Technical note: two programs for performing multigroup longitudinal data analyses.
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Analysis of Variance↗
Biomedical subjects
C J Kowalski
Publications and source records attributed to C J Kowalski.
A PC program for growth prediction in the context of Rao's polynomial growth curve model.
We consider the problem of growth prediction in the context of Rao's [1] one-sample polynomial growth curve model and provide a PC program, written in GAUSS, to perform the associated computations. Specifically, 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 leave-one-out method on a sample of N = 12 male rhesus monkeys whose mandibular ramus height was measured five times at yearly intervals.
Animals↗
A PC program for performing multigroup longitudinal comparisons using the Potthoff-Roy analysis and orthogonal polynomials.
A PC-program performing the Potthoff-Roy (PR) multigroup (G-sample) analysis of longtidinal data is described and illustrated. This program and the underlying statistical model are useful in the comparison of several longitudinal samples. Applications include the study of growth, development, adaptation, aging, and treatment effects (in short, any phenomenon in which the passage of time is important) for which serial data are available. Specifically, this method fits polynomials to the average growth curves in the samples, and tests hypotheses concerning the curves themselves and the individual coefficients of the polynomials. The program features the utilization of orthogonal polynomial regression coefficients (OPRCs) and is written in GAUSS, a relatively inexpensive yet comprehensive matrix programming language. It is documented that using OPRCs to comprise the within-individual or time design matrix has several advantages over the more usual choice of the successive-powers-of-t form of this matrix and an example of one important such advantage is provided. GAUSS was employed to make the program readily-accessible (i.e., executable code) to biomedical investigators. The GAUSS compiler is not required to run this program. Information regarding the availability of the program is provided in the Appendix.
Child↗
A utility analysis of dental implants.
By applying a utility (usefulness) scale termed the "Feeling Thermometer" to 111 edentulous patients, a measure of effectiveness (quality-adjusted prosthesis years) that can be compared across several treatment strategies was developed. The results suggest that the utility scale was a valid (known group, P < .05), reliable (intraclass correlation coefficient = .713) measure of patients' preferences for the three treatment strategies: (1) conventional complete dentures (controls, n = 77), (2) transosteal implant-supported prostheses (n = 19), and (3) endosseous implant-supported prostheses (n = 15). The implant-treated patients rated their prostheses as high or higher (Feeling Thermometer score of 86.3 [endosseous] and 82.3 [transosteal]) than a functional fitting, esthetic conventional denture (score of 85.0 [endosseous] and 82.0 [transosteal]). They were also younger, more educated, and had received more sets of dentures (P < .05) than conventional denture patients.
Age Factors↗
Rao's polynomial growth curve model for unequal-time intervals: a menu-driven GAUSS program.
For lack of alternatives, longitudinal data are often analyzed with cross-sectional statistical methods, for instance, t-tests, ANOVA and ordinary least-squares regression. Appropriate statistical software has been generally unavailable to investigators using serial records to study growth and development or treatment effects. In an earlier paper (Schneiderman and Kowalski, Am. J. Phys. Anthropol., 67 (1985) 323-333.) we described a suitable method, Rao's polynomial growth curve model (Rao, Biometrika, 46 (1959) 49-58), and provided an SAS computer program for the analysis of a single sample of complete longitudinal data. This method included the computation of an average polynomial growth curve, its 95% confidence band, its coefficients and corresponding confidence intervals. The present paper extends this method to accommodate a sample with observations made at unequal time-intervals. Significant improvements in the accessibility, operation and user-friendliness of the program have been made, facilitated by recent advances in microcomputer technology. This stand-alone GAUSS program (no compiler necessary) runs on PC-compatibles and is available at a nominal cost. In this report we provide an overview of the statistical model, the general structure of the program, and give an example in which a developmental variable (human upper incisor angulation) is analyzed. Ease of installation and use, speed of execution and color graphic displays of growth curves and confidence bands, and most importantly, suitability to longitudinal data, make this method/program a potentially valuable tool for those interested in growth, development, and treatment effects in humans and other species. Some areas in which this method will have immediate applications are orthodontics, maxillofacial surgery and pediatrics.
Adolescent↗
Chemoprophylaxis of prosthetic joint patients during dental treatment: a decision-utility analysis.
A decision-analytic model and a cost effectiveness analysis was performed on 1 million hypothetic prosthetic joint patients undergoing dental treatment, to determine the most cost-effective strategy to prevent late prosthetic joint infections. The cost per quality-adjusted life-year saved (QALY) was determined for three preventive strategies: no prophylaxis, oral penicillin, and oral cephalexin. The UCLA Pain-Walking-Function-Activity Scale was used to obtain quality-of-life adjustments (utility assessment) for the study population. Costs were derived from 70 patients hospitalized between July 1, 1982, and June 30, 1986, at the UCLA Center for Health Sciences. The most cost-effective preventive strategy was the no prophylaxis alternative ($196,500/QALY). However, by recommending a 1-day strategy of oral cephalexin only to those dental patients at high risk for late prosthetic joint infections rather than a 3-day regimen to all patients, the cost effectiveness improved from $1.1 million/QALY to $446,100/QALY while maintaining a low risk of death (0.38 deaths per 10(6) dental visits).
Cephalexin↗
Attitude variables of dentofacial deformity patients: demographic characteristics and associations.
For patients to obtain satisfaction from surgical orthodontic treatment, a concordance needs to exist between the patients' concerns and expectations and the clinician's outcome measures of success. In this study, 231 patients 16 years or older were analyzed to define attributes of treatment that relate to patient satisfaction with outcome. The most prevalent patient concerns were related to facial and dental esthetics, and the effect of the dentofacial deformity on the quality of life was associated with a significantly higher motivation for surgical treatment.
Adolescent↗
Consistency of orthodontic treatment decisions relative to diagnostic records.
The purpose of this study was to evaluate how incremental information obtained from different types of diagnostic records contributes to the determination of orthodontic treatment decisions. Pretreatment records of 57 orthodontic patients were assessed by five orthodontists who were part-time faculty members and also in private practice. This sample consisted of dental school orthodontic patients who had Class II malocclusions and included patients at three different dental developmental stages. The following diagnostic records were used: study models (S), facial photographs (F), a panoramic radiograph (P), a lateral cephalogram (C), and its tracing (T). Five combinations of diagnostic records were presented to the orthodontists in the following sequence: (1) S; (2) S + F; (3) S + F + P; (4) S + F + P + C; and (5) S + F + P + C + T. The simultaneous interpretation of all diagnostic records (S + F + P + C + T) was used as the "diagnostic standard." There was a diagnostic standard for each of the patients and for each of the orthodontists. The diagnostic standard was achieved: (1) S = 54.9%, (2) S + F = 54.2%, (3) S + F + P = 60.9%, and (4) S + F + P + C = 59.9%. Thus, in a majority of cases (55%), study models alone provided adequate information for treatment planning, and incremental addition of information from other types of diagnostic records made small differences.
Adult↗
In vivo fluoride uptake of human root lesions using a fluoride-releasing device (short communication).
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Acid Etching, Dental↗
The duration of orthodontic treatment with and without extractions: a pilot study of five selected practices.
Contemporary orthodontic practice is diverse, both in the variety of clinical problems treated and in the methods used. Practices differ with respect to their patient composition as well as in many variables relative to treatment protocols. Such heterogeneity makes it difficult to make valid generalizations concerning the characteristics of orthodontic treatment procedures or outcomes; yet data and methods are required for assessment of issues of efficacy and utility. The frequency of orthodontic extractions is an objective criterion that distinguishes practices and may also be related to differences in treatment outcome variables, such as duration. Following a telephone survey to estimate extraction rates in the practices of 238 Michigan orthodontists, five practices with very high or low reported rates were chosen for this pilot study. Our primary aim was to determine whether a systematic relationship existed between the relative frequency of extraction treatments and the duration of active appliance therapy. Records of 438 patients from these practices were examined. The extraction rates of the practices ranged from a low of 25% to a high of 84%. Treatment duration was affected by several variables, such as the number of arches treated, the number of treatment phases, and the practice selected. When the data for all five practices were pooled, and all of the extraction versus nonextraction treatments were compared, the mean durations of treatment were 31.2 and 31.3 months, respectively. Data from individual practices, however, indicated that extraction treatment in each of the practices was of longer duration than nonextraction therapy. These differences in duration were 3.0, 6.6, 2.4, 3.0, and 7.3 months in the five practices.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
The prevalence of orthodontic extractions.
The controversy regarding extractions for orthodontic treatment continues and today is invoked by some as a feature of the "standard of care." For this and other reasons, it is necessary to have contemporary data on the general prevalence of orthodontic extractions and the interpractice range of extraction rates in current specialty practice and, if possible, also to establish possible reasons for, and consequences of, the extraction versus nonextraction decision. Although all treatment decisions are made on a case-by-case basis, practitioners appear to have personal preferences for or against extractions and hence adopt policies with different degrees of aversion to or bias toward extraction therapy. A number of factors enter into the extraction decision. These include features of the malocclusion, objectives of treatment, and the technique selected to accomplish desired results. The present study does not address such issues but merely serves to provide epidemiologic data to estimate extraction frequency in contemporary orthodontic practice. Accordingly, a telephone survey of all licensed orthodontists in Michigan was conducted to determine their subjective estimates of extraction rates for patients in their practices. There were 238 respondents, for a response rate of 90.2%. Reported rates range from 5% to 87%. We then selected five practices from the extremes of the reported extraction rates. Three practices from the high end and two from the low end were included for an examination of patient records. Records of a total of 438 patient whose treatment had been completed were reviewed. The actual extraction rates for these practices ranged from 25% to 85%, which differed considerably from the clinicians' subjective estimates.(ABSTRACT TRUNCATED AT 250 WORDS)
Evaluation Studies as Topic↗
Humoral immune response to selected subgingival plaque microorganisms in insulin-dependent diabetic children.
Juvenile diabetics have been shown to have an increased susceptibility to gingivitis and periodontitis following puberty. However, little data are available on changes in the microbial flora that occur at the onset of puberty. This study was performed to determine if antibacterial antibody titers to selected periodontal disease-associated microorganisms might be helpful in revealing changes in plaque flora at the onset and conclusion of puberty. Sera was obtained from 35 subjects (ages 7 to 18 years) selected from a population of insulin-dependent diabetics. The subjects were given a thorough medical examination which included an assessment of sexual maturation and a dental examination which included the recording of onset and magnitude of bleeding according to the papillary bleeding score. Antibody titers to A. naeslundii (AN), B. intermedius (BI), B. gingivalis (BG), F. nucleatum (FN), A. actinomycetemcomitans (AA), C. ochracea (CO) and T. denticola (TD) were determined using the microELISA. Stratification of antibody titers by age groups (less than or equal to 12 years, 12 to 15 years, greater than 15 years) revealed that titers to AN increased significantly (P less than 0.025, ANOVA) and progressively (P less than 0.05, regression analysis) with increasing age. In contrast, the titers to FN were maximal in the under 12 year group and decreased with age (ANOVA, P less than 0.05; regression analysis, P less than 0.05). There were no significant variations in titers observed for the other microorganisms. Stratification by sexual maturity revealed a similar progressive decrease of the titer to FN (ANOVA, P less than 0.05; regression analysis, P less than 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)
Actinomyces↗
The effects of periodontal therapy on serum antibody (IgG) levels to plaque microorganisms.
The influence of periodontal therapy on serum antibody titers to selected periodontal disease-associated microorganisms was assessed in 23 patients having chronic inflammatory periodontal disease (CIPD). The immunoglobulin G (IgG) titers were determined by the microELISA technique in serum samples obtained prior to treatment; following a hygienic phase which included scaling, root planing, and oral hygiene instruction; following surgical treatment; and one year and two years following hygienic phase (maintenance phase). Considerable individual variability existed in the magnitude of immune response to specific bacterial preparations. Significant reductions in the mean antibody titers were seen to A. viscosus, S. sanguis, F. nucleatum, S. sputigena, B. gingivalis, B. intermedius, B. melaninogenicus, T. vincentii, and T. denticola by the end of the second year of maintenance. There was no consistent response to Capnocytophaga. When individual patient responses were examined, 6 of the 23 were found to have elevated titers to at least one of the microorganisms in the interval between pretreatment and the end of the hygienic phase; however, in all but one case, the titers at the end of the second year of maintenance were below pretreatment levels. Antibody levels to bacteria such as S. sanguis were modified during therapy. This would indicate that immune responses to microbes not generally considered to be "periodontal pathogens" may be modified by adjuvant activity associated with subgingival plaque or changes in the environment of the sulcus and that subsequent changes in titer do not necessarily reflect a role of that microorganism in the disease process.
Adult↗
On the use of Good's L-statistic in the analysis of bacteriologic samples.
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Bacteria↗
Comparison of the effects of two topical fluoride regimens on demineralized enamel in vivo.
The purpose of this investigation was to study the intra-oral remineralization of acid-softened enamel by a NaF dentifrice compared with that from a combination of topical F agents. Bovine enamel slabs were demineralized with 0.1 mol/L lactic acid at pH 4.0 for 14 hr and then mounted in a removable mandibular appliance. Control slabs were worn for 96 hr by seven adult males who brushed daily with a F-free dentifrice. Test slabs were brushed with a NaF dentifrice 4 x/day or with the same dentifrice 4 x/day and a 0.02% APF mouthrinse and a 0.4% SnF2 gel which were applied once/day for three days. The natural dentition was also brushed with the NaF dentifrice during both test periods. Microhardness testing was performed on sound enamel, and after acid-softening, intra-oral exposure (IOE), and acid resistance testing (ART) in 0.01 mol/L lactic acid at pH 4.0 for 24 hr. Control and test slabs were etched with 0.5 mol/L HC1O4 for from 15 to 60 sec. The F content was measured with a F electrode and PO4 by spectrophotometry. Contact microradiography and image analyses were performed on control and test slabs so that changes in mineral content resulting from treatment could be assessed. Both test groups were significantly harder after both IOE and ART than were controls, but no differences appeared between the effects of the two test groups. The F content of control slabs was significantly less than that of both test groups, and the combination-treated slabs showed greater F than did the dentifrice-treated slabs.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
In vitro calcium release from four calcium hydroxide liners.
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Calcium↗
Effect of fibronectin on healing of replanted teeth in monkeys: a histologic and autoradiographic study.
The purpose of this study was to evaluate the effect of fibronectin application on healing of replanted teeth. Three rhesus monkeys were used. Maxillary and mandibular incisors and premolars were extracted and replanted. Teeth were extracted with forceps and placed in saline solution. After 5 minutes, each tooth was returned to its socket and immobilized by interproximal acid-etch splints, which were removed after 1 week. Of the forty-eight teeth replanted, twenty-four control teeth were replanted as described. On each of the remaining teeth, the root surface and the inner walls of the socket were bathed with 1 ml of fibronectin in saline solution (400 micrograms/ml) during the 5-minute interval between tooth extraction and its replantation. Replanted teeth and animal killings were scheduled to provide observations 1, 3, 7, 14, 28, and 45 days after replantation. Each monkey received an intravenous injection of tritiated thymidine, 1 microCi/g body weight, 1 hour before it was killed. Tissue specimens were processed for histologic and autoradiographic evaluation following standard procedures. For each of the six points of time, four pairs of contralateral teeth were available for evaluation; four teeth were treated with fibronectin and four without it. The findings of this study indicate that fibronectin use resulted in enhanced healing by early replacement of the fibrin clot, increased connective tissue cell proliferation, reduction of the inflammatory response, and inhibition of both cementum resorption and dentoalveolar ankylosis.
Animals↗
Intra-oral effects on acid-softened enamel of NaF lozenges administered in divided daily doses.
The purpose of this investigation was to study the intra-oral effects of multiple daily applications of NaF lozenges upon acid-softened enamel. Bovine enamel slabs were softened with 0.1 mol/L lactate buffer at pH 4.0 for 14 hrs and subsequently mounted in a mandibular removable Hawley appliance. Control slabs were worn for seven days by eight adult male subjects who brushed their natural dentition daily with a fluoride-free dentifrice. Test slabs were exposed to one 0.55-mg NaF lozenge (0.25 mg F) 4x/day for seven days and the natural dentition brushed with a fluoride-free dentifrice. The efficacy of 0.25-mg F lozenges used 4x/day over that of a 1-mg F lozenge administered 1x/day was established by a pilot study with two subjects. Microhardness testing was performed after intra-oral exposure (IOE) and following immersion in 0.01 mol/L lactate buffer containing Ca and PO4 for 24 hrs at a pH of 4.0. Fluoride uptake was measured on separate control and test slabs after KOH wash and after acid-resistance-testing (ART). Recovery of microhardness following IOE was 40.9% for controls and 53.9% for treated slabs, while control slabs retained 1.3% resistance to ART, compared with 25.6% for test slabs. The F content of the control slabs was significantly less than that of lozenge-treated and lozenge-treated-ART slabs throughout the depth of the lesion. The F content of the lozenge-treated-ART slabs was significantly less than that of the lozenge-treated slabs only at the 0-5-microns depth.(ABSTRACT TRUNCATED AT 250 WORDS)
Administration, Oral↗