The purpose of the present study was to evaluate the marginal gap and influence of abutment thickness on the fracture force of zirconia and titanium custom abutments. The abutments were fabricated using CAD/CAM, and were classified into 12 groups (n=5) by material (yttria-stabilized tetragonal zirconia polycrystal: Y-TZP or pure titanium: Ti as a control), abutment thickness (0.4 mm, 0.6 mm or 1.0 mm) and joint system (external joint or internal joint). These abutments were attached to the implant body (3.8 mm in diameter, 13.0 mm in length) with a torque of 30 N. The marginal gap between the implant body and abutment was measured using a scanning electron microscope. Subsequently, the fracture force was measured by applying a static load to the abutments at an angle of 30° to the vertical axis according to ISO1480. On the Ti specimens that were not fractured, the yield force at which the load-displacement curves first deviated by 0.2% of displacement from the regression line was measured. The marginal gap between the implant body and abutment ranged from 2.5 to 5.6 μm in all conditions, showing superior dimensional accuracy. The fracture (yield) force decreased with decreasing abutment thickness. The fracture forces of the Y-TZP abutments with 0.6 mm thickness were 449 N and 527 N on the external and internal joint, respectively. The yield forces of the Ti abutments with 0.6 mm thickness were 615 N and 530 N on the external and internal joint, respectively. The fracture forces of the Y-TZP abutments with 0.4 mm thickness were 320 N and 298 N on the external and internal joint, respectively. The yield forces of the Ti abutments with 0.4 mm thickness were 361 N and 389 N on the external and internal joint, respectively. These results indicated that the Y-TZP abutments with a thickness of more than 0.6 mm could sustain the occlusal force.
The purpose of this study was to clarify the effects of a diamond-like carbon (DLC) coating for improving the water absorption, wear and cytotoxicity of resin teeth for dental implant prostheses. Two kinds of resin teeth composed of polyethyl-methacrylate (PMMA) and urethane dimethacrylate (UDMA) were used. The DLC film was coated on the resin teeth to a thickness of less than 0.1 μm without impairing the esthetics by chemical vapor deposition (CVD). A brushing test of the resin teeth was carried out in water at room temperature for 24 h using a brushing machine. Amounts of water absorption and wear were measured by the change in weight after brushing. The effects of the DLC coating on cytotoxicity of the resin teeth were examined by growth curves of MC3T3-E1 osteoblast-like cells. After the brushing test, the weight of the uncoated resin teeth increased with time because water absorption was larger than wear loss. On the other hand, no weight change was observed in the DLC-coated resin teeth. Strong adhesion between the resin teeth and DLC was observed by Raman spectrum analysis. Cytotoxicity tests of both the extracted solution and powder of resin teeth indicated positive results, but the positive cytotoxicity became negative with the DLC coating.These results verified that the DLC coating improves the water absorption, wear and cytotoxicity of resin teeth, and that DLC-coated resin teeth may be more suitable for implant prostheses.
Purpose: Peri-implantitis (PI) is often caused by infection from periodontopathic bacteria (PB). In partially edentulous patients, PI is reportedly characterized by transmission of PB from remaining teeth to implants, resulting in similar compositions of subgingival microbial flora in both areas. Recent prospective epidemiological studies have demonstrated that the risk of PB transmission increases in patients with untreated or severe periodontitis, in whom periodontal pockets tend to remain after treatment, thereby reducing rates of implant survival and success. The present study retrospectively evaluated case series study data to determine relationships between clinical course of implant therapy and detection (or non-detection) of PB from before implant therapy until post-treatment maintenance in patients with or without periodontitis. Methods: The subjects were 62 patients (including 22 patients with periodontitis) for whom at least 2 years had elapsed since placement and fitting of an implant and superstructure. Data were obtained from a battery of clinical tests (probing pocket depth, bleeding on probing, pus discharge, radiographic assessment of alveolar bone resorption) and PB testing conducted before implant placement (baseline), upon fitting of the superstructure,at least 2 years after fitting of the superstructure (re-evaluation 1) and 3-6 months after treatment of the implant site based on the cumulative interceptive supportive therapy (CIST) protocol (re-evaluation 2). Correlations between presence or absence of PB and presence or absence of PI at each test point as well as presence or absence of clinical improvement after PI treatment were then statistically evaluated. Results: 1. Patients who tested positive for PB in remaining teeth at baseline also had a significantly higher positive PB test rate in implants at fitting of the superstructure than patients who tested negative for PB at baseline. This trend was particularly pronounced among periodontitis patients. 2. PI patients had a significantly higher positive PB test rate at re-evaluation 1 and at superstructure fitting than their non-PI counterparts. 3. The clinical improvement rate after PI treatment was significantly lower in patients who tested positive for PB in remaining teeth at baseline and at superstructure fitting compared to patients who tested negative. Conclusion: The present results indicate that transmission of PB from remaining teeth to implants and subsequent persistent infection are prone to occur in periodontitis patients, suggesting that this transmission is a risk factor for both PI and diminished treatment response in peri-implantitis therapy.
Aim: We report a case in which new bone formed after removal of grafted material due to postoperative infection in an augmented maxillary sinus floor. Patient: The patient was a 62-year-old female who had suffered from denture incompatibility for several years. She had undergone a procedure to augment the sinus floor with a 1:1 mixture of Ceraform ® and autologous bone. We diagnosed that the graft was infected 1 month after surgery. We removed a part of the graft material through a lateral window surgical procedure. Consequently, the postoperative infection and inflammation were controlled. Seven months after the surgery to control the infection, cone-beam computed tomography (CBCT) images showed that the density in the cavity had increased. We biopsied the ossified tissue inside the augmented site, and placed implant bodies at the sites of #26 and #27. The biopsy specimen showed that new bone had formed and that the new bone was composed of lamellar bone (31.6%), residual HA particles (10.4%), and connective tissue. As of 4 years after placing the implant bodies, there continue to be no signs of implant failure. Conclusion: In the present case, the space under the dome of the closed cavity gradually filled with new bone growth, while the sinus membrane lying on the dome was undisturbed. We suggest that promoting new bone growth to fill such void spaces can be a useful therapeutic strategy.
Purpose: The aim of this study was to clarify the risk communication between dental care staff and patients for implant treatment. Methods: The subjects of this analysis comprised 497 patients including 47 oral implant patients who were randomly chosen from the consumer panel of goo Research, a web research company. We designed a questionnaire based on three concepts regarding risk communication, "Treatment information provided", "Patient's perception of treatment explanation", and "Exchange of opinions with dental care staff". There were 16 questions in total, such as "Experience in consulting a public agency". IBM SPSS Statistics 19.0 for Windows was used for the analysis. Results: A significantly higher percentage of oral implant patients felt that they were well informed compared to other prosthodontics patients in the questions "Treatment information provided" which included three questions such as "Various treatments" (p<0.01), "An estimate of treatment costs" (p<0.001) and "Demerits, disadvantages and risk of treatment" (p<0.05). In the area of exchange of opinions, a significantly higher percentage of implant patients answered that they had "chance to ask dental care staff" (p<0.01). There was no significant difference in whether the patients consulted public agencies. Conclusion: Most oral implant patients positively evaluated the information provided by dental care staff and communication with them.
Background: The Clinical Practice Guideline for Image Diagnosis in Implant Dentistry (GIDID) was drawn up by the Japanese Society for Oral and Maxillofacial Radiology (JSOMR) as a criterion for justification and optimization of image examination with radiation exposure in implant treatment. It was listed in the Medical Information Network Distribution Service (Minds) in 2008. The GIDID is intended for all dentists engaged in dental implant treatment. Objectives: The aim of this study was to find out the degree of recognition of the GIDID and the state of implementation of CT examination for implant treatment among general dental practitioners (GPs) . Methods: For 83 GPs engaged in implant therapy, we conducted a questionnaire survey on possession of dental cone-beam CT (CBCT) , number of dental implants placed in the most recent one year, membership of academic societies related to image diagnosis in implant dentistry, recognition of the GIDID and Minds, and the state of implementation of CT examination for preoperative diagnosis in implant treatment. Results: Among the 50 GPs who replied to the questionnaire (60.2%) , 7 GPs had CBCT (14%) , and 43 GPs did not (86%) . The owners group had placed more implants than the non-owners group over one year (median, 70 vs. 10; p=0.001) . In both groups, most GPs belonged to the Japanese Society of Oral Implantology (JSOI) (owners group: 71.4%; non-owners group: 27.9%) . There were no members of JSOMR. Regardless of possession of CBCT, most GPs were not aware of the GIDID (owners group: 42.9%; non-owners group: 52.3%) . Of the 50 GPs, 46 did not know about Minds (92%) , and 25 including all owners of CBCT performed CT examinations for all implant cases (50%) . Among the owners group, their rates of performing CT inspection before installing CBCTs in their clinics had ranged from 5 to 80% (median 50%) . Conclusion: The results suggest that the introduction of CBCT into clinics increases the indication of CT examination for dental implant treatment. The JSOI therefore has an important role to play in increasing awareness of the Guideline established using an evidence-based medicine approach to implant dentistry and listed in the Minds, even though it was drawn up by another society.