Ceramic Crowns Research Articles

Impact of Digital Manufacturing Methods on the Accuracy of Ceramic Crowns.

The purpose of this study was to assess the accuracy of full coverage crowns produced by two manufacturing methods: additive 3D printing and subtractive milling utilizing three different predefined cement spaces. Six groups were allocated based on the manufacturing method and the predefined cement space: printed wax with a 20 µm space (PW1); printed wax with a 50 µm space (PW2); printed wax with a 100 µm space (PW3); milled wax with a 20 µm cement space (MW1); milled wax with a 50 µm cement space (MW2); milled wax with a 100 µm cement space (MW3); milled zirconia coping with a 20 µm cement space (MZ1); milled zirconia coping with a 50 µm cement space (MZ2); milled zirconia with a 100 µm cement space (MZ3). All fabricated specimens were scanned using an Identica Blue 3D scanner and saved as standard tessellation language (STL) files. A triple scan method was performed using 3-matic software to assess accuracy. The discrepancy values were recorded in micrometers, and the analysis was conducted using one-way ANOVA. The wax printing method, with a cement gap design of 100 μm, demonstrated a significant improvement in the accuracy compared to the other methods (P<.01). In contrast, the zirconia milling method exhibited significantly lower accuracy relative to the other techniques (P<0.01). Moreover, different cement spaces resulted in various accuracy levels but the only statistically significant difference was observed for the 100 µm cement space in the printed wax group. The additive 3D printing method exhibited greater accuracy than the subtractive milling approach. Furthermore, altering the cement gap was found to impact the accuracy of both techniques, albeit without statistical significance. The accuracy of each CAM technique was investigated in this study, highlighting the promising accuracy of 3D-printed patterns for the lost-wax technique over direct crown milling. However, all methods produced reliable and accurate crown restorations.

Finite-element investigations on the influence of material selection and geometrical parameters on dental implant performance

Abstract Dental implants provide functional and aesthetically pleasing dental replacements, but their longevity depends on biomechanical factors, physical characteristics, and patient variability. The present study used finite-element analysis to reveal the biomechanical response and potential modes of failure of dental implant systems subjected to normal occlusal loads. A generalized comparative assessment was carried out to measure the effect of the choice of crown material with zirconia, porcelain-fused-to-metal, and ceramic crowns. Such simulations showed complex patterns of stress distribution and deformation in the implant assembly with significant variation due to the mechanical properties of the crown material. Stiffer zirconia crowns magnified stress concentrations by 12.6, 10.8, 11.4, and 9.1% in the implant fixture, crown, cortical bone, and cancellous bone, respectively, compared with more compliant ceramic crowns. Furthermore, the maximal deformation of both the cortical and cancellous bone induced by zirconia crowns was higher by 21.1 and 19.2%, respectively, compared with the ceramic crowns. These results emphasize that the crown material properties are significant for controlling and modulation biomechanical load transfer, which plays a decisive role in the long-term durability and resistance to failure mechanisms such as interfacial debonding, bone resorption, and fatigue cracking. This study provides valuable information for optimizing implant designs and material selection that may improve clinical results, positively affecting patient satisfaction with dental implant therapy.

Effect of Thermal Mismatch on Fracture Characteristics of Porcelain Veneered Lithia-Based Disilicate Posterior Ceramic Crown

(1) Background: Dental glass–ceramics shrink during crystallization, complicating restoration manufacturing. Thermo-pressure molding was introduced to address this, with lithium disilicate crystals providing high strength. Residual tensile stresses can influence the chipping strength of single tooth crowns. (2) Methods: Insync dentine was layered onto three lithia-based disilicate core ceramics (Amber Press, IPS e.max Press) for microtensile bond strength tests. The Vickers test assessed the residual tensile stress and interfacial bonding. Porcelain-veneered posterior ceramic crowns were fabricated and subjected to axial loading, measuring fracture loads (three per group). (3) Results: A chemical bonding layer formed at the interface, which was thicker in the Insync-IPS e.max Press and increased with more firings. The ultimate tensile bond strength was 28.5 MPa for the four-times-fired Insync-Amber Press, similar to the twice-fired Insync-IPS e.max Press. No residual tensile stress was found in the Insync-Amber Press; the Insync-IPS e.max Press showed crack growth within 250 μm of the bonded interface. The average fracture resistance was twice as high for the Insync-Amber Press. (4) Conclusions: The Insync-Amber Press exhibited better thermal harmony with no crack growth, while the IPS e.max Press showed crack growth due to residual tensile stress. Insync-Amber Press posterior ceramic crowns had significantly greater fracture resistance than Insync-IPS e.max Press crowns.

Evaluation of Wear on Primary Tooth Enamel and Fracture Resistance of Esthetic Pediatric Crowns Manufactured from Different Materials

Background and Objectives: Advances in dental materials and CAD-CAM technology have expanded crown options in primary teeth due to their improved appearance and mechanical properties. Thus, this study aimed to assess the enamel wear and fracture resistance of prefabricated, milled, and 3D-printed esthetic pediatric crowns. Materials and Methods: The study involved 60 extracted maxillary second primary molars and 60 3D-printed resin dies, divided into six groups based on different crown materials (n = 10): prefabricated zirconia, prefabricated composite, milled composite, milled resin matrix ceramic, milled PEEK, and 3D-printed resin. Prefabricated crowns were selected after the preparation of the typodont mandibular second primary molar tooth, while milled and 3D-printed crowns were custom produced. The specimens underwent mechanical loading of 50 N at 1.6 Hz for 250,000 cycles with simultaneous thermal cycling. The 3D and 2D wear amounts were evaluated by scanning the specimens before and after aging. Then, the fracture resistance and failure types of the restorations were recorded. Results: The results showed that the milled PEEK group had superior fracture resistance compared to the other groups, while prefabricated zirconia crown group had the lowest value. Milled resin matrix ceramic crown group displayed the lowest 3D wear volume, while 3D-printed crown group showed the highest 2D wear. Conclusions: The restorative material type did not have a significant effect on the wear of primary tooth enamel. The fracture resistance of the tested materials differed according to the material type. Although the milled PEEK group showed the highest fracture resistance, all tested materials can withstand chewing forces in children.

Impact of liner treatment on the translucency of CAD/CAM multi-colored lithium disilicate and multi-layered zirconia implant-supported crowns, and evaluation of fracture strength of ceramic crowns.

This study aimed to evaluate the optical properties of liner-treated CAD/CAM Multi-colored lithium disilicate (Amber Mill Direct; AMD) and multi-layered zirconia (Omega multi; OM) implant-supported crowns, as well as their effect on the fracture strength of Ti or Zr abutments to which they were applied. After sintering AMD and OM ceramic blocks, they were classified into three groups: untreated, liner-treated, and liner-treated with added color. Optical properties were evaluated by analyzing color differences using background materials to assess translucency and the masking ability of liner-treated ceramics. Subsequently, the fracture strength of implant-supported crowns applied to Ti or Zr abutments was measured, and statistical analysis was conducted using Weibull statistics. Untreated AMD exhibited the highest translucency. Liner treatment reduced translucency in both ceramics, while color-added liner treatment increased translucency. Liner-treated AMD showed greater color difference compared to OM, whereas color-added liner treatment reduced the color difference. Fracture strength was highest in Ti abutment-OM crowns (548.03 N) and lowest in Zr abutment-AMD crowns (283.58 N). Additionally, the Weibull coefficient was over twice as high in Ti abutment-AMD crowns (m = 17.500). Color liners can adjust the high translucency of lithium disilicate ceramics to block discoloration, providing natural tooth-like color and enabling the creation of esthetic restorations. Furthermore, lithium disilicate ceramic crowns applied to Ti abutments exhibited high Weibull coefficients and fracture strengths.

Ceramic Crown for Abutment Reconstitution: A Case Report

Ceramic Crown for Abutment Reconstitution: A Case Report

Effect of Occlusal Cement Space on the Marginal and Internal Fit of Vertiprep Zirconia and Hybrid Ceramic Crowns. An In-vitro Study

Effect of Occlusal Cement Space on the Marginal and Internal Fit of Vertiprep Zirconia and Hybrid Ceramic Crowns. An In-vitro Study

Cutting efficiency of different dental diamond rotary instruments for sectioning monolithic zirconia and lithium disilicate crowns

BackgroundThe aim of this study was to determine the cutting efficiency of different diamond rotary instrument types for sectioning monolithic zirconia and lithium disilicate anatomical crowns.Materials and methodsThe study used 30 diamond rotary instruments divided into three groups: Zirconia cutting diamond bur (White Z), super coarse grit diamond bur (KBlack), and medium coarse grit diamond bur (KBlue); Two subgroups were assigned based on the crown materials including monolithic zirconia (5YSZ) and lithium disilicate (e.max) ceramics. The cutting efficiency was assessed by measuring the time required to fully section the crowns, followed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) of the dental burs before use and after every sectioned crown. A three-way ANOVA examined the effects of bur type, material type, and sectioning stage. If interaction exists, one-way ANOVA was used to compare the different subgroups, followed by the Tukey post hoc test. The significance level was assigned at α ≤ 0.05.ResultsThe results exhibited various cutting efficiencies among diamond rotary instruments and ceramic crown materials. White Z demonstrated superior cutting efficiency of zirconia crown compared with KBlack and KBlue for the first cutting cycles (p ≤ 0.05); the results tend to be more comparable at the third cutting cycle. However, the super coarse diamond bur exhibited higher efficiency in cutting lithium disilicate crowns than white Z and KBlue burs through all three cutting cycles(p ≤ 0.05). The diamond bur-cutting efficiency diminished after each use, irrespective of the bur type or the crown material (p ≤ 0.05); this was represented by the reduction of carbon and increased nickel matrix ratio after each bur usage.ConclusionWhite Z diamond bur showed higher cutting efficiency of zirconia in the first two cutting cycles; super coarse diamond bur is more efficient for cutting lithium disilicate crown in all of the cutting cycles. The amount of diamond on the burs reduced after each use, with no great impact on the material type when sectioning lithium disilicate and 5YSZ crowns.Clinical significanceThis study provides valuable insights for dental practitioners in selecting the appropriate diamond rotary instrument for crown sectioning. Practitioners can minimize the risk of damage and reduce the time required for crown removal, improving patient outcomes.

Full-mouth rehabilitation with lithium disilicate ceramic crowns in hypoplastic amelogenesis imperfecta: a case report and review of literature

BackgroundAmelogenesis imperfecta (AI) is a group of genetic disorders characterized by tooth discoloration and enamel defects. Patients with AI always exhibit generalized attrition and defective tooth structure, leading to the loss of occlusal vertical dimension (OVD). Appropriate rehabilitation is challenging and essential to improve patients’ aesthetics and function.Case presentationThis case report presents a comprehensive management of a 30-year-old woman with hypoplastic AI. A 52-month follow-up revealed satisfactory full-mouth rehabilitation performances of lithium disilicate ceramic crowns after clinical crown lengthening, with increased vertical dimension.ConclusionsPatients with severe hypoplastic AI require proper full-mouth rehabilitation. Using full-crown lithium disilicate restorations to increase the OVD by 2‒4 mm is a safe and predictable recommendation for such cases. In addition, patients with AI require complex and comprehensive management. The long-term effects of full-mouth rehabilitation with lithium disilicate ceramic crowns still necessitate further follow-ups.

Clinical Outcome of Indirect Bonded Porcelain Restoration Versus Full-Coverage Crown on Endodontically Treated Teeth in Posterior Areas: A Systematic Review.

The significant loss of tooth structure that occurs after dental caries and endodontic therapy is a common clinical challenge. Several methods were discussed in the literature to treat badly damaged teeth. This systematic review aims to compare the clinical outcomes of partial indirect bonded porcelain restorations to full-coverage crowns of endodontically treated teeth in posterior areas. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Data included in the review were identified through bibliographic research on electronic databases (PubMed/Medline, Google Scholar, Cochrane Library, and Web of Science). The strategy was applied by searching for randomized clinical trials (RCTs), cohort studies, and case-control studies using keywords (partial indirect bonded porcelain restoration, partial indirect bonded restoration, inlay and onlay, full convergent crown, and ceramic crown). Asa resultof a literature search through selected databases using the keywords, 88,421 papers were identified. A total of 671 articles were related and screened for inclusion and exclusion criteria. Four hundred and eighty-two articles that did not meet the inclusion criteria were excluded. A total of 189 full-text papers were assessed, and 20 articles were included in this study. Nineteen cohort studies and one case-control study were included and assessed in this review. This studyconcludesthat both full-coverage crowns and partial indirect bonded restorations demonstrate comparable survival rates. However, limited studies exist regarding partial indirect bonded restorations on endodontically treated teeth, indicating the need for further updated studies.

Static Loading of Different Intraradicular Preparation Depths of Trinia Endocrowns in Maxillary Canines.

The aim of this study is to compare the fracture resistance of canine teeth restored using TRINIA Endocrowns with three different types of preparations (2, 3, and 4 intracanal preparations). Thirty maxillary-extracted canines were collected. All teeth were fixed in orthodontic acrylic resin and decapitated at the level of the proximal cemento-enamel junction (CEJ). After being endodontically treated, specimens were distributed equally between 3 groups (n = 10) with different preparation depths (GT: 2 mm Intraradicular Preparation, GH: 3 mm Intraradicular Preparation, GF: 4 mm Intraradicular Preparation). Thirty TRINIA endocrowns were dry milled. After surface treatment, all endocrowns were bonded to their corresponding roots using Permaflo a dual-cure resin cement. Each specimen was then fixed in the lower part of a universal testing machine with a load cell of 5 KN, at an angle of 45 degrees to the tooth long-axis at 0.5 mm/min crosshead speed. Failure loads were recorded in Newton's. Data were recorded, organized, and statistically investigated. Shapiro-Wilk tests revealed that the data were not normally distributed. Descriptive statistics revealed a high mean fracture resistance of GH (647 N), then GT (475.6 N), and finally GF (353.9 N). The Kruskal-Wallis test revealed a significant difference that existed between the groups being studied (p = 0.036). TRINIA endocrowns with intracanal preparations of 2 and 3 mm provide more promising fracture resistance than those with intracanal preparations of 4 mm as a way of treating of root-canal-treated maxillary canines. TRINIA endocrowns (2 and 3 mm intracanal preparations) are as promising as fiber posts and all ceramic crowns in terms of fracture resistance. TRINIA endocrowns with 2 mm intracanal preparations are mostly reparable after failure, but those of 3 and 4 mm are mostly irreparable after failure. Modifying endocrowns to have intraradicular projections, simulating Nayyar core, may improve the success and longevity of endocrowns in anterior teeth. How to cite this article: Alahmad AM, Alenezi AY, Rayyan M, et al. Static Loading of Different Intraradicular Preparation Depths of Trinia Endocrowns in Maxillary Canines. J Contemp Dent Pract 2024;25(6):575-580.

Stress-strain state of an intraosseous dental implant under stress under unfavorable biomechanical conditions

Biomechanical conditions affect the stress-strain state of teeth, dentures, implants and surrounding tissues, however, some biomechanical processes in implants and covering prosthetic structures have not been sufficiently studied under different operating conditions. The purpose of the study. А comparative analysis of the maximum stresses in titanium implants, abutments and covering ceramic crowns under different biomechanical operating conditions. Material and methods. Three-dimensional mathematical modeling of the stress-strain state of the implant, abutment, crown was carried out using the SolidWork computer program in a model of an implant immersed in a segment of the mandible and covered with a ceramic crown. Load conditions: vertical or inclined 45° with a value of 150 N. Well-known indicators of the physical and mechanical properties of fabrics and structural materials were used. Adverse biomechanical conditions were simulated: a 30% reduction in the length, diameter, length and diameter of the implant; an abutment slope of 15° and 30°; bone resorption by 30% and 50%; increased load by 30%; occlusive supracontact; contact with bone tissue by 50% (immediate load). Results and discussions. In comparison with optimal biomechanical conditions, the stresses in the implant and the covering crown increase under vertical and inclined loads only with an increase in load and the presence of occlusive supracontact. An increase in stresses only in the implant occurs with a decrease in the diameter of the implant, a combined decrease in the diameter and length of the implant, with an abutment tilt, resorption of periimplant bone tissue, incomplete contact of the implant with bone tissue under immediate load. Stress reduction in the implant and the covering crown occurs when the length of the implant decreases. Conclusions. Unfavorable biomechanical conditions in most cases lead to an increase in stresses in the implant, especially with inclined loading; the decrease in stresses in the implant with a decrease in the length of the implant is most likely due to an increase in stresses in the surrounding bone tissue.

The effect of two preparation designs on the fracture resistance and marginal adaptation of two types of ceramic crowns using CAD/CAM technology (In vitro study)

BackgroundRecently, prosthodontic approaches involve more conservative procedures that include less invasive finish line preparations that use less ceramic thickness.Aim of the studyThis in vitro study aimed to evaluate the effect of vertical preparation and modified vertical preparation designs on the marginal adaptation and fracture resistance of two types of ceramic crowns using CAD/CAM technology.Materials and methodsTwo typodont maxillary first premolars were embedded in acrylic resin. Forty positive replicas of epoxy resin dies were used that were divided into two groups depending on the preparation design (n = 20); Group V (Vertical): dies with feather edge finish line and Group MV (Modified vertical): dies with feather edge finish line, where a reverse shoulder of 1 mm depth was placed on the buccal surface 1.5 mm from the occlusal surface. Each group was further subdivided into two subgroups according to the type of ceramic material (n = 10): Subgroup Va and subgroup MVa for lithium disilicate (e.max CAD) and subgroup Vb and subgroup MVb for zirconia (zolid ht+). Crown restorations were made with CAD-CAM technology. The marginal adaptation was assessed using a stereomicroscope both prior to cementation and after cementation and aging. Fracture resistance was tested with a universal testing machine, and the data were statistically analyzed.ResultsMarginal adaptation showed no significant differences between subgroups before or after cementation and aging. Three-way ANOVA indicated that preparation design (p = 0.516) and material (p = 0.269) had no significant effect, but cementation had a significant effect (p < 0.0001) on the marginal adaptation. According to two-way ANOVA test, Subgroup (MVb) showed the highest result followed by subgroup (Vb) and subgroub (MVa) and the least was subgroub (Va). Fracture modes showed no significant differences among the subgroups (p = 0.982).ConclusionsMarginal adaptation of lithium disilicate and zirconia crowns remained clinically acceptable regardless of preparation design. While the modified vertical preparation with a reverse shoulder notably enhanced the fracture resistance of both materials, with zirconia demonstrating superior fracture resistance compared to lithium disilicate with average values exceeding premolar biting force.

Conventional all ceramic crowns versus CADCAM all ceramic laminates for esthetic rehabilitation of teeth with dental fluorosis: A 5 year follow-up study

Conventional all ceramic crowns versus CADCAM all ceramic laminates for esthetic rehabilitation of teeth with dental fluorosis: A 5 year follow-up study

Evaluating Retention of Onlay Versus Complete Coverage Using E.Max-Restoration

This study compared the retention of different types of indirect restorations (only or full coverage) utilized on endodontically treated molars. Fourteen patients requiring restoration of endodontically treated molars were randomly allocated into two groups (n = 7) according to the type of restoration used. lithium disilicate ceramic crowns were given to the control group. While lithium disilicate ceramic onlays were given to the intervention group. The heat pressing technique was used for the fabrication of both restorations. Following the final cementation with adhesive resin cement, the restoration was assessed at three, six, twelve, and twenty-four months using the modified USPHS criteria. Statistical analysis was performed using the chi-square test. Results: At all intervals, there was no statistically significant difference in retention (P &gt; 0.05) between the two tested groups. Both groups showed comparable results, with full coverage showing somewhat higher retention after 2 years. Regardless of the type of restoration, the emax-press produced high clinical performance in terms of retention. Compared to full coverage, onlay has proven to be a trustworthy substitute.

Impact of Cut-out-rescan and Data Exchange by Over-scanning Techniques on Marginal Fit of CAD/CAM Lithium Disilicate Crowns.

Evaluate the impact of adjustment procedures - cut-out-rescan (COR) and data exchange by over-scanning (DEOS) techniques - through CAD/CAM software on the marginal fit outcome of ceramic crowns. Twenty-eight de-identified teeth were adapted in a mandibular typodont set. Tooth #19 was prepared for a lithium disilicate crown and seven groups, G0 to G6 (n=10), were created based on the rescanned areas (mesial and/or buccal) on the typodont using an intraoral scanner through COR or DEOS techniques. A digital workflow was used to design and mill 70 crowns according to the groups. Each crown was temporarily cemented on tooth #19 and scanned with micro-computed tomography to measure the marginal fit. The data were analyzed statistically by the Kruskal-Wallis test followed by the Mann-Whitney test to compare the groups pairwise as a post-hoc (α=0.05). Statistically significant differences were found for vertical misfit (μm) between the groups for Marginal Gap Buccal (MGB) and Marginal Gap Mesial (MGM) (p=0.003 and p=0.029, respectively). No significant difference was found for Finish Line Buccal (FLB) and Finish Line Mesial (FLM) (p=0.062 and p=0.092, respectively). G3 (COR buccal and mesial) had the highest MGB (57.75 μm), statistically different from all other groups. G4 (DEOS buccal) (41.60 μm) was different from G6 (DEOS buccal and mesial) (44.21 μm) (p=0.023). For MGM, G0 (control) (53.96 μm) was different from G5 (DEOS mesial) (45.76 μm) and G6 (DEOS buccal and mesial) (48.56 vm) (p=0.013 and p=0.041, respectively) and G2 (COR mesial) (58.43 μm) was different from G5 (DEOS mesial) (45.76 μm) (p=0.016). Despite a statistically significant difference in certain groups for both techniques, COR and DEOS techniques are viable options for image editing during acquisition. Lithium disilicate crowns can be produced with satisfactory marginal gap values utilizing a chairside CAD/CAM system.

Impact of common social habits on optical properties of lithium disilicate glass ceramic crowns: An in vitro study

Statement of the problemPatient stratifications considered the stability of color and treatment longevity are key success of restoration. Daily consumption of colored beverages, such as coffee, tea, and soft drinks, as well as the use of globally consumed materials, such as smokeless tobacco (ST), snuff, Khat, and Yerba mate, can change the color of restorative materials, such as lithium disilicate glass ceramics (LDGC). These changes can ultimately lead to treatment failure. PurposeThis in vitro study aimed to evaluate color changes, translucency, and opalescence of full anatomical LDGC crowns exposed to commonly used and potentially colorant solutions. Materials and methodsNinety LDGC specimens/crowns were prepared and divided into nine groups according to immersion solution (control, Saudi Coffee, Cola, Khat, Yerba mate, Nescafe, ST Snuff, and Mixed Fruit Juice). The specimens were immersed in colorant solutions for 15 days with alternating twice daily at 37 °C. Color parameters were measured with a spectrophotometer and calculated using two backgrounds (black and white). Data were subjected to ANOVA followed by the Student t-test and Bonferroni test at a significant difference level (α = 0.05). ResultsThe greatest color change (ΔE*) among groups after immersion was observed in Yerba mate (7.6 ± 1.6). The mean difference of before and after staining within Yerba mate group was 3.14 ± 1.6 (p = 0.001). Translucency mean values of groups after immersion into staining media were ranging between 7.6 ± 1.2 and 9.1 ± 2, showing a slight decrease compared with pre-staining values but was not significantly different. Immersion in Mixed Fruit Juice significantly reduced opalescence (7.4 ± 1.9) compared to (8.8 ± 1.7) before staining. ConclusionThe findings confirm that appropriate user guidance helps to preserve both translucency and opalescence as well as prevent color changes. This can improve patient compliance and promote treatment longevity.

Retrospective, Multi-center, Cohort Study Evaluating Clinical, Technical, Biological, and Esthetic Outcomes of Implant Supported Zirconia Single Crowns Cemented on Titanium-base Abutments: 7-year Mean Follow-up.

To retrospectively evaluate the long-term clinical, technical, biological, and esthetic outcomes of implant supported single zirconia crowns (ISCs) intraorally cemented to Ti-base hybrid-abutments up to 16 years after placement. A total of 63 ISCs (Xive S, Camlog Screw Line, Replace Select TC NP, Branemark MK II, and 3i Osseotite) were evaluated in 36 patients at two different centers. Original Ti-bases were selected and zirconia meso structures and zirconia crowns were designed using CAD/CAM software and then milled from partially stabilized zirconia blocks. After the meso structures were cemented extraorally onto the Ti-bases, the ceramic crowns were intraorally luted to the hybrid abutments. The Ti-base ISC restorations were followed up for up to 16 years, and their clinical, biological, and esthetic outcomes were recorded at distinct time points (T1; T2) at three-year intervals. 36 patients (18 men, 18 women) received 32 ISCs in the anterior region and 31 in the posterior region of the maxilla and mandible. The mean follow-up of the Ti-base ISCs was 6.93 ± 2.60 years. The mean follow-up of the implants amounted to 8.11 ± 3.26 years. No implants were lost during follow-up, resulting in a cumulative implant survival rate of 100%. Abutment screw loosening was observed in two ISCs after one year in service. The overall cumulative restorative survival rate of the Ti-base restorations reached thus 96.83%. At T2 follow-up 24% of the ISCs exhibited an increase in PD despite maintaining clinically healthy peri-implant tissue. An 11% increase in BOP and a 3.17% decrease in PI were recorded. Despite spectrophotometrically measured ΔE values indicating visible discoloration of some restorations and their peri-implant soft tissue, a low incidence of esthetic complications was observed with an average PES/WES score of ≥ 12. No correlation was found between PES (R &#61; -0.25; p &#61; 0.27) and WES (R &#61; -0.18; p &#61; 0.43) scores and digital shade determination. The results of the present retrospective, multicenter, cohort study indicate satisfactory clinical outcomes for intraorally cemented single zirconia crowns (ISCs) supported by Ti-base hybrid abutments. An overall esthetic superiority of Ti-base ISCs could not be confirmed.

Fracture Resistance of Posterior Milled Nanoceramic Crowns after Thermomechanical Aging.

Fracture resistance is an important parameter used to predict the performance of indirect dental restorations. The purpose of this in vitro study was to assess the fracture load of posterior milled nanoceramic crowns, in comparison with the lithium disilicate crowns, after fatigue loading, for two different restoration occlusal thicknesses. Forty test metal dies were fabricated by duplicating a master metal model consisting of an anatomic abutment preparation of the maxillary first premolar for a single crown. The dies were divided into two groups of 20 each for the fabrication of nanoceramic (Lava Ultimate) and lithium disilicate (IPS e.max CAD) single crowns. Each material group was further divided into two sub-groups of 10 dies each, based on crown occlusal thickness, of 0.5-mm and 0.75-mm (n = 10). Dental Type V stone dies poured from polyvinyl siloxane impressions of the test metal dies were laboratory scanned in order to design and mill 40 ceramic crowns. The crowns were cemented on to the test metal dies with a self-adhesive resin luting cement. All crowns were thermocycled (2500 cycles) and mechanically loaded (250,000 cycles) in a chewing simulator followed by static loading until failure, and the values noted. The data were statistically analyzed by 2-way ANOVA and Tukey HSD post-hoc multiple comparison tests (α = 0.05). The mean fracture loads ranged from 1022 to 1322 N for nanoceramic crowns and from 1145 to 1441 N for the lithium disilicate crowns. Two-way ANOVA revealed insignificant differences between the nanoceramic and lithium disilicate crowns (p > 0.05) in terms of fracture load. Significant differences were noted in the fracture resistance of crowns based on occlusal thickness (303 N; p = 0.013) regardless of the material used. Multiple comparisons by Tukey HSD post-hoc test showed insignificant differences between the four material-occlusal thickness groups (p > 0.05). The nanoceramic crowns were found to be comparable with lithium disilicate crowns in terms of fracture load. The mean fracture loads of all of the tested crowns were within the normal physiological masticatory load limits. Based on the fracture-resistance results, nanoceramic crowns seem to be suitable for clinical use for the tested occlusal thicknesses.

Influence of crown-lengthening surgery on teeth rehabilitated with ceramic single crowns: A 12-month prospective clinical study

ObjectiveTo compare the clinical periodontal parameters of teeth restored with a single ceramic crown, with and without crown lengthening procedure. MethodsThis prospective, longitudinal, controlled, and single-blinded clinical trial involved 22 patients with a total of forty-one teeth with ceramic crowns. The teeth were divided into two groups: test (n = 21), comprising teeth rehabilitated post crown-lengthening surgery, and control (n = 20), comprising teeth rehabilitated without crown-lengthening surgery. Plaque index (PI), gingival index (GI), probing depth (PD), bleeding on probing (BoP), and clinical attachment level (CAL) were compared between groups (surgically treated and non-surgically treated) and within each group for each type of site (treated -tt; adjacent – ad; and nonadjacent - nad). Additionally, gingival phenotype (GP), gingival recession (GR), and keratinized tissue width (KTW) were also assessed post- restoration. Statistical analyses used a significance level set at 5 %. ResultsPI, GI, and BoP were reduced, but no statistically significant differences were observed within each group or between groups for most follow-up periods. CAL of the TT sites was consistently higher in the test group, and PD was also higher in the test group (p < 0.05), except at T3. adPD, nadPD, adCAL, and nadCAL demonstrated no significant differences between groups and periods. A significant association was identified between GP and the occurrence of GR, with the thick-flat phenotype demonstrating less association with GR, regardless of whether crown lengthening was performed or not. ConclusionCrown-lengthening surgery in rehabilitated teeth does not significantly affect PI and GI after 12 months. Although crown-lengthening surgery affected PD and CAL in TT sites, it did not affect adjacent and non-adjacent sites. Clinical relevanceThese findings emphasize the importance of considering individual patient factors and the potential impact on periodontal tissues when planning crown-lengthening surgery. Clinicians must have a comprehensive understanding of the dynamics of the periodontal tissues involved in restorative treatments to optimize the procedure, increase success rates, and minimize potential complications.