The effect of preparation designs on the marginal and internal gaps in Cerec3 partial ceramic crowns

Advantages and drawbacks of different methods to measure marginal gaps in fixed dental prostheses: A scoping review

OBJECTIVES

This review aimed to compare traditional and digital methods to assess marginal gaps in fixed dental prostheses. Each method's characteristics, advantages, and limitations were identified and discussed, also addressing the knowledge gaps in the current scientific literature.

DATA

Studies comparing currently available techniques for marginal gap examination were investigated. The main techniques analyzed were the Cross-Sectional Method (CSM), Direct View (DV), Silicone Replica Technique (SRT), Dual-Scan Method (DSM), Triple-Scan Method (TSM), Optical Coherence Tomography (OCT), and Micro-Computed Tomography (MCT).

SOURCES

Two experienced independent reviewers screened online databases (MEDLINE via PubMed and Scopus) to identify studies published in English up to March 2024. References from primary studies and the main peer-reviewed scientific journals were manually searched.

STUDY SELECTION

From an initial pool of 8126 articles, the reviewers meticulously selected 25 in vitro studies on objective comparisons between two or more methods for assessing marginal gaps in fixed dental prostheses on natural teeth. Publications that assessed marginal gaps in implant-supported fixed dental prostheses were excluded.

CONCLUSIONS

This study highlights that while traditional methods like CSM and SRT are widely used and validated, they have limitations in comprehensive gap assessment, often neglecting recommended measurement points. The DV technique, focusing solely on external gaps, may be less relevant for modern assessments. Conversely, three-dimensional techniques like TSM, DSM, OCT, and MCT offer a more thorough evaluation of dental restoration fit. Moreover, digital methods such as TSM and DSM have a significant potential for future clinical application.

CLINICAL SIGNIFICANCE

This review examined methods for evaluating marginal gaps in fixed dental prostheses. The review aids dental professionals and researchers in choosing the most suitable technique for clinical in vivo or laboratory assessment of the marginal adaptation of dental restorations. This study also indicates the need for an established and standardized assessment protocol for the marginal fit.

How do different intraoral scanners and milling machines affect the fit and fatigue behavior of lithium disilicate and resin composite endocrowns?

The aim of this in vitro study was to evaluate the effect of the combinations of two different intraoral scanners (IOS), two milling machines, and two restorative materials on the marginal/internal fit and fatigue behavior of endocrowns produced by CAD-CAM. Eight groups (n= 10) were considered through the combination of TRIOS 3 (TR) or Primescan (PS) IOS; 4-axes (CR; CEREC MC XL) or 5-axes (PM; PrograMill PM7) milling machines; and lithium disilicate (LD; IPS e.max CAD) or resin composite (RC; Tetric CAD) restorative materials. Specific surface treatments were applied to each material, and the bonding to its corresponding Endocrown-shaped fiberglass-reinforced epoxy resin preparations was performed (Variolink Esthetic DC). Computed microtomography (μCT) was performed to assess the marginal/internal fit, as well as a mechanical fatigue test (20 Hz, initial load = 100 N/5000 cycles; step-size = 50 N/10,000 cycles until a threshold of 1500 N, then, the step-size was increased if needed to 100 N/10,000 cycles until failure or a threshold of 2800 N) to evaluate the restorations long-term behavior. Complementary analysis of the fracture features and surface topography in scanning electron microscopy was performed. Three-way ANOVA and Kaplan-Meier test (α = 0.05) were performed for marginal/internal fit, and fatigue behavior data, respectively. PS scanner, CR milling machine, and RC endocrowns resulted in a better marginal fit compared to their counterparts. Still, the PM machine resulted in a better pulpal space fit compared to the CR milling machine. Regardless of the scanner and milling machine, RC endocrowns exhibited superior fatigue behavior than LD ones. LD endocrowns presented margin chipping regardless of the milling machine used. Despite minor differences in terms of fit, the 'IOS' and 'milling machine' factors did not impair the fatigue behavior of endocrowns. Resin-composite restorations resulted in a higher survival rate compared to glass-ceramic ones, independently of the digital devices used in the workflow.

Impact of different complete coverage onlay preparation designs and the intraoral scanner on the accuracy of digital scans

STATEMENT OF PROBLEM

The trueness and precision of intraoral scanners (IOSs) and the effect of intracoronal restorations have been reported. However, studies addressing the accuracy of IOSs in reproducing different complete coverage onlay preparation designs are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the influence of complete coverage onlay preparation design and intraoral scanning devices on the accuracy of digital scans in terms of trueness and precision.

MATERIAL AND METHODS

Three preparation designs on the mandibular first molar were considered: a traditional preparation design with isthmus reduction (IST), a traditional preparation design without isthmus reduction (wIST), and simplified nonretentive preparation (nRET). Digital scans of epoxy resin mandibular arch reference models of the preparations (containing second premolar, first molar, and second molar) were obtained by using 3 IOSs (iTero Element 2 [ELE], TRIOS 3 [TRI], and Primescan [PRI]) (n=10). Trueness (μm) and precision (μm) were analyzed by superimposing the digital scan on the digital reference models obtained with a high-accuracy industrial scanner (ATOS Core 80) in a tridimensional metrology software program. Accuracy was quantified by the absolute deviation (μm). Local and overall mean positive and negative deviations for trueness were also obtained. Data were analyzed by using the Kruskal-Wallis and Dunn tests with a statistical software program (α=.05).

RESULTS

The nonretentive preparation groups obtained higher trueness (3.8 μm) and precision (2.7 μm) than the IST and wIST groups (trueness=7.5 to 6.3 μm, precision=5.5 to 4.6 μm). Trueness values were lower with ELE×IST (16 μm), followed by ELE×wIST (13 μm), and PRI×IST (7.8 μm). In general, no difference was found between PRI and TRI scanners (6.3 to 5.9 μm), with lower performance for ELE (13 μm). Positive deviations were higher on the proximal box of the IST and wIST preparation and on the occlusal box of the IST group. Negative deviation was higher on the ELE×IST occlusal box.

CONCLUSIONS

Different intraoral scanners and preparation designs influenced the accuracy of digital scans. A more complex preparation such as IST and wIST showed higher deviation. The iTero Element 2 scanner exhibited higher deviation for both trueness and precision.

Influence of CAD-CAM milling strategies on the outcome of indirect restorations: A scoping review

STATEMENT OF PROBLEM

The influence of computer-aided manufacturing (CAM) parameters and settings on the outcomes of milled indirect restorations is poorly understood.

PURPOSE

The purpose of this scoping review was to summarize the current CAM systems, parameters, and setting changes, and their effects on different outcomes of milled indirect restorations and aspects related to their manufacture.

MATERIAL AND METHODS

The protocol of this review is available online (https://osf.io/x28ps/). Studies that used at least 2 different parameters (CAM units, number of axes, digital spacers, or protocols with different rotatory instruments, grit-sizes, milling speed, or others) for milling indirect restorations were included. A structured search up to July 2023 was performed by 2 independent reviewers for articles written in English in LILACS, MEDLINE via PubMed, EMBASE, Web of Science, and Scopus.

RESULTS

Of 1546 studies identified, 22 were included in the review. Discrepancies were found between the planned and actual measured cement space, with a decreasing linear relationship impacting restoration adaptation at different points. The CEREC MC XL milling machine was the most used system in the included studies, with variations in bur types, milling modes, and number of burs uses affecting internal fit and surface trueness. The results demonstrated the better adaptation of restorations made with 5-axis over 3-axis milling machines. Lithium disilicate and zirconia were the most commonly used materials, and crowns and inlays were popular designs. Marginal and internal adaptation were the primary outcomes assessed using the various techniques.

CONCLUSIONS

The study presented a comprehensive exploration of CAM systems and parameters, and their influence on indirect restorations. The planned cement space was not properly reproduced by the milling. Bur characteristics can affect restoration fit and trueness. The 5-axis units seem to result in better-adapted restorations compared with 3- and 4-axis units.

Influence of Immediate Dentin Sealing on Bond Strength of Resin-Based CAD/CAM Restoratives to Dentin: A Systematic Review of In Vitro Studies

Immediate dentin sealing (IDS) is a method of improving the bond strength of indirect dental restorative materials to dentin and belongs to the biomimetic protocols of contemporary dentistry. The purpose of this systematic review was to evaluate the effect of IDS on the bond strength of resin-based CAD/CAM materials to dentin. PubMed and MEDLINE, Scopus, and the Web of Science were searched by two individual researchers, namely for studies that have been published in English between 1 January 2005 and 31 December 2023 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The inclusion criteria encompassed articles related to in vitro studies, measuring the bond strength through microtensile bond strength (μ-TBS), micro-shear bond strength (μ-SBS), tensile bond strength (TBS) or shear bond strength (SBS) tests after the use of the IDS technique. The included restorative materials comprised resin-based CAD/CAM materials bonded to dentin. A total of 1821 studies were identified, of which 7 met the inclusion criteria. A meta-analysis was not deemed appropriate due to the high level of diversity inthe publications and techniques. The use of IDS yielded higher bond strength outcomesin various experimental conditions and resin-based CAD/CAM materials. Overall, IDS in CAD/CAM restorations may contribute to better clinical outcomesand improved restoration longevity due to this property.

Does the choice of the measuring technique affect the comparison of fit between zirconia and cobalt-chromium prostheses?

AIMS

The objectives of the study were to compare the adaptation of presintered zirconia and cobalt- chromium prostheses using microcomputed tomography (μCT), scanning electron microscopy (SEM), and stereomicroscope (SM).

MATERIALS AND METHODS

Twenty-four fixed dental prostheses (FDPs) were fabricated on metal abutments, duplicated from maxillary first premolar and first molar prepared on a typodont model. Teeth were reduced to obtain chamfer of 1.2 mm and reduction occlusaly of 2 mm occlusal. Scanning of the abutments was done with random assignment to two groups receiving the FDPs made from soft-milled Co-Cr (n = 12) and zirconia (n = 12). Marginal and internal gaps were assessed using three evaluation techniques (X-ray microcomputer tomography, SEM, and stereomicroscopy).

STATISTICAL ANALYSIS USED

Comparison of the results was made using Levene and analysis of variance tests (α =0.05).

RESULTS

Irrespective of the material tested, statistical differences were found between the measuring techniques (P = 0.001 overall); the obtained mean gaps were for CT scan (92.60 ± 13.31), for SEM (101.92 ± 23.03), and for SM (113.44 ± 14.68): the multiple comparisons between techniques found a significant difference between CT and SM (P < 0.001), and SEM and SM (P = 0.025). When materials were compared within each measuring technique, Co-Cr showed lower values compared to zirconia in SEM (P < 0.001) and Stereo (P = 0.049); similar results were found in CT.

CONCLUSIONS

Results values differed with the chosen measuring technique. Co-Cr prostheses had a better fit than zirconia prostheses in SEM and Stereo. µCT showed comparable results to SEM, smaller than SM results.

Marginal fit of three different nanocomposite inlays fabricated with computer-aided design/computer-aided manufacturing (CAD/CAM) technology: a comparative study

BACKGROUND

This study aimed to compare and evaluate the marginal fit of nanocomposite computer-aided design/computer-aided manufacturing (CAD/CAM) inlays. Three types of nanocomposite CAD/CAM blocks (HASEM, VITA Enamic, and Lava Ultimate) were used as materials.

METHODS

Class II disto-occlusal inlay restorations were prepared on a typodont mandibular right first molar using diamond rotary instruments. The inlays were fabricated using CAD/CAM technology and evaluated using the silicone replica technique to measure marginal gaps at five locations on each inlay. The data were analyzed by two-way analysis of variance and Tukey post hoc tests ( α=0.05).

RESULTS

There were no significant differences in the marginal gaps based on the type of nanocomposite CAD/CAM inlay used (p=0.209). However, there was a significant difference in the marginal gaps between the measurement regions. The gingival region consistently exhibited a larger marginal gap than the axial and occlusal regions (p<0.001).

CONCLUSION

Within the limitations of this in vitro study, the measurement location significantly influenced the marginal fit of class II disto-occlusal inlay restorations. However, there were no significant differences in the marginal gaps among the different types of CAD/CAM blocks. Furthermore, the overall mean marginal fits of the class II disto-occlusal inlay restorations made with the three types of nanocomposite CAD/CAM blocks were within the clinically acceptable range.

Examination of the effect of aging process on marginal fit and fractute strength of temporary crowns prepared from different materials

Aim

The aim of this study is to investigate the effect of the aging process on the marginal fit and fracture resistance of temporary crowns prepared using different materials.

Materials and method

The steel die to represent the maxillary first premolar used in this study was produced on a CNC turning machine to include an anatomical occlusal surface. A total of 160 epoxy resin dies were obtained by taking impressions with conventional impression methods on the metal die. Epoxy resin dies were randomly divided into four groups. Temporary crowns were prepared for each group from poly acrylic resin (Vita CADTemp®), bis-acryl composite resin (Protemp 4), poly methyl methacrylate (PMMA; Imident) and poly ethyl methacrylate (PEMA; Dentalon Plus) restorative materials. Half of the specimens (n = 20) in each group (n = 40) were randomly separated and the aging process was applied 5000 times in the device. Marginal gap measurements on epoxy resin dies were made using a stereomicroscope. The fracture strength test of the specimens was performed by using the Instron Universal Test Device. Jamovi 2.2.5 statistical program was used for statistical analysis.

Results

When compared to temporary crowns prepared from all other materials, poly acrylic resin (Vita CADTemp ®) temporary crowns observed significantly lower marginal gap values (59,05 μm) regardless of the aging process, and a significantly higher fracture resistance (478,44 N) in the presence of aging process (p < .05 for each). While the highest marginal gap value was detected in PMMA (Imident) (120.36 μm) temporary crowns with aging process, the lowest marginal gap value was observed in poly acrylic resin (Vita CADTemp®) (59.05 μm) crowns without non-aging process. The marginal fit and fracture resistance of all temporary crowns were negatively affected by the aging process.

Conclusion

Our findings revealed the superiority of poly acrylic resin (Vita CADTemp®) crowns to the temporary crowns prepared from all other materials in terms of the significantly lower marginal gap in the absence of aging process, and the significantly higher fracture resistance in the presence of aging process. Marginal fit and fracture resistance values for all materials were found to be within clinically acceptable limits.

Effect of ceramic materials and tooth preparation design on computer-aided design and computer-aided manufacturing endocrown adaptation and retentive strength: An in vitro study

OBJECTIVES

To evaluate how various tooth preparation designs impact the adaptation-both at the margins and internally-and the retentive strength of computer-aided design and computer-aided manufacturing (CAD/CAM) produced endocrowns.

MATERIALS AND METHODS

60 extracted human mandibular first molars were endodontically treated and assigned into three groups (n = 20) according to the tooth preparation design: Group N: butt joint design, Group F and F1 received 1- and 2-mm circumferential ferrule preparation, respectively. Endocrowns were milled using either lithium disilicate glass-ceramic (IPS emax ceramic) or monolithic zirconia. The internal and marginal adaptation of the endocrowns were evaluated using the replica technique. After cementation, the endocrowns of all test groups were dislodged axially at 0.5 mm/min using a universal testing machine. A 2-way ANOVA and the independent samples t-test (α = .05) were performed to statistically analyze the data.

RESULTS

The effect of changing the design of the tooth preparation (butt joint, ferrule) on the marginal and internal gap was shown to be statistically significant (p < .05); the lower gap values were recorded at the axial followed by cervical, marginal, and pulpal floor walls in both ceramic groups regardless of the teeth preparation design. The ANOVA test revealed similar average removal forces and stresses for the two types of tested ceramic materials.

CONCLUSION

IPS emax ceramic adapted better than monolithic zirconia ceramic, regardless of the preparation design. Ferrule preparation design is more retentive than butt joint preparation, regardless of the type of ceramic material used.

Fit analysis of stereolithography-manufactured three-unit resin prosthesis with different 3D-printing build orientations and layer thicknesses

STATEMENT OF PROBLEM

Printing conditions can affect the fit of a 3-dimensionally (3D) printed prosthesis. Therefore, it is important to determine the optimal printing conditions for stereolithography (SLA)-manufactured prostheses.

PURPOSE

The purpose of this study was to analyze the fit according to the build orientations and layer thicknesses in SLA-manufactured 3-unit resin prostheses.

MATERIAL AND METHODS

SLA 3D printed prostheses were produced in 5 build orientations (0, 30, 45, 60, and 90 degrees) and 2 layer thicknesses (50 and 100 μm). Milled prostheses were fabricated from the same design. The mounted prostheses on the master model were scanned with microcomputed tomography (μCT). Data were processed with the NRecon software program. For quantitative analysis, marginal and internal fits were measured by using the imageJ software program in terms of the following metrics: absolute marginal discrepancy, marginal gap, cervical area, midaxial wall area, line-angle area, and occlusal area. Internal gap volume was also measured with the CTAn software program. For statistical analysis, ANOVA and Tukey HSD tests were used (α=.05). For qualitative analysis, μCT cross-sections were compared among groups, and intaglio surfaces were imaged with a scanning electron microscope.

RESULTS

A layer thickness of 50 μm with build orientations of 45 and 60 degrees exhibited smaller mean gap values (P<.05) than the other conditions for all measurements except line-angle area and occlusal area. The scanning electron microscope images showed voids on the intaglio surfaces for the 0- and 90-degree groups.

CONCLUSIONS

For SLA 3D printed resin prostheses, a difference in fit occurred based on the printing conditions, although both 3D printed and milled prostheses showed a clinically acceptable fit. When an SLA 3D printed prosthesis is manufactured under appropriate conditions, a clinically acceptable fit can be obtained.

Clinical comparison of marginal fit of ceramic inlays between digital and conventional impressions

PURPOSE

The aim of this stuldy was to compare the clinical marginal fit of CAD-CAM inlays obtained from intraoral digital impression or addition silicone impression techniques.

MATERIALS AND METHODS

The study included 31 inlays for prosthodontics purposes of 31 patients: 15 based on intraoral digital impressions (DI group); and 16 based on a conventional impression technique (CI group). Inlays included occlusal and a non-occlusal surface. Inlays were milled in ceramic. The inlay-teeth interface was replicated by placing each inlay in its corresponding uncemented clinical preparation and taking interface impressions with silicone material from occlusal and free surfaces. Interface analysis was made using white light confocal microscopy (WLCM) (scanning area: 694 × 510 µm2) from the impression samples. The gap size and the inlay overextension were measured from the microscopy topographies. For analytical purposes (i.e., 95-%-confidence intervals calculations and P-value calculations), the procedure REGRESS in SUDAAN was used to account for clustering (i.e., multiple measurements). For p-value calculation, the log transformation of the dependent variables was used to normalize the distributions.

RESULTS

Marginal fit values for occlusal and free surfaces were affected by the type of impression. There were no differences between surfaces (occlusal vs. free). Gap obtained for DI group was 164 ± 84 µm and that for CI group was 209 ± 104 µm, and there were statistical differences between them (p = .041). Mean overextension values were 60 ± 59 µm for DI group and 67 ± 73 µm for CI group, and there were no differences between then (p = .553).

CONCLUSION

Digital impression achieved inlays with higher clinical marginal fit and performed better than the conventional silicone materials.

The loss of resin cement adhesion to ceramic influences the fatigue behavior of bonded lithium disilicate restorations

When partial and/or non-retentive preparation, such as those for occlusal veneers, is indicated, a proper and stable adhesion is essential. Therefore, the aim of this in vitro study was to evaluate the effect of loss of adhesion in different regions of the bonding interface on the fatigue behavior of simplified lithium disilicate restorations. For this, lithium disilicate (IPS e.max CAD) discs (1 mm thick and Ø = 10 mm) were fabricated, polished with #400-, #600-, #1200-grit silicon carbide (SiC) papers, and crystallized. As substrate, fiber-reinforced resin epoxy discs (2.5 mm thick and Ø = 10 mm) were fabricated and polished with #600-grit SiC paper. The ceramic bonding surface was treated with 5% hydrofluoric acid and a silane-containing primer (Monobond N), while the substrate was etched with 10% hydrofluoric acid followed by the application of the bonding system primers (Primer A + B). A lacquer (nail polish) was used to simulate the loss of adhesion in specific areas according to the study design to compose the testing groups: bonded (control; did not received nail polish application); - non-bonded (loss of adhesion in the whole specimen area); - margin (loss of adhesion in the ceramic margin); - center (loss of adhesion in the ceramic central area). The adhesive area of partially bonded groups was 50% of the adhesive surface. Then, the discs (n = 12) were bonded to the respective substrate using a resin cement (Multilink N), light-cured, water-stored for 90 days, and subjected to thermocycling (25,000 cycles, 5° to 55 °C) before testing. A cyclic fatigue test was run (20 Hz, initial load of 200 N for 5000 cycles, 50 N step size for 10,000 cycles each until specimen failure), and the fatigue failure load and number of cycles for failure were recorded. As complementary analysis, finite element analysis (FEA) and scanning electron microscopy analysis were performed. Kaplan-Meier log-rank (Mantel-Cox) was conducted for survival analysis. The results showed that as the loss of adhesion reaches the central area, the worse is the fatigue behavior and the higher is the stress peak concentration in the ceramic bonding surface. The bonded specimens presented better fatigue behavior and stress distribution compared to the others. In conclusion in a non-retentive preparation situation, proper adhesion is a must for the restoration fatigue behavior even after aging; while the loss of adhesion reaches central areas the mechanical functioning is compromised.

Marginal and internal fit of five-unit zirconia-based fixed dental prostheses fabricated with digital scans and conventional impressions: A comparative in vitro study

PURPOSE

This study aimed to compare the marginal and internal fit of five-unit zirconia-based fixed dental prostheses (FDPs) fabricated using digital scans and conventional impressions.

MATERIALS AND METHODS

Nine master models with three zirconia abutments were scanned with an intraoral scanner (test group), and nine conventional impressions (control group) of these same models were also made. The stone casts from these impressions were scanned with a laboratory extraoral scanner (D700, 3Shape, Copenhagen, Denmark). A total of 18 five-unit zirconia-based FDP frameworks (test group, n = 9; control group, n = 9) were manufactured. Marginal and internal fit (in μm) were evaluated using the replica method under micro-computed tomography. Analysis of variance (one-way ANOVA) and Kruskal-Wallis tests were used to compare continuous variables across two groups. A level of p < 0.05 was accepted as statistically significant.

RESULTS

The mean ± standard deviation of the marginal fit was 95.03 ± 12.74 μm in the test group and 106.02 ± 14.51 μm in the control group. The lowest marginal mean value was observed in the test group, with a statistically significant difference compared to the control group (F = 14.56, p < 0.05). The mean ± standard deviation of the internal fit was 103.61 ± 9.32 and 106.38 ± 7.64 μm, respectively, in the test and control groups, with no statistically significant difference (F = 1.56, p > 0.05). The mean values of both groups were clinically acceptable.

CONCLUSIONS

The five-unit zirconia-based FDPs fabricated with digital scans showed better fit than those in the conventional impression group. Within the limitations of this study, these results are encouraging, and continued progress in the digital field should allow for more accurate long-span restorations.

Effect of different impression techniques on marginal fit of restoration - An In Vitro study

Introduction

Impression making is one such important clinical step, which is critical in the accurate fitting of resulting prostheses. Impression making itself depends on the type of material and the impression technique used to record the details. Various combinations of material and the technique have been described in the literature.

Aim

To evaluate the effect of three different impression techniques on the marginal fit of computer-aided designed/computer-aided manufactured (CAD/CAM) single unit composite fixed dental prostheses (FDP), different consistencies of addition silicone impression material and different tray design were utilized.

Method

Impression of prepared tooth on typodont was made using Matrix impression system, two-step putty wash technique, and individual tooth tray technique. Prosthesis was fabricated using CAD/CAM technology and marginal accuracy was evaluated using scanning electron microscopy (SEM).

Result

In the present study, the matrix impression system resulted in less microgap in both mid-buccal and mid-mesial region, whereas putty wash technique showed very high standard deviation in the interproximal region.

Conclusion

Matrix impression system had the best results at both mid-buccal and mid-mesial position with least marginal discrepancy.

Clinical Implication

The findings of this study could be used by clinicians to help them choose the viscosity of polyvinylsiloxane material and impression techniques for FDP that will result in high-accuracy impressions and well-fitting prostheses.

Comparing the accuracy of distinct scanning systems and their impact on marginal/internal adaptation of tooth-supported indirect restorations. A scoping review

OBJECTIVE

To summarize the existing scientific evidence on the effect of distinct intraoral (IOS) and extraoral (EOS) scanners in terms of their accuracy for image acquisition and the marginal/internal adaptation of indirect restorations.

METHODS

The protocol of this scoping review is available online (https://osf.io/cwua7/). A structured search, with no date restriction, was performed in LILACS, MEDLINE via Pubmed, EMBASE, Web of Science, and Scopus, for articles written in English. The inclusion criteria were studies that considered at least two scanners, regardless of method (intra or extraoral), for the production of tooth-supported restorations. Two independent and blinded researchers screened the studies, collected and analyzed the data descriptively.

RESULTS

103 studies were included (55 on marginal/internal adaptation, 33 on accuracy, 5 on both outcomes, and 10 reviews). Most of them, shown clinically acceptable adaptation (<120 μm). Factors commonly related to the performance of scanners are: use of anti-reflection powders, method of image acquisition, and restoration/tooth characteristics. The need of anti-reflection powders was controversial. Different scanning principles seems to result on similar performance; IOS that combine them could be promising. The most explored systems were Omnicam - IOS, and inEos X5 - EOS, which showed similar performance on marginal/internal adaptation. Scarce studies explored the performance of EOS systems, especially in terms of accuracy. Different restoration designs as single-unit seemed not to modify the performance of scanners. Limited information is available regarding the planned cement space, restorative material and design (multi-unit restorations), as also techniques to measure adaptation.

CONCLUSIONS

Digital scanners are valid approaches to obtain accurate impressions resulting in clinically acceptable restorations. Systems that uses combined principles of image acquisition seems promising for optimal performance. Based on high discrepancy, the quality of evaluated evidence is low, and well-designed studies are still encouraged, especially considering validated IOS/EOS as a control comparison condition.

A Comparative Study of the Marginal Fit of Endocrowns Fabricated From Three Different Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) Ceramic Materials: An In Vitro Study

INTRODUCTION

The marginal seal and adaptation are important factors for successful restoration. An inadequate marginal seal can lead to bacterial microleakage, plaque accumulation, and eventually treatment failure This in vitro study aimed to compare the marginal gap of endocrowns fabricated from three different computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic materials.

METHODS

Thirty extracted mandibular molars were selected for the study. Endocrown preparations were completed after root canal treatment. Teeth were divided into three groups to receive endocrowns fabricated of lithium disilicate ceramic (IPS-e.max CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein), zirconia-reinforced lithium silicate ceramic (VITA Suprinity®, VITA Zahnfabrik, Bad Säckingen, Germany), and polymer-infiltrated ceramic (VITA Enamic®, VITA Zahnfabrik). The digital impressions were transferred to the design software to construct the endocrowns. The endocrowns were milled and cemented. The marginal fit was examined using a digital camera stereomicroscope at a magnification of 80X. Images were transferred to Image-J software (National Institutes of Health, Bethesda, Maryland, United States) to measure the marginal gap.

RESULTS

One-way ANOVA showed a significant difference in the marginal gap between the different ceramic groups (P=0.006). Tukey's Honest Significant Difference (HSD) post-hoc test showed that VITA Suprinity had significantly higher gap width values than VITA Enamic (P=0.005). No significant differences in gap width values were found between VITA Enamic and IPS e.max CAD or between VITA Suprinity and IPS e.max CAD (P>0.05).

CONCLUSION

The marginal gap of endocrown restorations varies with different CAD/CAM materials (zirconia-reinforced lithium silicate glass-ceramic, polymer-infiltrated hybrid ceramic, and lithium disilicate glass-ceramic), but are all within clinically acceptable marginal gap width.

Micro-CT analysis of marginal and internal fit of milled and pressed polyetheretherketone single crowns

STATEMENT OF PROBLEM

Polyetheretherketone (PEEK) has been increasingly used as a framework material in prosthetic dentistry. However, data on the marginal and internal fit of PEEK restorations fabricated by using either the computer-aided design and computer-aided manufacturing (CAD-CAM) or heat-pressing technique are sparse.

PURPOSE

The aim of this in vitro study was to assess the marginal and internal fit of milled and pressed PEEK single crowns by using microcomputed tomography (μCT).

MATERIAL AND METHODS

A custom-made, single stainless-steel die was designed to replicate a maxillary first premolar prepared for a ceramic crown. PEEK copings (N=30) were fabricated and allocated to 3 groups (n=10) according to the fabrication technique: milled from a prefabricated PEEK blank, heat pressed from PEEK pellets, and heat pressed from PEEK granules. All copings were veneered with a composite resin material. The marginal fit was recorded at 4 predetermined points and the internal fit at 8 predetermined points on each crown by using μCT. Two-way ANOVA, pair-wise Tukey honestly significant difference (HSD), and simple main effect tests were used for statistical analysis of the data (α=.05).

RESULTS

Concerning marginal fit, the milled crowns demonstrated the best marginal fit overall (44 ±3 μm), followed by those pressed from pellets (92 ±3 μm), and finally by those pressed from granules (137 ±7 μm) (P<.001). The interaction between the effects of the fabrication technique and the measurement point on the marginal fit was not statistically significant (P=.142). The milled crowns demonstrated the lowest mean gap values overall, followed by those pressed from pellets and those pressed from granules (P<.001). The interaction between the effects of the fabrication technique and the measurement point on the internal fit was statistically significant (P<.001). Except for the distal occlusal gap and mesial occlusal gap, all tested groups showed a statistically significant difference (P<.001). In addition, statistically significant differences were observed among all measurement points in different fabrication techniques (P<.001).

CONCLUSIONS

The marginal and internal fit of milled PEEK crowns was significantly better than pressed crowns. However, both CAD-CAM and heat-pressing techniques produced PEEK crowns with a clinically acceptable marginal and internal fit. The mean marginal gap of the PEEK crowns pressed from granules was above the range of clinically acceptable value.

The Effect of Firing Cycles on the Fit of Cobalt-Chromium Multiunit Prostheses Fabricated by Additive Manufacturing

PURPOSE

The effect of annealing and firing cycle on the adaptation of cobalt-chromium (CoCr) restorations fabricated by additive manufacturing has been poorly documented. This study compared the marginal and internal fit of CoCr three-unit fixed dental prostheses before and after firing cycles.

MATERIAL AND METHODS

The first right maxillary premolar (MP) and molar (MM) on a typodont model, were prepared with a circumferential 1.2 mm chamfer, 2 mm occlusal reduction, and total taper of 8 degrees, to receive 3-unit fixed dental prostheses (FDP). After the framework design, 20 framework specimens were fabricated using CoCr metal powder by selective laser melting. The replica technique was used for marginal and internal fit measurements in mesiodistal and buccolingual planes. The specimens were submitted to an annealing process, and to ceramic firing protocol. Measurements were repeated after each firing cycle. The data were compared by using Levene test, t-test, and analysis of variance (ANOVA) (α = 0.05).

RESULTS

A significant difference was found in the total intaglio surface discrepancy between the 3 treatments. The annealing treatment induced a statistical difference in the discrepancy value compared to the as printed state (p = 0.028). A significant difference was detected between the initial manufacturing phase and the ceramic layering firing cycle (p = 0.003).

CONCLUSIONS

Firing cycles induced an alteration of the frameworks adaptation.

A Micro-computed Tomography Analysis of Marginal and Internal Fit of Endocrowns Fabricated from Three CAD/CAM Materials

OBJECTIVE

To assess the marginal and internal misfit of endocrowns fabricated from a resin matrix ceramic (CS), a partially crystallized (EMC), and a fully crystallized (ILS) lithium disilicate glass-ceramic.

METHODS AND MATERIALS

Thirty human premolar teeth restored with endocrowns were investigated. Three CAD/CAM materials were used (n=10 per group): CS, EMC, and ILS. Two-dimensional (2D) analysis of marginal and internal misfit was performed on micro-computed tomography scans before and after adhesive bonding. Further, three-dimensional (3D) analysis was performed to determine the total internal volume discrepancy. Surface roughness of the fitting surfaces of endocrowns was characterized using optical profilometry and scanning electron microscopy.

RESULTS

Adhesive bonding did not significantly affect marginal or internal misfit (p≥0.093). Differences in marginal misfit among the experimental groups were not statistically significant (p≥0.221). However, differences in 2D internal misfit were statistically significant; the CS group exhibited the largest internal misfit (p=0.001), while no significant difference was found between other groups (p=0.123). The largest discrepancies were observed at the pulpal floor and cervical region of all investigated specimens. No statistically significant difference was found in 3D misfit between ILS and EMC groups (p=0.711); however both exhibited statistically lower 3D misfit values compared to the CS group (p≤0.037). ILS endocrowns exhibited the smoothest and most homogenous fitting surface profile (p<0.001). However, there was no significant correlation between 2D internal misfit and the surface roughness (p≥0.082).

CONCLUSIONS

The choice of CAD/CAM material may influence the fitting accuracy of endocrowns. The investigated lithium disilicate glass-ceramics conferred superior internal fit for endocrowns compared to resin matrix ceramic.

Does cad software affect the marginal and internal fit of milled full ceramic crowns?

Although the effects of different intraoral scanners, model scanners, and CAM units on the marginal and internal fitting of restorations have been investigated, the effects of CAD software in particular has not been evaluated. The marginal and internal fit of indirect restorations may vary according to the CAD software used, even when using the same intraoral scanner and milling machine. The purpose of this study was to evaluate the marginal and internal fit of milled full ceramic crowns designed with three different CAD systems. Eleven typodont maxillary first premolar teeth were prepared and scanned using a 3Shape TRIOS Intraoral Dental Scanner. The obtained STL scan data were exported and used to design a full crown using three different CAD systems (CEREC, KaVo, and Planmeca). An independent milling unit was used to manufacture the crowns for each group (n = 11). The marginal and internal fit were evaluated for each restoration using 2D and 3D micro-CT analysis. For 2D analysis, 18 measurements for each sample were made, covering the marginal (Marginal Gap Buccal (MG-A), Marginal Gap Palatinal (MG-B), Finish Line Buccal (FL-A), Finish Line Palatinal (FA-B)) and internal fit locations (Axial Wall Buccal (AW-A), Axial Wall Palatinal (AW-B), Lingual Cusp (LC), Buccal Cusp (BC), and Occlusal Central Fossa (OCF)). Statistical analyses were performed using Open Source R Statistical Software (α = 0.05) The results of Duncan's multiple range test showed that the values for the marginal measurement points MG-A, MG-B, FL-A, and FL-B in the Planmeca group were significantly higher than the values obtained in the CEREC and KaVo groups (p < 0.05). In AW1, values of the CEREC group were found to be higher than those of the KaVo and Planmeca groups (p < 0.05). CAD software showed an effect on the marginal fit values of crowns whereas no significant difference was observed in terms of the internal fit, except for a single measurement point made from the buccal direction.

Effect of cement space on marginal discrepancy and retention of CAD/CAM crown

This research aimed to evaluate the effect of cement space on the marginal discrepancy and retention of computer-aided design/computer-aided manufacturing (CAD/CAM) crowns. A total of 30 premolar Frasaco teeth were machined to receive crowns with cement spaces of 70, 90, and 110 μm. The marginal discrepancy measurements were done before and after cementation. Pull-off test was conducted using universal testing machine (UTM). Data was analyzed using two-way mixed ANOVA with post-hoc Bonferroni test and Kruskal-Wallis test. The crowns with cement space of 70 μm showed a significantly higher absolute marginal discrepancy than those with 90 and 110 μm. No significant effect on the crown retention was found. Within the limitations of this study, modifying cement space to 90 μm and 110 μm may improve the marginal adaptation of CAD/CAM crown, whereas adjusting cement space from 70 to 110 μm did not significantly affect the crown retention.

Effect of ceramic layering on the fit of cobalt-chromium alloy 3-unit fixed dental prostheses fabricated by additive, soft milling, and casting technologies

STATEMENT OF PROBLEM

The change in fit after ceramic layering of additively manufactured cobalt-chromium alloy frameworks has not been evaluated extensively.

PURPOSE

The purpose of this in vitro study was to compare the fit of cobalt-chromium alloy fixed dental prostheses fabricated by different techniques before and after ceramic layering.

MATERIAL AND METHODS

A cobalt-chromium alloy master model was prepared to receive a 3-unit fixed dental prosthesis. Sixty cobalt-chromium alloy frameworks (N=60) were manufactured by using 3 manufacturing techniques (n=20): selective laser melting (Mediloy S-Co), soft milling (Ceramill Sintron), and conventional casting as the control group (Girobond NB). The replica technique was used to measure the marginal and internal discrepancies. The frameworks were then layered with ceramic, and the same fit measuring procedure was repeated. The results were compared before and after ceramic layering within each group. The data were analyzed using the Levene, ANOVA, and paired-samples t tests (α=.05).

RESULTS

A significant difference was found within groups before and after ceramic layering for selective laser melting (P=.006) and soft milling (P=.009) but not for conventional casting (P>.05). No statistical difference was reported in the marginal region for conventional casting group (P=.155) in contrast with the soft milling and selective laser melting groups (P=.003). Soft milling showed increased gap values in the marginal (P=.006) and occlusal regions (P=.004).

CONCLUSIONS

Ceramic layering increased the discrepancy of the laser-sintered and milled frameworks, increasing the marginal discrepancy.

Evaluation of fits of metal copings fabricated by using selective laser melting at various angles

STATEMENT OF PROBLEM

Information on the fabrication of metal by selective laser melting (SLM) systems positioned at different angles is sparse.

PURPOSE

The purpose of this in vitro study was to evaluate the extent of marginal and internal gaps in metal copings fabricated at different angles by using an SLM fabrication system.

MATERIAL AND METHODS

A master metal model was produced and replicated (N=10) with silicone impressions and dental stone. Standard tessellation language (STL) files of the 10 coping designs were then obtained by using a model scanner and a 3D design software program on a scannable working die. Co-Cr alloy metal copings were fabricated by the SLM fabrication system at 45, 90, and 180 degrees. The marginal and internal gaps were measured by the silicone replica technique. The measured data were analyzed by using the nonparametric Kruskal-Wallis H test (α=.05).

RESULTS

The specimens fabricated at 180 degrees showed the best fit in terms of the marginal gap, while the worst fit was observed in the specimens fabricated at 90 degrees. Statistically significant differences were seen among the marginal gaps produced in the 3 groups (P<.001). In terms of internal fit, the axial wall gap showed the best fit, and the occlusal gap the worst. The best fit overall was 66 μm at the axial wall of the 180-degree group, and the worst in the 90-degree group, at 663 μm. Statistically significant differences were observed between the chamfers, axial walls, and the occlusal gaps of the 3 groups (P<.001).

CONCLUSIONS

Restorations fabricated by using an SLM system at 180 degrees were clinically acceptable. However, more research is required to investigate the performance of metal copings produced at 45 and 90 degrees to evaluate their clinical acceptability.

Fit Alteration of Presintered Co-Cr and Zirconia Multiple-Unit Prostheses After Ceramic Layering

PURPOSE

The fit alteration after ceramic layering of soft Cobalt-Chromium (Co-Cr) and zirconia is poorly documented. This study compared the marginal and internal fit of presintered Co-Cr and zirconia three-unit fixed dental prostheses before and after ceramic veneering.

MATERIALS AND METHODS

Co-Cr master model was prepared and duplicated 60 times to receive three-unit fixed dental prostheses (FDPs). Sixty dies were prepared, scanned and assigned to 3 groups (n = 20/group), to receive the FDPs made of presintered Co-Cr (CS), presintered zirconia (CZ) and cast Ni-Cr (Wi). Each framework was seated on its specific cast. A replica technique was used for marginal and internal discrepancy measurements in mesiodistal and buccolingual planes. Frameworks were ceramic veneered. Results were compared before and after ceramic layering within each group. Data were analyzed using the Levene, t test, and ANOVA (α = 0.05).

RESULTS

Significant difference was found when gaps were compared within groups for CS and CZ but not for Wi. At the abutments level, significant difference was found for both premolars and molars in the buccolingual planes (p < 0.001). A multiple comparison between materials tested showed significant differences between presintered and cast Ni-Cr. No significant difference was detected between CS and CZ (p = 1.000).

CONCLUSIONS

Although ceramic layering increased the discrepancy for presintered Co-Cr and zirconia, the marginal adaptation remained clinically acceptable.

Does overlay preparation design affect polymerization shrinkage stress distribution? A 3D FEA study

This study evaluated the polymerization shrinkage stress of three tooth preparation designs for indirect ceramic overlay by finite element analysis: isthmus preparation (IST); without isthmus preparation (wIST); and non-retentive preparation (nRET). The models were created based in prepared dental typodonts and were digitally impressed with an intraoral scanner. The interfaces in all models were considered perfectly bonded and all materials were considered homogeneous, linear, and isotropic. The polymerization shrinkage of the cement layer (100 µm) was simulated and evaluated by maximum principal stress criteria. The stress peaks followed this sequence: restoration = IST (13.4 MPa) > wIST (9.3 MPa) > nRET (9 MPa); cement layer = IST (16.9 MPa) > wIST (12.6 MPa) > nRET (10-7.5 MPa); and teeth = IST (10.7 MPa) > wIST (10.5 MPa) > (9 MPa). For the cement layer, the non-retentive preparation (nRET) had the lowest shrinkage stress from all the groups, obtaining a more homogeneous stress distribution on the cement surface. Regarding the abutment teeth, the IST generated a higher shrinkage stress area on the dental structure, concentrating higher stress magnitude at the axiopulpar and axiogingival angles. Non-retentive preparation seems to reduce polymerization shrinkage stress.

X-ray microtomographic evaluation of the absolute marginal fit of fixed prostheses made from soft Co-Cr and zirconia

STATEMENT OF PROBLEM

The absolute marginal fit of CAD-CAM presintered fixed partial dentures has been poorly documented.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal fit of presintered cobalt-chromium (Co-Cr) and zirconia 3-unit fixed partial dentures by using X-ray microcomputed tomography (μCT).

MATERIAL AND METHODS

A metal model was prepared from a typodont to receive fixed partial dentures (N=12). The maxillary first premolar and first molar were prepared with a circumferential 1.2-mm chamfer and 2-mm occlusal reduction. The dies were scanned and assigned to 1 of 2 groups to receive the prostheses made of presintered Co-Cr or presintered zirconia (n=6). Each framework was seated on its model without load application. The abutments were scanned by using μCT. A circle with 10 diameters, with a step of 18 degrees, was projected at the center of the obtained image. Absolute marginal discrepancy and marginal gap mean values were measured, and overextended and underextended margins determined. The data were analyzed by using the Levene t test and ANOVA (α=.05).

RESULTS

No statistically significant difference was found in the marginal fit between the materials tested (P=.939). The mean values were 66 ±14 μm for Co-Cr and 61 ±12 μm for zirconia. The absolute marginal discrepancy mean value for the premolar was 69 ±12 μm and 41 ±9 μm for the molar (P<.001). Overextension was predominant for both materials tested, with a higher percentage reported for the zirconia group.

CONCLUSIONS

Presintered alloys presented clinically acceptable adaptation with a predominance of marginal overextensions.

Comparison of marginal adaptation and internal fit of monolithic lithium disilicate crowns produced by 4 different CAD/CAM systems

OBJECTIVES

To evaluate the marginal adaptation and internal space of crowns produced by 4 CAD/CAM systems using microcomputed tomography (μCT) and replica technique (RT).

MATERIALS AND METHODS

Monolithic lithium disilicate crowns were milled (Ceramill, Cerec, EDG, and Zirkonzahn) (n = 10). The cement film obtained with low viscosity silicone was scanned by the μCT system and captured by a stereomicroscope, according to RT. Two-way ANOVA followed by Tukey's test were used for statistical analysis (α = 0.05). A uniformity index (UI) was idealized to describe the distribution of crowns' internal space and submitted to the Kruskal-Wallis and Tukey's test (α = 0.05). The correlation between μCT and RT was performed by Pearson's Correlation Coeficient (α = 0.05).

RESULTS

Marginal adaptation and internal space were statistically significant different between the experimental groups for the μCT and RT (p < 0.05). The medians of the 4 systems tested were within clinically acceptable range and the mean (± SD) highest marginal discrepancy was recorded in the Ceramill group at 133.0 ± 71.5 μm (μCT) and 90.6 ± 38.5 μm (RT). For internal fit, the UI disclosed a better distribution of the internal space for the Zirkonzahn group (p < 0.001). There was a strong correlation between the methods (p = 0.01 and r = 0.69).

CLINICAL RELEVANCE

Because of the variability of the CAD/CAM systems available, evaluating their accuracy is of clinical interest. The 4 systems are capable to produce restorations adaptated within clinically appropriate levels. The μCT and RT are efficient adaptation methodologies.

Influence of the Fabrication Technique on the Marginal and Internal Adaptation of Ceramic Onlays

This study aimed to evaluate the marginal and internal adaptation of partial coverage crowns (ceramic onlays) fabricated with Press, CEREC BlueCam, and CEREC OmniCam systems, using two preparation designs and evaluating the internal discrepancies at different locations. Two phantom maxillary premolars (master teeth) received different preparation designs, with (BX) and without (NB) a modified occlusal box with round internal angles. Sixty IPS e-max ceramic restorations were fabricated with three systems: Press (n=20), CEREC BlueCam (n=20), and CEREC OmniCam (n=20). Both marginal and internal discrepancy width were measured by using a stereomicroscope at ×25 magnification. The data were evaluated statistically using analysis of variance followed by Tukey's Honestly Significant Difference test (α=0.05). The ceramic restorations fabricated with the Press system presented significantly smaller marginal and internal disadaptations than the BlueCam and OmniCam CEREC systems (p&lt;0.0001). Regarding the preparation designs, preparation BX presented the smallest marginal discrepancies for all fabrication systems and larger internal discrepancies than for restorations fabricated with the Press system. The occlusal location presented a larger internal discrepancy compared with the axial locations. Although the three systems resulted in the fabrication of restorations within a clinically acceptable adaptation with marginal discrepancies below 100 μm, the Press system presented the smallest marginal and internal discrepancies. An improved marginal adaptation was observed in the preparation design with a modified occlusal box with rounded internal angles.

Effect of tooth preparation design on marginal adaptation of composite resin CAD-CAM onlays

STATEMENT OF PROBLEM

Although different preparation designs have been proposed for onlays fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM), their effect on marginal adaptation is unclear.

PURPOSE

The purpose of this in vitro study was to investigate the effect of tooth preparation designs on the marginal and internal adaptation of ceramic-reinforced composite resin CAD-CAM onlays.

MATERIAL AND METHODS

A traditional preparation with a heavy chamfer on the functional cusp and a contrabevel on the nonfunctional cusp and a shoulder preparation with equal reduction on all cusps were used for mesial-occlusal-distal (MOD) onlay preparations. Ceramic-reinforced composite resin onlays were designed and milled based on the scanned prepared teeth. A digital silicone replica technique was used to determine marginal discrepancies between preparations and onlay restorations. A total of 100 numeric distances (representations of the fit in each region) were measured in 3 distinct regions: the buccal margin, lingual margin, and internal area. Independent Student t tests were used to determine significant differences (α=.05).

RESULTS

Traditional preparation designs resulted in significantly smaller overall discrepancies (50.9 ±0.5 μm and 139.1 ±5.4 μm, P<.001) and smaller marginal discrepancies in the buccal (49.7 ±1.4 μm and 135.8 ±2.2 μm, P<.001) and lingual areas (47.1 ±1.0 μm and 133.4 ±1.1 μm, P<.001).

CONCLUSIONS

The marginal adaptation of ceramic-reinforced composite resin CAD-CAM onlays was affected by the preparation design. The traditional preparation design offered better marginal adaptation; therefore, it is recommended in clinical practice.

Effects of Printing Parameters on the Fit of Implant-Supported 3D Printing Resin Prosthetics

The purpose of the study was to investigate the influence of 3D printing parameters on fit and internal gap of 3D printed resin dental prosthesis. The dental model was simulated and fabricated for three-unit prostheses with two implants. One hundred prostheses were 3D printed with two-layer thicknesses for five build orientations using a resin (NextDent C&B; 3D systems, Soesterberg, The Netherlands) and ten prostheses were manufactured with a milling resin as control. The prostheses were seated and scanned with micro-CT (computerized tomography). Internal gap volume (IGV) was calculated from 3D reconstructed micro-CT data. IGV, marginal fit, and lengths of internal gaps were measured, and the values were analyzed statistically. For the 3D printed prostheses, IGV was smaller at 45°, 60°, and 90° compared to other build orientations. The marginal fit evaluated by absolute marginal discrepancy was smaller than other build orientations at 45° and 60°. IGV was smaller at 50 µm layer thickness than at 100 µm layer thickness, but the marginal fit was smaller at 100 µm layer thickness than at 50 µm layer thickness. The 3D printed prosthesis had smaller internal gap than the milled prosthesis. The marginal fit of the 3D printed resin prosthesis was clinically acceptable, and build orientation of 45° and 60° would be recommended when considering fit and internal gap.

Effect of different CAD-CAM materials on the marginal and internal adaptation of endocrown restorations: An in vitro study

STATEMENT OF PROBLEM

Recent resin-based and ceramic-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials have been used to restore endodontically treated teeth. Adaptation of the restoration is important for clinical success, but studies evaluating the effect of these materials on the adaptation of endocrowns are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of resin-based and ceramic-based materials on the marginal and internal adaptation of endocrowns.

MATERIAL AND METHODS

Forty mandibular molars were divided into 4 groups (n=10); each group was restored with a different CAD-CAM material: group C: hybrid nanoceramic (Cerasmart; GC Corp), group T: fiber-composite material (Trilor; Bioloren Srl), group E: lithium disilicate glass-ceramic (IPS e.max CAD; Ivoclar Vivadent AG), and group V: zirconia-reinforced lithium silicate glass-ceramic (Vita Suprinity; VITA Zahnfabrik GmbH). A digital scan was made with an intraoral digital scanner (TRIOS 3; 3Shape A/S), and endocrowns were milled with a 5-axis milling machine (Coritec 250i; imes-icore GmbH). The replica technique and a stereomicroscope (×70) were used to measure the marginal and internal adaptation of the endocrowns at 32 points. All data were statistically analyzed using 1-way ANOVA and the Tukey honestly significant difference test (α=.05).

RESULTS

Statistical tests showed significant differences among the tested groups (P<.001). The resin-based groups displayed larger discrepancies than the ceramic-based groups. The resin-based groups showed a mean marginal gap larger than the mean internal gap C (P=.009), T (P<.001), whereas the ceramic-based groups showed similar gaps, V (P=.396), E (P=.936). The largest gap was observed at the pulpal floor (P<.001).

CONCLUSIONS

All materials had clinically acceptable internal and marginal gaps (≤150 μm), except for the marginal gap of the Trilor group.

Marginal quality of ceramic inlays after three different instrumental cavity preparation methods of the proximal boxes

Objectives

The marginal quality of ceramic inlays was evaluated after the use of three different instrumental finishing methods in mesio-occluso-distal (mod) cavity boxes in vitro after hydrothermal loading (HTL).

Materials and methods

Caries-free human molars were divided into three groups. Mod-cavities were conventionally prepared. Box finishing was performed in every group with rotating (RI), sonic (SI), or ultrasonic (USI) instruments. Surface roughness was examined. Twelve mod-cavities remained untreated. Continuous margin quality was evaluated with scanning electron microscopy (SEM). Ceramic inlays were cemented into cavities. After HTL microleakage, marginal and absolute marginal gaps were examined. All data were analyzed statistically.

Results

Significant differences were found, between cavity surface roughness of RI and SI groups, the RI and USI groups, but not between microleakage, marginal, absolute marginal gaps after HTL and in proximal marginal quality. No correlations between microleakage and marginal gaps nor between microleakage and surface roughness were found.

Conclusion

Mod-cavity proximal box finishing with SI or USI resulted in a higher surface roughness than the use of RI. The type of the finishing method did not influence the marginal quality of ceramic inlays. For the mod-cavity finishing, the use of SI and USI could be an alternative instrumental method to conventional RI methods with a lower risk of iatrogenic damage of the adjacent teeth.

Clinical relevance

This study allows the practitioner to better determine the proper indications and limitations of the sonic and ultrasonic instruments for mod-cavity proximal box finishing.

Effect of total occlusal convergence on fit and fracture resistance of zirconia-reinforced lithium silicate crowns

Introduction

Computer-aided design (CAD) and computer-aided manufacturing (CAM) monolithic crowns are gaining momentum. Limited evidence exists about the effect of tooth preparation total occlusal convergence (TOC) on marginal and internal gap distances in addition to load to fracture values.

Aim

The aim of this study was to evaluate, by microcomputed tomography (µCT), the influence of 12° and 20° TOC on marginal and internal adaptation of zirconia-reinforced lithium silicate (ZLS) crowns. Moreover, values of load to fracture with and without initial cyclic loading (CL) were compared.

Material and methods

Forty ZLS crowns were fabricated on dies with TOC of 12° and 20°, 20 crowns for each group. µCT was used to compare marginal and internal adaptation. Each specimen was measured at 140 points distributed on all tooth preparation surfaces for 2D gap distance assessment. 3D gap volume was also evaluated. Crowns were then cemented and divided into two subgroups; the first was stored in distilled water (no cyclic loading [NCL] subgroup), the second was subjected to CL (CL subgroup).

Results

Factorial repeated measures ANOVA followed by Bonferroni post hoc in addition to independent and dependent t-tests were used for statistical analysis. Marginal gap, absolute marginal discrepancy, and occlusal gap measurements showed significant differences between the measurement sites. Static load to fracture values showed significant differences between TOC groups for both NCL (P=0.011) and CL (P=0.025) subgroups.

Conclusion

An increase of TOC from 12° to 20° did not affect marginal and internal adaptation but resulted in higher values of load to fracture of ZLS crowns. CL simulating 1 year of service did not result in fatigue failure.

Marginal and internal fit of CAD-CAM inlay/onlay restorations: A systematic review of in vitro studies

STATEMENT OF PROBLEM

Different parameters can influence the adaptation of computer-assisted design and computer-assisted manufacturing (CAD-CAM) inlay/onlay restorations. However, systematic reviews to identify and discuss these parameters are lacking.

PURPOSE

The purpose of this systematic review was to summarize the scientific literature investigating all parameters that can influence both the marginal and internal adaptation of CAD-CAM inlay/onlay restorations.

MATERIAL AND METHODS

An electronic search was conducted by 2 independent reviewers for studies published in English between January 1, 2007 and September 20, 2017 on the PubMed/MEDLINE, Scopus, and Web of Science databases and in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Factors investigated in the selected articles included the type of CAD-CAM system, virtual space parameters, version of the software, type of block, luting procedure, type of restoration, sample size and aging procedure, evaluation method, and number of measurement points per specimen.

RESULTS

A total of 162 articles were identified, of which 23 articles met the inclusion criteria. Nine studies investigated adaptation with different restorative materials, 2 evaluated adaptation according to the type of preparation design, 9 compared adaptation before/after thermomechanical loading, and 2 before/after cementation, 1 study investigated marginal adaptation based on whether the optical scan was made intraorally or extraorally, 1 compared adaptation with 5 and 3 axis CAM systems, and 1 assessed adaptation with 4 different intraoral scanners. The risk of bias was high for 7, medium for 15, and low for 1 of the studies reviewed. The high level of heterogeneity across the studies excluded meta-analysis.

CONCLUSIONS

Most of the studies reported clinically acceptable values for marginal adaptation. The performance of a CAD-CAM system is influenced by the type of restorative material. A nonretentive cavity preparation exhibited better adaptation than a retentive preparation. Most studies showed that thermomechanical loading affected the quality of marginal adaptation. Cementation increased marginal discrepancies. No statistically significant difference was found for marginal fit of onlays between intraoral and extraoral optical scans using a stone die. The number of milling axes, the type of digital camera, and the region measured were statistically significant in relation to marginal/internal adaptation. Values of adaptation recorded failed to reproduce the preestablished spacer parameters in the software. Clarification is needed concerning adaptation according to the type of preparation design, the type of material, the choice of intrinsic parameters for the CAD process, the type and shape of milling instruments, and the behavior of the material during milling. Adaptation of CAD-CAM inlay/onlays should be evaluated under clinical conditions.

Internal Adaptation of Implant-Supported, Polymer-Infused Ceramic Crowns Fabricated by Two CAD/CAM Systems

PURPOSE

The aim of this in vitro study was to compare the internal 3D adaptation of polymer-infused ceramic crowns fabricated using two CAD/CAM systems: CEREC inLab MC XL and Ceramill Motion 2 (5X).

MATERIALS AND METHODS

Twenty-five implant-supported metal-ceramic crowns were fabricated conventionally using the lost-wax technique, and the outer contour was scanned to serve as a guide for designing the polymer-infused ceramic CAD/CAM crowns. Twenty-five crowns were fabricated using CEREC, and 25 crowns were fabricated using Ceramill. The cement space was set to 20 μm. The Zeiss Accura Microsystem Coordinate Measuring Machine (CMM), Calypso, and Geomagic software were used to measure the 3D accuracy of fit of all crowns to their respective implant abutments. To test for the statistical significance between groups in terms of 3D total distortion, a one-way ANOVA was conducted. The Kolmogorov-Smirnov test was used to investigate the differences in the x, y, and z coordinates. A p-value of 0.05 or less was considered statistically significant at an alpha level of 0.05.

RESULTS

Comparing the 3D misfit of metal-ceramic crowns to those of CAD/CAM crowns fabricated using CEREC revealed no significant difference (88.20 ± 36.59 μm vs. 102.45 ± 36.58 μm, p = 0.161). Similarly, no significant difference in 3D total distortion was identified between metal-ceramic crowns and crowns fabricated using Ceramill (88.20 ± 36.59 μm vs. 78.40 ± 31.03 μm, p = 0.336); however, the 3D total distortion of polymer-infused crowns made by Ceramill was significantly reduced compared to that of crowns fabricated by CEREC (78.3 ± 31.0 μm vs. 102.4 ± 36.5 μm, p = 0.019).

CONCLUSIONS

Polymer-infused ceramic crowns fabricated using CEREC exhibited the least accurate 3D fit. All misfit values of the tested groups were within clinically acceptable levels.

Micro-CT Analysis of Y-TZP Copings Made by Different CAD/CAM Systems: Marginal and Internal Fit

Purpose

The aim of the study was to measure the marginal and internal adaptation (MIA) of zirconia copings, made of 4 ceramic systems for CAD/CAM, using microcomputed tomography (micro-CT) technology.

Material and Methods

Two identical stainless steel models were used, representing a preparation for full ceramic crown on a lower molar. The master models were then scanned for the production of copings from specific yttrium oxide partially stabilized tetragonal zirconia polycrystal ceramic blocks of each system (n=10): Cerec/inCoris Zi, Sirona; Cercon/Cercon base, Dentsply; Ceramill/Ceramill Zi, Amann Girrbach; and Lava/Lava Frame Zirconia, 3M ESPE. MIA was evaluated measuring 4 points as follows: marginal gap (MG), axial wall gap (AW), axio-occlusal angle gap (AO), and central occlusal area gap (CO). The data were statistically analyzed by ANOVA and Tukey's test (α = 0.05).

Results

The ceramic system Lava showed greater internal desadaptation (80.75 ± 22.69 µm) while CEREC presented the lowest values (49.92 ± 11.77 µm). There were significant differences between the measurement points evaluated. CO demonstrated the greater values (77.03 ± 22.61 µm). All marginal and internal adaptation values were considered clinically acceptable.

Conclusion

It was concluded that there was an influence of the type of ceramic system in marginal and internal adaptation of copings in zirconia.

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

PURPOSE

To 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 METHODS

From 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.

RESULTS

Mean 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).

CONCLUSION

The 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.

Micro-CT evaluation of marginal and internal fit of cemented polymer infiltrated ceramic network material crowns manufactured after conventional and digital impressions

PURPOSE

Purpose of this study was to evaluate the accuracy of fit of cemented polymer infiltrated ceramic network (PICN) material crowns manufactured after digital and conventional impression techniques using micro computed tomography (CT). Furthermore to determine the cement space volume and porosities in the cement layer.

METHODS

A molar typodont tooth was prepared for PICN material crowns and replicated thirty times. The dies were randomly divided into three groups of 10 specimens each according to the impression technique: 3M True Definition Scanner (TDS), cara TRIOS (Trios) and Impregum Penta Soft (Impregum). PICN material crowns were milled for each specimen from Vita Enamic blocks and cemented on their respective dies. The absolute marginal discrepancy (AMD), internal fit (IG), total cement space volume (TVC) and marginal porosities (VP) were measured using Micro-CT.

RESULTS

Mean and standard deviations values in μm for the AMD were: TDS 140.1 (28.4); Trios 253.7 (56.8); Impregum 220.2 (101.1). IG values in μm: TDS 173.1 (27.7); Trios 222.2 (22.4); Impregum 211.6 (55.9). TVC in mm³: TDS 19.82 (2.9); Trios 23.67 (2.01); Impregum 23.77 (5.09). VP in mm³: TDS 0.38 (0.09); Trios 0.36 (0.10); Impregum 0.51 (0.31).

CONCLUSIONS

TDS group showed significantly better marginal and internal fit than the Trios group. No difference of the parameters was detected between the Impregum and both digital groups which implies that the digital impression technique is suitable in the manufacturing process of PICN material crowns.

Marginal and internal fit of pre-sintered Co-Cr and zirconia 3-unit fixed dental prostheses as measured using microcomputed tomography

STATEMENT OF PROBLEM

Limited information is available on the precision of new metal processing technologies.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal and internal fit of pre-sintered cobalt-chromium (Co-Cr) and zirconia 3-unit fixed dental prostheses using x-ray microcomputed tomography.

MATERIAL AND METHODS

Three-unit fixed dental prostheses were prepared on metal dies (N=12) using a typodont model from the maxillary first premolar to the first molar. A standardized preparation with a 1.2-mm chamfer (360 degrees) and a 2-mm occlusal reduction was prepared on abutment teeth. The dies were scanned and divided into 2 groups to receive the fixed dental prostheses (n=6) made of pre-sintered Co-Cr and pre-sintered zirconia. Each framework was seated on its cast, and marginal and internal discrepancies were measured at 9 points, starting from the most distal point from the pontic for the maxillary first premolar and the first molar (points 1-4, mesial; point 5, occlusal; points 6-9, distal) of each abutment tooth using microcomputed tomography. The data were analyzed using the Levene test, t test, and ANOVA (α=.05).

RESULTS

When overall mean discrepancy values were compared, no significant difference was observed between pre-sintered Co-Cr and pre-sintered zirconia (P=.085). Discrepancy values for points 1, 2, and 3 were significantly different for pre-sintered Co-Cr and pre-sintered zirconia, with the lowest mean values for point 1 and the highest for point 5. On the abutment tooth basis, for the maxillary first premolar and the first molar, a significant difference was found only in points 6 (P<.001) and 8 (P<.003) for both materials. When the discrepancies for the maxillary first premolar were considered for pre-sintered Co-Cr and pre-sintered zirconia, the mean values were significantly different only at points 1 (P<.001), 2 (P=.007), and 3 (P=.003) and were smaller for pre-sintered zirconia. For the tooth the first molar, a significant difference was observed at point 2 (P=.002) and point 3 (P=.008) for both materials, where the mean values were higher for pre-sintered Co-Cr than for pre-sintered zirconia. The pairwise comparison between points showed a significant difference between measurement points within each material (P<.05). The increase in values between points 1 and 5 was evident for both pre-sintered Co-Cr and pre-sintered zirconia materials.

CONCLUSIONS

Three-unit fixed dental prostheses made of pre-sintered Co-Cr or zirconia showed similar marginal and internal discrepancy values, with the highest discrepancy values at the occlusal region in both the first premolar and first molar.

Marginal adaptation of lithium disilicate ceramic crowns cemented with three different resin cements

OBJECTIVES

The cementation process and cementation materials have an influence on the marginal adaptation of restorations. The gap could be affected by thermal and mechanical loading (TCML). The computerized x-ray microtomography (μCT) method offers the possibility of measuring the marginal gap without destruction of the restoration. The aim of this study was to evaluate the marginal gap (MG) and the absolute marginal discrepancy (AMD) before and after TCML.

MATERIALS AND METHODS

Thirty-nine human premolars were prepared for full ceramic crowns made of lithium disilicate. The crowns were cemented by three different resins-Panavia F 2.0, Variolink II, and Relyx Unicem. The MG and AMD were evaluated by μCT before and after TCML.

RESULTS

Panavia F 2.0 had the lowest MG (before 118 μm-after TMCL 124 μm) and AMD (before 145 μm-after TMCL 154 μm), followed by Relyx Unicem (MG: before 164 μm-after TCML 155 μm; AMD: before 213 μm-after TMCL 209 μm) and Variolink II (MG: before 317 μm-after TMCL 320 μm; AMD: before 412 μm-after TMCL 406 μm). The differences were statistically significant before and after TCML. Rather than TCML, it appeared the resin cement was responsible for differences between the MG and AMD before and after TCML.

CONCLUSIONS

μCT is an accurate technique for assessing cemented restorations. Panavia F 2.0 has the lowest MG and AMD before and after TCML.

CLINICAL RELEVANCE

The resin material that features a three-step protocol (Variolink II) produced higher MG and AMG values than the Panavia or Relyx Unicem varieties with less or no intermediate steps at all.

Evaluation of the fit of zirconia copings fabricated by direct and indirect digital scanning procedures

STATEMENT OF PROBLEM

Intraoral scanners are effective for direct digital scans when dental restorations are fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM); however, if the abutment tooth cannot be dried completely or the prepared margin is placed subgingivally, accurate digital images cannot always be guaranteed.

PURPOSE

The purpose of this in vitro study was to compare the internal and marginal discrepancies of zirconia copings fabricated directly using an intraoral scanner with those fabricated indirectly with impression scanning.

MATERIAL AND METHODS

Forty-five resin dies fabricated with a 3-dimensional (3D) printer were divided into 3 groups: direct scanning (DS), impression scanning (IMP), and lost-wax casting (LW). For the DS group, a resin die was scanned with an intraoral scanner (Trios; 3Shape), whereas for the IMP group, impressions made with polyether were scanned with a cast scanner (D700; 3Shape). The zirconia copings were fabricated in the same way in the DS and IMP groups. For the LW group, impressions were made in the same way as in the IMP group, and Ni-Cr alloy copings were fabricated using LW. The marginal and internal discrepancies of the copings were measured by cementing them onto resin dies, embedding them in acrylic resin, and sectioning them in a buccolingual direction. The cement layer was measured, and the Kruskal-Wallis test was used to detect significant differences (α=.05). A nonparametric Friedman test was also performed to compare the measurements of each group by location (α=.05).

RESULTS

The mean marginal discrepancies in the DS, IMP, and LW groups were 18.1 ±9.8, 23.2 ±17.2, and 32.3 ±18.6 μm (mean ±standard deviation), respectively. The mean internal discrepancies of the DS, IMP, and LW groups in the axial area were 38.0 ±9.1, 47.0 ±16.3, and 36.5 ±15.8 μm, and those in the occlusal area were 36.7 ±16.9, 33.4 ±21.6, and 44.5 ±31.9 μm, respectively. No statistically significant differences were found in marginal or internal discrepancies among groups (P>.05).

CONCLUSIONS

Within the limitations of this study, the zirconia copings fabricated with CAD-CAM using different digitization methods and Ni-Cr copings fabricated using the lost-wax technique and casting produced clinically acceptable marginal and internal discrepancies. No significant differences were found among the DS, IMP, and LW groups.

Evaluation of marginal and internal gap of three-unit metal framework according to subtractive manufacturing and additive manufacturing of CAD/CAM systems

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 (α=.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 ± 42.30 µm in the AM group, and the lowest gap was 24.40 ± 11.92 µm 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.

Custom Morse taper zirconia abutments: Influence on marginal fit and torque loss before and after thermomechanical cycling

The use of zirconia abutments has increased because of aesthetics, but sometimes customization is necessary and its effect is unclear. This study evaluated the marginal fit and torque loss of customized and non-customized aesthetic zirconia abutments associated with Morse taper implants before and after thermomechanical cycling. Twenty-four implant/abutment/crown sets were divided into three groups (N = 8): Zr - non-customized zirconia abutments, Zrc - customized zirconia abutments, and Ti - titanium abutments. The ceramic crowns of the upper canines were made. All of the abutments were tightened with 15-N.cm torque, and the crowns were cemented on the abutments. The misfits and torque loss were measured before and after thermomechanical cycling. The marginal fit was evaluated in two planes throughout 10 different slices, 30 measurements for each face (i.e., buccal, palatal, mesial and distal) and 120 measurements for each sample. A load of 100N, a frequency of 2Hz and 1000,000 cycles with temperature variation of 5°-55°C were used for thermomechanical cycling. Thermomechanical cycling significantly decreased the marginal misfit only with the Zrc (p = 0.002), and the Ti was significantly different from the Zr and Zrc before and after thermomechanical cycling. Thermomechanical cycling did not affect the torque losses of the groups, but a significant difference between the Zr and Zrc (p = 0.0345) before cycling was noted. Customization of zirconia abutments does not significantly affect torque loss and marginal misfit after thermomechanical cycling suggesting that they can be safe for clinical utilization.

Marginal Fit of Lithium Disilicate Crowns Fabricated Using Conventional and Digital Methodology: A Three-Dimensional Analysis

PURPOSE

To compare the marginal fit of lithium disilicate (LD) crowns fabricated with digital impression and manufacturing (DD), digital impression and traditional pressed manufacturing (DP), and traditional impression and manufacturing (TP).

MATERIALS AND METHODS

Tooth #15 was prepared for all-ceramic crowns on an ivorine typodont. There were 45 LD crowns fabricated using three techniques: DD, DP, and TP. Microcomputed tomography (micro-CT) was used to assess the 2D and 3D marginal fit of crowns in all three groups. The 2D vertical marginal gap (MG) measurements were done at 20 systematically selected points/crown, while the 3D measurements represented the 3D volume of the gap measured circumferentially at the crown margin. Frequencies of different marginal discrepancies were also recorded, including overextension (OE), underextension (UE), and marginal chipping. Crowns with vertical MG > 120 μm at more than five points were considered unacceptable and were rejected. The results were analyzed by one-way ANOVA with Scheffe post hoc test (α = 0.05).

RESULTS

DD crowns demonstrated significantly smaller mean vertical MG (33.3 ± 19.99 μm) compared to DP (54.08 ± 32.34 μm) and TP (51.88 ± 35.34 μm) crowns. Similarly, MG volume was significantly lower in the DD group (3.32 ± 0.58 mm³ ) compared to TP group (4.16 ± 0.59 mm³ ). The mean MG volume for the DP group (3.55 ± 0.78 mm³ ) was not significantly different from the other groups. The occurrence of underextension error was higher in DP (6.25%) and TP (5.4%) than in DD (0.33%) group, while overextension was more frequent in DD (37.67%) than in TP (28.85%) and DP (18.75%) groups. Overall, 4 out of 45 crowns fabricated were deemed unacceptable based on the vertical MG measurements (three in TP group and one in DP group; all crowns in DD group were deemed acceptable).

CONCLUSION

The results suggested that digital impression and CAD/CAM technology is a suitable, better alternative to traditional impression and manufacturing.