Restoration Failure Research Articles

Effect of etching time duration on the push out strength of self adhesive cement to root dentin

Introduction: Post debonding is one of the most important causes of restoration failure in endodontically treated teeth restored with fiber-post. The weakest connection in post-cement-dentin complex is cement-dentin bonding surface. In this study we evaluated the effect of etching with phosphoric-acid and its duration on push-out strength of self-adhesive resin cement to dentin. Materials and Method: Root canal therapy was done for fifty intact one-canal premolars then the crown was cut from CEJ. Fiber-post space was prepared in the root canal by FGM special drill. The teeth were randomly divided into five groups of ten teeth. Group without any intervention was considered as control-1 and the other groups were prepared for etching. Three groups were etched with 37%phosphoric-acid for 15seconds, 60seconds and 90seconds. In the last group, after preparation, etching protocol wasn't performed which was considered as control-2. In all samples, White post fiber-ost(FGM) size2 was cemented with self-adhesive cement TheraCem (Bisco) and divided into two 4mm pieces and then mounted in acryl. Push-out test was performed by Instron machine for each sample and the shear bond strength was obtained in MPa.

N Addition Mitigates Water Stress via Different Photosynthesis and Water Traits for Three Native Plant Species in the Qinghai–Tibet Plateau

Reseeding with native plants to rebuild alpine meadow has become a popular way of ecological restoration. However, the harsh environment poses a great challenge to the establishment of native plants due to poor management of water and nutrients. How water–fertilizer interaction influences dominant grass species is still unclear, and reasonable water and fertilizer conditions are still not determined. Our results showed that addition of nitrogen could mitigate the photosynthetic and water-use traits caused by water stress, i.e., a reduction in Pn and water use results from fewer and thinner leaves, weak stomatal traits, etc. Compared to the control, the peak Pn values of Poa crymophila, Festuca coelestis, and Stipa purpurea increased significantly (71.2%, 108.4%, and 25.4%, respectively). Under drought stress, Pn tended to decrease due to reduced stomatal conductance (Gs). However, appropriate fertilization buffered against Pn decreases by altering the stomatal size and regulating the Gs. Based on reduced water consumption, the water-use efficiency of P. crymophila and F. coelestis decreased whereas that of S. purpurea increased. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea growth were suitable for the alpine region. WHFH for P. crymophila and F. coelestis and WHFL for S. purpurea were suitable for their establishment in the alpine region. A reasonable water–fertilizer combination could effectively reduce the risk of establishment failure in ecological restoration.

The quality of energy- and macronutrient-balanced diets regulates host susceptibility to influenza in mice.

Modulation of individual macronutrients or caloric density is known to regulate host resistance to infection in mice. However, the impact of diet composition, independent of macronutrient and energy content, on infection susceptibility is unclear. We show that two laboratory rodent diets, widely used as standard animal feeds and experimental controls, display distinct abilities in supporting mice during influenza infection. Mice placed on the highly processed AIN93G showed increased mortality to infection compared with those on a grain-based chow diet, suggesting a detrimental role for highly processed food in host defense. We further demonstrate that the heightened susceptibility of AIN93G-fed mice was associated with the failure in homeostasis restoration mediated by the cytokine interferon (IFN)-γ. Our findings show that diet composition calibrates host survival threshold by regulating adaptive homeostasis and highlights a pivotal role for extrinsic signals in host phenotype and outcome of host-pathogen interaction.

Analysis of Mumbai Grid Failure Restoration on Oct 12, 2020: Challenges and Lessons Learnt

After any major blackout, recreating the exact scene is one of the crucial but foundation steps in postmortem analysis. This helps in identifying and understanding the exact causes and sequence of events to avoid such failures in the future. Rather, power system restoration demands critical skills which involves deployment of appropriate strategies based on information about various factors, notably the extent and duration of the blackout, location of black-started units, interconnections with neighbouring systems, generator capabilities, and selecting appropriate restoration paths. The actual execution of the restoration plan consists of many surprises of unique nature and a lot of learning’s to avoid future occurrences of such incidents. The restoration efforts and failure of Mumbai grid failure on October 12, 2020, are highlighted in this paper. The paper first proposes formulating the dynamic models to get a better insight of the restoration process in the event of critical issues during this incident. The various challenges faced in systematic recovery of such a large system and lessons learnt from it forms focus of the paper. The paper also discusses factors not covered in existing literature, such as weather, fuel availability, and water mass oscillations which plays an important role in the restoration.

Comparative microleakage outcomes of different techniques used for creating the occlusal anatomy in occlusal direct restorations using the dental operating microscope.

Microleakage in direct dental restorations is a primary causal factor in the restoration's failure. The aim of this study was to evaluate whether the technique for occlusal layering of the composite resin (the use of brush adaptation, the use of magnification, cusp build-up, stamp technique) has any effect on microleakage of direct restorations in occlusal cavities. One hundred extracted human molars were restored using five restoration techniques (Packable Bulk technique, Occlusal Stamp technique, Successive Cusp Build-up technique, Successive Cusp Build-up technique + Brush adaptation, Successive Cusp Build-up technique + brush adaptation + Dental Operative Microscope magnification). The teeth were subjected to thermal aging for 800 cycles at 5°C and 55°C, infiltrated with basic fuchsin dye for 24 h, and then sectioned buccolingually in the middle of the crown. Infiltration was measured in four areas of the tooth section by five different observers and then given a score from 1 to 3, proportional to infiltration depth. The lowest mean scores for infiltration (meaning less infiltration observed) were present in Group A (1.41 ± 0.878) and Group C (1.46 ± 0.679), while Group D showed the highest infiltration scores (1.75 ± 0.853). When comparing the groups for differences, no statistically significant difference in infiltration was found between any technique p < .586. The techniques examined for placing the occlusal layer of composite in direct restorations do not differ significantly in terms of marginal infiltration, although a slight improvement was found when using the bulk technique and the successive cusp build-up.

Evaluation of biofilm formation on acrylic resins used to fabricate dental temporary restorations with the use of 3D printing technology

BackgroundTemporary implant-retained restorations are required to support function and esthetics of the masticatory system until the final restoration is completed and delivered. Acrylic resins are commonly used in prosthetic dentistry and lately they have been used in three-dimensional (3D) printing technology. Since this technology it is fairly new, the number of studies on their susceptibility to microbial adhesion is low. Restorations placed even for a short period of time may become the reservoir for microorganisms that may affect the peri-implant tissues and trigger inflammation endangering further procedures. The aim of the study was to test the biofilm formation on acrylamide resins used to fabricate temporary restorations in 3D printing technology and to assess if the post-processing impacts microbial adhesion.MethodsDisk-shaped samples were manufactured using the 3D printing technique from three commercially available UV-curable resins consisting of acrylate and methacrylate oligomers with various time and inhibitors of polymerization (NextDent MFH bleach, NextDent 3D Plus, MazicD Temp). The tested samples were raw, polished and glazed. The ability to create biofilm by oral streptococci (S. mutans, S. sanguinis, S. oralis, S. mitis) was tested, as well as species with higher pathogenic potential: Staphylococcus aureus, Staphylococcus epidermidis and Candida albicans. The roughness of the materials was measured by an atomic force microscope. Biofilm formation was assessed after 72 h of incubation by crystal violet staining with absorbance measurement, quantification of viable microorganisms, and imaging with a scanning electron microscope (SEM).ResultsEach tested species formed the biofilm on the samples of all three resins. Post-production processing resulted in reduced roughness parameters and biofilm abundance. Polishing and glazing reduced roughness parameters significantly in the NextDent resin group, while glazing alone caused significant surface smoothing in Mazic Temp. A thin layer of microbial biofilm covered glazed resin surfaces with a small number of microorganisms for all tested strains except S. oralis and S. epidermidis, while raw and polished surfaces were covered with a dense biofilm, rich in microorganisms.ConclusionsUV-curing acrylic resins used for fabricating temporary restorations in the 3D technology are the interim solution, but are susceptible to adhesion and biofilm formation by oral streptococci, staphylococci and Candida. Post-processing and particularly glazing process significantly reduce bacterial biofilm formation and the risk of failure of final restoration.

Accelerated Fatigue Model for Predicting Composite Restoration Failure

An empirical method is proposed to predict the clinical performance of resin composite dental restorations by using laboratory data derived from simple specimens subjected to chemical degradation and accelerated cyclic fatigue. Three resin composites were used to fill dentin disks (2-mm inner diameter, 5-mm outer diameter, and 2 mm thick) made from bovine incisor roots. The specimens (n = 30 per group) were aged with different durations of a low-pH challenge (0, 24, and 48 h under pH 4.5) before being subjected to diametral compression with either a monotonically increasing load (fast fracture) or a cyclic load with a continuously increasing amplitude (accelerated fatigue). The data from 1 material were used to establish the relationship between laboratory time (number of cycles) and clinical time to failure (years) via the respective survival probability curves. The temporal relationship was then used to predict the clinical rates of failure for restorations made of the other 2 materials, and the predictions were compared with the clinical data to assess their accuracy. Although there were significant differences in the fast fracture strength among the groups of materials or durations of chemical challenge, fatigue testing was much better at separating the groups. Linear relationships were found between the laboratory and clinical times to failure for the first material (R2 = 0.90, 0.90, and 0.62 for the 0-, 24-, and 48-h low-pH groups, respectively). The clinical life of restorations made of the other 2 materials was best predicted with data from the 48-h low-pH groups. In conclusion, an accelerated fatigue model was successfully calibrated and applied to predict the clinical failure of resin composite restorations, and the predictions based on data obtained from chemically aged specimens provided the best agreement with clinical data.

Multidisciplinary management of an enamel–dentine crown fracture with insufficient inter-occlusal restorative space: A case report

Dental trauma occurs commonly in young patients, can be complex to treat and can have negative psychological and social impacts on patients' lives. This case report outlines a multidisciplinary team approach to restoration of a traumatized anterior tooth with delayed presentation, insufficient inter-occlusal space for restoration and history of multiple failed restorations. This case report demonstrates orthodontic and restorative techniques for the management of insufficient inter-occlusal space and the indirect restoration of a traumatized anterior tooth. CPD/Clinical Relevance: A multidisciplinary team approach can be used to reorganize a patients' occlusion to provide the inter-occlusal space required to provide restorations.

Novel rechargeable nano-calcium phosphate and nano-calcium fluoride resin cements

ObjectiveIn most clinical circumstances, secondary caries at the margin of fixed dental restorations leads to restoration failure and replacement. Accordingly, the objectives of this study were to: (1) develop a novel rechargeable nano-calcium phosphate (NACP) and nano-calcium fluoride (nCaF2) resin-based cement; and (2) investigate their mechanical properties and calcium (Ca), phosphate (P), and fluoride (F) ion release, recharge, and re-release for the first time. MethodsThe cement matrix consisted of pyromellitic glycerol dimethacrylate (PMGDM), ethoxylated bisphenol-A-dimethacrylate (EBPADMA) was denoted PEHB. Four cements were fabricated: (1) PEHB+0%NACP+0%nCaF2 (experimental control); (2) PEHB+25%NACP+0%nCaF2, (3) PEHB+0%NACP+25%nCaF2; (4) PEHB+12.5%NACP+12.5% nCaF2. RelyX luting cement was used as a commercial control. Mechanical properties and long-term Ca, P, and F ion release, recharge, and re-release were evaluated. ResultsAdding 25% NACP, 25% nCaF2 and adding both 12.5% NACP and 12.5% nCaF2 to the cement matrix presented a significantly higher shear bond strength, flexural strength compared to the commercial control (p < 0.05) with a comparable outcome with no significant different (p > 0.05) compared to experimental control. The film thickness results of all cement groups met the ISO requirement (<50 µm). The resin cement group with both 12.5% NACP and 12.5% nCaF2 successfully released Ca, P, and F ions at 3.1 ± 0.01, 1.1 ± 0.05, and 0.51±0.01 mmol/L respectively. Moreover, it showed the ability to re-release Ca, P, and F ions at 0.62±0.01, 0.12±0.01, and 0.42±0.01 mmol/L respectively. ConclusionsThe resin cement group with both 12.5% NACP and 12.5% nCaF2 demonstrated the advantages of both types of bio-interactive fillers as it could release a higher level of ions than the resin cement with 25%nCAF2 and exhibited a better rechargeability compared to the resin cement with 25%NACP. Clinical significanceThe ability of this novel resin-based cement to release, recharge, and re-release Ca, P, and F ions could be one of the keys to lengthening the survivability of fixed dental restorations. These features could help to reduce the onset of secondary caries by enhancing the remineralization and preventing the demineralization of tooth structures.

Are direct restorations an effective treatment strategy in the management of root caries lesions?

Data sources PubMed, Cochrane Library/Embase and Web of science.Study selection Randomised controlled trials and non-randomised trials reporting success or failure rates of direct restorative materials for managing root caries lesions and in vitro studies assessing performance of restorations for root caries lesions published between September 1990 and October 2021 and written in English were included.Data extraction and synthesis Data was extracted by one reviewer and quality assessment of the included clinical studies performed using the Cochrane risk-of-bias in non-randomised studies of interventions tools. Restoration success, survival and failure rates were presented for each included study with no data synthesis.Results A total of 11 clinical studies and 31 in vitro studies were included. Restoration failure rates ranged from 14-55% at 24-60 months. Success rates of atraumatic restorative technique (ART) ranged from 65-87% at 12-60 months.Conclusion There is a lack of high-quality evidence to provide a recommendation on the most appropriate restorative material for restoring root caries lesions. The survival rate of ART and conventional techniques are comparable and ART could be an optional treatment where conventional treatment is challenging.

Influence of Different Illuminants on Spectrophotometric Tooth Color Determination

Statement of problem: The vast majority of studies address the comparison of visual and instrumental tooth color determination. Although, the lighting conditions of the environment may affect the clinical shade matching performance. This study evaluated if and how different light sources can influence the spectrophotometric determination of natural tooth color. Purpose: The purpose of this study was to evaluate the precision of the spectrophotometer in tooth shade determination under the influence of different illuminants. Material and method: Three examiners, determined the shade of an upper central incisor with Vitapan 3D-Master (VITA Zahnfabrik, Bad Säckingen, Germany) and with the spectrophotometer (Vita Easyshade V, Vita Zahnfabrik, Bad Säckingen, Germany). A special fabricated device with eight light sources, designed to offer reproductible lighting conditions, was used to determine the efficiency of instrumental color determination under different illuminants. Results: Natural light (300 lux) and dental unit light at full intensity (32500 lux) produced the less ∆Eab modification. Color coordinates determined in the presence of halogen light (1800 lux), neon ambient light (3000 lux), LED with cold light (21200 lux), halogen light with neon ambient light (23400 lux), both warm and cold LED simultaneously (36000 lux) and all eight light sources of the device (44000 lux), suffered a slight modification of ∆E ab, which does not exceed the acceptability and the perceptibility threshold. The illuminant that caused the biggest modifications in color coordinates was LED warm light (1940 lux) with a ∆Eab 5.804 ± 0.271, that exceeds the acceptability and perceptability threshold. Conclusions: LED warm light influences the instrumental tooth color determination and when used, can lead to errors in communication of the color to the dental laboratory, which can cause esthetic failure of a prosthetic restoration. The best illuminant for color determination is natural light, or illuminants that simulate lighting in daily living conditions. Clinical implications: Based on the spectrophotometric readings, it was demonstrated that tooth color shifts with the change in ambient lighting conditions. Therefore, color determination should be performed with natural daylight illumination.

A quantitative synthesis of approaches, biases, successes, and failures in marine forest restoration, with considerations for future work

Abstract Marine forests is a term commonly used for coastal marine habitats formed by dense stands of brown macroalgae, typically consisting of kelp and fucoids. These habitats are highly productive, offer habitat to numerous marine organisms, and support a range of invaluable ecosystem services. Despite their importance, marine forests are declining in many regions around the world as a result of interacting global, regional, and local‐scale stressors. Consequently, interest in restoration as a tool to mitigate these declines and reinstate marine forests is growing. Recent reviews have provided insights into marine forest restoration; however, for the most part, a synthesis of restoration success is lacking. A meta‐analysis and quantitative review of published marine forest restoration efforts was conducted to examine: (i) how restoration affects the abundance and morphology of marine forest species; and (ii) trends in marine forest restoration success. The meta‐analysis of 25 studies revealed that restoration positively influences the abundance and morphology of marine forest species. The quantitative review of 63 studies demonstrated that taxa and restoration technique were important factors influencing restoration success, and revealed a bias towards the monitoring and reporting of abundance and morphological response variables. The review also highlighted a lack of monitoring and/or reporting of environmental variables at restoration sites, and limited comparative research across environmental contexts and restored species. It is shown that successful marine forest restoration is possible at experimental scales, but that better monitoring and reporting of restoration efforts, alongside increased project durations, could improve our understanding of restoration success at the ecosystem level. Considerations for future marine forest restoration efforts are also provided. It is hoped that the review will advance marine forest restoration efforts, allowing the preservation of these valuable ecosystems and their associated services.

Survival analysis of fragment reattachments and direct composite restorations in permanent teeth after dental traumatic injuries.

In case of crown fractures after traumatic dental injuries, the affected teeth can be restored either with reattachment of the fractured fragment or with a direct composite restoration. So far, longevity data for reattachments and direct composite restorations with regard to different failure types (pulp necrosis and infection, restoration loss) are scarce. Therefore, the aim of this retrospective study was to evaluate the restorative and biological survival of reattached fragments and composite restorations after crown fractures in permanent teeth. Dental records of patients treated between 2000 and 2018 were retrospectively analysed regarding the restoration (reattachment or direct composite restorations) of teeth with crown fractures. Survival (no further intervention) and restorative and/or biological failure of all restored teeth were recorded. Statistical analysis was performed using Kaplan-Meier statistics, and the mean annual failure rates for two and 5 years were calculated. Furthermore, the effect of potential risk factors on survival was assessed. Log-rank tests and univariate Cox regression models (likelihood ratio tests) were used to assess the univariate effect of all variables of interest. Variables with a p-value ≤.10 were included in a multivariate Cox regression model with shared frailty (p< .05). Overall, 164 patients with 235 teeth (uncomplicated crown fracture: N=201, complicated crown fracture: N=34) were included (1.6± 2.5 years observation time). Of these, 59 teeth were restored with reattachment of the fragment and 176 with a composite restoration. Overall, composite restorations had a significantly higher survival rate than reattachments (p= .002). The cumulative survival after 2 years was 42.9% and 65.0% for teeth treated with a reattachment (mAFR=34.5%) and a composite restoration (mAFR=19.3%), respectively. When differentiating between failure types, restoration failure and pulp necrosis were significantly more frequently detected in reattached crown fractures compared to composite restorations (restorative failure: p= .001; biological failure: p=.036). In the multivariate Cox regression model, the variable jaw and luxation significantly influenced the survival when the tooth was restored with a composite restoration. The survival was not influenced by the fracture type. Restorative and biological failures were more frequently detected when the tooth was restored with a reattached fragment compared to a direct composite restoration. Both, restoration failure and pulp necrosis with infection should be considered as frequent complications after restoration of crown-fractured teeth which emphasizes the necessity of regular and short follow-up intervals throughout the first 2 years.

Influence of the chemomechanical and mechanical carious tissue removal on the risk of restorative failure: a systematic review and meta-analysis.

To summarize and evaluate critically the results of clinical trials comparing the risk of failure of restorations after chemomechanical and mechanical carious tissue removal. The PubMed/MEDLINE, EMBASE, Scopus, LILACS, Web of Science, and Cochrane Central Register of Controlled Trials (CENTRAL) databases, and grey literature were searched to identify studies related to the research question and published up to January 2022. Two authors independently selected the studies, extracted the data, and assessed the risk of bias and the certainty of evidence. Meta-analysis was performed using a random effects model to compare the effect of chemomechanical and mechanical excavation on the outcome (restorative failure), considering the type of carious tissue removal (selective and complete) as subgroups. From 443 potentially eligible studies, 58 clinical studies were selected for full-text analysis, and 6 were included in the review. There was no statistically significant difference in the risk for failure of restorations performed after chemomechanical and mechanical excavation (RR: 1.26, 95% CI 0.93; 1.72, p = 0.14) either for complete (p = 0.97) or selective (p = 0.11) carious tissue removal. The heterogeneity found was null. The risk of bias was high and the certainty of evidence was low. Based on the low certainty of evidence, the risk of failure of restorations performed after chemomechanical and mechanical carious tissue removal is similar. Chemomechanical carious tissue removal may be performed before restoration placement, without jeopardizing the short-term longevity. Further studies are required before definitive conclusions can be drawn.

Interspecific associations of mangrove species and their preferences for edaphic factors and water quality

Abstract. Marpaung BA, Budiadi, Pertiwiningrum A, Lestari LD, Nurjanto HH, Widiyatno. 2022. Interspecific associations of mangrove species and their preferences for edaphic factors and water quality. Biodiversitas 23: 4626-4635. Scientists from different regions have reported failures of mangrove restorations that were predicted due to the unsuitability of the species for the habitats. Habitat preferences should become an important consideration for mangrove restoration and management. This study aimed to find interspecific associations between species and examine the edaphic factors and water quality suitable for mangroves. Eight research stations (and 24 sample plots) were established purposively based on the vegetation structure and salinity levels in successful mangrove restorations in East Lampung in 2020. In each plot, vegetal data and sediment and water samples were taken. The species domination was analyzed using the important value index (IVI), and interspecific associations were determined using a 2x2 contingency table. The edaphic factors and water quality were analyzed using principal component analysis (PCA) to find factors that had significant correlations among others. The effects of the edaphic factors and water quality on species regeneration were analyzed using multiple linear regression by backward elimination to develop a model of habitat preferences for mangroves. Based on the results, Avicennia marina and Rhizophora sp. were the dominant species in all the zones. Still, the lack of interspecific association ( ) showed that both species had different preferences for the habitat. We found four principal components (PCs) of edaphic factors—i.e., the environmental (soil and surface) temperature, dusty clay and Ca, inorganic nitrogen (NH4-N and NO3-N), and Mg—and two PCs of water quality, i.e., nontoxic pollutants (total suspended solids and turbidity) and anthropogenic factors (NO2-N and PO4-P), as predictors for multiple linear regression. The seedlings of A. marina had no specific preferences for edaphic factors but significantly preferred nontoxic pollutants (R2 = 0.619), while the seedlings of Rhizophora spp. significantly preferred a specific environmental temperature, dusty clay and Ca, and inorganic nitrogen (R2 = 0.768), and nontoxic pollutants (R2 = 0.755). Combining A. marina and Rhizophora spp. in mangrove restorations should be avoided. Therefore, spatial planting patterns or sequential planting based on the succession stages of the habitat could be established.

Randomized clinical split-mouth study on a novel self-adhesive bulk-fill restorative vs. a conventional bulk-fill composite for restoration of class II cavities – results after three years

ObjectivesThis randomized prospective split-mouth study evaluated the clinical performance of a novel, tooth-colored, self-adhesive bulk-fill restorative (SABF, 3M) for restoration of class II cavities as compared to a conventional bulk-fill composite (Filtek One, 3M; FOBF) over 36 months. The null-hypothesis was that both materials perform equally regarding clinical success and performance according to the FDI clinical criteria and scoring system. Methods30 patients received one SABF and one FOBF restoration each. For FOBF, Scotchbond Universal (3M) was used as adhesive (self-etch mode), whereas SABF was applied without adhesive. Two blinded examiners evaluated the restorations at baseline, 24 and 36 months using FDI criteria. Data were analyzed non-parametrically (χ2-tests; α=0.05). Results29 patients were available for the 24- and 36-month examinations. Clinical success rate was 96.6% for both materials at 36-mo (one restoration failure due to secondary caries each). All other restorations revealed clinically acceptable FDI scores at all recalls. FOBF performed significantly better than SABF at all time points regarding surface lustre (p<0.001) and color match and translucency (p<0.001) and regarding marginal staining at 36-months (p=0.008). Marginal staining and marginal adaptation deteriorated significantly over time for both materials (both p<0.001). ConclusionsThe null-hypothesis could only partially be rejected. Both materials performed similarly regarding clinical success and performance within 36 months of clinical service, but SABF exhibited significantly inferior, but clinically fully acceptable esthetic properties as compared to FOBF. Both restorative materials showed clinically fully acceptable results over 36 months of clinical service and thus may be recommended for clinical use. Clinical significanceThe novel tooth-colored self-adhesive bulk-fill restorative exhibited clinically fully acceptable results over 36 months of clinical service, similarly to a conventional bulk-fill restorative used with a universal adhesive, but with slight shortcomings in esthetic properties. Therefore, both restorative materials may be recommended for clinical use.

In vitro attrition wear resistance of four types of paste-like bulk-fill composite resins

BackgroundRecently, the application of bulk-fill composite resins has increased significantly. Attrition wear and the consequently increased surface roughness of composite resins are among the causes of restoration failure in the posterior teeth. This study aimed to compare the attrition wear and surface roughness of four types of bulk-fill composite resins compared to a conventional composite resin.MethodsEverX-Posterior, X-tra fil, SonicFill 2, and Filtek Bulk-Fill composites (bulk-fill) and Z250 composite (conventional resin composite) were evaluated. Thirty cylindrical specimens (n = 6) were weighed and monitored for 24 h until their weight was stabilized. The primary surface roughness of the specimens was measured by a profilometer. The specimens were then subjected to attrition wear in a chewing simulator. Next, the specimens were weighed, and the surface roughness was measured again. Data were analyzed by one-way ANOVA and Tukey’s post-hoc test at P < 0.05 significance level.ResultsAccording to one-way ANOVA, the difference in weight loss was significant among the groups (P = 0.004) but the difference in surface roughness of the groups was not significant after the attrition wear (P > 0.05). Tukey’s post-hoc test showed that the weight loss of bulk-fill composites was not significantly different from that of Z250 conventional composite after the attrition wear (P > 0.05).ConclusionWithin the limitations of this study, it appears that the tested bulk-fill composite resins are comparable to the conventional composite regarding their attrition wear, increased surface roughness, and weight loss.

Clinical outcomes of implant-supported monolithic zirconia crowns and fixed partial dentures: A systematic review.

To determine the survival rates of implant-supported monolithic zirconia crowns and fixed partial dentures (FPD). An electronic search for articles in the English language literature published from January 1, 2001 to September 17, 2021 was performed using PubMed, Scopus, and CENTRAL search engines. After applying predetermined inclusion and exclusion criteria, the definitive list of selected articles was used for calculating the interval survival rate (ISR) and cumulative survival rate (CSR). Restoration failure in this study was defined as the fracture or compromise of any part of the ceramic restoration that required the removal or remake of the implant-supported restoration. The electronic search resulted in 457 titles. The systematic application of inclusion and exclusion criteria resulted in 14 clinical studies that addressed the clinical outcomes of implant-supported monolithic zirconia crowns and fixed partial dentures. Of these, 3 were randomized controlled trials, 5 were prospective studies, and 6 were retrospective studies. Follow-up periods ranged from 1 to 5 years. Of the 644 implant-supported monolithic zirconia restorations computed in this systematic review, there was only 1 reported failure of the monolithic zirconia restorative material over a follow-up period of up to 5 years, for a cumulative survival rate of 99.84%. At the maximum follow-up interval of 5 years, the cumulative survival rate for monolithic zirconia single crowns was 100% and the cumulative survival rate for monolithic zirconia fixed partial dentures was 99.60%. Implant-supported monolithic zirconia single crowns and fixed partial dentures have excellent short-term (<5 years) survival rates but the evidence for medium-term survival (>5 years) and beyond is lacking.

Evaluation of a Method to Determine Wear Resistance of Class I Tooth Restorations during Cyclic Loading.

The aim of this study was the development of a test regime to determine the wear resistance and predict the clinical performance of conventional glass ionomer cement (GIC) restorations in Class I tooth cavities. Cavities were prepared in excised human teeth and restored using three conventional glass ionomer restorative materials: DeltaFil, Fuji IX GP and Ketac Universal. The restored teeth were mechanically and thermally stressed using a chewing simulator with a maximum number of 1,200,000 load cycles. Besides determining the number of cycles achieved, the abrasion volume after termination of the chewing simulation was calculated using µCT images. All teeth restored with DeltaFil reached 1,200,000 cycles without any restoration failure. Only 37.5% of the restorations each with Ketac Universal and Fuji IX GP were able to achieve the maximum cycle number. A significant lower abrasion volume for restorations with DeltaFil compared to Ketac Universal (p = 0.0099) and Fuji IX GP (p = 0.0005) was found. Laboratory chewing simulations are a useful tool to study basic wear mechanisms in a controlled setting with in-vivo related parameters. DeltaFil shows an improved wear resistance compared to other conventional GICs, indicating the high potential of this material for long-lasting Class I restorations.

Immune determinants of chronic sequelae after respiratory viral infection.

The acute effects of various respiratory viral infections have been well studied, with extensive characterization of the clinical presentation as well as viral pathogenesis and host responses. However, over the course of the recent COVID-19 pandemic, the incidence and prevalence of chronic sequelae after acute viral infections have become increasingly appreciated as a serious health concern. Post-acute sequelae of COVID-19, alternatively described as "long COVID-19," are characterized by symptoms that persist for longer than 28 days after recovery from acute illness. Although there exists substantial heterogeneity in the nature of the observed sequelae, this phenomenon has also been observed in the context of other respiratory viral infections including influenza virus, respiratory syncytial virus, rhinovirus, severe acute respiratory syndrome coronavirus, and Middle Eastern respiratory syndrome coronavirus. In this Review, we discuss the various sequelae observed following important human respiratory viral pathogens and our current understanding of the immunological mechanisms underlying the failure of restoration of homeostasis in the lung.