Keyvan Moharamzadeh

Tissue-engineered Oral Mucosa: a Review of the Scientific Literature

Tissue-engineered oral mucosal equivalents have been developed for clinical applications and also for in vitro studies of biocompatibility, mucosal irritation, disease, and other basic oral biology phenomena. This paper reviews different tissue-engineering strategies used for the production of human oral mucosal equivalents, their relative advantages and drawbacks, and their applications. Techniques used for skin tissue engineering that may possibly be used for in vitro reconstruction of human oral mucosa are also discussed.

Effect of resin matrix composition on the translucency of experimental dental composite resins

OBJECTIVES The purpose of this study was to investigate the effect of the resin matrix composition on the translucency of experimental dental composite resins. METHODS Three types of unfilled resin matrices (TEGDMA-, UDMA- and BisGMA-based) were formulated and light cured. In addition, six different experimental dental composite resins with constant filler loading but varying in the type of monomer and the content of BisGMA were fabricated. Discs of each test material with 15.5mm diameter and 1.0mm thickness were prepared (N=3) and light cured. Total and diffuse transmittance values for each sample were measured using a UV/VIS spectrophotometer with the range of readings from 380 to 700nm. Difference in color was measured using the CIE Lab system. RESULTS Statistical analysis by one-way ANOVA followed by Tukeys test showed that there was no statistically significant difference in transmittance values between the three unfilled resins. However, with the addition of filler, BisGMA-containing composite resins showed significantly higher transmittance values than the UDMA- and TEGDMA-based composite resins. Regression analysis revealed that there was a linear correlation between the percentage of BisGMA in the resin matrix and the total and diffuse translucency. SIGNIFICANCE The amount of BisGMA used in the resin matrix has a significant effect on the translucency of silica filler-containing dental composite resins.

Tissue-engineered Oral Mucosa

Advances in tissue engineering have permitted the three-dimensional (3D) reconstruction of human oral mucosa for various in vivo and in vitro applications. Tissue-engineered oral mucosa have been further optimized in recent years for clinical applications as a suitable graft material for intra-oral and extra-oral repair and treatment of soft-tissue defects. Novel 3D in vitro models of oral diseases such as cancer, Candida, and bacterial invasion have been developed as alternatives to animal models for investigation of disease phenomena, their progression, and treatment, including evaluation of drug delivery systems. The introduction of 3D oral mucosal reconstructs has had a significant impact on the approaches to biocompatibility evaluation of dental materials and oral healthcare products as well as the study of implant-soft tissue interfaces. This review article discusses the recent advances in tissue engineering and applications of tissue-engineered human oral mucosa.

Biocompatibility of Resin-based Dental Materials

Oral and mucosal adverse reactions to resin-based dental materials have been reported. Numerous studies have examined the biocompatibility of restorative dental materials and their components, and a wide range of test systems for the evaluation of the biological effects of these materials have been developed. This article reviews the biological aspects of resin-based dental materials and discusses the conventional as well as the new techniques used for biocompatibility assessment of dental materials.

Biologic Assessment of Antiseptic Mouthwashes Using a Three-Dimensional Human Oral Mucosal Model

BACKGROUND The biologic safety profile of oral health care products is often assumed on the basis of simplistic test models such as monolayer cell culture systems. We developed and characterized a tissue-engineered human oral mucosal model, which was proven to represent a potentially more informative and more clinically relevant alternative for the biologic assessment of mouthwashes. The aim of this study was to evaluate the biologic effects of alcohol-containing mouthwashes on an engineered human oral mucosal model. METHODS Three-dimensional (3D) models were engineered by the air/liquid interface culture technique using human oral fibroblasts and keratinocytes. The models were exposed to phosphate buffered saline (negative control), triethylene glycol dimethacrylate (positive control), cola, and three types of alcohol-containing mouthwashes. The biologic response was recorded using basic histology; a cell proliferation assay; 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide tissue-viability assay; transmission electron microscopy (TEM) analysis; and the measurement of release of interleukin (IL)-1beta by enzyme-linked immunosorbent assay. RESULTS Statistical analysis showed that there was no significant difference in tissue viability among the mouthwashes, cola, and negative control groups. However, exposure to the positive control significantly reduced the tissue viability and caused severe cytotoxic epithelial damage as confirmed by histology and TEM analysis. A significant increase of IL-1beta release was observed with the positive control and, to a lesser extent, with two of the tested mouthrinses. CONCLUSIONS The 3D human oral mucosal model can be a suitable model for the biologic testing of mouthwashes. The alcohol-containing mouthwashes tested in this study do not cause significant cytotoxic damage and may slightly stimulate IL-1beta release.

Mucotoxicity of dental composite resins on a tissue-engineered human oral mucosal model

OBJECTIVE Tissue-engineered human oral mucosal models have been developed for biocompatibility assessment of biomaterials. The aim of this study was to evaluate the biological effects of three different composite resin systems on a three-dimensional human oral mucosal model. METHODS Full-thickness oral mucosal models were engineered by air/liquid interface culture of a human oral keratinocyte cell line on a lamina propria composed of oral fibroblasts seeded into a porous scaffold. The surface of the tissue models was exposed to three types of experimental composite resins: a TEGDMA-based, a UDMA-based, and a BisGMA/TEGDMA (80:20)-based composite resin for 24h. The response of the engineered oral mucosa to the test materials was assessed using routine histology, the Alamar Blue tissue viability assay and IL-1beta release measured by ELISA. RESULTS Compared to the other materials tested, the TEGDMA-based composite resin caused significant damage to the oral mucosal model. Statistical analysis by one-way ANOVA followed by Tukeys analysis showed that there was a significant decrease in the viability of tissue models after 24h exposure to TEGDMA-based composite resin. Also exposure to TEGDMA-based composite resin significantly increased the amount of IL-1beta released from the oral mucosal model. CONCLUSION The 3D human oral mucosal model has the potential to be a more relevant and more informative model than monolayer cell culture systems for biocompatibility testing of dental materials. The results obtained from multiple-endpoint analysis of the oral mucosal model indicate significant mucotoxicity of high TEGDMA-containing composite resins.

Porous magnesium-based scaffolds for tissue engineering

Significant amount of research efforts have been dedicated to the development of scaffolds for tissue engineering. Although at present most of the studies are focused on non-load bearing scaffolds, many scaffolds have also been investigated for hard tissue repair. In particular, metallic scaffolds are being studied for hard tissue engineering due to their suitable mechanical properties. Several biocompatible metallic materials such as stainless steels, cobalt alloys, titanium alloys, tantalum, nitinol and magnesium alloys have been commonly employed as implants in orthopedic and dental treatments. They are often used to replace and regenerate the damaged bones or to provide structural support for healing bone defects. Among the common metallic biomaterials, magnesium (Mg) and a number of its alloys are effective because of their mechanical properties close to those of human bone, their natural ionic content that may have important functional roles in physiological systems, and their in vivo biodegradation characteristics in body fluids. Due to such collective properties, Mg based alloys can be employed as biocompatible, bioactive, and biodegradable scaffolds for load-bearing applications. Recently, porous Mg and Mg alloys have been specially suggested as metallic scaffolds for bone tissue engineering. With further optimization of the fabrication techniques, porous Mg is expected to make a promising hard substitute scaffold. The present review covers research conducted on the fabrication techniques, surface modifications, properties and biological characteristics of Mg alloys based scaffolds. Furthermore, the potential applications, challenges and future trends of such degradable metallic scaffolds are discussed in detail.

Development of bilayer and trilayer nanofibrous/microfibrous scaffolds for regenerative medicine

Many biomaterial scaffolds have been developed for use in tissue engineering usually for populating with a single cell-type. In this study we demonstrate the production of bilayer and trilayer nanofibrous/microfibrous biodegradable scaffolds suitable for the support, proliferation and yet segregation of different tissues - here used to separate soft tissue from bone forming tissue and keratinocytes from fibroblasts. Essentially we describe a nanofibre barrier membrane which is permeable to nutrients coupled with attached microfibers (either on one side or both sides) to support the proliferation of different cell types either side but prevents migration of cells across the barrier. Such membranes would be suitable for guided tissue regeneration in areas where one wishes to support both soft and hard tissues but keep them separated. We describe a sterile bilayer membrane electrospun from polyhydroxybutyrate-co-hydroxyvalerate (PHBV) (nanofibres) and polylactic acid (PLA) or poly ε-caprolactone (PCL) (microfibres) and a trilayer membrane electrospun in layers of PLA, PHBV, then PLA. These membranes are biocompatible, biodegradable and capable of supporting two different cell populations.

Development of a Novel Model for the Investigation of Implant–Soft Tissue Interface

BACKGROUND In dental implant treatment, the long-term prognosis is dependent on the biologic seal formed by the soft tissue around the implant. The in vitro investigation of the implant-soft tissue interface is usually carried out using a monolayer cell-culture model that lacks a polarized-cell phenotype. This study developed a tissue-engineered three-dimensional oral mucosal model (3D OMM) to investigate the implant-soft tissue interface. METHODS A 3D OMM was constructed using primary human oral keratinocytes and fibroblasts cultured on a skin-derived scaffold at an air-liquid interface. A titanium implant was inserted into the engineered oral mucosa and further cultured to establish epithelial attachment. The 3D OMM was characterized using basic histology and immunostaining for cytokeratin (CK) 10 and CK13. Histomorphometric analyses of the implant-soft tissue interface were carried out using a light-microscopy (LM) examination of ground sections and semi-thin sections as well as scanning electron microscopy (SEM). RESULTS Immunohistochemistry analyses suggests that the engineered oral mucosa closely resembles the normal oral mucosa. The LM and SEM examinations reveal that the 3D OMM forms an epithelial attachment on the titanium surface. CONCLUSION The 3D OMM provided mimicking peri-implant features as seen in an in vivo model and has the potential to be used as a relevant alternative model to assess implant-soft tissue interactions.

The biological seal of the implant–soft tissue interface evaluated in a tissue-engineered oral mucosal model

For dental implants, it is vital that an initial soft tissue seal is achieved as this helps to stabilize and preserve the peri-implant tissues during the restorative stages following placement. The study of the implant–soft tissue interface is usually undertaken in animal models. We have developed an in vitro three-dimensional tissue-engineered oral mucosal model (3D OMM), which lends itself to the study of the implant–soft tissue interface as it has been shown that cells from the three-dimensional OMM attach onto titanium (Ti) surfaces forming a biological seal (BS). This study compares the quality of the BS achieved using the three-dimensional OMM for four types of Ti surfaces: polished, machined, sandblasted and anodized (TiUnite). The BS was evaluated quantitatively by permeability and cell attachment tests. Tritiated water (HTO) was used as the tracing agent for the permeability test. At the end of the permeability test, the Ti discs were removed from the three-dimensional OMM and an Alamar Blue assay was used for the measurement of residual cells attached to the Ti discs. The penetration of the HTO through the BS for the four types of Ti surfaces was not significantly different, and there was no significant difference in the viability of residual cells that attached to the Ti surfaces. The BS of the tissue-engineered oral mucosa around the four types of Ti surface topographies was not significantly different.