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PubMed1993

Male antifertility compounds from Tripterygium wilfordii Hook f.

Extracts of the Chinese medicinal plant, Tripterygium wilfordii, cause reversible infertility in male animals. Sub-fractionation studies have now revealed that the plant extracts contain a number of compounds which are potent antifertility agents in male mammals, including the diterpenes triptolide and tripdiolide and an isomer of the latter. A triptolide, 12,13-chlorohydrin, which is a transformation product formed reversibly by interaction of triptolide with HCl, was also found to be active.

Animals↗

PubMed1991

Condylar position and maxillary first premolar extraction.

Condylar position in 17 patients whose Class II treatment (14 with edgewise appliances and 3 with Begg appliances) included extraction of the maxillary first premolars and in 17 control patients was compared by means of corrected tomography. The condyles in both groups were in an anterior position, and there were no statistical differences between the groups. In addition, no statistical correlation was found when the posttreatment bite depth, interincisal angle, and maxillary incisor inclination were correlated with condylar position. Thus, as determined in this study, condylar position was unrelated to treatment, bite depth, interincisal angle, and maxillary incisor inclination.

Adolescent↗

PubMed1990

Controversies in orthodontics.

Three controversial interrelated aspects of orthodontics have been reviewed: retention, the effect of third molars on lower anterior crowding, and extraction and nonextraction orthodontic treatment. Recent studies have shown that unacceptable lower anterior crowding occurs in 90 per cent of well-treated extraction cases. The implication is that nonextraction cases should be 90 per cent or higher. In view of our present general inability to identify the 10 per cent that will remain acceptable, some form of indefinite retention is advised. A literature review of the effect of third molars on lower anterior crowding finds strong opinions on both sides of the issue. Similar studies often show dissimilar conclusions, particularly when observing cases of third molar extraction or agenesis. Certainly the problem is multifactorial; however, the vast bulk of the evidence indicates that the third molars play an insignificant role in lower anterior crowding. Extraction of teeth for orthodontic treatment prior to 1900 was prevalent and indiscriminate. From the turn of the century to the mid-thirties Angle moved the specialty away from extractions to a relatively rigid nonextraction treatment philosophy. Dissatisified with relapsing Class II cases, recurrence and aggravation of crowding, and what he felt were bimaxillary full faces, Tweed and others, circa 1935, redirected the profession back to extractions with a more disciplined approach to treatment by the removal of four first premolars. Fifty years later we have found that extraction treatment and uprighting lower incisors does not prevent long-term postretention crowding and that flattened profiles are not always esthetically desirable. Earlier treatment of maxillomandibular basal discrepancies by old and new treatment philosophies and mechanics have produced more stable nonextraction corrections. Better control of leeway space and a reduction in caries has helped reduce the amount of lower anterior flaring that was seen in the nonextraction cases in the first third of the century. These reasons have moved the specialty of orthodontics to a mixed but more nonextraction-oriented approach to treatment.

Esthetics, Dental↗

PubMed1988

An evaluation of changes in mandibular anterior alignment from 10 to 20 years postretention.

Pretreatment, end of treatment, 10-year postretention, and 20-year postretention records of 31 four premolar extraction cases were assessed to evaluate stability and relapse of mandibular anterior alignment. Crowding continued to increase during the 10- to 20-year postretention phase but to a lesser degree than from the end of retention to 10 years postretention. Only 10% of the cases were judged to have clinically acceptable mandibular alignment at the last stage of diagnostic records. Cases responded in a diverse unpredictable manner with no apparent predictors of future success when considering pretreatment records or the treated results.

Adult↗

PubMed1998

Benefit of early Class II treatment: progress report of a two-phase randomized clinical trial.

Preadolescent children with overjet greater than 7 mm were randomly assigned to observation only, headgear (combination), or functional appliance (modified bionator) and were monitored for 15 months. Of the 166 patients who completed this first phase of the trial, 147 continued to a second phase of treatment. The data from the first 107 patients to complete phase 2 are available and form the basis of this progress report. During phase 1, on average there was no change in the jaw relationship of untreated children, but 5% showed considerable improvement and 15% demonstrated worsening. Both early-treatment groups had a significant average reduction in ANB angle, more by change in maxillary dimensions in the headgear group and mandibular growth in the functional appliance group. There were wide variations in response, however, with only 75% of the treated children showing favorable skeletal response. Failure to respond favorably could not be explained by lack of cooperation alone. The preliminary results from phase 2 show that, on average, time in fixed appliances was shorter for children who underwent early treatment, but the total treatment time was considerably longer if the early phase of treatment was included. Only small differences were noted in anteroposterior jaw position between the groups at the completion of treatment, and the changes in dental occlusion, judged on the basis of Peer Assessment Rating scores, were similar between groups. Neither the severity of the initial problem nor the duration of treatment was correlated with the occlusal result. The number of patients who required extraction of permanent teeth was greater in the early functional appliance group than in the headgear or control group. The option of orthognathic surgery was presented more often in the cases of children who did not undergo early treatment, but surgery was accepted or was still being considered almost as frequently in the previous headgear group as in the controls, less often in the patients previously treated with functional appliances.

Activator Appliances↗

PubMed1981

Stability and relapse of mandibular anterior alignment-first premolar extraction cases treated by traditional edgewise orthodontics.

Assessment at least 10 years postretention of sixty-five cases previously treated in the permanent-dentition stage with first-premolar extractions, traditional edgewise mechanics, and retention revealed considerable variation among patients. The long-term response to mandibular anterior alignment was unpredictable; no variables, such as degree of initial crowding, age, sex, Angle classification, etc., were useful in establishing a prognosis. Typically, arch width and length decreased after retention, regardless of treatment expansion or constriction. Two thirds of the patients had unsatisfactory lower anterior alignment after retention. Cases that were minimally crowded before treatment usually became more crowded, while initially severe crowding cases usually moderated.

Adolescent↗

PubMed1992

Relationship between orthodontic treatment, condylar position, and internal derangement in the temporomandibular joint.

The purpose of this study was to test the hypothesis that retraction of maxillary front teeth may lock the mandible in a posterior position, and to evaluate any relationship between condylar position and signs and symptoms of internal derangements in the temporomandibular joint. A total of 29 female patients treated for Angle Class II, Division 1 malocclusion with extraction of maxillary first premolars and 34 female patients treated for Angle Class I malocclusion without tooth extraction consented to participate in a radiographic and clinical follow-up examination. The mean ages of the patients were 16.9 (SD 3.0) and 16.6 (SD 2.6) years, and the mean times after treatment were 1.6 (SD 1.0) and 1.5 (SD 0.9) years, respectively. Condylar position was measured in percent anterior and posterior displacement from absolute concentricity on lateral, central, and medial tomographic sections of each joint. Mean condylar position was more posterior at right central (P less than 0.05) and medial (P less than 0.01) tomographic sections in patients treated with extraction. The difference was due to a higher frequency of anteriorly positioned condyles in the nonextraction cases. No intergroup differences in the sagittal occlusal slide from CR to CO and the number of patients with clicking were found. However, the condyles were located more posteriorly in all tomographic sections (P less than 0.05 for lateral, P less than 0.001 for central and medial) in patients with clicking than in those without.

Adolescent↗

PubMed1998

Evaluation of orthodontic relapse using the cubic spline function.

A sample of 72 orthodontically treated patients was reexamined many years out of retention. They had been treated either by the extraction of four premolars or without extractions. The average number of years between the end of treatment and the taking of follow-up records was 20, with a range of 12 to 35 years. Some conventional measurements were studied such as intertooth widths, arch perimeter, and incisor irregularity. In addition, a new method for comparison of arch form at different stages of treatment, which uses the cubic spline function, was used. Cases were grouped into extraction and nonextraction, and statistics were used to test the differences between the two groups. Correlations between the spline variables and conventional variables were computed, and multiple regression analysis was carried out using the spline variables as dependent variables. Some treatment and relapse changes were independent of whether the case was treated with extractions or not, whereas other trends were unique to one treatment group. The correlation analysis revealed strong relationships between variables that measured changes during the same treatment stage. There were also moderate correlations between some of the spline variables and the traditional measurements. Multiple regression analysis was used to account for changes in some spline variables, however, the usefulness of the model as a predictor is limited.

Bicuspid↗

PubMed1997

Dens evaginatus from an orthodontic perspective: report of several clinical cases and review of the literature.

The anomaly of dens evaginatus manifests itself as an innocuous-looking tubercle of enamel on the occlusal surface of a premolar tooth. Problems can arise when the tubercle is either worn, ground, or fractured off, resulting in pulpal exposure and possible loss of vitality of the tooth. Orthodontists should be particularly aware of this dental anomaly, which occurs in at least 2% of the Asian and Native Indian population. Premolar extraction cases should be planned to include extraction of the anomalous premolars instead of the normal ones. In addition, the orthodontist should be wary of occlusal changes during treatment or occlusal equilibration that might jeopardize the vitality of teeth with dens evaginatus. Pulp-capping or partial pulpotomy has been postulated as the most reliable form of treatment to prevent loss of vitality of the affected teeth and to allow continued root maturation where necessary.

Adolescent↗

PubMed1991

Mandibular second premolar extraction--postretention evaluation of stability and relapse.

The dental casts and cephalometric radiographs of 46 patients, treated with mandibular second premolar extraction and edgewise orthodontic mechanotherapy, were evaluated for changes over a minimum 10-year postretention period. The sample was divided into two groups: early (mixed dentition) extraction of mandibular second premolars and late (permanent dentition) extraction of mandibular second premolars. Results showed no difference in long-term stability between the two groups. Arch length and arch width decreased with time and incisor irregularity increased throughout the postretention period. No predictors or associations could be found to help the clinician in determining the long-term prognosis in terms of stability. The sample was regrouped according to the postretention degree of incisor irregularity. Statistically significant differences in cephalometric measurements were found between the minimally crowded group and the moderately to severely crowded group.

Adolescent↗

PubMed1987

Nonextraction orthodontic therapy: posttreatment dental and skeletal stability.

To assess the long-term stability of nonextraction orthodontic treatment, the dental cast and cephalometric records of 28 cases were evaluated. Thirty cephalometric and seven cast parameters were examined before treatment, posttreatment, and an average of almost 8 years postretention. Results showed overall long-term stability to be relatively good. Relapse patterns seen were similar in nature, but intermediate in extent, between untreated normals and four first premolar extraction cases. Significant decreases were seen in arch length and intercanine width during the postretention period despite minimal changes during treatment. Incisor irregularly increased slightly postretention; intermolar width, overjet, and overbite displayed considerable long-term stability. Mandibular incisor mesiodistal and faciolingual dimensions were not associated with either pretreatment or posttreatment incisor crowding. Class II malocclusions with large ANB values and shorter mandibular lengths showed increased incisor irregularity, shorter arch lengths, and deeper overbites at the postretention stage, suggesting that the amount and direction of facial growth may have been partially responsible for maturational changes seen during the postretention period.

Adolescent↗

PubMed2001

The time-factor in orthodontics: what influences the duration of treatments in National Health Service practices?

UNLABELLED: This study aimed to elucidate factors associated with duration of orthodontic treatment. METHODS: Retrospective analysis of a systematic 2% sample of cases completed in National Health Service practices in England and Wales. Records were collected during 1991. Characteristics of practitioners, patients, malocclusions, treatment variables and outcomes were evaluated. Data were submitted to multivariate analysis, with Log10 Time in Treatment as the dependent variable. RESULTS: Data were available for 1506 cases. The (geometric) mean time in treatment was 13 months. A model was found that explained 41% of the variance. Factors found to increase duration were fixed appliances, multiple stages in the treatments, premolar extractions, and correction of antero-posterior buccal occlusion. Age, buccal segment malocclusion, DHC (Dental Health Component of the Index of Orthodontic Treatment Need) grade 5 and orthodontically qualified practitioners were also associated with slightly longer treatments. CONCLUSIONS: Whilst briefer treatments may be attractive to purchasers, providers and recipients, it should be remembered that thorough treatment, and treatment of more complex malocclusions, tends to take longer. Economic pressures on practitioners to produce high turnovers of cases may be counterproductive in the quest for better outcomes.

Adolescent↗

PubMed1998

Eruption and function of maxillary third molars after extraction of second molars.

After extraction of maxillary second molars, will the third molars erupt into a functional position in a timely manner? To answer this question, 56 consecutively treated cases of maxillary second molar extraction were reviewed. The unerupted positions of the maxillary third molars were measured on cephalometric radiographs, ages of eruption were evaluated, positions of erupted third molars analyzed, and interproximal periodontal health of adjacent first molars compared. The results showed that, generally, the eruption of third molars was accelerated. Most of the third molars had acceptable interarch and intra-arch occlusal relationships. The interproximal periodontal health of the third molars was similar to that of adjacent first molars. Most maxillary third molars will successfully erupt into an acceptable position by the late teens.

Adolescent↗

PubMed1996

Stability of the palatal rugae as landmarks for analysis of dental casts in extraction and nonextraction cases.

To determine whether the positions of the palatal rugae were affected by orthodontic therapy, pre- and posttreatment maxillary dental casts of 57 adult patients treated in the graduate orthodontic clinic at the University of North Carolina were evaluated. The orthodontic extraction group (n = 27) was composed of patients whose treatment included the extraction of two maxillary premolars. The remaining patients (n = 30) had been treated without extractions. Transverse changes observed over time were significantly different from zero only for the medial points of the first rugae in the nonextraction group and for the lateral points of the first rugae in the extraction group. None of the changes observed in the transverse measures were statistically different between the two groups. In the extraction group, there were significant anteroposterior changes in the right lateral points between the first and second rugae and between the second and third rugae, and in the right medial points between the second and third rugae. There were no statistically significant anteroposterior changes observed in the nonextraction group over time. When the two groups were compared, the average distance between the lateral first and second right rugae, and the average distance between the lateral second and third right rugae were significantly different. The medial and lateral points of the third rugae appear to be stable landmarks for the construction of anatomic reference pints in longitudinal cast analysis.

Adolescent↗

PubMed1995

Stability of the lower labial segment following orthodontic treatment--a comparison of treatment with Andresen and Begg appliances.

This retrospective cephalometric study of Class II division 1 malocclusions investigates the effects on the lower labial segment of two forms of orthodontic treatment. Non-extraction Andresen myofunctional therapy and first premolar extraction Begg treatment are compared to the lower incisor changes found in appropriate non-extraction and first premolar extraction control groups, which also presented with Class II division 1 malocclusions. Using four angular and two linear measurements, the lower labial segment was found to procline during Andresen therapy (1-2 degrees, 1-2 mm), and on withdrawal of the appliance it retroclined by about one-half of the in-treatment proclination (0.4-0.8 degrees, 0.1-0.5 mm). During extraction Begg mechanics, the lower incisors were found to retrocline (1.3-1.5 degrees, 0.4-0.9 mm), and they continued to retrocline following removal of the appliance (0.2-3.0 degrees, 0.8-1.1 mm). In general, the variables used to measure lower incisor position demonstrated only very small changes, and were near method error. The reliability of these changes are discussed. It is considered that the axial inclination of the lower incisor in relation to the mandibular plane is the most consistent and therefore still the most useful clinical measurement of lower incisor change available from cephalometric radiographs.

Activator Appliances↗

PubMed1994

Predictors of relapse in orthodontically-treated Class III malocclusions.

This study aimed to investigate the possibility of predicting relapse from the pretreatment records of children with orthodontically treatable Class III malocclusions. Sixty-four patients were studied: 31 individuals had been treated by a non-extraction technique, the remaining 33 with mid-arch extractions. Cephalometric and model data taken at the start of treatment and at least 2 years after all treatment and retention had ceased were examined. An individual diagnosis of relapse or stability was made from the post-retention records and the start of treatment records analysed in relation to this information. The capacity for predicting the observed outcome of therapy was assessed in three ways: correlation coefficients, the number of cephalometric measurements exceeding two standard deviations from a control group mean, and discriminant analysis. Only the latter proved an effective indicator of relapse, with a separate discriminant model being necessary for each sub-group.

Adolescent↗

PubMed2000

Maxillary and mandibular width changes studied using metallic implants.

The purpose of this implant study was to evaluate the transverse stability of the basal maxillary and mandibular structures. The sample included 25 subjects between 12 and 18 years of age who were followed for approximately 2.6 years. Metallic implants were placed bilaterally into the maxillary and mandibular corpora before treatment. Once implant stability had been confirmed, treatment (4 first premolar extractions followed by fixed appliance therapy) was initiated. Changes in the transverse maxillary and mandibular implants were evaluated cephalometrically and two groups (GROW+ and GROW++; selection based on growth changes in facial height and mandibular length) were compared. The GROW++ group showed significant width increases of the posterior maxillary implants (P <.001) and the mandibular implants (P =.009); there was no significant change for the anterior maxillary implants. The GROW+ group showed no significant width changes between the maxillary and mandibular implants. We conclude that (1) there are significant width increases during late adolescence of the basal mandibular and maxillary skeletal structures and (2) the width changes are related with growth potential.

Adolescent↗

PubMed1999

Stability and relapse of mandibular anterior alignment: University of Washington studies.

For more than 40 years, research in the Department of Orthodontics, University of Washington (Seattle, WA) has focused on a growing collection of more than 800 sets of patient records to assess stability and relapse of orthodontic treatment. All patients had completed treatment a decade or more before the last set of data. Evaluation of treated premolar extraction patients, treated lower incisor extraction patients, treated non-extraction cases with generalized spacing, patients treated with arch enlargement strategies, and untreated normals showed similar physiologic changes: (1) Arch length decreases after orthodontic treatment. (2) Arch width measured across the mandibular canine teeth typically reduces posttreatment, whether or not the case was expanded during treatment. (3) Mandibular anterior crowding during the posttreatment phase is a continuing phenomenon well into the 20-to-40 years age bracket and likely beyond. (4) Third molar absence or presence, impacted or fully erupted, seems to have little effect on the occurrence or degree of relapse. (5) The degree of post-retention anterior crowding is both unpredictable and variable and no pretreatment variables either from clinical findings, casts, or cephalometric radiographs before or after treatment seem to be useful predictors.

Adult↗