Applications of microscale technologies for regenerative dentistry

Abstract

While widespread advances in tissue engineering have occurred over the past decade, many challenges remain in the context of tissue engineering and regeneration of the tooth. For example, although tooth development is the result of repeated temporal and spatial interactions between cells of ectoderm and mesoderm origin, most current tooth engineering systems cannot recreate such developmental processes. In this regard, microscale approaches that spatially pattern and support the development of different cell types in close proximity can be used to regulate the cellular microenvironment and, as such, are promising approaches for tooth development. Microscale technologies also present alternatives to conventional tissue engineering approaches in terms of scaffolds and the ability to direct stem cells. Furthermore, microscale techniques can be used to miniaturize many in vitro techniques and to facilitate high-throughput experimentation. In this review, we discuss the emerging microscale technologies for the in vitro evaluation of dental cells, dental tissue engineering, and tooth regeneration.

Figure 1.

Tooth morphogenesis from the dental lamina to tooth eruption supported and directed by a complex network of signaling, signal transduction, and subsequent gene regulation (Slavkin and Bartold, 2006). Copyright 2006 © Periodontology 2000. Reproduced by permission.

Figure 2.

(top) Tissue engineering concept for dental pulp regeneration and maturation of damaged young tooth. (bottom) Engineering of representative dental pulp tissue at (A) low magnification (100x) and (B) high magnification (400x) grown in the mouse. (C) Histology of a dental pulp of a human third molar (control tooth) (Nör, 2006). Copyright 2006 © Operative Dentistry, Inc. Reproduced by permission.

Figure 3.

Development of a bioengineered mouse incisor. (a) Schematic of the procedure. Reconstituted tooth germ cells cultured for 2 days were separated into single primordia prior to implantation into the subrenal capsule, then transplanted into a tooth cavity. (b) A bioengineered incisor developed in a subrenal capsule environment for 14 days (left) and a tooth separated from reconstituted tissue in the subrenal capsule and used for transplantation (right). (c) Separation of individual primordia (dotted circle) from a bioengineered tooth germ that had been cultured for 2 days. (d) Histological images of the explants at 14 days after transplantation into a tooth cavity. Images from the control experiment (left) and transplants isolated from a single incisor primordium (center) and a single tooth developed in the subrenal capsule (right) are shown and at higher magnification (boxes) (Nakao et al., 2007). Copyright 2007 © Nature Methods. Reproduced by permission.

Figure 4.

(Top) Fabrication of hydrogel microfluidic devices without (left) and with cells (right). (Middle) Diffusion of fluorescent dye from a microchannel within a hydrogel (A), also shown in cross-section (B). (Bottom) Cell viability of AML-12 murine hepatocytes encapsulated in agarose channels after 0 (left) and 3 days (right). Live (green)/dead (red) staining. Survival decreases with increasing distance from the microchannel. The microchannel is shown in cross-section and outlined for visibility as a small white rectangleat bottom of the image (Ling et al., 2007). Copyright 2007 © Lab on a Chip. Reproduced by permission.

Figure 5.

Rapid screening of a variety of polymer biomaterials is made possible by the use of biomaterial microarrays. (Top A, B) Light microscopy of 500-micrometer spaced polymer spots. Human mesenchymal stem cells grown on the polymer array and stained with phalloidin for F-Actin. Approximately 60 cells per polymer spot. hMSC cells grown on polymer microarrays. (C-F) One million hMSCs were grown on the polymer microarray and then stained 48 hrs later for actin (green). The blue channel can be used to identify the location of polymers spots. (E) Close-up of triplicates of polymer composed of (top row).(F) Close-up of polymer spot with hMSC cells, actin (green), and DNA/nucleus (blue).Scale bar (100 mm) is shown in white (Anderson et al., 2005. Copyright 2005 © Biomaterials Reproduced by permission.