Nancy F. Cheng

Functional Remineralization of Dentin Lesions Using Polymer-Induced Liquid-Precursor Process

It was hypothesized that applying the polymer-induced liquid-precursor (PILP) system to artificial lesions would result in time-dependent functional remineralization of carious dentin lesions that restores the mechanical properties of demineralized dentin matrix. 140 µm deep artificial caries lesions were remineralized via the PILP process for 7–28 days at 37°C to determine temporal remineralization characteristics. Poly-L-aspartic acid (27 KDa) was used as the polymeric process-directing agent and was added to the remineralization solution at a calcium-to-phosphate ratio of 2.14 (mol/mol). Nanomechanical properties of hydrated artificial lesions had a low reduced elastic modulus (ER = 0.2 GPa) region extending about 70 μm into the lesion, with a sloped region to about 140 μm where values reached normal dentin (18–20 GPa). After 7 days specimens recovered mechanical properties in the sloped region by 51% compared to the artificial lesion. Between 7–14 days, recovery of the outer portion of the lesion continued to a level of about 10 GPa with 74% improvement. 28 days of PILP mineralization resulted in 91% improvement of ER compared to the artificial lesion. These differences were statistically significant as determined from change-point diagrams. Mineral profiles determined by micro x-ray computed tomography were shallower than those determined by nanoindentation, and showed similar changes over time, but full mineral recovery occurred after 14 days in both the outer and sloped portions of the lesion. Scanning electron microscopy and energy dispersive x-ray analysis showed similar morphologies that were distinct from normal dentin with a clear line of demarcation between the outer and sloped portions of the lesion. Transmission electron microscopy and selected area electron diffraction showed that the starting lesions contained some residual mineral in the outer portions, which exhibited poor crystallinity. During remineralization, intrafibrillar mineral increased and crystallinity improved with intrafibrillar mineral exhibiting the orientation found in normal dentin or bone.

Methods and Software for Estimating Health Disparities: The Case of Children's Oral Health

The National Center for Health Statistics recently issued a monograph with 11 guidelines for reporting health disparities. However, guidelines on confidence intervals (CIs) cannot be readily implemented with the complex sample surveys often used for disease surveillance. In the United States, dental caries (decay) is the most common chronic childhood disease-5 times more common than asthma. Racial/ethnic minorities, immigrants, and persons of lower socioeconomic position (SEP) have a greater prevalence of caries. The authors provide methods for applying National Center for Health Statistics guidelines to complex sample surveys (health disparity indices and absolute and relative difference measures assessing associations of race/ethnicity and SEP to health outcomes with CIs); illustrate the application of those methods to childrens untreated caries; provide relevant software; and report results from a simulation varying prevalence. They use data on untreated caries from the California Oral Health Needs Assessment of Children 2004-2005 and school percentage of participation in free/reduced-price lunch programs to illustrate the methods. Absolute and relative measures, the Slope Index of Inequality, the Relative Index of Inequality (mean and ratio), and the Health Concentration Index were estimated. Taylor series linearization and rescaling bootstrap methods were used to estimate CIs. Oral health differed significantly between White children and all non-White children and was significantly related to SEP.

Language and literacy relate to lack of children’s dental sealant use

OBJECTIVES This study aimed to determine the percent of Californias third grade public school children lacking sealants by child and family factors and to measure social disparities for lacking sealants. METHODS The study analyzed data from the California Oral Health Needs Assessment (COHNA) 2004-2005, a complex stratified cluster sample of children (n = 10,450) from 182 randomly selected public elementary schools in California. The dependent variable was absence of sealants in first permanent molars. The independent variables included child race/ethnicity; socio-economic position (SEP) measured as childs participation in the free or reduced-price lunch program at the individual and school level; acculturation measured as language spoken at home and school level percent of English language learners; and parent functional health literacy measured as correctly following questionnaire instructions. Absolute differences and health disparity indices (i.e. Slope Index of Inequality, Relative Index of Inequality-mean, Absolute Concentration Index) were used to measure absolute and relative disparities. RESULTS The percent of children lacking sealants was high in all racial/ethnic groups; no child or school level SEP differences in lacking sealants were seen, but significant differences existed by acculturation (child and school level) and parental functional health literacy. CONCLUSIONS NonEnglish language and poor parental functional health literacy are potential barriers that need to be addressed to overcome disparities in sealant utilization.

Understanding Treatment Effect Mechanisms of the CAMBRA Randomized Trial in Reducing Caries Increment

The Caries Management By Risk Assessment (CAMBRA) randomized controlled trial showed that an intervention featuring combined antibacterial and fluoride therapy significantly reduced bacterial load and suggested reduced caries increment in adults with 1 to 7 baseline cavitated teeth. While trial results speak to the overall effectiveness of an intervention, insight can be gained from understanding the mechanism by which an intervention acts on putative intermediate variables (mediators) to affect outcomes. This study conducted mediation analyses on 109 participants who completed the trial to understand whether the intervention reduced caries increment through its action on potential mediators (oral bacterial load, fluoride levels, and overall caries risk based on the composite of bacterial challenge and salivary fluoride) between the intervention and dental outcomes. The primary outcome was the increment from baseline in decayed, missing, and filled permanent surfaces (ΔDMFS) 24 mo after completing restorations for baseline cavitated lesions. Analyses adjusted for baseline overall risk, bacterial challenge, and fluoride values under a potential outcome framework using generalized linear models. Overall, the CAMBRA intervention was suggestive in reducing the 24-mo DMFS increment (reduction in ΔDMFS: −0.96; 95% confidence interval [CI]: –2.01 to 0.08; P = 0.07); the intervention significantly reduced the 12-mo overall risk (reduction in overall risk: –19%; 95% CI, −7 to −41%;], P = 0.005). Individual mediators, salivary log10 mutans streptococci, log10 lactobacilli, and fluoride level, did not represent statistically significant pathways alone through which the intervention effect was transmitted. However, 36% of the intervention effect on 24-mo DMFS increment was through a mediation effect on 12-mo overall risk (P = 0.03). These findings suggest a greater intervention effect carried through the combined action on multiple aspects of the caries process rather than through any single factor. In addition, a substantial portion of the total effect of the CAMBRA intervention may have operated through unanticipated or unmeasured pathways not included among the potential mediators studied.

Developing an Acceptability Assessment of Preventive Dental Treatments

OBJECTIVES Early childhood caries (ECC) is very prevalent among young Hispanic children. ECC is amenable to a variety of preventive procedures, yet many Hispanic families underutilize dental services. Acceptability research may assist in health care planning and resource allocation by identifying patient preferences among efficacious treatments with the goal of improving their utilization. The purposes of this study were (a) to develop a culturally competent acceptability assessment instrument, directed toward the caregivers of young Hispanic children, for five preventive dental treatments for ECC and (b) to test the instruments reliability and validity. METHODS An instrument of five standard treatments known to prevent ECC was developed, translated, reviewed by focus groups, and pilot tested, then tested for reliability The instrument included illustrated cards, brief video clips, and samples of the treatments and was culturally appropriate for low-income Hispanic caregivers. In addition to determining the acceptability of the five treatments individually, the treatments were also presented as paired comparisons. RESULTS Focus groups and debriefing interviews following the pilot tests established that the instrument has good face validity. The illustrated cards, product samples, and video demonstrations of the five treatments resulted in an instrument possessing good content validity. The instrument has good to excellent test-retest reliability, with identical time 1-time 2 responses for each of the five treatments 92 percent of the time (range 87 to 97 percent), and the same treatment of the paired comparisons preferred 75 percent of the time (range 61 to 90 percent). CONCLUSIONS The acceptability instrument described is reliable and valid and may be useful in program planning efforts to identify and increase the utilization of preferred ECC preventive treatments for target populations.

Mediation analysis for count and zero-inflated count data

Different conventional and causal approaches have been proposed for mediation analysis to better understand the mechanism of a treatment. Count and zero-inflated count data occur in biomedicine, economics, and social sciences. This paper considers mediation analysis for count and zero-inflated count data under the potential outcome framework with nonlinear models. When there are post-treatment confounders which are independent of, or affected by, the treatment, we first define the direct, indirect, and total effects of our interest and then discuss various conditions under which the effects of interest can be identified. Proofs are provided for the sensitivity analysis proposed in the paper. Simulation studies show that the methods work well. We apply the methods to the Detroit Dental Health Project’s Motivational Interviewing DVD trial for the direct and indirect effects of motivational interviewing on count and zero-inflated count dental caries outcomes.

Randomized Trial of Motivational Interviewing to Prevent Early Childhood Caries in Public Housing

Introduction: Caries experience among preschool-age children has remained relatively unchanged for the past 2 decades, despite recently documented decreases in untreated decay. Objectives: In a community-based cluster-randomized controlled trial, a motivational interviewing (MI) intervention administered to primary caregivers was hypothesized to reduce caries increment over 2 y as compared with controls, among children aged 0 to 5 y at baseline living in public housing. Methods: Public housing residents, who served as interventionists, were trained in MI with a focus on early childhood caries prevention. All 26 eligible public housing developments were randomized to either control (quarterly clinical examinations, fluoride varnish applications, toothbrush/toothpaste, and educational brochures) or intervention (same procedures as control plus MI counseling). Quarterly MI sessions were delivered in English or Spanish over 2 y, audio recorded, and assessed for treatment fidelity. The primary outcome was the increment in dmfs (decayed, missing, and filled tooth surfaces) as assessed by clinical examination at baseline, 12 mo, and 24 mo. Secondary outcomes included caregiver oral health knowledge and child oral health behaviors (child toothbrushing and sugar-sweetened beverage intake). Baseline characteristics were compared between groups and adjusted for housing-site clusters. Longitudinal outcomes were analyzed with mixed models. Results: A total of 1,065 children (49% female, 55% non-White, 61% Hispanic, 89% below poverty level, n = 686 control) and their caregivers were enrolled. During 2 y of follow-up, the mean dmfs increment increased in both groups; however, there were no statistically significant group differences at 24 mo or group × time interactions. The mean increase in intervention caregivers’ knowledge was significantly greater than that of control, F(2, 1,593) = 3.48, P = 0.0310, but there were no significant intervention effects on caregiver-reported child sugar-sweetened beverage intake or child toothbrushing. Conclusion: MI counseling plus intensive caries prevention activities resulted in knowledge increases but did not improve oral health behaviors or caries increment (ClinicalTrials.gov NCT01205971). Knowledge Transfer Statement: When viewed in light of the findings from the companion Pine Ridge study and other recent MI studies, the results of this study suggest that when the complex disease of early childhood caries is addressed in high-risk populations, MI is not effective, and alternative approaches are warranted.

Dose-Weighted Adjusted Mantel-Haenszel Tests for Numeric Scaled Strata in a Randomized Trial

A recent three-arm parallel groups randomized clinical prevention trial had a protocol deviation causing participants to have fewer active doses of an in-office treatment than planned. The original statistical analysis plan stipulated a minimal assumption randomization-based extended Mantel-Haenszel (EMH) trend test of the high frequency, low frequency, and zero frequency treatment groups and a binary outcome. Thus, a dose-weighted adjusted EMH (DWAEMH) test was developed with an extra set of weights corresponding to the number of active doses actually available, in the spirit of a pattern mixture model. The method can easily be implemented using standard statistical software. A set of Monte Carlo simulations using a logistic model was undertaken with (and without) actual dose-response effects through 1000 replicates for empirical power estimates (and 2100 for empirical size). Results showed size was maintained and power was improved for DWAEMH versus EMH and logistic regression Wald tests in the presence of a dose effect and treatment by dose interaction.

Correction: Functional Remineralization of Dentin Lesions Using Polymer-Induced Liquid-Precursor Process.

There was an error in the same of the fourth author. The correct name is: Stefan Habelitz The correct citation is: Burwell AK, Thula-Mata T, Gower LB, Habelitz S, Kurylo M, et al. (2012) Functional Remineralization of Dentin Lesions Using Polymer-Induced Liquid-Precursor Process. PLoS ONE 7(6): e38852. doi:10.1371/journal.pone.0038852