Mean Marginal Fit Research Articles

Evaluation of the Accuracy of Intraoral Digital Impression Systems and CAD and CAM Workflows for Fabricating Dental Prostheses

ABSTRACT Background: Dental prosthesis manufacturing has undergone a radical change with the introduction of intraoral digital impression technologies and computer-aided design and computer-aided manufacturing (CAD and CAM) processes. Investigations into these systems’ accuracy in creating dental restorations that adhere to clinical standards are still underway. Materials and Methods: For this investigation, a total of 60 patients in need of single-unit crowns were chosen. They were divided into three groups of 20: Group A used intraoral digital impression systems, Group B used conventional impression procedures, and Group C combined digital impressions with CAD and CAM processes. The marginal fit and internal fit of the crowns were compared to assess the correctness of the dental prosthesis. A stereomicroscope was used to evaluate the marginal fit, and micro-CT imaging was employed to analyze the interior fit. ANOVA and Tukey’s post hoc test were used to examine the data, with a significance threshold of P < 0.05. Results: The mean marginal fit was 120 ± 15 μm for Group A, 80 ± 10 μm for Group B, and 75 ± 8 μm for Group C, according to the data. The internal fit values were 150 ± 20 μm for Group A, 90 ± 12 μm for Group B, and 85 ± 10 μm for Group C. According to statistical analysis, Group B and Group C outperformed Group A in terms of accuracy in both internal and marginal fits (P < 0.01). There was no discernible difference between Group B and Group C. Conclusion: When constructing dental prostheses, intraoral digital impression technologies and CAD and CAM workflows show better accuracy over conventional impression techniques. The greatest clinical results are obtained when digital impressions and CAD and CAM workflows are combined, indicating that these technologies need to be accepted as routine procedures in prosthetic dentistry.

Comparative Evaluation of the Marginal Fit and Internal Adaptation of Polymethyl Methacrylate Interim Crowns Fabricated using two different techniques- “Conventional” and “CAD-CAM Milling”: An In Vitro Study

Introduction Interim crowns provide valuable functional and esthetic information of the final outcome during the evaluation period and act as the blueprint for the design of definitive prostheses. The fabrication technique and material used are the key factors involved in the success of the prosthesis. However, marginal fit and internal adaptation of Polymethyl Methacrylate (PMMA) interim crowns fabricated using conventional and computer aided designing-computer aided machining (CAD-CAM) PMMA milling have not been well investigated. The inter-group statistical comparison of means of normally distributed continuous variables is done using independent sample t test. Material and Methods Typodont (Nissin, Japan) of the maxillary central incisor was scanned (Ceramill Map 600+, Amann Girrbach AG) and 3D printed (Form 4, Formlabs) to create the master die used in the study, while a Typodont of a prepared maxillary central incisor was scanned using a digital scanner (Ceramill Map 600+, Amann Girrbach AG) and a .STL file obtained was modified using Exocad software for designing the study models. Three equidistant points A, B and C passing from the center of the incisal edge to the root of the typodont were indented labially and A` B` and C` were indented palatally in the same plane using Exocad software for symmetrical sectioning while checking for marginal fit and internal adaptation. 50 3D printed (Form 4, Formlabs India) models of the prepared tooth were printed and 25 interim crowns were fabricated using Polymethyl Methacrylate (DPI Tooth moulding material, DPI India) by conventional and 25 interim crowns were fabricated using CAD-CAM PMMA (Ceramill a-temp, Amann Girrbach AG). They were then luted (Han Temp Cement eugenol free, NE Korea) to respective models and viewed under a stereomicroscope (Ziess) for marginal fit at 2 specific points and internal adaptation at 4 specific points. Results The mean SD of marginal fit measurements at buccal and site in Group A (conventional technique) and Group B (CAD-CAM milling) was 95.32 ± 7.78 µm and 66.92 ± 14.59 µm respectively. At lingual site in Group A and Group B was 94.84 ± 7.97 µm and 66.80 ± 10.93 µm respectively. The mean marginal fit measurement at lingual site is significantly higher in Group A compared to Group B (P-value%3C0.05). The mean SD of internal fit measurements at upper 1 site in Group A and Group B was 335.19 ± 94.70 µm and 226.76 ± 89.68 µm respectively. At upper 2 site in Group A and Group B was 368.88 ± 120.25 µm and 240.85 ± 93.72 µm respectively. At lower 1 site in Group A and Group B was 313.52 ± 99.92 µm and 262.49 ± 94.33 µm respectively. At lower 2 site in Group A and Group B was 367.93 ± 107.36 µm and 264.52 ± 86.97 µm respectively. The mean internal fit measurement is significantly higher in Group A compared to Group B (P-value%3C0.05). Conclusion The interim crowns fabricated using the conventional technique displayed a less favourable marginal fit and internal adaptation when compared to CAD-CAM fabricated interim crowns. Key Words CAD-CAM, Interim crowns, Marginal fit and internal adaptation

Marginal fit and fracture resistance of polyetheretherketone, zirconia, and titanium implant-supported prosthesis frameworks for a partially edentulous arch after thermomechanical aging

Although polyetheretherketone (PEEK) and zirconia (Zir) have been used as implant-supported prosthesis (ISP) frameworks, the long-term effects of thermomechanical aging on the marginal fit and fracture resistance of PEEK and Zir ISP frameworks with titanium (Ti) bases for patients with a partially edentulous arch are not clear. The purpose of this in vitro study was to determine the marginal fit and fracture resistance of PEEK and Zir ISP frameworks with Ti bases and Ti ISP frameworks for partially edentulous arches after aging. A total of 30 ISP epoxy resin casts were obtained from a typodont with 1 straight implant (Nobel Biocare) in the mandibular right canine region and 1 implant with a 30-degree distal tilt in the mandibular right first molar region. All frameworks (n=10) were fabricated on their own epoxy resin cast with multiunit abutment replicas by using a computer-aided design and computer-aided manufacturing system (exocad-Yenadent). The PEEK and Zir frameworks were fabricated with Ti-bases. Primer (MKZ) and resin cement (DTK adhesive) were used to cement the frameworks to the Ti-bases under a static load of 10N. After thermomechanical aging (1.2×106 cycles, 120N, 5°C-55°C), marginal gaps between the Ti-bases and cemented frameworks and vertical and passive fits between the Ti-bases and framework and multi-unit abutments were measured by using a stereomicroscope (Euromex) at ×100 magnification. Fracture resistances and types were then determined by using a universal test machine and a stereomicroscope at ×40 magnification. Data were analyzed by using 1-way analysis of variance (ANOVA) and the Tukey HSD and Fisher-Freeman-Halton tests (α=.05). The marginal gaps of the PEEK and Zir frameworks were respectively 83.5 ±27.1 and 81.8 ±17.8µm. PEEK (23.7 ±4.6) and Zir (32.9 ±8.7) had a better vertical fit (µm) than Ti (52.5 ±10.6) (P<.001). Zir (49.3 ±16.2) (P<.001) and PEEK (70.9 ±19.6) (P>.05) frameworks had better passive fit (µm) than Ti (91.3 ±24.2). Ti had the highest mean fracture resistance (N) (14800.2 ±3442.3) followed by Zir (7318.7 ±1385.1) and PEEK (3448.9 ±486.6) (P<.001). Fracture types were different in different groups (P<.001). The PEEK and Zir frameworks with Ti baseshad better vertical and passive fit than the Ti frameworks. All ISP frameworks represented mean marginal fit below 92µm and withstood physiologic occlusal forces after thermomechanical aging.

Evaluation of the marginal and internal fit of CAD/CAM crowns designed using three different dental CAD programs: a 3-dimensional digital analysis study.

The purpose of this in vitro study was to assess and compare the marginal and internal fit of machine-milled crowns designed using three different CAD software programs. Digital impressions of the master zirconia casts containing the prepared molar were obtained using an intraoral scanner. The obtained standard tessellation language (STL) files were imported into three CAD software programs (Multi-CAD, Blue-Sky CAD, and InLab), and crown designs were generated. Crown design digital STL files were used to mill crowns with a five-axis dental milling machine. The internal and marginal fits of the fabricated crowns over the master-prepared tooth were assessed using the triple-scan protocol and digital analysis techniques. The 3D marginal and internal fit values of the fabricated crowns from the designs generated by the three CAD programs were evaluated and statistically compared using one-way analysis of variance (ANOVA) and post hoc Tukey's tests (α = 0.05). There were no significant differences in the internal fit of the crowns designed by the three CAD programs (p > 0.05). However, there were significant differences in the mean marginal fit (p = 0.009) of the crowns. The marginal fit values for the InLab-designed crowns were significantly better than those for Multi-CAD (p = 0.03) and Blue-Sky CAD (p = 0.012) groups. All three CAD programs can design clinically acceptable crowns in terms of internal and marginal fit. InLab crowns outperformed the Multi-CAD and Blue-Sky CAD programs in terms of marginal fit. It is critical to test the ability of newly released CAD programs to design acceptable virtual crowns that can be transformed into actual crowns with optimal marginal and internal fit to existing clinical tooth preparations/conditions to ensure the high technical quality and long-term success of fabricated crowns.

Effect of different tooth preparation designs on the marginal and internal fit discrepancies of cobalt-chromium crowns produced by computer-aided designing and selective laser melting processes.

PURPOSETo evaluate the impact of five different tooth preparation designs on the marginal and internal fit discrepancies of cobalt-chromium (CoCr) crowns produced by computer-aided designing (CAD) and selective laser melting (SLM) processes.MATERIALS AND METHODSFive preparation data were constructed, after which design crowns were obtained. Actual crowns were fabricated using an SLM process. After the data of actual crowns were obtained with structural light scanning, intaglio surfaces of the design crown and actual crown were virtually superimposed on the preparation. The fit-discrepancies were displayed with colors, while the root means square was calculated and analyzed with one-way analysis of variance (ANOVA), Tukey’s test or Kruskal-Wallis test (α =.05).RESULTSThe marginal or internal color-coded images in the five design groups were not identical. The shoulder-lip and sharp line angle groups in the CAD or SLM process had larger marginal or internal fit discrepancies compared to other groups (P < .05). In the CAD process, the mean marginal and internal fit discrepancies were 10.0 to 24.2 µm and 29.6 to 31.4 µm, respectively. After the CAD and SLM processes, the mean marginal and internal fit discrepancies were 18.4 to 40.9 µm and 39.1 to 47.1 µm, respectively. The SLM process itself resulted in a positive increase of the marginal (6.0 – 16.7 µm) and internal (9.0 – 15.7 µm) fit discrepancies.CONCLUSIONThe CAD and SLM processes affected the fit of CoCr crowns and varied based on the preparation designs. Typically, the shoulder-lip and sharp line angle designs had a more significant effect on crown fit. However, the differences between the design groups were relatively small, especially when compared to fit discrepancies observed clinically.

The Effect of Different Wax Pattern Fabrication Techniques on the Marginal Fit of Customized Lithium Disilicate Implant Abutments.

To evaluate the effect of different wax pattern fabrication techniques on the fit of customized pressed lithium disilicate implant abutments on titanium inserts before and after pressing. The marginal fit results of pressed lithium disilicate implant abutments were then compared with those of milled lithium disilicate abutments. After scanning the titanium inserts and designing an implant abutment, wax patterns were fabricated with three techniques (n = 15 each): computer-aided design/computer-aided manufacturing (CAD/CAM) milling, 3D printing and conventional layering. The marginal fit (µm) was measured using a stereomicroscope for all the wax patterns before pressing them into the lithium disilicate abutments. The pressed implant abutments were measured again for marginal fit, and the results were compared to those of the milled lithium disilicate abutments. One-way analysis of variance (ANOVA) was used to assess different wax pattern fabrication techniques in each stage before and after pressing. One-way ANOVA was also used to compare the groups of pressed and milled lithium disilicate abutments. Multiple pairwise comparisons were performed using the Tukey post hoc test in each stage. There were statistically significant differences between the marginal fit of the three wax patterns groups (p < 0.001; f = 123.33), wherein the mean marginal fit was the highest for conventionally layered wax patterns (30 ± 13.09) µm. Furthermore, after pressing, there were statistically significant differences between the marginal fit of the three pressed abutments groups (p < 0.001; f = 518.62), wherein the mean marginal fit was the highest for pressed e.max abutments fabricated from conventionally layered wax patterns (25.26 ± 3.9) µm. There was no statistically significant difference between the mean marginal fit of the pressed abutments fabricated from conventional layered wax patterns and that of the milled CAD/CAM abutments. However, the mean marginal fit of the milled CAD/CAM abutments was higher than that of the pressed abutments fabricated from both CAD/CAM wax and 3D printed wax. All the tested fabrication methods provided degrees of accuracy that lie well within accepted limits. The use of pressed lithium disilicate abutments fabricated from conventional layering wax pattern technique should provide a more consistent better marginal fit between the titanium insert and the abutment and may therefore be the preferable fabrication method.

Marginal and internal fit of 3D printed resin graft substitutes mimicking alveolar ridge augmentation: An in vitro pilot study.

Recent improvements in additive manufacturing technologies may facilitate the use of customized 3D printed grafts for horizontal and vertical augmentation of the atrophic alveolar ridge. The accurate fit of such grafts could reduce the clinical treatment time and contribute optimal bone regeneration. The aim of this in vitro study was to evaluate the marginal and internal fit of 3D printed resin grafts as they could be used for alveolar ridge augmentation. Alveolar ridge morphologic data were derived from the Cone Beam Computed Tomography (CBCT) scans of six patients with alveolar bone defects. These data were transferred to a segmentation program to produce virtual 3D reconstructions of the alveolar ridge models. Using a Computer Aided Design (CAD) program, the alveolar bone defects were defined and customized grafts were designed and both the defects as well as the grafts generated (CAM) as 3D projects. These projects were imported into a 3D printer and were manufactured in resin. Hereafter, the grafts were fitted to the defect sites of the corresponding models and new CBCT scans were performed. Based on these scans, measurements were made at the marginal and internal part of the fitted grafts to evaluate the marginal and internal fit, respectively. The statistical analysis revealed that the mean marginal fit was significantly better (P < 0.05) than the mean internal fit. The fit of the grafts was dependent on the shape and on the size of the grafts. Specifically, the total void surface between the fitted graft and the corresponding defect site was significantly larger in the large-defect grafts than the small-defect grafts (P < 0.05). Within the limitations of the study, it could be demonstrated that it is possible to fabricate 3D printed resin grafts with acceptable fit in customized shapes, when combining CBCT scans and computer aided design and 3D printing techniques.

Marginal and internal fit of metallic and zirconia copings depending on manufacturing methods.

Background Accurate fit is one of the most important factors in the long term clinical outcomes of fixed dental prostheses. Therefore, evaluation of restorations fabricated by new technologies is needed. However studies comparing marginal and internal adaptations of the several CAD CAM systems are few. Aim/Hypothesis The aim of this in vitro study is to compare the marginal and internal fit of conventional casting metal copings, milling metal copings, milling zirconia copings, 3D printing metal copings. Material and Methods Each ten specimens were fabricated with casting Co-Cr alloy (CC), milling Co-Cr alloy (CS), milling zirconia (CZ), 3D printing Co-Cr alloy (EC). The marginal and internal gaps of the copings were measured using a replica technique with a light-body silicone impression material. The replica specimens were sectioned buccopalatally and mesiodistally and then examined using a microscope at 200× magnification. Sixteen reference points were used on each specimen. The data were statistically analyzed with One-way ANOVA and Scheffe significant difference tests (P > 0.05). Results The mean marginal fit of CC group was significantly better than other three groups. The mean internal gap of CC group was significantly smaller than those of groups. In all groups, the marginal mean values were the smallest among locations. Conclusions and Clinical Implications Within the limitations of this in vitro study, the marginal and internal fit of CC group were significantly better than those of CS, CZ and EC group. However CS, CZ and EC group fabricated by CAD CAM presented enough accuracy in the marginal and internal gap.

Assessment of the marginal fit, ceramo-metal shear bond strength and the fractographic analysis of sinter cast gold: An In-vitro study

Introduction: The fractographic analysis is performed by observing, measuring, and interpreting the fracture surface topography that can determine many features of the microstructure of materials and the mechanics of the fracture. The aim of this study was to assess the marginal fit and the ceramo-metal shear bond strength of sinter cast gold, and to analyze the debonded sample by fractography. Materials and Methods: A total of five sinter cast gold copings were prepared on a stainless master die resembling a maxillary 1st pre-molar to receive a ceramo-metal restoration. Each of the copings was then assessed for the marginal fit before and after ceramic firing. In addition, a total of five ceramo-metal discs were fabricated for testing shear bond strength at the metal-ceramic interface. The samples were subjected to increasing shear load on a universal testing machine with crosshead speed of 0.002 mm/s. The load at which the samples debonded completely was noted, and the fractographic analysis of the samples was performed. Results: The mean marginal fit found in this study for sinter cast gold before ceramic firing was found to be 11.5 μm with a standard deviation of ±4.64 μm, and after ceramic firing, it was found to be 9.38 μm with a standard deviation of ±3.57 μm. The average shear bond strength at the sinter cast gold ceramic interface was 18.216 MPa. The fractographic analysis showed the globular microstructure of sinter cast gold on sintering, adhesive, and mix-mode type of fracture with the presence of both gold and ceramic. Conclusion: The marginal fit observed before and after ceramic firing was within clinically acceptable range, whereas the ceramo-metal shear bond strength between sinter cast gold and ceramic was found to be inadequate.

Comparison of the marginal fit of milled yttrium stabilized zirconium dioxide crowns obtained by scanning silicone impressions and by scanning stone replicas.

PURPOSETo determine the discrepancy in monolithic zirconium dioxide crowns made with computer-aided design and computer-aided manufacturing (CAD/CAM) systems by comparing scans of silicone impressions and of master casts.MATERIALS AND METHODSFrom a Cr-Co master die of a first upper left molar, 30 silicone impressions were taken. The 30 silicone impressions were scanned with the laboratory scanner, thus obtaining 30 milled monolithic yttrium stabilized zirconium dioxide (YSZD) crowns (the silicone group). They were poured and the working models were scanned, obtaining 30 milled monolithic yttrium stabilized zirconium dioxide (YSZD) crowns (the plaster group). Three predetermined points were analyzed in each side of the crown (Mesial, Distal ,Vestibular and Palatal), and the marginal fit was evaluated with SEM (×600). The response variable is the discrepancy from the master model. A repeated measures ANOVA with two within subject factors was performed to study significance of main factors and interaction.RESULTSMean marginal discrepancy was 22.42±35.65 µm in the silicone group and 8.94±14.69 µm in the plaster group. The statistical analysis showed significant differences between the two groups and also among the four aspects. Interaction was also significant (P=.02).CONCLUSIONThe mean marginal fit values of the two groups were within the clinically acceptable values. Significant differences were found between the groups according to the aspects studied. Various factors influenced the accuracy of digitizing, such as the design, the geometry, and the preparation guidance, as well as the texture, roughness and the color of the scanned material.

Marginal and Internal Fit of CAD/CAM Crowns Fabricated Over Reverse Tapered Preparations.

Intraoral digital scanning can accurately record single abutment tooth preparations despite their geometry, and the algorithms of the CAD software can be set to manage different abutment forms. The purpose of this in vitro study was to evaluate the marginal and internal fit of CAD/CAM zirconia crowns fabricated over conventional and reverse-tapered preparations. Crown preparations with known total occlusal convergence (TOC) angles (-8°, -4°, 0°, 8°, 12°, 16°, and 22°) were digitally created from a maxillary left central incisor and printed in acrylic resin. Next, casts were scanned with a TRIOS intraoral scanner, and crowns were designed with KaVo multiCAD software using default parameters (50 μm cement space) on abutments with positive TOC angles, whereas reverse-tapered abutments (negative TOC angles) were digitally blocked out at 0° and had an extra mesiodistal gap set to 50 μm. Then, zirconia crowns were fabricated, and their marginal and internal discrepancies were recorded with the silicone replica technique. All replicas were examined under a stereomicroscope at 50× magnification. Collected data were analyzed with one-way ANOVA and post hoc Tukey test for marginal fit. For the axial and incisal fit, measured values did not follow a normal distribution; therefore, the Kruskal-Wallis and the Dunn/Bonferroni multiple comparison tests were applied (p = 0.05). The mean marginal fit of -8° crowns (58.2 ± 6.0 μm) was statistically different (p < 0.0001) from all the remaining crowns (range 42.1-47.3 μm). Also, the internal fit was statistically significant when comparing crowns fabricated over abutments with positive and negative TOC angles (p < 0.0001). The largest median axial discrepancies were found in the -8° (165.5 μm) and -4° (130.8 μm) groups; however, when evaluating the incisal fit, they showed the smallest discrepancies (67.3 and 81.8 μm, respectively). Under the conditions of this study, the marginal and internal fit of zirconia crowns fabricated over inverse-tapered preparations is within clinically accepted values.

Influence of scanner, powder application, and adjustments on CAD-CAM crown misfit

Statement of problemThe manufacturers of computer-aided design and computer-aided manufacturing (CAD-CAM) systems emphasize that new technologies can improve the marginal fit of dental crowns. However, data supporting this claim are limited. PurposeThe purpose of this in vitro study was to investigate the differences among the following fabrication methods on the marginal discrepancy of dental crowns: intraoral optical scanners, powder application, and adjustments of intaglio surface. Material and methodsA single human premolar was fixed on a typodont and prepared to receive crowns prepared by the CEREC CAD-CAM system. Three fabrication techniques were used: digital scans using the CEREC Bluecam scanner with titanium dioxide powder (TDP), digital scans using the CEREC Omnicam scanner without TDP, and digital scans using the Omnicam scanner with TDP. Five experimental groups (n=10) were designated: Bluecam (group B), Bluecam with adjustments (group BA), Omnicam (group O), Omnicam with adjustments (group OA), and Omnicam with TDP (group OP). The specimens were scanned using microcomputed tomography to measure the vertical, horizontal, and internal fit and volumetric 3-dimensional (3D) internal fit values of each luting space. The paired t test was used to evaluate mean marginal fit change after adjustments within the same group. One-way analysis of variance and post hoc tests were used to compare groups B, O, and OP (α=.05). ResultsMean vertical fit values ±standard deviations of group B=29.5 ±13.2 μm; BA=26.9 ±7.7 μm; O=149.4 ±64.4 μm; OA=49.4 ±12.7 μm; and OP=33.0 ±8.3 μm. Adjustments in the intaglio surface and TDP application statistically influenced the vertical fit of group O (P<.001). The percentage of vertical fit values <75 μm in group B=89.3%, BA=92.7%, O=31.0%, OA=73.5%, and OP=92.0%. Mean horizontal fit values for group B=56.2 ±21.5 μm; 85.8 ±44.4 μm for group BA; 77.5 ±11.8 μm for group O; 102.5 ±16.2 μm for group OA; and 91.4 ±19.4 μm for group OP. Results from group B were significantly different from those of the other test groups (P<.05). The percentages of horizontal misfit were 61.2% in group B; 73.5% in group BA; 88.1% in group O; 92.4% in group OA; and 85.0% in group OP. Volumetric 3D internal fit values in group B were 9.4 ±1.3 mm3; 10.7 ±1.0 mm3 in group BA; 11.8 ±2.1 mm3 in group O; 11.0 ±1.3 mm3 in group OA; and 9.6 ±0.9 mm3 in group OP. The overall results from groups B and OP were better than those of group O, with regard to vertical misfit and volumetric 3D internal fit. ConclusionsDifferent intraoral optical scanners, powder application, and internal adjustments influenced the marginal discrepancy of crowns. Crowns fabricated using the Omnicam system had significantly higher vertical discrepancy and volumetric 3D internal fit than those fabricated using the Bluecam scanner with TDP. Adjustments of the intaglio surface improved the vertical fit of crowns made using the Omnicam scanner; however, TDP application before Omnicam scanning improved the vertical fit as well as the volumetric 3D internal fit value of the luting space of crowns.

A Comparative Evaluation of the Marginal and Internal Fit of Laboratory-fabricated Monolithic Zirconia Crowns using Direct and Indirect Methods of Scanning: An in vitro Study

ABSTRACTAimTo evaluate the marginal and internal fit of laboratoryfabricated monolithic zirconia crowns using direct and indirect methods of scanning.Materials and methodsA stainless steel master model was selected, which included stainless steel die, outer cap, and inner cap. The study was divided into two groups. In group I, direct method of scanning was carried out in which the stainless steel die was scanned directly with chairside scanner, and in group II, impression of the stainless steel die was made and gypsum die was fabricated, which was then subjected to scanning. Zirconia blanks or blocks were milled, sintered, and polished to obtain 10 zirconia crowns of each group. Replica technique was used to evaluate fit of crowns by using light body as cement analog. The crowns were then sectioned, viewed under a stereomicroscope, and each predetermined region was measured and evaluated for marginal and internal fit.ResultsThe descriptive statistics showed that the mean marginal fit for indirect method was higher compared with that for direct method. The results of paired-sample t-test revealed that mean marginal and internal fit for indirect method was on the upper side of the scale, whereas the mean for the direct method is on the lower side of the scale. Thus, the difference in the means of two methods was quite large and likely to be significant.ConclusionThe results did show better marginal and internal fit in crowns fabricated by the direct method; however, the crowns fabricated by the indirect method had more discrepancy, but were in the clinically acceptable limit.Clinical significanceThe present study would serve as a useful guide in deciding which method of scanning would give a better marginal and internal fit of monolithic zirconia crowns for longevity of restorations.How to cite this articleGandhi KN, Ram SM. A Comparative Evaluation of the Marginal and Internal Fit of Laboratory-fabricated Monolithic Zirconia Crowns using Direct and Indirect Methods of Scanning: Anin vitroStudy. J Contemp Dent 2017;7(1):22-27.

Assessment of marginal fit, ceramometal shear bond strength, and fractographic analysis of sinter cast gold: An In vitro study

Introduction: Fractographic analysis is performed by observing, measuring, and interpreting the fracture surface topography that can determine many features of the microstructure of materials and the mechanics of the fracture. This study was planned to put through investigation, marginal fit and ceramo-metal shear bond strength with fractographic analysis of the debonded surfaces. The aim of this study was to assess the marginal fit, ceramo-metal shear bond strength of sinter cast gold and to analyze the debonded sample by fractography. Materials and Methods: A total of 5 sinter cast gold copings were prepared on a stainless master die resembling a maxillary 1st pre-molar to receive a ceramo-metal restoration. Each of the copings were, then, assessed for marginal fit before and after ceramic firing. Also, a total of 5 ceramo-metal discs were fabricated for testing shear bond strength at the metal-ceramic interface. The samples were subjected to increasing shear load on a Universal Testing Machine with crosshead speed of 0.002mm/sec. The load at which, the samples debonded completely, was noted and the samples put-to fractographic analysis. Results: The mean marginal fit found in this study for sinter cast gold before ceramic firing was measured to be 11.5 μm with a standard deviation of ±4.64 μm and after ceramic firing was found to be 9.38 μm with a standard deviation of ±3.57 μm. The average shear bond strength at the sinter cast gold ceramic interface was 18.216 MPa. The fractographic analysis showed the globular microstructure of sinter cast gold on sintering, adhesive, and mix-mode type of fracture with the presence of both gold and ceramic. Conclusion: The marginal fit observed before and after ceramic firing was within clinically acceptable range while the ceramo-metal shear bond strength between sinter cast gold and ceramic was found to be inadequate.

Fit of pressed crowns fabricated from two CAD-CAM wax pattern process plans: A comparative in vitro study

Statement of problemSubtractive and additive computer-aided design and computer-aided manufacturing (CAD-CAM) wax pattern processing are 2 methods of fabricating a pressed ceramic crown. Whether a subtractive milled wax pattern or a pattern from the micro-stereolithography additive process produces lithium disilicate crowns with better marginal and internal fit is unclear. Materials and methodsTen silicone impressions were made for a prepared canine tooth. Each die received 2 lithium disilicate (IPS e.max) copings, 1 from milled wax blocks and 1 from additive wax. The replica technique was used to measure the fit by scanning electron microscopy at ×80 magnification. Collected data were analyzed using the paired Student t test for the marginal and internal fit. For the occlusal fit, the difference in scores did not follow a normal distribution, and the Wilcoxon signed rank test was used (α=.05). ResultsThe mean marginal, axial, and occlusal fit showed no significant differences when the 2 CAD-CAM manufacturing processes were compared (P>.05). For the marginal fit, the mean (±SD) values were 105.1 μm ±39.6 with the milled process and 126.2 μm ±25.2 for the additive process. The mean values were 98.1 μm ±26.1 for the axial fit in the milled process and 106.8 μm ±21.2 in the additive process. For the occlusal fit, median values (interquartile interval) were 199.0 μm (141.5 to 269.9) for subtractive manufacturing and 257.2 μm (171.6 to 266.0) for micro-SLA manufacturing. ConclusionsNo significant difference was found between the fit of the 2 techniques. The mean values of axial and occlusal median values were 10 and 5 to 6 times greater than machine’s nominal values.

Clinical Marginal and Internal Fit of Crowns Fabricated Using Different CAD/CAM Technologies.

The aims of this in vivo investigation were to compare the marginal and internal fit of single-unit crowns fabricated using a selective laser melting (SLM) procedure with two CAD/CAM grinding procedures, and to evaluate the influence of tooth type on the parameters measured. A total of 270 crowns were evaluated, including 90 SLM metal-ceramic crowns (group B), 90 zirconium-oxide-based ceramic crowns (group L), and 90 lithium disilicate ceramic crowns (group C). The marginal and internal gaps of the crowns were recorded using a replica technique with a silicone indicator paste stabilized with a light-body silicone. The gap replica specimen were sectioned buccolingually and mesiodistally and then examined using a stereomicroscope at 30× magnification. Ten reference points were measured on each anterior and premolar specimen, and 20 reference points were measured on each molar specimen. Two-way ANOVA was performed to identify the significant differences between the groups. The mean marginal fit of group B was significantly better than those of group C and group L (p < 0.005), but a significant difference was not found between group C and group L (p > 0.05). The mean axial gap of group B was significantly smaller than those of group C and group L (p < 0.01), while group C was not different from group L (p > 0.05). The mean occlusal gap of group B was significantly higher than those of group C and group L (p < 0.05), and no difference was found between group C and group L (p > 0.05). The marginal and internal gaps of crowns varying according to tooth type were not significantly different (p > 0.05). The SLM system demonstrated better marginal and internal fit compared to the two CAD/CAM grinding systems examined. Tooth type did not significantly influence the marginal or internal fit.

Marginal fit and microleakage of cast and metal laser sintered copings—An in vitro study

PurposeThis study aimed to compare the marginal fit and microleakage of metal laser sintered Co–Cr alloy copings and conventional cast Ni–Cr alloy copings using a stereomicroscope. MethodsForty extracted maxillary premolars were randomly divided into two groups. One group was subjected to coping fabrication using conventional lost wax (LW) technique while the other group was subjected to coping fabrication using metal laser sintering (MLS) technology. The marginal fit of these copings were compared before and after ceramic addition using images obtained with a steromicroscope and an ImageJ analysis software. All the specimens were cemented using Type 1 glass ionomer cement and were subjected to thermocycling. The specimens were evaluated for microleakage using stereomicroscope and 2% methylene blue die used as a tracer. The data were subjected to statistical analysis using paired t-test, Mann–Whitney test and Chi-Square test. ResultsThe mean marginal fit of copings before and after ceramic addition in Group B (MLS) was better than the copings in Group A (LW) and was statistically significant (P<0.05). The influence of ceramic firing had a significant (P<0.05) increase in mean marginal gap in Group A (LW) but not in Group B (MLS). And the difference in mean microleakage between the groups was not statistically significant (P≥0.05). ConclusionThe copings fabricated using MLS technique had a better marginal fit and an observable decrease in microleakage when compared to the copings fabricated using the conventional lost wax (LW) technique.

Marginal and internal fit of four-unit zirconia fixed dental prostheses based on digital and conventional impression techniques

The aim of this in vitro study was to evaluate the marginal and internal fit of CAD/CAM-generated four-unit zirconia fixed dental prostheses made with digital and conventional impressions. A titanium master model was used. For group conventional impression (CI), 12 polyether impressions of the master model with Impregum(TM) were made. For group digital impression (DI), 12 digital impressions of the master model using Lava(TM) C.O.S. system were made. The replica technique was applied. The Mann-Whitney U statistical test was applied to detect statistical differences between the groups, in terms of marginal and internal fit. Face-by-face comparisons between groups were also carried out. Groups DI and CI presented mean marginal fit of 63.96 and 65.33 μm, respectively, and showed no statistically significant difference. Groups DI and CI presented significantly different internal fit with mean values of 58.46 and 65.94 μm, respectively. Group DI showed statistically significantly lower values for marginal and internal fit on premolar mesial face, and on molar distal and palatal faces. Frameworks fabricated from digital and conventional impressions showed clinically acceptable marginal fit. Frameworks fabricated from digital impression demonstrated better internal fit than ones fabricated from conventional impression. Reviewing each retainer face, digital impression showed better marginal and internal fit at the premolar mesial and molar distal faces. The results of this in vitro study show that digital impressions made with the Lava(TM) C.O.S. system and its digital workflow are suitable for fabricating four-unit zirconia frameworks, with regard to marginal and internal fit requirements.

코발트-크롬 합금으로 제작된 금속-도재관의 적합도 평가

Objectives : The purpose of this in vitro study was to evaluate the effect of firing cycles on the marginal and internal fit of metal ceramic crown. Methods : Ten same cases of stone models (abutment teeth 11) were manufactured. Ten cobalt-chrome cores were made per each models and the marginal and internal fit was evaluated through a silicone replica technique. The marginal and internal fit of specimens was measured twice. The first measurement was done after manufacturing cobalt-chrome alloy core and the second measurement was done after porcelain firing. T-test of paired sample for statistical analysis was executed with SPSS 12.0K for Windows (<TEX>${\alpha}$</TEX>=0.05). Results : Mean(SD) marginal and internal fit were 77.1(23.3) <TEX>${\mu}m$</TEX> for the cobalt-chrome alloy core group and 84.4(21.9) <TEX>${\mu}m$</TEX> for the metal-ceramic crown group. They were statistically significant differences between groups for marginal and internal fit (p<.05). Conclusions : All metal ceramic crowns showed marginal and internal fit ranged within the current clinical recommendations.

Accuracy of ceramic restorations made with two CAD/CAM systems

Different types of CAD/CAM systems are currently available, but information regarding which system produces the best marginal fit is lacking. The purpose of this study was to evaluate the effect of 2 different CAD/CAM systems (Cerec inLab, Kavo Everest) on the marginal fit of 2 types of zirconia-based and lithium disilicate crowns. Forty zirconia-based and lithium disilicate crowns, 20 each, were fabricated with the Cerec inLab and Everest CAD/CAM systems on a specially designed stainless steel die to ensure the standardization of specimen shape and dimensions. The vertical marginal fit for all tested crowns was evaluated by using a digital microscope at ×100 magnification, and the data were tabulated and statistically analyzed with 2-way ANOVA, followed by the Tukey honestly significant difference (HSD) test with a confidence level of .05 to determine the mean differences. The results showed that the CAD/CAM technique, ceramic type, and their interaction had a statistically significant effect on the mean marginal fit of both ceramic types tested. Better marginal fit values were exhibited by the Everest CAD/CAM technique for both ceramic types tested.