Types Of Crowns Research Articles

In vivo evaluation of the enamel wear of primary molar against four types of crowns using the intra-oral scanner

BackgroundPrimary tooth wear is a common phenomenon that affects chewing ability, dental sensitivity, aesthetics, and occlusion. This study was conducted to compare the antagonistic enamel wear of primary molars opposed to four different crown materials.MethodsForty lower second primary molars of children aged 4–8 years were allocated into 4 groups: Group 1 (n = 10): received stainless steel crowns; Group 2 (n = 10): received prefabricated commercially available zirconia crowns (NuSmile®); Group 3 (n = 10): received locally manufactured zirconia crowns created via the CAD/CAM system; and Group 4 (n = 10): received locally manufactured hybrid ceramic (Vita Enamic®) crowns created via the CAD/CAM system. All the crowns were cemented with resin-modified glass ionomer cement. The upper arch was scanned with a 3D intraoral scanner immediately (baseline), 6 months, and 1 year after crown cementation to evaluate the wear of the natural enamel of the antagonistic primary molar. The resultant scans were compared via Exocad software to measure the amount of linear wear of the mesiopalatal cusp of the primary upper second molar.ResultsThe analysed data revealed statistically significant differences between the studied groups. The highest mean wear was detected in the CAD/CAM zirconia crown group, followed by the NuSmile zirconia crown group and then the CAD/CAM hybrid crown group, and the lowest mean wear was detected for the stainless-steel crown group.ConclusionCompared with stainless steel crowns, aesthetic crowns cause more wear in the antagonistic primary molar enamel. CAD/CAM zirconia crowns induce the greatest amount of wear, followed by NuSmile zirconia crowns. The CAD/CAM hybrid crown is an aesthetic tooth-coloured crown that causes less wear of the opposing enamel than zirconia crowns do.Trial registrationThe ClinicalTrials.gov Protocol Registration and Results System (PRS) has this RCT registered as (NCT06456879) on 07/06/2024.

Microleakage of luting cements in CAD/CAM pediatric zirconia crowns: an in vitro study

The durability of pediatric zirconia crowns for primary teeth is influenced by the choice of luting cement, with the effectiveness of the cement being directly correlated to its ability to reduce microleakage. This in vitro study aimed to assess and compare the microleakage of custom-made zirconia crowns (CZCs) and prefabricated zirconia crowns (PZCs) on primary maxillary incisors when luted with self-adhesive resin cement, resin-modified glass ionomer cement (RMGIC), and bioactive cement. Sixty primary maxillary incisors were prepared and allocated into two groups, each corresponding to the two types of crowns. These groups were further divided into three subgroups each to test the different luting cements. Following the cementation process and thermocycling, the specimens were immersed in a 2% methylene blue solution for microleakage evaluation. The analysis involved sectioning the teeth and examining them under a stereomicroscope. Statistical analysis, using two-way ANOVA and post hoc Dunnett T3 tests (p < 0.05), revealed significant differences in microleakage among the cements. The study found that PZCs luted with RMGIC showed the highest level of microleakage, whereas those luted with bioactive cement exhibited the lowest, positioning bioactive cement as the preferable choice for minimizing microleakage. This finding illustrates the critical importance of selecting appropriate luting cements to optimize the clinical outcomes of zirconia crown restorations in pediatric dentistry, focusing on reducing microleakage to ensure the restoration’s durability and success.

Trueness and adaptation of screw-retained implant-supported monolithic zirconia crowns fabricated using 3-dimensional gel deposition

Implant-supportedmonolithic zirconia restorations manufactured using the additive 3-dimensional (3D) gel deposition technique have been introduced. However, studies determining the trueness and adaptation of implant-supported crowns made with the technique are lacking. The purpose of this in vitro study was to evaluate the trueness and adaptation of implant-supported zirconia crowns fabricated using additive 3D gel deposition in comparison with zirconia crowns made with the widely used subtractive milling technique. Crowns were fabricated for wide-diameter titanium implants and wide-neck abutments. Self-glazed zirconia (SGZ) crowns were fabricated using 3D gel deposition (n=10) and from 2 brands of zirconia blanks, Wieland and Upcera, using subtractive milling (WMZ and UMZ, n=10). All crowns were digitalized by a scanner, and then 3D deviation analysis was applied. The trueness was assessed by root mean square (RMS). Marginal and internal adaptations were evaluated using the direct-view technique (DT) and replica technique (RT). The results were analyzed by using the 1-way ANOVA and Kruskal-Wallis statistical tests (α=.05). The RMS and marginal discrepancy of SGZ exhibited the lowest values among the 3 groups (P<.05), and the 2 types of milled zirconia crowns had comparable RMS and marginal discrepancy values (P>.05). The internal discrepancy values of SGZ were significantly lower than those of WMZ and UMZ in all regions (P<.05). Compared with the WMZ, UMZ showed comparable internal discrepancy values in the axial and axio-occlusal transition regions (P>.05) but had significantly lower internal discrepancy value in the occlusal region (P<.05). The adaptation of 3 types of wide-diameter implant-supported zirconia crowns can meet the clinical requirements. Compared with the subtractive milling process, 3D gel deposition produced implant-supported zirconia crowns with improved trueness and adaptation.

Thermomechanical aging effects on vertical marginal gap and fracture resistance: a comparative study of Bioflx and traditional pediatric crowns

BackgroundVarious types of crowns are used for full-coverage restoration of primary teeth affected by caries, developmental defects, or after pulp therapy. Prefabricated Stainless Steel and Zirconia crowns are commonly utilized. Bioflx crowns, which blend the properties of Stainless Steel and Zirconia, provide a flexible and aesthetically pleasing alternative.AimThis study aimed to evaluate the vertical marginal gap and fracture resistance of Bioflx pediatric crowns compared to Zirconia and Stainless Steel crowns following thermomechanical aging.MethodsThis in-vitro study was conducted using mandibular second primary crowns of three different materials (n = 30). Crowns were divided into three groups; Zirconia crowns group (n = 10, Nu Smile, USA), Bioflx crowns group (n = 10, Nu Smile, USA) and Stainless Steel crowns group (n = 10, Nu Smile, USA). The crowns were cemented onto standardized acrylic resin dies and subjected to thermomechanical aging. Vertical marginal gap measurements were obtained using a USB digital microscope with an integrated camera, while fracture resistance was assessed with a universal testing machine. Data were analyzed for outliers and tested for normality using the Shapiro-Wilk or Kolmogorov-Smirnov tests, with statistical significance set at 0.05.ResultsSignificant differences were observed in the vertical marginal gaps among the groups after cementation and thermomechanical aging (P = 0.013 and P = 0.001, respectively). Zirconia crowns exhibited the largest average marginal gap, followed by Bioflx and Stainless Steel crowns. Stainless steel crowns demonstrated the highest fracture resistance, followed by Bioflx crowns, while Zirconia crowns showed the lowest.ConclusionsBioflx crowns exhibit the largest vertical marginal gap but show greater fracture resistance compared to Zirconia crowns, although they are still less resistant than Stainless Steel crowns after undergoing thermomechanical aging.

Examination of the Effectiveness of Fruit Thinning in the Case of Idaho and Gala Must Early Apple Varieties

Abstract Apple (Malus domestica Borkh.) is the most important fruit in the EU. The total yield is more than 11 million tons.year-1, 15% of which is that of the early apple varieties. Several papers have already been published on the efficacy of crown and fruit thinning in the 20th century. Nowadays, hybrid varieties and intensive crown types are used in modernized systems. Our research was carried out in a Hungarian orchard during two cultivation periods. We studied two early apple varieties (Idaho, Gala Must) to determine how fruit thinning affected the quantity and quality of fruits. We found that the effectiveness of non-thinned technology is similar or slightly better compared to fruit thinning, after the second harvest. The average yield of Idaho apples per tree per harvest was 35.9 vs. 24.8 kg, while that of Gala Must was 50.8 vs. 59.2 kg (with thinning vs. without thinning). To assess quality, we measured water-soluble sugars, NO3 -, NO2 and vitamin C content. Immediately, after the harvest, a surprisingly high vitamin C content was found in the fruits (4.4 mg.100 g-1 on average), which, however, decomposed after 3 months of storage. We also determined the pathway of the decomposition of vitamin C.

Crown control in a pair of cavitation bubbles close to a free surface: A numerical study

When a cavitation bubble re-expands near the surface of a liquid, an axisymmetric crown forms around the jet that is initially produced. Controlling this crown is essential if the first jet is to be used in engineering applications such as laser-induced transfer (LIT). Herein, we introduce a second cavitation bubble to control the formation and growth of the crown. Numerical simulations were performed using the compressibleInterIsoFoam solver within the open-source platform OpenFOAM, incorporating a geometric volume-of-fluid approach for tracking interfaces. Detailed analysis showed that a reversal in curvature across the concave interface indicates the moment of crown formation, and this is induced by flow focusing during bubble contraction or momentum transfer from a second expansion. In the presence of the second bubble, the crown type can be classified as either enhanced or inhibited in comparison with a single-bubble scenario. The velocity of crown formation, vcf, is defined to describe the crown type, and a parametric study of crown types was conducted based on the dimensionless stand-off distances, γ1 and γ2. The findings of this study offer new insights into the field of LIT.

Comparison of polishing methods for two types of monolithic all-ceramic crowns after occlusal adjustments: Polishing paste versus glazed porcelain.

This study compared the effects of two surface preparation methods on two types of zirconia. Immediately prior to the placement of a monolithic zirconia crown, its morphology may be modified using a rotary cutting instrument for occlusal adjustments. The crown surface is scratched during the grinding process and, thus, requires polishing. Simplified zirconia crowns of 3Y and 5Y were fabricated and used as specimens. The surface roughness and gloss of the occlusal surfaces of specimens were measured and compared when a polishing compound was used after polishing points and when a silica-based coating was sintered. No significant differences were observed in surface roughness between 3Y and 5Y zirconia. The use of polishing compounds was effective because polishing points alone only resulted in a level of surface roughness that may cause wear on antagonist teeth. Although the silica-based coating improved surface properties, the polishing compound more effectively improved surface roughness.

INFLUENCE OF ABUTMENT MATERIAL, CEMENT THICKNESS, AND CROWN TYPE ON THE FINAL COLOR OF IMPLANT-SUPPORTED RESTORATIONS.

To evaluate the influence of abutment material, cement thickness, and crown type on the esthetics of implant supported restorations. In total, 60 specimens were prepared to represent six abutment groups: Group PA &#61; pink-anodized Ti; Group GA &#61; gold-anodized Ti; Group T &#61; nonanodized Ti; Group H &#61; hybrid (Ti &#43; zirconia); Group P &#61; PEEK (Ti &#43; PEEK); and Group C &#61; composite resin (control). Crown specimens (n &#61; 120) were obtained from Vita Enamic (VE) and Vita Suprinity (VS). Two cement thicknesses (0.1 and 0.2 mm) were used. The color values of crown configura:ons were measured and ΔE00* values were calculated. Statistical analyses included were Shapiro Wilk, three-way ANOVA, and Tukey HSD tests (P ≤ .05). Abutment (P < .001) and crown materials (P &#61; .001) had a significant effect on ΔE00* values, while cement thickness did not. Groups PA and H resulted in significantly lower mean ΔE00* values than other abutments, whereas Group T revealed the highest. Unlike VS, cement thicknesses created a significant difference on the ΔE00* values for VE (P ≤.05). Pink-anodized Ti or hybrid abutments for VE and pink- or goldanodized Ti for VS seem to be better options, in terms of color change. Cement thickness of 0.1 mm resulted in higher ΔE00* value than 0.2 mm for VE (P ≤ .05).

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.

Anterior Crowns in Paediatric Dentistry

Abstract Primary dentition exposed to caries mainly affects the primary maxillary anterior teeth and primary molars. Restoring primary maxillary anterior teeth requires material to be retentive, resistant to fracture and should be esthetic. Anterior crowns thus help in phonation and aesthetics. Crowns available for restoration of primary anterior teeth include those that are directly bonded to the tooth and those crowns that are luted onto the tooth such as stainless steel crown and zirconia crowns. Over the years, many types of crowns have been developed and advanced to aid the clinician in rehabilitating deciduous anterior teeth. This review is to discuss various anterior crowns available for restoring anterior primary teeth.

Qualitative surface roughness of lithium disilicate endo-crown for pulpotomized primary molars

Rehabilitation of pulpotomized primary molars with an appropriate restoration is essential for recovering function and safeguarding the durability of the treatment. This study aimed to assess and compare the surface roughness of stainless steel (ST) crowns, zirconia (ZR) crowns, fiberglass (FG) crowns, and lithium disilicate (LD) endo-crowns as a restoration for pulpotomized primary molars also, evaluating the surface roughness of their antagonists. Sixty pulpotomized primary mandibular first molars were used for qualitative surface roughness evaluation and divided into four groups (n = 15/group) according to the crown type (group-ST, group-ZR, group-FG, group-LD). While the other sixty sound, unprepared primary maxillary first molars were used for evaluation of their surface roughness against the tested crowns. Specimens’ preparation and cementation were carried out according to each crown type and manufacturer’s instructions. The surface roughness was done using a two-body wear test. The data were statistically analyzed. All tested crowns showed an increased change in surface roughness, except group-ZR, which had the least change in surface roughness after mechanical wear with no statistically significant difference(P = 0.681). All crown types significantly increased the surface roughness of their antagonists after mechanical wear, except group-ST which showed insignificant affection (p ≥ 0.05). Zirconia crowns and lithium disilicate endo-crowns had the least change in surface roughness compared to other groups while SSCs showed the least tooth loss in the antagonist enamel.

Effect of the scanner type on the marginal gap and internal fit of two monolithic CAD/CAM esthetic crown materials: An in vitro study.

The durability of indirect restorations is significantly influenced by marginal adaptation and internal fit. The use of computer-aided design/computer-aided manufacturing (CAD/CAM) with digital impressions has reduced dental prosthesis fabrication errors, improving the long-term survivability of the restorations. The present study assessed the impact of intraoral and extraoral scanning methods on the marginal adaptation and internal fit of 2 different types of monolithic crowns manufactured using CAD/CAM. A total of 40 three-dimensional (3D) resin-printed dies were randomly assigned to 2 groups based on the type of crown material (n = 20 per group). Each group was divided into 2 subgroups (n = 10 per group) according to the die-scanning technique: subgroup A, scanned using the intraoral scanner (IOS) Primescan; and subgroup B, scanned using the extraoral scanner (EOS) inEos X5. The digitized photos were converted into a 3D virtual crown design using CAD software. The internal discrepancy values, and the marginal gap between the 3D resin-printed die and the crown were assessed using a ×50 digital microscope. The data was checked for normality with the Kolmogorov-Smirnov test, and the Mann-Whitney U test was used to compare the tested groups. The collected data was analyzed at a significance level set at p < 0.05. The different scanning techniques used had a statistically significant effect on the vertical marginal gap and the internal fit [μm] (p < 0.05). As far as the crown materials are concerned, BRILLIANT Crios showed a significantly higher marginal gap as compared to Tetric CAD when scanned with inEos X5 (p = 0.004), whereas the differences were insignificant with regard to the internal fit (p > 0.05).The crown parameters tested with both scanning systems were within the clinically acceptable ranges. Scanning methods and crown materials had an impact on the internal fit and vertical marginal gap of monolithic crowns.

Comparative Evaluation of Polymethyl Methacrylate and Thermoforming Crowns as Semipermanent Crowns in Primary Molars: An In Vivo Study.

The present randomized clinical trial is aimed at evaluating clinical efficiency of two different types of esthetic crowns-polymethyl methacrylate crowns and vacuum formed thermoformed crown as an alternative to full-coverage coronal restoration for deciduous molars. A total of 45 primary molars in pediatric patients were selected using randomization and split into three groups based on the technique used for preparation of crowns: group I-polymethyl methacrylate crowns; group II-thermoformed crown; and group III-stainless steel crowns (SSC). All crowns were clinically and radiographically evaluated at baseline, 1st month, and 3rd month for gingival health, retention, marginal integrity, proximal contacts, occlusion, alignment, and staining. The data was tabulated and analyzed by Statistical Package for the Social Sciences (SPSS) Version 23.0 software. The intergroup comparison was done by Kruskal-Wallis test, analysis of variance (ANOVA), and Mann-Whitney U test for continuous data. The intragroup comparison was done by Friedman test and Wilcoxon signed-rank test for categorical data. All p-values < 0.05 were considered statistically significant. With regard to the parameters of plaque score, gingival index score, occlusion, interproximal contacts, retention, alignment, and marginal adaptation, no statistical significance was noted between the three groups. However, with regard to the discoloration (staining) when the polymethyl methacrylate acrylic (PMMA) group was compared with thermoforming group, statistical significance was noted in 1st month with p-values of 0.04 and 0.03, respectively. On intragroup comparison, statistically significant values were obtained in SSC group for plaque score and thermoforming group for gingival index score. The study concluded that the PMMA and thermoforming crowns can be used as an alternative to SSC for restoring the primary molars as they showed equivalent results to that of standard SSC. Matha N, Kumar KS, Reddy BVT, et al. Comparative Evaluation of Polymethyl Methacrylate and Thermoforming Crowns as Semipermanent Crowns in Primary Molars: An In Vivo Study. Int J Clin Pediatr Dent 2024;17(S-1):S43-S54.

Crowns and Bridges Failure: Reasons and Type of Disassembly

Background: Crowns and fixed partial dentures are widely used for esthetics and function all over the world. During their service life such prostheses fail for various reasons where a need arise for removal or disassembly. Objectives: Objective of the study was to determine the reasons and types of crown and fixed partial denture disassembly.Materials and Methods: This cross-sectional study was conducted at Prosthodontics Department, Peshawar Dental College, Peshawar from April 1st 2022 to September 28th 2023. A total of 140 patients including males and females, who reported to department for disassembly of their failed metal-ceramic crowns and bridges, were included in the study. Fixed prostheses already decemented and who reported for re-cementation were excluded. Before performing disassembly of prostheses data was recorded about the age, gender, service life of prosthesis, location in either arch, place of preparation and reasons for removal. At the end technique of removal was observed to categorize it as conservative, semi-conservative and destructive. Frequencies and percentages were calculated for various variables of the study.Results: The study had 46% males (n=65) and 54% female (n=75) with a ratio of 0.85. Patients had an age ranging from 20 to 65 years (mean 44 years, SD ± 13.8 years). Failed crowns were more than bridges. Failed prostheses were found more in mandibular arch (59%, n=83) and mostly in posterior segments (74%, n=103) of arches. Majority of prostheses were porcelain fused to metal and biological failure (66%, n=93) was the main reason for prosthesis disassembly. In more than two thirds of cases prostheses were removed conservatively. Conclusions: Carious and pulpal involvement of abutments teeth was the main reason for removal of majority of porcelain fused to metal restorations. In majority of cases disassembly was performed conservatively.Keywords: Crown/bridge disassembly, Fixed partial dentures, Prosthesis failure, Survival of crown/ bridges

Survival analysis of teeth following clinical crown lengthening and crown insertion procedures up to 14 years: A retrospective cohort study.

The purpose of this study was to conduct survival analysis of teeth following clinical crown lengthening procedures (CLPs) and crown insertions via a retrospective cohort study. Patient- and tooth-related data were collected from 268 participants who received CLPs from 2009 to 2015. The Kaplan-Meier curve and the log-rank tests were used to estimate the probability of survival and compare the survival probabilities among different variables. A Cox multivariate proportional hazard regression model was used to investigate the collective effects of root canal treatment (RCT) and the types of opposing dentition. The rate of tooth loss was 21.6% during the observation period from 1 to 14 years, with 58 teeth extracted. The most attributable reason for tooth extraction was coronal tooth fracture, followed by endodontic failure such as root fracture. The survival probability was 0.87 at 5 years and 0.7 at 10 years. No significant differences in the survival probabilities were found among different providers and locations, the presence of a post, and the types of crowns. The hazard ratio for tooth loss was 6.3, 95% confidence interval (CI) [2.6 to 20.9] in the teeth with RCT (p<0.001) and 2.4, 95% CI [1.1 to 4.8] in the teeth occluding implant-retained prostheses (p=0.016). Tooth loss following CLPs and crown insertions appeared least among the teeth without RCT when occluding natural teeth, while tooth loss was most among the teeth with RCT when occluding implants.

PagKNAT2/6b promotes shoot branching by attenuating auxin-strigolactone signalling in poplar.

Shoot branching from axillary bud (AB) directly determines plant architecture. However, the mechanism through which AB remains dormant or emerges to form branches as plants grow remains largely unknown. Here, the auxin-strigolactone (IAA-SL) pathway was first shown to regulate shoot branching in poplar, and we found that PagKNAT2/6b could modulate this pathway. PagKNAT2/6b was expressed mainly in the shoot apical meristem and AB and was induced by shoot apex damage. PagKNAT2/6b overexpressing poplar plants (PagKNAT2/6b OE) exhibited multiple branches that mimicked the branching phenotype of nontransgenic plants after decapitation treatment, while compared with nontransgenic controls, PagKNAT2/6b antisense transgenic poplar and Pagknat2/6b mutant lines exhibited a significantly decreased number of branches after shoot apex damage treatment. In addition, we found that PagKNAT2/6b directly inhibits the expression of the key IAA synthesis gene PagYUC6a, which is specifically expressed in the shoot apex. Moreover, overexpression of PagYUC6a in the PagKNAT2/6b OE background reduced the number of branches after shoot apex damage treatment. Overall, we conclude that PagKNAT2/6b responds to shoot apical injury and regulates shoot branching through the IAA-SL pathway. These findings may provide a theoretical basis and candidate genes for genetic engineering to create new forest tree species with different crown types.

Phenotypic Diversity of Pomegranate Cultivars: Discriminating Power of Some Morphological and Fruit Chemical Characteristics

In modern agricultural production, where a small number of commercial cultivars dominate, the collection, evaluation, and preservation of germplasm are important tasks to reduce the erosion of genes and preserve biodiversity. The aim of this study is to characterize the morphological and fruit chemical properties of the pomegranate germplasm grown on the East Adriatic coast, including the commercial cultivars ‘Hicaznar’, ‘Granada’, and ‘Wonderful’, and to highlight the characteristics with the greatest discriminating power. The characterization of the tree, leaf, flower, arils, seed, and juice was carried out using the UPOV descriptor. The colors of the peel, arils, and juice were analyzed according to the CIEL*a*b* method, total soluble solids were measured using refractometers, and total acidity was determined by titration with 0.1 M NaOH. The research results showed significant diversity between the cultivars, which were grouped into several clusters using an unsupervised analysis technique. Factors such as plant vigor, plant growth habit, predominant number of leaves per node on young shoots, crown type, fruit shape, fruit shape in cross-section, peel weight, total aril weight, aril weight, number of arils per fruit, seed length and width, seed yield, total acidity, TSS/TA ratio, and color parameters of the peel, arils, and juice showed high variability, indicating their strong discriminating power in determining the phenotypic diversity of pomegranate.

The Effect of Thermocycling and Mechanical Loading on the Fracture Resistance of Graphene and All-Ceramic Anterior Crowns.

Introduction Fixed prosthodontic treatment involves the replacement of missing tooth structures with a variety of materials. Several newer metal-free ceramics have been developed in recent years to meet patients' aesthetic needs. The long-term performance of all ceramics, however, is unknown, necessitating a continuous evaluation of the materials' strength. Aim The aim of this study was to compare and evaluate the fracture resistance of IPS E max pressable crowns and graphene crowns, which are luted with Rely X U200 self-adhesive resin cement on the respective dies, as well as thermocycling of IPS E max pressable crowns and thermocycling of graphene crowns. The current review was conducted as an in vitro examination at the Division of Prosthodontics, GSL Dental School, Rajahmundry, Andhra Pradesh, India. Materials and methods On a typodont tooth, a shoulder finish line design was prepared and incisal reduction was performed. The tooth was scanned, designed, and milled to produce 18 metal dies made of cobalt-chrome alloy. These metal dies produced a total of (n=36) all-ceramic crowns, which were divided into two groups based on crown type: 18 IPS E max crowns and 18 graphene crowns. The participants were once again divided into two subgroups within each group, with the purpose of assessing fracture resistance. This evaluation was conducted using a universal testing machine both before and after subjecting the specimens to thermocycling. The obtained data were sent for statistical analysis. Results Fracture resistance values were reduced after thermocycling of both IPS E max and Graphene crowns. Without thermocycling, the fracture resistance values of IPS E max crowns were higher than those of graphene crowns. Conclusions The fracture resistance of IPS E max crowns exhibited a statistically significant increase when compared to graphene crowns. Additionally, it was shown that the fracture resistance of both materials was reduced upon exposure to thermocycling.

Validation of the pink esthetic score/white esthetic score at single tooth-supported prostheses in the esthetic zone: A randomized clinical trial.

To validate the reproducibility and inter/intra-observer variability of the Pink Esthetic Score/White Esthetic Score (PES/WES) of single tooth-supported prostheses in the maxillary esthetic zone (13-23). Forty-five patients were randomly assigned to one of the three treatment options (15 patients per group) receiving each one a different crown type: Porcelain fused to metal (PFM), monolithic zirconia, and lithium disilicate. Eight observers from each of four different specialties (Prosthodontists, Orthodontists, Periodontists, and Oral Surgeons) were recruited and assessed twice and four weeks apart (i.e., T1 and T2) 45 photographs of the single tooth-supported prosthesis using PES/WES and compared them with contralateral teeth. According to the ANOVA and post hoc tests, the zirconia crown type obtained the highest mean score by all observers, with a mean value of 16.70 ± 2.94. The prosthodontists and oral surgeons assigned the lowest mean score to PFM crowns, 13.03 ± 3.47 and 13.80 ± 3.17, respectively. Notably, the prosthodontists awarded the highest scores, specifically 17.50 ± 2.81 for the zirconia crowns. Intraobserver agreement was calculated utilizing the paired t-test. Pairwise comparisons between observers of different specialties revealed significant intraobserver agreement. Interclass correlation coefficient (ICC) scores were statistically significant among four specialties. No difference was detected concerning the interobserver agreement. The PES/WES index remains consistent across various observers from different specializations, yielding uniform results in the overall esthetic evaluation. Consequently, in light of the presented preliminary positive results, its use might also be considered for the esthetic assessment of single-tooth-supported prostheses. The PES/WES index may be employed clinically to evaluate single tooth-supported prostheses as it emerged as a reproducible esthetic scoring system.

Comparison of clinical outcomes between single metal-ceramic and zirconia crowns

Statement of problemEvidence comparing the survival of zirconia crowns with metal-ceramic crowns is sparse. Knowledge of their survival and a comparison of their clinical outcomes would improve clinical decision making. PurposeThe purpose of this university-based study was to compare the survival, failures, biological and technical complications encountered with zirconia and metal-ceramic crowns restored and followed up over a similar period. Material and methodsThis retrospective chart review consisted of 403 patients treated at the University of Toronto, Faculty of Dentistry, predoctoral dental clinic in whom zirconia (n=209) and metal-ceramic (n=306) crowns were inserted between September 2015 and July 2016 and followed for up to 7 years. Outcome measures included failure, causes for failure, and complications associated with survival. Inferential statistical analysis included the chi-squared test, t test, Mann-Whitney test, Bonferroni-adjusted z-test, Kaplan-Meier survival test, and logistic regression to examine differences between crown types and explore crown failures (α=.05). ResultsThe mean follow-up period was 3.00 years (median 2.58 years). Forty-one (8.0%) crowns had no follow-up, with no difference in follow-up between crown type: metal-ceramic n=23(7.5%), zirconia n=18(8.6%), χ²(1)=0.20, P=.652). Excluding those with no follow-up, the follow-up time between metal-ceramic (mean=3.07, median=2.58) and zirconia (mean=3.54, median=3.32) crowns was statistically similar (P=.052). There were 62 anterior crowns (12.0%) and 453 posterior crowns (88.0%), χ²(1)=22.40, P<.001, with no difference between groups. Overall, 44 crowns (8.5%) failed, 30 (9.8%) metal-ceramic and 14 (6.7%) zirconia, with no statistical difference in proportion of failed crowns between groups (χ²(1)=1.53, P=.216). There were 35 crowns with biological failures (6.8%), 26 (8.5%) in the metal-ceramic and 9 (4.4%) in the zirconia group, with no statistical difference between groups (χ²(1)=3.33, P=.068). Nine crowns had technical failures (1.7%), 4 (1.4%) in the metal-ceramic group and 5 (2.5%) in the zirconia group, with no statistical difference between groups (χ²(1)=0.73, P=.394). Biological (79.5%) rather than technical complications were found to be the most frequent cause of failure, goodness-of-fit χ²(1)=15.36, P<.001. Tooth fracture (50.0%) specifically was found to be the most frequent cause of failure, χ²(3)=21.27, P<.001. The total number of crowns that survived was 471 (91.5%); 276 (90.1%) were metal-ceramic and 195(93.3%) zirconia. The survival time (years) for metal-ceramic was mean=6.26, 95% CI [6.01–6.51] and for zirconia crowns mean=6.54, 95% CI [6.31–6.77]. Of the crowns that survived, 370 (78.6%) had no clinical complications, and 101 (21.4%) crowns demonstrated similar clinical complications, with no statistical differences between groups. ConclusionsWithin the study follow-up time, the survival of monolithic zirconia and metal-ceramic crowns was 91.5%, with similar clinical complications between groups. Biological complications, especially tooth fracture, were a significantly more frequent complication with both types of crowns.