Medical titanium alloys as biomedical materials in dentistry
June 05, 2024
Currently, Medical Titanium alloy is widely used in orthodontics, prosthodontics and implant dentistry in the field of dentistry.
(1) Orthodontics. Orthodontics is a science that refers to the correction of tooth misalignment through mechanical or functional instruments. In order to correct misaligned teeth, external forces must be applied through different instruments. The removable appliances consist of separated acrylic (PMMA) sheets that are fixed to the patient's teeth by means of filiform elements. Expansion screws (spindles with left-hand and right-hand threads) are used to separate the acrylic sheets and apply force to the teeth. In the fixation technique, shaped objects (brackets and oral tubes) are used to apply force to the teeth via filiform elements. Nowadays, in addition to stainless steel, pure titanium is used for fixation and as a fixation element due to its light weight and high corrosion resistance.
For arch wires and spring elements, titanium alloys are particularly attractive because they have a lower modulus of elasticity than stainless steel and a higher strength than Medical Grade Titanium. β-type titanium alloys have a tensile strength of up to 1,300 MPa after cold deformation. β-type alloys have better machinability, and they can even be produced in the form of fine filament components. Cold working state 4 grade pure titanium mechanical properties and β-type alloys are similar, thus can replace β-type alloys. In addition, titanium-nickel alloy wire shape memory alloy wire has been applied because of its pseudoelasticity, which is based on stress-induced martensitic phase transformation.
(2) Prosthetics. Prosthodontics refers to the use of prostheses to replace missing teeth or other parts in order to reproduce the masticatory function, aesthetic properties, and articulatory function of teeth. As a new material in the dental laboratory, titanium's early processing challenges have been solved, leading to increasingly successful applications in dental prosthetics.
Medical Titanium is used both as a general casting and as a ceramic-encrusted and tooth-bonded crown and bridge. Dental investment casting is often used to process Medical Titanium Bar components. For large structures with fixed implants, the electrochemical properties of cast titanium are comparable to those of industrially produced bone implants, mitigating the hazards of electrochemical and corrosive effects. In addition, titanium has economic advantages over gold-based alloys. Therefore, it is considered an ideal material for composite restorations, permanent restorations and removable restorations. Titanium has an extremely low coefficient of thermal expansion compared to other alloys with surface fused ceramics, thus requiring the inlay of a suitable ceramic. Titanium undergoes increased oxidation at elevated temperatures, grain and microstructure coarsening as well as a β-transformation at 882°C. Therefore, the maximum baking temperature for fused ceramics on titanium surfaces is 800°C.
(3) Implant dentistry. Implant dentistry refers to the transperiosteal or intraosseous implantation of (artificial) struts into the jawbone to fix a prosthesis in order to reproduce masticatory function, aesthetic characteristics and articulation. In modern dental surgery, intraosseous implants are a recognized method of disposition for replacing teeth, creating posts for permanent dentures, and stabilizing removable dentures. Titanium and titanium alloy dental implants have been used for more than forty years and are manufactured according to the appropriate standards. The surface of the implant is usually roughened by A1203 shot peening or titanium plasma flame treatment to promote adhesion of the implant to the bone. A localized layer of absorbable hydrocarbon-based apatite in the superficial area (cortical layer) will also promote adhesion of the implant to the bone in critical areas.
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