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Biomedical subjects

Alan G Glaros

Publications and source records attributed to Alan G Glaros.

At least 19 recordsLinked to original sources
PubMed2006

Properties of silorane-based dental resins and composites containing a stress-reducing monomer.

OBJECTIVE: To evaluate properties of silorane-based resins and composites containing a stress reducing monomer. METHODS: Resin mixtures and composites were formulated containing (a) a developmental stress reducing monomer [TOSU; Midwest Research Institute]; (b) Sil-Mix (3M-ESPE); (c) photo cationic initiator system. Standard BISGMA/TEGDMA resin (B/T) and composite (Filtek Z250) were used as controls. Polymerization volume change was measured using a NIST mercury dilatometer and polymerization stress using an Enduratec mechanical testing machine. Three point bend tests determined flexural elastic modulus, work of fracture, and ultimate strength (ADA 27; ISO 4049). Fracture toughness was measured using ASTM E399-90. Four groups of resins and composites were tested: Sil-Mix, methacrylate standard, and Sil-Mix with two addition levels of TOSU. An ANOVA was used and significant differences ranked using Student-Newman-Keuls test (alpha=0.05). RESULTS: Polymerization stress values for resins containing TOSU were significantly less than the other materials. Polymerization shrinkage values for Sil-Mix formulations were significantly less than for B/T, but were not different from each other. TOSU-containing formulations generally had somewhat lower mechanical properties values than Sil-Mix or B/T. Polymerization stress values for Sil-Mix-based composites were significantly less as compared to Z250. The 1wt.% TOSU composite had the lowest stress. No difference between composite groups was noted for fracture toughness or work of fracture. For ultimate strength, the 5wt.% TOSU formulation differed significantly from Z250. All Sil-Mix formulations had elastic modulus values significantly different from Z250. SIGNIFICANCE: The ability of TOSU to reduce polymerization stress without a proportional reduction in mechanical properties provides a basis for improvement of silorane-based composites.

Alkanes↗
PubMed2006

A comparison between two types of radiographic film for accuracy of measurements of approximal osseous defects.

AIM: The purpose of this study was to compare two types of conventional radiographic film: Ekta-speed plus and Insight (Eastman Kodak Co, Rochester NY, USA) for accuracy of measurements of approximal bone loss. METHODS AND MATERIALS: Four dried human mandibles with complete dentition were selected. Radiographic images were made with a standardized technique. Mesial and distal bone levels on the mandibular premolar and molar teeth were measured on the two types of radiographs (Ekta-speed plus and Insight) by nine observers. The data obtained by the observers were compared with the primary investigators' corresponding measurements, which served as "the ground truth" for this study. RESULTS: The results of the analysis of variance (ANOVA) demonstrated a significant difference for the Ekta-speed plus film (p = .001), but the difference was not clinically significant. The level of intra-rater reliability was high for the observers (0.969 to 0.990). CONCLUSION: Performance of Ekta-speed plus and Insight films was found to be similar.

Alveolar Bone Loss↗
PubMed2006

Perceived efficacy, indications, and information sources for medically indigent patients and their healthcare providers regarding dietary supplements.

BACKGROUND: Evidence exists that medically indigent and minority patients use dietary supplements at rates as high or higher than that of the general population. Safety concerns regarding the use of dietary supplements are further exacerbated by a suboptimal level of patient disclosure and provider inquiry. OBJECTIVE: To determine dietary supplement use, indications, perceived efficacy, and information sources of patients and providers using a pilot study in a clinic for the medically indigent. METHODS: Five hundred self-administered patient surveys and 50 healthcare provider surveys were made available to any patient at a free health clinic in Kansas City, MO. Surveys were collected and descriptive analyses were performed. RESULTS: Three hundred eleven patient surveys were returned. Of the 37.3% (116/311) of respondents who had used dietary supplements, 13.8% (n = 16) had 10 comorbid conditions. Ninety-six dietary supplements were used for 8 medical condition categories. The 9 agents most frequently reported used were garlic (n = 32), aloe/green tea (n = 27 each), chamomile/echinacea (n = 24 each), St. John's wort (n = 22), ginseng (n = 18), and cranberry/Ginkgo biloba (n = 17 each). Patients reported a broad range of indications for taking dietary supplements. Patients reported (mean +/- SD) 2.37 +/- 4.23 agents as effective and 0.78 +/- 1.73 as ineffective or harmful. Provider surveys revealed that 60% (21/35) and 74% (26/35) were currently or had ever used dietary supplements, respectively. Fifty-seven percent (20/35) of providers reported attending educational programs on dietary supplements, and providers perceived patient supplement use to be most influenced by advertisements (40%) and friends (40%). CONCLUSIONS: The medically indigent population uses a wide variety of dietary supplements. There is little consistency in perceived indications, which may prevent clinicians from accurately predicting specific herbal use rationale given any individual's or population's set of comorbid conditions. Clinicians are encouraged to accurately determine their individual practice setting's use pattern.

Adult↗
PubMed2006

Psychophysiological definitions of clenching.

This study tested the hypothesis that individuals show considerable variability in EMG activity produced by the masticatory muscles when they are instructed to clench than when they are instructed to make minimal or maximal contact. Twenty individuals without temporomandibular disorder (TMD) pain participated in a biofeedback-training task to establish a relaxed baseline. They were instructed to clench their teeth according to their personal definition of the term, while EMG data were collected. This process was repeated two more times, followed by similar instructions to make minimal and maximal contact between the teeth. Results showed that individual subjects were very consistent in their behavioral definition of clenching and that the subjects taken as a whole showed markedly greater variability. The precise behavioral meaning of clenching varies across individuals. The failure to account for these individual differences may explain in part reported discrepancies on the role of parafunctions in TMD.

Adolescent↗
PubMed2005

Efficacy of biofeedback-based treatments for temporomandibular disorders.

Bibliographic searches identified 14 controlled and uncontrolled outcome evaluations of biofeedback-based treatments for temporomandibular disorders published since 1978. This literature includes two randomized controlled trials (RCTs) of each of three types of biofeedback treatment: (1) surface electromyographic (SEMG) training of the masticatory muscles, (2) SEMG training combined with adjunctive cognitive-behavioral therapy (CBT) techniques, and (3) biofeedback-assisted relaxation training (BART). A detailed review of these six RCTs, supplemented with information from non-RCT findings, was conducted to determine the extent to which each type of intervention met treatment efficacy criteria promulgated by the Association for Applied Psychophysiology and Biofeedback (AAPB). We conclude that SEMG training with adjunctive CBT is an efficacious treatment for temporomandibular disorders and that both SEMG training as the sole intervention and BART are probably efficacious treatments. We discuss guidelines for designing and reporting research in this area and suggest possible directions for future studies.

Biofeedback, Psychology↗
PubMed2005

Alexithymia and pain in temporomandibular disorder.

OBJECTIVE: To clarify the relationship of global alexithymia and its facets with pain, assessed prospectively using experience sampling methods (ESMs), in temporomandibular disorder (TMD). METHODS: People with painful TMD (n=49), pain-free somatic controls (24 people with disk displacement), and healthy controls (n = 28) completed measures of alexithymia (Toronto Alexithymia Scale-20 [TAS-20]) and depressed mood. Patients with painful TMD used ESM to record jaw pain multiple times daily for a week. RESULTS: The somatic and the healthy controls were equivalent on alexithymia and were combined. The painful TMD group had higher difficulty in identifying feelings but lower externally oriented thinking (EOT); only the latter effect remained after covarying depressed mood. Among patients with painful TMD, the TAS-20 total and EOT correlated positively with pain severity after controlling for depressed mood. CONCLUSION: Findings highlight the complex relationships of alexithymia and its facets to TMD pain. Research should examine alexithymia facets separately and distinguish between methods that compare groups on alexithymia (e.g., pain patients versus controls) and those that correlate alexithymia with pain severity within a group.

Adult↗
PubMed2005

Tooth contact in patients with temporomandibular disorders.

Both experimental and retrospective studies suggest a link between parafunctions and pain in temporomandibular disorder (TMD) patients. To investigate the role of parafunctions in TMD, experience sampling methodology was used as a prospective test of the hypothesis that patients with TMD have higher levels of tooth contact and tension than non-TMD controls. Three groups of TMD patients and a group of normal controls carried pagers for one week, were contacted approximately every two hours by an automated calling system, and completed questionnaires assessing tooth contact, tension, and pain at each contact. Results showed that tooth contact was much more frequent among normal controls than is commonly presumed. Patients with myofascial pain with/without arthralgia reported more frequent contact, higher intensity contact, and more tension than patients with disk displacement or normal controls. Increased masticatory muscle activity responsible for tooth contact and tension may be an important mechanism in the etiology and maintenance of the myofascial pain and arthralgia of TMD.

Adult↗
PubMed2005

The role of parafunctions, emotions and stress in predicting facial pain.

BACKGROUND: The authors conducted a study to examine the degree to which parafunctions and emotional states predicted jaw pain in subjects with temporomandibular disorder (TMD) and control subjects. METHODS: Ninety-six subjects diagnosed with myofascial pain, myofascial pain and arthralgia, disk displacement or no TMD symptoms participated. The authors used experience sampling methodology to collect data on pain, behaviors and emotions. They paged subjects approximately every two hours, but not during sleep. When paged, subjects completed a brief questionnaire containing rating scales of jaw pain, masticatory muscle tension, time and intensity of tooth contact, mood and stress level. RESULTS: Analyses of variance showed that groups differed significantly (P < .05) in terms of pain; masticatory muscle tension; and a composite variable measuring time and intensity of contact; mood; and stress. The two myofascial pain groups scored higher on these measures than did the group with disk displacement and the control group. The authors used masticatory muscle tension, the composite variable, mood and stress to predict jaw pain using linear regression. The model was significant and accounted for 69 percent of the variance in jaw pain. Because tension was so highly correlated with jaw pain, the authors removed this variable and re-ran the analysis. The second model also was significant and accounted for 46 percent of the variance in jaw pain. CONCLUSIONS: Parafunctional behaviors, especially those that increase muscle tension, and emotional states are good predictors of jaw pain levels in patients with TMD and healthy control subjects. CLINICAL IMPLICATIONS: Treatment that helps patients reduce parafunctions, excess masticatory muscle tension, stress and emotional distress should be effective in reducing TMD pain.

Adult↗
PubMed2004

In vitro mutagenicity and metabolism of the cycloaliphatic epoxy Cyracure UVR 6105.

Cyracure UVR 6105 is a cycloaliphatic epoxy monomer and has both carboxylate and epoxy groups, with the potential for rapid polymerization. It is widely used in industry for the preparation of inks, resins, coatings, and was proposed for incorporation into dental composites. The objective of this study was to determine the mutagenic potential of this chemical related to its metabolite products. Several doses of Cyracure UVR 6105 were dissolved in DMSO and subjected to the Ames Salmonella mutagenicity assay. A metabolic activation system (S9-mix) was used consisting of Arochlor-induced liver S9 homogenate enriched with NADP and glucose-6-phosphate cofactors. In contrast to studies without S9-mix, Cyracure UVR 6105 exhibited enhanced genotoxic activities with strains TA100 and TA1535 in the presence of liver S9-mix. From in vitro metabolism of Cyracure UVR 6105 with S9-mix, as used in the Ames assay, several metabolites were identified. The alcohol metabolite, 3,4-epoxycyclohexylmethanol, containing intact epoxy group was identified in the organic solvent extract. This metabolite was synthesized and proved to be mutagenic against TA100 when assayed in the presence and absence of S9-mix. Results showed that the increased mutagenicity of Cyracure UVR-6105 in the presence of liver enzymes is due to the formation of the mutagenic metabolite 3,4-epoxycyclohexylmethanol.

Animals↗
PubMed2004

Parafunctional clenching, pain, and effort in temporomandibular disorders.

This study tested the hypotheses that (1) parafunctional clenching increases pain and can lead to a diagnosis of temporomandibular disorder (TMD) pain and (2) electromyographic (EMG) activity during parafunctional clenching is significantly and positively correlated with reports of pain. Fourteen individuals without TMD participated in 5 consecutive days of 20-min long EMG biofeedback training sessions of the left and right temporalis and masseter muscles. Subjects were randomly assigned to either a Decrease or Increase group and were instructed to maintain EMG activity below 2 microV or above 10 microV during training, respectively. Two Increase subjects and no Decrease subjects were diagnosed, by a blinded examiner, with TMD pain following training. Self-reported pain posttraining was significantly higher for the Increase group. Masseter EMG activity was strongly correlated with pain. Parafunctional clenching increases pain and can lead to a diagnosis of TMD in otherwise pain-free individuals. Pain reports are positively correlated with the activity of the masseter muscle.

Adult↗
PubMed2004

Statistical and clinical significance: alternative methods for understanding the importance of research findings.

Statistical significance is an important tool for interpreting a study's results, but statistical significance provides an incomplete picture of results. The likelihood of obtaining statistically significant results can be manipulated by a researcher who uses large sample sizes or who compares treatments that are expected to differ greatly in outcome. Measures of effect size provide an additional tool for understanding the results of a study and evaluating the importance of the results. Meta-analyses and estimates of clinical significance can also help clinicians properly evaluate research findings.

Bias↗
PubMed2003

In vitro effect of light-cure dental adhesive on IL-6 release from LPS-stimulated and unstimulated macrophages.

The objective of this study was to measure IL-6 release from LPS-stimulated and -unstimulated macrophages exposed to extracts from fresh and aged Scotchbond Multipurpose Plus adhesive disks (5 mm in diameter by 2 mm in thickness) light cured for 10, 20, or 40 s. One set of disks was aged for 16 weeks at 4 degrees C. Extracts were prepared by incubating three disks in 1 mL of serum-free culture medium for 72 h at 37 degrees C. Then macrophages (RAW 264.7) were exposed to the extracts (6.25-50 microL) for 72 h at 37 degrees C/5% CO(2). Supernatants were analyzed for cytokine levels (ELISA), and the monolayer of cells was assessed for viability (MTT assay). Unlike adhesive disk age, curing time affected cell viability. Disk extracts cured for 10 s were more cytotoxic (p < 0.05) than were extracts from 20- or 40-s cured disks. Macrophage release of IL-6 was stimulated significantly (p < 0.01) by extracts from fresh 10-s cured disks, up to 777 pg/mL and by 2 microg/mL of LPS (1174 pg/mL). The LPS response was significantly (p < 0.05) suppressed by 50 microL of extracts, which may be related to the enhanced cytotoxicity exhibited by LPS in combination with extracts. This study has demonstrated the possibility that IL-6 release is stimulated by light-cure dental adhesive applications using 10-s curings.

Adhesives↗
PubMed2002

Comparison of panoramic radiography and panoramic digital subtraction radiography in the detection of simulated osteophytic lesions of the mandibular condyle.

OBJECTIVE: The aim of this study was to compare panoramic temporomandibular joint radiography, unenhanced and color-enhanced digital-subtraction radiography with respect to detectability of simulated osteophytic lesions of the mandibular condyle. METHODS: Three dry human skulls with no obvious temporomandibular joint pathology were selected. Four sizes of bone chips were placed on the anterior aspect of the condyle at medial, central, and lateral locations. Panoramic radiographs were made with and without the chips in place. These paired radiographs were digitized, and unenhanced and color-enhanced digital-subtraction images of the original panoramic images were obtained. Eight observers evaluated 72 randomized images of each modality for the presence or absence of simulated osteophytic lesions of the mandibular condyle, grading the images on a 100-point scale. RESULTS: A(z) values for overall diagnostic accuracy of the three imaging modalities were 0.5376 for panoramic radiography, 0.7861 for unenhanced digital subtraction radiography, and 0.7923 for color-enhanced digital-subtraction radiography. Digital-subtraction radiography improved the detection accuracy of the original panoramic films. CONCLUSION: Panoramic radiographs were significantly less accurate in the detection of simulated osteophytic lesions of the mandibular condyle than the two digital-subtraction techniques.

Analysis of Variance↗
PubMedDate not supplied

Quantum mechanical structure-activity relationship analyses for skin sensitization.

Allergic contact dermatitis (ACD) results in inflammation of the skin due to sensitization of the immunologic system to a particular substance. The sensitization process is limited by the compound's ability to both permeate and react with proteins in the integumentary system. Currently, only in vivo animal tests such as the local lymph node assay (LLNA) are recognized by regulatory authorities for risk assessment of ACD. A quantitative structure-activity relationship has been developed to predict relative potency, which allows for the prediction of relative sensitization potentials. The experimental values used in this study include EC3 values (the concentration at which the stimulation index equals 3) from LLNA tests. The predictions in this model enable categorization of the compounds into three groups on the basis of risk of sensitization and enable screening of candidate molecules using rapid SAM1 semiempirical calculations prior to animal testing. The model may also be used to reduce the number of animals subjected to testing by providing estimated concentrations required for useful data of risk assessment. The effect of averaging available literature values on predictive ability is also investigated. The model includes halogenated compounds, aromatic compounds, alcohols, aldehydes, and ketones. The computational investigation resulted in a two-descriptor model that is consistent with the assumed mechanism for sensitization.

Hypersensitivity↗
PubMedDate not supplied

Chain melting temperature estimation for phosphatidyl cholines by quantum mechanically derived quantitative structure property relationships.

Geometries for 62 phosphatidylcholines (PC) were optimized using the AM1 semiempirical quantum mechanical method. Results obtained from these calculations were used to calculate 463 descriptors for each molecule. Quantitative Structure Property Relationships (QSPR) were developed from these descriptors to predict chain melting temperatures (Tm) for the 41 PCs in the training set. After screening each QSPR for statistical validity, the Tm values predicted by each statistically valid QSPR were compared to corresponding Tm values extracted from the literature. The most predictive, chemically meaningful QSPR provided Tm values which agreed with literature values to within experimental error. This QSPR was used to predict Tm values for the remaining 21 PCs to provide external validation for the model. These values also agreed with literature values to within experimental error. The descriptor developed by the final QSPR was the second order average information content, a topological information-theoretical descriptor.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

Effect of measurement site on the dimensional accuracy of die-forming materials and techniques.

To date, the comparisons of dimensional accuracy of various die materials has been investigated primarily by using a one-dimensional measurement on one die. However, a single measurement may not adequately represent the complex preparations that are encountered frequently in clinical dentistry. This investigation utilized a standardized model with two identical dies to measure die accuracy at four sites, using five different die-forming materials/techniques.

Analysis of Variance↗