Marginal Gap Values Research Articles

SEM Evaluation of the Marginal Accuracy of Zirconia, Lithium Disilicate, and Composite Single Crowns Created by CAD/CAM Method: Comparative Analysis of Different Materials.

(1) Background: The objective of this in vitro study is to evaluate the marginal accuracy of crowns created by CAD/CAM. (2) Methods: A customized chrome-cobalt (Cr-Co) implant abutment simulating a maxillary right first molar was fixed in a hemi-maxillary stone model and scanned. In total, 27 crowns were fabricated, including 9 lithium disilicate crowns, 9 composite crowns, and 9 zirconia crowns. The measurements were determined by scanning electron microscopy. Descriptive analysis was performed using the mean and standard deviation, while the Kruskal-Wallis test was performed to determine whether the marginal discrepancies were significantly different between each group (p < 0.05). (3) Results: The lowest marginal gap value was reported for zirconia (21.45 ± 12.58 µm), followed by composite (44.7 ± 24.96 µm) and lithium disilicate (62.28 ± 51.8 µm). The Kruskal-Wallis tests revealed a statistically significant difference (p-value < 0.05) in the mean marginal gaps between different materials. (4) Conclusions: The proposed digital workflow can be a viable alternative for fixed prosthetic rehabilitations. The best performance in terms of marginal gap was achieved by zirconia crowns, but all three materials demonstrate marginal closure below the clinically accepted threshold value (120 µm). Clinical significance: although significant differences were reported, the investigated CAD/CAM materials showed clinically acceptable marginal gaps.

Internal Adaptation and Marginal Accuracy of Two Different Techniques-based Poly (ether ether ketone) Single Crowns: An In Vitro Study.

The goal of this study was to evaluate how different fabrication techniques affected the marginal accuracy and internal adaptability of poly (ether ether ketone) (PEEK) molar single crowns. Twenty PEEK crowns were constructed using two different fabrication techniques, and they were divided into two main groups (PEEK-CAD and PEEK-pressed). PEEK-CAD crowns were numbered from 1 to 10. PEEK-pressed crowns were numbered from 11 to 20. Each group had 10 PEEK crowns, and both were constructed over a master die. For internal fit measurements, silicone replica bodies were built and cut into two halves buccolingually. Marginal accuracy was measured using three evenly spaced landmarks along the specimen's cervical circumference on each surface using a Leica L2 APO* microscope. In terms of marginal accuracy, the Press group had a statistically significant greater mean marginal gap value than the computer aided-designing (CAD) group. While in terms of internal fit, there was no statistically significant difference in internal fit between the CAD and Press groups. At a significance level of two-tailed p-value = 0.21 (p > 0.05). PEEK-CAD crowns demonstrated higher marginal accuracy and nearly similar internal fit when compared to PEEK-pressed crowns. PEEK material could be used as a substitute for zirconia for a full coverage posterior restoration.

Effect of Additive and Subtractive Coping Production Techniques on Retention and Marginal Fit of Implant Supported Crowns.

This study investigated the marginal and internal fit and retention of crowns fabricated using 4 different castable pattern production methods, namely plastic burn out coping, computer-aided design and computer-aided manufacturing (CAD-CAM) milled (CAD-CAM-M), CAD-CAM additive (CAD-CAM-A), and conventional. This study consisted of 5 groups including 2 different brands of burn out coping groups (Burn out-Straumann [Burn out-S] group and Burn out-Implance [Burn out-I] group), the CAD-CAM-M group, the CAD-CAM-A group, and the conventional group. A total of 50 metal crown copings were produced in each group with 10 metal crown copings. The marginal gap of the specimens was measured twice-both before and after the cementation and thermocycling processes using a stereomicroscope. A total of 5 specimens were selected randomly-1 from each group for scanning electron microscopy analysis and sectioned longitudinally. The pull-out test was performed on the remaining 45 specimens. The lowest marginal gap value was observed in the Burn out-S group before and after cementation with 88.54-97.48 μm, respectively, while the highest marginal gap was observed in the conventional group (186.27-200.58 μm). Implant systems did not significantly affect the marginal gap values (P > .05). Marginal gap values increased significantly after cementation and thermal cycling in all the groups (P < .0001). The highest retention value was measured in the Burn out-S group while the lowest in the CAD-CAM-A group. The highest occlusal cement gap values were observed in the coping groups (Burn out-S and Burn out-I groups), and the lowest in the conventional group in the scanning electron microscopy analysis. The marginal fit and retention values of the prefabricated plastic burn out coping technique was superior when compared with the other techniques, providing that internal fit was superior with the conventional technique.

Accuracy of digital impressions for implant-supported complete-arch prosthesis when using an auxiliary geometry device

Background/purposeDigital impressions using intraoral scanners have recently gained popularity. The aim of the present study was to evaluate the fit of full-arch screw-retained cobalt-chromium frameworks fabricated via two different digital impression methods. Materials and methodsAn edentulous resin master model with four dental implants was fabricated. Forty cobalt-chromium superstructures were fabricated and evaluated according to four groups. In Group 1, the superstructures were evaluated using an intraoral scanner to generate digital impressions. Group 2 relied on the help of an auxiliary geometric appliance in generation of digital impressions via intraoral scanner. The traditional method of splinted open-tray conventional impressions was designated for Group 3. Finally, the control group (Group 4) relied on scanning of the master model directly with a laboratory scanner. Vertical marginal discrepancy was evaluated, and data obtained were statistically analyzed. ResultsThe highest mean vertical marginal gap value (80.86 ± 50.06 μm) was observed for Group 1 and statistically higher than Group 2, 3, and 4 (P < 0.05). The lowest mean vertical marginal gap value (41.98 ± 26.33 μm) was measured from Group 4 and statistically similar to Group 2 and 3 (P > 0.05). ConclusionIt has been suggested that the use of auxiliary geometric appliances yields increased scanning accuracy. Frameworks fabricated using the traditional splinted open-tray technique were more reliable compared to those frameworks from digital impressions.

Evaluation of the marginal fit of finish line designs of novel CAD/CAM restoration materials

Aim: The purpose of this study is to compare the marginal fit of crowns manufactured using different CAD/CAM materials on 2 different types of finish line design.&#x0D; Material and method: Tooth preparations were made by creating 2 different finish lines (rounded shoulder, chamfer) on an acrylic mandibular second premolar model. Impressions were taken on each preparation using polyvinylsiloxane impression material, and blocks with three different compositions including lithium disilicate (LDS), zirconia-reinforced lithium silicate (ZLS), and monolithic zirconia (MZ) (UP.CAD, Celtra Duo, and VITA YZ HT) were produced using a CAD/CAM (computer-aided-design and computer-aided-manufacturing) milling device (VHF R5) (n=10). The marginal gap values of the crown restorations were measured by the same operator using a stereomicroscope (LEICA DVM6). Histogram plots and the Kolmogorov-Smirnov test were used to test the normality of the distributions of the variables. The non-normally distributed (nonparametric) variables were compared using the Mann-Whitney U test for two groups and the Kruskal-Wallis test for more than two groups.&#x0D; Results: The marginal gap values were compared between finish line designs separately for each material. Accordingly, the marginal gap values of the rounded shoulder finish line were smaller than those of the chamfer finish line in all materials. The marginal gap values were also compared among the materials separately for each finish line type. Accordingly, the marginal gap values of the VITA YZ HT material were smaller than those of the Celtra Duo (ZLS) and UP.CAD (LDS) materials for both finish line designs. There was no significant difference between Celtra Duo and UP.CAD.&#x0D; Conclusion: The finish line design is a factor that affects marginal fit. Monolithic zirconia is more appropriate for clinical use as it shows a better marginal fit compared to LDS and ZLS.

Marginal fit of interim restoration constructed by 3D printing versus conventional chair-side method: An in vitro study

Purpose: The aim of the present study was to assess the marginal fit of interim restorations fabricated by 3D printing technique compared to conventional technique. Methods: Typodont model of maxillary 1st molar was prepared for full coverage crowns. The prepared model was digitally scanned by 3D scanner. Duplication of master die into 20-epoxy resin dies. Interim crowns were constructed by two techniques: conventional chair side technology using a bis-acrylic based self-cure temporary material (structure-2- Voco, Germany) and 3D printing technology using (Next-dent C&B resin, Netherlands) material. The specimens were divided into 2 equal groups (n=10). Marginal adaptation was evaluated using stereomicroscope. Results: The mean marginal gap value of 3D printing interim crowns (38.76±27.21 μm) was significantly lower than that of conventional chair-side crowns (120.43±32.63 μm). Conclusion: Interim crowns fabricated by 3D printing showed superior marginal accuracy than conventionally constructed crowns.

Comparative evaluation of the marginal fitness of vonlay nanoceramic hybrid restorations using different computer-aided imaging techniques

Purpose The purpose of this in-vitro study was to evaluate the marginal fitness of vonlay nanoceramic hybrid restorations using different computer-aided imaging technique (an in-vitro study). Materials and methods Thirty 3D printed models of prepared premolar (no. 14) for vonlay restoration were fabricated using epoxy resin material and used for fabrication of thirty nanohybrid ceramic vonlays (Grandio Disc, VOCO). three groups (n = 10) of vonlays were fabricated using three different imaging technique: group 1: imaging of conventional impression of master die, group 2: imaging of stone master die and group 3: imaging of master die using chairside TRIOS Intraoral Scanners (3Shape). Vonlays were designed by using a CAD design software program (Exocad Dental CAD, Exocad. The vonlays were cemented over their corresponding dies with an automix dual cure adhesive cement system (Duo-Link universal resin cement, Bisco Inc.) under a static load by using custom made seating device. Digital microscope was used to measure the vertical marginal gap for each where a total of 120 measurements for the three groups (12 sites per vonlay and 10 vonlays per group) were evaluated. One-way analysis of variance test was used to analyze the results, Student sample t test was used to examine the marginal gap differences of each group and in the same group. Results A significant difference (P &lt; 0.001) was found between the marginal gap values of the vonlay restoration fabricated by using different imaging technique. The smallest marginal gaps were obtained with vonlay fabricated using chairside intraoral scanners as compared with imaging of master die impression and stone master die. But there was no significant difference between the marginal gap measurements of different sides in the same group. Conclusion The smallest marginal gaps were obtained with vonlay fabricated using chairside intraoral scanners.

Effect of sintering time on the marginal and internal fit of monolithic zirconia crowns containing 3–4 mol% Y2O3

BackgroundShort-term sintering may offer advantages including saving time and energy but there is limited evidence on the effect that altering sintering time has on the accuracy of monolithic zirconia crowns. The purpose of this in vitro study was to investigate the effect of shortened sintering time on the marginal and internal fit of 3Y-TZP and 4Y-TZP monolithic crowns.MethodsSixty monolithic zirconia crowns were fabricated for the maxillary first molar tooth on the prefabricated implant abutment. Groups were created according to the material composition: 3Y-TZP Generation 1, 3Y-TZP Generation 2 and 4Y-TZP. Two different sintering protocols were performed: same final sintering temperature (1500 °C) and various rates of heating (10 °C/min and 40 °C/min), cooling down speed (− 10 °C/min and − 40 °C/min), holding time (45 and 120 minutes), and total sintering time (approximately 2 and 7 hours, respectively). The marginal and internal fit of the crowns were determined using the silicone replica technique. Comparisons between groups were analyzed using two-way ANOVA. Pairwise multiple comparisons were performed using t-test (p < 0.05).ResultsThe mean marginal gap values of 4Y-TZP zirconia revealed statistically significant increase for the short-term sintering protocol (p < 0.0001), while no difference was observed between the sintering protocols for the mean marginal gap values of 3Y-TZP groups. Although all groups showed clinically acceptable gap values, altering the sintering time had an effect on marginal fit of the crowns manufactured from 4Y-TZP zirconia.ConclusionsShortening the sintering time may lead to differences within clinically acceptable limits. The manufacturer’s recommendations according to material composition should be implemented with care.

Reliability of Polyetherketoneketone as Definitive Implant-Supported Bridges in the Posterior Region—An In Vitro Study of the Ultimate Fracture Load and Vertical Marginal Discrepancy after Artificial Aging

Purpose: This study aims to investigate the ultimate fractural strength and marginal integrity of a three-unit implant-supported fixed partial denture (FPD) framework fabricated of polyetherketoneketone (PEKK) after simulated five-year clinical aging. Materials and Methods: Twelve FPD frameworks were milled (n = 6 per group). All experimental frameworks were cemented on identical stainless-steel abutment models and subjected to five years of clinically simulated thermomechanical aging. The vertical marginal gap values were analyzed using a scanning electron microscope before and after being subjected to each aging condition. A universal testing machine was used to evaluate the ultimate fracture load. Results: A significant increase in marginal gap values of the PEKK group was observed after five years of simulation aging (p &lt; 0.001), while no significant difference was seen in the titanium group (p = 0.071). After thermocycling, the PEKK group showed a higher statistically significant mean marginal gap value (84.99 + 44.28 μm) than before (81.75 + 44.53 μm). The titanium group exhibited superior mechanical strength, with a fracture load significantly higher than that of the PEKK group (3050 + 385.30 and 1359.14 + 205.49 N, respectively). Conclusions: Thermocycling affects the marginal gap discrepancy of PEKK restoration. However, the mean vertical marginal gap values in PEKK and titanium groups after a five-year clinical aging simulation were clinically acceptable. The ultimate fracture load values were higher than the maximum bite force reported in the posterior region. Thus, PEKK could serve as a suitable alternative material to metal in the framework of fixed dental prostheses.

Comparison of the marginal accuracy of metal copings fabricated by 3D-printed resin and milled polymethyl methacrylate - An in vitro study.

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems have gained popularity over the traditional laboratory procedures in dentistry. In the conventional metal casting technique by burnout of a pattern, instead of using a wax pattern (which has several disadvantages), milled polymethyl methacrylate (PMMA) and 3D-printed resin patterns can also be used. The objective of the study was to assess and compare the marginal accuracy of single-crown cobalt-chromium (Co-Cr) metal copings fabricated using milled PMMA and 3D-printed resin patterns. Digital designing was done for metal coping on a prepared typodont mandibular molar using 3Shape Dental Design software. Standard Tessellation Language document of CAD design was used to fabricate 3D-printed resin patterns (Sprintray 3D printer) and milled PMMA patterns (CAD/CAM milling machine CoriTEC). A total of ten Co-Cr copings were casted, of which five belonged to Group A: 3D-printed resin and the other five to Group B: milled PMMA. The copings were assessed for marginal fit at eight different points using a stereomicroscope. Statistical analysis was done using an independent t-test. The t-test revealed a significant difference between the mean marginal gap values of the two groups, with the marginal gap values for the 3D-printed resin group (82.21 ± 15.26 μm) being lesser than that of the milled PMMA group (106.75 ± 12.76 μm). The marginal accuracy of copings fabricated using 3D-printed resin patterns was superior to that of copings fabricated from milled PMMA patterns.

The Effect of Sintering Procedures on Fit and Color in Zirconia Crowns

Purpose: The aim of this study was to examine the effects of various sintering procedures on the color parameters, marginal, and internal fit of zirconia crowns. Materials and Methods: Overall, 60 zirconia crowns were produced using 3 distinct zirconia blocks (Wieland Zenostar, Zirkonzahn Ice Translucent, and Zirkonzahn Prettau). For the sintering procedure of the crowns, six groups were created as follows: Wieland-Standard, Wieland-Speed, Ice-Standard, Ice-Speed, Prettau-Slow, and Prettau-Standard programs. The crowns were assigned into groups ( n = 10 in each group). The color parameters, marginal fit, and internal fit of the crowns were evaluated. The normality of data distribution was evaluated with the Kolmogrov–Smirnov test. Two independent samples t-test and Mann–Whitney U test were used to compare the sintering groups. Results: Acceleration of sintering caused a significant change in the color parameters of the Wieland and Ice groups but not in the Prettau group. In the Wieland group, marginal ( p = .047) and internal ( p = .004) gap values of speed sintering were found to be significantly lower than those in standard sintering. In the Ice group, the marginal gap values of speed sintering were found to be significantly lower than those in standard sintering ( p = .019). In the Prettau group, the marginal gap values of standard sintering were found to be significantly higher ( p = .035) than those in slow sintering. Conclusions: It was concluded that the effects of sintering procedures on color parameters, and internal and marginal fit of zirconia crowns were clinically insignificant. Speed sintering can be recommended for zirconia restorations.

Effect of Different Wax Pattern Manufacturing Techniques on the Marginal Fit of Lithium Disilicate Crowns.

Purpose: The present study evaluated the marginal gap of lithium disilicate crowns fabricated through three different wax pattern techniques; Conventional, Milling and 3D-printing. Materials and Methods: Thirty stone models were replicated from a stainless-steel model representing a prepared tooth; ten were sent to make conventional wax patterns while the remaining were sent to a digital dental scanner. The computer aided design was completed and STL (Standard Tessellation Language) files were sent to either milling or 3D-printing machines. All wax patterns (n = 30) were pressed, and a stabilizing instrument was used to secure the crowns on the master model. The marginal gap was measured at 18 points for each crown using a digital microscope (µm) (n = 540) and compared using One-way ANOVA (p ≤ 0.05). Results: There was a significant difference in the marginal gap value between all three groups (p < 0.01) where the milled group showed the least mean gap (28.87 ± 30.18 µm), followed by 3D printed (47.85 ± 27.44 µm), while the highest mean marginal gap was found in the conventional group (63.49 ± 28.05 µm). Conclusion: Milled and 3D-printed wax patterns produced better fitting crowns compared to conventional techniques.

Marginal gap and fracture resistance of implant-supported 3D-printed definitive composite crowns: An in vitro study

ObjectivesTo compare the marginal gap and fracture resistance of implant-supported 3-dimensional (3D) printed definitive composite crowns with those fabricated by using 3 different millable materials. Material and methodsA prefabricated abutment was digitized by using a laboratory scanner (E4 Lab Scanner) and a complete-coverage maxillary first premolar crown was designed (Dental Designer). Forty crowns were fabricated either by 3D printing (Saremco Print Crowntec, SP) or milling (Brilliant Crios, BC; Vita Enamic, VE; Cerasmart 270, CS) (n = 10). Baseline marginal gap values were evaluated by measuring 60 predetermined points on an abutment (15 points for each side) with a stereomicroscope at ×40 magnification. Marginal gap values were reevaluated after adhesive cementation. Load-to-fracture test was performed by using a universal testing machine. Two-way analysis of variance (ANOVA) was used to evaluate the effect of material type and cementation on marginal gap values. While Tukey HSD tests were used to compare the materials’ marginal gap values before and after cementation, the effect of cementation on marginal gap values within each material was analyzed by using paired samples t-tests. Fracture resistance data were analyzed by using 1-way ANOVA (α=0.05). ResultsMaterial type and cementation significantly affected marginal gap values (P < .001). Regardless of cementation, SP had the lowest marginal gap values (P < .001), while the differences among milled crowns were nonsignificant (P ≥ .14). Cementation significantly increased the marginal gap values (P < .001). Material type did not affect fracture resistance values (F = 1.589, P = .209). ConclusionImplant-supported 3D-printed composite crowns showed higher marginal adaptation compared with the milled crowns before and after cementation. In addition, all crowns endured similar forces before fracture.

Marginal Accuracy of Lithium Disilicate Full-Coverage Single Crowns Made by Direct and Indirect Digital or Conventional Workflows: A Systematic Review and Meta-Analysis.

Several studies have compared digital intraoral scanners and conventional impressions. The accuracy of these two methods in terms of marginal accuracy of lithium disilicate crowns is not well-established, yet. The purpose of this study was to systematically review available publications on marginal fit of single-unit, full-coverage, tooth-supported lithium disilicate restorations. Pubmed, Web of Science, Cochrane, EMBASE, and Scopus were electronically searched along with a manual search. After critical appraisal, data from selected studies were extracted and mean marginal difference with a 95% confidence interval was calculated. Meta-analysis of the collected data was conducted using STATA software. The meta-analysis revealed similar marginal gap values in intraoral scanners with conventional groups (p>0.05) and in intraoral scanners with extraoral canners (p>0.05). No significant difference was seen between digital and conventional impressions or intra- and extraoral scanners for marginal accuracy of lithium disilicate crowns.

COMPARISON OF MARGINAL ADAPTATION OF DIFFERENT FRAMEWORK MATERIALS BEFORE AND AFTER CEMENTATION: AN IN VITRO STUDY

Purpose: This study aimed to compare the marginal adaptation of different framework materials polyetheretherketone (PEEK), zirconia, and cobalt-chromium (Co-Cr) through direct metal laser sintered (DMLS) and conventional casting (CC) in fixed prosthetic restorations. Materials and Methods: A total of 80 stainless steel dies were embedded in silicone molds, and the master models obtained were divided into four groups (n=20): PEEK, zirconia, Co-Cr through DMLS and CC frameworks. The vertical marginal gap was measured by stereomicroscope at ×20 magnification. In addition to descriptive statistics in the evaluation of data, one-way ANOVA was used with the post hoc multiple comparison test Tamhane’s T2, as the data were normally distributed and variances differed according to the Kolmogorov–Smirnov and Shapiro–Wilk tests. Results: There was a statistically significant difference in vertical marginal gap before and after cementation in all groups (p&amp;lt;0.05). Conclusion: Before and after cementation, vertical marginal gap values of laser sintered Co-Cr, zirconia, and PEEK frameworks were clinically acceptable. Keywords: PEEK; Marginal Adaptation; Laser Sintered Co-Cr; Zirconia; Framework

Evaluation of marginal adaptation of (CAD/CAM) Lava plus high translucent zirconia and (CAD/CAM) IPS-Emax Full Crowns

The purpose of this research to compare the internal and marginal fit of two full crown’s materials made by (Cad/Cam) machine “lava plus high translucent zirconia and Ips-Emax using replica technique. The research sample consisted of 60 premolars prepared to have a full crown and it was divided into two equal groups (n1=n2=30), in the first group the full crowns were fabricated by Lava Plus high translucent zirconia whereas in the second group the full crowns were fabricated by IPS-Emax. Marginal adaptation of the crowns was measured by (cement replica technique) before applying the cementation steps of crowns, gingivo-incisal sections and mesio-distal sections were made and measured the marginal adaptation in 3 points in the cervical area and 3 points in the contact area using the BX41 OLYMPUS optical microscope magnifying ×10. Normal distribution of data was confirmed by using Kolmogorov-Smirnov test, then data analysis was done using Independent samples t-test at significance level of (α=0.05). The average marginal gap of the Lava Plus and IPS-Emax full crowns were 105.72 and 152.57 micron respectively, therefor there is a statistically significant difference at 95% confidence level (p&lt;0.05), the average marginal gap value of the second group was higher than the first group by (46.85 micron). Among the limitations of this study we conclude that the marginal gap value of the full crowns varies according to the material which they were fabricated by it, Thus, LAVA Pluas high translucent zirconia Full crowns have more adaptation than Ips-Emax Full crowns as it represents less marginal gap values, although all values were within clinically acceptable limits.

Influence of dental bonding surface and bonding methods on marginal adaptation of occlusal veneer after thermal aging

Objectives: The aim of this study was to evaluate the influence of different dental bonding substrates and bonding methods on the marginal quality in mandibular molars restored using monolithic zirconia occlusal veneer after thermal aging. Materials and Methods: Eighty extracted mandibular molars were collected and divided, based on type of dental bonding surface and bonding method, into eight groups. A non-retentive occlusal veneer preparation was performed to be either within enamel, dentin, dentin with intra-coronal cavity, or dentin with composite filling. 1-mm zirconia occlusal veneers were fabricated. For each specimen, the marginal gap was measured (x40) using a stereoscope. Each occlusal veneer was bonded to its corresponding tooth using either etch-and-rinse or self-etch system. All specimens were thermal aged (555 °C) for 7500 cycles. The post-cementation marginal gap was measured. Two-way ANOVA test and post-hoc test were applied to test for significance in marginal gap values in relation to bonding substrates and bonding method. Results: No statistically significant difference in pre-cementation marginal gap values was detected between different bonding surfaces. For post-cementation, two-way ANOVA test indicated significant differences in marginal gap values in relation to bonding substrates and bonding method. Conclusions: The type of dental bonding surface (either enamel, dentin, dentin with composite filling, or dentin with intra-coronal cavity) can influence the marginal quality of zirconia occlusal veneers after thermal aging. Compared with self-etch, etch-and-rinse bonding method demonstrated superior marginal quality of zirconia occlusal veneer restoration after thermal aging.

Marginal Fit of Temporary Restorations Fabricated by the Conventional Chairside Method, 3D Printing, and Milling.

Objectives: This study aimed to compare the marginal fit of temporary restorations fabricated by the conventional chairside method, 3D printing, and milling. Materials and Methods: In this in vitro, experimental study, 14 temporary restorations were conventionally fabricated over an implant abutment and analog that had been mounted in a phantom model at the site of canine tooth, using auto-polymerizing acrylic resin and putty index. In digital manufacturing, the original model was scanned, and the final restoration was designed. Fourteen temporary restorations were milled out of polymethyl methacrylate (PMMA) blocks, and 14 others were printed by a 3D printer. Temporary crowns were placed on the abutment, and images were obtained from specific areas under a stereomicroscope at x100 magnification to measure the amount of marginal gap. Data were analyzed using one-way ANOVA and Tukey’s test (α=0.05). Results: The mean marginal gap values for the temporary crowns in the 3D printing, milling, and chairside groups were 91.40, 75.28 and 51.23 µm, respectively. The crowns that were conventionally fabricated chairside exhibited the lowest marginal gap, and the difference in this respect was significant among the three groups (P<0.05). Conclusion: Temporary crowns fabricated by the chairside method showed significantly smaller marginal gap; however, the marginal gap of all three groups was within the clinically acceptable range.

Evaluation of the marginal and internal gaps of partially crystallized versus fully crystallized zirconia-reinforced lithium silicate CAD-CAM crowns: An in vitro comparison of the silicone replica technique, direct view, and 3-dimensional superimposition analysis

Statement of problemThe crystallization process of lithium disilicate crowns has been reported to cause dimensional change, but whether the fit of chairside computer-aided design and computer-aided manufactured (CAD-CAM) zirconia-reinforced lithium silicate crowns is affected is unclear. PurposeThe purpose of this in vitro study was to evaluate with a 3-dimensional superimposition analysis technique the marginal and internal adaptation of fully crystallized versus partially crystallized zirconia-reinforced lithium silicate ceramic CAD-CAM fabricated crowns. Additionally, the silicone replica technique and direct viewing of marginal gap values were compared with the 3-dimensional superimposition analysis technique. Material and methodsThe marginal and internal adaptation of a fully crystallized zirconia-reinforced lithium silicate (CELTRA DUO) were compared with those of a partially crystallized zirconia-reinforced lithium silicate (VITA SUPRINITY) after crystallization. Sixteen crowns (n=8) were fabricated with a chairside CAD-CAM system. The crowns and die and crown assembly were scanned with an optical scanner for the 3-dimensional superimposition analysis. Four hundred sixty-eight measurements were made for each crown, 78 in each 2-dimensional section. Marginal discrepancy was measured by using the direct viewing technique. The internal adaptation of the shoulder area, axial space, and occlusal space was measured by using the silicone replica technique. Both gap values were compared with the 3-dimensional superimposition analysis results by using the independent t test. The 2-way ANOVA was used to detect the effect of each variable (group and site) (α=.05). ResultsThe VITA SUPRINITY crowns showed statistically higher marginal discrepancy values than the CELTRA DUO crowns in both 3-dimensional superimposition analysis and the direct viewing method, and the lingual aspect recorded the highest marginal discrepancy mean value when compared with other aspects. The 3-dimensional superimposition analysis and the direct viewing method were statistically similar (P=.076). The VITA SUPRINTY crowns showed higher internal gap mean values than the CELTRA DUO crowns in both 3-dimensional superimposition analysis and silicone replica techniques. The occlusal space recorded the highest mean value in both groups. Assessment by 3-dimensional superimposition analysis and silicone replica techniques showed statistical difference in internal gap values (P=.04). ConclusionsCELTRA DUO showed better precision fit values than VITA SUPRINITY. Three-dimensional superimposition analysis is a reliable method of evaluating marginal and internal adaptation.

Comparison of marginal and internal fit of 5-unit zirconia fixed dental prostheses fabricated with CAD/CAM technology using direct and indirect digital scans

Background/purposeAdvancements in digital dentistry and the development of intraoral scanners (IOS) have provided clinicians with an accurate and efficient alternative to analog impressions. The aim of this study was to assess the accuracy of the marginal and internal fit of 5-unit monolithic zirconia fixed dental prostheses (FDPs) fabricated with CAD/CAM technology using direct and indirect digitalization methods.Material and methodsThree teeth in a maxillary typodont model were prepared to receive a 5-unit zirconia FDP. Six different groups were created according to the type of scanner (intraoral and extraoral) and the type of workflow. For direct workflow, the typodont was scanned with two different IOS (3Shape Trios 3 [3S-IOS] and Cerec Omnicam [C-IOS]). For indirect workflow, after conventional impressions were obtained, the impressions (IMP) were scanned with two different laboratory scanners (3S-IMP and C-IMP). After the impressions were poured, the stone (STN) casts were scanned with the same laboratory scanners (3S-STN and C-STN). Sixty 5-unit monolithic zirconia FDPs (10 in each group) were designed and milled. The marginal and internal fit was assessed.ResultsThe mean marginal gap values were 78.2±9 μm in the IOS group, 82.6± 9 μm in the IMP group, and 82.6±9 μm in the STN group, indicating no statistically significant differences among groups (p > 0.05). The mean axial gap values were 77.7 ± 10 μm in IOS group, 83.61 ± 15 μm in the IMP group, and 84.5±9 μm in the STN group, indicating no statistically significant differences among groups (p > 0.05).ConclusionThe marginal and internal fit of 5-unit monolithic zirconia FDPs fabricated with direct and indirect digital scans were similar. The smallest gap values were observed at the marginal region while the greatest gap values were detected at the occlusal region.