Aditi Marie Diniz
A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose, either a therapeutic (to treat, augment, repair, or replace a tissue function of the body) or a diagnostic one. Biomaterials are widely used in dentistry.
Dental biomaterials are subjected to a very hostile environment, in which pH, salivary flow and mechanical loading fluctuate constantly and often rapidly. These challenges require substantial research and development to provide products for the clinician. Much of this is possible through the application of fundamental concepts of material sciences. Understanding properties of polymer ceramics and metal is crucial for their selection and design in dental restorations. It is important to know the comparative values properties in different restorative material; it is also essential to know quality of the supporting and investing hard and soft tissue.
Compatibility of Surgical Biomaterials and the Role of Synthetic Materials
The disciplines of biomaterials and biomechanics are complementary to the understanding of device-based function. The physical, mechanical, chemical, and electrical properties of the basic material components must always be fully evaluated for any biomaterial application because these properties provide key inputs into the interrelated biomechanical and biological analyses of function. It is important to separate the roles of macroscopic implant shape from the microscopic transfer of stress and strain along biomaterial–tissue interfaces. The macroscopic distribution of mechanical stress and strain is predominantly controlled by the shape and form of the implant device. One important material property related to design (shape and form) optimization is the elastic strain (one component of the elastic modulus) of the material.
The biocompatibility profiles of biomaterials used for the replacement or augmentation of biological tissues have always been a critical concern within the health care disciplines. Special circumstances are associated with dental implant prosthetic reconstruction of the oral-maxillofacial areas because the devices extend from the mouth, across the protective epithelial zones, and onto or into the underlying bone. The functional aspects of use also include the transfer of force from the occlusal surfaces of the teeth through the crown and bridge and neck-connector region of the implant into the implant for interfacial transfer to the supporting soft and hard tissues. This situation represents a very complex series of chemical and mechanical environmental conditions.
This most critical aspect of biocompatibility is, of course, dependent on the basic bulk and surface properties of the biomaterial. All aspects of basic manufacturing, finishing, packaging and delivering, sterilizing, and placing (including surgical placement) must be adequately controlled to ensure clean and non- traumatizing conditions. The importance of these considerations has been reemphasized through the concept and practice of osseointegration of endosteal root form implant systems.
The localized microscopic strain distribution is controlled more by the basic properties of the biomaterial (e.g., surface chemistry, microtopography, modulus of elasticity) and by whether the biomaterial surface is attached to the adjacent tissues. Engineering analyses of implant systems include optimization considerations related both to the design and to the biomaterial used for construction. Therefore, the desire to positively influence tissue responses and to minimize biodegradation often places restrictions on which materials can be safely used within the oral and tissue environments. Designs are often evolved for specific biomaterials because of the imposed environmental or restorative conditions.
Dental Resins
With the advancement in polymer science, new resin reinforced by means of fillers has been developed. In general, the properties of these composite resins are superior to those of conventional unfilled resins like acrylic resin. Historically, silicate cements were developed first as aesthetic material followed by acrylic resins, and then by composite resins.
Acrylic Resins: This type of unfilled direct resins have been largely replaced by the composite resins. Acrylic resins are reported to cause allergic reactions when used as denture base restorative material or provisional fixed partial denture resins. The primary risk of this material is an allergy in the form of contact dermatitis, or even anaphylactic reactions and their risk are the highest for dental professionals because of the frequent exposure to unpolymerized monomers. There is ample evidence that resins release unpolymerized component into the biological environment, although the release involved is not well-documented. The reaction may start shortly after insertion or manifested after a period of time.
Composite Resins: In material sciences it is defined as a product, which consists of at least two distinct phases normally formed by blending together components having different structures and properties. Composites are made by combining two or more dissimilar material in such a way that the resultant material has a property superior to any of its parental ones. Typical engineered composite materials include cement, concrete, reinforced plastics such as fibre reinforced polymer, metal composites and ceramic composites. Allergic reactions to composite resins may be related to contact allergy to formaldehyde formed in resin composite restorations. This formaldehyde found in chemically cured resins mainly produce lichenoid lesions on oral mucosa.
(Writer is a resident of Panaji, and currently an FY BTech student at Christ University)
