Warwick Duncan | University of Otago (original) (raw)

Papers by Warwick Duncan

Clinical Oral Implants Research, Jan 22, 2016

Spark discharge anodic oxidation forms a porous oxide film on titanium implant surfaces, which ma... more Spark discharge anodic oxidation forms a porous oxide film on titanium implant surfaces, which may increase surface roughness and enhance early osseointegration. This study aimed to clinically and histomorphometric compare commercially-available sandblasted (RBM) implants, treated with hydrothermal anodization and placed into an animal maxillary sinus model. Thirty 3.75 mm × 8.5 mm threaded titanium implants were placed into the maxillary sinuses of 10 sheep via an external approach, with three test groups and 10 implants per group: right side, Control = CP-titanium with RBM surface, Test group 1 = CP-titanium with RBM + anodized surface; left side, Test group 2 = Ti-6Al-7Nb with RBM + anodized surface. Schneiderian membranes were elevated but not bone grafted. Resonant frequency analysis (RFA) was measured at surgery. Animals were sacrificed after 1 month unloaded healing. Resin-embedded undemineralized ground-sections were digitised, and mean bone-implant contact (% BIC) was measured bilaterally for the best-three consecutive threads. Seven of 30 implants showed signs of failure. RFA was low at placement but did not differ between the groups (group mean ISQ values ranged from 23 to 35; χ(2) = 0.37). RFA was not repeated at sacrifice due to implant instability. Histomorphometric analysis showed % BIC was highest for control (34.8 ± 15.7), followed by Test 1 (29.6 ± 18.1) and Test 2 implants (23.3 ± 22.7), but this difference was not statistically significant (χ(2) = 0.3). Early integration of RBM implants placed into thin maxillary sinus walls was not enhanced by hydrothermal anodization of implant surfaces. This may be related to the initial low stability of the implants and the relatively short healing period. However, non-anodized RBM surfaces showed promising results, with % BIC values comparable to the best estimates of other studies using sinus grafting. Whether the modification of the implant surfaces through anodization with simultaneous sinus grafting would promote enhanced early osseointegration, is a subject of future research.

Journal of Biomedical Materials Research Part B, Dec 11, 2017

Aim: This study investigated whether a keratin hydrogel derived from wool enhances ossointegratio... more Aim: This study investigated whether a keratin hydrogel derived from wool enhances ossointegration of dental implants, using a cancellous bone model in sheep. Method: Ten female sheep received one dental implant per hind leg in the distal femoral condyles. Test implants were coated with 1 mL of keratin hydrogel containing sulphonated keratin and hydroxyapatite; control implants remained uncoated; implants were not functionally loaded axially. Biomechanical stability was tested with resonance frequency analysis (RFA) at placement and euthanasia. Animals were sacrificed after 4 weeks and resinembedded histomorphometry performed. Findings: Bone appeared denser and more mature around the keratin-treated test implants. Average % bone-implant contact was significantly increased for the test (58.1 6 4.6 [SD]%) compared to control implants (34.4 6 7.5%) (p 5 0.01). RFA values were lower for control (76.5 6 4.2 ISQ) than test implants (80.4 6 1.4) after 4 weeks (p 5 0.04). Conclusion: the increase in osseointegration found in this model suggests that keratin hydrogel has the potential to enhance the successful osseointegration of dental implants placed into poor quality bone. V

PubMed, Jun 1, 2008

Background: Spark discharge anodic oxidation forms a porous TiO2 film on the surface of titanium ... more Background: Spark discharge anodic oxidation forms a porous TiO2 film on the surface of titanium oral implants, increasing surface roughness and concentrations of calcium and phosphate ions. In this study, anodic-treated oral implants were placed in an animal model and analysed using clinical, micro-computerized tomographic (micro-CT) and histometric techniques. Methods: Pairs of 3.5 mm x 8.5 mm long titanium implants (Osstem Implant Co., Ltd. Seoul, Korea), with blasted (control) or blasted and oxidized surfaces (test), were placed into the right femoral condyles of 10 sheep. Animals were sacrificed after 1 month unloaded healing. Resonant frequency analysis (RFA) was measured in implant stability quotient (ISQ) using the Mentor II device. Specimens were scanned using medium resolution micro-CT (Skyscan 1172). Mean percent bone-to-implant contact (%BIC) was calculated from two images per implant by three different operators, using Image J software. Inter- and intra-examiner differences were calculated. Specimens were then embedded in methacrylate and undemineralized ground sections were digitized. Mean %BIC was measured using Image J at x 20 magnification for the best-three consecutive threads from the most central section. Results: Mean micro-CT %BIC was similar for control and test (57.2 +/- 0.05% versus 56.4 +/- 0.03%, p = 0.5). There was considerable inter-examiner variability (interclass correlation coefficient = 0.44). RFA showed no clinically-detectable difference between the two groups (control ISQ: 75.2 +/- 4.2; test ISQ: 76.3 +/- 1.7; p = 0.48). However, histometric analysis found a marked and highly statistically-significant difference (%BIC Test 72.5 +/- 8.6%, Control 46.2 +/- 12.1%, p = 0.01). Conclusions: The novel anodic oxidation technique increased early ossointegration of rough-surfaced implants by 157%. Neither clinical testing with resonant frequency analysis nor radiographic analysis using micro-CT had sufficient resolution to detect this improvement. Whether this gain in early bone-implant contact is clinically significant in the context of early occlusal loading is the subject of subsequent experiments.

Journal of biomedical materials research. Part B, Applied biomaterials, Jan 11, 2017

This study investigated whether a keratin hydrogel derived from wool enhances ossointegration of ... more This study investigated whether a keratin hydrogel derived from wool enhances ossointegration of dental implants, using a cancellous bone model in sheep. Ten female sheep received one dental implant per hind leg in the distal femoral condyles. Test implants were coated with 1 mL of keratin hydrogel containing sulphonated keratin and hydroxyapatite; control implants remained uncoated; implants were not functionally loaded axially. Biomechanical stability was tested with resonance frequency analysis (RFA) at placement and euthanasia. Animals were sacrificed after 4 weeks and resin-embedded histomorphometry performed. Bone appeared denser and more mature around the keratin-treated test implants. Average % bone-implant contact was significantly increased for the test (58.1 ± 4.6 [SD]%) compared to control implants (34.4 ± 7.5%) (p = 0.01). RFA values were lower for control (76.5 ± 4.2 ISQ) than test implants (80.4 ± 1.4) after 4 weeks (p = 0.04). the increase in osseointegration found i...

Clinical oral implants research, Jan 22, 2016

BioMed research international, 2015

Spark discharge anodic oxidation forms porous TiO2 films on titanium implant surfaces. This incre... more Spark discharge anodic oxidation forms porous TiO2 films on titanium implant surfaces. This increases surface roughness and concentration of calcium and phosphate ions and may enhance early osseointegration. To test this, forty 3.75 mm × 13 mm titanium implants (Megagen, Korea) were placed into healed mandibular postextraction ridges of 10 sheep. There were 10 implants per group: RBM surface (control), RBM + anodised, RBM + anodised + fluoride, and titanium alloy + anodised surface. Resonant frequency analysis (RFA) was measured in implant stability quotient (ISQ) at surgery and at sacrifice after 1-month unloaded healing. Mean bone-implant contact (% BIC) was measured in undemineralised ground sections for the best three consecutive threads. One of 40 implants showed evidence of failure. RFA differed between groups at surgery but not after 1 month. RFA values increased nonsignificantly for all implants after 1 month, except for controls. There was a marked difference in BIC after 1...

Annals of the Royal Australasian College of Dental Surgeons, 2008

Spark discharge anodic oxidation forms a porous TiO2 film on the surface of titanium oral implant... more Spark discharge anodic oxidation forms a porous TiO2 film on the surface of titanium oral implants, increasing surface roughness and concentrations of calcium and phosphate ions. In this study, anodic-treated oral implants were placed in an animal model and analysed using clinical, micro-computerized tomographic (micro-CT) and histometric techniques. Pairs of 3.5 mm x 8.5 mm long titanium implants (Osstem Implant Co., Ltd. Seoul, Korea), with blasted (control) or blasted and oxidized surfaces (test), were placed into the right femoral condyles of 10 sheep. Animals were sacrificed after 1 month unloaded healing. Resonant frequency analysis (RFA) was measured in implant stability quotient (ISQ) using the Mentor II device. Specimens were scanned using medium resolution micro-CT (Skyscan 1172). Mean percent bone-to-implant contact (%BIC) was calculated from two images per implant by three different operators, using Image J software. Inter- and intra-examiner differences were calculated....

Journal of materials science. Materials in medicine, 2016

A B S T R A C T The interaction of blood and fabrics is currently a 'hot topic', since the unders... more A B S T R A C T The interaction of blood and fabrics is currently a 'hot topic', since the understanding and interpretation of these stains is still in its infancy. A recent simplified perpendicular impact experimental programme considering bloodstains generated on fabrics laid the foundations for understanding more complex scenarios. Blood rarely impacts apparel fabrics perpendicular; therefore a systematic study was conducted to characterise the appearance of drip stains on inclined fabrics. The final drip stain appearance for 45 and 15 impact angles on torso apparel fabrics (100% cotton plain woven, 100% polyester plain woven, a blend of polyester and cotton plain woven and 100% cotton single jersey knit) that had been laundered for six, 26 and 52 cycles prior to testing was investigated. The relationship between drop parameters (height and volume), angle and the stain characteristics (parent stain area, axis 1 and 2 and number of satellite stains) for each fabric was examined using analysis of variance. The appearance of the drip stains on these fabrics was distorted, in comparison to drip stains on hard-smooth surface. Examining the parent stain allowed for classification of stains occurring at an angle, however the same could not be said for the satellite stains produced. All of the dried stains visible on the surface of the fabric were larger than just after the impacting event, indicating within fabric spreading of blood due to capillary force (wicking). The cotton-containing fabrics spread the blood within the fabrics in all directions along the stain's circumference, while spreading within the polyester plain woven fabric occurred in only the weft (width of the fabric) and warp (length) directions. Laundering affected the formation of bloodstain on the blend plain woven fabric at both impact angles, although not all characteristics were significantly affected for the three impact conditions considered. The bloodstain characteristics varied due to the fibre content and fabric structure for both impact angles investigated. It is therefore necessary to consider the age of the fabric (which is fabric specific), the fibre type (including blends) and the fabric structure, before interpreting bloodstain patterns. An understanding of this simplified inclined drip stain interaction has been investigated to generate a basis for more complex interactions, such as spatter bloodstains.

The choice of implant surface has a significant influence on osseointegration. Modification of Ti... more The choice of implant surface has a significant influence on osseointegration. Modification of TiZr surface by anodization is reported to have the potential to modulate the osteoblast cell behaviour favouring more rapid bone formation. The aim of this study is to investigate the effect of anodizing the surface of TiZr discs with respect to osseointegration after four weeks implantation in sheep femurs. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing DL-a-glycerophosphate and calcium acetate at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, atomic force microscopy and goniometry. Forty implant discs with thickness of 1.5 and 10 mm diameter (10 of each-titanium, titanium–zirconium, ano-dized titanium and anodized titanium–zirconium) were placed in the femoral condyles of 10 sheep. Histomor-phometric and histologic analysis were performed 4 weeks after implantation. The anodized implants displayed hydrophilic, porous, nano-to-micrometer scale roughened surfaces. Energy dispersive spectroscopy analysis revealed calcium and phosphorous incorporation into the surface of both titanium and titanium–zirconium after anodization. Histologically there was new bone apposition on all implanted discs, slightly more pronounced on anodised discs. The percentage bone-to-implant contact measurements of anodized implants were higher than machined/ unmodified implants but there was no significant difference between the two groups with anodized surfaces (P [ 0.05, n = 10). The present histomorphometric and histological findings confirm that surface modification of titanium– zirconium by anodization is similar to anodised titanium enhances early osseointegration compared to machined implant surfaces.

Background and Objectives: During the First World War, 10% of New Zealand's population served in ... more Background and Objectives: During the First World War, 10% of New Zealand's population served in the armed forces, and around one in five of those were killed. In commemoration of 100 years since WW1, this study uses retrospective data to report on the oral health of NZ service personnel.

Objectives: Spark discharge anodic oxidation forms a porous oxide film on titanium implant surfac... more Objectives: Spark discharge anodic oxidation forms a porous oxide film on titanium implant surfaces, which may increase surface roughness and enhance early osseointegration. This study aimed to clinically and histomorphometric compare commercially-available sandblasted (RBM) implants, treated with hydrothermal anodization and placed into an animal maxillary sinus model. Materials and Methods: Thirty 3.75 mm 9 8.5 mm threaded titanium implants were placed into the maxillary sinuses of 10 sheep via an external approach, with three test groups and 10 implants per group: right side, Control = CP-titanium with RBM surface, Test group 1 = CP-titanium with RBM + anodized surface; left side, Test group 2 = Ti-6Al-7Nb with RBM + anodized surface. Schneiderian membranes were elevated but not bone grafted. Resonant frequency analysis (RFA) was measured at surgery. Animals were sacrificed after 1 month unloaded healing. Resin-embedded undemineralized ground-sections were digitised, and mean bone-implant contact (% BIC) was measured bilaterally for the best-three consecutive threads. Results: Seven of 30 implants showed signs of failure. RFA was low at placement but did not differ between the groups (group mean ISQ values ranged from 23 to 35; v 2 = 0.37). RFA was not repeated at sacrifice due to implant instability. Histomorphometric analysis showed % BIC was highest for control (34.8 AE 15.7), followed by Test 1 (29.6 AE 18.1) and Test 2 implants (23.3 AE 22.7), but this difference was not statistically significant (v 2 = 0.3). Discussion and Conclusions: Early integration of RBM implants placed into thin maxillary sinus walls was not enhanced by hydrothermal anodization of implant surfaces. This may be related to the initial low stability of the implants and the relatively short healing period. However, non-anodized RBM surfaces showed promising results, with % BIC values comparable to the best estimates of other studies using sinus grafting. Whether the modification of the implant surfaces through anodization with simultaneous sinus grafting would promote enhanced early osseointegration, is a subject of future research.

Aim: The aim of this study was to investigate the capacity of adipose-derived stem cells (ADSC), ... more Aim: The aim of this study was to investigate the capacity of adipose-derived stem cells (ADSC), grown in serum-free conditions, to regenerate bone around titanium discs with different titanium surfaces. Material and methods: Ovine ADSC (oADSC) were isolated from seven sheep and cultured using serum-free and osteogenic conditions. Prior to in vivo testing, the growth and osteogenic behaviour of these cells were analysed in vitro using cell proliferation and extracellular matrix mineralisation assays. The bone regenerative capacity of autologous oADSC was evaluated in vivo on titanium discs in a sheep femur epicondyle model. Machined (MTi) and alumina-blasted (ABTi) titanium discs were used. Bone regeneration within the defects was evaluated after 1 month using histology and histomorphometry. PKH26 cell-tracking dye was used to verify the persistence of oADSC in the surgical wound. Results: oADSC sourced from five of seven sheep differentiated into osteoblast-like cells. Cellular proliferation was reduced only for osteogenically induced oADSC (oOS-ADSC) grown on ABTi, compared to non-induced oADSC grown on ABTi and tissue culture polystyrene (P = 0.03 and 0.02 respectively). There was no significant difference for in vitro mineralisation assays comparing oADSC with oOS-ADSC, regardless of implant surface type. oADSC labelled with PKH26 were detected 1 month after surgery within the defect. There was no difference in bone regeneration between the bone defects treated with oADSC vs. just blood clot.

Clinical Implant Dentistry and Related Research, 2007

Background: Conventional implant protocols advocate a two-stage technique with a load-free, subm... more Background: Conventional implant protocols advocate a two-stage technique with a load-free, submerged healing period. Recent studies suggest that immediate restoration of single implants may be a viable treatment option.Purpose: The purpose of this study was to evaluate prosthodontic and aesthetic peri-implant mucosal outcomes of immediately restored, Southern single-tapered implants in the anterior maxilla after 1 year.Materials and Methods: Participants (mean age: 43.25 years; range: 23–71 years) satisfying specified inclusion criteria were randomly allocated to conventional two-stage restoration (control group; n=14) and immediate restoration groups (test group; n =14) in a randomized controlled clinical trial. Tapered, roughened-surface Southern implants were placed using a standardized technique, and implant level bone impressions were made. Provisional screw-retained crowns, out of occlusion, were placed at second-stage surgery after 26 weeks for the conventional restoration group, and within 4 hours of implant placement for the immediate restoration group. Both groups had definitive screw-retained metal-ceramic crowns placed in occlusion 8 weeks later. Peri-implant mucosal response and papilla index were recorded 4 weeks after definitive crown placement to allow for mucosal maturation and at 1 year. Prosthodontic and aesthetic outcomes were assessed using established criteria.Results: There were no significant differences within, or between, the control and test groups for age, gender, bone quality or quantity, implant stability measurements at surgery, or implant length. There were no significant differences in the implant success rate as determined by radiographic bone loss and stability tests after 1 year. There were no significant differences in prosthodontic maintenance, peri-implant mucosal response, and papilla index between the two groups over 1 year.Conclusions: Tapered, roughened-surface implants immediately restored with single provisional crowns at surgery and definitive crowns 8 weeks later were as prosthodontically and aesthetically successful as conventionally restored two-stage implants during the first year of service. Restoring single implants immediately with screw-retained crowns is an efficient procedure, but the short-term outcome is by no means superior to a conventional two-stage approach.

Journal of Clinical Periodontology, 2003

: To investigate infection and host immunity patterns in sheep with naturally occurring &quot... more : To investigate infection and host immunity patterns in sheep with naturally occurring "broken-mouth" periodontitis. : Eight periodontally healthy (HS) and eight periodontally diseased ewes (PDS) were selected. Subgingival plaque and sera were collected and examined for evidence of human periodontitis-associated pathogens. Serum IgG titers were measured by ELISA to multiple strains of Porphyromonas gingivalis, Bacteroides forsythus, Dichelobacter nodosus, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Fusobacterium nucleatum as well as several purified antigens (cysteine proteases, LPS, K, and fimbriae). : Neither the organism Aa nor antigens to Aa were found in any animal. Most animals were positive for Pg, Bf, and Pi, but DNA probes detected no difference between HS and PDS relative to amounts of pathogens in subgingival plaque. PDS had significantly higher serum IgG titers to all Pg strains, to 50% of Bf strains, to the Pi and Fn strains, and to fimbriae and the two cysteine proteases (p-values ranging from 0.05 to 0.001). Regression analysis demonstrated a significant association between number of teeth lost and serum IgG antibody titers to whole-cell sonicate antigens of P. gingivalis strains (p<0.01) and body weight (p<0.01). : The presence of pathogens associated with periodontitis was reflected in differences in serum IgG titers between healthy and diseased sheep. This may have influenced animal body weight and might have systemic health and economic consequences. The data suggest that susceptible and non-susceptible sheep can be identified for periodontal research.

Forensic Science Medicine and Pathology

Understanding how bone behaves when subjected to ballistic impact is of critical importance for f... more Understanding how bone behaves when subjected to ballistic impact is of critical importance for forensic questions, such as the reconstruction of shooting events. Yet the literature addressing microscopic anatomical features of gunshot wounds to different types of bone is sparse. Moreover, a biomechanical framework for describing how the complex architecture of bone affects its failure during such impact is lacking. The aim of this study was to examine the morphological features associated with experimental gunshot wounds in slaughtered pig ribs. We shot the 4th rib of 12 adult pigs with .22 mm subsonic bullets at close range (5 cm) and examined resultant wounds under the light microscope, scanning electron microscope SEM and micro tomograph μCT. In all cases there was a narrow shot channel followed by spall region, with evidence of plastic deformation with burnishing of the surface bone in the former, and brittle fracture around and through individual Haversian systems in the latter. In all but one case, the entrance wounds were characterized by superficially fractured cortical bone in the form of a well-defined collar, while the exit wounds showed delamination of the periosteum. Inorganic residue was evident in all cases, with electron energy dispersive spectroscopy EDS confirming the presence of carbon, phosphate, lead and calcium. This material appeared to be especially concentrated within the fractured bony collar at the entrance. We conclude that gunshot wounds in flat bones may be morphologically divided into a thin burnished zone at the entry site, and a fracture zone at the exit.

Applied Surface Science, 2011

ABSTRACT A porous hydroxyapatite (HA) – incorporated TiO2 coating layer was deposited on the tita... more ABSTRACT A porous hydroxyapatite (HA) – incorporated TiO2 coating layer was deposited on the titanium substrate using a combination of micro-arc oxidation and electrophoretic deposition. The size of the synthesized HA nano-particles was approximately 10–20 nm in width and 30–40 nm in length. The microstructure, as well as elemental and phase composition of the coating layers were examined by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). XRD showed that the coating layers were composed mainly of HA and anatase phases. The composition and surface morphologies were strongly dependent on the applied voltages. The amount of HA deposited into the coating increased with increasing applied voltage. The corrosion behavior of the coating layers in the simulated body fluids (SBF) was evaluated using a potentiodynamic polarization test. The corrosion resistance of the coated sample was higher than that of the untreated titanium sample. Moreover, the corrosion resistance of the coated samples also showed a positive correlation with the applied voltage. In addition, the in vitro cellular responses to the coated samples were assessed to investigate the proliferation, differentiation and morphology of the osteoblast cell line.Highlights► Electrophoretic deposition and micro-arc oxidation are combined. ► The variation of applied voltage affects the surface characteristics of titanium implant. ► An applied voltage of 350 V is the optimal choice.

Journal of Biomechanical Science and Engineering, 2010

Surface and Interface Analysis, 2010

Well-ordered TiO2 nanotubes were prepared by the electrochemical anodization of titanium in an et... more Well-ordered TiO2 nanotubes were prepared by the electrochemical anodization of titanium in an ethylene glycol electrolyte containing 1 wt% NH4F and 10 wt% H2O at 20 V for 20 min, followed by annealing. The surface morphology and crystal structure of the samples were examined as a function of the annealing temperature by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), respectively. Crystallization of the nanotubes to the anatase phase occurred at 450 °C, while rutile formation was observed at 600 °C. Disintegration of the nanotubes was observed at 600 °C and the structure vanished completely at 750 °C. Electrochemical corrosion studies showed that the annealed nanotubes exhibited higher corrosion resistance than the as-formed nanotubes. The growth of hydroxyapatite on the different TiO2 nanotubes was also investigated by soaking them in simulated body fluid (SBF). The results indicated that the tubes annealed to a mixture of anatase and rutile was clearly more efficient than that in their amorphous or plain anatase state. The in vitro cell response in terms of cell morphology and proliferation was evaluated using osteoblast cells. The highest cell activity was observed on the TiO2 nanotubes annealed at 600 °C. Copyright © 2010 John Wiley & Sons, Ltd.

Aims: To assess the influence of an activated implant surface and a synthetic graft material in t... more Aims: To assess the influence of an activated implant surface and a synthetic graft material in the maxillary sinus in combination with sinus floor elevation on bone-to-implant contact (BIC) as compared to implants with conventional surfaces.