Dental reconstruction

Progressive dental reconstructions within the life-time of a patient, and in particular the use of different alloys for total or partial dentures, for dental fillings, for porcelain-fused restorations, and transcutaneous implants, generate unavoidable oral polymetallism. Indeed, two alloys of different composition have different electric potentials and inevitably induce corrosion and subsequently the release of metal ions into the human organism (Bundy 1994 Homez et al. 2000). 

To date, glass-ceramics have been used clinically for only limited applications. These include material for filling bony defects along the lines of a bone graft (Pavek et al., 1994), reconstruction of the ossicular bones (Hughes, 1987), spine reconstruction (Yamamuro and Shimizu, 1994), and dental reconstruction (Kudo et al., 1990 Yukna et al., 2001). 

SmartBone is a bone substitute used in maxillofacial and dental reconstruction. It is a class III MD. Industrie Biomediche Insubri SA, the manufacturer of this product, uses aliphatic polyesters to reinforce the fragile mineral bone matrix. This polymer is also involved in protection from an inflammatory reaction during the first days postsurgery. The choice of the polymer is critical and should have the following characteristics ... 

The excellent performance of GICs as dental materials has lead to their evaluation as biocompatible bone reconstruction materials. Initial results from in vivo and in vitro studies appear very promising [253-257]. 

The use of hydrogels in the preparation of scaffolds for other applications such as dental pulp tissue replacement or mandible condylar reconstruction has also been tackled. 

A portion of the dental papilla (DP) shows odontoblasts (Ob) adjacent to early dentine (D). E enamel, DF dental follicle outside the outer epithelium, AB alveolar bone. Scale bar = 70 pm (From Fig. 1 in Cerri PS, de Faria FP, Villa RG, et al. (2004) Light microscopy and computer three-dimensional reconstruction of the blood capillaries of the enamel organ of rat molar tooth germs. Journal of Anatomy 204 191-195. 

Behr et al. (2006) showed the benefits of electron-beam curing of glass-fibre-reinforced-composite veneer specimens for dental applications. Under electron-beam cure the reconstructions became stiffer and resisted higher load. 

The application of polymeric materials in medicine is a fairly specialized area with a wide range of specific applications and requirements. Although the total volume of polymers used in this application may be small compared to the annual production of polyethylene, for example, the total amount of money spent annually on prosthetic and biomedical devices exceeds 16 billion in the United States alone. These applications include over a million dentures, nearly a half billion dental fillings, about six million contact lenses, over a million replacement joints (hip, knee, finger, etc.), about a half million plastic surgery operations (breast prosthesis, facial reconstruction, etc.), over 25,000 heart valves, and 60,000 pacemaker implantations. In addition, over AO,000 patients are on hemodialysis units (artificial kidney) on a regular basis, and over 90,000 coronary bypass operations (often using synthetic polymers) are performed each year (]J. 

Other biomedical applications of polymers include sustained and controlled drug delivery formulations for implantation, transdermal and trans-cornealuses, intrauterine devices, etc. (6, 7). Major developments have been reported recently on the use of biomaterials for skin replacement (8), reconstruction of vocal cords (9), ophthalmic applications such as therapeutic contact lenses, artificial corneas, intraocular lenses, and vitreous implants (10), craniofacial, maxillofacial, and related replacements in reconstructive surgery (I), and neurostimulating and other electrical-stimulating electrodes (I). Orthopedic applications include artificial tendons (II), prostheses, long bone repair, and articular cartilage replacement (I). Finally, dental materials and implants (12,13) are also often considered as biomaterials. 

Fully densified bodies of hydroxylapatite have been employed for reconstruction of the middle ear (Shinohara et al. 2000), dental root implants (Ogiso 1998) and skull reconstruction (Koyama et al. 2000). 

Other important applications of poly(VPA) and its copolymers are as polymer electrolyte membranes for fuel cells,in the medical field as components in dental cements,bone reconstruction, hydrogels for drug delivery, and in ion exchange membranes. ... 

Alumina and zirconia ceramics are also being used for alveolar ridge reconstruction (20), maxillofacial reconstruction, as ossicular bone substitutes (21), and in ophthalmology (22), knee prosthesis (8), bone screws as well as other applications as dental biomaterials, such as dental crown core, post, bracket and inlay (23,24). 

---