THE EFFECT OF THE SUPERSATURATED SOLUTIONS CONTAINING HIGH CONCENTRATIONS OF FLUORIDE ON SEEDED CRYSTAL GROWTH

In biological systems, the mineral that forms hard tissue is of an apatitic nature, and hydroxyapatite($Ca_5OH(PO_4)_3$: HA) is generally considered as the prototype for such a mineral. Thus, the precipitation of HA, having biological implications, has been the subject of several investigations. Crystal growth studies using HA seeds in supersaturated solutions have enhanced our understanding of the process and mechanism involved in seeded crystal growth. From these studies, it has become apparent that the precipitation rate of HA onto the seed crystals depends on the various conditions, especially on the additives. The relation between the supersaturated solution containing fluoride and the process of HA crystal growth enhances the understanding of mechanism of HA crystal growth. Until recently, the studies have been on the crystal growth of enamel minerals and synthetic HA seeds in the supersaturated solution containing 1~2 ppm fluoride. The purpose of the present investigation is to study the effect that fluoride of high concentration has on the crystal growth kinetics of HA. In order to produce the composition found in the secretory enamel fluid, experimental solutions of 1mM Ca, 3mM P, and 100mM Tris as background electrolyte were used. Then this experimental solutions were added to 0, 2, 4, 6, 8, 10 ppm fluoride. The effect of fluoride at high concentrations on the precipitation was examined in a bench-top crystal growth model adopting a miniaturized reaction column. Chemical analysis was employed for characterization of working solutions before and after the experimentation. Remarkable findings were : 1) the amount of crystal growth was gradually accelerated as the fluoride concentration increased until 6 ppm, but decreased in 8 and 10 ppm fluoride; 2) the amount of fluoride ion consumed in crystal formation was constant despite the increase in fluoride concentration.ope

An Integrated Humanities-Social Sciences Course in Health Sciences Education: Proposed Design, Effectiveness, and Associated Factors

Background: Previous research has not provided enough direction regarding effective content design of courses integrating the humanities and social sciences in medical and dental education. This study aims at exploring how an Integrated Medical/Dental Humanities-Social Medicine/Dentistry course may be designed; how effective it may be in terms of student growth in knowledge, attitudes, skills, and aspirations; and associated factors. Methods: The course was designed by distilling commonalities in the international standards for medical/dental education proposed by seven major health organizations. This analysis resulted in a curriculum covering nine major topics: history, professionalism, communication, ethics, management, policy, insurance, law, and research methodology. During the 2017 calendar year, data was collected and statistically analyzed from 68 third-year pre-doctoral students enrolled in the resulting MDHS 13-week course. Results: Participants showed growth in skills, aspirations, knowledge, and attitudes, with the greatest change occurring in skills, then aspirations, knowledge, and attitudes. Knowledge growth was the only variable significantly related to student achievement of course objectives (β = 0.635, t (63) = 3.394, p = 0.001). The topics that students perceived as most critical were insurance, policy, management, and law. The perceived importance of research was most common among participants and was significantly related to all learning outcomes (For knowledge, β = 0.213, t (63) = 2.203, p = 0.031; for attitudes, β = 0.784, t (63) = 10.257, p = 0.000; for skills, β = 0.769, t (63) = 9.772, p = 0.000; and aspirations β = 0.639, t (63) = 7.595, p = 0.000). Conclusions: This study proposed a framework for humanities-social sciences education in health sciences education and analyzed its implementation. The empirical evaluation of its effectiveness and factors related to successful outcomes found that students perceived gains in their knowledge, attitudes, skills, and aspirations for humanistic and social aspects of dentistry/medicine. In addition, their recognition of the importance of research was associated with the greatest growth in all four learning outcomes. This study may contribute to the improved design of integrated humanities-social sciences courses.ope

Characteristics of Solar Desalination System Using Refrigerant As a Heating Source

The evaporative desalination system using solar thermal energy would be very efficient and attractive method to get fresh water from brine due to low carbon dioxide generation. In this research the solar desalination system as a heating source of refrigerant R123 and R141b in the evaporator was considered. The circulation of refrigerant in the evaporator can reduce the energy consumption of the system, through using the latent heat of the refrigerant instead of the sensible heat of present warm water. The system was composed of the single-stage fresh water production unit of 1 ton/day capacity with shell and tube type evaporator, heaters instead of solar collector for supplying proper heat to refrigerant, and refrigerant circulation system. Various operating flow rate and temperature ranges were imposed on the experiments to get the optimum design data. The experimental results showed that the optimum flow rate of brine feed to evaporator was 1.2Liter/min of R123 and 1.0Liter/min of R141b, and the yield of fresh water increased with brine temperature rise. It was confirmed that the flow rate of heating source of refrigerant as heating source decreased down to one fifth that of the present warm water system, and it was proven to be very efficient system for solar desalination.제 1 장 서 론 1 1.1 연구 배경 1 1.2 연구 목적 4 1.3 선행연구 조사 6 제 2 장 이론적 배경 8 2.1 해수 담수화 기술 8 2.1.1 다단 플래시 증발법 9 2.1.2 다중 효용 증발법 10 2.2 1단 증발법 공정 12 2.2.1 담수기 구조 및 운전 특성 12 2.2.2 1단 증발법 운전 조건 14 2.3 냉매 적용 담수 시스템 16 2.3.1 시스템 특징 16 2.3.1.1 냉매 적용 담수시스템의 장점 16 2.3.1.2 냉매 적용 담수시스템의 단점 17 2.3.2 냉매 적용 시스템 18 2.4 적용 냉매의 특징 20 2.4.1 상변화 온도와 압력 20 2.4.2 증발 잠열과 증기 및 액체의 현열 23 2.4.3 밀도 25 2.5 물의 증발 온도 26 2.6 냉매 증발기 열교환기 설계 27 2.6.1 냉매 R123 적용 시 증발기 열 교환 면적 산정 27 2.6.1.1 관 내부 응축 열전달계수 산정 27 2.6.1.2 관 외부 증발 열전달계수 산정 28 2.6.1.3 R123 냉매 증발기 열교환 면적 29 2.6.2 냉매 R141b 적용 시 증발기 열 교환 면적 산정 30 2.6.2.1 관 내부 응축 열전달계수 산정 30 2.6.2.2 관 외부 증발 열전달계수 산정 30 2.6.2.3 R141b 냉매 증발기 열교환 면적 30 2.7 응축기 열교환기 설계 32 2.8 태양열 집열기 집열면적 33 제 3 장 실험장치 및 실험방법 34 3.1 담수기 제작 34 3.1.1 담수기 본체 34 3.1.2 증발기 및 응축기 설계 36 3.1.2.1 증발기 설계 36 3.1.2.2 응축기 설계 36 3.1.3 응축기 유로 해석 39 3.1.4 이젝터 성능 해석 42 3.2 실험 장치 46 3.3 실험 방법 53 제 4 장 실험결과 및 고찰 54 4.1 냉매 R123 적용 시 실험 결과 54 4.1.1 Orifice 유무에 따른 담수 생성량 54 4.1.2 증발기 해수 주입량에 따른 담수 생성량 55 4.1.3 증발기 입구 냉매 온도에 따른 담수 생성량 58 4.1.4 증발기 해수 유입 온도에 따른 담수 생성량 58 4.1.5 냉매 R123 적용 실험 결과 분석 61 4.2 냉매 R141b 적용 시 실험 결과 63 4.2.1 증발기 해수 주입량에 따른 담수 생성량 63 4.2.2 증발기 입구 냉매 온도에 따른 담수 생성량 63 4.2.3 증발기 해수 유입 온도에 따른 담수 생성량 65 4.2.4 냉매 R141b 적용 실험 결과 분석 67 제 5 장 결론 69 참 고 문 헌 7

Identification of Porphyromonas gingivalis genes specifically expressed in human gingival epithelial cells by using differential display reverse transcription-PCR

Porphyromonas gingivalis, one of the causative agents of adult periodontitis, can invade and survive within host epithelial cells. The molecular mechanisms by which P. gingivalis induces uptake and adapts to an intracellular environment are not fully understood. In this study, we have investigated the genetic responses of P. gingivalis internalized within human gingival epithelial cells (GECs) in order to identify factors involved in invasion and survival. We compared the differential display of arbitrarily PCR-amplified gene transcripts in P. gingivalis recovered from GECs with the display of transcripts in P. gingivalis control cultures. Over 20 potential differentially expressed transcripts were identified. Among these, pepO, encoding an endopeptidase, and genes encoding an ATP-binding cassette (ABC) transporter and a cation-transporting ATPase were upregulated in GECs. To investigate the functionality of these gene products, mutants were generated by insertional inactivation. Compared to the parental strain, mutants of each gene showed a significant reduction in their invasion capabilities. In addition, GEC cytoskeletal responses to the mutants were distinct from those induced by the parent. In contrast, adhesion of the mutant strains to GECs was not affected by lack of expression of the gene products. These results suggest that PepO, a cation-transporting ATPase, and an ABC transporter are required for the intracellular lifestyle of P. gingivalis.ope

Differential Protein Expression by Porphyromonas gingivalis in Response to Secreted Epithelial Cell Components

The human oral pathogen Porphyromonas gingivalis colonizes the gingival crevice and invades gingival epithelial cells. Multi-dimensional capillary HPLC coupled with tandem mass spectrometry and 2D gel electrophoresis were used to analyze the proteome of P. gingivalis as it adapts to a set of experimental conditions designed to reflect important features of an epithelial cell environment. 1014 proteins (46% of the total theoretical proteome) were identified in four independent analyses. 479 of these proteins showed evidence of differential expression after exposure of P. gingivalis to either conditioned epithelial cell growth medium or control conditions: i.e. they were only detected under one set of conditions. Moreover, 276 genes annotated as hypothetical were found to encode expressed proteins. Among the proteins upregulated in the presence of epithelial cell components were a homolog of the internalin proteins of Listeria monocytogenes and subunits of the ATP-dependent Clp protease complex. Insertional inactivation of clpP, encoding the Clp proteolytic subunit, resulted in an approximately 50% reduction in invasion of P. gingivalis. These results suggest that adaptation to an epithelial cell environment induces a major shift in the expressed proteome of the organism. Furthermore, ClpP, that is upregulated in this environment, is required for optimal invasive activity of P. gingivalis.ope

고유 특성을 활용한 음악에서의 보컬 분리

학위논문 (박사)-- 서울대학교 대학원 : 융합과학기술대학원 융합과학부, 2018. 2. 이교구.보컬 분리란 음악 신호를 보컬 성분과 반주 성분으로 분리하는 일 또는 그 방법을 의미한다. 이러한 기술은 음악의 특정한 성분에 담겨 있는 정보를 추출하기 위한 전처리 과정에서부터, 보컬 연습과 같이 분리 음원 자체를 활용하는 등의 다양한 목적으로 사용될 수 있다. 본 논문의 목적은 보컬과 반주가 가지고 있는 고유한 특성에 대해 논의하고 그것을 활용하여 보컬 분리 알고리즘들을 개발하는 것이며, 특히 `특징 기반' 이라고 불리는 다음과 같은 상황에 대해 중점적으로 논의한다. 우선 분리 대상이 되는 음악 신호는 단채널로 제공된다고 가정하며, 이 경우 신호의 공간적 정보를 활용할 수 있는 다채널 환경에 비해 더욱 어려운 환경이라고 볼 수 있다. 또한 기계 학습 방법으로 데이터로부터 각 음원의 모델을 추정하는 방법을 배제하며, 대신 저차원의 특성들로부터 모델을 유도하여 이를 목표 함수에 반영하는 방법을 시도한다. 마지막으로, 가사, 악보, 사용자의 안내 등과 같은 외부의 정보 역시 제공되지 않는다고 가정한다. 그러나 보컬 분리의 경우 암묵 음원 분리 문제와는 달리 분리하고자 하는 음원이 각각 보컬과 반주에 해당한다는 최소한의 정보는 제공되므로 각각의 성질들에 대한 분석은 가능하다. 크게 세 종류의 특성이 본 논문에서 중점적으로 논의된다. 우선 연속성의 경우 주파수 또는 시간 측면으로 각각 논의될 수 있는데, 주파수축 연속성의 경우 소리의 음색적 특성을, 시간축 연속성은 소리가 안정적으로 지속되는 정도를 각각 나타낸다고 볼 수 있다. 또한, 저행렬계수 특성은 신호의 구조적 성질을 반영하며 해당 신호가 낮은 행렬계수를 가지는 형태로 표현될 수 있는지를 나타내며, 성김 특성은 신호의 분포 형태가 얼마나 성기거나 조밀한지를 나타낸다. 본 논문에서는 크게 두 가지의 보컬 분리 방법에 대해 논의한다. 첫 번째 방법은 연속성과 성김 특성에 기반을 두고 화성 악기-타악기 분리 방법 (harmonic-percussive sound separation, HPSS) 을 확장하는 방법이다. 기존의 방법이 두 번의 HPSS 과정을 통해 보컬을 분리하는 것에 비해 제안하는 방법은 성긴 잔여 성분을 추가해 한 번의 보컬 분리 과정만을 사용한다. 논의되는 다른 방법은 저행렬계수 특성과 성김 특성을 활용하는 것으로, 반주가 저행렬계수 모델로 표현될 수 있는 반면 보컬은 성긴 분포를 가진다는 가정에 기반을 둔다. 이러한 성분들을 분리하기 위해 강인한 주성분 분석 (robust principal component analysis, RPCA) 을 이용하는 방법이 대표적이다. 본 논문에서는 보컬 분리 성능에 초점을 두고 RPCA 알고리즘을 일반화하거나 확장하는 방식에 대해 논의하며, 트레이스 노름과 l1 노름을 각각 샤텐 p 노름과 lp 노름으로 대체하는 방법, 스케일 압축 방법, 주파수 분포 특성을 반영하는 방법 등을 포함한다. 제안하는 알고리즘들은 다양한 데이터셋과 대회에서 평가되었으며 최신의 보컬 분리 알고리즘들보다 더 우수하거나 비슷한 결과를 보였다.Singing voice separation (SVS) refers to the task or the method of decomposing music signal into singing voice and its accompanying instruments. It has various uses, from the preprocessing step, to extract the musical features implied in the target source, to applications for itself such as vocal training. This thesis aims to discover the common properties of singing voice and accompaniment, and apply it to advance the state-of-the-art SVS algorithms. In particular, the separation approach as follows, which is named `characteristics-based,' is concentrated in this thesis. First, the music signal is assumed to be provided in monaural, or as a single-channel recording. It is more difficult condition compared to multiple-channel recording since spatial information cannot be applied in the separation procedure. This thesis also focuses on unsupervised approach, that does not use machine learning technique to estimate the source model from the training data. The models are instead derived based on the low-level characteristics and applied to the objective function. Finally, no external information such as lyrics, score, or user guide is provided. Unlike blind source separation problems, however, the classes of the target sources, singing voice and accompaniment, are known in SVS problem, and it allows to estimate those respective properties. Three different characteristics are primarily discussed in this thesis. Continuity, in the spectral or temporal dimension, refers the smoothness of the source in the particular aspect. The spectral continuity is related with the timbre, while the temporal continuity represents the stability of sounds. On the other hand, the low-rankness refers how the signal is well-structured and can be represented as a low-rank data, and the sparsity represents how rarely the sounds in signals occur in time and frequency. This thesis discusses two SVS approaches using above characteristics. First one is based on the continuity and sparsity, which extends the harmonic-percussive sound separation (HPSS). While the conventional algorithm separates singing voice by using a two-stage HPSS, the proposed one has a single stage procedure but with an additional sparse residual term in the objective function. Another SVS approach is based on the low-rankness and sparsity. Assuming that accompaniment can be represented as a low-rank model, whereas singing voice has a sparse distribution, conventional algorithm decomposes the sources by using robust principal component analysis (RPCA). In this thesis, generalization or extension of RPCA especially for SVS is discussed, including the use of Schatten p-/lp-norm, scale compression, and spectral distribution. The presented algorithms are evaluated using various datasets and challenges and achieved the better comparable results compared to the state-of-the-art algorithms.Chapter 1 Introduction 1 1.1 Motivation 4 1.2 Applications 5 1.3 Definitions and keywords 6 1.4 Evaluation criteria 7 1.5 Topics of interest 11 1.6 Outline of the thesis 13 Chapter 2 Background 15 2.1 Spectrogram-domain separation framework 15 2.2 Approaches for singing voice separation 19 2.2.1 Characteristics-based approach 20 2.2.2 Spatial approach 21 2.2.3 Machine learning-based approach 22 2.2.4 informed approach 23 2.3 Datasets and challenges 25 2.3.1 Datasets 25 2.3.2 Challenges 26 Chapter 3 Characteristics of music sources 28 3.1 Introduction 28 3.2 Spectral/temporal continuity 29 3.2.1 Continuity of a spectrogram 29 3.2.2 Continuity of musical sources 30 3.3 Low-rankness 31 3.3.1 Low-rankness of a spectrogram 31 3.3.2 Low-rankness of musical sources 33 3.4 Sparsity 34 3.4.1 Sparsity of a spectrogram 34 3.4.2 Sparsity of musical sources 36 3.5 Experiments 38 3.6 Summary 39 Chapter 4 Singing voice separation using continuity and sparsity 43 4.1 Introduction 43 4.2 SVS using two-stage HPSS 45 4.2.1 Harmonic-percussive sound separation 45 4.2.2 SVS using two-stage HPSS 46 4.3 Proposed algorithm 48 4.4 Experimental evaluation 52 4.4.1 MIR-1k Dataset 52 4.4.2 Beach boys Dataset 55 4.4.3 iKala dataset in MIREX 2014 56 4.5 Conclusion 58 Chapter 5 Singing voice separation using low-rankness and sparsity 61 5.1 Introduction 61 5.2 SVS using robust principal component analysis 63 5.2.1 Robust principal component analysis 63 5.2.2 Optimization for RPCA using augmented Lagrangian multiplier method 63 5.2.3 SVS using RPCA 65 5.3 SVS using generalized RPCA 67 5.3.1 Generalized RPCA using Schatten p- and lp-norm 67 5.3.2 Comparison of pRPCA with robust matrix completion 68 5.3.3 Optimization method of pRPCA 69 5.3.4 Discussion of the normalization factor for λ 69 5.3.5 Generalized RPCA using scale compression 71 5.3.6 Experimental results 72 5.4 SVS using RPCA and spectral distribution 73 5.4.1 RPCA with weighted l1-norm 73 5.4.2 Proposed method: SVS using wRPCA 74 5.4.3 Experimental results using DSD100 dataset 78 5.4.4 Comparison with state-of-the-arts in SiSEC 2016 79 5.4.5 Discussion 85 5.5 Summary 86 Chapter 6 Conclusion and Future Work 88 6.1 Conclusion 88 6.2 Contributions 89 6.3 Future work 91 6.3.1 Discovering various characteristics for SVS 91 6.3.2 Expanding to other SVS approaches 92 6.3.3 Applying the characteristics for deep learning models 92 Bibliography 94 초 록 110Docto

The change of the configuration of hydroxyapatite crystals in enamel by changes of pH and degree of saturation of lactic acid buffer solution

Since it was reported that incipient enamel caries can be recovered, previous studies have quantitatively evaluated that enamel artificial caries have been remineralized with fluoride, showing simultaneously the increase of width of surface layer and the decrease of width of the body of legion. There is, however, little report which showed that remineralization could occur without fluoride. In addition, the observations on the change of hydroxyapatite crystals also have been scarcely seen. In this study, enamel caries in intact premolars or molars was induced by using lactic acidulated buffering solutions over 2 days. Then decalcified specimens were remineralized by seven groups of solutions using different degree of saturation (0.212, 0.239, 0.301, 0.355) and different pH (5.0, 5.5, 6.0) over 10 days. A qualitative comparison to changes of hydroxyapatite crystals after fracturing teeth was made under SEM (scanning electron microscopy) and AFM (atomic force microscopy). The results were as follows: 1. The size of hydroxyapatite crystals in demineralized area was smaller than the normal ones. While the space among crystals was expanded, it was observed that crystals are arranged irregularly. 2. In remineralized enamel area, the enlarged crystals with various shape were observed when the crystals were fused and new small crystals in intercrystalline spaces were deposited. 3. Group 3 and 4 with higher degree of saturation at same pH showed the formation of large clusters by aggregation of small crystals from the surface layer to the lesion body than group 1 and 2 with relatively low degree of saturation at same pH did. Especially group 4 showed complete remineralization to the body of lesions. Group 5 and 6 with lower pH at similar degree of saturation showed remineralization to the body of lesions while group 7 didn't show it. Unlike in Group 3 and 4, Group 5 and 6 showed that each particle was densely distributed with clear appearance rather than crystals form clusters together.ope

INFLUENCE OF POST TYPES AND SIZES ON FRACTURE RESISTANCE IN THE IMMATURE TOOTH MODEL

The purpose of this study was to determine the effect of post types and sizes on fracture resistance in immature tooth model with various restorative techniques. Bovine incisors were sectioned 8 mm above and 12 mm below the cementoenamel junction to simulate immature tooth model. To compare various post-and-core restorations, canals were restored with gutta-percha and resin core, or reinforced dentin wall with dual-cured resin composite, followed by placement of D.T. LIGHT-POST, ParaPost XT, and various sizes of EverStick Post individually. All of specimens were stored in the distilled water for 72 hours and underwent 6,000 thermal cycles. After simulation of periodontal ligament structure with polyether impression material, compressive load was applied at 45 degrees to the long axis of the specimen until fracture was occurred. Experimental groups reinforced with post and composite resin were shown significantly higher fracture strength than gutta-percha group without post placement (p < 0.05). Most specimens fractured limited to cervical third of roots. Post types did not influence on fracture resistance and fracture level significantly when cement space was filled with dual-cured resin composite. In addition, no statistically significant differences were seen between customized and standardized glass fiber posts, which cement spaces were filled with resin cement or composite resin individually. Therefore, root reinforcement procedures as above in immature teeth improved fracture resistance regardless of post types and sizesope

Effect of dentin treatment on proliferation and differentiation of human dental pulp stem cells

OBJECTIVES: Sodium hypochlorite (NaOCl) is an excellent bactericidal agent, but it is detrimental to stem cell survival, whereas intracanal medicaments such as calcium hydroxide (Ca[OH]2) promote the survival and proliferation of stem cells. This study evaluated the effect of sequential NaOCl and Ca[OH]2 application on the attachment and differentiation of dental pulp stem cells (DPSCs). MATERIALS AND METHODS: DPSCs were obtained from human third molars. All dentin specimens were treated with 5.25% NaOCl for 30 min. DPSCs were seeded on the dentin specimens and processed with additional 1 mg/mL Ca[OH]2, 17% ethylenediaminetetraacetic acid (EDTA) treatment, file instrumentation, or a combination of these methods. After 7 day of culture, we examined DPSC morphology using scanning electron microscopy and determined the cell survival rate with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. We measured cell adhesion gene expression levels after 4 day of culture and odontogenic differentiation gene expression levels after 4 wk using quantitative real-time polymerase chain reaction. RESULTS: DPSCs did not attach to the dentin in the NaOCl-treated group. The gene expression levels of fibronectin-1 and secreted phosphoprotein-1 gene in both the Ca[OH]2- and the EDTA-treated groups were significantly higher than those in the other groups. All Ca[OH]2-treated groups showed higher expression levels of dentin matrix protein-1 than that of the control. The dentin sialophosphoprotein level was significantly higher in the groups treated with both Ca[OH]2 and EDTA. CONCLUSIONS: The application of Ca[OH]2 and additional treatment such as EDTA or instrumentation promoted the attachment and differentiation of DPSCs after NaOCl treatment.ope

Efficacy of a Nickel-Titanium Ultrasonic Instrument for Biofilm Removal in a Simulated Complex Root Canal

This study evaluated the effectiveness of NiTi ultrasonic tips for Enterococcus faecalis (E. faecalis) biofilm removal in simulated complex root canals. Sixty root canal models consisting of a 30-degree curved main canal and two lateral canals were constructed from polydimethylsiloxane and incubated with E. faecalis. Irrigants in root canals were activated using a manual syringe (SI), a stainless steel (SS) instrument, a nickel-titanium (Ni-Ti) ultrasonic instrument, or a sonic instrument (EA). Instruments of SI, SS, and NiTi-9 groups were placed 9 mm from the apex, whereas those in NiTi-2 and EA groups were placed 2 mm from the apex. The efficacy of each method was determined as the ratio of fluorescence concentration before and after activation. In the apical curved canal, the highest efficacy was found in the NiTi-2 group (99.40%), followed by SI (84.25%), EA (80.38%), SS (76.93%), and NiTi-9 (67.29%) groups. In lateral canals 1 and 2, the efficacy was the highest in the NiTi-2 group and the lowest in the SI group. The NiTi ultrasonic instrument could effectively remove biofilms in the curved canal and lateral canals. This instrument should be introduced close to the working length. An up-and-down motion of the activation instrument is recommended.ope