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1.
Eun-Ha Kim Du-Hyeong Lee Sung-Min Kwon Tae-Yub Kwon 《The Journal of prosthetic dentistry》2017,117(3):393-399
Statement of problem
Although new digital manufacturing techniques are attracting interest in dentistry, few studies have comprehensively investigated the marginal fit of fixed dental prostheses fabricated with such techniques.Purpose
The purpose of this in vitro microcomputed tomography (μCT) study was to evaluate the marginal fit of cobalt-chromium (Co-Cr) alloy copings fabricated by casting and 3 different computer-aided design and computer-aided manufacturing (CAD-CAM)-based processing techniques and alloy systems.Material and methods
Single Co-Cr metal crowns were fabricated using 4 different manufacturing techniques: casting (control), milling, selective laser melting, and milling/sintering. Two different commercial alloy systems were used for each fabrication technique (a total of 8 groups; n=10 for each group). The marginal discrepancy and absolute marginal discrepancy of the crowns were determined with μCT. For each specimen, the values were determined from 4 different regions (sagittal buccal, sagittal lingual, coronal mesial, and coronal distal) by using imaging software and recorded as the average of the 4 readings. For each parameter, the results were statistically compared with 2-way analysis of variance and appropriate post hoc analysis (using Tukey or Student t test) (α=.05).Results
The milling and selective laser melting groups showed significantly larger marginal discrepancies than the control groups (70.4 ±12.0 and 65.3 ±10.1 μm, respectively; P<.001), whereas the milling/sintering groups exhibited significantly smaller values than the controls (P=.004). The milling groups showed significantly larger absolute marginal discrepancy than the control groups (137.4 ±29.0 and 139.2 ±18.9 μm, respectively; P<.05). In the selective laser melting and milling/sintering groups, the absolute marginal discrepancy values were material-specific (P<.05). Nonetheless, the milling/sintering groups yielded statistically comparable (P=.935) or smaller (P<.001) absolute marginal discrepancies to the control groups.Conclusions
The findings of this in vitro μCT study showed that the marginal fit values of the Co-Cr alloy greatly depended on the fabrication methods and, occasionally, the alloy systems. Fixed dental prostheses produced by using the milling/sintering technique can be considered clinically acceptable in terms of marginal fit. 相似文献2.
3.
Hang-Nga Mai Kyeong Eun Lee Jung-Hong Ha Du-Hyeong Lee 《The Journal of prosthetic dentistry》2018,119(4):600-605
Statement of problem
Various methods for measuring prosthesis misfit have been suggested. Although the cross-sectional images between the crown and abutment are used to evaluate the misfit, the effects of the image and the observer’s knowledge on the precision of measurement are unknown.Purpose
The purpose of this in vitro study was to investigate the effects of the image and of education on the precision of prosthesis misfit measurement methods using inter- and intraobserver variability analyses.Material and methods
The cross-sectional images in the margin were obtained using the computer-aided replica technique (CART), silicone replica technique (RT), and sectioning technique (ST). Twenty-five observers measured the absolute marginal discrepancy values in the images obtained from each group 4 times at an interval of 2 weeks; the observers went through different education sessions regarding the selection of the measurement points. The precision of measurement was determined and compared using the likelihood-ratio test statistic (α=.05) and the intraclass correlation coefficient with the linear mixed-effects model.Results
The CART group exhibited the smallest deviations in the measurement variations, followed by the ST and RT groups (P<.001). Additional education on misfit measurements generally decreased the deviation values in all the groups, but without any significant differences.Conclusions
The cross-sectional image obtained from the measurement methods and education on the evaluation method affected the precision of the prosthesis misfit measurement. Digital methods might be a useful tool to significantly enhance the precision of the measurements. 相似文献4.
Statement of problem
Dental clinical procedures are being replaced by digital workflows. Therefore, the time necessary to learn dental computer-aided design (CAD) software to achieve a change in the digital workflow should be evaluated.Purpose
The purpose of this study was to predict the learning curve according to the type of dental CAD software with the Wright model and to determine the rate of improvement in the learner’s working time with iterative learning.Material and methods
A total of 40 participants with various degrees of experience with dental computer-aided design and computer-aided manufacturing (CAD-CAM) systems were recruited. The 4 specified steps of a custom abutment design were performed with 3DSystem CAD software (Daesung) and exocad DentalCAD (exocad GmbH) software and were repeated 3 times in stages. The times were analyzed with repeated-measures 1-factor and 2-factor analyses. The learning time for 300 design iterations was estimated by applying the Wright model formula, and the 300-repetition times were analyzed with the Mann-Whitney U test (α=.05).Results
exocad had a longer mean learning time than the 3DSystem. The overall change with repeated learning was significantly different (P<.001), and all differences were found in the first to third iterations. Software-dependent differences were also observed (P=.005). The Mann-Whitney U test also revealed a significant difference between the 2 software programs (P=.015), but no significant difference was found after the 56th iteration (57th iteration: P=.051).Conclusions
As the time reduction patterns for iterative learning differ depending on the type of CAD software, the learning curves may differ according to the type of software. As the operator’s skill increased through iterative learning, the differences in learning times between the software programs gradually disappeared. 相似文献5.
Sung-Tak Lee Seong-Baek Jang Tae-Geon Kwon So-Young Choi 《The Journal of prosthetic dentistry》2019,121(2):225-228
Tuberculosis (TB) of the oral cavity may be overlooked in the differential diagnosis of oral lesions and can be misdiagnosed and managed incorrectly. A 66-year-old man with complete dentures presented with a nonhealing mucosal ulcer in the upper lip. Despite the treatments performed by a local medical clinic, the ulcerative lesion on the denture-bearing area had not improved over 5 months. A partial excisional biopsy was performed to investigate further. Histopathologic examination revealed granulomatous inflammation caused by TB, and a chest radiograph showed consolidation and cavitation of the upper lobes. The patient was diagnosed with pulmonary TB. This clinical report describes the management of oral TB mimicking a traumatic denture ulcer in a patient with long-term complete denture use. 相似文献
6.
Statement of problem
The introduction of intraoral scanners has increased the use of digital technology in dental procedures. However, research on the extent of clinically recommended scans is lacking.Purpose
The purpose of this in vitro study was to compare 3D arch distortion according to the distance from the tooth at the beginning of a complete-arch scan made using an intraoral scanner.Material and methods
An industrial scanner was used to digitize a master model for a computer-aided design (CAD) reference model. In addition, the master model was digitized using 4 intraoral scanners (TRIOS2, TRIOS3, CS3500, and CS3600) and 1 dental laboratory scanner (FREEDOM HD) to make the CAD test model (N=20). The scanned teeth were divided using an inspection software program (Geomagic control X), and overlapping and 3D analyses of the CAD reference model and CAD test model were performed. The presence or absence of normal distribution in the root mean square (RMS) values of all divided teeth was assessed and evaluated with the Kruskal-Wallis test (α=.05), and post hoc comparison was performed using the Mann-Whitney U-test and Bonferroni correction method (α=.005).Results
The overall RMS value was significantly different for all scanners (P<.001). The dental laboratory scanner showed the lowest value (47.5 ±1.6 μm), whereas TRIOS2 showed the highest value (343.4 ±56.4 μm). TRIOS3 (9.6 ±1.2 μm) showed the best trueness in those teeth where the scan started. However, the larger the scan range, the lower the RMS value difference between TRIOS3 and CS3500. The RMS values of the dental laboratory scanners were higher than those of the intraoral scanners in the narrow scan range. CS3600 showed an RMS value less than or equal to that of the dental laboratory scanner at 5 teeth scan ranges. However, the wider the scan range, the lower the RMS values of all the intraoral scanners.Conclusions
Current complete-arch scanning is not sufficiently accurate for fabricating fixed prostheses. However, intraoral scanners are useful for short scans, such as those for single (TRIOS2, TRIOS3, and CS3500) or short-span prostheses (CS3600). 相似文献7.
8.
Ju-Hyoung Lee 《The Journal of prosthetic dentistry》2019,121(5):749-753
Preparing appropriate guiding planes is essential for the success of a removable partial denture. Owing to the difficulty of determining the location and dimension of proximal reduction, establishing optimal guiding planes may challenge even skilled clinicians. This article introduces a digital workflow for fabricating a reduction guide to establish parallel guiding planes. 相似文献
9.
Soo Yeop Kim Soo-Yeon Shin Jong Hyuk Lee 《The Journal of prosthetic dentistry》2018,119(6):1027.e1-1027.e7
Statement of problem
Limited information is available regarding the mechanical properties of a partial removable dental prosthesis clasp fabricated by direct metal laser sintering (DMLS).Purpose
The purpose of this in vitro study was to measure the mechanical properties of cast clasps, DMLS clasps, and annealed DMLS clasps and to determine the correlation between cyclic bend loading, annealing, and mechanical properties.Material and methods
Sixty half round clasp specimens were fabricated, with a length of 20 mm and a diameter of 1.5 mm at 10 mm from the tip. The specimens were divided into 6 groups (n=10). Twenty specimens were fabricated by casting (CS, CSAC), and 40 specimens were fabricated by DMLS (DS, DSAC, ADS, ADSAC). Of the DMLS specimens, 20 underwent annealing (ADS, ADSAC). Equivalent to 5 years of clinical use, 0.25 mm of bending was applied to group CSAC, DSAC, and ADSAC 14?600 times. After cyclic bending loads, a cantilever bend test was conducted on all groups, and the loads were measured. To compare the load values, 1-way ANOVA and the Tukey HSD test were performed and statistical significance among the groups was evaluated (α=.05). Scanning electron microscopy and energy-dispersive spectroscopy analyses were also used for surface morphology evaluation and element analysis.Results
Bending loads of the DMLS specimens were significantly lower than those of the cast specimens (P<.05). The influence of cyclic bending loads was significant for cast specimens (P<.05), but not for DMLS specimens (P>.05), in terms of variation of loads. Annealed DMLS specimens had significantly higher bending loads than DMLS specimens (P<.05).Conclusions
The DMLS specimens had lower load values at 0.25 mm bending than cast specimens. The DMLS specimens were less influenced by cyclic bending loads than the cast specimens. Annealing increased load values of the DMLS specimens at 0.25 mm bending. 相似文献10.
Chan Park Mong-Sook Vang Sang-Won Park Hyun-Pil Lim 《The Journal of prosthetic dentistry》2017,117(3):430-437
Statement of problem
Although many systems are used to polish zirconia, a comparison of the performance of zirconia and feldspathic porcelain polishing systems is lacking.Purpose
The purpose of this in vitro study was to compare the effects of 3 polishing systems on surface roughness, zirconia phase transformation, and durability of the polishing systems when applied to zirconia and feldspathic porcelain.Material and methods
Three polishing systems were evaluated: Z1, a zirconia polishing system; Z2, a zirconia polishing system, and F1, a feldspathic porcelain polishing system. Three ceramic systems were evaluated: PR and ZM zirconia specimens (diameter 15 mm, height 2 mm; 23 specimens each) and CB feldspathic porcelain specimens of the same size (15 specimens). A rough surface was created on the 3 types of specimens (15 specimens each) to model an occlusal adjustment under the same conditions. Polishing was carried out with the 3 polishing systems for 2 minutes each. Surface roughness was measured with a 3-dimensional (3D) optical profiler. The surface was also observed with a scanning electron microscopy. X-ray diffraction analysis was performed for 8 PR or ZM zirconia specimens polished by using the Z1 and Z2 systems for 8 minutes to evaluate the phase transformation of zirconia before, during, and after polishing. These specimens were compared and analyzed for phase transformation that might have occurred during the polishing of the specimens. After finishing the surface roughness experiment and the phase transformation experiment, the volumes of the polishers were measured with a 3D volume scanner and compared with those before the experiments to evaluate the durability of the polishing system. A statistical analysis of all data was performed using 2-way ANOVA and the Tukey honest significant difference test (α=.05).Results
The 2 zirconia polishing systems (Z1, Z2) created a significantly (P<.001) smoother surface, regardless of the type of specimens used for polishing, than the feldspathic porcelain polishing system (F1). When polishing treatment was carried out on zirconia specimens for 8 minutes, the maximum percentages of monoclinic phase increased by 0.03% in the Z1 system and by 0.09% in the Z2 system. The volume change for the durability evaluation of the polishing system was 13.35 and 29.37% in the Z1 system, 2.05 and 5.92% in the Z2 system, and 3.60 and 4.95% in the F1 system, respectively.Conclusions
Zirconia polishing systems created a smoother surface on zirconia than the feldspathic porcelain polishing system. No significant changes in the phase transformation of zirconia were found before and after polishing. Each polishing system showed different levels of wear resistance. 相似文献11.
Joon-Soo Kim Ji-Hyeon Bae Mi-Jung Yun Jung-Bo Huh 《The Journal of prosthetic dentistry》2017,117(6):775-783
Statement of problem
Recently, zirconia removal diamond rotary instruments have become commercially available for efficient cutting of zirconia. However, research of cutting efficiency and the cutting characteristics of zirconia removal diamond rotary instruments is limited.Purpose
The purpose of this in vitro study was to assess and compare the cutting efficiency, durability, and diamond rotary instrument wear pattern of zirconia diamond removal rotary instruments with those of conventional diamond rotary instruments. In addition, the surface characteristics of the cut zirconia were assessed.Material and methods
Block specimens of 3 mol% yttrium cation-doped tetragonal zirconia polycrystal were machined 10 times for 1 minute each using a high-speed handpiece with 6 types of diamond rotary instrument from 2 manufacturers at a constant force of 2 N (n=5). An electronic scale was used to measure the lost weight after each cut in order to evaluate the cutting efficiency. Field emission scanning electron microscopy was used to evaluate diamond rotary instrument wear patterns and machined zirconia block surface characteristics. Data were statistically analyzed using the Kruskal-Wallis test, followed by the Mann-Whitney U test (α=.05).Results
Zirconia removal fine grit diamond rotary instruments showed cutting efficiency that was reduced compared with conventional fine grit diamond rotary instruments. Diamond grit fracture was the most dominant diamond rotary instrument wear pattern in all groups. All machined zirconia surfaces were primarily subjected to plastic deformation, which is evidence of ductile cutting. Zirconia blocks machined with zirconia removal fine grit diamond rotary instruments showed the least incidence of surface flaws.Conclusions
Although zirconia removal diamond rotary instruments did not show improved cutting efficiency compared with conventional diamond rotary instruments, the machined zirconia surface showed smoother furrows of plastic deformation and fewer surface flaws. 相似文献12.
Statement of problem
The long-term color stability of precolored monolithic zirconia has not been thoroughly investigated.Purpose
The purpose of this in vitro study was to evaluate the effect of hydrothermal aging on the optical properties, phase transformation, and surface topography of precolored monolithic zirconia ceramics.Material and methods
Precolored monolithic zirconia specimens (17.0×17.0×1.5 mm, n=50) and lithium disilicate glass-ceramic specimens (16.0×16.0×1.5 mm, n=50) were artificially aged in an autoclave at 134°C under 0.2 MPa for 0, 1, 3, 5, or 10 hours (n=10). CIELab color parameters were obtained from spectral measurements. The translucency parameter (TP) and CIEDE2000 color differences (ΔE00) were calculated. The microstructural and surface properties were analyzed by X-ray diffraction (XRD), atomic force microscope (AFM), and scanning electron microscope (SEM). Data were analyzed with 2-way ANOVA and pairwise comparison (α=.05).Results
Significant interactions were found between aging time and ceramic material on L*, a*, b*, and TP (P<.001) as follows: b* partial eta squared [ηp2]=0.689; L* ηp2=0.186; a* ηp2=0.176; and TP ηp2=0.137. The b* values significantly decreased after aging for zirconia (P<.001), whereas TP increased after aging for zirconia (P<.014) except at 10 hours (P=.389) and for lithium disilicate (P<.001). The ΔE00 values relative to baseline ranged from 2.03 to 2.52 for aged zirconia and from 0.07 to 0.23 for aged lithium disilicate. XRD analysis revealed that hydrothermal aging promoted an increase in m-phase contents. AFM and SEM demonstrated surface alterations after aging.Conclusions
Optical properties and microstructures of precolored monolithic zirconia ceramics were affected by hydrothermal aging, and translucency increased slightly with aging time. 相似文献13.
Wonsup Lee Young-Jun Lim Myung-Joo Kim Ho-Beom Kwon 《The Journal of prosthetic dentistry》2017,117(4):532-538
Statement of problem
A simplified mounting technique that adopts an average condylar guidance has been advocated. Despite this, the experimental explanation of how average settings differ from individual condylar guidance remains unclear.Purpose
The purpose of this in vitro study was to examine potential occlusal error by using average condylar guidance settings during nonworking side movement of the articulator.Material and methods
Three-dimensional positions of the nonworking side maxillary first molar at various condylar and incisal settings were traced using a laser displacement sensor attached to the motorized stages with biaxial freedom of movement. To examine clinically relevant occlusal consequences of condylar guidance setting errors, the vertical occlusal error was defined as the vertical-axis positional difference between the average setting trace and the other condylar guidance setting trace. In addition, the respective contribution of the condylar and incisal guidance to the position of the maxillary first molar area was analyzed by multiple regression analysis using the resultant coordinate data.Results
Alteration from individual to average settings led to a positional difference in the maxillary first molar nonworking side movement. When the individual setting was lower than average, vertical occlusal error occurred, which might cause occlusal interference. The vertical occlusal error ranged from -2964 to 1711 μm. In addition, the occlusal effect of incisal guidance was measured as a partial regression coefficient of 0.882, which exceeded the effect of condylar guidance, 0.431.Conclusions
Potential occlusal error as a result of adopting an average condylar guidance setting was observed. The occlusal effect of incisal guidance doubled the effect of condylar guidance. 相似文献14.
Statement of problem
The effects of the application of aqueous coloring liquids on the mechanical properties of zirconia have not yet been investigated.Purpose
The purpose of this in vitro study was to evaluate the effects of 3 different coloring techniques and the number of coloring liquid applications on the hardness of zirconia.Material and methods
Eighty specimens were divided into 8 groups (n=10); nonshaded zirconia, preshaded zirconia, acid-based coloring liquid zirconia, and aqueous coloring liquid zirconia (1, 3, 6). Vickers hardness was measured. Data were analyzed via 1-way and 2-way ANOVAs. Multiple comparisons were performed using a Scheffé test (α=.05).Results
Statistically significant differences in hardness were found between acid-based coloring liquid zirconia and aqueous coloring liquid zirconia (P<.001). Increasing the number of coloring liquid applications decreased the hardness value of acid-based coloring liquid zirconia (P<.001) but had no effect on the hardness of aqueous coloring liquid zirconia (P>.05).Conclusions
Within the limitations of this study, the hardness of zirconia was influenced to differing degrees depending on coloring technique. The number of coloring liquid applications affected the hardness of zirconia colored with the acid-based coloring liquid but not the hardness of zirconia colored with the aqueous coloring liquid. 相似文献15.
Most digital prosthesis designs consider only the maximal intercuspal position (MIP) and not the lateral movement. During the computer-aided design and computer-aided manufacture (CAD-CAM) prosthesis delivery process, the clinician has to adjust the prosthesis to avoid occlusal interference during lateral excursion. The novel digital workflow described in this report can be divided into 2 steps. After obtaining interocclusal records for the MIP and the lateral excursion position, the crown CAD data were designed using a general digital workflow considering only the MIP. The previous crown CAD data were then adjusted in the lateral excursion state before manufacturing the prosthesis. This process using information for 2 occlusal positions means that the definitive prosthesis design reflects not only static occlusion but also lateral mandibular relation. 相似文献
16.
17.
Statement of problem
Research of the ability of a cast mounted on an articulator on maintaining the identical position of a cast mounted on an articulator after repeated repositioning is lacking, despite the possible effects this may have on the occlusion of a mounted cast.Purpose
The purpose of this in vitro study was to verify and compare the vertical repositioning accuracy of 4 different, commercially available articulator magnetic mounting plate systems.Material and methods
Four articulators and their associated magnetic mounting plates were selected for the study. These were the Artex AR articulator (Amann Girrbach AG), the Denar Mark II articulator (Whip Mix Corp), the Kavo Protar Evo articulator (Kavo Dental GmbH), and the SAM3 articulator (SAM Präzisionstechnik GmbH). Three new magnetic mounting plates were prepared for each articulator system. The repositioning accuracy of each mounting plate was evaluated by comparing the standard deviation of the vertical distances measured between the mounting plate and a laser displacement sensor. The lower arm of the articulator was secured, and the vertical distance was measured by positioning the laser displacement sensor positioned vertically above the mounting plate. Once the vertical distance was measured, the mounting plate was detached from the articulator and reattached manually to prepare for the next measurement. This procedure was repeated 30 times for each of the 3 magnetic mounting plates. Data were analyzed by ANOVA for 2-stage nested design and the Levene test (α=.05).Results
Significant differences were detected among articulator systems and between magnetic mounting plates of the same type. The standard deviations of the measurements made with the Artex AR articulator, Denar Mark II articulator, Kavo Protar Evo articulator, and SAM3 articulator were 0.0027, 0.0308, 0.0214, and 0.0215 mm, respectively. Thus, the repositioning accuracy could be ranked in the order as follows: Artex AR, Kavo Protar Evo, SAM3, and Denar Mark II.Conclusions
The position of the magnetic mounting plate after repositioning did not maintain an identical position in the vertical dimension on any of the 4 articulator models tested. The repositioning accuracy of the mounting plates showed significant differences among the articulators tested in this study. 相似文献18.
This clinical report describes the management of a patient who had an excessively tight reconstructed lip because of oral cancer surgery and postoperative radiotherapy. The presented technique used an intraoral scanner for a preliminary impression and computer-aided design and computer-aided manufacturing (CAD-CAM) technology for preliminary laboratory procedures. This digital impression technique may reduce patient discomfort. 相似文献
19.
Jong-Eun Kim Joo Hyun Kwon Jee-Hwan Kim June-Sung Shim 《The Journal of prosthetic dentistry》2017,117(5):597-600
Various attempts have been made to transfer the transverse hinge axis and mandibular movement pattern to the mechanical articulator and to fabricate dental prostheses with the fewest errors. However, the occlusal adjustment of a dental prosthesis is always necessary to ensure a precise intraoral fit even when the facebow transfer technique is used in the cast mounting procedure. This is because the true hinge axis is not obtained when the facebow is applied to a patient who exhibits a variable mandible movement pattern rather than a single rotational axis. This technique merges facial scanning data and digital data obtained from a diagnostic cast based on measurements of several landmarks of the anterior teeth and makes it possible to design a dental prosthesis while considering the mandibular opening and closing movements of the patient. This technique could be used to design prosthetic restorations, occlusal splints, and intermediate splints for orthognathic surgery and for complete mouth rehabilitation when changes in vertical dimensions are needed. 相似文献
20.
Implant parallelism is rarely achieved, particularly when anatomic limitations are present. The problem of nonparallel implants has been addressed by using angled or bar abutments to compensate for the implant angulation. However, an angled abutment or bar attachment has disadvantages in terms of cost, laboratory process, and the maintenance of oral hygiene. In this clinical report, a solution for the management of an inclined implant is presented by using customized Locator abutment fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM). 相似文献