The anterior all-ceramic crown: a rationale for the choice of ceramic and cement

Clinical evaluation of cemented and adhesively resin-bonded monolithic and partially layered zirconia and lithium disilicate crowns

Purpose

Zirconia and lithium disilicate crowns are very popular dental restorations. The cement type and layering technique used can profoundly affect the clinical performance of these crowns.This retrospective study is designed to investigate the success rate of cemented and adhesively bonded monolithic and partially layered zirconia and lithium disilicate crowns placed in faculty practice settings.

Materials and Methods

Patients who had received zirconia or lithium disilicate crowns at the faculty practice were invited for clinical examination. The examiner used the modified United States Public Health Service (MUSPHS) evaluation criteria to evaluate the crowns. The crowns were either glass ionomer cemented zirconia (GIC-Zr), resin-bonded zirconia (Adh-Zr), or resin-bonded lithium disilicate (Adh-LD). The crowns were also divided into monolithic and layered groups. Inferential analysis was used to examine the differences through bivariate analysis using t-testing and one-way ANOVA.

Results

Thirty-five patients, with a combined total of 218 single crowns, agreed to participate in the study. No statistically significant differences in the quality outcome variables considered were found between the groups, except for marginal adaptation, where Adh-Zr achieved significantly higher scores compared to GIC-Zr and Adh-LD. Layered zirconia and lithium disilicate crowns have significantly higher quality outcomes in terms of anatomic form, marginal adaptation, and color match compared to monolithic zirconia and lithium disilicate crowns.

Conclusions

Conventionally cemented zirconia and adhesively bonded zirconia and lithium disilicate crowns are reliable treatment options with high short-term success rates. Clinical studies with longer follow-up times are needed to investigate their long-term success rates.

Current Protocols for Resin-Bonded Dental Ceramics

Resin-bonded ceramic restorations are common treatment options. Clinical longevity of resin-bonded ceramic restorations depends on the quality and durability of the resin-ceramic bond. The type and composition of the specific ceramic determines the selection of the most effective bonding protocol. Such protocol typically includes a surface pretreatment step followed by application of a priming agent. Understanding of fundamental ceramic properties and chemical compositions enables the clinician to make proper material selection decisions for clinically successful and long-lasting restorations. Based on research accrued over the past decades, this article reviews and discusses current resin-bonding protocols to most commonly used dental ceramics.

Cytotoxicity and Bonding Property of Bioinspired Nacre-like Ceramic-Polymer Composites

For clinical applications, non-cytotoxicity and good bonding property of dental restorative materials are the most essential and important. The aim of this study was to evaluate the potential for clinical applications of two novel bioinspired nacre-like ceramic (yttria-stabilized zirconia)-polymer (polymethyl methacrylate) composites in terms of the cytotoxicity and bonding property. The relative growth rates (24 h) of the Lamellar and Brick-and-mortar composites measured by CCK8 were 102.93%±0.04 and 98.91%±0.03, respectively. According to the results of cytotoxicity and proliferation experiments, the two composites were not cytotoxic to human periodontal ligament fibroblasts (HPDLFs) in vitro. Both composites exhibited improved bonding strength as compared to the Control group (Vita In-Ceram YZ). As the polymer content in the composite material increases, its bonding strength also increases, which enhances the application potential of the material in the field of dental restoration. Meanwhile, by controlling the direction of loading force in the shear test, the effect of microstructure on the bonding strength of anisotropic composites was studied. After sandblasted, the bonding strengths of the Lamellar group in the longitudinal and transverse shear directions were 17.56±1.56 MPa and 18.67±1.92 MPa, respectively, while of the Brick-and-mortar group were 16.36±1.30 MPa and 16.99±1.67 MPa, respectively. The results showed that the loading direction had no significant effect on the bonding strength of the composites.

Revolution of Current Dental Zirconia: A Comprehensive Review

The aim of this article is to comprehensively review the revolution of dental zirconia (Zir), including its types, properties, applications, and cementation procedures. A comprehensive search of PubMed and Embase was conducted. The search was limited to manuscripts published in English. The final search was conducted in October 2021. Newly developed monolithic Zir ceramics have substantially enhanced esthetics and translucency. However, this material must be further studied in vitro and in vivo to determine its long-term ability to maintain its exceptional properties. According to the literature, monolithic translucent Zir has had promising results and a high survival rate. Thus, the utilization of this material is indicated when strength and esthetics are needed. Both the materials and methods used for cementation of monolithic Zir have significantly improved, encouraging dentists to use this material, especially when a conservative approach is required. Zir restorations showed promising outcomes, particularly for monolithic Zir crowns supported with implant and fixed dental prostheses.

All-ceramic restorations: A review of the literature

Objectives

Ceramics can simulate the visual character of the tooth substance successfully and are biocompatible materials. However, a wide range of ceramic materials and systems on the market are available for use in dentistry. Therefore, it is the aim of this article to provide an overview of dental ceramics, their classifications, methods of construction, and clinically relevant aspects that enable the reader to select the most appropriate ceramic for a particular clinical situation.

Material and methods

The PubMed (MEDLINE) search engine was used to gather the most recent information on dental ceramics. The search was restricted to a ten-year period (January 1, 2010-December 31, 2019) and only English-language studies. A Boolean search of the PubMed data set was implemented to combine a range of keywords: (ceramics OR all-ceramics OR dental porcelain OR polycrystalline OR porcelain fused to metal OR ceramometal OR procera OR e max OR zirconia OR In-ceram OR Inlays OR Onlays OR Overlays OR Endocrown) AND (survival rate OR success rate OR clinical outcomes OR classification) AND (humans). Studies were also obtained by manual searches and from Google Scholar.

Results

By using this process, 2173 articles and studies were obtained. More studies were also obtained by manual searches and from Google Scholar. The most relevant published studies were chosen and used in the current review.

Conclusion

All-ceramic restoration use has increased in recent years. This increase has been attributed to patients' demand for good aesthetics and an improvement in the materials' mechanical and aesthetic properties as well as to required minimally invasive tooth preparation and the methods of fabrication. The success of ceramic restorations depends on several factors, such as selection of material, restoration design, occlusion, and cementation media.

Color compatibility between dental structures and three different types of ceramic systems

BACKGROUND

To assess color compatibility between dental structures (human enamel and dentine) and three different types of ceramic systems.

METHODS

Samples (1 and 2 mm-thick) of extracted tooth (containing dentine and enamel areas) and three ceramic systems with different shades and opacities (HT-High Translucent, T-Translucent) were prepared for this study: Vita Suprinity-VS (HT, T; A1, A2, A3, A3.5, B2, C2, D2) (Vita Zahnfabrik); Vita Enamic-VE (HT, T; 1M1, 1M2, 2M2, 3M2) (Vita Zahnfabrik) and Noritake Super Porcelain EX-3-NKT (A1, A2, A3, A3.5, B2, C2, D2) (Kuraray Noritake Dental). Reflectance measurements of all samples were performed over black backgrounds using a non-contact spectroradiometer (SpectraScan PR-670, Photo Research) under a CIE 45°/0° geometry. CIE L*a*b* color parameters were measured and CIELAB/CIEDE2000 color differences (ΔE₀₀/ΔE^*_ab) and corresponding Coverage Error (CE) of ceramic system for dentine or enamel samples were calculated. Color data was analyzed using one-way ANOVA and post-hoc multiple comparisons tests. CE values were interpreted by comparisons with available 50:50% acceptability color threshold (AT) for dentistry.

RESULTS

Statistically significant differences in lightness were found among all ceramic systems and human dentine (p < 0.001), while no significant differences were registered between enamel and VSHT, T and VEHT. 1 mm dentine showed no statistical differences with VST and VSHT for a* coordinate, while 2 mm dentine showed no significant differences (p > 0.05) with VEHT. Thin samples (1 mm) of dentine and enamel showed significant statistical differences (p < 0.05) for b* coordinate with less translucent materials (NKT, VET and VST). For dentine samples, none of the ceramic materials provided a CE lower than AT. VSHT provided the best CE for 1 mm-thick (CE₀₀ = 1.7, CE_ab = 1.9) and for 2 mm-thick (CE₀₀ = 2.3; CE_ab = 2.5) enamel samples.

CONCLUSIONS

Color coordinates of evaluated esthetic ceramic systems were statistically different from those of human dentine in almost all cases. The evaluated ZrO₂ lithium silicate glass-ceramic (VS), with its two levels of translucency, provided lower CE values with human enamel samples while conventional feldspathic ceramic (NKT) and hybrid ceramic systems (VE) demonstrated a better color compatibility with dentin samples.

Cement opacity and color as influencing factors on the final shade of metal-free ceramic restorations

OBJECTIVE

To investigate the influence of opacity and color of luting cements on the final shade of metal-free restorations.

MATERIALS AND METHODS

Five resin cement colors in combination with four different thicknesses of CAD/CAM ceramic materials were tested, and a composite substrate was used as dentin color reference (n = 3). Specimen color was measured with a spectrophotometer equipped with an integrating sphere before and after cementation (CIELAB). Cement and ceramic color and opacity (TP) were assessed by measuring the tested ceramic thickness as a 1-mm thick disk for each of the cement shades. The differences in color were evaluated (ΔE₀₀ ). Data were statistically analyzed by a Two-Way ANOVA followed by the Tukey Test for post-hoc comparison (P < .05) and multiple comparison Pearson's test (P < .05); the acceptability and perceptibility threshold were evaluated.

RESULTS

Statistically significant influence was found for factors ceramic thickness and cement shade (P < .001). Perceptible and unacceptable color changes were induced on the final restoration by resin cements (ranging from ΔE₀₀  = 0.69 ± 0.54 to ΔE₀₀  = 5.53 ± 0.46), the correlation between factors became strong (r²  > 0.6) in case of mismatch between color and translucency of cement and ceramic. Only the clear shade in combination with the thickest ceramic, resulted in an imperceptible color change (ΔE₀₀  = 0.69 ± 0.54).

CONCLUSIONS

The final shade of ceramic restorations can be influenced by resin cements; the magnitude of influence is related to the cement optical properties.

CLINICAL SIGNIFICANCE

In order to influence the final shade of a ceramic restoration, a cement more opaque than the restorative material should be used. Conversely, in the case of a fitting shade of the restoration, a cement more translucent than the restoration should be used to avoid undesired changes.

Marginal Adaptation of CAD/CAM All-Ceramic Crowns Made by Different Impression Methods: A Literature Review

All-ceramic crowns for teeth are widely used for restoring teeth. Stone casts have been made from conventional impression methods; however, newer techniques have made this process easier and faster for both the patient and the practitioner. Laboratory CAD/CAM technology mainly involves scanning the die stone, while other systems permit impression or intraoral scanning; however, one major concern remaining is the marginal fit of the restorations made using different methods for recording the prepared teeth. This study aims to review studies evaluating the marginal fit of all-ceramic crowns manufactured by CAD/CAM systems using different extra- and intra-oral scanners compared to conventional impressions.

Ceramic Fracture in Metal-Ceramic Restorations: The Aetiology

All dental restorations are liable to failure during function. Failure could be biologic, aesthetic, mechanical or a combination. Ceramic restorations in particular, including metal-ceramics, are prone to mechanical fracture, especially the fracture of veneering porcelain. Fracture of a metal-ceramic restoration jeopardizes function as well as aesthetics. It is equally onerous to manage for both patient and dentist. Optimal management of such cases requires a detailed knowledge of the aetiology behind this phenomenon. The current paper aims to highlight possible causative factors involved in the mechanical failures of metal-ceramic restorations. Clinical relevance: Ceramic fracture in metal-ceramic crowns and fixed partial dentures is routinely encountered in dental clinics. Knowledge of the aetiology is required to diagnose and manage such cases accurately as well as to avoid these errors in future.

Comparison of the marginal fit of lithium disilicate crowns fabricated with CAD/CAM technology by using conventional impressions and two intraoral digital scanners

STATEMENT OF PROBLEM

Conventional impression materials and techniques have been used successfully to fabricate fixed restorations. Recently, digital pathways have been developed, but insufficient data are available regarding their marginal accuracy.

PURPOSE

The purpose of this in vitro study was to compare the marginal gap discrepancy of lithium disilicate single crowns fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) technology by using both conventional and 2 digital impression techniques.

MATERIAL AND METHODS

One typodont maxillary right central incisor was prepared for a ceramic crown. Ten impressions were made by using each method: conventional with polyvinyl siloxane impression material, Lava COS (3M ESPE), and iTero (Cadent) intraoral scanning devices. Lithium disilicate (e.max CAD) crowns were fabricated with CAD/CAM technology, and the marginal gap was measured for each specimen at 4 points under magnification with a stereomicroscope. The mean measurement for each location and overall mean gap size by group were calculated. Statistically significant differences among the impression techniques were tested with F and t tests (α=.05).

RESULTS

The average (±SD) gap for the conventional impression group was 112.3 (±35.3) μm. The digital impression groups had similar average gap sizes; the Lava group was 89.8 (±25.4) μm, and the iTero group was 89.6 (±30.1) μm. No statistically significant difference was found in the effects among impression techniques (P=.185) CONCLUSIONS: Within the limitations of this study, digital and conventional impressions were found to produce crowns with similar marginal accuracy.

Enhanced aesthetics with all ceramics restoration

The demand for the dentist to achieve excellence in esthetics and function has driven modern advances in materials and restoration fabrication. The development of various casting alloys and precise casting systems has contributed to the successful use of metal-based restorations. However, patient requests for more aesthetic and biologically "safe" materials that have led to an increased demand for metal-free restorations. The following case presentation illustrates a successful aesthetic and functional application of this exciting computer-aided design/computer-aided manufacturing-digital zirconia-based system for a natural smile.

A rare case of impacted supernumerary premolar causing resorption of mandibular first molar

The management of patients with pain in today's general practice has become a major concern and sometimes this pain is related to some rare causes. A male patient aged 26 years reported with pain in the lower left molar region (36) and then an intra-oral periapical radiograph (IOPA), and orthopantomograph was taken. IOPA revealed the presence of supernumerary premolar causing pressure and root resorption of 36. Also, there was missing 21 and proximal decay in 11. Eleven was treated endodontically, and then bridge was done in relation to 11, 21 and 22. Lower anterior crowding was also present. The treatment plan was to extract 36 followed by orthodontic extrusion of the supernumerary premolar and also the correction of lower anterior crowding. Hidden approach (lingual orthodontics) was used as the patient was insisting upon the braces not being seen outside during the course of the treatment. Later all ceramic bridge was done in relation to 11, 21 and 22. Orthodontic tooth extrusion techniques offer excellent treatment options for Partially Impacted tooth. It is a well-documented clinical method for extruding sound tooth material from within the alveolar socket by light forces. The use of lingual technique for forced eruption enhance acceptance of orthodontic treatment by adults. The treatment of a young adult patient illustrates the importance of treatment planning from one discipline to another, communication among team members and the benefits of working together in an interdisciplinary approach

The comparative evaluation of the translucency of crowns fabricated with three different all-ceramic materials: an in vitro study

INTRODUCTION

All-ceramic crowns with different core materials of different strength and aesthetics are available in recent years. The aesthetics of the crown depends mainly on the shade and translucency. Clinician should be aware of the quality and characteristics of these materials so that they will be able to opt for good material for successful clinical use.

AIM AND OBJECTIVE

The aim of this study was to evaluate and compare the translucency of crowns fabricated with three different commercially available all-ceramic materials viz. Alumina - CAD-CAM Procera, Lithium disilicate - Pressable IPS e.max Press, Zirconia - CAD-CAM Lava.

MATERIALS AND METHODS

All-ceramic crowns (5 per each group and total of 15 samples) were made of Alumina - CAD-CAM Procera (Group I), Lithium disilicate - Pressable IPS e.max Press (Group II), Zirconia - CAD-CAM Lava (Group III) and veneered with their respective layering ceramic. Evaluation for the Translucency (CR=Yb/Yw) over the White (Yw) and Black (Yb) backgrounds at the Incisal, Middle, Cervical, Mesial and Distal thirds of each crown were done using the Spectrophotometer. The results obtained were statistically analyzed by Paired t-test (p<0.05) and Analysis of Variance (p<0.05) for the test of significance among the groups.

RESULTS

Significant differences in the contrast ratios were obtained among the three Groups (p<0.001). In this study, Group II Lithium disilicate-Pressable IPS e.max Press showed higher translucency (0.54). Group III Zirconia - CAD-CAM Lava showed the least translucency (0.75) and the translucency of Group I Alumina - CAD-CAM Procera (0.7) was in between both the groups.

CONCLUSION

Translucency of material gives fair idea to clinician for the choice of material in different zones during replacement and suitability for restoration in aesthetic zone. Selection of all ceramic system depends on the translucency needed for successful prosthesis of artificial tooth so that it mimics patient's natural dentition. The qualitative measurement of translucency will give the evidence for the clinicians during selection of high or low value translucent tooth for successful replacement. Lithium disilicate - Pressable IPS e.max Press is having better translucency in comparison with other two materials in our study.

Comparative analysis of transmittance for different types of commercially available zirconia and lithium disilicate materials

PURPOSE

Translucency and colour stability are two most important aspects for an aesthetic dental restoration. Glass ceramic restorations are popular amongst clinicians because of their superior aesthetic properties. In the last decade, zirconia has generated tremendous interest due to its favorable mechanical and biological properties. However, zirconia lacks the translucency that lithium disilicate materials possess and therefore has limitations in its use, especially in esthetically demanding situations. There has been a great thrust in research towards developing translucent zirconia materials for dental restorations. The objective of the study was to evaluate and compare the transmittance of a translucent variant of zirconia to lithium disilicate.

MATERIALS AND METHODS

Two commercially available zirconia materials (conventional and high translucency) and 2 lithium disilicate materials (conventional and high translucency) with standardized dimensions were fabricated. Transmittance values were measured for all samples followed by a microstructural analysis using a finite element scanning electron microscope. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P=.05).

RESULTS

High translucency lithium disilicate showed highest transmittance of all materials studied, followed by conventional lithium disilicate, high translucency zirconia and conventional zirconia. The difference between all groups of materials was statistically significant. The transmittance of the different materials correlated to their microstructure analysis.

CONCLUSION

Despite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.

Evaluation of air-particle abrasion of Y-TZP with different particles using microstructural analysis

BACKGROUND

This study evaluated the effect of air-particle abrasion with different particle sizes on the surface roughness and phase transformation of yttria-stabilized tetragonal zirconia ceramics (Y-TZP).

METHODS

Eighty-four Y-TZP discs of 15 mm diameter and 1.0 mm thickness were fabricated. The samples were divided into four groups (n = 21): (1) air-particle abrasion with 30 μm CoJet sand blast coating agent (CoJet, 3M ESPE); (2) 50 μm Al2O3 particles; (3) 110 μm Al2O3 particles; and (4) 250 μm Al2O3 particles. Each group was further divided into three subgroups each (n = 7) and treated for 5 seconds, 15 seconds and 30 seconds. Mean surface roughness was determined using a profilometer. The surfaces were analysed with a scanning electron microscope. XRD analysis was employed and the relative amount of the monoclinic phase was calculated. The results were statistically analysed by two-way analysis of variance (ANOVA, p < 0.05).

RESULTS

Air-particle abrasion with 250 μm Al2O3 particles for 30 seconds had the highest surface roughness (p < 0.001) and a significantly higher amount of monoclinic phase compared to air-particle abrasion with 30 μm, 50 μm and 110 μm particles (p < 0.001).

CONCLUSIONS

Duration and particle size of air-particle abrasion affects the roughness and phase transformation of Y-TZP. Longer treatment times with larger particles may result in degradation of material.

Effect of surface pre-treatments on the zirconia ceramic-resin cement microtensile bond strength

OBJECTIVE

To evaluate the influence of different surface treatments on the microtensile bond strength of resin cement to zirconia ceramic.

MATERIALS AND METHODS

Twelve cylinder-shaped (∅ 12×5.25 mm high) blocks of a commercial zirconium-oxide ceramic (Cercon® Zirconia, DENTSPLY) were randomly divided into 4 groups (n=3), based on the surface treatment to be performed: (1) airborne particle abrasion with 125 μm Al₂O₃ particles (S); (2) selective infiltration etching (SIE); (3) experimental hot etching solution applied for 30 min (ST) and (4) no treatment (C). Paradigm MZ100 blocks (3M ESPE) were cut into twelve cylinders of 4mm in thickness. Composite cylinders were bonded to conditioned ceramics using a resin cement (Calibra®, DENTSPLY), in combination with the proprietary adhesive system. After 24h bonded specimens were cut into microtensile sticks and loaded in tension until failure. Bond strength data were analyzed with Kruskall-Wallis and Dunn's Multiple Range test for multiple comparisons (p < 0.05). Failure mode distribution was recorded and the interfacial morphology of debonded specimens was analyzed using a scanning electron microscope (SEM).

RESULTS

Bond strength values achieved after SIE and ST treatment were significantly higher than after S treatment and without any treatment (p < 0.05). Premature failures were mostly recorded in the S group.

SIGNIFICANCE

Conditioning the high-strength ceramic surface with SIE and ST treatments yielded higher bond strengths of the resin cement than when zirconia ceramic was treated with airborne particle abrasion or left untreated.