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Biomimetic dentistry

Introduction

• Biomimetic dentistry is based on the philosophy that the intact tooth in its ideal hues and shades and, more importantly, its intracoronal anatomy, mechanics and location in the arch, is the guide to reconstruction and the determinant of success.
• This approach is conservative and biologically sound and in sharp contrast to the porcelain fused- to-metal technique in which the metal casting with its high elastic modulus makes the underlying dentin hypo functional.
• The goal of biomimetics in restorative dentistry is to return all of the prepared dental tissues to full function by the creation of a-tissue bond that allows functional stresses to pass through the tooth, drawing the entire crown into the final functional biologic and esthetic result.
• Bio: meaning life and mimesis meaning imitation are from Greek.
•  Biomimetics is the field of scientific endeavor which attempts to design system and synthesize materials through biomimicry.
• It’s the concept of taking ideas from nature and implementing them in another technology such as engineering design computing etc.
• The subject matter of biomimetics is known by several names bionics, biognosis etc .
• Biomimectics is an emerging inter disciplinary field that combines information from the study of  biological structures and their function with physics mathematics chemistry and engineering in the development of principles that are important for the generation of novel synthetic materials and organs.

History

• The name biomimeitcs was coined by Ottoschmit in the 1950s. The term bionics coined by JackE.Steele in 1960 at continence in Dayton.
• The foundation of this broad new field has ancient roots. Replacing body parts goes back at least 2,500 years when bridges made them artificial teeth carved them the bones or oxen.
• Evidence of crude dental implants dates back to roman population of the first or second century AD and to pre-Columbian cultures of central and south America.
•  The first use of dental amalgam to repair decayed teeth was recorded in the Chinese literature in the year 659.
• The middle of 20^th century same sophisticated inventions in the heart pacemaker the artificial heart valve and hip and knee joint replacement historically organ and tissue loss have been treated by surgical reconstruction and more recently the use of mechanical devices such as kidney dialyzers and the transplantations of organs from one individual to another.

REGENERATION OF DENTAL STRUCTURES

Regeneration of the dentin pulp complex :-

• The recombinant human BMP2 and BMP4 can induce new dentin .
• Recombinant BMP delivered in a scaffold of demineralized dentin matrix induces classic tubular dentin in amputated pulp where as BMP delivered using reconstituted type I collagen matrix induces instead osteodentin .
• Reparative dentin is also induced on freshly cut healthy pulp tissue in nonhuman primate using recombinant human BMP7 with an insoluble type I collagen matrix.
• The size and shape of the inductive material controls the size and shaped of the reparative dentin.
• The reparative dentin appears initially with cellularand soft tissue inclusions a portion of which (comprising only about 20% of the reparative dentin ) subsequently changes into a more tubular form of matrix with associated odontablast like cells attached to the mass of a tubular matrix.
• Therefore the extra cellular matrix scaffolding is a critical component and a prerequisite to odontoblast differentiation and tubular dentin formation.

Periodontal regeneration :-

• The periodontium which consist of cementum PDL and alveolar bone functions to anchor the teeth to the jaws.
• The morphogenetic potential of BMPs makes them ideal candidates for use in periodontal regeneration o p t i m i z i n g  t h e r e s p o n s e o f s t e m cells to BMP induction requires the use of a delivery system that is conducive to the migration and attachment of the responding stem cells on to the scaffolding using a baboon model recombinant BMP7 and baboon type I collagen has been used as a biomimetic scaffold to regenerate surgically created function defects in molars.
•  The formation of alveolar bone and the creation of cementum and sharpey’s fibers inserted at the optimal orientation into the root surface.
• Platelet rich plasma (PRP) used in different surgical procedures.
• It consists of thrombocyte concentrates and high amounts of growth factors (GFs) especially platelet desired growth factor (PDGF), insulin like growth factor (IGF -I) and transforming growth factor (TGF- beta ) which are important in wound healing and regeneration combination of PRP and tricalcium phosphate can be used in the treatment of periapical inflammatory lesion.
• Platelet gel biotechnology a method which has all the components of “tissue engineering” techniques with healing process of guided tissue regeneration procedures (GTR) by multiplying the number of molecules that activate the healing response and by grafting in the host site various cell types among which stem cell host is applied to regenerative surgery of intrabony defects in patients with refractory g e n e r a l i z e d a g g r e s s i v e p e r i d o n t i t i s .

THE BIOMIMETIC PRINCIPLE IN RESTORATIVE DENTISTRY

• There are two major perspectives to which the term “biomimetic” is applied: a purist perspective that focuses on recreating biological tissues and a descriptive perspective that focuses on using materials that result in a mimicked biological effect.
• Although different, both share a common goal of mimicking biology in restoration. This has been an increasingly common goal for dentists and patients alike in achieving esthetic and functional dentistry.
•  The goal of biomimetics in restorative dentistry is to return all of the prepared dental tissues to full function by the creation of a hard tissue bond that allows functional stresses to pass through the tooth drawing the entire crown into the final functional biologic and esthetic result .
•  Bonded porcelain restorations are recommended to treat the most perilous situation ( non vital or fractured teeth) thus avoiding the use of intraradiucular parts or full coverage crowns e.g.- inlay onlay laminates cemented with the adhesive resins .
• Biomimetic dentistry techniques provide the patient with minimally invasive options that conserve sound tooth structure as a clinical imperative.
•  Biomimetics is essentially described as a mimicking of natural life, which can be accomplished using contemporary composite resins and adhesive dental procedures.
• Conservation and biological mimicry make up the foundation of a biomimetic philosophy and together produce the effect that today’s patients expect.
• From an esthetic/restorative perspective, biomimetics or biomimicry is the application of methods and systems to artificially replace biologic elements in order to recreate optimal oral health.
•  Practicing interdisciplinary esthetic restorative dentistry enables dentists to achieve biomimetic results with cosmetic dentistry.
•  These techniques and materials are crucial to modern dentistry in that they combine a focus on dental health and appearance.
• A biomimetic material should match the part of the tooth that it’s replacing in several important ways, including the modulus of elasticity and function of the respective areas (e.g., pulp, dentin, enamel, dentoenamel junction)
• The low elastic modules of most composites can never fully compensate for the loss of strong proximal enamel ridges especially in extremely large class II restorations .
• In these situations including those with cusp coverage indirect ceramic inlays onlays seem to be best alternative .
•  In case of total occlusal coverage in vital teeth with a short clinical crown ceramic indirect overlays are indicated. .
• With the development of improved adhesives and immediate dentin sealing the use and indications for base lines have decreased.
• This group of materials traditionally performs many different function including the partial lining as a biologic protection for deep preparation areas the total lining for the dentin insulation against chemical or thermal injuries and the dentin replacement as a base prior to further restoration procedures.
• The indication for placing a linear under on adhesive restoration is mainly for pulp protection in the form of a partial lining using Ca (OH2) cements.
• Modern adhesives are capable replacing the total living function of former varnishes and cements.
•  Base materials are mainly indicated to reduce the volume of the inlay/ onlay (e.g.- excessive depth ) and to create an adequate preparation geometry by providing an even cavity floor and filling up internal undercuts .
• Endodontically treated teeth are more susceptible to fracture not because of pulp removal but due to the increased strain resulting them tooth substance loss.
• For posterior teeth total cuspal coverage with porcelain is recommended as it will significantly stiffen the crown and increase cusp stabilization for vital teeth
• .A composite resin base in indicated to reduce the volume of the inlay/onlay and to create an adequate preparation geometry (by providing an even cavity floor and filling up internal undercuts)

DEVELOPMENT OFARTIFICIAL SALIVARY GLAND

• Many people suffer a loss of salivary gland function as a result of radiation treatment for head and neck cancer, and also many people affected for sjogren’s syndrome an autoimmune disease whose symptoms include dry mouth and dry eyes without adequate saliva patient may experience difficulty in speaking, chewing and swallowing.
• The application of state – of – the- art methodologies include the use of adult and embryonic stem cells for the regeneration of the salivary glands, parenchyma and restorations of its secretary functions.
• Efforts have focused on creating a rather simple device a “blind- endtube” suitable to graft in the buccal mucosa of patients whose salivary parenchyma has been destroyed.
• The lumen of these tubes would be lined with compatible epithelial cells and be physiologically capable of unidirectional water movement. A realistic opportunity to develop a first generation artificial salivary gland suitable for clinical testing is believed to exists.

BIOMATERIALS

• According to Douglas A. Terry, DDS, in dentistry there is no one biomaterial that has the same physical, mechanical and optical  properties as tooth structure (i.e., dentin, enamel, cementum) and possesses the physiological characteristics of intact teeth in function.
•  By utilizing biomimetic therapeutic approaches, dentists can improve and become closer to natural biological structures and their function
• Synthetic Polymer: The polymer can be biodegradable or non degradable .biodegradable polymers include polylactic acid and polyglycolic acid and co polymers.
•  These polymers are used as suture materials but are also being examined for usage such as bone ,skin and liver substitutes.
• These polymers are broken down in the body hydrolytically to produce lactic acid and glycolic acid.
• Newer biomaterials are polyanhydrites, Polyphosphazenes. Polymethyl Methacrylate(PMMA),Polytetrafluoroethylene(PTFE)andPMMA, polyhydroxyethylmethacrylate (PHEMA) may be described as alloplastic , synthetic, Nonbiodegradable polymers.
• PMMA used for dentures and as a cement for many orthopedic prosthesis. PTFE used for augmentation and guided bone regeneration.

CERAMICS

• It is used in dental applications and are being examined for bone tissue engineering application.
• Two common ceramics used in dentistry and hip prosthesis are alumina and hydroxyapatite.
• Alumina has excellent corrosion resistance, high strength, high wear resistance.
• Hydroxyapatite is a calcium phosphate based ceramic and it is a major component of inorganic compartment of bone.
• Advantages of a BioMimetic crown

• Less healthy tooth structure is removed.

• Less potential chances of damaging the nerve inside the tooth.

• T he visual look of the restoration is identical to the natural tooth structure.

• Chances of decay getting under the restoration are small compared to a conventional crown.

• Disadvantages of a BioMimetic crown

• There is the possibility that the porcelain crown could fracture.

• T here is the possibility that the porcelain crown could de-bond (fall off) the tooth. This would require a new crown to be made.

BIOMIMETIC PRINCIPLES IN DENTAL IMPLANT

• Biomimetic dental implants may be the next development in the field.
• A variety of biomimetic coatings may prove helpful for application in individual patients.
•  For example, coating implants with factors known to induce endothelial cell differentiation and proliferation may promote greater vascularity in highly cortical bone, thereby improving conditions for early and long-term (in response to functional loading) bone remodelling.
• Ceramics such as the calcium phosphate hydroxyappatite and various types of aluminum oxides are proved to be bio compatible and they are coated to implant which increases osteointegration.
• Coating implants with pharmacological agents such as bisphosphonates6 may be a way of locally improving bone density in highly cancellous bone.
• Coating implants with BMPs may also accelerate initial healing times during integration of the dental implant, thereby reducing overall treatment times and improving implant success rates.
• Experimental investigations with a BMP known as recombinant human BMP-2 (rhBMP-2) in animal models have shown that it promotes initial integration of dental implants and “rescues” implants affected by experimentally induced peri-implant bone loss.
•  Modifying the surface characteristics of the implant can promote migration of mesenchymal cells to the implant surface, enhance attachment and proliferation of these cells, and, in some instances, stimulate osteoblastic differentiation.

SCOPE

• Biologist study biomimetics not only for an understanding of the biological processes but also to trace the evolution of various classes of organism biochemist have interest in the field due to the complexities associated with the interaction of biopolymers with ions of metal leading to the mineralization in living organisms.
• On the whole the field of biomimetics addresses more than one issue those engaged in this field of research activity try to mimic natural method of manufacture of chemicals in order to create new ones, learn new principles from phenomenon observed in nature, reproduce mechanism found in nature and copy the principles of synthesizing materials under ambient conditions and with easily available raw materials.
•  Design of biodegradable scaffolds to serve as platforms for cells to organize tissues for repair and regeneration of teeth and periodontal tissues.
• Develop biodegradable synthetic polymers for gene therapy identify isolate culture and characterize multipotent stem cells for adult tissues type for repair of TMJ associated structures.

CONCLUSION

• There is a need for a firmer scientific and technical basis in order to develop the next generation of medical implants that are safe reliable smart and long lasting integrated and multidisciplinary research should advance our understanding of biological system and provide the basis for the design and development of normal synthetic medical materials that are compatible with the environment of the host and significantly increase the functional life time of implants.
• Future advances in this field will require materials and computer scientist, physicists, bioengineers, clinicians, biologist and industries working together towards a shared vision rather than pursuing their separate objectives