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Biomedical subjects

S Baumrind

Publications and source records attributed to S Baumrind.

At least 19 recordsLinked to original sources
PubMed2002

The relationship between apical root resorption and orthodontic tooth movement in growing subjects.

OBJECTIVE: To investigate the relationship between apical root resorption and orthodontic tooth movement in growing subjects. METHODS: 58 growing subjects were collected randomly into the study sample and another 40 non-treated cases were used as control. The apical resoption of the upper central incisors was measured on periapical film and the incisor displacement was measured on lateral cephalogram. Using multiple linear regression analysis to examine the relationship between root resoption and the displacement of the upper incisor apex in each of four direction (retraction, advancement, intrusion and extrusion). RESULTS: The statistically significant negative association were found between resorption and both intrusion (P < 0.001) and extrusion (P < 0.05), but no significant association was found between resorption and both retraction and advancement. The regression analysis implied an average of 2.29 mm resorption in the absence of apical displacement. CONCLUSIONS: The likelihood that the magnitude of displacement of the incisor root is positively associated with root resoption in the population of treated growing subjects is very small.

Humans↗
PubMed2001

[Inferring landmark displacements from changes in cephalometric angles].

OBJECTIVE: To investigate the appropriateness of using changes in angular measurements to reflect the actually profile changes. METHODS: The sample consists of 48 growing malocclusion patients, contained 24 Class I and 24 Class II subjects, treated by an experienced orthodontist using Edgewise technique. Landmark and superimpositional data were extracted from the previously prepared numerical database. Three pairs of angular and linear measures were computed by the Craniofacial Software Package. RESULTS: Although the associations between all three angular measures and their corresponding linear measures are statistically significant at the 0.001 level, the disagreement between these three pairs of measures are 10.4%, 22.9% and 37.5% respectively in this sample. CONCLUSIONS: The direction of displacement of anterior facial landmarks during growth and treatment cannot reliably be inferred merely from changes in cephalometric Angles.

Cephalometry↗
PubMed2000

[Sensitivity of four representative angular cephalometric measures].

OBJECTIVE: Examined the sensitivity of four representative cephalometric angles to the detection of different vectors of craniofacial growth. METHODS: Landmark coordinate data from a stratified random sample of 48 adolescent subjects were used to calculate conventional values for changes between the pretreatment and end-of-treatment lateral cephalograms. By modifying the end-of-treatment coordinate values appropriately, the angular changes could be recalculated reflecting three hypothetical situations: Case 1. What if there were no downward landmark displacement between timepoints? Case 2. What if there were no forward landmark displacement between timepoints? Case 3. What if there were no Nasion change? These questions were asked for four representative cephalometric angles: SNA, ANB, NAPg and UI-SN. RESULTS: For Case 1, the associations (r) between the baseline and the modified measure for the three angles were very highly significant (P < 0.001) with r2 values no lower than 0.94! For Case 2, however, the associations were much weaker and no r value reached significance. CONCLUSIONS: These angular measurements are less sensitive for measuring downward landmark displacement than they are for measuring forward landmark displacement.

Cephalometry↗
PubMed1999

Some comments on clinical studies in orthodontics and their applications to orthodontic treatment.

This article indicates the origins and background of the current series of National Institute of Dental and Craniofacial Research-funded, university-based clinical studies of orthodontic treatment. It suggests that future studies should be less focused on refining our estimates of mean changes during treatment and concentrate research on the systematic analysis of individual differences among patients' responses to treatment, and study how skilled clinicians make in-course corrections in response to unexpected changes in treatment conditions. Finally, some suggestions are made concerning optimization of decision making in the presence of uncertainty.

Clinical Trials as Topic↗
PubMed1999

[Evaluation of Wits appraisal with superimposition method].

OBJECTIVE: To compare the conventional Wits appraisal with superimposed Wits appraisal in evaluation of sagittal jaw relationship change between pre and post orthodontic treatment. METHODS: The sample consists of 48-case pre and post treatment lateral head films. Computerized digitizing is used to get the cephalometric landmarks and measure conventional Wits value, superimposed Wits value and ANB angle. The correlation analysis among these three measures was done by SAS statistical package. RESULTS: The change of ANB angle has higher correlation with the change of superimposed Wits than that of the conventional Wits. The r-value is as high as 0.849 (P < 0.001). CONCLUSION: The superimposed Wits appraisal reflects the change of sagittal jaw relationship more objectively than the conventional one.

Cephalometry↗
PubMed1998

Etiology and sequelae of root resorption.

This article reviews the current status of investigation into apical root resorption within the context of orthodontic treatment. Treatment and patient factors that have traditionally been investigated are discussed, along with the results of current research in this area. The need for rethinking traditional research strategies in the quest for identifying both control and causative mechanisms is explored. Finally, proposals for key areas of future interest are highlighted.

Animals↗
PubMed1998

Unbiased quantitative testing of conventional orthodontic beliefs.

This study used a preexisting database to test in hypothesis from the appropriateness of some common orthodontic beliefs concerning upper first molar displacement and changes in facial morphology associated with conventional full bonded/banded treatment in growing subjects. In an initial pass, the author used data from a stratified random sample of 48 subjects drawn retrospectively from the practice of a single, experienced orthodontist. This sample consisted of 4 subgroups of 12 subjects each: Class I nonextraction, Class I extraction, Class II nonextraction, and Class II extraction. The findings indicate that, relative to the facial profile, chin point did not, on average, displace anteriorly during treatment, either overall or in any subgroup. Relative to the facial profile, Point A became significantly less prominent during treatment, both overall and in each subgroup. The best estimate of the mean displacement of the upper molar cusp relative to superimposition on Anterior Cranial Base was in the mesial direction in each of the four subgroups. In only one extraction subject out of 24 did the cusp appear to be displaced distally. Mesial molar cusp displacement was significantly greater in the Class II extraction subgroup than in the Class II nonextraction subgroup. Relative to superimposition on anatomical "best fit" of maxillary structures, the findings for molar cusp displacement were similar, but even more dramatic. Mean mesial migration was highly significant in both the Class II nonextraction and Class II extraction subgroups. In no subject in the entire sample was distal displacement noted relative to this superimposition. Mean increase in anterior Total Face Height was significantly greater in the Class II extraction subgroup than in the Class II nonextraction subgroup. (This finding was contrary to the author's original expectation.) The generalizability of the findings from the initial pass to other treated growing subjects was then assessed by retesting modified hypotheses against a second database stored sample that earlier had been drawn randomly from two other orthodontic practices. The implications of the author's study strategy to the design of future shared digital databases is discussed briefly.

Cephalometry↗
PubMed1998

Misinterpreting growth and treatment outcome from serial cephalographs.

This communication addresses the issue of interpretation of serial cephalometric records. Angular measurements provide information that combines the vertical and sagittal components of a landmark's displacement. For example, a decrease in the SNA angle following orthodontic treatment with a headgear demonstrates maxillary retraction relative to nasion, an important assessment to depict a change closely related to the facial profile. Upon superimposition on the anterior cranial base, however, the vertical movement of point A may be the prevalent displacement, which would still account for the decrease in the SNA angle. The superposition allows the evaluation of the displacement in its vertical and sagittal components separately, relative to a structure that is relatively more stable than nasion. The superimposition enhanced the precision of the information regarding the actual displacement of the jaw. A patient's cephalometric records are presented, further demonstrating that the interpretation of changes during growth and treatment should be based not only on angular measurements, but also on regional superpositions. The frames of reference of both procedures are needed to fully understand the facial changes.

Cephalometry↗
PubMed1998

Adult orthodontic therapy: extraction versus non-extraction.

This study addresses the problem of randomization of subjects with respect to an irreversible aspect of treatment strategy, namely, the extraction of teeth. The investigation includes both prospective and retrospective components. The data presented focus on clinician decision-making. Of the 1321 potential subjects for whom records were taken, 250 met the inclusion criteria. Of these subjects, 82 declined to participate and 20 were dropped because of difficulty in obtaining five independent evaluations of their records within a reasonable time frame. Thus, the final sample contained 148 subjects. Approximately one-third of the subjects in the sample are adult, somewhat more than half are female, and Class I malocclusions outnumber Class II malocclusions by a count of 95 to 53. Patterns of agreement and disagreement among five clinicians include: a) agreement/disagreement on the primary decision whether or not to extract: the data reveal a strong tendency towards consensus among the clinicians; b) agreement/disagreement on extraction pattern in patients in whom the clinician believes that extraction is indicated: the clinicians tended strongly to agree on extraction pattern; c) agreement/disagreement on the need for adjunctive orthognathic surgery: decisions favoring surgery were more common and more 'definite' than 'probable' in the adult cohort than in the adolescent cohort but this tendency was not as strong as had been anticipated; d) agreement/disagreement concerning Angle classification: disagreements were more common than had been anticipated; and e) differences among the individual clinicians as to their ratios of extraction/non-extraction decisions: overall, clinicians opted for extraction less frequently in the adolescent cohort than in the adult cohort (55 vs. 66%). Because the data are drawn from actual clinical experience, the conclusions involve a number of assumptions and their generalizability should be evaluated.

Adolescent↗
PubMed1998

Clinical studies in orthodontics--an overview of NIDR-sponsored clinical orthodontic studies in the US.

A number of clinical trials sponsored by the National Institutes of Health (NIH) use rigorous methods of data acquisition and analysis previously developed in fundamental biology and the physical sciences. The naive expectation that these trials would lead relatively rapidly to definitive answers concerning the therapeutic strategies and techniques under study is dispelled. This presentation focuses on delineating differences between the study of central tendencies and individual variation, more specifically on the strategy to study this variation: measure additional sources of variance within each patient at more timepoints and perhaps with greater precision. As rigorous orthodontic research is still in its infancy, the problem of defining the proper mix between prospective and retrospective trials is discussed. In view of the high costs of prospective clinical trials, many of the questions germane to orthodontics can be answered by well-conducted retrospective trials, assuming that properly randomized sampling procedures are employed. Definitive clinical trials are likely to require better theoretical constructs, better instrumentation, and better measures than now available. Reasons for concern are the restricted resources available and the fact that current mensurational approaches may not detect many of the individual differences. The task of constructing sharable databases and record bases stored in digital form and available either remotely from servers, or locally from CD-ROMs or optical disks, is crucial to the optimization of future investigations.

Clinical Trials as Topic↗
PubMed1997

Lower molar and incisor displacement associated with mandibular remodeling.

The purpose of this study was to quantify the amount of alveolar modeling at the apices of the mandibular incisor and first molar specifically associated with appositional and resorptive changes on the lower border of the mandible during growth and treatment. Cephalometric data from superimpositions on anterior cranial base, mandibular implants of the Björk type, and anatomical "best fit" of mandibular border structures were integrated using a recently developed strategy, which is described. Data were available at annual intervals between 8.5 and 15.5 years for a previously described sample of approximately 30 children with implants. The average magnitudes of the changes at the root apices of the mandibular first molar and central incisor associated with modeling/remodeling of the mandibular border and symphysis were unexpectedly small. At the molar apex, mean values approximated zero in both anteroposterior and vertical directions. At the incisor apex, mean values approximated zero in the anteroposterior direction and averaged less than 0.15 mm/year in the vertical direction. Standard deviations were roughly equal for the molar and the incisor in both the anteroposterior and vertical directions. Dental displacement associated with surface modeling plays a smaller role in final tooth position in the mandible than in the maxilla. It may also be reasonably inferred that anatomical best-fit superimpositions made in the absence of implants give a more complete picture of hard tissue turnover in the mandible than they do in the maxilla.

Adolescent↗
PubMed1996

The decision to extract: part II. Analysis of clinicians' stated reasons for extraction.

In a recently reported study, the pretreatment records of each subject in a randomized clinical trial of 148 patients with Class I and Class II malocclusions presenting for orthodontic treatment were evaluated independently by five experienced clinicians (drawn from a panel of 14). The clinicians displayed a higher incidence of agreement with each other than had been expected with respect to the decision as to whether extraction was indicated in each specific case. To improve our understanding of how clinicians made their decisions on whether to extract or not, the records of a subset of 72 subjects randomly selected from the full sample of 148, have now been examined in greater detail. In 21 of these cases, all five clinicians decided to treat without extraction. Among the remaining 51 cases, there were 202 decisions to extract (31 unanimous decision cases and 20 split decision cases). The clinicians cited a total of 469 reasons to support these decisions. Crowding was cited as the first reason in 49% of decisions to extract, followed by incisor protrusion (14%), need for profile correction (8%), Class II severity (5%), and achievement of a stable result (5%). When all the reasons for extraction in each clinician's decision were considered as a group, crowding was cited in 73% of decisions, incisor protrusion in 35%, need for profile correction in 27%, Class II severity in 15% and posttreatment stability in 9%. Tooth size anomalies, midline deviations, reduced growth potential, severity of overjet, maintenance of existing profile, desire to close the bite, periodontal problems, and anticipation of poor cooperation accounted collectively for 12% of the first reasons and were mentioned in 54% of the decisions, implying that these considerations play a consequential, if secondary, role in the decision-making process. All other reasons taken together were mentioned in fewer than 20% of cases. In this sample at least, clinicians focused heavily on appearance-related factors that are qualitatively determinable by physical examination of the surface structures of the face and teeth. They appear to have made primary use of indicators available on study casts and facial photographs and relatively little use of information that is available only on cephalograms or that involves the application of specialized orthodontic theories.

Adolescent↗
PubMed1996

The decision to extract: Part 1--Interclinician agreement.

As part of an ongoing prospective clinical trial of conventional orthodontic treatment, the decision making patterns of a representative group of orthodontic clinicians were examined. Data were available for 148 subjects (100 adolescents and 48 adults) who had presented at the University of California San Francisco Graduate Orthodontic Clinic requesting treatment for correction of a Class I or Class II malocclusion. The records for each subject were evaluated independently by each of five members of the clinical faculty, making available a total of 740 independent patient evaluations. With regard to the primary decision as to whether extraction or nonextraction treatment was to be preferred, agreement among clinicians was higher than had been anticipated. In almost two thirds of the cases, the decisions of all five clinicians were in agreement as to whether extraction or nonextraction was the preferred treatment modality. (This figure included 59 cases of complete agreement for extraction therapy (40%) and 38 cases of complete agreement for nonextraction therapy (26%)). In only 51 cases (34%), did the reviewing clinicians disagree as to whether extraction or nonextraction was the preferred modality of treatment. The clinicians were also asked to indicate their opinions as to whether orthognathic surgery was likely to be a part of the ultimate treatment course for each individual subject. Nine percent of the 740 patient evaluations contained a clinician judgement that surgery would be a probable or definite component of the orthodontic treatment plan. For 29% of the adult subjects (14 cases) and 23% of the adolescent subjects (23 cases), one or more of the five examining clinicians believed that adjunctive surgical intervention would probably or definitely be appropriate. These high values were unexpected, particularly because the sample had been prescreened by a single clinician to exclude subjects who might require orthognathic surgery. Clinician agreement of Angle classification was also evaluated. Disagreements were observed in 14 adult subjects (29%) and 27 adolescent subjects (27%). Little association was observed between clinician agreement on Angle classification and clinician agreement on whether or not to extract.

Adolescent↗
PubMed1996

Apical root resorption in orthodontically treated adults.

This study analyzed the relationship in orthodontically treated adults between upper central incisor displacement measured on lateral cephalograms and apical root resorption measured on anterior periapical x-ray films. A multiple linear regression examined incisor displacements in four directions (retraction, advancement, intrusion, and extrusion) as independent variables, attempting to account for observed differences in the dependent variable, resorption. Mean apical resorption was 1.36 mm (sd +/- 1.46, n = 73). Mean horizontal displacement of the apex was -0.83 mm (sd +/- 1.74, n = 67); mean vertical displacement was 0.19 mm (sd +/- 1.48, n = 67). The regression coefficients for the intercept and for retraction were highly significant; those for extrusion, intrusion, and advancement were not. At the 95% confidence level, an average of 0.99 mm (se = +/- 0.34) of resorption was implied in the absence of root displacement and an average of 0.49 mm (se = +/- 0.14) of resorption was implied per millimeter of retraction. R2 for all four directional displacement variables (DDVs) taken together was only 0.20, which implied that only a relatively small portion of the observed apical resorption could be accounted for by tooth displacement alone. In a secondary set of univariate analyses, the associations between apical resorption and each of 14 additional treatment-related variables were examined. Only Gender, Elapsed Time, and Total Apical Displacement displayed statistically significant associations with apical resorption. Additional multiple regressions were then performed in which the data for each of these three statistically significant variables were considered separately, with the data for the four directional displacement variables. The addition of information on Elapsed Time or Total Apical Displacement did not explain a significant additional portion of the variability in apical resorption. On the other hand, the addition of information on Gender to the information on the four directional displacement variables yielded an R2 value of 0.35, which indicated that these variables taken together could account for approximately a third of the observed variability in apical resorption in this sample.

Adult↗
PubMed1996

Partitioning the components of maxillary tooth displacement by the comparison of data from three cephalometric superimpositions.

Using roentgenographic cephalograms from a sample of subjects with metallic implants, appropriately superimposed tracings were used to distinguish developmental and treatment-associated displacements of the maxillary central incisor and first molar associated "local" changes within the periodontium from "secondary" changes which reflect sutural and appositional growth at more distant osseous loci. Tracings were superimposed on anterior cranial base (ACB), on the maxillary implants only (IMP_MAX), and according to the best fit of maxillary anatomic structures without reference to the implants (A_MAX). Using the IMP_MAX superimposition, one could measure total local displacement at any landmark taking into consideration the effects of all appositional and resorptive changes on the superior and anterior surfaces of the palate, whereas using the A_MAX superimposition one could measure local displacement without consideration of surface appositional and resorptive changes. If the second of these measurements were subtracted from the first, the result would be a direct measurement of the effects of surface appositional and resorptive changes as they are expressed at that particular landmark. This strategy has enabled us to quantify and report the amount of accommodation which occurs at the location of each dental landmark in association with the resorptive and appositional changes which occur through time on the superior and anterior surfaces of the hard palate.

Adolescent↗
PubMed1993

An inventory of United States and Canadian growth record sets: preliminary report.

A listing and description of longitudinal craniofacial growth record sets currently extant on the North American continent is provided. An argument is made for the preservation of these resources and for the generation of a pooled or shared image base of duplicate craniofacial physical records. This is a preliminary report and is assumed to be incomplete. In an effort to improve our accuracy and completeness, we invite corrections and additions.

Adolescent↗