Immunological and Regenerative Implications of Corrosion of Dental Materials

Tooth movement with appliances based on nickel and titanium has got great osteogenic potential and can regenerate deficient parts of alveolar bone and gingiva and rehabilitate compromised occlusal relations and a patient's masticatory function. Due to the extended duration of this therapy, different procedures are carried out and materials are applied for prevention and regeneration of damaged enamel and oral mucosa. The oral cavity may be considered a galvanic cell in which dental alloys act as electrodes, while saliva and oral preventive and regenerative agents act as electrolites. The interaction causes corrosion, reduction of elasticity and increase of stiffness of appliances, which may in turn result in excessive forces, a disruption of tissue regeneration and irreparable damage of tooth roots, surrounding alveolar bone, periodontal ligament, gingiva and pulp.

During the extended exposion, released corrosive products in surrounding tissues and those transported in saliva and blood may cause a series of side effects from hypersensitivity reactions and soft tissue proliferation to cyto and genotoxicity. Today, allergies are ever more frequent and arise earlier in life. A specific group are children and young adolescents in pubertal growth, a period in which the immune system develops. Nickel is one of the strongest contact allergens, present in numerous dental alloys. Nickel allergy is occurs in up to 28.5% of population and cannot be deemed as low potential risk anymore.

In contrast, titan was considered a biocompatible material of no allergic potential. However, there is an increase in the frequency of presentations of different hypersensitivity reactions to titan, especially in patients with pacemakers. Numerous patients with hip endoprostheses, stents, dental implans and orthodontic appliances are exposed to titan. Titan allergy may be the cause of unexplained cases of failure and rejection of dental implants. Nickel and titan could cause bacterial resistance to antibiotics which may complicate treatment of a series of infections that are more frequent in children and adolescents.

Regulations for safety of medical products regulate safety issues of materials through mandatory laboratory testing and expertise. However, the testing of interactions of these materials with newly formed materials for prevention of damage and regeneration of orodental tissues is not obligatory prior to the start of their commercial use. Such testing should be conducted by independent scientific insitutions and not by producers with direct commercial interest.

The aim of this project is to investigate:

• the corrosion of dental materials and appliances based on nickel and titan (in saliva and due to interaction with probiotics, remineralising agents and antiseptics)
• the immune potential of nickel and titan ions (development of allergies, changes in cariogenic potential of dental plaque, resistency of gingivitis to therapy, and bacterial resistance to antibiotics)
• the effect of nickel and titan ions cellular level
• changes in performance of dental appliances with repercussion on regeneration of bone and periodontal tissues.

Inclusion criteria

• patients with fixed orthodontic appliances
• must be able to do a mouthwash

Exclusion criteria

• patients allergic to fluoride agents and chlorhexidine gluconate