The influence of surface nanoroughness, texture and chemistry of TiZr implant abutment on oral biofilm accumulation.

OBJECTIVES: The aim of the study was to examine surface nanoroughness, texture and chemistry of dental implant abutment and to investigate how these parameters influence oral biofilm formation in healthy subjects. MATERIALS AND METHODS: Eight different nanorough TiZr surfaces were produced by polishing, machining, cathodic polarization and acid etching. Surface topography was examined using field emission scanning electron microscope and a blue light laser profilometer. Surface chemistry was analyzed by secondary ion mass spectrometry and X-ray photoelectron spectroscopy. Surface hydrophilicity was tested by measuring contact angle on the surfaces. A human in vivo study using a splint model was employed to evaluate oral biofilm accumulation on these surfaces. RESULTS: Different surface textures (flat, grooved and irregular) were created with nanoroughness from 29 to 214 nm. Some test surfaces were incorporated with hydrogen by cathodic polarization and/or acid etching with HCl/H(2)SO(4). Nanoroughness (S(a)) positively correlated with microbial adhesion. Biofilm accumulation was less pronounced on flat and grooved than on irregular surfaces. No significant association between hydrogen content or hydrophilicity of the surface and biofilm accumulation was observed. CONCLUSIONS: Nanoroughness (< 214 nm) and surface texture influence oral biofilm accumulation independent of surface chemistry and hydrophilicity. Surface hydrogen, which has previously been shown to promote fibroblast growth, does not affect biofilm formation.

Surface hydride on titanium by cathodic polarization promotes human gingival fibroblast growth.

Connective tissue seal to dental abutment is crucial for peri-implant health. Several efforts have been made previously to optimize abutment surfaces, but no consensus has been reached regarding the optimal surface architecture and/or composition for soft tissue seal. Here, we report on experiments using cathodic polarization in organic acids to optimize titanium (Ti) surfaces for use as abutments. The three main factors affecting surface topography and chemistry were electrolyte composition, current density, and polarization time. Under identical conditions, oxalic acid created rougher surfaces than tartaric acid and acetic acid, and acetic acid produced more surface hydride. Surface hydride amount was suggested to first increase and then decrease with current density from 1 mA/cm(2) to 15 mA/cm(2) . The complexity of the surface topography and hydride production both increased with polarization time. Proliferation rate of human gingival fibroblasts (HGFs) was positively correlated with surface hydride content, suggesting the positive effect of surface hydride on connective tissue growth around dental abutment. Changes in surface topography and hydrophilicity did not significantly influence HGF growth.

Effect of chemical and mechanical debridement techniques on bacterial re-growth on rough titanium surfaces: an in vitro study.

OBJECTIVE: The aim of this in vitro study was to compare the effect of combined chemical and mechanical debridement of titanium (Ti) surfaces inoculated with Staphylococcus epidermidis, compared with the effect of chemical debridement alone. MATERIAL AND METHODS: Different Ti surfaces were characterized with respect to roughness and subsequently inoculated with S. epidermidis. NaCl (0.9 vol.%), EDTA (12 vol.%), H2O2 (3 vol.%) or H2O2 + TiO2 nanoparticles served as chemical debridement agents, while TiBrush was used as the mechanical debridement tool. Safranin staining assessed biomass still attached to surfaces after debridement. Biofilm viability was assessed after re-incubation of the debrided samples. SEM analysis was performed before and after the cleaning process. RESULTS: Surface average roughness (Sa ) of the samples was measured at 2.22 ± 0.19 µm for group A, 0.19 ± 0.02 µm for group B, and 1.99 ± 0.10 µm for group C. When chemical debridement agents were used alone, H2O2-containing products were most efficient in reducing the biomass load. The surface roughness did not affect the outcome of chemical debridement. However, when combining chemical and mechanical debridement, a further reduction of biofilm load and viability was observed with best effect on the smoothest surface. CONCLUSIONS: Combining H2O2-containing chemical agents with mechanical debridement (TiBrush) provided best reduction in biofilm mass and re-growth, when studied in vitro.

Correlation between molecular signals and bone bonding to titanium implants.

OBJECTIVES: A better understanding of the biological processes controlling osseointegration at the bone-to-implant interface is needed. The aim of this study was to examine which are the molecular and biochemical variables that are significantly related to osseointegration, using multiple regression analysis. MATERIALS AND METHODS: Titanium coins were placed into the tibial cortical bone of New Zealand White rabbits and evaluated using pull-out test after 4 and 8 weeks of healing. Correlations between pull-out and several markers from tissue fluid (Lactate dehydrogenase [LDH] and Alkaline phosphatase [ALP] activities and total protein content) and peri-implant bone tissue (total protein, RNA and DNA content, implant area covered with bone and gene expression of osteoblast, osteoclast and inflammation markers) were used to assess the importance of these parameters in bone healing and in relation to implant performance. RESULTS: Our results showed a negative correlation between the content of DNA, RNA and total protein at the peri-implant bone tissue and the pull-out force, indicating that as bone matures and implant becomes more osseointegrated, the organic content of bone decreases. The negative correlation found between pull-out force and ALP activity pointed to a delayed healing in implants with lower pull-out values and primary mineralization still ongoing. LDH activity and total protein content in the tissue fluid were as well negatively correlated with the pull-out force. Finally, a positive correlation was observed between the pull-out force and the expression of the osteoblast and the bone resorption markers, being osteocalcin and collagen-I the best predictive markers for osseointegration after 4 and 8 weeks of healing respectively. CONCLUSIONS: These results suggest that the evaluation of these markers could be relevant for the assessment of new implant surfaces for rapid bone healing and improved implant performance.

Identification of early response genes to roughness and fluoride modification of titanium implants in human osteoblasts.

PURPOSE: Tissue response after implantation determines the success of the healing process. This response is not only dependent on the chemical properties of the implant surface but also by the surface topography or its roughness. Although in vitro and in vivo studies show improved results with rough- and fluoride-modified implants, the mechanisms behind these findings are still unknown. METHODS AND MATERIALS: Here, we have used a two-step procedure to identify novel genes related to the early response of primary human osteoblasts to roughness and fluoride-modified titanium implants. RESULTS: Two hundred seventeen genes responding to roughness were identified by microarray analysis and 198 genes responding to fluoride, 33 genes were common. Those identified genes related to bone and mineralization were further investigated by real-time reverse-transcriptase polymerase chain reaction. After 1 day of culture, toll-like receptor 3, ankylosis-progressive homolog, decorin, osteocalcin, and runt-related transcription factor-2 were classified as responsive genes to roughness; Distal-less homeobox-2 and Tuftelin-1 as responsive genes to fluoride treatment. Responsive genes to both treatments were collagen type I, parathyroid hormone-like hormone, hairy and enhancer of split-1, follistatin, ectonucleotide pyrophosphatase/phosphodiesterase-1, and thyroid hormone receptor-alpha. CONCLUSION: Our strategy was useful for identifying novel genes that might be involved in the early response of osteoblasts to rough and fluoride-modified titanium implants.

Wear model simulating clinical abrasion on composite filling materials.

The aim of this study was to establish a wear model for testing composite filling materials with abrasion properties closer to a clinical situation. In addition, the model was used to evaluate the effect of filler volume and particle size on surface roughness and wear resistance. Each incisor tooth was prepared with nine identical standardized cavities with respect to depth, diameter, and angle. Generic composite of 3 different filler volumes and 3 different particle sizes held together with the same resin were randomly filled in respective cavities. A multidirectional wet-grinder with molar cusps as antagonist wore the surface of the incisors containing the composite fillings in a bath of human saliva at a constant temperature of 37°C. The present study suggests that the most wear resistant filling materials should consist of medium filling content (75%) and that particles size is not as critical as earlier reported.

Controlled electro-implementation of fluoride in titanium implant surfaces enhances cortical bone formation and mineralization.

Previous studies have shown that bone-to-implant attachment of titanium implants to cortical bone is improved when the surface is modified with hydrofluoric acid. The aim of this study was to investigate if biological factors are involved in the improved retention of these implants. Fluoride was implemented in implant surfaces by cathodic reduction with increasing concentrations of HF in the electrolyte. The modified implants were placed in the cortical bone in the tibias of New Zealand white rabbits. After 4 weeks of healing, wound fluid collected from the implant site showed lower lactate dehydrogenase activity and less bleeding in fluoride-modified implants compared to control. A significant increase in gene expression levels of osteocalcin and tartrate-resistant acid phosphatase (TRAP) was found in the cortical bone attached to Ti implants modified with 0.001 and 0.01 vol.% HF, while Ti implants modified with 0.1% HF showed only induced TRAP mRNA levels. These results were supported by the performed micro-CT analyses. The volumetric bone mineral density of the cortical bone hosting Ti implants modified with 0.001% and 0.01% HF was higher both in the newly woven bone (<100 microm from the interface) and in the older Haversian bone (>100 microm). In conclusion, the modulation of these biological factors by surface modification of titanium implants with low concentrations of HF using cathodic reduction may explain their improved osseointegration properties.