The effect of preparation procedure on implant-abutment joint stability / 대한치과보철학회지

STATEMENT OF PROBLEM: Little is known about the effect of abutment preparation procedure on de-torque values in different implant platform and the relationship of final de-torque values with different implant platform size. PURPOSE: This study evaluated the effect of abutment preparation procedure on de-torque values in different implant platform and the relationship of final de-torque values with different implant platform size. MATERIAL AND METHOD: Six ITI implants (2 narrow-neck implants, 2 regular-neck implants, 2 wide-neck implants) and six Bra.nemark implants (2 narrow platforms, 2 regular platforms, 2 wide platforms) were embedded in each acrylic resin block with epoxy resin. Eighteen synOcta(R) abutments (6 narrow-neck implant-abutments, 6 regular-neck implant-abutments, 6 wide-neck implant-abutments) and eighteen esthetic abutments (6 narrow platform-abutments, 6 regular platform-abutments, 6 wide platform-abutments) were tightened to each implant with digital torque gauge. Initial de-torque values were measured using digital torque gauge. After preparation of abutments, Final de-torque values were measured with digital torque gauge. RESULTS AND CONCLUSION: 1. Screws loosening or abutments motion were not detected in all experimental group, but some scratches of implant-abutment joints were detected in all group. 2. Reduction ratios of final de-torque values were greater than initial de-torque values in all measured group, except in narrow-neck implant-abutment group (p<0.05). 3. Reduction ratios of final de-torque values in wide-neck implant-abutment group were greater than regular-neck implant-abutment group (p<0.01). 4. The greatest standard deviation value was detected in wide platform group in both implant systems.

Comparative accuracy of the splinted and unsplinted impression methods for internal connection / 대한치과보철학회지

STATEMENT OF PROBLEM: Accurate impression is essential to success of implant prostheses. But there have been few studies about the accuracy of fixture-level impression techniques in internal connection implant systems. PURPOSE: The purpose of this study was to compare the accuracy of two fixture-level impression techniques in two conditions (parallel and divergent) and to assess the effect of tightening sequences and forces on stresses generated on superstructures in internal connection implant system (Astra Tech). MATERIAL AND METHODS: Two metal master frameworks made from two abutments (Cast-to Abutment ST) each and a corresponding, passively fitting, dental stone master cast with four fixture replicas (Fixture Replica ST) were fabricated. Ten dental stone casts for each impression techniques (direct unsplinted and splinted technique) were made with vinyl polysiloxane impressions from the master cast. Strain gauges for each framework were fixed midway between abutments to measure the degree of framework deformation on each stone cast. Pairs of strain gauges placed opposite each other constituted one channel (half Wheatstone bridge) to read deformation in four directions (superior, inferior, anterior, and posterior). Deformation data were analyzed using one-way ANOVA and the Tukey test at the .01 level of significance. And the effect of tightening sequences (right-to-left and left-to-right) and forces (10 Ncm and 20 Ncm) were assessed with ten stone casts made from parallel condition by the splinted technique. Deformation data were analyzed using paired t-test at the .01 level of significance. CONCLUSIONS: Within the limitations of this study, the following conclusions could be drawn. 1. Frameworks bent toward the inferior side on all casts made by both direct unsplinted and splinted impression techniques in both parallel and divergent conditions. 2. There was no statistically significant difference of accuracy between the direct unsplinted and splinted impression techniques in both parallel and divergent conditions (P>.01). 3. There was no statistically significant difference of stress according to screw tightening sequences in casts made by the splinted impression technique in parallel condition (P>.01). 4. Greater tightening force resulted in greater stress in casts made by the splinted impression technique in parallel condition (P<.01).

Surface characteristics and biological responses of hydroxyapatite coating on titanium by hydrothermal method: an in vitro study / 대한치과보철학회지

STATEMENT OF PROBLEM: Hydroxyapatite(HA) coated titanium surfaces have not yet showed the reliable osseointegration in various conditions. PURPOSE: This study was aimed to investigate microstructures, chemical composition, and surface roughness of the surface coated by the hydrothermal method and to evaluate the effect of hydrothermal coating on the cell attachment, as well as cell proliferation. MATERIAL AND METHODS: Commercially pure(c.p.) titanium discs were used as substrates. The HA coating on c.p. titanium discs by hydrothermal method was performed in 0.12M HCl solution mixed with HA(group I) and 0.1M NaOH solution mixed with HA(group II). GroupI was heated at 180degrees C for 24, 48, and 72 hours. GroupII was heated at 180degrees C for 12, 24, and 36 hours. And the treated surfaces were evaluated by Scanning electron microscopy(SEM), Energy dispersive X-rayspectroscopy(EDS), X-ray photoelectron spectroscopy(XPS), X-ray diffraction method(XRD), Confocal laser scanning microscopy(CLSM). And SEM of fibroblast and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide(MTT) assay were used for cellular responses of the treated surfaces. RESULTS: The color of surface changed in both groups after the hydrothermal process. SEM images showed that coating pattern was homogeneous in group II, while inhomogeneous in group I. H72 had rosette-like precipitates. The crystalline structure grew gradually in group II, according to extending treatment period. The long needle-like crystals were prominent in N36. Calcium(Ca) and phosphorus(P) were not detected in H24 and H48 in EDS. In all specimens of group II and H72, Ca was found. Ca and P were identified in all treated groups through the analysis of XPS, but they were amorphous. Surface roughness did not increase in both groups after hydrothermal treatment. The values of surface roughness were not significantly different between groups I and II. According to the SEM images of fibroblasts, cell attachments were oriented and spread well in both treated groups, while they were not in the control group. However, no substantial amount of difference was found between groups I and II. CONCLUSIONS: In this study during the hydrothermal process procedure, coating characteristics, including the HA precipitates, crystal growth, and crystalline phases, were more satisfactory in NaOH treated group than in HCl treated group. Still, the biological responses of the modified surface by this method were not fully understood for the two tested groups did not differ significantly. Therefore, more continuous research on the relationship between the surface features and cellular responses seems to be in need.

The effect of internal implant-abutment connection and diameter on screw loosening / 대한치과보철학회지

STATEMENT OF PROBLEM: One of the common problems of dental implant prosthesis is the loosening of the screw that connects each component, and this problem is more common in single implant-supported prostheses with external connection, and in molars. PURPOSE: The purposes of this study were: (1) to compare the initial abutment screw detorque values of the six different implant-abutment interface designs, (2) to compare the detorque values of the six different implant-abutment interface designs after cyclic loading, (3) to compare the detorque values of regular and wide diameter implants and (4) to compare the initial detorque values with the detorque values after cyclic loading. MATERIAL AND METHODS: Six different implant-abutment connection systems were used. The cement retained abutment and titanium screw of each system were assembled and tightened to 32Ncmwith digital torque gauge. After 10 minutes, initial detorque values were measured. The custom titanium crown were cemented temporarily and a cyclic sine curve load(20 to 320N, 14Hz) was applied. The detorque values were measured after cyclic loading of one million times by loading machine. One-way ANOVA test, scheffe's test and Mann-Whitney U test were used. RESULTS: The results were as follows : 1. The initial detorque values of six different implant-abutment connections were not significantly different(p> 0.05). 2. The detorque values after one million dynamic cyclic loading were significantly different (p <0.05). 3. The SS-II regular and wide implant both recorded the higher detorque values than other groups after cyclic loading(p <0.05). 4. Of the wide implants, the initial detorque values of Avana Self Tapping Implant, MIS and Tapered Screw Vent, and the detorque values of MIS implant after cyclic loading were higher than their regular counterparts(p <0.05). 5. After cyclic loading, SS-II regular and wide implants showed higher detorque values than before(p <0.05).

Application of finite element analysis to evaluate platform switching / 대한치과보철학회지

STATEMENT OF PROBLEM: Platform switching in implant prosthesis has been used for esthetic and biological PURPOSE: But there are few reports for this concept. PURPOSE: The purpose of this study is evaluation of platform switching in wide implant by three dimensional finite element analysis. MATERIALS AND METHODS: The single implant and prosthesis was modeled in accordance with the geometric designs for Osstem implant system. Three-dimensional finite element models were developed for (1) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with wide cemented abutment, titanium alloy abutment screw, and prosthesis (2) a wide diameter 3i type titanium implant 5 mm in diameter, 13 mm in length with regular cemented abutment, titanium alloy abutment screw and prosthesis(platform switching) was made for finite element analysis. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized to 650 N, and round and flat type prostheses were loaded to 200 N. Four loading offset point (0, 2, 4, 6 mm from the center of the implants) were evaluated. Models were processed by the software programs HyperMesh and ANSA. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView were used for post processing. RESULTS: The results from experiment were as follows; 1. von Mises stress value is increased in order of bone, abutment, implant and abutment screw. 2. von Mises stress of abutment screw is lower when platform switching. 3. von Mises stress of implant is lower when platform switching until loading offset 4 mm. 4. von Mises stress of abutment is similar between each other. 5. von Mises stress of bone is slightly higher when platform switching. CONCLUSION: The von Mises stress pattern of implant components is favor when platform switching but slightly higher in bone stress distribution than use of wide abutment. The research about stress distribution is essential for investigation of the cortical bone loss.

A study on the responses of osteoblasts to various surface-treated titanium / 대한치과보철학회지

STATEMENT OF PROBLEM: The long-term success of implants is the development of a stable direct connection between bone and implant surface, which must be structural and functional. To improve a direct implant fixation to the bone, various strategies have been developed focusing on the surface of materials. Among them, altering the surface properties can modify cellular responses such as cell adhesion, cell motility and bone deposition. PURPOSE: This study was to evaluate the cellular behaviors on the surface-modified titanium by morphological observation, cellular proliferation and differentiation. MATERIAL AND METHODS: Specimens were divided into five groups, depending on their surface treatment: electropolishing(EP) anodizing(AN), machining(MA), blasting with hydroxyapatite particle(RBM) and electrical discharge machining(EDM). Physicochemical properties and microstructures of the specimens were examined and the responses of osteoblast-like cells were investigated. The microtopography of specimens was observed by scanning electron microscopy(SEM). Surface roughness was measured by a three-dimensional roughness measuring system. The microstructure was analyzed by X-ray diffractometer(XRD) and scanning auger electron microscopy(AES). To evaluate cellular responses to modified titanium surfaces, osteoblasts isolated from neonatal rat were cultured. The cellular morphology and total protein amounts of osteoblast-like cell were taken as the marker for cellular proliferation, while the expression of alkaline phosphatase was used as the early differentiation marker for osteoblast. In addition, the type I collagen production was determined to be a reliable indicator of bone matrix synthesis. RESULTS: 1. Each prepared specimen showed specific microtopography at SEM examination. The RBM group had a rough and irregular pattern with reticulated appearance. The EDM-treated surface had evident cracks and was heterogeneous consisting of broad sheet or plate with smooth edges and clusters of small grains, deep pores or craters. 2. Surface roughness values were, from the lowest to the highest, electropolished group, anodized group, machined group, RBM group and EDM group. 3. All groups showed amorphous structures. Especially anodized group was found to have increased surface oxide thickness and EDM group had titaniumcarbide(TiC) structure. 4. Cells on electropolished, anodized and machined surfaces developed flattened cell shape and cells on RBM appeared spherical and EDM showed both. After 14 days, the cells cultured from all groups were formed to be confluent and exhibited multilayer proliferation, often overlapped or stratified. 5. Total protein amounts were formed to be quite similar among all the group at 48 hours. At 14 days, the electropolished group and the anodized group induced more total protein amount than the RBM group(P<.05). 6. There was no significant difference among five groups for alkaline phosphatase(ALP) activity at 48 hours. The AN group showed significantly higher ALP activity than any other groups at 14 days(P<.05). 7. All the groups showed similar collagen synthesis except the EDM group. The amount of collagen on the electropolished and anodized surfaces were higher than that on the EDM surface(P<.05).

The effect of abutment height on screw loosening in single implant-supported prostheses after dynamic cyclic loading / 대한치과보철학회지

STATEMENT OF PROBLEM: One of the common problems of dental implant prosthesis is the loosening of the screw that connects each component, and this problem is more common in single implant-supported prostheses with external connection. PURPOSE: The purpose of this study was to examine the changes of detorque values of abutment screws with external connection in different abutment heights. MATERIALS AND METHODS: After cyclic loading on three different abutment heights, detorque values were measured. Abutments were retained with titanium abutment screws tightened to 30 Ncm (30.5 kgmm) with digital torque gauge as recommended by the manufacturer. Replacing abutments, implants and titanium abutment screws with new ones at every measurement, initial detorque values were measured six times. In measuring detorque values after cyclic loading, Avana Cemented Abutments of 4.0 mm collar, 7.0 mm height (Osstem Co., Ltd., Seoul, Korea) were used with three different lengths of 5.0, 8.0, 11.0 mm. Shorter abutments were made by milling of 11.0 mm abutment to have the same force-exercised area of 4.5 mm diameter. Sine curve force (20N-320N, 14Hz) was applied, and detorque values were measured after cyclic loading of 2 million times by loading machine. Detorque values of initial and after-loading were measured by digital torque gauge. One-way ANOVA was employed to see if there was any influence from different abutment heights. RESULTS: The results were as follows : 1. The initial detorque value was 27.8+/-0.93 kgmm, and the ratio of the initial detorque value to the tightening torque was 0.91(27.8/30.5). 2. Measured detorque values after cyclic loading were declined as the height of the abutment increased, that was, 5.0 mm; 22.3+/-0.82 kgmm, 8.0 mm; 21.8+/-0.93 kgmm, and 11.0 mm; 21.3+/-0.94 kgmm. 3. One-way ANOVA showed no statistically significant differences among these (p> 0.05). 4. Noticeable mobility at the implant-abutment interface was not observed in any case after cyclic loading at all.

Bone response of three different surface implants: histomorphometric and resonance frequency analysis in dogs / 대한치과보철학회지

STATEMENT OF PROBLEM: Reducing treatment time in implant dentistry is a matter of main concern. There are so many factors affecting the success rate of immediate or early loaded implant for the initial bone response. The especially microscopic properties of implant surfaces play a major role in the osseous healing of dental implant. PURPOSE: The aims of this study were to perform a histologic and histomorphometric comparison of the healing characteristics anodically roughened surface, HA coated surface and RBM surface implant, and to compare of ISQ values measured by Osstell(TM) for resonance frequency analysis in dogs mandible during 2 weeks. MATERIAL AND METHOD: Bone blocks from 2 dogs were caught after covered healing for 0 day(2h); Group I, 1 week; Group II and 2 weeks; Group III. One longitudinal section was obtained for each implant and stained with hematoxylin and eosin. Histomorphometric analysis was done with Kappa Imagebase system to calculate bone-to-implant contact and bone volumes inside the threads. ISQ values were measured in every time of surgery schedule. CONCLUSION: The experiment revealed that : 1. The percentages of bone-to-implant contact on the fixture in each group were not significantly different(P > 0.05). 2. The percentages of bone area inside the threads on the fixture in each group were not significantly different(P > 0.05). 3. The ISQ level showed clinical stability of each fixture during 2 weeks(all ISQ level >_71).

The effect of growth factors in platelet-rich plasma on the activity of osteoblast cell line / 대한치과보철학회지

STATEMENT OF PROBLEM: Platelet-rich plasma(PRP) is well known to be very effective method to stimulate and accelerate the healing of bone and soft tissue. However, there are few reports which deal with the mechanisms of the PRP on the activation of the osteoblasts. PURPOSE: This study was aimed to investigate the effect of growth factors in PRP on the activity of osteoblasts. MATERIAL AND METHOD: To evaluate the effect on human, human osteoblast cell line was cultured. PRP was extracted from the blood of a healthy volunteer. Using the recombinant growth factors of PDGF, TGF-beta, IGF-1, bFGF which are mainly found at bone matrix and their neutralizing antibody, the effect of PRP on the attachment and proliferation of osteoblasts was evaluated. To evaluate the autocrine and paracrine effects, conditioned media(CM) of PRP was made and compared with PRP. By the western blot analysis, the expression of growth factors in PRP, CM was examined. Cell morphology was compared by the light microscope. RESULTS: 1) The effects of CM on osteoblast were similar to the effects of PRP. 2) PRP, CM, recombinant TGF-beta, bFGF, IGF-1 showed significantly higher cellular attachment than control(P<0.05) in the cell attachment assay. In the cell proliferation assay, PRP, CM, recombinant TGF-beta, IGF-1, bFGF, PDGF increased significantly cell proliferation(P<0.01). Among the recombinant growth factors, IGF-1 showed the highest cellular attachment and proliferation. 3) In the western blot assay, bFGF, IGF-1, PDGF were equally expressed in PRP and CM. 4) The attachment of osteoblast cell decreased significantly after the addition of neutralizing antibody against TGF-beta, IGF-1(P<0.05). In the cell proliferation assay, the addition of neutralizing antibody against TGF-beta, bFGF, PDGF, IGF-1 decreased significantly the cellular proliferation(P<0.05). The amount of decreasing in the cell attachment and proliferation is the highest in ab-IGF-1. 5) The cells in control group were flattened and elongated with a few cellular processes in the a light microscope. But, the cells appeared as spherical, plump cells with well developed cellular processes in experimental groups. The cells in PRP and CM had more prominent developed features than recombinant growth factor groups. CONCLUSIONS: These findings imply that PRP maximize the cellular activity in early healing period using the synergistic effect, autocrine, paracrine effects of growth factors and increase the rate and degree of bone formation.

Effect of the surface modifications and the use of washer on the reverse torque of the implant prosthetic gold retaining screw / 대한치과보철학회지

The screw loosening is one of the complications that happen frequently in dental implant prostheses. The purpose of this study was to evaluate the changes of reverse/loosening (opening) torque of the screw according to the surface modifications by sandblasting and 24K gold electroplating as well as to determine the possibility of the clinical use of a washer in dental implant. The reverse torque of 4 experimental conditions(control, sandblasted, use of washers, electroplasted) was measured by digital torque gauge (Model MGT50Z, Mark-10 Corp., 458 West John Street Hicksville, NY 11801 USA). Electronic torque controller (Nobel Biocare DEA 020) was used in fastening the gold screws into abutment replicas. Mixed Linear Model Analysis method was used for statistical analysis. To examine the changes of screw thread surface, microphotographs were taken by Olympus PME-3 metallurgic microscope (Olympus Optical Co. Ltd., Tokyo, Japan). Within the limitations of this study, the following results were drawn: 1. The surface modifications of the gold screws and the use of a washer have significantly affected the reverse torque value compared to the control group (p<0.01). 2. Sandblasting and electroplating treatments demonstrated significantly higher reverse torque val-ue than that of control group. 3. The use of a washer may be one of the useful clinical methods that prevent the screw loosening. However, further studies are necessary for the material selection and design of the washer.

A Study On The Temperature Changes Of Bone Tissues During Implant Site Preparation / 대한치과보철학회지

The purpose of this study is to examine the possibility of thermal injury to bone tissues during an implant site preparation under the same condition as a typical clinical practice of Branemark implant system.All the burs for Branemark implant system were studied except the round bur.The experiments involved 880 drilling cases:50 cases for each of the 5 steps of NP, 5 steps of RP,and 7 steps of WP,all including srew tap,and 30 cases of 2mm twist drill. For precision drilling,a precision handpiece restraining system was developed(Eungyong Machinery Co.,Korea).The system kept the drill parallel to the drilling path and allowed horizontal adjustment of the drill with as little as 1 mu m increment.The thermocouple insertion hole.that is 0.9mm in diameter and 8mm in depth,was prepared 0.2mm away from the tapping bur,the last drilling step.The temperatures due to countersink,pilot drill,and other drills were measured at the surface of the bone,at the depths of 4mm and 8mm respectively. Countersink drilling temperature was measured by attaching the tip of a thermocouple at the rim of the countersink.To assure temperature measurement at the desired depths,''bent-thermocouples'' with their tips of 4 and 8mm bent at 120 were used.The profiles of temperature variation were recorded continuously at one second interval using a thermometer with memory function (Fluke Co.,U.S.A.)and 0.7mm thermocouples (Omega Co.,U.S.A.). To simulate typical clinical conditions,35mm square samples of bovine scapular bone were utilized.The samples were approximately 20mm thick with the cortical thickness on the drilling side ranging from 1 to 2mm.A sample was placed in a container of saline solution so that its lower half is submerged into the solution and the upper half exposed to the room air,which averaged 24.9 degrees C.The temperature of the saline solution was maintained at 36.5 degrees C using an electric heater (J.O Tech Co.,Korea).This experimental condition was similar to that ofa patient's opened mouth. The study revealed that a 2mm twist drill required greatest attention.As a guide drill, a twist drill is required to bore through a '' virgin bone,''rather than merely enlarging an already drilled hole as is the case with other drills.This typically generates greater amount of heat.Furthermore,one tends to apply a greater pressure to overcome drilling difficulty, thus producing even greater amount heat. 150 experiments were conducted for 2mm twist drill.For 140 cases,drill pressure of 750g was sufficient,and 10 cases required additional 500 or 100g of drilling pressure.In case of the former,3 of the 140 cases produced the temperature greater than 47 degrees C,the threshold temperature of degeneration of bone tissue (1983.Eriksson et al.5))which is also the reference temperature in this study.In each of the 10 cases requiring extra pressure,the temperature exceeded the reference temperature.More significantly,a surge of heat was observed in each of these cases.This observations led to addtional 20 drilling experiments on dense bones.For 10 of these cases,the pressure of 1,250g was applied.For the other 10,1,750g were applied.In each of these cases,it was also observed that the temperature rose abruptly far above the thresh-old temperature of 47 degrees C,sometimes even to 70 or 80 degrees C.It was also observed that the increased drilling pressure influenced the shortening of drilling time more than the rise of drilling temperature.This suggests the desirability of clinically reconsidering application of extra pressures to prevent possible injury to bone tissues. An analysis of these two extra pressure groups of 1,250g and 1,750g revealed that the t-statistics for reduced amount of drilling time due to extra pressure and increased peak temperature due to the same were 10.80 and 2.08 respectively suggesting that drilling time was more influenced than temperature. All the subsequent drillings after the drilling with a 2mm twist drill did not produce excessive heat, i.e.the heat generation is at the same or below the body temperature level. Some of screw tap,pilot,and countersink showed negative correlation coefficients between the generated heat and the drilling time,indicating the more the drilling time,the lower the temperature. The study also revealed that the drilling time was increased as a function of frequency of the use of the drill.Under the drilling pressure of 750g, it was revealed that the drilling time for an old twist drill that has already drilled 40 times was 4.5 times longer than a new drill. The measurement was taken for the first 10 drilings of a new drill and 10 drillings of an old drill that has already been used for 40 drillings. ''Test Statistics''of small samples t-test was 3.49,confirming that the used twist drills require longer drilling time than new ones.On the other hand,it was revealed that there was no significant difference in drilling temperature between the new drill and the old twist drill. Finally,the following conclusions were reached from this study: 1.Used drilling bur causes almost no change in drilling temperature but increase in drilling time through 50 drillings under the manufacturer-recommended cooling conditions and the drilling pressure of 750g. 2.The heat that is generated through drilling mattered only in the case of 2mm twist drills,the first drill to be used in bone drilling process;for all the other drills there is no significant problem. 3.If the drilling pressure is increased when a 2mm twist drill reaches a dense bone, the temperature rises abruptly even under the manufacturer-recommended cooling conditions. 4.Drilling heat was the highest at the final moment of the drilling process.

THREE DIMENSIONAL FINITE ELEMENT ANALYSIS OF BRANEMARK NOVUM(R)IMMEDIATE IMPLANT PROSTHODONTIC PROTOCOL / 대한치과보철학회지

Since the treatment of edentulous patients with osseointegrated implant was first introduced more than 30 years ago, implant therapy has become one of the most important dental treatment modalities today. Based on the previous experience and knowledge. Branemark Novum(R) protocol was introduced with the concept of simplifying surgical and prosthetic technique and reducing healing time recently. This protocol recommends the installation of three 5mm wide diameter fixtures in anterior mandible and the prefabricated titanium bars for superstructure fabrication. This study was designed to analyze the stress distribution at fixture and superstructure area according to changes of fixture number, diameter and superstructure materials. Four 3-dimensional finite element models were fabricated. Model 1 - 5 standard fixtures (13mm long and 3.75mm in diameter) & superstructure consisted of type IV gold alloy and resin Model 2 - 3 wide diameter fixtures (13mm long and 5.0mm in diameter) )& superstructure consisted of type IV gold alloy and resin Model 3 - 3 wide diameter fixtures (13mm long and 5.0mm in diameter) )& superstructure consisted of titanium and resin Model 4 - 3 wide diameter fixtures (13mm long and 5.0mm in diameter)& superstructure consisted of titanium and porcelain A 150N occlusal force was applied on the 1st molar of each model in 3 directions-vertical(90degree)horizontal(0degree)and oblique (120degree). After analyzing the stress and displacements, following results were obtained. 1. There were no significant difference in stress distribution among experimental models. 2. Model 2,3,4 showed less amount of compressive stress than that of model 1. However, tensile stress was similar. 3. Veneer material with a high modulus of elasticity demonstrated less stress accumulation in the superstructure. Within the limits of this study.Branemark Novum(R) protocol demonstrated comparable biomechanical properties to conventional protocol.

INHIBITORY EFFECT OF ANTIFUNGAL AGENTS INCORPORATED IN DENTURE LINING MATERIALS AGAINST CANDIDA ALBICANS / 대한치과보철학회지

The purpose of this study was to evaluate the in vitro antifungal effect of several kinds of denture lining materials containing nystatin and silver-zeolite on Candida albicans. Three commercially available tissue conditioners (Soft-Liner, Coe-Comfort, Coe-Soft) and two direct denture relining materials (Tokuso Rebase, Durabase) were selected. In terms of the zone of inhibition and some basic physical properties, I could find the following results ; 1. Nystatin or silver-zeolite included in those relining materials had definite antifungal activities against the Candida albicans. 2. As times went on, both of the antifungal agents's activities decreased gradually. 3. Antifungal agents did not affect the relining materials' basic physical properties. 4. Direct chairside relining materials showed unfavorable dark discoloration with response to sil-ver-zeolite.