Enhanced bone apposition to a chemically modified SLA titanium surface.

Increased surface roughness of dental implants has demonstrated greater bone apposition; however, the effect of modifying surface chemistry remains unknown. In the present study, we evaluated bone apposition to a modified sandblasted/acid-etched (modSLA) titanium surface, as compared with a standard SLA surface, during early stages of bone regeneration. Experimental implants were placed in miniature pigs, creating 2 circular bone defects. Test and control implants had the same topography, but differed in surface chemistry. We created the test surface by submerging the implant in an isotonic NaCl solution following acid-etching to avoid contamination with molecules from the atmosphere. Test implants demonstrated a significantly greater mean percentage of bone-implant contact as compared with controls at 2 (49.30 vs. 29.42%; p = 0.017) and 4 wks (81.91 vs. 66.57%; p = 0.011) of healing. At 8 wks, similar results were observed. It is concluded that the modSLA surface promoted enhanced bone apposition during early stages of bone regeneration.

Stress protection due to plates: myth or reality? A parametric analysis made using the composite beam theory.

A generally accepted idea has been that plate fixation of fractures may result in the structural adaptation of bone (bone loss) to reduced stress (stress protection) with the subsequent danger of refracture after implant removal. This was the negative aspect of stress protection. For this reason, it was proposed that plates made from more deformable materials be used (titanium, polymers or carbon fibres). A theoretical analysis using composite beam theory, with different loading conditions (axial load and bending), demonstrates that stress protection, i.e. early temporary porosis, is a myth. Mechanics of materials shows that when an over-large plate is fixed to small bones (as in small animals, e.g. rabbits), the reduction of bone strain is exaggerated; in contrast, using plates of varying flexibility (steel, titanium or carbon fibre) on large bones leads to strain reduction with an astonishingly similar amplitude.

Metal implants and surface reactions.

A metal in living tissue is prone to corrosion. The interaction of the foreign body with the tissue involves the redox reaction (an electron exchange) at the interface, the hydrolysis (a proton exchange) of oxide-hydrates as products of corrosion, and the formation of metal-organic complexes in the electrolyte. Denatured tissue in contact with the foreign body is the consequence. But behaviour of metals is variable; gold, stainless steel and most other metals react as described while few others like titanium and tantalum do not. The absence of a foreign body effect of a chemical kind is, without doubt, favorable in terms of tissue susceptibility to infection in the presence of titanium.

Light and transmission electron microscopy of the intact interfaces between non-submerged titanium-coated epoxy resin implants and bone or gingiva.

This experiment was aimed at studying the intact tissue/implant interface of non-submerged dental implants with a titanium surface. Epoxy-resin replicas were fabricated from 3.05 x 8 mm cylindrical titanium implants with a plasma-sprayed apical portion and a smooth coronal collar. The replicas were coated with a 90-120-nm-thick layer of pure titanium and autoclaved. The coated replicas were inserted as non-submerged endosseous implants in the edentulous premolar region of dog mandibles and allowed to heal for three months. Jaw sections containing the implants were processed for light and electron microscopic study of the intact tissue/implant interface with and without prior demineralization. Gingival connective tissue fibers were closely adapted to the titanium layer, in an orientation more or less parallel to the implant surface. There was no evidence of any fiber insertions into the surface irregularities of the smooth or rough titanium surface. Undemineralized bone was intimately adapted to the titanium surface without any intervening space. In demineralized sections, the collagen fibers of the bone matrix tended to be somewhat thinner and occasionally less densely packed in the vicinity of the implant surface. However, they extended all the way to the titanium surface, without any intervening fibril-free layer.

[Removal torques of small screws of steel and titanium with different surfaces]. / Lösemomente an Kleinschrauben aus Stahl und Titan mit unterschiedlichen Oberflächen.

This study was designed to investigate the relationship between metal surfaces and bone holding strength and the safety margin against breakage available in small screws at implant removal. Small cortical bone screws of 1.5 and 2 mm outer diameter (mini-screws) made of stainless steel or commercially pure titanium have been mechanically and chemically treated to give different surface conditions. They were implanted in randomized groups of four or five speciments into the proximal halves of rabbit tibiae. Tightening was performed with a standardized torque of 10 or 18 Ncm by means of an instrumented screwdriver. The animals were sacrificed after 12 weeks and screw removal torques were measured. Stainless steel screws used as reference screws were found to have loosened their seat by 27% compared with the original tightening torque. Titanium implants, in contrast, revealed improved bone contact with higher removal torques varying from 130% to 160%. No correspondence could be found between these values and the surface roughness of glass-ball-blasted versus polished screws.