Discussion - References.
Rough surfaces have been shown to be advantageous to osseointegration. They can provide a better initial stability to dental implants. Additionally and most importantly, they can promote the differentiation of osteoblasts at the bone interface and enhance their osteogenic function. This can accelerate the bone healing process and increase the bone contact rate. These effects of rough surface on the osteogenesis at the bone interface are considered to be functions of its roughness and topography. The modified sandblasted rough surface described herein features the formation of numerous secondary micropores and a rough and round profile. These characteristics happen to be consistent with Wong’s concept concerning an ideal rough surface. He held that, as far as interfacial biomechanics is concerned, the rough surface with more small peaks is better than that with fewer larger peaks.
In this in vitro study, the modified sandblasted surface’s biologic effects on the initial healing process at the dental implant-bone interface were investigated by using an experimental three-dimensional model of biomaterial-osteoblast culture developed by the authors. After Ti discs were put into this model, osteoblastic cells migrated from the confluent cell layer to the disc circumference and attached to it, forming a three dimensional interface of osteoblasts to the Ti disc. On the first day, the variance between the two surface groups could not be discerned. By the third day, the effects of the modified sandblasted surface had become apparent. It induced a perpendicular attachment with the triangular or multangular cells at the interface. These were reflected by the nonuniform and broader refractile band under the phase-contrast microscope, having cell contour perpendicular to the disc circumference and reflected by the perpendicularly attaching cells and collagen-like fibers in the cytohistologic sections. Meanwhile, a circular parallel attachment of long spindle-shaped cells occurred in the smooth surface group. Based on this in vitro study, it can be concluded that the real perpendicularly connecting bone-fiber osseointegration can be achieved by the modified sandblasting surface treatment at the dental implant bone interface. The osseointegration of this pattern will possibly enhance the bonding strength of the bone interface and favor the distribution of occlusive force at the interface when compared with the capsule-like adaptation of a smooth surface dental implant. This was also implied by Schroeder’s findings during his study of the histologic effects of titanium plasma spray on the tissue interface of dental implants. He found functionally oriented fibroblastic cells and collagen fibers at the gingival interface that attached to the abutment at angles. This functional connection seemed to increase the bonding strength at the gingival interface.
Another distinction in the osteogenic functions of interfacial osteoblasts was revealed by using cytomorphologic methods. Apart from the implication of cell morphology, the active secretion of collagen fibrils, the bone-matrix-vesicles–mediated mineralization, and the formation of osteocytes suggest that the modified sandblasted surface can definitely improve the osteogenic function of interfacial osteoblasts and can be expected to accelerate the process of bone healing at the interface of implants. The same conclusion has been reached by other researchers who have used a two dimensional cell culture model (that is, seeding and culturing cells on designed surfaces). In the present study, the results, based on this more closely in vivo-simulating model, are more significant and more convincing. They confirm the findings of a previous in vivo study and indicate that the modified sandblasted surface accelerates osseointegration through its influence on the morphology and function of interfacial osteoblasts. They also indicate that the surface topography is a factor in biomaterial biocompatibility.
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