Wear resistance of dental temporary restorations manufactured using different additive manufacturing technologies / 대한치과재료학회지

Recently, the digital industry has established itself as a major technology in the field of dentistry, while additive manufacturing (AM), commonly known as 3D printing. Temporary dental restorations are being produced using various additive manufacturing technologies. Also, changes in eating habits expose these temporary restorations to various acidity. Thus, this study was to investigate that wear resistance of dental temporary restorations manufactured using different additive manufacturing technologies according to the acidity of artificial saliva. A total of 120 rectangular parallelepipeds specimens were prepared with three different types of printing method used for the dental resin crown production: Stereo Lithography Apparatus (SLA), Digital Light Processing (DLP), Fused Deposition Modelling (FDM). The antagonists were made of zirconia and cobalt–chrome alloy.Each specimen was then loaded at 5 kg for 20,000 cycle chewing simulations with 5 mm vertical descending movement and 2 mm horizontal movement. The wear resistance test through chewing simulator was conducted in two different pH of 4 and 6. The SLA and DLP group showed no significant difference, however, the FDM group showed significantly increased maximal depth loss and volume loss of wear compared to the other two samples (p0.05), but when looking at the specimens, volume loss and depth loss deviation were generally lower when zirconia was used than when the CoCr alloy was used as the abrader. In conclusion, despite the limitations with this in vitro experiment, the SLA and DLP group showed greater mechanical properties compared to the FDM group. The acidic pH environment resulted in more destructive and weak mechanical properties in all groups. When temporary restorations clinically used in additive manufacturing technology, it is believed that it is necessary to determine the method of additive manufacturing and pay attention to acidity.

Effect of silane incorporated adhesive or adhesive using separate silane on bonding of silica-based ceramics / 대한치과재료학회지

The purpose of this study was to evaluate the effectiveness of silane on the surface treatment of silica-based ceramic when silane is incorporated into the universal adhesive versus using silane separately from the adhesive. The materials used in this study are as follows: 1) All-Bond Universal, 2) Silane mixed with All-Bond Universal, 3) Porcelain primer (as a regular silane primer), and 4) Scoth Bond Universal (which is a commercial silane-containing universal adhesive). IPS e-Max press, a lithium disilicate, was used as the silica-based ceramic. Contact angle test was measured to evaluate hydrophobicity on a silica-based ceramic surface. Shear bond strength was tested by universal testing machine. The surfaces of the specimen were polished in order to eliminate any bias from micro mechanical retention due to an uneven surface. The results indicated that only silane applied to the silica based ceramic surface resulted in highest contact angle and shear bond strength. Using silane separately and using silane incorporated into the universal adhesive (contains hydrophobic resin) resulted in different performance on silica-based ceramic. Therefore, it was concluded that the silane should be used separately from a hydrophobic resin monomer in order to maximize its porcelain surface treatment function.

Effects of Zero Suck-back Control Box (ZSCB) on prevention of external contaminants suction by various handpieces / 대한치과재료학회지

The dental high-speed air turbine handpiece operates by rotating the impeller inside the handpiece with compressed air. However, even if the inflow of the powered compressed air is stopped, the impeller rotates due to inertial rotation and creates negative pressure inside the handpiece (backflow suction, commonly known as suck-back). Organic matter and microorganisms in the patient’s oral cavity flow into not only the inside of the handpiece but also other parts connected to the handpiece, causing contamination. In this study, the Zero Suck-back Control Box (ZSCB) device, which was developed to prevent the reverse suction of the handpiece, was applied to five different handpieces and tested. After driving the five different handpieces with or without ZSCB in the air, the presence or absence of suck-back was observed when they were stopped. In addition, when the handpiece was driven using the fluorescent solution to imitate the oral environment, the fluorescent solution flowing into the inside due to the reverse suction phenomenon was observed. It was evident that operating different handpieces with the ZSCB is effective in preventing the inhalation of external contaminants. In two different experiments conducted in this study, the use of ZSCB was shown to be effective in preventing regurgitation in both atmospheric and immersion conditions.

Antibacterial properties of dental resin incorporated with nano-silver doped silica in accordance with exposure of visible light / 대한치과재료학회지

This study investigated reduction of the bandgap of silica by applying nano-silver doping technique and possible application of such silica as a filler in dental resin. Due to reduce band gap, newly fabricated nano-silver doped silica was able to release ROS in accordance with exposure of visible light. Nano-silver doped silica was composed of below 20 nm size crystal silver nanoparticle and 100~500 nm size amorphous silica. These two components were chemically attached to each other (Si-O-Ag). The reduced bandgap was 2.10 eV, which the value could be interpreted as occurrence of surface plasmon resonance generating ROS in visible light exposure conditions. When such nano-silver doped silica was used as a filler in dental resin, increased antibacterial property of nano-silver ion was observed which was related to releasing of ROS when exposed in visible light. The antibacterial properties were statistically significant following exposure to visible light when 0.7 to 1.5 wt% of nano-silver doped silica were incorporated into resin. When the contents of nano-silver doped silica were below 0.7 wt%, minimal ROS release resulted in no significant increase in antibacterial properties as there would be less exposed nano-silver doped silica on the resin surface by visible light. Meanwhile, more than 1.5 wt% of nano-silver doped silica also resulted no significant increase in antibacterial properties following exposure to visible light as the antibacterial effects from nano-silver ion itself were greater than effects from released ROS. Hence, it was concluded that dental resin containing 0.7 to 1.5 wt% of nano-silver doped silica would provide antibacterial properties when exposed to visible light, significantly greater than in dark conditions.

Effect of low temperature degradation on multi-layered zirconia block for dental CAD/CAM / 대한치과재료학회지

Ceramic prosthesis fabrication using CAD/CAM has advantages such as high convenience, fast fabrication speed, and high esthetics, resulted in increasing use in clinical practice. Among them, the multi-layered zirconia block for dental CAD/CAM is a product that consists of a single block with layers of different shades, so that natural tooth color can be reproduced.However, research on the material is insufficient, and in particular, the study on the characteristics of low-temperature degradation, which is known to be important for zirconia-based medical devices, is required to evaluate the performance and safety of the material. In this study, in order to evaluate the effect of low-temperature degradation on the properties of multi-layered zirconia blocks, three-point flexural strength, fracture surface and phase changes before and after low-temperature degradation of three companies’ dental CAD/CAM multi-layered zirconia block products were compared. As a result of this experiment, all products of the three manufacturers met International Standards, and there was no change in strength even after low-temperature degradation. However, it was found that there were differences in monoclinic content, three-point flexural strength, and the surface crystal structure for each zirconia block.

Mechanical and physico-chemical properties of premixed-MTA in contact with three different types of solutions / 대한치과재료학회지

The study aims to analyze the compressive strength, pH, and surface properties of mineral trioxide aggregates (MTA), which can be used as a pulp capping and root canal filling material. The tests were performed after immersing premixed types of MTA for seven days into three different solutions: simulated body fluid (SBF), saline, and distilled water (DW). A universal testing machine was used to measure the compressive strength after one and seven days of immersion. The un-immersed MTA was used as the control. To investigate the pH variation, MTA specimens were immersed in each solution and the pH was measured using a pH meter after 3, 6, 12, 24, 72, and 168 h. Changes on the MTA surface were also observed by SEM-EDS after seven days of immersion. Moreover, statistical analysis was performed by one-way ANOVA, Tukey's post-hoc test, and independent sample t-test. All experimental groups showed significantly higher compressive strengths compared to the control group (p0.05). As the immersion time increased, the pH increased among all the groups, and the pH of samples immersed in saline and DW was significantly higher than that in SBF. The MTA surface immersed in each solution for seven days showed precipitates which mainly composed of Ca and Zr ions. Therefore, the type of contact solution does not significantly affect the compressive strength of MTA, but it significantly influences both the pH and surface condition

Cytokine Release from Organotypic Human Oral Tissue Following Exposure to Oral Care Product Chemicals

Purpose@#Measuring viability of a three-dimensional in vitro organotypic human oral tissue model has been suggested as an alternative test method to the oral mucosa irritation test of oral care products. The aim of this study was to investigate the production of two different cytokines using organotypic human oral tissue model following exposure to chemicals that are commonly used in oral care products. @*Materials and Methods@#The organotypic human oral tissues were exposed to ethanol, sodium lauryl sulphate or hydrogen peroxide for 90 minutes. Following exposure, interleukin (IL)-1α and IL-8 productions were assessed and correlated with cell viability testing as well as histology of the organotypic human oral tissues.Result: High levels of IL-8 were released from organotypic human oral tissues in all of the test and control groups without any significant differences between them. In contrast, differences were found in IL-1α release between the test and control groups. Additionally, the trend of IL-1α release corresponded to the phenotypes observed in histological analysis while different trend existed between IL-1α release and cell viability. @*Conclusion@#The study concluded the non-specific release of IL-8 for the assessment of oral care product chemicals’ toxicity, while potential of measuring IL-1α cytokine level as the possible alternative test method.

Physical and biodegradable properties of 3D printed resorbable membranes for periodontal guided tissue regenerations / 대한치과재료학회지

The purpose of this study was to compare physical and biodegradable properties of 3D printed resorbable membranes that are used for guided tissue regenerations in periodontal tissues. Three types of 3D printed membranes (two types of non β-TCP and one type of β-TCP) were considered. The form and element compositions of 3D printed membranes were analyzed by field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS). Porosity and pore size were measured using Micro-CT. Also, tensile strength, biodegradability tests were performed. Statistical analyses were carried in tensile strength and cell viability test (p<0.05). The result of SEM images with EDS analyses showed linear layers of lattice structure with presence of C and O in all groups. There was a slight difference in Ca and P among some groups. Tensile strength was significantly different among all groups (p<0.05), and biodegradability showed that the group containing β-TCP resulted in the fastest degradation rate. Therefore, the results of this study concluded that the 3D printed resorbable membrane has variable physical and biodegradable properties for clinical use, where such information would be useful to be considered for the future development of related products and clinical application of the products.

Application of GLP in identification and quantification of degradation products from bone graft materials / 대한치과재료학회지

Biocompatibility testing of bone graft materials are important aspect for development of the device as well as the approval and certification by each individual country’s regulatory authority. Recently, importance in identification and quantification of degradation product as well as application of Good Laboratory Practice (GLP) in the process of biocompatibility testing has been emphasized. Hence, here identification and quantification of degradation products from bone graft materials were carried out in accordance with GLP process. Commercially available bone graft material from the animal source was used in this study.The test was carried out in accordance with International Standard, ISO 10993-14 Biological evaluation of medical devices -Part 14: Identification and quantification of degradation products from ceramics. Also, entire process followed Institute for Management of Good Laboratory Practice, published by Ministry of Food and Drug Safety, Korea. Degradation test of the bone graft materials resulted in degradation of bone graft, ranging between 0.32 g to 0.86 g, while Ca and P were detected. In terms of GLP process, it has been noted that consideration of other International Standard such as ISO 10993-12 is required for planning of the GLP test, especially during the sample preparation.

Physical and biodegradable properties of 3D printed resorbable membranes for periodontal guided tissue regenerations / 대한치과재료학회지

The purpose of this study was to compare physical and biodegradable properties of 3D printed resorbable membranes that are used for guided tissue regenerations in periodontal tissues. Three types of 3D printed membranes (two types of non β-TCP and one type of β-TCP) were considered. The form and element compositions of 3D printed membranes were analyzed by field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray spectroscopy (EDS). Porosity and pore size were measured using Micro-CT. Also, tensile strength, biodegradability tests were performed. Statistical analyses were carried in tensile strength and cell viability test (p<0.05). The result of SEM images with EDS analyses showed linear layers of lattice structure with presence of C and O in all groups. There was a slight difference in Ca and P among some groups. Tensile strength was significantly different among all groups (p<0.05), and biodegradability showed that the group containing β-TCP resulted in the fastest degradation rate. Therefore, the results of this study concluded that the 3D printed resorbable membrane has variable physical and biodegradable properties for clinical use, where such information would be useful to be considered for the future development of related products and clinical application of the products.

Application of GLP in identification and quantification of degradation products from bone graft materials / 대한치과재료학회지

Biocompatibility testing of bone graft materials are important aspect for development of the device as well as the approval and certification by each individual country’s regulatory authority. Recently, importance in identification and quantification of degradation product as well as application of Good Laboratory Practice (GLP) in the process of biocompatibility testing has been emphasized. Hence, here identification and quantification of degradation products from bone graft materials were carried out in accordance with GLP process. Commercially available bone graft material from the animal source was used in this study.The test was carried out in accordance with International Standard, ISO 10993-14 Biological evaluation of medical devices -Part 14: Identification and quantification of degradation products from ceramics. Also, entire process followed Institute for Management of Good Laboratory Practice, published by Ministry of Food and Drug Safety, Korea. Degradation test of the bone graft materials resulted in degradation of bone graft, ranging between 0.32 g to 0.86 g, while Ca and P were detected. In terms of GLP process, it has been noted that consideration of other International Standard such as ISO 10993-12 is required for planning of the GLP test, especially during the sample preparation.

Comparison of color stability, mechanical and chemical properties according to temporary crown resin type / 대한치과재료학회지

Objective of this study was to compare the color stability, mechanical and chemical properties of three different types of temporary crown resins. Commercially available powder-liquid (Group PL), light-cured (Group LC) and auto-mix syringe (Group AM) types' temporary crown resins were used as experimental groups for each of the evaluation. All the test groups were evaluated after 1 day and 7 days of immersion in various staining solutions. The colors of all groups before and after storage in the staining solutions were measured by a spectrophotometer based on CIE Lab system, and the color differences (ΔE(*)) thereby calculated. Micro hardness test was performed before water storage and aging after 7 days at 37 ℃. In addition, flexural strength, water sorption and solubility tests were performed according to international standard, ISO 10477. All experimental groups showed significant color change in staining solutions when compared to those stored in the control solution (distilled water) (p PL > LC (p<0.05). Water sorption and solubility increased in the following order: AM < PL < LC (p<0.05). The results of this study would provide useful information when choosing temporary crown resin types in various clinical situations.

Discoloration and radiopacity of white mineral trioxide aggregate with various radiopacifiers / 대한치과재료학회지

The use of the mineral trioxide aggregate (MTA) has been expanded as the material can be applied on various treatment of endodontic care, which also has many advantages including bioactivity. Still, the discolorations of the materials have been presented as a concern related to esthetic appearances, which is caused by the presence of radiopacifiers. Therefore, the aim of this study was to investigate the color stability and radiopacity of white MTA with various radiopacifiers. Four different radiopacifiers [bismuth oxide (BM), calcium tungstate (CT), barium oxide (BO), and zirconium oxide (ZO)] were used. The radiopacity was tested according to ISO 6876, and the color change before and after immersing in a 5% hypochlorite solution was tested using a spectrophotometer. The group with no radiopacifier (NR) was used as a negative control and ProRoot MTA (PR) was used as the commercial control. The immersion of the PR and BM in sodium hypochlorite resulted in a dark brown discoloration, in which the values were higher than the rest of the group (p0.05). In terms of the radiopacity, the NR showed the lowest value as expected (p<0.05). Meanwhile, the BM showed the highest value (p<0.05), followed by PR and BO (p<0.05). The NR showed the lowest radiopacity values. The result of this study will be useful for future development of MTA that would have clinically adequate radiopacity with minimum discoloration.

Comparison of physical properties of the various 3D printing temporary crown and bridge resin / 대한치과재료학회지

Conventional dental resins for crown and bridge fulfill ISO 10477 and ISO 10993 before clinical application. Although 3D printing or rapid prototyping (RP) for the fabrication of temporary crown and bridge have been proposed, a little studies were reported for 3D printing resin for temporary crown and bridge. The purpose of this study was to evaluate the physical properties (such as water sorption and solubility, color stability and flexural strength) of the various 3D printing temporary crown and bridge resin following the ISO 10477:2018 and estimate the effect of chemical composition of resin on the physical properties. Four resins approved by KFDA and 4 experimental resins developed by different manufacturer were tested in this study. Samples were prepared with DLP typed 3D Printer (G-Printer) and post-cured using UV-light Cure Unit (Cure M). Proper 3D printing and post-curing conditions were selected for different 3D printing resins. Each test was performed according to the ISO 10477 and results were statistically analyzed using Tukey-multiple comparison test (p=0.05). Only group-B did not satisfied the ISO requirement ( 60 MPa). Resin components may affect the flexural strength, then user should check the components of 3D printing resin. Deficient degree of polymerization may lead to large water sorption, water solubility and color changes. Further study should be done comparison between specimens printed with specific 3D printer recommended by manufacturer and specimens used in this study.

Therapeutic Intervention for Visuo-Spatial Neglect after Stroke: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVES: The aims of this meta-analysis were to examine intervention methods of qualitatively, well-designed studies from the past 10 years for treating visuo-spatial neglect (VSN) in patients who had suffered a stroke, and to evaluate the combined effects of intervention. METHODS: Studies published between 2008 and 2017 on the theme of VSN were collected from PubMed, CINAHL, and MEDLINE, representative academic databases and search engines. The PEDro scale was used for evaluating the quality of methodology. The sample size, mean, and standard deviation of identified studies were used for meta-analysis. RESULTS: Eight studies were selected for analysis. The PEDro scores of the selected studies were ≥ 7, with 237 subjects analyzed. The results of intervention were classified into “mental function” and “activity and participation” based on the International Classification of Functioning, Disability and Health. The analyzed effect sizes for combined outcomes, mental function and, activity and participation, were 0.728 (medium effect size), 0.850 (large effect size), and 0.536 (medium effect size), respectively. CONCLUSION: Intervention methods for treating VSN had a short-term effect on cognitive function (visual perception). In particular, non-invasive brain stimulation therapy showed a large effect size for VSN treatment.

Effects of thermoforming on the physical and mechanical properties of thermoplastic materials for transparent orthodontic aligners / 대한치과교정학회지

OBJECTIVE: The aim of this systematic multiscale analysis was to evaluate the effects of thermoforming on the physical and mechanical properties of thermoplastic materials used to fabricate transparent orthodontic aligners (TOAs). METHODS: Specimens were fabricated using four types of thermoplastic materials with different thicknesses under a thermal vacuum. Transparency, water absorption and solubility, surface hardness, and the results of three-point bending and tensile tests were evaluated before and after thermoforming. Data were analyzed using one-way analysis of variance and Student's t-test. RESULTS: After thermoforming, the transparency of Duran and Essix A+ decreased, while the water absorption ability of all materials; the water solubility of Duran, Essix A+, and Essix ACE; and the surface hardness of Duran and Essix A+ increased. The flexure modulus for the 0.5-mm-thick Duran, Essix A+, and eCligner specimens increased, whereas that for the 0.75-/1.0-mm-thick Duran and eClginer specimens decreased. In addition, the elastic modulus increased for the 0.5-mm-thick Essix A+ specimens and decreased for the 0.75-mm-thick Duran and Essix ACE and the 1.0-mm-thick Essix ACE specimens. CONCLUSIONS: Our findings suggest that the physical and mechanical properties of thermoplastic materials used for the fabrication of TOAs should be evaluated after thermoforming in order to characterize their properties for clinical application.

Nutrient Intakes and the Physical Activities of the Mentally Retarded Persons According to the Degree of Handicap Who Were Accommodated in Institutions in Andong Area / 대한지역사회영양학회지

This study was conducted to evaluate the nutrient intakes and the physical activities of mentally retarded persons (MRPs) accommodated in welfare institutions. A total of 194 cases of MRPs (130 males and 64 females) were surveyed through interviews of the 35 caregivers of the institutions during the period from March 2 to 12, 2005. The mean age of the 2nd degree is the highest, and the duration of institution stay of the 2nd degree is the longest. There were no significant differences in height, weight, but there were still significant differences in BMI by the degree of handicap. The MRPs with the 1st degree handicap consumed less nutrients than the MRPs with 2nd or 3rd degree handicaps, except for vitamins C and E. The mean activity factor was 1.737 +/- 0.422 meaning 'active'. Among the comparative groups, the activity factor of the 2nd handicap degree MRPs was the highest. Note that the percentage of protein is the lowest in the case of the 1st degree handicap. The intake of the folic acid, in particular, was less than the Estimated Average Requirement (EAR) in case of all the MRPs while that of vitamin C, riboflavin and calcium was less than the EAR in case of 65~80% of the MRPs. MRPs with higher activity factors showed higher intakes of most nutrients except vitamin C. MRPs with higher marks in the 'balanced dietary habit' field showed more nutrient intakes. More consumption of vegetables and fruits by the MRPs was recommended. Also, more efficient dietary guidance was recommended for the MRPs.

Changes in Retinal Neuronal Population in DBA/2J Mice with Topical Intraocular Pressure Lowering Drugs

PURPOSE: The DBA/2J (D2) mouse is a transgenic mouse with pigmentary glaucoma. In a previous study, we found a reduction of inner retinal thickness in D2 mice. We attempted to discover the effect of eye drops on the retina of D2 mice. METHODS: Ten-month-old D2 mouse eyes were treated with Timoptic XE(R), Cosopt(R), and Xalacom(R) eye drops for a 1-month period. Immunohistochemical staining was performed on the mouse eye sections for analysis. RESULTS: In the control group, GABA and OPN immunoreactivity were markedly decreased and NOS immunoreactivity was increased. In all experimental group, GABA and OPN immunoreactivity were increased, and OPN immunoreactivity was markedly increased especially in the Cosopt(R) group. NOS immunoreactivity was decreased in all experimental groups. There was no difference in glycine immunoreactivity between the control and experimental groups. CONCLUSIONS: Combination anti-glaucoma eye-drops to the D2 mouse changed the retinal neuronal population and these drugs might play an important role in the mechanisms of retinal neuronal death; potential strategies for neuroprotection should therefore be evaluated.

A Case of Sponataneous Regressing Retroperitoneal Fibrosis after Ureteral Stent Insertion / 대한신장학회잡지

A 76 year old man was admitted because of periumbilical aMominal pain and nausea for 20days before admission. Initial serum creatinine level was 6.1mg/dL. Radioisotope renography showed obstruc- tive uropathy in both ureters. Retrograde pyelography of the left kidney revealed about 1cm of filling defect on the level of L5. Percutaneous nephrostomography of the right kidney revealed ureteral stricture in the lower ureter. In order to preserve renal function, a double J stent was inserted into each ureter. Serum creatinine level decreased to 1.5mg/dL after the insertion of ureteral stents. 12 weeks later, both stents were removed. 3 months after removal of the ureteral stents, retroperitoneal fibrosis and hydronephrosis disappeared in follow up abdominal CT. Recent his serum creatinine has shown about 1.5mg/dL. The patient is under continuing observation with serum creatinine level and sonography for detection of recurrence. This is a rare case of retroperitoneal fibrosis which showed spontaneous regression after ureteral stent insertion for 12 weeks without ureterolysis or corticosteroid therapy. In this case, the ureteral stent played a important role in preserving renal function by relieving ureteral obstruction. But the key point was that in the early stage in the early stage of retroperitoneal fibrosis, it was thaught having reversible process. There are some reports that ureteral obstruction was relieved only by correction of fluid and electrolytes balance or ureter diversion such as percutaneous nephro-stomy. Corticosteroid therapy promotes this rever-sible change in early stage of this disease by immunosuppression and antiinflammatory reaction. But once fibrosis has established in late stage of retroperitoneal fibrosis, corticosteroid is not effective for reducing the fibrosis and ureteral obstruction. In that case, operation is the choice for preservation of renal function. We reported an idiopathic retroperitoneal fibrosis case which showed spontaneous regression after preserving renal function by double J stent insertion without ureterolysis or corticosteroid therapy. We thought that idiopathic retroperitoneal fibrosis is a reversible process in the early stage.

Comparison of Thallium-201, Tc-99m MIBI and I-131 Scan in the Follow-up Assessment after I-131 Ablative Therapy in Differentiated Thyroid Cancer / 대한핵의학회잡지

PURPOSE: We conducted a comparative study to evaluate the diagnostic values of Tl-201, Tc-99m MIBI and I-131 scans in the follow-up assessment after ablative I-131 therapy in differentiated thyroid cancer. MATERIALS AND METHODS: The study population consisted of 20 patients who underwent surgical removal of thyroid cancer and ablative radioactive iodine therapy, and followed by one or more times of I-131 retreatments (33 cases). In all patients, Tl-201, Tc-99m MIBI, diagnostic and therapeutic I-131 scans were performed and the RESULTS were analyzed retrospectively. Also serum thyroglobulin levels were measured in all patients. The final diagnosis of recurrent or metastatic thyroid cancer was determined by clinical, biochemical, radiologic and/or biopsy findings. RESULTS: Positive rates (PR) of Tc-99m MIBI, Tl-201, diagnostic and therapeutic I-131 scans in detecting malignant thyroid tissue lesions were 70% (19/27), 54% (15/28), 35% (17/48) and 63% (30/48), respectively. The PR in the group of 20 cases (28 lesions) who underwent concomitant Tl-201 and I-131 scans were in the order of therapeutic 131 scan 71%, Tl-201 scan 54% and diagnostic I-131 scan 36%. There was no statistically significant difference between Tl-201 and diagnostic I-131 scans (p>0.05). In the group of 20 cases (27 lesions) who underwent concomitant Tc-99m MIBI and I-131 scans, the PR were in the order of Tc-99m MIBI scan 70%, I-131 therapeutic scan 52% and I-131 diagnostic scan 33%. The PR of Tc-99m MIBI was significantly higher than that of diagnostic I-131 scan (p<0.05). CONCLUSION: Tc-99m MIBI scan is superior to diagnostic I-131 scan in detecting recurrent or metastatic thyroid cancer following ablation therapy in patients with differentiated thyroid cancer. Tl-201 scan did not showed significantly higher positive rate than diagnostic I-131 scan. Instead of diagnostic I-131 scan before the I-131 retreatment, Tc-99m MIBI scan without discontinuing thyroid hormone replacement would be a prudent and effective approach in the management of these patients.