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

Papers by Warwick Duncan

International Journal of Oral & Maxillofacial Implants, May 1, 2018

To investigate whether human adipose-derived stem cells will form a functional bone-like matrix o... more To investigate whether human adipose-derived stem cells will form a functional bone-like matrix on titanium substrates. The behavior of human adipose-derived stem cells was examined when grown in either serum-free, xeno-free stem cell growth medium or osteogenic differentiation medium and cultured on either machined titanium (MTi) or on roughened alumina-blasted titanium (ABTi) discs. Materials and Methods: Cellular proliferation, extracellular mineralized matrix production, osteogenic-related protein production (RUNX2 and osteocalcin), and gene expression for pluripotency and self-renewal (TERT and OCT4) and osteogenic-related (MSX2, RUNX2, and BGLAP) genes were performed. Results: Human adipose-derived stem cells in serum-free medium (hADSC) proliferated at a higher rate compared with osteogenically differentiated cells (hOS-ADSC); however, the osteogenically committed cells produced more mineralized matrix on the titanium surfaces compared with either tissue culture plastic or the undifferentiated cells. The immunofluorescence analysis showed that human adipose-derived stem cells cultured in serum-free medium and osteogenic differentiation medium produced RUNX2 on both the machined titanium surface and on the alumina-blasted titanium surface after 7 days in culture. Only osteogenically differentiated cells produced osteocalcin after 21 days. Relative gene expression showed stable expression of MSX2, RUNX2, and BGLAP over time on all surfaces. Only osteogenically differentiated cells displayed osteogenic characteristics over time. Conclusion: This study confirmed that human adipose-derived stem cells could be successfully grown in serum-free, xeno-free culture medium suitable for clinical use. Adipose-derived stem cells thus show potential utility for bone regeneration in association with titanium surfaces.

Bioengineering, Apr 13, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of The Mechanical Behavior of Biomedical Materials, Sep 1, 2020

Bite forces are studied in order to understand a wide range of factors pertaining to the masticat... more Bite forces are studied in order to understand a wide range of factors pertaining to the mastication system. Various strain gauge transducers have been employed to measure bite forces, with several descriptions of these available in the literature; unfortunately, many reports provide insufficient detail to enable accurate reproduction. The aim of this project was to develop a bite force transducer with the capability of measuring maximum voluntary bite forces between individual opposing tooth surfaces. Furthermore, in an attempt to address the issue of vague device descriptions in the available literature, a detailed account of the transducer development has been included. A novel strain gauge transducer was designed and built. Bite forces of forty individuals were measured to verify the capabilities and clinical application of the device.

Journal of Periodontal Research, Sep 4, 2017

Background and ObjectiveThe aim of this pilot study was to characterize surface morphology and to... more Background and ObjectiveThe aim of this pilot study was to characterize surface morphology and to evaluate resorption and osseous healing of two deproteinated bovine bone graft materials after sinus grafting in a large animal model.Material and MethodsSurfaces of a novel particulate bovine bone graft, Moa‐Bone® were compared with Bio‐Oss® using scanning electron microscopy. Six sheep then had maxillary sinus grafting bilaterally, covered with BioGide®. Grafted maxillae were harvested after 4, 6 and 12 weeks. Healing was described for half of each site using resin‐embedded ground sections. For the other half, paraffin‐embedded sections were examined using tartrate resistant acid phosphatase staining for osteoclast activity, runt‐related transcription factor2 immunohistochemistry for pre‐osteoblasts and osteoblasts and proliferating cell nuclear antigen for proliferative cells.ResultsMoa‐Bone® had a smoother, more porous fibrous structure with minimal globular particles compared with Bio‐Oss®. After 4 weeks, woven bone formed on both grafts and the Moa‐Bone® particles also showed signs of resorption. After 12 weeks, Moa‐Bone® continued to be resorbed, however Bio‐Oss® did not; both grafts were surrounded by maturing lamellar bone. Moa‐Bone® was associated with earlier evidence of runt‐related transcription factor 2‐positive cells. Moa‐Bone® but not Bio‐Oss® was associated with strong tartrate resistant acid phosphatase‐positive osteoclasts on the graft surface within resorption lacunae at both 4 and 6 weeks post‐grafting.ConclusionBoth materials supported osseous healing and maturation without inflammation. Moa‐Bone® showed marked osteoclast activity after 4 and 6 weeks and demonstrated positive attributes for grafting, if complete remodeling of the graft within the site is desired. Further optimization of Moa‐Bone® for maxillofacial applications is warranted.

The Saudi Dental Journal, Nov 1, 2021

Introduction: Titanium (Ti) is widely accepted as a biomaterial for orthopaedic and dental implan... more Introduction: Titanium (Ti) is widely accepted as a biomaterial for orthopaedic and dental implants, primarily due to its capacity to integrate directly into the bone and its superior corrosion resistance. It has been suggested that titanium-zirconium alloy (TiZr), with 13-17% of zirconium, has better mechanical properties than pure Ti, but there are very few published studies assessing the suitability of TiZr for high-load-bearing implants. This study aimed to compare the mechanical properties and microstructures of TiZr and commercially pure titanium (Ti). Methodology: Pure Ti and TiZr alloy discs were prepared and subjected to characterisation by nanoindentation, electron dispersive spectroscopy (EDS), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). Results: The TiZr alloy was found to have significantly lower elastic modulus value (p < 0.0001) and greater hardness than Ti (p < 0.05). The EDS results confirmed the presence of Zr (13-17%) in the TiZr alloy, with XRD and EBSD images showing microstructure with the alpha phase similar to commercially available Ti. Conclusion: The lower elastic modulus, higher hardness, presence of alpha phase, and the finer grain size of the TiZr alloy make it more suitable for high-load-bearing implants compared to commercially available Ti and is likely to encourage a positive biological response.

Materials

Zirconia ceramic (ZC) implants are becoming more common, but comparisons between preclinical hist... more Zirconia ceramic (ZC) implants are becoming more common, but comparisons between preclinical histology and long-term clinical trials are rare. This investigation comprised (1) 8-year clinical follow-up of one-piece ZC or titanium (Ti) implants supporting full overdentures and (2) histomorphometric analysis of the same implants in an animal model, comparing implants with various surface treatments. Methods: (1) Clinical trial: 24 completely edentulous participants (2 groups of N = 12) received 7 implants (one-piece ball-abutment ZC or Ti; maxilla N = 4, mandible N = 3) restored with implant overdentures. Outcomes after 8-years included survival, peri-implant bone levels, soft-tissue responses, and prosthodontic issues. (2) Preclinical trial: 10 New Zealand sheep received 4 implants bilaterally in the femoral condyle: Southern Implants ZC or Ti one-piece implants, identical to the clinical trial, and controls: Southern ITC® two-piece implants with the same surface or Nobel (NBC) anodi...

Nanomaterials

There is a need to develop bifunctional scaffolds that provide antibacterial protection while enc... more There is a need to develop bifunctional scaffolds that provide antibacterial protection while encouraging host cell attachment/proliferation. This study evaluates HyStem®-C, and photo-cross-linked GelMA hydrogels for encapsulation and stabilisation of silver nanoparticles (AgNPs). We studied the behaviour of AgNPs and matrix interactions within both hydrogel systems. The cell viability of encapsulated human gingival fibroblasts (HGFs) was determined by Prestoblue® assay and live/dead staining. The release of AgNPs was monitored by inductively coupled plasma–mass spectroscopy. The antibacterial properties of the GelMA-AgNP constructs were determined using disc diffusion. Even distribution of AgNPs in GelMA induced a significant decrease in cell viability (p < 0.0001), whereas AgNP aggregates did not induce cytotoxicity in HyStem®-C. AgNPs doses ≥ 0.5 µg/mL in GelMA were significantly toxic to the HGFs (p < 0.0001). The release of AgNPs from GelMA after 48 h was 20% w/w for 0.1 ...

Materials

Bovine bone grafts (BBX) require protein removal as part of the manufacturing process to reduce a... more Bovine bone grafts (BBX) require protein removal as part of the manufacturing process to reduce antigenicity and, in consequence, to be safely used in humans. Deproteinisation may have direct effects on the characteristics of the bone material and on in vivo material performance. This research aimed to comprehensively study the physicochemical and mechanical properties of BBX processed at low deproteinisation processing temperatures. Cubes of bovine bone (8 mm3) were treated with temperatures between 100 °C and 220 °C at 30 °C intervals and with pressures ranging from 1.01 to 24.58 Bar. The samples were characterised topographically and mechanically using scanning electron microscopy (SEM), atomic force microscopy (AFM), and uniaxial bending tests. The organic content and the chemical composition were determined using thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) and FTIR were also used to quantitatively determine the sp...

Journal of Periodontal Research

Objective and BackgroundResorption of alveolar bone after tooth extraction is a common problem of... more Objective and BackgroundResorption of alveolar bone after tooth extraction is a common problem often requiring bone grafting. The success of the grafting procedures is dependent on multiple factors including the presence of growth factors. This is the first in vivo study to investigate the role of the pleiotrophin family of cytokines in alveolar bone regeneration. This research investigated the role of the pleiotrophin–midkine (PTN–MDK) axis during osteogenesis, with and without a grafting material, after tooth extraction in a sheep model.MethodsThirty Romney‐cross ewes were anesthetized, and all premolar teeth on the right side were extracted. The sockets were randomized to controls sites with no treatment and test sites with Bio‐Oss® graft material and Bio‐Gide® membrane. Samples were harvested after sacrificing animals 4, 8, and 16 weeks post‐grafting (n = 10 per time‐point). Tissue for qRT2‐PCR gene analysis was recovered from the socket next to the first molar using a trephine ...

Infection Control & Hospital Epidemiology

Objective:Exposure to aerosol spray generated by high-speed handpieces (HSHs) and ultrasonic scal... more Objective:Exposure to aerosol spray generated by high-speed handpieces (HSHs) and ultrasonic scalers poses a significant health risk to oral health practitioners from airborne pathogens. Aerosol generation varies with different HSH designs, but to date, no study has measured this.Materials and methods:We measured and compared aerosol generation by (1) dental HSHs with 3 different coolant port designs and (2) ultrasonic scalers with no suction, low-volume evacuation (LVE) or high-volume evacuation (HVE). Measurements used a particle counter placed near the operator’s face in a single-chair, mechanically ventilated dental surgery. Volume concentrations of aerosol, totaled across a 0.3–25-µm size range, were compared for each test condition.Results:HSH drilling and scaling produced significantly high aerosol levels (P < .001) with total volume concentrations 4.73×108µm3/m3 and 4.18×107µm3/m3, respectively. For scaling, mean volume of aerosol was highest with no suction followed by L...

IIUM Journal of Orofacial and Health Sciences, 2022

An increase in dental implant placements in recent years has seen a growth in the reported cases ... more An increase in dental implant placements in recent years has seen a growth in the reported cases of post-operative complications such as peri-implantitis. One of the available treatment modalities to overcome such complications is implantoplasty. Although this procedure is not new, the long-term effect of implantoplasty has not been addressed extensively. The aim of this systematic review was to investigate the change in fracture resistance of dental implants after implantoplasty. Three electronic databases and reference lists of included studies were searched to assess the potential effect of implantoplasty on implant fracture resistance. Titles and abstracts were screened by two reviewers in parallel. The extracted information regarding implant fracture resistance was reported based on the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. A total of 56 studies were identified, of which, nine studies were included. Narrow p...

Nanomedicine: Nanotechnology, Biology and Medicine, 2021

Silver nanoparticles (AgNPs) are increasingly used in combination with biomaterials, such as bone... more Silver nanoparticles (AgNPs) are increasingly used in combination with biomaterials, such as bone grafts, to provide antimicrobial properties. Our research focused on the cytotoxic and intracellular uptake mechanism of AgNPs on osteogenic cells, and the affected gene expression of osteoblasts exposed to AgNPs. Osteoblast cells were found to be relatively resistant to AgNP exposure, compared to osteoclasts, with a higher IC50 and fewer adverse morphological features. AgNPs were endocytosed within lysosomes, which resulted in the secondary internal formation of curved AgO nano-chains assemblies within the cytosol. Furthermore, osteoblasts demonstrated an oxidative stress response, with autophagic cell death mechanisms, as indicated from qRT2-PCR analysis, with sustained upregulation of the protective gene Heme Oxygenase 1 reaching 86-fold by 48hours (10μg/mL). The internalization and fate of AgNPs in osteogenic cells, and the resulting impact on gene expression over time provide further understanding of the nanotoxicity mechanism of AgNPs.

Journal of Oral Science, 2021

This study aimed to determine expressions of hepatocyte growth factor (HGF) and MET proto-oncogen... more This study aimed to determine expressions of hepatocyte growth factor (HGF) and MET proto-oncogene receptor tyrosine kinase (MET) in palatal periosteum (PP) and to examine the effect of HGF/MET on osteogenic differentiation of human palatal periosteum-derived mesenchymal stem cells (PD-MSCs). Methods: HGF/MET proteins in human palatal periosteum (n = 3) were localized using immunohistochemistry. PD-MSCs (n = 3) were cultured in serum-free Essential 8 (E8) medium or osteogenic medium with and without Capmatinib, a selective ATP-inhibitor of MET. HGF concentration in vitro was measured with ELISA. Relative gene expression was quantified from PD-MSCs by quantitative reverse transcription real-time polymerase chain reaction. Results: Immunohistochemistry detected co-localization of HGF and MET protein in PP. HGF protein levels were significantly higher (P < 0.05) in osteogenic media (day 21: 12.19 ± 8.36 ng/mL) than in E8 medium (day 21: 0.42 ± 0.72 ng/mL). MET inhibitor had a limited feedback effect on the expression profile of the osteogenic genes tested. Gene expression levels for all but three genes were comparable in serum-free and osteogenic media at all time points. Conclusion: HGF/MET present in human PP and HGF is upregulated in vitro during osteogenesis; however the targeted pathways controlled by MET may not involve osteoblast maturation.

Planta Medica, 2021

Manuka oil, an essential oil derived from the Leptospermum scoparium, has been traditionally used... more Manuka oil, an essential oil derived from the Leptospermum scoparium, has been traditionally used for wound care and as a topical antibacterial, antifungal, and anti-inflammatory. However, the essential oil is not well retained at mucosal sites, such as the oral cavity, where the benefits of the aforementioned properties could be utilized toward the treatment of persistent biofilms. Within this study, L. scoparium essential oil was incorporated into a semisolid emulsion for improved delivery. The safety profile of L. scoparium essential oil on human gingival fibroblasts was determined via cell viability, cytotoxicity, and caspase activation. The minimal bactericidal concentration of L. scoparium essential oil was determined, and the emulsionʼs antibiofilm effects visualized using confocal laser scanning microscopy. L. scoparium essential oil demonstrated a lower IC50 (0.02% at 48 h) when compared to the clinical control chlorhexidine (0.002% at 48 h) and displayed lower cumulative c...

International Journal of Paediatric Dentistry, 2020

BackgroundThe Hall Technique (HT) is a method of restoring decayed primary teeth using stainless ... more BackgroundThe Hall Technique (HT) is a method of restoring decayed primary teeth using stainless steel crowns (SSCs) without tooth preparation, caries removal, or local anaesthetic.AimTo investigate the ultrastructural, biomechanical, and chemical characteristics of teeth managed with the Hall Technique in comparison with conventional SSC (controls).DesignTwelve HT‐treated primary molars and four controls were analysed. Teeth were dehydrated in ethanol, embedded in methylmethacrylate, mesio‐distally sectioned, X‐rayed, mounted, and polished. Biomechanical, ultrastructural, and chemical characterisation was performed for carious lesion and sound areas of each specimen.ResultsPre‐treatment and post‐treatment X‐rays showed evidence of little to no caries progression over time. In carious lesions, mean hardness and elastic modulus values were lower in HT‐treated teeth than in controls. In both controls and HT‐treated teeth, carious lesions had the lowest %wt of Ca and P of all tissues s...

Journal of the Royal Society of New Zealand, 2019

All-ceramic dental restorations are now regularly being used in clinical situations. Forces appli... more All-ceramic dental restorations are now regularly being used in clinical situations. Forces applied to ceramic dental restorations can result in failure due to cracking. Dental restorations may be subjected to significant loads in the mouth and small contact points between opposing teeth may result in markedly high stress when a high bite force is encountered. This study recorded maximum voluntary bite forces on the posterior teeth of 40 participants and inter-occlusal contact points were identified by digitally scanning the teeth and calculating the surface area by accompanying software. Bite forces from as low as 83.9 Newton (N) to the highest at 1642.8 N, with a mean of 430.4 N (sd = 279.4) were recorded. Inter-occlusal contact points as small as 0.065 mm 2 were measured. The resultant stress teeth may experience has been shown to potentially exceed the flexural strength of even the strongest dental ceramic available on the market for 21.8% of the teeth tested. This study aimed to describe the stresses that teeth experience, and thus predict the stresses that future restorations on those teeth may experience. This approach may prove valuable in guiding clinicians in their material selection as well as the design of all-ceramic restorations.

International Journal of Oral & Maxillofacial Implants, May 1, 2018

To investigate whether human adipose-derived stem cells will form a functional bone-like matrix o... more To investigate whether human adipose-derived stem cells will form a functional bone-like matrix on titanium substrates. The behavior of human adipose-derived stem cells was examined when grown in either serum-free, xeno-free stem cell growth medium or osteogenic differentiation medium and cultured on either machined titanium (MTi) or on roughened alumina-blasted titanium (ABTi) discs. Materials and Methods: Cellular proliferation, extracellular mineralized matrix production, osteogenic-related protein production (RUNX2 and osteocalcin), and gene expression for pluripotency and self-renewal (TERT and OCT4) and osteogenic-related (MSX2, RUNX2, and BGLAP) genes were performed. Results: Human adipose-derived stem cells in serum-free medium (hADSC) proliferated at a higher rate compared with osteogenically differentiated cells (hOS-ADSC); however, the osteogenically committed cells produced more mineralized matrix on the titanium surfaces compared with either tissue culture plastic or the undifferentiated cells. The immunofluorescence analysis showed that human adipose-derived stem cells cultured in serum-free medium and osteogenic differentiation medium produced RUNX2 on both the machined titanium surface and on the alumina-blasted titanium surface after 7 days in culture. Only osteogenically differentiated cells produced osteocalcin after 21 days. Relative gene expression showed stable expression of MSX2, RUNX2, and BGLAP over time on all surfaces. Only osteogenically differentiated cells displayed osteogenic characteristics over time. Conclusion: This study confirmed that human adipose-derived stem cells could be successfully grown in serum-free, xeno-free culture medium suitable for clinical use. Adipose-derived stem cells thus show potential utility for bone regeneration in association with titanium surfaces.

Bioengineering, Apr 13, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Journal of The Mechanical Behavior of Biomedical Materials, Sep 1, 2020

Bite forces are studied in order to understand a wide range of factors pertaining to the masticat... more Bite forces are studied in order to understand a wide range of factors pertaining to the mastication system. Various strain gauge transducers have been employed to measure bite forces, with several descriptions of these available in the literature; unfortunately, many reports provide insufficient detail to enable accurate reproduction. The aim of this project was to develop a bite force transducer with the capability of measuring maximum voluntary bite forces between individual opposing tooth surfaces. Furthermore, in an attempt to address the issue of vague device descriptions in the available literature, a detailed account of the transducer development has been included. A novel strain gauge transducer was designed and built. Bite forces of forty individuals were measured to verify the capabilities and clinical application of the device.

Journal of Periodontal Research, Sep 4, 2017

Background and ObjectiveThe aim of this pilot study was to characterize surface morphology and to... more Background and ObjectiveThe aim of this pilot study was to characterize surface morphology and to evaluate resorption and osseous healing of two deproteinated bovine bone graft materials after sinus grafting in a large animal model.Material and MethodsSurfaces of a novel particulate bovine bone graft, Moa‐Bone® were compared with Bio‐Oss® using scanning electron microscopy. Six sheep then had maxillary sinus grafting bilaterally, covered with BioGide®. Grafted maxillae were harvested after 4, 6 and 12 weeks. Healing was described for half of each site using resin‐embedded ground sections. For the other half, paraffin‐embedded sections were examined using tartrate resistant acid phosphatase staining for osteoclast activity, runt‐related transcription factor2 immunohistochemistry for pre‐osteoblasts and osteoblasts and proliferating cell nuclear antigen for proliferative cells.ResultsMoa‐Bone® had a smoother, more porous fibrous structure with minimal globular particles compared with Bio‐Oss®. After 4 weeks, woven bone formed on both grafts and the Moa‐Bone® particles also showed signs of resorption. After 12 weeks, Moa‐Bone® continued to be resorbed, however Bio‐Oss® did not; both grafts were surrounded by maturing lamellar bone. Moa‐Bone® was associated with earlier evidence of runt‐related transcription factor 2‐positive cells. Moa‐Bone® but not Bio‐Oss® was associated with strong tartrate resistant acid phosphatase‐positive osteoclasts on the graft surface within resorption lacunae at both 4 and 6 weeks post‐grafting.ConclusionBoth materials supported osseous healing and maturation without inflammation. Moa‐Bone® showed marked osteoclast activity after 4 and 6 weeks and demonstrated positive attributes for grafting, if complete remodeling of the graft within the site is desired. Further optimization of Moa‐Bone® for maxillofacial applications is warranted.

The Saudi Dental Journal, Nov 1, 2021

Introduction: Titanium (Ti) is widely accepted as a biomaterial for orthopaedic and dental implan... more Introduction: Titanium (Ti) is widely accepted as a biomaterial for orthopaedic and dental implants, primarily due to its capacity to integrate directly into the bone and its superior corrosion resistance. It has been suggested that titanium-zirconium alloy (TiZr), with 13-17% of zirconium, has better mechanical properties than pure Ti, but there are very few published studies assessing the suitability of TiZr for high-load-bearing implants. This study aimed to compare the mechanical properties and microstructures of TiZr and commercially pure titanium (Ti). Methodology: Pure Ti and TiZr alloy discs were prepared and subjected to characterisation by nanoindentation, electron dispersive spectroscopy (EDS), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). Results: The TiZr alloy was found to have significantly lower elastic modulus value (p < 0.0001) and greater hardness than Ti (p < 0.05). The EDS results confirmed the presence of Zr (13-17%) in the TiZr alloy, with XRD and EBSD images showing microstructure with the alpha phase similar to commercially available Ti. Conclusion: The lower elastic modulus, higher hardness, presence of alpha phase, and the finer grain size of the TiZr alloy make it more suitable for high-load-bearing implants compared to commercially available Ti and is likely to encourage a positive biological response.

Materials

Zirconia ceramic (ZC) implants are becoming more common, but comparisons between preclinical hist... more Zirconia ceramic (ZC) implants are becoming more common, but comparisons between preclinical histology and long-term clinical trials are rare. This investigation comprised (1) 8-year clinical follow-up of one-piece ZC or titanium (Ti) implants supporting full overdentures and (2) histomorphometric analysis of the same implants in an animal model, comparing implants with various surface treatments. Methods: (1) Clinical trial: 24 completely edentulous participants (2 groups of N = 12) received 7 implants (one-piece ball-abutment ZC or Ti; maxilla N = 4, mandible N = 3) restored with implant overdentures. Outcomes after 8-years included survival, peri-implant bone levels, soft-tissue responses, and prosthodontic issues. (2) Preclinical trial: 10 New Zealand sheep received 4 implants bilaterally in the femoral condyle: Southern Implants ZC or Ti one-piece implants, identical to the clinical trial, and controls: Southern ITC® two-piece implants with the same surface or Nobel (NBC) anodi...

Nanomaterials

There is a need to develop bifunctional scaffolds that provide antibacterial protection while enc... more There is a need to develop bifunctional scaffolds that provide antibacterial protection while encouraging host cell attachment/proliferation. This study evaluates HyStem®-C, and photo-cross-linked GelMA hydrogels for encapsulation and stabilisation of silver nanoparticles (AgNPs). We studied the behaviour of AgNPs and matrix interactions within both hydrogel systems. The cell viability of encapsulated human gingival fibroblasts (HGFs) was determined by Prestoblue® assay and live/dead staining. The release of AgNPs was monitored by inductively coupled plasma–mass spectroscopy. The antibacterial properties of the GelMA-AgNP constructs were determined using disc diffusion. Even distribution of AgNPs in GelMA induced a significant decrease in cell viability (p < 0.0001), whereas AgNP aggregates did not induce cytotoxicity in HyStem®-C. AgNPs doses ≥ 0.5 µg/mL in GelMA were significantly toxic to the HGFs (p < 0.0001). The release of AgNPs from GelMA after 48 h was 20% w/w for 0.1 ...

Materials

Bovine bone grafts (BBX) require protein removal as part of the manufacturing process to reduce a... more Bovine bone grafts (BBX) require protein removal as part of the manufacturing process to reduce antigenicity and, in consequence, to be safely used in humans. Deproteinisation may have direct effects on the characteristics of the bone material and on in vivo material performance. This research aimed to comprehensively study the physicochemical and mechanical properties of BBX processed at low deproteinisation processing temperatures. Cubes of bovine bone (8 mm3) were treated with temperatures between 100 °C and 220 °C at 30 °C intervals and with pressures ranging from 1.01 to 24.58 Bar. The samples were characterised topographically and mechanically using scanning electron microscopy (SEM), atomic force microscopy (AFM), and uniaxial bending tests. The organic content and the chemical composition were determined using thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) and FTIR were also used to quantitatively determine the sp...

Journal of Periodontal Research

Objective and BackgroundResorption of alveolar bone after tooth extraction is a common problem of... more Objective and BackgroundResorption of alveolar bone after tooth extraction is a common problem often requiring bone grafting. The success of the grafting procedures is dependent on multiple factors including the presence of growth factors. This is the first in vivo study to investigate the role of the pleiotrophin family of cytokines in alveolar bone regeneration. This research investigated the role of the pleiotrophin–midkine (PTN–MDK) axis during osteogenesis, with and without a grafting material, after tooth extraction in a sheep model.MethodsThirty Romney‐cross ewes were anesthetized, and all premolar teeth on the right side were extracted. The sockets were randomized to controls sites with no treatment and test sites with Bio‐Oss® graft material and Bio‐Gide® membrane. Samples were harvested after sacrificing animals 4, 8, and 16 weeks post‐grafting (n = 10 per time‐point). Tissue for qRT2‐PCR gene analysis was recovered from the socket next to the first molar using a trephine ...

Infection Control & Hospital Epidemiology

Objective:Exposure to aerosol spray generated by high-speed handpieces (HSHs) and ultrasonic scal... more Objective:Exposure to aerosol spray generated by high-speed handpieces (HSHs) and ultrasonic scalers poses a significant health risk to oral health practitioners from airborne pathogens. Aerosol generation varies with different HSH designs, but to date, no study has measured this.Materials and methods:We measured and compared aerosol generation by (1) dental HSHs with 3 different coolant port designs and (2) ultrasonic scalers with no suction, low-volume evacuation (LVE) or high-volume evacuation (HVE). Measurements used a particle counter placed near the operator’s face in a single-chair, mechanically ventilated dental surgery. Volume concentrations of aerosol, totaled across a 0.3–25-µm size range, were compared for each test condition.Results:HSH drilling and scaling produced significantly high aerosol levels (P < .001) with total volume concentrations 4.73×108µm3/m3 and 4.18×107µm3/m3, respectively. For scaling, mean volume of aerosol was highest with no suction followed by L...

IIUM Journal of Orofacial and Health Sciences, 2022

An increase in dental implant placements in recent years has seen a growth in the reported cases ... more An increase in dental implant placements in recent years has seen a growth in the reported cases of post-operative complications such as peri-implantitis. One of the available treatment modalities to overcome such complications is implantoplasty. Although this procedure is not new, the long-term effect of implantoplasty has not been addressed extensively. The aim of this systematic review was to investigate the change in fracture resistance of dental implants after implantoplasty. Three electronic databases and reference lists of included studies were searched to assess the potential effect of implantoplasty on implant fracture resistance. Titles and abstracts were screened by two reviewers in parallel. The extracted information regarding implant fracture resistance was reported based on the guidelines set by the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. A total of 56 studies were identified, of which, nine studies were included. Narrow p...

Nanomedicine: Nanotechnology, Biology and Medicine, 2021

Silver nanoparticles (AgNPs) are increasingly used in combination with biomaterials, such as bone... more Silver nanoparticles (AgNPs) are increasingly used in combination with biomaterials, such as bone grafts, to provide antimicrobial properties. Our research focused on the cytotoxic and intracellular uptake mechanism of AgNPs on osteogenic cells, and the affected gene expression of osteoblasts exposed to AgNPs. Osteoblast cells were found to be relatively resistant to AgNP exposure, compared to osteoclasts, with a higher IC50 and fewer adverse morphological features. AgNPs were endocytosed within lysosomes, which resulted in the secondary internal formation of curved AgO nano-chains assemblies within the cytosol. Furthermore, osteoblasts demonstrated an oxidative stress response, with autophagic cell death mechanisms, as indicated from qRT2-PCR analysis, with sustained upregulation of the protective gene Heme Oxygenase 1 reaching 86-fold by 48hours (10μg/mL). The internalization and fate of AgNPs in osteogenic cells, and the resulting impact on gene expression over time provide further understanding of the nanotoxicity mechanism of AgNPs.

Journal of Oral Science, 2021

This study aimed to determine expressions of hepatocyte growth factor (HGF) and MET proto-oncogen... more This study aimed to determine expressions of hepatocyte growth factor (HGF) and MET proto-oncogene receptor tyrosine kinase (MET) in palatal periosteum (PP) and to examine the effect of HGF/MET on osteogenic differentiation of human palatal periosteum-derived mesenchymal stem cells (PD-MSCs). Methods: HGF/MET proteins in human palatal periosteum (n = 3) were localized using immunohistochemistry. PD-MSCs (n = 3) were cultured in serum-free Essential 8 (E8) medium or osteogenic medium with and without Capmatinib, a selective ATP-inhibitor of MET. HGF concentration in vitro was measured with ELISA. Relative gene expression was quantified from PD-MSCs by quantitative reverse transcription real-time polymerase chain reaction. Results: Immunohistochemistry detected co-localization of HGF and MET protein in PP. HGF protein levels were significantly higher (P < 0.05) in osteogenic media (day 21: 12.19 ± 8.36 ng/mL) than in E8 medium (day 21: 0.42 ± 0.72 ng/mL). MET inhibitor had a limited feedback effect on the expression profile of the osteogenic genes tested. Gene expression levels for all but three genes were comparable in serum-free and osteogenic media at all time points. Conclusion: HGF/MET present in human PP and HGF is upregulated in vitro during osteogenesis; however the targeted pathways controlled by MET may not involve osteoblast maturation.

Planta Medica, 2021

Manuka oil, an essential oil derived from the Leptospermum scoparium, has been traditionally used... more Manuka oil, an essential oil derived from the Leptospermum scoparium, has been traditionally used for wound care and as a topical antibacterial, antifungal, and anti-inflammatory. However, the essential oil is not well retained at mucosal sites, such as the oral cavity, where the benefits of the aforementioned properties could be utilized toward the treatment of persistent biofilms. Within this study, L. scoparium essential oil was incorporated into a semisolid emulsion for improved delivery. The safety profile of L. scoparium essential oil on human gingival fibroblasts was determined via cell viability, cytotoxicity, and caspase activation. The minimal bactericidal concentration of L. scoparium essential oil was determined, and the emulsionʼs antibiofilm effects visualized using confocal laser scanning microscopy. L. scoparium essential oil demonstrated a lower IC50 (0.02% at 48 h) when compared to the clinical control chlorhexidine (0.002% at 48 h) and displayed lower cumulative c...

International Journal of Paediatric Dentistry, 2020

BackgroundThe Hall Technique (HT) is a method of restoring decayed primary teeth using stainless ... more BackgroundThe Hall Technique (HT) is a method of restoring decayed primary teeth using stainless steel crowns (SSCs) without tooth preparation, caries removal, or local anaesthetic.AimTo investigate the ultrastructural, biomechanical, and chemical characteristics of teeth managed with the Hall Technique in comparison with conventional SSC (controls).DesignTwelve HT‐treated primary molars and four controls were analysed. Teeth were dehydrated in ethanol, embedded in methylmethacrylate, mesio‐distally sectioned, X‐rayed, mounted, and polished. Biomechanical, ultrastructural, and chemical characterisation was performed for carious lesion and sound areas of each specimen.ResultsPre‐treatment and post‐treatment X‐rays showed evidence of little to no caries progression over time. In carious lesions, mean hardness and elastic modulus values were lower in HT‐treated teeth than in controls. In both controls and HT‐treated teeth, carious lesions had the lowest %wt of Ca and P of all tissues s...

Journal of the Royal Society of New Zealand, 2019

All-ceramic dental restorations are now regularly being used in clinical situations. Forces appli... more All-ceramic dental restorations are now regularly being used in clinical situations. Forces applied to ceramic dental restorations can result in failure due to cracking. Dental restorations may be subjected to significant loads in the mouth and small contact points between opposing teeth may result in markedly high stress when a high bite force is encountered. This study recorded maximum voluntary bite forces on the posterior teeth of 40 participants and inter-occlusal contact points were identified by digitally scanning the teeth and calculating the surface area by accompanying software. Bite forces from as low as 83.9 Newton (N) to the highest at 1642.8 N, with a mean of 430.4 N (sd = 279.4) were recorded. Inter-occlusal contact points as small as 0.065 mm 2 were measured. The resultant stress teeth may experience has been shown to potentially exceed the flexural strength of even the strongest dental ceramic available on the market for 21.8% of the teeth tested. This study aimed to describe the stresses that teeth experience, and thus predict the stresses that future restorations on those teeth may experience. This approach may prove valuable in guiding clinicians in their material selection as well as the design of all-ceramic restorations.