A study on the effective cleaning of healing abutment using healing abutment case / 대한치과보철학회지

Purpose@#The present study aimed to investigate the effective cleaning of healing abutment (HA) using Healing abutment case (HA case) by observing oral microorganisms with phase contrast microscope. @*Materials and methods@#32 patients with two or more implants placed in the same jaw, a total of 64 HAs (experimental group 32, control group 32) were selected and the control was cleaned with an alcohol swab. At the first and second visits, each group was observed before cleaning, and the experimental group was additionally observed after cleaning at the first visit. A 400× phase contrast microscope was used for the observation of oral microorganisms for its amounts. @*Results@#There was no significant difference in the amount of oral microorganisms was found between the groups at the first visit, no significant difference according to gender, maxilla or mandible, and buccal or lingual surface. There was a statistically significant difference in the amount of oral microorganisms according to supra-gingival and sub-gingival (P<.05), There was also a significant difference in the comparison before and after cleaning in the experimental group (P<.05). There was a significant difference in the amount of oral microorganisms in each group at second visit (P<.05). @*Conclusion@#Healing abutment cleaning using healing abutment case solution is more effective than simple cleaning with alcohol swab.

Ginseng berry extract increases nitric oxide level in vascular endothelial cells and improves cGMP expression and blood circulation in muscle cells.

PURPOSE: The purpose of this study was to determine whether ginseng berry extract improves blood circulation by regulating vasodilator expression in exposed to tumor necrosis factor alpha (TNF-α)-exposed endothelial cells and muscle cells. METHODS: Nitric oxide (NO) and cGMP levels in human umbilical vein endothelial cells (HUVECs) and A7r5 cells exposed to ginseng berry extract were investigated. Based on the in vitro results, healthy participants were treated with ginseng berry extract for 4 weeks and then a non-invasive vascular screening device was used to confirm the improvement of blood circulation. RESULTS: When TNF-α-treated cells were exposed to the ginseng berry extract, the expression levels of endothelial nitric oxide synthase (eNOS), NO, and cGMP were recovered to almost normal levels. In addition, TNF-ɑ-induced overexpression of vascular cell adhesion molecule 1 (VCAM-1), intracellular adhesion molecule 1 (ICAM-1), e-selectin, and p-selectin was lowered by ginseng berry extract. The ginseng berry extract significantly increased ankle brachial pressure index compared to placebo (p < 0.05). CONCLUSION: This study confirmed that the intake of ginseng berry extract improved blood circulation and therefore, its intake would be helpful for people having problems with blood circulation.

Study of the Heavy Metals in Fume of Buckshot, Blood Lead Concentration and Self-Rated Health Status of National Clay Shooting Athletes / 대한스포츠의학회지

PURPOSE: This study was conducted to investigate the levels of heavy metals and self-rated health status of the national clay shooting athletes. METHODS: Fourteen subjects' blood lead level and index of liver damage (aspartate aminotransferase, alanine aminotransferase, and γ-glutamyl transferase) were measured. Heavy metal content in training environment was measured by collecting the buckshot fume. In addition, subjects completed a questionnaire assessing self-rated health status (Todai Health Index). RESULTS: Antimony and lead were detected much more than other heavy metals in the air of the shooting range. The average blood lead level of 14 subjects was significantly higher than the upper limit of normal Korean adults. Blood lead level of male is significantly higher than female and training frequency and the total training time per week were positively correlated to the blood lead level. In the result of survey on self-rated health, the higher the blood lead level, the lower the score of the common subjective physical symptoms. By age, the younger the subjects are, the higher the score of the common subjective symptoms. CONCLUSION: Although the level of heavy metals in fume of buckshot and blood lead was high, national clay shooting athletes thought that they are healthy.

A study on the changes in attractive force of magnetic attachments for overdenture

PURPOSE: Although magnetic attachment is used frequently for overdenture, it is reported that attractive force can be decreased by abrasion and corrosion. The purpose of this study was to establish the clinical basis about considerations and long term prognosis of overdenture using magnetic attachments by investigating the change in attractive force of magnetic attachment applied to the patients. MATERIALS AND METHODS: Among the patients treated with overdenture using magnetic attachments in Dankook University Dental Hospital, attractive force records of 61 magnetic attachments of 20 subjects who re-visited from July 2013 to June 2014 were analyzed. Dental magnet tester (Aichi Micro Intelligent Co., Aichi, Japan) was used for measurement. The magnetic attachments used in this study were Magfit IP-B Flat, Magfit DX400, Magfit DX600 and Magfit DX800 (Aichi Steel Co., Aichi, Japan) filled with Neodymium (NdFeB), a rare-earth magnet. RESULTS: Reduction ratio of attractive force had no significant correlation with conditional variables to which attachments were applied, and was higher when the maintenance period was longer (P<.05, r=.361). Reduction ratio of attractive force was significantly higher in the subject group in which attachments were used over 9 years than within 9 years (P<.05). Furthermore, 16.39% of total magnetic attachments showed detachment of keeper or assembly. CONCLUSION: Attractive force of magnetic attachment is maintained regardless of conditional variables and reduction ratio increased as the maintenance period became longer. Further study on adhesive material, attachment method and design improvement to prevent detachment of magnetic attachment is needed.

The treatment of an edentulous patient with DENTCA(TM) CAD/CAM Denture / 대한치과보철학회지

Nowadays, CAD/CAM is broadly used in dentistry for inlays, crowns, implant abutments and its spectrum is expanding to complete dentures. Utilizing CAD/CAM to fabricate complete dentures is expected to decrease chair time and the number of visits, thus decreasing total fabrication time, expenses and errors caused during fabrication processes. One of the systems using CAD/CAM, DENTCA(TM) CAD/CAM denture (DENTCA Inc. Los Angeles, USA) scans edentulous impressions, designs dentures digitally, fabricates try-in dentures by 3D printing and converts them into final dentures. Patients can wear final dentures after only 2 - 3 visits with satisfying adaptation. This case report introduces a 71-year-old male patient who visited to consult remaking of existing old dentures. Residual teeth with bad prognosis and root remnants were extracted and the patient used reformed existing mandibular denture for 2 months. And then DENTCA system started. One-step border molding was done using conventional tray of adequate size provided by DENTCA system and wash impression was taken. Gothic arch tracing was completed based on the vertical dimension of existing dentures. Both maxillary and mandibular trays were placed to the resultant centric relation and bite registration was taken. Then DENTCA scanned the bite registration, arranged the teeth, completed the festooning and fabricated the try-in dentures by 3D printing. The try-in dentures were positioned, occlusal plane and occlusal relations were evaluated. The try-in dentures were converted to final dentures. To create bilateral balanced occlusion, occlusal adjustment was done after clinical remounting using facebow transfer. The result was satisfactory and it was confirmed by patient and operator.

Residual bone height measured by panoramic radiography in older edentulous Korean patients

PURPOSE: The aim of this study was to obtain statistical data on the residual bone height at different natural tooth positions by panoramic radiography in edentulous Korean patients aged 60-90 years. MATERIALS AND METHODS: The study included the diagnostic panoramic radiographs of 180 randomly selected edentulous patients without systemic diseases affecting bone. The radiographic selection criteria included absence of obvious facial asymmetry, clearly visible anatomic structures, and no surgical and fracture history. The panoramic radiographs of 79 patients met these criteria and were used in the analysis. The same researcher processed all the radiographs by using a standardized method. The height of the residual bone was measured at 18 predetermined sites (7 in the maxilla and 11 in the mandible) on digitized and printed radiographs by using a Digimatic caliper, triangle, and ruler. Gender- and age-related differences were statistically analyzed by using the t-test and rank-sum test (alpha=0.05). RESULTS: The maxillary residual bone height did not show significant gender-related differences, but male patients had significantly higher residual bone in the mandible(P<.05). No significant height differences at the measured sites were noted among the 60s, 70s, and 80s age groups. CONCLUSION: Dentists should pay greater attention to older female edentulous patients because they are more prone to rapid residual bone resorption. Residual bone resorption may not be affected by age.

On the osseointegration of zirconia and titanium implants installed at defect site filled with xenograft material / 대한치과보철학회지

PURPOSE: The purpose of this study was to compare zirconia implants with titanium implants from the view point of biomechanical stability and histologic response on osseointegration when those were placed with xenograft materials. MATERIALS AND METHODS: Specimens were divided into two groups; the control group was experimented with eighteen titanium implants which had anodized surface and the experimental group was experimented with eighteen sandblasted zirconia (Y-TZP) implants. At the tibias of six pigs, implants were installed into bone defect sites prepared surgically and treated with resorbable membranes and bovine bone. Two pigs were sacrificed after 1, 4 and 12 weeks respectively. Each implant site was sampled and processed for histologic and histomorphometric analysis. The stability of implants was evaluated with a Periotes(R). And the interfaces between bone and the implant were observed with a scanning electron microscope. RESULTS: In stability analysis there was no significant difference between Periotest values of the control group and the experimental group. In histologic analysis with a light microscope after 4 weeks, there was new bone formation with the resorption of bovine bone and the active synthesis of osteoblasts in both groups. In bone-implant contact percentage there was significant difference between both groups (P<.05). In bone area percentage there was no significant difference between both groups. In analysis of both groups with a scanning electron microscope there was a gap between bone and a surface at 4 weeks and it was filled up with bone formed newly at 12 weeks. CONCLUSION: When accompanied by xenograft using membrane, bone to implant contact percentage of zirconia implants used in this experiment was significantly less than that of the titanium implants by surface treatment of anodic oxidation. So, it is considered that the improvement of zirconia implant is needed through ongoing research on surface treatment methods for its practical use.

Characteristics and osteogenic effect of zirconia porous scaffold coated with beta-TCP/HA

PURPOSE: The purpose of this study was to evaluate the properties of a porous zirconia scaffold coated with bioactive materials and compare the in vitro cellular behavior of MC3T3-E1 preosteoblastic cells to titanium and zirconia disks and porous zirconia scaffolds. MATERIALS AND METHODS: Titanium and zirconia disks were prepared. A porous zirconia scaffold was fabricated with an open cell polyurethane disk foam template. The porous zirconia scaffolds were coated with beta-TCP, HA and a compound of beta-TCP and HA (BCP). The characteristics of the specimens were evaluated using scanning electron microscopy (SEM), energy dispersive x-ray spectrometer (EDX), and x-ray diffractometry (XRD). The dissolution tests were analyzed by an inductively coupled plasma spectrometer (ICP). The osteogenic effect of MC3T3-E1 cells was assessed via cell counting and reverse transcriptase-polymerase chain reaction (RT-PCR). RESULTS: The EDX profiles showed the substrate of zirconia, which was surrounded by the Ca-P layer. In the dissolution test, dissolved Ca2+ ions were observed in the following decreasing order; beta-TCP > BCP > HA (P<.05). In the cellular experiments, the cell proliferation on titanium disks appeared significantly lower in comparison to the other groups after 5 days (P<.05). The zirconia scaffolds had greater values than the zirconia disks (P<.05). The mRNA level of osteocalcin was highest on the non-coated zirconia scaffolds after 7 days. CONCLUSION: Zirconia had greater osteoblast cell activity than titanium. The interconnecting pores of the zirconia scaffolds showed enhanced proliferation and cell differentiation. The activity of osteoblast was more affected by microstructure than by coating materials.

Osseointegration of zirconia implant in the tibia of pigs / 대한치과보철학회지

PURPOSE: The purposes of this study were to investigate osseointegration around zirconia implants which had machined or alumina sandblasted surface, and to compare the results with titanium implants. MATERIALS AND METHODS: The study was performed on the tibia of 6 pigs. Three types of implants were investigated: group T-titanium implant, group Z-machined zirconia implant, group ZS-alumina sandblasting treated zirconia implant. Zirconia implants were manufactured from yttria-stabilized tetragonal zirconia polycrystalline (Acucera Inc., Pocheon, Korea). A total of 36 implants were installed in pigs' tibias. After 1, 4 and 12 weeks of healing period, the periotest and the histomorphometric analysis were performed. The data were analyzed using one-way ANOVA and significance was assessed by the Scheffe test (alpha=.05). RESULTS: In the measurement of surface roughness, highest Ra value was measured in group T with significant difference. No significant differences were found among groups regarding Periotest values. After 1 week, in comparison of bone to implant contact (BIC), group Z showed higher value with significant difference. In comparison of bone area (BA), group T and group Z showed higher value with significant difference than group ZS. After 4 weeks, in comparison of BIC, group T showed higher value with significant difference. Comparison of BA showed no significant difference among each implant. After 12 weeks, the highest mean BIC values were found in group T with significant difference. Group ZS showed higher BIC value with significant difference than group Z. In comparison of BA, group T and group ZS showed higher value with significant difference than group Z. CONCLUSION: Zirconia implant showed low levels of osseointegration in this experiment. Modification of surface structure should be taken into consideration in designing zirconia implants to improve the success rate.

Evaluation on the efficacy and safety of calcium metaphosphate coated fixture

PURPOSE: The purpose of this study was to assess the difference in efficacy between calcium metaphosphate (CMP)-coated implant fixtures and conventional resorbable blasted media (RBM) processed implant fixtures. MATERIALS AND METHODS: This study targeted 50 implants from 44 patients who visited Dankook University Dental Hospital. Implantations were done separately for RBM treated and CMP-coated implants, although their design was the same. Calcium metaphosphate has a quicker biodegradation process through hydrolysis compared to other phosphate calcium groups. For the first year of the implantation, the resorption volume of marginal bone analyzed via radiography and perio-test value were measured, under the check plan. Their analyses were composed of a non-inferiority trials test. A 95% level of reliability was used. RESULTS: In the comparative analysis of the resorption volume of marginal bone and the perio-test value, no statistically significant difference was found between the CMP-coated implants and RBM implants. CONCLUSION: One year after the implant placement, CMP-coated implants were found not to be inferior to the conventional RBM implants.

Cleansing effect of the alkaline ionized water on microorganisms of the denture surface / 대한치과보철학회지

PURPOSE: The purpose of this study was to evaluate the cleansing effect of recently developed alkaline ionized water, e-WASH, on microorganisms of the denture surface. MATERIALS AND METHODS: Removable partial and complete dentures were randomly assigned to the experimental group of 41 dentures, and the control group of 26. The denture was immersed in the e-WASH solution (experimental group), or tap water (control group) for 5 minutes. The plaque was collected from the denture surface before and after immersion, and smeared on the slide glass. Amount and motility of microorganisms were compared according to the morphology and strain of microorganisms, using the phase contrast microscope. Statistical analysis was accomplished with paired t-test and independent t-test at 95% confidence level (P<.05). RESULTS: 1. The amount of cocci, bacilli, filamentous, spiral/comma, and the motility of bacilli, filamentous, and spiral/comma were decreased after denture cleansing with the alkaline ionized water, e-WASH (P<.05). But in the control group, only the amount of cocci showed a significant difference (P<.05), but no difference from the others. There were no differences in other analysis. 2. In the experimental group, the amount of cocci, bacilli, filamentous, spiral/comma, and the motility of bacilli, filamentous, and spiral/comma were smaller and more inactive compared to the control group (P<.05). CONCLUSION: These results indicated that the alkaline ionized water, e-WASH could effectively reduce the amount and motility of the experimented microorganisms on the denture surface, and that e-WASH could be recommended as an effective denture cleanser.

The effect of PostGraft(TM) on implants were installed at the tibia of ovariectomized rats / 대한치과보철학회지

PURPOSE: This study evaluated PostGraft(TM) which enhances implant stability and bone density. MATERIALS AND METHODS: Forty eight implants were installed at the tibia of ovariectomized rats. The group administrated with PostGraft(TM) was the experimental group, and the control group was not administrated. Implant stability was evaluated at the 2nd, 4th and 6th week by Periotest value, bone mineral density, bone-to-implant contact. These values were analyzed statistically with Mann-Whitney U test (P<.05). Histological analysis was evaluated at the 2nd, 4th and 6th week. RESULTS: According to the Periotest(R) measurement, both experimental and control groups showed decrease in values as time elapsed. Greater decrease was observed in the experimental group but there was no significant difference. By examining the radiographic images, both experimental and control groups showed tendency of increase in bone density. Greater increase was seen in the experimental group but there was no significant difference. According to the bone-to-implant contact measurement, both experimental and control groups showed increase in values as time elapsed. Greater increase was seen in the experimental group. At the 2nd and 4th week, there was no significant difference. But at the 6th week, there was significant difference (P<.05). By histological analysis, both experimental and control groups showed increase in bone formation as time elapsed. In addition, greater increase was seen in the experimental group. CONCLUSION: It could be concluded that the PostGraft(TM) medicated group showed better results in the bone density and osseointegration.

An effect of immediate dentin sealing on the shear bond strength of resin cement to porcelain restoration

PURPOSE: The aim of this study was to determine differences in shear bond strength to human dentin using immediate dentin sealing (IDS) technique compared to delayed dentin sealing (DDS). MATERIAL AND METHODS: Forty extracted human molars were divided into 4 groups with 10 teeth each. The control group was light-cured after application of dentin bonding agent (Excite(R) DSC) and cemented with Variolink(R) II resin cement. IDS/SE (immediate dentin sealing, Clearfil(TM) SE Bond) and IDS/SB (immediate dentin sealing, Adapter(TM) Single Bond 2) were light-cured after application of dentin bonding agent (Clearfil(TM) SE Bond and Adapter(TM) Sing Bond 2, respectively), whereas DDS specimens were not treated with any dentin bonding agent. Specimens were cemented with Variolink(R) II resin cement. Dentin bonding agent (Excite(R) DSC) was left unpolymerized until the application of porcelain restoration. Shear strength was measured using a universal testing machine at a speed of 5 mm/min and evaluated of fracture using an optical microscope. RESULTS: The mean shear bond strengths of control group and IDS/SE group were not statistically different from another at 14.86 and 11.18 MPa. Bond strength of IDS/SE group had a significantly higher mean than DDS group (3.14 MPa) (P < .05). There were no significance in the mean shear bond strength between IDS/SB (4.11 MPa) and DDS group. Evaluation of failure patterns indicates that most failures in the control group and IDS/SE groups were mixed, whereas failures in the DDS were interfacial. CONCLUSION: When preparing teeth for indirect ceramic restoration, IDS with Clearfil(TM) SE Bond results in improved shear bond strength compared with DDS.

A Case of Functionary Cystic Parathyroid Adenoma with Papillary Thyroid Carcinoma / 영남의대학술지

Cystic parathyroid adenoma is one of rare causes of hyperparathyroidism, and tends to cause increased serum level of parathyroid hormone, alkaline phosphate and serum calcium level similar to when compared to those of solid adenoma.

The efficacy evaluation of PostPlant(TM) Calcium in dental implant placement / 대한치과보철학회지

PURPOSE: The aim of this study was to evaluate the changes in bone density and reduction of time consumed for osteogenesis by PostPlant(TM) Calcium and to find out efficacy of PostPlant(TM) Calcium by comparing the group prescribed with PostPlant(TM) Calcium with the group without PostPlant(TM) Calcium prescription. MATERIAL AND METHODS: The experimental group of 18 patients with 25 dental implant placement and the control group of 7 patients with 9 dental implant placement were randomly selected from the patients who visited prosthetic department of Dankook University Dental Hospital since July, 2006 (IRB Number : 20060710). The experimental group was instructed to take PostPlant(TM) Calcium for 6 months after the implant surgery while the control group was instructed not to. Both experimental and control group were assigned for measurement using Osstell(TM) Mentor and Periotest(R) and radiographic examination was performed using specifically manufactured Aluminum Step Wedge. The results were compared and analyzed. RESULTS: 1. According to the Osstell(TM) Mentor measurement, both the experimental and control group showed increase in values as time elapses and the experimental group showed significantly higher rate of increase (P < .05). 2. According to the Periotest(R) measurement, both the experimental and control group showed decrease in values as time elapses. In addition, greater decrease can be seen in the experimental group but no statistical significance was found. 3. By examining the radiographic images, both the experimental and control group showed tendency of increase in bone density. In addition, greater increase can be seen in the experimental group but no statistical significance was found. CONCLUSION: Clinically, taking PostPlant(TM) Calcium medicine for a long period of time after implant placement is expected for a better prognosis.

A comparative study on the accuracy of the devices for measuring the implant stability

STATEMENT OF PROBLEM: How the ISQ values measured by Osstell(TM) and Osstell(TM) Mentor are related, and whether the ISQ values acquired from the two machines changes in accordance with changes in implant stability are not yet fully understood. PURPOSE: The aim of this study was to find out correlation between the ISQ values acquired from Osstell(TM) and Osstell(TM) Mentor, and to evaluate the clinical effectiveness and accuracy of two devices. MATERIAL AND METHODS: Sixty two implants were inserted into 47 patients, and their ISQ values were measured using Osstell(TM) and Osstell(TM) Mentor. In the first stage surgery, the ISQ values of forty four implants inserted into thirty five patients were measured. In the second stage surgery, the values of fifty implants inserted into thirty seven patients were measured. The values were analyzed to determine the difference between the mean ISQ values of Osstell(TM) and Osstell(TM) Mentor. In addition, the correlation between implants used in the first and second stage of surgery with regard to their types and areas of insertion were analyzed. The difference between the ISQ values of 32 implants in each patient during the first and second stage was analyzed. The statistical assessment was carried out using SPSS V. 12.0 for Win. (SPSS Inc., Chicago, USA). The Pearson correlation coefficient was used to examine the correlation between Osstell(TM) and Osstell(TM) Mentor in the first and second stages of surgery, whereas the difference between their ISQ values was evaluated using a paired t-test. RESULTS: In the first stage, the mean ISQ value for Osstell(TM) and Osstell(TM) Mentor was 70.84 and 75.09, respectively, showing a significant difference (P < .01). In the second stage, the mean ISQ value of Osstell(TM) and Osstell(TM) Mentor was 71.76 and 75.94, respectively, also showing a significant difference (P < .01). The difference between the ISQ values in patients in the first and the second stages was significant with both instruments. CONCLUSION: The significant difference in the values obtained using the Osstell(TM) and Osstell(TM) Mentor between the first and second stages of implant surgery indicates that these values can be a convenient and precise way for evaluating the implant stability in clinical practice.

The effect of various foods on the color stability of artificial teeth / 대한치과보철학회지

STATEMENT OF PROBLEM: Recently, as patients'expectation and interest for esthetics are increasing, concerns of esthetic restoration for removable dentures as well as fixed prosthodontics are also increasing. And the color stability of artificial teeth will affect a long term success rate of the denture. But the stain or discoloration of these artificial teeth as well as denture resin has caused esthetic problem. PURPOSE: This study was designed to evaluate the influence on color stability of artificial teeth when soy sauce, red pepper paste and coffee which many Koreans have eaten were applied. MATERIAL AND METHODS: For artificial teeth type (Endura Anterio(R), Physio Duracross(R), Trubyte Biotone(R)) selected for the study, 10 specimens each were soaked into individual beakers of soy sauce, red pepper paste, coffee and distilled water. And L*, a*, b* value were measured for evaluation of the color difference (delta E*) with spectrophotometer on the 1 day, 1 week, 2 weeks, 4 weeks and 8 weeks after immersion. RESULTS: 1. delta E* value of artificial teeth which were soaked in soy sauce and coffee was various according to soaking periods. However there was significant difference between Trubyte Biotone(R) and Physio Duracross(R) in red pepper paste regardless of soaking period (P < .05). 2. Except for 8 weeks of Endura Anterio(R), 4 weeks and 8 weeks of Physio Duracross(R), artificial teeth soaked in red pepper paste regardless of the type had significant difference of _E* value compared with other groups (P < .05). 3. a*, b* value of Endura Anterio(R) and Trubyte Biotone(R) which were soaked in red pepper paste had significant difference compared with the value of other group (P < .05). CONCLUSION: Red pepper paste had the greatest effect on color difference of artificial tooth. Physio Duracross(R) showed relatively less color difference than Trubyte Biotone(R) and Endura Anterio(R). But as delta E* difference were all less than 3.3, these artificial resin teeth seemed appropriate for clinical use.

A retrospective statistical analysis of dental implants / 대한치과보철학회지

STATEMENT OF PROBLEM: The number of edentulous patients is increasing due to an aging society, which leads to increased demands and interests on implant restorations. Implant restorations are an effective treatment method for both complete and partially edentulous patients, and the success rate has been reported to be high. But because of the increased use of implants in various situations have resulted in frequent reports of failures on implant restorations. Various efforts to overcome these failures have been made. PURPOSE: The aim of this study was to investigate the statistic survival rate of dental implants on patients who were treated at Dankook University Dental Hospital during the past 10 years based on their charts. Materials and methods :The research was made for two different periods of time; The first investigation was for patients from August, 1998 to August, 2003 and the second was for patients from September, 2003 to April, 2007. Information on the number of implants placed, the location and distribution of implants, the duration between the first and second surgery, and the survival rate of implants were investigated from the patients' charts. RESULTS: 1. According to the first investigation, 1680 implants were placed on 612 patients and the second investigation showed 2438 implants placed on 933 patients. Thus a total of 4118 implants on 1545 patients. 2. Among the 1545 patients, 884 patients were male (57.2%) and 661 patients were female (42.8%). Out of 4118 implants, 1739 implants (42.2%) were placed on the maxilla, and 2379 implants (57.8%) on the mandible. Implants were placed most frequently in the posterior region of the mandible. A total of 2043 implants (53.2%) were placed in this region. 3. According to the first investigation, 57 out of 1680, implants failed, while from the second investigation, 17 out of 2438 implants were reported as failure. In total, 74 implants failed, which results in a 98.2% survival rate. 4. The average duration between the first and the second surgeries in maxillas decreased from 7.4 months to 6.8 months. The duration also decreased from 5.6 months to 5.0 months in mandibles. CONCLUSION: As shown in the results, the number of placed implants and the survival rate of implants were higher in the second investigation than that of the first investigation. And the time spent after the first surgery to the second surgery was less in the second investigation. Consequently, it can be presumed that the demand and consumption of dental implants as well as the survival rate will increase in the future.

Fatigue fracture of different dental implant system under cyclic loading / 대한치과보철학회지

STATEMENT OF PROBLEM: Problems such as loosening and fractures of retained screws and fracture of implant fixture have been frequently reported in implant prosthesis. PURPOSE: Implant has weak mechanical properties against lateral loading compared to vertical occlusal loading, and therefore, stress analysis of implant fixture depending on its material and geometric features is needed. MATERIAL AND METHODS: Total 28 of external hexed implants were divided into 7 of 4 groups; Group A (3i, FULL OSSEOTITE(R)Implant), Group B (Nobelbiocare, Branemark System(R)Mk III Groovy RP), Group C (Neobiotec, SinusQuick(TM) EB), Group D (Osstem, US-II). The type III gold alloy prostheses were fabricated using adequate UCLA gold abutments. Fixture, abutment screw, and abutment were connected and cross-sectioned vertically. Hardness test was conducted using MXT-alpha. For fatigue fracture test, with MTS 810, the specimens were loaded to the extent of 60 - 600 N until fracture occurred. The fracture pattern of abutment screw and fixture was observed under scanning electron microscope. A comparative study of stress distribution and fracture area of abutment screw and fixture was carried out through finite element analysis. RESULTS: 1. In Vicker's hardness test of abutment screw, the highest value was measured in group A and lowest value was measured in group D. 2. In all implant groups, implant fixture fractures occurred mainly at the 3 - 4th fixture thread valley where tensile stress was concentrated. When the fatigue life was compared, significant difference was found between the group A, B, C and D (P<.05). 3. The fracture patterns of group B and group D showed complex failure type, a fracture behavior including transverse and longitudinal failure patterns in both fixture and abutment screw. In Group A and C, however, the transverse failure of fixture was only observed. 4. The finite element analysis infers that a fatigue crack started at the fixture surface. CONCLUSION: The maximum tensile stress was found in the implant fixture at the level of cortical bone. The fatigue fracture occurred when the dead space of implant fixture coincides with jig surface where the maximum tensile stress was generated. To increase implant durability, prevention of surrounding bone resorption is important. However, if the bone resorption progresses to the level of dead space, the frequency of implant fracture would increase. Thus, proper management is needed.

The influence of magnet on tissue healing after immediate implantation in fresh extraction sites in dogs / 대한치과보철학회지

STATEMENT OF PROBLEM: The clinical use of electric and electomagnetic fields for fracture healing applications began in the early 1970s. Since then, several technologies have been developed and shown to promote healing of fractures. Developments of these devices have been aided in recent years by basic research and several well controlled clinical trials not only in the medical field but in dentistry. PURPOSE: The purpose of this study was to compare alveolar bone reduction following immediate implantation using implants onto which magnets were attached in fresh extracted sockets. MATERIAL AND METHODS: Four mongrel dogs were involved. Full buccal and lingual mucoperiosteal flaps were elevated and third and fourth premolars of the mandible were removed. Implants with magnets and implants without magnets were installed in the fresh extracted sockets and after 3 months of healing the animals were sacrificed. The mandibles were dissected and each implant sites were sampled and processed for histological examination. RESULTS: The marginal gaps that were present between the implant and walls of the sockets at the implantation stage disappeared in both groups as a result of bone fill and resorption of the bone crest. The buccal bone crests were located apical of its lingual counterparts. At the 12 week interval the mean of marginal bone resorption in the control group was significantly higher than that of the magnet group. The majority of specimens in magnet group presented early bone formation and less resorption of the buccal marginal bone compared to the control group. CONCLUSION: Within the limitations of this study, it could be concluded that implants with magnets attached in the early stages of implantation may provide more favorable conditions for early bone formation and reduce resorption and remodeling of marginal bone.