Commonly used implant abutment materials can be divided into 5 categories: Titanium (machining, polishing, laser etching), surgical grade stainless steel, cast gold alloy, zirconia, polyether ether ketone (PEEK), then how to make a reasonable choice in clinical practice What about the abutment material? The author mainly considers the following aspects.
1. Material Performance
Titanium is the only material that can perfectly combine toughness, lightweight, good biocompatibility, and durability with high strength. Titanium has higher corrosion resistance and the highest strength-to-weight ratio than any known element. The titanium abutment is made of industrial pure titanium or titanium alloy. Industrial pure titanium is widely used in medicine because of its corrosion resistance, high strength, and biocompatibility.
Adding a small amount of oxygen and iron will affect the mechanical properties of industrial pure titanium. By strictly controlling the addition of these ingredients, various grades (grade 1-4) of industrial pure titanium can be produced to meet different applications. Industrial pure titanium with the lowest oxygen and iron content is the easiest to process and shape, and gradually increasing the oxygen content can increase the strength of the material.
Titanium alloy (Ti-6Al-4V, Ti6Al4V, or Ti-6-4). Titanium alloy is also called grade five titanium. Titanium alloy contains 6% aluminum, 4% vanadium, 0.25% (maximum) iron, 0.2% (maximum) oxygen, and the rest is titanium. Ti-6Al-4V alloy is significantly stronger than industrial pure titanium and can provide higher tensile strength and fracture resistance.
Due to the unique physical characteristics, titanium abutments are the first choice for posterior dental implant restoration (Figure 3). These abutments can be pre-fabricated abutments or customized abutments for CAD/CAM grinding.
1.2 Surgical Stainless Steel
Surgical stainless steel is a special type of stainless steel used in the medical field, containing alloying elements such as chromium, nickel, and molybdenum. Stainless steel is easy to clean and disinfect, has high strength and corrosion resistance. Nickel-chromium-molybdenum alloys are sometimes used for implant abutments, but the immune system is potentially allergic to nickel. Surgical-grade stainless steel can be used as a temporary abutment, but it is not an ideal material for restoring abutments.
1.3 Casting Gold Alloy
The cast gold alloy composition of the implant abutment is 60%-65% gold, 20%-25% palladium, 19% platinum, and 1% iridium. The implant manufacturer recognized the limitations of the early “finished abutments” and developed a castable abutment called UCLA abutment
This abutment is composed of a machined gold alloy base and a plastic sleeve connected to it; the gold alloy base matches the implant; the plastic sleeve can be cut and modified to make wax molds for gold alloy casting. Since the end of the 1990s in the 20th century, there has been a consensus that compared with alumina (outdated all-ceramic materials) and titanium, the soft tissue reaction of gold and porcelain is inferior. These viewpoints come from the 1998 zoology study by Abrahamsson et al. Due to the results of this study, many clinicians completely reject the use of gold alloy cast abutments. Abrahamson and Welander’s later research (Welander et al., 2008) once again emphasized that compared with gold, titanium and zirconia have superior soft tissue response.
For different abutment materials, we will pay attention to their ability to form and maintain “implant closure”; from this point of view, gold alloys have disadvantages compared with titanium and zirconia, so try not to use them in clinical practice.
The main form that exists in nature is the mineral oblique zircon with a monoclinic crystal structure. Advances in biomaterials and ceramic manufacturing technology have enabled zirconia with high strength and good biocompatibility to be used in biomedical equipment and implant abutments. The application of yttrium oxide partially stabilized tetragonal polycrystalline zirconia (Y-TZP), powder injection molding (PIM), and hot isostatic pressing (HIP) is a sign of the development of zirconia. Other developments, such as the application of alumina toughened zirconia and cerium-doped zirconia, can prevent the aging progress of zirconia and control its influence to a minimum.
Due to its superior material properties and strength, zirconia materials can be used regardless of aesthetic considerations or high-load requirements (such as cases in aesthetic areas, posterior fixed restoration bridges, implant abutments, multi-unit implant restorations). Zirconia has high flexural strength, fracture toughness, and Young’s modulus, similar to steel. In addition to strength, the biggest advantage of zirconia is its excellent organizational integration ability. Various studies have confirmed the success of zirconia abutment in maintaining the stability of soft tissue and marginal bone. The results show that the type of abutment material affects the amount and texture of the surrounding tissue (comparison between zirconia and cast gold alloy). In addition, the zirconia abutment can greatly reduce the adhesion of bacteria and plaque and prevent soft tissue inflammation.
It is important to note that the modification and polishing of zirconia present challenges for dentists and technicians. Modification of the sintered zirconia component will significantly increase the risk of microcracks, which may cause cracks during the subsequent use of the masticatory function; the abutment-implant connection that has been used in clinics before is basically destroyed Eliminated, currently, it is often recommended to use zirconia abutment in combination with Ti-base, which is routinely used for planting restoration in aesthetic areas.
1.5 Polyetheretherketone (PEEK)
PEEK has become the most popular temporary abutment material. It is a beige or white organic polymer and crystalline thermoplastic with excellent mechanical properties and corrosion resistance. Young’s modulus is 3.6 GPa, and the tensile strength is 90～100 MPa. It has high thermal degradation resistance, and the ability to resist the corrosion of organic matter and humid environment.
These powerful properties make PEEK the perfect material for temporary abutments (Figure 7). As early as 1987, animal studies conducted by Williams et al. proved that PEEK materials are biocompatible. In 1995, Hunter et al. used PEEK, titanium, and chromium cobalt (CoCr) for plastic surgery and compared them; they found no difference in the attachment of fibroblasts or osteoblasts.
In the dental field, PEEK polymer is used for repair abutments and healing abutments; PEEK abutments are the first choice for temporary repair abutments or healing abutments. Although the research on PEEK polymer is limited, its application is promising.
The surface of the titanium abutment can be treated as a gold coating. The golden coating on the surface of the abutment is called titanium nitride. The titanium nitride coating is formed by titanium and nitrogen in the form of plasma, and then molecularly bonded to the titanium surface of the abutment
In the 1980s, titanium nitride was first used in the medical device industry. The biocompatibility test of titanium nitride has been carried out for many years. These tests and subsequent clinical applications have proved that titanium nitride is biocompatible and can be used in implantable medical treatments in contact with bone, skin, tissue or blood. In the device.
The Ability Of The Abutment To Form A Soft Tissue Seal
One of the key factors in choosing an implant abutment is its cleaning performance. The formation of plaque begins when glycoproteins adhere to the enamel and the surface of the implant, forming a thin layer called a film. Although the film itself is harmless, it provides an environment for bacteria to attach. Biofilm is an aggregate formed by the aggregation of a variety of organic components. Initially, gram-positive aerobic cocci are adsorbed on this thin glycoprotein layer or film. As these bacterial colonies multiply, an anaerobic environment is created. This environment provides favorable conditions for the invasion and accumulation of more harmful Gram-negative bacilli. Biofilms form an acidic environment that causes tooth decay and can also cause periodontal disease.
The destruction of the mucosal closure around the implant is caused by the production and development of membranes and biofilms and subsequent bone resorption caused by inflammation. Therefore, the ability of abutment materials and soft tissues to form and maintain tissue closure is our focus.
In summary, the clinical recommendations for choosing implant abutments are: titanium abutments are the first choice for implant restoration in the posterior tooth area, and zirconia abutments or zirconia abutments are the first choices when the thickness of the soft tissue in the aesthetic area or the transgingival area is insufficient For titanium abutments coated with titanium nitride, PEEK abutments are preferred for temporary restoration abutments or healing abutments; cast gold alloys are carefully selected to make restoration abutments, and stainless steel materials are not used to make restoration abutments.