Ionic spiderwebs.

Spiders use adhesive, stretchable, and translucent webs to capture their prey. However, sustaining the capturing capability of these webs can be challenging because the webs inevitably invite contamination, thus reducing its adhesion force. To overcome these challenges, spiders have developed strategies of using webs to sense prey and clean contaminants. Here, we emulate the capturing strategies of a spider with a single pair of ionic threads based on electrostatics. Our ionic spiderwebs completed consecutive missions of cleaning contamination on itself, sensing approaching targets, capturing those targets, and releasing them. The ionic spiderwebs demonstrate the importance of learning from nature and push the boundaries of soft robotics in an attempt to combine mutually complementary functions into a single unit with a simple structure.

Finite Element Analysis of Novel Separable Fixture for Easy Retrievement in Case with Peri-Implantitis.

Peri-implantitis is a common complication following dental implant placement, which may lead to bone loss and fixation failure. With the conventional fixture, it is difficult to perfectly clear-up the infection. To solve this, we have designed a separable fixture of which the top part is replaceable. This study aimed to compare the structural and biomechanical stability of the separable and conventional fixture. A single surgical model corresponding to the first molar in a virtual mandible model and conventional/separable implants were reproduced to compare the biomechanical characteristics of the implants using finite element analysis (FEA). The loading condition was 200N preload in the first step, and 100N (Axial), 100N (15°), and 30N (45°) in the second step. The stress distribution on the cortical bone in the separable implant was lower than the conventional implant. In particular, the Peak von Mises Stress (PVMS) values of the separable implant under lateral load was found to be about twice as low as that of the conventional implant. In this study, we suggest that the separable implant has an equivalent biomechanical stability compared to the conventional implant, is easy to retrieve in the case of peri-implantitis, and has an excellent initial stability after the surgery when used in stage 2.

The effect of diabetes on tooth loss caused by periodontal disease: A nationwide population-based cohort study in South Korea.

BACKGROUND: Our purpose was to compare the risk of tooth loss caused by periodontal disease between diabetic and nondiabetic individuals and to estimate the relative risk of tooth loss according to the severity and control of diabetes. METHODS: We selected 10,215 individuals who were diagnosed as diabetics in the Korean National Health Insurance Service-National Sample Cohort (NHIS-NSC) database in 2003 and the same number of individuals who had never been diagnosed with diabetes during the period covered by the NHIS-NSC (2002-2013) with propensity score matching. Diabetic individuals were divided into two groups according to the treatment modality. We counted the number of teeth lost in each group to determine the difference in the risk of tooth loss among groups and used the Cox proportional hazards model to calculate hazard ratios (HRs) of tooth loss caused by periodontitis. RESULTS: Diabetic individuals had a higher risk of tooth loss than nondiabetic individuals (HR = 1.298, 95% confidence interval [CI]: 1.233 ≤ HR ≤ 1.366; P < 0.01). The severer the degree of diabetes, the higher the risk of tooth loss. As the number of dental visits increased, the risk of tooth loss declined (HR = 0.998, 95% CI: 0.996 ≤ HR ≤ 0.999; P < 0.01). CONCLUSIONS: Within the limits of this retrospective cohort study, the risk of tooth loss among diabetic individuals was higher than that among nondiabetic individuals. The risk of tooth loss declined with increasing numbers of dental visits and increased with the severity of diabetes.

Hollow Abutment Screw Design for Easy Retrieval in Case of Screw Fracture in Dental Implant System.

The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access hole for easy retrieval. This study aimed to introduce this modified design of the abutment screw, the concept of easy retrieval, and to compare the mechanical strengths of the conventional and hollow abutment screws by finite element analysis (FEA) and mechanical test. In the FEA results, both types of abutment screws showed similar stress distribution in the single artificial tooth system. A maximum load difference of about 2% occurred in the vertical load by a mechanical test. This study showed that the hollow abutment screw may be an alternative to the conventional abutment screws because this is designed for easy retrieval and that both abutment screws showed no significant difference in the mechanical tests and in the FEA.

The prognosis of splinted restoration of the most-distal implants in the posterior region.

PURPOSE: The aim of this study was to compare the efficacies of two-implant splinting (2-IS) and single-implant restoration (1-IR) in the first and second molar regions over a mean functional loading period (FLP) of 40 months, and to propose the appropriate clinical considerations for the splinting technique. MATERIALS AND METHODS: The following clinical factors were examined in the 1-IR and 2-IS groups based on the total hospital records of the patients: sex, mean age, implant location, FLP, bone grafting, clinical crown-implant ratio, crown height space, and horizontal distance. The mechanical complications [i.e., screw loosening (SL), screw fracture, crown fracture, and repeated SL] and biological complications [i.e., peri-implant mucositis (PM) and peri-implantitis (PI)] were also evaluated for each patient. In analysis of two groups, the chi-square test and Student's t-test were used to identify the relationship between clinical factors and complication rates. The optimal cutoff value for the FLP based on complications was evaluated using receiver operating characteristics analysis. RESULTS: In total, 234 patients with 408 implants that had been placed during 2005 - 2014 were investigated. The incident rates of SL (P<.001), PM (P=.002), and PI (P=.046) differed significantly between the 1-IR and 2-IS groups. The FLP was the only meaningful clinical factor for mechanical and biological complication rates in 2-IS. CONCLUSION: The mechanical complication rates were lower for 2-IS than for 1-IR, while the biological complication rates were higher for 2-IS. FLP of 39.80 and 46.57 months were the reference follow-up periods for preventing biological and mechanical complications, respectively.

Mechanical and biological complication rates of the modified lateral-screw-retained implant prosthesis in the posterior region: an alternative to the conventional Implant prosthetic system.

PURPOSE: The modified lateral-screw-retained implant prosthesis (LSP) is designed to combine the advantages of screw- and cement-retained implant prostheses. This retrospective study evaluated the mechanical and biological complication rates of implant-supported single crowns (ISSCs) inserted with the modified LSP in the posterior region, and determined how these complication rates are affected by clinical factors. MATERIALS AND METHODS: Mechanical complications (i.e., lateral screw loosening [LSL], abutment screw loosening, lateral screw fracture, and ceramic fracture) and biological complications (i.e., peri-implant mucositis [PM] and peri-implantitis) were identified from the patients' treatment records, clinical photographs, periapical radiographs, panoramic radiographs, and clinical indices. The correlations between complication rates and the following clinical factors were determined: gender, age, position in the jaw, placement location, functional duration, clinical crown-to-implant length ratio, crown height space, and the use of a submerged or nonsubmerged placement procedure. RESULTS: Mechanical and biological complications were present in 25 of 73 ISSCs with the modified LSP. LSL (n=11) and PM (n=11) were the most common complications. The incidence of mechanical complications was significantly related to gender (P=.018). The other clinical factors were not significantly associated with mechanical and biological complication rates. CONCLUSION: Within the limitations of this study, the incidence of mechanical and biological complications in the posterior region was similar for both modified LSP and conventional implant prosthetic systems. In addition, the modified LSP is amenable to maintenance care, which facilitates the prevention and treatment of mechanical and biological complications.

Safe Removal of a Broken Abutment Screw with Customized Drill Guide and Rotary Instrument: A Clinical Report.

This clinical report introduces a method for safe retrieval of a broken implant abutment screw. A reverse-tapping rotary instrument has been introduced in the market and is widely used to retrieve broken screws; however, it is difficult to use the rotary instrument unless an access hole for engagement of the rotary instrument is positioned directly on the center of the top of the broken screw remnant. Poor visibility is another limitation to make an access hole. To keep the position of the rotary instrument at the center of the broken screw, a customized drill guide was fabricated, modifying an implant impression coping with self-cured acrylic resin, all easily found in daily practice. The broken screw was easily removed, not damaging the internal threads of the implant. This technique could be applied to most implant systems when a specific removal kit for each implant system is not prepared.