Abstract. This paper make a review of some researches, including material selection and performance, surface treatment,manufacturing technology,biocompatibility. Meanwhile, it points out that the development potential of the dental implant materials and its prospects.
Keywords: Dental Implant; Materials; Research Status;dental laser handpiece
1 Introduction
The teeth are one of the vital organs of the human body. We normally call a part which expose in oral cavity the dental crown, and the root, buried in mandible or maxilla, they support each other.
However, when the teeth loose due to periodontal disease, trauma, tilt bone tumor operation or developmental disorders may cause some problems with residual teeth and temporomandibular joint disorder, experiencing symptoms such as masticatory function decline, appearance and phonic function, have adverse effects on people's work and daily life. According to statistics, the rate of dentition defects is very high in China, especially true of the elderly, their dentition defect rate reaches as high as 90% above , loosing an average of 9.86 per person[1]. There will have a huge market prospective for development in our country. With the development of Modern Stomatology,people constantly explore a variety of methods of prosthodontics, such as Fixed prosthodontics,Removable partial denture and dental implant.
Fixed prosthesis used natural teeth as a support to connect artificial tooth (pontic) by a rigid connector, with the aid of dental cements fixed the denture on natural teeth. Patients do not take to wear on their own. The removable artificial tooth is the use of natural teeth and mucosa as support,can be fixed within the dentition by something such as retainer (clasp) or Denture bases , patients can choose their own wearing. Dental implants, also known as an artificial tooth root, will be selected within the material artificial device implanted in mandible or maxilla by the way of surgical operation, with the merit of beauty, comfort, reliance, etc., received widespread attention of the detect missing patient as “ the third tooth” . And with the theory of Osseointegration being brought out, it accomplished the first leap in dental implants[2]. It is not too hard to make the case that the teeth implant has a large advantage in many ways(table1). With the continuous emergence of new technologies and applications, implant is necessarily the best option in patients with missing teeth in the future, though high cost, longer treatment period and advanced technology.
2 The development of dental implant [9-11]
Countries all over the world began to study Oral Implantology in the late 1970s. It came into clinical at the beginning of the 1980s, reached its climax in European and the US, and get into a maturity stage at present. Now, the common dental implant systems are Branemark, 3I, ITI, Osstem,Friadent, and so on(Table 2).With osseointegration proposed and other theories introduced, Oral Implantology is developed in china. Although Oral Implantology develops comparatively late in our country, it makes a great progress. In the middle of 1980s, West China Medical University and The Fourth Military Medical University that study on the basic theory and the system of dental implant set up research groups in succession, and have independent developed the tooth implantation system, and oral implantology is closing to advanced international levels. But, there are some problems exist: ① unbalanced development, ②regional academic organization are rare, ③there is a lack of professional training base，④ A big gap compared with developed countries in specialized equipment and materials.
3 Dental implant Material Selection
The selections of dental implant material are thought to reckon from pre-Christian times. Wood,stone and animal bone all had been used in making human dentures, the ancient Egyptians gold teeth in the jaw and Mayan implanted lapidary. With the development of science and technology,more materials can be chose in making dental implant. People continue to pursue the ideal biological material (with good biocompatibility, high strength, fatigue resistant, non-toxic corrosion resistance, aesthetic characteristics, etc.) to replace the natural teeth, metal and alloy materials clinical appears gradually, including ceramic material, carbon material, polymer material and composite materials and so on (Table 3).
Polymer materials have advantages in forming and improving the reaction of fabric, but its mechanical properties and chemical reaction is poorer, allowing the in vivo degradation aging activity to occur, producing a lot of irritant substances to body tissue[12]. Therefore polymeric materials used for a long term might be questioned by the profession. Ceramic that has lower solubility, low melting point and easy forming begins to use in the 1960s and 1970s, and people paid attention in it for a long time, but it just use for coating at present because of low mechanical properties [13]. The carbon material has a high stability under physiological conditions, no biological degradation, have good biocompatibility and physical and chemical properties, its elastic modulus are similar to bone, and thus can form a good interface. But its color is not beautiful, more fragile,no mechanical deformation, therefore it is easier to break, no need to use. Metal material as one of the earliest application planting materials, still being rewarded and respected due to having the desirable mechanical strength and biocompatibility, such as gold alloy,Ta-Zr alloy, Co-Cr alloy, etc.
They all have good performance, but the material for clinical use with the combination of bone is still fiber, far away from the standard that people pursue.
Pure titanium and titanium alloys, non-toxic, light quality, high strength, good biocompatibility, is the optimum replacement materials for the surgical implants. Compared with other implant materials, titanium is much closer to the human tissue in its density and elastic modulus, as shown in Table 4. Pure titanium is moderately hard and strong between dentin and enamel, its ductility,hardness, elastic modulus and strength are equivalent to ADAS (the American dental association)gold alloy III, IV type[14]. Titanium alloys have higher strength and hardness than pure titanium, but lower than Co-Cr alloy and Ni-Cr alloy, and the bending strength of titanium alloys just like Co-Cr alloy in bending fatigue test[15-16]. Titanium alloys are widely used in the medical field, but they can release micro of Al and V ions which harm to human body. In such a situation, Britain , America and Japan have been developed new materials without Al and V. Japanese ɑ+β-titanium alloys which include Zr4Nb4Ta0.2Pd etc, have a higher fatigue strength and a better corrosion-resistant than Ti-6Al-4V. β-titanium alloys have a better toughness than ɑ+β-titanium alloys, TMZF and Ti13Nb13Zr are widely used in American medical field[17]. The property of titanium can be improved by addition of small amounts of impurities, such as: Fe and V for corrosion-resistant,oxygen and Al for strength [18-22].
Form table 4, we can know that the elastic modulus of pure titanium and titanium alloys are closest to the human hard tissues in all materials, this enhance the adaptability between implant and bone tissue, and benefit to transmit the interfacial stress to bone tissues [23][24]. Titanium has been chosen by many internationally renowned brands to improve long-term treatment effects (table 2).
Nowadays, in order to obtain a better biological properties and clinical results, some research institutions began to try to use composite materials (to the metal or alloy for implantation of core,with other materials for coating or active material), and lots of achievements have been obtained[25].
4 Biocompatible
Biocompatibility not only reflected on whether it is harmful to the human body, but also observes the responding relationship between functional materials and human tissues[45]. Therefore, the implanted materials for biological compatibility depend on the host itself and material itself. A number of factors will make an effect on biocompatibility, such as host genetic factors, implant position and the implant environment, structure, shape, size, surface roughness of materials[46-49].For this reason, researchers through constantly exploring and summarizing, has sought suitable dental implant biological materials and processing technology for human beings, by selecting,designing and treating and other aspects.
5 Summary
The biology function of implant materials receives more and more attention, people pay more attention whether the materials can achieves the osseointegration effect [50]. Only those who have the excellent biocompatibility, can achieve a good osseointegration and biological mixture, the ideal implant material must have ability to assume a certain amount of pressure load, which also the target for modern people[51].
With the development of science and technology, the material selection of dental implant experience the transformation from simple to complicated. People constantly search for more excellent, more suitable ideal biological material for human tissues and try to get this goal step by step by the way of improving manufacturing process and surface processing craft. It is generally believed that in the future a better biological material can be completely replaced with the natural human tooth. While prospects are bright, the roads have twists and turns for all.