Endoscopic Resection for Gastric Adenocarcinoma of the Fundic Gland Type: A Case Series / 대한소화기학회지

The fundic gland type (GA-FG) of gastric adenocarcinoma is a rare variant of gastric cancer recently included in the 5th edition of the World Health Organization’s classification of digestive system tumors. Five patients with GA-FG underwent an endoscopic resection at our institution. None of the patients had a Helicobacter pylori infection. Four lesions were located in the upper third of the stomach, and one was in the lower third. Three lesions had a IIa shape, while two resembled a subepithelial tumor. An endoscopic submucosal dissection was performed in four patients and endoscopic mucosal resection in one. Tumor cells were composed of well-differentiated columnar cells mimicking fundic gland cells, and the median tumor size was 10 mm. Three lesions exhibited submucosal invasion. No lymphatic or venous invasion was observed. Tumor cells were positive for MUC6 in all five cases; one case was focally positive for MUC5AC. No recurrence was observed during a median follow-up period of 13 months. An endoscopic resection can be a safe treatment modality for GA-FG, considering its small size and low risk of recurrence or metastasis. (Korean J Gastroenterol 2023;81:259-264)

Enhanced Antioxidant and Anticancer Properties of Processed Eucommiae Cortex

Eucommiae Cortex (EC), bark of Eucommia ulmoides, has been known as a traditional medicine to regulate hypertension and immune system. Because silk of gum in the EC blocks the release of active ingredients, EC generally has been utilized after processing with carbonization or salt-water to breakdown it. This study aimed to investigate the differences of non-processed EC and processed EC on antioxidant and anticancer properties. Antioxidant capacity was assessed by measuring the content of total polyphenols, reducing power, and ABTS radical scavenging effect. And anticancer effects were examined by evaluating the viability of pancreatic cancer cells and wound healing ability. The results demonstrated that processed EC contained more content of polyphenols and exhibited more potent reducing power and radical scavenging effect than non-processed EC. In addition, processed EC more efficiently inhibited proliferation and migration of pancreatic cancer cells. These results suggest that processing of medicinal plants can improve the biological properties such as antioxidant or anticancer activity, which may lead to the development of herbal medicine treatment technology.

Generalization of Conscious Fear Is Positively Correlated with Anxiety, but Not with Depression

Generalization of learned fear has been considered to be critical for our survival. Patients with anxiety problems show overgeneralization of learned fear, as reflected by defensive physiological responses to harmless stimuli. Together with these physiological responses, conscious feeling of fear is a seminal part of emotional process that is directly related to the suffering of anxiety patients. However, the effect of anxiety on the generalization of conscious feeling remains unclear. We thus focused on the question whether the generalization of conscious feeling of fear depends on individual anxiety level in nonpatient participants. To address this question, we developed a fear generalization paradigm using natural scene images. We found that subjective feeling of fear was generalized to similar stimuli with the conditioned stimuli (CS), and that this generalization of conscious fear was positively correlated with the level of individual anxiety. Anxiety and depression frequently co-occur, but the individual depression level was not correlated with the fear generalization. These suggest that individual anxiety level mainly affects the generalization of conscious fear.

Repeated injections of botulinum toxin into the masseter muscle induce bony changes in human adults: A longitudinal study / 대한치과교정학회지

OBJECTIVE: To evaluate soft- and hard-tissue changes in the mandibular angle area after the administration of botulinum toxin type A (BoNT-A) injection to patients with masseteric hypertrophy by using three-dimensional cone-beam computed tomography (3D-CBCT). METHODS: Twenty volunteers were randomly divided into two groups of 10 patients. Patients in group I received a single BoNT-A injection in both masseter muscles, while those in group II received two BoNT-A injections in each masseter muscle, with the second injection being administered 4 months after the first one. In both groups, 3D-CBCT was performed before the first injection and 6 months after the first injection. RESULTS: Masseter muscle thicknesses and cross-sectional areas were significantly reduced in both groups, but the reductions were significantly more substantial in group II than in group I. The intergonial width of the mandibular angle area did not change significantly in either group. However, the bone volume of the mandibular gonial angle area was more significantly reduced in group II than in group I. CONCLUSIONS: The repeated administration of BoNT-A injections may induce bone volume changes in the mandibular angle area.

Inhibitory Effect of a Sesquiterpene from Artemisia iwayomogi on Expression of Inducible Nitric Oxide Synthase by Suppression of I-κBα Degradation in LPS-stimulated RAW 264.7 Cells

A sesquiterpene was purified from Artemisia iwayomogi methanolic extract during the course of searching anti-inflammatory principle from medicinal plants. A sesquiterpene identified as armefolin inhibited the production of nitric oxide (NO) and attenuated inducible nitric oxide synthase (iNOS) protein level in lipopolysaccharide (LPS)-activated RAW 264.7 cells. Armefolin also down-regulated mRNA expressions of iNOS and pro-inflammatory cytokines, interleukin-1β and interleukin-6 in LPS-activated macrophages. Moreover, armefolin suppressed the degradation of inhibitory-κBα (I-κBα) in LPS-activated macrophages. These data suggest that armefolin from A. iwayomogi can suppress the LPS-induced production of NO and the expression of iNOS gene through inhibiting the degradation of I-κBα. Taken together, armefolin from A. iwayomogi might be a candidate as promising anti-inflammatory agent.

Atractylochromene Is a Repressor of Wnt/beta-Catenin Signaling in Colon Cancer Cells

Wnt/beta-catenin signaling pathway was mutated in about 90% of the sporadic and hereditary colorectal cancers. The abnormally activated beta-catenin increases the cancer cell proliferation, differentiation and metastasis through increasing the expression of its oncogenic target genes. In this study, we identified an inhibitor of beta-catenin dependent Wnt pathway from rhizomes of Atractylodes macrocephala Koidzumi (Compositae). The active compound was purified by activity-guided purification and the structure was identified as 2,8-dimethyl-6-hydroxy-2-(4-methyl-3-pentenyl)-2H-chromene (atractylochromene, AC). AC suppressed beta-catenin/T-cell factor transcriptional activity of HEK-293 reporter cells when they were stimulated by Wnt3a or inhibitor of glycogen synthase kinase-3beta. AC down-regulated the nuclear level of beta-catenin through the suppression of galectin-3 mediated nuclear translocation of beta-catenin in SW-480 colon cancer cells. Furthermore, AC inhibits proliferation of colon cancer cell. Taken together, AC from A. macrocephala might be a potential chemotherapeutic agent for the prevention and treatment of human colon cancer.

Comparison of success rates of orthodontic mini-screws by the insertion method / 대한치과교정학회지

OBJECTIVE: The aim of this study was to compare the success rates of the manual and motor-driven mini-screw insertion methods according to age, gender, length of mini-screws, and insertion sites. METHODS: We retrospectively reviewed 429 orthodontic mini-screw placements in 286 patients (102 in men and 327 in women) between 2005 and 2010 at private practice. Age, gender, mini-screw length, and insertion site were cross-tabulated against the insertion methods. The Cochran-Mantel-Haenszel test was performed to compare the success rates of the 2 insertion methods. RESULTS: The motor-driven method was used for 228 mini-screws and the manual method for the remaining 201 mini-screws. The success rates were similar in both men and women irrespective of the insertion method used. With respect to mini-screw length, no difference in success rates was found between motor and hand drivers for the 6-mm-long mini-screws (68.1% and 69.5% with the engine driver and hand driver, respectively). However, the 8-mm-long mini-screws exhibited significantly higher success rates (90.4%, p < 0.01) than did the 6-mm-long mini-screws when placed with the engine driver. The overall success rate was also significantly higher in the maxilla (p < 0.05) when the engine driver was used. Success rates were similar among all age groups regardless of the insertion method used. CONCLUSIONS: Taken together, the motor-driven insertion method can be helpful to get a higher success rate of orthodontic mini-screw placement.

Nurses' Question and Explanation Strategies for Effective Communication with Cancer Patients / 기본간호학회지

PURPOSE: This study was conducted to identify communication principles for nurses in cancer units according to Grice's theory. METHODS: This study was a secondary analysis of qualitative research using conversational analysis. RESULTS: The principles consisted of four maxims: Quality, quantity, relevance and manner and 14 strategies. For the quality maxim, 'asking what you believe to be true' and 'saying the facts you know' were strategies were identified. In the quantity maxim, the strategies were 'asking single questions', 'asking open questions' and 'asking optimistic questions'. In the relevance maxim, 'asking about the same theme' and 'giving relevant explanations' were the strategies identified. In the manner maxim, the strategies were 'using clear expressions in asking questions', 'asking in an orderly way', 'verifying answers', 'using clear expressions in explanations', 'explaining in an orderly way' and 'verifying understanding'. CONCLUSION: It is expected that these strategies will help and increase the degree of cooperation for nurses in effectively communicating with cancer patients.

An Analysis of Nurses' Behavior for Politeness in Cancer Patient-Centered Conversation / 성인간호학회지

PURPOSE: The purpose of this study was to describe and to analyze real conversation about polite behavior of nurses in cancer units. METHODS: This study was conducted using a Brown & Levinson(1987) theory to analyze the polite behavior of nurses in cancer units. Five nurses who participated in this research gave permission to be videotaped. The data was collected from January to February, 2006. RESULTS: Polite behavior of nurses in cancer units consisted of greetings, emotional support, open questions and indirect direction. And impolite behavior of nurses in cancer units was using the medical terminology, repetition of direct speech acts and task-oriented conversation. CONCLUSION: This study suggests polite behavior strategies for effective nursing conversation with cancer patients. Therefore, the findings may provide basic raw materials for educational programmes and intervention studies.

Illness Experience of People with Chronic Hepatitis B in Korea / 간호학회지

PURPOSE: The purpose of this study was to explore the experiences of people with chronic hepatitis B (CHB) in Korea. The specific aim was to identify major problems that people with CHB face and strategies that they are dealing with. METHODS: A grounded theory method was utilized. The data were collected by individual in-depth interviews from 12 CHB patients from one of the major hospitals in Korea. RESULTS: After constant comparative analysis, a core category emerged as "illness management with self-reliance and will." Seven major strategies that were identified in dealing with the illness were maintaining receptive and positive attitudes; restraining excessive work and greed; searching for information; controlling illness information; adhering to practices for not spreading the viral disease; abstaining from alcohol and smoking and maintaining healthy eating habits; nd using alternative therapies. The outcomes that result from employing these strategies were identified as burden, depression and helplessness, stress for maintaining compliance, and dispirited interpersonal relationships. CONCLUSION: The results of this study suggest that most people with CHB in Korea have problems in psychosocial area. Thus health professionals need to provide not only informational support but also emotional one to improve quality of life of the people with CHB.

A Conversational Analysis about Patient's Discomfort between a Patient with Cancer and a Nurse / 간호학회지

PURPOSE: The purpose of this study was to describe and to analyze real communication about a patient's discomfort between a patient with cancer and a nurse. METHOD: A dialogue analysis method was utilized. Fifteen patients and 4 nurses who participated in this research gave permission to be videotaped. The data was collected from January, 3 to February 28, 2006. RESULTS: The communication process consisted of 4 functional stages: 'introduction stage', 'assessment stage', 'intervention stage' and 'final stage'. After trying to analyze pattern reconstruction in the 'assessment stage' and 'intervention stage', sequential patterns were identified. In the assessment stage, if the nurse lead the communication, the sequential pattern was 'assessment question-answer' and if the patient lead the communication, it was 'complaint-response'. In the intervention stage, the sequential pattern was 'nursing intervention-acceptance'. CONCLUSION: This research suggests conversation patterns between patients with cancer and nurses. Therefore, this study will provide insight for nurses in cancer units by better understanding communication behaviors.

Adjustment of Middle-aged People with Hemiplegia after a Stroke / 간호학회지

PURPOSE: The purpose of this study was to understand the adjustment process of middle-aged people in Korea with hemiplegia after a stroke. METHOD: For this study, the grounded theory method was utilized. RESULTS: After constant comparative analysis, the core category emerged as 'rebuilding the body which was ruined'. In addition, the causal conditions were 'restriction of physical function', and 'loss of roles'. The adjustment process consisted of the 'facing reality phase', 'overcoming depression phase', 'overcoming physical limits phase' and 'reestablishing roles phase'. The main strategies in the facing reality phase were 'holding on to a glimmer of hope', 'getting away from the harsh reality' and 'facing up to the reality'. The main strategies in the overcoming depression phase were 'soothing oneself', 'Self-introspection' and 'restoring self-esteem'. In addition, the main strategies in the self-initiative overcoming physical limits phase was 'discovering personal strategies and striving to recover'. The main strategies in the reestablishing roles phase were 'reestablishing a parents' role', 'reestablishing a spouse's role' and 'reestablishing social roles'. CONCLUSION: In conclusion, even though many middle aged stroke patients remained in the depression phase, most of them who overcame depression strived to conquer physical limits on their own initiative.

A proposal of soft tissue landmarks for craniofacial analysis using three-dimensional laser scan imaging / 대한치과교정학회지

Three-dimensional (3-D) laser scans can provide a 3-D image of the face and it is efficient in examining specific structures of the craniofacial soft tissues. Due to the increasing concerns with the soft tissues and expansion of the treatment range, a need for 3-D soft tissue analysis has become urgent. Therefore, the purpose of this study was to evaluate the scanning error of the Vivid 900 (Minolta, Tokyo, Japan) 3-D laser scanner and Rapidform program (Inus Technology Inc., Seoul, Korea) and to evaluate the mean error and the magnification percentage of the image obtained from 3-D laser scans. In addition, soft tissue landmarks that are easy to designate and reproduce in 3-D images of normal, Class II and Class III malocclusion patients were obtained. The conclusions are as follows; scanning errors of the Vivid 900 3-D laser scanner using a manikin were 0.16 mm in the X axis, 0.15 mm in the Y axis, and 0.15 mm in the Z axis. In the comparison of actual measurements from the manikin and the 3-D image obtained from the Rapidform program, the mean error was 0.37 mm and the magnification was 0.66%. Except for the right soft tissue gonion from the 3-D image, errors of all soft tissue landmarks were within 2.0 mm. Glabella, soft tissue nasion, endocanthion, exocanthion, pronasale, subnasale, nasal alare, upper lip point, cheilion, lower lip point, soft tissue B point, soft tissue pogonion, soft tissue menton and preaurale had especially small errors. Therefore, the Rapidform program can be considered a clinically efficient tool to produce and measure 3-D images. The soft tissue landmarks proposed above are mostly anatomically important points which are also easily reproducible. These landmarks can be beneficial in 3-D diagnosis and analysis.

A study of facial soft tissue of Korean adults with normal occlusion using a three-dimensional laser scanner / 대한치과교정학회지

Developments in computer technology have made possible the 3-dimensional (3-D) evaluation of hard and soft tissues in orthodontic diagnosis, treatment planning and post-treatment results. In this study, Korean adults with normal occlusion (male 30, female 30) were scanned by a 3-D laser scanner, then 3-D facial images formed by the Rapidform 2004 program (Inus Technology Inc., Seoul, Korea.). Reference planes in the facial soft tissue 3-D images were established and a 3-D coordinate system (X axis-left/right, Y axis-superior/inferior, Z axis-anterior/posterior) was established by using the soft tissue nasion as the zero point. Twenty-nine measurement points were established on the 3-D image and 43 linear measurements, 8 angular measurements, 29 linear distance ratios were obtained. The results are as follows; there were significant differences between males and females in the nasofrontal angle (male: 142 degrees, female: 147 degrees) and transverse nasal prominence (male: 112 degrees, female: 116 degrees) (p < 0.05). The transverse upper lip prominence was 107 degrees in males, 106 degrees in females and the transverse mandibular prominence was 76 degrees in both males and females. Li-Me' was 0.4 times the length of Go-Me' (mandibular body length) and the mouth height was also 0.4 times the width of the mouth width. The linear distance ratio from the coronal reference plane of FT, Zy, Pn, ULPm, Li, Me' was -1/-1/1/0.5/0.5/-0.6 respectively. The 3-D facial model of Korean adults with normal occlusion were be constructed using coordinate values and linear measurement values. These data may be used as a reference in 3-D diagnosis and treatment planning for malocclusion and dentofacial deformity patients and applied for 3-D analysis of facial soft tissue changes before and after orthodontic treatment and orthognathic surgery.

Descriptive Study of Relationships between Depression, Family Support, and Rehabilitation-motivation in Patients with Cerebrovascular Accident / 재활간호학회지

PURPOSE: This study was conducted to identify relationships between depression, family support, and rehabilitation-motivation in patients with cerebrovascular accident. METHOD: The data were collected from 'S' hospital in Seoul from Feb. 1, 2004 to Apr. 30, 2004. The data were analyzed using a SPSS 10.0 program for descriptive statistics, Pearson correlation coefficients and stepwise multiple regression. RESULT: The results were as follows: The mean rehabilitation-motivation was 119.89, which was slightly high. The rehabilitation-motivation was influenced by religion, education level, occupation, economic status, treatment fee, duration of hospitalization, level of language ability and ADL. Rehabilitation-motivation has showed correlation with family support (r=.538, p=.000) and depression (r=-.417, p=.000). The variables related to rehabilitation-motivation were identified as family support, level of ADL, occupation, depression, and education level, using stepwise multiple regression. They were accounted for 57% of predictability of the rehabilitation-motivation, with the family support the highest at 29.3%. CONCLUSION: With increasing post stroke patients in Korea, we need to pay more attention to the rehabilitation of them. This study indicates that health professionals need to focus on the intervention especially in increasing family support and in decreasing depression of the patients with cerebrovascular accident.

Fragile X Premutation in Patients with Idiopathic Premature Ovarian Failure / 대한산부인과학회잡지

OBJECTIVE: To explore the incidence of fragile X premutation in patients with idiopathic premature ovarian failure, particularly in the Korean population. DESIGN: A prospective study. MATERIALS AND METHODS: Eighty-three women affected by idiopathic premature ovarian failure were recruited for this study. Patient with known causes of premature ovarian failure were excluded: cytogenetic abnormalities, prior chemotherapy, prior bilateral oophorectomy. DNA was extracted from peripheral blood. Fragile X (FRAXA) premutation was evaluated by PCR amplification of and Southern blot analysis for FMR1 gene. RESULTS: The FRAXA premutation was detected in three (3.6%) out of 83 patients with idiopathic premature ovarian failure. CONCLUSION: This result suggests that fragile X premutation screening is indicated in patients with idiopathic premature ovarian failure, particularly in the Korean population.

Prenatal Aneuploidy Detection in Uncultured Amniotic Fluid Interphase Cells by Fluorescence in situ Hybridization (FISH) / 대한불임학회지

OBJECTIVE: The aim of the present study was to evaluate the clinical efficiency of fluorescent in situ hybridization (FISH) in the prenatal diagnosis of chromosomal aneuploidy. METHODS: We reviewed data of 268 cases to identify women undergoing genetic amniocentesis at cytogenetic laboratory, from January 2000 to December 2002. Amniotic fluid was submitted for both rapid FISH on uncultured interphase amniocytes using a commercially available DNA probe for chromosome 13, 18, 21, X, Y and standard karyotyping on cultured metaphase amniocytes. Results from FISH and full karyotype were compared. RESULTS: There were 251 cases (84%) normal and 17 cases (16%) abnormal in FISH results. All 17 cases of trisomy 13, 18, 21 including two cases of mosaicism and sex chromosome aneuploidies which are detected by FISH were confirmed with conventional cytogenetics and there was no false positive result. Twenty two cases had karyotypically proven abnormalities that could not have been detected by the targeted FISH. CONCLUSION: Interphase FISH analysis of uncultured amniotic fluid cells has been shown to be an effective and reliable technique for rapid fetal aneuploidy screening during pregnancy as an adjunctive test to conventional cytogenetics.

The Reliability and Validity of Korean Version of Questionnaire for Nicotine Dependence

BACKGROUND: Although the Fagerstrom Tolerance Questionnaire (FTQ) and the Fagerstrom Test for Nicotine Dependence (FTND), which are the tools to measure Nicotine Dependence, have a high internal reliability and a high test-retest reliability, they have not been tested domestically. A Korean-Version Questionnaire for Nicotine Dependence was assessed to find out the internal reliability, test-retest reliability and validity. METHODS: The research subjects were adult smokers of ages between 19 and 77 among hospital visitors, hospital staffs, inpatients and outpatients. The smokers had their carbon monoxide measured after responding to the questionnaire. The questionnaire consisted of Nicotine Dependence (FTQ & FTND), the history of smoking, the variables related to Nicotine Dependence, and factors that influence carbon monoxide(CO) measurement. Micro II smokerlyzer (Bedfont Instruments Ltd, England) was used to analyze CO concentration in expired air. The method used for measuring CO concentration was to deeply inhale and hold one's breath for 15 seconds and measure CO concentration while exhaling. RESULTS: The total number of subjects was 205 (199 males, 6 females) consisting of 124 hospital visitors, 67 hospital staff, 8 inpatients, and 6 inpatients. The average FTQ was 4.68 and the average FTND was 3.95. Cronbach's alpha, which indicates the internal reliability, was 0.6679 for FTQ and 0.6913 for FTND. The correlation coefficient which indicates test-retest reliability was 0.783 for FTQ and 0.880 for FTND. The correlation coefficient which indicates the relationship between the level of Nicotine Dependence and expired air CO concentration was 0.484 for FTQ and 0.563 for FTND. The correlation coefficient of the smoking period was 0.247 for FTQ and 0.252 for FTND. CONCLUSION: This Korean-Version Questionnaires for Nicotine Dependence (FTQ & FTND) were both satisfactory from the aspects of reliability and validity. It was concluded that the Korean-Version of FTND was a reliable method to reflect the level of nicotine dependence of smokers from the fact that the reliability and validity of FTND was higher than that of FTQ.

Predictive Factors of Hope in Patients with Cancer / 성인간호학회지

It has been believed that cancer is an omnious factor threatening the future and life itself. Patients having the disease experience anxiety, fear, feeling of weakness, depression and feelings of uncertainty and hopelessness. Most cancer patients, however, have expectations of possible recovery and a better future, very different from the patients who feel hopeless. Therefore. hope allows people to respond effectively to the fatal disease they have and prevents them from detoriorating physically and spiritually, positively influencing their survival, response to treatment and sense of security. Studies previously performed showed that hope is positively correlated with social and family supports, self-esteem, spiritual well-being, responsive action, health promotion behavior and quality of life. Thus, the study attempted to provide basic information on nursing cancer patients by investigating their levels of hope and determining predictive factors which influence hope. For the study 200 cancer patients in two university hospitals located in Pusan were sampled as subjects. Data were collected for twenty nine days from Feburary 1, 1999 to March 1. Instrumets for the study included 10 items from the self-esteem scale by Rosenberg (1965), 39 hope measurements by Kim and Lee(1965), 16 of the social support scale by Tae(1986) and 16 of the general characteristics scale, all of which totaled 81 items. The data were analyzed using the SPSS program. General characteristics of the investigated based on numbers and percentage. Hope, self-esteem and social support were analyzed using means, minimum, maximum and standard deviation. Relations among the foregoing three factors were analyzed using Pearson' correlation coefficient. Levels of hope in cancer patients were determined using t-test, ANOVA and Scheffe test. Predictive factors influencing hope were investigated using multiple stepwise regression analysis. Results of the study are summarized as follows: 1. An average level of hope was 185.55+/-23.39 points(96 min. and 234 max.) 2.Levels of hope showed a significant difference among them according to sex (t=-3.69, P=.000), age(F=4.714, P=.000), job(F=3.247, P=.008), monthly income (F=6.113, P=.003), treatment charge (F=3.796, P=.011), supportive resources (F=10.554, P=.000), diagnosis(F=2.287, P=.029), perceived health status(F=22.184, P=.000), level of pain(F=3.334, P=.021), religion (F=4.911, P=.001) and religion's effect in life (F=11.706, P=.000), 3. For the subjects, self-esteem and social support were 38.32+/-7.21(13 min, and 50 max.) and 52.97+/-8.49points(28 min, 80 max.). Concerning social support, average levels of family support and medical support were found 35.95+/-6.05(18 min, and 40 max) and 27.02+/-4.99 points(20 min and 40 max). The hope the cancer patients showed significant correlations with self-esteem (r=.588, P=.000), family support(r=.224, p=.001) and medical support(r=.221, P=.002). 4.The five variables related to hope (self-esteem, religion's effect in life, perceived health status, social support and age) accounted for 54.2 percent of the hope level; especially, self-esteem was the highest at 34.6%. As shown in the above results, predictive factors which most influence hope in cancer patients were self-esteem and religion's effect of life. Therefore, nursing interventions to increase self-esteem should be developed. Regarding religion's effects, studies on spiritual aspects should be carried out in a way that contributes to promotion of hope.

EFFECT OF CeCO2 ADDITION IN GLASS COMPOSITION ON THE STRENGTH OF ALUMINA-GLASS COMPOSITES / 대한치과보철학회지

Dental ceramics have good aesthetics, biocompatibility, low thermal conductivity, abrasion resistance, and color stability. However, poor resistance to fracture and shrinkage during firing process have been limiting factors in their use, particularly in multiunit ceramic restorations. A new method for making all-ceramic crowns that have high strength and low processing shrinkage has been developed and is referred to as the Vita In-Ceram method. This study was performed to investigate the effect of Ce02 addition in borosilicate glasses on the strength of alumina-glass composites. Porous alumina compacts were prepared by slip casting and sintered at 1,100 degrees C for 2 hours. Dense composites were made by infiltration of molten glass into partially sintered alumina at 1,140 C for 4 hours. Specimens were polished sequentially from #800 to #2000 diamond disk, and the final surface finishing on the tensile side was received an additional polishing sequence through 1,cm diamond paste. Biaxial flexure test was conducted by using ball-on-three-ball method at a crosshead speed of 0.5mm/min. To examine the microstructural aspect of crack propagation in the alumina-glass composites, Vickers-produced indentation crack was made on the tensile surface at a load of 98.0 N and dwell time of 15 sec, and the radial crack patterns were examined by an optical microscope and a scanning electron microscope. The results obtained were summarized as follows ; 1. The porosity rates of partially sintered alumina decreased with the rising of firing temperature. 2. The maximum biaxial flexure strength of 423.5MPa. in alumina-glass composites was obtained with an addition of 3 mol% Ce02 in glass composition and strength values showed the aspect of decrease with the increase of Ce02 content. 3. The biaxial flexure strength values of alumina-glass composites were decreased with rising the firing temperature. 4. Observation of the fracture surfaces of alumina-glass composites indicated that the enhancement of strength in alumina-glass composites was due to the frictional or geometrical interlocking of rough fracture surfaces and ligamentary bridging by intact islands of materials left behind the fracture front.