Reinforcement determines the timing dependence of corticostriatal synaptic plasticity in vivo.

Plasticity at synapses between the cortex and striatum is considered critical for learning novel actions. However, investigations of spike-timing-dependent plasticity (STDP) at these synapses have been performed largely in brain slice preparations, without consideration of physiological reinforcement signals. This has led to conflicting findings, and hampered the ability to relate neural plasticity to behavior. Using intracellular striatal recordings in intact rats, we show here that pairing presynaptic and postsynaptic activity induces robust Hebbian bidirectional plasticity, dependent on dopamine and adenosine signaling. Such plasticity, however, requires the arrival of a reward-conditioned sensory reinforcement signal within 2 s of the STDP pairing, thus revealing a timing-dependent eligibility trace on which reinforcement operates. These observations are validated with both computational modeling and behavioral testing. Our results indicate that Hebbian corticostriatal plasticity can be induced by classical reinforcement learning mechanisms, and might be central to the acquisition of novel actions.Spike timing dependent plasticity (STDP) has been studied extensively in slices but whether such pairings can induce plasticity in vivo is not known. Here the authors report an experimental paradigm that achieves bidirectional corticostriatal STDP in vivo through modulation by behaviourally relevant reinforcement signals, mediated by dopamine and adenosine signaling.

The biology, prevention, diagnosis and treatment of periodontal diseases: scientific advances in the United States.

BACKGROUND: Major scientific advances in periodontology in the past 150 years have fundamentally changed how clinicians detect and treat periodontal diseases. These advances include the demonstration that gingivitis and periodontitis are biofilm-induced infections caused by components of the indigenous oral microbiota, and that host inflammatory-immunologic responses to these microbial challenges are responsible for most of the observed tissue damage. TYPES OF STUDIES REVIEWED: In this brief overview, the authors focus on the discovery of the relationships between dental plaque and the host periodontal tissues. They highlight some of the pioneers in the United States who shaped new approaches to prevention and treatment of periodontal disease. RESULTS: Biofilms that cause gingivitis and periodontitis are complex polymicrobial communities that are resistant to antimicrobial agents and host defense mechanisms. An increased understanding of natural inflammation-resolving mechanisms suggests that control of inflammation is at least as important as is antimicrobial therapy in the treatment of periodontal infections. Data from randomized controlled clinical trials have shown that most conventional forms of periodontal therapy are effective as long as patients comply with posttreatment maintenance programs. CONCLUSIONS: Many mechanisms involved in the repair and regeneration of periodontal tissues have been identified. Results of laboratory studies of factors that enhance prevention and treatment of periodontal disease have made the transition to clinical practice. Advances in the fields of molecular biology, human genetics and stem cell biology have set the stage for significant discoveries that will pave the way for the development of procedures needed for the predictable regeneration of periodontal tissues. As a result, new generations of people in the United States can expect to retain a healthy and functional dentition for a lifetime.

The ecological future of the North American bison: conceiving long-term, large-scale conservation of wildlife.

Many wide-ranging mammal species have experienced significant declines over the last 200 years; restoring these species will require long-term, large-scale recovery efforts. We highlight 5 attributes of a recent range-wide vision-setting exercise for ecological recovery of the North American bison (Bison bison) that are broadly applicable to other species and restoration targets. The result of the exercise, the "Vermejo Statement" on bison restoration, is explicitly (1) large scale, (2) long term, (3) inclusive, (4) fulfilling of different values, and (5) ambitious. It reads, in part, "Over the next century, the ecological recovery of the North American bison will occur when multiple large herds move freely across extensive landscapes within all major habitats of their historic range, interacting in ecologically significant ways with the fullest possible set of other native species, and inspiring, sustaining and connecting human cultures." We refined the vision into a scorecard that illustrates how individual bison herds can contribute to the vision. We also developed a set of maps and analyzed the current and potential future distributions of bison on the basis of expert assessment. Although more than 500,000 bison exist in North America today, we estimated they occupy <1% of their historical range and in no place express the full range of ecological and social values of previous times. By formulating an inclusive, affirmative, and specific vision through consultation with a wide range of stakeholders, we hope to provide a foundation for conservation of bison, and other wide-ranging species, over the next 100 years.

The effect of patient-centered plaque control and periodontal maintenance therapy on adverse outcomes of periodontitis.

The purpose of this study was to evaluate systematic reviews that addressed the effectiveness of periodontal maintenance therapy for the management of patients with periodontitis. Recent surveys of dental care patterns suggest a marked increase in preventive and maintenance periodontal care in populations that retain the dentition for an increasingly longer lifetime. A considerable body of clinical investigation concludes that a multitherapy periodontal maintenance approach is effective in improving periodontal outcomes in patients treated for periodontitis. Individual components of such maintenance therapy were assessed, including the effects of an oral examination, personal oral hygiene instructions, supragingival scaling and polishing, subgingival scaling and root planing, adjunctive procedures, and maintenance frequency. There is much controversy about improvement in oral health that may accrue from the placebo effect of an examination and the maintenance ritual. Improved plaque control by the patient in anticipation of a forthcoming examination alone might be reflected in decreased measurements for plaque accumulation and gingival inflammation but the role of placebo effects on periodontitis remains unclear. There are insufficient randomized controlled trials to reach conclusions regarding the individual beneficial effects of repeated oral hygiene instructions or routine scaling/polishing on the recurrence of periodontitis. While subgingival root planing seems an effective component of periodontal maintenance, neither clinical investigations nor randomly controlled trial evidence have established an ideal maintenance frequency based on individual patient risk for periodontitis. The adjunctive beneficial effects of both locally and systemically administered antimicrobial agents were statistically significant for some formulations, and may be particularly useful clinically in patients who are resistant to mechanical therapy. We conclude that few clinical or randomized controlled studies have evaluated the individual benefit or required frequency of the periodontal maintenance ritual for patients who are relatively resistant or susceptible to periodontitis.

Cessation of periodontal care during pregnancy: effect on infant birthweight.

The goal of this study was to assess whether interruption of care for chronic periodontitis during pregnancy increased the risk of low-birthweight infants. A population-based case-control study was designed with 793 cases (infants < 2,500 g) and a random sample of 3,172 controls (infants >or= 2,500 g). Generalized estimating equation models were used to relate periodontal treatment history to low birthweight risk and to common risk factors. The results indicate that periodontal care utilization was associated with a 2.35-fold increased odds of self-reported smoking during pregnancy (95% confidence interval: 1.48-3.71), a 2.19-fold increased odds for diabetes (95% confidence interval: 1.21-3.98), a 3.90-fold increased odds for black race (95% confidence interval: 2.31-6.61), and higher maternal age. After adjustment for these factors, interruption of periodontal care during pregnancy did not lead to an increased risk for a low-birthweight infant when compared to women with no history of periodontal care (odds ratio, 0.96; 95% confidence interval, 0.60-1.52). In conclusion, women receiving periodontal care had genetic and environmental characteristics, such as smoking, diabetes and race, that were associated with an increased risk for low-birthweight infants. Periodontal care patterns, in and of themselves, were unrelated to low-birthweight risk.

Practice patterns among male and female general dentists in a Washington State population.

BACKGROUND: Women make up about 14 percent of general dentists in the United States, and the proportion is projected to exceed 29 percent by 2020. METHODS: The authors obtained dental benefits claims data from the Washington Dental Service (WDS), Seattle, and used them to examine the practice patterns of 265 women and 1,947 men engaged in general dentistry for at least 26 days in 2001. Practice variables of interest included age, days worked, procedures performed and total income from WDS reimbursements and patient copayments. The number, age and sex of patients treated also were obtained. Using productivity data, the authors also estimated the potential impact of an increase in the percentage of female dentists in the state. RESULTS: The authors found no differences between male and female dentists in the number of procedures per patient, income per patient or income per day of work. Frequency distributions of various services were highly similar for both groups. Multiple regression models showed no influence of dentist's sex on total income. However, the mean and median numbers of days worked were about 10 percent lower for female dentists than for male dentists. This difference was consistent with the finding that female dentists treated approximately 10 percent fewer patients, performed about 10 percent fewer procedures and had a combined income of about 10 percent less than that of male dentists. CONCLUSION: Practice patterns of male and female dentists generally were equivalent in this WDS population. CLINICAL IMPLICATIONS: Female and male dentists provided a similar range of services and earned an equal income per patient treated and per day worked. However, women worked fewer days per year than did men, irrespective of age. If the dental work force and practice patterns remain unchanged otherwise, the total number of patients treated per dentist will decrease slightly as women make up an increasing proportion of dentists.

Patterns of endodontic care for a Washington state population.

Endodontic care, provided by 3,402 dental offices, was assessed from claims data maintained by the Washington Dental Service for 1999. Approximately 5.7 million dental procedures were provided to 880,317 patients by 2,796 general practitioners, 105 endodontists, and 494 other specialists. Of all dental services, 63,321 (1%) were endodontic procedures involving 52,911 (6%) patients. General dentists, endodontists, and other specialists performed 64.7%, 33.7%, and 1.6% of endodontic procedures, the majority of which were root canal therapy. The most frequent tooth types treated by root canal therapy were mandibular first molars (17.0%), maxillary first molars (15.2%), mandibular second molars (11.8%), maxillary second bicuspids (10.3%), maxillary second molars (9.1%), maxillary central and lateral incisors (8.8%), and mandibular second bicuspids (8.0%). Direct and indirect pulp caps by generalists and conventional retreatment and surgical therapy by endodontists made up the majority of the remaining endodontic services. Men had a greater procedure rate than women for most endodontic procedures.

Patterns of oral care in dental school and general dental practice.

This study compared patterns of oral care provided by predoctoral dental students for patients seeking treatment at the University of Washington (UW) with patterns reported for general dental offices by the Washington Dental Service (WDS). Dental care included about 5 million services provided to 880,317 patients by 2,803 WDS general dentists and about 45,600 dental services provided to 9,488 patients by 155 UW dental students during 1999. There was high fidelity between databases and randomly surveyed patient records for treatment provided in both UW (95 percent) and WDS (97 percent) populations. While patient age patterns were generally similar, UW students completed more procedures for young children and for adults older than seventy-four years but completed fewer procedures for age groups of from thirteen to eighteen and from forty-five to fifty-four than general dental offices. The relative mix of all services completed by UW and WDS providers was similar (ANOVA, P=0.82). Within categories of service, the percentage of total services completed by students compared to those submitted by community dentists to WDS was about the same for examinations, radiographs, fluoride and sealants, amalgams, composites, single crowns, and endodontics. The percentage of total procedures completed showed a greater emphasis by UW students on inlays/onlays, dentures, extractions, and periodontal maintenance, and lesser experience with implants, orthodontics, sedation, and emergency procedures than general dental offices. We conclude that the relative distribution of clinical services provided by UW dental students is comparable to those procedures reported to WDS by dental offices in the adjacent community.

Patterns of oral care in a Washington State dental service population.

BACKGROUND: The authors compare patterns of oral health care reported by the Washington Dental Service, or WDS, Seattle, in 1993 and 1999 to assess changes in patient populations, practice characteristics, procedures and treatment costs in the state. METHODS: Data were obtained from dental benefits claims from a population of about 1.25 million people. Variables of interest included patient age and other demographic information, character of dental practice, dental procedures and treatment costs that combined WDS payment and patient copayment. RESULTS: The results showed high agreement (97 percent) between the database and randomly surveyed patient records. For both 1993 and 1999, general dental offices were responsible for more than 80 percent of patient care. Single crowns (21 percent), restorative services (15 percent) and dental prophylaxis (13 percent) made up about half of the costs of dental care. Broad categories of service were similar in 1993 and 1999, and anticipated major declines in restorative procedures related to caries were not apparent. The mix of services varied considerably by patient age and between generalists and specialists in both years. CONCLUSIONS: Patterns of oral health care among this insured patient population largely remained unchanged from 1993 to 1999, with some shifts in specific procedures and specialty care. During this period, dentists saw more patients and performed fewer treatments per patient, while total treatment costs per patient increased. CLINICAL IMPLICATIONS: Patterns of oral health care in the United States are projected to undergo major changes linked to improved oral health, declining trends in caries and periodontal diseases, scientific advances in treatment approaches and a patient population that is living longer. Changes in care patterns during this six-year period may reflect patient and provider preferences, as well as the influence of reimbursement policies. Dental benefits databases can serve as a critical resource for monitoring such changes.