm titanium-zirconium implants. Each participant received a two-implant-supported multi-unit FDP. The primary outcome was marginal bone level (MBL) change at 12 months after prosthesis delivery. Secondary outcomes included implant stability quotient (ISQ), peri-implant indices, Healing Index and patient-reported outcomes.

Of 88 enrolled participants, 83 (166 implants) were evaluated. Implant survival was 100%, with no peri-implantitis. At 12 months, MBL did not differ significantly between the ⌀3.3 mm [0.27 mm (IQR, 0.07-0.68)] and ⌀4.1 mm groups [0.27 mm (IQR, -0.04 to 0.54); p = 0.078]. Participants with HbA1c ≥ 7% had approximately sevenfold higher odds of MBL ≥ 0.5 mm than those with HbA1c < 7%. Secondary ISQ was significantly higher with ⌀4.1 mm implants (79.6 vs. 76.1; p < 0.001), whereas early healing was better with ⌀3.3 mm implants (p = 0.005). Chewing ability improved significantly from baseline to 12 months irrespective of implant diameter or HbA1c category (p < 0.0001).

At 1 year, ⌀3.3 mm and ⌀4.1 mm hydrophilic Ti-Zr implants demonstrated no statistically significant difference in MBL although ⌀4.1 mm implants demonstrated higher stability. Patient-reported chewing ability improved substantially following rehabilitation for both implant diameters. Higher HbA1c was associated with greater odds of clinically relevant MBL.

The trial was registered prospectively with the Clinical Trials Registry-India (CTRI/2017/08/009315).