Fifty four years have passed since the clinical application of dental implants, which have become widely known as a prosthetic treatment for obtaining a good prognosis for missing teeth. On the other hand, maintaining oral function is considered important for elderly Japanese citizens, who are aging at the fastest rate in the world, in view of the impact on health. Elderly patients are more likely to want dental implant treatment as a prosthetic therapy for missing teeth. Elderly people have advanced aging of biological functions compared to when they were younger, and the aging of oral function is often a particular problem in dental treatment. Dentists should consider surgical and prosthetic options for dental implant treatment of the elderly.
In addition, patients who have received dental implant treatment when they were younger inevitably become older. Therefore, in dental implant treatment, it is necessary to consider prosthetic treatment and the tissues surrounding the implant to cope with changes over time in the oral cavity.
Japan has evolved into a super-aged society unlike any other country. This presents increased opportunities to examine elderly patients with dental implant and medical problems. This paper describes the important characteristics of patients with implant prosthesis in this super-aged society, from an oral surgery and oral medicine perspective.
The tissue surrounding the implant (peri-implant tissue) changes with age. Clinically, the most important factor in cell metabolism and aging is the cancerous growth of cells. In Japan, one in two people suffer from cancer. Malignant tumors may also develop in the peri-implant tissue.
Apart from oral cancer, malignant tumors may also occur. These require standardized therapy, including chemotherapy or radiotherapy, which might also affect the peri-implant tissue. With aging, disease, and treatment, the body, including the periimplant tissue, is affected both systemically and locally.
Therefore, best therapeutic care with a thorough understanding of the patient's condition is essential for safe implant treatment in a super-aged society.
Antiresorptive agent-related osteonecrosis of the jaw (ARONJ) has recently become known as a side effect in cancer patients with bone metastasis and patients with osteoporosis who are treated with antiresorptive agents. Invasive dental treatments such as tooth extraction including implant surgery are risk factors for ARONJ. The number of patients treated with antiresorptive agents is increasing year by year in Japan, and so we have opportunities to encounter patients who will be treated with antiresorptive agents under implant treatment and maintenance. Even if the patient does not receive antiresorptive therapy at the time of implant treatment, it is not rare to receive antiresorptive therapy in the future. There are no guidelines on implant treatment of patients receiving antiresorptive therapy. Implant treatment should be planned, including bone strength and risk of ARONJ. Placed implants are not likely to be associated with subsequent occurrence of ARONJ, if oral health is appropriately managed. Peri-implantitis is a risk of peri-implant ARONJ. If peri-implantitis occurs, it is necessary to control infection. Oral implantologists should have knowledge of ARONJ.
Important factors for successful oral implant treatment include the height, width, and angulation of the alveolar ridge ; quality of bone at the implant site ; and the relationship of the implant site to adjacent structures such as the mandibular canal, maxillary sinus and nasal cavity. A major advancement in the preoperative evaluation of oral implant patients is the development of computer software capable using computed tomography (CT) to generate multi-axis, cross-sectional, panoramic images and 3-dimensional images (3-D) of the jaw. This review discusses the fundamentals of CT, the importance of differential diagnosis for oral implant treatment, and applications of CT software programs for dental implant treatment.
Purpose : When dental implants are placed, it is common to go blindly into the deeper parts of the maxillofacial area. It is therefore essential to have a detailed grasp of the basic morphology of the jawbone and its surrounding tissues, as well as structural changes when teeth are lost. This paper explains the anatomical structures of the maxilla and mandible, which are essential for implant therapy.
Materials and Methods : Dentulous and edentulous jawbone specimens for practical training and autopsy cadavers in the possession of the Department of Anatomy of Tokyo Dental College were used. Sites relating to implant therapy were exposed, the external form and inner structure were classified, and basic data were obtained. These data were also examined together with data from research carried out to date at the Department of Anatomy and related data published in Japan and elsewhere, and a commentary was given.
Results : Structures such as the maxillary sinus and the mandibular canal, which are included in the jawbone, are anatomical structures with particular importance for dental implant therapy. Their 3-dimensional positional relationship should be estimated through the use of X-ray imaging or other methods prior to therapy. Furthermore, it is necessary to gain an understanding of the area through which the vascular channels and nerves that are distributed around the jawbone run, and to bear in mind when carrying out therapy that this is a high-risk area.
Conclusion : It is essential to have a good 3-dimensional understanding of the positional traits and variations of dentulous and edentulous jaws when carrying out implant therapy in order to ensure that no unexpected situations occur.
Objectives : In this study, we investigated the influence of differences of prosthetic mode of maxillary molars on the thickness of mandibular cortical bone.
Subjects and Methods : The subjects were women aged 45 years or older who agreed to this research by January 2017 in two branches of our research institute, with healthy lower jaw dentition, and a fixed-type prosthesis or implant-supporting prosthetic device. The mandibular cortical width (MCW) with respect to the difference in prosthetic mode on each side of the maxilla was measured using a computer aided diagnostic system (CAD) on a panoramic X-ray photograph.
Results : The subjects were 90 women aged 45 to 90 with an average age of 67.4 years. The target prostheses were 135 fixed-type prostheses and 22 restorative prostheses for each side on maxillary molars The 135 cases of fixed-type prostheses included 56 fixed prostheses and 79 implant support prostheses in the mandibular molars. On the other hand, the 22 restorative prostheses were 18 fixed prostheses and 4 implant-supported prostheses in the mandibular molars.
The average MCW was 3.84 mm for the fixed-type prostheses and 3.63 mm for the implant-supported prostheses, both decreasing with age. The MCW for the prosthetic mode of the maxillary molars was as follows. The average MCW of the 135 fixed-type prostheses was 3.70 mm, which showed a decrease with age. The average MCW of the 22 restorative prostheses was 3.14 mm, which showed a decrease with age like the fixed prostheses.
Conclusion : The loss of teeth in the maxilla and mandible affected MCW, and the MCW decreased with age. It is suggested that the occlusal force had an influence on MCW.
Purpose : In Japan, there are few reports about following a protocol for the immediate function of four implants supporting a fixed prosthesis in the completely edentulous maxilla (the “All-on-4” concept). The purpose of this study was to evaluate the outcomes after 3 or more years of following the “All-on-4” concept in the completely edentulous maxilla.
Materials and Methods : This retrospective clinical study included 150 patients with 662 maxillary implants rehabilitated according to the All-on-4 concept. Clinical examinations were performed to investigate the risk factors (number of implants per case, implant systems, implant lengths, primary implant stability, implant orientation, medical history and smoking habit) of implant failure.
Results : Seventeen implants were lost, giving an estimated survival rate of 97.4% at the implant level. Implant survival rates of the left posterior position (95.3%) were significantly lower than those of the right anterior position (98.4%). Smokers showed significantly lower implant survival rates (94.8%) compared to nonsmokers (98.8%).
Conclusion : The high implant survival rate of the All-on-4 concept indicates that it is an effective treatment for the completely edentulous maxilla with small residual alveolar bone volume in the molar region.
Implants demand the taking of more accurate impressions than those required for the preparation of prostheses for dentulous jaws. The recent advent of technologies such as computer-aided design and computer-aided manufacturing has enabled frames to be produced as a single unit ; impressions thus have a major effect on the accuracy of superstructures, and it is essential that they are taken accurately. We carried out an X-ray study to investigate errors arising when implant impressions are taken, with the objective of obtaining highly accurate impressions for the production of implant prostheses. To investigate the conditions under which errors are overlooked when X-rays are used to check the accuracy of impressions, we made impressions of implants with 10-100 μm thick celluloid strips inserted between the impression coping and the fixture and of implants without this artificial gap, and scanned these impressions at angles ranging from 0°-25° to the horizontal with respect to the platform. A digital X-ray scanner was used with either a charge-coupled device (CCD) or an imaging plate (IP). The X-rays obtained were randomized and reviewed by multiple dentists, who assessed whether or not a gap was present. Visualization limits were better for the CCD than the IP. When scanning was performed at an angle, the proportion of reviewers recognizing the presence of a gap on IP images started to change when the angle exceeded 5°, and the proportion of those overlooking the presence of a gap increased at angles exceeding 10°. On CCD images, the proportion began to change when the angle exceeded 10°, but while the scanning angle was within 15° there was no major change in the proportion of reviewers who overlooked the presence of a gap. When using X-rays to check the fit of the impression coping in the process of taking implant impressions, an indicator or similar method should be used to ensure that the scanning angle is properly oriented horizontally with respect to the platform.
Purpose : The passivity of the superstructure is one of the important factors for long-term stability. The screw-retained su perstructure is an excellent method with no risk of excess cement and retrievability for long-term maintenance, but the man ufacturing procedure is complicated and the passivity may be dependent on the skill of the dentist and technician. This paper proposes a method that improves passivity by a relatively simple esthetic technique that is strong enough and not dependent on skill.
Method : Intermediate structures with an abutment form are fabricated on a regular screw-retaining type abutment, and a bridge form cast metal superstructure with screw holes is made on them for test-fitting. Fitting and occlusal adjustment are made intra-orally using the metal superstructure, then it is scanned to fabricate the zirconia superstructure. Screw-retaining intermediate structures and zirconia superstructure are cemented together intra-orally. For removing excess cement and pol ishing, the combined structure is unscrewed, then is later reinstalled with screws.
Conclusion : By using the screw retention with cementation (SRC) technique in the superstructure, it is possible to reduce complications for the patient and dentist. It will easily improve the passivity with the esthetics. In addition, it will not cause excessive cement in the gingival sulcus.
In recent years, digital technology for dental implant prosthesis has developed and improved the quality of life (QOL) of patients. Among these advancements, the intraoral scanner has been attracting attention because it is expected to prevent vomiting reflex, resolve distortion of impression or expansion of plaster on hardening, reduce infectious waste, and other advantages. Currently, the intraoral scanner is widely used for manufacturing fixed dental prostheses for devices such as single crowns or bridges. However, there are still many unknown points regarding application to the fabrication of removable dental prostheses and adaptation to full arch implant cases. This article reports on the following cases of good application: fabrication of implant superstructures in full arch implant cases using an intraoral scanner, fabrication of implant superstructures faithfully reproducing the form of the final provisional restoration, fabrication of surgical guides for immediate implantation after tooth extraction in cases with loose remaining teeth, fabrication of provisional restoration immediately after tooth extraction by obtaining an optical impression, fabrication of complete dentures using a 3D printer after obtaining an optical impression of the ridge mucosa, and fabrication of copy dentures outside the oral cavity by obtaining an optical impression of the existing dentures.
It is suggested that the intraoral scanner is indicated not only for single crown or bridge cases, but also for full arch implant cases. Furthermore, the intraoral scanner may be indicated for a wide range of clinical applications including fabrication of provisional restorations, surgical guides or complete dentures.