• The Journal of Korean Academy of Prosthodontics
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• v.43 no.5
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• pp.611-621
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• 2005

State of problem: Zirconia all-ceramic restoration fabricated with CAM system is on an increasing trend in dentistry. However, evaluation of the marginal and internal fits of zirconia bridge seldomly have been reported. Purpose: This study was to evaluate the at of margin and internal surface in posterior 3-unit zirconia bridge framework fabricated with CAM system(DeguDent, Germany). Material and Method: Preparations of secondary premolar and secondary molar on artificial resin model were performed for fabrication of 3-unit posterior bridge framework. Fits of 5 zirconia bridge framework were compared with 5 precious ceramo-metal alloy framework(V-GnathosPlus, Metalor, Switzerland), and prepared margins were designed to chamfer and shoulder finishing line. Each framework was cemented to epoxy resin model with reinforced glass ionomer(FujiCEM, GC Co., Japan), embedded in acrylic resin and sectioned in two planes, mesio-distal and buccolingual. Samples were divided into six pieces by sectioning and had two pieces of each surface(i.e mesial, distal, buccal and lingual surface) per abutment, so there were eight measuring points in each abutment. External gap was measured at the margin and internal gaps were measured at the margin, axial and occlusal surface. Gaps were observed under the measuring microscope(Compact measuring microscope STM5; Olympus, Japan) at a magnification of $\times100$. T-test were used to determine the statistic significance of the different gaps between zirconia and metal framework. Results and Conclusion: 1. External and internal marginal gaps of zirconia and metal framework were in clinically acceptable range. External marginal gaps were not different significantly between zirconia$(81.9{\mu}m)$ and metal $(81.3{\mu}m)$ framework and internal marginal gaps of zirconia $(44.6{\mu}m)$ were smaller than those of metal framework $(58.6{\mu}m)$. 2. Internal axial gaps of zirconia framework$(96.7{\mu}m)$ were larger than those of metal frame-work$(78.1{\mu}m)$ significantly and adversely, internal occlusal gaps of zirconia frame-work$(89.4{\mu}m)$ were smaller than those of metal framework $(104.9{\mu}m)$ significantly. 3. There were no significant differences in external and internal marginal gaps between chamfer and shoulder finish line when zirconia frameworks were fabricated.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.6
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• pp.707-716
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• 2005

Statement of problem. Collarless metal ceramic fixed partial dentures(FPDs) had an esthetic problem such as opaque reflection in cervical region. To overcome this, modified coping which removed its facial cervical metal could be used. The marginal quality could be worsen according to the amount of its facial metal reduction. Purpose. The purpose of this study was to evaluate marginal fits of collarless metal ceramic FPDs with retainers of modified copings. Material and method. Dentoform maxillary left central incisor and right lateral incisor were prepared for 3-unit collarless metal ceramic FPD and fixed in yellow stone. This model was duplicated to PBT resin dies via CAD/CAM and injection molding. Four different facial margin design groups were investigated. Group A was a coping with a thin facial metal collar, group B was a collarless coping with its facial metal to the shoulder, group C was a collarless coping with its facial metal 1 mm short of the shoulder, and group D was a collarless coping with its facial metal 2 mm short of the shoulder. Seven collarless metal ceramic FPDs per group were fabricated. They were cemented to PBT resin dies with resin cement. After removal of pontics, each retainers were separated and observed under Accura 2000 optical microscope. Then, retainers were embeded in orthodontic resin and cross sectioned faciopalatally. Internal marginal fits of midfacial porcelain margins were observed under FE-SEM. Result and conclusion. Within the limitations of this in vitro study. The following conclusions were drawn. 1. Mean marginal gaps of collarless FPDs were in the $50-60{\mu}m$ range. 2. In midfacial margin, marginal discrepancies were greater in group A than in the experimental groups(p<0.05). 3. In midpalatal margin, marginal gaps were greater in group C and D than in group A and B(p<0.05). 4. Marginal fits of porcelain margins were better than those of metal margins in collarless metal ceramic FPDs. 5. In both teeth, internal marginal gaps of group C and D were greater than those of group A and B(p<0.05).

• Journal of Technologic Dentistry
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• v.41 no.2
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• pp.63-69
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• 2019

Purpose: The purpose of this study is to evaluate the effect of CAD/CAM system milling tool wear on the marginal and internal fit of PMMA implant interim prosthesis three-dimensional manner. Methods: A total of 20 crowns were fabricated with CAD/CAM method. Their designs were unified to first molar of the left maxilla. The Customized abutments were prepared and scanned with on optical model scanner. Five crowns were milled by the newly replaced tool (1st milling), and 15 crowns were milled by 2nd, 3rd, 4th milling tool. The marginal and internal fit of 20 interim crowns were measured using the triple-scan protocol. Results: Statistically significant difference was found between the $1^{st}$ milling group ($51.8{\pm}14.6{\mu}m$) and the $3^{rd}$, $4^{th}$ milling group ($128.6{\pm}43.8{\mu}m$, $146.2{\pm}38.1{\mu}m$, respectively) at the distal margins. In the mesial margins, There was a statistically significant difference between the $1^{st}$ milling group ($63.6{\pm}25.9{\mu}m$) and the $3^{rd}$, $4^{th}$ milling group ($137.2{\pm}25.9{\mu}m$, $186.8{\pm}70.6{\mu}m$, respectively). In the distal line angle, significant difference was found between the $1^{st}$, $2^{nd}$, $3^{rd}$ milling groups and the $4^{th}$ milling group. In the mesial axial wall, significant difference was found between the $1^{st}$ milling group ($52.2{\pm}20.3{\mu}m$) and the $3^{rd}$, $4^{th}$ milling groups ($22.8{\pm}8.8{\mu}m$, $7.8{\pm}5.7{\mu}m$). Conclusion: As a result of the experiment, decrease of the marginal and internal fit was statistically significant as the number of machining cycles increased. In order to produce clinically excellent restorations, it is recommandable to consider the condition of the milling tool wear, when designing the restoration with CAD program.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.4
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• pp.366-376
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• 2013

The purpose of this study is to evaluate the marginal and internal fit of coping made by CAD/CAM using different scanning methods. Zirconia coping was made by each CAD/CAM system followed by intra-oral scanning, model optical scanning and model contact scanning. It was embedded into Epoxy Resin and was cut by buccal to lingual. AMD (Absolute marginal discrepancy), MG (Marginal gap), GA (Gap of axial), GL (Gap of line angle) and GO (Gap of occlusal) of each sample were measured. The result is as followed; 1. The mean value of AMD in Group 1, Group 2, Group 3 are $141.21{\pm}42.94{\mu}m$, $140.63{\pm}31.64{\mu}m$, $109.37{\pm}28.42{\mu}m$. The averages of MG in Group 1, Group 2, Group 3 are $82.52{\pm}43.99{\mu}m$, $90.28{\pm}27.93{\mu}m$, $66.55{\pm}28.77{\mu}m$. Statistically there is no difference in AMD and MG among the three Groups (Anova, P>0.05). 2. GA of Group 2 revealed statistically difference compared with Group 1 and Group 3 (Anova, P<0.05). 3. GL and GO of Group 1 showed statistically significant differences compared with Group 2 and Group 3 (Mann-whitney test (P<0.05). Zirconia copings made by 3 ways of scanning methods have no difference with conventional ceramics in AMD and MG which are known as the most important factors.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.2
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• pp.135-143
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• 2017

Purpose: This research was conducted to compare the marginal and internal fit of zirconia prostheses fabricated with the model scan method and the intraoral scan method. Materials and methods: In this study, 20 extracted human mandibular first molar was used in the preparation of abutment tooth for the fabrication of zirconia prostheses. In the first group, the model scan method was applied on 10 prepared teeth. In the other group, the intraoral scan method was used on other 10 prepared teeth. Datum of both groups were transmitted to the software system. Afterwards, 20 zirconia prostheses were fabricated using the Ceramill system. Weight technique was used to evaluate the internal gap of the zirconia prostheses. In the Replica technique, marginal gap of the zirconia prostheses were analyzed by optical microscopy. Statistical analysis was based on one-way ANOVA. Results: Model scan group showed lower average weight than intraoral scan group when weight technique was applied, which has significance (P < .05). Also, model scan group showed significantly lower figures in all 5 measurements of replica technique than intraoral scan group (P < .05). Conclusion: Zirconia prostheses of both groups demonstrated clinically acceptable margin and internal fit. However, model scanned zirconia prostheses showed higher marginal and internal fit than intraoral scanned crowns.

• The Journal of Korean Academy of Prosthodontics
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• v.54 no.2
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• pp.93-102
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• 2016

Purpose: The aim of this study was to evaluate the fit accuracy of two zirconia and titanium abutments in internal hexagonal implants. Materials and methods: One titanium abutment and two zirconia abutments were tested in internal hexagonal implants (TSV, Zimmer). Prefabricated zirconia abutments (ZirAce, Acucera) and customized zirconia abutments milled by the Zirkonzahn system (Zirkonzahn Max, Zirkonzahn) were selected and prefabricated titanium abutments (Hex-Lock, Zimmer) were used as a control. Eight abutments per group were connected to implants with 30 Ncm torque. The marginal gaps at abutment-implant interface, the internal gaps at internal hex, vertical and horizontal gaps between screws and screw seats in abutments were measured after sectioning the embedded specimens using a scanning electron microscope. Data analysis included one-way analysis of variance and the Scheffe test (n=16, ${\alpha}=0.05$). Results: The mean marginal gap of customized zirconia abutment was higher than those of two prefabricated zirconia and titanium abutments. The internal gaps at internal hex showed no significant differences between customized and prefabricated abutments and were higher than those of prefabricated titanium abutments. The mean vertical and horizontal gaps at screw in prefabricated zirconia abutment were higher than those of prefabricated titanium abutment. In the case of customized zirconia abutment, the mean horizontal gap at screw was higher than those of both the prefabricated zirconia and the titanium abutment but the mean vertical gap was not even measureable. The screw seats were clearly formed but did not match with abutment screws in prefabricated zirconia abutments. They were not, however, precisely formed in the case of customized zirconia abutments. Conclusion: Within the limitations of this study, the prefabricated titanium abutments showed better fit than the zirconia abutments, regardless of customized or prefabricated. Also, the customized zirconia abutments showed significantly higher marginal gaps and the fit was less accurate between screws and screw seats than the prefabricated abutments, titanium and zirconia.

• Journal of Technologic Dentistry
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• v.36 no.2
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• pp.75-81
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• 2014

Purpose: This study was to compare adaptations of lithium disilicate CAD/CAM crowns fabricated with different scanning systems. Methods: This study selected the mandibular right first molar as an abutment for experiments and produced 10 working models. Lithium disilicate crowns appropriate for each abutment were produced by using a CEREC$^{(R)}$ CAD/CAM system. The independent t-test was then used to compare and analyze the data obtained from the two groups(${\alpha}$=0.05). Results: Mean(SD) adaptation were $86.93(22.82){\mu}m$ for the InS group, $88.42(26.77){\mu}m$ for the ExS group. They were no statistically significant differences between groups for adaptation(p>0.05). Conclusion: Within the limitations of this study, the results suggest that the accuracy of all investigated optical scanner were satisfactory for clinical use. Further assessment and improvement of the lithium disilicate ceramic for the fabrication of FPDs is evidently still required.

• Journal of Korean Dental Hygiene Science
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• v.5 no.1
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• pp.13-19
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• 2022

Background: In this study, zirconia copings were fabricated by setting clinically acceptable inner values for prostheses using computer-aided design/computer-aided manufacturing (CAD/CAM). The processed copings were evaluated for the marginal and internal fit of each abutment shape with a CAD program using the silicone replica technique. Methods A total of 20 copings was produced by selecting models commonly used in clinical practice. After injecting the sample, the minimum thickness, internal adhesion interval, and distance to the margin line were set to 0.5, 0.05, and 1.00 mm using a dental CAD program, respectively. It was measured using a 2D section function in a three-way program of the silicon replication technology. Although the positions and number of measurements of the anterior and posterior regions differed, nine parts of each pre-tube were designated and measured by referring to a previous study to compare the two samples. Results As a result, the average margin of the mesial, distal, and buccal (labial) surfaces was 59.90 ㎛ in the anterior region and 60.40 ㎛ in the posterior region. The mean axial wall margin was 67.25 ㎛ in the anterior region and 69.25 ㎛ in the posterior region. In occlusion, the anterior teeth (77.70 ㎛), posterior teeth (77.60 ㎛), and both anterior and posterior regions were within the clinically acceptable range. Conclusion The edge and inner fit of zirconia coping manufactured using the CAD/CAM system showed clinically applicable results. To reduce errors and increase accuracy, materials and machine errors that affect the manufacture of prosthetics should be investigated. Based on our results, the completeness of prosthetics could increase if the inner value and characteristics of the material are adjusted when applied in clinical practice.

• The Journal of Advanced Prosthodontics
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• v.7 no.2
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• pp.122-128
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• 2015

PURPOSE. To assess the marginal and internal gaps of the copings fabricated by computer-aided milling and direct metal laser sintering (DMLS) systems in comparison to casting method. MATERIALS AND METHODS. Ten metal copings were fabricated by casting, computer-aided milling, and DMLS. Seven mesiodistal and labiolingual positions were then measured, and each of these were divided into the categories; marginal gap (MG), cervical gap (CG), axial wall at internal gap (AG), and incisal edge at internal gap (IG). Evaluation was performed by a silicone replica technique. A digital microscope was used for measurement of silicone layer. Statistical analyses included one-way and repeated measure ANOVA to test the difference between the fabrication methods and categories of measured points (${\alpha}$=.05), respectively. RESULTS. The mean gap differed significantly with fabrication methods (P<.001). Casting produced the narrowest gap in each of the four measured positions, whereas CG, AG, and IG proved narrower in computer-aided milling than in DMLS. Thus, with the exception of MG, all positions exhibited a significant difference between computer-aided milling and DMLS (P<.05). CONCLUSION. Although the gap was found to vary with fabrication methods, the marginal and internal gaps of the copings fabricated by computer-aided milling and DMLS fell within the range of clinical acceptance (< $120{\mu}m$). However, the statistically significant difference to conventional casting indicates that the gaps in computer-aided milling and DMLS fabricated restorations still need to be further reduced.

• The Journal of Advanced Prosthodontics
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• v.9 no.6
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• pp.463-469
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• 2017

PURPOSE. To evaluate the fit of a three-unit metal framework of fixed dental prostheses made by subtractive and additive manufacturing. MATERIALS AND METHODS. One master model of metal was fabricated. Twenty silicone impressions were made on the master die, working die of 10 poured with Type 4 stone, and working die of 10 made of scannable stone. Ten three-unit wax frameworks were fabricated by wax-up from Type IV working die. Stereolithography files of 10 three-unit frameworks were obtained using a model scanner and three-dimensional design software on a scannable working die. The three-unit wax framework was fabricated using subtractive manufacturing (SM) by applying the prepared stereolithography file, and the resin framework was fabricated by additive manufacturing (AM); both used metal alloy castings for metal frameworks. Marginal and internal gap were measured using silicone replica technique and digital microscope. Measurement data were analyzed by Kruskal-Wallis H test and Mann-Whitney U-test (${\alpha}=.05$). RESULTS. The lowest and highest gaps between premolar and molar margins were in the SM group and the AM group, respectively. There was a statistically significant difference in the marginal gap among the 3 groups (P<.001). In the marginal area where pontic was present, the largest gap was $149.39{\pm}42.30{\mu}m$ in the AM group, and the lowest gap was $24.40{\pm}11.92{\mu}m$ in the SM group. CONCLUSION. Three-unit metal frameworks made by subtractive manufacturing are clinically applicable. However, additive manufacturing requires more research to be applied clinically.