Polymers for Dental Restorative Applications

A particularly wide-spread application of non-biodegradable polymer systems is replacements for amalgam in dental restorations such as dental fillings. The utilization of polymer systems in dental restorations is typically determined by a) Mechanical durability b) bio-compatibility c) ease of application and d) aesthetic properties. The characteristics and performance of such dental restorative materials have been formalized via standards established by the

Fig. 2.3 Calcium alginate biopolymer microcapsules and tissue scaffolds in aqueous media (Courtesy: Desai et al., Invention Disclosure, NC A&T SU[11])

Fig. 2.3 Calcium alginate biopolymer microcapsules and tissue scaffolds in aqueous media (Courtesy: Desai et al., Invention Disclosure, NC A&T SU[11])

International Standards Organization and the American Dental Association [12-15].

Traditionally, methacrylate based photopolymerizable resins have been utilized since their introduction by R. F. Bowen [16,17]. Typically bis-Phenol A-glycidyl methacrylate (Bis-GMA) in combination with different fractions of Triethylene glycol dimethacrylate (TEGDMA) are photo-polymerized with visible light in the presence of suitable photo-initiators to create dental fillings. Such polymer based fillings possess two significant advantages in comparison to traditional amalgams. Firstly, they eliminate entirely the utilization of toxic heavy metals such as mercury in a biomedical application. Secondly, the optical characteristics of polymer systems enhance their aesthetic characteristics and these restorations essentially blend in with the surrounding dental structure. In comparison the amalgams are characterized by a typically metallic luster and thus, they do not compare well with the polymer systems. However, currently prevalent polymer-based dental restorations suffer significant shortcomings that have stimulated considerable amount of research. Polymeric systems are mechanically weaker and concomitantly much less durable than say, the traditional amalgams. In fact, it was determined that resin based restorations typically lasted ^7.8 years in comparison to ^12.8 years for amalgam based fillings [16].

The poor durability of the polymer systems can be traced to their intrinsically poor yield and fracture strengths, a typical characteristic of several metha-crylate-based polymers. Another debilitating aspect of these polymer systems is the shrinkage that accompanies the polymerization process. Such shrinkage would inevitably lead to the formation of gaps between the restoration and the surrounding dental structure. This leads to microleakage and the deposition and entrapment of fluids, food debris and microorganisms in the gap between the filling and the tooth. In turn, this can further engender tooth decay and overall failure of the restoration. Several developments recently have focused on overcoming these two limitations of dental restorative polymers by developing a) Reinforced polymers for improved strength and b) Low-shrinkage polymer systems for reduced microleakage.

0 0

Post a comment