Fabrication Of Crowns Research Articles

A Comparative Analysis of the Accuracy of Crown Fabricated from Conventional Wax Patterns and CAD/CAM Technology – Milling and 3D Printing

ABSTRACT Background: Digital manufacturing techniques such as milling (subtractive) and 3D printing (additive) are increasingly used in dental restorations. These technologies promise enhanced precision and efficiency compared to traditional methods. However, the accuracy of marginal and internal fits of crowns produced by these techniques remains under-explored. Objective: To evaluate and compare the marginal and internal fit of dental crowns fabricated using two digital manufacturing techniques: Milling (subtractive) and 3D printing (additive). Materials and Methods: A maxillary first molar was replicated to create seven representative dies for each technique. Crowns were fabricated using both milling and 3D printing methods. The fit of the crowns was assessed using the silicone replica technique, measuring occlusal, axial, marginal gaps, and internal fit. Results: 3D printing demonstrated the most precise fit across all measurement points, with significantly smaller discrepancies compared to milling. The two-way ANOVA analysis confirmed a significant effect of the fabrication method on marginal and internal gaps, highlighting the superior performance of 3D printing. However, the silicone replica technique revealed fewer significant differences between the two methods. Conclusion: 3D printing offers enhanced precision and consistency in crown fabrication compared to milling. Despite promising results, further research is necessary to confirm the long-term efficacy and cost-effectiveness of these techniques. Future studies should focus on larger clinical cohorts to validate these findings.

Assessment of Marginal Fit and Accuracy of Crowns Fabricated Using CADCAM Milling and 3D Printing Technology

ABSTRACT Background: This study evaluates the accuracy of marginal and internal fits of dental crowns fabricated using CAD/CAM milling and 3D printing technologies. The hypothesis posited significant differences between these techniques, confirmed by data showing notable disparities. Materials and Methods: Using the silicone replica technique, 44 points on each crown were measured, with seven crowns per method to ensure reliability. Results: Results indicated that 3D printing demonstrated superior precision, with the smallest discrepancies in occlusal, axial, and marginal gaps. While milling faced challenges such as material wastage and potential ceramic microfractures, it remained a viable option. Conclusion: The findings suggest that 3D printing could significantly improve crown quality and patient outcomes, despite higher upfront costs. Further research is necessary to validate these results and explore the long-term efficacy and cost-effectiveness of these techniques. This study underscores the clinical implications of choosing appropriate crown fabrication methods, highlighting the potential of advanced CAD/CAM technologies to enhance dental prosthetic manufacturing.

Reliability of the digital functionally generated path technique for assessing occlusal interferences and adjusting CAD-CAM zirconia crowns: an in vivo study

BackgroundDesigning the occlusal surface of a prosthesis to ensure optimal eccentric occlusion is challenging without precisely replicating the patient’s mandibular movements. During the CAD-CAM prosthesis delivery process, clinicians often need to make adjustments to the prosthesis to avoid occlusal interferences that may occur during lateral excursions. Recently, there have been developments in the field of mandibular motion tracking using optical devices. These approaches seek to incorporate an individual’s functional movement into the research field of occlusal morphology.AimThis study aimed to assess the accuracy of digitally replicating mandibular movements to identify and correct occlusal interferences in monolithic CAD-CAM zirconia crowns.MethodsAn intraoral scanner (IOS) was used to capture complete arch maxillary and mandibular teeth and record buccal and lateral interocclusal records of maxillary first premolar abutment teeth of thirteen participants. For each patient, two monolithic zirconia crowns were fabricated following the standard digital workflow. The crowns were categorized based on the virtual method used for adjusting occlusal interferences into two groups: Group I, where occlusal interferences in CAD-CAM zirconia crowns were adjusted using buccal interocclusal records, and Group II, where adjustments were made using both buccal and lateral interocclusal records. After crown fabrication following the manufacturer’s instructions, occlusion was analyzed using an electronic pressure analyzer. The mean, standard deviation and median values of the recorded data were measured. Paired t test and Wilcoxon Sign Rank test were executed for analyzing differences between groups (p value ≤ 0.05).ResultsGroup I recorded higher maximum pressure at lateral mandibular movement with mean ± standard deviation value of 26.00 ± 4.95% than Group II with 20.62 ± 3.38%. Regarding pressure recorded at maximum intercuspation (MI) Group I showed higher results; 8.08 ± 1.50% compared to Group II with 7.23 ± 1.59% mean ± standard deviation value. The average value of crown volume for Group I was (160.36 ± 15.94) mm3, while for Group II was (157.63 ± 14.45) mm3.ConclusionsThe digital functionally generated path technique allows for identifying occlusal interferences and modifying CAD-CAM zirconia crown designs.

Lithium disilicate, full coverage crowns: what is the effect of using conventional impressions compared to digital impression with respect to the internal fit of the restoration? A systematic review.

Digital dentistry provides an alternative to fabrication of crowns. This systematic review focuses on the accuracy of the mean internal space of lithium disilicate crowns when comparing intraoral scanning to conventional impressions. Ovid Medline, Cochrane and PUBMED were searched and the review protocol followed the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42023379908) and guided by The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Cohen Kappa coefficient confirmed the agreement of data. The revised Cochrane Risk of Bias tool was utilised to evaluate randomised controlled trials The Methodological Index for non-randomised controlled trials. Of the six in vivo studies, three concluded that digital techniques improved the internal fit over their conventional counterparts. Two found that there was no significant difference and one indicated that digital technique resulted in an inferior internal fit. Of the eight in vitro studies, two concluded digital techniques to be superior, two found digital techniques to be inferior and four found no significant difference. Significant heterogeneity between studies limits the potential any systematic review of the internal fit of dental crowns when comparing conventional and optical impressions. This systematic review indicates digital methodology is comparable to that of conventional impressions.

Analysis of occlusal clearance of crown preparations in a predoctoral clinical setting.

This study sought to assess the presence and location of inadequate tooth preparation performed by predoctoral dental students by scanning mounted casts submitted for monolithic zirconia crown fabrication METHODS: An intraoral scanner capable of volumetric measurements of crown preparations was used to analyze 56 crown preparations on mounted stone casts before submission to a lab for crown fabrication. The mounted casts were scanned individually and then a buccal bite was scanned to stitch the models together into virtual occlusion. The distance between the crown preparations and opposing dentition was displayed volumetrically, and the minimum clearance of each preparation was recorded for both the functional and non-functional cusps. Preparations were evaluated for adequate interocclusal clearance and comparisons were made using a Chi-square test with α=0.05 with respect to tooth location, functional versus nonfunctional cusp, and or single versus multi-unit preparation. Over 47% of mounted casts with crown preparations analyzed for the study exhibited a lack of occlusal clearance in at least one area. Functional cusps were more often under-reduced than non-functional (p<0.001). No other comparisons were statistically significant. The present study demonstrates a high percentage of under-reduced crown preparations in a predoctoral clinic and emphasizes the utility of quality control and analysis via digital scanning of crown preparations prior to crown fabrication.

A feasibility study on the use of an intraoral optical coherence tomography system for scanning the subgingival finish line for the fabrication of zirconia crowns: An evaluation of the marginal and internal fit

ObjectivesThis study aimed to evaluate the marginal and internal fit of zirconia crowns were fabricated using scan data from an intraoral optical coherence tomography (OCT) scanner and an intraoral scanner (IOS) for scanning the subgingival finish line. MethodsAn extracted maxillary left central incisor was prepared for a zirconia crown. The prepared tooth was placed in artificial gingiva, created using silicone with a refractive index similar to that of the tooth, ensuring a subgingival depth of 0.50 to 0.70 mm from the labial finish line. Scanning data were obtained from four types of models as follows. (1) CAD reference model (CRM) excluding the gingiva and scanned using a laboratory scanner. (2) IOS group excluding the gingiva (IOS only, IOSO group). (3) IOS group with scanned attached artificial (IOS with gingiva, IOSG group). (4) OCT post-processed data of the subgingival finish line and IOSG data (OCT group). Zirconia crowns were fabricated based on these data, and their marginal and internal fit were evaluated using the silicone replica technique. Statistical analyses were conducted using one-way and two-way ANOVA (α = 0.05). ResultsThe OCT group exhibited a significantly smaller marginal gap than the IOSG group (P < 0.05). The marginal fit of the OCT group did not significantly differ from that of the CRM group (P > 0.05). The IOSG group exhibited a significantly larger chamfer gap, while both the IOSG and OCT groups had significantly larger axial gaps. Furthermore, the OCT group showed a significantly larger incisal gap (P < 0.05). ConclusionsAn intraoral OCT system can enhance the fabrication accuracy of zirconia crowns by achieving superior marginal fit for crowns with subgingival finish lines. Clinical significanceThe use of an IOS for subgingival finish lines without gingival displacement cords may result in a suboptimal marginal fit. However, integrating OCT technology can effectively address this issue, leading to improved clinical outcomes.

Research on Textured Polishing Wheel (TPW) patterns for polishing dental ceramic materials in anhydrous environments

Abstract Dental ceramics commonly utilize high-hardness fused silica materials for the fabrication of inlays, crowns, and artificial dental implants, with their processing efficiency and surface roughness (Ra) directly influencing manufacturing costs and product quality. This study presents the development of a Textured Polishing Wheel (TPW) featuring three distinct surface patterns (spiral, linear, and radial), achieved through single-point diamond and pulsed laser processing techniques. It investigates the effects of these patterns on the removal rate and surface roughness (Ra) of dental ceramics during the polishing process. Results indicate that while TPW demonstrates comparable material removal depth to non-textured polishing wheels, it marginally increases surface roughness (Ra). Moreover, TPW significantly reduces burning and wear on the wheel surface during polishing. Pulsed laser ablation of TPW leads to further improvement in surface roughness, thereby enhancing the processing of dental ceramics. Experimental findings highlight the superior performance of spiral TPW, achieving a material removal rate of 4.2 μm/h and a surface roughness (Ra) of approximately 2.2 nm , thus meeting the manufacturing and functional requirements of dental ceramics.

Zirconia crowns manufactured using digital light processing: Effects of build angle and layer thickness on the accuracy

ObjectivesThis study investigated the effects of build angle and layer thickness on the trueness and precision of zirconia crowns manufactured using digital light processing (DLP) technology. Materials and MethodsSingle crowns were fabricated from zirconia using DLP technology. The crowns were manufactured with three different representative build angles (0°, 45°, and 90°) and two different layer thicknesses (30 μm and 50 μm). After printing, the specimens were non-contact-scanned, and their accuracy was assessed using a 3D analysis software. Root mean square (RMS) values were used to determine trueness and precision. Color maps were generated to detect deviations within the specimens. Statistical analyses were conducted using two-way ANOVA. ResultsBuild angle and layer thickness significantly affected trueness and precision (p < 0.05). At a 30-μm layer thickness, the crowns printed at angles of 0° (32.2 ± 3.2 μm) and 45° (33.9 ± 2.4 μm) demonstrated the best marginal trueness compared to those in other groups (p < 0.05). Notably, those printed at an angle of 90° exhibited the best intaglio surface trueness (37.4 ± 4.0 μm). At a 50-μm layer thickness, the crowns printed at an angle of 90° exhibited the lowest accuracy concerning marginal and intaglio surface aspects (27.7 ± 8.2 μm). ConclusionsBoth the build angle and layer thickness significantly affected the dimensional accuracy of DLP-printed zirconia crowns, with the 30-μm layer thickness offering superior trueness. Optimal results were achieved using build angles of 0° and 45° in conjunction with thinner layers, minimizing marginal defects. Clinical SignificanceAll zirconia crowns produced at different build angles and layer thicknesses satisfied clinical requirements. Specific combinations of these factors realized the fabrication of single crowns that possessed the highest accuracy.

Fit comparison of interim crowns manufactured with open and proprietary 3D printing modes versus milling technology: An in vitro study.

This study aimed to assess the fit of interim crowns produced using DLP-based 3D printing with different manufacturing workflows-open and proprietary-versus milling technology. A total of 120 crowns were evaluated using the replica technique. The control group (Mill, n = 30) was manufactured via subtractive technology. Experimental groups were printed using a DLP printer (SprintRay Pro95). In the proprietary mode (SR100, n = 30), manufacturer resin was used with a 100-μm layer thickness (LT) and a splashing cleaning postprocessing. In the open mode, validated resin was used. Group B100 (n = 30) had a 100-μm LT, and group B50 (n = 30) had a 50-μm followed by postprocessing in an ultrasonic bath with full immersion in isopropyl alcohol. Kruskal-Wallis tests with Bonferroni correction was applied after normal analysis (α = 0.05). Group B50 exhibited the best overall fit (123.87 ± 67.42 μm), which was comparable to the gold standard Milling group, which demonstrated the lowest marginal fit (p = 0.760). SR100 showed significantly poorer performance compared to Mill, B50, and B100 (p < 0.001). 3D printed and milled interim crowns generally demonstrated clinically acceptable fit, with the exception of the SR100 group. Postprocessing notably influenced crown fit, with the open mode with total immersion in isopropyl alcohol being superior. The present study demonstrates that the selection of an optimal manufacturing and postprocessing workflow results in superior fit for interim crowns. This enables dental professionals to evaluate protocols and ensure reliable outcomes with improved clinical outcomes in interim crown fabrication.

A Comparative Evaluation of Marginal and Internal Fitness of Zirconia Monolithic Crown Fabricated with Different CAD\CAM Systems: (In Vitro Study)

The precision of computer-aided design/computer-aided manufacturing (CAD/CAM) systems is reliant upon their technical attributes and reliability in producing the designated restorations. The evaluation of this precision is primarily conducted through the examination of the marginal and internal fitness of said restorations. Consequently, the objective of this research endeavor was to analyze and compare the marginal and internal fitness of zirconia crowns fabricated using various CAD/CAM systems. The samples were categorized into four groups, each consisting of 10 samples, based on the specific CAD/CAM equipment employed for crown fabrication as follows: Group I fabricated using Sirona CAD\CAM milling machine, Group II fabricated using Dentium CAD\CAM machine, Group III fabricated using XTCERA CAD\CAM machine and Group IV fabricated using IMES-ICORE CAD\CAM machine. Tooth preparation done following the guidelines recommended by KATANA TM Zirconia (Kurary Noritake Dental Inc., Japan). To ensure standardization, one CAD/CAM program designed parameters was selected to be used for all CAD/CAM machines. Cement thickness was directly measured using sectioning technique to assess the crown's internal and marginal fitness. After performing sectioning, measurements were conducted using a digital microscope with a magnification of 230x. Eleven predetermined measuring locations were selected for each sample, representing four distinct areas: two marginal points, two chamfer points, four axial points, and three occlusal points. Results showed that none of four CAD\CAM machines tested was able to accurately reproduce the designed cement space parameter except Group I (Sirona) showed the closest results. As a conclusion, no CAD\CAM system is 100% accurate however, crowns fabricated using Sirona CAD\CAM milling machine showed the closest recordings to selected parameters among other CAD\CAM milling machines tested.

A Simple Modified Open Tray Implant Impression Technique in a Patient with Fixed Orthodontic Appliance Therapy

Background: Implant based restorations are an integral part of orthodontic treatment currently and this combination provides increased treatment options. Making impressions for implant based restorations in subjects undergoing orthodontic treatment is a challenging task. Aim: This article presents a simple technique to achieve precise impressions utilizing commonly available materials in dental operatory. Case Description: Patient undergoing orthodontic therapy requiring replacement of missing lateral incisor was planned for implant placement and crown fabrication simultaneously during fixed appliance therapy. A modified open tray implant impression with polyvinyl siloxane was made during the prosthetic phase for successful rehabilitation of the edentulous space in the anterior region. Clinical Significance: Multidisciplinary approach to treatment is time saving, which includes simultaneous Orthodontic and Prosthodontic procedures. A simple modification of the open tray impression procedure can result in an accurate final cast in the region of interest to overcome the difficulties of impression making in a patient with fixed orthodontic appliance.

A comparative in vitro analysis of various temporization materials with respect to pulp chamber temperature changes during polymerization.

(1) To compare the temperature rise in the pulp chamber with different resin materials used for making provisional fixed partial dentures in anterior and posterior region while using Polyvinylsiloxane impression materials as matrix. (2) To identify a superior provisionalization material based on the amount of heat dissipated suitable for anterior and posterior provisional fixed partial denture fabrication. Temporary crowns and bridges are integral to Fixed Prosthodontics. It has been observed that conventional fixed prosthesis temporisation materials release heat due to the exothermic polymerisation reaction. When such a provisional material is directly let to set on a vital tooth, the heat transfer causes irreversible changes in the pulp tissue depending of the degree of change. Hence, this study observes amount of heat generation in various materials during temporisation procedure, by simulating similar conditions. Two Models were fabricated, one simulating missing lateral incisor (Model A) and another simulating missing first molar (Model B). Intact maxillary central incisors and canine for Model A and intact mandibular Second Premolar and Second Molar were selected to act as abutments. These abutment teeth were fitted with the tip of a K-type Thermocouple inside their pulp chambers and these were connected to a digital thermometer. Five temporisation materials were chosen for fabrication of temporary crowns through Direct technique. (1) polymethy methacrylate (Self Cure acrylic), (2) bisacryl composite (Protemp 4), (3) visible light cure urethane dimethacrylate (Revotec LC), (4) barium glass and fumed silica infused methacrylate (Dentsply Integrity) and (5)nano-hybrid composite (VOCO Structur 3). Ten observations were made for each provisional material on each model. During each observation, temperature rise was recorded at 30s interval from the time of application, through the peak and till a decrease in temperature is observed. Polyvinyl siloxane was used as matrix for all except light cure resin, where polypropylene sheet was used. Anova test used for statistical. ANOVA test revealed that there was a significant difference in the temperature changes associated with the provisional restorative materials used. Among the five, polymethy methacrylate (self cure resin) showed the maximum rise in temperature, followed by bisacryl composite (Protemp 4), visible light cure urethane dimethacrylate (Revotec LC), barium glass and fumed silica infused methacrylate (Dentsply Integrity) and nano-hybrid composite (VOCO Structur 3). There was no comparable difference between Model A and B but an overall reduction of temperature rise was observed in model B. VOCO Structur 3 showed the least temperature rise in the pulp chamber, and overall temperature rise was less for model B which can be attributed to the residual dentin thickness.

Comparative Analysis of Periodontal Parameters and Patient Satisfaction Utilising Different Temporary Crown Fabrication Techniques: A Parallel-Group Randomised Controlled Trial.

Aim The study aims to evaluate the efficacy of different techniques for temporary crown fabrication in maintaining periodontal health and patient satisfaction, addressing a critical gap in the existing literature and informing evidence-based clinical practices. Materials and methods This study, conducted in accordance with CONSORT guidelines, was a parallel-group randomised trial conducted at a dental institute in India. In total, 36 participants aged 18-65 requiring anterior tooth region crowns were randomly assigned to three groups: direct (control), indirect (Test Group 1) and direct-indirect (Test Group 2) fabrication techniques. Participants were selected from outpatient departments based on eligibility criteria, and interventions were allocated using randomization tables. Outcome assessments included gingival health metrics and patient satisfaction levels, with statistical analyses performed using the Kruskal-Wallis test. Results Significant differences were observed in the pink esthetic score (PES) and patient satisfaction (P=0.029) among the three groups, with the direct-indirect technique group demonstrating the highest median PES (9 out of 10). However, no significant disparities were noted in the plaque index (PI) or probing depth (PD) among the groups. Conclusion The direct-indirect technique demonstrated superior PES and patient satisfaction, indicating potential benefits for periodontal health and patient experiences. Integration of virtual preparation workflows may optimise outcomes, but further research is needed for validation and guideline development.

Patient-reported outcome measures (PROMs) of digital and conventional impression methods for fixed dentures.

Digital impression technique or computer-aided impression (CAI) has been recently concluded as a clinically acceptable alternative to conventional impression method (CIM) in the fabrication of crowns, short fixed partial dentures (FPDs), and implant-supported crowns. The purpose of this study was to investigate the patients' opinion and subjective perception of two different ways of impression - digital and conventional. A total of 45 patients were treated with CAI and CIM for the fabrication of tooth or implant-supported crowns. They fulfilled a questionnaire including 11 questions regarding the treatment time, gag reflex, discomfort related to manipulation, and other aspects of treatment. CAI was considered the preferential method for future treatment in 53% of patients, whereas 28.9% of the respondents preferred CIM. The preference for the impression method was influenced by the total time spent with the procedure, discomfort during manipulation with the tray or scanning head, size of the tray or scanning head, maximal opening discomfort, and (the tendency towards) gag reflex. CAI was considered a more comfortable and preferential method. Discomfort or difficulties during CAI negatively affected the patients' attitude to CAI, whereas the difficulties associated with CIM did not have any influence on the preferred method.

28Assessment of thermal variations in the pulpal chamber during fabrication of provisionals using two different techniques and three materials.

The issue of an increase in pulpal temperature affects direct and indirect techniques, where the fabricating material will come in direct contact with the prepared teeth. The aim of this study was to assess the pulpal thermal variations during provisional fabrication using direct and indirect-direct techniques, with three commonly commercially available provisional fabricating materials. In this vitro analytical study, 120 extracted human teeth were placed in a dentulous mould and dental stone was poured, to create a working model with an embedded natural right maxillary central incisor. Recording of thermal changes in the pulp chamber during provisionalization with direct (technique 1) and indirect-direct (technique 2) using three common types of provisional crown materials. 120 provisional crowns were fabricated using polymethyl methacrylate (DPI) (Group 1), Bis-acryl composite (Protemp 4) (Group 2) and Visible-light polymerizing (VLP) Urethane Dimethacrylate (Revotek LC) (Group 3) by two techniques and recording of peak temperature changes were done. Temperature rise in the pulp chamber was recorded using a thermocouple. The mean initial and final temperature of the pulp chamber recorded for Groups 1, 2 and 3 was 31.52, 32.56; 31.01, 32.34; 32.29, 34.47 for technique 1 and 29.13, 30.5; 29.29, 31.11; 30.31, 32.65 for technique 2. The mean change in temperature was higher in Group 3 compared to the other groups. The temperature rise detected according to this study was within the safer pulpal health limits with all the investigated materials and techniques. The resin material recommended for clinical use when the direct technique is employed for the fabrication of provisional crowns is bis-acryl composite resin (Protemp-4) as it caused minimal temperature rise in the pulpal chamber.

Fracture strength of preformed zirconia crown and CAD-CAM zirconia, ceramic, and hybrid composite crowns for the restoration of primary molars: An invitro study.

Paediatric-preformed zirconia crowns have been associated with several issues, primarily their inability to be crimped and the need for extensive tooth preparation. Additionally, the capacity to adjust the size, shape, and fit of these crowns is very limited. To evaluate and compare the fracture strength of four different types of dental crowns intended for paediatric patients. The fracture resistance of four types of paediatric crowns was evaluated using the universal testing machine; freshly extracted primary molars received one of the following: preformed zirconia crowns, custom-made computer-aided design and computer-aided manufacturing (CAD-CAM) zirconia crowns, custom-made CAD-CAM ceramic crowns, and custom-made CAD-CAM hybrid composite crowns. Data were statistically compared using the Kruskal-Wallis test followed by the Bonferroni test, and the level of significance was set at 5%. Results showed that there was a statistically significant difference among the four groups (p < .001). The highest value of fracture force was observed for the milled zirconia crown and the lowest for the prefabricated zirconia. The implementation of the CAD-CAM digital crown fabrication technique has the potential to address issues associated with preformed crowns in paediatric patients, particularly in terms of fracture resistance.

СРАВНИТЕЛЬНЫЙ АНАЛИЗ ИТТРИЙСОДЕРЖАЩИХ БЛОКОВ ДИОКСИДА ЦИРКОНИЯ

The aim of this review is to determine the positive and negative qualities and properties of zirconium dioxide blocks of different generations, namely 3Y-TZP, 5Y-TZP, 4Y-TZP. &#x0D; Materials and methods. A systematic literature review in the electronic databases Google Scholar and Pubmed was conducted. The articles whose content was based on mechano-optical and physicochemical properties of zirconium dioxide blocks of 1, 3 and 4 generations and their application in practice were considered.&#x0D; Results: 57 articles were reviewed during the analysis, of which 47 from Pubmed and 10 from Google Scholar were selected. After selecting the articles according to the criteria, the total number of studies was 27. The studies evaluated the mechanical and optical properties of different generations of zirconia blocks.&#x0D; Conclusion: The use of yttrium-stabilized zirconium dioxide ceramics of different generations in dental practice provides opportunities to obtain quality results in the fabrication and placement of crowns, dentures, veneers and other prosthetic structures. Speaking about physical, mechanical and optical properties, it should be noted that each generation has different indicators. Specialists should be careful when choosing zirconium dioxide ceramics, as optical properties are not always a decisive factor when selecting a material for fabrication of fixed structures.

Evaluation of the Bonding Shear Strength between Enamel and Dentin Feldspathic Porcelain and Two Different Monolithic Zirconia with Low and High Translucency.

The utilization of ceramics in the field of dentistry has seen a significant rise owing to their esthetic appeal and excellent functional properties. The use of ceramics in the field of dentistry has witnessed a notable surge, driven by their appealing esthetics and exceptional functional attributes. Zirconia, distinguished by its exceptional mechanical strength, plays a pivotal role in the fabrication of posterior crowns and bridges. Among zirconia variants, monolithic zirconia stands out, where the entire restoration is crafted from zirconia material. In parallel, feldspathic porcelain, chosen for its remarkable resemblance to natural tooth enamel, represents another significant ceramic type. This study aims to evaluate the shear bond strength (SBS) between two types of monolithic zirconia with two types of feldspathic porcelain. Forty-four monolithic zirconia veneered discs with feldspathic porcelain were subjected to SBS testing. The dimensions of the discs were 7 mm in diameter and 5 mm in height (3 mm of zirconia and 2 mm of porcelain). Subsequently, the specimens were subjected to a universal testing machine at a speed of 0.5 mm/min until failure occurred. The type of failure was examined using scanning electron microscopy. One-way analysis of variance (ANOVA), two-way ANOVA, Fisher's test, and multiple Tukey comparisons were used as statistical analyses. The highest SBS was achieved by the high-translucency monolithic zirconia with enamel porcelain group (18.81 ± 3.18 MPa) and the high-translucency monolithic zirconia with dentin porcelain group (17.89 ± 2.75 MPa), followed by the low-translucency monolithic zirconia with dentin porcelain group (15.04 ± 2.24 MPa) and the low-translucency monolithic zirconia with enamel porcelain group (14.33 ± 2.00 MPa), respectively. Additionally, the most common type of failure pattern observed was mixed, followed by adhesive failure. The translucency of the porcelain did not significantly affect SBS, while the type of monolithic zirconia used had a significant impact. Furthermore, there was no discernible relationship between the four groups in terms of the distribution of failure patterns.

Fabrication of ZTA crowns with simultaneously improved isotropy on mechanical property and surface quality by DLP

AbstractZirconia‐toughened alumina (ZTA) composite ceramics show great potential for use in dental repair applications due to their unique properties. Complex‐shaped ZTA all‐porcelain crowns can be accurately fabricated using digital light processing (DLP) technology. However, effectively controlling both the anisotropy on mechanical property and surface quality of ZTA composites shaped by DLP remains a critical challenge that requires further research and innovation. In this work, we propose an efficient method to synchronously enhance the isotropy on mechanical performance and surface quality of DLP formed ZTA all‐porcelain crowns by controlling contents of yttria‐stabilized zirconia (YSZ) powders. When enhancing contents of YSZ from 5 to 20 wt%, multilayer microstructure with obvious interlayer gaps transformed into uniform microstructure with strong interlayer bonding, and the smaller alumina grain was observed on the stair‐stepping microstructure. Finally, the ZTA composites exhibited flexural and comprehensive strength as high as 640.3 and 6.9 MPa, and dimensional precision as low as 37.5 and 43.5 μm on top and side surface, together with simultaneously enhanced isotropy on mechanical property and surface quality, well satisfying the demands for all‐porcelain crowns fabricating. This study provides thorough understandings on isotropy regulating of DLP‐shaped ZTA all‐porcelain crowns with excellent mechanical performance and surface quality.

Application of 3D digital smile design based on virtual articulation analysis in esthetic dentistry: A technique

A technique for the application of a virtual articulation system in 3-dimensional digital smile design (DSD) during esthetic restoration is described. To acquire stable occlusion and a smooth jaw movement pattern without premature contacts or interference, a digital facebow and a virtual articulator were used to collect and analyze a patient’s occlusal data and jaw movement information. The original pattern of occlusal contacts and jaw movements were diagnosed as stable and copied to the digital design of the new prostheses. Preparation of the abutments, crown lengthening surgery, and definitive crown fabrication and cementation were performed according to the design. After 9 months, the occlusion remained stable, and the patient was satisfied with the outcome.