Randomized Trial of 2 Self-Titrated Oral Appliances for Airway Management.

The effectiveness and predictability of 2 different oral appliance (OA) designs to reduce the respiratory event index (REI) in moderate and severe obstructive sleep apnea (OSA) patients requires elucidation. The primary aim of the trial was to determine if 2 widely used midline-traction and bilateral-thrust OA designs differ in effectiveness to reduce the REI within a single test population categorized by OSA severity. Moderate and severe adult OSA patients, who were previously prescribed continuous positive airway pressure therapy (CPAP) but were dissatisfied with it (n = 56), were studied by home-polygraphy in a randomized crossover trial using either midline-traction with restricted mouth opening (MR) or bilateral thrust with opening permitted (BP) design OAs. OAs were used nightly for 4 wk (T2) followed by a 1-wk washout period, then 4 wk (T4) using the alternate OA. REI and oxygen saturation (SaO2) were primary outcomes, while predictability and efficacy comparison of the 2 OAs were secondary outcomes. Thirty-six participants had used MR and BP OAs during both 4-wk study legs. Twenty (55.6%) MR OA-using participants, 25 (69.4%) BP OA-using participants, and 16 (44.4%) participants using both OAs had significant REI reductions. Overall baseline (T0) median REI (interquartile range) of 33.7 (20.7-54.9) was reduced to 18.0 (8.5-19.4) at T2 and to 12.5 (8.2-15.9) at T4 (P < 0.001). Comparison of the 2 sequence groups' (MR-BP and BP-MR) REI showed the median differences between T0 and T2 and T4 were highly significant (P < 0.001). Regression analysis predicted about half of all users will have REIs between 8 and 16 after 2 mo. Baseline overjet measures >2.9 mm predicted greater OA advancement at T4. Mean and minimum SaO2 did not change significantly from T0 to T2 or T4. MR and BP OA designs similarly attenuated REI in moderate and severe OSA individuals who completed the 8-wk study protocol with greater REI reduction in those with severe OSA (ClinicalTrials.gov NCT03219034).

Rapid determination of surfactant critical micelle concentrations using pressure-driven flow with capillary electrophoresis instrumentation.

This work demonstrates a novel, convenient utilization of capillary electrophoresis (CE) instrumentation for the determination of critical micelle concentrations (CMCs). Solution viscosity differences across a range of surfactant concentrations were monitored by hydrodynamically forcing an analyte towards the detector. Upon reaching the surfactant's CMC value, migration times were observed to change drastically. CMC values for four commonly employed anionic surfactants were determined-sodium dodecyl sulfate: 8.1mM; sodium caprylate: 300 mM; sodium decanoate: 86 mM; sodium laurate: 30 mM; and found to be in excellent agreement with values previously reported in the literature. The technique was then applied to the less well-characterized nonionic surfactants poly(oxyethylene) 8 myristyl ether (CMC approximately 9 M), poly(oxyethylene) 8 decyl ether (CMC approximately 0.95 mM) and poly(oxyethylene) 4 lauryl ether.

Use of dyes to investigate migration of the chiral selector in CFFE and the impact on the chiral separations.

Continuous free flow electrophoresis was investigated as a tool for the preparative chiral separation of piperoxan enantiomers using sulfated beta-cyclodextrin (sbeta-CD) as the chiral additive. Bulk migration of sbeta-CD was confirmed using LC-MS analysis of the individual fractions collected and visualized with the addition of crystal violet to the separation buffer. In the absence of sbeta-CD, the crystal violet-containing buffer was reddish/purple and the crystal violet was deflected cathodically in the chamber. In the presence of sbeta-CD, the crystal violet-containing buffer was blue and was deflected anodically. However, formation of accumulation and depletion zones was apparent in both cases. The addition of sbeta-CD to the cathodic wash solution allowed for almost complete resolution of the piperoxan enantiomers with a processing rate of 0.45 mg/ h.

A performance examination for assessing dental hygiene competencies.

A performance assessment was developed to assess multiple skills from a new competency document. Faculty members developed the tasks that each student would perform, the evaluation criteria, and the testing procedures. Grant project leaders consolidated these materials into the Senior Exit Examination (SEE). The 11 tasks included interpreting a research article, solving an ethical dilemma, and developing a community intervention. An objective, structured clinical examination had stations for interpreting radiographs, describing oral lesions, taking vital signs, taking and analyzing health histories, and communicating with "difficult" patients. Pilot administration of the SEE was conducted in April 1995 and 1996. The majority of the students passed 4 of the 11 tasks on the first attempt in 1995, and 7 passed in 1996. Following changes to the exam and the curriculum, the SEE was conducted four times from 1997 to 2000. Student performance for all tasks in 2000 was at the approximate level of > or = 80% pass rate. Pearson chi-square tests showed that student performance significantly improved over the years from 1995 to 2000 for 9 of the 11 tasks (p < 0.001); a high performance level was maintained in ethics and community intervention with no significant change. The SEE is now considered an important measure for assessing student competence and program outcomes.

Cyclodextrins: a versatile tool in separation science.

Cyclodextrins have been used extensively in separation science because they have been shown to discriminate between positional isomers, functional groups, homologues and enantiomers. This property makes them one of the most useful agents for a wide variety of separations. The main goal of this review is a discussion of somewhat more exotic applications of cyclodextrins to separation methods. Techniques examined in detail include gel electrophoresis, isotachophoresis, isoelectric focusing, preparative scale electrophoretic techniques, thin-layer chromatography, electrochemically modulated liquid chromatography, use of monolithic media in liquid chromatography, microdialysis, separation on hollow fibers, foam flotation enrichment, solid- and liquid-phase extractions, countercurrent chromatography, separation through liquid and composite membranes, and cyclodextrin applications in molecularly imprinted polymers. Since a lot of attention has been paid to use of cyclodextrins in capillary electrophoresis, liquid, gas and supercritical fluid chromatography, these techniques will be only briefly discussed. The second goal of this review is a discussion of a scaling-up the analytical separations to semi-preparative or preparative techniques. It was found that despite a need for large scale separations in the industry, development of these techniques has been somewhat lagging behind development of miniaturized analytical separations. It is hoped that the focus on areas outside more traditional separation applications might stimulate further research.

The temporomandibular joint in juvenile rheumatoid arthritis: Part II. Relationship between computed tomographic and clinical findings.

A study was undertaken to examine the relationship between the clinical signs and symptoms of temporomandibular joint (TMJ) disorder and computed tomographic (CT) evidence of destruction of these joints in children afflicted with juvenile rheumatoid arthritis (JRA). A thorough clinical examination including determination of the craniomandibular index (CMI) was performed on each of 37 consecutive JRA patients (6-17 years old), who had also received comprehensive evaluations of TMJ morphology by axial CT (see Part I, Pediatr Dent, 17:46-53, 1995). Measures of facial asymmetry (photographic) and mandibular size (cephalometric) also were collected. Published norms for mandibular dimensions and for prevalences of symptoms and signs of TMJ disorders served as control data. Various ANOVA and nonparametric statistical models were used for analysis. Average maximal opening was significantly less in the JRA subjects compared with the controls, and more than 50% of the JRA children manifested chin deviations or vertical disparities between mandibular angle regions, indicating compromised mandibular function and form. With the exception of facial asymmetry, however, none of the clinical signs or symptoms of TMJ dysfunction were remarkable predictors of bony destruction of the TMJ. Subjects with definitive evidence (CT) of TMJ destruction (62%) could not be identified reliably by any of the clinical measures used here. These findings indicate that clinical examination alone is inadequate for detecting condylar degeneration in the TMJ of children with JRA.

Condylar movement and centric relation in patients with internal derangement of the temporomandibular joint.

This study was designed to compare the reproducibility of the condylar translation pathway and the centric relation position in patients with and without internal derangement of the temporomandibular joint. Reproducibility of condylar movement and variability of the axis point of condylar rotation in centric relation was studied in 15 patients with internal derangement of the temporomandibular joint and 15 patients with no history or clinical signs of mandibular dysfunction. Condylar movement and axis point location were recorded with a sagittal recording device at three separate recording sessions. Lead markers were placed on the skin over the axis and orbital points, and lateral cephalometric radiographs were taken at each session. Analysis of cephalometric and axiographic recordings included both linear and angular measurements. Analysis of the condylar movement pathway revealed greater within-subject reproducibility in the control group for both the right and left condyles (p < 0.0005 and p < 0.0003, respectively). The axis point of condylar rotation in centric relation, as shown by cephalometric analysis, had significantly more within-subject variability in the horizontal plane for the control group (p < 0.003). There was no significant difference between groups for within-subject variability of condylar position in the vertical direction. These findings are consistent with the contemporary concept of centric relation that a vertically stable condyle with a disk interposed against the anterior eminence is capable of functional adaptation in the horizontal plane. The results have implications with regard to treatment and rehabilitation of patients with temporomandibular joint internal derangement.

Program assessment practices in dental hygiene education.

A survey asked U.S. dental hygiene program directors to describe their assessment programs and satisfaction with these programs. A 65 percent response rate (138/212) resulted. The directors were less than satisfied with their assessment practices and how they use their assessment data. The majority use alumni (78 percent) and employer (61 percent) surveys and curriculum evaluations by students (57 percent). Fewer use patient satisfaction surveys (40 percent) and exit interviews (33 percent). Only 35 percent of the programs formally validate any instruments. They share the results with faculty (92 percent) but not students (42 percent) and alumni (25 percent). They use the data for curriculum revision (84 percent) but not for adding assessment measures (26 percent), remediation of students (25 percent), or gaining resources for the program (22 percent). Dental hygiene education needs a more comprehensive assessment model that is clearly linked to improvement.

The effectiveness of an interactive instructional context. Principles from the parent-child interaction literature.

In the present study, the effectiveness of embedding a targeted linguistic structure within an interactive instructional context is examined. Ten subjects participated in a communication-games intervention which contained seven interactive elements drawn from the parent-child interaction literature. Ten subjects were assigned to a control group. A comparison of student performance before and after intervention supports the effectiveness of adopting instructional strategies that are consistent with a social-interaction perspective on language development. Qualitative results are presented that illustrate each of the interactional characteristics of the intervention. Implications for practice are discussed.

PC program for assessing the effect of a treatment when subjects are growing: comparative studies.

We describe, illustrate, and make available a menu-driven PC program which can be used to assess the effect of a treatment on growth when random allocation of subjects to the treatment and control groups is not feasible. Three different estimators of, and confidence intervals for, this effect are computed, namely, the simple gains, standardized gains, and covariance adjusted estimators. It is shown by means of several examples that these estimators can differ substantially, and some guidelines for choosing between them in specific circumstances are provided.

PC program for comparing two regression lines over a specified finite interval.

A method due to Tsutakawa and Hewett (Biometrics 34 (1978) 391-398) for comparing two regression lines over a specified, finite interval has been implemented. We describe and illustrate the procedure and program, and make the latter available to interested readers.

PC program for determining the dose necessary to produce a given amount of change.

Given a simple linear regression equation of the form D = alpha + beta Z, it is well-known how to predict, and construct confidence intervals for, the value of D corresponding to a given Z. In this paper we describe, illustrate and make available a menu-driven PC program which can be used to solve the inverse problem, namely, to estimate and construct confidence intervals for the value of Z corresponding to a given value of D. We describe the procedure in the context of a dose-response relationship, where it is desired to estimate the dose (Z) to effect a given amount of change (D), but the method is more general than this. In particular, it may be usefully applied in calibration problems where one may wish to estimate the true value of a measurement given the value as read from a measuring device.

PC program for simultaneously testing equality of means and variances for paired bivariate normal data.

A menu-driven PC program for simultaneously testing the equality of means and variances for paired bivariate normal data is described, illustrated and made available. While the corresponding tests for independent samples are well-known and widely implemented, in the paired situation only the test for no change in mean values (the paired t-test) has been similarly covered. Tests for no change in variability, while important, are less well-known and not implemented in most commercial statistical computing programs.

PC program extending the Potthoff-Roy longitudinal data analysis model to allow missing data: Kleinbaum's method.

Potthoff and Roy (Biometrika, 51 (1964) 313-326) generalized the multivariate analysis of variance model into a form that is especially useful for the study of longitudinal growth curve data. Applications of this method have, however, been limited by the requirement that each case in the sample be measured at the same set of time points, i.e. there can be no missing data. In this paper we describe, illustrate, and make available a user-friendly, interactive PC program implementing Kleinbaum's (J Mult Anal, 3 (1973) 117-124) extension of the Potthoff-Roy model to allow incomplete measurement sequences. These missing data are permitted to arise either randomly or by design as in mixed longitudinal studies.

The temporomandibular joint in juvenile rheumatoid arthritis: I. Computed tomographic findings.

The temporomandibular joints (TMJ) of children afflicted with juvenile rheumatoid arthritis (JRA) were evaluated with clinical examinations and computed tomography (CT). Thirty-seven consecutive patients (6-17 years old) from the Texas Scottish Rite Hospital arthritis clinic were studied to investigate morphological abnormalities in the TMJ by CT. Both qualitative and quantitative measures of TMJ morphology were made from axial CT scans. Ten children without JRA served as a control group. Various ANOVA and nonparametric statistical models were used for analysis. Evidence of TMJ abnormalities from the CTs was found in 62% of these JRA children. The TMJ pathosis indices for left and right joints were significantly higher in the JRA subjects than those in the control children (P < 0.03) and joint spaces were narrower (P < 0.02). These features are indicative of TMJ destruction. Thus, there is considerable risk for TMJ involvement and its debilitating and deforming sequelae in children afflicted with JRA.

Biomechanical properties of small bone screws.

PURPOSE: To evaluate systematically the biomechanical properties of 13 popular screw designs, ranging from 0.8 to 2.0 mm in diameter. METHODS: Screws were characterized in terms of external, core, and drill diameter; cutting flute and head design; material; pitch, thread depth; and height of shank (unthreaded portion) and shank with plate. They were tested in standardized bone specimens (2 x 2.5cm slabs of fresh bovine femur) 1, 2, 3, and 4-mm thick. For each screw-bone thickness combination, 10 trials were conducted to determine push-out force (POF) and another 10 trials to determine insertion (IT) and maximum torque (MT) yielding a total of 1,040 tests. RESULTS: Among the 13 different screws, in 1-mm thick bone, both the lowest (108.5 N) and highest (294.9 N) POF were created by 2-mm screws (P < .001); that with the lowest POF had a long unthreaded shank and pitch, that with highest POF had a short unthreaded shank and pitch. Screws with 0.8- to 1.5-mm diameters showed no differences in POF. The 2-mm screw with the lowest POF also had the lowest MT in 1-mm thick bone compared with the other 2-mm screws (P < .001). In thicker bones (> 2 mm), two 2-mm screws showed 30% to 50% lower MT than the other same size screws (P < .001) because their head slots stripped easily. When all screws were considered together for a particular bone thickness, torque was strongly predicted by screw diameter (MT: r = .94, P < .001; IT: r = 0.92, P < .001). Screws with the same diameters varied significantly in IT because of differences in self-tapping cutting flute design. CONCLUSION: External diameter, unthreaded shank height, head slot, and self-tapping cutting flute design had the greatest impact on screw strength and efficiency in thin cortical bone. Thread depth, core diameter, and metal type did not affect performance significantly. Under these highly standardized in vitro conditions, the ideal 2-mm screw has an unthreaded shank that is as short as possible, and the pitch is about 0.8 mm. Additional aspects of a clinical situation beside holding strength must, however, be considered when choosing a screw.

PC program implementing an alternative to the paired t-test which adjusts for regression to the mean.

In many biomedical research contexts, treatment effects are estimated from studies based on subjects who have been recruited because of high (low) measurements of a response variable, e.g., high blood pressure or low scores on a stress test. In this situation, simple change scores will overestimate the treatment effect; and the use of the paired t-test may find significant change due not to the treatment per se but, rather, due to regression towards the mean. A PC program implementing a procedure for adjusting the observed change for the regression effect in simple pre-test-post-test experiments is described, illustrated, and made available to interested readers. The method is due to Mee and Chua (Am Stat, 45 (1991) 39-42) and may be considered as an alternative to the paired t-test which separates the effect of the treatment from the so-called regression effect.

ANCOVA for nonparallel slopes: the Johnson-Neyman technique.

The Johnson-Neyman (JN) procedure, as originally formulated (Stat Res Mem, 1 (1936) 57-93), applies to a situation in which measurements on 1 dependent (response) variable, X, and 2 independent (predictor) variables, Z1 and Z2, are available for the members of 2 groups. The expected value of X is assumed to be a linear function of Z1 and Z2, but not necessarily the same function for both groups. The JN technique is used to obtain a set of values for the Z variables for which one would reject, at a specified level of significance alpha (e.g., alpha = 0.05), the hypothesis that the 2 groups have the same expected X values. This set of values, or 'region of significance,' may then be plotted to obtain a convenient description of those values of Z1 and Z2 for which the 2 groups differ. The technique can thus be described as a generalization of the analysis of covariance (ANCOVA) which does not make the assumption that the regression coefficients for the regression of X on the covariates, Z1 and Z2, are equal in the groups being compared. In this paper we describe, illustrate and make available a menu-driven PC program (TXJN2) implementing the JN procedure.

PC program for assessing the relationship between rate of change and initial value.

A menu-driven PC program implementing Blomqvist's [J. Am. Stat. Assn. 72, 746-749, 1977] method for assessing the relationship between rate of change and initial value is described, illustrated and made available. It is shown that the naive approach to this problem--computing the correlation between the initial value and either the amount or rate of change--results in a negatively biased estimator. The extent of this bias can be dramatic and may lead investigators to conclude that a negative correlation is present when none exists; or that there is no correlation when in fact the correlation is positive. Blomqvist's (maximum likelihood) estimator avoids this bias, and is obtained by a transformation of the naive estimator.

Extension of the Carter-Yang polynomial growth curve model to allow unique times of measurement for subjects.

A PC program extending the procedure due to Carter and Yang (Commun Stat: Theory Methods, 8 (1986) 2507-2526) to allow unique times of measurement for subjects is described, illustrated and made available. Given longitudinal observations on each of N subjects comprising a single group, this program determines the lowest degree polynomial in time adequate to fit the average growth curve (AGC); estimates this curve and provides confidence bands for the AGC, and confidence intervals for the corresponding polynomial regression coefficients; and so-called prediction intervals which, with a given level of confidence, will contain the growth curve of a 'new' subject from the same population of which the N subjects constitute a random sample. Two kinds of missing data are accommodated. First, in the context of studies planned so that subjects will be measured at identical times and, second, in unstructured studies where subjects may present with their own, unique times of measurement.