Biodontics

Biodontics is the developing branch of dentistry that repairs, restores, and replaces dental, oral, and craniofacial structures with natural biological materials of cellular origin and it will replace xenodontics, the practice of dentistry that uses foreign materials (e.g, metals and plastics) for this purpose.

Materials with cellular origin used in tissue engineering are the adult stem cells and not the contentious embryonic stem cells These cells have distinctive properties of:

• Self-renewal: Stem cells can proliferate themselves almost indefinitely.
• Differentiation: Stem cells can metamorphose into cells with specialized characteristics and function. Teeth produced from stem cells are known as tissue-engineered teeth.

Major factors that play a role in tissue engineering

Morphogenic signals

Growth factors and differentiation factors play an important role in multiplication and differentiation of stem cells. BMPs (bone morphogenic proteins),which are the multifunctional growth factors, belong to the transforming growth factor beta superfamily and cytokines of the immune system play a vital part in organogenesis, e.g. in differentiation of dental pulp stem cells into odontoblasts which is the main requirement of teeth tissue engineering.

Responding stem cells

They are initially attained from the patient and preserved under good conditions to uphold their distinctive capability to differentiate into a wide ranging cells, are later coaxed in the lab to transform it into a tooth bud.

Scaffold

• It provides a mechanical support to the cells required for regeneration of any tissue and it has to be biodegradable and speed of degradation has to coincide with the speed of tissue development. The scaffold has to be permeable which aids in cell nutrition, proliferation and migration for tissue vascularization as well as formation of new tissues. Mechanical stability of the implant is improved by the porous surface by the mechanical interlocking between the scaffolds and surrounding tissues.
• Titanium scaffolds are bio-compatible and suitable for hard-tissue applications, such as the growth and differentiation of rat dental pulp progenitor cells into odontoblast-like cells. To improve their efficacy, metal scaffolds can be covered with biological compounds, like titanium fibres pre-coated with extracellular matrix (ECM) components that support the osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs). A second class of scaffold is naturally occurring organic material that provides a bio-mimetic environment for stem cells.
• Natural scaffolds provide mechanical strength. Additionally, they can contain biological agents that influence stem cell fate.
• Scaffold having a biocompatible configuration and a porous structure, adult stem cells and their differentiated progeny, signalling molecules to regulate stem cell fate comprising covalently bound ligands and controlled release agents incorporated into scaffold design, physical forces for the stimulation of spatial organization and differentiation, and microvasculature comprising endothelial progenitor cells to ameliorate tissue survival.

Mechanical Forces

After embedding stem cells in a 3D scaffold, physical forces lead to spatial organization and differentiation, simulating signs the cells receive in vivo. Human BMSCs in hyaluronan-gelatin scaffolds, in the presence of chondrogenic medium show more cartilaginous matrix formation when the scaffolds are exposed to cyclic physical compression than do uncompressed samples.

Various methods can be followed in building a bio tooth. They are:

• By the reconstruction of a mature tooth as is evident in the oral cavity.
• By the replication of embryonic evolution in the oral cavity.
• By the induction of third dentition.
• A scaffold in the shape of tooth is created, few cells are placed in the scaffold and are allowed to grow.

Recreate the Mature Tooth as is Evident in the Oral Cavity

The components of a tooth, i.e, crown, dental pulp, enamel and root are distinctly created from the materials and right embryonic cells. The disadvantage of this method is that the process has a high level of procedural difficulty. Contrarily, the advantage is a high level of control on the process and the possible automation and scale-up.

Inducing a Third Dentition

It works with the addition of molecules of either of the earlier two dentitions in the growth of initiating the de novo of the tooth after tooth loss or the de novo restraint or stimulation of candidate genes such as RUNX2 or USAG-1 could stimulate the third dentition so that new tooth formation is induced.

Build a Tooth Shaped Scaffold, Place few Cells in them, and let the Cells Grow

This method is highly productive, and practices tissue engineering procedure. It includes seeding of biodegradable scaffolding with cells, and generation of these tissues will mold on to the form of the scaffolding. These scaffolds can be used in several ways, and they may even be capable of regenerating teeth and other organs, but this concept is yet under research.

Formation of a Biotooth

• Biomembrane scaffolds are seeded with stem cells implanted in the jaw at socket or prepared site. (BMSC and DPSC) scaffold may be collagen hydrogel, chitosan, poly-LLactic acid, poly-L-Glycolic acid, HA+TCP8.
• Scaffold implantation done (Orthotopic or ectopic) by soak system, low pressure system, pipette system or syringe system. Osteogenic differentiation takes around 2 weeks.
• Osteogenic differentation-SDF1 and BMP 7 plays role in angiogenesis.
• Positional information and tooth morphogenesis (barx1, 3-D bioprinting, EDA, TRAF6) play role.
• Bone regeneration and alveolodental ligament regeneration.

Stem (somatic) Cells Storage

Stem cells can be stored as

1. Cryopreservation
2. Magnetic freezing

Uses in Dentistry

In the knowledge domain of dental research, stem cell study targeted towards the accomplishment of following; redevelopment of impaired coronal dentine, pulp, resorbed roots, cervical or apical dentine and alveolodental ligament; besides plugging of perforations, repair of craniofacial defects and whole tooth regeneration. Dental pulp stem cells (DPSCs) characterize a kind of adult cell colony which have the strong capability of self–renewal and multiline differentiation. These somatic cells appear to be the basis of odontoblasts that donate to the formation of dentin pulp complex. Few research works have evidenced that DPSCs have the capability of producing dental tissues in vivo including dentin, pulp and crown like structures, where as further research suggested that these stem cells can bring about formation of bonelike structures. Hypothetically, a biotooth produced from autogenous PSCs should be the best option for experimental tooth restoration. It was established by Granthos et al, that in both in vitro and in vivo, dental pulp stem cells (DPSCs) of animals were capable of forming ectopic dentin and associated pulp tissue. An in vivo stem cell transplantation system by Batouli et al was used to study differential regulatory mechanisms of bone marrow stromal stem cells (BMSCs) and DPSCs. It was found out that DPSCs were capable of generating a reparative dentine like tissue on the superficial part of human dentin in vivo.

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