Umbilical cord mesenchymal stem cells and lung cancer: We should be hopeful or hopeless?

Lung cancer (LC) is one of the leading causes of cancer-caused death that possesses a poor prognosis and low survival rate worldwide. In general, LC is classified into small-cell (SCLC) and non-small-cell carcinoma (NSCLC) (involving 80% of patients). Although chemotherapy, radiotherapy, surgery, and molecular-targeted therapy are considered standard approaches for LC treatment, these options have low success with detrimental effects on the life quality of patients. Ergo, recommending treatment with maximum effectiveness and minimum side effects for LC patients has been a substantial challenge for researchers and clinicians in the present era. Recently, mesenchymal stem cells (MSCs)-based strategies have sparked much interest in preventing or treating numerous illnesses. These multipotent stem cells can be isolated from diverse sources, such as umbilical cord, bone marrow, and adipose tissue. Among these sources, umbilical cord mesenchymal stem cells (UC-MSCs) have been in the spotlight of MSCs-based therapies thanks to their considerable advantages, such as high proliferation ability, low immune reactions and tumorigenesis, and easiness in collection and isolation. Some experimental studies have investigated the functionality of intact UC-MSCs and extracellular vesicles, exosomes, and conditioned medium derived from UC-MSCs, as well as genetically engineered UC-MSCs. In this review, we aimed to highlight the influences of these UMSCs-based methods in LC treatment with cellular and molecular insights.

Profiloplasty and facial contouring with injectables: A holistic, practical, and user-friendly approach.

BACKGROUND: Expansion of the aesthetic treatment armamentarium with novel injectable products has greatly improved our ability to reshape and enhance the facial profile. However, full-face "profiloplasty" with injectables remain a nascent concept and is insufficiently considered in daily practice. While techniques have been widely published for treating the individual facial areas that constitute an attractive profile-including the forehead, nose, lips, jawline, and chin-the literature remains fragmented on more universal methods for profile improvement. AIMS: To collate disparate knowledge on profile optimization with injectables, and define a holistic, practical, and user-friendly approach to profiloplasty and facial contouring. METHODS: Consideration is given to key anatomical aspects and the changes that occur with age; patient assessment parameters for planning profiloplasty; and the technical specifications, product selection, and essential safety considerations for minimizing the risk of complications and optimizing the effectiveness of treatment. RESULTS: Relevant case studies are presented. CONCLUSIONS: Holistic approaches of this type are essential if we are to maximize the potential of full-face treatment with injectables-both now and in the future.

The validity and reliability of the Persian version of the Athlete Sleep Screening Questionnaire.

Background: Sleep as a biological phenomenon is effective in the performance and recovery of athletes. Questionnaires can be used as a cost-effective initial assessment tool for sleep. The Athlete Sleep Screening Questionnaire (ASSQ) demonstrated a clinically valid instrument for screening relevant sleep issues in athletic populations. Due to the lack of validated tools for adequate screening for sleep difficulties in the Iranian athlete population, the present study was conducted to evaluate the validity and reliability of the Persian version of the ASSQ. Materials and Methods: The translation process was performed using instructions by Beaton et al. Content validity was assessed by a panel of experts. Exploratory and confirmatory factor analysis was performed for two 5-item sleep difficulty scores (SDS) and a 4-item chronotype score. Internal consistency based on Cronbach's alpha and McDonald's omega and stability reliability were used to evaluate reliability. Results: The ASSQ achieved conceptual and semantic equivalence with the original scale. The item-level content validity index (I-CVI) of each item ranged from 0.87 to 1, and the averaging scale-level CVI/average was 0.95. In factor analysis, one factor for SDS and one factor for chronotype score were identified and confirmed. The internal consistency of the SDS scale (α =0.77, Ω =0.83) and chronotype (α =0.74, Ω =0.77) was acceptable. Stability reliability was confirmed for SDS scale (intra-class correlation [ICC] =0.87) and for chronotype (ICC = 0.83). Conclusion: Persian ASSQ has acceptable psychometric measurement properties as a screening tool to assess sleep in Iranian athletes.

A controlled randomized trial with a 12-week follow-up investigating the effects of medium-frequency neuromuscular electrical stimulation on pain, VMO thickness, and functionality in patients with knee osteoarthritis.

BACKGROUND: One of the major contributors to disability in Knee osteoarthritis (KOA) patients is weakness in the Quadriceps Femoris muscle. Neuromuscular electrical stimulation (NMES) has been used in rehabilitation for patients suffering from muscle weakness. Thus, the purpose of the study was to assess the effectiveness of NMES and exercise therapy, for improving pain, muscle weakness and function among patients with KOA. METHODS: A randomized controlled trial was conducted with 75 female patients diagnosed with KOA. Participants were divided into three intervention groups: NMES-only, exercise therapy (Exs) alone, and a combination of NMES and exercise (NMES + Exs). All patients underwent 12 supervised treatment sessions, three times a week. Outcome measures included pain intensity measured by visual analog scale (VAS), knee flexion range of motion (FROM), thigh muscle girth (TG), thickness of the Vastus Medialis Oblique (VMO), timed up and go test (TUG), six-minute walk test (6MWT), and WOMAC scores. Statistical analyses (ANOVA and Kruskal-Wallis) methods were done to compare the amounts at the baseline, immediately after treatment and after 12 weeks. RESULTS: The NMES group exhibited a significant reduction in pain at the 12-week follow-up compared to the other groups(p = 0.022). The NMES + Exs group showed better outcomes in terms of FROM, TG, and VMO thickness post-intervention (p < 0.0001, p < 0.004, p = 0.003, respectively) and at the 12-week follow-up (p < 0.0001, p < 0.0001, p < 0.0001, respectively). Additionally, NMES was superior in improving TUG and 6MWT post-intervention (p < 0.0001, p = 0.038, respectively) and during the follow-up assessments (p < 0.0001, p = 0.029, respectively). The NMES + Exs group achieved better WOMAC stiffness scores at both post-intervention and follow-up evaluations (p < 0.0001, p < 0.0001, respectively). Furthermore, at the 12-week follow-up, NMES + Exs group outperformed the others in WOMAC pain and function subscales (p = 0.003, p = 0.017, respectively), while the NMES group demonstrated better WOMAC total scores compared to the other groups (p = 0.007). CONCLUSION: The combination of NMES and exercise seems to be an efficient approach for managing KOA, as it enhances knee flexion range and TG, increases VMO thickness, and improves WOMAC scores. On the other hand, NMES alone was found to be effective in improving the physical function of KOA patients. TRIAL REGISTRATION: IRCT20101228005486N7 (06-02-2020).

Does crocin create new hope for the treatment of oral problems? A focus on periodontitis.

According to the World Health Organization (WHO) reports, oral health has an indispensable role in the maintenance of human public health. However, oral problems, especially periodontitis, are known as bad players in this issue. Periodontitis, as the most prevalent oral disease, is a type of chronic illness mediated by bacterial pathogens and immune system reactions, which is linked with the destruction of tooth-protecting tissues, such as alveolar bone and periodontal ligament. Periodontitis has a high prevalence (over 40% in the United States) and can be associated with other systemic ailments, for instance, arthritis, osteoporosis, metabolic syndrome, cancer, respiratory diseases, chronic kidney disease, and Alzheimer's disease. The common treatments for periodontitis are classified into invasive (surgical) and noninvasive (antibiotic therapy, scaling, and root planning) methods; however, these therapies have not reflected enough effectiveness for related patients. New documents inform the beneficial effects of plant-based compounds in healing various disorders, like periodontitis. In conjunction with this subject, it has been revealed that crocin, as an active component of saffron, regulates the balance between osteoclasts and osteoblasts and has a stroking role in the accumulation of the most common collagen in teeth and bone (type 1 collagen). Besides, this carotenoid compound possesses anti-inflammatory and anti-oxidative effects, which can be associated with the therapeutic processes of crocin in this oral disease. Hence, this narrative review study was performed to reflect the reparative/regenerative aspects of crocin agonist periodontitis.

A state-of-the-art review of the recent advances in exosome isolation and detection methods in viral infection.

Proteins, RNA, DNA, lipids, and carbohydrates are only some of the molecular components found in exosomes released by tumor cells. They play an essential role in healthy and diseased cells as messengers of short- and long-distance intercellular communication. However, since exosomes are released by every kind of cell and may be found in blood and other bodily fluids, they may one day serve as biomarkers for a wide range of disorders. In many pathological conditions, including cancer, inflammation, and infection, they play a role. It has been shown that the biogenesis of exosomes is analogous to that of viruses and that the exosomal cargo plays an essential role in the propagation, dissemination, and infection of several viruses. Bidirectional modulation of the immune response is achieved by the ability of exosomes associated with viruses to facilitate immunological escape and stimulate the body's antiviral immune response. Recently, exosomes have received a lot of interest due to their potential therapeutic use as biomarkers for viral infections such as human immunodeficiency virus (HIV), Hepatitis B virus (HBV), Hepatitis C virus (HCV), Epstein-Barr virus (EBV), and SARS-CoV-2. This article discusses the purification procedures and detection techniques for exosomes and examines the research on exosomes as a biomarker of viral infection.

The Effect of Berberine Supplementation on Glycemic Control and Inflammatory Biomarkers in Metabolic Disorders: An Umbrella Meta-analysis of Randomized Controlled Trials.

PURPOSE: Several meta-analyses reported berberine (BBR) supplementation improves glycemic parameters and inflammatory marker, but findings remain inconsistent. Therefore, this study was conducted. METHODS: We systematically searched PubMed, Embase, Web of Science, Scopus, and Google Scholar to identify the relevant meta-analyses up to April 2023. FINDINGS: BBR supplementation was effective in reducing fasting blood glucose (FBG) (ESWMD: -0.77; 95% CI: -0.90 to -0.63, and ESSMD: -0.65; 95% CI: -0.83 to -0.47), hemoglobin A1C (HbA1C) (ESWMD: -0.57; 95% CI: -0.68 to -0.46), homeostasis model assessment for insulin resistance (HOMA-IR) (ESWMD: -1.04; 95% CI: -1.66 to -0.42, and ESSMD: -0.71; 95% CI: -0.97 to -0.46), insulin (ESWMD: -1.00; 95% CI: -1.70 to -0.30, and ESSMD: -0.63; 95% CI: -0.94 to -0.32), interleukin (IL)-6 (ESSMD: -1.23; 95% CI: -1.61 to -0.85), tumor necrosis factor-α (TNF-α) (ESSMD: -1.04; 95% CI: -1.28 to -0.79), and C-reactive protein (CRP) (ESWMD: -0.62; 95% CI: -0.74 to -0.50, and ESSMD: -1.70; 95% CI: -2.21 to -1.19). IMPLICATIONS: The finding of our umbrella showed that the supplementation of BBR could be effective in improving glycemic parameters and inflammatory marker in adults.

The effect of flaxseed supplementation on sex hormone profile in adults: a systematic review and meta-analysis.

Inconsistent data suggest that flaxseed supplementation may have a role in sex hormones. We aimed to carry out a systematic review and meta-analysis of randomized controlled trials (RCTs) investigating effects of flaxseed supplementation on sex hormone profile. PubMed, Scopus, Embase, Cochrane Library, Web of Science databases, and Google Scholar were searched up to March 2023. Standardized mean difference (SMD) was pooled using a random-effects model. Sensitivity analysis, heterogeneity, and publication bias were reported using standard methods. The quality of each study was evaluated with the revised Cochrane risk-of-bias tool for randomized trials, known as RoB 2. Finding from ten RCTs revealed that flaxseed supplementation had no significant alteration in follicle-stimulating hormone (FSH) (SMD: -0.11; 95% CI: -0.87, 0.66: p = 0.783), sex hormone-binding globulin (SHBG) (SMD: 0.35; 95% CI: -0.02, 0.72; p = 0.063), total testosterone (TT) levels (SMD: 0.17; 95% CI: -0.07, 0.41; p = 0.165), free androgen index (FAI) (SMD = 0.11, 95% CI: -0.61, 0.83; p = 0.759), and dehydroepiandrosterone sulfate (DHEAS) (SMD: 0.08, 95%CI: -0.55, 0.72, p = 0.794). Flaxseed supplementation had no significant effect on sex hormones in adults. Nevertheless, due to the limited included trials, this topic is still open and needs further studies in future RCTs.

Nano-scale delivery systems for siRNA delivery in cancer therapy: New era of gene therapy empowered by nanotechnology.

RNA interference (RNAi) is a unique treatment approach used to decrease a disease's excessive gene expression, including cancer. SiRNAs may find and destroy homologous mRNA sequences within the cell thanks to RNAi processes. However, difficulties such poor cellular uptake, off-target effects, and susceptibility to destruction by serum nucleases in the bloodstream restrict the therapeutic potential of siRNAs. Since some years ago, siRNA-based therapies have been in the process of being translated into the clinic. Therefore, the primary emphasis of this work is on sophisticated nanocarriers that aid in the transport of siRNA payloads, their administration in combination with anticancer medications, and their use in the treatment of cancer. The research looks into molecular manifestations, difficulties with siRNA transport, the design and development of siRNA-based delivery methods, and the benefits and drawbacks of various nanocarriers. The trapping of siRNA in endosomes is a challenge for the majority of delivery methods, which affects the therapeutic effectiveness. Numerous techniques for siRNA release, including as pH-responsive release, membrane fusion, the proton sponge effect, and photochemical disruption, have been studied to overcome this problem. The present state of siRNA treatments in clinical trials is also looked at in order to give a thorough and systematic evaluation of siRNA-based medicines for efficient cancer therapy.

The effectiveness of treatment with probiotics in Helicobacter pylori eradication: results from an umbrella meta-analysis on meta-analyses of randomized controlled trials.

Background and aims: The purpose of this umbrella meta-analysis was to quantitatively summarize meta-analyses of randomized controlled trial (RCT) studies regarding the effects of probiotic supplementation on Helicobacter pylori (H. pylori) eradication. Methods: A thorough search of the electronic databases including PubMed, Web of Science, Embase, Scopus, and Google Scholar was carried out from the inception up to May 2022. For the evaluation of overall effect sizes, the pooled relative risk (RR) or odds ratio (OR) and their corresponding 95% confidence intervals (CI) were calculated. The random-effects model was used for the meta-analysis. Results: Overall, 18 eligible studies (47 278 participants in total) were included in the study. The findings revealed that probiotics have a beneficial impact on H. pylori eradication (pooled ESRR: 1.13; 95% CI: 1.11, 1.14, p < 0.01, and ESOR = 1.86, 95% CI: 1.70, 2.03, p < 0.01). Greater effects on H. pylori eradication were observed when higher doses (>10 × 1010 CFU) and mixed strains were supplemented. Conclusion: The present umbrella meta-analysis suggests that supplementation with probiotics may be considered as an efficient approach to ameliorate H. pylori complications, particularly probiotics with higher CFUs and mixed strains.

Profiling inflammatory mechanisms, hyperphosphorylated tau of hippocampal tissue and spatial memory following vitamin D3 treatment in the mice model of vascular dementia.

BACKGROUND: The aim of this study was to investigate the effect of vitamin D3 (VitD3) on inflammatory mechanisms, hyperphosphorylated tau (p-tau) in the hippocampus, and cognitive impairment of the mouse model of vascular dementia (VaD). METHODS: In this study, 32 male mice were randomly assigned to the control, VaD, VitD3 (300 IU/Kg/day), and VitD3 (500 IU/Kg/day) groups. VaD and VitD3 groups were gavaged daily for 4 weeks with a gastric needle. For biochemical assessments, blood samples and the hippocampus were isolated. IL-1ß and TNF-α were analyzed by ELISA, and p-tau and other inflammatory molecules were measured by western blot. RESULTS: VitD3 supplements significantly (P < 0.05) decreased the level of inflammatory factors in the hippocampus and prevented apoptosis. However, regarding p-tau in hippocampal tissue, this decrease was not statistically significant (P > 0.05). The results of behavioral assessments showed that VitD3 significantly improved the spatial memory of treated mice. CONCLUSION: These results suggest that the neuroprotective effects of VitD3 are mainly associated with their anti-inflammatory effects.

Cytokine sustained delivery for cancer therapy; special focus on stem cell- and biomaterial- based delivery methods.

As immune regulators, cytokines serve critical role as signaling molecules in response to danger, tissue damage, or injury. Importantly, due to their vital role in immunological surveillance, cytokine therapy has become a promising therapeutics for cancer therapy. Cytokines have, however, been used only in certain clinical settings. Two key characteristics of cytokines contribute to this clinical translational challenge: first, they are highly pleiotropic, and second, in healthy physiology, they are typically secreted and act very locally in tissues. Systemic administration of the cytokines can consequently result in serious side effects. Thus, scientists have sought various strategies to circumvent theses hurdles. Recent in vivo reports signify that cytokine delivery platforms can increase their safety and therapeutic efficacy in tumor xenografts. Meanwhile, cytokine delivery using multipotent stem cells, in particular mesenchymal stem/stromal cells (MSCs), and also a diversity of particles and biomaterials has demonstrated greater capability in this regards. Herein, we take a glimpse into the recent advances in cytokine sustained delivery using stem cells and also biomaterials to ease safe and effective treatments of a myriad of human tumors.

A state-of-the-art review on the MicroRNAs roles in hematopoietic stem cell aging and longevity.

Aging is a biological process determined through time-related cellular and functional impairments, leading to a decreased standard of living for the organism. Recently, there has been an unprecedented advance in the aging investigation, especially the detection that the rate of senescence is at least somewhat regulated via evolutionarily preserved genetic pathways and biological processes. Hematopoietic stem cells (HSCs) maintain blood generation over the whole lifetime of an organism. The senescence process influences many of the natural features of HSC, leading to a decline in their capabilities, independently of their microenvironment. New studies show that HSCs are sensitive to age-dependent stress and gradually lose their self-renewal and regeneration potential with senescence. MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally inhibit translation or stimulate target mRNA cleavage of target transcripts via the sequence-particular connection. MiRNAs control various biological pathways and processes, such as senescence. Several miRNAs are differentially expressed in senescence, producing concern about their use as moderators of the senescence process. MiRNAs play an important role in the control of HSCs and can also modulate processes associated with tissue senescence in specific cell types. In this review, we display the contribution of age-dependent alterations, including DNA damage, epigenetic landscape, metabolism, and extrinsic factors, which affect HSCs function during aging. In addition, we investigate the particular miRNAs regulating HSCs senescence and age-associated diseases. Video Abstract.

A comprehensive survey into the role of exosomes in pancreatic cancer; from the origin of cancer to the progress and possibility of diagnosis and treatment.

Pancreatic cancer is the fourth most common malignant tumor in the world, which has a high mortality rate due to high invasiveness, early metastases, lack of specific symptoms, and high invasiveness. Recent studies have shown that exosomes can be essential sources of biomarkers in pancreatic cancer. Over the past ten years, exosomes have been implicated in multiple trials to prevent the growth and metastasis of many cancers, including pancreatic cancer. Exosomes also play essential roles in immune evasion, invasion, metastasis, proliferation, apoptosis, drug resistance, and cancer stemness. Exosomes help cells communicate by carrying proteins and genetic material, such as non-coding RNAs, including mRNAs and microRNAs. This review examines the biological significance of exosomes in pancreatic cancer and their functions in tumor invasion, metastasis, treatment resistance, proliferation, stemness, and immune evasion. We also emphasize recent advances in our understanding of the main functions of exosomes in diagnosing and treating pancreatic cancer.

What challenges do people face in response to the long-term use of face masks?

BACKGROUND: The world is ceaselessly adapting to the ever-changing circumstances surrounding the COVID-19 pandemic, and face masks have become a part of our daily routine. Considering the fact that face masks are here to stay, there are challenges people experience regarding wearing them. In this descriptive study, we aimed to investigate the frequent outcomes of long-term use of face masks in the general population. METHODS: Twenty-five nursing students who attended the university wearing face masks owing to the current pandemic were selected. The data were collected using semi-structured interviews. The interviews were transcribed verbatim and analyzed according to the qualitative content analysis according to the Graneheim and Lundman method. RESULTS: The mean current age of the students was 20 (standard deviation [SD] = 2.5) years, and 60% of the students were women. The two main themes that emerged during data analysis were: 1. Physical health related problems, which included 3 categories; a) skin reactions, b) respiratory consequences, and c) visual complaints 2. Socioeconomic problems, including the 3 categories of; a) communication failure, b) personal style and appearance, and c) economic factors. CONCLUSION: We support the necessity of face masks for a safe reopening of communities. Considering their advantages, some basic measurements are necessary to reduce the abovementioned concerns.

Efficacy of high-intensity laser therapy in comparison with conventional physiotherapy and exercise therapy on pain and function of patients with knee osteoarthritis: a randomized controlled trial with 12-week follow up.

Knee osteoarthritis (KOA) is one of the most common musculoskeletal disorders causing pain and functional impairment. The purpose of the study is to compare the effects of high-intensity laser therapy (HILT), conventional physical therapy (CPT), and exercise therapy (ET) on pain and function in patients with KOA. The study was designed as an assessor-blind randomized controlled trial. Ninety-three patients (aged between 50 and 75 years) with proved KOA were included and randomly allocated into three groups, and received 12 sessions of HILT, CPT, or ET. The outcomes were pain intensity measured by visual analog scale (VAS), knee flexion range of motion (FROM), timed up and go test (TUG), 6-min walk test (6MWT), and functionality of knee measured by the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire. Statistical analyses were done to compare the amounts at the baseline, immediately after treatment and after 12 weeks. HILT was significantly more effective than the other groups in decreasing the VAS, increasing FROM and improving the scores of WOMAC (total and function subscale) both after treatment and after 12 weeks. The effect of HILT and CPT on the TUG, 6MWT, and WOMAC pain subscale was not significantly different after treatment, and both were better than ET. HILT was significantly better than the others after follow-up, particularly more effective on the stiffness subscale of WOMAC. HILT combined with exercise therapy, as a useful therapeutic approach, could have positive influences on KOA patients.

Paediatric forearm fractures: functional outcome of conservative treatment.

BACKGROUND: Forearm fractures are common in the paediatric age group. Closed reduction and casting are the primary means of treatment in over 90% of these fractures. Resultant deformities are usually a product of indirect trauma involving angular loading combined with rotational deformity and fragment displacement. MATERIALS AND METHODS: Retrospectively, 48 patients aged between 4 to 12 years with forearm fractures, were treated conservatively with closed reduction and a cast during a 2-year period. Functional outcomes were measured in terms of pronation and supination. RESULTS: All fractures united before the final visit. Most forearm bone fractures were complete fractures at the mid shaft. Eighty-six percent of the patients had excellent functional outcomes and none had poor outcomes. There were significantly reduced angles of deformities before and after treatment (p < 0.05). Radiographically, in the frontal plane, 57.1% of radius and 73.9% of ulnar fractures achieved perfect reduction (i.e. a degree of deformity of less than 5 degrees). However, in the lateral plane, there were fewer perfect reductions for the radius and ulna, at 14.6% and 54.3%, respectively. All except for one patient were satisfied with the outcomes. The level of fracture did not influence the outcomes. CONCLUSION: Conservative treatment is still an acceptable form of treatment especially for stable forearm fractures in children achieving excellent outcomes (Tab. 1, Fig. 7, Ref. 20).

A comparison of fatigue crack growth in human enamel and hydroxyapatite.

Cracks and craze lines are often observed in the enamel of human teeth, but they rarely cause tooth fracture. The present study evaluates fatigue crack growth in human enamel, and compares that to the fatigue response of sintered hydroxyapatite (HAp) with similar crystallinity, chemistry and density. Miniature inset compact tension (CT) specimens were prepared that embodied a small piece of enamel (N=8) or HAp (N=6). The specimens were subjected to mode I cyclic loads and the steady state crack growth responses were modeled using the Paris Law. Results showed that the fatigue crack growth exponent (m) for enamel (m=7.7+/-1.0) was similar to that for HAp (m=7.9+/-1.4), whereas the crack growth coefficient (C) for enamel (C=8.7 E-04 (mm/cycle)x(MPa m(0.5))(-m)) was significantly lower (p<0.0001) than that for HAp (C=2.0 E+00 (mm/cycle)x(MPa m(0.5))(-m)). Micrographs of the fracture surfaces showed that crack growth in the enamel occurred primarily along the prism boundaries. In regions of decussation, the microstructure promoted microcracking, crack bridging, crack deflection and crack bifurcation. Working in concert, these mechanisms increased the crack growth resistance and resulted in a sensitivity to crack growth (m) similar to bone and lower than that of human dentin. These mechanisms of toughening were not observed in the crack growth response of the sintered HAp. While enamel is the most highly mineralized tissue of the human body, the microstructural arrangement of the prisms promotes exceptional resistance to crack growth.

A comparison of fatigue crack growth in resin composite, dentin and the interface.

OBJECTIVES: The objective of this in vitro study was to evaluate the fatigue crack growth properties of the dentin/resin adhesive interface. METHODS: Compact tension (CT) specimens were prepared from coronal dentin, resin composite, and dentin bonded to resin composite using Optibond Solo Plus adhesive. All specimens were then subjected to cyclic Mode I loading while fully hydrated at a stress ratio of R=0.1 and frequency of 5 Hz. Steady state fatigue crack growth was modeled using the Paris Law in terms of the exponent (m) and coefficient (C). RESULTS: The average fatigue crack growth rates in the resin composite ranged from 1.6E-06 to 3.8E-05 mm/cycle with growth occurring over a stress intensity range from 0.40 to 0.77 MPa m(1/2); the average growth exponent was 6.9+/-3.1. Average fatigue crack growth rates for the dentin/resin interface specimens ranged from 5.5E-07 to 6.4E-03 mm/cycle with growth occurring over a stress intensity range from 0.37 to 0.64 MPa m(1/2). The Paris Law exponent for these specimens ranged from 16

Age, dehydration and fatigue crack growth in dentin.

A preliminary study of the effects from age and dehydration on fatigue crack growth in human dentin was conducted. Compact tension (CT) fatigue specimens of coronal dentin were prepared from extracted molars and subjected to high cycle fatigue (10(5)