Comparison of wear and marginal fitness of 3D-printed deciduous molar crowns: An in vitro study

This study aimed to evaluate the wear resistance of primary tooth enamel and 3 kinds of 3D printing materials and to compare the marginal fitness and internal suitability of prefabricated all-ceramic crowns, computer-aided design/manufacturing (CAD/CAM) all-ceramic crowns, and three 3D-printed deciduous molar crowns. Multifunctional friction wear testing machine was used to image the wear surface of the sample and calculate the maximum wear depth and volume loss value of each sample. The internal fit evaluation used the silicon replica method, The four points were measured using scanning electron microscopy (SEM). The obtained data were statistically analyzed using ANOVA and Tukey HSD-test with a fully randomized design (p<0.05). The results showed the wear resistance of E-Dent400 was better than that of PEEK and three different 3D printed materials have good wear resistance compared with the primary tooth enamel. The measured values at M1 and M4 of E-Dent400 were both the smallest.

Sixty-month comperative evaluation of a glass hybrid restorative and a composite resin in non-carious cervical lesions of bruxist individuals

OBJECTIVE

To compare the clinical performance of a glass hybrid (GH) restorative and a nano-ceramic composite resin (CR) in the restoration of non-carious cervical lesions (NCCLs) of bruxist individuals in a 60-month randomized clinical trial.

MATERIALS AND METHODS

Twenty-five bruxist candidates having NCCLs were recruited in this clinical study. The depth, height (cervico-incisal), width (mesio-distal), internal angles of the NCCLs, degree of tooth wear (TWI) and gingival index (GI) were measured. One hundred-and-forty-eight NCCLs were restored either with a GH restorative (Equia Forte Fil) or a CR (Ceram.X One Universal). Modified USPHS criteria was used to evaluate restorations after 1 week and 12, 24, 36 and 60 months. Pearson's Chi-Square, Fisher's Exact and Cochran Q tests were run for analysis. Survival rates of the restorations were compared with Kaplan-Meier analysis (p < 0.05).

RESULTS

After 60 months, 97 restorations in 15 patients were examined. The recall rate was 60.0%. Retention rates were 73.5% for CR and 66.7% for GH. A total of 29 restorations were lost (13CR (26.5%), 16GH (33.3%)). There was not a significant difference between tested restoratives in retention (p = 0.464), marginal adaptation (p = 0.856) and marginal discoloration (p = 0.273). There was no relationship between internal angle, depth, height or width and retention of the GH or CR restorations (p > 0.05). The increase in retention loss and marginal discoloration of both restorations over time were significant (p < 0.001). Sensitivity or secondary caries were not detected after 60 months.

CONCLUSION

GH and nano-ceramic CR showed similar clinical performances in NCCLs after 60 months in patients with bruxism.

CLINICAL SIGNIFICANCE

After 60 months, CR and GH materials showed clinically acceptable performances in restoration of NCCLs in patients with bruxism.

Prolonged polymerization of a universal adhesive in non-carious cervical lesions: 36-month double-blind randomized clinical trial

OBJECTIVE

To evaluate the effect of prolonged (P) polymerization time of a universal adhesive system applied in etch-and-rinse (ER) or self-etch (SE) strategies on the clinical performance of restorations in non-carious cervical lesions (NCCLs), after 36 months of clinical service.

METHODS

A total of 140 restorations were randomly placed in 35 subjects according to the polymerization time groups: ER (10 s); ER-P (40 s); SE (10 s); and SE-P (40 s) at 1,200 mW/cm2. Composite resin was placed incrementally. The restorations were evaluated immediately and after 6, 12, 18, and 36 months using the FDI criteria. Data were analyzed using the Kaplan-Meier survival test for retention loss, and the Kruskal-Wallis' test for secondary outcomes (α = 0.05).

RESULTS

After 36 months, 19 restorations were lost: ER 6, ER-P 2, SE 9, SE-P 2. The retention rates were 82.3% for ER; 94.1 % for ER-P; 73.5 % for SE; and 94.1 % for SE-P, with a significant difference between ER vs. ER-P and SE vs. SE-P, as well as ER vs. SE-P and ER-P vs. SE (p < 0.0001). Minor defects were observed in 18 restorations for the marginal staining criteria: ER 5, ER-P 2, SE 8, SE-P 3; and in 33 restorations for the marginal adaptation criteria: ER 11, ER-P 4, SE 12, and SE-P 6 (p > 0.05). No restorations showed recurrence of caries or postoperative sensitivity.

CONCLUSIONS

A prolonged polymerization time of 40 s improves the clinical performance of the universal adhesive for both adhesive strategies evaluated, even after 36 months.

CLINICAL SIGNIFICANCE

Prolonging the polymerization time of a universal adhesive from 10 to 40 s has been shown to improve its clinical performance when used in NCCLs.

A comparative analysis of the passivity of fit of complete arch implant-supported frameworks fabricated using different acquisition techniques

STATEMENT OF PROBLEM

The accuracy of intraoral scanners (IOSs) in recording edentulous jaws has improved recently. However, improvement in accuracy does not necessarily imply the clinical validity of the scans, and limited information is available regarding the manufacture of passively fitting prostheses.

PURPOSE

The purpose of this in vitro study was to analyze the passivity of complete arch screw-retained frameworks fabricated using different acquisition techniques.

MATERIAL AND METHODS

A 3-dimensional maxillary edentulous model to receive all-on-4 screw-retained frameworks was prototyped. Eighteen polymethylmethacrylate (PMMA) frameworks were fabricated with a 5-axis milling machine and divided into 3 groups according to the acquisition technique (n=6): scanned by using an IOS (CEREC Primescan; Dentsply Sirona), scanned with the aid of an auxiliary device by using the same IOS, and by using a conventional impression and then scanning the stone cast with an extraoral scanner (EOS). The passivity of fit of the frameworks was tested with the 1-screw test, the terminal screw of the framework assembly was tightened on the multiunit abutment (MUA), and the vertical marginal gap (µm) was measured at the other 3 framework-to-abutment interfaces by using a digital microscope at ×40 magnification. A modification to the 1-screw test was analyzed by tightening all screws and then unscrewing all except 1 of the anterior abutments. Data were explored for normality by using the theoretical quantile-quantile (Q-Q) plots and the Shapiro-Wilk test of normality. The Friedman test compared data between the different acquisition techniques; the tightening methods and locations (buccal and palatal) were used as the block variable. The post hoc Dunn test was used when the Friedman test was significant. The Kruksal-Wallis test compared the data from the 2 groups of the tightening methods and the 2 location groups. The aligned rank transformation (ART) ANOVA test was used for the interaction effects among the 3 variables. A multiway ANOVA was applied to the ranked data. (α=.05 for all tests).

RESULTS

Significant differences were found among all groups (P<.001). Regarding the passivity of fit, the mean vertical marginal gap was 50 µm for frameworks fabricated from an intraoral scan with the aid of an auxiliary device, 62 µm for frameworks fabricated by using an IOS, and 140 µm for frameworks fabricated by using an EOS. No significant difference was found among all groups regarding the tightening method (P=.355) or location measured (P=.175).

CONCLUSIONS

Digital scanning with the aid of an auxiliary device resulted in the best fit; however, digital approaches with or without the auxiliary device resulted in a more accurate fit with a smaller marginal gap than with the conventional impression.

Influence of surface sealants on the quality of posterior restorations with bulk-fill composites: A 4-year randomized clinical trial

OBJECTIVES

The aim of this study was to evaluate the clinical performance of surface sealants associated with a bulk-fill composite in posterior restorations after 4 years.

METHODS

A total of 174 posterior restorations were performed on 57 participants using a self-etch adhesive system and a bulk-fill composite. The groups were then divided into the following categories: 1) without surface sealant (NoS), 2) with surface sealant Biscover (Bisco, SBi), and 3) with surface sealant Permaseal (Ultradent, SPe). Restorations were evaluated using FDI criteria at baseline and after 1 and 4 years. Statistical analysis was conducted using Kaplan-Meier survival analysis and the Chi-square test (α = 0.05).

RESULTS

After 4 years, only one restoration was lost (1 in the NoS group). The fracture/retention rate (with 95% confidence interval) was 98% for NoS and 100% for both SBi and SPe (p = 0.76). The majority of secondary outcomes showed minor defects, with no significant differences among the groups (p > 0.05). However, significant differences were observed among the groups in terms of marginal staining and marginal adaptation (p = 0.03). In both items, twelve restorations (nine in NoS, one in SBi, and two in SPe) showed minor marginal discrepancies favoring the sealant groups (SBi and SPe).

SIGNIFICANCE

Regardless of the use of surface sealants, the bulk-fill composite restorations showed excellent clinical performance after 4 years. However, the groups that received sealants showed better marginal adaptation and less marginal discoloration compared to those that did not receive sealants.

Digitally manufactured partial coverage restorations: is it time to down the impression trays or still a work in progress?

DATA SOURCES

Pubmed, EMBASE, Scopus, Web of Science and Cochrane library databases were used as the data sources for this systematic review. Manual search of the reference lists of the included studies was also conducted.

STUDY SELECTION

The aim of the systematic review was to compare a fully digital workflow to a fully conventional workflow in the fabrication of partial coverage restorations. Partial coverage restorations were defined as inlays, onlays, overlays and endocrowns. Four independent calibrated reviewers screened studies that fulfilled a predefined PICOS framework. Population was specified as an abutment tooth requiring a partial coverage restoration. The intervention was a fully digital workflow compared to a fully conventional workflow. Outcomes were accuracy, marginal and internal fit, success, survival, complication rates and patient-reported outcomes. Study design included both clinical and in vitro studies.

DATA EXTRACTION AND SYNTHESIS

A total of 23 articles were included in qualitative synthesis ranging from 2007 to 2021. Twenty-one of these were in vitro studies. Two authors independently reviewed the included articles, performed data extraction, and evaluated the risk of bias via an adapted Checklist for Reporting In Vitro studies (CRIS) for in vitro studies and Reporting Randomised Clinical studies (RoB2) for clinical studies.

RESULTS

Seventeen studies assessed the marginal and internal fit of onlay and inlay restorations, eight of which found that a conventional workflow demonstrated improved fit compared to digital, whilst the remaining nine studies found the contrary. Differing methods were utilised across the studies to assess fit, including: the silicone replica method, microcomputed tomography, microscopy and software-based measurements. Similar fracture strengths were reported between both conventional and digital workflows in three studies. One clinical study assessed survival rates of both pressed and CAD/CAM ceramic restorations and found the survival outcomes to be similar after seven years. No studies were found that investigated patient-reported outcomes or endocrowns.

CONCLUSIONS

No consensus was reached as to whether the digital or conventional workflow is better.

Precision Matters: The Evolution of Impression Systems and Materials

The clinical success of indirect restorations is directly correlated with their specific anatomic shape and design as well as marginal accuracy and overall precision of fit. These factors require a precise impression of the preparation and, to the extent necessary and possible, other teeth and supporting hard and soft tissues.

Influence of the Manufacturing Trinomial (Technology, Printer, and Material) on the Marginal and Internal Discrepancies of Printed Metal Frameworks for the Fabrication of Tooth-Supported Prostheses: A Systematic Review and Meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to compare the influence of fabrication method (conventional, subtractive, and additive procedures) and manufacturing trinomial (technology, printer, and material combination) on the marginal and internal fit of cobaltchromium (Co-Cr) tooth-supported frameworks.

MATERIALS AND METHODS

An electronic systematic review was performed in five data bases: MEDLINE/PubMed, Embase, World of Science, Cochrane, and Scopus. Studies that reported the marginal and internal discrepancies of tooth-supported Co-Cr additive manufacturing (AM) frameworks were included. Two authors independently completed the quality assessment of the studies by applying the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Studies. A third examiner was consulted to resolve lack of consensus.

RESULTS

A total of 31 articles were included and classified based on the evaluation method: manufacturing accuracy, the dual- or triple-scan method, stereomicroscope, optical coordinate measurement machine, microCT, profilometer, and silicone replica. Six subgroups were created: 3D Systems, Bego, Concept Laser, EOS, Kulzer, and Sisma. Due to the heterogeneity and limited data available, only the silicone replica group was considered for meta-analysis. The metaanalysis showed a mean marginal discrepancy of 91.09 μm (I2 = 95%, P < .001) in the conventional group, 77.48 μm (I2 = 99%, P < .001) in the milling group, and 82.92 μm (I2 = 98%, P < .001) in the printing group. Additionally, a mean internal discrepancy of 111.29 μm (I2 = 94%, P < .001) was obtained in the conventional casting group, 121.96 μm (I2 = 100%, P < .001) in the milling group, and 121.25 μm (I2 = 99%, P < .001) in the printing group.

CONCLUSIONS

Manufacturing method and selective laser melting (SLM) metal manufacturing trinomial did not impact the marginal and internal discrepancies of Co-Cr frameworks for the fabrication of tooth-supported restorations.

Accuracy and Efficiency of Digitally Fabricated All-Ceramic Crowns from Conventional Impressions and Intraoral Scans: A Single-Blind Clinical Randomized Controlled Trial

PURPOSE

To evaluate the accuracy of intraoral scanners by comparing the marginal fit of 70 all-ceramic crowns fabricated from both conventional impressions and intraoral scans.

MATERIALS AND METHODS

A total of 70 posterior teeth requiring single-crown restorations randomly underwent either intraoral scanning or conventional impression-taking, followed by laboratory scanning of the casts in a parallel-group randomized controlled trial (RCT). Subsequently, 70 monolithic all-ceramic crowns were CAD/CAM fabricated; only the impression technique differed. The marginal fit, internal fit, adjustment time required for insertion and occlusal contacts, and visual analog scale (VAS) scores assessing dentists' satisfaction with the crowns were clinically evaluated by a calibrated examiner who was blinded to the groups. Data were analyzed using independent samples t test and likelihood-ratio test or Fisher exact test. All tests were performed with α = .05.

RESULTS

The mean marginal fit with intraoral scanning (57.94 Å} 22.51 μm) was better than with diagnostic cast scanning (82.98 Å} 21.72 μm). The difference was statistically significant (P = .000). The differences in internal fit, adjustment time for crown insertion and occlusal contacts, and VAS scores were also significant, and the secondary outcomes were in favor of intraoral scanning.

CONCLUSIONS

Within the limitations of this clinical trial, CAD/CAM-fabricated single-tooth restorations in the posterior region produced with an intraoral scanning technique using TRIOS were found to be a more accurate, efficient alternative to restorations based on conventional impressions in combination with the laboratory scanning technique.

Accuracy of Dental Restorations Fabricated Using Milling vs 3D-Printed Molds: A Pilot Study

PURPOSE

To compare the accuracy of 12 different dental restorations fabricated with milling or 3D-printed molds and robotically controlled casting.

MATERIALS AND METHODS

Twelve dental restorations (11 inlays and onlays and 1 crown) were made per restoration type, one per each of the 12 different teeth models (total of 24 restorations). On each tooth preparation, two restorations were manufactured using different CAD/ CAM techniques: (1) milling and (2) robotically controlled casting and 3D-printed molds. In addition, twolayer restorations were manufactured with 3D-printed molds. The marginal and internal gaps were evaluated at 120 points per restoration based on micro-CT 3D imaging. Internal gaps were evaluated using a replica technique with silicone.

RESULTS

Median values (interquartile ranges) for marginal gaps, middle internal gaps, and central internal gaps were significantly lower for 3D-printed mold restorations (44.3 [65.4] μm, 95.4 [96.2] μm, and 104.6 [78.1] μm) compared to milled restorations (58.4 [93] μm, 145.9 [85.8] μm, and 138.6 [65.7] μm). Internal gaps in the 3D-printed mold group were 6% to 51% smaller than in the milled group.

CONCLUSIONS

The accuracy of restorations fabricated with 3D-printed molds may be preferable compared to milled restorations, except in the case of crown restoration. However, additional studies with a larger number of samples and different types of restorations are needed to confirm the results.

Marginal Fit and Internal Adaptation of Monolithic Zirconia 3-Unit Fixed Dental Prosthesis: In Vitro Study

PURPOSE

To compare the marginal and internal fit of monolithic zirconia (MZ) 3-unit fixed dental prostheses (FDPs) fabricated using two CAD/CAM workflows: full-chairside (FCH) and lab (LAB).

MATERIALS AND METHODS

The right maxillary first premolar and first molar were prepared for MZ 3-unit FDPs on a typodont. CEREC Primescan digitized the typodont model 15 Omes. A total of 30 FDPs was fabricated using two processes: FCH (n = 15) and LAB (n = 15). FCH and LAB FDPs were designed using CEREC SW 4.5.1 and Exocad and milled using CEREC MC X and Zirkonzhan 600/V3, respectively. A fast-sintering protocol was used in both groups. A dual-scan technique was used to assess the cement space at the occlusal surface (OC), axial wall (AX), and margin (MA). Statistical analysis of the results was performed using univariate ANOVA with Scheff. post hoc test (a = .05).

RESULTS

Measurements in the FCH and LAB groups were within the clinically acceptable marginal and internal fit. The fit of FCH FDPs at MA, AX, and OC was 77.50 ± 29.99 μm, 99.67 ± 21.58 μm, and 150.03 ± 30.78 μm, respectively. The fit of LAB FDPs at MA, AX, and OC was 100.27 ± 27.06 μm, 116.53 ± 17.90 μm, and 142.30 ± 19.00 μm, respectively. The difference between the two groups was not statistically significant.

CONCLUSIONS

MZ 3-unit FDPs fabricated using FCH have clinically acceptable marginal and internal fit. This result verifies the ability of FCH workflow to fabricate MZ mulOunit FDPs in a single visit.

Manufacturing Accuracy, Intaglio Surface Adaptation, and Survival of Additively and Subtractively Manufactured Definitive Resin Crowns After Cyclic Loading: An In Vitro Study

PURPOSE

To assess the manufacturing accuracy, intaglio surface adaptation, and survival of resin-based CAD/CAM definitive crowns created via additive manufacturing (AM) or subtractive manufacturing (SM).

MATERIALS AND METHODS

A maxillary right first molar crown was digitally designed and manufactured using AM hybrid resin composite (VarseoSmile Crown Plus, Bego [AM-HRC]), AM glass filler-reinforced resin composite (Crowntec, Saremco Dental [AM-RC]), and SM polymer-infiltrated ceramic (Vita Enamic, VITA Zahnfabrik [SM-PICN]). Manufacturing accuracy (trueness and precision) was assessed by computing the root mean square (RMS) error (in μm; n = 15 per material). Intaglio surface adaptation was assessed by calculating the average gap distance (μm). Ten crowns from each group were cemented on fiberglass-reinforced epoxy resin dies and cyclically loaded to simulate 5 years of functional loading. One-way ANOVA, post hoc Bonferroni comparison tests, and Levene's test were used to analyze the data (α = .05).

RESULTS

AM-RC had higher overall trueness than AM-HRC and SM-PICN (P ≤ .05), whereas the trueness of AM-RC on the external surface was similar to that of SM-PICN (P = .99) and higher than AM-HRC (P = .001). SM-PICN had lower precision than AM-RC and AM-HRC overall and at internal occlusal surfaces (P ≤ .05). Overall intaglio surface adaptation was similar between all groups (P = .531). However, for the axial intaglio surface, AM-RC and AM-HRC had higher adaptation than SM-PICN (P ≤ .05). All tested crowns survived the cyclic loading simulation of 5 years clinical use.

CONCLUSIONS

AM-RC showed high manufacturing accuracy and adaptation. The tested resin-based CAD/CAM materials demonstrated clinically acceptable manufacturing accuracy and simulated medium-term durability, justifying the initiation of clinical investigations to determine their potential implementation in daily clinical practice.

Fabrication Trueness, Intaglio Surface Adaptation, and Marginal Integrity of Resin-Based Onlay Restorations Fabricated by Additive and Subtractive Manufacturing

PURPOSE

To evaluate the fabrication trueness, intaglio surface adaptation, and marginal integrity of resin-based onlay restorations made via additive manufacturing (AM) or subtractive manufacturing (SM).

MATERIALS AND METHODS

An onlay restoration was designed (DentalCAD Galway 3.0) and saved as an STL file to generate a design STL file (DO-STL). Using this design, 45 onlays were fabricated either with AM (3D-printed resin for definitive [AM-D; Tera Harz TC-80DP] and interim [AM-I; Freeprint temp] restorations) or SM (composite resin, Tetric CAD) technologies. Onlays were scanned with an intraoral scanner (CEREC Primescan SW 5.2), and the scans were saved as test STL files (TO-STLs). For trueness evaluation, TO-STLs were superimposed over the DO-STL, and root mean square (RMS) values of overall and intaglio surfaces were measured (Geomagic Control X). For the intaglio surface adaptation and marginal integrity, a triple-scan protocol was performed. Kolmogorov-Smirnov, one-way ANOVA, and post-hoc Tukey honestly significant difference tests were used to analyze data (α = .05).

RESULTS

RMS values of intaglio and overall surfaces, intaglio adaptation, and marginal integrity varied among test groups (P < .001). AM-D had the greatest overall surface RMS (P < .001), while SM had the greatest intaglio surface RMS (P < .001). SM had the highest average distance deviations for intaglio surface adaptation and marginal integrity, whereas AM-D had the lowest (P < .001).

CONCLUSIONS

AM-D onlays showed lower overall trueness than AM-I onlays and SM definitive onlays. However, AM-D onlays presented high intaglio surface trueness, intaglio surface adaptation, and marginal integrity.

Comparison of 3D-Printed Single Crown Outcomes Among Different Computer-Aided Design Software Programs

PURPOSE

Low-cost resin 3D printers have been used to produce affordable interim single crowns in public and private dental practices. The purpose of this study was to assess the impact of different computer-aided design (CAD) software programs on 3D trueness, microscopic marginal and internal gaps, time to design, and interproximal contacts of low-cost 3D-printed single crowns.

MATERIALS AND METHODS

This in vitro study was performed on a total of 90 standardized resin-prepared teeth adapted to a dental manikin. For comparison among CAD software programs, 45 tooth preparations received 3D-printed crowns designed with one of three CAD software programs by an experienced technician and identified as groups TRIOS (n = 15), EXOCAD (n = 15), and ZZ (Zirkonzahn; n = 15). To assess interoperator reproducibility, 15 additional crowns were designed by a dental clinician (group ZZ-DENT) and 15 by a dental prosthetic technician (group ZZ-PROS), both with basic 1-week CAD/CAM training. Finally, as a control group, 15 crowns were milled using a high-end five-axis milling device (group ZZ-CONTROL). Statistically significant differences for 3D trueness, microscopic gaps, time to design, and interproximal contacts among groups were assessed with the Kruskal-Wallis test.

RESULTS

No statistically significant differences in 3D trueness or marginal or internal gaps were found, either among different software programs or CAD operators (P > .05). However, Group TRIOS took significantly longer to design than EXOCAD and ZZ groups (P = .001). Less-experienced operators were significantly outperformed in time and interproximal contacts (P = .001) by the CAD technician using the same software program. Finally, control milled crowns (ZZ-CONTROL) significantly outperformed the respective 3D-printed copies (ZZ) in all assessed variables (P < .001).

CONCLUSIONS

Different CAD software programs may affect the time required to design, but they do not significantly affect clinical outcomes of low-cost 3D-printed resin crowns if designed by an experienced CAD technician.

Fit and Strength of a Three-Unit Temporary Prosthesis Made by Different Manufacturing Techniques: An In Vitro Study

PURPOSE

To compare the fit and fracture load of temporary fixed partial prostheses fabricated by means of a conventional direct technique, milling, or 3D printing.

MATERIALS AND METHODS

A maxillary right first premolar and molar were prepared on a Frasaco cast, which was then duplicated 40 times. In total, 10 provisional three-unit fixed prostheses (Protemp 4, 3M) were made using the conventional technique with a putty mold. The 30 remaining casts were scanned to design a provisional restoration using CAD software. A total of 10 designs were milled (CEREC MC X5/shaded PMMA Disk, Dentsply Sirona), while the other 20 were 3D printed with one of the two 3D printers (Asiga UV MAX or Nextdent 5100, C&B, Nextdent). Internal and marginal fit were examined using the replica technique. Next, the restorations were cemented on their respective casts and loaded until fracture using a universal testing machine. The location and propagation of the fracture were also evaluated.

RESULTS

3D printing demonstrated the best internal fit. Nextdent (median internal fit: 132 μm) was significantly better compared to the milled (median internal fit: 185 μm; P = .006) and conventional restorations (median internal fit: 215 μm; P < .001), while the fit of Asiga (median internal fit: 152 μm) was only significantly better than the conventional restorations (P < .012). The lowest marginal discrepancy was found for the milled restorations (median marginal fit: 96 μm), but this was only significant when compared to the conventional group (median internal fit: 163 μm; P < .001). The conventional restorations demonstrated the lowest fracture load (median fracture load: 536 N), which was only significant when compared to Asiga (median fracture load: 892 N; P = .003).

CONCLUSIONS

Within the present in vitro study's limitations, CAD/CAM demonstrated superior fit and strength compared to the conventional technique.

Does the Build Orientation Parameter Affect the Fit of Fixed Partial Dentures Fabricated by Additive Manufacturing?

PURPOSE

This in vitro study evaluated the adaptation of cobalt-chromium (Co-Cr) fixed dental prostheses (FDPs) fabricated by selective laser melting (SLM) with different build angles.

MATERIALS AND METHODS

Maxillary right first premolars and first molars from a typodont were prepared with 1-mm chamfer, 2-mm occlusal reduction, and total taper of 8 degrees to receive three-unit FDPs. After framework design, data were sent to a laser machine, and 30 specimens were fabricated from Co-Cr metal powder by SLM. Specimens were assigned to three groups (n = 10 per group) with different build angles of 0 (A0), 30 (A30), and 45 (A45) degrees. Marginal and internal fit were evaluated. Results were compared among build orientation groups and abutments. Data were analyzed using the Levene test, t test, and analysis of variance (α = .05).

RESULTS

A statistical difference was found between different angle groups (P = .015). At the abutment level, a significant difference was found in the gap values between build orientation groups for the molars (P = .048). Group A0 reported the smallest mean discrepancy values, and group A45 the highest. Statistical differences were found between group A45 and groups A0 (P < .001) and A30 (P < .024).

CONCLUSIONS

The fit of printed metal FDPs was affected by the build orientation but remained clinically acceptable.

Effect of a modified laminate veneer preparation design on absolute margin discrepancy and marginal overhang

STATEMENT OF PROBLEM

Veneer preparation designs impact veneer accuracy. However, whether a modified design could reduce absolute margin discrepancy and marginal overhangs is unclear.

PURPOSE

The purpose of this in vitro study was to investigate whether a modified veneer preparation design enhances the absolute margin discrepancy and marginal overhang.

MATERIAL AND METHODS

The absolute margin discrepancy and the marginal overhang of 3 different veneer preparation designs on a typodont tooth (n=20): feather edge, shoulder, and shoulder with wings were measured. The feather edge design was prepared first and subsequently modified to create the shoulder and shoulder with wings preparations. Ceramic veneers were fabricated using computer-aided design and computer-aided manufacture with each veneer assessed for fit before cementation. Ten specimens were cut vertically, and 10 were cut horizontally in each group. The absolute margin discrepancy and marginal overhangs were measured for each cross-section with scanning electron microscopy. Descriptive data analysis and hypothesis testing were conducted using the nonparametric Kruskal Wallis test (α=.05).

RESULTS

On the vertical sections, the shoulder with wings preparation had the best absolute margin discrepancy and overhang. The design was also best for mesial overhang and mesial absolute margin discrepancy when measuring horizontally.

CONCLUSIONS

The shoulder with wings preparation design produced the smallest cervical absolute margin discrepancy and overhang. This design also produced absolute margin discrepancy and overhangs comparable with those of the shoulder design in the proximal areas.

Effect of a new support design on the marginal and internal gap of additively manufactured interim crowns using direct light deposition technology

PURPOSE

To investigate the design and location of supporting structures on the marginal and internal gap of interim restorations.

MATERIALS AND METHODS

A mandibular right first molar resin tooth was prepared for a full coverage crown and scanned using a laboratory scanner (3Shape D900). The scanned data were converted into standard tessellation language (STL) format and an indirect prosthesis was designed using computer-aided design (CAD) software (exocad DentalCAD). The STL file was used to fabricate a total of 60 crowns with a 3D printer (EnvisionTEC Vida HD). The crowns were printed using E-Dent C&B MH resin and divided into 4 groups based on four different support structure designs, including supports on the occlusal (0° group), buccal and occlusal (45° group), buccal (90° group), and a new design consisting of horizontal bars placed on all surfaces and line angles (Bar) (n = 15). The silicone replica technique was used to determine the gap discrepancy. Fifty measurements were obtained for each specimen to examine the marginal and internal gaps by using a digital microscope (Olympus SZX16) at ×70 magnification. Additionally, the marginal discrepancy at different locations of the tested crowns, including buccal (B), lingual (L), mesial (M), and distal (D), as well as the maximum and minimum marginal gap intervals among groups, were analyzed. The collected data were analyzed using factorial ANOVA, followed by the Tukey HSD test for multiple comparisons (a = 0.05).

RESULTS

There was a significant difference in marginal and internal gaps among the groups (p < 0.001). The buccal placement supports (90° group) had the least marginal and internal discrepancies (p < 0.001). The new design group showed the highest marginal and internal gap. The marginal discrepancy in different locations of the tested crowns (B, L, M, D) was found to be significantly different among the groups (p < 0.001). The mesial margin of the Bar group had the largest marginal gap, whereas the buccal margin of the 90° group had the lowest marginal gap. The new design had a significantly smaller difference between the maximum and minimum marginal gap intervals than other groups (p < 0.001).

CONCLUSION

The location and design of the supporting structures affected the marginal and internal gaps of an interim crown. The buccal placement of supporting bars (90° printing orientation) showed the smallest mean internal and marginal discrepancies.

Effect of different restorative systems and aging on marginal adaptation of resin composites to deep proximal margins

OBJECTIVES

To evaluate and compare the marginal integrity of different restorative systems bonded to proximal gingival dentin, and determine the consistency level of the results obtained by two in vitro methods.

MATERIALS AND METHODS

Thirty molars received occluso-mesial preparations with dentin/cementum gingival margins. They were divided into three groups and restored using different restorative systems with light-cured (Adhese Universal), self-cured (Palfique universal bond), and dual-cured (Futurabond U) adhesives. The restoration/gingival dentin interfaces were observed using scanning electron microscopy (SEM) and evaluated based on the World Dental Federation (FDI) criteria. After 10,000 thermal cycles, the marginal integrity was re-evaluated. Marginal integrity was evaluated by the percentage of continuous margin (% CM) at ×200 for SEM and as the frequency of each score within the FDI ranking.

RESULTS

No significant differences were found between the restorative systems immediately, however, the system with the light-cured adhesive had the lowest marginal integrity after aging. All tested restorative systems were adversely affected by aging. A moderate inverse correlation was identified between evaluation techniques.

CONCLUSION

The tested restorative systems utilizing self-cured and dual-cured adhesives may be preferable for achieving optimal marginal integrity when bonding to deep proximal margins, compared to the tested system with light-cured adhesive.

CLINICAL SIGNIFICANCE

When performing deep margin elevation, it is important to consider the adhesive system being used.

Tooth morphology, internal fit, occlusion and proximal contacts of dental crowns designed by deep learning-based dental software: A comparative study

OBJECTIVES

This study compared the tooth morphology, internal fit, occlusion, and proximal contacts of dental crowns automatically generated via two deep learning (DL)-based dental software systems with those manually designed by an experienced dental technician using conventional software.

METHODS

Thirty partial arch scans of prepared posterior teeth were used. The crowns were designed using two DL-based methods (AA and AD) and a technician-based method (NC). The crown design outcomes were three-dimensionally compared, focusing on tooth morphology, internal fit, occlusion, and proximal contacts, by calculating the geometric relationship. Statistical analysis utilized the independent t-test, Mann-Whitney test, one-way ANOVA, and Kruskal-Wallis test with post hoc pairwise comparisons (α = 0.05).

RESULTS

The AA and AD groups, with the NC group as a reference, exhibited no significant tooth morphology discrepancies across entire external or occlusal surfaces. The AD group exhibited higher root mean square and positive average values on the axial surface (P < .05). The AD and NC groups exhibited a better internal fit than the AA group (P < .001). The cusp angles were similar across all groups (P = .065). The NC group yielded more occlusal contact points than the AD group (P = .006). Occlusal and proximal contact intensities varied among the groups (both P < .001).

CONCLUSIONS

Crowns designed by using both DL-based software programs exhibited similar morphologies on the occlusal and axial surfaces; however, they differed in internal fit, occlusion, and proximal contacts. Their overall performance was clinically comparable to that of the technician-based method in terms of the internal fit and number of occlusal contact points.

CLINICAL SIGNIFICANCE

DL-based dental software for crown design can streamline the digital workflow in restorative dentistry, ensuring clinically-acceptable outcomes on tooth morphology, internal fit, occlusion, and proximal contacts. It can minimize the necessity of additional design optimization by dental technician.

Trueness, precision, time-efficiency and cost analysis of chairside additive and subtractive versus lab-based workflows for manufacturing single crowns: An in vitro study

PURPOSE

To evaluate the trueness, precision, time efficiency, and cost of three different workflows for manufacturing single crowns (SCs).

METHODS

A plaster model with a prepared tooth (#15) was scanned with an industrial scanner, and an SC was designed in computer-assisted-design (CAD) software. Ten SCs were printed with a hybrid composite (additive chairside) and a stereolithographic (SLA) printer (Dfab®), 10 SCs were milled in lithium disilicate (subtractive chairside) using a chairside milling unit (inLab MC XL®), and 10 SCs were milled in zirconia (lab-based) using a five-axis laboratory machine (DWX-52D®). All SCs were scanned with the same scanner after polymerization/sinterization. Each scan was superimposed to the marginal area of the original CAD file to evaluate trueness: absolute average (ABS AVG), root mean square (RMS), and (90˚-10˚)/2 percentile were calculated for each group. Marginal adaptation and quality of the occlusal and interproximal contact points were also investigated by two prosthodontists on 3D printed and plaster models. Finally, the three workflows' time efficiency and costs were evaluated.

RESULTS

Additive chairside and subtractive lab-based SCs had significantly better marginal trueness than subtractive chairside SCs in all three parameters (ABS AVG, p < 0.01; RMS, p < 0.01; [90˚-10˚]/2, p < 0.01). However, the two prosthodontists found no significant differences between the three manufacturing procedures in the quality of the marginal closure (p = 0.186), interproximal (p = 0.319), and occlusal contacts (p = 0.218). Both time efficiency and cost show a trend favoring the chairside additive workflow.

CONCLUSIONS

Chairside additive technology seems to represent a valid alternative for manufacturing definitive SCs, given the high marginal trueness, precision, workflow efficiency and low costs.

STATEMENT OF CLINICAL RELEVANCE

Additive chairside manufacturing of definitive hybrid composite SCs is now possible and shows high accuracy, time efficiency, and competitive cost.

Deep Margin Elevation - A Retrospective Clinical Study

PURPOSE

The aim of this retrospective study was to assess the short- to mid-term restorative and periodontal outcome of deep margin elevation (DME) performed using resin composite.

MATERIALS AND METHODS

Twenty-eight teeth treated with DME and indirect adhesive restorations were followed-up for a mean of 25.4 months (minimum: 12 months). Clinical and radiographic examination assessed the adaptation of the DME material and indirect restorations, presence of recurrent caries or discoloration, periodontal health at DME and non-DME sites, and periapical health.

RESULTS

The overall success rate was 96.6%. One tooth showed signs and symptoms of apical pathology after 34 months following DME. No caries, discoloration, or periodontal pockets were detected in any of the treated teeth. DME had no detrimental effect on the gingival/periodontal health or plaque accumulation. There was no correlation between the distance from the DME material to the marginal bone level and pocket depth, gingival inflammation, and plaque accumulation (p > 0.05).

CONCLUSION

Deep margin elevation might be considered a safe procedure for teeth with deep subgingival proximal caries in the short- and mid-term.

Color Match of a Universal-shade Composite Resin for Restoration of Non-carious Cervical Lesions: An Equivalence Randomized Clinical Trial

PURPOSE

The objective of this double-blind, split-mouth, randomized clinical trial was to evaluate the color match of a single-shade composite resin Admira Fusion X-tra in comparison with a multi-shade composite resin Admira Fusion in non-carious cervical lesion restorations (NCCLs).

METHODS AND MATERIALS

One hundred and twenty restorations were performed on NCCLs with two restorative materials (n=60). After prophylaxis, the teeth were isolated with a rubber dam, and one universal adhesive was applied in the selective enamel etching strategy. For both groups, the restorations were inserted incrementally and light-cured. The values of the coordinates L*, a*, and b* in the cervical third before vs after the restorations and cervical vs middle third after the restorations were evaluated using a digital spectrophotometer after the coordinate values were used to calculate the CIEDE (ΔE00). The restorations were evaluated at baseline and after 7 days of clinical performance according to the FDI criteria. Statistical analysis was performed using the Chi-square test for all parameters. Color change was analyzed by Student t-test for paired samples (α=0.05).

RESULTS

All restorations were evaluated after 7 days. Regarding the color measurement, no significant difference was observed when Admira Fusion was compared to Admira Fusion X-tra for any of the comparisons performed (p>0.05). However, the values of ΔE00 in the cervical third before vs after the restorations were higher when compared with ΔE00 observed when the cervical vs middle third after restorations were compared. All restorations received the score "clinically very good" after 7 days for all outcomes, including the subjective color match, when evaluated for FDI criterion.

CONCLUSIONS

The single-shade composite resin used achieves the same color match when compared to a multi-shade composite resin after 7 days in NCCLs.

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

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