Randomized controlled within-subject evaluation of digital and conventional workflows for the fabrication of lithium disilicate single crowns. Part III: marginal and internal fit

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

STATEMENT OF PROBLEM

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

PURPOSE

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Accuracy of the intaglio surface of 3D-printed hybrid resin-ceramic crowns, veneers and table-tops: An in vitro study

OBJECTIVES

The present study aims to examine the influence of the build angle on the accuracy (trueness and precision) of 3D printed crowns, table-tops and veneers with a hybrid resin-ceramic material.

METHODS

One crown, on table-top and one veneer were printed in five different build angles (0°, 30°, 45°, 60°, 90°) (n = 50) with the digital light processing (DLP) system (Varseo XS, Bego) using hybrid resin (Varseo Smile Crownplus A3, Bego). All printed restorations were scanned using the laboratory scanner (D2000, 3Shape) and matched onto the initial reference design in metrology software (Geomagic Control X, 3D Systems). The root mean square error (RMSE) was calculated between the scanned and reference data. The data was statistically analyzed using the Tukey multiple comparison test and Wilcoxon multiple comparison test.

RESULTS

The crown group showed higher trueness at 30° (0.021 ± 0.002) and 45° (0.020 ± 0.002), and table-tops at 0° (0.015 ± 0.001) and 30° (0.014 ± 0.001) (p < 0.0001). Veneers demonstrated higher trueness at 30° (0.016 ± 0.002) (p < 0.0001). All three restoration types demonstrated the lowest trueness at a 90° build angle and portrayed deviations along the z axis. The veneer and table-top groups showed the lowest precision at 90° (veneers: 0.021 ± 0.008; table-tops: 0.013 ± 0.003). The crown group portrayed the lowest precision at 45° (0.017 ± 0.005) (p < 0.0001).

CONCLUSION

The build angle of DLP-printed hybrid resin-ceramic restorations influences their accuracy.

CLINICAL SIGNIFICANCE

Considering the build angle is important to achieve a better accuracy of 3D-printed resin-ceramic hybrid restorations. This may help predict or avoid the interference points between a restoration and a die and minimize the clinical adjustments.

Influence of sterilization on the retention forces of lithium disilicate and polymer-infiltrated ceramic-network crowns bonded to titanium base abutments: An in-vitro study

OBJECTIVES

The aim of this study was to evaluate the effect of sterilization on the retention forces of lithium disilicate (LD) and polymer-infiltrated ceramic network (PICN) crowns bonded to titanium base (Ti-base) abutments.

MATERIALS AND METHODS

Forty LD and 40 PICN crowns were milled and then bonded to 80 Ti-bases with two resin composite cements: Multilink Hybrid Abutment (mh) and Panavia V5 (pv) for a total of 8 groups (n = 10). Half of the specimens (test) underwent an autoclaving protocol (pressure 1.1 bar, 121°C, 20.5 min) and the other half not (control). Restorations were screw-retained to implants, and retention forces (N) were measured with a pull-off testing machine. The surfaces of the Ti-bases and the crowns were inspected for the analysis of the integrity of the marginal bonding interface and failure mode. Student's t-test, chi-square test, and univariate linear regression model were performed to analyze the data (α = 0.05).

RESULTS

The mean pull-off retention forces ranged from 487.7 ± 73.4 N to 742.2 ± 150.3 N. Sterilized groups showed statistically significant overall higher maximum retention forces (p < .05), except for one combination (LD + mh). Sterilization led to an increased presence of marginal gaps and deformities compared to no-sterilization (p < .001), while no statistically significant relationship was found between failure mode and sterilization (p > .05).

CONCLUSIONS

Sterilization may have a beneficial effect on the retention forces of LD and PICN crowns bonded to titanium base abutments, although it may negatively influence the integrity of the marginal bonding interface.

Effect of intraoral scanning distance on the marginal discrepancy of milled interim crowns

PURPOSE

To compare the marginal discrepancy between milled interim crowns fabricated using intraoral digital scans acquired at different scanning distances.

MATERIALS AND METHODS

Ten acrylic typodont teeth were prepared for interim crowns. Three different resin frames of 2.5-, 5-, and 7.5-mm heights were fabricated and attached to an intraoral scanner (Omnicam). Three groups were created based on the different scanning distances tested: 2.5 mm (Group A), 5 mm (Group B), and 7.5 mm (Group C). Intraoral digital scans were performed on four tooth surfaces: mesial, distal, buccal, and lingual (n = 10). Each experimental scan was used to design and fabricate a milled polymethylmethacrylate anatomically contoured crown. Vinyl polyether silicone was used three times to assess the marginal discrepancy of the specimens by measuring five marginal points on digital photographs. One-way analysis of variance test was used to analyze the data, followed by Tukey's honestly significant difference test (α = 0.05).

RESULTS

The mean marginal discrepancy values in Group C were significantly higher than those in Groups A (p ≤ 0.000) and B (p = 0.001). There was no significant difference between Groups A and B (p = 0.702). There were no significant differences among the four surfaces in any of the scanning distance groups (p1  = 0.583, p2  = 0.390, and p3  = 0.135; p > 0.05).

CONCLUSIONS

The interim crowns fabricated with a scanning distance of 7.5 mm showed the greatest marginal discrepancy when compared with crowns fabricated using 2.5- and 5-mm scanning distances.

The impact of digitization and conventional techniques on the fit of fixed partial dentures FPDs: systematic review and Meta-analysis

PURPOSE OF THE STUDY

The goal behind this study is to answer the question "In tooth-supported fixed partial dentures (FPDs), does the digital impression techniques compared to fabrications using conventional impression methods improve the marginal and internal fit?

BACKGROUND

The incorporation of digital technology in the fabrication of fixed partial dentures (FPDs) has accelerated over the past decade. This study is directed at evaluating the marginal and internal fit of FPDs manufactured using digital approaches compared to conventional techniques. The need for updated data has encouraged this review.

MATERIALS AND METHODS

An electronic search was conducted in PubMed, Scopus, Web of Science, and the Grey Database to identify relevant studies. The Modified Methodological Index for Non-Randomized Studies (MINORS) was used to assess the risk of bias in in vitro experiments. The key results of this meta-analysis were the standard mean differences (SMDs) and 95% confidence intervals (CI) of each main variance, marginal fit, and internal fit between the digital and conventional techniques. Additional analyses were performed to assess the significance of three subgroup parameters: method of digitalization, cement spacer thickness, and span length, and their influence on the fit of the FPDs.

RESULTS

Based on predefined criteria, of the seven articles included in this systematic review, only five were selected for the quantitative data analysis. The marginal fit results were (P = 0.06; SMD: -1.88; 95% CI: - 3.88, 0.11) (P > 0.05) and the internal fit results were (P = 0.02; SMD: -0.80; 95% CI: - 1.49, - 0.10) (P < 0.05). Regarding the subgroup analyses, the method of digitalization subgroup results were (P = 0.35; SMD: -1.89; 95% CI: - 3.89, 0.11) and (P = 0.80; SMD: -0.80; 95% CI: - 1.49, - 0.11) for marginal and internal fit, respectively. The span length results were (P = 0.10; SMD: -1.89; 95% CI: - 3.89, 0.11) for marginal fit and (P = 0.02; SMD: -0.80; 95% CI: - 1.49, - 0.11) for internal fit. The cement spacer thickness (P = 0.01; SMD: -1.89; 95% CI: - 3.89, 0.11) and (P = 0.04; SMD: -0.80; 95% CI: - 1.49, - 0.11) for marginal and internal fit, respectively.

CONCLUSION

Tooth-retained fixed partial dentures FPDs produced by digital scanning and computer-aided design/computer-aided manufacturing (CAD/CAM) systems can significantly enhance the internal fit compared with those manufactured by traditional methods. Intraoral scanners can replace conventional impressions for the fabrication of FPDs because they minimize the operating time and reduce patient pain. Further clinical studies are required to obtain more conclusive results.

SYSTEMATIC REVIEW REGISTRATION

This systematic review and meta-analysis was registered in the International Prospective Register of Systematic Reviews (PROSPERO), registration number CRD42021261397.

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Influence of interdental spaces and the palate on the accuracy of maxillary scans acquired using different intraoral scanners

PURPOSE

To assess the influence of interdental spaces and scanning the palate on the accuracy of maxillary scans acquired using three intraoral scanners (IOSs).

MATERIALS AND METHODS

A virtual completely dentate maxillary cast without interdental spaces was obtained and modified to create 1, 2, and 3 mm of interdental spacing between the anterior teeth. These three files (reference standard tessellation language files) were used to print three reference casts. The reference casts were scanned using three IOSs: TRIOS4, iTero Element 5D, and Aoralscan2. Three groups were created based on the interdental spaces: 0, 1, 2, and 3 mm (n = 10). The groups were subdivided into two subgroups: no palate (NP subgroup) and palate (P subgroup). The reference STL files were used to measure the discrepancy with the experimental scans by calculating the root mean square (RMS) error. Three-way analysis of variance (ANOVA) and post hoc Tukey pairwise comparison tests were used to analyze trueness. The Levene test was used to analyze precision (α = 0.05).

RESULTS

Trueness ranged from 91 to 139 μm and precision ranged from 5 to 23 μm among the subgroups tested. A significant correlation was found between IOS*group (p<0.001) and IOS*subgroup ( p<0.001). Tukey test showed significant trueness differences among the interdental spaces tested (p<0.001). The 1- and 2-mm groups obtained better trueness than the 0- and 3-mm groups (p<0.001). An 11 μm mean trueness discrepancy was measured among the different interdental space groups tested. The P subgroups demonstrated significantly higher trueness when compared to the NP subgroups (p<0.001). The discrepancy between the maxillary scans with and without the palate was 4 μm. Significant precision discrepancies were found (p = 0.008), with the iTero group showing the lowest precision.

CONCLUSION

Interdental spaces and incorporation of the palate on maxillary intraoral scans influenced trueness and precision of the three IOSs tested. However, the scanning discrepancy measured may be of no clinical relevance.

Digital measurement method for comparing the absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated using conventional and digital technologies

BACKGROUND

In clinical practice, control of the marginal fit of fixed dental prostheses is hindered by evaluation method, which needs to be further improved to increase its clinical applicability. This study aimed to quantitatively analyze the absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated by conventional and digital technologies using a digital measurement method based on the digital impression technology and open source software.

METHODS

A digital workflow and the conventional impression combined with the lost-wax heat-pressed technique were adopted to separately fabricate 10 glass ceramic fixed dental prostheses. Three-dimensional data for the abutments, fixed dental prostheses, and fixed dental prostheses seated on the abutments, were obtained using a dental scanner. The two datasets were aligned using registration technology, specifically "multi-points registration" and "best fit alignment," by reverse engineering software. Subsequently, the three-dimensional seated fit between the fixed dental prostheses and abutments were reconstructed. The margin of the abutment and crown was extracted using edge-sharpening and other functional modules, and the absolute marginal discrepancy was measured by the distance between the margin of the abutment and crown. One-way analysis of variance was used to statistically analyze the measurement results.

RESULTS

Using the digital measurement method, the mean value of absolute marginal discrepancy for fixed dental prostheses fabricated by the conventional method was 106.69 ± 6.46 μm, and that fabricated by the digital workflow was 102.55 ± 6.96 μm. The difference in the absolute marginal discrepancy of three-unit all-ceramic fixed dental prostheses fabricated using the two methods was not statistically significant (p > 0.05).

CONCLUSIONS

The digital measurement method for absolute marginal discrepancy was preliminarily established based on open source software and applied in three-unit ceramic fixed dental prostheses. The absolute marginal discrepancy of three-unit ceramic fixed dental prostheses fabricated using digital technology was comparable to that of conventional technique.

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.

Clinical outcomes of implant-supported and tooth-supported fixed prostheses fabricated from digital versus analogue impression: a systematic review and meta-analysis

OBJECTIVE

To analyze the clinical outcomes of implant-supported prostheses and tooth-supported fixed prostheses, fabricated from digital and conventional impression.

MATERIALS AND METHODS

The literature search was carried out on two electronic databases (PubMed and Cochrane Library). Randomized controlled trials (RCT) published from January 2011 to September 2022 were included. The bias risk was evaluated using Cochrane Risk of Bias Tool 2.0. Further screening was done for meta-analysis according to modified Newcastle-Ottawa scoring criteria. Forest plot was generated using a statistical method of inverse variance of random effect with 95% confidence interval.

RESULTS

A total of 8 randomized controlled trials were included for systematic review out of which four studies were based on tooth-supported fixed prosthesis and remaining four were based on implant-supported prosthesis. Further screening was conducted and three studies were eligible for meta-analysis. Tooth-supported fixed prosthesis fabricated from digital impression showed no significant difference in the marginal fit in any region measured, except for occlusal region where conventional impression showed more favorable marginal fit. Implant-supported prosthesis fabricated from digital impression showed survival rates ranging from 97.3 to 100% and there was no statistically significant difference in marginal bone loss (p = 0.14).

CONCLUSION

Implant-supported prostheses fabricated from digital and conventional impressions show no significant differences in their clinical outcomes. Tooth-supported fixed prostheses fabricated from digital impression have shown favorable findings in terms of marginal fit. Despite that, there is still lack of clinical trials with larger sample size and longer follow-up periods. Future studies that fulfill these two criteria are deemed necessary.

Clinical outcomes of single full-coverage lithium disilicate restorations: A systematic review

Introduction

Lithium disilicate glass-ceramic (LDC) restorations exhibit microorganism infiltration, recurrent caries, pulpal lesions, periodontal inflammation, and cement exposure to the oral environment over time. All these factors lead to restoration failure. This systematic review aimed to investigate the clinical outcomes of LDC full-coverage crowns (FCC) in permanent teeth compared with those of other full-coverage restoration materials.

Materials & Methods

Search strategies were developed for four databases: Web of Science, OVID, PubMed, and Scopus. Data extraction and quality appraisals were performed by two independent reviewers. Data on the presence of caries, post-operative sensitivity, and periodontal changes were extracted from the included clinical studies. In addition to the outcome measures, data on the sample size, study groups, method of restoration fabrication, type of impression, and type of abutment were recorded.

Results

We retrieved 3989 records for the title and abstract screening. Of these, 19 clinical studies met the inclusion criteria. The overall quality of the included studies indicates a low risk of bias. Most studies reported no pulpal involvement, recurrent caries, or post-operative sensitivity and presented a favorable periodontal response after the cementation of LDC-FCC during different follow-up periods.

Conclusion

Based on the endodontic and periodontic clinical responses of natural tooth abutments and their supporting periodontium, LDC-FCC can be considered a clinically successful restorative option.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Long-term survival of monolithic tooth-supported lithium disilicate crowns fabricated using a chairside approach: 15-year results

OBJECTIVES

To investigate the clinical performance of chairside fabricated tooth-supported posterior single crowns from lithium disilicate ceramic.

MATERIALS AND METHODS

Thirty-four crowns (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein) were inserted between 2006 and 2007 and again evaluated after 15 years. Survival and success rates were calculated according to Kaplan-Meier, and the quality of the crowns was evaluated by using modified United States Public Health (USPHS) criteria.

RESULTS

Twenty-two crowns were available for recall; six patients were defined as dropouts. The mean observation period was 15.2 years (± 0.2). Six failures occurred (1 technical/5 biological) resulting in a survival rate of 80.1%. The success rate was 64.2%. The roughness of the crowns increased (p = 0.021) and the majority of adhesive gaps were discolored (p = 0.001) in comparison to baseline. The color, tooth, and crown integrity remained stable over the follow-up period (p ≥ 0.317).

CONCLUSION

The fabrication of tooth-supported lithium disilicate crowns using a chairside approach yielded acceptable long-term survival and success rates. Due to discoloration, the long-term use of dual-cure self-adhesive resin cements might result in unpleasing esthetic results.

CLINICAL RELEVANCE

The performance of posterior lithium disilicate single crowns revealed excellent to good clinical quality and an acceptable number of events after 15 years of clinical service.

Trueness and precision of milled and 3D printed root-analogue implants: A comparative in vitro study

OBJECTIVES

The present study aimed to evaluate the accuracy (trueness and precision) of titanium and zirconia multi-rooted root analogue implants (RAIs) manufactured by milling and 3D-printing.

METHODS

A multi-rooted RAI was designed based on a mandibular second molar segmented from cone-beam computed tomography (CBCT). The manufactured RAIs were divided into four groups: 3D-printed titanium (PT) and 3D-printed zirconia (PZ) (n=10 each), as well as milled titanium (MT) and milled zirconia (MZ) (n=5 each). The specimens were scanned with a high-precision scanner, and the scanned data were imported into 3D-measurement software to evaluate the precision and trueness of each group. Root mean square (RMS) deviations were measured and statistically analysed (One-way ANOVA, Tukey's, p≤0.05).

RESULTS

PZ showed the highest precision with RMS value of 21±6 µm. Nevertheless, there was no statistically significant difference in precision among the other groups. Regarding trueness, MZ showed the highest trueness with RMS value of 66±3 µm, whereas MT showed the lowest trueness result. Inspection sections showed that MT had significantly high RMS deviation in the furcation area (612±64 µm), whereas PZ showed significantly high RMS deviation at the apical area (197±17 µm).

CONCLUSIONS

The manufacturing process significantly influenced the RAI accuracy. PZ exhibited the highest precision, whereas MZ exhibited the highest trueness, followed by PT. Finally, our results suggest that 3D-printing can reproduce concave surfaces and less accessible areas better than milling.

CLINICAL SIGNIFICANCE

Milled and 3D-printed RAIs showed promising results in terms of precision and trueness. However, further clinical research is needed to advocate their use as immediate implants. Additionally, the inherent volumetric changes of the various materials during manufacturing should be considered.

The Complete Digital Workflow in Fixed Prosthodontics Updated: A Systematic Review

Digital applications have changed therapy in prosthodontics. In 2017, a systematic review reported on complete digital workflows for treatment with tooth-borne or implant-supported fixed dental prostheses (FDPs). Here, we aim to update this work and summarize the recent scientific literature reporting complete digital workflows and to deduce clinical recommendations. A systematic search of PubMed/Embase using PICO criteria was performed. English-language literature consistent with the original review published between 16 September 2016 and 31 October 2022 was considered. Of the 394 titles retrieved by the search, 42 abstracts were identified, and subsequently, 16 studies were included for data extraction. A total of 440 patients with 658 restorations were analyzed. Almost two-thirds of the studies focused on implant therapy. Time efficiency was the most often defined outcome (n = 12/75%), followed by precision (n = 11/69%) and patient satisfaction (n = 5/31%). Though the amount of clinical research on digital workflows has increased within recent years, the absolute number of published trials remains low, particularly for multi-unit restorations. Current clinical evidence supports the use of complete digital workflows in implant therapy with monolithic crowns in posterior sites. Digitally fabricated implant-supported crowns can be considered at least comparable to conventional and hybrid workflows in terms of time efficiency, production costs, precision, and patient satisfaction.

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.

Comparative assessment of marginal and internal gaps of cast-free monolithic zirconia crowns fabricated from 2 intraoral scanners: A prospective, double-blind, randomized clinical trial

STATEMENT OF PROBLEM

Despite the introduction of intraoral scanners (IOSs) with dual camera triangulation, only a few comparative clinical studies have evaluated their clinical performances in the digital workflow for cast-free restorations.

PURPOSE

The purpose of this clinical trial was to assess the clinical efficacy of 2 different technology-based IOSs by evaluating the marginal and internal gaps of cast-free monolithic zirconia crowns fabricated by using a fully digital workflow.

MATERIAL AND METHODS

A prospective randomized clinical trial was conducted in 35 participants requiring a single-unit restoration. One crown was fabricated from the scan data obtained with a confocal microscopy-based IOS (Group T), while the other was made with the scan data obtained from an IOS using dual camera triangulation (Group I). A replica technique was used to assess the marginal and internal gaps. The buccolingual and mesiodistal cross-sections were measured, and noninferiority trials were performed.

RESULTS

A total of 39 teeth from 35 participants were restored with a single-unit crown. The marginal and axial wall gaps of the crowns in Group I was not inferior to that of the crowns in Group T (upper limit confidence interval [CI] <30). In contrast, the gap of the crowns at the line angle in Group T was inferior to that of the crowns in Group I (lower limit CI <-30). From an occlusal space perspective, the gap of the crowns in Group I was inferior to that of the crowns in Group T (upper limit CI >30). Twenty-five crowns were selected from Group I, and 14 crowns were selected from Group T for definitive placement.

CONCLUSIONS

The marginal gap of the crown fabricated by using the scan data obtained from the dual camera triangulation-based IOS was noninferior to that obtained from the confocal microscopy-based IOS and was within the clinically applicable limit.

A Scoping Review of Marginal and Internal Fit Accuracy of Lithium Disilicate Restorations

OBJECTIVE

To assess and compare the accuracy of the marginal and internal fit of lithium disilicate crowns and onlays fabricated by conventional and digital methods.

SOURCES

An electronic search was carried out on MEDLINE, Embase, Web of Science and Cochrane Library between 2010 and 2021.

STUDY SELECTION

Seventeen studies published between 2014 & 2021 were included, of which thirteen were in vitro laboratory-based studies; three were in vivo clinical studies and one randomised controlled trial.

DATA

Twelve studies focused on the marginal fit, five focused on the marginal and internal fit. Five studies found that the marginal and internal fit of crowns were more accurate using digital techniques. Five studies noted that there was no difference using either technique and two noted that conventional methods had a more accurate marginal fit.

CONCLUSION

Digital techniques were comparable to conventional methods in terms of accuracy although there was insufficient evidence to indicate that one technique was more accurate than the other with respect to Lithium Disilicate restorations.

CLINICAL SIGNIFICANCE

Digital impressions are reliable and viable alternatives for clinicians compared to conventional impression techniques when restoring teeth with lithium disilicate restorations.

Evaluation of marginal/internal fit of fixed dental prostheses after digital, conventional, and combination impression techniques: A systematic review

Advances of digital technology are rapidly adopted in dental practice. This systematic review aimed to collect evidence on the accuracy of fit of different types of fixed dental prostheses (FDPs) fabricated through digital, conventional, or combination impression techniques. Data collection was based on the guidelines of the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Two databases (PubMed, Scopus) were searched for articles in English published between 2010 and 2021 resulting in 480 articles. Of those, 35 studies fulfilled the inclusion criteria. These articles referred to three groups of materials/techniques including all-ceramic (zirconia; lithium disilicate) and porcelain-fused-to-metal (PFM) restorations. Results showed clinically acceptable marginal fit (< 120 μm) for all materials and impression techniques. Α fully digital workflow appears more promising for the construction of short-span zirconia FDPs. Nevertheless, most articles evaluated marginal/internal fit of single crowns or short-span FDPs in vitro, while clinical data are limited for long-span FDPs. The necessity for gingival retraction remains a major drawback of all impression techniques, increasing procedural time and patient discomfort. Besides, factors related to the fabrication process, including milling and 3D printing of working models significantly influence the outcome. Overall, there still some way to go before digital technology can be incorporated in complex treatment plans in prosthodontics.

Effect of preparation type on the accuracy of different intraoral scanners: An in vitro study at different levels of accuracy evaluation

OBJECTIVE

Evaluation of the effect of preparation type (inlay, onlay, and crown) on the accuracy of different intraoral scanning (IOS) systems at the preparation and arch segment levels.

MATERIALS AND METHODS

Three molars were prepared for inlay, onlay, and crown. Each preparation was scanned 10 times by CEREC Omnicam, Trios 3 (TS), and Medit i500 scanners. Each image was trimmed twice. The first trimming produced a preparation image (PI), and the second trimming extracted a segment image (SI) that involved the preparation with the adjacent teeth. Trueness and precision were calculated at the PI and SI levels.

RESULTS

At the PI level, all IOS systems had similar trueness pattern for all preparations, where the inlay had the best trueness followed by the crown and onlay. At the SI level, the different preparations showed similar trueness. The precision did not show a clear pattern of superiority for any preparation. The TS was significantly more precise than other IOS systems at the PI and SI levels, for every preparation. The proximal areas suffered from the greatest errors, regardless of preparation type.

CONCLUSIONS

The preparation type influenced PI trueness, and the IOS system affected PI and SI precisions.

CLINICAL SIGNIFICANCE

The smaller and less complex preparations have greater IOS accuracy than larger and more complex preparations. As the proximal areas are more affected regardless of the preparation, a more accessible proximal area for scanning is desirable.

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

PURPOSE

Several studies have compared digital intraoral scanners and conventional impressions. The accuracy of these two methods in terms of marginal accuracy of lithium disilicate crowns is not well-established, yet. The purpose of this study was to systematically review available publications on marginal fit of single-unit, full-coverage, tooth-supported lithium disilicate restorations.

METHODS

Pubmed, Web of Science, Cochrane, EMBASE, and Scopus were electronically searched along with a manual search. After critical appraisal, data from selected studies were extracted and mean marginal difference with a 95% confidence interval was calculated. Meta-analysis of the collected data was conducted using STATA software.

RESULTS

The meta-analysis revealed similar marginal gap values in intraoral scanners with conventional groups (p>0.05) and in intraoral scanners with extraoral canners (p>0.05).

CONCLUSION

No significant difference was seen between digital and conventional impressions or intra- and extraoral scanners for marginal accuracy of lithium disilicate crowns.

Outcome measurements and quality of randomized controlled clinical trials of tooth-supported fixed dental prostheses: A systematic review and qualitative analysis

STATEMENT OF PROBLEM

The lack of consensus regarding a standardized set of outcome measurements and noncompliance with current reporting guidelines in clinical trials of tooth-supported fixed dental prostheses (FDPs) hamper interstudy comparability, compromise scientific evidence, and waste research effort and resources in prosthetic dentistry.

PURPOSE

The primary objective of this systematic review was to identify all primary and secondary outcome measurements assessed in randomized controlled trials (RCTs) of tooth-supported FDPs. Secondary objectives were to assess their methodological quality by using the Cochrane Collaboration's risk of bias tool (RoB, v2.0) and their reporting quality by means of a standardized 16-item CONSORT assessment tool through published reports.

MATERIAL AND METHODS

An electronic search was conducted in MEDLINE, EMBASE, and Cochrane library to identify all RCT-related articles published in the past 10 years. Differences in RoB were tested with the Pearson chi-square test, and those in CONSORT score with the Student t test.

RESULTS

A total of 64 RCTs from 79 publications were deemed eligible. The diversity of outcome measures used in the field is apparent. Twenty percent of the included studies had a low RoB, 79% showed some concerns, and 1% had a high RoB. The mean ±standard deviation CONSORT compliance score was 22.56 ±3.17. Trials adhered to the CONSORT statement reported lower RoB than those that did not adhere (P<.001). RCTs with a low RoB reported more comprehensive adherence to CONSORT guidelines than those with some concerns (MD 4 [95% CI 1.52-6.48]; P=.004).

CONCLUSIONS

A standardized core outcome reporting set in clinical research on tooth-supported FDPs remains evident. Adherence to the CONSORT statement continues to be low, with some RoB concerns that can be improved.

Comparative assessment of complete-coverage, fixed tooth-supported prostheses fabricated from digital scans or conventional impressions: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Intraoral scanners have significantly improved over the last decade. Nevertheless, data comparing intraoral digital scans with conventional impressions are sparse.

PURPOSE

The purpose of this systematic review and meta-analysis was to determine the impact of impression technique (digital scans versus conventional impressions) on the clinical time, patient comfort, and marginal fit of tooth-supported prostheses.

MATERIAL AND METHODS

The authors conducted a literature search based on the Population, Intervention, Comparison, and Outcome (PICO) framework in 3 databases to identify clinical trials with no language or date restrictions. The mean clinical time, patient comfort, and marginal fit values of each study were independently extracted by 2 review authors and categorized according to the scanning or impression method. The authors assessed the study-level risk of bias.

RESULTS

A total of 16 clinical studies met the inclusion criteria. The mean clinical time was statistically similar for digital scan procedures (784 ±252 seconds) and for conventional impression methods (1125 ±159 seconds) (P>.05). The digital scan techniques were more comfortable for patients than conventional impressions; the mean visual analog scale score was 67.8 ±21.7 for digital scans and 39.6 ±9.3 for conventional impressions (P<.05). The mean marginal fit was 80.9 ±31.9 μm and 92.1 ±35.4 μm for digital scan and conventional impressions, respectively, with no statistically significant difference (P>.05).

CONCLUSIONS

Digital scan techniques are comparable with conventional impressions in terms of clinical time and marginal fit but are more comfortable for patients than conventional impression techniques.

Production time, effectiveness and costs of additive and subtractive computer-aided manufacturing (CAM) of implant prostheses: A systematic review

OBJECTIVE

To systematically review the dental literature for clinical studies reporting on production time, effectiveness and/or costs of additive and subtractive computer-aided manufacturing (CAM) of implant prostheses.

MATERIALS AND METHODS

A systematic electronic search for clinical studies from 1990 until June 2020 was performed using the online databases Medline, Embase and Cochrane. Time required for the computer-aided design (CAD) process, the CAM process, and the delivery of the CAD-CAM prostheses were extracted. In addition, articles reporting on the effectiveness and the costs of both manufacturing technologies were included.

RESULTS

Nine clinical studies were included reporting on subtractive CAM (s-CAM; 8 studies) and additive CAM (a-CAM; 1 study). Eight studies reported on the s-CAM of prosthetic and auxiliary components for single implant crowns. One study applied a-CAM for the fabrication of an implant bar prototype. Time was provided for the CAD process of implant models (range 4.9-11.8 min), abutments (range 19.7-32.7 min) and crowns (range 11.1-37.6 min). The time for s-CAM of single implant crown components (abutment/crown) ranged between 8.2 and 25 min. Post-processing (e.g. sintering) was a time-consuming process (up to 530 min). At delivery, monolithic/veneered CAD-CAM implant crowns resulted in additional adjustments chairside (51%/93%) or labside (11%/19%).

CONCLUSIONS

No scientific evidence exists on production time, effectiveness and costs of digital workflows comparing s-CAM and a-CAM. For both technologies, post-processing may substantially contribute to the production time. Considering effectiveness, monolithic CAD-CAM implant crowns may be preferred compared to veneered CAD-CAM crowns.

Marginal and internal fit of crowns based on additive or subtractive manufacturing

OBJECTIVE

To assess the marginal and internal fit of crowns manufactured by additive and subtractive manufacturing technique.

MATERIALS AND METHODS

Twenty extracted teeth prepared for complete coverage crowns were scanned with an intra-oral scanner (Omnicam, DentsplySirona). For the subtractive manufacturing (SM) group, ten crowns were manufactured in a hybrid resin block (Vita Enamic, Vita Zahnfabrik). For the additive manufacturing (AM) group, the crowns were manufactured in a hybrid resin material (NextDent C&B, 3D systems). The design parameters were identical for the two groups. The marginal and internal fit (determined at the axial wall, the cusp tip and occlusally) was assessed before cementation with the replica technique and after cementation under stereomicroscope after sectioning of the crowned teeth.

RESULTS

For the SM group, the marginal fit was 91 µm (±28 µm) before cementation and 85 µm (±18 µm) after cementation. In the AM group, the marginal fit was 75 µm (±29 µm) before cementation and 71 µm (±18 µm) after cementation. The differences were not statistically significant. As regards the internal fit, the fit at the axial wall was statistically significantly better in the SM group than in the AM group (p=.009 before cementation and .03 after cementation). Occlusally the fit in the AM group was significantly better than in the SM group after cementation (p<.001).

CONCLUSION

Within the limitations of the current study, the marginal fit of additively manufactured crowns is comparable to crowns manufactured with chair-side subtractive technique and within the clinically acceptable range. As regards the internal fit no one technique was consistently superior.

Clinical performance of intraoral digital impression for fixed prosthodontics: a Meta-analysis

OBJECTIVES

To analyze the clinical performance of the intraoral digital impression (IDI) in the fixed prosthodontics.

METHODS

Databases of Medline (Ovid), EMBASE, Cochrane Central Register of Controlled Trials, and CNKI were searched for randomized controlled trial (RCT) on the use of IDI in fixed prosthodontics until May 2020. Two reviewers independently screened literature, extracted data, and assessed the risk of bias of included studies. A Meta-analysis was conducted when available.

RESULTS

Eleven RCTs involving 618 patients were included in this study. A total of 2 and 3 studies had low and high risks of bias, respectively, and other included studies had a medium risk of bias. Results illustrated that the IDI group could shorten the impression-taken time [SMD=-5.63, 95%CI (-11.25, -0.01), P=0.05] and improve the accuracy of the marginal fit [SMD=-0.53, 95%CI (-0.84, -0.22), P=0.000 7] compared with the conventional impression group. However, no significant difference was observed in the internal fit.

CONCLUSIONS

Evidence indicated a good clinical performance of IDI for fixed prosthodontics. Notably, high-quality studies are expected to further support the conclusion.

An in vitro comparison of the marginal and internal adaptation of ultrathin occlusal veneers made of 3D-printed zirconia, milled zirconia, and heat-pressed lithium disilicate

STATEMENT OF PROBLEM

Whether additively produced zirconia could overcome problems with conventional computer-aided design and computer-aided manufacture (CAD-CAM) such as milling inaccuracies and provide accurate occlusal veneers is unclear.

PURPOSE

The purpose of this in vitro study was to compare the marginal and internal fit of 3D-printed zirconia occlusal veneers with CAD-CAM-fabricated zirconia or heat-pressed lithium disilicate ceramic (LS2) restorations on molars.

MATERIAL AND METHODS

The occlusal enamel in 60 extracted human molars was removed, with the preparation extending into dentin. Occlusal veneers at a thickness of 0.5 mm were designed and manufactured according to their group allocation: 3DP, 3D-printed zirconia; CAM, milled zirconia; and HPR, heat-pressed LS2. The prepared teeth and restorations were scanned and superimposed, and the marginal and internal adaptation were measured 2- and 3-dimensionally; the production accuracy (trueness) was also measured. The comparisons of the group medians were performed with nonparametric methods and a pairwise group comparison (α=.05).

RESULTS

Three-dimensionally printed zirconia revealed median outcomes of 95 μm (margin), 252 μm (cusp), 305 μm (fossa), and 184 μm (3D internal adaptation). CAM showed median values of 65 μm (margin), 128 μm (cusp), 203 μm (fossa), and 120 μm (3D internal adaptation). The respective values for the group HPR were 118 μm (margin), 251 μm (cusp), 409 μm (fossa), and 180 μm (3D internal adaptation). Significant differences (P<.001) between CAM and 3DP (cusp, fossa, 3D internal adaptation) and between CAM and HPR (all regions) were found, with the former group showing higher accuracies. The trueness showed median discrepancies of 26 μm (3DP), 13 μm (CAM), and 29 μm (HPR) with significant differences (P<.001) for the comparisons 3DP-CAM and CAM-HPR.

CONCLUSIONS

Three-dimensionally printed zirconia occlusal veneers produced by means of lithography-based ceramic manufacturing exhibit a marginal adaptation (95 μm) and a production accuracy (26 μm) similar to those of conventional methods.

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.

Effect of Adhesive Gap Setting on Fracture Resistance of All-ceramic Crowns

Background:

Several factors might affect the fracture resistance of all-ceramic crowns, including cement thickness.

Aim:

To evaluate the influence of cement thickness on the fracture resistance.

Objective:

To determine the effect of varying the adhesive gap thickness on the fracture loads of all-ceramic CEREC 3D molar crowns.

Methods:

Standardized prepared epoxy resin molar dies (Viade Inc.) were fabricated. A standard molar crown was designed using a CEREC 3D machine (Sirona Dental Systems). Twenty-four crowns were milled from Vita Mark II blocks (Vita Zahnfabrik), using adhesive gap settings of 30, 60 and 90 µm (n=8). A dual-cure resin cement (PanaviaF 2.0, Kuraray) was used to cement the crowns to their respective dies, following manufacturer's recommendation. After 1 week of storage in distilled water at 37°C, each crown was loaded in compression until complete failure in a universal testing machine (Instron 8501) and fracture loads (N) were recorded. Fractured specimens were sectioned to determine cement thickness. Sections were examined using a traveling light microscope to measure cement thickness. Data were statistically analyzed using one-way ANOVA test and Pearson's correlation at (α=0.05).

Results:

The mean fracture loads and standard deviation values in N were 1,267.57 (122.82), 1,225.20 (179.46) and 1,180.76 (161.77) for the crowns with 30, 60 and 90µm, respectively. ANOVA indicated no significant differences among mean fracture strength values (p = 0.55). All crowns failed in a catastrophic mode and were not repairable.

Conclusions:

Adhesive cement gap as achieved with three CEREC 3D settings from 30 to 90µm had no significant effect on fracture strength of crowns made from Vita Mark II blocks.

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.

Clinical Evaluation of Time Efficiency and Fit Accuracy of Lithium Disilicate Single Crowns between Conventional and Digital Impression

The purpose of this study was to demonstrate the time-efficiency and the clinical effectiveness of chairside-fabricated lithium disilicate single crowns by digital impressions compared to the conventional method. Thirteen patients requiring a single crown on the maxillary or mandibular premolar or first molar were assigned as study subjects. The impressions were obtained using the conventional method and two digital methods with intraoral scanners: AEGIS.PO (Digital Dentistry Solution, Seoul, Korea) and CEREC Omnicam (Sirona, Bensheim, Germany). Two types of lithium disilicate single crowns were obtained; a reference crown (by conventional workflow) and a chairside crown (by digital workflow). The total time taken for fabricating the chairside crown was recorded. The replica technique was performed to compare the marginal and internal fit of the two types of crowns. In addition, accuracy of the intraoral scanners was evaluated by the best-fit alignment method. The difference between the groups was analyzed using the two-tailed paired t-test or one-way ANOVA, followed by the Student–Newman–Keuls test for multiple comparisons. Statistical significance was accepted at p < 0.05 for all statistical tests. The time required to obtain the impressions by the AEGIS (7:16 ± 1:50 min:s) and CEREC (7:29 ± 2:03 min:s) intraoral scans was significantly lower than the conventional method (12:41 ± 1:16 min:s; p < 0.001). There was no significant difference between the intraoral scanners. The total working time to fabricate the chairside crown averaged 30:58 ± 4:40 min:s. The average marginal gap was not significantly different between the reference (107.86 ± 42.45 µm) and chairside (115.52 ± 38.22 µm) crowns (p > 0.05), based on results of replica measurement. The average internal gaps were not significantly different. The average value of the root mean square between the AEGIS (31.7 ± 12.3 µm) and CEREC (32.4 ± 9.7 µm) scans was not significantly different (p > 0.05). Intraoral scans required a significantly shorter impression time than the conventional method, and it was possible to fabricate a lithium disilicate crown in a single visit. There were no statistically significant differences in the fit of the restorations and accuracy of the intraoral scanners compared to the conventional workflow.

Retention of zirconia crowns to Ti-base abutments: effect of luting protocol, abutment treatment and autoclave sterilization

PURPOSE

To evaluate the influence of resin cement type, surface pretreatment and autoclave sterilization on the retention of Y-TZP crowns to Ti-base abutments.

METHODS

Y-TZP crowns were designed and milled to fit Ti-base abutments. Crowns were cemented using either a conventional resin cement (conventional) with a universal adhesive or a self-adhesive resin cement (self-adhesive), both following no surface pretreatment (No) or Ti-base abutment sandblasting (SB) (n=20/group). Half of the cemented samples were subjected to in-office autoclave sterilization. Pullout testing was performed in a universal testing machine at a speed of 1 mm/min until crown displacement. Data were statistically evaluated through a linear mixed model following post hoc comparisons by LSD test.

RESULTS

Pullout data as a function of cement type demonstrated higher retention for conventional relative to self-adhesive cement (p < 0.001). Ti-base sandblasting (SB) favored crown retentiveness over No pretreatment (p < 0.001). Sterilized crowns exhibited higher pullout values than non-sterile (p=0.036). All the two- and three-factor interaction analyses corroborated with the superior adhesive strength of conventional compared to self-adhesive cement (all, p < 0.011), as well as, SB relative to No pretreatment (all, p < 0.024). While autoclave sterilization maximized bond strength when self-adhesive cement (data collapsed over surface pretreatment, p < 0.050) and No pretreatment were evaluated (data collapsed over surface pretreatment, p < 0.013), no significant difference was observed for conventional resin cement (p=0.280) and SB (p=0.878) groups.

CONCLUSIONS

Conventional resin cement and/or Ti-base sandblasting increased Y-TZP crown retentiveness, with no significant influence of autoclave sterilization. Autoclaving increased retentiveness when self-adhesive cement and/or no Ti-base pretreatment were used.

3D Digital Impression Systems Compared with Traditional Techniques in Dentistry: A Recent Data Systematic Review

The advent of new technologies in the field of medicine and dentistry is giving improvements that lead the clinicians to have materials and procedures able to improve patients' quality of life. In dentistry, the last digital techniques offer a fully digital computerized workflow that does not include the standard multiple traditional phases. The purpose of this study is to evaluate all clinical trials and clinical randomized trials related to the digital or dental impression technique in prosthetic dentistry trying to give the readers global information about advantages and disadvantages of each procedure. Data collection was conducted in the main scientific search engines, including articles from the last 10 years, in order to obtain results that do not concern obsolete impression techniques. Elsevier, Pubmed and Embase have been screened as sources for performing the research. The results data demonstrated how the working time appears to be improved with digital workflow, but without a significant result (P = 0.72596). The papers have been selected following the Population Intervention Comparison Outcome (PICO) question, which is related to the progress on dental impression materials and technique. The comparison between dentists or practitioners with respect to classic impression procedures, and students open to new device and digital techniques seem to be the key factor on the final impression technique choice. Surely, digital techniques will end up supplanting the analogical ones altogether, improving the quality of oral rehabilitations, the economics of dental practice and also the perception by our patients.

Accuracy of marginal adaptation of posterior fixed dental prosthesis made from digital impression technique: A systematic review

Aim

The aim of this systematic review was to investigate the marginal adaptation of three or four unit fixed dental prosthesis (FDP) fabricated with digital impression techniques to those fabricated using any other impression technique.

Settings and Design

Database/electronic searches were conducted till August 2019 in PUBMED-MEDLINE, SCOPUS, and Cochrane library. To identify published articles, multiple keywords were used to develop a search strategy in various combinations. Manual searching of articles was also done. Clinicaltrials.gov.in WHOICTRP and CTRI websites were also searched. Two independent reviewers (TP and VK) assessed eligibility for inclusion, extracted data, and assessed quality using the Cochrane risk of bias tool.

Results

Database search identified 497 citations and four citations through manual search. After removing duplicates and going through abstracts, 23 articles were perused for full-text screening. Two articles met the inclusion criteria; characteristics were described qualitatively, with two studies having overall low risk of bias.

Conclusions

Marginal adaptation of FDPs fabricated using the digital and conventional impressions method was within the clinically acceptable limits. However, more robust clinical trials need to be conducted with large sample size to validate the conclusions.

Comparison of crown fit and operator preferences between tooth preparation with electric and air-turbine handpieces

STATEMENT OF PROBLEM

Tooth preparations for ceramic crowns require precision and accuracy, which may be influenced by the choice of dental handpiece. However, comparisons of the accuracy of tooth preparations made with traditional air-turbine handpieces and electric handpieces are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate operator preferences and tooth preparation performance by using electric and air-turbine handpieces with self-reported preferences, sound levels, surface roughness, and the fit of the crown produced.

MATERIAL AND METHODS

Twenty dentists were asked to use the air-turbine or the electric handpiece. Feedback on the noise, weight, feel of grip, flexibility, and tooth preparation in general was scored according to a visual analog scale (VAS). Additionally, the dentists were asked to complete a questionnaire on their handpiece preference. The noise of the 2 handpieces was measured by using a precision sound level meter. The surface roughness of 10 teeth was measured by using a profilometer. The other 18 teeth were prepared to measure the marginal and internal fit of ceramic crowns by the replica technique. The VAS scores of operator preferences were analyzed with the Wilcoxon signed ranks test. Decibel levels were analyzed with the Mann-Whitney U test. The McNemar test was used to compare the ratio of preferred handpiece. The surface roughness and marginal and internal fit were analyzed with the independent t test to determine significant differences (all α=.05).

RESULTS

The electric handpiece was heavier, had a poorer grip feel, was less flexible (P<.001), produced lower noise and better feeling of the tooth preparation in general (P<.001), and was preferred in the finishing stage for its greater smoothness (P<.05). The noise produced by the electric handpiece was lower during both idling and tooth preparation at 15-cm, 30-cm, and 45-cm distances (P<.01). The electric handpiece produced surface roughness values (Sa) similar to those of the air-turbine handpiece (P>.05). No significant differences were noted for the marginal and internal crown fit between the air-turbine handpiece and electric handpiece groups (P>.05).

CONCLUSIONS

Despite its heavier weight, poorer grip feel, and less flexibility, the electric handpiece emitted lower noise, produced better feeling of the tooth preparation in general, and was preferred in the finishing step of tooth preparation for its greater smoothness than the air-turbine handpiece. The surface roughness of the prepared teeth and the crown fit between the tooth and ceramic crown were not affected by the air-turbine or electric handpiece.

Randomized clinical trial of a conventional and a digital workflow for the fabrication of interim crowns: An evaluation of treatment efficiency, fit, and the effect of clinician experience

STATEMENT OF PROBLEM

Limited information is available regarding the fabrication of tooth-supported interim single crowns (SCs) with either a digital or a conventional workflow.

PURPOSE

The purpose of this randomized clinical trial was to compare the time efficiency and fit of interim crowns fabricated by using either a digital or a conventional workflow.

MATERIAL AND METHODS

Forty participants in need of posterior tooth-supported SCs were enrolled and randomly allocated to either the digital or conventional group. In the digital group, the interim SCs were fabricated by using digital sextant scans and computer-aided design and computer-aided manufacturing (CAD-CAM) technology without definitive casts. The conventional group included conventional impressions and direct fabrication of the interim restorations intraorally. Five experienced and 5 less experienced clinicians were randomly assigned to fabricate the interim SCs. The total fabrication time (laboratory and clinical) was recorded for time efficiency. The fit assessment included marginal fit, proximal contact, occlusal contact, and crown morphology. The evaluated parameters were analyzed with the Mann-Whitney U Test (α=.05).

RESULTS

The digital workflow required significantly less total fabrication time (laboratory and clinical) than the conventional workflow (P<.001). The less-experienced clinicians needed longer clinical time with the conventional workflow than the experienced ones (P=.023). In contrast, the laboratory time and total fabrication time were shorter for less-experienced clinicians using the digital workflow (P=.005 and P=.015). The interim SCs fabricated with the digital workflow had significantly better fit and occlusal contacts than those fabricated with the conventional workflow (P=.005 and P<.001). With the digital workflow, the interim SCs made by less-experienced clinicians were of the same quality as those made by experienced clinicians. When using the conventional workflow, the fit of the experienced clinicians was significantly better than that of the less-experienced clinicians.

CONCLUSIONS

The interim SCs fabricated with a digital workflow required a shorter fabrication time and resulted in better fit than those fabricated with a conventional workflow, especially for less-experienced clinicians.

The segmental impression technique: A straightforward solution to a difficult problem

Trying to capture all the details of multiple teeth preparation in one impression is challenging. Techniques have been suggested to extend the working time of an impression material. This article describes a segmental impression technique to accurately capture all the preparation margins while allowing additional impression-making time.

Fabricating a crown under an existing removable partial denture with impression scanning and CAD-CAM technology

Retrofitting a new crown to an existing removable partial denture (RPD) is a challenging procedure. Recently, intraoral scanners (IOSs) have been successfully used to solve this issue. However, purchase of IOSs is necessary, and most clinicians still use the conventional impression technique. This article describes a combined conventional and digital approach to fabricating a new crown under an RPD without an IOS.

Digital versus conventional impressions for full-coverage restorations: A systematic review and meta-analysis

BACKGROUND

The primary objective of this systematic review was to investigate the survival of full-coverage restorations fabricated by using digital impressions (DIs) versus that of those fabricated by using conventional impressions. The authors also compared secondary outcomes of marginal and internal fit and occlusal and interproximal contacts.

TYPES OF STUDIES REVIEWED

The authors conducted a systematic literature search in multiple databases to identify clinical trials with no restrictions by publication type, date, or language. The authors assessed study-level risk of bias and outcome-level strength of evidence. The authors performed a meta-analysis by using a random-effects model.

RESULTS

Ten studies met the inclusion criteria. The authors identified no studies in which the investigators compared the impression techniques with respect to survival of full-coverage restorations. Mean differences for marginal gap and internal gap were -9.0 micrometers (95% confidence interval, -18.9 to 0.9) and -15.6 μm (95% confidence interval, -42.6 to 11.4), respectively. Studies assessing internal gap were substantially heterogeneous (I² = 72%; P = .003).

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Research is lacking to draw robust conclusions about the relative benefits of DIs in terms of restoration survival. Low-quality evidence for marginal fit and internal fit suggested similar performance for both techniques. Evidence quality for interproximal contact and occlusal contact was very low and insufficient to draw any conclusions regarding how the impression techniques compared. Given the uncertainty of the evidence, results should be interpreted with caution. With increasing popularity and adoption of digital scanners by dentists, pragmatic practice-based trials involving standardized, patient-centered outcomes may improve confidence in the comparative effectiveness of DIs.

Clinical performance of chairside monolithic lithium disilicate glass-ceramic CAD-CAM crowns

OBJECTIVES

To evaluate the clinical performance and the effect of various patient and provider-related factors on the longevity of chairside monolithic posterior lithium disilicate glass-ceramic (LDGC) computer-aided design (CAD)-computer-aided manufacturing (CAM) crowns provided by predoctoral students.

MATERIALS AND METHODS

A sample of posterior LDGC CAD-CAM crowns was evaluated. Crown preparations were milled chairside using the CEREC Omnicam system and cemented with Rely-X Unicem or Calibra Universal resin cements. Clinical assessment of the crowns and supporting periodontal structures was performed using the modified California Dental Association (CDA) criteria. Intraoral photographs as well as radiographs were taken for further assessment by two evaluators. Kaplan-Meier survival analysis was performed.

RESULTS

A total of 40 crowns were inserted in 32 patients and evaluated for 4 years. Three complications were observed (two-technical and one-biological). No chipping or fracture of crowns was observed. No significant association was found between age, sex, periodontal condition, tooth type, tooth vitality, cement type, and longevity. The 4-year cumulative survival and success rates were 95.0 and 92.3%, respectively.

CONCLUSION

Chairside LDGC CAD-CAM crowns exhibited a high survival rate after 4 years in function and were shown to be a viable and reliable treatment option for posterior teeth.

CLINICAL SIGNIFICANCE

The high survival rate of chairside CAD-CAM crowns observed in this study suggests the likelihood of predictable performance in the predoctoral setup.

Current status on lithium disilicate and zirconia: a narrative review

Background

The introduction of the new generation of particle-filled and high strength ceramics, hybrid composites and technopolymers in the last decade has offered an extensive palette of dental materials broadening the clinical indications in fixed prosthodontics, in the light of minimally invasive dentistry dictates. Moreover, last years have seen a dramatic increase in the patients’ demand for non-metallic materials, sometimes induced by metal-phobia or alleged allergies. Therefore, the attention of scientific research has been progressively focusing on such materials, particularly on lithium disilicate and zirconia, in order to shed light on properties, indications and limitations of the new protagonists of the prosthetic scene.

Methods

This article is aimed at providing a narrative review regarding the state-of-the-art in the field of these popular ceramic materials, as to their physical-chemical, mechanical and optical properties, as well as to the proper dental applications, by means of scientific literature analysis and with reference to the authors’ clinical experience.

Results

A huge amount of data, sometimes conflicting, is available today. Both in vitro and in vivo studies pointed out the outstanding peculiarities of lithium disilicate and zirconia: unparalleled optical and esthetic properties, together with high biocompatibility, high mechanical resistance, reduced thickness and favorable wear behavior have been increasingly orientating the clinicians’ choice toward such ceramics.

Conclusions

The noticeable properties and versatility make lithium disilicate and zirconia materials of choice for modern prosthetic dentistry, requiring high esthetic and mechanical performances combined with a minimal invasive approach, so that the utilization of such metal-free ceramics has become more and more widespread over time.

Comparative Study of the Trueness of the Inner Surface of Crowns Fabricated from Three Types of Lithium Disilicate Blocks

This study set out to compare the three-dimensional (3D) trueness of crowns produced from three types of lithium disilicate blocks. The working model was digitized, and single crowns (maxillary left second molar) were designed using computer-aided design (CAD) software. To produce a crown design model (CDM), a crown design file was extracted from the CAD software. In addition, using the CDM file and a milling machine (N = 20), three types of lithium disilicate blocks (e.max CAD, HASS Rosetta, and VITA Suprinity) were processed. To produce a crown scan model (CSM), the inner surface of each fabricated crown was digitized using a touch-probe scanner. In addition, using 3D inspection software, the CDM was partitioned (into marginal, axis, angular, and occlusal regions), the CDM and CSM were overlapped, and a 3D analysis was conducted. A Kruskal–Wallis test (α = 0.05) was conducted with all-segmented teeth with the root mean square (RMS), and they were analyzed using the Mann–Whitney U-test and the Bonferroni correction method as a post hoc test. There was a significant difference in the trueness of the crowns according to the type of lithium disilicate block (p < 0.001). The overall RMS value was at a maximum for e.max (42.9 ± 4.4 µm), followed by HASS (30.1 ± 9.0 µm) and then VITA (27.3 ± 7.9 µm). However, there was no significant difference between HASS and VITA (p = 0.541). There were significant differences in all regions inside the crown (p < 0.001). There was a significantly high trueness in the angular region inside the crown (p < 0.001). A correction could thus be applied in the CAD process, considering the differences in the trueness by the type of lithium disilicate block. In addition, to attain a crown with an excellent fit, it is necessary to provide a larger setting space for the angular region during the CAD process.

Accuracy of crowns based on digital intraoral scanning compared to conventional impression-a split-mouth randomised clinical study

OBJECTIVES

The aim of this prospective in vivo study was to evaluate the accuracy of the marginal and internal fit of crowns based on conventional impression (CI) or intraoral scan (IOS) in a randomised, split-mouth set-up.

MATERIALS AND METHODS

Nineteen patients needing full coverage crowns, fitting a split-mouth design, were provided with two lithium disilicate crowns: one based on a CI and one based on an IOS. The marginal and internal accuracy of the crowns were assessed with the replica technique and clinically using a modified California Dental Association (CDA) quality evaluation system.

RESULTS

At the preparation margin, the median gap was 60 μm for IOS and 78 μm for CI. For the other points, the median gap ranged from 91 to 159 μm for IOS and 109 to 181 μm for CI. The accuracy of the IOS was statistically significantly better at all point except at the cusp tip. All crowns where rated R or S at both the 6- and 12-month follow-up appointments. The results for the clinical evaluation with CDA for marginal integrity showed no statistically significant difference between the two impression methods at both the 6- and 12-month evaluations.

CONCLUSIONS

Crowns based on IOS show statistically significantly better marginal and internal adaptation before cementation compared to conventional impression. However, the clinical evaluation showed similar marginal adaptation.

CLINICAL RELEVANCE

Crowns based on a fully digital workflow can provide clinically acceptable marginal adaptation, comparable to crowns based on CI.

Production tolerance of conventional and digital workflow in the manufacturing of glass ceramic crowns

OBJECTIVES

To measure and compare the size of the cement gap of wax and polymer copings and final glass-ceramic crowns, produced from conventional and digital workflows, one additive and one subtractive.

METHODS

Thirty wax copings were made by conventional manual layering technique and modeling wax on stone models with spacer varnish simulating a cement spacer. The wax copings were embedded and press-cast in lithium disilicate glass ceramic. Thirty wax copings were produced by milling from a wax blank, i.e. subtractive manufacturing, and thirty polymer burn-out copings were produced by stereolithography, i.e. additive manufacturing. These copings were embedded and press-cast in lithium disilicate glass ceramic in the same manner as the conventional group. The fit of the wax/polymer copings and subsequent crowns was checked using an impression replica method. Mean values for cement gap for marginal, axial, and occlusal areas were calculated and differences were analyzed using Student's t-test.

RESULTS

There were significant differences in mean values for accuracy/production tolerance among different manufacturing techniques for both production stages: wax and polymer copings and final pressed glass-ceramic crowns. In general, crowns produced from a digital additive workflow showed smaller mean cement gaps than crowns produced from a conventional workflow or a digital subtractive workflow. Additive polymer copings showed significantly smaller cement gaps than milled wax copings (p≤.001) and conventional wax copings (p≤.001) in the axial area. In the occlusal area, both additive polymer copings and conventional wax copings showed significantly smaller cement gaps than milled wax copings (p=.002 and p≤.001 respectively). Crowns produced from conventional manual build-up wax copings showed significantly larger mean cement gaps than crowns produced from milled wax and additively manufactured polymer copings in the marginal and axial areas (p≤.001). Among the crowns with smaller cement gaps, crowns produced from additively manufactured polymer copings showed significantly smaller mean cement gaps than crowns produced from milled wax in the marginal and axial areas (p≤.001). In the occlusal areas, the differences in mean cement gaps were only statistically significant between crowns produced from conventional manual build-up wax copings and crowns produced from milled wax where the latter ones showed smaller mean cement gaps (p=.025).

SIGNIFICANCE

The present study suggests that an additive manufacturing technique produces smaller mean cement gaps in glass-ceramic crowns than a conventional or subtractive manufacturing technique.