The Simons Observatory: Cryogenic half wave plate rotation mechanism for the small aperture telescopes.

We present the requirements, design, and evaluation of the cryogenic continuously rotating half-wave plate (CHWP) for the Simons Observatory (SO). SO is a cosmic microwave background polarization experiment at Parque Astronómico de Atacama in northern Chile that covers a wide range of angular scales using both small (⌀0.42 m) and large (⌀6 m) aperture telescopes. In particular, the small aperture telescopes (SATs) focus on large angular scales for primordial B-mode polarization. To this end, the SATs employ a CHWP to modulate the polarization of the incident light at 8 Hz, suppressing atmospheric 1/f noise and mitigating systematic uncertainties that would otherwise arise due to the differential response of detectors sensitive to orthogonal polarizations. The CHWP consists of a 505 mm diameter achromatic sapphire HWP and a cryogenic rotation mechanism, both of which are cooled down to ∼50 K to reduce detector thermal loading. Under normal operation, the HWP is suspended by a superconducting magnetic bearing and rotates with a constant 2 Hz frequency, controlled by an electromagnetic synchronous motor. We find that the number of superconductors and the number of magnets that make up the superconducting magnetic bearing are important design parameters, especially for the rotation mechanism's vibration performance. The rotation angle is detected through an angular encoder with a noise level of 0.07 µrad s. During a cooldown process, the rotor is held in place by a grip-and-release mechanism that serves as both an alignment device and a thermal path. In this paper, we provide an overview of the SO SAT CHWP: its requirements, hardware design, and laboratory performance.

Oral Health Status of New Zealand Defence Force Recruits.

INTRODUCTION: The demands of operational deployment mean that defense force personnel must be dentally fit. Although medical evacuation for dental causes should be avoided, dental emergencies are a major non-combat-related contributor to withdrawal from deployment. Information on the oral health status of recruits and officer cadets entering the New Zealand Defence Force (NZDF) is scarce, yet it is useful for service and workforce planning. We investigated oral health status and its associations in new recruits and officer cadets entering the NZDF over a 13-month period. MATERIALS AND METHODS: This study used data from recruits' initial dental examination (including baseline forensic charting), posterior bitewing radiographs, orthopantomograph radiograph, and a socio-dental questionnaire. The impaction status of third molar teeth was evaluated. Ethical approval was obtained from the University of Otago Ethics Committee (reference number D18/200) and the NZDF Organisational Research Committee. RESULTS: Of the 874 (83%) of the 1,053 recruits (age range 17-59 years) who participated, one in five were Maori. Nearly two-thirds were Army recruits. Caries prevalence was almost 70%. Mean Decayed, Missing, and Filled Teeth (DMFT) (3.0 overall) was higher among females and Maori. Few teeth were missing due to caries. Third molars were common, seen in 745 (88.3%). One in four maxillary third molars (but only one in six mandibular ones) had fully erupted. The most common type of impaction among mandibular third molars was the mesioangular type, followed by vertical, horizontal, and distoangular. Almost 60% of recruits had one or more potentially problematic third molars. The prevalence was highest in the youngest age groups, those of medium or low socioeconomic status and in Army or Navy recruits. CONCLUSIONS: Recruits' oral health was acceptable, but potentially problematic third molars were common, indicating a need for careful assessment (and their possible removal) before operational deployment.

Concurrent validity of the short-form Family Impact Scale (FIS-8) in 4-year-old US children.

BACKGROUND: US data on the validity and reliability of the short-form Family Impact Scale (FIS-8; a scale for measuring the impact of a child's oral condition on his/her family) are lacking. METHODS: Cross-sectional analysis of data on four-year-old US children taking part in a multi-center cohort study. For child-caregiver dyads recruited at child age 12 months, the impact of the child's oral condition on the family was assessed at age 48 months using the FIS-8, with a subsample of 422 caregivers (from 686 who were approached). Internal consistency reliability was assessed using Cronbach's α, with concurrent validity assessed against a global family impact item ("How much are your family's daily lives affected by your child's teeth, lips, jaws or mouth?") and a global oral health item ("How would you describe the health of your child's teeth and mouth?"). RESULTS: Cronbach's alpha was 0.83. Although gradients in mean scores across ordinal response categories of the global family impact item were inconsistent, there were marked, consistent gradients across the ordinal categories of the global item on the child's oral health, with scores highest for those rating their child's oral health as 'Poor'. CONCLUSIONS: While the findings provide some evidence for the utility of the FIS in a US child sample, the study's replication in samples of preschoolers with greater disease experience would be useful.

A Primary Care Randomized Controlled Trial of Hall and Conventional Restorative Techniques.

OBJECTIVES: To investigate treatment outcomes of different restorative techniques undertaken by dental therapists for primary molar carious lesions in a sample of children in New Zealand primary care. METHODS: This was a randomized controlled trial with children aged 3 to 8 y in New Zealand's Whanganui region. Children meeting inclusion criteria were randomly allocated to treatment with either the Hall technique (HT), in which a stainless-steel crown (SSC) is placed without any carious tissue removal or tooth preparation, or a non-Hall conventional restorative approach (NHT), including tooth preparation with selective carious tissue removal; this included SSC, amalgam, composite, or glass ionomer cement (GIC) restorations. Restorative outcomes after 12 and 24 mo were categorized as success, minor failure, or major failure. RESULTS: Of the 295 eligible children, 149 and 146 were allocated to the HT and NHT groups, respectively, with a total of 570 carious primary molars treated by 13 dental therapists. The participant follow-up rates at 12 and 24 mo were 95% and 91%. SSCs were the most commonly used restoration in the NHT group (60%), followed by GIC (28%). SSCs were the most successful restorations regardless of whether they were placed with the HT or NHT, with success rates of 89% and 92% at 12 mo and 85% and 86% at 24 mo. In the NHT group, the treatment material was a predictor of minor failure at 12 and 24 mo, with significantly more failures with GICs. CONCLUSIONS: SSCs placed by dental therapists are a highly successful restoration for the primary dentition, regardless of whether they are placed with the HT or conventionally. The high failure rate of glass ionomer restorations means that they cannot be recommended for widespread use in New Zealand primary care (Australian New Zealand Clinical Trials Registry, ACTRN12614000844640). KNOWLEDGE TRANSFER STATEMENT: The findings of this study can be used by policy makers and clinicians when deciding on which materials and which approach to use to maximize success and to minimize retreatment rates when providing restorative treatment for carious primary molars in children's primary oral health care. Results also suggest that undertaking research in the primary care setting may enhance translation of new knowledge and techniques into clinicians' hands.

Dental trauma experience and oral-health-related quality of life among university students.

BACKGROUND: This study aimed to investigate the impact of self-reported dental trauma on oral-heath-related quality of life (OHRQoL) of young adults and determine whether personality characteristics influenced how it was reported. METHOD: A cross-sectional study was carried out using a sample of 435 university students. A questionnaire sought data on previous dental trauma. OHRQoL was assessed using the short-form of the oral health impact profile (OHIP-14); the outcome being one or more impacts occurring 'fairly often'/'very often'. Personality was assessed using the Positive and Negative Affect Scale (PANAS). RESULTS: The participation rate was 87.2%. Dental trauma experience was reported by 110 participants (25.3%), and 242 (55.6 %) indicated previous dental caries experience. Among those with dental trauma history, one or more OHIP-14 impacts was reported by 29.1% (with 21.2% among those with no history). Impact prevalence was higher among those who had previous dental caries experience (29.8%) than among those who had not (14.7%; P < 0.001). Higher PANAS negative affect scores were observed among those reporting one or more OHIP-14 impacts (P < 0.001). CONCLUSION: While dental trauma does not appear to have a negative impact on OHRQoL in young adults, past dental caries experience does. Negative emotionality influences self-reported oral health.

Caries-preventive efficacy of a supervised school toothbrushing programme in Northland, New Zealand.

BACKGROUND: Toothbrushing with fluoride toothpaste reduces the incidence of dental caries. OBJECTIVE: To evaluate a supervised school toothbrushing programme to reduce dental caries experience in children. BASIC RESEARCH DESIGN: Quasi-experimental study. All children had routine dental examinations at baseline using the ICDAS to record dental caries, along with bitewing radiographs. Half of the children were involved in a supervised toothbrushing programme. Examinations were repeated at the end of the school year. CLINICAL SETTING: Northland, New Zealand. PARTICIPANTS: 335 10-13-year-old New Zealand children with high caries experience. INTERVENTIONS: Half of the children participated in the supervised toothbrushing session each school day; the other half had no intervention. MAIN OUTCOME MEASURES: Caries increment, determined by comparing the baseline and follow-up status of each tooth surface. RESULTS: At baseline, there were 335 children, of whom 240 (71.6%) were followed up. The ICDAS net caries increment for those in the toothbrushing group was a mean of 11.7 surfaces improved; the control group had a mean of 8.6 surfaces which had deteriorated. Caries incidence for those in the toothbrushing group was 7.3%; that for the control group was 71.5%. Multivariate analysis showed that membership of the brushing group was the only statistically significant predictor of a lower net caries increment. CONCLUSION: A supervised school toothbrushing programme can reduce caries increment in a population experiencing high levels of dental disease.

The effect of bitewing radiography on estimates of dental caries experience among children differs according to their disease experience.

BACKGROUND: Radiography is a regularly used and accepted adjunct to visual examination in the diagnosis of dental caries. It is assumed that not using radiographs can lead to underestimation of dental caries experience with most reports having involved studies of young adults or adolescents, and been focused on the permanent dentition. The aim of this study was to determine the relative contributions of bitewing radiography and clinical examination in the detection of dental caries in primary molars and to determine whether those contributions differ according to caries experience. METHODS: A cross-sectional study was conducted, involving examinations undertaken in dental clinics. Bitewing radiographs taken at the time of the clinical examination were developed and read later, with the data from those used at the analysis stage to adjust the caries diagnosis for the mesial, occlusal and distal surfaces of the primary molar teeth. Children's clinically determined dmfs score was used to allocate them to one of three caries experience groups (0 dmfs, 1-8 dmfs, or 9+ dmfs). RESULTS: Of the 501 three-to-eight-year-old children examined, nearly three-quarters were younger than six. Caries prevalence and mean dmfs after clinical examination alone and following radiographs were 63.1% and 4.6 (sd, 6.2), and 74.7% and 5.8 (sd, 6.5) respectively. Among children with a dmfs of 1-8, the number of lesions missed during the clinical examination was greater than the number of 106 (25.6%) in children with a dmfs of 9+. In the 185 children with no apparent caries at clinical examination, 124 lesions were detected radiographically, among 58 (46.8%) of those. CONCLUSIONS: Taking bitewing radiographs in young children is not without challenges or risks, and it must be undertaken with these in mind. Diagnostic yields from bitewing radiographs are greater for children with greater caries experience. The findings of this study further support the need to consider using bitewing radiographs in young children to enhance the management of lesions not detected by a simple visual examination alone. TRIAL REGISTRATION: ACTRN12614000844640 .

To fill or not to fill: a qualitative cross-country study on dentists' decisions in managing non-cavitated proximal caries lesions.

BACKGROUND: This study aimed to identify barriers and enablers for dentists managing non-cavitated proximal caries lesions using non- or micro-invasive (NI/MI) approaches rather than invasive and restorative methods in New Zealand, Germany and the USA. METHODS: Semi-structured interviews were conducted, focusing on non-cavitated proximal caries lesions (radiographically confined to enamel or the outer dentine). Twelve dentists from New Zealand, 12 from Germany and 20 from the state of Michigan (USA) were interviewed. Convenience and snowball sampling were used for participant recruitment. A diverse sample of dentists was recruited. Interviews were conducted by telephone, using an interview schedule based on the Theoretical Domains Framework (TDF). RESULTS: The following barriers to managing lesions non- or micro-invasively were identified: patients' lacking adherence to oral hygiene instructions or high-caries risk, financial pressures and a lack of reimbursement for NI/MI, unsupportive colleagues and practice leaders, not undertaking professional development and basing treatment on what had been learned during training, and a sense of anticipated regret (anxiety about not restoring a proximal lesion in its early stages before it progressed). The following enablers were identified: the professional belief that remineralisation can occur in early non-cavitated proximal lesions and that these lesions can be arrested, the understanding that placing restorations weakens the tooth and inflicts a cycle of re-restoration, having up-to-date information and supportive colleagues and work environments, working as part of a team of competent and skilled dental practitioners who perform NI/MI (such as cleaning or scaling), having the necessary resources, undertaking ongoing professional development and continued education, maintaining membership of professional groups and a sense of professional and personal satisfaction from working in the patient's best interest. Financial aspects were more commonly mentioned by the German and American participants, while continuing education was more of a focus for the New Zealand participants. CONCLUSIONS: Decisions on managing non-cavitated proximal lesions were influenced by numerous factors, some of which could be targeted by interventions for implementing evidence-based management strategies in practice.

Composite reflective/absorptive IR-blocking filters embedded in metamaterial antireflection-coated silicon.

Infrared (IR)-blocking filters are crucial for controlling the radiative loading on cryogenic systems and for optimizing the sensitivity of bolometric detectors in the far-IR. We present a new IR filter approach based on a combination of patterned frequency-selective structures on silicon and a thin (25-75 µm thick) absorptive composite based on powdered reststrahlen absorbing materials. For a 300 K blackbody, this combination reflects ∼50% of the incoming light and blocks >99.8% of the total power with negligible thermal gradients and excellent low-frequency transmission. This allows a reduction in the IR thermal loading to negligible levels in a single cold filter. These composite filters are fabricated on silicon substrates, which provide excellent thermal transport laterally through the filter and ensure that the entire area of the absorptive filter stays near the bath temperature. A metamaterial antireflection coating cut into these substrates reduces in-band reflections to below 1%, and the in-band absorption of the powder mix is below 1% for signal bands below 750 GHz. This type of filter can be directly incorporated into silicon refractive optical elements.

Self-report of temporomandibular joint clicking and psychological factors: is there an association?

The objectives of this study were to test the hypothesis that self-reported TMJ clicking sounds in adolescents are positively associated with non-specific somatic symptoms, self-perception of body image and care-seeking behaviour. A cross-sectional study was carried out in 353 young adolescents (48·4% females) recruited from community (N = 272) and orthodontic clinic (N = 81) settings. Assessments included self-reported TMJ clicking, non-specific physical symptoms, body image concerns and for the clinic sample only, the source of motivation for treatment. TMJ sounds were self-reported by 19% of the sample and were associated with higher scores for non-specific physical symptoms and body image concerns (P < 0·001). Adolescents who were self-motivated to seek orthodontic treatment had greater scores for non-specific physical symptoms, more body image concerns and tended to report TMJ sounds more often (26·3% and 7·7% respectively; P = 0·41) than those who were solely parent/family-motivated to seek treatment. Self-reported TMJ sounds in adolescents were associated with a propensity to somatisation and concerns with body image. Care-seeking adolescents have greater non-specific physical symptoms and body image concerns and tend to report more frequent TMJ sounds.

Resin Infiltration of Caries in Primary Molars in a Community Setting: 24-Month Randomized Controlled Trial Findings.

This study aimed to assess whether resin infiltration of primary molar proximal lesions is more effective than noninvasive measures in radiographically controlling carious lesion progression into the dentin. A split-mouth randomized controlled trial included 90 children, each with 2 proximal lesions confined to the inner half of the enamel or ≤0.5 mm into the dentin. For each child, lesions were randomly allocated to test (infiltration: DMG Icon preproduct and fluoride varnish) or control (fluoride varnish) status. The primary outcome measure was 24-mo radiographic lesion progression. Placement of a restoration during the study period was counted as lesion progression. Proportions of teeth with progressed lesions were compared using the McNemar test. Children also reported on the treatment's acceptability to them. Children (46% female) ranged in age from 6 to 9 y. Their mean number of decayed, missing, and filled teeth (d3mft) was 2.8 (SD 2.6). At baseline, 58% and 42% of children were at moderate and low risk, respectively. Test and control lesions presented with similar radiographic lesions at baseline. At the 24-mo follow-up, 6 children had moved and 30 teeth had exfoliated. In the test and control groups, 15 of 66 lesions (22.7%) and 30 of 69 lesions (43.5%) had progressed, respectively (P < 0.05). The 2-y therapeutic effect (based on pairwise radiographic readings) of infiltration over fluoride varnish was 20.8% (95% confidence interval, 10.6%-30.2%). Nearly all children (96.7%) had enjoyed their visit to the clinic, and more than two-thirds (72.2%) were not worried about returning for treatment. Infiltration is more efficacious than fluoride varnish for controlling carious lesion progression in proximal lesions in primary molars, and most children find the treatment acceptable (Australian New Zealand Clinical Trials Registry ANZCTR.org.au ACTRN12611000827932). Knowledge Transfer Statement: These study findings can help clinicians decide which caries management approach they wish to use to prevent progression of proximal lesions in primary molars. With consideration of cost and patient preference, this information could lead to more appropriate therapeutic decisions.

On the redshift distribution and physical properties of ACT-selected DSFGs.

We present multi-wavelength detections of nine candidate gravitationally-lensed dusty star-forming galaxies (DSFGs) selected at 218GHz (1.4mm) from the ACT equatorial survey. Among the brightest ACT sources, these represent the subset of the total ACT sample lying in Herschel SPIRE fields, and all nine of the 218GHz detections were found to have bright Herschel counterparts. By fitting their spectral energy distributions (SEDs) with a modified blackbody model with power-law temperature distribution, we find the sample has a median redshift of z = 4.1 - 1.0 + 1.1 (68 per cent confidence interval), as expected for 218GHz selection, and an apparent total infrared luminosity of log 10 ( µ L IR / L ⊙ ) = 13.86 - 0.30 + 0.33 , which suggests that they are either strongly lensed sources or unresolved collections of unlensed DSFGs. The effective apparent diameter of the sample is µ d = 4.2 - 1.0 + 1.7 kpc , further evidence of strong lensing or multiplicity, since the typical diameter of dusty star-forming galaxies is 1.0-2.5 kpc. We emphasize that the effective apparent diameter derives from SED modelling without the assumption of optically thin dust (as opposed to image morphology). We find that the sources have substantial optical depth. ( τ = 4.2 - 1.9 + 3.7 ) to dust around the peak in the modified blackbody spectrum (λ obs ⩽ 500µm), a result that is robust to model choice.

Systematic effects from an ambient-temperature, continuously rotating half-wave plate.

We present an evaluation of systematic effects associated with a continuously rotating, ambient-temperature half-wave plate (HWP) based on two seasons of data from the Atacama B-Mode Search (ABS) experiment located in the Atacama Desert of Chile. The ABS experiment is a microwave telescope sensitive at 145 GHz. Here we present our in-field evaluation of celestial (Cosmic Microwave Background (CMB) plus galactic foreground) temperature-to-polarization leakage. We decompose the leakage into scalar, dipole, and quadrupole leakage terms. We report a scalar leakage of ∼0.01%, consistent with model expectations and an order of magnitude smaller than other CMB experiments have been reported. No significant dipole or quadrupole terms are detected; we constrain each to be <0.07% (95% confidence), limited by statistical uncertainty in our measurement. Dipole and quadrupole leakage at this level lead to systematic error on r ≲ 0.01 before any mitigation due to scan cross-linking or boresight rotation. The measured scalar leakage and the theoretical level of dipole and quadrupole leakage produce systematic error of r < 0.001 for the ABS survey and focal-plane layout before any data correction such as so-called deprojection. This demonstrates that ABS achieves significant beam systematic error mitigation from its HWP and shows the promise of continuously rotating HWPs for future experiments.

Psychometric assessment of the short-form Child Perceptions Questionnaire: an international collaborative study.

OBJECTIVE: To examine the factor structure and other psychometric characteristics of the most commonly used child oral-health-related quality-of-life (OHRQoL) measure (the 16-item short-form CPQ11-14 ) in a large number of children (N = 5804) from different settings and who had a range of caries experience and associated impacts. METHODS: Secondary data analyses used subnational epidemiological samples of 11- to 14-year-olds in Australia (N = 372), New Zealand (three samples: 352, 202, 429), Brunei (423), Cambodia (244), Hong Kong (542), Malaysia (439), Thailand (220, 325), England (88, 374), Germany (1055), Mexico (335) and Brazil (404). Confirmatory factor analysis (CFA) was used to examine the factor structure of the CPQ11-14 across the combined sample and within four regions (Australia/NZ, Asia, UK/Europe and Latin America). Item impact and internal reliability analysis were also conducted. RESULTS: Caries experience varied, with mean DMFT scores ranging from 0.5 in the Malaysian sample to 3.4 in one New Zealand sample. Even more variation was noted in the proportion reporting only fair or poor oral health; this was highest in the Cambodian and Mexican samples and lowest in the German sample and one New Zealand sample. One in 10 reported that their oral health had a marked impact on their life overall. The CFA across all samples revealed two factors with eigenvalues greater than 1. The first involved all items in the oral symptoms and functional limitations subscales; the second involved all emotional well-being and social well-being items. The first was designated the 'symptoms/function' subscale, and the second was designated the 'well-being' subscale. Cronbach's alpha scores were 0.72 and 0.84, respectively. The symptoms/function subscale contained more of the items with greater impact, with the item 'Food stuck in between your teeth' having greatest impact; in the well-being subscale, the 'Felt shy or embarrassed' item had the greatest impact. Repeating the analyses by world region gave similar findings. CONCLUSION: The CPQ11-14 performed well cross-sectionally in the largest analysis of the scale in the literature to date, with robust and mostly consistent psychometric characteristics, albeit with two underlying factors (rather than the originally hypothesized four-factor structure). It appears to be a sound, robust measure which should be useful for research, practice and policy.

Overcoming structural inequalities in oral health: the role of dental curricula.

To date the role of health professional schools in addressing oral health inequalities have been minimal, as attempts have focused principally upon systemic reform and broader societal obligations. Professionalism is a broad competency that is taught throughout dental schools and encompasses a range of attributes. Professionalism as a competency draws some debate and appears to be a shifting phenomenon. We may ask if professionalism in the dental curricula may be better addressed by social accountability? Social accountability directs oral health professional curricula (education, research, and service activities) towards addressing the priority health concerns of the community, in our case oral health inequalities. Although working toward dental schools becoming more socially accountable seems like a sensible way to address oral health inequalities, it might have limitations. We will consider some of the challenges in the dental curricula by considering some of the political, structural, social and ethical factors that influence our institutions and our graduates.

Oral Health-related Beliefs, Behaviors, and Outcomes through the Life Course.

Complex associations exist among socioeconomic status (SES) in early life, beliefs about oral health care (held by individuals and their parents), and oral health-related behaviors. The pathways to poor adult oral health are difficult to model and describe, especially due to a lack of longitudinal data. The study aim was to explore possible pathways of oral health from birth to adulthood (age 38 y). We hypothesized that higher socioeconomic position in childhood would predict favorable oral health beliefs in adolescence and early adulthood, which in turn would predict favorable self-care and dental attendance behaviors; those would lead to lower dental caries experience and better self-reported oral health by age 38 y. A generalized structural equation modeling approach was used to investigate the relationship among oral health-related beliefs, behaviors in early adulthood, and dental health outcomes and quality of life in adulthood (age, 38 y), based on longitudinal data from a population-based birth cohort. The current investigation utilized prospectively collected data on early (up to 15 y) and adult (26 and 32 y) SES, oral health-related beliefs (15, 26, and 32 y), self-care behaviors (15, 28, and 32 y), oral health outcomes (e.g., number of carious and missing tooth surfaces), and oral health-related quality of life (38 y). Early SES and parental oral health-related beliefs were associated with the study members' oral health-related beliefs, which in turn predicted toothbrushing and dental service use. Toothbrushing and dental service use were associated with the number of untreated carious and missing tooth surfaces in adulthood. The number of untreated carious and missing tooth surfaces were associated with oral health-related quality of life. Oral health toward the end of the fourth decade of life is associated with intergenerational factors and various aspects of people's beliefs, SES, dental attendance, and self-care operating since the childhood years.

Validity of self-reported periodontal questions in a New Zealand cohort.

OBJECTIVE: This study aims to assess the validity of four self-reported questions for measuring periodontitis in a birth cohort. METHODS: Full-mouth periodontal examinations (three sites/tooth) were undertaken at age 38 in a complete birth cohort born in 1972/1973 in New Zealand. Four self-reported periodontal screening questions were included ("Do you think you have gum disease"; "Has a dental professional ever told you that you have lost bone around your teeth"; "Have you ever had scaling, root planing, surgery, or other treatment for gum disease" and "Have you ever had any teeth that have become loose by themselves without some injury"), and the sensitivity and specificity of those self-reported items were calculated for individual questions and using a multivariable binary logistic regression model. Generalised linear models were used to compare relative risks for periodontitis and smoking, using the (a) clinical measures and (b) self-reported questions. RESULTS: Among the 895 who had periodontal examinations, the prevalence of periodontitis was 43.7, 22.8 and 12.0 %, respectively, for one or more sites with ≥4, ≥5 and ≥6 mm clinical attachment loss (AL). The specificity of the four self-reported questions was high (82-94 %), but the sensitivity was low for all, except the question: "Do you think you have gum disease". The four questions' highest combined sensitivity + specificity value was 1.33 for one or more sites with ≥4 mm AL, with the area under the receiver operating characteristic (ROC) curve being greatest for one or more sites with ≥6 mm AL, at 0.84. For the smoking-periodontitis association, the estimates of relative risk for periodontitis among smokers were as follows: (a) 1.81, 2.88 and 5.79, respectively, clinically determined to have one or more sites with ≥4, ≥5 and ≥6 mm AL and (b) 2.19, 2.17, 1.23 and 1.89, respectively, for the four self-reported questions. CONCLUSION: The four self-reported periodontal screening questions performed adequately in identifying clinically determined periodontal disease, and they showed moderate validity when used together as a set. However, the strength of the association between smoking and periodontitis was underestimated when they were used instead of clinically determined periodontal disease. CLINICAL RELEVANCE: These findings suggest that clinical examinations remain to be the desired approach for periodontal surveys, but where resource constraints preclude those, self-reported methods can provide useful information; after all, some periodontal information is better than none at all.

Changes in students' perceptions of their dental education environment.

OBJECTIVES: To examine the 'Expected' and 'Actual' educational environment experienced by a cohort of Bachelor of Dental Surgery (BDS) students at the University of Otago's Faculty of Dentistry using the Dundee Ready Educational Environment Measure (DREEM). METHODS: Cohort members were asked to complete five DREEM surveys over the four-year BDS programme. Student expectations at the beginning of their first year were assessed using a modified version of the DREEM questionnaire, while following (standard) DREEM questionnaires at the end of each professional year addressed students' 'Actual' perception of the educational environment. RESULTS: Sixty-six students (99%) completed at least one questionnaire. Overall, the BDS students' perceptions of their educational environment tended to be positive and students identified both perceived strengths and weaknesses in the BDS programme. However, more negative than positive shifts were reported between the 'Expected' and 'Actual' individual DREEM individual items, suggesting that BDS students initially expected more from their educational environment than they actually experienced. Individual DREEM outcomes undergoing negative and positive shifts differed over the years and varied in number. These may be explained, in part, by changes in the curriculum focus from year to year. CONCLUSION: The students' changing DREEM responses over time revealed anticipated and perceived strengths and weaknesses of the BDS curriculum, as well as shifts in students' perceptions in response to curricular changes. However, our findings highlight the potential usefulness for dental education of a measure for use that takes the unique aspects of the dental education environment into account.

Modulation of cosmic microwave background polarization with a warm rapidly rotating half-wave plate on the Atacama B-Mode Search instrument.

We evaluate the modulation of cosmic microwave background polarization using a rapidly rotating, half-wave plate (HWP) on the Atacama B-Mode Search. After demodulating the time-ordered-data (TOD), we find a significant reduction of atmospheric fluctuations. The demodulated TOD is stable on time scales of 500-1000 s, corresponding to frequencies of 1-2 mHz. This facilitates recovery of cosmological information at large angular scales, which are typically available only from balloon-borne or satellite experiments. This technique also achieves a sensitive measurement of celestial polarization without differencing the TOD of paired detectors sensitive to two orthogonal linear polarizations. This is the first demonstration of the ability to remove atmospheric contamination at these levels from a ground-based platform using a rapidly rotating HWP.