Claus W. Schwarze

Post-retention Crowding and Incisor Irregularity: A Long-term Follow-up Evaluation of Stability and Relapse

The aim of the present long-term follow-up study of orthodontically-treated patients (mean: 15·7 years) was to analyse post-retention changes and to reveal factors which may play a role as predictors for long-term prognosis. Pretreatment, end-of-treatment, and post-retention models of 226 cases with all types of anomaly were used to measure intercanine and intermolar width, arch length, and sum of the mesiodistal dimension of the incisors, Irregularity Index, crowding, molar and canine relationship, overjet, and overbite. In order to assess the influence of sex, initial and end-of-treatment alignment, type of therapy, amount of tooth movement, and presence of third molars on the extent of postretention changes, the total sample was divided into subgroups. Findings indicated that post-retention crowding and incisor irregularity increased more frequently in the mandible than in the maxilla. Pretreatment variables such as increased mesiodistal incisor dimension, severe crowding and incisor irregularity, arch length deficiency, arch constriction, and increased overbite as well as post-treatment spacing, arch expansion, increased arch length, and residual Class II or III molar relationships were found to be associated factors in the process of post-retention increase of crowding and incisor irregularity. ‘Overexpansion’ was found to be a factor in mandibular incisor relapse.

Treatment and postretention changes in dental arch width dimensions—a long-term evaluation of influencing cofactors

The aim of the present long-term follow-up study of orthodontically treated patients was to analyze postretention changes in arch width dimension and to isolate factors that may serve as predictors of long-term prognosis. Pretreatment, end-of-treatment, and postretention (at least 10 years) models of 226 cases with different malocclusions were used to measure intercanine and intermolar width, arch length, sum of the mesiodistal dimension of the incisors, irregularity index, crowding, molar and canine relationship, overjet, and overbite. To assess the influence of initial and end-of-treatment alignment, kind of treatment (extraction versus nonextraction) and the amount of expansion in postretention stability, the sample was divided into different subgroups. The findings indicate that postretention arch width relapse occurred more frequently in the upper intermolar (25.8%) and lower intercanine region (23.9%) than in the lower intermolar (19.0%) and upper intercanine (13.8%) region. Pretreatment and posttreatment alignment as well as the kind of treatment and the amount of expansion were found to be influencing factors. The study concludes by proposing a reassessment of the definition of stability. The influence of the pretreatment anomaly, kind of treatment, amount of expansion, and posttreatment alignment on long-term stability should be recognized. Patients should be apprised of treatment limitations before treatments.

How to deal with the drop-out in clinical follow-up studies: Results of a long-term follow-up study of orthodontically treated patients

The drop-out in a long-term follow-up study of former orthodontically treated patients was analyzed to avoid biased results. Since structural conformity of the responders (n = 299) and the potential study population (n = 1464) cannot be presumed on the basis of the clinical results, roentgenologic results, and questionnaires, analysis of the participating patients, the follow-up method was used. By means of questionnaires sent to all nonresponders, a comparison of responding and nonresponding patient characteristics was completed to find a presumed selectivity bias. The comparison of the participating patients (n = 299) and the total sample revealed that the responders live closer to the health center, had a longer treatment time, and a shorter posttreatment interval. Compared with nonresponders (n = 266), the responders were satisfied with the treatment result and had a higher dental Intelligence Quotient (IQ, concerning tooth and jaw position). Although a definite answer to the question of validity of the examined subsample was difficult to give, the description and evaluation of the parameters that might be reasons for missing at random respectively, not missing at random was recommended.

[Ethyl cyanoacrylate (Cyano-Veneer) as an orthodontic bracket adhesive. A comparative in-vitro study with Cyano-Veneer and a conventional orthodontic bracket adhesive].

ZusammenfassungCyano-Veneer®, ein Äthylcyanoacrylat, soll laut Herstellerangaben zur Befestigung von Brackets geeignet sein und wird bereits von einigen Kieferorthopäden dazu verwendet. Bisher wurde das Material jedoch noch nicht auf seine Eignung als Bracketkleber geprüft. In dieser Studie wurde die Frage nach seiner Haftfestigkeit auf Zugkraft direkt nach dem Kleben und nach 50, 100 und 150 Tagen Lagerung in physiologischer Kochsalzlösung untersucht. Hierzu wurden für jeden der vier Zeitpunkte 40 obere Rinderschneidezähne von 20 Tieren extrahiert. Anhand einer Randomisierungsliste wurden die Brackets mit Cyano-Veneer® oder Mono-LokTM, als Vergleichskleber, auf die Zähne geklebt. Die Abzugskraft der Brackets auf Zugbelastung wurde mit der Zwickzugmaschine gemessen. Unmittelbar nach dem Kleben lag die Haftfestigkeit von Cyanoacrylat deutlich über der des Vergleichsklebers (p=0,0008). Zu den späteren Zeitpunkten (nach 50, 100 und 150 Tagen) bestand kein signifikanter Unterschied in der Haftfestigkeit der beiden Kleber. Es ergibt sich als Schlußfolgerung, daß die Gefahr des Bracketverlusts beim Einligieren von Bögen direkt nach dem Kleben mit Äthylcyanoacrylat geringer ist, was für Patient und Behandler als Vorteil anzusehen ist.SummaryAccording to the claims of the manufacturer, aethylcyanoacrylate can be used to bond orthodontic brackets and some orthodontists have already adopted its use for this purpose. Because, however, the use of the material as thus applied has not yet been the object of research, the question of its adhesion to tensil forces immediately after bonding and after 50, 100, and 150 days of placement in a physiologic saline solution (0.9% NaCl) is the subject of this study. 40 bovine upper incisors were extracted from 20 animals for each of the four points in-time. The brackets were bonded with Cyano-Veneer® and Mono-LokTM according to a randomized list. Mono-LokTM, an adhesive from the group of common orthodontic adhesives, functioned as the reference material. The bonding strength of the brackets in relation to the tensil forces was measured by means of a “Zwickuniversalprüfmaschine” (Zwick universal testing machine). Immediately after bonding, the cyanoacrylate demonstrated significantly higher bonding strength values than Mono-LokTM. At 50, 100, and 150 days in the physiologic saline solution, the bonding strength of both materials showed no significant difference. It can thus be concluded that, when wires are employed immediately after bonding, the danger of bracket loss is significantly reduced through the use of cyanoacrylate.

Postretention Changes in Canine Position Results of a Long-Term Follow-Up

Abstract: The aim of the present study was to evaluate sagittal, vertical and transverse changes in canine position and a possible correlation with relapse of lower anterior crowding. From a sample with a long-term follow-up of 15.7 ± 4.4 years after treatment, patients with a full dentition were enrolled in the study. Post-treatment and long-term follow-up casts of 117 patients were measured and statistically analyzed. A decrease in intercanine width was found between post-treatment and long-term follow-up records, with more lingual inclination of the mandibular canine axis in the transverse plane. There was a significant correlation between maxillary and mandibular canine inclination. Concomitant changes were an increase in lower anterior crowding and a decrease in mandibular intercanine width. Relapse of anterior crowding has a multifactorial etiology. The results of this study suggest a possible influence of the canines. Functional causes in particular might have a profound influence and should be considered during treatment planning.Zusammenfassung: Ziel der vorliegenden Untersuchung war die Evaluierung der sagittalen, vertikalen und transversalen Veränderungen der Eckzahnposition und deren möglicher Zusammenhang mit einem Rezidiv des unteren Frontengstandes. Aus einem Langzeitnachuntersuchungsgut durchschnittlich 15,7 ± 4,4 Jahre nach Behandlungsabschluss wurden die zum Untersuchungsdatum vollbezahnten Patienten selektiert. Die End- und Nachuntersuchungsmodelle von 117 Patienten wurden hinsichtlich der oben genannten Parameter vermessen und die Ergebnisse statistisch ausgewertet. Es zeigte sich eine Abnahme der interkaninen Distanz zwischen Abschluss- und Nachuntersuchungszeitpunkt, die Neigung der unteren Eckzahnachsen nahm in der Transversalen nach lingual hin zu. Es konnte auch ein statistisch nachweisbarer Zusammenhang zwischen oberer und unterer Eckzahnneigung festgestellt werden. Des Weiteren kam es zu einer Zunahme des unteren Engstandes und zu einer Abnahme der interkaninen Distanz in Abhängigkeit von den zuvor genannten Befunden. Der rezidivierende Frontengstand hat eine multifaktorielle Genese. Die beschriebenen Ergebnisse zeigen eine Mitbeteiligung der Eckzähne. Insbesondere funktionelle Ursachen könnten hier maßgeblichen Einfluss haben und sollten in die therapeutischen Überlegungen mit einbezogen werden.

A retrospective examination of the acceptance of removable appliances

ZusammenfassungZur Berteilung der subjektive Einstellung der Patienten und ihrer Eltern zur kieferorthopädischen Behandlung, insbesondere zu herausnehmbaren Apparaturen, wurde Fragebögen ausgeteilt. 145 Patientenfragebögen und 114 Elternfragebögen kamen zur Auswertung. Der größte Teil der Prolanden konnte bestimmte Fragen zur ihrer Behandlubng nur teilweise richtig beantworten. Sprachbehinderung, Druck und zu viel Speichel standen als störend im Vordergrund. Die Mehrzahl der Petienten und eltern zog die Behandlung mit herausnehmbaren Geräten einer Multibandbehandlung vor. Seitens de soziialen Umfeldes scheint keine Negativbeeionflussung bezüglich der kieferorthopädische Behandlung zu bestehen.SummaryIn order to study the subjective attitudes of patients and their parents to orthodontic treatment questionnaires were handed out to both groups. One hundred and forty five patient questionnaires and those answered by 114 parents formed the base of the study. The majority of the patients were only able to provide partial answers to precise quesions about their treatment.Speech impairment, pressure, and salivation were given as being the moist vexation aspects of the treatment. The majority of the patients and the majority, of parents favored removable appliances over fixed appliances. The patients social environment did not negatively influence their attitude to orthodontic treatment.

[Early deciduous tooth loss--the mature or immature eruption of their permanent successors].

On the basis of 147 panoramic radiographs of 49 patients, this study investigated the influence of the premature loss of deciduous teeth on the formation of their permanent successors at the time of their eruption. Furthermore the study investigated the eruptive movement of the successor teeth at the time of eruption. In addition to detecting the accelerated emergence of still immature successor premolars, the study also determined that the extraction ot the deciduous molars before the age of eight years delayed the eruption of the permanent successors given the absence of an infected deciduous tooth with abscess formation. In relation to the eruptive movement of the permanent molars due to the premature loss of the second deciduous molar, the study ascertained a mesial movement of the first permanent molars and an accelerated eruption of the second permanent molars.ZusammenfassungDer Einfluß des frühzeitigen Milchzahnverlustes auf den Reifegrad der bleibenden Nachfolger zum Durchbruchszeitpunkt sowie auf deren Durchbruchsverhalten wurde anhand von 147 Panoramaröntgenschichtaufnahmen (OPG) von 49 Patienten untersucht. Neben einem unmittelbaren Nachfolgen der noch unreifen bleibenden Nachfolger konnte eine Durchbruchsverzögerung der Ersatzzähne bei Entfernung der Milchmolaren vor dem achten Lebensjahr und fehlender apikaler Entzündung festgestellt werden. Hinsichtlich des Durchbruchsverhaltens der Molaren bei vorzeitigem Verlust der Milchfünfer konnten eine Mesialwanderung der Sechsjahrmolaren sowie eine Durchbruchsbeschleunigung der Zwölfjahrmolaren nachgewiesen werden.SummaryOn the basis of 147 panoramic radiographs of 49 patients, this study investigated the influence of the premature loss of deciduous teeth on the formation of their permanent successors at the time of their eruption. Furthermore the study investigated the eruptive movement of the successor teeth at the time of eruption. In addition to detecting the accelerated emergence of still immature successor premolars, the study also determined that the extraction of the deciduous molars before the age of eight years delayed the eruption of the permanent successors given the absence of an infected deciduous tooth with abscess formation. In relation to the eruptive movement of the permanent molars due to the premature loss of the second deciduous molar, the study ascertained a mesial movement ot the first permanent molars and an accelerated eruption of the second permanent molars.

Druck und Volumen im Mundraum

ZusammenfassungMit Hilfe eines neuartigen Untersuchungsverfahrens wurden die Raumverhältnisse des Cavum oris proprium und Vestibulum oris sowie das Funktionsvolumen der Zunge untersucht. Es stellte sich heraus, daß Cavum o. p. und Vestibulum oris etwa gleich groß sind und sich mit zunehmendem Alter vergrößern. Bei 37 von 100 Probanden lag ein Größenmißverhältnis zwischen dem Funktionsvolumen der Zunge und dem Rauminhalt des Cavum oris proprium vor, so daß vermutet werden kann, daß hier ein ursächlicher Zusammenhang zwischen Zungengröße und Anomalie besteht. Weiterhin wurden der Zungendruck sowie der in der Mundhöhle erzeugte maximale Druck und Unterdruck gemessen. Auch hier konnte ein Anstieg der Werte mit zunehmendem Alter beobachtet werden.

Materialeigenschaften der Werkstoffe für Positioner — eine In-vitro-Untersuchung

ZusammenfassungEs wurden 15 handelsübliche und vier Versuchsmaterialien auf ihr plastoelastisches Verhalten im Zugversuch bei 20%iger Dehnung untersucht. Gleichzeitig die zeitliche Veränderung der Elastizität über drei Monate bei Lagerung im feuchten, der Mundtemperatur angenäherten Milieu registriert. Die gemessenen Werte der Elastizitätsmoduln umfaßten materialbedingt einen Bereich von 24,9 MPa bis 1,5 MPa. Die meisten Materialien zeigten eine Zunahme des Betrages des Elastizitätsmoduls über drei Monate, nur bei einem Material war diese Zunahme statistisch signifikant (t-Test, pmax<0,00005).SummaryThe purpose of this study was to compare the physical and mechanical properties of materials for tooth positioners. 15 of these materials are in general use and four are experimental. Tensile strength at 20% elongation was observed and analyzed over a three-month period during which time the specimens were stored at 37°±1°C in an aqueous environment. The values of tensile strength covered a range from 24.9 MPa to 1.5 MPa depending on the particular material. Most of the materials displayed an increase in the module of elasticity over three-month period, but this increase was statistically significant in only one material (t-test, pmax<0.00005).The purpose of this study was to compare the physical and mechanical properties of materials for tooth positioners. 15 of these materials are in general use and four are experimental. Tensile strength at 20% elongation was observed and analyzed over a three-month period during which time the specimens were stored at 37 degrees +/- 1 degree C in an aqueous environment. The values of tensile strength covered a range from 24.9 MPa to 1.5 MPa depending on the particular material. Most of the materials displayed an increase in the module of elasticity over three-month period, but this increase was statistically significant in only one material (t-test, pmax < 0.00005).

Die Kraftabgabe von Positionern bei unterschiedlicher Schneidezahnprotrusion

The purpose of this study was to examine the forces exerted on protruded upper incisors by tooth positioners. Methodologically an in vitro force measurement model was used. The tooth positioners were made of 7 readily available materials commonly used in orthodontics. The study found that the values of the forces, which ranged from 0.4 N to 14.0 N per tooth, are dependent on the material used and the degree of tooth protrusion. In addition, the study analyzed the changes in force over a 3-month period during which time the positioners were stored at 37 degrees +/- 1 degree C in an aqueous environment. This environment corresponds closely to that found in the mouth.ZusammenfassungEs wurde die Kraftabgabe von Positionern auf die oberen Schneidezähne quantitativ untersucht. Die Positioner wurden aus sieben handelsüblichen Materialien gefertigt. Die gemessenen Kraftgrößen bewegten sich in Abhängigkeit von Material und Ausmaß der Protrusion in einem Bereich von 0,4 N bis 14,0 N. Zudem wurde die zeitliche Veränderung der Kraftabgabe über einen Zeitraum von drei Monaten bei Lagerung im feuchten, der Mundtemperatur angenäherten Milieu registriert.SummaryThe purpose of this study was to examine the forces exerted on protruded upper incisors by tooth positioners. Methodologically an in vitro force measurement model was used. The tooth positioners were made of 7 readily available materials commonly used in orthodontics. The study found that the values of the forces, which ranged from 0.4 N to 14.0 N per tooth, are dependent on the material used and the degree of tooth protrusion. In addition, the study analyzed the changes in force over a 3-month period during which time the positioners were stored at 37°±1°C in an aqueous environment. This environment corresponds closely to that found in the mouth.