Evaluation of marginal and internal adaptation of hybrid and nanoceramic systems with microcomputed tomography: An in vitro study

Marginal gap measurement of ceramic single crowns before cementation: A systematic review

STATEMENT OF PROBLEM

Different instruments have been used to measure the marginal gaps of crowns in vitro. However, a comprehensive systematic review is lacking.

PURPOSE

The purpose of this systematic review was to evaluate the existing literature on the instruments used for the in vitro marginal gap measurement of ceramic single crowns before cementation and to determine whether the crown material and method of fabrication influenced the marginal gap.

MATERIAL AND METHODS

The search was conducted in 2024 across the EBSCO Host, Scopus, PubMed, and Web of Science databases by following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and predefined eligibility criteria. Eligible articles were screened to evaluate 6 instruments for measuring crown marginal gaps: direct view microscopy, scanning electron microscopy, impression replica, cross-sectioning, microcomputed tomography, and 3-dimensional (3D) superimposition. The normality of the data was assessed by using the Kolmogorov-Smirnov test, and the differences in mean marginal gap were statistically evaluated using the Welch ANOVA (α=.05).

RESULTS

Ninety-two articles were included, with 77 documenting single measurement instruments and 15 using a combination of 2 or more measurement instruments. Direct view microscopy was the most used instrument and appeared in 31 (40%) of the studies. No significant differences in mean marginal gap (F=2.09, P=.077) were found across the 6 measurement instruments. Across all studies, excluding those using 3D superimposition, the mean ±standard deviation number of marginal gap measurements per crown was 34.3 ±50.6. Among the 77 studies using a single measurement instrument, 64 used computer-aided design and computer-aided manufacturing (CAD-CAM) technology to fabricate the crowns. CAD-CAM crowns had a mean ±standard deviation marginal gap of 78.9 ±28.6 µm (n=64) compared with 71.6 ±29.5 µm (n=13) for crowns manufactured using conventional methods. Zirconia and lithium disilicate were the most researched materials. Zirconia crowns recorded a mean ±standard deviation marginal gap of 69.4 ±34.2 µm for 972 crowns, which was significantly different (P=.045) from lithium disilicate with a mean ±standard deviation marginal gap of 92.2 ±42.5 µm for 602 crowns.

CONCLUSIONS

Direct view microscopy was the most used marginal gap measurement instrument for ceramic single crowns before cementation, and CAD-CAM was the most used crown fabrication method. No significant differences in mean marginal gap were found among the 6 marginal gap measurement instruments.

Marginal and internal adaptation and absolute marginal discrepancy of 3D-printed, milled, and prefabricated crowns for primary molar teeth: an in vitro comparative study

BACKGROUND

The quality of marginal and internal adaptation plays a crucial role in the clinical longevity of pediatric crowns. This study aimed to evaluate the effect of restoration type (3D-printed, milled, and prefabricated) on the marginal and internal adaptation and absolute marginal discrepancy (AMD) values of crowns for primary molar teeth.

METHODS

Three restoration groups were created: 3D-printed resin, milled resin-matrix ceramic, and prefabricated zirconia crowns (n = 10 per group). A typodont tooth was prepared according to the guidelines for prefabricated zirconia crowns and scanned to design restorations. 3D-printed and milled crowns were fabricated from the same design. All crowns were cemented on standardized 3D-printed resin dies with self-adhesive resin cement. Marginal and internal adaptation and AMD values were evaluated using micro-computed tomography (micro-CT) at multiple measurement points. Data were analyzed using one-way analysis of variance (ANOVA) and Tukey HSD tests, with statistical significance set at P < 0.05.

RESULTS

The restoration type significantly influenced the marginal and internal gap and AMD values (P < 0.05). The prefabricated crown group exhibited the highest marginal gap (233.5 ± 33.4 μm) and internal gap (538.6 ± 47.4 μm). The 3D-printed group showed the highest AMD value (299.5 ± 70.2 μm). The milled group demonstrated the lowest gap values, which remained within clinically acceptable limits.

CONCLUSIONS

Prefabricated zirconia crowns displayed the highest marginal and internal gaps, whereas milled crowns exhibited the most favorable adaptation values within clinically acceptable limits. Given their superior adaptation, CAD-CAM-produced restorations may be a recommendable alternative for pediatric patients.

Tooth Preparation Assessment Criteria for All-Ceramic CAD/CAM Posterior Crowns: An Evidence Map

BACKGROUND

An evidence map review was used to determine universal criteria for all-ceramic CAD/CAM posterior crowns to ensure standardized assessments by dental faculty, students, and practitioners.

MATERIALS AND METHODS

Covidence was used to perform the evidence map review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Web of Science (WOS), Embase, Dentistry and Oral Sciences Source (EBSCO), and MEDLINE (Ovid) were searched over a 10-year range (January 2012-December 2023), English only. This was complimented by a manual search. Descriptive statistics (i.e. frequencies and modes) and a chi-square goodness of fit test were used.

RESULTS

A total of 640 articles were identified, out of which 73 were selected for review across six reduction parameters: occlusal reduction, axial reduction, finish line reduction, total occlusal convergence (TOC), preparation surface finish, and anatomic form. Zirconia was excluded from this analysis. Significant differences were found between the observed and expected frequencies of consolidated parameters associated with occlusal reduction and finish line shoulder parameters at the p ≤ 0.05 level. There were no significant differences found between the observed and expected frequencies of the consolidated reduction parameters associated with finish line chamfer, axial reduction, surface finish, or TOC (p > 0.05).

CONCLUSIONS

Recommendation parameters for all-ceramic CAD/CAM posterior crown preparations are 1.5-2.0 mm for the occlusal reduction and 1.0 mm for the reduction of the shoulder finish line. Recommendations of at least 1.0 mm for the chamfer reduction, 12° for the TOC, 1.0-1.5 mm for the axial reduction, and a smooth preparation surface finish with internally rounded angles were also made, though none of these results were statistically significant. The literature review revealed the "finish line" category is multi-dimensional suggesting a more encompassing term as "finish boundary profile (FBP)."

Dimensional accuracy of additive and subtractive manufactured ceramic-reinforced hybrid composite inlays: a CBCT-based in vitro study

The dimensional accuracy of digitally processed inlays is often questioned because of inherent manufacturing inconsistencies associated with computer-aided design and manufacturing (CAD/CAM). This study aimed to compare the absolute marginal discrepancy (AMD), marginal gap (MG), internal gap (IG), and overall discrepancy (OD) of three-dimensional (3D) printed, milled and conventional inlays. Forty resin dies were 3D-printed from a class II mesiococclusodistal preparation on a typodont and randomly distributed into four groups of 10 each. Optical impressions were taken for three groups to fabricate CAD/CAM inlays: Group PVC, 3D printed VarseoSmile Crownplus; Group PVT, 3D printed VarseoSmile TriniQ; and Group MVE, milled using Vita Enamic. For Group CGP (control), CGP was conventionally fabricated using Gradia Plus. These inlays were stabilized on dies and subjected to cone‒beam computed tomography to measure discrepancies in mesiodistal and buccolingual sectional images. All the discrepancies differed significantly among the groups (one-way ANOVA, P > 0.05). The mean OD was significantly greater in the MVE than in the PVT and CGP; the mean AMD and MG were significantly greater in the PVC than in the PVT (Tukey test, P > 0.05). Compared with the other groups, the 3D-printed inlays, especially the VarseoSmile TriniQ, presented a closer marginal and internal fit.

Comparative Analysis of the Marginal Fit and Internal Adaptation of CAD-CAM-Fabricated Versus Conventionally Fabricated Ceramic Crowns: A Systematic Review

This systematic review compared the marginal fit and internal adaptation of ceramic crowns and fixed dental prostheses (FDPs) fabricated using CAD-CAM technology versus conventional methods. A literature search from 2000 to 2024, following PRISMA guidelines, identified relevant studies. Three studies with a total of 60 patients were included, evaluating both marginal fit and internal adaptation of crowns made using CAD-CAM and conventional techniques. Overall, CAD-CAM-fabricated crowns exhibited smaller marginal discrepancies and better internal adaptation, although the differences were not statistically significant. The findings suggest that CAD-CAM technology may improve the fit of ceramic crowns and FDPs, but variations in study outcomes emphasize the impact of factors like material choice and fabrication methods.

Effects of a hollow pontic design with various wall thicknesses on the axial internal fit and failure load of 3D printed three-unit resin prostheses

STATEMENT OF PROBLEM

A 3-dimensionally (3D) printed 3-unit interim fixed dental prosthesis (FDP) undergoes inward polymerization shrinkage to the pontic region, leading to nonuniform internal fit and improper accuracy. Whether axial wall thickness influences accuracy is unclear.

PURPOSE

The purpose of this in vitro study was to analyze the axial internal fit and failure load associated with a hollow pontic design of varying wall thicknesses in stereolithography (SLA) 3D printed 3-unit interim FDPs.

MATERIAL AND METHODS

A master model for a 3-unit interim FDP with 2 implant abutments was designed. Two master models were produced by using milling and direct metal laser sintering (DMLS). Sixty SLA 3D printed specimens were produced with a hollow pontic design of 4 wall thicknesses (solid and 2.5, 2.0, and 1.5 mm). Fifteen milled specimens were produced with a solid pontic design. The axial internal fit in the coronal section was measured in terms of intaglio and cameo mid-axial wall areas relative to the abutments by using microcomputed tomography (μCT). The failure load was measured by using a universal testing machine at a loading rate of 1 mm/minute. For statistical analysis, parametric tests were performed (α=.05). Horizontal μCT sections were compared qualitatively, and failure patterns were categorized among groups.

RESULTS

The hollow pontic designs with 2.0- and 1.5-mm wall thicknesses presented significantly lower mean intaglio mid-axial gaps than the solid pontic design (P<.001) and similar intaglio and cameo mid-axial gaps in the horizontal μCT sections. The hollow pontic design with the 2.0-mm wall thickness had a significantly higher mean failure load than that with the 1.5-mm wall thickness (P<.001) and a statistically similar mean failure load to that of the solid pontic design (P=.549). As the wall thickness of the hollow pontic decreased from 2.5 to 1.5 mm, the ratio of pontic fracture to complete fracture of the prosthesis increased.

CONCLUSIONS

For SLA 3D printed 3-unit interim FDPs, axial internal fit was enhanced by the application of an appropriate hollow pontic design. Considering both the structural strength and fit, a hollow pontic design with a 2.0-mm wall thickness should be selected.

Evaluation of zirconia crowns restoring endodontically treated posterior teeth with 2 finish line designs and 2 occlusal reduction schemes: A randomized clinical trial

STATEMENT OF PROBLEM

Preparation design has been linked to restoration survival, and the finish line geometry, such as a deep chamfer or shoulder, has been linked to marginal integrity. However, limited data are available for restoration success with the feather-edge finish line when used with monolithic zirconia crowns with different occlusal reduction schemes.

PURPOSE

The purpose of this randomized clinical trial was to evaluate the clinical performance of 2 finish line designs (feather-edge and rounded shoulder) in relation to 2 occlusal designs (flat and planar) in endodontically treated teeth restored with monolithic zirconia crowns.

MATERIAL AND METHODS

Sixty-six complete-coverage monolithic zirconia crowns were provided for posterior endodontically treated teeth. The participants were divided into 3 groups based on the preparation design: the control group (PS) had a planar occlusal scheme with a rounded shoulder finish line; the first intervention group (FF) had a flat occlusal scheme with a feather-edge finish line; and the second intervention group (FS) had a flat occlusal scheme with a rounded shoulder finish line. The crowns were designed with the exocad software program and milled with a 5-axis machine. After cementation, clinical performance in terms of marginal adaptation, marginal discoloration, fracture, and secondary caries was evaluated by using the modified United States Public Health Service (USPHS) criteria. The gingival index score system was used to evaluate the gingival response. The scores were recorded immediately after cementation and at 3 subsequent follow-up visits every 3 months for 1 year. The chi-squared test was used in all comparisons of outcomes and follow-up durations (α=.05).

RESULTS

In terms of marginal adaptations, the control group (PS) demonstrated the best marginal adaptation scores during follow-up visits, followed by intervention 2 (FS), and lastly, intervention 1 (FF), which was scored mostly with Bravo. At the third follow-up visit, the intervention 1 (FF) group reported the most gingival responses of all groups. No significant difference among the groups was found in terms of marginal discoloration, fracture, or secondary caries at any of the follow-up visits. Each group received a perfect Alfa score of 100% on all 3 follow-up assessments.

CONCLUSIONS

In this 1-year randomized clinical trial, all evaluated preparation schemes and corresponding crowns were clinically successful. The clinical performance of monolithic zirconia crowns of the novel preparation design (FF) was successful in terms of marginal adaption, fracture, secondary caries, and marginal discoloration.

CAD-CAM and heat-press: Comparison of internal and marginal fit of lithium disilicate copings

The aim of this in vitro study is to compare the performance of digital and conventional methods in the manufacture of single copings in terms of the internal and marginal fit. Twenty-four prefabricated titanium Cone Morse Exact abutments of the lateral anatomical type were used to manufacture 24 lithium disilicate copings in the CAD-CAM Ceramill (n = 12) and heat-press (n = 12) systems. The copings were cemented using a self-adhesive resin cement (RelyX U-200; 3M ESPE) and then cut vertically. The cement line was photographed using an optical microscope at ×100 and ×200 magnification and then the internal and marginal regions were measured. The mean values of fits, for the CAD-CAM and heat-press techniques, respectively, were (μm): angular regions, 81.8 and 75.3; linear regions, 63.1 and 60.1; incisal regions, 171.1 and 114.7; marginal discrepancy, 74.1 and 75.2; and absolute marginal discrepancy, 99.5 and 96.2. MANOVA test showed that there is an effect of the techniques on the regions (p < .05). The effects of laboratories and the interaction between laboratories and techniques on the regions were not statistically significant (p > .05). The techniques evaluated presented clinically acceptable results for the marginal fit. However, the conventional method performed better for the internal fit. RESEARCH HIGHLIGHTS: Scientific evidence regarding the methods of making prosthesis can help the dental professional in decision-making. Digital and conventional methods is both good in the manufacture of single copings in terms of the internal and marginal fit.

Marginal adaptation and fracture resistance of milled and 3D-printed CAD/CAM hybrid dental crown materials with various occlusal thicknesses

PURPOSE

To evaluate the marginal adaptation and fracture resistance of three computer-aided design/computer-assisted manufacturing hybrid dental materials with different occlusal thicknesses.

METHODS

Ninety single-molar crowns were digitally fabricated using a milled hybrid nanoceramic (Cerasmart, CE), polymer-infiltrated ceramic network (PICN, Vita Enamic, VE), and 3D-printed materials (Varseosmile, VS) with occlusal thicknesses of 0.8, 1, and 1.5 mm (10 specimens/group). Anatomical 3D-printed resin dies (Rigid 10K) were used as supporting materials. A CEREC MCX milling unit and a DLP-based 3D printer, Freeform Pro 2, were utilized to produce the crown samples. Before cementation, the marginal adaptation, absolute marginal discrepancy (AMD), and marginal gap (MG) were assessed using micro-CT scanning. After cementation with self-adhesive resin cement, fracture resistance was evaluated using a universal testing machine. The number of fractured crowns and the maximum fracture values (N) were recorded. Data were statistically analyzed using both one- and two-way ANOVA, followed by Tukey's honestly significant difference (HSD) test.

RESULTS

For all occlusal thicknesses, the VS crowns demonstrated the lowest AMD and MG distances, significantly different from those of the other two milling groups (P < 0.05), whereas CE and VE did not differ significantly (P > 0.05). All VS crowns were fractured using the lowest loading forces (1480.3±226.1 to 1747.2±108.7 N). No CE and 1 and 1.5 mm VE crowns fractured under a 2000 N maximum load.

CONCLUSIONS

All hybrid-material crowns demonstrated favorable marginal adaptation within a clinically acceptable range, with 3D printing yielding superior results to milling. All materials could withstand normal occlusal force even with a 0.8 mm occlusal thickness.

Clinical performance comparison between lithium disilicate and hybrid resin nano-ceramic CAD/CAM onlay restorations: a two-year randomized clinical split-mouth study

A total of 20 lithium disilicate glass-ceramics (IPS e.max CAD, Ivoclar Vivadent) and 20 resin nano-ceramic (Voco Grandio Blocks) onlay restorations were performed in 20 patients using a split-mouth design to compare the two-year clinical performance of lithium disilicate and resin nano-ceramic onlay restorations. Both restorations were evaluated at baseline, one-year, and two-year clinical follow-ups based on the modified United States Public Health Service (USPHS) criteria. Chi-square and Fisher's exact tests showed no statistically significant difference between Voco Grandio and IPS e.max ceramic restorations for all evaluated parameters during the different follow-up periods (p > 0.05). Cochrane's and MC-Nemar's tests indicated statistically significant differences regarding color match within the Voco Grandio group. They also indicated statistically significant differences in marginal discoloration, marginal adaptation, surface texture, and postoperative hypersensitivity within both ceramic material groups (p < 0.05). Kaplan-Meier curve indicated that the survival rate of both ceramic materials was 90%. After two years of clinical service, IPS e.max CAD and Voco Grandio onlay restorations exhibited similar clinical performance.

Effects of design software program and manufacturing method on the marginal and internal adaptation of esthetic crowns for primary teeth: A microcomputed tomography evaluation

STATEMENT OF PROBLEM

The adaptation of digitally produced crowns is affected by the design software program and manufacturing method. The effect of artificial intelligence (AI) software program design on the adaptation of the crowns is unclear and comparative evaluations should be documented.

PURPOSE

The purpose of this study was to assess the marginal and internal gaps, the absolute marginal discrepancies, and the 3-dimensional (3D) discrepancy volumes of the resin-based milled and 3D printed crowns for primary teeth designed with computer-aided design (CAD) and AI software programs by using microcomputed tomography (µCT).

MATERIAL AND METHODS

A total of 40 resin-based esthetic crowns were produced for a prepared typodont tooth (right mandibular primary second molar) according to the design software program (CAD and AI) and manufacturing method (milling and 3D printing) (n=10). Four experimental groups were generated as CAD-milled, CAD-3D printed, AI-milled, and AI-3D printed. The marginal, axial, and occlusal gap values, the absolute marginal discrepancies, and the 3D discrepancy volumes of the specimens were measured by using µCT. The data were analyzed by using 2-way ANOVA and the Tukey HSD tests (α=.05).

RESULTS

The lowest value for the marginal gap (54 ±43 µm) was observed in the CAD-milled group and the marginal gap value of the AI-3D printed group was significantly lower than the AI-milled group (P<.05). The lowest value for the axial gap (63 ±7 µm) was observed in the AI-3D printed group, and the highest value (145 ±58 µm) was observed in the CAD-milled group; the result for the occlusal gap value was opposite. The highest absolute marginal discrepancy value was observed in the CAD-milled group. The 3D discrepancy volumes increased in the order of the CAD-3D printed, AI-milled, CAD-milled, and AI-3D printed groups.

CONCLUSIONS

The marginal and internal gap values of the resin-based crowns were affected by the design software program and manufacturing method; however, tested groups showed clinically acceptable gap values.

Comparative analysis of endocrown fracture resistance and marginal adaptation: CAD/CAM technology using lithium disilicate vs. zirconia-reinforced lithium silicate ceramics

Aims

The present study aimed to compare the fracture resistance and marginal adaptation of endocrowns fabricated using lithium disilicate (LDS) and zirconia-reinforced lithium silicate 9ZLS) ceramics by the computer-aided design and computer-aided manufacturing (CAD/CAM) technology.

Materials and Methods

In this in vitro experimental study, 24 extracted mandibular first molars received standard endocrown preparation and were randomly assigned to two groups (n = 12) for the fabrication of endocrowns with ZLS (Suprinity) and LDS (IPS e.max CAD) ceramics. After scanning the teeth with a CAD scanner, endocrowns were designed by inLab Software version 15 (inLab SW 15) and prepared by an imes-icore 350i milling machine. The vertical marginal gap of endocrowns was measured under a stereomicroscope at three steps before and after cementation and after thermomechanical cycles. The fracture resistance of specimens was then measured by load application at a 45° angle. Mode of failure was also determined as reparable or irreparable. Data were analyzed using Pearson's correlation test and t-test.

Results

The mean fracture resistance of ZLS endocrowns was significantly higher than that of LDS endocrowns (P = 0.000). The reparability of ZLS endocrowns was zero, while that of LDS endocrowns was 83.33 %. The vertical marginal gap was significantly smaller in ZLS than in LDS endocrowns at all three time points (P < 0.05). Also, the marginal gap increased by cementation and thermomechanical cycles in both groups.

Conclusion

ZLS and LDS endocrowns both showed acceptable vertical marginal adaptation. ZLS had superior marginal adaptation and higher fracture resistance.

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.

Two‑year clinical performance of indirect restorations fabricated from CAD/CAM nano hybrid composite versus lithium disilicate in mutilated vital teeth. A randomized controlled trial

TRIAL DESIGN

This is a randomized, controlled, superiority, double-blinded, parallel-group, two-arms trial with an allocation ratio of 1:1. The aim of this trial was to compare the two-year clinical performance of partial indirect restorations fabricated from CAD/CAM nano-hybrid composite and ceramic lithium disilicate blocks using the modified USPHS criteria.

METHODS

In two parallel groups (n = 50 restorations), fifty participants having mutilated vital teeth with a minimum of two remaining walls were randomly enrolled in this trial and received indirect restorations of either nano-hybrid composite resin blocks (Brilliant, Coltene, Switzerland) or Lithium Disilicate (IPS Emax CAD). The restorations were assessed using modified USPHS criteria by two independent blinded assessors at baseline, six months, one-year and two years follow-up visits. Categorical and ordinal data were presented as frequencies and percentages. Categorical data were analyzed using the chi-square test. Ordinal data were analyzed using the Mann-Whitney U test for intergroup comparisons and Freidman's test followed by the Nemenyi post hoc test for intragroup comparisons. Numerical data were presented as mean and standard deviation values. They were analyzed for normality using the Shapiro-Wilk test. Data were found to be normally distributed and were analyzed using the independent t-test. The significance level was set at p ≤ 0.05 within all tests.

RESULTS

Forty-eight participants received the allocated intervention and completed the follow-up periods. There was a statistically significant difference between both tested materials for all USPHS criteria regarding Marginal integrity and Marginal discoloration at six-months Follow-up, but with no statistically significant difference at one- and two-year follow-up.

CONCLUSIONS

Both materials showed an acceptable, successful clinical performance along the two-years follow-up period.

CLINICAL RELEVANCE

The CAD/CAM nano-hybrid composite blocks are as reliable as Lithium disilicate for restoring mutilated vital teeth.

The effect of pre-ceramic soldering on marginal and internal fit of 4-unit zirconia frameworks and monolithic zirconia fixed dental prostheses

The aim of this study is to evaluate the effect of pre-ceramic soldering on the marginal and internal fit of 4-unit zirconia fixed dental prostheses (FPDs) that have two abutments and two pontics. 4-unit zirconia frameworks (Zirkonzahn ICE Translucent) (Z Group) and monolithic zirconia (Zirkonzahn Prettau) (M Group) FPDs were manufactured. Groups were divided into two groups (n = 10) control (ZC and MC) and soldering (ZS and MS). Samples of ZS and MS groups were cut into two pieces under cooling water and soldered with a bonding material (DCM Zircon HotBond). The marginal and internal fit of the restorations were measured from 36 points of each sample and cement space volume was calculated using reverse engineering software (Geomagic Design X). The mean and standard deviations were submitted to Generalized Linear Mixed Model (GLMM) analysis (α = 0.05). Statistical differences between groups before and after pre-ceramic soldering on point measurements were found. In total cement spacing measurements, a significant difference was found amongst all groups (P < 0.05). However, in premolars, a statistically significant difference was found between ZC and ZS groups and MC and MS groups (P < 0.05). All discrepancies after pre-ceramic soldering were found to be lower than before.

Marginal Discrepancy of Five Contemporary Dental Ceramics for Anterior Restorations

OBJECTIVES

 This study aimed to compare marginal accuracy of five contemporary all-ceramic crowns indicated for anterior restorations.

MATERIALS AND METHODS

 A master die of maxillary central incisor was prepared for all-ceramic crown and duplicated to produce 50 replicas of epoxy resin material. Five ceramic materials were used to mill the crowns (n = 10). All crowns were manufactured following the same digital workflow; same master die, scanning unit and design software, and the recommended manufacturing protocol. Final seating of crown was secured by a small droplet of temporary cement on its incisal edge. Marginal accuracy was evaluated by scanning electronic microscope with a magnification of 300 × . Vertical marginal gap was measured for each crown at predefined four points.

STATISTICAL ANALYSIS

 One-way analysis of variance was used to test differences between groups and Tukey test was used for multiple comparisons between group combinations. A level of significance at 95% was set for all statistics.

RESULTS

 The highest mean marginal gap and mean maximum gap calculated were for the e.max CAD crowns (49.2 µm, 87.6 µm), while the lowest values were for the Cercon xt crowns (10.2 µm, 21.7 µm). The mean marginal gap and the mean maximum gap of the e.max CAD crowns were statistically significantly greater than those of all other groups (p < 0.05). However, the differences between all other combinations were insignificant (p > 0.05).

CONCLUSION

 Marginal accuracy of lithium disilicate crowns is clinically acceptable. Zirconia and zirconia-reinforced lithium silicate materials can produce a greater level of marginal accuracy compared to lithium disilicate.

Effect of virtual cement space and restorative materials on the adaptation of CAD-CAM endocrowns

BACKGROUND

This study aimed to evaluate the effect of virtual cement space and restorative materials on the fit of computer-aided design and computer-aided manufacturing (CAD-CAM) endocrowns.

METHODS

A mandibular first molar tooth model received a butt joint margin endocrown preparation with a 2-mm occlusal thickness. Then, using a 3D-printing system, 120 copies of this prepared die were printed and assigned equally to three groups with different cement space settings (30, 60, and 120 μm) during the chairside CAD design. In the milling process, CAD-based models with a particular space setting were subdivided into four groups (n = 10) and fabricated from different CAD-CAM materials: Vita Suprinity (VS), Celtra Duo (CD), Lava Ultimate (LU), and Grandio blocs (GR). Finally, the endocrowns were stabilized over their corresponding models with siloxane and subjected to micro-computed tomography to measure the fit.

RESULTS

The cement space that was predesigned at 30 μm generated the largest marginal discrepancy (from 144.68 ± 22.43 μm to 174.36 ± 22.78 μm), which was significantly different from those at 60 μm and 120 μm (p < 0.001). The combination of VS or CD with a pre-setting cement space of 60 μm and the combination of LU or GR with a cement space of 120 μm showed better agreement between the predesigned and actual measured marginal gap widths. For internal adaptation, only the cement space set to 30 μm exceeded the clinically acceptable threshold (200 μm).

CONCLUSIONS

The setting of the cement space and restorative material significantly affected the marginal adaptation of CAD-CAM endocrown restorations. Considering the discrepancy between design and reality, different virtual cement spaces should be applied to ceramic and resin composite materials.

Marginal and Internal Misfit of Occlusal Veneers Made in Resin-matrix Ceramics

Objective

Considering that misfit is a significant predictor of the clinical success of indirect restorations, the objective of this study was to evaluate the marginal and internal misfit of two computer-aided design and manufacturing (CAD/CAM) RMC ceramic materials used as occlusal veneers (OVs) of different thicknesses.

Methods and Materials

A CAD model of a mandibular first molar was obtained and OV preparations 0.5-, 1.0-, and 1.5-mm thick were modeled and milled in two different materials (n=10/group): resin nanoceramic (RNC) and polymer-infiltrated ceramic network (PICN). Using the same CAD model, tooth preparations were milled in fiber-reinforced epoxy resin (n=20/thickness). The marginal and internal misfit of the restorations was assessed by X-ray microtomography. The measurements of the marginal gap (MG) and absolute marginal discrepancy were performed in two locations on each slice, whereas internal gap (IG) measurements were performed at ten locations on each slice. The data obtained were analyzed using two-way analysis of variance and Tukey post-hoc tests (α=0.05).

Results

No significant effect was attributable to the material type or material–thickness interaction for the MG, absolute marginal discrepancy (AMD), or IG (p&gt;0.05). However, the thickness significantly affected the IG of the restorations (p&lt;0.05). CAD/CAM RNC and PICN systems presented similar MG and AMD for OVs 0.5-, 1.0-, and 1.5-mm thick. However, the IG varied between thicknesses.

Influence of restorative materials on occlusal and internal adaptation of CAD-CAM inlays

Aim: To evaluate the occlusal and internal marginal adaptation of inlay restorations made of different materials, using CAD-CAM. Methods: Preparations were made for MOD inlays of one-third intercuspal width and 4 mm depth in 30 third human molars. The teeth were restored using CAD-CAM materials (n=10) of nanoceramic resin (Lava Ultimate), polymer-infiltrated ceramic network (VITA ENAMIC), or lithium disilicate glass-ceramic (IPS e.max CAD). The specimens were cemented with dual resin cement and sectioned at the center of the restoration, after which the two halves were evaluated, and photographed The occlusal and internal discrepancy (μm) was determined at five points: cavosurface angle of the occlusal-facial wall (CA-O); center of the facial wall (FW); faciopulpal angle (FPA); center of the pulpal wall (PW); and center of the lingual wall (LW). The data were submitted to the Kruskal-Wallis and the Dunn tests (α=0.05). Results: No difference was observed among the materials regarding the occlusal discrepancy at the CA-O, FPA, or PW internal points. The e.max CAD measurement at FW showed larger internal discrepancy than that of Lava (p=0.02). The internal discrepancy at LW was greater for e.max CAD than VITA ENAMIC (p=0.02). Conclusion: Lithium disilicate glass-ceramic presented greater internal discrepancy in relation to the surrounding walls of the inlay preparations.

MicroCT evaluation for CAD/CAM occlusal veneer fit using two materials and three cement space settings

This study was aimed to evaluate the fit of occlusal veneer restoration for two CAD/CAM materials with different cement space settings, using microCT scans. Sixty resin dies were made and divided into two groups (n=30) according to the materials, (I): Hybrid all-ceramic, and (II): zirconia-reinforced lithium silicate glass-ceramic. Each group was subdivided into three subgroups (n=10) according to the cement space parameters (30, 40, and 50 µm). Occlusal veneers for the six subgroups were milled. A circle with 20 different sections was placed at the center of every scanned specimen to measure four different locations (Occlusal, Axial, Marginal, and Absolute marginal discrepancy). Data were analyzed using two-way ANOVA at a 0.05 level of significance. There was no statistically significant effect of material type on the mean values of internal and marginal gaps for the three cement space parameters (P>0.05). There were no statistically significant differences in the occlusal and axial gap between the cement space parameters, furthermore, there were statistically significant differences in marginal gap distances and absolute marginal discrepancies (P>0.05). Hybrid all-ceramic showed smaller marginal and internal discrepancies than zirconia-reinforced lithium silicate glass-ceramic without statistically significant differences, and, for both materials, 50 µm cement space significantly improved the marginal fit and absolute marginal discrepancy.

Clinical performance of resin-matrix ceramic partial coverage restorations: a systematic review

OBJECTIVE

To evaluate clinical performance of the new CAD/CAM resin-matrix ceramics and compare it with ceramic partial coverage restorations.

MATERIALS AND METHODS

An electronic search of 3 databases (The National Library of Medicine (MEDLINE/PubMed), Scopus, and the Cochrane Central Register of Controlled Trials) was conducted. English clinical studies published between 2005 and September 2020 that evaluated the clinical performance of CAD/CAM resin-matrix ceramics inlays, onlays, or overlays were selected. The primary clinical question was applied according to PICOS strategy (Population, Intervention, Comparison, Outcome, Study design). The included studies were individually evaluated for risk of bias according to the modified Cochrane Collaboration tool criteria.

RESULTS

A total of 7 studies were included according to the established inclusion and exclusion criteria. From the included studies, 6 were randomized clinical trials while one study was longitudinal observational study without control group. According to the results of the included studies, the success rate of CAD/CAM resin-based composite ranged from 85.7 to 100% whereas the success rate reported for ceramic partial coverage restorations ranged from 93.3 to 100%. Fractures and debondings are found to be the most common cause of restorations failure.

CONCLUSION

CAD/CAM resin-based composite can be considered a reliable material for partial coverage restorations with clinical performance similar to glass ceramic restorations. However, this result needs to be confirmed in long-term evaluations.

CLINICAL RELEVANCE

CAD/CAM resin-based composites provide a potential alternative to ceramic indirect restorations. However, clinicians must be aware of the lake of knowledge regarding long-term outcome.

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.

Comparison of Marginal and Internal Adaptation in Endocrowns Milled from Translucent Zirconia and Zirconium Lithium Silicate

Purpose

This study aimed to compare marginal and internal adaptation in endocrowns made from translucent zirconia and zirconium lithium silicate using CAD-CAM technology.

Materials and Methods

Twenty-eight freshly extracted upper molars were mounted in acrylic resin and underwent root canal therapy and endocrown preparation up to 2 mm above the cementoenamel junction. Endocrowns were CAD-CAM milled from zirconium lithium silicate (ZLS) and translucent zirconia (Zr). Internal and marginal adaptation was assessed by the replica technique before cementation. Marginal adaptation was evaluated by a stereomicroscope (×32) before and after cementation and also after thermomechanical aging.

Results

The ZLS group showed significantly higher internal adaptation compared to the Zr group (P = 0.028), while the marginal adaptation differences, at different times with different methods, were not statistically significant (P > 0.05). Axiomarginal angle had the highest and axiopulpal angle showed the lowest adaptation in both groups. The cementation process and thermomechanical aging increased the marginal gap in both groups significantly (P < 0.001). The marginal gap assessed by the replica technique before cementation was 7.11 µm higher than direct view under a stereomicroscope with intraclass correlation coefficient of 0.797.

Conclusion

Zirconia seems to be an acceptable material for endocrown with comparable internal and marginal adaptation to ZLS. Cementation and thermomechanical aging had significantly negative effects on marginal gap. The marginal gap assessed by the replica technique was higher than direct view under the stereomicroscope technique.

Evaluation of Marginal/Internal Fit and Fracture Load of Monolithic Zirconia and Zirconia Lithium Silicate (ZLS) CAD/CAM Crown Systems

Fit accuracy and fracture strength of milled monolithic zirconia (Zi) and zirconia-reinforced lithium silicate (ZLS) crowns are important parameters determining the success of these restorations. This study aimed to evaluate and compare the marginal and internal fit of monolithic Zi and ZLS crowns, along with the fracture load, with and without mechanical aging. Thirty-two stone dies acquired from a customized master metal molar die were scanned, and ceramic crowns (16 Zi Ceramill Zolid HT⁺ and 16 ZLS Vita Suprinity) were designed and milled. Absolute marginal discrepancies (AMD), marginal gaps (MG), and internal gaps (IG) of the crowns, in relation to the master metal die, were evaluated using x-ray nanotomography (n = 16). Next, thirty-two metal dies were fabricated based on the master metal die, and crowns (16 Zi; 16 ZLS) cemented and divided into four groups of eight each; eight Zi with mechanical aging (MA), eight Zi without mechanical aging (WMA), eight ZLS (MA), and eight ZLS (WMA). Two groups of crowns (Zi-MA; ZLS-MA) were subjected to 500,000 mechanical cycles (200 ± 50 N, 10 Hz) followed by axial compressive strength testing of all crowns, until failure, and the values were recorded. Independent sample t tests (α = 0.05) revealed no significant differences between Zi and ZLS crowns (p > 0.05); for both internal and marginal gaps, however, there were significant differences in AMD (p < 0.005). Independent samples Mann–Whitney U and Kruskal–Wallis tests revealed significant differences between the two materials, Zi and ZLS, regardless of fatigue loading, and for the individual material groups based on aging (α = 0.05). Multiple comparisons using Bonferroni post-hoc analysis showed significant differences between Zi and ZLS material groups, with or without aging. Within the limitations of this study, the ZLS crown fit was found to be on par with Zi, except for the AMD parameter. As regards fracture resistance, both materials survived the normal range of masticatory forces, but the Zi crowns demonstrated greater resistance to fracture. The monolithic Zi and ZLS crowns seem suitable for clinical application, based on the fit and fracture strength values obtained.

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 PROBLEM

The 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.

PURPOSE

The 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 METHODS

The 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).

RESULTS

The 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).

CONCLUSIONS

CELTRA DUO showed better precision fit values than VITA SUPRINITY. Three-dimensional superimposition analysis is a reliable method of evaluating marginal and internal adaptation.

Correlation between 2D and 3D measurements of cement space in CAD-CAM crowns

STATEMENT OF PROBLEM

Although the 2D analysis of prosthesis cementation space has been popular, its correlation with volumetric comparison (3D data) of cement space is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the cement space in computer-aided design and computer-aided manufacturing (CAD-CAM) crowns of different materials and correlate 2D measurements of cement space with their corresponding 3D values (volume of cement space) by using microcomputed tomography (μCT) analysis of regions of interest.

MATERIAL AND METHODS

Ten molar crowns were milled in lithium disilicate (LD), resin nanoceramic (RN), and zirconia (Z) ceramics. Silicone replicas were produced and used as the analog cement layer and scanned with a desktop X-ray microfocus CT scanner. Twenty-eight slices were evaluated in 3 regions: marginal, axial, and occlusal (n=84 measurement points/specimen). After 3D reconstruction of the cement space, the volume was calculated. Data were statistically evaluated through 2-way ANOVA and Bonferroni test (α=.05). The Pearson correlation test was used to investigate the correlation between the 2D and 3D data.

RESULTS

The volumes of the occlusal (LD 10 ±1 mm³; RN 9 ±1 mm³) and axial regions (LD 9 ±2 mm³; RN 8 ±1 mm³) were significantly higher than the volume of the marginal region for LD and RN specimens (LD 6 ±2 mm³; RN 4 ±1 mm³) (both P<.001). For the Z group, the axial region had the highest volume (19 ±2 mm³), followed by the volumes of the occlusal (15 ±1 mm³) and marginal regions (12 ±1 mm³). The Pearson correlation test determined a moderate positive correlation of the marginal area (r=0.606, P<.001) and of the axial region (r=0.588, P<.001). However, a moderate negative correlation was found between volume and thickness of the occlusal area (r=-0.437, P=.016).

CONCLUSIONS

Z showed more volume of cement space, as well as thicker cement space than LD and RN. The μCT analysis is an efficient method of analyzing cement thickness and volume in ceramic crowns at the selected regions of interest. A moderate positive correlation was found between the 2D and 3D analyses for the axial and marginal regions of ceramic crowns.

Analysis of The Reproducibility of Subgingival Vertical Margins Using Intraoral Optical Scanning (IOS): A Randomized Controlled Pilot Trial

Background: The aim of this randomized controlled trial was to evaluate the capability of an IOS (Intra Oral Scanner) device, used in standardized conditions, to detect margins of abutments prepared with knife-edge finishing line located at three different levels in relation to the gingival sulcus. Methods: sixty abutment teeth for treatment with full crowns were selected and randomly divided in three groups accordingly to the depth of the finishing line: Group A: supragingival margin; Group B: 0.5–1.0 mm into the sulcus; Group C: 1.5–2.0 mm into the sulcus. Temporary crowns were placed for two weeks and then digital impressions (Aadva IOS 100, GC, Japan) were made of each abutment. As controls, analog impressions were taken, poured, and scanned using a laboratory scanner (Aadva lab scanner, GC, Japan). Two standard tessellation language (STL) files were generated for each abutment, subsequently processed, and superimposed by Exocad software (Exocad GmbH, Darmstadt, Germany), applying the “best-fit“ algorithm in order to align the scan of the conventional with the digital impressions. The distances between each preparation margin and the adjacent gingival tissue were measured. Four measures were taken, two interproximally and buccally, for a total of six measures of each abutment considering three modes of impressions. The data were statistically evaluated using two-way analysis of variance (ANOVA) for each site and the Bonferroni test. Results: there was no difference between the two kinds of impression in Group A in both sites, in Group B a difference of 0.483 mm and 0.682 mm at interproximal and buccal sites, respectively, and in Group C 0.750 mm and 0.964 mm at interproximal and buccal sites, respectively. The analysis performed on a site level (mesial/distal/vestibular) for the depth of both vertical preparations revealed significant differences (p < 0.0001). After a post hoc analysis (Bonferroni), vestibular sites of the shallow vertical preparations resulted in significantly lower values compared to the other sites prepared deeply. Conclusions: the results showed that the location of the margin is an important factor in making a precise and complete impression when IOS (Intra Oral Scanner) is used. Moreover, deep preparation into the sulcus is not recommended for IOS (Intra Oral Scanner) impressions.

How adjustment could affect internal and marginal adaptation of CAD/CAM crowns made with different materials

PURPOSE

Recently introduced hybrid and reinforced glass ceramic computer-aided design/computer-aided manufacturing (CAD/CAM) materials have been used for full-coverage restorations. However; the effect of adjustment and type of materials on internal and marginal adaptation are unknown. This study aimed to evaluate and compare the marginal and internal adaptations of crowns made of three different CAD/CAM materials before and after adjustment.

MATERIALS AND METHODS

One acrylic resin maxillary first molar was prepared and served as the master die. Thirty-six restorations were fabricated using CAD/CAM system (CEREC Omnicam, MCXL) with three materials including lithium disilicate (IPS e.max CAD), zirconia-reinforced lithium silicate (Suprinity), and hybrid ceramic (Enamic). Internal and marginal adaptations were evaluated with the reference point matching technique before and after adjustment. The data were analyzed using mixed ANOVA considering α=.05 as the significance level.

RESULTS

The effect of adjustment and its interaction with the restoration material were significant for marginal, absolute marginal, and occlusal discrepancies (P<.05). Before adjustment, Suprinity had lower marginal discrepancies than IPS e.max CAD (P=.18) and Enamic (P=.021); though no significant differences existed after adjustment.

CONCLUSION

Within the limitations of this study, crowns fabricated from IPS e.max CAD and Suprinity resulted in slightly better adaptation compared with Enamic crowns before adjustment. However, marginal, axial, and occlusal discrepancies were similar among all materials after the adjustment.

Examining the adaptation of modified endocrowns prepared with CAD-CAM in maxillary and mandibular molars: A microcomputed tomography study

STATEMENT OF PROBLEM

Endocrowns have been reported to be successful restorations for endodontically treated molars. However, comparisons between maxillary and mandibular molars, with different pulp chamber configurations are lacking. Information on the influence of venting on the adaptation of endocrowns is also lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the adaptation of endocrowns in maxillary and mandibular molars by means of microcomputed tomography (μCT).

MATERIAL AND METHODS

Mandibular and maxillary first molars were divided into 4 groups (n=10): ManE: mandibular endocrown; ModManE: modified mandibular endocrown; MaxE: maxillary endocrown; and ModMaxE: modified maxillary endocrown. Endocrowns were produced by using computer-aided design and computer-aided manufacture (CAD-CAM). Modification was carried out on the part of the endocrown that extended into the pulp chamber by preparing vents. The specimens were cemented and scanned by using μCT, the images reconstructed, and the internal and marginal adaptation examined. Statistical analyses were performed by using a 3-way ANOVA, 2-way ANOVA, and the independent samples t test (α=.05).

RESULTS

ManE displayed better mean ±standard deviation internal adaptation (182 ±59 μm) than MaxE (215 ±55 μm) (P<.01). Regardless of the groups, the pulpal floor was the area with the poorest fit (P<.001). The marginal gap of mandibular molars (91 ±20 μm) was lower than that of maxillary molars (110 ±26 μm) (P<.05). The effect of modifying endocrowns on the marginal gap was not found to be statistically significant (P>.05).

CONCLUSIONS

Internal and marginal adaptation of endocrowns differ between maxillary and mandibular molars.

Effect of various digital cement space settings on the adaptation of CAD/CAM occlusal veneer "micro-ct evaluation"

The aim was to evaluate the adaptation of CAD/CAM occlusal veneer with different cement space settings using micro CT scan. Three groups of IPS e.max-CAD lithium disilicate occlusal veneers with different cement space settings (30, 40, and 50 µm) were produced. A circle with 20 different diameters was centered at the center of the same image position of every scanned specimen using micro CT scan to measure four different locations [Occlusal (OCG), axial (AXG), Marginal (MAG), and absolute marginal discrepancy values (AMD)]. Kruskal-Wallis test revealed that there were no statistical differences between (OCG), (AXG), and (AMD) tested groups (p>0.05), and statistical differences between (MAG) group and other two groups (p<0.05). An increase in the digital cement space significantly improved the marginal fit of IPS e.max-CAD occlusal veneer.

Comparison of Marginal Adaptation of Different Resin-Ceramic CAD/CAM Crowns: An In Vitro Study

Aim:

To compare the marginal adaptation of crowns fabricated by using three different resin-ceramic computer-aided design/computer-aided manufacturing (CAD/CAM) materials.

Materials and Methods:

Crowns fabricated from three different resin-ceramic CAD/CAM blocks, applied on a typodont premolar (#14), were tested with regard to marginal adaptation, in this in vitro study. The typodont maxillary first premolar was prepared to serve as the master die and digitized with an intraoral scanner. The same virtual crown design was used to fabricate all specimens. Forty-eight crowns were fabricated from the same virtual crown design using three different CAD/CAM resin-ceramic blocks as follows ( n = 16): Lava Ultimate (LU), GC Cerasmart (GC), Vita Enamic (VE). Master die and crowns were scanned with a laboratory scanner and three-dimensional data were transferred into three-matic software. The software calculated the mean of the marginal discrepancy (MD) for each crown in negative and positive values, representing under and over estimation of the crown margin, respectively. A marginal discrepancy index (MDI) was obtained for each group using negative and positive MDs. All data were statistically analyzed using one-way analysis of variance and Tukey’s honest significance test ( α = 0.05).

Results:

The analysis of variance showed no statistical differences between materials regarding the negative and positive MDs ( P > .05). The MDI for LU was lower than GC and VE ( P < .05).

Conclusion:

The marginal adaptation of different resin-ceramic materials was different with regard to MDI values. Nevertheless, the MD values of all groups were within the clinically acceptable range.

Monitoring fatigue damage in different CAD/CAM materials: A new approach with optical coherence tomography

PURPOSE

To investigate fatigue damage over time, monolithic posterior computer-aided-designed/computer-aided-manufactured (CAD/CAM) crowns were artificially aged in a mouth-motion-simulator, and damage was monitored with optical coherence tomography (OCT).

METHODS

Forty-eight crowns were milled of six different CAD/CAM-materials (n=8), including 3Y-TZP (Lava Plus,'3Y'), 4Y-PSZ (Pritidentamultidisc,'4Y'), 5Y-PSZ (Prettauanterior,'5Y'), zirconia-reinforced lithium silicate (CeltraDuo,'ZLS'), hybrid ceramic (Vita Enamic,'VE'),and resin composite (BrilliantCrios,'COM'), and were adhesively luted on CAD/CAM-milled human molars. Specimens were artificially aged in a mouth-motion-simulator (50-500N, 2Hz, 37°C) for a period of 1 million cycles. Before loading and every 250,000 cycles, the specimens were investigated with spectral domain (SD)-OCT (RS-3000). The maximum vertical and horizontal damage were measured with imaging-processing-software (ImageJ). After testing, the specimens were sliced and analysed via light microscope (Zeiss) to compare the new OCT method with the established light microscope method. Data were subjected to ANCOVA and 2x4-ANOVA.

RESULTS

No failure occurred during mouth-motion-simulation. However, all specimens (except for 3Y and 4Y) showed fatigue damage. There was a significant difference in the maximum damage between the CAD/CAM-materials (p<.05). ZLS exhibited the highest damage, followed by VE, COM and 5Y. While damage associated with 5Y was initially noticed after 750,000 cycles, all other materials already showed crack formation after 250,000 cycles. Furthermore, a linear increase in damage over time was noticed in all materials. Due to the shallow light penetration of OCT, damage in the outer area could only be visualized with light microscope.

CONCLUSIONS

OCT is feasible for monitoring fatigue damage over time within different CAD/CAM-materials, particularly for subsurface damages.

[Influence of preparation height and cement space on the fit and retention of computer aided design/computer aided manufacturing zirconia crown]

OBJECTIVE

To investigate the effects of preparation height and cement space on the fit and retention of computer aided design (CAD)/computer aided manufacturing (CAM) zirconia crown, and to provide reference for the clinical design and fabrication of CAD/CAM crowns.

METHODS

3D printing system was used to fabricate resin abutment teeth with convergence angle of 2° and height of 1-3 mm. The models' optical impressions were collected by the three-shape scanner. Then, the cement spaces were set by Cradle CAD/CAM system at 10-50 μm to create an all-ceramic zirconia crown. The fit of the crowns was measured by using silicone rubber interstitial impression method. The retention of the crowns was measured by pull-off test with uniaxial tensile force after the crown was bonded. The data were analyzed by SPSS 22.0 soft-ware.

RESULTS

When the preparation height was fixed, the fitness values of different cement space groups have statistical difference (P<
0.05), whereas the retention values of different cement space groups have no statistical difference (P>0.05). The fitness values of different preparation height groups have no statistical difference (P>0.05), and the retention values of different preparation height groups have statistical difference (P<0.05) when the cement space was fixed. No interaction was observed between the cement space and the preparation height (P>0.05).

CONCLUSIONS

When cradle CAD/CAM system is used to create a full crown in the clinic, the preparation height should be set to more than 3 mm, and the cement space should be set at 30 μm.

Fracture Resistance of Partial Indirect Restorations Made With CAD/CAM Technology. A Systematic Review and Meta-analysis

Background: The aim of this systematic review and meta-analysis was to determine the fracture resistance and survival rate of partial indirect restorations inlays, onlays, and overlays fabricated using computer-aided design and computer-aided manufacturing (CAD-CAM) technology from ceramics, composite resin, resin nanoceramic, or hybrid ceramic and to analyze the influence of proximal box elevation on fracture resistance. Materials and methods: This systematic review was based on guidelines proposed by the preferred reporting items for systematic reviews and meta-analyses (PRISMA). An electronic search was conducted in databases US National Library of Medicine National Institutes of Health (PubMed), Scopus, Web of Science (WOS), and Embase. In vitro trials published during the last 10 years were included in the review. Results: Applying inclusion criteria based on the review’s population, intervention, comparison, outcome (PICO) question, 13 articles were selected. Meta-analysis by restoration type estimated the fracture resistance of inlays to be 1923.45 Newtons (N); of onlays 1644 N and of overlays 1383.6 N. Meta-analysis by restoration material obtained an estimated fracture resistance for ceramic of 1529.5 N, for composite resin of 1600 Ne, for resin nanoceramic 2478.7 N, and hybrid ceramic 2108 N. Conclusions: Resin nanoceramic inlays present significantly higher fracture resistance values. Proximal box elevation does not exert any influence on the fracture resistance of indirect restorations.

Three-dimensional trueness analysis of ceramic crowns fabricated using a chairside computer-aided design/manufacturing system: An in vitro study

PURPOSE

This study analyzed the trueness of polymer-infiltrated ceramic and glass ceramic crowns manufactured using the chairside computer-aided design/manufacturing (CAD/CAM) system.

METHODS

The master model designs crowns using a CAD program after acquiring a digital impression with an intraoral scanner. Vita Enamic (VE), Vita Suprinity (VS), and IPS e.max CAD (IPS) were used to manufacture 10 crowns each (total: 30 crowns), using the chairside CAD/CAM system (inLab MC XL). Trueness was evaluated by superimposing the CAD data on the scan data using a three-dimensional program. The Kruskal-Wallis H test, a nonparametric test, and the Mann-Whitney U test were performed by applying the significance level (0.05/3=0.016), which was adjusted by post-analysis Bonferroni testing.

RESULTS

There was a significant difference in the trueness between the samples (p<0.05). However, there was no statistically significant difference in the outer surface trueness between the samples (p>0.05).

CONCLUSIONS

These findings show that the milling accuracy of VE is better than that of VS and IPS.

Influence of two different cement space settings and three different cement types on the fit of polymer-infiltrated ceramic network material crowns manufactured using a complete digital workflow

OBJECTIVES

The study evaluates the influence of two spacer settings and three resin luting materials on the marginal and internal fit of polymer-infiltrated ceramic network (PICN) material crowns manufactured using a complete digital workflow.

METHODS

Optical impressions of fifty identical dies were performed using the 3M scanner (software version 5.0.2). Twenty crowns were designed using Ceramill Mind (version 3.4.10.1163), from which ten with spacer setting of 50 μm (G1) and ten with 80 μm (G2). Thirty crowns (spacer setting of 50 μm) were divided into three groups corresponding to the resin materials used as follows: RelyX Unicem (RX), Variolink Esthetic (VLE), and Nexus 3 (NX3). All crowns were milled from Vita Enamic blocks. After micro-CT scanning, absolute marginal discrepancy (AMD), internal gap (IG), total cement space volume (TCV), and marginal porosities (VP) were measured.

RESULTS

Significant difference was detected on the VP between the RX and NX3 group (p = 0.033). The mean values of all parameters were the following: AMD (μm): G1 182.6, G2 253.7, RX 210.8, VLE 195.5, NX3 186.6; IG (μm): G1 215.6, G2 173.1, RX 171.1, VLE 198.6, NX3 203; TCV (mm³): G1 22.9, G2 20.49, RX 17.57, VLE 17.49, NX3 20.59; VP (mm³): G1 0.26, G2 0.34, RX 0.32, VLE 0.46, NX3 0.54.

CONCLUSIONS

Fit of PICN material crowns was not significantly influenced by increasing the spacer settings and cementation with different resin materials. Additionally, RelyX Unicem showed significantly less porosities as compared with Nexus3.

CLINICAL RELEVANCE

Both 50 μm and 80 μm virtual spacer settings can be suggested for the manufacture of PICN crowns when Ceramill Mind (version 3.4.10.1163) is used. Furthermore, a self-adhesive system can be recommended for the cementation.

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 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.

Comparison between direct chairside and digitally fabricated temporary crowns

The mechanical properties of temporary crowns are considered to be crucial in order to achieve successful definite restorations. This study compared marginal fit, internal fit, fracture strength and mode of fracture of CAD/CAM temporary crowns to direct chairside counterparts. An upper left first premolar Frasaco tooth was prepared for all-ceramic crown. The materials used for comparison were VITA CAD-Temp^®, ArtBloc^®Temp, PMMA DISK and Acrytemp (control group). The crowns were divided into four groups (n=10). Each crown was investigated for the above parameters. Statistical analysis was performed using SPSS v.20. The average marginal gap, internal gap and fracture strength showed statistically significant difference between groups (p<0.01). The fracture mode showed statistically non-significant difference (p>0.05) among experimental groups. The CAD/CAM temporary crowns demonstrated superior mechanical properties compared to direct handmade counterparts.

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.

Microleakage of composite crowns luted on CAD/CAM-milled human molars: a new method for standardized in vitro tests

OBJECTIVES

To investigate debonding of full crowns made of CAD/CAM composites, CAD/CAM technology was applied to manufacture standardized test abutments to increase the reproducibility of human teeth used in in vitro studies.

MATERIALS AND METHODS

A virtual test abutment and the corresponding virtual crown were designed and two STL data sets were generated. Sixty-four human third molars and CAD/CAM blocks were milled using a CNC machine. Crowns of four different composite blocks (Lava Ultimate (LU), Brilliant Crios (BC), Cerasmart (CS), Experimental (EX)) were adhesively bonded with their corresponding luting system (LU: Scotchbond Universal/RelyX Ultimate; BC: One Coat 7 Universal/DuoCem; CS: G-PremioBond/G-Cem LinkForce; EX: Experimental-Bond/Experimental-Luting-Cement). Half of the specimens were chemical-cured (CC) and the others were light-cured (LC). Afterwards, specimens were artificially aged in a chewing simulator (WL-tec, 1 million cycles, 50-500 N, 2 Hz, 37 °C). Finally, a dye penetration test was used to detect debonding. For inspection, the specimens were sliced, and penetration depth was measured with a digital microscope. Data were analyzed with the Mann-Whitney U test.

RESULTS

No cases of total debonding were observed after cyclic loading. However, the LC specimens showed a significantly lower amount of leakage than the CC ones (p < 0.05). Furthermore, the CC specimens exhibited broad scattering. Only the LC-EX blocks showed no debonding. The CC-CS blocks showed the highest leakage and scattering of all tested specimens.

CONCLUSIONS

Natural human teeth can be manufactured by CAD/CAM technology in highly standardized test abutments for in vitro testing. For CAD/CAM composites, light curing should be performed.

CLINICAL RELEVANCE

The success of a restoration depends on the long-term sealing ability of the luting materials, which avoids debonding along with microleakage. For CAD/CAM composites, separate light curing of the adhesive and luting composite is highly recommended.