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Biomedical subjects

I Y Guo

Publications and source records attributed to I Y Guo.

At least 19 recordsLinked to original sources
PubMed1998

Oral/pharyngeal, laryngeal, and lung cancer discharge trends in Department of Veterans Affairs hospitals.

OBJECTIVE: This paper describes trends in oral and pharyngeal (O/P) cancer diagnoses in Department of Veterans Affairs (VA) hospitals from 1983 to 1993 and compares these trends to those of laryngeal and lung cancers. METHODS: The VA patient treatment file was used to identify unique hospital discharges from 1983 to 1993 having ICD-9-CM codes for O/P, laryngeal, and lung cancers. Descriptive statistics were tabulated to determine prevalence and distribution. Trends of change over time were analyzed using regression analyses of the percent rate on year. RESULTS: Between 1983 and 1993 the annual number of O/P cases among users of VA hospitals decreased from 4,983 to 3,298. Despite overall declines in O/P cancer discharges in VA, cancer of the pharynx, tongue, and salivary gland continues to increase. O/P cancer in younger persons also continues to increase in VA. Overall, laryngeal cancers significantly increased, while no significant change was associated with lung cancer. CONCLUSIONS: VA needs to evaluate the changes in the patterns of O/P cancer to ascertain whether this represents a shift in care from inpatient to outpatient care. VA should seek further information regarding these trends to better plan, implement, and evaluate programs to provide early diagnosis and treatment targeted to veterans.

Age Factors↗
PubMed1997

Condylar change after upward and forward rotation of the maxillomandibular complex.

Tomographic radiographs of 44 healthy temporomandibular joints in 22 patients undergoing large upward and forward rotations of the maxillomandibular complex were evaluated. Immediate postsurgery results showed decreases in all areas of the joint space. Long-term results showed a decrease in the superior and posterior regions, 14.8% and 19.7%, with no significant change anteriorly. Simple and multiple regression analysis did not show any relationship with age, gender, or degree of change in the decrease of the occlusal plane angle, to the temporomandibular joint changes described. Some condylar remodeling was noted.

Adaptation, Physiological↗
PubMed1997

Handling characteristics of a gallium alloy triturated with alcohol.

PURPOSE: To assess the handling characteristics of a gallium alloy triturated with one drop (10 microL) of ethyl alcohol and compare them to those of a high-copper amalgam. MATERIALS AND METHODS: A commercial gallium alloy (Gallium Alloy GFII) and a high-copper amalgam (Tytin) were used. Ten dentists each restored four identical MO preparations in acrylic typodont teeth (two for each material). Each restoration was immediately evaluated by the operator for placement, condensation, proximal contact, carving, and resistance to fracture during matrix removal and overall quality according to a method used previously. The rating scale for each criterion ranged from 1 (very poor) to 5 (very good). Scores for each criterion for the amalgam and gallium alloy restorations were statistically compared. RESULTS: The gallium alloy tested was still rated significantly worse (P < or = 0.05) than amalgam for placement, condensation and carving but there were no significant differences in scores for other criteria. The dentists judged the handling of the gallium alloy in all criteria as fair to good and evaluated it as better in placement, condensation and establishment of proximal contact compared to a previous study, mainly because the pre-set material was no longer sticky.

Dental Alloys↗
PubMed1996

Influence of three membrane types on healing of bone defects.

OBJECTIVES: To determine and compare osseous regeneration associated with three guided tissue regeneration membrane types (expanded polytetrafluoroethylene, dense polytetrafluoroethylene, and an absorbable polylactic acid/citric acid ester base) and removal forces required for expanded and dense polytetrafluoroethylene membranes. STUDY DESIGN: Bilateral osseous defects were created in 30 adult rat calvaria; one defect was covered with a test membrane and the other received no membrane (control). After 2 or 4 weeks, forces required for membrane removal from the tissues were electronically determined, and the calvaria removed and decalcified. Sections through the defects were stained and evaluated electronically and microscopically. Data were analyzed statistically. RESULTS: Microscopic evaluation with Mann-Whitney U test revealed that dense polytetrafluoroethylene was associated with significantly greater bone formation than expanded polytetrafluoroethylene (p = 0.02) at 2 weeks and absorbable polylactic acid/citric acid ester base (p = 0.004) at 4 weeks. Electronic evaluation of the linear degree of fill with one way ANOVA and Tukey's test found no significant difference (p > 0.05) among the experimental or the control groups. In addition, the Mann-Whitney U test indicated that removal forces required for dense polytetrafluoroethylene were significantly less than for expanded polytetrafluoroethylene (p = 0.003). CONCLUSIONS: The use of dense polytetrafluoroethylene as a membrane barrier deserves further investigation as it allows osseous regeneration, it is easier to remove from healing soft tissues, and it is inexpensive. A study with larger sample sizes should be conducted.

Analysis of Variance↗
PubMed1996

Apical and coronal seal of roots obturated with a dentine bonding agent and resin.

The efficacy of sealing root canal systems with a dentine bonding agent and resin cement was compared with that of a glass ionomer sealer. Scanning electron microscopic examination of the bonding agent-dentine interface was also performed. The root canals of 50 single rooted teeth with mature apices were prepared chemomechanically and the smear layer removed with 17% REDTA and 5.25% NaOCl. Specimens were divided into two groups of 24 teeth each. One group had the dentine conditioned with a 10:3 citric acid-ferric chloride solution and obturated with the dentine bonding agent and resin, radiopaque C & B Metabond. The other group was obturated with the glass ionomer sealer, Ketac-Endo and a single cone of gutta-percha. After immersion in Indian ink for 90 h, the teeth were cleared and the quality of the apical and coronal seal was assessed using India ink dye penetration. There was a significantly better seal in both the apical and coronal directions when using the dentine bonding agent and resin obturation material. Scanning electron microscopic examination of the demineralized dentine and the C & B Metabond interface revealed the presence of the characteristic hybrid layer along with microtags of resin penetrating deep into the dentine tubules.

Boron Compounds↗
PubMed1995

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.

Analysis of Variance↗
PubMed1994

A PC program for computing confidence bands for average and individual growth curves.

Dawson et al. (Am. J. Med. Genet. 7, 529-536, 1980) developed a procedure for constructing confidence bands for both average and individual growth curves which may be of considerable value in the study of growth and development. This paper describes their method for constructing, and provides a menu-driven GAUSS386i program for computing these confidence bands. It is demonstrated how these bands are useful for both the diagnosis and prognostication of growth patterns with known levels of confidence. It is assumed that the study is planned so that individuals will be measured at the same times, but missing data are allowed.

Confidence Intervals↗
PubMed1994

PC program for growth prediction in the two-stage polynomial growth curve model.

We consider the problem of growth prediction in the context of the two-stage (or random coefficients) one-sample polynomial growth curve model and provide a PC program, written in GAUSS386i, to perform the associated computations. The problem considered is that of estimating the value of the measurement under consideration for a 'new' individual at the Tth time point given measurements on that individual at T-1 previous points in time and the values of the measurement on N 'similar' individuals at all T time points. The times of measurement t1, t2, ..., tT need not be equally spaced, but we assume that each of the N individuals comprising the normative sample were measured at these times. The method and the program are illustrated using the data set previously considered (Schneiderman and Kowalski, Am J Phys Anthrop, 67 (1985) 323-333) consisting of mandibular ramus height measurements (in mm) for 12 male rhesus monkeys at T = 5 yearly intervals (coded 1, 2, 3, 4, and 5). Results are compared with those obtained under a less restrictive set of assumptions concerning the covariance matrix of the observations than is made in the context of the two-stage model. It is seen that the accuracies of prediction of the two methods, for this and other data sets, are quite close, suggesting that the less restrictive model may be preferred in many situations.

Animals↗
PubMed1994

Implementation of exact and approximate randomization tests for polynomial growth curves.

Two stand-alone, menu-driven PC programs, written in GAUSS386i, which compare groups of growth curves in a completely randomized design using either (a) exact or (b) approximate randomization tests, are described, illustrated, and made available to interested readers. The programs accommodate missing data in the context of studies planned to have common times of measurement, but where some of the measurement sequences are incomplete. The measurement whose growth is being monitored need not have a Gaussian distribution. We consider the hypothesis that the mean growth curves in G groups are the same; and either compute the exact P value (exact test), or estimate, and provide a confidence interval for, the P value (approximate test).

Algorithms↗
PubMed1994

Ultrasonic root-end preparation. Part 1. SEM analysis.

Preparations of apical cavities in resected root ends using rotary burs, with and without citric acid rinse, and ultrasonic tips were compared based on the presence or absence of superficial debris and smear layer. Three groups of 20 extracted teeth each were prepared as follows; I, a size 010 round bur was used to prepare an apical cavity 2-3 mm down the long axis of the root; II, treatment as per group I followed by a 60-s rinse with a solution of 10:3 (10% citric acid, 3% Fe2Cl3); and III, an ultrasonic retrotip was used to prepare a 2-3 mm deep apical cavity. Roots were grooved longitudinally, split and prepared for SEM analysis at x100 and x780 magnification. Examiners were calibrated to a standardized grading system. Extensive statistical analyses indicated statistically significant differences within and among the groups (P < 0.05). Root-end preparation with a bur created a heavy smear layer at all levels of the preparation. This layer was partially removed during ultrasonic preparation in the apical two-thirds. A greater removal of the smear layer was achieved with the citric acid rinse (P < 0.05). Coronally, root-end preparations were contaminated with moderate to heavy amounts of debris with all techniques.

Citrates↗
PubMed1994

A PC program for diagnosing abnormal growth, growth velocity and acceleration from longitudinal observations.

A PC program, written in GAUSS386i, implementing Zerbe's (Growth, 43 (1979) 263-272) procedure for diagnosis on the basis of longitudinal data is described, illustrated and made available to interested readers. Given longitudinal observations on N normal individuals, this technique can be used to characterize normal growth, velocity and acceleration, and to determine whether or not a new individual can be considered normal with respect to any or all of these parameters. Missing data are allowed, and there is no requirement that the variable whose growth is being monitored has a normal distribution. The method and program are illustrated using a data set with a substantial amount of missing data. Information on obtaining a copy of the program and hardware requirements are given in the Appendix.

Algorithms↗
PubMed1994

A PC program for computing McMahan's tracking indices from one-sample longitudinal data sets.

Tracking refers to regular, predictable growth behavior. Most definitions of the term are related to the idea that tracking occurs to the extent that individuals' repeated measurements maintain their relative positions in the distribution of the measurement whose growth is being monitored as that distribution changes over time. In this paper we describe four indices of tracking, all due to McMahan (Biometrics, 37 (1981) 447-455), which may be used to measure the extent to which a given longitudinal sample exhibits this 'regular behavior,' and we provide a program, written in GAUSS386i, for performing the associated computations. An example is given, and the values of McMahan's indices are compared to several alternative measures of tracking.

Algorithms↗
PubMed1993

Handling characteristics of gallium alloy for dental restoration.

The handling characteristics of a gallium alloy (Gallium Alloy GF) were compared to those of a spherical high-copper amalgam (Tytin). Ten dentists each restored four identical MO preparations in acrylic typodont teeth (no. 30), two with amalgam and two with gallium alloy. Each restoration was evaluated immediately following completion by the operator for six clinically relevant criteria. Each criterion was scored between 1 and 5, where 1 = very poor, 2 = poor, 3 = fair, 4 = good, and 5 = very good. Three two-sided Mann-Whitney tests were used to compare the median scores for significant differences (P < 0.05). The first test indicated no significant difference between scores for the first- and second-placed restorations, within criteria and within alloy type (n = 10). The second test indicated a significant difference between amalgam and gallium alloy, within criteria and within restoration sequence (n = 10), for each criterion except resistance to fracture during removal of the matrix band. The third test indicated a significant difference between amalgam and gallium alloy, within each criteria, combining scores for first- and second-placed restorations (n = 20). During simulated clinical placement, amalgam was rated significantly higher than gallium alloy in each handling characteristic evaluated.

Dental Alloys↗
PubMedDate not supplied

The level of cariogenic micro-organisms in patients with Sjögren's syndrome.

Sixteen patients with caries-inactive sjögren's syndrome with low parotid salivary flow rates (< 0.25 mL/min) and 18 caries-inactive control subjects with higher salivary flow rates were compared. Mutans streptococci (MS) and lactobacilli (LB) counts were measured by means of Dentocult SM strip mutans and LB assays. The group with Sjögren's syndrome displayed higher counts of MS (P = 0.014) and LB (p = 0.003) when compared with controls. The results of this study indicate that patients with caries-inactive Sjögren's syndrome and low salivary flow may have higher colonization of cariogenic micro-organisms than healthy individuals.

Aged↗
PubMedDate not supplied

The effect of glutaraldehyde pulpotomy treatment on pulpal enzymes.

The enzymes lactate dehydrogenase (LD), succinate dehydrogenase (SD), alkaline phosphatase (AP), and glucose-6-phosphate dehydrogenase (G-6-PD) were evaluated at specific locations in pulp tissue following glutaraldehyde pulpotomies. Pulpotomies were performed on maxillary first molars in 40 rats after sacrifice at times 0, 24 hr, seven days, or one month, and experimental teeth were treated with 6% buffered glutaraldehyde. Teeth were prepared for frozen sectioning and the sections were subjected to incubation media to detect each enzyme. Significant differences were found regarding the location of staining and the time intervals at which stain was present or absent. Staining for LD and AP was the most intense throughout the four observation time periods, though staining for these enzymes as well as for G-6-PD had begun to diminish by day seven in the coronal thirds. Staining was completely absent in the coronal thirds at one month but remained in the middle and apical thirds throughout one month. SD was the only enzyme that was totally absent in the coronal third at seven days and totally absent in the middle third at one month. These findings suggest that LD, AP, and the biochemical mechanisms that they represent remain active longer than SD and G-6-PD following exposure to glutaraldehyde. This information is important in identifying mechanisms that are important for repair, healing, and recovery following pulpal injury.

Alkaline Phosphatase↗
PubMedDate not supplied

Examination of esthetic improvement and surface alteration following microabrasion in fluorotic human incisors in vivo.

Improvement of appearance and alteration in surface enamel was evaluated following microabrasion of teeth with differing degrees of fluorosis stain in vivo. Eighty-two fluorotic permanent maxillary central incisors from 41 patients were divided into categories of mild (32), moderate (30), and severe (20). Teeth received 30-sec applications of PREMA until no stain remained or for a maximum of 10 min of treatment. Ten teeth needed only 5 min of treatment. All others received the maximum. Standardized intraoral photographs and duplicate polysiloxane impressions were taken prior to treatment, after 5 and 10 min of treatment, and at least 4 days after treatment. Slides were randomized and viewed independently by two standardized observers and rated for area of white spot lesions (WS), stain amount (SA), and stain intensity (SI). The Wilcoxon's signed rank test indicated a significant difference in the area of WS (P < 0.05) and SA and SI (P < 0.005) from pretreatment to successive ratings. Kruskal-Wallis analysis revealed significant differences among the three severity groups for amount of WS, SA, and SI (P < 0.005). Mildly stained teeth had the best esthetic result, moderately stained teeth improved but continued to demonstrate WS and staining, and severely stained teeth showed some improvement, but more than 50% of the surface had WS and > 25% of the surface was stained. SEMs at 10X magnification were made of the models and randomly rated for type, depth, description, and area of surface defects by the two observers. Mild teeth showed no significant changes from pretreatment to 10 min of treatment. Moderate and severe teeth showed no significant change in type and depth of defects from pretreatment to 10 min of treatment but were significantly worse in description and area of defects. Despite esthetic improvement in all groups, moderate and severe teeth showed more defective surfaces following microabrasion. This technique can only be recommended as definitive treatment for teeth with mild fluorosis.

Analysis of Variance↗