Effect of different preparation finishing procedures on the marginal and internal fit of CAD-CAM-produced restorations: A microcomputed tomography evaluation

STATEMENT OF PROBLEM

Accurate fit is an important factor for the longevity of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic restorations. Few studies have compared how restoration finishing procedures affect the marginal and internal fit of these restorations by using microcomputed tomography (μCT).

PURPOSE

The purpose of this in vitro study was to evaluate the preparations with different surface finishing procedures for the fit of CAD-CAM restorations by using μCT.

MATERIAL AND METHODS

A total of 28 anatomic contour monolithic feldspathic ceramic crowns were produced for 4 typodont teeth prepared according to the different surface finishing procedures (n=7). The generated experimental groups were finishing with extra-coarse (181 μm) diamond rotary instruments (EC), finishing with fine (40 μm) diamond rotary instruments after extra-coarse diamond rotary instruments (F), finishing with very fine (20 μm) diamond rotary instruments after extra-coarse and fine diamond rotary instruments (VF), and finishing with extra-coarse, fine, and very fine diamond rotary instruments followed by polishing rubber points (P). μCT scans were obtained to measure the gaps between the typodont teeth and the crowns. Reference points such as the margin, chamfer (the deepest point), cusp tips, and central fossa were determined, and 196 measurements were made. Data were analyzed by using 2-way analyses of variance and the Tukey HSD test (α=.05).

RESULTS

The highest gap values in all sections were observed in the finishing with extra-coarse (181 μm) diamond rotary instruments group. The lowest gap value in the marginal point was observed in the P group (P<.05). In total, the gap values of the reference points were in the order of margin, chamfer, cusp, and central fossa.

CONCLUSIONS

μCT evaluation showed that tooth preparation finishing procedure with finer grit rotary instruments yielded better marginal fit for monolithic feldspathic CAD-CAM restorations. The internal gap values of all groups were also in the range of clinically acceptable values, important for mechanical properties.

An in vitro comparison of the marginal fit of provisional crowns using the virtual tooth preparation workflow against the traditional technique

Aim

This study investigates the effectiveness of an innovative virtual tooth preparation workflow for the fabrication of dental crowns using cone-beam computed tomography (CBCT) and intraoral scanners (IOSs) with conventional workflow using extraoral/laboratory scanners.

Settings and Design

This in vitro experimental study was conducted in the laboratory of a university in Chennai, India. The dental laboratory and research facilities at the institution were utilized for the fabrication of the temporary crowns and the data acquisition process.

Materials and Methods

Institutional approval was obtained from the university. It was basically a comparison between the virtual prep technique using CBCT and IOS and the conventional digital technique using extra oral scanners (EOS) for temporary crown fabrication. The sample size was estimated using an effect size of 1.5004, assuming a normal distribution, a significance level of 0.05, and a power of 0.95 in G power software. Based on this calculation, an extracted second lower molar was used to fabricate 10 samples in each group. The samples were divided into three groups: the CBCT (Group 1), the IOS (Group 2), and laboratory scanner (Group 3 as control) groups. The vertical marginal gap of all the surfaces of the crown was evaluated using a scanning electron microscope.

Statistical Analysis Used

Data were analyzed using one-way ANOVA using the SPSS software version 26.0, IBM, Armonk, NY, USA.

Results

Acceptable marginal discrepancy values were obtained in all three groups. There was no significant difference in the marginal discrepancy recorded (P = 0.113).

Conclusion

Virtual tooth preparation using CBCT and IOSs can be used as an alternative to the conventional workflow for provisional crown and bridge fabrication.

Effect of build angle on the dimensional accuracy of monolithic zirconia crowns fabricated with the nanoparticle jetting technique

STATEMENT OF PROBLEM

The build angle is an essential parameter in additive manufacturing. Its effect on the dimensional accuracy of zirconia restorations fabricated using the nanoparticle jetting (NPJ) technique is unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of the build angle on the dimensional accuracy of monolithic zirconia complete crowns fabricated by using NPJ.

MATERIAL AND METHODS

Standardized artificial right maxillary incisors and mandibular first molars were prepared for ceramic complete crowns. In total, 100 monolithic zirconia crowns were fabricated using NPJ at build angles of 0, 45, 90, 135, and 180 degrees (n=10/angle for incisors and molars). The dimensional accuracies in the external, marginal, and intaglio regions were determined by superimposing the scanned data and computer-aided design data on the crowns. Root mean square (RMS) values were used to analyze the accuracy of the zirconia crowns overall and at the external, marginal, and intaglio surfaces. The Shapiro-Wilk test was used to examine the normality of data distribution. Differences among test groups were assessed using a 1-way analysis of variance and the post hoc least significant difference test (α=.05).

RESULTS

Significant differences were found in the accuracy of monolithic zirconia incisor and molar complete crowns in the external, marginal, and intaglio regions among the 5 build angles (P<.05). For incisors, the external RMS value was lowest for a build angle of 45 degrees (18.2 ±3.0 µm), the marginal and intaglio RMS values were lowest for a build angle of 135 degrees (47.4 ±10.7 and 26.5 ±6.1 µm, respectively), and the overall RMS values did not differ significantly among the 5 build angles (P>.05). For molars, build angles of 0 degrees and 180 degrees yielded the lowest RMS values overall (22.3 ±1.5 and 21.8 ±3.2 µm, respectively) and in the external (23.2 ±2.9 and 22.3 ±2.5 µm, respectively) and intaglio (22.2 ±3.7 and 21.2 ±4.6 µm, respectively) regions. No significant difference was observed in the marginal area among the 5 build angles (P>.05). The overall RMS values reflecting dimensional accuracy for the 5 build angles were between 23.5 and 26.7 µm for incisors and 21.8 and 26.2 µm for molars.

CONCLUSIONS

The dimensional accuracy of monolithic zirconia crowns fabricated by using NPJ was affected by the build angle and was within clinically acceptable limits.

Marginal Accuracy of Monolithic and Veneered Zirconia Crowns Fabricated by Conventional and Digital Workflows

PURPOSE

To compare the marginal accuracy of zirconia crowns fabricated by different workflows (conventional and digital) and designs (monolithic and veneered).

MATERIALS AND METHODS

A prepared maxillary first molar was used for the study. Four workflow combinations were evaluated: (1) intraoral scanning and monolithic zirconia (IOS-M), (2) intraoral scanning and veneered zirconia (IOS-V), (3) conventional impression and monolithic zirconia (IMP-M), and (4) conventional impression and veneered zirconia (IMP-V). All of the specimens had similar designs. The veneered groups had a buccal cutback for esthetic veneer application. A total of 10 crowns were produced in each workflow. The vertical and horizontal marginal accuracies were measured with a traveling microscope. Depending on the normality of the data, one-way analysis of variance test or Kruskal-Wallis test were applied to evaluate the differences among the groups (α = 0.05).

RESULTS

The most superior vertical marginal accuracy was observed for IOS-V (mean = 22.5 μm; SD = 6.7 μm), followed by IMP-V (mean = 23.9 μm; SD = 7.8 μm), IOS-M (mean = 28.7 μm; SD = 10.3 μm), and IMP-M (mean = 39.8 μm; SD = 22.0 μm), respectively (p < 0.001). The IOS-M had the greatest mean horizontal discrepancies (mean = 23.9 μm; SD = 4.3 μm) followed by IMP-M (mean = 21.3 μm; SD = 5.7 μm), IMP-V (mean = 19.2 μm; SD = 5.3 μm) and IOS-V (mean = 17.6 μm; SD = 5.7 μm) (p < 0.001).

CONCLUSIONS

Monolithic zirconia crowns fabricated digitally had superior marginal accuracy than monolithic zirconia crowns fabricated conventionally. Esthetic buccal veneering of predominantly monolithic zirconia copings improved the vertical and horizontal marginal accuracies.

[Deep Margin Elevations, clinical considerations]

Subgingival restorations are problematic due to reduced visibility at the preparation margins, humidity (saliva, crevicular fluid and/or blood), problems with taking impressions (digital or analogue) and problems with the application of a rubber dam. Solutions, such as the use of a surgical microscope, retraction cord and Teflon tape, are available. Since modern dentistry largely relies upon adhesive techniques with hydrophobic materials, these require a clean and dry working area. One solution is to place the preparation margin supragingivally. This can be done in three ways: a local build-up using a direct composite restoration, a surgical clinical crown lengthening or an extrusion (orthodontic or surgical). Since in practice only a small part is usually located subgingivally, placing a direct composite restoration is often sufficient. The term Deep Margin Elevation is generally used in the international English-language literature for this approach. If the area located subgingivally is larger, then techniques like crown lengthening and extrusion might be better.

Evaluation of marginal and internal fit of single crowns manufactured with an analog workflow and three CAD-CAM systems: A prospective clinical study

PURPOSE

This prospective clinical study evaluated and compared the marginal and internal fit of crowns fabricated with an analog workflow and three different computer-aided design and computer-aided manufacturing (CAD-CAM) systems.

MATERIALS AND METHODS

Twenty-five participants in need of a single complete-coverage molar or premolar crown were recruited in the study. Twenty-two completed the study, and three participants dropped out. Teeth were prepared according to a standardized protocol by one operator. For each participant, one final impression was made with polyether material (PP) and three intraoral scanners: CEREC Omnicam (C), Planmeca Planscan (PM), and True Definition (TR). For the PP group, crowns were fabricated with a pressable lithium disilicate ceramic, whereas for the other three groups (C, PM, and TR), crowns were designed and milled with dedicated CAD-CAM systems and materials. Marginal (vertical and horizontal) and internal discrepancies between the crowns and tooth preparation were measured at various locations with digital superimposition software. Data was analyzed for normality with Kolmogorov-Smirnov and Shapiro-Wilk tests and then compared with one-way ANOVA and Kruskal-Wallis tests.

RESULTS

Mean vertical marginal gap values were 92.18 ± 141.41 μm (PP), 150.12 ± 138.06 μm (C), 129.07 ± 109.96 μm (PM), and 135.09 ± 112.03 μm (TR). PP group had statistically significantly smaller vertical marginal discrepancy (p = 0.001) than all other groups, whereas no significant difference was detected among the three CAD-CAM systems (C, PM, and TR). Horizontal marginal discrepancies were 104.93 ± 111.96 μm (PP), 89.49 ± 119.66 μm (C), 113.36 ± 128.49 μm (PM), and 136.39 ± 142.52 μm (TR). A significant difference was detected only between C and TR (p < 0.0001). Values for the internal fit were 128.40 ± 49.31μm (PP), 190.70 ± 69.79μm (C), 146.30 ± 57.70 μm (PM), and 168.20 ± 86.67 μm (TR). The PP group had a statistically significant smaller internal discrepancy than C (p < 0.0001) and TR groups (p = 0.001), whereas no significant difference was found compared to the PM group.

CONCLUSION

Posterior crowns fabricated with CAD-CAM systems showed vertical margin discrepancy greater than 120 μm. Only crowns fabricated with the conventional methodology had vertical margins below 100 μm. Horizontal marginal discrepancy was different among all groups, and only CEREC CAD-CAM was below 100 μm. Internal discrepancy was less for crowns fabricated with an analog workflow.

Zirconia restorations and the tool diameter compensation

AIM

The aim of the present article is to describe a new method to reduce the undesirable loss of material thickness that results from overmilling due to the tool diameter compensation correction of common CAD/CAM software.

MATERIALS AND METHODS

Today's CAD/CAM software (eg, 3Shape or Exocad) specifies the same tool diameter compensation for different ceramics. In the case of zirconia ceramics milled in the raw state, this leads to excessive milling of the inner surfaces of crowns, which results in unnecessarily large cementation gaps and a restoration that is thinned out from the inside. By manually reducing the preset correction in the digital design process by the volumetric sintering shrinkage factor specified by the manufacturer, excessive thinning of the zirconia can be avoided.

RESULTS

The inner geometry of the restorations changes only slightly after manually reducing the preset tool diameter compensation correction. Consequently, a design of the restoration with the required minimum interocclusal thickness yet with accurate passive seating and marginal fit is possible without any further interventions.

CONCLUSIONS

Understanding the specifics of the subtractive fabrication process as well as the properties of the restorative materials is a key factor in achieving optimal clinical outcomes with all-ceramic restorations fabricated with CAD/CAM technology. The use of monolithic zirconia combined with a calculated reduction in the preset tool diameter compensation correction might be beneficial in cases with thin or uneven geometry.

Zirconia CAD/CAM machining vibrations related to zirconia blank shape and initial digital nesting

AIM

To evaluate CAD/CAM milling vibrations related to zirconia disk design, framework, and location of digital crown nesting during zirconia soft milling.

MATERIALS AND METHODS

In the present in vitro study, 25 round zirconia disks of 98 mm (R group) and 15 D-shaped zirconia disks of 71 mm (D group) were placed in a 5-axis CAD/CAM milling unit. The R group had 3 crown milling sites (n = 75) and the D group had 2 crown milling sites (n = 30). In the R group, site A was located 57 mm, site B was 92 mm, and site C was 123 mm from the machine holder attachment. In the D group, site A was 57 mm and site C was 123 mm from the machine holder attachment. A vibration meter (VB-8200; Lutron) was connected to the disk holder, and data (mm/second) were collected during the milling process at the different nesting locations. One-way ANOVA with post-hoc tests and Bonferroni correction for multiple tests were used to compare the groups (α = 0.05).

RESULTS

In the R group, site C exhibited the highest mean vibration values compared with site A (P = 0.001). The first and second cutting tools (2.5 and 1 mm) exhibited statistically significant differences between the D and R groups at milling sites A and C (P < 0.001 and P = 0.003, respectively).

CONCLUSIONS

Milling vibration increased as the distance between the machine holder arm and a digitally nested site increased. Round zirconia disks induced higher vibration values compared with D-shaped disks.

Fit and fatigue behavior of CAD-CAM lithium disilicate crowns

STATEMENT OF PROBLEM

New computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate glass-ceramics have been marketed. However, information concerning their biomechanical behavior is lacking.

PURPOSE

The purpose of this in vitro study was to compare the fit and fatigue behavior of two recently introduced CAD-CAM lithium disilicate materials with the standard IPS e.max CAD ceramic and to investigate the effect of the thermal treatment for crystallization on crown fit.

MATERIAL AND METHODS

Monolithic crowns (n=15) were milled from 3 CAD-CAM lithium disilicates: IPS e.max CAD (Ivoclar AG), Rosetta SM (Hass), and T-lithium (Shenzhen Upcera Dental Technology). Marginal and internal fit were evaluated using the replica technique before and after crystallization, and the fatigue behavior of the luted crowns was evaluated by the step-stress method. One-way ANOVA and the Tukey test were used to compare fit among the materials. Fatigue failure load was evaluated by the Kaplan-Meier and Mantel-Cox tests. The effect of crystallization on fit was evaluated with the paired t test (α=.05).

RESULTS

Marginal fit was different between IPS e.max CAD (74 μm) and Rosetta SM (63 μm) (P=.02). T-lithium was similar to the other ceramics (68 μm) (P>.05). Occlusal internal space was similar among all materials (P=.69). Fatigue failure loads of Rosetta SM (1160 N) and T-lithium (1063 N) were similar to IPS e.max CAD (1082 N) (P>.05). The fatigue failure load of Rosetta SM was higher than that of T-lithium (P=.04). Crystallization reduced the axial internal space of all materials (P<.05) without significantly affecting marginal fit (P>.05).

CONCLUSIONS

The fit and fatigue behavior of Rosetta SM and T-lithium were similar to that of IPS e.max CAD. Crystallization reduced the internal space of the crowns.

Marginal fit of monolithic versus layered zirconia crowns assessed with 2 marginal gap methods

STATEMENT OF PROBLEM

Zirconia can be used either monolithically or veneered with porcelain. However, whether veneering zirconia affects marginal fit is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the marginal fit of the monolithic and layered zirconia prostheses using 2 different assessment methods.

MATERIAL AND METHODS

An ideal complete crown with a chamfer finish line was prepared on an extracted maxillary central incisor. Two prosthesis designs, a framework and a monolithic design, and 2 marginal fit evaluation methods, the silicone replica and the triple scanning techniques, were used. In the first group, 10 crowns were fabricated with the framework design followed by porcelain veneering, and 10 crowns were fabricated monolithically in the second group. The marginal gap in each group was evaluated with both the silicone replica and triple scan methods. Data were statistically analyzed with a 2-way repeated measures ANOVA (α=.05).

RESULTS

A significant difference was found in the mean marginal gap by design type (P=.003), with the monolithic prostheses having lower mean marginal gaps (31.0 and 84.0 µm). However, both groups showed clinically acceptable marginal fit. No significant difference was found between the assessment methods (P=.092).

CONCLUSIONS

Monolithic zirconia crowns had a better marginal fit than veneered zirconia frameworks. Both the replica and triple scan techniques for marginal gap assessment yielded similar results.

Various ways of pre-heating a bulk-fill thermoviscous composite in restoration in non-carious cervical lesions: 12-month randomized clinical trial

OBJECTIVE

The objective of the study is to evaluate through a randomized clinical trial the best method to preheat a composite resin, if using a Caps dispenser device associated with Caps Warmer (CD) or with a VisCalor Caps dispenser/warmer (VD) for restorations in non-carious cervical lesions (NCCLs).

MATERIAL AND METHODS

One hundred and twenty restorations were distributed to two groups (n = 60) according to the pre-heating way of thermoviscous bulk-fill composite resin. For the CD group, pre-heating was carried at 68 °C using a heating bench for 3 min. For the VD group, pre-heating was performed at 68 °C using a heating gun for 30 s. After that, pre-heated bulk-fill composites were directly inserted in the NCCLs. The total working time was recorded. The restorations were evaluated after 6 and 12 months of clinical performance according to the FDI criteria. Statistical analysis was performed using the Student's t test for unpaired samples for working time, and the Chi-square test for restoration clinical performance (α = 0.05).

RESULTS

Working time was shorter for VD with a statistically significant difference compared to CD (p = 0.01). Few restorations were lost or fractured after 12 months of clinical evaluation (p > 0.05). The retention rates were 96.7% (CI 95 %: 88.6-99.1%) for CD and 98.3% (CI 95 %: 91.1-99.7%) for VD. The other FDI parameters were considered clinically acceptable.

CONCLUSIONS

The different pre-heating ways did not influence the clinical performance of thermoviscous bulk-fill composite restorations in NCCLs after 12 months.

CLINICAL RELEVANCE

Regardless of the bulk-fill thermoviscous composite resin pre-heating ways, the restorations are clinically acceptable after 12 months.

A micro-computed tomography analysis of internal and marginal fits of fixed partial dentures: Effect of preparation finish line designs on monolithic zirconia and heat-pressed zirconia-reinforced lithium disilicate

PURPOSE

To evaluate the effect of finish line design (chamfer and feather-edge) and ceramic type on the internal and marginal fits of fixed partial dentures on abutment teeth.

MATERIALS AND METHODS

Two typodont mandibular casts, missing right first premolar tooth, received tooth preparation on canine and second premolar abutments (one cast with chamfer finish line and the other cast with feather-edge finish line). The preparation segment of each typodont model was scanned, 3D printed in resin, and then invested and casted in metal to obtain two metal models. Polyvinyl siloxane impressions were made for the metal models and poured in type IV stone. The stone models (n = 40) were randomly assigned into four groups (n = 10): chamfer finish line with heat-pressed zirconia reinforced lithium disilicate fixed partial denture (CL), chamfer finish line with monolithic zirconia fixed partial denture (CZ), feather-edge finish line with heat-pressed zirconia-reinforced lithium disilicate fixed partial denture (FL), and feather-edge finish line with monolithic zirconia fixed partial denture (FZ). After the fabrication of ceramic restoration, micro-computed tomography was used to evaluate the internal and marginal fits of each fixed partial denture. Data were statistically analyzed with three-way ANOVA (α = 0.05).

RESULTS

There were no significant interactions between preparation type, material type, and tooth type at any of the areas assessed. There was significant difference (p = 0.01) between CZ (59.15 ± 4.6 µm) and FZ (73.6 ± 17.1 µm) groups at the finish line area. Regarding the horizontal marginal discrepancy area, there were significant differences between CZ (62.65 ± 10.5 µm) and FZ (90.05 ± 5.6 µm) groups (p < 0.001), CL (77.45 ± 8.1 µm) and CZ (62.65 ± 10.5 µm) groups (p < 0.001), and FZ (90.05 ± 5.6 µm) and CL (77.45 ± 8.1 µm) groups (p < 0.001). At finish line area, there was a significant difference (p = 0.018) between feather-edge with canine (72.75 ± 13.3 µm) and chamfer with canine (59.05 ± 5.8 µm); however, there was no significant difference (p = 0.774) between feather-edge with premolar (69.45 ± 12 µm) and chamfer with premolar (65.1 ± 7.4 µm). Moreover, there was no significant difference (p = 0.886) between feather-edge with canine and feather-edge with premolar.

CONCLUSIONS

The internal and marginal fits of the ceramic fixed partial dentures can be affected by the finish line design and ceramic type. The feather-edge finish line had a negative impact on the marginal and internal fits of ceramic fixed partial dentures at certain measurement points. Regarding the effect of finish line design on abutment teeth, the difference in fit was only detected at the finish line area of the anterior abutment (canine) with the feather-edge finish line.

Revised FDI criteria for evaluating direct and indirect dental restorations-recommendations for its clinical use, interpretation, and reporting

OBJECTIVES

The FDI criteria for the evaluation of direct and indirect dental restorations were first published in 2007 and updated in 2010. Meanwhile, their scientific use increased steadily, but several questions from users justified some clarification and improvement of the living document.

MATERIALS AND METHODS

An expert panel (N = 10) initiated the revision and consensus process that included a kick-off workshop and multiple online meetings by using the Delphi method. During and after each round of discussion, all opinions were collected, and the aggregated summary was presented to the experts aiming to adjust the wording of the criteria as precisely as possible. Finally, the expert panel agreed on the revision.

RESULTS

Some categories were redefined, ambiguities were cleared, and the descriptions of all scores were harmonized to cross-link different clinical situations with possible management strategies: reviewing/monitoring (score 1-4), refurbishment/reseal (score 3), repair (score 4), and replacement (score 5). Functional properties (domain F: fracture of material and retention, marginal adaptation, proximal contact, form and contour, occlusion and wear) were now placed at the beginning followed by biological (domain B: caries at restoration margin, hard tissue defects, postoperative hypersensitivity) and aesthetic characteristics (domain A: surface luster and texture, marginal staining, color match).

CONCLUSION

The most frequently used eleven categories of the FDI criteria set were revised for better understanding and handling.

CLINICAL RELEVANCE

The improved description and structuring of the criteria may help to standardize the evaluation of direct and indirect restorations and may enhance their acceptance by researchers, teachers, and dental practitioners.

[Effect of polishing method and time on the fitness of CAD/CAM zirconia ceramic crown]

PURPOSE

To compare the effect of different polishing methods and time treatment on the fitness of CAD/CAM zirconia ceramic crowns.

METHODS

Sixteen intact maxillary premolars were randomly divided into two groups, group A was treated with silicon carbide burs, while group B was treated with tungsten steel burs. At different polishing time points of the same tooth, digital impressions of each group were obtained, which were used to manufacture CAD/CAM zirconium ceramic crowns. After trial fitting, the gap impressions were obtained by using silicone rubber replication method, and the marginal and internal discrepancies were assessed. The data were statistically analyzed with SPSS 21.0 software package.

RESULTS

The difference between the gap values of the marginal and internal markers of group A and group B was not statistically significant(P＞0.05). Compared with the no-polishing process, the differences of the marginal gap (39.67±8.35) μm and internal gap (45.18±7.16) μm of group A polished for 4 min, and the marginal gap (51.25±14.73) μm, and internal gap (48.56±6.45) μm of group B polished for 3 min, as well as the marginal gap (48.87±8.90) μm, and internal gap (45.99±7.12) μm of group B polished for 4 min, were all significant(P＜0.05).

CONCLUSIONS

CAD/CAM zirconia ceramic crowns treated with silicon carbide bur for polishing 4 min and tungsten steel for 3 min has the best fitness.

Deep margin elevation. A case report study

Deep subgingival margins are a much-debated topic in adhesive and restorative dentistry. The hydrophobic trait of direct composite resin materials challenges the restorative procedure of cavities with deep subgingival margins since isolation is complicated. A correct indication for a deep margin elevation (DME) treatment is the key to its clinical success, and adequate adaptation of the DME is crucial to its clinical performance. An adequate adaptation of the DME may potentially reduce bacterial accumulation and reduce the incidence of secondary caries as well as maintain periodontal health. The present case report aims to provide a step-by-step overview of the DME technique when applied in combination with a partial indirect glass-ceramic restoration and also provides clinical guidelines to tackle deep subgingival cavities. The indication for a DME and the selection of appropriate materials are explained, supported by the literature.

Marginal Quality and Wear of Bulk-fill Materials for Class-II Restorations in Primary Molars

PURPOSE

The aim of this in-vitro study was to evaluate the marginal integrity and wear of eight bulk-fill materials in comparison to a compomer in Class-II cavities in primary molars after thermomechanical loading (TML).

MATERIALS AND METHODS

Prepared Class-II cavities in 72 extracted primary molars were filled with eight bulk-fill materials. A compomer served as the control group. After water storage (incubator, 28 days, 37°C), samples were subjected to TML (2500 thermal cycles 5°C/55°C; 100,000 load cycles, 50 N, 1.67 Hz). Before and after TML, replicas were made which were used for both SEM analysis of marginal integrity and 3-D wear analysis. Statistical analysis was performed using Kruskal-Wallis and Wilcoxon tests (p < 0.05).

RESULTS

A significant reduction in perfect margins was observed for all groups, while marginal gap formation increased (Wilcoxon test, p < 0.02) for all groups but the compomer. Significant interindividual differences were observed between the tested materials regarding marginal integrity (Kruskal-Wallis test, p < 0.05). Wear analysis revealed no significant differences between groups (Kruskal-Wallis test, p > 0.05).

CONCLUSION

Some of the bulk-fill materials investigated here achieved better results than the compomer and should be further evaluated clinically.

Evaluation of the marginal fit of full contoured zirconia, lithium disilicate and metal crowns fabricated using CAD-CAM: An in vitro study

Introduction

The marginal fit of any dental restoration is vital to its long-term success. Lack of adequate fit is potentially detrimental to both the tooth and the supporting periodontal tissues. The purpose of this study was to evaluate the marginal fit of monolithic zirconia, monolithic lithium disilicate and monolithic metal crowns and compare the three groups.

Methods

The study was conducted by fabricating ten samples for each group, total of 30 samples. A premolar stainless steel die was used to standardize the preparation. PVS putty material was used to make impressions of the model and was poured using type IV die stone. The samples were all fabricated using CAD-CAM. The marginal gap was measured by SEM, and the results were analysed using SPSS software.

Results

The mean marginal gap of zirconia, metal and lithium disilicate crowns was 79.49 μm, 46.83 μm and 70.79 μm, respectively.

Discussion

The metal group showed the lowest marginal gap among the groups. This difference in marginal fit is due to the sintering process where the organic binders in soft metal burn out and the metallic powder particles are being sintered (caked) without creating a fused phase.

Clinical Significance

Marginal fit plays a very important role in the long-term success of a crown. Discrepancy in marginal fit results in food and plaque accumulation causing caries and periodontal breakdown, eventuating the failure of the restoration. A perfect marginal fit would enhance the longevity of any indirect restoration. Knowledge about which indirect restoration has the best marginal fit is critical.

Evaluation of a novel restorative protocol to treat non-carious cervical lesion associated with gingival recession: a 2-year follow-up randomized clinical trial

OBJECTIVE

To compare 2 different resin composites and 2 adhesive systems used in a new restorative protocol (partial restoration) to treat non-carious cervical lesions associated with gingival recession type 1 (RT1).

MATERIAL AND METHODS

Eighty combined defects (CDs) were treated with a partial restoration and periodontal plastic surgery for root coverage. The CDs were randomly assigned to one of the following groups: NP + TE (n = 20), nanofilled composite and 2-step total-etch adhesive system; NP + UA (n = 20), nanofilled composite and universal adhesive system; MH + TE (n = 20), microhybrid composite and 2-step total-etch adhesive; MH + UA (n = 20), microhybrid composite and universal adhesive. Restorations were assessed using the United States Public Health Service (USPHS) criteria at 1 week (baseline) and 6, 12, and 24 months. Survival rate, periodontal parameters, dentin hypersensitivity (DH), and aesthetics were also evaluated.

RESULTS

After 24 months, only the MH + TE group did not lose any restoration, with no significant differences between groups. For surface roughness parameter, MH presented 83.3% of the restorations scoring Bravo, whereas NP presented 48.5% of the restorations scoring Bravo. All groups presented restorations with marginal discoloration. All periodontal parameters behaved similarly, regardless of the restorative material. All groups presented significant reductions of dentin hypersensitivity and improved aesthetic perceptions (p < 0.05).

CONCLUSION

Both resin composites and adhesives tested can be combined for partial restorations to treat CDs.

CLINICAL RELEVANCE

This new restorative-surgical protocol to treat CDs presents satisfactory outcomes. The partial restorations can be successfully executed with both combinations of adhesives and resin composites evaluated in this investigation. TRN : ClinicalTrial.gov: NCT03215615; registration date July 12, 2017.

Accuracy of single-unit ceramic crown fabrication after digital versus conventional impressions: A systematic review and meta-analysis

In the present era when interest in digital dentistry is increasing, the published literature is still confusing about whether digital impression provides similar accuracy as provided by a conventional impression for the fabrication of a single-unit ceramic crown. The aim of the study was to systematically review the in vivo studies comparing marginal, axial, and occlusal fit of single-unit ceramic crowns fabricated after digital impressions with the ones fabricated after conventional impressions. The PubMed, Scopus, and Cochrane online databases were searched for studies comparing the digital impression technique with the conventional technique for single-unit ceramic crowns. Data extraction was done for the year of publication, type of study, country, number of patients, impression system (intraoral scanner [IOS] or conventional impression), marginal fit, axial fit, and occlusal fit. Ten studies were included for meta-analysis regarding the discrepancy in marginal fit, axial fit, and occlusal fit. The digital impression proved to be better than the conventional impression. The mean difference for marginal fit was 6.54 μm (heterogeneity P < 0.00001, I2 = 93%), for axial fit 24.69 μm (heterogeneity P = 0.34, I2 = 11%), and for occlusal fit 6.99 μm (heterogeneity P = 0.03, I2 = 59%). The results of meta-analyses suggest that there is no significant difference between the impression systems (marginally favoring digital impression). The digital impression technique provided better marginal and internal fit of single-unit ceramic crowns than the conventional impression technique. The digital workflow using IOS provided a clinically acceptable marginal fit for single-unit crowns.

A 24-month clinical evaluation of composite resins with different viscosity and chemical compositions: a randomized clinical trial

OBJECTIVES

To evaluate the clinical performance of two methacrylate-based flowable composites and an ormocer-based flowable composite in noncarious cervical lesions (NCCLs) in adult participants.

METHOD AND MATERIALS

In total, 183 restorations were performed on NCCLs. All cavities were restored using a universal adhesive system (Futurabond U, Voco) with selective enamel etching and with one of the three evaluated flowable composites (n = 61): low-viscosity methacrylate-based composite (GrandioSO Flow, LV), high-viscosity methacrylate-based composite (GrandioSO Heavy Flow, HV), and an ormocer-based flowable composite (Admira Fusion Flow, ORM). All restorations were evaluated using FDI and USPHS criteria after 24 months. Kruskall-Wallis analysis of variance rank (α = .05) was used for statistical analysis.

RESULTS

After 24 months of clinical evaluation, 16 restorations were lost (LV = 3, HV = 10, ORM = 3) and the retention rates (95% confidence interval) were 95.0% for LV, 82.2% for HV, and 95.0% for ORM, with statistical differences observed between HV and LV as well as HV and ORM (P < .05). When secondary parameters were evaluated, no significant differences between groups were observed (P > .05). Thirty-three restorations (LV = 8, HV = 13, ORM = 12) showed minor marginal staining, 71 restorations (LV = 26, HV = 20, ORM = 25) presented small marginal adaptation defects, and one restoration for HV presented recurrence of caries.

CONCLUSION

The universal adhesive associated with the ormocer-based and methacrylate-based flowable composite showed promising clinical performance after 24 months. However, the heavy-flow restorations showed significantly more failures. (Quintessence Int 2023;54:186-199; doi: 10.3290/j.qi.b3631841).

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

PURPOSE

The goal of this study was to evaluate how different fabrication techniques affected the marginal accuracy and internal adaptability of poly (ether ether ketone) (PEEK) molar single crowns.

MATERIALS AND METHODS

Twenty PEEK crowns were constructed using two different fabrication techniques, and they were divided into two main groups (PEEK-CAD and PEEK-pressed). PEEK-CAD crowns were numbered from 1 to 10. PEEK-pressed crowns were numbered from 11 to 20. Each group had 10 PEEK crowns, and both were constructed over a master die. For internal fit measurements, silicone replica bodies were built and cut into two halves buccolingually. Marginal accuracy was measured using three evenly spaced landmarks along the specimen's cervical circumference on each surface using a Leica L2 APO* microscope.

RESULTS

In terms of marginal accuracy, the Press group had a statistically significant greater mean marginal gap value than the computer aided-designing (CAD) group. While in terms of internal fit, there was no statistically significant difference in internal fit between the CAD and Press groups. At a significance level of two-tailed p-value = 0.21 (p > 0.05).

CONCLUSION

PEEK-CAD crowns demonstrated higher marginal accuracy and nearly similar internal fit when compared to PEEK-pressed crowns.

CLINICAL SIGNIFICANCE

PEEK material could be used as a substitute for zirconia for a full coverage posterior restoration.

Comparative Evaluation of Retention and Vertical Marginal Accuracy of Co–Cr Copings Fabricated Using Three Different Techniques: An In Vitro Study

AIM

This study was conducted to comparatively assess the retention and vertical marginal fit of cobalt-chromium copings fabricated by the conventional casting technique, 3D-printed resin pattern, and with direct metal laser sintering (DMLS) technique.

MATERIALS AND METHODS

Out of the total 60 test samples, 20 copings were obtained from inlay-casting wax and 20 from casting of 3D-printed resin patterns. In total, 20 copings were obtained from the laser sintering technique. All 60 test samples were then cemented serially on the prepared maxillary-extracted premolars and were evaluated for vertical marginal gap in 8 pre-established reference areas. Retention was evaluated using a universal testing machine.

RESULTS

Results obtained for both marginal gap and retention were statistically analyzed, and the values fall within the clinically acceptable range. The DMLS technique proved precedence over the other two techniques used, as it exhibited maximum retention and marginal accuracy, which is an area of prime concern.

CONCLUSION

The results from this study encourage further research with different pattern-forming materials and techniques and the need to identify the factors that facilitate better marginal fit and retention of cast restorations.

CLINICAL SIGNIFICANCE

This study has myriad of applications in clinical dentistry mainly in decision-making for casting procedure to provide better retention and marginal accuracy for fabrication of Co-Cr crowns. It also aims to aid the clinician to minimize errors by using different techniques for fabrication of wax pattern as well as the coping, keeping abreast with the recent technology to evaluate the accuracy of 3D-printed resin pattern over conventional wax pattern.

Assessment of the fit of lithium disilicate crowns at various locations fabricated by three different methods using the triple-scan protocol

AIM

The present study aimed to evaluate the marginal and internal fit of lithium disilicate crowns at various locations.

MATERIALS AND METHODS

A typodont maxillary left first molar was prepared for a lithium disilicate crown, scanned, and a master die fabricated. Three groups were created according to fabrication method (n = 10): conventional impression and press method (group C); scanning of definitive cast and milling method (group D); and intraoral scanning and milling method (group I). Assessment was performed using the triple-scan protocol. At the buccopalatal and mesiodistal sections, the absolute marginal discrepancy (AMD), marginal gap (MG), axial internal gap (AI), and line angle internal gap (LI) were measured. One-way analysis of variance (ANOVA) and post hoc Tukey HSD tests were used for statistical analysis (α = 0.05).

RESULTS

AMD values were significantly lower in group C than in groups D and I (P < 0.05). MG values in group C were significantly lower than those in the buccal and distal areas in group D and all areas in group I (P < 0.05). AI values in the buccal and palatal areas in group D were significantly lower than those in the mesial and distal areas in group D and all areas in groups C and I (P < 0.05). LI values were significantly lower in group C than in groups D and I (P < 0.05).

CONCLUSION

All three methods were clinically acceptable except for the marginal fit of the intraoral scanning and milling method, which was on the borderline of a clinically acceptable fit. (Int J Comput Dent 2023;26(1): 37-0; doi: 10.3290/j.ijcd.b3818305).

Marginal Accuracy of CAD/CAM Frameworks Fabricated by Presintered Cobalt-Chromium Alloy: A Systematic Review and Meta-analysis

Purpose: To evaluate the marginal accuracy of soft-milled cobalt-chromium (Co-Cr) compared to other construction methods/restorative materials in tooth/implant-supported restorations. Materials and Methods: PICO questions were defined, and a systematic search was conducted in six electronic databases. Titles and abstracts were collected and screened by two independent reviewers. After removing duplicate articles, the full texts of relevant articles were gathered, and the required information and data were extracted. Risk of bias was assessed and meta-analyses of the collected data were conducted using STATA software version 16. Results: A total of 1,914 experimental and clinical articles were reviewed, and 18 studies were selected for qualitative analysis. The 16 studies that were included in the meta-analysis showed no significant marginal gap differences between soft-milled Co-Cr and the following methods/materials: hard-milled Co-Cr (I² = 92.9%, P = .86), casting wax (I² = 90.9%, P = .42), laser-sintered Co-Cr (I² = 93.3%, P = .46), and zirconia (I² = 0.00%, P = .47). However, a significantly higher marginal accuracy of soft-milled Co-Cr was observed when compared to milled-wax casting (I² = 93.1%, P < .001). Conclusion: The marginal gap of soft-milled Co-Cr restorations is within the acceptable clinical range and provides an accuracy similar to other available methods/materials for both the prepared implant abutment and tooth.

Marginal adaptation of CAD-CAM and heat-pressed lithium disilicate crowns: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Lithium disilicate crowns can be manufactured by computer-aided design and computer-aided manufacturing (CAD-CAM) or with the heat-pressed technique. The outcome of studies comparing the effect of the manufacturing method on the marginal adaptation of these crowns is not clear.

PURPOSE

The purpose of this systematic review and meta-analysis was to investigate the effect of the CAD-CAM system and pressing technique on the marginal adaptation of lithium disilicate crowns.

MATERIAL AND METHODS

This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. A literature research was conducted in MEDLINE via PubMed and Scopus databases, relevant journal sites, and the authors' collected references, from January 2009 to April 2019.

RESULTS

The electronic and manual searches that could be read in full totaled 24 studies; of which, 9 were included in the systematic review and meta-analysis, 7 of which were in vitro and 2 in vivo. Statistical analyses were conducted by using Review Manager software program. Meta-analyses were performed with the random effects model (α=.05). In vitro studies showed no difference in the manufacturing (P>.001; 95% confidence interval -0.687 to 0.632), and no significant difference was found for in vivo studies (P=.7, 95% confidence interval 0.00 to 54.77). In the joint analysis of the in vivo and in vitro articles, there was a significant difference between the manufacturing methods (P<.001).

CONCLUSIONS

Differences were detected between the marginal adaptation of lithium disilicate crowns fabricated with the CAD-CAM system and the pressing technique, but the accuracy values were clinically acceptable.