The purpose of this study was to compare the microleakage of the composite resin cores according to surface treatment, dentin bonding agents, and thermocycling. For this study, 120 extracted premolar teeth were used. Flat occlusal surfaces were prepared with diamond disk, and treated with air-abrasion, acid-etching, combination. The composite resin core was built with Z-100 after application of Scotchbond Multi-Purpose and All-Bond 2. Prepared specimens were thermocycled for 2,000 cycles. Specimens were immersed in 1% methylene blue solution for 24hours at 371C. The microleakage was measured with a inverted metallurgical microscope(BHS313, Olympus, Japan). The following conclusions were drawn from this study 1. The microleakages in the groups treated with air-abrasion and with acid etching were greater than that of the groups treated with combination method before thermocycling(p<0.05), the microleakages of the groups treated with air-abrasion were greater than that of the groups treated with acid-etching and combination method after thermocycling(p<0.05). 2. There were no significant difference between groups using Scotchbond Multi-Purpose and the groups using All-Bond 2. 3. Thermocycling didri t affect the change of microleakage in all cases.
Bicuspid ; Dentin-Bonding Agents ; Diamond ; Methylene Blue ; Tooth

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth' s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin, Futar' occlusion, Blu-mousse) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by X-PLAN360d to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference. 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less mar ginal discrepancy than groups with 0.5mm-marginal-vent-space(p<0.05). In summary, these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.
Humans ; Jaw Relation Record ; Prostheses and Implants ; Tooth*

The purpose of this study was to compare the microleakage of the composite resin cores according to surface treatment, dentin bonding agents, and thermocycling. For this study, 120 extracted premolar teeth were used. Flat occlusal surfaces were prepared with diamond disk, and treated with air-abrasion, acid-etching, combination. The composite resin core was built with Z-100 after application of Scotchbond Multi-Purpose and All-Bond 2. Prepared specimens were thermocycled for 2,000 cycles. Specimens were immersed in 1% methylene blue solution for 24hours at 371C. The microleakage was measured with a inverted metallurgical microscope(BHS313, Olympus, Japan). The following conclusions were drawn from this study 1. The microleakages in the groups treated with air-abrasion and with acid etching were greater than that of the groups treated with combination method before thermocycling(p<0.05), the microleakages of the groups treated with air-abrasion were greater than that of the groups treated with acid-etching and combination method after thermocycling(p<0.05). 2. There were no significant difference between groups using Scotchbond Multi-Purpose and the groups using All-Bond 2. 3. Thermocycling didri t affect the change of microleakage in all cases.
Bicuspid ; Dentin-Bonding Agents ; Diamond ; Methylene Blue ; Tooth

Accurate impression is very important to achieve desirable prosthesis and there are many factors in taking a good impression. For example, types of impression material, types of impression tray, impression taking methods and so on. Recently individual tooth tray technique is accepted as obtaining good impression that can be applied to multiple abutment impression, heavy salivated patient, to minimize the effect of natural teeth' s undercuts and to reduce pain during cord packing procedures. The purpose of this study was to compare the accuracy according to materials and forms of the individual tooth tray which is clinically applied nowadays. Used materials in experiment were divided into 3 types (acrylic resin, Futar' occlusion, Blu-mousse) and forms were divided into 2 types (forming occlusal vent hole or not and forming marginal vent space or not). Stone master model from impression body and metal master model were measured by X-PLAN360d to compare occlusal surface discrepancy and marginal discrepancy. The results were as follows 1. In comparison of occlusal surface discrepancy and marginal discrepancy according to materials, groups with three materials showed no statistical difference. 2. In comparison of occlusal surface discrepancy and marginal discrepancy according to occlusal vent hole, groups with occlusal vent hole showed significantly less marginal discrepancy than groups with no occlusal vent hole(p<0.05). 3. In comparison of occlusal surface discrepancy and marginal discrepancy according to 0.5mm marginal-vent-space, groups with no 0.5mm-marginal-vent-space showed significantly less mar ginal discrepancy than groups with 0.5mm-marginal-vent-space(p<0.05). In summary, these results suggest that individual tooth tray made of 3 types of materials with occlusal vent hole and individual tooth tray made of acrylic resin with no marginal vent space showed good accuracy of impression. In addition, individual tooth tray which is made of bite registration materials may be more useful because of advantage in facility and timesaving aspect of fabrication.
Humans ; Jaw Relation Record ; Prostheses and Implants ; Tooth*

The purposes of this study were to evaluate the adherence of bacteria on various denture base resin materials and effects of chitosan, added to denture base materials on bacterial adherence. PMMA denture base resin such as heat-cured Vertex-RS, self-cured Vertex-SC and 4-META denture base resin such as heat-cured Meta-Dent, self-cured Meta-Fast were used in this study. Samples were divided into two groups: the denture base resin with chitosan, without chitosan. Streptococcus mutans and Lactobacillus casei were used in this study. The surface of samples was observed by SEM. When chitosan was added to M17 and MRS broth, viable cell count of bacteria was reduced. Viable cell count of Streptococcus mutans on the samples decreased as follows: Meta-Dent, Vertex-SC, Meta-Fast, Vertex-RS. Viable cell count of Lactobacillus casei on the samples decreased as follows: Vertex-RS, Meta-Dent, Meta-Fast, Vertex-SC. The resin with chitosan showed lower adherence of bacteria than without chitosan. The images of SEM showed that the surface of the resin with chitosan was rougher than that of without chitosan. These results showed that the denture base resin materials with chitosan have rougher surface than without chitosan,but less bacteria adhered on them.
Bacteria* ; Cell Count ; Chitosan* ; Denture Bases* ; Dentures* ; Lactobacillus casei ; Polymethyl Methacrylate ; Streptococcus mutans

Load transfer of implant overdenture varies depending on anchorage systems that are the design of the superstructure and substructure and the choice of attachment. Overload by using improper anchorage system not only will cause fracture of the framework or screw but also may cause failure of osseointegration. Choosing anchorage system in making prosthesis, therefore, can be considered to be one of the most important factors that affect long-term success of implant treatment. In this study, in order to determine the effect of anchorage systems on load transfer in mandibular implant overdenture in which 4 implants were placed in the interforaminal region, patterns of stress distribution in implant supporting bone in case of unilateral vertical loading on mandibular left first molar were compared each other according to various types of anchorage system using three-dimensional photoelastic stress analysis. The five photoelastic overdenture models utilizing Hader bar without cantilever using clips(type 1), cantilevered Hader bar using clips(type 2), cantilevered Hader bar with milled surface using clips(type 3), cantilevered milled-bar using swivel-latchs and frictional pins(type 4), and Hader bar using clip and ERA attachments(type 5), and one cantilevered fixed-detachable prosthesis(type 6) model as control were fabricated. The following conclusions were drawn within the limitations of this study. 1. In all experimental models, the highest stress was concentrated on the most distal implant supporting bone on loaded side. 2. Maximum fringe orders on ipsilateral distal implant supporting bone in a ascending order is as follows; type 5, type 1, type 4, type 2 and type 3, and type 6. 3. Regardless of anchorage systems, more or less stresses were generated on the residual ridge under distal extension base of all overdenture models. To summarize the above mentioned results, in case of the patients with unfavorable biomechanical conditions such as not sufficient number of supporting implants, short length of the implant and unfavorable antero-posterior spread,selecting resilient type attachment or minimizing distal cantilever bar is considered to be appropriate methods to prevent overloading on implants by reducing cantilever effect and gaining more support from the distal residual ridge.
Denture, Overlay* ; Friction ; Humans ; Models, Theoretical ; Molar ; Osseointegration ; Prostheses and Implants

Recently as the esthetic concerns about dental prosthesis have been increased, the nonmetallic post and core systems have been introduced clinically to improve the color and the low optical transmittance of conventional casting metal post and core systems. The purpose of this study was to compare and analyze the optical transmittance and the shade changes of all-ceramic crowns with two nonmetallic post and core systems. The experimental groups were classified as follows: Total 27 specimens(9 samples in each group) were evaluated. Group I: Natural teeth as a control group. Group II: CosmoPost and Empress(R) core (Ivoclar-Vivadent, Liechtenstein). Group III: LIGHT-POST(TM) and LIGHT-CORE(TM)(Bisco, U.S.A.). In all groups, all-ceramic crowns were fabricated with the same shade of IPS Empress(R)II(Ivoclar-Vivadent, Liechtenstein) after abutment preparation, and then two kinds of spectrophotometers, UV 3101 PC(Shimadzu,Japan) and CM 503i(Minolta Co., Ltd., Japan), were used to measure the optical transmittance and the color value. The following results were obtained: 1. The optical transmittance of each group without all-ceramic crowns, was siginificantly decreased in order of Group III, I and II(p<0.05). 2. The optical transmittance of each group with all-ceramic crowns cemented, were siginificantly decreased in order of Group I, II and III(p<0.05). 3. In comparison with the shade of all-ceramic crowns, there were no significant differences between groups regardless of the cementation. 4. In comparison with the shade changes in each group after the cementation of all-ceramic crowns, there were no significant differences between groups. From the above results, it is thought that the selection among materials used in this study doesn't influence greatly the esthetic restoration, because the differences of optical transmittance were so small that those were clinically insignificant.
Cementation ; Crowns* ; Dental Prosthesis ; Tooth

The selection of the maxillary anterior artificial teeth is made primarily for esthetics and they must be in harmony with the surrounding oral environment. However the selection of artificial teeth is based on the large degree of subjective judgement of the dentists, therefore, this is one of the most unscientific processes. This study was performed to determine clinically whether there is correlation among the width of the maxillary central incisor(WMCI), the intercanine distance(ICD), the facial width(FW), and the interalar nasal width(IAW)in Korean adults, and to provide the selection standards for the maxillary anterior artificial teeth. The casts were obtained from 91 undergraduate dental students(49 males and 42 females) with Angle's class I occlusion presenting well-arranged intact anterior teeth. The WMCI and ICD were measured on the casts with a vernier calipers(Miltex(R), Germany). The photographic procedures under standardized conditions were performed to record each subject's frontal face using digital camera(Olympus(R), C-2500L, Japan). The FW and IAW were measured with image analyzer(Image-Pro(R) PLUS, media cybermetrics, USA). The results were obtained as follows: 1. The mean WMCI was 8.11+/-0.67 mm, ICD was 37.88+/-2.15 mm, FW was 141.29+/-5.84 mm, and IAW was 37.85+/-2.29 mm. 2. The ratios of FW/WMCI, FW/ICD, IAW/ICD were 17.4, 3.7, 1.0 respectively. 3. All measurements(WMCI, ICD, FW, and IAW) of male group were longer than those of female group significantly in Student's t-test(p<0.01). 4. There was significant correlation between WMCI, ICD, FW, and IAW in Pearson's correlation analysis(p<0.01). 5. The relationship between IAW and ICD shows the strongest correlation among six combinations in linear regression analysis(R2=0.753, Y=7.046+0.815X). The FW and IAW could be very reliable guides for the selection of the maxillary anterior artificial teeth.
Adult* ; Dentists ; Esthetics ; Female ; Humans ; Linear Models ; Male ; Tooth ; Tooth, Artificial*

The purpose of this study was to investigate further the mechanics of failure of magnets used for denture retention. Dyna magnets were retrived from denture that had failed after 34 months of clinical use. The magnets were observed and sectioned in order to analyse with high resolution scanning electron microscope. From this study, corrosion behaviors of used magnetic attachment were analysed. The results were as follows: 1. In Nd-Fe-B based magnetic materials, the erosion-corrosion was started at ununiformed part of stainless steel cover. 2. Corrosion was initiated at weared stainless steel surface and then magnetic materials were spalled by corrosive solution. 3. Spalling was occurred in Nd-Fe-B magnet materials due to corrosion products and then corrosion rate was increased drastically. 4. Corrosion started from ununiformed stainless steel surface as well as welded zone. In conclusion, the failure of magnets may occur by either breakdown of the welding or breakdown of the encapsulating material. So, it is considered that the corrosion problem of dental magnetic materials could be solved to some extent with surface treatment of dental magnetic materials.
Corrosion* ; Denture Retention ; Dentures ; Mechanics ; Stainless Steel ; Welding

The purpose of this study was to estimate the effect of a bleaching agent on tooth surfaces and to evaluate the resin bond strength according to different surface treatments on bleached teeth.To prepare for the experimental samples,first,extracted human third molars were used and the body portions of the crowns were cut into four equal-sized specimens.Next,each specimen was mounted in an plastic bottle with self-cured resin and highly polished to have them reveal the enamel or dentin surfaces.Then,the enamel(E)and dentin(D)specimens were divided into four; 1) non-bleached,laser-treated(NBLA)group 2)bleached,laser-treated(BLLA)group 3)non-bleached,acid-treated(NBAC)group and 4)bleached,acid-treated(BLAC)group.Here,opales-cence(R)(10%carbamide peroxide)was used for bleaching agent.The treated specimens were observed by confocal laser scanning microscopy and bonded with composite resin for shear bond test. The following results were obtained from this experiment : 1. Compared with the ENB group,the EBL group was shown to be dyed about 20 micrometer deeper with rhodamine B.The DBL group appeared to be caved in at the entry part of the dentinal tubules, was dyed about 20 micrometer deeper and 5 micrometer wider in diameter,compared with the DNB group. 2. In comparison with the EBLAC group,the ENBAC group looked evenly bonded with the resin, while the DNBAC group,compared to DBLAC group,was observed to have its resin tags penetrated about 50 micrometer deeper.Other than those,however,no observable differences between ENBLA and EBLLA group or between DNBLA and DBLLA group were found. 3. At the shear bond test,the ENBAC group was shown to have statistically significant higher shear bond strength than the EBLAC group(p<0.05).No statistically significant differences between the ENBLA and the EBLLA groups were observed(p>0.05). 4. At the shear bond test,the DNBAC group was shown to have statistically significant higher shear bond strength than the DBLAC group(p<0.05).No statistically significant differences between the DNBLA and the DBLLA groups were observed(p>0.05). The in vitro observations above suggest that tooth-bleaching procedure brings a certain change on enamel and dentin surfaces and it weakens the shear bond strength with composite resin when the bleached tooth was acid-treated.
Crowns ; Dental Enamel* ; Dentin* ; Humans ; Microscopy, Confocal* ; Molar, Third ; Plastics ; Rhodamines ; Tooth