Update to U.S. Selected Practice Recommendations for Contraceptive Use: Self-Administration of Subcutaneous Depot Medroxyprogesterone Acetate.

U.S. Selected Practice Recommendations for Contraceptive Use (U.S. SPR), adapted by CDC from global guidance developed by the World Health Organization (WHO), provides evidence-based guidance on contraceptive use for U.S. health care providers (1). During January-February, 2021, CDC evaluated the 2019 WHO recommendation on self-administered subcutaneous depot medroxyprogesterone acetate (DMPA-SC) (2). CDC adopted the WHO recommendation on the basis of moderate-certainty evidence that self-administered DMPA-SC is safe and effective, and has higher continuation rates compared with provider-administered DMPA. The new U.S. SPR recommendation states that self-administered DMPA-SC should be made available as an additional approach to deliver injectable contraception. Provider-administered DMPA should remain available. Self-administered DMPA-SC is a user-controlled method that has the potential to improve contraceptive access and increase reproductive autonomy. Self-administered DMPA-SC should be offered in a noncoercive manner through a shared decision-making process between patients and their health care providers, with a focus on patient preferences and equitable access to the full range of contraceptive methods.

Iron and Sulfur Precursors Affect Crystalline Structure, Speciation, and Reactivity of Sulfidized Nanoscale Zerovalent Iron.

The reactivity of sulfidized nanoscale zerovalent iron (SNZVI) is affected by the amount and species of sulfur in the materials. Here, we assess the impact of the Fe (Fe2+ and Fe3+) and S (S2O42-, S2-, and S62-) precursors used to synthesize both NZVI and SNZVI on the resulting physicochemical properties and reactivity and selectivity with water and trichloroethene (TCE). X-ray diffraction indicated that the Fe precursors altered the crystalline structure of both NZVI and SNZVI. The materials made from the Fe3+ precursor had an expanded lattice in the Fe0 body-centered-cubic (BCC) structure and lower electron-transfer resistance, providing higher reactivity with water (∼2-3 fold) and TCE (∼5-13 fold) than those made from an Fe2+ precursor. The choice of the S precursor controlled the S speciation in the SNZVI particles, as indicated by X-ray absorption spectroscopy. Iron disulfide (FeS2) was the main S species of SNZVI made from S2O42-, whereas iron sulfide (FeS) was the main S species of SNZVI made from S2-/S62-. The former SNZVI was more hydrophobic, reactive with, and selective for TCE compared to the latter SNZVI. These results suggest that the Fe and S precursors can be used to select the conditions of the synthesis process and provide selected physicochemical properties (e.g., S speciation, hydrophobicity, and crystalline structure), reactivity, and selectivity of the SNZVI materials.

Concise review: MicroRNA function in multipotent mesenchymal stromal cells.

Multipotent mesenchymal stromal cells (MSCs) are ideal candidates for different cellular therapies due to their simple isolation, extensive expansion potential, and low immunogenicity. For various therapeutic approaches, such as bone and cartilage repair, MSCs are expected to contribute by direct differentiation to replace the damaged tissue, while many other applications rely on the secretion of paracrine factors which modulate the immune response and promote angiogenesis. MicroRNAs (miRNAs), which target messenger RNA for cleavage or translational repression, have recently been shown to play critical functions in MSC to regulate differentiation, paracrine activity, and other cellular properties such as proliferation, survival, and migration. The global miRNA expression profile of MSC varies according to the tissue of origin, species, and detection methodology, while also certain miRNAs are consistently found in all types of MSC. The function in MSC of more than 60 different miRNAs has been recently described, which is the subject of this review. A special emphasis is given to miRNAs that have demonstrated a function in MSC in vivo. We also present in detail miRNAs with overlapping effects (i.e., common target genes) and discuss future directions to deepen our understanding of miRNA biology in MSC. These recent discoveries have opened the possibility of modulating miRNAs in MSC, in order to enhance their proregenerative, therapeutic potential.

Maternal Risk Conditions and Outcomes by Levels of Maternal Care.

Objectives: To (1) determine associations between maternal risk conditions and severe adverse outcomes that may benefit from risk-appropriate care and (2) assess whether associations between risk conditions and outcomes vary by level of maternal care (LoMC). Methods: We used the 2017-2019 National Inpatient Sample (NIS) to calculate associations between maternal risk conditions and severe adverse outcomes. Risk conditions included severe preeclampsia, placenta accreta spectrum (PAS) conditions, and cardiac conditions. Outcomes included disseminated intravascular coagulation (DIC) with blood products transfusion or shock, pulmonary edema or acute respiratory distress syndrome (ARDS), stroke, acute renal failure, and a composite cardiac outcome. Then we used 2019 delivery hospitalization data from five states linked to hospital LoMC. We calculated associations between risk conditions and outcomes overall and stratified by LoMC and assessed for effect modification by LoMC. Results: We found positive measures of association between risk conditions and outcomes. Among patients with severe preeclampsia or PAS, the magnitudes of the associations with DIC with blood products transfusion or shock, pulmonary edema or ARDS, and acute renal failure were lower in Level III/IV compared with

Identification of pregnancies and their outcomes in healthcare claims data, 2008-2019: An algorithm.

Pregnancy is a condition of broad interest across many medical and health services research domains, but one not easily identified in healthcare claims data. Our objective was to establish an algorithm to identify pregnant women and their pregnancies in claims data. We identified pregnancy-related diagnosis, procedure, and diagnosis-related group codes, accounting for the transition to International Statistical Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) diagnosis and procedure codes, in health encounter reporting on 10/1/2015. We selected women in Merative MarketScan commercial databases aged 15-49 years with pregnancy-related claims, and their infants, during 2008-2019. Pregnancies, pregnancy outcomes, and gestational ages were assigned using the constellation of service dates, code types, pregnancy outcomes, and linkage to infant records. We describe pregnancy outcomes and gestational ages, as well as maternal age, census region, and health plan type. In a sensitivity analysis, we compared our algorithm-assigned date of last menstrual period (LMP) to fertility procedure-based LMP (date of procedure + 14 days) among women with embryo transfer or insemination procedures. Among 5,812,699 identified pregnancies, most (77.9%) were livebirths, followed by spontaneous abortions (16.2%); 3,274,353 (72.2%) livebirths could be linked to infants. Most pregnancies were among women 25-34 years (59.1%), living in the South (39.1%) and Midwest (22.4%), with large employer-sponsored insurance (52.0%). Outcome distributions were similar across ICD-9 and ICD-10 eras, with some variation in gestational age distribution observed. Sensitivity analyses supported our algorithm's framework; algorithm- and fertility procedure-derived LMP estimates were within a week of each other (mean difference: -4 days [IQR: -13 to 6 days]; n = 107,870). We have developed an algorithm to identify pregnancies, their gestational age, and outcomes, across ICD-9 and ICD-10 eras using administrative data. This algorithm may be useful to reproductive health researchers investigating a broad range of pregnancy and infant outcomes.

Molecular recognition of chymotrypsin by the serine protease inhibitor ecotin from Yersinia pestis.

Resistance to antibiotics is a problem not only in terms of healthcare but also biodefense. Engineering of resistance into a human pathogen could create an untreatable biothreat pathogen. One such pathogen is Yersinia pestis, the causative agent of plague. Previously, we have used a bioinformatic approach to identify proteins that may be suitable targets for antimicrobial therapy and in particular for the treatment of plague. The serine protease inhibitor ecotin was identified as one such target. We have carried out mutational analyses in the closely related Yersinia pseudotuberculosis, validating that the ecotin gene is a virulence-associated gene in this bacterium. Y. pestis ecotin inhibits chymotrypsin. Here, we present the structure of ecotin in complex with chymotrypsin to 2.74 Å resolution. The structure features a biologically relevant tetramer whereby an ecotin dimer binds to two chymotrypsin molecules, similar to what was observed in related serine protease inhibitor structures. However, the vast majority of the interactions in the present structure are distinctive, indicating that the broad specificity of the inhibitor for these proteases is based largely on its capacity to recognize features unique to each of them. These findings will have implications for the development of small ecotin inhibitors for therapeutic use.

Three-dimensional printing of bone repair and replacement materials: impact on craniofacial surgery.

Solid freeform fabrication techniques such as direct write technology can be used to fabricate tissue-engineering scaffolds in 3 dimensions with high levels of reproducibility and precision. These can comprise complex structures made of osteoconductive, remodelable lattices to conduct bone ingrowth and solid barriers to prevent soft tissue invasion. As such, they act as a combination of bone graft and barrier membrane. Results from animal studies have shown that these structures fill rapidly with healing bone and can conduct bone across critical-size defects to fill large defects in rabbit skull. Results indicate that this technology can be used to produce both off-the-shelf and custom-fabricated bone graft substitutes. These may initially be used to restore alveolar ridge defects, but could also be used, in the future, to repair or replace complex craniofacial bone defects such as cleft palate defects. In the more distant future, these technologies could be combined with controlled-release bioactive substances such as growth factors and pharmaceuticals to regenerate complex structures comprising multiple tissue types.

"They're forcing people to have children that they can't afford": a qualitative study of social support and capital among individuals receiving an abortion in Georgia.

Abortion is common but highly stigmatized in the United States, and the overturning of Roe v. Wade severely restricted abortion access in many states across the nation. Data reveal that maternal morbidity and mortality are already increasing, and research suggests existing inequities in abortion access across racial/ethnic and socioeconomic groups will be exacerbated. Research has shown that social support (perceived and received aid from one's social network) and social capital (resources accessed through those social connections) can improve access to health services and decrease barriers to care. Given the escalating barriers to abortion, including longer travel distances, it is imperative to better understand the roles of social support and social capital within abortion access, especially for people living on lower incomes and people of color. Our team conducted in-depth interviews with post-abortion patients (n = 18) from an urban abortion clinic in Georgia in 2019 and 2020, shortly after a six-week gestational age abortion limit had been passed but before it was enacted. We examined how people described their social support and social capital - or lack thereof - when making decisions about their pregnancy and their ability to access abortion. We found that social support and social capital - economic support in particular - were key facilitators of both abortion access and parenting, but participants often experienced barriers to economic support within their social networks due to poverty, unstable partnerships, structural inequality, and abortion stigma. Women experienced constraints to their reproductive autonomy, wherein they had no alternatives but abortion. Our findings suggest that increased economic support and de-stigmatization of abortion are needed to improve reproductive autonomy. Our findings also indicate that restricting and outlawing abortion services is significantly detrimental to the well-being of pregnant people, their families and networks, and their communities by perpetuating cycles of poverty and deepening socioeconomic and racial/ethnic inequities.

Abortion restrictions in the state of Georgia: Anticipated impact on people seeking abortion.

OBJECTIVE: To explore the impact of restrictive abortion policies in the state of Georgia on the lives of people seeking abortion and how they would manage unwanted pregnancies. STUDY DESIGN: We conducted a cross sectional study of English and Spanish-speaking people seeking abortion from three high-volume outpatient abortion clinics in Atlanta, Georgia from April 2019 through August 2019. Participants completed a multiple-choice questionnaire. We used bivariable and multivariable analysis to explore relationships between demographic characteristics and how people would manage their unwanted pregnancies if abortion were illegal in the state. Two researchers (EC and SC) conducted qualitative analysis on free response answers and coded them by key emotion. RESULTS: Of the 382 participants, 312 (81.9%) considered at least one way to end their pregnancy if abortion were illegal in Georgia: 252 (66.1%) by traveling to another state, 85 (22.3%) by self-management with medications and/or herbs, and 32 (8.4%) considered self-harm behaviors. When asked how they would feel about not being able to have a desired abortion, 94% reported negative emotions, ranging from "scared" to "enslaved." CONCLUSIONS: Limiting access to legal abortion in Georgia would negatively impact the lives of people seeking abortion and has the potential to drive individuals to seek more costly and risky alternatives to end their pregnancy. IMPLICATIONS: Restricting abortion in Georgia may cause medically unnecessary delays in care, increased travel time, cost and negative emotional responses to people seeking abortion. Mitigating strategies include legislative challenges to restrictive laws as well as harm reduction education.

Effects of Premedication With Midazolam on Recovery and Discharge Times After Tonsillectomy and Adenoidectomy.

Background Midazolam is commonly used preoperatively for anxiety. Adverse effects data in pediatric patients with obstructive sleep apnea (OSA) undergoing tonsillectomy and adenoidectomy (T&A) is limited. Aims We hypothesized that preoperative midazolam increases the time to emergence from anesthesia and postoperative discharge. Secondary objectives assessed if patients receiving midazolam experienced increased side effects or complications from treatment. Methods This study was a retrospective chart review of patients undergoing T&A from July 2014 to December 2015. Midazolam receiving patients (midazolam group: MG) were compared to patients who did not (non-midazolam group: NMG). Multivariable analyses were performed and adjusted for predefined potential cofounder variables. Results Emergence and discharge times were 5.2 minutes (95% CI [-7.1, 17.4]; p=0.41) and 10.1 minutes (95% CI [-6.7, 26.8]; p=0.24) longer in MG. These results were not statistically significant. Comparing by OSA status, there was no statistical difference in emergence and discharge times between mild, moderate and severe OSA groups or between MG and NMG within each OSA group. Emergence and discharge times in moderate OSA was 6.1 minutes (95% CI [-17.6, 29.8]; p=0.61) and 18.8 minutes (95% CI [-16.4, 53.9]; p=0.29) longer than mild OSA, and in the severe OSA group, 2.6 minutes (95% CI [-19.9, 25.1]; p=0.82) shorter and 2.8 minutes (95% CI [-30.3, 35.9]; p=0.87) longer. The incidence of postoperative complications was comparable between MG and NMG groups. Conclusions Premedication with midazolam was not associated with prolonged emergence or discharge time or higher incidence of complications after anesthesia for T&A in patients with OSA.

Bespoke 3D-Printed Polydrug Implants Created via Microstructural Control of Oligomers.

Controlling the microstructure of materials by means of phase separation is a versatile tool for optimizing material properties. Phase separation has been exploited to fabricate intricate microstructures in many fields including cell biology, tissue engineering, optics, and electronics. The aim of this study was to use phase separation to tailor the spatial location of drugs and thereby generate release profiles of drug payload over periods ranging from 1 week to months by exploiting different mechanisms: polymer degradation, polymer diluent dissolution, and control of microstructure. To achieve this, we used drop-on-demand inkjet three-dimensional (3D) printing. We predicted the microstructure resulting from phase separation using high-throughput screening combined with a model based on the Flory-Huggins interaction parameter and were able to show that drug release from 3D-printed objects can be predicted from observations based on single drops of mixtures. We demonstrated for the first time that inkjet 3D printing yields controllable phase separation using picoliter droplets of blended photoreactive oligomers/monomers. This new understanding gives us hierarchical compositional control, from droplet to device, allowing release to be "dialled up" without manipulation of device geometry. We exemplify this approach by fabricating a biodegradable, long-term, multiactive drug delivery subdermal implant ("polyimplant") for combination therapy and personalized treatment of coronary heart disease. This is an important advance for implants that need to be delivered by cannula, where the shape is highly constrained and thus the usual geometrical freedoms associated with 3D printing cannot be easily exploited, which brings a hitherto unseen level of understanding to emergent material properties of 3D printing.

The moderating effect of obesity on cognitive-behavioral pain treatment outcomes.

OBJECTIVE: To assess the effects of body mass index on cognitive-behavioral pain treatment outcomes for chronic low back pain. DESIGN: Retrospective analyses of data from a clinical trial were performed, with body mass index used to divide patients into obese and non-obese groups for comparison. SETTING: VA medical center outpatient clinic. PATIENTS: Veterans (N = 74) receiving outpatient care through the VA. INTERVENTIONS: Delivery of a 10-week cognitive-behavioral pain treatment intervention. OUTCOME MEASURES: The Numerical Rating Scale (pain intensity), Roland Morris Disability Questionnaire (disability), Veteran's SF-36 (health-related quality of life), and Beck Depression Inventory (emotional functioning) were administered pre- and post-treatment. RESULTS: The study included 42 obese and 32 non-obese participants, most of whom were male (89%). The average body mass index was 32.44 kg/m², with average pain intensity rated as 6.59 out of 10. There were no pre-treatment differences in outcome measures between the groups. Repeated measures ANOVAs revealed main effects of Time on all but one outcome (Mental Component score), indicating that the cognitive-behavioral interventions were largely effective. However, Time-body mass index (BMI) group interactions revealed that non-obese participants showed greater improvement following treatment than did their obese counterparts on measures of disability (P < 0.05), physical aspects of quality of life (P < 0.01), and emotional functioning (P < 0.05). CONCLUSIONS: Standard cognitive-behavioral pain treatment did not yield comparable outcomes for obese and non-obese participants. Results suggest a potential moderating role of BMI in low back pain outcomes. Future work with other pain conditions, including examination of potential mechanisms through which BMI impacts treatment outcomes, is recommended.

Making tablets for delivery of poorly soluble drugs using photoinitiated 3D inkjet printing.

In this study, we investigate the viability of three-dimensional (3D) inkjet printing with UV curing to produce solid dosage forms containing a known poorly soluble drug, carvedilol. The formulation consists of 10 wt% carvedilol, Irgacure 2959, and a photocurable N-vinyl-2-pyrrolidone (NVP) and poly(ethylene glycol) diacrylate matrix, with the intention of forming an amorphous solid solution for release of carvedilol. Characterization of the printed tablets showed that the drug is an amorphous state and indicated hydrogen bonding interactions between the drug and cross-linked matrix. Several simple geometries (ring, mesh, cylinder, thin film) were printed, and the surface area to volume ratio of the prints was estimated. Over 80% carvedilol release was observed for all printed tablet geometries within ten hours. The release behaviour of carvedilol was fastest for the thin films, followed by the ring and mesh geometries, and slowest in the cylindrical forms. More rapid release was correlated to an increased surface area to volume ratio. This is the first study to implement 3D UV inkjet to make solid dispersion tablets suitable for poorly soluble drugs. Results also demonstrate that high drug-loaded tablets with a variety of release profiles can successfully be accessed with the same UV-curable inkjet formulation by varying the tablet geometry.

The Facial Action Coding System for Characterization of Human Affective Response to Consumer Product-Based Stimuli: A Systematic Review.

To characterize human emotions, researchers have increasingly utilized Automatic Facial Expression Analysis (AFEA), which automates the Facial Action Coding System (FACS) and translates the facial muscular positioning into the basic universal emotions. There is broad interest in the application of FACS for assessing consumer expressions as an indication of emotions to consumer product-stimuli. However, the translation of FACS to characterization of emotions is elusive in the literature. The aim of this systematic review is to give an overview of how FACS has been used to investigate human emotional behavior to consumer product-based stimuli. The search was limited to studies published in English after 1978, conducted on humans, using FACS or its action units to investigate affect, where emotional response is elicited by consumer product-based stimuli evoking at least one of the five senses. The search resulted in an initial total of 1,935 records, of which 55 studies were extracted and categorized based on the outcomes of interest including (i) method of FACS implementation; (ii) purpose of study; (iii) consumer product-based stimuli used; and (iv) measures of affect validation. Most studies implemented FACS manually (73%) to develop products and/or software (20%) and used consumer product-based stimuli that had known and/or defined capacity to evoke a particular affective response, such as films and/or movie clips (20%); minimal attention was paid to consumer products with low levels of emotional competence or with unknown affective impact. The vast majority of studies (53%) did not validate FACS-determined affect and, of the validation measures that were used, most tended to be discontinuous in nature and only captured affect as it holistically related to an experience. This review illuminated some inconsistencies in how FACS is carried out as well as how emotional response is inferred from facial muscle activation. This may prompt researchers to consider measuring the total consumer experience by employing a variety of methodologies in addition to FACS and its emotion-based interpretation guide. Such strategies may better conceptualize consumers' experience with products of low, unknown, and/or undefined capacity to evoke an affective response such as product prototypes, line extensions, etc.

The Relationship between Protein Intake and Source on Factors Associated with Glycemic Control in Individuals with Prediabetes and Type 2 Diabetes.

Type 2 diabetes (T2D) is a major contributor to morbidity and mortality largely due to increased cardiovascular disease risk. This study examined the relationships among protein consumption and sources on glycemic control and cardiovascular health in individuals with prediabetes and T2D. Sixty-two overweight or obese participants with prediabetes or T2D, aged 45-75 years were stratified into the following three groups based on protein intake: <0.8 g (gram)/kg (kilogram) body weight (bw), ≥0.8 but <1.0 g/kg bw, and ≥1.0 g/kg bw as below, meeting, and above the recommended levels of protein intake, respectively. Body mass, body mass index (BMI), hip circumference (HC), waist circumference (WC), lean mass, and fat mass (FM) were significantly higher in participants who consumed below the recommended level of protein intake as compared with other groups. Higher animal protein intake was associated with greater insulin secretion and lower triglycerides (TG). Total, low-density, and high-density cholesterol were significantly higher in participants who met the recommended protein intake as compared with the other groups. These data suggest that high protein consumption is associated with lower BMI, HC, WC, and FM, and can improve insulin resistance without affecting lipid profiles in this population. Furthermore, higher intake of animal protein can improve ß-cell function and lower plasma TG.

Effects of Montmorency Tart Cherry Juice Consumption on Cardiometabolic Biomarkers in Adults with Metabolic Syndrome: A Randomized Controlled Pilot Trial.

Greater than one-third of adults in the United States have metabolic syndrome (MetS), a cluster of risk factors highly associated with the development of cardiovascular diseases. Premature vascular dysfunction in MetS may lead to accelerated age-related atherogenesis and arterial stiffening, thereby increasing cardiovascular risk. Montmorency tart cherries (Prunus cerasus L.) are rich in bioactive compounds, such as anthocyanins, known to exert cardiovascular protective effects. Previous research suggests that tart cherry juice consumption may improve cardiovascular health. The objective of this study was to evaluate the effects of daily consumption of tart cherry juice on hemodynamics, arterial stiffness, and blood biomarkers of cardiovascular and metabolic health in men and women with MetS. In a randomized, single-blind, placebo-controlled, parallel-arm pilot clinical trial, 19 men and women 20 to 60 years of age with MetS consumed 240 mL of tart cherry juice (Tart Cherry; n = 5 males, 4 females) or an isocaloric placebo-control drink (Control; n = 5 males, 5 females) twice daily for 12 weeks. Arterial stiffness (pulse wave velocity), brachial and aortic blood pressures, wave reflection (augmentation index), and blood biomarkers of cardiovascular and metabolic health were assessed at baseline and 6 and 12 weeks. Oxidized low-density lipoprotein and soluble vascular cell adhesion molecule-1 were significantly lower (P = .047 and P = .036, respectively) in Tart Cherry than Control at 12 weeks, but were not significantly lower than baseline values. There was a trend for total cholesterol to be lower (P = .08) in Tart Cherry than Control at 12 weeks. No significant changes were observed in hemodynamics, arterial stiffness, or other blood biomarkers assessed. These results suggest that daily tart cherry consumption may attenuate processes involved in accelerated atherogenesis without affecting hemodynamics or arterial stiffness parameters in this population. The pilot nature of this study warrants interpreting these findings with caution, and future clinical trials with a larger sample size are needed to confirm these findings.

Comparison of the marginal fit of pressable ceramic to metal ceramic restorations.

PURPOSE: The aim of this in vitro study was to compare the marginal adaptation of a pressed ceramic material, when used with and without a metal substructure, to a traditional feldspathic porcelain-fused-to-metal restoration with a porcelain butt margin. MATERIALS AND METHODS: A maxillary central incisor typodont tooth was prepared with a 1.5 mm 360 degrees shoulder with rounded internal line angle, and 30 polyether impressions were made. Dies were poured in type IV dental stone, and 30 restorations were fabricated: 10 metal ceramic restorations (MCR) with porcelain butt joints, 10 pressed to metal restorations (PTM), and 10 all-ceramic restorations (PCR). All restorations were evaluated on their respective dies at 45x magnification using an Olympus SZX-12, measurements of the marginal openings were made, and ANOVA and Scheffé post hoc tests were used to evaluate the data. RESULTS: The mean marginal opening was 72.2 +/- 5.9 microm for MCR, 49.0 +/- 5.9 microm for PTM, and 55.8 +/- 5.9 microm for PCR. The post hoc tests showed that there was a statistical difference between the marginal adaptation of the PTM and MCR groups (p < 0.05). There was no significant difference in marginal adaptation between the PTM and the PCR groups, or the PCR and the MCR groups. CONCLUSIONS: The PTM group demonstrated a smaller mean marginal opening than the MCR group. The mean marginal openings of all three groups were within a clinically acceptable range.

Hertzian contact response of dentin with loading rate and orientation.

OBJECTIVE: To test the hypothesis that dentin Hertzian contact response varies with loading rate and tubule orientation. DESIGN: Sound teeth (n=12) were cut either parallel or perpendicular to the axial direction to expose dentin (n=6 each). The cut specimens were embedded (poly-methyl-methacrylate (PMMA) and divided into two groups: (GL) load applied parallel to dentin tubule direction and (GP) load applied perpendicular to tubule direction. A 1.5mm diameter tungsten-carbide ball was used for Hertzian contact testing with a maximum load of 150 N load and loading rates of 0.1, 1, 100, and 1000 N/s on each specimen. Indented specimens were observed microscopically and photomicrographs acquired. Hertzian contact diameter and modulus were analysed (p<0.05) by one-way ANOVA and Tukey test. RESULTS: There were significant differences (p<0.05) in Hertzian response with respect to loading rate for GL (0.1N/s versus 1000 N/s, 0.1N/s versus 100 N/s, 1N/s versus 1000 N/s, and 1N/s versus 100 N/s), and GP (0.1N/s versus 1000 N/s, 0.1N/s versus 100 N/s, and 1N/s versus 1000 N/s). Contact modulus was higher for GL compared to GP at all loading rates (p<0.05). CONCLUSION: The results suggest that dentin contact modulus is loading rate dependent. Tubule orientation of dentin did not influence contact modulus values (p>0.05).

Effect of water storage time and composite cement thickness on fatigue of a glass-ceramic trilayer system.

AIM: Static Hertzian contact tests of monolayer glass-ceramics in trilayer configurations (glass-ceramic/cement/composite) have shown that thick cement layers lower strength. This study sought to test the hypothesis that thick resin cement layers lower mouth motion fatigue reliability for flat glass-ceramic/cement/composite trilayer systems and that aging in water reduces reliability. METHODS: Dicor plates (n > or = 12 per group) (10 x 10 x 0.8 mm(3)) were aluminum-oxide abraded (50 microm), etched (60 s), silanized, and bonded (Rely X ARC) to water aged (30 days) Z100 resin blocks (10 x 10 x 4 mm(3)). Four groups were prepared: (1) thick cement layer (>100 microm) stored in water for 24-48 h, (2) thick cement layer stored for 60 days, (3) thin cement layer (< or =100 microm) stored for 24-48 h, and (4) thin cement layer stored for 60 days. The layered structures were fatigued (2 Hz) utilizing mouth motion loading with a step-stress acceleration method. A master Weibull distribution was calculated and reliability determined (with 90% confidence intervals) at a given number of cycles and load. RESULTS: The aged group (60 d) with thick cement layer had statistically lower reliability for 20,000 cycles at 150 N peak load (0.11) compared with both nonaged groups (24-48 h) (thin layer = 0.90 and thick layer = 0.82) and aged group with thin cement layer (0.89). CONCLUSION: Trilayer specimens with thick cement layers exhibited significantly lower reliability under fatigue testing only when stored for 60 days in water. The hypothesis was accepted. These results suggest that diffusion of water into the resin cement and also to the glass-ceramic interface is delayed in the thick cement specimens at 24-48 h. .