It has become necessary to consider how to deal with implant patients when they reach a very old age or require nursing care. In the case of patients who are no longer able to visit the dentist for maintenance or who require nursing care due to aging or disease, it will be difficult to manage the implant prosthetic device and respond to changes in the oral cavity. In addition, it is difficult to cope with peri-implantitis, implant mobility, fracture of the superstructure or abutment due to age-related changes, and loosening of screws due to deterioration of oral hygiene.

In future implant treatment, prosthetic devices that can adapt to changes in the patient's oral cavity and maintain long-term stability during the patient's life stages will be required.

In Japan, hydroxyapatite (HA) was approved as an artificial bone for dentistry in 1985. Since then, various bone substitutes have been developed and distributed.

However, there are only two bone filling materials that are indicated for bone regeneration based on the placement of the implant body in implant treatment : apatite carbonate granules and octacalcium phosphate (OCP)/collagen complex.

We have previously evaluated bone substitutes that have not been approved for use in implant treatment in cell cultures or animal experiments. This review describes the characteristics and indications of ultra-porous HA granules with excellent new bone formation and biodegradable low-crystal HA/collagen composite sponge. In addition, cases of bone augmentation using these bone substitutes are introduced.

Implant treatment has become an essential option in the prosthetic treatment strategy and the number of indications based on scientific evidence has increased. Therefore, the development of a novel bone substitute superior to the conventional ones such as hydroxyapatite (HA) and beta tricalcium phosphate (β-TCP) for bone augmentation has long been awaited. Bone substitutes for dental implant treatment must meet various requirements including biocompatibility, resorbability, osteoconductivity and osteoinductivity, and the ability to achieve long-term osseointegration. We have focused on octacalcium phosphate (OCP) as a precursor of biological apatite and have been researching its clinical application as a novel bone substitute. Though OCP has superior resorption and osteogenic potential compared to hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP), OCP alone is difficult to handle because it is a granular material and sintered molding is impossible due to its chemical structure. Therefore, in 2006 we developed a composite with collagen (OCP/Col), and after a number of both basic and clinical studies, in 2019 the Ministry of Health, Labour and Welfare approved its production and marketing as “Bonarc^®”. This article describes our basic research on OCP, translational research for clinical application, clinical trials and case reports, and the latest information on OCP/Col.

Bone apatite is not hydroxyapatite, but carbonate apatite (CO₃Ap), which contains 6-9 wt% carbonate in its apatitic structure. Hydroxyapatite is not resorbed in the body but CO₃Ap can be resorbed and replaced with bone. Therefore, CO₃Ap has the potential to be an ideal artificial bone substitute. We have succeeded in fabricating chemically pure low crystalline CO₃Ap through a dissolution-precipitation reaction using precursors, such as calcium carbonate, dicalcium phosphate dihydrate, and calcium sulfate, without sintering. Some animal experiments revealed that the fabricated CO₃Ap was resorbed by osteoclasts and replaced with new bone similar to an autogenous bone graft, and it also exhibited high osteoconductivity.

In Japan, there was no artificial bone substitute allowed for use adjacent to dental implants. Based on clinical trials for sinus floor augmentation, granular-type CO₃Ap was approved as an artificial bone substitute that can be used in all dental fields, including those adjacent to dental implants, as Cytrans^® Granules (GC Corp., Tokyo, Japan).

This comprehensive review introduces clinical cases of sinus floor augmentation, reconstruction of bone defects after cystectomy of the jaw and alveolar ridge augmentation by using Cytrans^® and instructions and directions for its clinical use. Furthermore, we have succeeded in fabricating porous CO₃Ap. The porous CO₃Ap was useful for reconstructing a rabbit mandibular bone defect model and could also be an excellent candidate for a scaffold in bone regenerative medicine because it has higher osteoconductivity and is replaced with bone.

Diagnostic imaging including computed tomography (CT) is very important for dental implant treatment. The precise information obtained by imaging examination can ensure safe, effective implant treatment. CT data is the ultimate private information, and so it should be handled carefully to protect privacy. This review explains the rules to be followed for protecting private information when handling digital data including CT data. It also explains how to obtain appropriate CT data to be used for implant simulation, as well as important diagnostic findings on CT for implant treatment.

In recent years, simulation software, which is obtained by digital matching of optical impression data of the oral cavity or plaster models with CBCT data, has been widely used for implant placement. In addition, the digital data of the implants in the simulation software is used to plan the dimensions and placement positions of the implants, enabling accurate placement.

However, overconfidence in the accuracy of these digital data compared to the actual values may cause problems for safe and reliable implant treatment.

We examined the dimensional reproducibility of multiple CT (CBCT, MDCT), scanners, and simulation software. As a result, it was found that the various digital data were larger or smaller compared to the actual values. The results also suggest that distortions occur in the matching digital data due to differences in the respective dimensional change rates.

Therefore, for safe and reliable treatment, it is important to pursue not only the accuracy of digital data compared to the actual values, but also the consistency of these data. In addition, to avoid problems it is important to be familiar with the limitations of digital data, in other words, to take into account experience of analog treatment.

In recent years, digital workflows for guided surgery, optical impression-taking with an intraoral scanner, custom abutments using CAD/CAM systems, and fabrication of superstructures have been examined for digitizing implant treatment. The objective is to avoid technical and engineering errors in surgical treatment and indirect methods so that the same results can be achieved by anyone. As a result, safe and secure implant treatment has become possible, and improvements have been made in terms of optical impressions, the accuracy and method of CAD/CAM systems, and materials ; the digital approach has brought benefits compared to the analog.

The purpose of implant treatment is to provide prostheses to restore occlusal support and function, and to improve esthetics and the patient's quality of life. This requires not only simulating the position, direction, and depth of implant placement, but also reconstructing the occlusal height, occlusal plane, occlusal curvature, jaw movement, etc. in order to construct the superstructure. It is important to formulate a treatment plan that includes these elements. Based on the literature, we have studied clinical practice based on our knowledge and experience. However, examinations and diagnoses related to treatment plans, such as panorama, cephalogram, and jaw movement imaging, are often performed by independent analogs.

We consider that digitization should combine data that has been independently examined and diagnosed into one three dimensional data, to assist the initial examination and diagnosis as an index, and to reduce the differences from past studies.

In this study, three types of jaw models were fabricated with different implant depths, and the three-dimensional accuracy of the scan body was compared between the conventional silicone impression and intraoral scanner-assisted optical impression methods.

Three master models were fabricated by implanting the dental implant in 22 (maxillary left incisor) defect models at 1.0 mm, 3.0 mm, and 5.0 mm below the gingival margin, respectively. Subsequently, the scan body was attached to the implant of the master model, and basic data were scanned with a dental lab scanner. Further, using the conventional open tray method, the implant work models were fabricated and fitted with scan bodies ; the data were scanned using the dental lab scanner (WM-1, WM-3, WM-5, n＝5). Furthermore, using three types of intraoral scanners, namely Medit i700 (M7), Trios3 (T3), and Primescan (PS), optical impressions of the master models were obtained (M7-1, T3-1, PS-1, M7-3, T3-3, PS-3, M7-5, T3-5, PS-5, n＝5). The scanning data were imported into 3D analysis software, and superimposed with WM, M7, T3, and PS at the same implant depth and compared.

The concordance rates of M7, T3, and PS were significantly higher than those of WM at all implant depths ; the amounts of displacement of M7, T3, and PS were smaller than that of WM in color mapping. As the implant depth increased, the concordance rates of WM decreased, while the interquartile range increased.

Thus, the implant-position reproducibility of the silicone impression method decreased significantly when the implant depth was 5.0 mm below the gingival margin ; however, the optical impression method using various intraoral scanners showed high implant-position reproducibility.

Implants for intermediate defects are an effective prosthetic treatment for defects. In order to perform highly reliable prosthetic treatment, it is important to understand the causes of the defect. Zirconia, which is often used for occlusal recovery, has excellent mechanical strength, and its range of application has expanded in recent years. Unlike conventional occlusal surface materials, there is less concern about chipping and wear with zirconia, but more concern about the effects of stress transfer during occlusion on the implant body and periodontium. We report a case where a thermoplastic resin material was clinically applied as an abutment to provide a buffering function.

In this case, a polyetherketoneketone (PEKK) material abutment and zirconia crown were fixed together to form a superstructure that helped alleviate the occlusal pressure from the defect, which could have led to root fracture and ultimately tooth extraction. The occlusal force applied to the zirconia crown and the stress on the adjacent tooth were matched ; the prosthetic treatment was successfully performed without any treatment intervention for the remaining tooth. As a result, a balanced occlusal contact state was obtained, and high patient satisfaction and a good long-term prognosis were achieved.

We report a case of medication-related osteonecrosis of the jaw (MRONJ) in a 47-year-old woman with rheumatoid arthritis, who was treated with implant prosthodontics after extirpation of necrotic bone. The patient had been taking alendronate sodium hydrate, which is a bisphosphonate, for one year and two months. She lost the lower right canine and first premolar, and MRONJ occurred in the right side of the mandible. We extirpated necrotic bone with MRONJ and extracted several teeth in the region. After these treatments, normal healing of the mucosa was seen. Two implants were placed in the residual ridge of the mandible. These implants were successfully integrated and functioned well. These results suggested that implant treatment could be a treatment choice after extirpation of necrotic bone with MRONJ, but careful consideration is necessary.

Purpose : The quality of case presentation papers has improved over the past 10 years following the revision of the guidelines for papers. Therefore, we investigated the kinds of cases described with chief complaints, diagnoses, and postoperative evaluations in the latest case presentation papers.

Methods : We surveyed 77 case presentation papers published in the Journal of the Japanese Society of Oral Implantology, Vol. 34, No. 3 (September 2021) to Vol. 35, No. 2 (June 2022), to determine the chief complaints, diagnoses, and postoperative evaluations.

Results : The chief complaints were difficulty in mastication, swelling/pain, desire for prosthesis, and desire for implantation. Four of the difficulties in mastication complaints were described as “mastication disorder.” Diagnoses were a large number of tooth defects, followed by periodontitis, root fracture, and caries. As postoperative evaluations, mastication, occlusion, satisfaction, and quality of life were often described, but functional examination and subjective evaluation were not described.

Conclusion : In several articles, the chief complaint (desire for prosthesis, or implantation) and the diagnosis (tooth defect or masticatory disorder) were described as possible improvements. It is suggested that further description and examination of preoperative and postoperative functional evaluation are needed.