Understanding dentists’ capacity to supply dental services over time is a key element in the process of planning for the future. The aim was to identify time trends and estimate age, period and cohort effects in patients’ visits supplied per dentist per year.
Mailed questionnaires were collected from a random sample of Australian private general practice dentists. The response rates were 73%, 75%, 74%, 71%, 76% and 67% in 1983, 1988, 1993, 1998, 2003 and 2009, respectively. The time trends in the mean number of patient visits supplied per dentist per year (PPY) was described by using a standard cohort table and age-period-cohort analyses applying a nested general linear regression models approach.
The mean number of PPY decreased across most age groups of dentists over the time of study. The age-period model showed that younger dentists (20–29 years) and older dentists (65–74 and 80–84 years) had lower PPY than middle-aged dentists, and the age-cohort model showed higher PPY among earlier cohorts, and lower PPY among more recent cohorts.
The study found a period effect of declining PPY over the observation period. More recent cohorts of dentists provide lower numbers of PPY than earlier cohorts at similar ages, but the provision of PPY among these younger cohorts appeared to be stable as they moved into middle age.
Age; Period; Cohort; Patient visits
Hyperoxia during T2*-weighted magnetic resonance imaging (oxygen challenge imaging (OCI)) causes T2*-weighted signal change that is dependent on cerebral blood volume (CBV) and oxygen extraction fraction (OEF). Crossed cerebellar diaschisis (CCD), where CBV is reduced but OEF is maintained, may be used to understand the relative contributions of OEF and CBV to OCI results. In subjects with large hemispheric strokes, OCI showed reduced signal change in the contralesional cerebellum (P=0.027, n=12). This was associated with reduced CBV in contralesional cerebellum (P=0.039, n=9). CCD may be a useful model to determine the relative contribution of CBV to signal change measured by OCI.
diaschisis; magnetic resonance imaging; stroke
The cost of dental care may be a barrier to regular dental attendance with the proportion of the Australian population avoiding or delaying care due to cost increasing since 1994. This paper explores the extent to which age, period and cohort factors have contributed to the variation in avoiding or delaying visiting a dentist because of cost.
Data were obtained from four national dental telephone interview surveys of Australian residents aged five years and over conducted in 1994, 1999, 2004 and 2010 (response rates 48% - 72%). The trend in the percentage of persons avoiding or delaying visiting a dentist because of cost was analysed by means of a standard cohort table and more formal age-period-cohort analyses using a nested models framework.
There was an overall increase in the proportion of people avoiding or delaying visiting a dentist indicating the presence of period effects. Financial barriers were also associated with age such that the likelihood of avoiding because of cost was highest for those in their mid-late twenties and lowest in both children and older adults. Cohort effects were also present although the pattern of effects differed between cohorts.
The findings of this study suggest that, in addition to the increase in costs associated with dental care, policies targeting specific age groups and income levels may be contributing to the inequality in access to dental care.
Age; Period; Cohort; Financial barriers; Dental; Access
Potential items to be included in an HIV Treatment Optimism scale were reviewed by 17 HIV-positive gay and bisexual men (GBM), resulting in a 21-item test instrument. After pilot testing, data were collected from a multi-city sample of high-risk HIV-positive GBM (n = 346), who were currently on treatment and were recruited to attend a two-day sexual health seminar. The scale items were analyzed utilizing Principal Components Analysis and reliability testing. The factor analysis resulted in the development of three separate scales. The Susceptibility scale contained 10 items associated with a belief that HIV is less transmissible while on HIV treatment. The Condom Motivation scale contained five items addressing a decreased motivation to use condoms while on treatment and the Severity scale contained four items associated with a decreased sense of the severity of an HIV diagnosis. Reliability coefficients (α ) and mean inter-item correlations (M) for the three scales were acceptable (Susceptibility, α = 0.86, M = 0.39; Condom Motivation, α = 0.84, M = 0.50; Severity, α = 0.71, M = 0.37). Combined as one scale, the reliability coefficient was respectable (α = 0.76), but the mean inter-item correlation was 0.14. Based on this analysis, use of a single measure was not supported and three separate scales were developed. The scales were equivalent across racial groups except White men were more like to report a decreased motivation to use condoms compared to Black or Latino men. Three separate scales addressing beliefs about the transmissibility of HIV while on treatment (Susceptibility), the quality of life while on HIV treatment (Severity) and the motivation to use condoms consistently while on treatment (Condom Motivation) may be better markers for assessing optimistic beliefs about HIV treatment among HIV-positive GBM.
HIV optimism; gay men; HIV; scale development
This study was designed to examine the impact of HIV treatment optimism on sexual risk among a racially diverse sample of HIV-positive MSM. Survey data were collected from 346 racially diverse HIV-positive MSM. Inclusion criteria: 18 years of age, male, at least one incident of unprotected anal intercourse (UAI) in the last year, currently on treatment. Other variables included demographics, sexual risk, depression, internalized homonegativity, HIV treatment history, alcohol/drug use and beliefs about HIV treatments (Susceptibility to transmit HIV, Severity of HIV infection and Condom Motivation). Those with lower income were more likely to report that HIV was less transmissible. A self-reported decrease in condom motivation was associated with being White, well-educated and increased alcoho/drug use. A decrease in Severity of HIV was associated with better mental health, being non-White and undetectable viral load. Sexual risk appears related to beliefs about how treatment affects the transmissibility of HIV. Race, socioeconomic status, alcoho/drug use, mental health and viral load were also associated with treatment beliefs.
The association between HIV treatment optimism—beliefs about susceptibility to transmit HIV, motivation to use condoms, and severity of HIV—and sexual risk behavior was examined among HIV-positive African American men who have sex with men (MSM). Participants were 174 men recruited in four major metropolitan areas of the United States to participate in a weekend HIV risk reduction intervention. Baseline results revealed that beliefs in less susceptibility to transmit HIV and less motivation to use condoms were significantly associated with more unprotected anal intercourse among serodiscordant casual partners. Less motivation to use condoms also predicted more unprotected insertive and receptive anal sex and was more important than susceptibility beliefs in predicting these behaviors. Suggestions are offered of ways to better inform HIV-positive African American MSM about their misperceptions about HIV treatment and how their level of optimism about HIV treatment may diminish or encourage condom use.
African American; HIV treatment optimism; condom use
Brain morphometry is extensively used in cross-sectional studies. However, the difference in the estimated values of the morphometric measures between patients and healthy subjects may be small and hence overshadowed by the scanner-related variability, especially with multicentre and longitudinal studies. It is important therefore to investigate the variability and reliability of morphometric measurements between different scanners and different sessions of the same scanner.
We assessed the variability and reliability for the grey matter, white matter, cerebrospinal fluid and cerebral hemisphere volumes as well as the global sulcal index, sulcal surface and mean geodesic depth using Brainvisa. We used datasets obtained across multiple MR scanners at 1.5 T and 3 T from the same groups of 13 and 11 healthy volunteers, respectively. For each morphometric measure, we conducted ANOVA analysis and verified whether the estimated values were significantly different across different scanners or different sessions of the same scanner. The between-centre and between-visit reliabilities were estimated from their contribution to the total variance, using a random-effects ANOVA model. To estimate the main processes responsible for low reliability, the results of brain segmentation were compared to those obtained using FAST within FSL.
In a considerable number of cases, the main effects of both centre and visit factors were found to be significant. Moreover, both between-centre and between-visit reliabilities ranged from poor to excellent for most morphometric measures. A comparison between segmentation using Brainvisa and FAST revealed that FAST improved the reliabilities for most cases, suggesting that morphometry could benefit from improving the bias correction. However, the results were still significantly different across different scanners or different visits.
Our results confirm that for morphometry analysis with the current version of Brainvisa using data from multicentre or longitudinal studies, the scanner-related variability must be taken into account and where possible should be corrected for. We also suggest providing some flexibility to Brainvisa for a step-by-step analysis of the robustness of this package in terms of reproducibility of the results by allowing the bias corrected images to be imported from other packages and bias correction step be skipped, for example.
We describe a novel magnetic resonance imaging technique for detecting metabolism indirectly through changes in oxyhemoglobin:deoxyhemoglobin ratios and T2* signal change during ‘oxygen challenge’ (OC, 5 mins 100% O2). During OC, T2* increase reflects O2 binding to deoxyhemoglobin, which is formed when metabolizing tissues take up oxygen. Here OC has been applied to identify tissue metabolism within the ischemic brain. Permanent middle cerebral artery occlusion was induced in rats. In series 1 scanning (n = 5), diffusion-weighted imaging (DWI) was performed, followed by echo-planar T2* acquired during OC and perfusion-weighted imaging (PWI, arterial spin labeling). Oxygen challenge induced a T2* signal increase of 1.8%, 3.7%, and 0.24% in the contralateral cortex, ipsilateral cortex within the PWI/DWI mismatch zone, and ischemic core, respectively. T2* and apparent diffusion coefficient (ADC) map coregistration revealed that the T2* signal increase extended into the ADC lesion (3.4%). In series 2 (n = 5), FLASH T2* and ADC maps coregistered with histology revealed a T2* signal increase of 4.9% in the histologically defined border zone (55% normal neuronal morphology, located within the ADC lesion boundary) compared with a 0.7% increase in the cortical ischemic core (92% neuronal ischemic cell change, core ADC lesion). Oxygen challenge has potential clinical utility and, by distinguishing metabolically active and inactive tissues within hypoperfused regions, could provide a more precise assessment of penumbra.
diffusion-weighted imaging; MCAO; oxygen challenge; rat brain; stroke; T2*
Responsibility loadings determine relative value units of dental services that translate services into a common scale of work effort. The aims of this paper were to elicit responsibility loadings for a subset of dental services and to relate responsibility loadings to ratings of importance of the components of responsibility.
Responsibility loadings and ratings of components of responsibility were collected using mailed questionnaires from a random sample of Australian private general practice dentists in 2007 (response rate = 77%).
Median responsibility loadings were 1.25 for an initial oral examination and for a 3+-surface amalgam restoration, 1.50 for a simple extraction and for root canal obturation (single canal), and 1.75 for subgingival curettage (per quadrant). Across the five services coefficients from a multivariate logit model showed that ratings of importance of knowledge (0.34), dexterity (0.24), physical effort (0.28) and mental effort (0.48) were associated with responsibility loadings (P < 0.05).
The elicited median responsibility loadings showed agreement with previous estimates indicating convergent validity. Components of responsibility were associated with loadings indicating that components can explain and predict responsibility aspects of dental service provision.
Structural Magnetic Resonance Imaging (sMRI) of the brain is employed in the assessment of a wide range of neuropsychiatric disorders. In order to improve statistical power in such studies it is desirable to pool scanning resources from multiple centres. The CaliBrain project was designed to provide for an assessment of scanner differences at three centres in Scotland, and to assess the practicality of pooling scans from multiple-centres.
We scanned healthy subjects twice on each of the 3 scanners in the CaliBrain project with T1-weighted sequences. The tissue classifier supplied within the Statistical Parametric Mapping (SPM5) application was used to map the grey and white tissue for each scan. We were thus able to assess within scanner variability and between scanner differences. We have sought to correct for between scanner differences by adjusting the probability mappings of tissue occupancy (tissue priors) used in SPM5 for tissue classification. The adjustment procedure resulted in separate sets of tissue priors being developed for each scanner and we refer to these as scanner specific priors.
Voxel Based Morphometry (VBM) analyses and metric tests indicated that the use of scanner specific priors reduced tissue classification differences between scanners. However, the metric results also demonstrated that the between scanner differences were not reduced to the level of within scanner variability, the ideal for scanner harmonisation.
Our results indicate the development of scanner specific priors for SPM can assist in pooling of scan resources from different research centres. This can facilitate improvements in the statistical power of quantitative brain imaging studies.
An experiment investigated the assumption that natural indicators which exploit
existing learned associations between a signal and an event make more effective
warnings than previously unlearned symbolic indicators. Signal modality (visual,
auditory) and task demand (low, high) were also manipulated. Warning
effectiveness was indexed by accuracy and reaction time (RT) recorded during
training and dual task test phases. Thirty-six participants were trained to
recognize 4 natural and 4 symbolic indicators, either visual or auditory, paired
with critical incidents from an aviation context. As hypothesized, accuracy was
greater and RT was faster in response to natural indicators during the training
phase. This pattern of responding was upheld in test phase conditions with
respect to accuracy but observed in RT only in test phase conditions involving
high demand and the auditory modality. Using the experiment as a specific
example, we argue for the importance of considering the cognitive contribution
of the user (viz., prior learned associations) in the warning design process.
Drawing on semiotics and cognitive psychology, we highlight the indexical nature
of so-called auditory icons or natural
indicators and argue that the cogniser is an indispensable element
in the tripartite nature of signification.
auditory warnings; workload; modality; icons; semiotics
While the majority of dental care in Australia is provided in the private sector those patients who attend for public care remain a public health focus due to their socioeconomic disadvantage. The aims of this study were to compare dental service profiles provided to patients at private and public clinics, controlling for age, sex, reason for visit and income.
Data were collected in 2004–06, using a three-stage, stratified clustered sample of Australians aged 15+ years, involving a computer-assisted telephone interview (CATI), oral examination and mailed questionnaire. Analysis was restricted to those who responded to the CATI.
A total of 14,123 adults responded to the CATI (49% response) of whom 5,505 (44% of those interviewed) agreed to undergo an oral epidemiological examination. Multivariate analysis controlling for age, sex, reason for visit and income showed that persons attending public clinics had higher odds [Odds ratio, 95%CI] of extraction (1.69, 1.26–2.28), but lower odds of receiving oral prophylaxis (0.50, 0.38–0.66) and crown/bridge services (0.34, 0.13–0.91) compared to the reference category of private clinics.
Socio-economically disadvantaged persons who face barriers to accessing dental care in the private sector suffer further oral health disadvantage from a pattern of services received at public clinics that has more emphasis on extraction of teeth and less emphasis on preventive and maintenance care.
The aims of the study were to assess the impact of both positive (PA) and negative affect (NA) on self-reported oral health-related quality of life and to determine the effect of including affectivity on the relationship between oral health-related quality of life and a set of explanatory variables consisting of oral health status, socio-economic status and dental visiting pattern.
A random sample of 45–54 year-olds from metropolitan Adelaide, South Australia was surveyed by mailed self-complete questionnaire during 2004–05 with up to four follow-up mailings of the questionnaire to non-respondents (n = 986 responded, response rate = 44.4%). Oral health-related quality of life was measured using OHIP-14 and affectivity using the Bradburn scale. Using OHIP-14 and subscales as the dependent variables, regression models were constructed first using oral health status, socio-economic characteristics and dental visit pattern and then adding PA and NA as independent variables, with nested models tested for change in R-squared values.
PA and NA exhibited a negative correlation of -0.49 (P < 0.01). NA accounted for a larger percentage of variance in OHIP-14 scores (3.0% to 7.3%) than PA (1.4% to 4.6%). In models that included both PA and NA, PA accounted for 0.2% to 1.1% of variance in OHIP-14 scores compared to 1.8% to 3.9% for NA.
PA and NA both accounted for additional variance in quality of life scores, but did not substantially diminish the effect of established explanatory variables such as oral health status, socio-economic status and dental visit patterns.
A summary utility index is useful for deriving quality-adjusted life years (QALY) for cost analyses or disability weights for burden of disease studies. However, many quality of life instruments provide descriptive profiles rather than a single utility index. Transforming quality of life instruments to a utility index could extend the use of quality of life instruments to costs analyses and burden of disease studies. The aims of the study were to map a specific oral health measure, the Oral Health Impact Profile to a generic health state measure, the EuroQol, in order to enable the estimation of health state values based on OHIP data.
Data were collected from patients treated by a random sample of South Australian dentists in 2001–02 using mailed self-complete questionnaires. Dentists recorded the diagnosis of dental conditions and provided patients with self-complete questionnaires to record the nature, severity and duration of symptoms using the EuroQol (EQ-5D) and 14-item version of the Oral Health Impact Profile (OHIP-14) instruments. Data were available from 375 patients (response rate = 72%). A random two-thirds sample of patients was used in tobit regressions of EQ-5D health state values estimated using OHIP-14 in a model with categories of OHIP responses as indicator variables and in a model with OHIP responses as continuous variables. Age and sex were included as covariates in both models. The remaining one-third sample of patients was used to test the models.
The OHIP item 'painful aching in mouth' was significantly related to health state values in both models while 'life less satisfying' was also significant in the continuous model. Mean forecast errors relative to the mean observed health state value were higher when fitted to the categorical model (17.4%) compared to the continuous model (15.2%) (P < 0.05).
The findings enable health state values to be derived from OHIP-14 scores for populations where utility has not or cannot be measured directly.
The aim of this study was to describe practice activity trends among oral and maxillofacial surgeons in Australia over time.
All registered oral and maxillofacial surgeons in Australia were surveyed in 1990 and 2000 using mailed self-complete questionnaires.
Data were available from 79 surgeons from 1990 (response rate = 73.8%) and 116 surgeons from 2000 (response rate = 65.1%). The rate of provision of services per visit changed over time with increased rates observed overall (from 1.43 ± 0.05 services per visit in 1990 to 1.66 ± 0.06 services per visit in 2000), reflecting increases in pathology and reconstructive surgery. No change over time was observed in the provision of services per year (4,521 ± 286 services per year in 1990 and 4,503 ± 367 services per year in 2000). Time devoted to work showed no significant change over time (1,682 ± 75 hours per year in 1990 and 1,681 ± 94 hours per year in 2000), while the number of visits per week declined (70 ± 4 visits per week in 1990 to 58 ± 4 visits per week in 2000).
The apparent stability in the volume of services provided per year reflected a counterbalancing of increased services provided per visit and a decrease in the number of visits supplied.
Australian burden of disease estimates appeared inconsistent with the reported repetitive and ubiquitous nature of dental problems. The aims of the study were to measure the nature, severity and duration of symptoms for specific oral conditions, and calculate disability weights from these measures.
Data were collected in 2001–02 from a random sample of South Australian dentists using mailed self-complete questionnaires. Dentists recorded the diagnosis of dental problems and provided patients with self-complete questionnaires to record the nature, severity and duration of symptoms using the EuroQol instrument. Data were available from 378 dentists (response rate = 60%).
Disability weights were highest for pulpal infection (0.069), caries (0.044) and dentinal sensitivity (0.040), followed by denture problems (0.026), periodontal disease (0.023), failed restorations (0.019), tooth fractures (0.014) and tooth wear (0.011). Aesthetic problems had a low disability weight (0.002), and both recall/maintenance care and oral hygiene had adjusted weights of zero.
Disability weights for caries (0.044), periodontal disease (0.023) and denture problems (0.026) in this study were higher than comparable oral health conditions in the Australian Burden of Disease and Injury Study (0.005 for caries involving a filling and 0.014 for caries involving an extraction, 0.007 for periodontal disease, and 0.004 for edentulism). A range of common problems such as pulpal infection, failed restorations and tooth fracture that were not included in the Australian Burden of Disease and Injury Study had relatively high disability weights. The inclusion of a fuller range of oral health problems along with revised disability weights would result in oral health accounting for a larger amount of disability than originally estimated.
Oral disease; Burden of disease; EuroQol; Disability weight
The aims of the study were to compare the dimensions of oral-health-related quality-of-life measured by a generic health state measure, the EuroQol, and a specific oral health measure, the Oral Health Impact Profile.
Data were collected in 2001–02 from a random sample of South Australian dentists using mailed self-complete questionnaires. Dentists recorded the diagnosis of dental problems and provided patients with self-complete questionnaires to record the nature, severity and duration of symptoms using the EuroQol (EQ-5D+) and 14-item version of the Oral Health Impact Profile (OHIP-14) instruments.
Data were available from 375 patients (response rate = 72%). The EuroQol items of mobility, self care and usual activities formed a separate cluster of variables, as did anxiety/depression and cognition, while pain clustered with items from the OHIP physical pain subscale. OHIP items tended to form clusters consistent with the subscales of social disability, physical disability, physical pain, functional limitation and psychological discomfort. The OHIP handicap items clustered between the OHIP social disability and physical disability subscales. The OHIP psychological disability items split between the social disability and psychological discomfort subscales.
The observed clusters of variables empirically supported most of the conceptual dimensions of the OHIP. Both instruments covered symptom experience of pain indicating overlapping domains. However there was partial separation of the generic and specific items, EuroQol covered daily activities such as self-care and usual activities and OHIP covered oral health-specific aspects of functional limitation and physical disability as well as psychological and social aspects of disability and handicap.