# Nanomaterials in Craniofacial Tissue Regeneration: A Review
## 1 Introduction  
The interest of nanomaterials in dentistry is growing rapidly and has allowed for improvements in various biomedical applications, such as that of tissue regeneration [1]. Nanomaterials are materials whose components, in at least one dimension, measure 100 nm or less [2]. Sheets are nanomaterials in one dimension, nanowires and nanotubes are those in two dimensions, and quantum dots in three dimensions [2]. Nanomaterials can be synthesized either top-down (to scale down an existing structure to a nanoscale level) or bottom-up (to create by manipulating atoms and molecules) [3]. The enhanced utility of nanomaterials can be attributed to the physical and chemical properties of nanomaterials, such as strength, conductivity, color, and toxicity, which differ at the nanoscale size due to an increase in surface area and quantum effects [3].  
The application of a nanofiller material for restorations, in 2002, marked the first time that nanomaterials were used in dentistry [4]. By integrating the three principal elements of tissue engineering (stem cells, scaffolds, and signaling molecules) with the prospect of nanotechnology,nanostructured products that could provide mechanical support and promote biointegration for osteoblastic cell precursors were created [5]. Bone engineering scaffolds have been designed based on the following criteria: (1) The ability to mediate cell attachment, differentiation, and proliferation; (2) strong osteoconductivity with the host bone; (3) biodegradability; (4) mechanical strength; (5) porosity; (6) fabrication into irregular shapes; and (7) suitability for commercialization and clinical procedures [3]. As an example, scaffolds designed for the bone are to be rigid, while those designed for the pulp-dentin complex are to be soft and injectable [4].  
The incorporation of nanomaterials into dentistry has been associated with many potential benefits [6]. In areas of preventative health care, nanomaterials can exhibit antimicrobial and restorative properties, while in restorative dentistry, nanofillers can enhance the mechanical and bioactive properties of restoration materials [6]. Stem cell treatments or dental fillings, to contrast, do not provide protection against future dental diseases or restore the native tooth structure, respectively [1]. Additionally, the rejection rate of dental implants may be improved by the use of nanomaterials to increase osseointegration, infection control, and biocompatibility [6]. Although some studies have shown benefits of nanomaterials, others have shown no significant findings [6]. A drawback of nanomaterials, however, is the presence of low amounts of oral toxicity and of potential systemic disturbances caused by their translocation to the gut [6]. As nanomaterial-based studies become more prevalent for dentistry, the potential benefits and risks of nanomaterials as an alternative or complementary treatment should be considered and further examined.  
This review presents updates on the current state of nanomaterials used in craniofacial tissue regeneration: We examine the various types of nanomaterials, followed by a focus on specific clinical applications.