Japan, with an increasing number of elderly people needing long-term care in a super-aged society, urgently needs to develop clinical guidelines on implant maintenance for elderly people with declining independence. The purpose of this position pa per is to categorize the troubles encountered in the care of patients with dental implants and to indicate actual practices and key points. From the members of the Japanese Society of Oral Implantology, 12 expert panelists who had experience of many problems of implant maintenance during dental visits and were familiar with their solutions were selected. Through repeated discussions in many panel meetings, the problems of implant maintenance during dental visits were identified.
During a dental visit, state of the oral cavity, general conditions, and background of elderly patients who cannot orally care for themselves must be grasped, and medical staff, care managers, and patients should understand the changes in these factors over time. The solutions and responses that can be made differ greatly depending on the medical care facilities, the environment, differences in the experience of medical staff, and the patient's background. Thus, it is necessary to select safe treatments appropriate to each situation. Since the inability to distinguish implant manufacturers is a serious problem, the spread of implant cards should be actively encouraged, and a system for sharing patients' oral information should be created.
This paper features many opinions based on clinical experience. However, clinical guidelines on implant management during dental visits should be formulated in the future based on the accumulation of evidence through clinical research.
Determining whether to extract teeth has been a problem in dental therapy to date. Many patients do not visit a dental office to have their teeth extracted in the first place, but to resolve toothache or swelling, or to recover masticatory function. The accumulated know-how and mid- to long-term successful prognosis of implant therapy have spurred indications for dental implant. Moreover, as techniques and mid- to long-term successful prognosis of treatment have improved, periodontology has met patients' expectations and raised their hope for retaining their own teeth. Those two outcomes have made it much harder to determine whether to extract teeth. We must perform appropriate implant therapy for the indicated tooth-extracted site while trying to retain the natural teeth as long as possible. Determining whether to extract a tooth that is suffering progressive periodontal disease requires a comprehensive evaluation of periodontal parameters, prosthetic design and the patient's psychology.
Root fracture remains a serious clinical problem, even as advances in comprehensive plaque control mean that caries and periodontitis, which used to be common bacterial infectious diseases, are mostly preventable.
Research by American endodontists showed that patients aged over 40 are vulnerable to vertical root fractures in upper premolars and upper and lower molars, especially in pulpless teeth, regardless of their experience of root canal treatment. In most cases, the teeth had to be extracted. A similar tendency was found in the data of Japanese patients; interestingly, the cracks in the teeth of Japanese patients initiated from cervical and apical areas with almost the same frequencies.
There is a consensus among clinicians that teeth with vertical root fractures need surgical treatments, such as extraction or root resection. However, modern dental microscopes and CBCT can often detect cracks at the initial stage. Based on our clinical experience, it is possible to preserve such vertically fractured teeth with initial cracks after they have been strengthened by modern adhesive materials. However, there is a risk of re-fracture and further extensive loss of periodontal tissue in the preserved teeth. In this article, I discuss the principles for deciding which endodontically treated teeth with vertical root fracture could or should be rescued.
Long-term etiological studies demonstrate that the best option for preventing root fracture is to preserve dental pulp. I outline a way to protect pulp better by indirect pulp capping with stepwise excavation.
In the symposium entitled “Reconsideration of tooth extraction criteria during implant treatment” held at the 47th Annual Meeting of the Japanese Society of Oral Implantology, I gave a lecture. Since I was asked to speak from the standpoint of an endodontist, I discussed the kinds of endodontic diseases where tooth extraction is indicated.
Clinically, there are five major scenarios when tooth extraction is considered from an endodontic point of view :
1. Complete vertical root fracture
2. Shortage of residual sound dentin
3. Lesion at the root apex with zipping that cannot be modified or broken files in a root canal that cannot be removed and for which root apex resection is difficult for anatomical reasons
4. Large perforation
5. Endo-perio lesion with communication (Periodontal regeneration therapy cannot be expected in such cases.) In this symposium, cases with perforation were discussed. The approach to perforation depends on its location. When the perforation is visible, physical sealing is performed using a biomaterial such as mineral trioxide aggregate (MTA). When it cannot be confirmed visually, induction of hard tissue (cementum) is attempted using a calcium hydroxide agent. However, when physical sealing is difficult or when biological cure cannot be expected, tooth extraction might be conducted.
Here, through several clinical cases, I discuss the causes and treatments of perforations in the sidewalls and furcation area of the root.
It has been pointed out that the granule components in toothpaste penetrate and remain in the peri-implant sulcus, where they may cause inflammation of the peri-implant tissue. The aim of this clinical study was to evaluate the effect of penetration of granule components on inflammation of peri-implant tissue in patients visiting for maintenance after implant treatment, by investigating the condition of peri-implant tissue and performing the tooth-brushing test using toothpaste mixed with a granule component.
Fifty-five patients and 145 implants for supporting 78 screw-retained superstructures of the molar sites were investigated. The adhesion of dental plaque around the superstructure and the presence of inflammation of peri-implant tissue were evaluated. Additionally, the morphology of peri-implant tissue was measured. In the users of toothpaste with a granule component, residual granules of peri-implant sulcus were observed. After performing the tooth-brushing test using a toothpaste with granule component, the penetration of granules into the peri-implant sulcus was investigated. From the observation survey and the tooth-brushing test, the relationship among the presence of inflammation of peri-implant tissue, the morphology of the peri-implant tissue and the invasion of granule components was evaluated.
In 19 patients who used the toothpaste with granule components daily, granule components remained in 14 implants of 6 patients. There was no correlation with the presence of inflammation and the remnants of granule components. In the tooth brushing test, 22 implants in 13 patients showed penetration of granule components. No correlation was found with the presence of inflammation and the penetration of granule components.
From the results of this study, it was inferred that there was little relation between the penetration of the granule components of toothpaste and the inflammation of the peri-implant tissue.
This study examined the effect of inserting an implant at a specific angle of inclination on its maximum bending load and the strain in its collar portion. Implant bodies and abutments were made from cold-worked JIS type-2 titanium (GWGW), JIS type-4 titanium (G4G4), and Ti-6Al-4V alloy (G5G5). The implant bodies and abutments of the same material were used in combination. Strain gages were fixed to the collar portions of the two-piece implants at angles of inclination of 10°, 20°, and 30°. Loads were applied using a universal testing machine while the maximum bending load on the implant and the strain in its collar portion were measured. In addition, the inside of the implant was observed by CT before and after measurement of maximum bending load.
Based on the results of these tests the following conclusions were drawn.
The maximum bending load of the GWGW, G5G5, and G5G5 implants was the highest at an angle of inclination of 10° and decreased as the angle of inclination was increased. When the angle of inclination was increased from 10° to 20°, the maximum bending load decreased by 58.5%, 60.9%, and 60% in the GWGW, G4G4, and G5G5 implants respectively. Furthermore, the maximum bending load at an angle of inclination of 30° decreased by 75.8%, 78.2%, and 76% in the GWGW, G4G4, and G5G5 implants, in comparison with that at an angle of inclination of 10°. Based on the strain measurements, when a load of 300 N was applied, the strain in the collar portion of all implants was 0.1% or less at an angle of inclination of 10°, 20°, and 30°. This was also observed for the implants with an angle of inclination of 10° and 20° when a load of 400 N was applied and for those with an angle of inclination of 10° when loads of 500 N and 600 N were applied. However, when a load greater than or equal to 400 N was applied to implants with an angle of inclination of 30°, the strain exceeded 0.1%. The GWGW implant exhibited the highest strain. CT observation of the implant before the bending test showed adaptability with an excellent abutment and implant body. After the bending test measurement, the abutment fractured at the boundary of the taper part and part of the screw. When the screw did not fracture, plastic deformation and cracking of the abutment were observed. Hence, the experimental findings suggest that when inserting an implant at an angle of inclination greater than 20°, it is essential to select an implant with a collar portion made of a high-strength material.
Purpose : When complications, it is not easy to remove a cement-retained superstructure. Temporary cement is used to avoid such problems, and its application is becoming more versatile. Therefore, to overcome the disadvantages of the conventional removal method, we formed a slot hole on the interface between the crown and abutment using the electrical discharge method, inserted an angled removal tool exerting a wedge effect, and determined whether the crown attached using temporary cement can be removed from the abutment using a clinically applicable method.
Method : We then formed an original slot by die-sinking a box shape for the original removal tool. This was formed in the intermediate section on the lingual side between the frame of the superstructure and the abutment using an electrical discharge machine. The superstructure was attached using cement, and inserted the two types of removal tool (angle of 18° and 24°) inside the slot and checked if the superstructure could be removed. Multiple comparison tests were used to compare the bonding strengths and thickness of the cement films.
Results : Comparison between the two types of angled removal tool with different angles showed that the tool with an angle of 24° can produce a wedge effect with any cement and separate the copings with a smaller load than the removal tool with an angle of 18° (t-test, p＜0.01). The cement film was the thinnest in TB and the thickest in TH. There was no significant difference between TB and TP.
Conclusions : This removal method can expand the scope of application of electrical discharging in the dental field and can be recognized as an innovative method for the fabrication of cemented superstructures. From a clinical viewpoint, cements with high bonding strengths and thin film thicknesses, such as IP and FT, are considered to be ideal.
In recent years, digital technology for implant prostheses has greatly advanced and the method of using an intraoral scanner to take optical impressions has attracted attention. However, there are still many unclear points about the reproducibility of implant position in cases with full arch implants. Therefore, the aim of this study was to evaluate the optical impression captured by the intraoral scanner and the silicone impression by 3-dimensional analysis software, using a maxillary edentulous jaw model with six implants implanted in 16, 14, 12, 22, 24, 26(the master model).
The master model was fitted with six scan bodies, which provided the basic data. Then, the scanning data of the optical impression recommended by the manufacturer (IOS1) and optical impression omitting the scanning process (IOS2) were both provided. Next, the impression of the master model was obtained by the open-tray method, and the cast model was fabricated by both the one-time injection method (IMP1) and the two-times injection method using a drinking straw (IMP2) to obtain respective data. The basic data as well as IOS1, IOS2, IMP1, and IMP2 were superimposed by software respectively, and the data were evaluated based on the adaptation ratio and the color mapping image. IOS2 showed a statistically significant difference from IOS1, IMP1 and IMP2. Since the alveolar ridge was the landmark before scanning the scan bodies, the positional relationship of the scan bodies was clarified. IOS1 showed a higher adaptation ratio than IOS2. On the other hand, since there was no statistically significant difference between IOS1, IMP1, and IMP2, it became clear that the accuracy of optical impressions taken by the intraoral scanner by the manufacturer was comparable to that of silicone impressions. In addition, since the IMP2 data showed smaller dispersion than that of IMP1, it was proven that the dental stone injection method using drinking straws was more accurate than the standard method. IOS1 showed smaller vertical error than IMP1 and IMP2 from the color mapping image. Therefore, it will be simple to adjust the occlusion of the implant superstructure fabricated by the intraoral scanner. However, since IMP1 and IMP2 showed displacement in the vertical error, occlusion adjustment of the implant superstructure and accuracy of the framework must be done carefully.
This study found that the method of taking optical impressions by an intraoral scanner could be applied to cases of full arch implants.
In this paper, we report a case of a wide jawbone-anchored prosthetic device for full dental rehabilitation after resection of the left upper gingival carcinoma in situ.
An 87-year-old woman was referred to our department because of left upper gingival pain. Histological diagnosis was gingival carcinoma in situ of the left upper gingiva and leukoplakia of the right upper gingiva. Bilateral maxillary tumor extirpation and two dental implant placements were carried out. After surgery, the masticatory function decreased because the ability to maintain the denture was extremely decreased. Because exposed necrotic bone was observed in the left anterior maxilla, the sequestrum was extirpated and two dental implants were placed into the left posterior maxillary bone 7 months after the first surgery. One year 3 months later, we applied an implant-supported prosthesis with locator attachment for postoperative maxillary gingival carcinoma in situ. As a result, the masticatory function and QOL were remarkably improved. Although 4 years have passed since the implant superstructures were placed, the patient has followed a favorable clinical course.