Dental implants have seen greater advances and more innovations in recent years than any other field of dentistry. In fact, we attribute this to the development of new implant systems, new and improving diagnostic procedures and innovative surgical techniques. The fabrication process of advanced technicians has also benefited from the use of CADCAM technology in restorative dentistry, allowing for more precise seating of restorations, including those with suboptimal implant placement. The aim of modern oral implants is no longer simply successful osseointegration. Today’s surgeons can confidently recommend implant restorations to their patients and can predict the success of the osseointegration of the implants. In order to demonstrate the success of the final restoration, normal form, function, esthetics, speech and gingival health must be achieved. Clinically, implant success in treating patients with full or partial tooth loss has been well documented in the literature. Many clinicians have recognized the benefits of opting for implant treatment. Implant treatment is more advantageous than traditional fixed bridges and partial removable dentures and will provide more benefits to the patient. However, there are still a number of practitioners who prefer to wear down the patient’s neighboring teeth for fixed bridge restorations instead of adopting implant restorations. A certain amount of tooth tissue is unavoidable to be worn down in order to get an objective aesthetic result. Sometimes, root canal treatment may be necessary due to problems with the orientation of the tooth axis, periodontal problems due to problems with the crown margins that may later cause periodontal problems, and further loss of tooth structure. The advantages of implant-supported restorations are many, and we have grouped them into four categories: 1) Preservation of dental tissue 2) Preservation of bone volume 3) Provision of additional strength support 4) Resistance to disease We will talk about these points in more detail in the following sections: Preservation of dental tissue As mentioned earlier, when making fixed bridges, some of the dental tissue has to be abraded in order to make them aesthetically pleasing. This grinding of the tooth tissue affects the longevity of that tooth and may sometimes require root canal treatment, as well as later periodontal treatment and mechanical complications. A long-term study of fixed bridges showed that the survival rate of fixed bridges was 87% at 10 years and 69% at 15 years. Reasons for failure include inactivity of the anterior and posterior abutments, e.g., when preparing the tooth tissue for a fixed bridge, the amount of grinding must reach a certain depth in order to achieve adequate retention and long-term stability, and in the case of abutments with large pulpal cavities, a root canal may be necessary. Although there are not many long-term studies on the results of single-tooth implants in the literature, we counted the clinical results of single-tooth implants from 1981 to 1997. The article reported that implant complications were related to the type of restoration, span, time, implant length, and bone quality. Compared with other restorative designs, single-crown implant restorations had the lowest failure rate, about 2.7%. These reports also stated that most of these failures occurred in the first year, and that the chance of implant failure gradually decreased in subsequent years. This suggests to us clinicians that if single tooth implants are used after one year of loading, then they can be used for a considerable period of time. The results of one scholar’s study showed that the success rate of single tooth implants at 11 years was at 96.5%. All the reports mentioned that there was no loss of teeth adjacent to the dental implants, which is quite different compared to some complications of neighboring teeth caused by fixed bridge restorations if they are used as we mentioned above. Therefore, if a fixed bridge restoration is chosen, then both the patient and the surgeon have to take into account these potential risks of failure, as well as the physical and financial damage caused to the patient in a few years. Bone Preservation There is a close relationship between teeth and alveolar bone height throughout life, and every change in alveolar bone function is accompanied by a change in alveolar bone structure and shape. The alveolar bone needs to come to maintain its form and function. When a tooth is missing, the lack of physiologic stimulation of the alveolar ridge leads to a decrease in trabecular bone and a decrease in bone density, and eventually a loss of alveolar ridge height and width occurs. A 25-year study showed that patients with complete dentures continue to experience bone resorption throughout their lives and that the rate of resorption in the maxilla is four times faster than in the mandible. Resorption of the alveolar bone in complete denture patients begins in the upper jaw, upward and toward the center, and in the lower jaw it is downward and laterally, often resulting in category 3 jaw misalignment. Considering these natural factors, the teeth are lined up with the maxillary teeth on the lateral side of the maxilla and the mandibular teeth are lined up as far as possible towards the lingual side. It is mentioned in the literature that the teeth need the support of the alveolar bone, and with the loss of teeth the alveolar bone is no longer physiologically stimulated. So, the question now is can partial removable dentures and complete dentures provide enough physiologic stimulation to the alveolar ridge to preserve the level of the alveolar ridge? Based on the above studies, there is no confirmation in this regard. Instead of preserving the level of the alveolar ridge, partial removable dentures and complete dentures may accelerate the resorption of the alveolar ridge if the denture is not properly fitted. These patients were not told by their doctors that the alveolar bone would resorb after the teeth were extracted, nor were they told that this resorption was ongoing. Continued bone resorption can lead to poor denture stability. Loss of lateral stability can lead to increased friction and irritability of the mucous membranes. Sometimes the bone resorption is so severe that even if the patient wants to opt for an implant restoration the bone must be augmented with an iliac bone graft to accommodate the implant restoration. Along with bone resorption the soft tissues can change to the point where the entire face is affected aesthetically. The face changes with age, especially with missing teeth, which accelerates the changes of facial aging. The loss of tooth support and the decrease in vertical distance give us a very typical facial appearance of a patient with a full mouth of missing teeth, with a shorter lower 1/3 of the face and a receding upper lip. These changes seriously affect the patient’s aesthetics. And these changes can be avoided, if the implant restoration is performed in time, the implant restoration stimulates the bone tissue and avoids the occurrence of bone resorption. Patients with full dentures are unaware of the range of changes that occur after tooth loss, and many patients use the same set of dentures for years and do not come in for follow-up appointments. Patients should be informed that dental implants can prevent these bone resorptions from occurring, and since implants prevent bone resorption and as well as soft tissue complications can also be avoided. Providing more support The use of dental implants provides more support, which translates into improved functioning of the muscles of the stomatognathic system. A patient who chews or grinds his teeth can have a bite force of up to 1,000 psi, whereas a patient with a full denture has a bite force of only 50 psi. It has been documented that the longer a full denture is in place, the lower the bite force becomes. Therefore, many patients with complete dentures suffer from masticatory muscle dysfunction. This complication affects the patient’s general health status and, in fact, many patients suffer gastrointestinal discomfort as a result. If we are to restore the patient’s gastrointestinal function to a normal level, then we must first restore his masticatory muscle function in order to improve his quality of life. Replacing a patient’s full denture with a fixed restoration of a full implant denture will make a big difference in the patient’s chewing power. A patient with a full denture limits his biting power due to the increased pressure that can result in mucosal tenderness. An implant-supported fixed denture can provide about the same biting force as a patient with a natural tooth-supported fixed denture, and an implant-supported removable denture can also provide a significant improvement in retention over a purely mucous-supported removable denture. Some patients have bilateral or unilateral loss of the free end of the posterior teeth, and in such cases, a removable denture is not a necessary option. However, the traditional restorative approach is to perform a partial removable denture restoration that is supported by both teeth and mucous membranes in the Ken’s Class 1. Such a denture can increase the occlusal area and reestablish posterior support. It has been reported that the tension that occurs between the teeth and the mucosa after weight bearing is quite different. The authors’ opinion is that a partial removable denture supported by both teeth and mucosa does not rebuild the occlusion of the posterior area well in the long term, mainly due to the elasticity of the mucosa and some of the resulting effects. Another advantage of implant-supported restorations is that they can be modified. Implant-supported prostheses can be screw-retained, bonded-retained, or a combination of both. Screw-retained restorations have a large body of literature reporting on its ease of use, and authors do prefer to use screw-retained whenever possible. The advantage of being modifiable is that the restoration is more convenient when it needs to be redone or repaired. Prosthodontists often encounter the following situations: 1) loosening of the retention screw; 2) ceramic tautness; 3) fracture of the abutment; and 4) modification of the restoration due to implant dislodgement. Screw-retained restorations are easier to remove and repair than cement-retained restorations. Resistance to disease Secondary caries may occur below the restoration, at the edge of the restoration, or on the heel surface. Caries has been reported to be the most significant cause of restoration failure. Evaluation and control of disease susceptibility must precede the development of a final restoration plan. Root surface caries is more prevalent in the elderly population, which may be related to a decrease in salivary volume. In patients who are susceptible to these diseases, it is important to take these issues into account when choosing a restorative modality and try to preserve teeth or replace missing teeth with dental implants. Studies have shown that patients who wear removable dentures have a detrimental effect on the health of the remaining teeth and the surrounding soft tissues. Patients wearing removable dentures often experience loosening of the abutment teeth, extensive plaque buildup, bleeding on probing, more caries, and accelerated bone loss at the abutment site. One scholar reported that 44% of patients with removable dentures were at risk of abutment loss after 10 years. Another advantage of an implant denture is that it is caries-free and preserves neighboring teeth. Often, restorative options should be thought of at the time of extraction, and implants are a viable option.