Using entropy balancing to strengthen an observational cohort study design: lessons learned from an evaluation of a complex multi-state federal demonstration

We conducted an evaluation of a patient-centered medical home demonstration sponsored by the Centers for Medicare & Medicaid Services. We implemented a quasi-experimental pre-post with a comparison group design. Traditional propensity score weighting failed to achieve balance (exchangeability) between the two groups on several critical characteristics. In response, we incorporated a relatively new alternative known as entropy balancing. Our objective is to share lessons learned from using entropy balancing in a quasi-experimental study design. We document the advantages and challenges with using entropy balancing. We also describe a set of best practices, and we present a series of illustrative analyses that empirically demonstrate the performance of entropy balancing relative to traditional propensity score weighting. We compare alternative approaches based on: (i) covariate balance (e.g., standardized differences); (ii) overlap in conditional treatment probabilities; and (iii) the distribution of weights. Our comparison of overlap is based on a novel approach we developed that uses entropy balancing weights to calculate a pseudo-propensity score. In many situations, entropy balancing provides remarkably superior covariate balance compared to traditional propensity score weighting methods. Entropy balancing is also preferred because it does not require extensive iterative manual searching for an optimal propensity score specification. However, we demonstrate that there are some situations where entropy balancing “fails”. Specifically, there are instances where entropy balancing achieves adequate covariate balance only by using a distribution of weights that dramatically up-weights a small set of observations, giving them a disproportionately large and undesirable influence.     

A comparison of the casting ability of precious and nonprecious alloys for porcelain veneering.

The alloys tested varied with respect to their castability. This variability is related to density. Problems caused by low density may be solved by increasing the casting force. For all parameters measured in the laboratory, Thermocraft, a precious alloy, proved to be the most satisfactory- Wiron S, a nonprecious alloy, was comparable to Degudent Universal, a gold alloy. The application of Wiron S as a successful gold substitute should, therefore, be further investigated clinically. Equipment, investment, and casting techniques, all designed for the casting of gold alloys, were also used for the nonprecious alloys. These are standard facilities readily available in clinical practice. Modifications or technical improvement to these factors may result in more successful application to the other nonprecious alloys.     

Pemphigus vulgaris: a case-based update

Pemphigus vulgaris (PV) is an autoimmune disease accounting for 80% of all cases of pemphigus. Before the advent of corticosteroid therapy, pemphigus was fatal, with a mortality rate of up to 75% in the first year. It is still a serious disorder, but the 5% to 10% mortality rate is now primarily due to the side effects of therapy. In 75% to 80% of cases, PV lesions first appear in the oral cavity. Dentists are therefore in a unique position to recognize the oral manifestations of the disease, allowing early diagnosis and initiation of treatment. The diagnosis is based on pathological examination and immunofluorescence testing. Systemic corticosteriods and steroid-sparing agents are the mainstays of treatment; topical corticosteroids may also be used to accelerate healing of persistent oral lesions. This article describes a 71-year-old woman with multiple chronic ulcers in the oral cavity, in whom PV was diagnosed 4 months after the symptoms first appeared. The article also reviews the current literature on diagnosis and treatment of the condition.     

Prostaglandin E2 and interleukin-1 levels in smokeless tobacco-induced oral mucosal lesions

Inflammatory mediators released as a result of smokeless tobacco (ST)-induced irritation may play a role in the development of oral mucosal lesions at habitual tobacco placement sites in ST users. The present study examined levels of interleukin-1 (IL-1) and prostaglandin E2 (PGE2) in ST-induced mucosal lesions and compared these to mediator levels in clinically normal mucosa. Soft tissue biopsies were obtained from white mucosal lesions at habitual placement sites and normal alveolar mucosal tissue at non-placement sites in 18 ST users. Fifteen non-tobacco using subjects also provided normal alveolar mucosal biopsies. IL-1 and PGE2 were recovered from the specimens, and mediator levels were determined by enzyme immunoassay. Prostaglandin E2 levels (pg/mg) were lower in both regions in the ST subjects, but values did not vary significantly between the regions with 2.77±0.72 and 2.86±0.99 at placement and non-placement sites, respectively, in ST users and 7.31±3.84 in non-tobacco users. Both IL-1α and IL-lβ (pg/mg) were significantly (p < 0.0I) elevated in ST lesions (IL-lã=25.56±4.00; IL-1β=7.76±1.68) compared to either non-placement sites in ST users (IL-lα=14.64±2.65; IL-lβ=1.63±0.72) or non-tobacco users (IL-lα=12.84±2.60; IL-lβ=2.04±0.75). In view of IL-l's role in keratinocyte proliferation and its inflammatory effects, this cytokine may contribute to mucosal and gingival alterations observed in ST users.     

A study of Streptococcus mutans levels in both infants with bottle caries and their mothers

A bstract — A relationship was sought between the rampant form of caries in infants known as bottle caries and Streptococcus mutans levels in both these infants and their mothers. Streptococcus mutans scores in children with active bottle caries were high. Mothers' and children's scores were significantly related, providing a basis for further studies of efficient primary prevention.     

Visual-tactile examination compared with conventional radiography,digital radiography,and Diagnodent in the diagnosis of occlusal occult caries in extracted premolars

PURPOSE: This laboratory study compared visual-tactile examination with conventional radiographs, digital radiographs, and laser fluorescence in the detection of occlusal occult caries on extracted premolar teeth. METHODS: Extracted premolars without obvious caries or restorations were collected from school dental clinics. Occlusal surfaces of 320 extracted premolars were examined visually with an explorer, then examined using the KaVo Diagnodent unit and scored using specific criteria. The teeth were exposed using conventional and digital radiography, respectively. The radiographs were assessed for dentin radiolucencies beneath the occlusal surface. RESULTS: Of the 320 teeth used in this study, 302 were scored as sound by visual-tactile examination. Of these, 57 (19%) demonstrated dentin radiolucency on conventional bite-wings, and 245 (81%) were scored as radiographically sound. Thus, the sensitivity and specificity values of the visual-tactile examination compared with conventional radiography were 81% and 44%, respectively. In contrast, Diagnodent produced results of 82% sensitivity and 36% specificity when compared with conventional radiography. When compared to digital radiography, the sensitivity and specificity values of the visual-tactile examination were 90% and 44%, respectively. In contrast, when compared to digital radiography, Diagnodent showed a very low specificity of only 32%, although sensitivity was still high at 91%. Differences in specificity among the techniques were statistically significant (P < .03), whereas differences in sensitivity were not (P > .01). CONCLUSIONS: Although the diagnosis of occult dentinal caries may be further enhanced by the Diagnodent, a combination of visual-tactile examination and either conventional or digital radiography should identify over 80% of lesions.     

The masticatory system under varying functional load. Part 2: Effect of reduced masticatory load on the degree and distribution of mineralization in the rabbit mandible

A reduction in mechanical loading of the mandible brought about by mastication of soft food is assumed to decrease the remodelling rate of bone, which, in turn, might increase the degree of bone mineralization. The effect of a reduction in masticatory functional load on the degree and distribution of mineralization of mandibular bone was investigated in male juvenile New Zealand White rabbits. The experimental animals (n=8) had been raised on a diet of soft pellets from 8 to 20 weeks of age, while the controls (n=8) had been fed pellets of normal hardness. The degree of mineralization of bone (DMB) was assessed at the attachment sites of various jaw muscles, the condylar head, and the alveolar process. Differences between groups and among sites were tested for statistical significance using a Student's t-test and one-way analysis of variance, respectively. The DMB did not differ significantly between the experimental and control animals at any of the sites assessed. However, in the rabbits that had been fed soft pellets, both cortical bone at the attachment sites of the temporalis and digastric muscles and cortical bone in the alveolar process had a significantly higher DMB than cortical bone at the attachment site of the masseter muscle, while there were no significant differences among these sites in the control animals. The results suggest that a moderate reduction in masticatory functional load does not significantly affect the remodelling rate and the DMB in areas of the mandible that are loaded during mastication but might induce a more heterogeneous mineral distribution.     

Current therapy: complications associated with rigid internal fixation of facial fractures

Rigid internal fixation (RIF) is commonly used for the anatomical reduction and fixation of facial fractures. This technique has many advantages over more traditional methods, such as wire osteosynthesis and maxillomandibular fixation. Properly placed RIF ensures a stable anatomical reduction and allows for immediate or early restoration of function. RIF has a number of complications associated with its use in facial trauma surgery including metal sensitivity, infection, neurologic injury, dental trauma, stress shielding, and malocclusion. Complication rates appear to be inversely proportional with operator skill and experience when using RIF.     

Gingival retraction techniques for implants versus teeth: current status

BACKGROUND: The authors reviewed and compared gingival retraction techniques used for implants and teeth. TYPES OF STUDIES REVIEWED: The authors searched the literature using article databases Ovid MEDLINE up to May 2008, PubMED and Google Scholar (advanced search) and the following search terms: gingival retraction, implant abutment, impressions, cement-retained implant restoration, impression coping, peri-implant tissue, emergence profile and tissue conditioning. RESULTS: The authors found insufficient evidence relating to gingival displacement techniques for impression making for implant dentistry. Gingival retraction techniques and materials are designed primarily for peridental applications; the authors considered their relevance to peri-implant applications and determined that further research and new product development are needed. CLINICAL IMPLICATIONS: The use of injectable materials that form an expanding matrix to provide gingival retraction offers effective exposure of preparation finish lines and is suitable for conventional impression-making methods or computer-aided design/computer-aided manufacturing digital impressions in many situations. There are, however, limitations with any retraction technique, including injectable matrices, for situations in which clinicians place deep implants.