Search

This study analyzed the trueness of polymer-infiltrated ceramic and glass ceramic crowns manufactured using the chairside computer-aided design/manufacturing (CAD/CAM) system.The master model designs crowns using a CAD program after acquiring a digital impression with an intraoral scanner. Vita Enamic (VE), Vita Suprinity (VS), and IPS e.max CAD (IPS) were used to manufacture 10 crowns each (total: 30 crowns), using the chairside CAD/CAM system (inLab MC XL). Trueness was evaluated by superimposing the CAD data on the scan data using a three-dimensional program. The Kruskal-Wallis H test, a nonparametric test, and the Mann-Whitney U test were performed by applying the significance level (0.05/3=0.016), which was adjusted by post-analysis Bonferroni testing.There was a significant difference in the trueness between the samples (p0.05). However, there was no statistically significant difference in the outer surface trueness between the samples (p0.05).These findings show that the milling accuracy of VE is better than that of VS and IPS.

Objectives. In this study, a clear aligner was moved at intervals of 0.25 mm and pressure variations were assessed using a sensor. Methods. The model used for producing the clear aligner was created using a 3-dimensional printer. A clear, circular thermoplastic of 0.75 mm thickness was used for making the clear aligner using the vacuum forming method. A pressure sensor was used to assess the pressure in the device, and the variation in the sheet pressure was statistically analyzed tooth movement using the clear aligner, moving at an interval of 0.25 mm, is recommended. Results. The results of pressure sensor assessment showed that the pressure of the devices with 0.25 mm and 1.00 mm movements was identical to that of the device with 0 mm movement. In other words, the pressure sensor could not distinguish the pressure of devices that moved 0.25 mm and 1.00 mm. Conclusions. This experiment demonstrated that a movement of more than 0.50 mm is needed to apply the appropriate pressures needed for orthodontics in a clear polymer sheet.

PURPOSE The purpose of the present study was to compare scanning trueness and precision between an abutment impression and a stone model according to dental computer-aided design/computer-aided manufacturing (CAD/CAM) evaluation standards. MATERIALS AND METHODS To evaluate trueness, the abutment impression and stone model were scanned to obtain the first 3-dimensional (3-D) stereolithography (STL) file. Next, the abutment impression or stone model was removed from the scanner and re-fixed on the table; scanning was then repeated so that 11 files were obtained for each scan type. To evaluate precision, the abutment impression or stone model was scanned to obtain the first 3-D STL file. Without moving it, scanning was performed 10 more times, so that 11 files were obtained for each scan type. By superimposing the first scanned STL file onto the other STL files one by one, 10 color-difference maps and reports were obtained; i.e., 10 experimental scans per type. The independent t-test was used to compare root mean square (RMS) data between the groups (α=.05). RESULTS The RMS±SD values of scanning trueness of the abutment impression and stone model were 22.4±4.4 and 17.4±3.5 µm, respectively (P

PURPOSE To compare and analyze trueness and precision of provisional crowns made using stereolithography apparatus and subtractive technology. MATERIALS AND METHODS Digital impressions were made using a master model and an intraoral scanner and the crowns were designed with CAD software; in total, 22 crowns were produced. After superimposing CAD design data and scan data using a 3D program, quantitative and qualitative data were obtained for analysis of trueness and precision. Statistical analysis was performed using normality test combined with Levene test for equal variance analysis and independent sample t-test. Type 1 error was set at 0.05. RESULTS Trueness for the outer and inner surfaces of the SLA crown (SLAC) were 49.6±9.3 µm and 22.5±5.1 µm, respectively, and those of the subtractive crown (SUBC) were 31.8±7.5 µm and 14.6±1.2 µm, respectively. Precision values for the outer and inner surfaces of the SLAC were 18.7±6.2 µm and 26.9±8.5 µm, and those of the SUBC were 25.4±3.1 µm and 13.8±0.6 µm, respectively. Trueness values for the outer and inner surfaces of the SLAC and SUBC showed statistically significant differences (P

PURPOSE The purpose of this study was to compare the cutting method and the lamination method to investigate whether the CAD data of the proposed inlay shape are machined correctly. MATERIALS AND METHODS The Mesial-Occlusal shape of the inlay was modeled by changing the stereolithography (STL). Each group used SLS (metal powder) or SLA (photocurable resin) in the additive method, and wax or zirconia in the subtractive method (n=10 per group, total n=40). Three-dimensional (3D) analysis program (Geomagic Control X inspection software; 3D systems) was used for the alignment and analysis. The root mean square (RMS) in the 2D plane state was measured within 50 µm radius of eight comparison measuring points (CMP). Differences were analyzed using one-way analysis of variance and post-hoc Tukey's test were used (α=.05). RESULTS There was a significant difference in RMS only in SLA and SLS of 2D section (P

Purpose To evaluate the accuracy (trueness and precision) of dental replica models produced by using photopolymer materials in additive manufacturing. Materials and methods A complete arch model was scanned using an extraoral scanner (Identica Blue) and established as reference. For the control group, 10 stone models were acquired through the conventional method from the reference model. For the experimental groups, digital data were acquired using an intraoral scanner (CEREC Omnicam), and 10 stereolithographic apparatus (SLA) models and 10 PolyJet models were made. All models were scanned with an extraoral scanner. Three-dimensional analysis software was used to measure differences between the 3D scanned images in root mean square values. The ISO-5725-1 specification was followed to measure trueness and precision between two 3D scanned data. Trueness was calculated by overlapping scanned data with the reference model and precision by performing pairwise intragroup comparisons. Also the ratio of region out of tolerance (> ±50 μm) was measured. One-way ANOVA and Tukey's post hoc analysis were applied. Results There was no statistically significant difference in trueness between the stone and the SLA models (p > 0.05). Dental replica models using photopolymer materials showed statistically significantly better precision than that of the stone model (p 0.05). Conclusions Although the dental replica models using photopolymer materials did not show better trueness than the conventional stone models, there was no significant difference between the SLA and the stone models. Concerning precision, dental replica models using photopolymer materials presented better results than that of the conventional stone models. In sum, dental replica models using photopolymer materials showed sufficient accuracy for clinical use.

PURPOSE This in vitro study aimed to analyze and compare the reproducibility of zirconia and lithium disilicate crowns manufactured by digital workflow. MATERIALS AND METHODS A typodont model with a prepped upper first molar was set in a phantom head, and a digital impression was obtained with a video intraoral scanner (CEREC Omnicam; Sirona GmbH), from which a single crown was designed and manufactured with CAD/CAM into a zirconia crown and lithium disilicate crown (n=12). Reproducibility of each crown was quantitatively retrieved by superimposing the digitized data of the crown in 3D inspection software, and differences were graphically mapped in color. Areas with large differences were analyzed with digital microscopy. Mean quadratic deviations (RMS) quantitatively obtained from each ceramic group were statistically analyzed with Student's t-test (α=.05). RESULTS The RMS value of lithium disilicate crown was 29.2 (4.1) µm and 17.6 (5.5) µm on the outer and inner surfaces, respectively, whereas these values were 18.6 (2.0) µm and 20.6 (5.1) µm for the zirconia crown. Reproducibility of zirconia and lithium disilicate crowns had a statistically significant difference only on the outer surface (P

Statement of problem Microstereolithography (μ-SLA), a form of additive manufacturing, can produce one or more platforms of resin copings. However, no evaluation has been made of the variation in marginal discrepancy using this method, even though this is an important factor for a successful restoration. Purpose The purpose of this in vitro study was to evaluate the reproducibility and marginal discrepancy of resin copings fabricated using dental μ-SLA. Material and methods A master die of a mandibular right first molar tooth was made from Type IV stone and scanned to produce a stereolithography file. Resin copings were then fabricated using μ-SLA additive manufacturing by repeating 1, 3, or 6 arrays to give a total number of 18. The marginal discrepancies of these resin copings were measured using digital microscopy (at ×160 magnification), and the data obtained were analyzed using a nonparametric Kruskal-Wallis H test, post hoc Mann-Whitney U -test, and Bonferroni correction. Results The mean ±SD total marginal discrepancies of 1, 3, and 6 arrays were found to be 72.2 ±39.1 μm, 61.2 ±37.3 μm, and 92.5 ±54.1 μm. Statistically significant differences were found among the compared groups ( P Conclusions Based on the marginal discrepancy, μ-SLA of additive manufacturing is more precise when 3 arrays are used than when 1 or 6 arrays are used on a single build platform. Because the fit is affected by the number of copings fabricated, further research of multiple resin copings is required.

Fit is an important factor influencing the success or failure of restorations. Recently, there has been increasing use of a newly developed pre-sintered soft alloy for use in computer-aided design and computer-aided manufacturing (CAD-CAM) of cobalt-chromium alloys for the fabrication of metal ceramic restorations. However, almost no studies are available on the fit of restorations fabricated in this way.The purpose of this in vitro study was to evaluate the fit of metal coping fabricated from a newly developed CAD-CAM soft alloy in order to investigate its clinical applicability.Metal coping was categorized as casting alloy (CA), fully sintered hard alloy (FHA), or pre-sintered soft alloy (PSA) depending on the material, and 10 specimens of each category were fabricated. Seven measurement locations were selected in both the mesiodistal and labiolingual directions. For measurement of the marginal and internal discrepancies, silicone molds produced using a silicone replica technique were divided into mesiodistal and labiolingual cross-sections, and the width was measured. The Kruskal-Wallis and Mann-Whitney U test were performed (corrected α error level=.05/3).The mean values of the total discrepancy were smallest in the CA group (52.53 ±33.40 μm) and largest in the FHA group (87.84 ±39.43 μm). The CA group and the PSA group were not significantly different from each other (P.05) but were statistically significantly different from the FHA group (P.001). In particular, the absolute marginal discrepancy did not differ significantly between the CA (33.68 ±8.44 μm) and PSA groups (37.01 ±8.04 μm) (P.05).The fit of the PSA restorations determined by this study was similar to that of conventional cast restorations. Both FHA and PSA restorations demonstrated clinically acceptable values (120 μm).

The goal of this study was to evaluate the effects of different core and veneer thicknesses on the translucency (T%), average light transmittance (T), translucency parameter (TP), contrast ratio (CR), and spectral reflectance (R) of glass-ceramics using a computer-aided design/computer-aided manufacturing (CAD-CAM) process. In all, 42 specimens (11mm × 11mm) were prepared and divided into six groups (n = 7 for each group). Core materials (IPS e.max CAD; IPS Empress CAD, LT A2 shade) of different thicknesses (0.8, 1.0, and 1.2mm) were fabricated. Each veneer material (thicknesses of 0.7, 0.5, and 0.3mm) was combined with its compatible core ceramic. Each core material was overlapped with its corresponding veneer material to obtain a 1.5-mm thickness by using three different combinations: (0.8+0.7), (1.0+0.5), and (1.2+0.3) mm. A spectrophotometer and color data software were used to measure the T%, T, TP, CR, and R values of each ceramic. The results were statistically analyzed using two-way analysis of variables (ANOVA) and regression analysis (pp

Purpose The purpose of this study was to evaluate the marginal discrepancy of heat-pressed ceramic veneers manufactured using a CAD/CAM system. Materials and methods The ceramic veneers for the abutment of a maxillary left central incisor were designed using a CAD/CAM software program. Ten veneers using a micro-stereolithography apparatus (AM group), ten veneers using a five-axis milling machine (SM group), and ten veneers using a traditional free-hand wax technique (TW group) were prepared according to the respective manufacturing method. The ceramic veneers were also fabricated using a heat-press technique, and a silicone replica was used to measure their marginal discrepancy. The marginal discrepancies were measured using a digital microscope (×160 magnification). The data were analyzed using a nonparametric Kruskal-Wallis H test. Finally, post-hoc comparisons were conducted using Bonferroni-corrected Mann-Whitney U tests (α=.05). Results The mean±SD of the total marginal discrepancy was 99.68±28.01 µm for the AM group, 76.60±28.76 µm for the SM group, and 83.08±39.74 µm for the TW group. There were significant differences in the total marginal discrepancies of the ceramic veneers (P Conclusion The SM group showed a better fit than the AM and TW groups. However, all values were within the clinical tolerance. Therefore, CAD/CAM manufacturing methods can replace the traditional free-hand wax technique.

Information on the accuracy of intraoral video scanners for long-span areas is limited.The purpose of this in vitro study was to evaluate and compare the trueness and precision of an intraoral video scanner, an intraoral still image scanner, and a blue-light scanner for the production of digital impressions.Reference scan data were obtained by scanning a complete-arch model. An identical model was scanned 8 times using an intraoral video scanner (CEREC Omnicam; Sirona) and an intraoral still image scanner (CEREC Bluecam; Sirona), and stone casts made from conventional impressions of the same model were scanned 8 times with a blue-light scanner as a control (Identica Blue; Medit). Accuracy consists of trueness (the extent to which the scan data differ from the reference scan) and precision (the similarity of the data from multiple scans). To evaluate precision, 8 scans were superimposed using 3-dimensional analysis software; the reference scan data were then superimposed to determine the trueness. Differences were analyzed using 1-way ANOVA and post hoc Tukey HSD tests (α=.05).Trueness in the video scanner group was not significantly different from that in the control group. However, the video scanner group showed significantly lower values than those of the still image scanner group for all variables (P.05), except in tolerance range. The root mean square, standard deviations, and mean negative precision values for the video scanner group were significantly higher than those for the other groups (P.05).Digital impressions obtained by the intraoral video scanner showed better accuracy for long-span areas than those captured by the still image scanner. However, the video scanner was less accurate than the laboratory scanner.

Purpose The precision of two types of surface digitization devices, i.e., a contact probe scanner and an optical scanner, and the trueness of two types of stone replicas, i.e., one without an imaging powder (SR/NP) and one with an imaging powder (SR/P), were evaluated using a computer-aided analysis. Methods A master die was fabricated from stainless steel. Ten impressions were taken, and ten stone replicas were prepared from Type IV stone (Fujirock EP, GC, Leuven, Belgium). The precision of two types of scanners was analyzed using the root mean square (RMS), measurement error (ME), and limits of agreement (LoA) at each coordinate. The trueness of the stone replicas was evaluated using the total deviation. A Student's t -test was applied to compare the discrepancies between the CAD-reference-models of the master die (m-CRM) and point clouds for the two types of stone replicas ( α =.05). Results The RMS values for the precision were 1.58, 1.28, and 0.98μm along the x -, y -, and z -axes in the contact probe scanner and 1.97, 1.32, and 1.33μm along the x -, y -, and z -axes in the optical scanner, respectively. A comparison with m-CRM revealed a trueness of 7.10μm for SR/NP and 8.65μm for SR/P. Conclusions The precision at each coordinate ( x -, y -, and z -axes) was revealed to be higher than the one assessed in the previous method (overall offset differences). A comparison between the m-CRM and 3D surface models of the stone replicas revealed a greater dimensional change in SR/P than in SR/NP.

【Purpose: The purpose of this in vitro study was to evaluation the effect of shade on all ceramic restoration based zirconia according to cooling rate on Firing. Methods: 10 specimens applied to the dentin porcelain were made on the zirconia. After 5 specimens of the first group were burned in the furnace, these were put out rapidly. And after 5 specimens of the second group were burned in the furnace, these were put out slowly later 15 min. All specimens were measured $L^*$ , $a^*$ , $b^*$ using spectrophotometer, there were calculated 10 mean(SD) of descriptive statistics with SPSS program. These data were used for ${\Delta}E^*$ with color difference equation. Independent t tests were performed between 2 groups. Results: $L^*$ , $a^*$ , $b^*$ of 2 groups was statistically significant respectively (p ${\Delta}E^*$ was 4.55 value. Conclusion: This study showed effect of shade on all ceramic restoration based zirconia according to cooling rate on Firing.】

Background/aims Previous studies have compared the thickness of the device with and without grooves. The result was a difference in thickness of the device along the groove. The aim of this study was to assess the differences in thickness of mouthguards that result from different groove shapes of ethylene vinyl acetate sheets used to make these appliances. Materials and method Mouthguards were made using a 3-dimensional printer, and produced by softening 4 mm transparent circular sheets. Four different shapes of sheets were evaluated: normal sheets, sheets with anterior V-shaped grooves, sheets with anterior A-shaped grooves, and sheets with posterior A-shaped grooves. The groove was 3 mm deep and 5 mm wide. The thickness of the appliance was assessed with respect to the anterior incisal edge, labial surface, palatal surface, posterior cusp, buccal surface, and palatal surface. The Kruskal-Wallis test was used to analyze differences in thickness among the different groove shapes. Results No significant difference was detected between the thickness of mouthguards made using sheets with grooves and that of mouthguards made using sheets without grooves (P > .05). Conclusion The presence of grooves on the sheets did not influence mouthguard thickness.

Three-dimensional (3D)-printed casts are used successfully as diagnostic casts in orthodontics. However, whether 3D-printed casts are sufficiently accurate to be used as definitive casts for fixed dental prostheses (FDPs) is unclear.The purpose of this in vitro study was to evaluate the fit of 3-unit FDPs fabricated on 3D-printed casts made by digital light processing and to investigate the clinical applicability of 3D printing.A master model was fabricated from epoxy resin. Stone casts were made from dual viscosity impressions (conventional stone cast [CS] group, n=10). The 3D-printed casts were fabricated using a 3D printer after obtaining digital virtual casts by digital scans (3D-printed cast [3DP] group, n=10). All FDPs were fabricated with a 5-axis milling machine. The master model and intaglio surface of the milled FDPs was superimposed using 3D analysis software to measure the accuracy. Two-way ANOVA was performed to identify a significant difference between the groups (3DP and CS) and sides (pontic side, nonpontic side) and their interactive effects (α=.05). The Tukey honestly significant difference test was used for post hoc analysis.Two-way ANOVA showed significant differences between the 2 groups (3DP and CS) in the marginal and internal root mean square (RMS) values (P.001). However, no significant difference was found in the marginal RMS values (P=.762) between the pontic and nonpontic sides. The 3DP showed significantly higher RMS values than the CS (P.001).The fit of FDPs produced from 3D-printed casts was inferior to that of conventional stone casts; however, all FDPs showed clinically acceptable accuracy. These results suggest that 3D-printed casts have clinical applicability but that further improvement of the 3D printer is necessary for their application in prosthodontics.

Purpose To evaluate the accuracy (trueness and precision) of dental replica models produced by using photopolymer materials in additive manufacturing. Materials and Methods A complete arch model was scanned using an extraoral scanner (Identica Blue) and established as reference. For the control group, 10 stone models were acquired through the conventional method from the reference model. For the experimental groups, digital data were acquired using an intraoral scanner (CEREC Omnicam), and 10 stereolithographic apparatus (SLA) models and 10 PolyJet models were made. All models were scanned with an extraoral scanner. Three‐dimensional analysis software was used to measure differences between the 3D scanned images in root mean square values. The ISO‐5725‐1 specification was followed to measure trueness and precision between two 3D scanned data. Trueness was calculated by overlapping scanned data with the reference model and precision by performing pairwise intragroup comparisons. Also the ratio of region out of tolerance (> ±50 μm) was measured. One‐way ANOVA and Tukey's post hoc analysis were applied. Results There was no statistically significant difference in trueness between the stone and the SLA models (p > 0.05). Dental replica models using photopolymer materials showed statistically significantly better precision than that of the stone model (p 0.05). Conclusions Although the dental replica models using photopolymer materials did not show better trueness than the conventional stone models, there was no significant difference between the SLA and the stone models. Concerning precision, dental replica models using photopolymer materials presented better results than that of the conventional stone models. In sum, dental replica models using photopolymer materials showed sufficient accuracy for clinical use.

The purpose of this study was to evaluate the marginal and internal gap of Cobalt (Co)-Chromium (Cr) sintering metal coping fabricated by dental computer-aided design/computer-aided manufacturing systems. Abutment tooth 46 of universal numbering system was selected for the study. Twenty Co-Cr metal copings of two groups were manufactured and scanned. Co-Cr cast metal copings (CCM) group of ten were fabricated using investment, burnout and casing after subtractive manufacturing of wax block. Also, Co-Cr sintering metal copings (CSM) group of ten were fabricated using sintering processing after subtractive manufacturing of Co-Cr soft metal bock. Marginal and internal gap of Co-Cr metal copings of twenty were measured by digital microscope () with silicone replica technique. The data was analyzed from IBM SPSS Statistics ver. 22.0 Statistical software for Mann-Whitney U test (). deviation of marginal gap of CCM group was of CSM group was . However, two groups was statistically not different (p>0.05). This study showed that CSM group was clinically acceptable adaptation.

Digital scanning is increasingly used in prosthodontics. Three-dimensional (3D) evaluations that compare the repeatability of the blue-light scanner with that of the white-light scanner are required.The purpose of this in vitro study was to evaluate the repeatability of conventional impressions of abutment teeth digitized with white- and blue-light scanners and compare the findings for different types of abutment teeth.Impressions of the canine, premolar, and molar abutment teeth were made and repeatedly scanned with each scanner type to obtain 5 sets of 3D data for each tooth. Point clouds were compared, and error sizes per tooth and scanner type were measured (n=10). One-way ANOVA with Tukey honest significant differences multiple comparison and independent t tests were performed to evaluate repeatability (α=.05).Repeatability (mean ±SD) of the white- and blue-light scanners for canine, premolar, and molar teeth was statistically significant (means: P=.001, P.001, P.001; ±SD: P.001, P.001, P=.003). Means of discrepancies with the white-light scanner (P.001) were 5.8 μm for the canine, 5.9 μm for the premolar, and 8.6 μm for the molar teeth and 4.4 μm, 2.9 μm, and 3.2 μm, respectively, with the blue-light scanner (P.001). Corresponding SDs of discrepancies with the white-light scanner (P.001) were 15.9 μm for the canine, 23.2 μm for the premolar, and 14.6 μm for the molar teeth and 9.8 μm, 10.6 μm, and 11.2 μm, respectively, with the blue-light scanner (P=.73).On evaluation of the digitized abutment tooth impressions, the blue-light scanner exhibited greater repeatability than the white-light scanner.

Purpose: The aim of this study was to evaluate the marginal and internal gap of wax copings fabricated from extraoral scanning with intraoral scanning. Methods: Fifteen study models(abutment of teeth 16) were made by PMMA. STL files of thirty abutment were prepared by intraoral scanning with extraoral scanning. Wax copings of thirty fabricated using CAD/CAM system. Marginal and internal gap of wax copings of thirty were measured by silicone replica technique and digital microscope( 140). Date were analyzed by using independent samples t-test. Results: Mean (SD) of two group were measured 55.61(27.42) for totally gap of ES group and 60.67 (33.14) for totally gap of IS group. But marginal and internal gap of two group were not differences statistically significant(p>0.05). Conclusion: Evaluation of marginal and internal gap of two group showed that no differences statistically significant and clinically acceptable results.

The purpose of this study was to evaluate the marginal and internal gap of metal coping fabricated using additive manufacturing (AM) group and subtractive manufacturing (SM) group by dental computer-aided design (CAD)/computer-aided manufacturing (CAM) systems. Twenty same cases of stone models of abutment teeth 16 by the universal numbering system were manufactured and scanned. Ten metal copings of control group were fabricated using SM and ten metal coping of experimental group were fabricated using AM. Marginal and internal gap of copings were measured using the silicone replica technique and digital microscope (). The data were analyzed using IBM SPSS 21.0 Statistical Software for independent samples t-test (${\alpha}

The purpose of this study was to evaluate the digitization of alginate impressions by analyzing differences between the scan data of two types of impressions (alginate and rubber) taken from the master die and the scan data for the master die. The master die and impressions were digitized using a dental laser scanner (7 series, Dental Wings, Montreal, Canada). The crown portion of the abutment teeth in the digital data of 20 impressions was divided into three regions: cervical surface, middle surface, and occlusal surface. An independent t-test showed a significant difference (p

In this study, we evaluated the repeatability of scans of stone models and impressions of abutment teeth using a blue LED scanner and compared the findings between different abutment teeth types. For the stone models as well as impression of the canines, premolars, and molars, we generated 10 color-difference-maps and reports for each tooth type (n=10 per tooth type). One-way analysis of variance (ANOVA) and independent t-tests were performed to evaluate the repeatability of scans of the stone models and impressions obtained from a blue LED scanner. Our results indicate a high repeatability of scans of stone models and impressions of abutment teeth using the blue LED scanner and suggest a possible clinical advantage for scanning impressions of different abutment teeth types.

One of the most important factors in determining the clinical outcomes of fixed dental prostheses is the gap between the fixed dental prosthesis and the abutment. However, reports that investigated these gaps in the context of fixed dental prostheses fabricated with new technologies are few.The purpose of this study was to measure and analyze the fit of fixed dental prostheses. The fixed dental prostheses for the study were produced with the subtractive method (milling soft metal blocks), additive method (selective laser sintering), and traditional method (lost wax and casting).Ten specimens were fabricated with the soft metal block, selective laser sintering, and lost wax and casting methods. The 3-dimensional measurement method was adopted to obtain the measure gap figures of the specimens. To fabricate a digital replica, computer-aided design reference casts were prepared by scanning the study casts, and silicone replicas were fabricated for each specimen. These silicone replicas were scanned and obtained 40,000 point cloud data. The study also defined the mean gap for each specimen by averaging approximately 40,000 gap points to evaluate the fit of the specimens. Data were analyzed with 1-way ANOVA and the Tukey honestly significant difference (α=.05).The mean gap was the smallest for fixed dental prostheses fabricated with the soft metal block, followed by the selective laser sintering, then the lost wax and casting. One-way ANOVA revealed statistically significant differences in the size of the gap among the 3 groups (P.001), and the Tukey honestly significant difference test confirmed the specific differences among the groups (P.05).The fit obtained with the new soft metal block and selective laser sintering techniques was better than that obtained with the traditional lost wax and casting method. Thus, fixed dental prostheses produced by using these new techniques can be considered clinically acceptable.

PURPOSE. This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types. MATERIALS AND METHODS. To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10°–20° and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal–Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann–Whitney U test with Bonferroni correction (α=.05). RESULTS. Precision discrepancies for the canine, premolar, and molar were 3.7 µm, 3.2 µm, and 7.3 µm, respectively, indicating the poorest precision for the molar (P

This study aimed to evaluate and compare the accuracy.A reference model was prepared with three prepared teeth for three types of restorations: single crown, 3-unit bridge, and inlay. Stone models were fabricated from conventional impressions. Digital impressions of the reference model were created using an intraoral scanner (digital models). Physical models were fabricated using a three-dimensional (3D) printer. Reference, stone, and 3D printed models were subsequently scanned using an industrial optical scanner; files were exported in a stereolithography file format. All datasets were superimposed using 3D analysis software to evaluate the accuracy of the complete arch and trueness of the preparations. One-way and two-way analyses of variance (ANOVA) were performed to compare the accuracy among the three model groups and evaluate the trueness among the three types of preparation.For the complete arch, significant intergroup differences in precision were observed for the three groups (p.001). However, no significant difference in trueness was found between the stone and digital models (p.05). 3D printed models had the poorest accuracy. A two-way ANOVA revealed significant differences in trueness among the model groups (p.001) and types of preparation (p.001).Digital models had smaller root mean square values of trueness of the complete arch and preparations than stone models. However, the accuracy of the complete arch and trueness of the preparations of 3D printed models were inferior to those of the other groups.

The objective of the present study was to compare and evaluate the accuracy of three-dimensional (3D) image data acquired from cone beam computed tomography (CBCT) and a dental scanner using 3D software.After selecting the full-arch forms of the maxilla and mandible as the master cast, the master cast was scanned via a high-precision optical scanner for use as master model data. The model was scanned 12 times each using CBCT and a dental scanner. Scanned data were superimposed onto the master cast data for evaluation of accuracy and repeatability.Although significant differences in both accuracy and repeatability were seen between CBCT and dental scanner (P0.05), repeatability of the maxillary arch showed little difference, with CBCT and scanner having values of 17 ± 2 µm and 22 ± 5 µm, respectively. Meanwhile, repeatability of the mandibular arch with CBCT and scanner was 15 ± 0 µm and 19 ± 3 µm, respectively. Since good repeatability was shown, this demonstrated that data can be stably acquired.The present study demonstrated the feasibility of using a dental scanner to create a digital model as a substitute for a plaster model for use in orthodontic diagnosis and device fabrication.

Purpose: The aim of this study was analyzed by comparing the effect of glass fiber reinforcement addition on the strength of resin denture base. It was intended to provide a reference data useful for clinical application. Methods: The test specimens (length 64.0 0.1 , width 10.0 0.1 , thickness 1.0 0.1 , 1.5 0.1 , and 2.0 0.1 respectively) were made. In the experimental groups resin denture base reinforced with glass fiber were fabricated. In the control groups resin denture base were fabricated by conventional method. After specimen fabrication was completed, transverse test was performed using a universal testing machine. Results: The transverse strength value in CON group was 83.08 9.07 for 1.0 mm, which ranked the highest in value. On the other hand, the value was 56.07 5.15 for 2.0 , which ranked the lowest in value. And CON+SES group was 119.80 30.70 for 1.0 , which ranked the highest in value. On the other hand, the value was 84.00 7.97 for 2.0 , which ranked the lowest in value. Also, the flexural modulus value in CON group was 2,983.10 506.92 for 1.0 , which ranked the highest in value. On the other hand, the value was 1,257.64 230.48 for 2.0 , which ranked the lowest in value. And CON+SES group was 4,679.41 1578.29 for 1.0 , which ranked the highest in value. On the other hand, the value was 2,512.36 527.09 for 2.0 , which ranked the lowest in value. Conclusion: The reinforced glass fiber increased the strength of resin denture base, effected to reduce the thickness of resin denture base. [Abstract]

Purpose: The purpose of this study is to investigate the improvement measure of dental technician practical examination. Methods: A survey was performed on 111 dental technicians who were self-written questionnaire. The results were analyzed by SPSS 12.0. The collected data was analyzed by frequency and chi-square test. Results: Questions most necessary work tools with the articulator was the highest with 55.9%, Electric wax carver(16.2%), heating clear(14.4%), CAD/CAM program(9.0%) was in the order. The need for additional practical test in response to actions included maxillary and mandibular comments occlusal work that you have to wax up the highest rate of 63.8%. Items most in need of improvement was strengthen of clinically oriented(48.0%), separation of written and practical(14.6%), control the degree of difficulty(11.4%) were the next order. Conclusion: Based on the results of this study, the current dental technician did not show major problems in the practical test. However, clinicians should be strengthened mainly. To do this, the use of the articulator is essential.

PURPOSE. This study aimed to investigate the potential clinical application of digitized silicone rubber impressions by comparing the accuracy of zirconia 3-unit fixed partial dentures (FPDs) fabricated from 2 types of data (working model and impression) obtained from a laser scanner. MATERIALS AND METHODS. Ten working models and impressions were prepared with epoxy resin and vinyl polysiloxane, respectively. Based on the data obtained from the laser scanner (D-700; 3Shape A/S, Copenhagen, Denmark), a total of 20 zirconia frameworks were prepared using a dental CAD/CAM system (DentalDesigner; 3shape A/S, Copenhagen, Denmark / Ener-mill, Dentaim, Seoul, Korea). The silicone replicas were sectioned into four pieces to evaluate the framework fit. The replicas were imaged using a digital microscope, and the fit of the reference points (P1, P2, P3, P4, P5, P6, and P7) were measured using the program in the device. Measured discrepancies were divided into 5 categories of gaps (MG, CG, AWG, AOTG, OG). Data were analyzed with Student’s t-test (α=0.05), repeated measures ANOVA and twoway ANOVA (α=0.05). RESULTS. The mean gap of the zirconia framework prepared from the working models presented a narrower discrepancy than the frameworks fabricated from the impression bodies. The mean of the total gap in premolars (P=.003) and molars (P=.002) exhibited a statistical difference between two groups. CONCLUSION. The mean gap dimensions of each category showed statistically significant difference. Nonetheless, the digitized impression bodies obtained with a laser scanner were applicable to clinical settings, considering the clinically acceptable marginal fit (120 μm). [J Adv Prosthodont 2014;6:22-9]

The purpose of this study was to investigate, by measuring the gap, the possible clinical use of three-unit fixed dental prostheses (FDPs) manufactured using stereolithography. A total of 20 epoxy models were built with a same case (abutment teeth 14, 16). The 40 specimens were produced using the stereolithography (SLA) and wax-up (LW). The 960 gaps of the 40 specimens produced were measured by a silicone replica. The Wilcoxon rank sum test was then used to compare and analyze the data obtained from the two groups (α=0.05). The total gap, as measured from the SLA and LW groups, was 98.6 and 66.6 µm, respectively. The results indicate that the gap in the SLA group is statistically significantly greater than that in the LW group (p

PURPOSE. The aim of this study was to evaluate the repeatability of the digitizing of silicon rubber impressions of abutment teeth by using a white light scanner and compare differences in repeatability between different abutment teeth types. MATERIALS AND METHODS. Silicon rubber impressions of a canine, premolar, and molar tooth were each digitized 8 times using a white light scanner, and 3D surface models were created using the point clouds. The size of any discrepancy between each model and the corresponding reference tooth were measured, and the distribution of these values was analyzed by an inspection software (PowerInspect 2012, Delcamplc., Birmingham, UK). Absolute values of discrepancies were analyzed by the Kruskal–Wallis test and multiple comparisons (α=.05). RESULTS. The discrepancy between the impressions for the canine, premolar, and molar teeth were 6.3 μm (95% confidence interval [CI], 5.4-7.2), 6.4 μm (95% CI, 5.3-7.6), and 8.9 μm (95% CI, 8.2-9.5), respectively. The discrepancy of the molar tooth impression was significantly higher than that of other tooth types. The largest variation (as mean [SD]) in discrepancies was seen in the premolar tooth impression scans: 26.7 μm (95% CI, 19.7-33.8); followed by canine and molar teeth impressions, 16.3 μm (95% CI, 15.317.3), and 14.0 μm (95% CI, 12.3-15.7), respectively. CONCLUSION. The repeatability of the digitizing abutment teeth’s silicon rubber impressions by using a white light scanner was improved compared to that with a laser scanner, showing only a low mean discrepancy between 6.3 μm and 8.9 μm, which was in an clinically acceptable range. Premolar impression with a long and narrow shape showed a significantly larger discrepancy than canine and molar impressions. Further work is needed to increase the digitizing performance of the white light scanner for deep and slender impressions. [J Adv Prosthodont 2013;5:452-6]

Purpose: In this study, in order to provide objective standard of the mixed concentration of the zirconia coloringliquids, compare the shade differences after colored zirconia blocks from different concentrations. Methods: After immersion for 2 minutes zirconia specimen (1.5 1.5 0.6 0.01 ) in coloring-liquids that produced different concentrations, were sintered in furnace dedicated. Then, it was measured in spectrophotometer and Shadepilot. It has been determined mean and standard deviation of the color difference for each group, and verified by one-way ANOVA using the (version12.0) SPSS WIN Program the difference in shade according to the concentration at the significance level of 95% confidence, it conducted a Tukey’s multiple range test to post-test. Results: The mean of L was decreased toward LN35 group, however the mean of a and b was increased(p

여러가지원인으로인하여결손된치아및치아주위조직의기능회복을위하여대체수복물이다양한재료로제작되고있다. 기존의금속도재관으로제작된보철물의사용은충분한강도와변연적합성을가져기능적인면에서환자나의사에게적절한보철재료로여겨져왔으나(MaLean, 1983), 단점으로치경부위의잇몸색의변색등심미적인면에서취약점이있어최근그대안으로지르코니아를사용한전부도재관의적용이빠른속도로확대되고있다(Belles DM, 1991). 그결과현재상실된치아의기능회복과더불어심미성을더중요시하는환자가늘면서전치부수복물의코아재료로금속을대체하여지르코니아재료가널리사용되고있다. 지르코니아는높은기계적인물성을보이기때문에최근부하를많이받는구치부에도그사용이확대되고있는추세이다(Suarez etal, 2004).지르코니아를이용한전부도재관은구조에따라크게코어와상부도재로이루어지는이중구조전부도재관과단일구조로이루어진단일구조전부도재관으로나눌수있다. 이중구조전부도재관은상부도재축성을위해추가적인소성을필요로하며심미성이뛰어나지만, 상부도재의파절강도가약하고지대치의삭제량이많다는단점이있다(정희찬, 2006). 또한, 지르코니아코어는금속에비해심미적이지만불투명한백색이므로자연치의심미성을구현하는데한계가있다. 따라서지르코니아를절삭한후코어를용액에담궈색을부여하는침전법(dippingmethod)을사용하여색을보완하거나처음부터색조가가미된유색지르코니아를사용하기도한다(Shah K etal, 2008). 코어를제작할때사용하는침전법은예비소결된지르코니아를담구는착색용액(colour liquid)의농도및시간을변화시킴으로써원하는색조를얻는다(Ocana M et al, 1998). 단일구조로이루어진단일구조전부도재관은기존의제작법과는달리한번의CAD/CAM 작업으로제작된다(Bindl A et al, 2006). 전자에비해제작시간이단축되고최소한의삭제량으로충분한강도를얻을수있는장점이있으나상부도재가생략되어심미성구현에한계가있으므로구치부의수복에주로사용된다. 단일구조전부도재관의색조를부여하기위하여일반적으로도포법(coating method)을사용하는데제조사의지시에따라해당하는착색용액에붓을담근후반소결된지르코니아표면에칠하여색조의종류및칠하는횟수로적정량을침투시켜색조를재현한다. 도포한후에소결과정을거쳐이를통하여자연치와유사한색을재현한다. 이중구조전부도재관에주로이용되는색조의침전법이용과관련하여많은연구가이루어진바있다. 백기현등(2008)은지르코니아코어의색조부여가이중구조전부도재관의색조의영향에대하여연구하였고, 최성민과남상용(2011)은지르코니아의색조침전에따른착색시간은색조에영향을미친다고하였다. 염미옥등(2011)은지르코니아최종색조가전부도재관제작방법에따라영향을미친다고하였고, 허성윤등(2012)은지르코니아코어두께에따라전부도재관의축성방법이색조에미치는영향을미친다고하였다. 이와같이core와veneer의색과두께, 그리고제작방법이색조에영향을미친다는연구가보고되고있다. 반면지르코니아단일구조전부도재관의경우, 강도(Guazzato M et al, 2003; Preis V etal, 2012)나투명도(Beuer F et al, 2011)에관한연구가일부보고되고있으나착색용액에붓을이용하여도포횟수를달리한도포법의색조재현성에관한연구는현재까지거의없는실정이다. 그러므로단일구조전부도재관의색조처리에관한기존연구가거의없어제조사의지시에따른방법이실제색조를제대로구현해내는지에관한실증적평가가이루어지지않았고실제임상에서도제조사의지시에따라적용한결과가기대하는색조에맞지않아치과기공사가임의로조절하여사용하는등혼란스러운상황이므로도포법의색조재현성에관한실증연구검증이필요하다고여겨진다.따라서본연구에서는단일구조전부도재관의색조를재현시사용되는도포법의색조재현성을알아보고자일반적으로많이사용되고있는침전법과비교하여색조재현정도를비교분석하고자한다.186

Purpose: The purpose of this study was to evaluate the repeatability of dental white light scanner. Methods: The impression(Zerosil, Dreve, Germany) were digitized in white light scanner(Identica, Medit, Korea) to create 3-dimensional surface-models. The distribution of the discrepancies between the number of points in the corresponding CRM models and the point clouds in the others were measured by a matching-software(PowerInspect 2012, Delcam Plc, UK). The discriptive statistics were used for statistical analysis(SPSS 20.0). Results: The measurement of repeatablity showed very good reliability. The mean(SD) discrepancy value on the white light scanner digital models was 8.7(0.67) , based on SD and absolute mean values. Conclusion: These in vitro studies showed that repeatability of dental white light scanner is high reliability. These results can be confirmed in further clinical studies.

Purpose: The aim of this study measured and compared the marginal and internal fit of metal cores with two basemetal alloy (Ni-Cr alloy(non-beryllium), Co-Cr alloy).Methods: Maxillary right first molar abutment fabricated by titanium was prepared for this study.Impressions(10ea) were made from titanium model, and study models were poured with improved dental stone.Wax cores of twenty were prepared for burn-out and casting. Ten wax cores cast Ni-Cr alloy(non-Be), and finallyten cast Co-Cr alloy. Marginal and internal fit of cores was evaluated using silicone replica technique and digitalmicroscope(x160). The data were statistically analyzed with the independent samples