Clinical Decision Support to Reduce Opioid Prescriptions for Dental Extractions using SMART on FHIR: Implementation Report.

BACKGROUND: Clinical decision support (CDS) has the potential to improve clinical decision-making consistent with evidence-based care. CDS can be designed to save health care providers time and help them provide safe and personalized analgesic prescribing. OBJECTIVE: The aim of this report is to describe the development of a CDS system designed to provide dentists with personalized pain management recommendations to reduce opioid prescribing following extractions. The use of CDS is also examined. METHODS: This study was conducted in HealthPartners, which uses an electronic health record (EHR) system that integrates both medical and dental information upon which the CDS application was developed based on SMART (Substitutable Medical Applications and Reusable Technologies) on FHIR (Fast Healthcare Interoperability Resources). The various tools used to bring relevant medical conditions, medications, patient history, and other relevant data into the CDS interface are described. The CDS application runs a drug interaction algorithm developed by our organization and provides patient-specific recommendations. The CDS included access to the state Prescription Monitoring Program database. IMPLEMENTATION (RESULTS): The pain management CDS was implemented as part of a study examining opioid prescribing among patients undergoing dental extraction procedures from February 17, 2020, to May 14, 2021. Provider-level use of CDS at extraction encounters ranged from 0% to 87.4% with 12.1% of providers opening the CDS for no encounters, 39.4% opening the CDS for 1%-20% of encounters, 36.4% opening it for 21%-50% of encounters, and 12.1% opening it for 51%-87% of encounters. CONCLUSIONS: The pain management CDS is an EHR-embedded, provider-facing tool to help dentists make personalized pain management recommendations following dental extractions. The SMART on FHIR-based pain management CDS adapted well to the point-of-care dental setting and led to the design of a scalable CDS tool that is EHR vendor agnostic. TRIAL REGISTRATION: ClinicalTrials.gov NCT03584789; https://clinicaltrials.gov/study/NCT03584789.

Periodontal treatment and subsequent clinical outcomes and medical care costs: A retrospective cohort study.

INTRODUCTION: Periodontitis is a common oral disease associated with coronary artery disease (CAD), cerebrovascular disease (CBVD) and type 2 diabetes (T2D). We studied if periodontitis treatment improves clinical outcomes and reduces medical care costs in patients with CAD, CBVD or T2D. METHODS: We used clinic records and claims data from a health care system to identify patients with periodontitis and CAD, CBVD or T2D, and to assess periodontal treatments, hospitalizations, medical costs (total, inpatient, outpatient, pharmacy), glycated hemoglobin, cardiovascular events, and death following concurrent disease diagnoses. We compared clinical outcomes according to receipt of periodontal treatment and/or maintenance care in the follow-up period, and care costs according to treatment status within one year following concurrent disease diagnoses, while adjusting for covariates. The data were analyzed in 2019-21. RESULTS: We identified 9,503 individuals, 4,057 of whom were in the CAD cohort; 3,247 in the CBVD cohort; and 4,879 in the T2D cohort. Patients who were selected and elected to receive treatment and maintenance care were less likely to be hospitalized than untreated individuals (CAD: OR = 0.71 (95% CI: 0.55, 0.92); CBVD: OR = 0.73 (0.56, 0.94); T2D: OR = 0.80 (0.64, 0.99)). Selection to treatment and/or maintenance care was not significantly associated with cardiovascular events, mortality, or glycated hemoglobin change. Total care costs did not differ significantly between treated and untreated groups over 4 years. Treated patients experienced lower inpatient costs but higher pharmacy costs. CONCLUSIONS: Patients with periodontitis and CAD, CBVD or T2D who were selected and elected to undergo periodontal treatment or maintenance care had lower rates of hospitalizations, but did not differ significantly from untreated individuals in terms of clinical outcomes or total medical care costs.

A randomized controlled trial of an intervention to reduce stigma toward people with opioid use disorder among primary care clinicians.

BACKGROUND: Many primary care clinicians (PCCs) hold stigma toward people with opioid use disorder (OUD), which may be a barrier to care. Few interventions exist to address PCC stigma toward people with OUD. This study examined whether an online training incorporating patient narratives reduced PCCs' stigma toward people with OUD (primary) and increased intentions to treat people with OUD compared to an attention-control training (secondary). METHODS: PCCs from 15 primary care clinics were invited to complete a 30 min online training for an electronic health record-embedded clinical decision support (CDS) tool that alerts PCCs to screen, diagnose, and treat people with OUD. PCCs were randomized to receive a stigma-reduction version of the training with patient narrative videos or a control training without patient narratives and were blinded to group assignment. Immediately after the training, PCCs completed surveys of stigma towards people with OUD and intentions and willingness to treat OUD. CDS tool use was monitored for 6 months. Analyses included independent samples t-tests, Pearson correlations, and logistic regression. RESULTS: A total of 162 PCCs were randomized; 88 PCCs (58% female; 68% white) completed the training (Stigma = 48; Control = 40) and were included in analyses. There was no significant difference between intervention and control groups for stigma (t = - 0.48, p = .64, Cohen's d = - 0.11), intention to get waivered (t = 1.11, p = .27, d = 0.26), or intention to prescribe buprenorphine if a waiver were no longer required (t = 0.90, p = 0.37, d = 0.21). PCCs who reported greater stigma reported lower intentions both to get waivered (r = - 0.25, p = 0.03) and to prescribe buprenorphine with no waiver (r = - 0.25, p = 0.03). Intervention group and self-reported stigma were not significantly related to CDS tool use. CONCLUSIONS: Stigma toward people with OUD may require more robust intervention than this brief training was able to accomplish. However, stigma was related to lower intentions to treat people with OUD, suggesting stigma acts as a barrier to care. Future work should identify effective interventions to reduce stigma among PCCs. TRIAL REGISTRATION: ClinicalTrials.gov NCT04867382. Registered 30 April 2021-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT04867382.

De-implementing opioid prescribing in a dental group practice: Lessons learned.

BACKGROUND: Drug overdose has become a leading cause of accidental death in the United States. Between 2000 and 2015, the rate of deaths from drug overdoses increased 137%, including a 200% increase in the rate of overdose deaths involving opioids (including opioid pain relievers and heroin). Unnecessary opioid prescribing is one of the factors driving this epidemic. OBJECTIVES: The primary objective of this paper is to share lessons learned while conducting a randomized trial to de-implement opioids for post-extraction pain management utilizing clinical decision support (CDS) with and without patient education. The lessons learned from conducting this trial in a real-world setting can be applied to future dissemination and implementation oral health research. METHODS: The sources informing lessons learned were generated from qualitative interviews conducted with 20 of the forty-nine dental providers involved in the study following the implementation phase of the trial. Ongoing policy, social and environmental factors were tracked throughout the study. RESULTS: Dental providers in the trial identified the impact of training that involved health professionals sharing information about the personal impact of pain and opioid use. Additionally, they found utility in being presented with a dashboard detailing their prescribing patterns related to other dentists. For the 30 general dentists with access to the CDS, use of its portal varied widely, with most using it 10%-49% of the time related to extractions. CONCLUSIONS: In the context of a downward trend in opioid prescribing and considering the influence of the COVID pandemic during the trial, dental providers indicated benefit in training about negative personal impacts of prescribing opioids, and personally relevant feedback about their prescribing patterns. Only modest use of the CDS was realized. Implementation of this trial was impacted by governmental and health system policies and the COVID pandemic, prompt the consideration of implications regarding continuing ways to limit opioid prescribing among dental providers.

Impact of the COVID-19 Pandemic on Type 2 Diabetes Care Delivery.

The coronavirus disease 2019 (COVID-19) pandemic instigated major changes in care delivery, but our understanding of how the rapid transition from in-person to telehealth encounters affected the care of patients with chronic conditions such as type 2 diabetes remains incomplete. This study examined changes in primary care encounters, A1C testing rates, and the likelihood of meeting A1C guidelines before and during the first 9 months of the COVID-19 pandemic in a large health care system. It found significant decreases in utilization and testing rates and the likelihood of meeting A1C guidelines, primarily driven by missing A1C tests. Patients who had all telehealth encounters or no encounters, who identified as racial or ethnic minorities, or had Medicaid or no insurance were significantly more likely to miss A1C tests.

Depression and cardiovascular risk in primary care patients.

OBJECTIVE: This study assessed the relationship of both depression diagnosis and clinically significant depressive symptoms with individual cardiovascular risk factors and estimated total cardiovascular risk in primary care patients. METHODS: This study used a cross-sectional and retrospective design. Patients who had a primary care encounter between January 2016 and September 2018 and completed depression screening (PHQ-9) during the year prior to their appointment (N = 70,980) were included in this study. Data examining estimated total cardiovascular risk, specific cardiovascular risk factors, and relevant clinical diagnoses (including depression diagnosis) were extracted from the electronic health record. Patients were categorized into three groups: no depression (PHQ-9 < 10 and no depression diagnosis), controlled depression (PHQ-9 < 10 with previous depression diagnosis), and current depression (PHQ-9 ≥ 10). Groups were compared on estimated total risk and specific cardiovascular risk factors (e.g., body mass index [BMI], smoking status, lipids, blood pressure, and glucose). RESULTS: In adjusted analyses, patients with current depression (n = 18,267) demonstrated significantly higher 10-year and 30-year cardiovascular risk compared to patients with controlled depression (n = 33,383; 10-year: b = 0.59 [95% CI = 0.44,0.74]; 30-year: OR = 1.32 [95% CI = 1.26,1.39]) and patients without depression (n = 19,330; 10-year: b = 0.55 [95% CI = 0.37,0.73]; 30-year: OR = 1.56 [95% CI = 1.48,1.65]). Except for low-density lipoprotein (LDL), patients with current depression had the greatest cardiovascular risk across specific risk factors. CONCLUSIONS: Individuals who had a depression diagnosis and clinically significant depressive symptoms had the greatest cardiovascular risk. Pathways to prevent cardiovascular disease in those with depression might focus on treating depressive symptoms as well as specific uncontrolled cardiovascular risk factors.

Patient, Provider Type, and Procedure Type Factors Associated with Opioid Prescribing by Dentists in a Health Care System.

INTRODUCTION: Reports examining opioid prescribing for dental conditions are limited and do not examine patient-level factors. This study examines the association of patient age, sex, race, ethnicity, Medicaid coverage, and the need for an interpreter in addition to procedure type and dental provider type with receipt of an opioid prescription in dental care settings within a large health system. MATERIALS AND METHODS: This study was conducted utilizing data from the electronic health record of HealthPartners, a large dental practice embedded within a health care system. The analytic sample consisted of all 169,173 encounters from 90,487 patients undergoing a dental procedure in the baseline period (9/1/2018 to 8/30/2019), prior to implementing a clinical trial to de-implement opioids in dentistry. RESULTS: Opioids were prescribed at 1.9% of all 169,173 encounters and rates varied by patient factors, procedure category, and provider type. Opioid prescriptions were most likely for extraction encounters (25.9%). In a multivariable analysis of 8760 extraction encounters, all patient age groups were more likely than those age 66+ to receive an opioid prescription, particularly those age 18-25 (OR=6.94). Patients having a complex rather than simple extraction were more likely to receive an opioid prescription (OR=6.31) and those seen by an oral surgeon rather than a general dentist (OR=9.11) were more likely to receive an opioid prescription. Among 108,748 encounters with a diagnostic procedure, opioid prescribing was more likely among male than female patients (OR=1.20), Black patients relative to White (OR=1.69), patients with Medicaid coverage (OR=1.86), and patients seeing an oral surgeon rather than a general dentist (OR=27.81). CONCLUSION: Opioid prescribing rates vary considerably depending on procedure type. Patterns of associations between patient factors and opioid prescribing also vary considerably across procedure type. To understand which patient groups are more at risk of being prescribed opioids, it is essential to consider the procedures they are receiving.

De-Implementing Opioid Use and Implementing Optimal Pain Management Following Dental Extractions (DIODE): Protocol for a Cluster Randomized Trial.

BACKGROUND: Overdose deaths from prescription opioid analgesics are a continuing crisis in the United States. Opioid analgesics are among the most frequently prescribed drugs by dentists. An estimated 5 million people undergo third-molar extractions in the United States each year, resulting in postoperative pain. Studies show that, in most cases, the combination of ibuprofen and acetaminophen is an effective alternative to commonly prescribed opioid analgesics for the management of postextraction pain. Nevertheless, many dentists routinely prescribe opioids after dental extractions. OBJECTIVE: We describe the rationale, design, and methods for a randomized trial of interventions designed to de-implement opioid prescribing by dentists while implementing effective nonopioid analgesics following dental extractions. METHODS: Using a prospective, 3-arm, cluster randomized trial design with dentists as the unit randomized and patient-level prescribing data as the primary outcome, we will compare different strategies to reduce the reliance on opioids and increase the use of alternative pain management approaches utilizing information support tools aimed at both providers and their patients. The study will test the efficacy of 2 interventions to decrease opioid prescribing following dental extractions: clinical decision support with (CDS-E) and without patient education (CDS). Providers will be randomized to CDS, CDS-E, or standard practice. Patient-level outcomes will be determined via review of comprehensive electronic health records. We will compare study arms on differential change in prescribing patterns from pre- to postimplementation of the intervention. The primary outcome of interest is a binary indicator of whether or not the patient received an opioid prescription on the day of the extraction encounter. We will also examine recommendations or prescriptions for nonopioid analgesics, patients' perceptions of shared decision making, and patients' pain experiences following the extraction. RESULTS: The HealthPartners Institutional Review Board approved the study. All study materials including the CDS and patient education materials have been developed and pilot tested, and the protocol has been approved by the National Institute of Dental and Craniofacial Research. The intervention was implemented in February 2020, with 51 dentists who were randomized to 1 of the 3 arms. CONCLUSIONS: If the intervention strategies are shown to be effective, they could be implemented more broadly in dental settings with high levels of opioid prescribing. TRIAL REGISTRATION: ClinicalTrials.gov NCT03584789, https://clinicaltrials.gov/ct2/show/NCT03584789. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/24342.

Quantifying Dental Office-Originating Adverse Events: The Dental Practice Study Methods.

BACKGROUND: Preventable medical errors in hospital settings are the third leading cause of deaths in the United States. However, less is known about harm that occurs in patients in outpatient settings, where the majority of care is delivered. We do not know the likelihood that a patient sitting in a dentist chair will experience harm. Additionally, we do not know if patients of certain race, age, sex, or socioeconomic status disproportionately experience iatrogenic harm. METHODS: We initiated the Dental Practice Study (DPS) with the aim of determining the frequency and types of adverse events (AEs) that occur in dentistry on the basis of retrospective chart audit. This article discusses the 6-month pilot phase of the DPS during which we explored the feasibility and efficiency of our multistaged review process to detect AEs. RESULTS: At sites 1, 2, and 3, respectively, 2 reviewers abstracted 21, 11, and 23 probable AEs, respectively, from the 100 patient charts audited per site. At site 2, a third reviewer audited the same 100 charts and found only 1 additional probable AE. Of the total 56 probable AEs (from 300 charts), the expert panel confirmed 9 AE cases. This equals 3 AEs per 100 patients per year. Patients who experienced an AE tended to be male and older and to have undergone more procedures within the study year. CONCLUSIONS: This article presents an overview of the DPS. It describes the methods used and summarizes the results of its pilot phase. To minimize threats to dental patient safety, a starting point is to understand their basic epidemiology, both in terms of their frequency and the extent to which they affect different populations.

Implantation and Extraction of Penetrating Electrode Arrays in Minipig Retinas.

Purpose: This work was motivated by the goals of demonstrating methods to fabricate and implant large numbers of penetrating arrays into the retina and the feasibility of extraction. Methods: Arrays of inactive, three-dimensional (3D) SU-8 structures were microfabricated onto 13-µm polyimide substrates. Standard vitreoretinal surgical techniques were used with an ab externo approach for subretinal implantation of arrays in 12 mini-pigs. In the first three surgeries, different post-geometries were explored, while a preferred design (128-µm tall, 30-µm diameter, 200-µm spacing) was used for the remaining nine implantations. Two arrays were extracted. Funduscopy, optical coherence tomography (OCT) and immunohistochemistry of the retinae were performed. The unoperated eyes and tissue far from implantation served as controls. A thirteenth pig was implanted with a planar array. Results: Ten implant surgeries had no significant complication, and two arrays were successfully extracted. One retinal tear occurred after implantation due to too long posts in an early surgery. In "successful" cases, OCT showed close apposition of the arrays to the retina and integration of the posts, the tops of which were positioned at the junction of the inner plexiform and ganglion cells, without significant gliosis. Conclusions: These results provide a proof-of-concept that relatively large numbers of 3D posts can be implanted into, and extracted from, the retina of mini-pigs. Our surgical numbers were relatively small, especially for the extractions, and our conclusions must be viewed with that limitation. Our methods are applicable for human surgeries. Translational Relevance: This study provides results of implantation and extraction of relatively large numbers of 3D posts from the retina of minipig eyes. If similar technology were used in humans, a 3D array of this type should lower perceptual thresholds, provide safer long-term stimulation, and perhaps provide better perceptual outcomes.

Dental Decision Simulation (DDSim): Development of a virtual training environment.

PURPOSE: Case-based simulations are powerful training tools that can enhance learning and drive behavior change. This is an overview of the design/development of Dental Decision Simulation (DDSim), a web-based simulation of an electronic dental record (EDR). The purpose was to use DDSim to train dentists to make evidence-based treatment planning decisions consistent with current evidence. This simulated EDR provides case-based information in support of a set of defined evidence-based learning objectives. METHODS: The development of this complex simulation model required coordinated efforts to create several components: identify behavior changes, case authoring mechanism, create virtual patient visits, require users to make treatment plan decisions related to learning objectives, and a feedback mechanism to help users recognize departures from those learning objectives. This simulation was evaluated in a 2-arm, clinic-randomized, controlled pilot study examining the extent to which DDSim changed dentists' planned treatment to conform to evidence-based treatment guidelines relative to change in dentists not exposed to DDSim. Outcomes were measured by comparing preintervention and postintervention patient EDR treatment data. RESULTS: Changes in behavior over time did not favor intervention or control clinics. CONCLUSION: DDSim provides a standardized learning platform that cannot be achieved through the use of live patients. Both live patients and case-based simulations can be used to transfer knowledge and skill development. DDSim offers the advantage of providing a platform for developing treatment planning skills in a low-risk environment. However, further research examining behavior change is needed.

Predicting neutropenia risk in patients with cancer using electronic data.

OBJECTIVES: Clinical guidelines recommending the use of myeloid growth factors are largely based on the prescribed chemotherapy regimen. The guidelines suggest that oncologists consider patient-specific characteristics when prescribing granulocyte-colony stimulating factor (G-CSF) prophylaxis; however, a mechanism to quantify individual patient risk is lacking. Readily available electronic health record (EHR) data can provide patient-specific information needed for individualized neutropenia risk estimation. An evidence-based, individualized neutropenia risk estimation algorithm has been developed. This study evaluated the automated extraction of EHR chemotherapy treatment data and externally validated the neutropenia risk prediction model. MATERIALS AND METHODS: A retrospective cohort of adult patients with newly diagnosed breast, colorectal, lung, lymphoid, or ovarian cancer who received the first cycle of a cytotoxic chemotherapy regimen from 2008 to 2013 were recruited from a single cancer clinic. Electronically extracted EHR chemotherapy treatment data were validated by chart review. Neutropenia risk stratification was conducted and risk model performance was assessed using calibration and discrimination. RESULTS: Chemotherapy treatment data electronically extracted from the EHR were verified by chart review. The neutropenia risk prediction tool classified 126 patients (57%) as being low risk for febrile neutropenia, 44 (20%) as intermediate risk, and 51 (23%) as high risk. The model was well calibrated (Hosmer-Lemeshow goodness-of-fit test = 0.24). Discrimination was adequate and slightly less than in the original internal validation (c-statistic 0.75 vs 0.81). CONCLUSION: Chemotherapy treatment data were electronically extracted from the EHR successfully. The individualized neutropenia risk prediction model performed well in our retrospective external cohort.

SiC protective coating for photovoltaic retinal prosthesis.

OBJECTIVE: To evaluate plasma-enhanced, chemically vapor deposited (PECVD) amorphous silicon carbide (α-SiC:H) as a protective coating for retinal prostheses and other implantable devices, and to study their failure mechanisms in vivo. APPROACH: Retinal prostheses were implanted in rats sub-retinally for up to 1 year. Degradation of implants was characterized by optical and scanning electron microscopy. Dissolution rates of SiC, SiN x and thermal SiO2 were measured in accelerated soaking tests in saline at 87 °C. Defects in SiC films were revealed and analyzed by selectively removing the materials underneath those defects. MAIN RESULTS: At 87 °C SiN x dissolved at 18.3 ± 0.3 nm d(-1), while SiO2 grown at high temperature (1000 °C) dissolved at 0.104 ± 0.008 nm d(-1). SiC films demonstrated the best stability, with no quantifiable change after 112 d. Defects in thin SiC films appeared primarily over complicated topography and rough surfaces. SIGNIFICANCE: SiC coatings demonstrating no erosion in accelerated aging test for 112 d at 87 °C, equivalent to about 10 years in vivo, can offer effective protection of the implants. Photovoltaic retinal prostheses with PECVD SiC coatings exhibited effective protection from erosion during the 4 month follow-up in vivo. The optimal thickness of SiC layers is about 560 nm, as defined by anti-reflective properties and by sufficient coverage to eliminate defects.

Correlations between histology and neuronal activity recorded by microelectrodes implanted chronically in the cerebral cortex.

OBJECTIVE: To quantify relations between the neuronal activity recorded with chronically-implanted intracortical microelectrodes and the histology of the surrounding tissue, using radial distance from the tip sites and time after array implantation as parameters. APPROACH: 'Utah'-type intracortical microelectrode arrays were implanted into cats' sensorimotor cortex for 275-364 days. The brain tissue around the implants was immuno-stained for the neuronal marker NeuN and for the astrocyte marker GFAP. Pearson's product-moment correlations were used to quantify the relations between these markers and the amplitudes of the recorded neuronal action potentials (APs) and their signal-to-noise ratios (S/N). MAIN RESULTS: S/N was more stable over post-implant time than was AP amplitude, but its increased correlation with neuronal density after many months indicates ongoing loss of neurons around the microelectrodes. S/N was correlated with neuron density out to at least 140 µm from the microelectrodes, while AP amplitude was correlated with neuron density and GFAP density within ∼80 µm. Correlations between AP amplitude and histology markers (GFAP and NeuN density) were strongest immediately after implantation, while correlation between the neuron density and S/N was strongest near the time the animals were sacrificed. Unlike AP amplitude, there was no significant correlation between S/N and density of GFAP around the tip sites. SIGNIFICANCE: Our findings indicate an evolving interaction between changes in the tissue surrounding the microelectrodes and the microelectrode's electrical properties. Ongoing loss of neurons around recording microelectrodes, and the interactions between their delayed electrical deterioration and early tissue scarring around the tips appear to pose the greatest threats to the microelectrodes' long-term functionality.

Evidence Supports No Relationship between Obstructive Sleep Apnea and Premolar Extraction: An Electronic Health Records Review.

OBJECTIVE: A controversy exists concerning the relationship, if any, between obstructive sleep apnea (OSA) and the anatomical position of the anterior teeth. Specifically, there has been speculation that extraction orthodontics and retraction of the anterior teeth contributes to OSA by crowding the tongue and decreasing airway space. This retrospective study utilized electronic medical and dental health records to examine the association between missing premolars and OSA. METHODS: The sample (n = 5,584) was obtained from the electronic medical and dental health records of HealthPartners in Minnesota. Half of the subjects (n = 2,792) had one missing premolar in each quadrant. The other half had no missing premolars. Cases and controls were paired in a 1:1 match on age range, gender, and body mass index (BMI) range. The outcome was the presence or absence of a diagnosis of OSA confirmed by polysomnography. RESULTS: Of the subjects without missing premolars, 267 (9.56%) had received a diagnosis of OSA. Of the subjects with four missing premolars, 299 (10.71%) had received a diagnosis of OSA. The prevalence of OSA was not significantly different between the groups (OR = 1.14, p = 0.144). CONCLUSION: The absence of four premolars (one from each quadrant), and therefore a presumed indicator of past "extraction orthodontic treatment," is not supported as a significant factor in the cause of OSA.

Electrical performance of penetrating microelectrodes chronically implanted in cat cortex.

Penetrating microelectrode arrays with 2000 µm (2) sputtered iridium oxide (SIROF) electrode sites were implanted in cat cerebral cortex, and their long-term electrochemical performance evaluated in vivo by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and current pulsing. Measurements were made from days 33 to 328 postimplantation. The CV-defined charge storage capacity, measured at 50 mV/s, increased linearly with time over the course of implantation for two arrays and was unchanged for one array. A modest decrease in 1 kHz impedance was also observed. These results suggest an ongoing increase in the apparent electrochemical surface area of the electrodes, which is attributed to electrical leakage pathways arising from cracking of Parylene insulation observed by SEM of explanted arrays. During current pulsing with a 0.0 V interpulse bias, the electrodes readily delivered 8 nC/phase in vitro, but some channels approached or exceeded the water reduction potential during in vivo pulsing. The charge injection capacity in vivo increased linearly with the interpulse bias (0-0.6 V Ag\vert AgCl) from 11.5 to 21.8 nC/ph and with pulse width (150-500 µs) from 8.8 to 14 nC/ph (at 0.0 V bias). These values are lower than those determined from measurements in buffered physiological saline, emphasizing the importance of in vivo measurements in assessing chronic electrode performance. The consequence of current leakage pathways on the charge-injection measurements is also discussed.

Electrical performance of penetrating microelectrodes chronically implanted in cat cortex.

Penetrating multielectrode arrays with electrode coatings of sputtered iridium oxide (SIROF) have been implanted chronically in cat cortex for periods over 300 days. The ability of these electrodes to inject charge at levels above expected thresholds for neural excitation has been examined in vivo by measurements of voltage transients in response to current-controlled, cathodal stimulation pulsing. The effect of current pulse width from 150 µs to 500 µs and voltage biasing of the electrodes in the interpulse period at two levels, 0.0 V and 0.6 V vs. Ag|AgCl, were also investigated. The results of in vivo characterization of the electrodes by open-circuit potential measurements, cyclic voltammetry and impedance spectroscopy are also reported.

Microscale wear behavior and crosslinking of PEG-like coatings for total hip replacements.

The predominant cause of late-state failure of total hip replacements is wear-mediated osteolysis caused by wear particles that originate from the ultrahigh molecular weight polyethylene (UHMWPE) acetabular cup surface. One strategy for reducing wear particle formation from UHMWPE is to modify the surface with a hydrophilic coating to increase lubrication from synovial fluid. This study focuses on the wear behavior of hydrophilic coatings similar to poly(ethylene glycol) (PEG). The coatings were produced by plasma-polymerizing tetraglyme on UHMWPE in a chamber heated to 40 degrees C or 50 degrees C. Both temperatures yielded coatings with PEG-like chemistry and increased hydrophilicity relative to uncoated UHMWPE; however, the 40 degrees C coatings were significantly more resistant to damage induced by atomic force microscopy nanoscratching. The 40 degrees C coatings exhibited only one damage mode (delamination) and often showed no signs of damage after repeated scratching. In contrast, the 50 degrees C coatings exhibited three damage modes (roughening, thinning, and delamination), and always showed visible signs of damage after no more than two scratches. The greater wear resistance of the 40 degrees C coatings could not be explained by coating chemistry or hydrophilicity, but it corresponded to an approximately 26-32% greater degree of crosslinking relative to the 50 degrees C surfaces, suggesting that crosslinking should be a significant design consideration for hydrophilic coatings used for total hip replacements and other wear-dependent applications.

Characterization and tribology of PEG-like coatings on UHMWPE for total hip replacements.

A crosslinked hydrogel coating similar to poly(ethylene glycol) (PEG) was covalently bonded to the surface of ultrahigh molecular weight polyethylene (UHMWPE) to improve the lubricity and wear resistance of the UHWMPE for use in total joint replacements. The chemistry, hydrophilicity, and protein adsorption resistance of the coatings were determined, and the wear behavior of the PEG-like coating was examined by two methods: pin-on-disk tribometry to evaluate macroscale behavior, and atomic force microscopy (AFM) to simulate asperity wear. As expected, the coating was found to be highly PEG-like, with approximately 83% ether content by x-ray photoelectron spectroscopy and more hydrophilic and resistant to protein adsorption than uncoated UHMWPE. Pin-on-disk testing showed that the PEG-like coating could survive 3 MPa of contact pressure, comparable to that experienced by total hip replacements. AFM nanoscratching experiments uncovered three damage mechanisms for the coatings: adhesion/microfracture, pure adhesion, and delamination. The latter two mechanisms appear to correlate well with wear patterns induced by pin-on-disk testing and evaluated by attenuated total reflection Fourier transform infrared spectroscopy mapping. Understanding the mechanisms by which the PEG-like coatings wear is critical for improving the behavior of subsequent generations of wear-resistant hydrogel coatings.

ATR-FTIR as a thickness measurement technique for hydrated polymer-on-polymer coatings.

Hydrated polymer coatings on polymer substrates are common for many biomedical applications, such as tissue engineering constructs, contact lenses, and catheters. The thickness of the coatings can affect the mechanical behavior of the systems and the cellular response, but measuring the coating thickness can be quite challenging using conventional methods. We propose a new method, that is, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) to determine the relative thickness, combined with atomic force microscopy to calibrate the ATR-FTIR measurements. This technique was successfully employed to determine the hydrated thickness of a series of crosslinked tetraglyme coatings on ultrahigh molecular weight polyethylene substrates intended to reduce wear of acetabular cups in total hip replacements. The hydrated coatings ranged from 30 to 200 nm thick and were accurately measured despite the relatively high root-mean-square (RMS) roughness of the substrates, 20-35 nm (peak-to-peak roughness 55-100 nm). The calibrated ATR-FTIR technique is a promising new method for measuring the thickness of many other polymer-on-polymer and hydrated coatings.