Jungwon Lee

Protecting the method of auxiliary sources (MAS) solutions from the interior resonance problem

The method of auxiliary sources (MAS) has been used for the numerical solution of a variety of electromagnetic problems successfully. Since MAS can be considered as a modified or generalized version of the standard surface integral equation technique (SIE), it has the interior resonance problem, but the remedies to this problem have not been investigated yet. In this letter, it is shown that the interior resonance problem in applying MAS can be completely removed using combined-source solution (CSS).

An iterative FEM for scattering by a 3-D cavity-backed aperture

A finite-element method (FEM)-based hybrid method (or iterative FEM) is successfully applied to a three-dimensional (3-D) scattering problem without the effect of internal resonance. With only a small number of meshes around a 3-D scatterer, this FEM is shown to give an accurate result through several iterative updates of the boundary conditions. To confirm the efficiency of this method, scattering from a 3-D cavity-backed aperture is analyzed and the results obtained are compared with the same obtained by another conventional method.

Relief of Injection Pain During Delivery of Local Anesthesia by Computer-Controlled Anesthetic Delivery System for Periodontal Surgery: Randomized Clinical Controlled Trial

BACKGROUND Pain from local anesthetic injection makes patients anxious when visiting a dental clinic. This study aims to determine differences in pain according to types of local anesthetizing methods and to identify the possible contributing factors (e.g., dental anxiety, stress, and sex). METHODS Thirty-one patients who underwent open-flap debridement in maxillary premolar and molar areas during treatment for chronic periodontitis were evaluated for this study. A randomized, split-mouth, single-masked clinical trial was implemented. The dental anxiety scale (DAS) and perceived stress scale (PSS) were administered before surgery. Two lidocaine ampules for each patient were used for local infiltration anesthesia (supraperiosteal injection). Injection pain was measured immediately after local infiltration anesthesia using the visual analog pain scale (VAS) questionnaire. Results from the questionnaire were used to assess degree of pain patients feel when a conventional local anesthetic technique (CNV) is used compared with a computer-controlled anesthetic delivery system (CNR). RESULTS DAS and PSS did not correlate to injection pain. VAS scores were lower for CNR than for CNV regardless of the order in which anesthetic procedures were applied. VAS score did not differ significantly with sex. Pearson coefficient for correlation between VAS scores for the two procedures was 0.80, also indicating a strong correlation. CONCLUSION Within the limitations of the present study, relief from injection pain is observed using CNR.

Flap Management in Alveolar Ridge Preservation: A Systematic Review and Meta-Analysis

PURPOSE This systematic review aimed to identify the effects of certain flap management procedures on ridge preservation on the basis of existing literature. MATERIALS AND METHODS Electronic (MEDLINE, EMBASE, and Cochrane Central Register of controlled trials) and manual searches of the literature were conducted until February 2017. Randomized controlled trials (RCTs), controlled clinical trials (CCTs), and prospective cohort studies that involved at least 10 subjects were eligible for this systematic review. To evaluate the beneficial effects of flap management on ridge preservation, changes in the bone width, bone height, and keratinized gingiva width were calculated using a random effects model. RESULTS Eleven studies (nine RCTs and two CCTs) were included in this review. No statistically significant differences in bone width and height changes were identified between the flapped and flapless ridge preservation techniques and between the free gingival graft and flapless ridge preservation techniques. A statistically significant shrinkage in keratinized gingiva width was noted with flapped ridge preservation compared with flapless ridge preservation (weighted mean differences, -3.21 mm; 95% confidence interval, -4.10 to -2.33; P < .00001; heterogeneity, 51%; χ2, 0.15). CONCLUSION Within the limitations, this review reveals that flapless ridge preservation was more effective in preserving bone width, bone height, and keratinized gingiva width. To present pertinent evidence regarding which flap management should be recommended for ridge preservation, more controlled and high-quality studies are warranted.

Comparison of immediate implant placement in infected and non-infected extraction sockets: a systematic review and meta-analysis

Abstract Objective: This review aimed to investigate the feasibility of immediate implant placement in infected extraction sockets. Material and methods: We performed electronic and manual searches up to March 2017 to obtain data from randomized controlled trials (RCTs) and nonrandomized controlled clinical trials (CCTs). Using a fixed-effects model to assess the difference in survival rate (primary outcome), we evaluated the risk difference for immediate implant placement in infected and non-infected sites. We estimated the weighted mean differences (WMDs) of the change in marginal bone loss (MBL), probing depth (PD), modified bleeding index (mBI), marginal gingival level (MGL) and width of keratinized gingiva (WKG) at baseline and latest follow-up. Results: In total, five studies (0 RCT, five CCTs) were included in the systematic review and three studies were included in the meta-analysis. The risk difference for immediate implant placement in an infected extraction socket compared with that in a non-infected socket was −0.02. WMDs for MBL, PD, mBI, MGL and WKG between the two groups were 0.32, 0.12, 0.07, −0.06, 0.20 and 0.51, respectively. No statistical differences were observed between the two groups, except for the change in WKG. Conclusions: Implants can be placed in infected extraction sockets after thorough socket debridement. For aesthetics, WKG should be considered when performing immediate implant placement in infected sites.

Influence of rhBMP-2 on Guided Bone Regeneration for Placement and Functional Loading of Dental Implants: A Radiographic and Histologic Study in Dogs

PURPOSE Evidence on the outcomes of functional loading placed in recombinant human bone morphogenetic protein 2 (rhBMP-2)/acellular collagen sponge (ACS)-induced bone is lacking. The aim of this study was to verify whether guided bone regeneration (GBR) with rhBMP-2/ACS enhances regeneration of missing bone and osseointegration of dental implants subject to functional loading. MATERIALS AND METHODS Two bilateral standardized large saddle-type defects (≈10 × 10 × 6 mm) were surgically created in each mandible of seven beagle dogs 2 months after tooth extraction. Defects were immediately reconstructed randomly using rhBMP-2 (O-BMP or InFuse) soaked in ACS, deproteinized bovine bone mineral (DBBM) granules, or ACS alone as surgical control and subsequently covered with collagen membrane. Screw-type sand-blasted, acid-etched dental implants were placed 3 months later into the reconstructed defects and into adjacent bone. Osseointegration was allowed to progress for 3 months before functional loading of 3 months until sacrifice. RESULTS Significantly more bone fill was radiographically observed for GBR with rhBMP-2/ACS (O-BMP: 92.5%, InFuse: 79%) in comparison to the DBBM (52%) and ACS alone groups (56.6%). Osseointegration was achieved and maintained in all experimental defects challenged by prostheses-driven functional load. The bone density ranged from 37.49% in the ACS group to 64.9% in the rhBMP-2/ACS (InFuse) group with no significance. The highest mean percentage of BIC was found in rhBMP-2/ACS (InFuse: 52.98%) with no statistical difference. Crestal bone resorption was observed around implants placed in reconstructed areas without any significant difference. CONCLUSION GBR with rhBMP-2/ACS provided the greatest bone fill among the three treatment procedures. GBR with rhBMP-2/ACS showed efficacy for placement, osseointegration, and functional loading of titanium implants in alveolar ridge defects.

Efficacy of sonic-powered toothbrushes for plaque removal in patients with peri-implant mucositis

Purpose The aim of this study was to evaluate the effectiveness of powered toothbrushes for plaque control in patients with peri-implant mucositis, in comparison with manual toothbrushes. Methods This randomized, prospective, controlled, clinical parallel study compared the efficacy of manual and powered toothbrushes for plaque control in implant restorations. Patients with bleeding on probing, no residual pocket depth (as indicated by a pocket probing depth ≥ 5 mm), and no radiological peri-implant bone loss were eligible for this study. Patients were requested to complete a questionnaire describing their oral hygiene habits. The duration and frequency of tooth brushing were recorded by subjects in order to assess their compliance. Clinical parameters, including the modified plaque index (mPI), the modified sulcus bleeding index (mSBI), and clinical photographs (buccal and lingual views) were recorded at baseline and at one-month and two-month follow-up visits. Results Statistically significant differences between patients who used manual toothbrushes and those who used powered toothbrushes were found regarding the frequency of tooth brushing per day and the duration of brushing at one-month and two-month follow-up visits, while no statistically significant differences were found relating to other oral hygiene habits. A statistically significant difference in patient compliance for tooth brushing was found at one month, while no difference was found at two months. Statistically significant decreases in the mPI and the mSBI were observed in both groups from baseline to the one- and two-month follow-ups. The overall reduction of these parameters was not significantly different between the two groups, except for mPI reduction between baseline and one month of follow-up. Conclusions Sonic-powered toothbrushes may be a useful device for plaque control in patients with peri-implant mucositis. Graphical Abstract

Workplace guidelines for nanomaterials

Examples of workplace guidelines are collected globally and reviewed. Recently established Korea Standard guideline for safe handling of manufactured nanomaterials in workplace/laboratories (KSA6202) is introduced and compared to the examples from abroad. It is noted that the lack of information or information gap concerning human health and environmental safety of nanpomaterials prohibits exact description for the detailed practices. However, precautionary steps for handling nanomaterials are necessary despite the lack of information. Possible evolution of the guidelines is also discussed.

Ethical Issues in Nanomaterials Technology and Relevant Policy Recommendations

For sustainable and responsible development of nanomaterials technology, the establishment of ethical system for sound social acceptance of the technology as well as the development of the technology itself is necessary. In this paper, global efforts to identify and resolve the ethical issues regarding nanotechnology is reviewed, in particular the environmental, health and safety issues in nanomaterials, and the tools such as communication and engagement of stakeholders, regulations, certifications and workplace guidelines are scrutinized. Finally the policy recommendations for the establishment of ethical systems for safe usage of nanomaterials.