We looked at the criteria for implant removal and the selection criteria for retreatment after removal. Matters to be considered at the time of removal include:1) the stage of progression of peri-implantitis;2) the patient's general condition;3) the difficulty of maintaining implants;4) the number of years after implantation;and 5) the wishes of the patient's family.

The criteria for removal from the perspective of dentists are as follows:1) the stage of progression of peri-implantitis;2) bone resorption after removal;3) the risk of complications after removal;4) movement of the implant body;5) the necessity of implant reimplantation;and 6) early-age patients (the more serious the situation, the more aggressively implants can be removed).

The criteria for removal from the perspective of patients are as follows:1) pain;2) request for reimplantation;3) less pain during removal surgery;4) low cost of surgery;5) safety of surgery;6) early age;and 7) the patient's family's desire for removal (the more serious the situation and request, the more aggressively implants can be removed).The recovery procedure after removal is divided into three parts:1) reimplantation of implants;2) prosthesis using dentures;and 3) follow-up observation without doing anything. The "3) follow-up observation without doing anything" includes a sleeping implant in which residual implants are left in the bone. The "1) reimplantation of implants" is classified into the following three categories:1) Reimplantation of all areas from which implants were removed;2) Reimplantation of partially removed areas;and 3) Recovery using residual implants after removal (Implant Over Denture:change to IOD, change of superstructure, etc.).

The advantage of reimplantation treatment is that the function prior to removal can be restored. Disadvantages include the need for re-surgery, the need for additional surgeries such as bone grafting and gingival grafting, the need to eliminate the cause that led to removal, and the need to wait six months to a year for reimplantation. (Similar to the removal criteria, these also partially differ depending on the perspective of the dentist and patient.)

Reimplantation of implants is selected only when desired by both the patient and the dentist. When patients do not wish to undergo treatment or when reimplantation treatment is difficult, it is necessary to consider recovery treatments other than implants.

The objectives of prosthetic treatment are diverse, ranging from esthetic recovery and functional improvement to contributing to general health. Implant treatment is now widely established as one of the prosthetic treatments for missing dentition and is expected to have a good long-term prognosis. Compared to conventional fixed and/or removable dentures, implant prostheses are the most preferable prosthetic treatment in terms of tooth preparation and the burden on adjacent teeth. Subjective evaluations such as patient satisfaction and oral health-related quality of life, as well as objective evaluations such as masticatory performance, occlusal force, and prognosis such as success and/or survival rate of prostheses, have been used as treatment outcomes after prosthetic treatment for missing dentition. On the other hand, scientific evidence focusing on the impact of prosthetic treatment on the prognosis of remaining teeth is still limited. Therefore, we conducted a literature review on how prosthetic dental treatment contributes to preventing the expansion of missing dentition. The results suggested that 1) there is an increasing number of scientific papers examining the impact of prosthetic treatment on preventing the progression of defects, 2) prosthetic dental treatment using partial dentures, which was thought to be disadvantageous in terms of preventing the progression of missing dentition, actually contributes significantly to preventing an expansion of missing dentition, 3) a fixed implant prosthesis can contribute to preventing an expansion of missing dentition more than a fixed prosthesis or removable partial denture, and 4) the prognosis of remaining teeth is influenced by not the type of prosthesis but other factors such as a history of root canal treatment, crown-root ratio, number of occlusal supports, and so on. These findings indicate the necessity of carefully considering the long-term effects on human health when selecting the type of prosthesis.

Periodontitis is the leading cause of tooth loss among Japanese adults. Although periodontitis exhibits site-specific characteristics, it often develops and progresses throughout the dentition. In severe cases, this leads to tooth loss, which tends to expand gradually without appropriate intervention.

This article discusses dental treatments for patients with periodontitis to prevent the progression of tooth loss. Tooth loss can occur through natural exfoliation and extraction. However, because the decision for extraction varies among clinicians, careful judgment is required. Preserving teeth is the first step in preventing tooth loss; however, such preservation must be based on the assumption that the tooth can be maintained functionally over the long term.

Nonsurgical approaches, such as oral hygiene instruction and scaling and root planing, are fundamental in periodontal treatment. If performed appropriately, they can improve deep periodontal pockets and reduce tooth mobility. The success of these treatments depends the clinician's technical skills and acquisition and maintenance of patient motivation. Furthermore, by employing techniques, such as periodontal tissue regeneration therapy, orthodontic extrusion, and intentional replantation, teeth with poor prognosis may be preserved, allowing for long-term functionality.

However, post-extraction implant treatment is a viable option for teeth that are difficult to preserve. Patients with a history of periodontitis are at a higher risk of developing peri-implantitis. Therefore, management of inflammation based on standard periodontal treatment protocols and regular maintenance is essential. Moreover, by using implants, the need to cut or lose the remaining teeth can be avoided, thereby preventing further tooth loss.

Overall, implementing dental treatment strategies that prevent the expansion of tooth loss greatly contributes to the long-term maintenance of oral function and improves patients' quality of life.

Even the most difficult cases, such as Eichner classification C1 and edentulous jaw with severe ridge resorption, start with only one or two missing teeth. Therefore, when faced with a case of missing teeth, prosthetic treatment must be performed to prevent further tooth loss. The cause of the loss, the condition of the remaining teeth, and risk factors must be considered. However, the cases of missing teeth encountered in clinical practice are extremely diverse, and even if similar prosthetic treatment is performed, there are often large differences in the postoperative course.

This paper reviews 10 cases with relatively long progression, including cases with poor prognoses, and examines what type of implant prosthetic treatment may stop further loss. In order to prevent the loss from expanding, appropriate prosthetic treatment should be performed while the area of loss is small to ensure continuity of the dentition, and sufficient occlusal support should be secured to stabilize the occlusion. Risk factors that promote further tooth loss, such as the patient's age, the distribution of tooth loss, occlusal support, condition of periodontal tissues, parafunction, occlusal force, and inferior condition of opposing teeth, must be accurately determined. Careful preoperative examination and diagnosis, flexible intraoperative modification of the treatment plan, and a continuous postoperative approach are very important. Further, constant maintenance after delivering the superstructure, force control, plaque control, and early response to changes are essential.

Objective:Since full-arch implant-supported fixed prostheses based on the All-on-4 concept often have an artificial gingival component, the prostheses' basal surface morphology is very different from that of the normal superstructure. In this study, we compared the plaque removal effect of two types of sonic toothbrushes with different brush shapes on the basal surface of prostheses, and discussed the oral hygiene condition and basal surface morphology.

Subjects and Methods:Among patients who had been undergoing maintenance every 6 months for 5 to 8 years after having their final prostheses fitted, and who had been using a sonic toothbrush with a standard brush tip (Sonicare FlexCare Sensitive Brush Head Regular:SC, Philips) as a home care tool, consent was obtained to switch to a sonic toothbrush with a different tufted tip (PriniaSmile One-Tuft Brush Taper:PS, GC) and use this for 6 months. A statistical comparison was conducted on the differences in the amount of residual plaque on the base of the prosthesis within the same patients in 10 patients (6 men and 4 women) (p<0.05).

Results:The amount of residual plaque on the entire base surface was 35.6% in the SC group, and 12.5% in the PS group, and the amount of residual plaque was significantly less in the PS group compared to the SC group. Furthermore, when comparing by site, the amount of residual plaque was 27.8% in the anterior, 33.8% in the middle, and 45.8% in the posterior when SC was used, and 5.0% in the anterior, 10.3% in the middle, and 23.3% in the posterior when PS was used, and the amount of residual plaque was significantly greater in the posterior region in both the SC and PS groups. In addition, the residual plaque rate around the anterior abutment was 38.5% in the SC group and 16.6% in the PS group, and that around the posterior abutment was 52.4% in the SC group and 27.5% in the PS group, which was significantly lower than the SC group. In both the SC and PS groups, the amount of residual plaque around the posterior abutment was significantly greater than that in the anterior region.

Conclusion:In the oral cleaning of full-arch prostheses based on the All-on-4 concept, it was considered that the reachability of the sonic toothbrush was important due to the shape of the brush, and that cleaning was more difficult in the posterior region.

Introduction:Magnetic attachments for implant overdentures (IOD) cause metal artifacts during magnetic resonance imaging (MRI). Recently, thinner keepers have been developed. The purpose of this study was to evaluate MRI metal artifacts of new-type keepers using IOD with a magnetic attachment.

Materials and Methods:A cylindrical acrylic phantom (20.0 cm diameter) filled with baby oil was used. New-type keepers (MagTeeth^®, 4.0 mm diameter, 0.1, 0.2, 0.4 mm thick) and a conventional keeper (Physio Magfit^®, 4.0 mm diameter, 0.8 mm thick) were placed on a removable rod at the phantom's center. MRI scanning was performed using a 1.5 T MRI scanner (Intera Achieva^® 1.5T, Philips Medical Systems) with a phased array coil using head and neck and neurosurgical imaging protocols. Artifact sizes were measured as the maximum diameter on axial, coronal, and sagittal images. Statistical analysis was conducted using the Kruskal-Wallis test.

Results:The new-type keepers significantly reduced artifacts compared with the conventional keeper in all imaging sequences (p<0.01). The thinnest keeper showed the smallest artifact in all imaging sequences.

Conclusion:MRI metal artifacts of the new-type keepers were significantly reduced compared with the conventional type of keeper.

This study evaluated the reproducibility of the three-dimensional implant positions obtained using a wireless intraoral scanner compared to the silicone impression method under varying scanning conditions of scanbodies.

To fabricate a master model, six implants were placed at positions corresponding to 47, 44, 42, 32, 34, and 37 of the plaster models of the edentulous mandible. Master data were subsequently acquired using a dental laboratory scanner under six different conditions, with one to six scanbodies attached. For the optical impression method, one to six scanbodies were attached to the implants of the master model and scanned using a wireless intraoral scanner (SIRIOS, Straumann) in accordance with the manufacturer's guidelines, resulting in six sets of data. For the silicone impression method, working models were fabricated by taking one to six impressions of the master model implants, generating six sets of data. The master data, intraoral scanner data, and data obtained using the silicone impression method were superimposed using software to calculate the concordance rate of the scanbodies, which were subsequently color-mapped.

The reproducibility of implant positions obtained using the optical impression method with a wireless intraoral scanner and the silicone impression method decreased as the number of implants increased. On the other hand, it was suggested that the reproducibility of implant positions achieved with a wireless intraoral scanner was comparable to that of the silicone impression method when one, two, five, or six implants were present.

There has been much discussion on various prosthetic materials used for dental implants. Various attempts have been made to develop esthetic implants that positively affect occlusion and do not damage the gingiva.

Hybrid ceramics have the advantage of wearing down like natural teeth;however, they easily discolor and irritate the gingiva. Moreover, ceramic materials trade off their esthetic appeal for strength. Zirconia is debatable in occlusion because it is strong.

We report a case where we combined materials to produce a suitable one with favorable outcome using an implant superstructure.

In this case, we tried to reduce the risk of occlusion and damage to surrounding tissues by fixing a crown made of hybrid ceramic to a zirconia frame.

Although a 5-year observation period is short, the outcome was favorable.

Long-term follow-up and large-scale studies are necessary, but the high level of patient satisfaction and the stability of occlusion and periodontal tissues suggest that this method is useful.

Extreme atrophy of the maxilla generally makes the fixation of implants difficult. In such cases, we have been applying the bone ring technique since 2010. This technique consists of five steps, as follows. First, the sinus membrane is lifted using a lateral approach. Second, the implant bed is prepared at the alveolar crest. Third, a ring-shaped bone block (8 mm outer diameter, 4 mm inner diameter) is harvested from the chin bone. Finally, the harvested bone and crestal bone were fixed with the implant body. In this technique, sinus floor augmentation and simultaneous implant placement can be completed in one surgery. The purpose of this case report was to describe observations from 11 years of follow-up examinations after conducting this technique.

The patient was a 68-year-old man who complained of difficulty in mastication because of loss of the upper posterior teeth. Sinus floor augmentation and simultaneous implant placement were performed using the bone ring technique. Decisive prosthetic rehabilitation was performed 10 months later. This patient was followed up for 11 years using annual cone beam computed tomography observation. No bone resorption around the implant tip and neck was observed in this technique. These results suggest that the bone ring technique is a highly predictable surgical technique.

We report a case of mandibular fracture caused by peri-implantitis in a patient undergoing hemodialysis treatment.

Case Summary:The patient was a 69-year-old woman undergoing dialysis treatment who developed peri-implantitis 3 years after implant treatment, which was accompanied by a pathological fracture of the mandible.

Progress:The patient underwent implant insertion surgery in location 46 at another hospital in June 2018. Approximately three years later, swelling and purulent discharge were observed in the mucosa around the implant in the right mandibular molar area, and the patient was referred to our department. A panoramic X-ray revealed bone resorption around the implant body, and a cytological examination of the drainage area was determined to be benign. A diagnosis of peri-implantitis was made, and implant body removal surgery was performed in location 46 in December 2021. However, three months later, the inflammation could not be controlled and a mandibular fracture occurred. Due to the patient's overall condition being subject to dialysis treatment, active treatment was difficult, and a follow-up observation policy was adopted.

Consideration:Because the patient was undergoing dialysis treatment, active anti-inflammatory treatment was difficult. For patients undergoing dialysis treatment, it is necessary to carefully consider the suitability of implant treatment in view of the present case.

In the esthetic zone following tooth extraction, hard and soft tissue resorption often occurs, making surgical tissue augmentation necessary during implant treatment. This introduces risks associated with surgical invasiveness, complications, and long-term stability. Zachrisson (2003) reported that when a tooth is orthodontically moved into an edentulous area, the periodontal tissues move along with it, creating a space suitable for implant placement. We applied horizontal tooth movement in the esthetic zone for implant treatment, achieving favorable long-term results. The patient was a 40-year-old female who was diagnosed with a root fracture of tooth 21, which required extraction. Significant bone and soft tissue defects were anticipated after the extraction. The patient declined surgical hard and soft tissue augmentation and the use of biomaterials. Therefore, we planned to move tooth 22 into the space of tooth 21 and place an implant at site 22. After the extraction of tooth 21, tooth 22 was orthodontically moved mesially, resulting in the formation of a wide alveolar ridge, keratinized mucosa, and sufficient bone width and height, allowing for implant placement without the need for surgical bone augmentation. Teeth 11 and 21 (formerly tooth 22) were restored with laminate veneers, avoiding tooth structure removal, while a ceramic crown was placed on the implant. Twelve years later, CT imaging revealed that more than 2 mm of bone was maintained on the labial side of the implant. Although root resorption was observed in the moved tooth, healthy periodontal tissues were maintained. Both objective and subjective esthetic evaluations showed favorable outcomes, suggesting that horizontal tooth movement is a minimally invasive and predictable long-term approach for tissue augmentation in implant treatments in the esthetic zone.