THE EFFECT OF CYCLIC LOADING ON THE RETENTIVE STRENGTH OF FULL VENEER CROWNS / 대한치과보철학회지

Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with 8degrees or 16degrees convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1: 16degrees taper die, cementation with zinc phosphate cement, without loading Group 2: 16'taper die, cementation with zinc phosphate cement, with loading Group 3: 8degrees taper die, cementation with zinc phosphate cement, without loading Group 4: 8degrees taper die, cementation with zinc phosphate cement, with loading Group 5: 16degrees taper die, cementation with Panavia 21, without loading Group 6: 16degrees taper die, cementation with Panavia 21, with loading Group 7: 8degrees taper die, cementation with Panavia 21, without loading Group 8: 8degrees taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed ac cording to the manufacturer' s recommendations. A static load of 5 kg was then applied for 10 min utes with static loading device. Twenty-four hours later, group 1,3,5,7 were only thermocycled, group 2,4,6,8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From, the finding of this study, the following conclusions were obtained. 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups(p0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups (p<0.05) . 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the 16degrees taper die, 25% in the 8degrees taper die, and for Panavia 21, 21% in the 16degrees taper die, 18% in the 8degrees taper die.

A STUDY ON FRACTURE STRENGTH OF COLLARLESS METAL CERAMIC CROWN WITH DIFFERENT METAL COPING DESIGN / 대한치과보철학회지

The metal ceramic crown is currently the most popular complete veneer restoration in dentistry, but in many cases, the metal cervical collar at the facial margin is unesthetic and unacceptable. Facial porcelain margin has been used in place of it. But this dose not solve the problems, such as dark gingival discoloration and cervical opaque reflection of porcelain veneer. Recently, metal copings which were designed to terminate its labio-cervical end on the axial walls coronal to the shoulder have been clinically used to solve the esthetic problem of metal ceramic crown. But in this design, porcelain veneer of labio-cervical area which is not supported by metal may not be able to resist the stress during cementation and mastication. The purpose of this study was to evaluate fracture strength and fractured appearance of crowns according to different coping designs. A resin maxillary left central incisor analogue was prepared for a metal ceramic crown, and metal dies were made with duplication mold. Metal copings were made and assigned to one of four groups based on facial framework designs: group 1, coping with 0.5mm metal collar; group 2, metal extended to the shoulder; group 3, metal extended to 1 mm coronal to the shoulder; group 4, metal extended to 2mm coronal to the shoulder. Copings and crowns were adjusted to be same size and thickness, and cemented to metal dies with zinc phosphate cement by finger pressure. Fracture strength was measured with Instron Universal Testing Machine. Metaldies were anchored in Three-way-vice at 3mm below finish line and at 130degree inclined to the lone axis of the crown. Load was directed lingually at 2mm below midincisal edge. Load value at initial crack and at catastrophic fracture was recorded. The results obtained were as follows: 1. Fracture strength values at initial crack were higher in groups 1, 2 than in groups 3, 4 but this difference was not statistically significant(P<0.05). 2. Conventional metal collared crown had greater catastrophic fracture strength than any other collarless crowns. 3. The greater the labial metal coping reduction, the lower the catastrophic fracture strength of crowns but when more than 1mm of labial metal reduction was done, the difference in strengths was not statistically significant(p<0.05). 4. The strongest collarless coping design was group 2.

Shoulder Impingement Syndrome: Evaluation of the Causes with MRI

PURPOSE: Various mechanical causes which induce shoulder impingement syndrome have been identified with the help of MRI. The aim of this study is to evaluate the incidence of such causes. MATERIALS AND METHODS: A total of 54 patients with clinically confirmed shoulder impingement syndrome and a normal control group(n=20) without symptoms were included. We evaluated the incidence of hook shaped acromion, low lying acromion, downward slope of the acromion, subacromial spur, acromioclavicular joint hypertrophy, coracoacromial ligament hypertrophy, high cuff muscle bulk, and os acromiale. RESULTS: Among the 54 patients, the following conditions were present: acromioclavicular joint hypertrophy(n=36), coracoacromial ligament hypertrophy(n=20), subacromial spur(n=18), downward sloping of the acromion(n=16), hook shaped acromion(n=11), relatively high cuff muscle bulk(n=6), low lying acromion relative to the clavicle(n=3), and os acromiale(n=1). In the normal control group there were nine cases of acromioclavicular joint hypertrophy, nine of coracoacromial ligament hypertrophy, nine of downward sloping acromion, and three of low lying acromion, but hook shaped acromion, high cuff muscle bulk, and os acromiale were not found. Among 54 patients, the syndrome was due to five simultancous causes in one patient, four causes in two, three causes in 12, two causes in 22, and one cause in 17. CONCLUSION: Hook shaped acromion and subacromial spur are the statistically significant causes of shoulder impingement syndrome. In 69 % of patients, the condition was due to more than one cause.

THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF STRESS DISTRIBUTION IN PORCELAIN LAMINATE VENEERS WITH VARIOUS AMOUNTS OF INCISAL COVERAGE AND TYPES OF INCISAL FINISH LINE UNDER TWO LOADING CONDITIONS / 대한치과보철학회지

The success of porcelain laminate veneer depends on the bond strength between tooth structure and ceramic restoration and the design of tooth preparation. In particular, incisal coverage and incisal finish line are the two most important factors in long-term fracture resistance. Although the majority of clinicians are practicing incisal coverage and there are various opinions on the geometrical ratio between the clinical crown length of the remaining tooth structure and the length of incisal extension in porcelain laminate veneer and the optimal incisal finish lines, scientific evidence still leaves much to be desired. The purpose of this study was to determine the effects of the amounts of incisal coverage and the types of incisal finish line on th stress distribution in maxillary anterior porcelain laminate veneers under two different loading conditions. Three-dimensional finite element models of a maxillary anterior porcelain veneer with different amounts of incisal coverage ; 0, 1, 2, and 3mm and different incisal finish lines ; feathered edge, incisal bevel, reverse bevel and lingual chamfer with various amounts of lingual extension were developed. 300N force was applied at the point 0.5mm cervical of the linguoincisal edge in two loading conditions ; A) 125 degrees, B) 132 degrees. tensile and compressive stress in ceramic and shear stress in the resin cement layer wee analyzed using three-dimensional finite element method. The results were as follows : 1. The types of incisal finish line had more influence on the stress distribution in porcelain laminate veneer than the amounts of incisal coverage. 2. In case of no incisal coverage, incisal beveled laminate exhibited more evenly distributed tensile stress than feathered edged laminate. And in case of incisal coverage, reverse beveled laminate and lingual chamfered laminate with 1mm lingual extension exhibited more evenly distributed tensile stress than lingual chamfered laminates with 2 mm and 3mm lingual extension. 3. As long as the lingual chamfer goes, less tensile stress was found at the incisal edge, while much more tensile stress was found at the lingual margin area in proportion to length of lingual extension. 4. Under 125 degree load, tensile stress in porcelain laminate veneer had increased compared with that under 132 degree load and the difference exhibited by the change of the amount of tooth support was larger. 5. The types of incisal finish line and the distance from the incisal finish line to the loading point had more influence on the shear stress distribution in the resin cement layer than the amount of incisal coverage. In contrast loading condition had little influence.

A STUDY OF ION BEAM ASSISTED DEPOSITION(IBAD) OF TiN ON Ni-Cr Be ALLOY FOR SURFACE CHARACTERISTIC / 대한치과보철학회지

Dental restorative materials must have the physical properties to withstand wear and corrosion. Base metal alloys possess better mechanical properties and lower price than the gold alloys. For these reason such alloys have largely replaced the precious metal alloys. One aspect to consider is the release of metal substances to oral environment. The release of elements from dental alloys is a continuing concern because the elements may have the potentially harmful biological effects on local tissue. The purpose of this study was to minimize metal release on the nonprecious metal surfaces by ion bea assisted deposition(IBAD) of titanium nitride (TiN). Ni-Cr-Be alloys with and without TiN coatings were secured in an wear test machine opposing ruby ball to determine their relative resistance to wear with 100m, 200m, 300m and 400m sliding distance. And the corrosion behavior of the Ni-Cr-Be alloys with and without TiN coating and 3 dental noble alloys have been studied. Potentiodynamic curves were used to analyse the corrosion characteristics of the alloys. The measurement of the released Ni and Ci ions was conducted by analysis of the electrolyte solution with atomic absorption spectroscopy. The results were as follows : 1. The critical sliding distance that wore down TiN coating of 2.5micrometer thickness in this study condition was 300m. 2. Ion beam assisted deposition of TiN showed a good surface modification with respect to the properties of wear and corrosion resistance. 3. X-ray diffraction showed that the strongest peak of TiN(111) in the coatings. 4. The release of Ni and Cr ions from alloys measured by means of atomic absorption spectroscopy was reduced by ion beam assisted deposition of TiN.

AN IN-VITRO WEAR STUDY OF DENTAL PORCELAINS AND HUMAN ENAMEL / 대한치과보철학회지

Dental porcelain is one of the materials of choice for restoration where esthetics is of concern, but has a considerable potentials of wear. The wear of enamel is variable when opposed by different porcelain systems and surface conditions, and the exposed dentine and opaque porcelain due to clinical failure is expected to have high potentials of wear. The purpose of this study was to investigate the wear effects of self-glazed, polished incisal porcelain, polished dentine and opaque porcelain against human enamel in the laboratory by use of a pin-on-disk type wear tester. 4 types of dental porcelain(Vita-omega, Ceramco-II, Vintage powder, Vita-alpha of In-Ceram system) and type IV gold alloy as cotrol group were used for test specimens. Intact buccal cusps of maxillary premolar were used for enamel specimens, and the cusp converged to a point and was devoid of visible abrasion, caries, decalcification. The upper part was the cusp of a maxillary premolar and the lower part was a porcelain specimen. The enamel wear was determined by weighing the cusp before and after each test. Surface profilometer was used to quantitate wear of the porcelain specimens. Vicker's hardness tester was used to evaluate the surface hardness of test specimens. The SEM was used to evaluate the wear surfaces. The results were as follows : 1.Self-glazed porcelain produced more enamel wear than polished porcelain, especially the enamel wear of Vita-alpha self-glazed porcelain was 3.2 times more than that of other groups. 2.Opaque porcelain produced least porcelain wear, Vita-alpha self-glazed porcelain produce greatest porcelain wear, but there was no statistically significant difference between the groups(p>0.05). 3.The enamel wear of dentine porcelain was 3.8 times more than that of polished inisal porcelain(p0.05). 4.Overglazed porcelain produced less enamel wear than self-glazed porcelain, and more enamel wear than polished porcelain, but there was no statistically significant difference between the groups(p>0.05). 5.The hardness number of Vita-omega dentine and Ceramco-II opaque porcelain was larger, but that of Vintage dentine and Vita-alpha self-glazed porcelain was similar to other groups. 6.Examination of SEM photographs revealed that overglazed porcelain had smoother surface than self-glazed porcelain, and self-glazed porcelain had smoother surface than polished porcelain. Much polishing scratches and larger porosities were observed on the opaque porcelain specimen, and much polishing scratchess and small porosities were observed on the dentine porcelain specimen.

Changes of Tuberculous Cavities after Antituberculous Therapy: Analysis with High-Resolution CT

PURPOSE: To evaluate changes in tuberculous cavities, one of the major factors used to determine the activityof tubereulosis, by high-resolution CT(HRCT) in active pulmonary tuberculosis patients after antituberculoustherapy. MATERIALS AND METHODS: The HRCT findings of 41 patients with active tuberculosis were analyzed withparticular emphasis on the appearance of tuberculous cavities before and after therapy. We measured the largestdiameter and maximal wall thickness of the cavities, as well as accompanying changes occurring during follow-up.The mean interval between initial and follow-up study was 8.7 months(minimum:4.1, maximum:33.2;S.D.: +/-5.0) andthe mean duration of antituberculous therapy was 7.5 months(minimum:4.7, maximum:14.8;S.D.: RESULTS: Among 41patients, 54 cavities were found on initial HRCT. Thirty one(57.4%) of these disappeared during follow up HRCTwith residual changes such as residual fibrotic scar(n=15), granuloma(10), paracicatrical emphysema(7),calcification(3), traction bronchiectasis(3), consolidation(3) and bullous emphysema(1). Twenty three of thecavities(42.6%) decreased in size and wall thickness, but did not disappear completely during follow-upexamination. Mean largest diameter and maximal thickness of 23 cavities were 32.0mm(+/-13.9) and 7.9mm(+/-4.8) oninitial HRCT, falling to 20.9mm(+/-12.5) and 4.1mm(+/-2.6), respectively, during follow-up HRCT. Among four patientswho underwent a second follow-up, the largest diameter and maximal thickness of the cavities decreasedcontinuously. In two patients, however, the cavities did not did not disappeas, though in the other two they haddisappeared by the time follow-up HRCT was performed a second time. CONCLUSION: During follow-up HRCT afterantituberculous therapy(mean duration of 7.5 months), 57.4%(31/54) of cavities were seen to have disappeared, withresidual changes such as fibrotic scars, granulomas, paracicatrical emphysema and calcification ; 42.6% of thecavitivies still remained, however, with retractive and fibrotic change. Such fibrotic and retractive changesshould not, therefore, be taken as indicative of active tuberculosis, especially in patients who have successfullycompleted their medication.

A STUDY ON DIMENSIONAL STABILITY OF IMPRESSION MATERIALS FOLLOWING IMMERSION DISINFECTION / 대한치과보철학회지

Dental practice can produce and spread some infetious diseases from patients to dentist, dental assistant, and dental labors. One possible method for preventing these cross-contamination is to immerse dental impression in chemical disinfectants. So far many investigators studied on the dimensional changes of dental impressions and on the surface qualities of stone casts made from impression following immersion in disinfectants. This study was proposed to evaluate some popular impression/disinfectant combination from the point of dimensional stability. Impression was taken from dental arch-shaped metal model. Irreversible hydrocolloid and 3 elastomers(polyvinyl siloxane, polysulfide, polyether) were immersed in 3 disinfectants (2% glutaraldehyde, 1% povidone-iodine, 0.5% sodium hypochlorite) for 10 minutes and measured both cross-arch and anterior-posterior distance under stereo microscope to evaluate dimensional change. The results obtained were as follows: 1. Dimensional changes of irreversible hydrocolloid impression was statistically different in crossarch and anterior-posterior distance when immersed in 2% glutaraldehyde solution and in anterior-posterior distance when immersed in 0.5% sodium hypochlorite solution from control group(p0.05). 3. Dimensional changes of polyether impression was statistically different in cross-arch distance when immersed in 0.5% sodium hypochlorite solution and in anterior-posterior distance when immersed in 1% povidone-iodine solution from control group (p<0.05). 4. In all cases, dimensional changes were less than 0.1% from the original dimension and concluded clinically acceptable

THE EFFECT OF SURFACE TREATMENT ON FRACTURE STRENGTH OF DENTAL CERAMICS / 대한치과보철학회지

The major influencing factors on the strength of all-ceramic crowns are types of dental ceramics, fabrication techniques, methods of abutment preparation and cementation modes of all ceramic restorations. Zine phosphate cement and glass-ionomer cement were used as an early luting media for all-ceramic crowns. Recently many studies have reported that resin cements have more advantages in increasing the fracture strength of restorations comparing with zincphosphate cement and glass-ionomer cement. The purpose of this study is to investigate the effect of etching, silane treatment, sandblasting and dentin bonding agents on fracture strengths of dental ceramics. 40 flat dentin specimens and 40 ceramic discs of 1.5mm thickness and 8mm diameter were fabricated, and divided into 4 groups according to surface treatments. Surface treatments before cementation were as follows. Group I : (ceramic) : HF etching - silane treatment - application of bonding resin (dentin) : application of dentin bonding agent Group II : (ceramic) : sandblasting - application of bonding resin (dentin) : application of dentin bonding agent Group III : (ceramic) : application of bonding resin (dentin) : application of dentin bonding agent Group IV : (ceramic) : HF etching - silane treatment - application of bonding resin (dentin) : no dentin bonding procedure Dentin specimens and ceramic discs were cemented with dual cure resin cement, and went through thermocycling. Compressive stress es were loaded on the centers of ceramic discs with Instron testing machine, and fracture strengths resista' nce for catastrophic fracture were measured The results were as follows. 1. The group I showed the highest fracture resistance. The next was group II. And group III, IV followed. 2. There was a significant difference in the mean value of fracture strengths between group I and group III (p0.05). 3. There was a significant difference in the mean value of fracture strengths between group I and group IV (p<0.05).

Comparison of Split Renal Function on DTPA Renal Scan and Endogenous Creatinine Clearance Ratio in Obstruction of Upper Urinary Tract / 대한비뇨기과학회지

PURPOSE: Split renal function on diuretic renography has been considered to be a good tool for evaluating renal function, selecting treatment modalities and assessing efficacy of surgery in hydronephrosis, especially in ureteropelvic junction(UPJ) obstruction. However, contradictory supranormal function on renography has provided controversy with urologists. Is the phenomenon the result of fact or artifact? The authers thought that contradictory supranormal renal function measured with 99mTc-DTPA Is fundamentally related with a question. How accurately does the split renal function test represent the real renal function, namely, glomerular filtration rate(GFR)? To know relation of split renal function with real renal function(GFR) and to disclose clinical significance of contradictory supranormal renal function on diuretic renal scan, a prospective study was performed. MATERIALS AND METHODS: Diuretic renography was done in 14patients with upper urinary tract obstruction including UPJ obstruction, ureteral stone and lower urethral obstruction. Afer the first diuretic renography using 99mTc-DTPA percutaneous nephrostomy was performed on affected kidney, which was followed by the second diuretic renography. Endogenous creatinine clearance tests were done on the patients. Urine was collected through the nephrostomy tube, self voiding or indwelling Foley catheter, respectively So the endogenous creatinine clearance was determined respectively on both the renal unit. Also the endogenous creatinine clearance ratio of affected kidney was determined to compare with split renal function on renography. RESULTS: In 7patients, ratio of endogenous creatinine clearance on affected kidney was less than 40%. In the other 7patients, the ratio was more than 48%. In patients with less than 40% of endogenous creatinine clearance ratio on affected kidney, split renal function was overestimated by 10.3% to 27.5%(19.5+/-4.9%) comparing to endogenous creatinine clearance ratio. In the other 7patients split renal function had a little difference from endogenous creatinine clearance ratio (4.5+/-2.5%). The endogenous creatinine clearance ratio was not closely related with split renal function(correlation coefficients: 0.65). Split renal function of the first renography was closely related with that of the second renography(correlation coefficients: 0.88). Contradictory supranormal function occurred in 4cases. In 2cases it was real finding, in the other it was not. CONCLUSIONS: It appears that split renal function is overestimated in poor renal function and split renal function is closely related with real renal function in good renal function slate. Supranormal renal function is real finding in part, not in part. Clinical significance of split renal function should be cautiously and basically reevaluated through further study.

A STUDY ON THE MARGINAL FIT OF ALL-CERAMIC CROWN USING CCD CAMERA / 대한치과보철학회지

The purpose of this study was to evaluate marginal fit of four all-ceramic crown systems 1) conventional In-Ceram, 2) copy-milled In-Ceram using Celay system, 3) IPS Empress, 4) OPC(Optimal Pressable Ceramic). All ceramic crowns were made on epoxy dies. The fabricated crowns were sandblasted, cleaned with ultrasonic cleansing, silanated, and cemented with Bistite composite resin cement. The selected marginal areas of the crowns were the labial, lingual, mesial, and distal surface. Each selected area of surface was 0.6Xl.6mm in dimension. The image of each marginal area was captured to computer files using DT-55 Frame Grabber and light microscope connected CCD camera. The marginal gaps were measured every 70mm using computer image analysis program. The results obtained were summarized as follows : 1. The marginal fit of four all-ceramic crowns were significantly different from each other(p<0.01), and mean marginal fit values obtained were 31.42 +/- 16.52mm in conventional In-Ceram, 55.45 +/- 27.90mm in copy-milled In-Ceram using Celay-system, 44.36 +/- 24.59mm in IPS Empress, 47.21 +/- 20.42mm in OPC. 2. In the marginal fit of conventional In-Cerani and copy-milled In-Ceram crowns using Celay-system there was no significant difference between mesiodistal and buccolingual surface. but in the marginal fit of IPS Empress and OPC crowns, there was significant difference between mesiodistal and buccolingual surface(p <0.01). 3. The marginal fit of four hinds of all-ceramic crowns was clinically acceptable.

A STUDY OF THE MICROLEAKAGE AT THE POST AND CORE AND TOOTH INTERFACE / 대한치과보철학회지

Post and core is used to restore endodontically treated teeth, and it is a very important part which supplies retention and support to the prosthesis. But occasionally, caries occurred due to the microleakage at the post and core and tooth interface, the failure of prosthesis has happened. In this study, the microleakage of cast gold post and core, amalgam core, and composite resin core was investigated and compared. The coronal part of the extracted upper anterior teeth were removed and endodontically treated with conventional method. The teeth were divided into three groups. In group 1, cast gold post and core was cemented with resin cement and in group 2, ready-made post was cemented with resin cement and amalgam core was built. In group 3, ready-made post was cemented with resin cement and composite resin core was built. All specimens were thermocycled between 5degrees C and 55degrees C with dwell time of 15 seconds, and immersed in 0.5degrees C aqueous solution of basic fuchsin dye for 24 hours. After embedded in the epoxy resin, the specimens were sectioned longitudinally and observed with stereomicroscope with the magnification of 25. From the findings of this study, the following conclusions were obtained. 1. There was microleakage at the core/tooth interface of all specimens. 2. The microleakage of gold post and core was significantly less than those of the other two groups. 3. There was no significant difference between the microleakage of amalgam core and that of composite resin core.

Early Experience of Laparoscopic Renal Cyst Marsupialization / 대한비뇨기과학회지

PURPOSE: To evaluate the eligibility of laparoscopic surgery for the treatment of renal cysts, we analysed our clinical results of laparoscopic renal cyst marsupialization in 9 patients. MATERIALS AND METHODS: Between January 1994 and February 1997, a total of 9 patients with renal cyst underwent laparoscopic surgery. They were 2 men and 7 women 42 to 67 years old. Mean cyst size of the patient was 7.3cm(5-10cm). Presenting symptoms were flank pain in 8 and palpable mass in 1. One patient had previously undergone ultrasonography guided percutaueous aspiration and ablation. One patient had bilateral renal cyst. Initially the procedures had been performed via the transperitoneal approach in 4 patients after that we attempted retroperitoneal access for laparoscopy in 5 patients(6 renal units). During the operation cyst fluid was obtained for cytologic examination and cyst walls were excised and sent for pathological examination. RESULTS: Mean operation time was 2 hours and 14 minutes. Mean hospital stay was 5.9 days. Perioperative complications were pain(20%), bleeding(10%), subcutaneous emphysema(20%) and pneumothorax(10%). Bleeding was minimal but 2 units of packed red cell were needed in 1 patient. Conversion to open surgery from laparoscopic procedure was needed in 1 patient. Biopsy results were negative for carcinoma. All patients were asymptomatic at a mean follow up of 12.5 months. CONCLUSIONS: Laparoscopic renal cyst marsupialization for symptomatic renal cysts seems to be a safe and effective alternative to open surgery.

Effects of Nitric Oxide and Peroxynitrite Peroxynitrite on Sperm Motility and Viability / 대한비뇨기과학회지

PURPOSE: Recently, in assisted reproductive technologies(ART) programs theme Is an increasing Interest in the use of agents for the enhancement of sperm motility for assisted fertilization. In an attempt to improve the motility at the cryopreserved human semen and hence the fertilizing capacity of asthenospermic semen samples, different semen preparation techniques have been attempted and the effects of chemical stimulants as nitric oxide(NO) have been studied extensively. Superoxide anions cause lipid peroxidative damage to cell membrane phospholipids, and sperm are known to be particularly susceptible to lipid peroxidation. Such sperm with damaged membranes are impaired functionally. Recently, peroxynitrite, an anion and a potent oxidant, generated by the interaction of nitric oxide and superoxide anions has been demonstrated In macrophages and other cellular systems. Also this anion cause lipid peroxidative damage to cell membrane phospholiplds. We therefore Investigated whether NO and peroxynitrite have the roles to modulate sperm motility and to affect Its viability. MATERIALS AND METHODS: Normal human semen samples(as per World health Organization (WHO) criteria) were obtained after 3day period of abstinence by donors. The samples(n=5) were incubated with either sodium nitroprusside(SNP; 0.1, 05, 1 or 2mM) or peroxynitrite (10, 50 or 100 micrometer ) and the percent viability and motility were assessed at various time inteval up to 4hr. The human semen samples were treated with N-acetyl-L-cystein(NAC;10mM), SNP (0.5mM), phorbol myristate acetate(PMA; 100nM), of SNF plus PMA. Both superoxide and peroxynitrite release were measured directly by chemiluminometer. Percent viability and motility were assessed at 4hr of Incubation. A sample of each aliquot was placed in a Mauler chamber for videomicrography Percent motility were analyzed by using the sperm analysis imaging system. The sperm vlability was assessed by flow cytometer using LIVE/DEAD sperm viability kIt. The production of superoxide and peroxynitrite were measured by the method of chemiluminescence assay. Result : All results represent a mean +/-SEM, n=5. Treatment of human semen samples for 4hr with SNP, a NO generating agent, significantly decreased sperm motility and viability in high concentration [relative motility(% of control); 38 +/-4 and 30 +/-5, relative viability; 42 +/-4 and 30 +/-3 by 1 and 2mM of SNP]. In the presence of low concentration SNP(0.5mM), the sperm viability was not significantly affected(82 +/-3), whereas the sperm motility was affected(64 2). SNP(0.5mM) also decreased sperm motility(80 +/-2 at 2hr 64 +/-3 at 4hr, 44 +/-3 at 6hr, and 38 +/-4 at 8hr) in a time dependent manner. Since it was demonstrated that superoxide anions are one of the common source of lipid peroxidation, we investigated whether superoxide anions produced by human semens could Interact wlth NO to generate peroxynitrite. Adding N-acetyl-L-cystein(NAC) to the human semen samples partially blocked spontaneous release of superoxide, whereas PMA augmented the release of superoxide from human semen samples (control:0.9 106 0.3, NAC: 0.5 106 +/-0.4, and PMA: 2.5 106 +/-0.4photons/60min). The production of superoxide was corresponded with the production of peroxynltrite(control: 1.0 104CPM, SNP: 3.8 106CPM, SNP plus PMA. 12chi106CPM). In addition, SNP in combination with PMA(65 +/-3) markedly decreased sperm motility than that of SNP alone(77 +/-2.5) at 4hr, implying that nitric oxide might inhibit sperm motility via the formation of peroxynitrite In human semen samples. Exogenous peroxynitrite also decreased sperm motility in a dose dependent manner(10 micrometer : 64 +/-2, 50rM: 53 +/-3, and 1 0 micrometer of peroxynitrite: 23 4). CONCLUSIONS: These results suggest that NO inhibits sperm motility via the formation of peroxynltrite and further demonstrate that NO-induced inhibition of sperm motility is depended on the production of superoxide from human semens because peroxynitrite is generated by the interaction of NO and superoxide.

A STUDY ON THE SURFACE ROUGHNESS OF GLAZED PORCELAIN AND POLISHED PORCELAIN / 대한치과보철학회지

Porcelain is considered to be one of the materials of choice for restoration where esthetics is of concern. But porcelain surface without final glazing treatment may induce undesirable results such as inflammatory respones on adjacent soft tissues due to plaque accumulation and increased wear of opposing teeth. Therefore, rough porcelain surface must be smoothened by final glazing treatment or chairside polishing procedure. The purpose of this study was to compare the surface roughness among self-glazed, overglazed and polished porcelain with various polishing kit, and to detect which phase of polishing is optimal in clinic. Specimens were fabricated with Vita VMK porcelain. The surface treatment of each group was performed as follows. Group 1 : overglazing treatment Group 2 : self-glazing treatment Group 3 : polishing with the Truluster Polishing System for Porcelain(Brasseler, U.S.A.) Group 4 : polishing with the Exa Cerapol Adjustment kit (Edenta dental products, Switzerland) followed by finishing with diamond-filled polishing paste Group 5 : polishing with the Shofu Porcelain Adjustment kit (Shofu inc., Japan) followed by finishing with diamond-filled polishing paste. At each polishing steps, the measurement of Ra and Rq values were performed, and the surface was examined by scanning electron microscope. The results were as follows: 1. Overglazing treatment brought smoother surface than self-glazing treatment. 2. Polishing systems without porcelain polishing paste did not make better result than self-glazing treatment. 3. Polishing system with porcelain polishing paste made similar result to overglazing treatment. 4. Applying diamond-filled polishing paste after using polishing system which has porcelain polishing paste produced surface as smooth as overglazing treatment does.

SHEAR BOND STRENGTH OF RESIN ADHESIVE CEMENT TO ENAMEL AND Ni-Cr-Be ALLOY / 대한치과보철학회지

This study was executed to measure the shear bond strength of Panavia EX and Panavia 21 when the Ni-Cr-Be alloy castings were cemented to the enamel surfaces with these cements. The cast metsl plates of Ni-Cr-Be alloy were sandblasted and cemented to acid etched enamel surface with Panavia EX or Panavia 21. Their shear bond strength were measured with Instron Universal Testing machine. Within the limits of this study, following conclusions were withgdrawn. 1. The mean shear bond strength were 26.85.7Mpa, in Panavia EX and 28.35.2Mpa, in Panavia 21. 2. t-Test revealed no statistical significance between two groups(.05 level) 3. Macroscopically, bond failures were revealed compound fracture at metal and enamel interfaces, in cases of both cements, as the cement attached partly on both metal and enamel surface.

A STUDY ON FRACTURE STRENGTH OF CONVENTIONAL AND COPY-MILLED IN-CERAM CROWNS / 대한치과보철학회지

The purpose of this study was to compare the fracture resistance of copy-milled and conventional In-Ceram crown. Four groups of ten uniform sized all-ceramic crowns were fabricated. In-Ceram Spinell and In-Ceram Alumina crowns were fabricated as control group, Celay In-Ceram Spinell and Celay In-Ceram Alumina crowns were fabricated as test group. All specimen were cemented on stainless steel master die with resin cement, and stored in 37degrees C water for 1 day prior to loading in Instron testing machine. Using a steel ball at a crosshead speed of 0.5mm/min, the crowns were loaded at 30degree angle until catastrophic failure occurred. The results obtained were as follows : 1. With the value of 984.8N+/-103.67N, the strength of Celay In-Ceram Alumina crowns had a significantly higher fracture strength than conventional In-Ceram Alumina crowns(876.2N+/-92.20N) (P0.05). 3. The In-Ceram Alumina crowns had a significantly higher fracture strength than In-Ceram Spinell crowns in both methods(P<0.05). 4. Ther order of fracture strength was as followed : Celay In-Ceram Alumina, In-Ceram Alumina, Celay In-Ceram Spinell and In-Ceram Spinell crowns

A STUDY ON THE DISTORTION OF THE COPINGS FOR CERAMOMETAL CROWNS DURING REPEATED FIRING / 대한치과보철학회지

Ceramometal crowns are common restorations in fixed prosthodontics because of their casting accuracy, the high strength properties of the metal, and the cosmetic appearance of porcelain. However, deterioration of the initial fit of the metal coping has been observed after the porcelain firing cycle. The distortion due to repeated firing makes it difficult to fit crown margin and elicits microleakage. The major causes of distortion are the residual stress that accumulate during wax-up, casting, cold work and the induced stress caused by the mismatch of porcain-metal thermal contraction. This study examined the marginal fit changes of metal copings in relation to repeated firing and the effects of heat treatment that reduce the distortion resulted from residual stress. The marginal changes of the copings that were treated with conventional method and those treated with heat before repeated firing, were evaluated. The metal die which represented preparations of a maxillary central incisor was fabricated, and 45 wax patterns were cast with nonprecious metal alloys. The heat treatment of each group was performed as follows. Group 1(control) : Casting - Devesting - Cold work - Firing Group 2 : Casting - Heat treatment - Devesting - Cold work - Firing Group 3 : Casting - Deveting - Cold work - Reinvesting - Heat treatment - Devesting - Firing The copings were fired 3 times. After each firing, the marginal fit changes were measured with inverted metallurgical microscope at the 4 reference points located at labial, lingual, and both proximal surface. Measurements were compared, and statistically analyzed. The results were as follows ; 1. In all groups, the highest value of marginal fit changes of the copings studied were found after the first firing cycle. 2. When the distortion of each experimental group at the first firing cycle were compared, group 1 exhibited the greatest changes(20-27micrometer), fullowed by group 2(9-13micrometer), and group 3(8-10micrometer). 3. The copings treated with heat before devesting(group 2) revealed significantly smaller marginal fit changes than the copings treated with conventional method(group 1). (p0.01)

THREE-DIMENSIONAL FINITE ELEMENT ANALYSIS OF STRESS DISTRIBUTION IN ALL-CERAMIC CROWNS WITH VARIOUS FINISH LINE DESIGNS AND INCISAL REDUCTIONS UNDER DIFFERENT LOADING CONDITIONS / 대한치과보철학회지

The purpose of this study was to determine the effect of finish line design, amount of incisal reduction, and loading condition on the stress distribution in anterior all-ceramic crowns. Three-dimensional finite element models of an incisor all-ceramic crown with 3 different finish line designs : 1) shoulder with sharp line angle 2) shoulder with rounder line angle 3) chamfer : and 2 different incisal reductions : 2mm and 4mm were developed. 300 N force with the direction of 45 degree to the long axis of the tooth was applied at 3 different positions : A) incisal 1/3, B) incisal edge, C) cervical 1/5. Stresses developed in ceramic and cement were analyzed using three-dimensional finite element method. The results were as follows : 1. Stresses were concentrated in the margin region, which were primarily compressive in the labil and tensile in the lingual. 2. Stresses were larger in the area near line angle than on the crown surface of the margin region. In case of shoulder with sharp line angle, stresses were highly concentrated in the porcelain near line angle. 3. At the interface between porcelain and cement and at the porcelain above the margin on crown surface, stresses were the highest in chamfer, and decreased in shoulder with sharp line angle and shoulder with rounded line angle, respectively. 4. At the interface between cement and abutment on crown surface, stresses were the highest in shoulder with sharp line angle, and decreased in shoulder with rounded line angle and chamfer, respectively. 5. The amount of incisal reduction had little influence on the stress distribution in all-ceramic crowns. 6. When load was applied at the incisal edge, higher stresses were developed in the margin region and the incisal edge than under the other loading conditions. 7. When load was applied at the cervical 1/5, stresses were very low as a whole.

An Experience of Vaginoplasty with Bilateral Labioscrotal Flap (M-shaped flap) for Female Pseudohermaphroditism in Congenital Adrenal Hyperplasia / 대한비뇨기과학회지

The most common etiology for female pseudohermaphroditism is congenital adrenal hyperplasia, which accounts for more than 60 percent of children with ambiguous genitalia, and is treated with cortisol replacement and surgical correction of ambiguous genitalia. Flap vaginoplasty, the inverted U-Shaped type has been applied worldwide to the patient with low vaginal entry. The most frequent complication of the operation is contraction of the new vaginal introitus as a result of ischemic and fibrotic changes in the overlapping suture line between the flap and posterior vaginal wall. Maintenance of a good blood supply for the flap and tension free anastomosis should always be kept in mind to avoid this complication. We experienced a vaginoplasty with labioscrotal flap instead of the inverted U-shaped flap and achieved a good result in a 14-year-old girl with low vaginal entry due to congenital adrenal hyperplasia. The labioscrotal flap seems to be more suitable than inverted U-shaped flap for vaginoplasty because the labioscrotal skin is more elastic and more easily elongated than the perineal skin.