Comparison of mouse models of microbial experience reveals differences in microbial diversity and response to vaccination

Specific pathogen-free (SPF) laboratory mice dominate preclinical studies for immunology and vaccinology. Unfortunately, SPF mice often fail to accurately model human responses to vaccination and other immunological perturbations. Several groups have taken different approaches to introduce additional microbial experience to SPF mice to better model human immune experience. How these different models compare is unknown. Here, we directly compare three models: housing SPF mice in a microbe-rich barn-like environment (feralizing), adding wild-caught mice to the barn-like environment (fer-cohoused), or cohousing SPF mice with pet store mice in a barrier facility (pet-cohoused); the two latter representing different murine sources of microbial transmission. Pet-cohousing mice resulted in the greatest microbial exposure. Feralizing alone did not result in the transmission of any pathogens tested, while fer-cohousing resulted in the transmission of several picornaviruses. Murine astrovirus 2, the most common pathogen from pet store mice, was absent from the other two model systems. Previously, we had shown that pet-cohousing reduced the antibody response to vaccination compared with SPF mice. This was not recapitulated in either the feralized or fer-cohoused mice. These data indicate that not all dirty mouse models are equivalent in either microbial experience or immune responses to vaccination. These disparities suggest that more cross model comparisons are needed but also represent opportunities to uncover microbe combination-specific phenotypes and develop more refined experimental models. Given the breadth of microbes encountered by humans across the globe, multiple model systems may be needed to accurately recapitulate heterogenous human immune responses.IMPORTANCEAnimal models are an essential tool for evaluating clinical interventions. Unfortunately, they can often fail to accurately predict outcomes when translated into humans. This failure is due in part to a lack of natural infections experienced by most laboratory animals. To improve the mouse model, we and others have exposed laboratory mice to microbes they would experience in the wild. Although these models have been growing in popularity, these different models have not been specifically compared. Here, we directly compare how three different models of microbial experience impact the immune response to influenza vaccination. We find that these models are not the same and that the degree of microbial exposure affects the magnitude of the response to vaccination. These results provide an opportunity for the field to continue comparing and contrasting these systems to determine which models best recapitulate different aspects of the human condition.

Pathogen-driven CRISPR screens identify TREX1 as a regulator of DNA self-sensing during influenza virus infection

Host:pathogen interactions dictate the outcome of infection, yet the limitations of current approaches leave large regions of this interface unexplored. Here, we develop a novel fitness-based screen that queries factors important during the middle to late stages of infection. This is achieved by engineering influenza virus to direct the screen by programming dCas9 to modulate host gene expression. Our genome-wide screen for pro-viral factors identifies the cytoplasmic DNA exonuclease TREX1. TREX1 degrades cytoplasmic DNA to prevent inappropriate innate immune activation by self-DNA. We reveal that this same process aids influenza virus replication. Infection triggers release of mitochondrial DNA into the cytoplasm, activating antiviral signaling via cGAS and STING. TREX1 metabolizes the DNA, preventing its sensing. Collectively, these data show that self-DNA is deployed to amplify innate immunity, a process tempered by TREX1. Moreover, they demonstrate the power and generality of pathogen-driven fitness-based screens to pinpoint key host regulators of infection.

Emulation of Community Water Fluoridation Coverage Across US Counties

INTRODUCTION

Expansion of community water fluoridation has stalled in the United States, leaving 115 million Americans without fluoridated drinking water.

OBJECTIVE

This study used spatial regression methods to assess contributions of supply-side factors (neighboring counties' fluoridation coverage) and demand-side factors (health literacy, education, and population density of the local county) in predicting the extent of fluoridation in US counties.

METHODS

For this cross-sectional ecological analysis, data from the 2014 Water Fluoridation Reporting System for all 3,135 US counties were merged with sociodemographic data from the 2014 American Community Survey and county-level estimates of health literacy based on the National Association of Adult Literacy Survey. We employed multilevel geographically weighted autoregressive models to predict fluoridation coverage of each county as a function of fluoridation coverage of neighboring counties and local-county covariates: either health literacy or sociodemographic characteristics. Akaike's Information Criterion was used to distinguish the better model in terms of explanatory power and parsimony.

RESULTS

In the best-fit model, an increase from the first to third quartile of neighboring counties' fluoridation coverage was associated with an increase of 27.76 percentage points (95% confidence limits [CI] = 27.71, 27.81) in a local county's fluoridation coverage, while an increase from the first to third quartile of local county's health literacy was associated with an increase of 2.8 percentage points (95% CL = 2.68, 2.89). The results are consistent with a process of emulation, in which counties implement fluoridation based upon their population's health literacy and the extent of fluoridation practiced in neighboring counties.

CONCLUSION

These results suggest that demand for community water fluoridation will increase as health literacy increases within a county. Furthermore, when considering expansion of fluoridation, non-fluoridated communities can benefit from precedents from nearby communities that are fluoridated.

KNOWLEDGE TRANSFER STATEMENT

Expanded coverage of community water fluoridation has stalled in the United States. The economic theory of diffusion describes how, over time and space, policy enacted in one community can influence public opinion in a neighboring community. This study applies geospatial analysis of county-level data and the theory of policy diffusion to demonstrate that fluoridated counties can promote the implementation of community water fluoridation in their neighboring, non-fluoridated communities.

Long-chain omega-3 fatty acids and headache in the U.S. population

The objective of this study was to assess whether dietary intake of long-chain omega-3 polyunsaturated fatty acids (PUFAs) is associated with lower prevalence of headache in the U.S.

POPULATION

This cross-sectional study used data for a nationally representative sample of 12,317 men and women aged ≥ 20 years participating in the National Health and Nutrition Examination Surveys of 1999-2004. Interviewers recorded self-report of severe headache or migraine in the past three months. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were quantified from 24-hour dietary recall using the U.S. Department of Agriculture National Nutrient Database. Serum concentration of C-reactive protein, a marker of inflammation and potential mediator of PUFA's analgesic properties, was quantified by latex-enhanced nephelometry. Multivariable generalized linear models estimated prevalence ratios (PR) with 95% confidence limits (CL) for severe headache or migraine adjusting for NHANES cycle, sociodemographic characteristics, body mass index and total energy intake. The unadjusted prevalence of severe headache or migraine was 22.0% (females 28.2%, males 15.5%). In multivariable analysis, greater intake of omega-3 PUFAs was associated with lower prevalence of severe headache or migraine: PR 0.94 (95% CL: 0.88, 0.99, p = 0.035) per log unit increase in EPA, and PR 0.94 (95% CL: 0.90, 0.99, p = 0.023) per log unit increase in DHA. The strength of association was greater for non-Mexican Hispanics than for other racial/ethnic groups but was not attenuated after adjustment for C-reactive protein. In conclusion, higher dietary intakes of EPA and DHA were associated with lower prevalence of headache supporting the hypothesis that omega-3 PUFAs may prevent or reduce headache.

Water Fluoridation and Dental Caries in U.S. Children and Adolescents

Fluoridation of America's drinking water was among the great public health achievements of the 20th century. Yet there is a paucity of studies from the past 3 decades investigating its dental health benefits in the U.S.

POPULATION

This cross-sectional study sought to evaluate associations between availability of community water fluoridation (CWF) and dental caries experience in the U.S. child and adolescent population. County-level estimates of the percentage of population served by CWF (% CWF) from the Centers for Disease Control and Prevention's Water Fluoridation Reporting System were merged with dental examination data from 10 y of National Health and Nutrition Examination Surveys (1999 to 2004 and 2011 to 2014). Dental caries experience in the primary dentition (decayed and filled tooth surfaces [dfs]) was calculated for 7,000 children aged 2 to 8 y and in the permanent dentition (decayed, missing, and filled tooth surfaces [DMFS]) for 12,604 children and adolescents aged 6 to 17 y. Linear regression models estimated associations between % CWF and dental caries experience with adjustment for sociodemographic characteristics: age, sex, race/ethnicity, rural-urban location, head-of-household education, and period since last dental visit. Sensitivity analysis excluded counties fluoridated after 1998. In unadjusted analysis, caries experience in the primary dentition was lower in counties with ≥75% CWF (mean dfs = 3.3; 95% confidence limit [CL] = 2.8, 3.7) than in counties with <75% CWF (mean dfs = 4.6; 95% CL = 3.9, 5.4), a prevented fraction of 30% (95% CL = 11, 48). The difference was also statistically significant, although less pronounced, in the permanent dentition: mean DMFS (95% CL) was 2.2 (2.0, 2.4) and 1.9 (1.8, 2.1), respectively, representing a prevented fraction of 12% (95% CL = 1, 23). Statistically significant associations likewise were seen when % CWF was modeled as a continuum, and differences tended to increase in covariate-adjusted analysis and in sensitivity analysis. These findings confirm a substantial caries-preventive benefit of CWF for U.S. children and that the benefit is most pronounced in primary teeth.

GWAS Identifies New Loci for Painful Temporomandibular Disorder: Hispanic Community Health Study/Study of Latinos

Temporomandibular disorder (TMD) is a musculoskeletal condition characterized by pain and reduced function in the temporomandibular joint and/or associated masticatory musculature. Prevalence in the United States is 5% and twice as high among women as men. We conducted a discovery genome-wide association study (GWAS) of TMD in 10,153 participants (769 cases, 9,384 controls) of the US Hispanic Community Health Study/Study of Latinos (HCHS/SOL). The most promising single-nucleotide polymorphisms (SNPs) were tested in meta-analysis of 4 independent cohorts. One replication cohort was from the United States, and the others were from Germany, Finland, and Brazil, totaling 1,911 TMD cases and 6,903 controls. A locus near the sarcoglycan alpha ( SGCA), rs4794106, was suggestive in the discovery analysis ( P = 2.6 × 10⁶) and replicated (i.e., 1-tailed P = 0.016) in the Brazilian cohort. In the discovery cohort, sex-stratified analysis identified 2 additional genome-wide significant loci in females. One lying upstream of the relaxin/insulin-like family peptide receptor 2 ( RXP2) (chromosome 13, rs60249166, odds ratio [OR] = 0.65, P = 3.6 × 10^-8) was replicated among females in the meta-analysis (1-tailed P = 0.052). The other (chromosome 17, rs1531554, OR = 0.68, P = 2.9 × 10^-8) was replicated among females (1-tailed P = 0.002), as well as replicated in meta-analysis of both sexes (1-tailed P = 0.021). A novel locus at genome-wide level of significance (rs73460075, OR = 0.56, P = 3.8 × 10^-8) in the intron of the dystrophin gene DMD (X chromosome), and a suggestive locus on chromosome 7 (rs73271865, P = 2.9 × 10^-7) upstream of the Sp4 Transcription Factor ( SP4) gene were identified in the discovery cohort, but neither of these was replicated. The SGCA gene encodes SGCA, which is involved in the cellular structure of muscle fibers and, along with DMD, forms part of the dystrophin-glycoprotein complex. Functional annotation suggested that several of these variants reside in loci that regulate processes relevant to TMD pathobiologic processes.

Chronic Periodontitis Genome-wide Association Study in the Hispanic Community Health Study / Study of Latinos

Chronic periodontitis (CP) has a genetic component, particularly its severe forms. Evidence from genome-wide association studies (GWASs) has highlighted several potential novel loci. Here, the authors report the first GWAS of CP among a large community-based sample of Hispanics/Latinos. The authors interrogated a quantitative trait of CP (mean interproximal clinical attachment level determined by full-mouth periodontal examinations) among 10,935 adult participants (mean age: 45 y, range: 18 to 76 y) from the Hispanic Community Health Study / Study of Latinos. Genotyping was done with a custom Illumina Omni2.5M array, and imputation to approximately 20 million single-nucleotide polymorphisms was based on the 1000 Genomes Project phase 1 reference panel. Analyses were based on linear mixed models adjusting for sex, age, study design features, ancestry, and kinship and employed a conventional P < 5 × 10^-8 statistical significance threshold. The authors identified a genome-wide significant association signal in the 1q42.2 locus ( TSNAX-DISC1 noncoding RNA, lead single-nucleotide polymorphism: rs149133391, minor allele [C] frequency = 0.01, P = 7.9 × 10^-9) and 4 more loci with suggestive evidence of association ( P < 5 × 10^-6): 1q22 (rs13373934), 5p15.33 (rs186066047), 6p22.3 (rs10456847), and 11p15.1 (rs75715012). We tested these loci for replication in independent samples of European-American ( n = 4,402) and African-American ( n = 908) participants of the Atherosclerosis Risk in Communities study. There was no replication among the European Americans; however, the TSNAX-DISC1 locus replicated in the African-American sample (rs149133391, minor allele frequency = 0.02, P = 9.1 × 10^-3), while the 1q22 locus was directionally concordant and nominally significant (rs13373934, P = 4.0 × 10^-2). This discovery GWAS of interproximal clinical attachment level-a measure of lifetime periodontal tissue destruction-was conducted in a large, community-based sample of Hispanic/Latinos. It identified a genome-wide significant locus that was independently replicated in an African-American population. Identifying this genetic marker offers direction for interrogation in subsequent genomic and experimental studies of CP.

Painful Temporomandibular Disorder: Decade of Discovery from OPPERA Studies

In 2006, the OPPERA project (Orofacial Pain: Prospective Evaluation and Risk Assessment) set out to identify risk factors for development of painful temporomandibular disorder (TMD). A decade later, this review summarizes its key findings. At 4 US study sites, OPPERA recruited and examined 3,258 community-based TMD-free adults assessing genetic and phenotypic measures of biological, psychosocial, clinical, and health status characteristics. During follow-up, 4% of participants per annum developed clinically verified TMD, although that was a "symptom iceberg" when compared with the 19% annual rate of facial pain symptoms. The most influential predictors of clinical TMD were simple checklists of comorbid health conditions and nonpainful orofacial symptoms. Self-reports of jaw parafunction were markedly stronger predictors than corresponding examiner assessments. The strongest psychosocial predictor was frequency of somatic symptoms, although not somatic reactivity. Pressure pain thresholds measured at cranial sites only weakly predicted incident TMD yet were strongly associated with chronic TMD, cross-sectionally, in OPPERA's separate case-control study. The puzzle was resolved in OPPERA's nested case-control study where repeated measures of pressure pain thresholds revealed fluctuation that coincided with TMD's onset, persistence, and recovery but did not predict its incidence. The nested case-control study likewise furnished novel evidence that deteriorating sleep quality predicted TMD incidence. Three hundred genes were investigated, implicating 6 single-nucleotide polymorphisms (SNPs) as risk factors for chronic TMD, while another 6 SNPs were associated with intermediate phenotypes for TMD. One study identified a serotonergic pathway in which multiple SNPs influenced risk of chronic TMD. Two other studies investigating gene-environment interactions found that effects of stress on pain were modified by variation in the gene encoding catechol O-methyltransferase. Lessons learned from OPPERA have verified some implicated risk factors for TMD and refuted others, redirecting our thinking. Now it is time to apply those lessons to studies investigating treatment and prevention of TMD.

COMT Diplotype Amplifies Effect of Stress on Risk of Temporomandibular Pain

When measured once, psychological stress predicts development of painful temporomandibular disorder (TMD). However, a single measurement fails to characterize the dynamic nature of stress over time. Moreover, effects of stress on pain likely vary according to biological susceptibility. We hypothesized that temporal escalation in stress exacerbates risk for TMD, and the effect is amplified by allelic variants in a gene, catechol-O-methyltransferase (COMT), regulating catechol neurotransmitter catabolism. We used data from the Orofacial Pain: Prospective Evaluation and Risk Assessment prospective cohort study of 2,707 community-dwelling adults with no lifetime history of TMD on enrollment. At baseline and quarterly periods thereafter, the Perceived Stress Scale (PSS) measured psychological stress. Genotyped DNA from blood samples determined COMT diplotypes. During follow-up of 0.25 to 5.2 y, 248 adults developed examiner-verified incident TMD. PSS scores at baseline were 20% greater (P < 0.001) in adults who developed incident TMD compared with TMD-free controls. Baseline PSS scores increased by 9% (P = 0.003) during follow-up in cases but remained stable in controls. This stress escalation was limited to incident cases with COMT diplotypes coding for low-activity COMT, signifying impaired catabolism of catecholamines. Cox regression models confirmed significant effects on TMD hazard of both baseline PSS (P < 0.001), modeled as a time-constant covariate, and change in PSS (P < 0.001), modeled as a time-varying covariate. Furthermore, a significant (P = 0.04) interaction of COMT diplotype and time-varying stress showed that a postbaseline increase of 1.0 standard deviation in PSS more than doubled risk of TMD incidence in subjects with low-activity COMT diplotypes (hazard ratio = 2.35; 95% confidence limits: 1.66, 3.32), an effect not found in subjects with high-activity COMT diplotypes (hazard ratio = 1.42; 95% confidence limits: 0.96, 2.09). Findings provide novel insights into dynamic effects of psychological stress on TMD pain, highlighting that effects are most pronounced in individuals whose genetic susceptibility increases responsiveness to catecholamine neurotransmitters.

Projections of U.S. Edentulism prevalence following 5 decades of decline

After decades of decline in prevalence of complete tooth loss (edentulism), the trend continues to be misinterpreted, producing flawed projections and misdirected health goals. We investigated population trends in edentulism among U.S. adults aged ≥ 15 yr by creating time-series data from 5 national cross-sectional health surveys: 1957-1958 (n ≈ 100,000 adults), 1971-1975 (n = 14,655 adults), 1988-1998 (n = 18,011 adults), 1999-2002 (n = 12,336 adults), and 2009-2012 (n = 10,522 adults). Birth cohort analysis was used to isolate age and cohort effects. Geographic and sociodemographic variation in prevalence was investigated with a sixth U.S. survey of 432,519 adults conducted in 2010. Prevalence through 2050 was projected with age-cohort regression models using Monte-Carlo simulation of prediction intervals. Across the 5-decade observation period, edentulism prevalence declined from 18.9% in 1957-1958 (95% confidence limits: 18.4%, 19.4%) to 4.9% in 2009-2012 (95% confidence limits: 4.0%, 5.8%). The most influential determinant of the decline was the passing of generations born before the 1940s, whose rate of edentulism incidence (5%-6% per decade of age) far exceeded later cohorts (1%-3% per decade of age). High-income households experienced a greater relative decline, although a smaller absolute decline, than low-income households. By 2010, edentulism was a rare condition in high-income households, and it had contracted geographically to states with disproportionately high poverty. With the passing of generations born in the mid-20th century, the rate of decline in edentulism is projected to slow, reaching 2.6% (95% prediction limits: 2.1%, 3.1%) by 2050. The continuing decline will be offset only partially by population growth and population aging such that the predicted number of edentulous people in 2050 (8.6 million; 95% prediction limits: 6.8 million, 10.3 million) will be 30% lower than the 12.2 million edentulous people in 2010.

Sleep apnea symptoms and risk of temporomandibular disorder: OPPERA cohort

The authors tested the hypothesis that obstructive sleep apnea (OSA) signs/symptoms are associated with the occurrence of temporomandibular disorder (TMD), using the OPPERA prospective cohort study of adults aged 18 to 44 years at enrollment (n = 2,604) and the OPPERA case-control study of chronic TMD (n = 1,716). In both the OPPERA cohort and case-control studies, TMD was examiner determined according to established research diagnostic criteria. People were considered to have high likelihood of OSA if they reported a history of sleep apnea or ≥ 2 hallmarks of OSA: loud snoring, daytime sleepiness, witnessed apnea, and hypertension. Cox proportional hazards regression estimated hazard ratios (HRs) and 95% confidence limits (CL) for first-onset TMD. Logistic regression estimated odds ratios (OR) and 95% CL for chronic TMD. In the cohort, 248 individuals developed first-onset TMD during the median 2.8-year follow-up. High likelihood of OSA was associated with greater incidence of first-onset TMD (adjusted HR = 1.73; 95% CL, 1.14, 2.62). In the case-control study, high likelihood of OSA was associated with higher odds of chronic TMD (adjusted OR = 3.63; 95% CL, 2.03, 6.52). Both studies supported a significant association of OSA symptoms and TMD, with prospective cohort evidence finding that OSA symptoms preceded first-onset TMD.

Effects of fluoridated drinking water on dental caries in Australian adults

Systematic reviews produce conflicting conclusions regarding dental caries-preventive effects of water fluoridation in adults. The authors investigated the relationship using data from the nationally representative 2004-2006 Australian National Survey of Adult Oral Health. Effects were compared between the pre-fluoridation cohort born before 1960 (n = 2,270) and the cohort born between 1960 and 1990 (n = 1,509), when widespread implementation of fluoridation increased population coverage from < 1% to 67%. Residential history questionnaires determined the percentage of each person's lifetime exposed to fluoridated water. Examiners recorded decayed, missing, and filled teeth (DMF-Teeth) and decayed and filled tooth surfaces (DF-Surfaces). Socio-demographic and preventive dental behaviors were included in multivariable least-squares regression models adjusted for potential confounding. In fully adjusted models, > 75% of lifetime exposure to fluoridation relative to < 25% of lifetime exposure was associated with 11% and 10% fewer DMF-Teeth in the pre-1960 (p < .0001) and 1960-1990 cohorts (p = .018), respectively. Corresponding reductions in DF-Surfaces were 30% (p < .001) and 21% (p < .001). Findings for intermediate fluoridation exposure suggested a dose-response relationship. Results were consistent in sensitivity analyses accounting for missing data. In this nationally representative sample of Australian adults, caries-preventive effects of water fluoridation were at least as great in adults born before widespread implementation of fluoridation as after widespread implementation of fluoridation.

National prevalence of oral HPV infection and related risk factors in the U.S. adult population

This article reviews the rapidly growing evidence that oral human papilloma viruses (HPV) infection contributes to the risk of oral squamous cell carcinoma. It also reports the first nationally representative estimates of oral HPV prevalence in the United States adult population. An estimated 7.3% (95% CI: 6.0, 8.9) of the U.S. population had one or more oral HPV types detected in oral rinse; 3.1% (95%CI: 2.4, 3.9) of the U.S. population had one or more oncogenic HPV types. A substantial excess risk of HPV infection in men is not explained by education, smoking, age of sexual debut, or number of lifetime sex partners. Based on the published finding from a case-control study, where there was an odds ratio of 2.6 (95% CI: 1.5, 4.2) for the association of head and neck cancer oncogenic oral HPV infection, the estimated population attributable risk for head and neck cancer in the U.S. population was 4.7%. In other words, there would be a 4.7% reduction in incidence rate of head and neck cancer in the United States if oncogenic HPV infection could be prevented. The results also provide population data that help evaluate the likely public health benefits of prophylactic vaccination against oral HPV acquisition.

Apgar score and dental caries risk in the primary dentition of five year olds

BACKGROUND

Conditions in utero and early life underlie risk for several childhood disorders. This study tested the hypothesis that the Apgar score predicted dental caries in the primary dentition.

METHODS

A retrospective cohort study conducted in 2003 examined associations between conditions at birth and early life with dental caries experience at five years. Dental examination data for a random sample of five-year-old South Australian children were obtained from School Dental Service electronic records. A questionnaire mailed to the parents obtained information about neonatal status at delivery (five-minute Apgar score, birthweight, plurality, gestational age) and details about birth order, weaning, and behavioural, familial and sociodemographic characteristics.

RESULTS

Of the 1398 sampled children with a completed questionnaire (response rate=64.6%), 1058 were singleton term deliveries among whom prevalence of dental caries was 40.1%. In weighted log-binomial regression analysis, children with an Apgar score of <=8 relative to a score of 9-10 had greater probability of dental caries in the primary dentition after adjusting for sociodemographic and behavioural covariates and water fluoridation concentration (adjusted PR=1.47, 95% CI=1.11, 1.95).

CONCLUSIONS

Readily accessible markers of early life, such as the Apgar score, may guide clinicians in identifying children at potentially heightened risk for dental caries and aid decision-making in allocating preventive services.

A cross-national comparison of income gradients in oral health quality of life in four welfare states: application of the Korpi and Palme typology

BACKGROUND

The extent to which welfare states may influence health outcomes has not been explored. It was hypothesised that policies which target the poor are associated with greater income inequality in oral health quality of life than those that provide earnings-related benefits to all citizens.

METHODS

Data were from nationally representative surveys in the UK (n = 4064), Finland (n = 5078), Germany (n = 1454) and Australia (n = 2292) conducted from 1998 to 2002. The typology of Korpi and Palme classifies these countries into four different welfare states. In each survey, subjects completed the Oral Health Impact Profile (OHIP-14) questionnaire, which evaluates the adverse consequence of dental conditions on quality of life. For each country, survey estimation commands were used to create linear regression models that estimated the slope of the gradient between four quartiles of income and OHIP-14 severity scores. Parameter estimates for income gradients were contrasted across countries using Wald chi(2) tests specifying a critical p value of 0.008, equivalent to a Bonferroni correction of p<0.05 for the six pairwise tests.

RESULTS

Statistically significant income gradients in OHIP-14 severity scores were found in all countries except Germany. A global test confirmed significant cross-national differences in the magnitude of income gradients. In Australia, where a flat rate of benefits targeted the poor, the mean OHIP-14 severity score reduced by 1.7 units (95% CI -2.15 to -1.34) with each increasing quartile of household income, a significantly steeper gradient than in other countries.

CONCLUSION

The coverage and generosity of welfare state benefits appear to influence levels of inequality in population oral health quality of life.

Affluent neighborhoods reduce excess risk of tooth loss among the poor

The effect of neighborhood on health may vary according to the characteristics of the residents. We tested the hypothesis that, in affluent neighborhoods, low-income adults retain more teeth than their income-equivalent peers in poor neighborhoods. In 2003, the Adelaide Small Area Dental Study collected sociodemographic and tooth retention information from 2860 adults in 60 neighborhoods. Neighborhood socio-economic position was a census-based composite measure. Using multilevel modelling, we fitted a series of two-level random intercept variance component models. Findings revealed significant main effects for individual and neighborhood predictors and a significant interaction between neighborhood disadvantage and low income. In affluent areas, disparities in tooth retention were negligible, but in poor neighborhoods, substantial variation in tooth retention between individuals was found based on their level of income. Low-income adults appeared to benefit from living in affluent areas, while wealthier adults living in poor neighborhoods did not lose their oral health advantage.

Impact of dental care on oral health-related quality of life and treatment goals among elderly adults

BACKGROUND

General dental care can effectively control disease and restore damaged tissue, yet little is known about its impact on patients' subjective oral health, namely treatment goals and oral health-related quality of life (OHRQoL). This study aimed to evaluate change in both aspects of subjective oral health among elderly adults receiving publicly-funded, general dental care.

METHODS

We conducted a prospective, single-group intervention study of adults aged 75+ years receiving care through the South Australian Dental Service (SADS). Before receiving dental care, subjects completed the Oral Health Impact Profile (OHIP-14) questionnaire which evaluates OHRQoL. In this questionnaire, subjects rated the extent to which they had attained a self-nominated oral health goal. Dentists provided standard-of-care treatment and six months later the OHIP-14 and goal attainment questions were re-administered.

RESULTS

Among the 253 adults studied, overall improvements in OHRQoL were observed (p < 0.05), although the effect was dependent on pre-treatment goal: mean OHIP-14 scores did not change significantly for subjects whose goal was less pain/discomfort while significant improvements were observed for subjects with other treatment goals. In contrast, mean goal attainment ratings improved significantly (P < 0.05), regardless of treatment goal categories.

CONCLUSIONS

Dental care was associated with improvements in subjective oral health, although different patterns of improvement were observed for OHRQoL compared with goal attainment ratings.

Risk factors for dental caries in the five-year-old South Australian population

BACKGROUND

This study tested the hypothesis that risk behaviours in disadvantaged groups would explain socio-economic inequality in dental caries prevalence among preschool children.

METHODS

Using a case-control study, children with caries experience (one or more decayed, missing or filled primary tooth surfaces) and with no caries experience were sampled with known probabilities from among five year olds attending the South Australian Dental Service (SADS). Dental caries experience of primary teeth was recorded by SADS clinicians. Social and behavioural information was collected using a questionnaire mailed to parents. Prevalence rates, prevalence ratios (PR) and 95 per cent confidence intervals (95% CI) were computed, taking into account sampling probabilities.

RESULTS

Questionnaires were obtained for 64.6 per cent of sampled children (n = 1398) and 40.2 per cent (95% CI = 37.8-42.6) of them had caries experience. Five statistically significant risk factors were identified relating to previous feeding, current oral hygiene and parent's own oral health perceptions. The prevalence of four risk factors was greater in low-income households compared with high-income households (P < or = 0.01). In multivariate analysis, after adjusting for age of tooth cleaning onset, age at which toothpaste was introduced was not significantly associated with caries prevalence. Behavioural risk factors did not explain income-related gradients in caries prevalence but modified the level of risk associated with delayed onset of tooth cleaning. Children who delayed tooth cleaning until the age of 24 months or more and who were from low-income households had a 2.7-fold increase in caries prevalence (95% CI = 2.1-3.4).

CONCLUSIONS

Caries prevention efforts need to target behaviours in infancy and non-behavioural risk factors among preschoolers in low-income households.

An empirically derived population-response model of the short form of the Oral Health Impact Profile

OBJECTIVE

The aim of this paper was to model the consequences of dental conditions from an empirical basis and to test the model's ability to predict response combinations.

METHODS

The model was derived from responses to the short-form Oral Health Impact Profile (OHIP14) obtained from a UK population sample of 5281 dentate adults. This model was then used to predict OHIP14 response combinations obtained from a sample of 3973 dentate and edentulous adults in Australia.

FINDINGS

The empirically derived population-response model accounted for over 98% of response combinations of Australian dentate adults.

CONCLUSIONS

The empirically derived model followed a similar hierarchical pattern to the base model underlying the long-form version of the measure (thereby supporting the validity of the OHIP14 measure) and was strongly predictive of the pattern of responses obtained from Australian adults.

Why do poor adults rate their oral health poorly?

BACKGROUND

The reasons why socioeconomic circumstances are associated with oral health are not well understood. This study investigated whether psychosocial factors might play an explanatory role.

METHODS

Cross-sectional survey data were used from the 1999 National Dental Telephone Interview Survey together with information from an accompanying questionnaire sent to adult interviewees. Household income and self-rated oral health were assessed with single items and life dissatisfaction, personal constraint and perceived stress were evaluated with standard psychometric scales. Bivariate associations were tested using chi-square and ANOVA and odds ratios estimated for low self-rated oral health using logistic regression.

RESULTS

Response to the questionnaire was 64.6 per cent and analysis was limited to dentate adults (n = 3678). Low household income was positively associated with low self-rated oral health. Higher dissatisfaction with life, personal constraint and perceived stress scores were associated with low income and with low self-rated oral health. After adjusting for gender, age, income and missing teeth, adults with high personal constraint scores had greater odds of low self-rated oral health (OR 1.26; 1.10-1.43) as had adults with higher perceived stress scores (OR 1.69; 1.34-2.13).

CONCLUSION

Psychosocial factors are important in understanding pathways between socioeconomic position and oral health status.

Impacts of oral disorders in the United Kingdom and Australia

BACKGROUND

Surveys of oral health have not previously compared national adult populations using measures of subjective oral health.

AIMS

To compare subjective oral health of adults in the UK and Australian populations.

METHODS

Cross sectional studies were conducted of people aged 18+ years in the 1998 UK Adult Dental Health Survey and the 1999 Australian National Dental Telephone Interview Survey. Subjective oral health was measured using the 14-item Oral Health Impact Profile questionnaire (OHIP-14).

RESULTS

Among dentate people, the percentage reporting impacts 'fairly often' or 'very often' was marginally greater in Australia (18.2%, 95% confidence interval (CI) = 16.2-20.2) than the UK (15.9%, 95%CI = 14.4-17.4). There were larger regional variations in prevalence within populations, ranging from 14.8% to 22.3% among Australian states/ territories, and from 13.6% to 19.8% among countries within the UK. However, the mean number of impacts and rated severity of impacts was significantly greater in Australia than the UK.

CONCLUSIONS

While the percentage of adults reporting adverse impacts of oral health was similar, Australians reported a larger number of impacts and more severe impacts than dentate people in the UK. Differences in the number and severity of impacts between the two populations may be an artifact of different data collection methods or may reflect relatively subtle socio-cultural differences in subjective oral health between these populations.

Sources of stress for Australian dental students

The Dental Environment Stress questionnaire was used to identify and quantify sources of stress for 205 Australian Bachelor of Dental Surgery students. A factor analysis revealed negative self-efficacy beliefs accounted for almost one third of the total variance, and despite higher stress levels reported by females, a marked similarity in the dominant patterns emerged for males and females. In testing for differences in residency status, international students expressed significantly more stress from peer pressure, and this is discussed within a socio-cultural context. Irrespective of gender, residency status, and class year, students ranked examinations and grades as the single most stress-inducing concern. Overall, stress intensity tended to escalate over time, peaking in the fourth year of training. It is suggested that dental students may be prone to unhealthy perfectionism, placing them at risk for the harmful consequences of chronically elevated stress levels.

A preliminary investigation of shape memory alloys in the surgical correction of scoliosis

Nitinol, a shape memory alloy, is flexible at low temperatures but retains its original shape when heated. This offers interesting possibilities for scoliosis correction. Of the shape memory alloys, nitinol is the most promising medically because of biocompatibility and the ability to control transition temperature. In vivo: Six goats with experimental scoliosis were instrumented with 6-mm nitinol rods. The rods were transformed, and the scoliosis corrected, in the awakened goats by 450-kHz radio frequency induction heating. The curves averaged 41 degrees before instrumentation, 33 degrees after instrumentation, and 11 degrees after rod transformation. The animals tolerated the heating without discomfort, neurologic injury, or evidence of thermal injury to the tissues or the spinal cord. In vitro: Nitinol rods were tested under both constant deflection and constant loading conditions and plotted temperature versus either force or displacement. The 6-mm rod generated forces of 200 N. The 9-mm rod generated up to 500 N. We safely coupled shape memory alloy transformation to the spine and corrected an experimental spinal deformity in awake animals. The forces generated can be estimated by the rod's curvature and temperature. The use of shape memory alloys allows continuous neurologic monitoring during awake correction, true rotational correction by rod torsion, and the potential option of periodic correction to take advantage of spinal viscoelasticity and the potential of true rotational correction by rod torsion.

Mechanisms of curve progression following sublaminar (Luque) spinal instrumentation

Fifty-two patients with Luque instrumentation were reviewed for spinal deformities. Forty-two patients were reviewed during 1 year (longest 7.2 years) at follow-up. Two patients were included who lost correction within 1 year (both 8 months). Follow up averaged 2.9 years. Curve causes primarily were neuromuscular but included one was caused by idiopathic scoliosis, four by Scheuermann's disease, and 1 by post-laminectomy kyphosis. The Cobb angle progressed in 45% of patients postoperatively. Factors contributing to progression included progressive vertebral rotation or the crankshaft phenomenon (11), wire pull out (7), progressive pelvic obliquity (4), rod bending (3), pseudarthrosis (2), and rod migration (2). Factors correlating with progression were kyphosis, postoperative curve greater than 35 degrees, preoperative curve greater than 60 degrees, and not fusing to the pelvis in nonambulators. Crankshaft was common in patients Risser II or less but did not occur in more mature patients.

Using the shape recovery of nitinol in the Harrington rod treatment of scoliosis

Nitinol, a metal alloy which is able to remember (and return to with slight heating) the shape it had before it was deformed, is demonstrated to be useful in the Harrington rod treatment of scoliosis. A bent nitinol rod can return to its original straight length, applying both axial and lateral forces to the spine during the operation of postoperatively by means of external heating. A research program using simulated spinal forces in a test fixture and implantation in a cadaver was undertaken to show the feasibility of modifying the existing procedure.