Clinically used implant systems usually consist of three parts: 1. Implant: the part that is implanted in the bone, which is still popularly prefabricated. However, in any case, the implant must be made of materials with excellent biocompatibility, such as titanium and bioceramics. To date, titanium is still the material of choice for dental implants. Titanium is a rare metal with a periodic table of 22, an atomic weight of 47.9 and a specific gravity of 4.5. It can be classified into 4 grades according to its purity, with grade 4 being the hardest but less tough than grade 1. grade 4 contains more than 99% pure titanium, while 100% pure titanium cannot be used and is not economical. Most dental implants are made of commercially pure titanium, i.e. grade 4 titanium. It is generally accepted that an osseous implant made of pure titanium can produce a good osseointegration interface and can be cylindrical or conical in shape, with or without threads; a rough surface with acid etching, sandblasting or titanium ion surface spraying is best because the rough surface can increase the contact area between the implant and the bone cells. 2. Abutment: This is the part of the implant that passes through the soft tissue and is usually fixed to the implant with screws. It can be made from prefabricated parts or, alternatively, from custom-made parts. The abutment must also be made of materials with excellent biocompatibility, such as pure titanium, precious metals, zirconium oxide, etc., and be machined to an appropriate shape and high surface finish to ensure the health of the soft tissue. 3. Superstructure: This refers to the structure of the crown, bridge, bracket, attachment, etc. that the restoration usually has. Compared to conventional prostheses, implant prostheses can be more easily and precisely connected to the implant through abutments with standard prefabricated components. Indications 1. Subjective reluctance to accept a large number of dental preparations as a conventional fixed bridge restoration or adhesive bridge restoration. 2. Severe alveolar ridge resorption, poor soft tissue tolerance in the bearing area, and failure of conventional removable prostheses to restore ideal function. 3.The masticatory system has some behavioral abnormalities (such as excessive jaw movement) that make it impossible to wear removable prostheses. 4.After jaw resection for various reasons, the conventional restoration is difficult to implement. 5.Muscle coordination dysfunction of the masticatory system (such as Parkinson’s syndrome, etc.). 6, psychologically resistant to wear removable denture. The design of the denture 1, the choice of implant denture fixation: The anastomosis error between the implant components and between the implant and the restoration can lead to the restoration, implant, bone in a long-term static load state, is an important reason for the failure of the implant restoration. The advantage is that it is easy to set up, can be loosened and removed without damage, and can achieve sufficient retention with a small gingival space. However, it is important to recognize that the threaded bevel has a high mechanical efficiency and is not relinquishable, so it can be very destructive when there is an error in the anastomosis surface that generates a static load. The adhesive retention method for conventional fixed restorations has many advantages: it is simple, it compensates for anastomotic errors, it closes micro-voids between implant, abutment and denture, it reduces the risk of facial breakage due to screw hole weaknesses, and it requires less time and cost. However, the disadvantages of the adhesive retention method are also obvious: the denture must be removed only to destroy, need a certain axial surface height to obtain sufficient retention, spillage of the adhesive residue in the gingival sulcus can lead to implantitis. 2, the aesthetics of implant prosthetics: the expectations of dentists and patients for implant prosthetics are not satisfied with the restoration of function and long-term survival of the implant, the pursuit of aesthetics has become an increasingly important goal. In some cases, the reason for failure is the patient’s dissatisfaction with the aesthetic outcome of the implant. This often results from a failure to adequately communicate between the patient and the physician and between the physician and the technician to develop a detailed treatment plan before and during the surgery. The area exposed below the lip smile line of the upper anterior teeth is most closely related to the aesthetic result of the implant denture and is therefore called the “aesthetic area”. The main factors affecting the aesthetic result are: a) Ideal soft and hard tissue morphology: the aesthetic factors involved in the restoration of individual missing teeth include the symmetry (shape, color, gingival margin morphology, etc.) of the restoration with the adjacent and/or contralateral teeth of the same name, which is very difficult. b) The higher the labial line, the more the cervical and gingival margins of the patient are easily exposed and the more difficult it is to achieve the aesthetic results of the restoration. Sometimes surgical procedures such as soft tissue molding and soft tissue grafting are required to restore the desired amount of soft tissue. c) The thickness of the gingival tissue also affects the gingival margin, the shape of the gingival papilla, and the ability to expose the metallic shade, among other aesthetic results. d) Implant placement in the ideal position: Due to the complexity of the factors involved, it is advisable to confirm the position of the artificial tooth with the ideal aesthetic effect after a “diagnostic trial” with the patient and the technician. Clinical and Technical I. Oral Implant Surgery The correct implementation of the implant surgery is the basis for the success of the implant restoration, which will create good conditions for the later restorative work. Therefore the primary responsibilities of the implant surgeon are: selection of the indication; selection of the appropriate implant; correct placement and orientation of the implant; ensuring the initial stability of the implant; mastering various bone augmentation techniques, such as, bone extrusion, bone splitting, GBR (guided bone regeneration), autologous bone grafting, maxillary sinus floor lifting technique, inferior alveolar nerve free technique, bone traction, etc. Before surgery, the height and width of the jawbone should be measured using X-rays combined with CT, especially near the nasal floor, the maxillary sinus and the areas where the inferior alveolar nerve canal may be involved. It is important to choose the right length of implant and to use the height of the jaw bone in a reasonable way, while avoiding damage to these important structures. The basic procedure of implant surgery varies depending on the implant system and can be divided into phase I and phase II surgery. After implantation, the implant is completely covered with a mucoperiosteal flap so that the implant can be successfully osseointegrated in the jawbone under weightless conditions (usually 4-6 months in the upper jaw and 2-3 months in the lower jaw), and then the implant tip is exposed and the healing abutment is installed in phase II surgery. After implant placement and before the completion of the implant restoration, there is a healing period of 3-6 months or even longer, during which the transitional denture can be used to provide functional and aesthetic needs for the patient. In addition, the patient’s subjective perception of the transition denture, self-cleaning effect and plaque adhesion can be used as a reference for the design of the superstructure of the permanent implant denture. Transitional dentures are mostly removable restorations, which are made by the adhesive method and can be easily adjusted. The patient’s old denture can be changed to a transitional denture after examination. The design of the transition denture is the same as that of the conventional denture, but the transition denture should be trialed and adjusted before surgery to avoid repeated adjustments when wearing the denture after surgery when the wound has not healed completely. After implant placement, the transition denture can be worn, but remember to cushion the tissue side of the denture to avoid pressure on the wound, which may affect the implant and soft tissue healing. After the implant abutment connection surgery, the transition denture can still be used after a lot of grinding and modification until the permanent implant denture is worn. (2) Full crown restoration of individual missing teeth Depending on the depth of implant placement and gingival spacing, adhesive retention or screw retention should be considered. (1) Measures to reduce lateral forces: a) Reduce the area of the dental abutment, i.e., the width of the buccolingual diameter of the tooth surface, to 2/3 to 1/2 of the real tooth. b) Form an adequate drainage channel pattern on the tooth surface. c) The cusps, fossae, sulci and crests of the tooth surface are formed by rounded convex surfaces in order to create point and linear tooth contacts. d) When restoring upper anterior teeth with implants, a lighter contact or even no contact can be considered. e) The resin material has a certain buffering effect on the tooth surface. (2) Soft tissue margin design of implant denture: self-cleaning and easy to clean, restoration of aesthetic and articulation functions, comfortable feeling, sufficient strength to withstand chewing and other external forces. (3) Implant fixed bridge restoration Intraosseous implants can expand the range of indications for fixed restorations. When fixed bridges involve implant abutments, the traditional principles of fixed restorations should be followed in addition to the principles of implant-supported full-crown restorations. (4) Implant Removable Partial Denture When the number of real abutment teeth and implants is insufficient, the abutment must assume part of the force, which becomes an implant removable partial denture, a special type of overdenture. In this case, it is necessary to take into account the reasonable loading of the implant and the maintenance of the soft tissue health around the implant neck. (5) Implant full denture restoration Implant denture restoration of missing teeth can be done in two ways: fixed bracket full denture and covered full denture. a) Fixed bracket complete denture: The metal bracket is fixed to the implant abutment by screws and cannot be removed by the patient. Usually four to six implants are required to support a maxillary or mandibular complete denture. Due to jaw conditions, these implants are often distributed in the anterior half of the upper and lower jaws, i.e. near the middle of the maxillary sinus and chin foramen. By providing good retention and stability with a small abutment area, patients experience a significant improvement in chewing efficiency and comfort. b) Covered complete denture: A portion of edentulous patients are more suitable to be restored with a covered denture, mainly because of: poor jawbone conditions that cannot accommodate a sufficient number of implants; patients cannot tolerate long surgical procedures and multiple follow-up visits; patients’ poor ability to maintain oral hygiene; and financial inability to afford a fixed bracket complete denture. The design of overdentures must use at least four implants in the upper jaw, and one to four implants can be applied in the lower jaw. The implants are used as the basis for the overdenture restoration in combination with the superstructure of various attachments (ball caps, Locator, Taiji clasps, rod-and-clip type, magnetic attachments, etc.).