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PubMed2004

The impact of post space preparation with Gates-Glidden drills on residual dentin thickness in distal roots of mandibular molars.

BACKGROUND: Posts frequently are used to retain buildups. The authors examined the effects of post space preparation with Gates-Glidden drills on residual dentin thickness in distal roots of mandibular molars. METHODS: The authors embedded 26 root-treated mandibular molars in endodontic cubes and sectioned them perpendicularly to their long axis at 1.8-millimeter intervals. They placed Gates-Glidden drills nos. 3, 4, 5 and 6 sequentially to 5 mm short of working length in the distal canals. After using each drill size, the authors measured the dentin thickness from light microscopic images of the tooth slices. RESULTS: The authors analyzed data to detect changes resulting from canal instrumentation. They performed statistical analysis by partitioning the variability in a nested analysis of variance. Strip perforations occurred with a no. 4 Gates-Glidden drill 7.3 percent of the time and more frequently with larger drills. After endodontic treatment alone, the canal wall on the furcal side was less than 1 mm thick 82 percent of the time and less than 0.5 mm thick 17.5 percent of the time. CONCLUSIONS: Dentin thickness correlates inversely to post space diameter. A no. 4 Gates-Glidden drill caused strip perforations in 7.3 percent of the canals studied, and therefore the authors recommend that Gates-Glidden drills larger than a no. 3 not be used in these roots. After endodontic treatment, the furcation-side dentin thickness was less than 1 mm in 82 percent of the teeth. CLINICAL IMPLICATIONS: Post space preparation in mandibular molars carries significant risk of perforation. Post space in such teeth should be limited to the endodontically prepared canal.

Dental Instruments↗

PubMed2005

Threshold and variability properties of matrix frequency-doubling technology and standard automated perimetry in glaucoma.

PURPOSE: To compare test results from second-generation Frequency-Doubling Technology perimetry (FDT2, Humphrey Matrix; Carl-Zeiss Meditec, Dublin, CA) and standard automated perimetry (SAP) in patients with glaucoma. Specifically, to examine the relationship between visual field sensitivity and test-retest variability and to compare total and pattern deviation probability maps between both techniques. METHODS: Fifteen patients with glaucoma who had early to moderately advanced visual field loss with SAP (mean MD, -4.0 dB; range, +0.2 to -16.1) were enrolled in the study. Patients attended three sessions. During each session, one eye was examined twice with FDT2 (24-2 threshold test) and twice with SAP (Swedish Interactive Threshold Algorithm [SITA] Standard 24-2 test), in random order. We compared threshold values between FDT2 and SAP at test locations with similar visual field coordinates. Test-retest variability, established in terms of test-retest intervals and standard deviations (SDs), was investigated as a function of visual field sensitivity (estimated by baseline threshold and mean threshold, respectively). The magnitude of visual field defects apparent in total and pattern deviation probability maps were compared between both techniques by ordinal scoring. RESULTS: The global visual field indices mean deviation (MD) and pattern standard deviation (PSD) of FDT2 and SAP correlated highly (r > 0.8; P < 0.001). At test locations with high sensitivity (>25 dB with SAP), threshold estimates from FDT2 and SAP exhibited a close, linear relationship, with a slope of approximately 2.0. However, at test locations with lower sensitivity, the relationship was much weaker and ceased to be linear. In comparison with FDT2, SAP showed a slightly larger proportion of test locations with absolute defects (3.0% vs. 2.2% with SAP and FDT2, respectively, P < 0.001). Whereas SAP showed a significant increase in test-retest variability at test locations with lower sensitivity (P < 0.001), there was no relationship between variability and sensitivity with FDT2 (P = 0.46). In comparison with SAP, FDT2 exhibited narrower test-retest intervals at test locations with lower sensitivity (SAP thresholds <25 dB). A comparison of the total and pattern deviation maps between both techniques showed that the total deviation analyses of FDT2 may slightly underestimate the visual field loss apparent with SAP. However, the pattern-deviation maps of both instruments agreed well with each other. CONCLUSIONS: The test-retest variability of FDT2 is uniform over the measurement range of the instrument. These properties may provide advantages for the monitoring of patients with glaucoma that should be investigated in longitudinal studies.

Aged↗

PubMed1998

Effects of systemic hypoxia on R-R interval and blood pressure variabilities in conscious rats.

The effects of systemic hypoxia with different levels of CO2 on R-R interval (RRI) and systolic blood pressure (SBP) variabilities were investigated in conscious rats. Wistar rats chronically instrumented for the measurement of blood pressure, electrocardiogram, and renal sympathetic nerve activity (RSNA) were exposed to hypocapnic (Hypo), isocapnic (Iso), and hypercapnic (Hyper) hypoxia. On another day, the rats were treated with atropine and exposed to the same type of hypoxia. Sinoaortic denervation (SAD)-treated rats were exposed to Iso and Hyper, and RRI and SBP variabilities before and during hypoxia were analyzed using the maximum-entropy method with high resolution. With regard to RRI variability, very low frequency (VLF), low frequency (LF), and high frequency (HF) powers all decreased during Hypo, increased during Hyper, and did not change during Iso in intact rats. Changes during Hypo were attenuated by atropine, and those during Hyper were abolished by either atropine or SAD. The ratio of LF power to HF power decreased independently of increases in RSNA during each type of hypoxia. On the other hand, there were no changes in VLF, LF, or HF power in SBP variability during each type of hypoxia in intact rats. In atropine-treated rats, LF power increased during Iso and Hyper and HF power increased during each type of hypoxia. There was no difference in respiratory frequency among the three kinds of hypoxia in both intact and atropine-treated rats. The results suggest that arterial PCO2 level rather than respiration frequency produces changes in powers of RRI variability through changes in parasympathetic nerve activity and that with regard to SBP variability, parasympathetic nerve activity masks changes in LF power that reflect an increase in RSNA and those in HF power that reflect a mechanical consequence of respiration.

Animals↗

PubMed1999

Performance on the Wisconsin Card Sorting Test after traumatic brain injury.

The performance of 100 patients with traumatic brain injury (TBI) on the Wisconsin Card Sorting Test (WCST) was examined to determine the underlying latent structure as well as profile subtypes. Exploratory factor analysis with oblique rotation identified three factors: response accuracy, learning, and failure to maintain set. Marker variables from each factor were then included in a two-stage cluster analysis, which identified two reliable subtypes. Level of performance differences between these subtypes were meaningfully related to both demographic background and length of coma. It is concluded that interpretation of the WCST results of patients with TBI should consider the multifactorial nature of the instrument in combination with injury severity characteristics and demographic variables.

Adolescent↗

PubMed1999

Differences in whole body measurements by DXA-scanning using two Lunar DPX-L machines.

OBJECTIVE: To compare bone mineral and body composition results of two dual-energy X-ray absorptiometry (DXA) instruments from the same manufacturer. SETTINGS: The Medical departments of Sahlgrenska University Hospital, Göteborg and University Hospital, Uppsala, Sweden. DESIGN: Unique aluminium spine phantoms (Phant A and B) delivered with each DXA machine (DXA-A and DXA-B) were cross-checked on the other machine by using the 'AP spine mode'. Eight adolescents were examined on both instruments within 5 h to ascertain total body variables by using standard, as well as extended, modes of analysis. All these double-examinations were undertaken on two occasions, before and after exchange of a detector on the DXA-B. SUBJECTS: Four males and four females aged 15.4-19.2 y with normal body weights, were examined on both occasions. On each occasion, the first examination was performed in Göteborg on four individuals and in Uppsala on four individuals. RESULTS: On the first occasion the phantom measurements resulted in much lower bone mineral density (BMD) values on the DXA-B than on the DXA-A. Later it was detected that a so-called R-value and the corresponding '%-fat' value were out of range on the DXA-B. After exchange of detector, the difference in phantom BMD-values between the two machines had diminished. On the first occasion in vivo BMD values were lowest on the DXA-B (P < 0.01), while on the second occasion they were significantly lower on the DXA-A (P < 0.05). Soft tissue differences were greater after detector exchange and as compared to DXA-A, DXA-B underestimated body fat by 3.5 kg (13.2 vs 9.7 kg, P < 0.001) and overestimated lean tissue mass by 3.8 kg (47.1 vs 50.9 kg, P < 0.001) on the second occasion. CONCLUSIONS: The differences in results between two apparently identical Lunar DPX-L machines were not acceptable. In multicenter studies, it may be necessary to standardise results of participating machines into results of one machine by means of regression equations obtained by examining subsamples of individuals on one master machine and other participating instruments.

Absorptiometry, Photon↗

PubMedDate not supplied

An examination of bias in shoulder scoring instruments among healthy collegiate and recreational athletes.

This investigation examined whether gender, activity level, hand dominance, or age displayed bias for 5 common shoulder scores among 120 healthy collegiate or recreational athletes. Data were collected for 5 instruments: Constant-Murley, UCLA rating, pre-1994 American Shoulder and Elbow Surgeons, Shoulder Pain and Disability Index, and Oxford. Normalized total and subscale scores and effect sizes were analyzed to determine how each demographic variable affected the scores. The normalized scores for the 5 instruments were not equivalent. The normalized total scores were significantly lower for the Constant-Murley score (P <.0001) compared with those for the other instruments. Men had significantly higher Constant-Murley scores, primarily because of the strength subscale. The Constant-Murley score also displayed gender and age biases. The other instruments had mostly negligible variance attributable to gender, activity level, hand dominance, or age. In the absence of a universal validated method, shoulder scoring instruments should be carefully chosen to match the population and the purpose of the study.

Adolescent↗

PubMed2005

Real-time synthesis of clarinet-like instruments using digital impedance models.

A real-time synthesis model of wind instruments sounds, based upon a classical physical model, is presented. The physical model describes the nonlinear coupling between the resonator and the excitor through the Bernoulli equation. While most synthesis methods use wave variables and their sampled equivalent in order to describe the resonator of the instrument, the synthesis model presented here uses sampled versions of the physical variables all along the synthesis process, and hence constitutes a straightforward digital transposition of each part of the physical model. Moreover, the resolution scheme of the problem (i.e., the synthesis algorithm) is explicit and all the parameters of the algorithm are expressed analytically as functions of the physical and the control parameters.

Journal Article↗

PubMed2001

Paranoid ideation among elderly African American persons.

PURPOSE: The prevalence and correlates of paranoid ideation were investigated. DESIGN AND METHODS: On the basis of a sample of 998 independently living elderly African American persons in a cross-sectional study, the study used the Brief Symptom Inventory to measure paranoid ideation and 14 independent variables, including demographic characteristics, cognitive deficit, depression, self-reported memory functioning, emotional and instrumental support, stressful life events, limitation of daily activities, self-rated health status, and self-rated hearing and vision. RESULTS AND IMPLICATIONS: Paranoid ideation (symptoms of paranoia) was found in 10% of this sample. A multiple regression analysis of the data revealed that of the 14 independent variables used in this study, 6 (income, instrumental support, hearing, stressful life events, self-reported memory deficit, and depression) showed a significant relationship with paranoid ideation.

Black or African American↗

PubMed2001

An electropalatographic investigation of middorsum palatal stops in an adult with repaired cleft palate.

OBJECTIVE: Middorsum palatal stops are compensatory articulations that occur relatively frequently in cleft palate speech. This study used electropalatographic (EPG) and acoustic data to investigate /t/ and /k/ targets produced as middorsum palatal stops ([c]) by an adult with an articulation disorder associated with a repaired cleft palate. RESULTS: Two novel observations were made from the instrumental data. First, although /t/ and /k/ targets were judged by phonetically trained listeners as homophonous (i.e., both produced as [c]), the EPG data revealed that the place of articulation for the [c] produced for /t/ was more anterior than the place of articulation for the [c] produced for /k/. Second, production of palatal stops involved lateral release followed by a variable period of lateral friction. Measurements made from the instrumental data quantified the temporal extent of lateral friction during the aspiration period. CONCLUSIONS: These observations merit further systematic investigation in cleft palate speech, and the procedures reported in this study are considered appropriate for such future research.

Adult↗

PubMed1989

High-frequency monitoring using an electrostimulation audiometer.

Electrostimulation audiometry can provide high-frequency bone-conduction threshold measurements. To evaluate the use of such an audiometer in monitoring hearing, the following areas were investigated. (1) The variability and repeatability of threshold measurements. (2) To see if the instrument could be used on the ward where the patient would have to wear ear plugs to attenuate background noise, the effect of occluding the ears was assessed. (3) The applicability of the instrument to the range of patients in whom monitoring would be appropriate, specifically the relationship between the patient's age and the effective upper frequency limit of the audiometer. The data showed a variability in threshold measurement that is quite comparable with that obtained with conventional audiometry but which became smaller at frequencies of 12 kHz and higher. There was no overall effect on the threshold of occluding the ears, which meant that the instrument can be used to monitor a non-isolated environment such as a ward. The effective cut-off frequency was about 9 kHz for patients aged 55 years, and so the use of an electrostimulation audiometer to monitor high-frequency auditory thresholds is restricted to younger patients.

Adult↗

PubMed1993

An analysis of variability of left ventricular pressure decay.

This study evaluated whether the time course of left ventricular (LV) pressure decay is consistent from beat to beat in the normal heart under tightly controlled experimental conditions. We determined the variability of LV isovolumic relaxation and compared it with that of other hemodynamic parameters. Pressure decay was evaluated using a monoexponential time constant (T), a half-time (T1/2), and an average rate (Ravg) in nine chronically instrumented dogs. To eliminate physical factors that could lead to variability, the dogs were studied at paced heart rates after autonomic blockade and during apnea. At a heart rate of 160 beats/min the coefficient of variation (SD/mean, expressed as a percent) was higher for T (4.7%, P < 0.005), T1/2 (5.0%, P < 0.005), and Ravg (3.2%, P < 0.005) than for dP/dtmax (1.9%), as well as for end-diastolic volume (1.2%), end-systolic volume (1.2%), or end-systolic pressure (1.8%). Similar differences were present at 200 beats/min. Pressure decay was also assessed during major loading shifts induced by rapid caval occlusion. Surprisingly, comparison of first and last beats did not show significant differences for T or T1/2 but did for all standard hemodynamic parameters and for Ravg. While the best correlation with a relaxation parameter and hemodynamic parameters during changing loading conditions was for Ravg, the correlations were not consistent in every case. We conclude that LV pressure decay shows marked variability, unrelated to the algorithm used to assess it. Ravg, a model independent parameter, may be a useful way to quantify LV pressure fall.

Animals↗

PubMed2000

Evaluation of a new body composition phantom for quality control and cross-calibration of DXA devices.

This study evaluated a new body composition phantom and its use for quality control and cross-calibration of dual-energy X-ray absorptiometry (DXA) instruments for measurements of body composition. We imaged the variable composition phantom (Lunar, Madison, WI) on eight different DXA devices. Deviations of up to 7% fat were observed when we compared the percent fat values measured by the different devices with the nominal values provided by the manufacturer. Absolute precision error of percent fat measurements for the phantom ranged from 0.6 to 0.8%. The phantom's percent fat values were also compared with whole body composition measurements from 130 female and male volunteers. The phantom detected differences in percent fat values that were similar to those found by comparing in vivo measurements with values from different DXA scanner models from the same manufacturer. When comparing different models of scanners from different manufacturers, such as the Hologic QDR-4500 and the Lunar DPX-IQ, the phantom showed a different relationship than was seen for patients. Therefore, corrections or comparisons based on the phantom data alone would be incorrect. In conclusion, the Lunar variable composition phantom is capable of accurately measuring the fat calibration of DXA devices and may be suitable for cross-sectional cross-calibration between scanners from the same manufacturer; however, for comparison of DXA scanners from different manufacturers, in vivo cross-calibration is still the only accurate method. The phantom may be used in longitudinal quality control to verify an instrument's temporal stability.

Absorptiometry, Photon↗

PubMed2003

Experimental factors affecting the quality and reproducibility of MALDI TOF mass spectra obtained from whole bacteria cells.

Numerous experimental factors are shown to significantly influence the spectra obtained when bacteria are analyzed by MALDI TOF/MS. Detailed investigation of the instrument parameters and sample preparation are all shown to influence the spectra. Of these, the preanalysis sample preparation steps incorporate the most important elements influencing the quality and reproducibility of the spectra. Some of the most important sample preparation factors include the method employed for sterilization, the type of matrix, the matrix solvent and concentration of cells in the matrix, as well as the type and concentration of acid added to the matrix. The effects of these parameters, as well as other aspects of sample preparation and the effects of several instrumental parameters on spectra are presented. Optimization and control of all experimental variables leads to a stable protocol for analysis of bacteria. The protocol employs a Nd:Yag laser and describes both sample handling and instrument conditions which consistently yield reproducible MALDI TOF mass spectra with greater than 25 peaks from both gram-positive and gram-negative bacteria.

Acids↗

PubMed2003

Predicting clinical end points: treatment nomograms in prostate cancer.

Due to the generally indolent nature of prostate cancer, patients must decide among a wide range of treatments, which will significantly affect both quality of life and survival. Thus, there is a need for instruments to aid patients and their physicians in decision analysis. Nomograms are instruments that predict outcomes for the individual patient. Using algorithms that incorporate multiple variables, nomograms calculate the predicted probability that a patient will reach a clinical end point of interest. Nomograms tend to outperform both expert clinicians and predictive instruments based on risk grouping. We outline principles for nomogram construction, including considerations for choice of clinical end points and appropriate predictive variables, and methods for model validation. Currently, nomograms are available to predict progression-free probability after several primary treatments for localized prostate cancer. There is need for additional models that predict other clinical end points, especially survival adjusted for quality of life.

Algorithms↗

PubMed1995

A critical appraisal of toxicity indexes in rheumatology.

Our objective was to design a grading system to judge the methodological quality of toxicity symptoms assessment in rheumatologic randomized controlled trials, and to use this grading system to evaluate rheumatology case report forms. For comparison, we also evaluated instruments derived in other clinical specialties. To further determine whether variability seen on the rheumatology case report forms would lead to variability of side effect measurement in a clinical trial setting, we conducted a survey of investigators and their coordinators in a multicenter randomized trial. We used Feinstein's definition of sensibility and a conceptual model of the process of toxicity measurement in the clinical trial setting to develop a grading system. Thirty case report forms were obtained from a convenience sample, and 7 other instruments from other disciplines were obtained through literature review. These forms were evaluated in a blinded manner by 3 reviewers. A survey of 30 trial staff from 15 centers involved in a multicenter, randomized trial of 2 active nonsteroidal antiinflammatory drugs (NSAID) in rheumatoid arthritis (RA) was undertaken to evaluate whether the variability identified in the review of the case report forms translated into variability in the measurement of side effects in clinical trial setting. The rheumatology case report forms had a mean score of 9.1 (SD = 2.6) out of 20, where 0 is the worst score and 20 is a perfect score. The structured instruments from other disciplines had a mean score of 14.9 (SD = 2.7). These means were significantly different, with p = 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)

Adverse Drug Reaction Reporting Systems↗

PubMed1999

Reliability of an ear-bow arbitrary face-bow transfer instrument.

STATEMENT OF PROBLEM: Accuracy of techniques for recording the orientation of the maxillary arch to the articulation of the temporomandibular joints has been reported. The variability contributed by the dentist and the equipment within a technique may also contribute to technical error. PURPOSE: This study investigated the variability of a group of dentists who used an arbitrary ear-face-bow instrument to mount a maxillary cast. MATERIAL AND METHODS: The same maxillary cast on a single experimental subject was mounted on an articulator with a common arbitrary ear-face-bow instrument. This cast was equipped with 4 reference points for the measurement of changes of spatial orientation of the cast, which were determined through coordinate measurements with a machinist's microscope. A repeated measures analysis of variance was used to determine statistically significant changes in spatial orientation with a Wilks' Lambda test to compare mean values. RESULTS: A confidence interval of 95% demonstrated that any dentist might expect a range of +/-1.2 mm error in using this instrument/articulator combination. The 3 dentists did not demonstrate any significant differences in the spatial orientation of their mountings in the vertical or horizontal directions. However, there were significant differences in their mountings in linear distance changes of the patient's posterior right side. CONCLUSION: A range of inherent error attributable to the operator using this instrument was recorded.

Analysis of Variance↗

PubMed2006

The high variability of tibial rotational alignment in total knee arthroplasty.

Although various techniques are advocated to establish tibial rotational alignment during total knee arthroplasty, it is unknown which is most repeatable. We evaluated the precision and accuracy of five tibial rotational alignment techniques to determine whether computer-assisted navigation systems can reduce variability of tibial component rotational alignment when compared to traditional instrumentation. Eleven orthopaedic surgeons used four computer-assisted techniques that required identification of anatomical landmarks and one that used traditional extramedullary instrumentation to establish tibial rotational alignment axes on 10 cadaver legs. Two computer-assisted techniques (axes between the most medial and lateral border of the tibial plateau, and between the posterior cruciate ligament [PCL] and the anterior tibial crest) and the traditional technique were least variable, with standard deviations of 9.9 degrees, 10.8 degrees, and 12.1 degrees, respectively. Computer-assisted techniques referencing the tibial tubercle (axes between the PCL and the medial border or medial 1/3 of the tubercle) were most variable, with standard deviations of 27.4 degrees and 28.1 degrees. The axis between the medial border of the tibial tubercle and the PCL was internally rotated compared to the other techniques. None of the techniques consistently established tibial rotational alignment, and navigation systems that establish rotational alignment by identifying anatomic landmarks were not more reliable than traditional instrumentation.

Arthroplasty, Replacement, Knee↗

PubMed1990

Patient satisfaction survey instrument for use in health maintenance organizations.

The objective of this research was to devise a survey instrument specifically applicable to prepaid health care plans that could accurately predict whether patients would disenroll from their current plan because of dissatisfaction when given the opportunity to do so. A "prequestionnaire" was sent to all employees at a southwestern university whose employee benefit package included the option of selecting one of several health maintenance organizations (HMOs) as a source of health care. The prequestionnaire included 90 variables reported in the literature as related to patient satisfaction. The prequestionnaire was mailed two months before "open enrollment," the time at which subjects would have the opportunity, if desired, to change HMOs. After open enrollment, a "postquestionnaire" was sent to the same subjects, asking whether or not they did change plans during open enrollment. There were 2,365 respondents enrolled in HMOs who formed the study population. Of these, 189 (8.0%) changed HMOs during open enrollment. Discriminant function analysis was used to identify prequestionnaire variables which were predictive that subjects had changed plans; 10 variables were identified. They were combined into a survey instrument, which can be scored to predict an individual subject's probability of changing plans.

Arizona↗