Fabrication Of Restorations Research Articles

Speed-sintering and the mechanical properties of 3-5mol% Y2O3-stabilized zirconias.

Ever faster workflows for the fabrication of all-ceramic restorations are of high economic interest. For that purpose, sintering protocols have been optimized for use in modern sintering furnaces, the so-called speed-sintering. However, conventional furnaces are still the most widely used equipment to sinter zirconia restorations. In this in-vitro study, we evaluated the feasibility of a speed-sintering protocol using a conventional sintering furnace to sinter different dental zirconias (stabilized with 3mol% up to 5.4mol% Y2O3) in comparison to a conventional sintering program. The properties evaluated were Young's modulus, Poisson's ratio, density, biaxial flexural strength, and fracture toughness. We show here that despite differences being dependent on material, the physical and mechanical properties of speed-sintered zirconia are comparable to those obtained by the conventional sintering.

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

To evaluate the effect of finish line design (chamfer and feather-edge) and ceramic type on the internal and marginal fits of fixed partial dentures on abutment teeth. Two typodont mandibular casts, missing right first premolar tooth, received tooth preparation on canine and second premolar abutments (one cast with chamfer finish line and the other cast with feather-edge finish line). The preparation segment of each typodont model was scanned, 3D printed in resin, and then invested and casted in metal to obtain two metal models. Polyvinyl siloxane impressions were made for the metal models and poured in type IV stone. The stone models (n=40) were randomly assigned into four groups (n=10): chamfer finish line with heat-pressed zirconia reinforced lithium disilicate fixed partial denture (CL), chamfer finish line with monolithic zirconia fixed partial denture (CZ), feather-edge finish line with heat-pressed zirconia-reinforced lithium disilicate fixed partial denture (FL), and feather-edge finish line with monolithic zirconia fixed partial denture (FZ). After the fabrication of ceramic restoration, micro-computed tomography was used to evaluate the internal and marginal fits of each fixed partial denture. Data were statistically analyzed with three-way ANOVA (α=0.05). There were no significant interactions between preparation type, material type, and tooth type at any of the areas assessed. There was significant difference (p=0.01) between CZ (59.15±4.6µm) and FZ (73.6±17.1µm) groups at the finish line area. Regarding the horizontal marginal discrepancy area, there were significant differences between CZ (62.65±10.5µm) and FZ (90.05±5.6µm) groups (p<0.001), CL (77.45±8.1µm) and CZ (62.65±10.5µm) groups (p<0.001), and FZ (90.05±5.6µm) and CL (77.45±8.1µm) groups (p<0.001). At finish line area, there was a significant difference (p=0.018) between feather-edge with canine (72.75±13.3µm) and chamfer with canine (59.05±5.8µm); however, there was no significant difference (p=0.774) between feather-edge with premolar (69.45±12µm) and chamfer with premolar (65.1±7.4µm). Moreover, there was no significant difference (p=0.886) between feather-edge with canine and feather-edge with premolar. The internal and marginal fits of the ceramic fixed partial dentures can be affected by the finish line design and ceramic type. The feather-edge finish line had a negative impact on the marginal and internal fits of ceramic fixed partial dentures at certain measurement points. Regarding the effect of finish line design on abutment teeth, the difference in fit was only detected at the finish line area of the anterior abutment (canine) with the feather-edge finish line.

Maxillary anterior teeth with extensive root resorption treated with multidisciplinary approach: A case report

Invasive cervical resorption is a type of external resorption, which is generally located in the cervical region of the tooth. The resorptive process can be caused by physiological, pathological, hormonal, and trauma factors. The present study aimed to report a case of invasive cervical resorption in tooth 12 identified as an incidental finding, in which all available clinical resources were used, as well as a combined multidisciplinary treatment of endodontics, orthodontics, surgery, and prosthesis. At the initial consultation, the tooth presented with Heithersay’s class II resorption, undergoing endodontic treatment and traction for subsequent cavity sealing. After completion of orthodontics, an increase in the resorptive pocket was observed (Class III of Heithersay), which led to endodontic retreatment and subsequent surgical intervention to remove the granulation tissue and fill it with bioceramic material. The preparation of the coronal remnant and fabrication of a prosthetic restoration were performed, with the aim of shielding the endodontic cavity and functionally restoring the tooth. With the case presented, it was possible to conclude that incidental findings are part of the endodontist’s daily life, requiring a constant search both for early diagnosis and effective multidisciplinary treatment, which contributes to the restoration of aesthetics and function, contributing to the tooth longevity.

Influences of Different CAD/CAM Ceramic Compositions and Thicknesses on the Mechanical Properties of Ceramic Restorations: An In Vitro Study.

The aim of this study was to assess the influences of different CAD/CAM ceramic compositions and thicknesses on the surface roughness and hardness of ceramic restorations. Four different ceramics were used in the current study: lithium disilicate (LD), leucite reinforced (LE), advanced lithium disilicate (ALD), and zirconia-reinforced lithium silicate (ZLS). Each group included 30 specimens subdivided into three different ceramic thicknesses (0.5, 1 and 1.5 mm thicknesses). The microhardness was measured for all the specimens using a microhardness testing machine, while the surface roughness was measured using a non-contact optical profilometer at three intervals (before toothbrushing and after toothbrushing, with and without toothpaste). Three-way and two-way ANOVA were used to determine the factors influencing the surface roughness and microhardness. There was a significant difference in the surface roughness between the studied groups for all the thicknesses. The findings showed that ALD had the lowest surface roughness, while ZLS showed the highest surface roughness. Moreover, ALD, followed by ZLS, had the highest hardness, while LD and LE had the lowest hardness values. Regarding the thicknesses, both the 0.5 and 1 mm ceramic thicknesses showed a significantly lower surface roughness than the 1.5 mm thickness, while the 1.5 mm thickness showed a significantly higher microhardness than the 0.5 mm thickness. The surface roughness and hardness were significantly affected by the ceramic composition and type of filler. It is recommended to use 1.5 mm-thick ceramic materials for the fabrication of definitive full-coverage ceramic restorations, while veneers require 0.5 mm-thick materials. ALD is a promising CAD/CAM material that can be used for the fabrication of restorations with a proper strength in both anterior and posterior regions.

Comparison of marginal and internal adaptation of provisional polymethyl methacrylate restorations fabricated by two three-dimensional printers: An in vitro study

Background: Chairside fabrication of provisional restorations using three-dimensional (3D) printers is rising in digital dentistry. The purpose of this research was to compare the marginal and internal adaptation of provisional polymethyl methacrylate (PMMA) restorations fabricated by two different 3D printers. Materials and Methods: In this in vitro investigation, an intact maxillary 1st molar acrylic model was first digitalized by a laboratory scanner. It was then prepared for an all-ceramic restoration and scanned again by the same scanner. The final restoration was designed in Exocad according to the scan files with a 50 μm cement gap. PMMA restorations were printed by two 3D printers; Group 1: Asiga (n = 10) and Group 2: Digident (n = 10). The replica technique was used to assess the marginal and internal fit of the restorations, and one-way ANOVA was used to analyze the data. P &lt;0.05 was regarded as statistically significant. Results: The mean marginal gap of crowns in Group 1 was significantly lower than that of Group 2 (75 vs. 195 μ, P = 0.001). Regarding internal adaptation, no significant difference was found between the axial gap values in both groups (P &gt; 0.05). The mean occluso-axial gap (90 vs. 140 μ, P = 0.026) and the mean occlusal gap (116 vs. 300 μ, P = 0.001) of crowns in Group 1 were significantly smaller compared to the equivalent values in Group 2. Conclusion: Provisional PMMA crowns fabricated by the Asiga printer showed significantly higher marginal and internal adaptation than those manufactured by Digident at all points except for the axial surface.

A digital workflow to predict facial aesthetics in patients with maxillofacial trauma with implant retained prostheses.

Purpose To introduce a digital workflow for the prediction of facial aesthetics, especially in patients with dentation deformity caused by maxillofacial trauma.Methods Cone-beam computed tomography (CBCT) and three-dimensional facial scans of patients with radiographic prostheses were collected. The aforementioned data were uploaded to ProPlan CMF software and merged to generate a virtual patient with craniofacial hard tissue, realistic facial soft tissue, and remaining dentition. The radiographic prostheses were scanned to form a digital cast, which was fitted with its CBCT image to create the virtual prostheses. Postoperative facial soft tissue was simulated according to the movement of the virtual prostheses. An appropriate virtual diagnostic prosthesis plan was selected by the patient and dentist. Subsequently, prosthetically driven implant guide and restoration were designed and fabricated.Conclusions A virtual patient was successfully constructed. A 4-mm protrusion of the virtual prosthesis was chosen. Subsequently, implant surgery was performed, and dental prostheses were fabricated based on this location. The fusion of the postoperative facial scan and preoperative facial prediction was found to be coincident. This technique can effectively predict facial aesthetic features of patients with maxillofacial trauma, facilitate communication with patients, reduce chairside time, and guide the multidisciplinary design of implant placement and restoration fabrication.

Digital workflow in implant prosthodontics: The critical aspects for reliable accuracy.

This paper is a comprehensive treaty about the variables that influence the transfer of the position of an implant to the laboratory when using a digital workflow. The aim is to provide operators and manufacturers with a guide on how to improve certain aspects of the digital workflow specific to the fabrication of implant-supported restorations. It addresses intraoral scanning issues and CAD software issues. In the former, the variables that play a part in the quality of the scan file are investigated: the implant scan body, the IOS and the operator. For the latter, instead, the focus is on those aspects that still today may create inaccuracies in the workflow and in the final product being fabricated: the identification of the specific implant placed in the patient and the generation of a virtual model with the representation of that implant platform correctly positioned in the three dimensions of space. Suggestions and recommendations are given to improve the control on the quality of the digital workflow's output. In a digital workflow for the fabrication of an implant-supported restoration, the selection and use of the implant scan body, the use of an effective scan strategy and the appropriateness of the best fit function in the CAD software, that is, the procedure of superimposing the library of geometric shapes of the ISB linked to the implant with the shape acquired intraorally, are variables that can influence the positional precision of the FDP. Fully understanding the importance of the information enclosed in the ISBs themselves can be crucial in the digital workflow. A proper ISB's selection, a correct scan of the ISB's shape and an accurate CAD superimposition of the ISB's library can lead the clinician to reduce the variables that affect the final result in daily practice.

Manufacturing of zirconia restorations by means of additive fabrication. Part 2

Additive fabrication (AF) or layer-by-layer synthesis technologies is one of the most dynamically developing areas of digital production. Modern additive technologies can be used to fabricate zirconia-based restorations. The second part of this article will present the fabrication of zirconia restorations using additive technologies such as selective laser sintering (SLS), selective laser melting (SLM), binder jetting (BJ), robocasting (fusion deposition modeling, FDM), as well as the advantages and disadvantages of the mentioned technologies. The analysis of the presented works indicates the need for further research aimed at optimizing 3D printing of zirconia restorations.

Mechanical Properties of New Generations of Monolithic, Multi-Layered Zirconia.

New monolithic multi-layered zirconia restorations are gaining popularity due to their excellent aesthetic properties. However, current knowledge of these newest multi-layer ceramics in terms of mechanical properties is scarce. Three monolithic, multi-layered zirconia materials (Katana, Kuraray Noritake, Japan) were selected for comparison: High Translucent Multi-layered zirconia (HTML), Super Translucent Multi-layered zirconia (STML) and Ultra Translucent Multi-layered zirconia (UTML). Fifteen specimens per group were cut from pre-sintered blocs in each of the four layers (L1, L2, L3, L4) and in different thicknesses (0.4 mm, 0.8 mm and 1.2 mm). Critical fracture load (Fcf) was recorded in 3-point-bending. Flexural strength (σ) in MPa, Vickers hardness (HV) in N/mm2, fracture toughness (KIc) in MPa*m1/2, Weibull Modulus (m) and characteristic Weibull strength (σw) in MPa were assessed. Statistical analysis was performed using ANOVA analysis. FS and KIc were significantly higher (p &lt; 0.05) for Katana™ HTML (652.85 ± 143.76-887.64 ± 118.95/4.25 ± 0.43-5.01 ± 0.81) in comparison to Katana™ STML (280.17 ± 83.41-435.95 ± 73.58/3.06 ± 0.27-3.84 ± 0.47) and UTML (258.25 ± 109.98-331.26 ± 56.86/2.35 ± 0.31-2.94 ± 0.33), with no significant differences between layers and layer thicknesses. The range of indications should be carefully considered when selecting the type of monolithic zirconia for fabrication of dental restorations, as materials widely differ in mechanical properties.

The Effect of the Digital Manufacturing Technique, Preparation Taper, and Cement Type on the Retention of Aged Anterior Provisional Crowns: An In Vitro Study

A well-made provisional fixed prosthesis must present as a preview of the future prosthesis and may also augment the health of the abutments and periodontium. Provisional restorations have been prepared chairside with polymethyl methacrylate (PMMA) since time immemorial. CAD/CAM additive and subtractive technologies have revolutionized the fabrication of interim restorations in dental clinics. The current literature lacks substantial data about retention of provisional crowns manufactured using Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) additive and subtractive techniques with various temporary cements. This in vitro study aims to assess and compare the retention of temporary/provisional anterior crowns based on the combined effect of different digital manufacturing techniques, preparation tapers, and the temporary cements used for cementation. Two maxillary right central incisor typodont teeth were prepared to receive all-ceramic crowns, one with a 10-degree taper and the other with a 20-degree taper. Forty 3D-printed working models with the 10° taper and forty working models with the 20° taper were prepared to receive the temporary crowns. Forty temporary crowns were 3D-printed and forty crowns were milled (20 from each taper group). Kerr Temp-Bond NE conventional cement and Kerr Temp-Bond clear cement were used for cementation in the two groups. The number of samples per test group was 10. All samples were thermocycled and subjected to a universal testing machine to measure the pull-off force until retention loss (N) under tension with a crosshead speed of 5 mm/min. The pull-off force was highest for group 8, i.e., 3D-printed crowns with a 20° taper and cemented with Kerr Temp-Bond clear cement, followed by groups 6, 7, 4, 5, 3, and 2. Group 1, i.e., milled crowns with 10° taper cemented with Kerr Temp-Bond NE conventional cement, exhibited the lowest pull-off retentive force. The clinical selection of long-term provisional crowns fabricated using 3D-printing technology, prepared with 10° or 20° tapers, and cemented with clear cement, is the most favorable in terms of the retention of provisional crowns. 3D-printed provisional crowns can be used as an alternative to conventional and CAD/CAM-milled crowns for long-term provisionalization.

Cytotoxicity of Commercially Pure Titanium (cpTi), Silver-Palladium (Ag-Pd), and Nickel-Chromium (Ni-Cr) Alloys Commonly Used in the Fabrication of Dental Prosthetic Restorations.

The longevity of dental implants is affected by the ability to avoid any hypersensitivity or corrosive reactions in the oral cavity. The aim of the current study was to evaluate the cytotoxic effect of commercially pure titanium (cpTi), silver-palladium (Ag-Pd), and nickel-chromium (Ni-Cr) on human gingival fibroblast (HGF). The sample size used was 10 discs from each alloy used with dimensions of 4x3mm. The HGF was derived from healthy patients subjected to gingivectomy procedures. Of the specimens,50% were incubated in artificial saliva and the other half in Dulbecco's Modified Eagle medium (DMEM). The extract of each alloy in both media was collected and applied on HGF. After 24 hours the morphology of the HGF cells was examined to detect any apoptosis or cell death. Also, cell viability was evaluated by the use of a 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Statistical analysis was performed using students' t-test and two-way ANOVA with a significance level of p<0.05. In the case of morphological examination of HGF and MTT assessment, only cpTi alloy specimens didn't display any cytotoxic effect. Ni-Cr was the most cytotoxic alloy of the three. Also, MTT activities of all three alloys were decreased when they were incubated in artificial saliva. cpTi exhibited the highest corrosion resistance in comparison to Ag-Pd and Ni-Cr alloys. Ag-Pd alloys showed acceptable resistance to corrosion that is due to the passivity effect. Also, artificial saliva increased the cytotoxic effect of the tested alloys more than DMEM.

An Indirect Digital Technique to Transfer 3D Printed Casts to a Mechanical Articulator With Individual Sagittal Condylar Inclination Settings Using CBCT and Intraoral Scans.

With the widespread application of digital impression techniques in prosthetic dentistry, accurate intraoral scan mounting, and virtual articulator parameters setting as per patients' anatomic structures are essential for treatment planning and restoration fabrication, especially for complex rehabilitation cases; meanwhile, marginal fit checking, occlusal adjustment, and porcelain layering of restorations are also crucial procedures in all cases in which the analog procedure to mount maxillary arches on a mechanical articulator is still required. This technique article presents an indirect digital approach that can first achieve virtual intraoral scan mounting and sagittal condylar inclination value setting of an Artex virtual articulator based on bony structures provided by a single cone beam computed tomography scan. It then facilitates the transfer of virtually mounted intraoral scans from the virtual articulator to the matched Artex mechanical articulator by relating a digitally scanned mounting plate of the Artex mechanical articulator to the virtual articulator, printing the intraoral scan and mounting plate scan assembly, and then mounting the printed casts on the mechanical articulator based on the printed mounting plate. This technique eliminates the conventional facebow transfer and protrusive bite registration procedures and offers a straightforward approach for the seamless integration of virtual environments and analog workflows into clinical practice. It aids in the design of restorations that are harmonious with the mandibular movements and reduces chairside adjustment time.

Survival analysis up to 7 years of 621 zirconia monolithic single crowns with feather-edge margins fabricated with a cast-free workflow starting from intraoral scans: A multicentric retrospective study

Statement of problemClinical studies on the fabrication of monolithic zirconia restorations with a feather-edge tooth preparation from digital scans and a cast-free fully digital workflow are lacking. PurposeThe purpose of this retrospective multicentric study in private practices was to evaluate the outcomes of monolithic zirconia crowns fabricated with feather-edge margins and a cast-free approach. Material and methodsA total of 621 teeth were prepared with feather-edge margins and restored with monolithic zirconia crowns fabricated with a fully digital cast-free workflow. Data were analyzed by using the Kaplan–Meier test and descriptive statistics. The clinical evaluation adopted the California Dental Association–modified criteria after recalling all patients between April and July 2021. ResultsThe clinical survival of 619 of 621 crowns, including recemented crowns placed in 427 patients (217 men, 220 women) over 5 years (2014 to 2019 with crowns in service between 12 and 85 months), was analyzed. The 2 excluded crowns were delivered to patients who dropped out of the study. Of the 619 crowns, 5 failed during the follow-up period: 4 teeth were extracted because of fracture and 1 restoration fractured. No other technical or biological failures were observed. The mean overall survival time was 84.4 months (standard error, 0.255; 95% confidence interval for the mean, 83.92 to 84.92). The overall survival probability was 99.1% up to 85 months. ConclusionsThe clinical outcomes of the monolithic zirconia crowns with feather-edge margins evaluated were comparable with outcomes reported using other margin designs and materials.

Editorial: Is Zirconia the Holy Grail of All-Ceramic Restorations?

Editorial: Is Zirconia the Holy Grail of All-Ceramic Restorations?

Two-piece magnet-retained shell manufactured by using milled and vat-polymerized methods for direct interim restorations

The shell technique has been described for fabricating direct interim restorations by using conventional and computer-aided design and computer-aided manufacturing (CAD-CAM) methods. However, the positioning of the shell over the tooth preparations can be challenging. In the present manuscript, the clinical and laboratory steps for manufacturing a 2-piece magnet-retained shell for direct interim restoration fabrication are described. The 2-piece shell was produced by combining milling and additive manufacturing procedures. The described technique aims to simplify the correct positioning of the shell and facilitate direct interim restoration fabrication.

Restoring non-restorable with the help of customized digital solutions: A review

This article aims to provide a comprehensive literate review on endocrown / customized digital restoration and how they might be a better option for hopeless decayed tooth. Dentist might be hesitant to apply such a successful treatment option for grossly decayed /fractured /traumatic teeth in their clinical practice because it’s not as widely used as other conventional methods. Here we review about innovative treatment approach for endodontically treated teeth, using a digital workflow with IOS and computer-aided design/computer-assisted manufacturing (CAD/CAM) fabrication of restoration. Endocrowns/ customized digital restoration constitutes a reliable approach for restoring severely damaged tooth as they are more precise, aesthetic and time saving.

Fabrication of Porcelain Veneer Provisional Restorations: A Critical Review

Fabrication of provisional restorations for porcelain veneers can be a difficult and time-consuming procedure, often being poorly done or even omitted altogether at times which can lead to undesired consequences. The purpose of this article is to review and describe several of the most commonly used techniques for fabrication of provisional restorations for porcelain veneers. The clinical techniques include direct composite resin, indirectly fabricated provisionals, direct-indirect technique, rapid simplified veneer provisional system (RSVP), and the shrink wrap technique. These methods will be described in detail for each technique, along with the indications and contraindications thus providing the practitioner with guidelines to assist in selection of the provisionalization technique best suited for the clinical scenario.

Shifting focus from subtractive to additive technology in digital prosthodontics

The advancements in digital technologies have found a widespread application in fabrication of dental restoration with adequate precision and accuracy. Digital methods which are commonly used for fabrication of prosthesis include subtractive methods such as milling and additive methods such as photomelting and photopolymerizing. Digitalization and accuracy are paving the way toward additive technology. The main purpose of this short communication is to mention the advantages, applications, and studies comparing additive and subtractive technology.

A digital workflow for the fabrication of an immediate implant-supported interim restoration

Immediate interim restorations in the esthetic region are usually fabricated in situ by using the pick-up technique, which is time-consuming and has a potential for cross-infection. This article describes a rapid and precise workflow for the fabrication of an immediate implant-supported interim restoration. A cast with gingival contours and an extended tube to accommodate the implant analogs is generated preoperatively based on the virtual implant planning and a predesigned restoration. After guided osteotomy and implant insertion, the actual three-dimensional (3D) implant position is transferred precisely from the mouth to the printed cast by using the surgical guide. This technique can achieve the rapid and precise fabrication of the interim restoration with guidance immediately after the surgery, decreasing the risk of cross-infection and reducing clinical steps and time.

Editorial: Are Big Data, Artificial Intelligence, Augmented Reality, Robotics, Teledentistry, and Metaverse Just Buzz Terms, or Do They Indicate a Paradigm Shift in Prosthodontics?

Editorial: Are Big Data, Artificial Intelligence, Augmented Reality, Robotics, Teledentistry, and Metaverse Just Buzz Terms, or Do They Indicate a Paradigm Shift in Prosthodontics?