Three-dimensional accuracy of different correction methods for cast implant bars

PURPOSE: The aim of the present study was to evaluate the accuracy of three techniques for correction of cast implant bars. MATERIALS AND METHODS: Thirty cast implant bars were fabricated on a metal master model. All cast implant bars were sectioned at 5 mm from the left gold cylinder using a disk of 0.3 mm thickness, and then each group of ten specimens was corrected by gas-air torch soldering, laser welding, and additional casting technique. Three dimensional evaluation including horizontal, vertical, and twisting measurements was based on measurement and comparison of (1) gap distances of the right abutment replica-gold cylinder interface at buccal, distal, lingual side, (2) changes of bar length, and (3) axis angle changes of the right gold cylinders at the step of the post-correction measurements on the three groups with a contact and non-contact coordinate measuring machine. One-way analysis of variance (ANOVA) and paired t-test were performed at the significance level of 5%. RESULTS: Gap distances of the cast implant bars after correction procedure showed no statistically significant difference among groups. Changes in bar length between pre-casting and post-correction measurement were statistically significance among groups. Axis angle changes of the right gold cylinders were not statistically significance among groups. CONCLUSION: There was no statistical significance among three techniques in horizontal, vertical and axial errors. But, gas-air torch soldering technique showed the most consistent and accurate trend in the correction of implant bar error. However, Laser welding technique, showed a large mean and standard deviation in vertical and twisting measurement and might be technique-sensitive method.

A comparative study on the initial stability of different implants placed above the bone level using resonance frequency analysis

PURPOSE: This study evaluated the initial stability of different implants placed above the bone level in different types of bone. MATERIALS AND METHODS: As described by Lekholm and Zarb, cortical layers of bovine bone specimens were trimmed to a thickness of 2 mm, 1 mm or totally removed to reproduce bone types II, III, and IV respectively. Three Implant system (Branemark System(R) Mk III TiUnite(TM), Straumann Standard Implant SLA(R), and Astra Tech Microthread(TM)-OsseoSpeed(TM)) were tested. Control group implants were placed in level with the bone, while test group implants were placed 1, 2, 3, and 4 mm above the bone level. Initial stability was evaluated by resonance frequency analysis. Data was statistically analyzed by one-way analysis of variance in confidence level of 95%. The effective implant length and the Implant Stability Quotient (ISQ) were compared using simple linear regression analysis. RESULTS: In the control group, there was a significant difference in the ISQ values of the 3 implants in bone types III and IV (P<.05). The ISQ values of each implant decreased with increased effective implant length in all types of bone. In type II bone, the decrease in ISQ value per 1-mm increase in effective implant length of the Branemark and Astra implants was less than that of the Straumann implant. In bone types III and IV, this value in the Astra implant was less than that in the other 2 implants. CONCLUSION: The initial stability was much affected by the implant design in bone types III, IV and the implant design such as the short pitch interval was beneficial to the initial stability of implants placed above the bone level.

Accuracy of a proposed implant impression technique using abutments and metal framework

PURPOSE: This study compared the accuracy of an abutment-framework (A-F) taken with open tray impression technique combining cementon crown abutments, a metal framework and resin cement to closed tray and resin-splinted open tray impression techniques for the 3-implant definitive casts. The effect of angulation on the accuracy of these 3 techniques was also evaluated. MATERIAL AND METHODS: Three definitive casts, each with 3 linearly positioned implant analogs at relative angulations 0, 30, and 40 degrees, were fabricated with passively fitted corresponding reference frameworks. Ten impressions were made and poured, using each of the 3 techniques on each of the 3 definitive casts. To record the vertical gap between reference frameworks and analogs in duplicate casts, a light microscope with image processing was used. Data were analyzed by two-way analysis of variance and the Tukey test. RESULTS: The open tray techniques showed significantly smaller vertical gaps compare to closed tray technique (P .05). CONCLUSION: The accuracy of the A-F impression technique was superior to that of conventional techniques, and was not affected by the angulation of the implants.

Effect of casting procedure on screw loosening of UCLA abutment in two implant-abutment connection systems / 대한치과보철학회지

STATEMENT OF PROBLEM: The cast abutment has advantages of overcoming angulation problem and esthetic problem. However, when a gold-machined UCLA abutment undergoes casting, the abutment surfaces in contact with the implant may change. PURPOSE: The purpose of this study was to compare the detorque values of prefabricated machined abutments with gold-premachined cast-on UCLA abutments before and after casting in two types of internal implant-abutment connection systems: (1) internal hexagonal joint, (2) internal octagonal joint. Furthermore, the detorque values of two implant-abutment connection systems were compared. MATERIALS AND METHODS: Twenty internal hexagonal implants with an 11-degree taper and twenty internal octagonal implants with an 8-degree taper were acquired. Ten prefabricated titanium abutments and ten gold-premachined UCLA abutments were used for each systems. Each abutment was torqued to 30 Ncm according to the manufacturer's instructions and detorque value was recorded. The detorque values were measured once more, after casting with gold alloy for UCLA abutment, and preparation for titanium abutments. Group means were calculated and compared using independent t-test and paired t-test (alpha=0.05). RESULTS: The results were as follows: 1. The detorque values between titanium abutments and UCLA-type abutments showed significant differences in internal octagonal implants (P0.05). 2. In comparison of internal hexagonal and octagonal implants, the detorque values of titanium abutments had significant differences between two connection systems on the initial analysis (P0.05) and the detorque values of UCLA-type abutments were not significantly different between two connection systems (P>0.05). 3. The detorque values of titanium abutments and UCLA-type abutments decreased significantly on the second analysis than the initial analysis in internal hexagonal implants (P0.05). CONCLUSION: Casting procedures of UCLA-type abutments had no significant effect on screw loosening in internal implant-abutment connection systems, and UCLA-type abutments showed higher detorque values than titanium abutments in internal octagonal implants.

Finite element stress analysis of maxillary two implants-retained overdenture according go position of implant fixtures / 대한치과보철학회지

STATEMENT OF PROBLEM: There have been a few studies about unsplinted implant retainted maxillary overdenture. PURPOSE: The purpose of this study was to examine the effect of different position of implant for 2 implants-retained maxillary overdenture. MATERIALS AND METHODS: Three-dimensional finite element models were used to reproduce an edentulous human maxilla with an implant-retained overdenture. Two implants in the canine tooth positions on both side and in the second premolar tooth positions on both side models were examined. Axial loads of 100 N were applied to the occlusal surface at the right first molar tooth positions. Maximum stress at the implant-bone interface and stress at the cortical bone surface just under the loading point were observed. RESULTS AND CONCLUSION: Within the limits of this study, maximum stresses were concentrated around implant of canine position at loading side. The second premolar area was thought to be more favorable to distribution of stress on mucosa, alveolar bone and implants than canine area for maxillary overdenture.

Comparative accuracy of new implant impression technique using abutments as impression copings with an angulated implant model / 대한치과보철학회지

STATEMENT OF PROBLEM: A new implant impression technique which use abutments as impression coping, and use resin cement as a splinting material was described. Accuracy of this technique was compared with conventional closed tray and resin splinted open tray technique for a 15degrees angled 3-implant model MATERIAL AND METHODS: A dental stone master model with 3 linearly positioned implant analogue and a reference framework which was passively fitted to it were fabricated. The center analogue was perpendicular to the plane of model and the outer analogues had a 15degrees angulation forward or backward. 10 closed tray impressions, 10 resin splinted open tray impressions, 10 abutment-resin framework cementation impressions and 10 abutment-metal framework cementation impressions were made with additional silicone material and poured with dental stone. A light microscope with image processing was used to record the vertical gap dimension between reference framework and analogue of duplicated cast made with each 4 impression techniques. Statistical analysis used one-way ANOVA with post-hoc tests Tukey test of .05 level of significance RESULTS: Significant difference in the vertical gap dimension was found between closed tray technique; 74.3 (+/-33.4)micrometer and resin splinted open tray technique, and two other new technique. (P>.05) Abutment-metal framework cementation technique;42.5 (+/-11.9)micrometer was significantly different from resin splinted open tray technique. (P.05) CONCLUSION: Within limitations of this study, the accuracy of implant level impressions of resin splinted open tray technique was superior to that of closed tray technique. A new technique using abutment and metal framework cementation was more accurate than resin splinted open tray technique.

Surface analyses of titanium substrate modified by anodization and nanoscale Ca-P deposition / 대한치과보철학회지

STATEMENT OF PROBLEM: Nano-scale calcium-phosphate coating on the anodizing titanium surface using ion beam-assisted deposition (IBAD) has been recently introduced to improve the early osseointegration. However, not much is known about their surface characteristics that have influence on tissue-implant interaction. PURPOSE. This study was aimed to investigate microtopography, surface roughness, surface composition, and wettability of the titanium surface modified by the anodic oxidation and calcium phosphate coating using IBAD. MATERIAL AND METHODS: Commercially pure titanium disks were used as substrates. The experiment was composed of four groups. Group MA surfaces represented machined surface. Group AN was anodized surface. Group CaP/AN was anodic oxidized and calcium phosphate coated surfaces. Group SLA surfaces were sandblasted and acid etched surfaces. The prepared titanium discs were examined as follows. The surface morphology of the discs was examined using SEM. The surface roughness was measured by a confocal laser scanning microscope. Phase components were analyzed using thin-film x-ray diffraction. Wettability analyses were performed by contact angle measurement with distilled water, formamide, bromonaphtalene and surface free energy calculation. RESULTS: (1) The four groups showed specific microtopography respectively. Anodized and calcium phosphate coated specimens showed multiple micropores and tiny homogeneously distributed crystalline particles (2) The order of surface roughness values were, from the lowest to the highest, machined group, anodized group, anodized and calcium phosphate deposited group, and sandblasted and acid etched group. (3) Anodized and calcium phosphate deposited group was found to have titanium and titanium anatase oxides and exhibited calcium phosphorous crystalline structures. (4) Surface wettability was increased in the order of calcium phosphate deposited group, machined group, anodized group, sandblasted and acid etched group. CONCLUSION: After ion beam-assisted deposition on anodized titanium, the microporous structure remained on the surface and many small calcium phosphorous crystals were formed on the porous surface. Nanoscale calcium phosphorous deposition induced roughness on the microporous surface but hydrophobicity was increased.

The effect of gold electroforming procedure on gold-silver-palladium alloy / 대한치과보철학회지

STATEMENT OF PROBLEM: The effect of gold electroforming on gold alloy was not studied. PURPOSE: This in vitro study investigate the effect of gold electroforming on gold-silver-palladium alloy. MATERIAL AND METHODS: Three pieces of gold strips had undergone the electroforming procedures on one side and then half of the side again electroformed. The set mode for this study was program 1 (200 micrometer). And the processing time was 15min (1/20 time to form 200 micrometer coping). The confocal laser scanning microscope (PASCAL 5, Carl Zeiss, Bernried, Germany) was used to measure the thickness of the pure gold layer electroformed on the gold strips. Half of the gold strip was coated two times with electroformed gold, and the other half one time. The data from the cone focal laser system was processed to get the vertical profile of the strips and the difference of the vertical height between the double coated and single coated layer was regarded as the thickness of the gold coating. The layer thickness value to built 3D image of the cone-focal laser was set 0.5 micrometer. Next to the measurement of the thickness of the coating, the Vicker's hardness test was done. It was performed on the double coated surface, single coated surface and non-coated surface (back side) three times each. RESULTS: The mean thickness value gained from gold electroforming technique was measured to be 22 micrometer for sample 1, 23 micrometer for sample 2, 21 micrometer for sample 3. In the same condition of time, power and the amount of electrolyte, the data showed no difference between samples. According to the results of variance analysis, the differences among the variations in number of coating were statistically insignificant (p>0.05), meaning that the two times of gold electroforming coating did not change the hardness of gold-silver-palladium alloy. CONCLUSION: The test of thickness of gold coating proved the coherency of the gold electroforming procedure, in other words, when the power, the exposed surface area, processing time and the amount of electrolytes were set same, the same thickness of gold would be coated on. The hardness test showed that the electroformed gold coating did not change the hardness of the gold-silver-palladium alloy when it is coated not more than 45 micrometer.

Strength of glass fiber reinforced PMMA resin and surface roughness change after abrasion test / 대한치과보철학회지

STATEMENT OF PROBLEMS: The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured acrylic resin using glass fibers, have been suggested over the years. But problems such as poor workability, rough surface, poor adhesion of glass fiber resin complex are not solved yet. PURPOSE: The aim of the present study was to investigate the effect of short glass fibers on the transverse strength of heat-polymerized denture base acrylic resin and roughness of resin complex after abrasion test. MATERIAL AND METHODS: To avoid fiber bunching and achieve even fiber distribution, glass fiber bundles were mixed with acrylic resin powder in conventional mixer with a non-cutting blade, to produce the glass fiber(10 micrometer diameter, 3 mm length, silane treated) resin composite. Glass fibers were incorporated at 0%, 3%, 6% and 9% by weight. Transverse strength were measured. After abrasion test, surface roughness was evaluated and scanning electron microscope view was taken for clinical application. RESULTS: 1. 6% and 9% incorporation of 3mm glass fibers in the acrylic resin enhanced the transverse strength of the test specimens(p0.05). 3. After abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically(p>0.05). 4. In SEM, surface roughness increased as the percentage of the fibers increased. 5. In the areas where glass fiber bunchings are formated, a remarkably high roughness was noticed. CONCLUSION: 6% and 9% addition of silane-treated short glass fibers into denture base acrylic resin increased transverse strength significantly. Before and after abrasion test, incorporation of 0%, 3%, 6% glass fiber in the resin showed same surface roughness value statistically.

The dimensional change of cast implant bars after laboratory procedure / 대한치과보철학회지

STATEMENT OF PROBLEMS: The precision of fit between the bearing surfaces of implant abutments and the prosthesis framework has been considered fundamental to implant prosthodontic protocol. PURPOSE: The study aimed to investigate the effect of laboratory procedure on the dimensional accuracy of cast implant bars. MATERIAL AND METHODS: Thirty implant bars were fabricated on a metal master model. The gap distances were measured at the right implant abutment replica-gold cylinder interface after casting procedure. The bar length data of precasting and postcasting state were collected and analyzed. RESULTS: The mean gap distance found after casting was 106.3 micrometer for buccal side, 122.1 micrometer for distal side and 117.1 micrometer for the lingual side. The mean bar length was 17964.7 micrometer at precasting measurement, 17891.6 micrometer at postcasting measurement. The mean change of bar length was - 73.1 micrometer. CONCLUSION: Even though the techniques used in this study strictly followed the guidelines established in the literature, the 30 cast implant bars evaluated all yielded gap distances that were beyond acceptable accuracy. There was a statistically significant difference between precasting and postcasting bar length (P<0.01). There was a decreasing tendency in bar length after casting procedure. It was necessary to correct this dimensional change from laboratory procedure by some corrective methods.

Effects of various silane coupling agents on the strength and the surface roughness of glass fiber-added PMMA resin / 대한치과보철학회지

STATEMENTS OF PROBLEM: The fracture of acrylic resin dentures remains an unsolved problem. Therefore, many investigations have been performed and various approaches to strengthening acrylic resin, for example, the reinforcement of heat-cured acrylic resin using glass fibers, have been suggested over the years. Silane is important for bonding between glass fiber and resin. PURPOSE: The aim of the present study was to investigate the effect of various silane on the strength of PMMA resin and roughness of resin-glass fiber complex after abrasion test. MATERIAL AND METHODS: 3mm glass fiber (Chopped strand, Hankuk fiber Co., Milyang, Korea) was treated with 3 kinds of silane (MPS, EPS, APS) (Sila-ace, Chisso chemical, Tokyo, Japan) and mixed with PMMA resin(Vertex RS, Vertex Dental B.V., Zeist, Netherlands). Transverse strength and Young's modulus was measured using Instron (Instron model 4466, Instron, Massachusetts, USA). After abrasion test (The 858 Mini Bionix II Test System, MTS System Co., Minnesota, USA) surface roughness was evaluated using tester (Form Talysurf plus, Taylor Hopson Ltd., Leicester, England). Examination of scanning electron microscope was also performed RESULTS: Within this study, the following conclusions were drawn. 1. Surface treatment of glass fiber with MPS and APS increased transverse strength of PMMA resin complex, but surface treatment with EPS decreased transverse strength of PMMA resin complex (p0.05).

The effect of autoclave sterilization and reuse of Smartpeg(TM) on the implant stability quotient (ISQ) measurement / 대한치과보철학회지

STATEMENT OF PROBLEM: Resonance frequency analysis is evaluated as the non-invasive and objective method for the evaluation of implant stability and has been increasingly used. It is necessary to evaluate the factors affect the ISQ measurement stability. PURPOSE: This study was performed to evaluate the effect of the autoclave sterilization and reuse of Smartpeg(TM) on ISQ measurement. MATERIAL AND METHODs: SmartPeg(TM) (Integration Diagnostics Ltd., Goteborg, Sweden) of autoclave group (A) was autoclave sterilized 9 times and Smartpeg(TM) of reuse group (R) was reused 9 times. Ten SmartPeg(TM)s were allocated to each group and after each autoclave sterilization and reuse, implant stability quotient (ISQ) values were measured 3 times from the two directions a and b at a right angle. Osstell(TM) mentor (Integration Diagnostics Ltd., Goteborg, Sweden) was used and type 1 (article no. 100353) Smartpeg(TM) was selected according to SmartpegTM reference list. Osstem Implant US II fixture (Osstem Co., Seoul, Korea) in 4.0 mm x 11.5 mm was embedded in the self-curing acrylic resin (Orthojet(R), Lang Dental, U.S.A.). Data was statistically analyzed by one-way ANOVA (alpha= .05) and scheffe test was done where a significant difference exist. Correlation test was also done between ISQ value and the number of autoclave sterilization or reuse. RESULTS: 1. In autoclave group, the means and sd. of ISQ value before autoclave sterilization were 84.97 +/-0.41, 84.93+/-0.74 at direction a and b. There was significant differences between autoclave groups at direction a and b (P=.000). 2. In reuse group, the means and sd. of ISQ value before reuse were 85.40+/-0.62, 85.50+/-0.57 at direction a and b. There was no significant difference between reuse groups at direction a and b (P>.05). 3. There was a weak positive correlation between the number of reuse and ISQ value at direction a and b (gamma=.207 and .246, P<.01). CONCLUSION: Within the limitations of this study, the following CONCLUSIONs were drawn. Till ninth reuse of Smartpeg(TM), the ISQ measurement stability did not be affected. After twice autoclave sterilization of Smartpeg(TM), the ISQ measurement stability was affected.

The effect of screw tightening sequence and tightening method on the detorque value in implant-supported superstructure / 대한치과보철학회지

STATEMENT OF PROBLEM: The screw detorque value is a measure of the preload remaining in the screw just before detorquing. PURPOSE: This study evaluated the effect of different screw tightening sequences and tightening methods on detorque values for a well-fitting implant superstructure. MATERIAL AND METHOD: An implant superstructure that connected directly to four implants (Astra Tech) was fabricated on a fully edentulous mandibular acrylic resin model. Six wellfitting dental stone casts were made with a pickup impression of the superstructure from the acrylic resin model. To evaluate the effect of three screw tightening sequences (1-2-3-4, 2-4-3-1, and 2-3-1-4) and two tightening methods (2-step and 1-step) on the stability of screw joint, the detorque values for a well-fitting implant superstructure were measured twice after screw tightening using 20 Ncm. Detorque values were analyzed using multi-way analysis of variance and two-way analysis of variance at a .05 level of significance. RESULTS: 1. The mean detorque values for three screw tightening sequences were 12.3 Ncm, 12.6 Ncm, and 12.0 Ncm, respectively. 2. The mean detorque values for two screw tightening methods were 12.0 Ncm, and 12.2 Ncm, respectively. 3. The mean of mimimum detorque values for three screw tightening sequences and for two tightening methods were 10.6 Ncm, 11.1 Ncm, 10.5 Ncm, and 9.8 Ncm, respectively. 4. No statistically significant differences among the variables of screw tightening sequence and tightening method were found (p>.05) for detorque values and for mimimum detorque values. CONCLUSION: Within the limitations of this study, the screw tightening sequence and tightening method did not have a significant effect on the detorque values for a well-fitting implant superstructure.

A comparative study on the dimensional change of the different denture bases / 대한치과보철학회지

STATEMENT OF PROBLEM: Acrylic resin is most commonly used for denture bases. However, acrylic resin has week points of volumetric shrinkage during polymerization that reduces denture fit. The expandability of POSS (Polyhedral Oligomeric Silsesquioxane) containing polymer could be expected to reduce the polymerization shrinkage of denture bases and would increase the adaptability of the denture to the tissue. PURPOSE: The purpose of this study was to compare the dimensional stability in the conventional acrylic resin base, POSS-containing acrylic resin base, and metal bases. MATERIALS AND METHODS: Thirty six maxillary edentulous casts and dentures of different base were fabricated. Tooth movement and tissue contour change of denture after processing (resin curing, deflasking, decasting and finishing without polishing) and immersion in artificial saliva at 37 degrees C for 1 week and 4 weeks were measured using digital measuring microscope and threedimensional laser scanner. RESULTS: The results were as follows: 1. The conventional resin group showed significant (p<0.01) dimensional change throughout the procedure (processing and immersion in artificial saliva). 2. After processing, the metal group and POSS resin group showed lower linear and 3-dimensional change than conventional resin group (p<0.01). 3. There was no statistically significant linear and 3-dimensional change after immersion for 1 week and 4 weeks in metal and POSS resin group. 4. In all groups, the midline and alveolar ridge crest area presented smaller 3-dimensional change compared with vestibule and posterior palatal seal area after processing and soaking in artificial saliva for 1 week and 4 weeks (p<0.01). CONCLUSION: In this study, a reinforced acrylic-based resin with POSS showed good dimensional stability.

Application of finite element analysis to evaluate implant fractures / 대한치과보철학회지

Statement of problem. Higher fracture rates were reported for Branemark implants placed in the maxilla and for 3.75 mm diameter implants installed in the posterior region. Purpose. The purpose of this study was to investigate the fracture of a fixture by finite element analysis and to compare different diameter of fixtures according to the level of alveolar bone resorption. Material and Methods. The single implant and prosthesis was modeled in accordance with the geometric designs for the 3i implant systems. Models were processed by the software programs HyperMesh and ANSA. Three-dimensional finite element models were developed for; (1) a regular titanium implant 3.75 mm in diameter and 13 mm in length (2) a regular titanium implant 4.0 mm in diameter and 13 mm in length (3) a wide titanium implant 5.0 mm in diameter and 13 mm in length each with a cementation type abutment and titanium alloy screw. The abutment screws were subjected to a tightening torque of 30 Ncm. The amount of preload was hypothesized as 650 N, and round and flat type prostheses were 12 mm in diameter, 9 mm in height were loaded to 600 N. Four loading offset points (0, 2, 4, and 6 mm from the center of the implants) were evaluated. To evaluate fixture fracture by alveolar bone resorption, we investigated the stress distribution of the fixtures according to different alveolar bone loss levels (0, 1.5, 3.5, and 5.0 mm of alveolar bone loss). Using these 12 models (four degrees of bone loss and three implant diameters), the effects of loading offset, the effect of alveolar bone resorption and the size of fixtures were evaluated. The PAM-CRASH 2G simulation software was used for analysis of stress. The PAM-VIEW and HyperView programs were used for post processing. Results. The results from our experiment are as follows: 1. Preload maintains implant-abutment joint stability within a limited offset point against occlusal force. 2. Von Mises stress of the implant, abutment screw, abutment, and bone was decreased with increasing of the implant diameter. 3. With severe advancing of alveolar bone resorption, fracture of the 3.75 and the 4.0 mm diameter implant was possible. 4. With increasing of bending stress by loading offset, fracture of the abutment screw was possible.

Surface characteristics of anodic oxidized titanium according to the pore size / 대한치과보철학회지

Statement of problem. The success of osseointegration can be enhanced with an implant that has improved surface characteristics. Anodic oxidation is one of the surface modifying method to achieve osseointegration. Voltage of anodic oxidation can change surface characteristics and cell activity. Purpose. This study was performed to evaluate MG63 cell responses such as affinity, proliferation and to compare surface characteristics of anodic oxidized titanium in various voltage. Material and method. The disks for cell culture were fabricated from grade 3 commercially pure titanium, 1 mm in thickness and 12 mm in diameter. Surfaces of 4 different roughness were prepared. Group 1 had a machined surface, used as control. Group 2 was anodized under 220 V, group 3 was anodized under 300 V and group 4 was anodized under 320 V. The microtopography of specimens was observed by scanning electron microscope (JSM-840A, JEOL, Japan) and atomic force microscope(Autoprobe CP, Park Scientific Instrument, USA). The surface roughness was measured by confocal laser scanning microscope(Pascal, LSM5, Zeiss, Germany). The crystal structure of the titanium surface was analyzed with x-ray diffractometer(D8 advanced, Bruker, Germany). MG63 osteoblast-like cells were cultured on these specimens. The cell morpholgy was observed by field emission electron microscope(Hitachi S-4700, Japan). The cell metabolic and proliferative activity was evaluated by MTT assay. Results and conclusion. With in limitations of this in vitro study, the following conclusions were drawn. 1. In anodizing titanium surface, we could see pores which did not show in contol group. In higher anodizing voltage, pore size was increased. 2. In anodizing titanium surface, we could see anatase. In higher anodizing voltage, thicker oxide layer increased crystallinity(anatase, anatase and rutile mixed). 3. MG63 cells showed more irregular, polarized and polygonal shape and developed more lamellipodi in anodizing group as voltage increased. 4. The activity of cells in MTT assay increased significantly in group 3 and 4 in comparison with group 1 and 2. However, there was no difference between group 3 and 4 at P<0.05. Proliferation of MG63 cells increased significantly in pore size(3-5.5 micrometer) of group 3 and 4 in comparison with in pore size(0.2-1 micrometer) of group 2.

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).