Marginal Fitness Research Articles

Effect of cement-space thickness on the marginal fitness of all zirconium oxide crowns—An in vitro study

Effect of cement-space thickness on the marginal fitness of all zirconium oxide crowns—An in vitro study

The influence of different CAD/CAM materials on the marginal fit of endocrown with different cavity depths (A comparative in-vitro study)

To evaluate and compare the influence of dissimilar CAD-CAM material on the marginal fitness of endocrown with different cavity depths. Freshly extracted human maxillary first premolar teeth (n = 40) were selected for this study. Teeth were decapitated 2 mm above the cement-enamel junction from proximal surface and endodontic treatment were performed for all teeth. Samples were allocated at two main groups (n = 20), according to cavity depth. Group A: 2 mm cavity depth; Group B: 4 mm cavity depth; and further subdivided into two sub-groups according to material used (n = 10): (A1 and B1) resin-based material; (A2 and B2) ceramic-based material. Teeth were prepared with butt joint margin and 10° internal axial wall divergence. Afterwards, samples scanning was performed using InLab digital scanner. Endocrown restoration fabricated by Sirona Cerec InLab MCXL milling device and adhesively luted with a resin cement (RelyX™ Ultimate ClickerTM, 3 M ESPE). All samples were subjected to thermocycling. After thermocycling, marginal gaps were measured using stereomicroscope at a magnification of 45X. The recorded measurements were collected, scaled and statistically analyzed. A resin-based endocrown showed significantly a smaller vertical marginal gap than ceramic-based, an endocrown with 2-mm cavity depth showed significantly lower marginal gap than one with 4-mm cavity depth. Increasing the cavity depth of endocrown preparation negatively affect the marginal fit. Resin-nanoceramic endocrown showed better marginal fit than glass ceramic endocrown. Both tested CAD/CAM materials showed clinically acceptable vertical marginal gap.

Determinants of offspring sex in kangaroos: a test of multiple hypotheses

Abstract When the fitness costs and benefits of sons and daughters differ, offspring sex ratio manipulation could be an important reproductive tactic. We explored the effects of environment and maternal caring ability on offspring sex to test four adaptive sex ratio modification hypotheses: the extrinsic modification hypothesis (EMH), carrying capacity hypothesis (CCH), Trivers-Willard hypothesis (TWH), and cost-of-reproduction hypothesis (CRH). The EMH and CCH propose that environmental conditions shape offspring sex ratios, directly or in interaction with maternal condition. The TWH and CRH predict a positive relationship between maternal condition and production of the costlier sex. The TWH predicts that mothers with superior caring ability should produce more of the sex that can provide the greatest fitness returns from additional maternal allocation, and the CRH proposes that females with limited caring ability should reduce fitness costs by producing the cheaper sex. Repeated measures on 83 known-age eastern gray kangaroos, polygynous marsupials with strong sexual dimorphism, revealed that offspring sex ratio was independent of per capita forage, supporting neither the EMH nor CCH, but was dependent on maternal mass, consistent with the TWH and CCH. Our results, however, cannot clearly identify the ultimate cause of the relationship between maternal mass and greater production of sons. One of the three assumptions of the TWH could not be verified, and mothers of sons suffered only marginal additional fitness costs. Sex ratios in higher vertebrates are likely not solely explained by factors dependent on maternal control.

Comparison of the marginal discrepancy of PFM crowns in the CAD/CAM and lost-wax fabrication techniques by triple scanning.

Computer-aided design/computer-aided manufacturing (CAD/CAM) systems are widely used for the fabrication of porcelain-fused-to-metal (PFM) crowns. This study was conducted to compare PFM crowns through triple scanning in terms of marginal discrepancy between the CAD/CAM and lost-wax fabrication techniques. Twenty uniform resin dies of a prepared maxillary first molar were randomly divided into 2 groups: conventional lost-wax; and milling. Marginal discrepancy was evaluated at the framework and porcelain steps through triple scanning and direct visualization under a stereomicroscope. Then, the crowns were cemented to the related die and the marginal gap was measured with triple scanning, direct visualization under a stereomicroscope and scanning electron microscopy (SEM). The data was analyzed using the independent t test and the one-way analysis of variance (ANOVA). The significance level was set at 0.05. Differences in the mean marginal gap were measured by the various evaluation methods. Triple scanning and stereomicroscopy identified increasing discrepancy during the fabrication process. According to the results of the independent t test, stereomicroscopy showed no difference after cementation between the CAD/CAM and lost-wax groups (p > 0.05), triple scanning showed higher fitness in the CAD/CAM group (p < 0.05), and SEM showed better adaptation in the lost-wax group (p < 0.05); however, there was a positive correlation between the findings of stereomicroscopy and SEM (p < 0.05). The cobalt-chromium crowns had clinically acceptable marginal fitness from both the CAD/CAM and lost-wax techniques; however, the lost-wax group showed lower marginal discrepancy after cementation according to SEM.

Strain analysis of anterior resin-bonded fixed dental prostheses with different thicknesses of high translucent zirconia

Background/purposeHigh translucent zirconia has been used as a new monolithic zirconia prosthesis, which has the potential to make anterior resin-bonded fixed dental prostheses (RBFDPs) without veneering porcelain. However, it is unclear whether the RBFDPs retainer can be thinned as much as conventional zirconia RBFDPs. The aim of this study was to assess the usability of high translucent zirconia RBFDPs with a thin retainer thickness by evaluating differences in retainer thickness on the surface strain. Materials and methodsA model with a missing upper lateral incisor was used. The abutment teeth were upper central incisor and canine. Three types of RBFDPs were fabricated as follows: metal RBFDPs with a retainer thickness of 0.8 mm (0.8M), and high translucent zirconia RBFDPs with a retainer thicknesses of 0.8 and 0.5 mm (0.8Z, 0.5Z) (n = 10). The fitness of the margins was evaluated by the silicone replica technique. The surface strain of each retainer under static loading was measured and statistically analyzed using a t-test with Bonferroni correction. ResultsThe marginal fitness of all RBFDPs was under 76.1 μm, which was clinically acceptable. Each strain of the 0.8Z and 0.5Z groups was significantly lower than that of the 0.8M (p < 0.05). There was no difference in strain of the zirconia RBFDPs even if the retainer thickness was changed. ConclusionOur results suggest that the high translucent zirconia RBFDPs can be manufactured with a retainer thickness of 0.5 mm, which reduces the amount of tooth preparation compared to the metal RBFDPs.

An analytical theory of balanced cellular growth

The biological fitness of microbes is largely determined by the rate with which they replicate their biomass composition. Mathematical models that maximize this balanced growth rate while accounting for mass conservation, reaction kinetics, and limits on dry mass per volume are inevitably non-linear. Here, we develop a general theory for such models, termed Growth Balance Analysis (GBA), which provides explicit expressions for protein concentrations, fluxes, and growth rates. These variables are functions of the concentrations of cellular components, for which we calculate marginal fitness costs and benefits that are related to metabolic control coefficients. At maximal growth rate, the net benefits of all concentrations are equal. Based solely on physicochemical constraints, GBA unveils fundamental quantitative principles of cellular resource allocation and growth; it accurately predicts the relationship between growth rates and ribosome concentrations in E. coli and yeast and between growth rate and dry mass density in E. coli.

Assessment of Bioactive Resin-Modified Glass Ionomer Restorative as a New CAD/CAM Material. Part I: Marginal Fitness Study

The objective of this in vitro study was to evaluate and compare the marginal fitness of monolithic crowns fabricated from a newly developed bioactive CAD/CAM resin block and reinforced resin CAD/CAM block pre-and post-cementation with adhesive and self-adhesive resin cements. Bioactive CAD/CAM block were fabricated from ACTIVA BioACTIVE-RESTORATIVE (Pulpdent Corporation, USA) using a clear rectangular Teflon mold. Thirty-two human maxillary first premolar teeth were prepared to receive full crowns then divided into two main groups of 16 teeth each according to the type of block used to fabricate the crowns: Group A: crowns fabricated from the bioactive resin block, Group B: crowns fabricated from reinforced composite block (BRILLIANT Crios, Coltene). Each group was then subdivided into two subgroups according to the type of resin cement used for cementation, Subgroups (A1, B1): RelyX Ultimate cement, Subgroups (A2, B2): ACTIVA BioACTIVE-cement. The prepared teeth were scanned using CEREC Omnicam digital intra-oral and the crowns were then designed using CEREC Premium software (version 4.4.4) and milled using CEREC MC XL milling unit. The marginal gap of each crown was measured before cementation at four points on each tooth surface using a digital microscope at a magnification of 230x. Each crown was then cemented on its respective tooth according to the manufacturers’ instructions of each cement, and the marginal gap was measured again at the same aforementioned points. The results of this study showed that the marginal gap of all groups are below the clinically acceptable limit. Meanwhile, the marginal gap of the crowns fabricated from both block types increased significantly after cementation with both types of cement. Pre-cementation, student’s t-test revealed that there is no statistically significant difference in the marginal gap of crowns fabricated from both block types (p&gt; 0.05). Post-cementation, a statistically highly significant difference was seen between both block types with both types of cement (p&lt;0.01). From the results of this study, the newly developed bioactive resin block seems a promising material for CAD/CAM applications in terms of marginal fitness.

A novel retentive type of dental implant prosthesis: marginal fitness of the cementless double crown type implant prosthesis evaluated by bacterial penetration and viability.

PURPOSEThis study aims to compare the marginal fitness of two types of implant-supported fixed dental prosthesis, i.e., cementless fixation (CL.F) system and cement-retained type.MATERIALS AND METHODSIn each group, ten specimens were assessed. Each specimen comprised implant lab analog, titanium abutment fabricated with a 2-degree tapered axial wall, and zirconia crown. The crown of the CL.F system was retained by frictional force between abutment and relined composite resin. In the cement-retained type, zinc oxide eugenol cement was used to set crown and abutment. All specimens were sterilized with ethylene oxide, immersed in Prevotella intermedia culture in a 50 mL tube, and incubated with rotation. After 48 h, the specimens were washed thoroughly before separating the crown and abutment. The bacteria that penetrated into the crown-abutment interface were collected by washing with 500 µL of sterile saline. The bacterial cell number was quantified using the agar plate count technique. The BacTiter-Glo Microbial Cell Viability Assay Kit was used to measure bacterial adenosine triphosphate (ATP)-bioluminescence, which reflects the bacterial viability. The t-test was performed, and the significance level was set at 5%.RESULTSThe number of penetrating bacterial cells assessed by colony-forming units was approximately 33% lower in the CL.F system than in the cement-retained type (P<.05). ATP-bioluminescence was approximately 41% lower in the CL.F system than in the cement-retained type (P<.05).CONCLUSIONThe CL.F system is more resistant to bacterial penetration into the abutment-crown interface than the cement-retained type, thereby indicating a precise marginal fit.

Evaluation of marginal and internal adaptation of zirconia crowns constructed from traditional and digital impressions

Background and objective: Recent advancement in restorative dentistry from impression to fabrication is toward digital workflow. There are very few studies, evaluating the internal and marginal fitness of full anatomic zirconia crowns fabricated with different impression techniques. The aim of this study was to determine whether improved technology of digital workflow results in better fitting crowns. Methodology: The mandibular right first molar of a dentoform model was prepared for a full ceramic crown with deep shoulder finish line. Two impression techniques were used,for group one, ten traditional impressions with addition silicone were obtained, while in group two, ten digital intraoral impressions were captured.Twenty full anatomic zirconia crowns were designed and milled using dental CAD/CAM system . The internal and marginal gaps were measured for each crown on the master die with the aid of a stereomicroscope. Results: The average (±SD) for the internal and marginal adaptation was: 145 μm (±39) and 85 μm (±17) for the digital impression group, 188 μm (±141) and 178 μm (±41) for the traditional impression group, respectively. The Kruskal -Wallis test showed no statistically significant difference between the two groups regarding marginal and internal adaptation. Conclusion: Full anatomic zirconia crowns fabricated from intraoral digital impressions demonstrated comparable or even better marginal and internal fit than crowns fabricated with traditional silicone impressions.

Comparison of 2-dimensional marginal and internal fitness for the monolithic zirconia prosthesis using intraoral scanner and extraoral scanner: in vitro

Comparison of 2-dimensional marginal and internal fitness for the monolithic zirconia prosthesis using intraoral scanner and extraoral scanner: in vitro

The extraction method of tooth preparation margin line based on S-Octree CNN.

The tooth preparation margin line has a significant impact on the marginal fitness for dental restoration. Among the previous methods, the extraction of margin line mainly relies on manual interaction, which is complicated and inefficient. Therefore, we propose a method to extract the margin line with the convolutional neural network based on sparse octree (S-Octree) structure. First, the dental preparations are rotated to augment the dataset. Second, the preparation models are treated as the sparse point cloud with labels through the spatial partition method of the S-Octree. Then, based on the feature line, the dental preparation point cloud is automatically divided into two regions by the convolutional neural network (CNN). Third, in order to obtain the margin line, we adopt some methods such as the dense condition random field (dense CRF), point cloud reconstruction, and back projection to the original dental preparation model. Finally, based on the measurement indicators of accuracy, sensitivity, and specificity, the average accuracy of the label predicted by the network model can reach 97.43%. The experimental results show that our method can automatically accomplish the extraction of the tooth preparation margin line.

Effect analysis of ceramic onlay to repair serious dental defects in young permanent molars

To analyze the effect of ceramic onlay to repair serious defects in young permanent molars. Sixty patients with defects in young permanent molars were selected. The patients were randomly divided into two groups. One group was restored with ceramic onlay, and the other used resin composite to direct filling. Follow-up visit was conducted at 3, 6, 12, and 24 months after treatment. Modified USPHS/Ryge criteria were used to evaluate the effect of restoration. The occlusal courses were recorded by the T-Scan Ⅲ system in intercuspal position. Gingival and food impaction were recorded. The effect of the two restorative methods, the recovery of occlusal function, and the gingival and approximal conditions were analyzed. At 12 months after restoration, the marginal fitness in the onlay group was significantly better than that in the resin group (P<0.05). At 12 and 24 months after restoration, the surface smoothness in the onlay group was significantly better than that in the resin composite group (P<0.05). At each follow-up visit, the resin group had significantly lower per-cen-tage of occlusal force than contralateral molar (P<0.05). The percentage of occlusal force in the onlay group and the con-trala-teral molar showed no statistical difference (P>0.05). The gingival and approximal conditions also demon-strated no stati-stical differences (P>0.05). The ceramic onlay repair method is better than resin composite filling in marginal fitness, surface smoothness, and recovery of the occlusal function when restoring young permanent molars with serious defects.

A Dynamic Game Approach to Uninvadable Strategies for Biotrophic Pathogens

This paper studies a zero-sum state-feedback game for a system of nonlinear ordinary differential equations describing one-seasonal dynamics of two biotrophic fungal cohorts within a common host plant. From the perspective of Adaptive Dynamics, the cohorts can be interpreted as resident and mutant populations. The invasion functional takes the form of the difference between the two marginal fitness criteria and represents the cost in the definition of the value of the differential game. The presence of a specific competition term in both equations and marginal fitnesses substantially complicates the reduction of the game to a two-step problem that can be solved by using Optimal Control Theory. Therefore, a general game-theoretic formulation involving uninvadable strategies has to be considered. First, the related Cauchy problem for the Hamilton-Jacobi-Isaacs equation is investigated analytically by the method of characteristics. A number of important properties are rigorously derived. However, the complete theoretical analysis still remains an open challenging problem due to the high complexity of the differential game. That is why an ad hoc conjecture is additionally proposed. An informal but rather convincing and practical justification for the latter relies on numerical simulation results. We also establish some asymptotic properties and provide biological interpretations.

Sexual selection, phenotypic plasticity and female reproductive output.

In a rapidly changing environment, does sexual selection on males elevate a population's reproductive output? If so, does phenotypic plasticity enhance or diminish any such effect? We outline two routes by which sexual selection can influence the reproductive output of a population: a genetic correlation between male sexual competitiveness and female lifetime reproductive success; and direct effects of males on females' breeding success. We then discuss how phenotypic plasticity of sexually selected male traits and/or female responses (e.g. plasticity in mate choice), as the environment changes, might influence how sexual selection affects a population's reproductive output. Two key points emerge. First, condition-dependent expression of male sexual traits makes it likely that sexual selection increases female fitness if reproductively successful males disproportionately transfer genes that are under natural selection in both sexes, such as genes for foraging efficiency. Condition-dependence is a form of phenotypic plasticity if some of the variation in net resource acquisition and assimilation is attributable to the environment rather than solely genetic in origin. Second, the optimal allocation of resources into different condition-dependent traits depends on their marginal fitness gains. As male condition improves, this can therefore increase or, though rarely highlighted, actually decrease the expression of sexually selected traits. It is therefore crucial to understand how condition determines male allocation of resources to different sexually selected traits that vary in their immediate effects on female reproductive output (e.g. ornaments versus coercive behaviour). In addition, changes in the distribution of condition among males as the environment shifts could reduce phenotypic variance in certain male traits, thereby reducing the strength of sexual selection imposed by females. Studies of adaptive evolution under rapid environmental change should consider the possibility that phenotypic plasticity of sexually selected male traits, even if it elevates male fitness, could have a negative effect on female reproductive output, thereby increasing the risk of population extinction. This article is part of the theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.

The Effect of Pollen Limitation on the Evolution of Mating System and Seed Size in Hermaphroditic Plants.

Pollen limitation, when inadequate pollen receipt results in a plant setting fewer seeds and fruits, can reduce plant reproductive success and promote the evolution of self-fertilization as a mechanism of reproductive assurance. However, the effect of pollen limitation on the joint evolution of mating system and seed size is not known. Using an evolutionarily stable strategy resource allocation model, we show that where moderate pollen limitation and strong inbreeding depression select for complete outcrossing, pollen limitation should also increase the optimal seed size. In contrast, pollen limitation should not affect the optimal seed size under complete selfing, in which case ovule fertilization is certain. Under intermediate conditions, a mixed mating system evolves if the probability of ovule fertilization declines as more ovules are produced, so that a selfed seed with inbreeding depression provides equal marginal fitness returns to a larger outcrossed seed that may result from pollen limitation. Under mixed mating, outcrossed seeds should be larger than selfed seeds, and pollen limitation should not affect the optimal size of either outcrossed or selfed seeds. Our results identify a novel pathway through which pollen limitation selects for mixed mating and provide an adaptive explanation as to why selfed seeds are often smaller than outcrossed seeds.

Phenological and fitness responses to climate warming depend upon genotype and competitive neighbourhood in Arabidopsis thaliana

Abstract Increasing temperatures during climate change are known to alter the phenology across diverse plant taxa, but the evolutionary outcomes of these shifts are poorly understood. Moreover, plant temperature‐sensing pathways are known to interact with competition‐sensing pathways, yet there remains little experimental evidence for how genotypes varying in temperature responsiveness react to warming in realistic competitive settings. We compared flowering time and fitness responses to warming and competition for two near‐isogenic lines (NILs) of Arabidopsis thaliana transgressively segregating temperature‐sensitive and temperature‐insensitive alleles for major‐effect flowering time genes. We grew focal plants of each genotype in intraspecific and interspecific competition in four treatments contrasting daily temperature profiles in summer and fall under contemporary and warmed conditions. We measured phenology and fitness of focal plants to quantify plastic responses to season, temperature and competition and the dependence of these responses on flowering time genotype. The temperature‐insensitive NIL was constitutively early flowering and less fit, except in a future‐summer climate in which its fitness was higher than the later flowering, temperature‐sensitive NIL in low competition. The late‐flowering NIL showed accelerated flowering in response to intragenotypic competition and to increased temperature in the summer but delayed flowering in the fall. However, its fitness fell with rising temperatures in both seasons, and in the fall its marginal fitness gain from decreasing competition was diminished in the future. Functional alleles at temperature‐responsive genes were necessary for plastic responses to season, warming and competition. However, the plastic genotype was not the most fit in every experimental condition, becoming less fit than the temperature‐canalized genotype in the warm summer treatment. Climate change is often predicted to have deleterious effects on plant populations, and our results show how increased temperatures can act through genotype‐dependent phenology to decrease fitness. Furthermore, plasticity is not necessarily adaptive in rapidly changing environments since a nonplastic genotype proved fitter than a plastic genotype in a warming climate treatment. A plain language summary is available for this article.

Evaluation of the Marginal and Internal Fitness of Monolithic CAD/CAM Zirconia Crowns Using Two Software Design and Different Open System Milling Machines

Evaluation of the Marginal and Internal Fitness of Monolithic CAD/CAM Zirconia Crowns Using Two Software Design and Different Open System Milling Machines

Effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fitness

Effect of additional firing process after sintering of monolithic zirconia crown on marginal and internal fitness

Marginal Fitness of Monolithic Zirconia Crowns Fabricated from Direct Digital Scanning, Impression Scanning &amp; Indirect Digital Scanning Using Different Impression Materials

Marginal Fitness of Monolithic Zirconia Crowns Fabricated from Direct Digital Scanning, Impression Scanning &amp; Indirect Digital Scanning Using Different Impression Materials

A Comparative Evaluation of Internal Adaptation and Marginal Fitness of Two Zirconium Design Fabricated by CAD/CAM

Objective: Full anatomic zirconia crowns had been launched to overcome the problems associated with veneering porcelain. The aim of this study was to evaluate the internal and marginal adaptation of CAD/CAM milled zirconia core to full anatomic zirconia crown.&#x0D; Methods: The mandibular right first molar of a dentaform model was prepared for the full ceramic crown with deep shoulder finish line. The model was scanned using intra-oral scanner to produce ten full anatomic zirconia crowns and ten zirconia cores. The internal and marginal adaptations (that represents the cement analog) were evaluated using the replica technique with the aid of a stereomicroscope.&#x0D; Results: All There was no statistically significant difference between the internal and marginal adaptation of core and full anatomic zirconia crown, while a significant difference exists between them at the occlusal point that was greater in full anatomic crown. Both groups revealed the mean gap width of 146.7 +- 18 which is significant when compared to the standard value.&#x0D; Conclusions: Both zirconia core and crown revealed comparable results of marginal and internal adaptation after sintering without any effect of bulk thickness. The obtained results were greater than the acceptable range.