Anisotropic nanospikes on micro and nanoscale hierarchical titanium surfaces enhance early osseointegration of dental implants.

Anisotropic titanium nano-surfaces produced by alkali etching exert diverse biological effects through physicochemical cues derived from anisotropically distributed nanospikes. These effects can be further enhanced by hierarchically superimposing nanostructures onto micro-roughened surfaces. This study aimed to investigate the effects of micro/nano three-dimensionally hierarchical titanium surfaces on the osteoblastic functions and osseointegration of dental implants. Three-dimensionally nano-roughened titanium surfaces fabricated using a combination of hot acid and alkaline treatments showed a higher density and anisotropic distribution of nanospikes than that on conventional nano-roughened surfaces, while exhibiting key physicochemical features similar to those of conventional nano-roughened surfaces, including superhydrophilicity and negative surface potential associated with surface hydroxyl groups. These three-dimensionally nano-roughened surfaces significantly enhanced bovine serum albumin adsorption. They also promoted the proliferation and osteoblastic differentiation of mouse bone marrow stromal cells compared with conventional micro-roughened or nano-roughened titanium surfaces. In vivo, titanium implants with three-dimensional nano-surfaces showed significantly greater osseointegration strength than that of micro-roughened implants when placed in the rat maxillary molar region. This enhancement was associated with enhanced early bone formation and increased contact and distant osteogenesis. Exploratory association analysis suggested that the composite topographical descriptor reflecting nanospike density and spatial heterogeneity was associated with increased albumin adsorption under controlled in vitro conditions. Collectively, micro/nano three-dimensionally hierarchical titanium surfaces are associated with enhanced early osseointegration and promoted osteoblastic differentiation, highlighting their potential for advanced implant surface design.