Journal of Japanese Society of Oral Implantology
Online ISSN : 2187-9117
Print ISSN : 0914-6695
ISSN-L : 0914-6695
Volume 33 , Issue 1
Showing 1-8 articles out of 8 articles from the selected issue
Review
  • Kazuhiro FUKUNISHI, Tomohiro ISHIKAWA, Hajime KITAJIMA
    Type: Review
    2020 Volume 33 Issue 1 Pages 6-13
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    Although dental implants fill gaps where teeth are missing, they do not replace natural teeth. As such, dental implants are not the only treatment option ; other options for missing teeth include bridges, dentures, and tooth autotransplantation. Each option has its own benefits and drawbacks. The advantages of dental implants include fixability, adjacent teeth do not have to be drilled (no invasion into other teeth), and less discomfort. As long-term clinical studies have reported favorable outcomes, the current preferred treatment plan of dentists seems to be tooth extraction without careful consideration and prioritization of dental implant over other treatment options. However, peri-implantitis has become a serious problem due to the accelerated aging of society.

    In this context, it is important to carefully consider the necessity of tooth extraction in the case of refractory apical periodontitis. This paper proposes returning to the basics and making every effort to preserve natural teeth before planning dental implant treatment with tooth extraction. In addition, the great contribution of surgical endodontics to tooth preservation is discussed.

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  • Kiminori SATO
    Type: Review
    2020 Volume 33 Issue 1 Pages 14-20
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    In order to maintain the normal function of the maxillary sinus, ventilation and drainage of the maxillary sinus via the natural ostium and ostiomeatal complex should be preserved. The maxillary sinus is ventilated via the natural ostium, which is approximately 5 mm in diameter, and drained by the mucociliary transport system of the maxillary sinus epithelium. Consequently, lesions around the natural ostium and ostiomeatal complex inhibit the ventilation and drainage of the maxillary sinus.

    Regarding factors that hinder the treatment of sinusitis, mucociliary function, bacteria and virus infections, and occlusion of the ostiomeatal complex, or a combination of these three factors, cause an inflammatory vicious cycle in the closed maxillary sinus and result in intractable maxillary sinusitis.

    The treatment philosophy for paranasal sinusitis including maxillary sinusitis is to sufficiently improve ventilation and drainage of each sinus, to reacquire the ventilation and drainage function of each sinus, to normalize the sinus epithelium, and to lead to the cure of sinusitis. Treatment of the hindering factors should be performed simultaneously.

    Even though the maxillary sinus mucosae are thick, the mucociliary transport system and ventilation and drainage of the maxillary sinus are maintained when the natural ostium of the maxillary sinus is open, secretion is not observed in the maxillary sinus and patients complain of no symptom.

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  • Yo SHIBATA, Takashi MIYAZAKI
    Type: Review
    2020 Volume 33 Issue 1 Pages 21-27
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    Recent advances in titanium implantation enable early bone fixation almost entirely associated with physico-chemical sur face modification techniques. Unlike natural periodontal tissues, less immune response at the bone-implant interface does not allow antibacterial property against oral microorganisms. More innovative surface modification techniques for dental implants that attain antibacterial effects and enhanced osteoconductivity have long been needed. So far, selective toxicity to oral bacte ria and osteoconductivity of implants have been entirely different concepts, yet our studies revealed that the reactive oxygen species spontaneously generated on the superficial passive oxide layer of titanium genuinely addresses those issues. A certain modified titanium surface appears to amplify the oxidation effects of reactive oxygen species so that the dental implant gains antibacterial potential and osteoconductivity in parallel. A non-enzymatic intracellular scaffold protein is responsible for tumor stroma stiffening together with the elevated sensitivity to oxidative stress. Our recent pilot studies found a striking resem blance between tumor stroma stiffening and enhanced mechanical properties of mineralized tissues induced by reactive oxy gen species on an amorphous titanium dioxide layer most likely through the above pathological cascade. Contemporary sur face modified dental implants are likely to enable enhanced bone fixation given by such pathological mechanism, far from the initial concept advocated by Professor Brånemark in the 1960s. Further investigation of the antibacterial property on titanium implants will clarify the biological role of titanium, thus extending the field of biomaterials research.

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Original Papers
  • Akihiro TAKAHASHI, Chiharu IMAKITA, Makoto SHIOTA, Kazuhiro KON, Norik ...
    Type: Original Paper
    2020 Volume 33 Issue 1 Pages 28-35
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    Objective : Implant prostheses contribute to the recovery of oral functions, nevertheless the lack of periodontal membrane might have a significant influence on antagonistic teeth. In this study, we investigated the factors associated with implant antagonistic natural tooth loss in long-term follow-up cases.

    Methods : This retrospective clinical study included 358 patients (237 females, 121 males, average age of 65.8 years) who were rehabilitated with fixed implant prostheses in the molar region between 2005 and 2008, and who have been followed for 10 years or more. 700 implants (maxilla : 397, mandible : 303), 358 prostheses (maxilla : 201, mandible : 157) and 667 antagonists (maxilla : 378, mandible : 289) were investigated. The primary outcomes were the survival rates of implants, implant prostheses and antagonists. The secondary outcomes were X-ray film analysis of the antagonist's position (maxilla or mandible), antagonist's vitality (vital or non-vital), history of periodontitis, and gonial angle. Statistical analysis was performed with the binary logistic-regression analysis (p<0.01).

    Results : A total of 10 implants/8 patients, 0 prosthesis, and 62 antagonists/32 patients were lost. The survival rates of implants, prostheses and antagonists were 98.5, 100, and 90.7%, respectively. A statistically significant difference was observed for history of periodontitis (p< 0.01) and gonial angle (p< 0.01) at the patient level, while it was observed for vitality of antagonist (p< 0.01), history of periodontitis (p< 0.01) and gonial angle (p< 0.01) at the antagonist level. No significant difference was observed for antagonist position (p = 0.1304).

    Conclusions : It is suggested that vitality of antagonist, history of periodontitis and gonial angle have significant influences on antagonistic teeth in implant prostheses.

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Original Papers
  • Ryuichi USUI, Takeo MATSUDA, Yasuki SEKIYA, Kenju NATORI, Ken ITO, Tos ...
    Type: Original Paper
    2020 Volume 33 Issue 1 Pages 36-44
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    This study was conducted to clarify the relation between the maximum bending load, deflection and strain applied to an implant collar and the ratio of superstructure length to implant body length. The length I of the implant body was maintained at 12.4 mm, whereas the superstructure length was varied (9, 10, 12, or 15 mm). For each superstructure length, the distance (1.5 mm) between the superstructure margin and bone level was added and this length (i.e., superstructure length + 1.5 mm) was denoted as C. Thus, the C/I ratios were 0.85, 0.93, 1.09, and 1.33, respectively, for the four superstructure lengths. The implant with its mounted superstructure was fixed at an inclination angle of 30°. The maximum bending load tended to decrease as the superstructure length increased and was the lowest when the C/I ratio was 1.33, where its value was 57.6% of the maximum bending load that was observed for a C/I ratio of 0.85. The deformation increased up to the maximum bending load as the superstructure length increased. For C/I ratios of 0.85 and 0.93, the strain on the implant collar was <0.1% when the load was 150-250 N ; for C/I ratios of 1.09 and 1.33, the strain was >0.1% when the load was 150 N. When the load was 300 N, the strain was >0.1% for all the C/I ratios. Further, the maximum and minimum strains were 0.36% and 0.11% for C/I ratios of 1.33 and 0.85, respectively. When the load was 500 N or more, for the C/I ratio of 1.33, the strain was the limit value (2.1%) of the strain gauge. We observed that the strain applied to the implant collar increased as the superstructure length increased. This indicated that the superstructure length should be considered to be relative to the length of the implant in implant treatments.

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  • Kurito YASUDA, Kazuto MAKIGUSA, Daisuke EHARA, Isumi TODA
    Type: Original Paper
    2020 Volume 33 Issue 1 Pages 45-51
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    Several previous studies have demonstrated that platform-switching is effective for preventing the resorption of peri implant bone and its surrounding soft tissue. This approach requires two adjacent implants at least 3 mm apart. This study aimed to clarify the effect of platform-switching on the bone between two adjacent implants when the inter-implant distance is shorter than 3 mm.

    In adult macaques (Macaca fascicularis), two adjacent implants that were 1.5 mm (mesiodistal distance) apart were placed in close proximity to the mandibular posterior tooth site, and temporary abutments were used such that one was a platform switching implant and the other was a non-platform-switching implant.

    After 8 weeks, the tissue between the implants was observed under a scanning electron microscope and an optical microscope. In the non-platform-switching group, the alveolar bone was resorbed in the horizontal and vertical directions near the platform. However, in the platform-switching group, the alveolar bone was vertically preserved near the platform, and a new bone was horizontally formed ; the range considered to represent the infiltration of inflammatory cells was further reduced.

    These results suggest that the use of platform-switching may help to preserve healthy peri-implant tissue even when the distance between two adjacent implants is less than 3 mm.

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Case Report
  • Jun KUSAMA, Satoru MATSUDA, Masumi OZAWA, Hirotaka SAITO, Youko HASEGA ...
    Type: Case Report
    2020 Volume 33 Issue 1 Pages 52-58
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    In recent years, dental implants as prosthodontic treatment for missing teeth have become widespread as highly predictable prostheses for defects. Following dental implant treatment, the number of cases where dental implant bodies can be left in situ while maintaining a comfortable oral environment has increased. However, there has also been a rise in the number of cases where dental implant bodies must be removed due to poor prognosis.

    In the present case study, a dental implant body required removal due to poor placement position, having been left in situ for about 5 years 6 months until it was completely covered by alveolar bone. We performed computer-guided surgery to remove it. A surgical template created using preoperative computed tomography was applied for removal, enabling us to approach just above the implant body. Six months after removal, a new implant body was embedded at an appropriate placement position using computer-guided surgery, with good results. Computer-guided surgery enabled us to verify the exact placement position of the new implant body, and provided a less surgically invasive procedure with better outcome than if computer-guided surgery had not been used.

    Digital technologies such as computer-guided surgery are expected to be used for various clinical applications in the future.

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Survey, Statistics and Materials
  • Michiro KAWAMAE, Masashi FUJIGAKI, Fujio MUKAE, Ritsumei SASAKI, Yuki ...
    Type: Survey, Statistics and Materials
    2020 Volume 33 Issue 1 Pages 59-67
    Published: March 31, 2020
    Released: May 10, 2020
    JOURNALS FREE ACCESS

    Introduction : Periodic maintenance therapy is necessary to maintain long-term stability of implant prosthetics. Many re gions in Japan are facing depopulation and an aging population, resulting in decreasing availability of public transportation. Consequently, social and other activities among the elderly are impacted negatively, including visits to clinics. This study ex amined the state of patient attendance of post-implant maintenance programs (PIMP) in five areas in Kyushu where depopu lation is increasing.

    Methods : A questionnaire was sent by post to the head of each of the five clinics who had consented to participate in this study. The questionnaire was on the status of patient attendance for maintenance therapy and asked about the following items. (1) The patients were divided into three groups based on their attendance status for PIMP : group 1 ─ those with pe riodic attendance for maintenance, group 2 ─ those with irregular attendance, and Group 3 ─ those with complete non-atten dance. (2) The patients with non-attendance were phoned to ask about the reasons for complete non-attendance in PIMP. (3) The patients were asked about modes of transport to clinics and the time required for transport.

    Results : There was a total of 1,036 maintenance patients among the five clinics. They consisted of 58.2% women and 41.8% men, and the age ranged from 19 to 92 years. Of the 1,036 patients, 63.9% had periodic attendance for maintenance, 14.7% had irregular attendance, and 21.4% had complete non-attendance. The attendance rates (periodic and irregular attendance) by age group were 61.4% for patients younger than 40 and approximately 80% for those 40 or older, indicating a significant dif ference between these age groups. Of the 1,036 patients, 825 patients required less than 30 minutes for transport to the clinic. The attendance rate was 79.4% for patients requiring less than 30 minutes, which was significantly higher than that for pa tients requiring 30 minutes or more. Regarding modes of transport to clinics, the majority of patients in every clinic used their own car. A few of the patients traveled on foot, public bus, or train.

    Discussion and Conclusion : The time required for transport to clinics and the patient's age were factors that influenced the attendance rates for implant maintenance visits. Among the elderly patients, an increase in death and illness was the rea son for non-attendance. Since the majority of the patients traveled to clinics in their own car, it is a concern that patients who have difficulty getting to hospitals and clinics will likely increase as they age.

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