Sintering Method-Dependent Hydroxyapatite Coatings Drive Enhanced Gingival Fibroblast Behavior on Titanium Implant Surfaces

Implant surface optimization aims to reduce osteointegration process time and prevent failures. Here, we report a novel laser-assisted approach for incorporating hydroxyapatite into titanium implant surfaces and evaluate the resulting biological response. Titanium discs were fabricated by Nd:YVO4 laser texturing and coated with hydroxyapatite using either conventional or laser sintering, according to seven study groups: flat titanium (TiL), laser-textured titanium with 0.25 and 0.8 mm patterns (TiT025 and TiT08), and laser-textured titanium with 0.25 and 0.8 mm patterns plus bioactive coating using conventional sintering (TiT025CS and TiT08CS) or laser sintering (TiT025LS and TiT08LS). Human gingival fibroblasts (HGF hTERT) were cultured on discs to assess adhesion, morphology, viability, and cytokine secretion. Surface texturing alone did not significantly affect fibroblast viability over 7 days (p > 0.05). Hydroxyapatite coatings significantly reduced viability on both patterns when conventionally sintered (p < 0.05), whereas laser-sintered coatings did not cause a significant decrease; overall viability was higher in LS than in CS samples (p < 0.05). Scanning electron microscopy after 24 h showed adherent cells on all surfaces. IL-1β secretion was consistently lower than IL-10 secretion during the 3-day study period. When normalized to cell viability, these findings remained consistent. At day 1, IL-1β/viability and IL-10/viability ratios were similar across groups. By day 3, the IL-1β/viability ratio decreased in all groups, with TiT08 showing significantly lower values than TiT08CS (p < 0.05). In contrast, the IL-10/viability ratio increased in coated patterned samples (TiT025, TiT025CS, TiT025LS, TiT08, TiT08CS, and TiT08LS). In conclusion, the 0.25 mm laser-textured pattern combined with optimized hydroxyapatite sintering elicited a more favorable cytokine secretion profile compared to the 0.8 mm pattern, suggesting a reduced pro-inflammatory response.