J Wolke

Publications of J Wolke

• Bone reaction adjacent to microplasma-sprayed calcium phosphate-coated oral implants subjected to an occlusal load, an experimental study in the dog.

  Authors: R Junker, P J D Manders, J Wolke, Y Borisov, I Braceras, John A Jansen

  Clinical oral implants research. 11/2010; 22(2):135-42.

  A new microplasma spraying equipment (MSE) to deposit calcium phosphate (CaP) ceramic coatings onto titanium substrates has been developed. With this system, it is possible to spray fine particlesA new microplasma spraying equipment (MSE) to deposit calcium phosphate (CaP) ceramic coatings onto titanium substrates has been developed. With this system, it is possible to spray fine particles and to apply textured hydroxylapatite coatings onto titanium surfaces. Moreover, due to the low heat power of the microplasma jet, overheating of the powder particles as well as excessive local overheating of the substrate are diminished. Furthermore, because of the small laminar plasma jet, it is possible to achieve high spray efficiency in the case of spraying for dental implants. Also, the low level of noise (25-50 dB) and hardly any dust makes it possible to operate MSE under conditions of normal workrooms. The aim was to investigate, in a mandibular dog model, the effect of functional load on soft-tissue adaptation as well as crestal bone-level changes around titanium implants provided with newly developed microplasma-sprayed CaP coatings. For histomorphometrical evaluation, 56 screw-type titanium implants were inserted into the mandibles of seven adult Beagle dogs. The implants were either acid etched without an additional coating, coated with a conventionally plasma-sprayed CaP ceramic (PS), coated with a microplasma-sprayed CaP ceramic (MPS) or with a microplasma-sprayed coating at only the apical part (aMPS). To assess the effect of occlusal loading, a split-mouth design was used. Six weeks after implantation, the implants in one half of the mandible of each dog were functionally loaded whereas the contra lateral implants served as control. One year after loading, the animals were sacrificed. Soft-tissue dimension as well as marginal bone level were histologically assessed. Histometric analysis of undecalcified histologic sections included the evaluation of the sulcus depth, the dimension of the junctional epithelium and the connective tissue as well as the first bone-to-implant contact. For MPS-surfaced implants, functional loading was associated with--compared with the non-loaded state--unchanged soft-tissue dimension. Furthermore, the soft-tissue dimension did not differ from the dimensions around non-coated, PS and aMPS implants. Moreover, the first bone-to-implant contact was not significantly altered by functional loading and comparable non-coated, PS and aMPS implants. Conclusion: Within the limits of the experiment, we conclude that, in comparison, functional loading does not affect the marginal soft-tissue response to MPS CaP-coated implants. However, in comparison, functional loading might affect marginal bone response to MPS CaP-coated implants.

• Bone reaction adjacent to microplasma-sprayed CaP-coated oral implants subjected to occlusal load, an experimental study in the dog. Part I: short-term results.

  Authors: R Junker, P J D Manders, J Wolke, Y Borisov, J A Jansen

  Clinical oral implants research. 11/2010; 21(11):1251-63.

  A new microplasma spraying equipment (MSE) to deposit calcium phosphate ceramic (CaP) coatings onto titanium substrates has been developed. With this system, it is possible to spray fine particlesA new microplasma spraying equipment (MSE) to deposit calcium phosphate ceramic (CaP) coatings onto titanium substrates has been developed. With this system, it is possible to spray fine particles and to apply textured hydroxylapatite coatings onto titanium surfaces. Moreover, due to the low heat power of the microplasma jet, overheating of the powder particles as well as excessive local overheating of the substrate is diminished. Furthermore, because of the small laminar plasma jet, it is possible to achieve high spray efficiency in the case of spraying for dental implants. Also, the low level of noise (25-50 dB) and hardly any dust makes it possible to operate MSE under conditions of normal workrooms. The aim was to investigate, in a mandibular dog model, bone biological properties and the occlusal loading effects of titanium implants provided with newly developed microplasma-sprayed CaP coatings. For histomorphometrical evaluation, 48 screw-type titanium implants were inserted into the mandibles of six adult beagle dogs. The implants were either acid etched without additional coating, coated with a conventionally plasma-sprayed CaP ceramic, coated with a microplasma-sprayed CaP ceramic or with a microplasma-sprayed coating at the apical part only. To assess the effect of occlusal loading, a split-mouth design was used. Six weeks after implantation, the implants in one half of the mandible of each dog were functionally loaded, while the contra lateral implants served as control. Six weeks after loading, the animals were sacrificed and bone-to-implant contact as well as the amount of bone around the implants were assessed. Irrespective of surface and functional load, no statistically significant differences (P>0.05) were found either for bone-to-implant contact or for the amount of bone between the various implant surfaces. On the other hand, functional loading of the non-coated implants was associated with a tendency towards crestal bone loss. Within the limits of the experiment, we conclude that functional loading of MPS CaP coatings induces a favorable bone response, and furthermore, that the bone response, irrespective of the loading condition, does not differ from conventional plasma-sprayed CaP coatings.

• Loaded microplasma-sprayed CaP-coated implants in vivo.

  Authors: R Junker, P J D Manders, J Wolke, Y Borisov, I Braceras, J A Jansen

  Journal of dental research. 10/2010; 89(12):1489-93.

  Microplasma spray equipment to deposit calcium phosphate ceramic (CaP) coatings has been developed. Fifty-six titanium implants were inserted into the mandibles of 7 adult beagle dogs. The implantsMicroplasma spray equipment to deposit calcium phosphate ceramic (CaP) coatings has been developed. Fifty-six titanium implants were inserted into the mandibles of 7 adult beagle dogs. The implants were either acid-etched (NC), conventionally plasma-sprayed (PS), micro-plasma-sprayed (MPS), or micro-plasma-sprayed (aMPS) only at the apical part. After 6 weeks, implants in one half of the mandible were subjected to load. Fifty-two weeks thereafter, the animals were killed. Regardless of load, bone healing was comparable for all surfaces tested. It was concluded that loading of MPS CaP-coated implants evokes a favorable bone response, and that the bone response does not differ from that of PS CaP-coated implants. However, functional loading of PS as well as MPS CaP-coated implants might be associated with increased crestal bone maintenance as compared with non-coated implants.

• Bone-supportive behavior of microplasma-sprayed CaP-coated implants: mechanical and histological outcome in the goat.

  Authors: R Junker, P J D Manders, J Wolke, Y Borisov, J A Jansen

  Clinical oral implants research. 12/2009;

  Background: New microplasma spray (MPS) equipment to deposit calcium phosphate (CaP) ceramic coatings onto titanium substrates has been developed. With this apparatus, it is possible to spray fineBackground: New microplasma spray (MPS) equipment to deposit calcium phosphate (CaP) ceramic coatings onto titanium substrates has been developed. With this apparatus, it is possible to spray fine particles, as well as to apply textured hydroxylapatite coatings onto titanium surfaces. Moreover, due to the low heat power of the microplasma jet, overheating of the powder particles as well as excessive local overheating of the substrate is reduced. Furthermore, because of the small laminar plasma jet, it is possible to achieve high spray efficiency in the case of spraying of dental implants. Additionally, the low level of noise (25-50 dB) and hardly any dust makes it possible to operate the MSE under normal workroom conditions. Objective: The aim of this study was to examine the biological properties of different MPS - CaP coatings on titanium implants when inserted into the femoral condyle of goats. Material and methods: For histomorphometrical evaluation as well as mechanical testing, 48 screw-type titanium implants were inserted into the femoral condyles of 12 goats each. The implants were either coated with a conventionally plasma-sprayed CaP ceramic, MPS CaP ceramic, or acid-etched without an additional CaP coating. Six and 12 weeks after implantation, the animals were sacrificed and bone-to-implant contact, amount of bone, as well as mechanical bone fixation were evaluated. Results: For bone-to-implant contact no statistically significant difference was found between the different CaP coatings. However, statistically significant differences were found between non-coated, acid-etched titanium implants and CaP-coated implants after 6 and 12 weeks of healing. The bone values were not statistically significantly different between the different CaP coatings at 6 and 12 weeks. Furthermore, CaP ceramic-coated implants showed statistically significantly higher torque values compared with the non-coated implants after 6 and at 12 weeks of healing. No significant differences existed between the various types of CaP coatings. Conclusion: On the basis of our observations, we conclude that conventionally plasma-sprayed CaP ceramic-coated implants, as well as MPS-coated implants have a comparable effect on adjacent bone response. To cite this article: Junker R, Manders PJD, Wolke J, Borisov Y, Jansen JA. Bone-supportive behavior of microplasma-sprayed CaP-coated implants: mechanical and histological outcome in the goat.

• Clinical and SEM assessment of ART high-viscosity glass-ionomer sealants after 8-13 years in 4 teeth.

  Authors: J E Frencken, J Wolke

  Journal of dentistry. 09/2009;

  OBJECTIVES: Resin composite sealants are retained longer than low-viscosity glass-ionomer sealants. Nevertheless, a systematic review showed that there is no evidence that resin composite sealantsOBJECTIVES: Resin composite sealants are retained longer than low-viscosity glass-ionomer sealants. Nevertheless, a systematic review showed that there is no evidence that resin composite sealants are superior to low-viscosity glass-ionomers in preventing dentine carious lesion development. This case study aimed to investigate reasons for this. METHODS: 4 teeth were sealed with 2 brands of high-viscosity glass-ionomer according to the ART technique in 2 children aged 10 and 11.5 years, having a low caries-risk status, and followed clinically for between 8 and 13 years. At the final year, impressions were taken for SEM images that were assessed by two evaluators. RESULTS: Pits and fissures that were clinically diagnosed as free of sealant material appeared to contain remnants of high-viscosity glass-ionomer sealant material in the deeper parts of pits and fissures, on SEM images of 3 teeth. CONCLUSION: This study confirms the likelihood that remnants of high-viscosity glass-ionomer sealant material are retained and block the deeper parts of pits and fissures even after the sealant appears to have disappeared clinically, exercising their carious lesion preventive effect.

• The properties of biomimetically processed calcium phosphate on bioactive ceramics and their response on bone cells.

  Authors: M Vaahtio, T Peltola, T Hentunen, H Ylänen, S Areva, J Wolke, J I Salonen

  Journal of materials science. Materials in medicine. 12/2006; 17(11):1113-25.

  This study looks for grounds to alter the chemical composition (phosphate, calcium, silica and carbonate), dissolution properties, structure and nanotopography of the biomimetically processedThis study looks for grounds to alter the chemical composition (phosphate, calcium, silica and carbonate), dissolution properties, structure and nanotopography of the biomimetically processed surfaces on bioactive ceramics to optimize their shown ability to influence bone cell behaviour and production of new bone. In the bone environment desirable characteristic of these materials is their ability to be remodeled by natural osteoclastic resorption. Different silica and carbonate containing calcium phosphate layers were prepared on bioactive glasses 9 (S53P4) and 1-98 (S53P2) and sol-gel processed pure silica SiO2 in C- and R-SBF (conventional and revised simulated body fluid) for varying periods of time. It was shown that in R-SBF the CaP layer formed faster compared to C-SBF. The CaP layer in the R-SBF contained more carbonate (CO3(2-)) compared to that formed with the same immersion time in C-SBF. The CaP so formed in R-SBF with faster precipitation is more amorphous than the bonelike HCA formed in C-SBF. The results indicate that the most suitable surface for both osteoblasts and osteoclasts was found to be an amorphous CaP having mesoporous nanotopography and proper dissolution rate of calcium and silica.

• Influence of deposition parameters on chemical properties of calcium phosphate coatings prepared by using electrostatic spray deposition.

  Authors: S Leeuwenburgh, J Wolke, J Schoonman, J A Jansen

  Journal of biomedical materials research. Part A. 09/2005; 74(2):275-84.

  The electrostatic spray deposition (ESD) technique offers the possibility of depositing calcium phosphate (CaP) coatings onto various substrate materials with defined chemical and morphologicalThe electrostatic spray deposition (ESD) technique offers the possibility of depositing calcium phosphate (CaP) coatings onto various substrate materials with defined chemical and morphological properties. The relationship between physical, apparatus-related deposition parameters, and the chemical characteristics of ESD coatings was investigated by means of X-ray diffraction, Fourier transform infrared spectroscopy, and energy dispersive spectroscopy to be able to deposit CaP coatings with tailored chemical properties. The results showed that the chemical characteristics of CaP coatings, deposited with use of the ESD technique, were strongly dependent on the deposition temperature, the nozzle-to-substrate distance, the liquid flow rate, and the geometry of the spraying nozzle. By investigating the influence of the deposition temperature, information could be obtained on the formation mechanism of CaP coatings-and specifically the biologically interesting carbonate apatite phase-using the ESD technique. CaP coatings were not formed merely because of solvent evaporation; a chemical reaction was needed to synthesize the coatings. This reaction involved thermal decomposition of the organic solvent butyl carbitol into carbonate ions via formation of intermediate oxalate ions. The amount of carbonate incorporation, and consequently, the Ca/P ratios of the deposited coatings, was shown 1) to decrease with increasing nozzle-to-substrate distance, 2) to decrease with increasing liquid flow rate, and 3) to decrease by making use of a novel two-component nozzle geometry.

• Electrostatic spray deposition (ESD) of calcium phosphate coatings.

  Authors: S Leeuwenburgh, J Wolke, J Schoonman, J Jansen

  Journal of biomedical materials research. Part A. 09/2003; 66(2):330-4.

  Using electrostatic spray deposition (ESD), thin calcium phosphate layers were deposited onto commercially pure cp-Ti substrates. ESD is a thin-film technique that enables the deposition of inorganicUsing electrostatic spray deposition (ESD), thin calcium phosphate layers were deposited onto commercially pure cp-Ti substrates. ESD is a thin-film technique that enables the deposition of inorganic thin films onto metallic substrates using a simple and cheap experimental set-up. The results show that coating structure and morphology can be tailored by choosing the appropriate combination of deposition parameters. Scanning electron microscopy revealed that various surface morphologies, ranging from dense to very porous coatings, can be obtained. Particularly interesting was a unique reticular coating morphology characterized by a three-dimensionally interconnected pore network. X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FTIR) analyses showed that crystalline carbonate apatite coatings were formed after heat treatment of as-deposited ESD coatings.

• In-vitro apatite formation on phosphorylated bamboo.

  Authors: S Li, Q Liu, J de Wijn, J Wolke, B Zhou, K de Groot

  Journal of materials science. Materials in medicine. 10/1997; 8(9):543-9.

  Natural self-reinforced composite, bamboo, was surface modified by phosphorylation with urea-H3PO4 and NaOH-H3PO4 methods; then precalcification was performed by immersing samples in saturatedNatural self-reinforced composite, bamboo, was surface modified by phosphorylation with urea-H3PO4 and NaOH-H3PO4 methods; then precalcification was performed by immersing samples in saturated Ca(OH)2 solution. After that, calcium phosphate can be formed on the surface of bamboo samples in calcification media: simulated body fluid (1.5 SBF) and accelerated calcification solution (ACS). Experimental results reveal that pre-calcification is an inevitable step for the formation of calcium phosphate. The calcium phosphate formed in 1.5 SBF was identified by thin-film X-ray diffraction as apatite which was not well crystallized. Compared with the urea-H3PO4 method, the NaOH-H3PO4 method has the advantages of quicker and continuous apatite formation and stronger adhesive between apatite and bamboo.