Clinical and biochemical assessment of soft tissue response to printed versus milled polymethylmethacrylate custom...

This randomized controlled clinical trial compared peri-implant soft tissue responses to CAD-CAM-milled versus 3D-printed polymethylmethacrylate (PMMA) custom healing abutments following second-stage implant surgery.

Twenty-two osseointegrated implants were randomly allocated to receive either CAD-CAM-milled (Group I, n = 11) or 3D-printed (Group II, n = 11) PMMA custom healing abutments. Peri-implant crevicular fluid IL-1β was quantified via ELISA at 1, 2, and 4 weeks. Modified gingival index, bleeding on probing, plaque index, and probing depth were recorded concurrently. Abutment surface roughness and degree of monomer conversion were also assessed. Intergroup and intragroup comparisons utilized appropriate parametric and nonparametric tests (α = 0.05).

The 3D-printed group showed significantly higher gingival index scores at week 4 (p = 0.001) and greater bleeding on probing at weeks 2 and 4 (p < 0.05). Both groups demonstrated significant increases in probing depth and plaque index over time (p < 0.05), without significant intergroup differences. IL-1β concentrations rose significantly in both groups (p < 0.001), remaining consistently and significantly elevated in the 3D-printed group throughout all time points (p < 0.001). 3D-printed abutments exhibited significantly greater surface roughness values for Ra (p < 0.001), Rp (p = 0.001), and Rz (p = 0.03), alongside a lower degree of monomer conversion (84.8% vs. 94.1%), indicating inferior polymerization efficiency.

Clinical, biochemical, and biomaterial evidence collectively demonstrate that CAD-CAM-milled PMMA healing abutments promote a more favorable peri-implant soft tissue response than 3D-printed alternatives, suggesting that the fabrication method critically influences early biological tissue healing.