Biomedical subjects

S A Gansky

Publications and source records attributed to S A Gansky.

16 recordsLinked to original sources

PubMed2001

Mechanical properties of the dentinoenamel junction: AFM studies of nanohardness, elastic modulus, and fracture.

The dentinoenamel junction (DEJ) is a complex and poorly defined structure that unites the brittle overlying enamel with the dentin that forms the bulk of the tooth. In addition, this structure appears to confer excellent toughness and crack deflecting properties to the tooth, and has drawn considerable interest as a biomimetic model of a structure uniting dissimilar materials. This work sought to characterize the nanomechanical properties in the region of the DEJ using modified AFM based nanoindentation to determine nanohardness and elastic modulus. Lines of indentations traversing the DEJ were made at 1-2 microm intervals from the dentin to enamel along three directions on polished sagittal sections from three third molars. Nanohardness and elastic modulus rose steadily across the DEJ from bulk dentin to enamel. DEJ width was estimated by local polynomial regression fits for each sample and location of the mechanical property curves for the data gradient from enamel to dentin, and gave a mean value of 11.8 microm, which did not vary significantly with intratooth location or among teeth. Nanoindentation was also used to initiate cracks in the DEJ region. In agreement with prior work, it was difficult to initiate cracks that traversed the DEJ, or to produce cracks in the dentin. The fracture toughness values for enamel of 0.6-0.9 MPa . m(1/2) were in good agreement with recent microindentation fracture results. Our results suggest that the DEJ displays a gradient in structure and that nanoindenation methods show promise for further understanding its structure and function.

Algorithms↗

PubMed2001

Demineralization of caries-affected transparent dentin by citric acid: an atomic force microscopy study.

OBJECTIVES: This study determined recession rates of peritubular dentin and intertubular dentin in citric acid solution (0.018M, pH=2.5) for caries-affected transparent dentin, one of the major components of dentin substrate as altered by caries, with comparisons made with non-carious dentin. METHODS: Transparent dentin was identified by sagittally sectioning five obviously carious teeth. Sections were then cut through the transparent dentin area perpendicular to the course of the dentinal tubules. Polished dentin samples of the transparent dentin and non-carious dentin were prepared with an internal reference layer and studied at specific intervals for citric acid etching in an atomic force microscope (AFM). RESULTS: At baseline, transparent dentin was identified by dentinal tubules that were largely occluded with mineral deposits that on etching proved to be acid resistant. Peritubular dentin etched rapidly and linearly over time until it could no longer be measured, yielding etching rates for transparent dentin that could not be distinguished from normal dentin. The normal and transparent intertubular dentin surfaces began etching at nearly the same rate, but then surface recession stabilized after less than 1 microm depth change for both dentin types. SIGNIFICANCE: Most previous studies have focused on demineralization and bonding to normal dentin, although many bonding procedures involve altered dentin substrates, such as those modified by caries. In this study, peritubular and intertubular dentin from normal and caries-affected dentin exhibited similar behavior. The major difference was the presence of acid resistant mineral in most of tubule lumens in the transparent dentin.

Acid Etching, Dental↗

PubMed2001

Etching characteristics of dentin: effect of ferric chloride in citric acid.

Citric acid etchants with ferric chloride (10-3) promote adhesion and are effective etchants. We used atomic force microscopy (AFM) to determine the dentin etching characteristics of 10% citric acid etchant with various additions of ferric chloride. AFM was used to measure the surface recession and morphology of dentin etching for a variety of 10% citric + Fe-Cl etchants. Commercial 10-3 was used as the control. Dentin disks were prepared and partially masked during etching so that the unetched dentin served as a reference. AFM images of the same samples were taken at each of the seven experimental steps using 10% citric acid with various quantities of ferric chloride ranging from 0 to 3% (denoted 10-0, 10-1, 10-1.8 and 10-3, respectively) which altered the pH from 1.63 to 0.42. Changes in depth (nm) relative to the reference height for intertubular dentin were determined after etching 15 s; clinical air drying, rewet for 1-5 min; desiccation for 24 h; rehydration for 24 h. Differences of log(depth change) were tested with mixed effects cell mean models. Overall differences were significant (P < 0.001). Significant differences were found between etchants and the extent of collapse on drying was dependent on pH and Fe-Cl content. Following long-term rehydration, samples recovered, but those with 0 or 1% Fe-Cl did not recover as completely (P < 0.01). Etching and collapse depended on Fe-Cl content. The collapse was nearly reversed on rehydration. Ten per cent citric acid with ferric chloride did not prevent the collapse of etched dentin. Ferric chloride additions reduced pH and increased the collapse of dentin on drying for either brief or prolonged periods. Brief rewetting can reverse the effect of brief air drying. For fully desiccated samples the effect was not reversed after 30 s, but was largely or completely reversed at 24 h in solution depending on Fe-Cl content.

Acid Etching, Dental↗

PubMed2000

Citric acid etching of cervical sclerotic dentin lesions: an AFM study.

Atomic force microscopy (AFM) has been used to determine microstructural changes, etching rates of peritubular dentin, and intertubular dentin recession during demineralization in dilute acidic solutions. These studies have not included many forms of altered dentin, including noncarious sclerotic root dentin associated with Cl V (abfraction) lesions. We sought to determine microstructural changes and recession rates during demineralization in citric acid (pH 2.5, 0.018M) for the transparent/sclerotic zone. Highly polished dentin disks were prepared from teeth with noncarious C1 V lesions (n = 3) and compared with normal root dentin (n = 3). Samples were etched at 5-s intervals for 1 min and at longer intervals up to 30 min. The depth changes in various portions of the dentin with respect to the reference layer were measured and changes in microstructure observed in solution in the wet cell of the AFM. In sclerotic dentin, most tubule lumens were occluded with crystalline deposits that etched more slowly than the other dentin components, but etching rates could not be determined due to their irregular geometry. The intertubular dentin recession quickly reached a plateau after a depth change of <1 microm for all dentin types, in agreement with prior work. Mixed linear regression models indicated an important difference between the etching of sclerotic intertubular dentin and that of non-sclerotic root dentin that became apparent after 600 s (p = 0.037). The sclerotic intertubular dentin underwent less depth change at the plateau (558 nm) compared to normal root dentin (744 nm). In addition, normal root dentin underwent significantly greater recession than coronal dentin (p = 0.002). The results of this study indicate that intertubular sclerotic dentin from Cl V lesions etches differently than normal root dentin, and this may help explain the difficulties in restoring such lesions with current bonding procedures.

Acid Etching, Dental↗

PubMed1999

The relationship between chronic facial pain and a history of trauma and surgery.

OBJECTIVE: Because pain is the most commonly reported symptom of patients presenting to temporomandibular disorders clinics, it is important to identify factors that modify the perception or reality of such pain. The purpose of this study was to investigate the hypothesis that a patient with a history of trauma and/or non-temporomandibular joint surgery might be sensitized to pain and might report increased pain levels if a temporomandibular disorder later developed. STUDY DESIGN: This was a retrospective study of 778 consecutive patients seen over a 1-year period in an Orofacial Pain Clinic. Study parameters included gender, lifetime number of self-reported traumas, lifetime number of non-temporomandibular joint operations, and location, intensity, frequency, and type of temporomandibular disorder-related pain. RESULTS: There were significantly more women than men in the study (609 to 169). There was no relationship between numbers of previous traumas and non-temporomandibular joint operations and types of temporomandibular disorder. However, there were statistically significant relationships between the severity of facial pain and the frequency of facial pain as well as between the severity and frequency of joint pain and the number of traumas. There were also statistically significant associations between the severity and frequency of facial pain and the number of non-temporomandibular joint-related surgical procedures that the patient had undergone. CONCLUSIONS: There is a relationship between a patient's reported history of trauma and/or non-temporomandibular joint-related operations and the severity and frequency of facial and temporomandibular joint pain, should it develop. It is possible that such traumas and operations sensitize the patient in such a way that the pain of subsequent temporomandibular joint disorders is heightened.

Adolescent↗

PubMed1999

Cysteine protease inhibitory activity and levels of salivary cystatins in whole saliva of periodontally diseased patients.

The 3 human salivary cystatins S, SA and SN are multifunctional proteins that possess a cysteine protease inhibitory property, but their ability to act as such is very different (SN > SA >> S). One form, S, also appears to possess antibacterial properties towards the bacterium Porphyromonas gingivalis, often associated with periodontal diseases. In this study we measured the total cystatin inhibitory activity and the levels of each salivary cystatin in the whole saliva of 8 periodontally diseased patients and 2 groups of control subjects (n = 6 and n = 10). The total cystatin inhibitory activity and the total salivary cystatin concentration in the periodontally diseased patients were found to be lower than the controls (p < or = 0.005). The concentration of S was depleted to levels that would not allow it to be an effective antibacterial agent, and the concentration of SA, although depleted in some cases, was still present at sufficient levels to allow it to act as an effective physiological inhibitor of cathepsin L. The concentration of cystatin SN was also depleted in the periodontally diseased patients, but was still present in sufficient quantities to act as an effective physiological cysteine protease inhibitor of cathepsins H and L. In comparison, the concentration of all 3 salivary cystatins in the control subjects were sufficient to enable these proteins to be both effective physiological cysteine protease inhibitors and antibacterial agents.

Adult↗

PubMed1999

Complex sampling: implications for data analysis.

Investigators in dental public health often use strategies other than simple random sampling to identify potential subjects; however, their statistical analyses do not always take into account the complex sampling mechanism. Often it is not clear whether a given strategy requires adjustment for stratification and/or cluster sampling of observations. We propose that the need for such adjustment depends on the primary study objective. As a general rule, we recommend that if the study goal is to estimate the magnitude of either a population value of interest (e.g., prevalence), or an established exposure-outcome association, adjustment of variances to reflect complex sampling is essential because obtaining appropriate variance estimates is a priority. However, if the study goal is to establish the presence of an association, especially in a preliminary investigation of novel conditions or understudied populations, obtaining appropriate variance estimates may not be of primary importance; hence, adjustment of variances for complex sampling is not always required, but often is recommended. This paper describes several types of complex sampling designs, methods of adjusting for complex sampling strategies, examples illustrating the effect of adjustment, and alternative approaches for analysis of complex samples.

Analysis of Variance↗

PubMed1999

A public health vs a risk-based intervention to improve cardiovascular health in elementary school children: the Cardiovascular Health in Children Study.

OBJECTIVES: This study sought to determine the population effects of both classroom-based and risk-based interventions designed to reduce cardiovascular disease risk factors in children. METHODS: Elementary school children (n = 2109; age range: 7-12 years) were randomized by school to a classroom-based intervention for all third and fourth graders, a risk-based intervention only for those with 1 or more cardiovascular disease risk factors, or a control group. The 8-week interventions involved both knowledge--attitude and physical activity components. RESULTS: School-level analyses showed that physical activity in the risk-based group and posttest knowledge in the classroom-based group were significantly higher than in the control group. With regard to trends shown by individual-level analyses, cholesterol dropped more in the classroom-based than in the control group, and skinfold thickness decreased 2.9% in the classroom-based group and 3.2% in the risk-based group (as compared with a 1.1% increase in the control group). CONCLUSIONS: Both classroom-based and risk-based interventions had positive effects on physical activity and knowledge, with trends toward reduced body fat and cholesterol. However, the classroom-based approach was easier to implement and evidenced stronger results than the risk-based intervention.

Analysis of Variance↗

PubMed1999

AFM study of citric acid-ferric chloride etching characteristics of dentin.

PURPOSE: To determine the etching characteristics of 10% citric acid etchant with 3% ferric chloride (10-3) compared with related etchants without ferric chloride (10-0), or one of similar pH (36% citric acid). MATERIALS AND METHODS: Atomic force microscopy (AFM) was used to measure the surface recession and morphology of dentin. AFM images were taken of the same samples at seven steps of an etching and drying procedure using 10-3 (pH = 1.09), 10-0 (pH = 1.87) or 36% (pH = 1.08) citric acid solutions: at baseline, after etching 15 s, after 5-s air-drying, after rewetting, after 24-hr desiccation, after 30 s rewetting and after 24 hrs rewetting in filtered and purified water. RESULTS: 10-3 etched surfaces receded more than either 10-0 or 36% etched surfaces, and underwent greater collapse on 5-s air-drying. On rewetting all surfaces re-expanded to near their as-etched level. Following prolonged desiccation (24 hrs) all samples collapsed to the level seen after brief air-drying. 30-s rewetting did not restore the surface, but re-expansion of the collapsed collagen matrix was seen at 24 hrs.

Acid Etching, Dental↗

PubMed1998

Failure load of acrylic resin denture teeth bonded to high impact acrylic resins.

STATEMENT OF PROBLEM: Techniques for bonding denture teeth to an acrylic resin denture base remain empirical, with little consensus from the literature, among clinicians, or among dental laboratories. PURPOSE: This study evaluated the failure load of acrylic resin teeth bonded to 2 high impact acrylic resins. METHODS AND MATERIAL: The ridge lap portion on 120 identical denture teeth were modified with 3 variables: (1) placing a diatoric, (2) using monomer to prewet the denture tooth, and (3) breaking the glaze. Variables were combined to form 6 groups of 10 teeth each, and processed with Lucitone 199 (Lucitone) or SR-Ivocap (Ivocap) acrylic resin. Data analysis included the use of a heterogeneous variance linear regression model. RESULTS: Mean (+/- SD) failure load ranged between 10.25 +/- 1.48 Kg to 28.43 +/- 11.05 Kg for the 6 Ivocap groups and 16.63 +/- 5.87 Kg to 28.05 +/- 5.35 Kg for the Lucitone groups. For Lucitone 199 acrylic resin, the highest failure loads resulted when the ridge lap was left with an intact glaze and did not have a diatoric, with no significant influence from the use of monomer. For Ivocap resin, the highest failure loads resulted when the ridge lap had a diatoric but did not have monomer placed, with no significant influence from glaze. CONCLUSION: Failure load of bonding highly cross-linked denture teeth to SR-Ivocap or Lucitone 199 acrylic resin was significantly influenced by modifications to the ridge lap before processing.

Acrylic Resins↗

PubMed1998

School-based interventions improve heart health in children with multiple cardiovascular disease risk factors.

OBJECTIVE: To determine the immediate effects of two types of elementary school-based interventions on children with multiple cardiovascular disease (CVD) risk factors. DESIGN: Randomized, controlled field trial. SETTING: Conducted in 18 randomly selected elementary schools across North Carolina. STUDY PARTICIPANTS: Four hundred twenty-two children age 9 +/- 0.8 years with at least two risk factors at baseline: low aerobic power and either high serum cholesterol or obesity. INTERVENTION: Both 8-week interventions consisted of a knowledge and attitude program and an adaptation of physical education. The classroom-based intervention was given by regular teachers to all children in the 3rd and 4th grades. The risk-based intervention was given in small groups only to children with identified risk factors. Children in the control group received usual teaching and physical education. OUTCOME MEASURES: The primary outcome measure was cholesterol; additional measures were blood pressure, body mass index, body fat, eating and activity habits, and health knowledge. RESULTS: Both interventions produced large reductions in cholesterol (-10.1 mg/dL and -11.7 mg/dL) compared with a small drop (-2.3 mg/dL) in the controls. There was a trend for systolic blood pressure to increase less in both intervention groups than in the controls. Both intervention groups had a small reduction in body fat and higher health knowledge than the control group. CONCLUSIONS: Both brief interventions can improve the CVD risk profile of children with multiple risk factors. The classroom-based approach was easier to implement and used fewer resources. This population approach should be considered as one means of early primary prevention of CVD.

Cardiovascular Diseases↗

PubMed1997

Two-year incidence of tooth loss among South Australians aged 60+ years.

UNLABELLED: Tooth loss diminishes oral function and quality of life, and national health targets aim to reduce population levels of tooth loss. OBJECTIVES: The purpose of this study was to determine tooth loss incidence and predictors of tooth loss among older adults in South Australia. METHODS: Data were obtained from a cohort study of a stratified random sample of community-dwelling dentate people aged 60+ years. Interviews and oral examinations were conducted among 911 individuals at baseline and among 693 of them (76.1%) 2 years later. Incidence rates and relative risks were calculated for population subgroups and multivariate logistic regression was used to construct risk prediction models. A method was developed to calculate 95% confidence intervals (95% CI) for relative risks (RR) from logistic regression models using a Taylor series approximation. RESULTS: Some 19.5% (95% CI = 15.4-23.6%) of people lost one or more teeth during the 2 years. Men, people with a recent extraction, people who brushed their teeth infrequently, smokers and people born outside Australia had significantly (P < 0.05) greater risk of tooth loss. Baseline clinical predictors of tooth loss included more missing teeth, retained roots, decayed root surfaces, periodontal pockets and periodontal recession. In a multivariate model that controlled for baseline clinical predictors, former smokers (RR = 2.55, 95% CI = 1.48-4.40) and current smokers (RR = 2.06, 95% CI = 0.92-4.62) had similarly elevated risks of tooth loss compared with non-smokers. CONCLUSIONS: The findings from this population suggest that a history of smoking contributes to tooth loss through mechanisms in addition to clinical disease processes alone.

Cohort Studies↗

PubMed1996

Effects of a school-based intervention to reduce cardiovascular disease risk factors in elementary-school children: the Cardiovascular Health in Children (CHIC) study.

OBJECTIVE: To test a classroom-based intervention to reduce cardiovascular disease risk factors in elementary school children. STUDY DESIGN: This was a randomized, controlled field trial in 12 schools across North Carolina, stratified by geographic region and urban/rural setting. Subjects were 1274 third and fourth graders (48% boys). The intervention, taught by regular classroom and physical education teachers, provided all children an 8-week exercise program and 8 weeks of classes on nutrition and smoking. Data were analyzed at the school level with survey regression models and at the individual level with multivariate analysis of variance and analysis of covariance models; 95% confidence intervals were computed. RESULTS: Children in the intervention group had significantly greater knowledge (7.9% more correct) and a significant increase in self-reported physical activity than children in the control group. Trends for the intervention group were a reduction in total cholesterol level (-5.27 mg/dl), an increase in aerobic power, a reduction in body fat, and smaller rise in diastolic blood pressure than control children. CONCLUSIONS: This classroom-based, public health approach improved children's cardiovascular disease risk profiles; it is practical and fairly easy to incorporate into the school day. All children directly receive the potential benefits of the intervention without a risk of labeling. This program can improve health knowledge, habits, and health outcomes of young children at a time when health habits are being formed.

Cardiovascular Diseases↗

PubMed1995

Childhood obesity elevates blood pressure and total cholesterol independent of physical activity.

OBJECTIVE: To compare the habitual physical activity, blood pressure, total cholesterol levels of obese and non-obese matched children. SUBJECTS: 546 obese children (BMI and sum of skinfolds > or = 90% tile) were matched for gender, race, age, and height (within 2 cm) with non-obese controls for a total sample of 1092 children. MEASUREMENTS: Systolic (BPsys) and diastolic (BPdia) blood pressure by mercury sphygmomanometer, total cholesterol by reflectance photometry, and physical activity by questionnaire. RESULTS: Mean comparisons indicated the obese children, regardless of gender, had higher BPsys (108 +/- 11 vs 104 +/- 10 mm Hg, P = 0.0001), BPdia (70 +/- 9 vs 68 +/- 8 mm Hg, P = 0.002), and greater total cholesterol levels (4.47 +/- 0.80 vs 4.11 +/- 0.75 mmol/L, P = 0.0001) than the non-obese subjects. Self-reported physical activity scores were not significantly different when comparing the obese and non-obese children. Correlations between self-reported activity and cholesterol or blood pressure were all very low and not significant (r < or = 0.06). CONCLUSION: These results suggest that childhood obesity is associated with higher blood pressures and greater circulating cholesterol levels independent of physical activity levels.

Aging↗

PubMed1994

Statistical evaluation of relationships between analgesic dose and ordered ratings of pain relief over an eight-hour period.

Statistical considerations are discussed for the application of alternative methods to a clinical trial involving repeated ordinal ratings and multiple dosage levels of active drugs. Analyses included summary measures traditionally employed in studies of acute pain: sum of pain intensity differences from baseline, total pain relief, and total pain half gone. Estimators and confidence intervals of relative potency are developed for univariate and multivariate situations, using weighted least squares analysis with mean response and variances from Taylor series linearizations. The estimates from these methods are compared to those from traditional methods, such as ordinary least squares regression and Fieller's method for confidence intervals, as well as those from more recent developments, such as generalized estimating equations and sample survey data regression. A double-blind, two-center, randomized clinical trial of acute pain relief comparing placebo with two analgesics, each at two dosage levels, over an 8-hr period serves as an illustrative example for these techniques and comparisons.

Adolescent↗

PubMedDate not supplied

Leisure time activities of elementary school children.

The three most common leisure time activities of 2,200 third and fourth grade children (mean age 8.8 + 0.8; 50.7% girls) and the association of the intensity levels of those activities with demographic variables and risk factors for cardiovascular disease are reported. Activities reported most often by boys were playing video games (33%), playing football (32%), bicycling (31%), watching television (28%), and playing basketball (26%). The girls reported doing homework (39%), bicycling (31%), watching television (30%), dancing (27%), and reading (23%). Overall, the children, especially girls, reported fairly sedentary activities, with an average metabolic equivalent level of 4.2 for girls and 4.8 for boys. Among boys, African Americans reported more vigorous activities than Whites, but the activities reported by White girls were somewhat more vigorous than those reported by non-White girls. Children from a higher socioeconomic status (SES), especially boys, reported a greater proportion of sedentary activities than lower SES children. The risk factors of cholesterol, blood pressure, skinfold thickness, and body mass index were not significantly associated with total activity score. However, significantly more nonobese than obese children reported a vigorous (high-intensity) activity as one of their top three activities.

Black or African American↗