Enhanced bone healing around nanohydroxyapatite-coated polyetheretherketone implants: An experimental study in rabbit bone.

OBJECTIVE: To investigate the bone response to threaded polyetheretherketone (PEEK) implants coated with nanohydroxyapatite. MATERIALS AND METHODS: A total of 39 PEEK implants were coated with nanocrystalline hydroxyapatite and 39 uncoated implants were used as controls. The implant surface was characterized by optical interferometry and scanning electron microscope. The implants were inserted in the tibia and femur of 13 rabbits. After 6 weeks of healing, quantitative and qualitative analyses were performed. RESULTS: The test implants showed significantly higher removal torque test values compared with the control group. Histomorphometric evaluation demonstrated higher bone-to-implant contact for the test implants; however, there were no differences in bone area between the groups. Qualitative histological analyses demonstrated inflammatory cellular reactions in close vicinity of both implant surfaces. A two-cell layer of foreign body giant cells was observed irrespective of sample type. CONCLUSION: Our findings demonstrate that implants with a threaded design render good stability to PEEK in both coated and uncoated implants. Nanohydroxyapatite-coated PEEK implants demonstrated improved bone formation compared with uncoated controls.

Nano hydroxyapatite-coated implants improve bone nanomechanical properties.

Nanostructure modification of dental implants has long been sought as a means to improve osseointegration through enhanced biomimicry of host structures. Several methods have been proposed and demonstrated for creating nanotopographic features; here we describe a nanoscale hydroxyapatite (HA)-coated implant surface and hypothesize that it will hasten osseointegration and improve its quality relative to that of non-coated implants. Twenty threaded titanium alloy implants, half prepared with a stable HA nanoparticle surface and half grit-blasted, acid-etched, and heat-treated (HT), were inserted into rabbit femurs. Pre-operatively, the implants were morphologically and topographically characterized. After 3 weeks of healing, the samples were retrieved for histomorphometry. The nanomechanical properties of the surrounding bone were evaluated by nanoindentation. While both implants revealed similar bone-to-implant contact, the nanoindentation demonstrated that the tissue quality was significantly enhanced around the HA-coated implants, validating the postulated hypothesis.

The effect of hydroxyapatite nanocrystals on early bone formation surrounding dental implants.

The knowledge of how nanostructures might affect early bone healing and osseointegration is limited. The aim of this study was to investigate if nanometer thick coatings of hydroxyapatite nanocrystals applied on a moderately rough surface might enhance early bone healing on screw-shaped dental implants and to evaluate if the thickness of the coat influences healing. Sandblasted and acid etched titanium implants coated with two different thicknesses of hydroxyapatite (test implants) and sandblasted and acid etched titanium implants (control implants), were inserted in rabbit tibia. After a healing time of 2, 4 and 9 weeks, a removal torque analysis and a histological evaluation were performed. The results from the removal torque analysis showed a tendency for higher values for the double coated hydroxyapatite after 4 weeks and for both the coated surfaces after 9 weeks of healing. The histological evaluations indicated slightly more new bone formation with the coated implants compared with the control; the differences did not reach statistical significance. The present study could not support the importance of nanometer thick coatings of hydroxyapatite nanocrystals in early bone healing, at least not when applied on a blasted and etched surface and placed in a cortical bone.

An in vitro comparison of possibly bioactive titanium implant surfaces.

The aim of the study was to compare Ca and P formation (CaP) and subsequent bone cell response of a blasted and four different possibly bioactive commercially pure (cp) titanium surfaces; 1. Fluoride etched (Fluoride), 2. Alkali-heat treated (AH), 3. Magnesium ion incorporated anodized (TiMgO), and 4. Nano HA coated and heat treated (nano HA) in vitro. Furthermore, to evaluate the significance of the SBF formed CaP coat on bone cell response. The surfaces were characterized by Optical Interferometry, Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). CaP formation was evaluated after 12, 24 and 72 h in simulated body fluid (SBF). Primary human mandibular osteoblast-like cells were cultured on the various surfaces subjected to SBF for 72 h. Cellular attachment, differentiation (osteocalcin) and protein production (TGF-beta(1)) was evaluated after 3 h and 10 days respectively. Despite different morphological appearances, the roughness of the differently modified surfaces was similar. The possibly bioactive surfaces gave rise to an earlier CaP formation than the blasted surface, however, after 72 h the blasted surface demonstrated increased CaP formation compared to the possibly bioactive surfaces. Subsequent bone cell attachment was correlated to neither surface roughness nor the amount of formed CaP after SBF treatment. In contrast, osteocalcin and TGF-beta(1) production were largely correlated to the amount of CaP formed on the surfaces. However, bone response (cell attachment, osteocalcin and TGF-F production) on the blasted controls were similar or increased compared to the SBF treated fluoridated, AH and TiMgO surface.

Precipitation of calcium phosphate in the presence of albumin on titanium implants with four different possibly bioactive surface preparations. An in vitro study.

The aim of the present study was to compare the nucleating behaviour on four types of bioactive surfaces by using the simulated body fluid (SBF) model with the presence albumin. Titanium discs were blasted (B) and then prepared by alkali and heat treatment (AH), anodic oxidation (AO), fluoridation (F), or hydroxyapatite coating (HA). The discs were immersed in SBF with 4.5 mg/ml albumin for 3 days, 1, 2, 3 and 4 weeks and analysed with scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and X-ray photoelectron spectroscopy (XPS). Topographic surface characterisation was performed with a contact stylus profilometer. The results demonstrated that the bioactive surfaces initiated an enhanced calcium phosphate (CaP) formation and a more rapid increase of protein content was present on the bioactive surfaces compared to the blasted control surface. The observation was present on all bioactive surfaces. The fact that there was a difference between the bioactive surfaces and the blasted control surface with respect to precipitation of CaP and protein content on the surfaces support the fact that there may be biochemical advantages in vivo by using a bioactive surface.

A pilot study to establish a randomized trial methodology to test the efficacy of a behavioural intervention.

How can pregnant women be helped to stop smoking? This was a pilot study of midwife home-based motivational interviewing. Clients were 100 consecutive self-reported smokers booking at clinics in Glasgow from March to May 1997. Smoking guidance is routinely given at booking. In addition, intervention clients received a median of four home-based motivational interviewing sessions from one specially trained midwife. All sessions (n = 171) were audio-taped and interviews (n = 49) from 13 randomly selected clients were transcribed for content analysis. Three 'experts' assessed intervention quality using a recognized rating scale. Cotinine measurement on routine blood samples confirmed self-reported smoking change from late pregnancy telephone interview. Postnatal telephone questionnaire measured client satisfaction. Focus groups of routine midwives explored acceptability, problems and disruption of normal care. Fisher exact, chi 2 and Mann-Whitney tests compared enrolment characteristics. Two-sample t-tests assessed outcome between groups. Motivational interviewing was satisfactory in more than 75% of transcribed interviews. In this pilot study, self-reported smoking at booking (100 of 100 available) corroborated by cotinine (93 of 100) compared with late pregnancy self-reports (intervention 47 of 48; control 49 of 49) and cotinine (intervention 46 of 48; control 47 of 49) showed no significant difference between groups. Tools have been developed to answer the question: 'Can proactive opportunistic home-based motivational interviewing help pregnant smokers reduce their habit?'.

Pyranoisoflavones from Rinorea welwitschii.

Reversed-phase HPLC analysis of a dichloromethane extract of the stem-barks of Rinorea welwitschii has afforded two pyranoisoflavones, alpinumisoflavone (1) and di-O-methylalpinumisoflavone (2).

N.m.r. and conformational analysis of the capsular polysaccharide from Streptococcus pneumoniae type 4.

The 1H- and 13C-n.m.r. data on the capsular polysaccharide (1) produced by Streptococcus pneumoniae type 4, the depyruvated polysaccharide (2), and a tetrasaccharide (3a) derived by Smith degradation of 2 were used as constraints on a computer-generated model of the conformation of 1 and to assess the effects of the pyruvic acetal substituent on the conformation. The dynamics of the polysaccharide systems and the influence of the pyruvic acetal were investigated using 13C-n.m.r. relaxation measurements.

Control of components of bacterial polysaccharide vaccines by physical methods.

Analysis of polysaccharide components of meningococcal- and pneumococcal vaccines was carried out by proton n.m.r. spectroscopy and gas chromatography. The meningococcal polysaccharides were of high purity but showed differences in degree and position of O-acetylation between manufacturers. The level of contamination of the pneumococcal polysaccharides by C-substance was quantified. These methods provide an alternative to immunological methods for determining serotype and purity.