Publications by authors named "Kourosh Nakhaei"

9 Publications

  • Page 1 of 1

Ultraviolet Light Treatment of Titanium Enhances Attachment, Adhesion, and Retention of Human Oral Epithelial Cells via Decarbonization.

Materials (Basel) 2020 Dec 31;14(1). Epub 2020 Dec 31.

Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, CA 90095, USA.

Early establishment of soft-tissue adhesion and seal at the transmucosal and transcutaneous surface of implants is crucial to prevent infection and ensure the long-term stability and function of implants. Herein, we tested the hypothesis that treatment of titanium with ultraviolet (UV) light would enhance its interaction with epithelial cells. X-ray spectroscopy showed that UV treatment significantly reduced the atomic percentage of surface carbon on titanium from 46.1% to 28.6%. Peak fitting analysis revealed that, among the known adventitious carbon contaminants, C-C and C=O groups were significantly reduced after UV treatment, while other groups were increased or unchanged in percentage. UV-treated titanium attracted higher numbers of human epithelial cells than untreated titanium and allowed more rapid cell spread. Hemi-desmosome-related molecules, integrin β4 and laminin-5, were upregulated at the gene and protein levels in the cells on UV-treated surfaces. The result of the detachment test revealed twice as many cells remaining adherent on UV-treated than untreated titanium. The enhanced cellular affinity of UV-treated titanium was equivalent to laminin-5 coating of titanium. These data indicated that UV treatment of titanium enhanced the attachment, adhesion, and retention of human epithelial cells associated with disproportional removal of adventitious carbon contamination, providing a new strategy to improve soft-tissue integration with implant devices.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ma14010151DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7796045PMC
December 2020

UV-Photofunctionalization of Titanium Promotes Mechanical Anchorage in A Rat Osteoporosis Model.

Int J Mol Sci 2020 Feb 12;21(4). Epub 2020 Feb 12.

Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, CA 90095-1668, USA.

Effects of UV-photofunctionalization on bone-to-titanium integration under challenging systemic conditions remain unclear. We examined the behavior and response of osteoblasts from sham-operated and ovariectomized (OVX) rats on titanium surfaces with or without UV light pre-treatment and the strength of bone-implant integration. Osteoblasts from OVX rats showed significantly lower alkaline phosphatase, osteogenic gene expression, and mineralization activities than those from sham rats. Bone density variables in the spine were consistently lower in OVX rats. UV-treated titanium was superhydrophilic and the contact angle of ddHO was ≤5°. Titanium without UV treatment was hydrophobic with a contact angle of ≥80°. Initial attachment to titanium, proliferation, alkaline phosphatase activity, and gene expression were significantly increased on UV-treated titanium compared to that on control titanium in osteoblasts from sham and OVX rats. Osteoblastic functions compromised by OVX were elevated to levels equivalent to or higher than those of sham-operated osteoblasts following culture on UV-treated titanium. The strength of in vivo bone-implant integration for UV-treated titanium was 80% higher than that of control titanium in OVX rats and even higher than that of control implants in sham-operated rats. Thus, UV-photofunctionalization effectively enhanced bone-implant integration in OVX rats to overcome post-menopausal osteoporosis-like conditions.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/ijms21041235DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7072956PMC
February 2020

Ultraviolet Light Treatment of Titanium Suppresses Human Oral Bacterial Attachment and Biofilm Formation: A Short-Term In Vitro Study.

Int J Oral Maxillofac Implants 2019 September/October;34(5):1105–1113. Epub 2019 Feb 26.

Purpose: Antibacterial dental implants and related prosthetic components could help to reduce infection and prevent peri-implantitis. The purpose of this study was to determine the effect of ultraviolet (UV) light treatment of titanium on biofilm formation of human oral bacteria.

Materials And Methods: Machine-prepared commercially pure titanium disks were treated with UV light for 12 minutes. Human oral bacteria were seeded onto untreated and UV-treated disks. Early bacterial attachment to titanium was assessed at 12 hours. Surface topography of initial biofilms was evaluated by 3D scanning electron microscopy at 24 hours. The quantity and morphology of subsequent colony development and biofilm formation were examined by confocal laser scanning microscopy for up to 7 days.

Results: Throughout the time course, significantly fewer bacterial cells attached to UV-treated titanium surfaces compared to untreated ones. While biofilm developed rapidly to a final thickness of about 16 μm by day 3 on untreated titanium, on UV-treated surfaces it remained below 8 μm, even at day 7. Similarly, UV treatment resulted in 70% less exopolysaccharides (EPS) volume than on untreated surfaces at day 7. This is consistent with the finding that EPS production per cell was significantly lower on UV-treated surfaces. Untreated titanium surfaces covered with biofilm were 5-fold rougher than the original machined surface, while UV-treated surfaces remained 2-fold rougher due to a significantly less biofilm formation.

Conclusion: UV treatment of titanium surfaces significantly reduces attachment of human oral bacteria and subsequent biofilm formation as well as EPS production for at least 7 days. UV treatment prevented the escalation of surface colonization, mitigating an unfavorable bacteriophilic cascade and environmental trigger for biofilm formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.11607/jomi.7444DOI Listing
December 2019

Ultraviolet treatment restores bioactivity of titanium mesh plate degraded by contact with medical gloves.

J Oral Sci 2018 ;60(4):567-573

Division of Advanced Prosthodontics, Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry.

Titanium mesh plate (Ti mesh) used for bone augmentation inadvertently comes into contact with medical gloves during trimming and bending. We tested the hypotheses that glove contact degrades the biological capability of Ti mesh and that ultraviolet treatment (UV) can restore this capability. Three groups of Ti mesh specimens were prepared: as-received (AR), after glove contact (GC), and after glove contact followed by UV treatment. The AR and GC meshes were hydrophobic, but GC mesh was more hydrophobic. AR and GC meshes had significant amounts of surface carbon, and Si content was higher for GC mesh than for AR mesh. UV mesh was hydrophilic, and carbon and silicon content values were significantly lower in this group than in the AR and GC groups. The number, alkaline phosphatase activity, and mineralization ability of attached osteoblasts were significantly lower in the GC group than in the AR group and markedly higher in the UV group than in the AR group. In conclusion, glove contact caused chemical contamination of Ti mesh, which significantly reduced its bioactivity. UV treatment restored bioactivity in contaminated Ti mesh, which outperformed even the baseline Ti mesh.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2334/josnusd.17-0443DOI Listing
May 2019

Biological and osseointegration capabilities of hierarchically (meso-/micro-/nano-scale) roughened zirconia.

Int J Nanomedicine 2018 8;13:3381-3395. Epub 2018 Jun 8.

Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, CA, USA.

Purpose: Zirconia is a potential alternative to titanium for dental and orthopedic implants. Here we report the biological and bone integration capabilities of a new zirconia surface with distinct morphology at the meso-, micro-, and nano-scales.

Methods: Machine-smooth and roughened zirconia disks were prepared from yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), with rough zirconia created by solid-state laser sculpting. Morphology of the surfaces was analyzed by three-dimensional imaging and profiling. Rat femur-derived bone marrow cells were cultured on zirconia disks. Zirconia implants were placed in rat femurs and the strength of osseointegration was evaluated by biomechanical push-in test.

Results: The rough zirconia surface was characterized by meso-scale (50 µm wide, 6-8 µm deep) grooves, micro-scale (1-10 µm wide, 0.1-3 µm deep) valleys, and nano-scale (10-400 nm wide, 10-300 nm high) nodules, whereas the machined surface was flat and uniform. The average roughness (Ra) of rough zirconia was five times greater than that of machined zirconia. The expression of bone-related genes such as collagen I, osteopontin, osteocalcin, and BMP-2 was 7-25 times upregulated in osteoblasts on rough zirconia at the early stage of culture. The number of attached cells and rate of proliferation were similar between machined and rough zirconia. The strength of osseointegration for rough zirconia was twice that of machined zirconia at weeks two and four of healing, with evidence of mineralized tissue persisting around rough zirconia implants as visualized by electron microscopy and elemental analysis.

Conclusion: This unique meso-/micro-/nano-scale rough zirconia showed a remarkable increase in osseointegration compared to machine-smooth zirconia associated with accelerated differentiation of osteoblasts. Cell attachment and proliferation were not compromised on rough zirconia unlike on rough titanium. This is the first report introducing a rough zirconia surface with distinct hierarchical morphology and providing an effective strategy to improve and develop zirconia implants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2147/IJN.S159955DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5997135PMC
July 2018

Biological and Physicochemical Characteristics of 2 Different Hydrophilic Surfaces Created by Saline-Storage and Ultraviolet Treatment.

Implant Dent 2018 Aug;27(4):405-414

Professor, Division of Advanced Prosthodontics, Weintraub Center for Reconstructive Biotechnology, UCLA School of Dentistry, Los Angeles, CA.

Objectives: Hydrophilicity/hydrophobicity of titanium surfaces may affect osseointegration. Ordinary titanium surfaces are hydrophobic. Recently, 2 different methods of storing titanium in saline solution or treating it with ultraviolet (UV) light were introduced to generate surface hydrophilicity. This study compared biological and physicochemical properties of 2 different hydrophilic titanium surfaces created by these methods.

Materials: Acid-etched control, saline-stored, and UV-treated titanium surfaces were assessed by scanning electron microscopy, energy dispersive spectroscopy, and x-ray photoelectron spectroscopy. The attachment, spreading behaviors, mineralization, and gene expression of osteoblasts were examined.

Results: Similar microroughness was found on control and UV-treated surfaces, whereas foreign deposits were observed on saline-stored surfaces. Control and UV-treated surfaces consisted of Ti, O, and C, whereas saline-stored surfaces showed Na and Cl in addition to these 3 elements. Atomic percentage of surface carbon was higher in order of control, saline-stored, and UV-treated surfaces. Osteoblasts cultured on saline-stored surfaces showed higher levels of calcium deposition and collagen I expression than control. Osteoblasts on UV-treated surfaces showed significantly increased levels for all parameters related to cell attachment, cell spreading, the expression of adhesion and cytoskeletal proteins, mineralization, and gene expression compared with control, outperforming saline-stored surfaces for most parameters.

Conclusion: Despite similar hydrophilicity, saline-stored and UV light-treated surfaces showed substantially different biological effects on osseointegration, associated with different surface chemistry and morphology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/ID.0000000000000773DOI Listing
August 2018

Effect of UV Photofunctionalization on Osseointegration in Aged Rats.

Implant Dent 2016 Dec;25(6):744-750

*Visiting Scholar, Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, CA; Research Assistant, Department of Partial Denture Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan. †Visiting Scholar, Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, CA. ‡Associate Professor, Department of Partial Denture Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan. §Professor, Weintraub Center for Reconstructive Biotechnology, Division of Advanced Prosthodontics, UCLA School of Dentistry, Los Angeles, CA.

Objectives: This study evaluated the effect of photofunctionalization on osseointegration under the biologically adverse conditions of aging.

Materials: First of all, bone marrow-derived osteoblastic cells from young (8 weeks old) and aged (15 months old) rats were biologically characterized. Then, the osteoblasts from aged rats were seeded on titanium discs with and without photofunctionalization, and assessed for initial cell attachment and osteoblastic functions. Titanium mini-implants, with and without photofunctionalization, were placed in the femur of aged rats, and the strength of osseointegration was measured at week 2 of healing. Periimplant tissue was examined morphologically and chemically using scanning electron microscopy and energy dispersive x-ray spectroscopy, respectively.

Results: Cells from the aged rats showed substantially reduced biological capabilities compared with those derived from young rats. The cells from aged rats showed significantly increased cell attachment and the expression of osteoblastic function on photofunctionalized titanium than on untreated titanium. In addition, the strength of osseointegration was increased by 40% in aged rats carrying the photofunctionalized implants. Robust bone formation was observed around the photofunctionalized implants with strong elemental peaks of calcium and phosphorus, whereas the tissue around untreated implants showed weaker calcium and phosphate signals than titanium ones.

Conclusion: These in vivo and in vitro results corroboratively demonstrate that photofunctionalization is effective for enhancing osseointegration in aged rats.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/ID.0000000000000459DOI Listing
December 2016

Multiple vascular malformations in head and neck - Rare case report.

J Oral Maxillofac Pathol 2014 Jan;18(1):137-42

Department of Oral and Maxillofacial Surgery, Sri Rajiv Gandhi College of Dental Sciences and Hospital, Bangalore, Karnataka, India.

Multiple venous malformations (VMs) pose some of the most difficult challenges in the practice of medicine today. Clinical manifestations of these lesions are extremely protean. Because of the rarity of these lesions, experience in their diagnosis and management by most clinicians is limited. This augments the enormity of the problem and can lead to misdiagnoses, inadequate treatment, high complication rates and poor patient outcomes. Because these lesions can recur, removal of the nidus is the main priority. Vascular malformations are best treated in medical centers where patients with these maladies are seen regularly and the team approach is utilized. The presence of intralesional nerve in arteriovenous malformation (AVM) and sometimes in VMs, as reported in this study, provides an additional diagnostic criterion that is simple and reliable and can be readily used to differentiate VMs from hemangiomas.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4103/0973-029X.131944DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4065433PMC
January 2014

Oral verruciform xanthoma: a case report and literature review.

Case Rep Dent 2013 16;2013:528967. Epub 2013 Dec 16.

Sri Rajiv Gandhi College of Dental Sciences and Hospital, Cholanagar, RT Nagar, Bangalore 560032, India.

Verruciform xanthoma is a benign mucocutaneous, uncommon, nonsymptomatic lesion of uncertain etiopathology, which occurs mostly on the oral mucosa of middle-aged individuals. Histopathologically, VX is diagnosed by presence of lipid-laden foam cells in papillary region of connective tissue. A 60-year-old male patient presented with a painless growth on the left buccal mucosa. On clinical examination a yellowish white exophytic lesion, measuring 11 × 7 mm in size, was found, which was cauliflower-shaped on inspection and painless on palpation. Histopathological examination revealed varying degrees of surface parakeratosis and the accumulation of numerous foam cells in the connective tissue papillae among the uniformly elongated epithelial ridges. On immunohistochemical staining, there was a neutrophilic infiltrate of the epidermis with CD68 positive xanthoma cells restricted to the papillary dermis, mixed with other chronic inflammatory cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1155/2013/528967DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3876769PMC
January 2014