Zirconia Crowns Research Articles

Invitro fracture and fatigue resistance of monolithic zirconia crowns fabricated by stereolithography.

Stereolithography has been used to print zirconia ceramic crowns with acceptable dimensional accuracy and fracture force. However, studies that compared the fatigue resistance of zirconia crowns fabricated by stereolithography are lacking. The purpose of this invitro study was to compare the fracture and fatigue resistance of monolithic zirconia crowns printed by stereolithography apparatus (SLA) and digital light processing (DLP) with those of zirconia crowns milled by computer numerical control (CNC). A total of 120 crowns were fabricated (n=40/material) and underwent 0, 104, 105, or 106 dynamic loading cycles of 30 to 300 N in artificial saliva, followed by a static fracture loading test (n=10). After fracture, 1 crown from each group was selected for fractography analysis by scanning electron microscopy (SEM). Data were statistically analyzed through 2-way ANOVA and post hoc analysis for multiple comparisons (α=.05). The 2-way ANOVA results showed that the mean ±standard deviation force at fracture was the highest for CNC (before fatigue loading: 5154 ±568 N, 104: 5735 ±1231 N, 105: 5523 ±797 N, and 106: 6007 ±1258 N), followed by DLP (before fatigue loading: 3381 ±612 N, 104: 4046 ±1146 N, 105: 2929 ±559 N, and 106: 3223 ±739 N), and the lowest for SLA (before fatigue loading: 2956 ±598 N, 104: 2757 ±421 N, 105: 3326 ±391 N, and 106: 3103 ±246 N) (P<.01). The fracture force of the crowns was not significantly affected by the number of fatigue cycles (P>.05). Fractography analysis showed that the number of arrest lines increased for crowns of all 3 materials. SEM images also showed the steps of SLA and DLP from their layer-by-layer printing and small cracks between layers of SLA after 106 loading cycles. The fracture force of monolithic zirconia crowns milled by CNC was significantly higher than that of zirconia crowns printed by stereolithography. Zirconia crowns printed by SLA and DLP could withstand typical clinical conditions, and their fracture and fatigue resistance exceeded the clinically estimated average occlusal forces.

Evaluation of fit and accuracy of single crowns fabricated from self-glazed zirconia compared with milled zirconia

Statement of problemSelf-glazed zirconia is a novel dental material fabricated with a combination of subtractive and additive manufacturing techniques. However, how the marginal and internal fit of these restorations compare with conventionally fabricated zirconia is unclear. PurposeThe purpose of this in vitro study was to evaluate the marginal and internal fit and internal accuracy of single crowns made from self-glazed zirconia compared with those made from milled zirconia. Material and methodsA metal die was scanned, and a crown was designed using a computer-aided-design program. The computer-aided-manufacturing milling method (conventional technique) was used to produce 10 zirconia crowns, and additive manufacturing was used to produce 10 self-glazed zirconia crowns. Internal and marginal fit measurements were made by using the silicone replica method; marginal fit was also measured by using the direct-view technique. An independent t test was performed to compare both types of crowns and test the null hypothesis (α=.05). ResultsFor the occlusal, internal, and total mean distances, significant differences were found between self-glazed and milled zirconia crowns (P<.001). With the direct-view technique, a significant difference (P=.004) between the 2 techniques was found in the marginal area. The accuracy for the axial and occlusal areas combined for self-glazed and milled zirconia was 27 μm and 49 μm, respectively. ConclusionsBoth techniques produced crowns with clinically acceptable marginal and internal fit. The self-glazed zirconia crowns had higher accuracy of internal fit than milled zirconia crowns.

A digital workflow for complete arch rehabilitation with zirconia crowns on restored posterior teeth and a polyetheretherketone framework denture.

A clinical and laboratory workflow for the digital design and fabrication of zirconia crowns and polyetheretherketone removable partial dentures for complete arch rehabilitation is described. The definitive crowns and polyetheretherketone framework can be delivered simultaneously because of the digital design and milling fabrication with retentive areas, guide planes, and rest seats in high-translucency zirconia crowns. The workflow helps simplify clinical and laboratory procedures and reduces patient visits and chairside time.

Fracture Resistance of CAD/CAM Monolithic Zirconia Crowns Supported by Titanium and Ti-Base Abutments: The Effect of Chewing Simulation and Thermocyclic Aging.

Purpose: To evaluate the effect of chewing simulation and thermocyclic aging on the fracture resistance of CAD/CAM monolithic zirconia crowns supported by titanium and Ti-base abutments. Materials and Methods: Two implant abutment groups-titanium (Ti) and titanium base (Ti-base; Medentika)-were used. A total of 40 mandibular first molar CAD/CAM monolithic zirconia crowns (Vita YZ T) were fabricated, then cemented onto the abutments with Panavia V5. Each abutment group was divided into two subgroups (n = 10). The Ti and Ti-base groups were subjected to a single load until fracture, and the Ti/CT and Ti-base/CT groups (CT: chewing simulation and thermocyclic aging) underwent chewing simulation (1.2 × 106 cycles × 50 N load, 1.4 Hz) and thermocylic aging (3,911 cycles/5°C to 55°C). The fracture resistances of the crowns were tested with a universal testing machine (1 mm/minute). Shapiro-Wilk and one-way ANOVA test were used for statistical analysis (P = .05). Results: The survival rates after chewing simulation and thermocyclic aging were 100% for both CT groups. The fracture resistance values (mean ± SD) of the groups were as follows: Ti = 1,718.18 ± 331.06 N, Ti-base = 1,713.53 ± 233.24 N, Ti/CT = 1,664.82 ± 188.62 N, and Ti-base/CT = 1,551.28 ± 344.79 N. According to one-way ANOVA test results, there was no statistically significant difference between the four groups (P = .526). Conclusion: CAD/CAM monolithic zirconia crowns supported by Ti-base or titanium abutments were found to have sufficient fracture resistance in the treatment of an absent single posterior tooth. However, more in vitro and clinical studies are required to evaluate the long-term performance of Ti-base abutments and CAD/CAM zirconia crowns.

A digital protocol for the fabrication of anatomic-contour implant zirconia crowns directly screwed on external hexagonal implant connections without the interposition of a Ti-base component

A straightforward and effective restorative option is proposed for implant-supported fixed prostheses with external connections by using monolithic zirconia without the interposition of a Ti-base component. The technique is based on a modification of the Brånemark connection used to link metal-ceramic or metal-composite resin restorations directly to the implant.

Assessment of Diamond Rotary Instruments Advertised for Cutting 3Y-TZP Restorations. A Scanning Electron Microscope Analysis

Aim: To examine the cutting efficiency and amount of material removed from crown-cutting diamond burs from a different manufacturer on zirconia using an electric handpiece. Material and Methods: The performance of super coarse diamond bur round-end from five different manufacturers that were commercially advertised as zirconium crown cutters were assessed. The five manufacturers and their respective diamond bur models tested were super coarse Group 1: Dimond bur, Group 2: Zirconia Diamond Bur, Round End Cylinder, Meisinger, Group 3: 4ZR Zirconia Cutter Diamond Crown Removal Bur, Group 4: Brasseler Dental Diamond Bur, Group 5: Expanded SS White® Lineup of Zirconia Cutting Diamonds. The qualitative assessment of diamond burs (before zirconia cutting) and (after zirconia cutting) was assessed using a scanning electron microscope. The mean cutting distance and material removed for each group were calculated and analyzed using one-way ANOVA. Results: The highest cutting efficiency was found in group 2 and the lowest efficiency was observed in group 5. Post-SEM images of rotary zirconia cutting instruments in groups (Post G1-G5) demonstrate pullout, wear, chipping, and loss of the diamond grains in general. Conclusion: Zirconia Diamond Bur (G2) was found to be suitable. Whereas, (G5) Expanded SS White® Lineup of Zirconia Cutting Great White®Z Diamonds is less effective.

Reverse Torque Value of Angulated Screw Channel Abutment before and after Cyclic Loading: An In Vitro Study

This in vitro experiment aimed to understand the difference in preload acting on an abutment screw under different angles of angulated screw-retained crown and the performance after cyclic loading. In total, thirty implants with angulated screw channel (ASC) abutments were divided into two parts. The first part consisted of three groups: a 0° access channel with a zirconia crown (ASC-0) (n = 5), a 15° access channel with a specially designed zirconia crown (sASC-15) (n = 5), and a 25° access channel with a specially designed zirconia crown (sASC-25) (n = 5). The reverse torque value (RTV) was measured at 0° for each specimen. The second part consisted of three groups: a 0° access channel with a zirconia crown (ASC-0) (n = 5); a 15° access channel with a zirconia crown (ASC-15) (n = 5), and a 25° access channel with a zirconia crown (ASC-25) (n = 5). The manufacturer's recommended torque was applied to each specimen, and baseline RTV was measured before cyclic loading. Each ASC implant assembly was cyclically loaded at 0 to 40 N with 1 million cycles at 10 Hz. RTV was measured after cyclic loading. Kruskal-Wallis test and Jonckheere-Terpstra test were used for statistical analysis. All specimens were examined under a digital microscope and scanning electron microscope (SEM) to observe the wear of the screw head before and after the whole experiment. A significant difference in the different percentages of straight RTV (sRTV) between the three groups was found (p = 0.027). The angle of ASC to the different percentages of sRTV showed a significant linear trend (p = 0.003). No significant differences were found in RTV difference after cyclic loading among the ASC-0, ASC-15, and ASC-25 groups (p = 0.212). The ASC-25 group had the most serious degree of wear based on a digital microscope and SEM examination. The ASC angle will affect the actual preload acting on a screw: the larger the ASC angle, the smaller the preload. The performance of the angled ASC groups in RTV difference was comparable to that of 0° ASC after cyclic loading.

Fracture Strength of Thin Monolithic Zirconia Crowns with Varying Thickness and Configuration of Finish LinesAn In Vitro Study

Aim- The current study sought to assess the fracture strength of thin monolithic zirconia crowns of varying thickness and finish line configuration. Study design- The current study was carried out to evaluate and compare the fracture strength of monolithic zirconia crowns with chamfers and radial shoulder finish lines of 0.5, 0.8, and 1.1 mm thickness. Result- Monolithic zirconia crowns with merely 0.5 mm reduction demonstrated adequate strength for use in posterior areas. On evaluation and comparison it was observed that no statistically significant difference was found in the fracture strength of monolithic zirconia crowns with different thicknesses and finish lines was investigated. Conclusion- The 0.5 mm thickness of monolithic zirconia crowns demonstrated significant fracture resistance to withstand physiological performance, regardless of finish line type.

Clinical Outcomes of Monolithic Zirconia Crowns on Posterior Natural Abutments Performed by Final Year Dental Medicine Students: A Prospective Study with a 5-Year Follow-Up.

The conventional metal-ceramic is still considered the gold standard in fixed prosthetics especially in terms of longevity. Among alternative materials used, Monolithic Zirconia has shown the capability to reconcile excellent biomechanical properties with acceptable aesthetic performance and to overcome several inconveniences related to veneer restorations. This study aims to clinically evaluate Monolithic Zirconia prosthetic crowns on natural abutments in the posterior sectors, performed by final-year dental medicine students (undoubtedly with less experience in the management of such material) by the standardized California Dental Association score system evaluation, to better understand the viability of Monolithic Zirconia. This prospective study was carried out at the Dental School of the University of Bari "Aldo Moro", Italy. Prosthetic rehabilitation included single crowns or a short pontic prosthesis with maximum one intermediate. Final-year dental students performed tooth reduction under the supervision of three expert tutors. The California Dental Association systematics (based on color, surface, anatomical shape, and marginal integrity) were adopted to evaluate the prosthetic maintenance status over time. Annual follow-up visits were re-evaluated by the same parameters each year. Univariate logistic regression analysis was performed to evaluate outcomes and the Kaplan-Meier plot to report survival. The sample consists of 40 crowns performed on 31 patients, 15 males (48.4%) and 16 females (51.6%) with an average age of 59.3 years. The clinical cases subjected to experimental study were found to be "Excellent" (1a/2a/3a/4a) in 34 cases (85%), "Acceptable" in 4 cases (10%), and "To be re-done" in 2 cases (failures) (5%). Our conclusive data support the predictability of Monolithic Zirconia restorations on natural posterior abutments at a long-term follow-up of five years, even when performed by less-experienced clinicians.

Accuracy of two best-fit alignment strategies with different reference areas for wear measurement with an intraoral scanner: An in vitro study.

The aim of this in vitro study was to assess and compare the accuracy of 2 best-fit alignment strategies with different reference areas for wear measurement with an intraoral scanner. 8 anatomic-contour zirconia crowns were fabricated and scanned twice with an intraoral scanner. One of the scan data (Data Trueness) was duplicated and wear facets were simulated (Data Wear). The other scan data (Data Baseline) was aligned to Data Wear by 2 best-fit alignment strategies with different reference areas (the occlusal surface with no signs of wear and the axial surface), and 3D deviation analysis was performed to detect the wear loss. The 3D deviation between Data Trueness and Data Wear was calculated as the truth-value for accuracy evaluation. Color-difference map showed Group Occlusal had a similar wear-facet distribution to Group Trueness, while Group Axial showed an obvious tilting position and the obtained height loss values were larger and with large standard deviations. Both Group Occlusal and Group Axial showed significant differences from Group Trueness in maximum height loss and mean height loss(P<.05), while no significant difference in mean distance(P>.05). Paired t test showed significant differences between Group Occlusal and Group Axial in maximum height loss and mean height loss(P<.05), while no significant difference in mean distance (P>.05). Best-fit alignment with the occlusal reference area produces a better alignment result than that with the axial reference area. Wear measurement with an intraoral scanner is potential but prone to overestimate the height loss.

In Vitro Investigation of Material Combinations for Meso- and Suprastructures in a Biomimetic Approach to Restore One-Piece Zirconia Implants

The aim of this study was to find a suitable material combination to avoid cement excess in the marginal region of one-piece zirconia implant-supported restorations by means of a hybrid crown consisting of a meso- and a suprastructure. One-piece zirconia implants (n = 120) were embedded in epoxy resin. Microfilled resin composite mesostructures (n = 60), designed as caps, were bonded on the implant abutment with a primer only. A molar crown was constructed and cemented with a resin cement on top of the mesostructure as a suprastructure out of feldspar ceramic (n = 12), lithium-disilicate (n = 24), or zirconia (n = 24). Fracture load (n = 6) and retention force (n = 6) were measured immediately after storage in distilled water at 37 °C for 24 h, as well as after an additional exposure to artificial aging in a chewing simulator and simultaneous thermal cycling. For the measurement of the fracture load, monolithic crowns made of the employed restorative materials and identical in shape to the hybrid crowns served as controls (n = 6 each). Fracture load values for feldspar ceramic and lithium-disilicate hybrid crowns were slightly higher than those for the respective monolithic crowns at baseline and after aging, which was statistically significant only for feldspar crowns after aging. In contrast, fracture load values for zirconia monolithic crowns were higher than those for zirconia hybrid crowns, which was only statistically significant after aging. Artificial aging reduced the fracture load of feldspar and lithium-disilicate crowns both for hybrid and monolithic crowns. The effect was only statistically significant for lithium disilicate hybrid crowns. The fracture load for hybrid and monolithic zirconia crowns was increased by artificial aging without reaching statistical significance. The retention force of lithium-disilicate and zirconia hybrid crowns was not affected by artificial aging. Taking into account retention force and fracture load, lithium-disilicate hybrid crowns showed promising results.

Failure behavior of zirconia crowns subjected to air abrasion with different particle sizes.

This study aimed to investigate the failure behavior of 3 mol.% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) prosthetic crowns air-abraded with aluminum oxide (AO) particles of different sizes. Ninety ceramic premolar crowns were produced with 3Y-TZP frameworks veneered with porcelain. Crowns were randomly divided into three groups, according to the size of the air abrasion AO particles (n = 30): (GC) untreated (control); (G53) 53 µm; (G125) 125 µm. Air abrasion was performed with 0.25 mpa pressure, 10-mm distance, for 10 s. Crowns were adhesively cemented to dentin analog abutments. Specimens were loaded in compression to failure, in 37oC distilled water, using a universal testing machine (n = 30). Fractographic analysis was performed using a stereomicroscope and SEM. The roughness of the crown's inner surface was evaluated using an optical profilometer (n = 10). Fracture load data were statistically analyzed with Weibull analysis and roughness data with Kruskal-Wallis (α = 0.05). GC had the lowest characteristic fracture load (L0), while G53 and G125 had higher and statistically similar L0 values. The Weibull modulus (m) was similar among groups. The failure modes observed were catastrophic failure and porcelain chipping. There were no differences between the roughness parameters for the experimental groups (p > 0.05). The size of the AO particles did not affect the fracture load and failure mode of 3Y-TZP crowns. Air abrasion with 53 µm and 125 µm particles resulted in a higher fracture load of ceramic crowns than the untreated group while maintaining their reliability and surface characteristics.

Synchronous Fabrication of Custom One-piece Glass Fiber Post-and-core and Zirconia Crown by a Fully Digital Workflow.

Combined crown and post-and-core treatment often requires multiple intermittent appointments and takes a long time. This article describes a novel method for simultaneously fabricating a custom glass fiber post-and-core and the corresponding crown. The critical step, defined as a post-and-core virtual try-in, is to construct a virtual crown abutment that mimics the profile of a real one gained after post-cementation and tooth preparation. The fully digital workflow optimizes the treatment and saves time by accomplishing restorations on the first visit.

Trueness of stereolithography ZrO2 crowns with different build directions.

This study aims to measure the trueness of zirconia crowns with different build directions of materials fabricated using the stereolithography (SLA) method. The anatomic contour crown of prepped maxillary right first molar was designed using CAD software to obtain the standard tessellation language (STL) file. Two different build directions were set for the crowns using Materialize Magics software. One group was built with a margin base platform, while the other group was built in the direction opposite to the occlusal surface base platform. The 20 crown-shaped parts were printed. The STL files of scanned printing zirconia crowns were superimposed each segment by the 3D analysis software. The two groups were statistically analyzed using t-tests. Significant differences were found in the marginal and internal discrepancies between the groups. The build direction had a significant influence on the accuracy of the zirconia crown. The results indicate the most effective build direction for manufacturing SLA 3D-printed crowns.

Effect of Different Veneering Techniques on the Mechanical Failure of Tooth-supported Veneered Zirconia Crowns: A Systematic Review

Effect of Different Veneering Techniques on the Mechanical Failure of Tooth-supported Veneered Zirconia Crowns: A Systematic Review

Prosthetic Rehabilitation of Endodontically Treated Tooth by Using CAD-CAM Milled Zirconia Post and Core System: A Clinical Report

Background: Maxillary central incisor is the most commonly affected tooth during trauma followed by maxillary lateral incisor and mandibular incisors. Trauma to the anterior tooth requires urgent care because of the essentiality of preserving the natural tooth. When a complicated crown a fracture takes place, it necessitates endodontic treatment and restoration of a fractured crown segment with post in the canal. This case report describes a patient with a broken central incisor and treated with a Zirconia crown. Keywords: CAD/CAM, Esthetics, Post &amp; Core.

An In Vitro Comparison of Zirconia and Hybrid Ceramic Crowns With Heavy Chamfer and Shoulder Finish Lines.

Purpose This in vitro study aimed to compare the marginal fit and internal adaptation of computer-aided designed and computer-aided manufactured (CAD-CAM) zirconia and hybrid ceramic crowns on heavy chamfer and shoulder finish line designs using silicon replica method. Materials and methods Forty die samples were divided into four groups of 10 dies each. Out of 40 diecasts scanned, zirconia crowns were milled on 20 casts (10 prepared with shoulder and 10 prepared with heavy chamfer finish line design), whilehybrid ceramic crowns were milled on the rest of the 20 casts. After milling crowns, the silicone replica technique measured the marginal fit and internal adaptation. Results The heavy chamfer finish line design provided a better marginal fit than the shoulder finish line design for zirconia and hybrid ceramic crowns. Hybrid ceramic crowns had a better marginal fit and internal adaptation than zirconia crowns, both at heavy chamfer and shoulder finish line design. The gap at the margin was less than the axial and occlusal walls, and the maximum gap was observed in the occlusal area. In addition, the marginal gap was less than the internal gap, which showed a positive correlation with each other. Conclusion The study concluded that the difference in CAD-CAM materials and finish line designs influences marginal fit and crown restoration's internal adaptation.A heavy chamfer finish line design provides a better marginal fit for zirconia and hybrid ceramic crowns than a shoulder finish line design. Hybrid ceramic crowns have a better marginal fit and internal adaptation than zirconia crowns in heavy chamfer and shoulder finish lines.

Digital impression and CAD/CAM system applications in pediatric dentistry: Case series

Computer-Aided Design/Computer-Aided Manufacture (CAD/CAM) and digital imprint systems offer several benefits compared to traditional techniques. Use of CAD/CAM system to scan preparations and generate restorations in-office, removes second appointment for patient. In present case series we describe use of digital dentistry in pediatric patients and will fabricate space maintainer and zirconia crown using digital impression and digital workflow.

Three-Dimensional Finite Element Study of Endodontically Treated Maxillary Central Incisors Restored Using Different Post and Crown Materials.

Restoring endodontically treated teeth is a common problem in dental practice. Post and core restorations are one of the major options in the rehabilitation of these teeth. However, there is no final decision regarding the best material or technique to be used with these restorations. So, this study aimed to evaluate the effect of different post and crown materials on the biomechanical behavior of restored maxillary central incisor using the finite element method. A total of 10 3D models of endodontically treated maxillary central incisors restored with two prefabricated posts and three custom-made posts were modeled and grouped according to post material (gold, nickel-chrome, zirconia, and glass fiber) and crown material (lithium disilicate, and zirconia). Finite element analysis was conducted, and stress distribution was evaluated using von Mises criteria. Both crown materials showed stress concentration at the force application site mainly on the intaglio palatal surface of the crown. However, more stress values were observed within zirconia crowns. All posts showed stress concentration at their buccal sides. However, more stress values were observed in zirconia and metal cast posts compared to glass fiber posts that transfer more stress to root dentin. Post and crown materials affect the stress distribution in the tooth-restoration complex. Using high elastic modulus posts slightly decreased stress in root dentin despite concentrating more stress within their structure. However, glass fiber posts resulted in more homogenous stress distribution in the tooth-restoration complex. Crown material did not influence the stress distribution in root dentin. Custom-made posts decreased stress within crowns, regardless of the crown material. However, more stress values were observed within zirconia crowns. Custom-made zirconia posts and cores showed a similar stress distribution as non-precious metal cast posts, so they may be used as a suitable option where esthetic is desirable.

The effect of thermomechanical aging on the retention of a conometric system in a chewing simulator.

To evaluate the retention force of a novel conometric system after thermomechanical aging. In addition, the conometric system's retention force was compared with that of the cemented implant-retained crowns. Two systems to retain implant crowns were tested in this study: a conometric system and a cement-retained system. Forty-eight zirconia crowns were fabricated using computer-aided design and computer-aided manufacturing technology. Twenty-four zirconia crowns were cemented onto conometric caps with resin-modified glass ionomer cement, which were then connected with abutments. These specimens were divided into three groups, and each group was subjected to the pull-out test. A-control group: 12 specimens directly subjected to pull-out test; A-aged group: 12 specimens subjected to thermomechanical aging followed by pull-out test; A-repeat group: After the pull-out, the specimens in the aging group (A-aged) were reconnected, and the pull-out test was repeated once more. The remaining 24 zirconia crowns were cemented on standard abutments with zinc phosphate cement, and two groups were formed. C-control group: 12 specimens directly subjected to the pull-out test; C-aged group: 12 specimens subjected to thermomechanical aging followed by pull-out. Scanning electron microscope (SEM) was used to evaluate the surfaces of caps and abutments. To analyze the data, repeated measures, one-way ANOVA, and Bonferroni tests were used (p<0.05). The mean retention force value of the A-control group was 148.22±16.37N. The highest mean retention force value was measured in the A-aged group (204.93±51.67N), and the lowest mean retention force value was seen in the A-repeated group (77.02±21.48N). Thermomechanical aging had a significant influence (p<0.05) on both systems. No significant differences in retention force were found between the thermomechanical aged groups of both systems (p>0.05). SEM analysis revealed that aging had an impact on the surface of the conometric system's caps and abutments. The retention force of the conometric system increased significantly following thermomechanical aging. No crown separation occurred during the thermomechanical aging of the conometric system. There was no significant difference in the retention of the conometric and cemented systems after thermomechanical aging.