Dual Acid-etched Research Articles

The effect of enzymatically degradable IPN coatings on peri‐implant bone formation and implant fixation

Short-term osseointegration of orthopedic implants is critical for the long-term stability of the implant-bone interface. To improve initial implant stability, one strategy under consideration involves the presentation of adhesion ligands on the implant surface to stimulate bone regeneration in the peri-implant region. To assess the relative effects of implant surface chemistry and topography on osseointegration within the rat femoral ablation implant model, a nonfouling, enzymatically degradable interpenetrating polymer network (edIPN) of poly(AAm-co-EG/AAc) amenable to presenting the cell signaling domain Arg-Gly-Asp (RGD), was developed. Moderate enhancement of peri-implant bone formation was found after 28 days using the edIPN without peptide modification (p = 0.032). However, no data supported a benefit of peptide modification, as bone-implant contact, normalized bone volume and normalized fixation strength was equivalent or poorer than dual acid-etched (DAE) treated implants after 28 days. Surface topography was determined to be the dominant factor in modulating osseointegration, as DAE implants produced equivalent roughness-normalized fixation strength versus previously reported data on plasma-sprayed hydroxyapatite/tricalcium phosphate-coated implants (Barber et al., J Biomed Mater Res A, forthcoming). An ideal osseointegrated implant will require optimization of all three aforementioned parameters, and may take the form of biomolecule delivery from thin degradable polymer networks.

Molecular and Biomechanical Characterization of Mineralized Tissue by Dental Pulp Cells on Titanium

The application of implant therapy is still limited, because of various risk factors and the long healing time required for bone-titanium integration. This study explores the potential for osseointegration engineering with dental pulp cells (DPCs) by testing a hypothesis that DPCs generate mineralized tissue on titanium. DPCs extracted from rat incisors positive for CD44, alkaline phosphatase activity, and mineralizing capability were cultured on polystyrene and on machined and dual-acid-etched (DAE) titanium. Tissue cultured on titanium with a Ca/P ratio of 1.4 exhibited plate-like morphology, while that on the polystyrene exhibited fibrous and punctate structures. Tissues cultured on titanium were harder than those on polystyrene, 1.5 times on the machined and 3 times on the DAE. Collagen I, osteopontin, and osteocalcin genes were up-regulated on titanium, especially the DAE surface. In conclusion, DPCs showing some characteristics of the previously identified dental pulp stem cells can generate mineralized tissue on titanium via the osteoblastic phenotype, which can be enhanced by titanium surface roughness.

Five‐Year Survival Distributions of Short‐Length (10 mm or less) Machined‐Surfaced and Osseotite® Implants

In cases of reduced alveolar bone height, implants of short length (10 mm or less) may be employed although there is a perceived risk that because of their small stature they will be unable to tolerate occlusal loads and will fail to osseointegrate. This report describes an analysis of prospective multicenter clinical studies evaluating the risk for failure of short-length implants, comparing dual acid-etched (DAE) Osseotite implants (Implant Innovations, Inc., Palm Beach Gardens, FL, USA) to machined-surfaced implants. Admission criteria were the same for both data sets. Baseline variables of demographics including age, gender and smoking status, bone quality, location, implant dimensions, and types of prostheses were compared to ensure balance among groups. Cumulative survival rates (CSRs) were calculated with the Kaplan-Meier estimator. The implant data included 2294 implants for the DAE series and 2597 implants for the machined-surfaced series. Patient demographics showed similar percentages of occurrence for all variables. The distributions of implants between short- and standard-length data sets for baseline variables including width, location, and restorative type were similar, qualifying these data sets for comparison of the independent variable of length. Overall, there was a 2.2% difference in 5-year CSRs between the machined-surfaced short- and the standard-length implants. For these implants a 7.1% difference was observed in the posterior maxilla and an 8.5% difference in the anterior maxilla. For DAE implants the overall difference between "standards" and "shorts" was 0.7%, which is not statistically significant. In this analysis the difference in CSRs between short- and standard-length implants was greater for machined-surfaced implants than for DAE implants.

The removal torque of titanium screw inserted in rabbit tibia treated by dual acid etching

Chemical acid etching alone of the titanium implant surface have the potential to greatly enhance osseointegration without adding particulate matter (e.g. TPS or hydroxyapatite) or embedding surface contaminants (e.g. grit particles). The aims of the present study were to evaluate any differences between the machined and dual acid etching implants with the removal torque as well as topographic analysis. A total of 40 custom-made, screw-shaped, commercially pure titanium implants with length of 5 mm and an outer diameter of 3.75 mm were divided into 4 groups, 10 screws in each, and chemical modification of the titanium implant surfaces were achieved using HF and HCl/H 2SO 4 dual acid etching. The first exposure was to hydrofluoric acid and the second was to a combination of hydrochloric acid and sulfuric acid. The tibia metaphysics was exposed by incisions through the skin, fascia, and periosteum. One implant of each group was inserted in every rabbit, 2 in each proximal tibia metaphysics. Every rabbit received 3 implants with acid etched surfaces and 1 implant with a machined surface. Twelve weeks post-surgically, 7 rabbits were sacrificed, Subsequently, the leg was stabilized and the implant was removed under reverse torque rotation with a digital torque gauge (Mark-10 Corporation, USA) (Fig. 1). Twelve weeks after implant placement, the removal torque mean values were the dual acid etched implants (24%HF+HCl/H 2SO 4, group C) required a higher average force (34.7 Ncm), than the machined surface implants (group A) ( p=0.045) (Mann-Whiteney test). Scanning electron micrographs of acid etching of the titanium surface created an even distribution of very small (1–2 μm) peaks and valleys, while machining of the titanium surface created typical microscopically grooved surface characteristics. Nonetheless, there was no difference in surface topography between each acid etched implant groups. Therefore, chemically acid etching implant surfaces have higher strengths of osseointegration than machined implant surfaces. There is less correlation between removal torque and the difference in HF volume%.

Modulated bone matrix-related gene expression is associated with differences in interfacial strength of different implant surface roughness.

The objective of this study was to examine the effect of implant surface topography on biomechanical strength and expression patterns of bone extracellular matrix (ECM)-related genes during implant healing. Cylinder implants with turned or dual acid-etched (DE) surface were placed into the femurs of female Sprague-Dawley rats. At 2 and 4 weeks after the implantation, the implant push-in test was performed to measure the load-bearing strength of the bone-tissue interface. T-shaped hollow implants were separately placed and the total RNA was extracted from the ingrown tissue within the hollow chamber. The RNA was subjected to reverse transcriptase polymerase chain reaction to analyze the expression pattern of selected bone extracellular matrix-related genes. The push-in value of the DE implant is approximately 300% greater than that of the turned implant at weeks 2 and 4 (p=.0090). The expression of collagen II, osteocalcin and biglycan was higher in the week 2 DE implant group than the turned implant group. At week 4 the expression of collagen II and IX was 7- and 26-fold, respectively, greater in the DE implant group than in the turned implant group. The surface topography of implants may induce the phenotypic alteration of wound healing cells. The increased interfacial strength of the DE implant may be associated with the modulated expression of the selected set of bone extracellular matrix genes.

Modulated bone matrix‐related gene expression is associated with differences in interfacial strength of different implant surface roughness

Purpose The objective of this study was to examine the effect of implant surface topography on biomechanical strength and expression patterns of bone extracellular matrix (ECM)‐related genes during implant healing.Materials and Methods Cylinder implants with turned or dual acid‐etched (DE) surface were placed into the femurs of female Sprague‐Dawley rats. At 2 and 4 weeks after the implantation, the implant push‐in test was performed to measure the load‐bearing strength of the bone‐tissue interface. T‐shaped hollow implants were separately placed and the total RNA was extracted from the ingrown tissue within the hollow chamber. The RNA was subjected to reverse transcriptase polymerase chain reaction to analyze the expression pattern of selected bone extracellular matrix‐related genes.Results The push‐in value of the DE implant is approximately 300% greater than that of the turned implant at weeks 2 and 4 (p=.0090). The expression of collagen II, osteocalcin and biglycan was higher in the week 2 DE implant group than the turned implant group. At week 4 the expression of collagen II and IX was 7‐ and 26‐fold, respectively, greater in the DE implant group than in the turned implant group.Conclusions The surface topography of implants may induce the phenotypic alteration of wound healing cells. The increased interfacial strength of the DE implant may be associated with the modulated expression of the selected set of bone extracellular matrix genes.

Platelet interactions with titanium: modulation of platelet activity by surface topography

Endosseous implants initially come into contact with blood. Thus, the nature of the interactions between blood and implanted endosseous implants may influence subsequent bone healing events in the peri-implant healing compartment. We conducted studies to address the following question: Does implant surface microtexture modulate platelet activity? We used commercially pure Ti (cpTi) disks with four different surface finishes: dual acid-etched (DAE), 320 grit (320G) abraded, machined, and p1200 polished cpTi. Surfaces were characterized by scanning electron microscopy (SEM) and optical profilometry. The DAE and 320G surfaces presented more complex microtextures than the machined or polished surfaces. Platelet activities were measured by quantifying platelet adherence, platelet-derived microparticle (MP) formation, and P-selectin expression as function of surface type. Platelet adhesion, measured using a lactate dehydrogenase (LDH) assay, was increased on DAE and 320G surfaces compared to machined and polished surfaces ( p<0.05). MP formation and P-selectin expression, assayed by flow cytometry, also showed increased activation of platelets on DAE and 320G surfaces. Because increased activation of platelets may lead to up-regulation of osteogenic responses during bone healing, these results may explain the enhanced osteoconductivity known to occur with DAE cpTi surfaces in comparison with machined cpTi surfaces.

Red blood cell and platelet interactions with titanium implant surfaces.

The influence of the micro-roughened surface, produced by dual acid-etching (DAE) of machined commercially pure titanium, on initial blood cell/implant interactions was investigated by observing the blood components remaining at the implant surface following freeze-fracture of clotted, and fixed, human blood. Glass surfaces were also used for immunolabelling studies to identify fibrin and platelets. The interface comprised predominantly fibrin and red blood cells (RBCs). The difference in distribution of RBCs was statistically significant (P < 0.05) at 10 min of blood/implant contact, but diminished thereafter. Micro-roughened DAE implant surfaces showed, qualitative, more platelets than machined surfaces, while the textured glass surfaces demonstrated increased platelet aggregation. We believe that these early blood cell/implant interactions may play a key role in the osteoconduction stage of peri-implant bone healing response to micro-roughened implants.