Biomechanics of the mandible and growth extension

Background and objective

One way of determining the direction of growth of the mandible is to consider the temporomandibular joint and movement of the mandible as a four-joint gear system, regarding growth then as an extension of the gear system. Our aim was to examine any correlations between the type of biomechanical growth extension and change in the maxilomandibular relation after Class?II therapy.

Subjects and methods

A total of 130?lateral cephalograms??before and after orthodontic treatment??were available from 65?adolescent class?II patients with open bite or deep bite. The two lateral cephalograms from each patient were superimposed on the occlusal plane. Cephalometric values and the vertical base point deviation were determined from biomechanical analyses, together with three distances and three angles.

Results

No correlation between the cephalometric data and distances or angles were observed. Although there were no significant differences in the distances, we did note significant differences in all three angles (p?Conclusion If gear system extension during growth is considered, this can be interpreted as meaning that the occlusal plane of those patients with an initially open bite dropped during treatment, but that it rose in patients with an initially deep bite.     

Reference Values for Craniofacial Structures in Children 4 to 6 Years Old: Review of the Literature

This review article addresses the question as to what methods can be used to investigate cranial structure and growth development in children 4 to 6 years old, and what the relevant reference values are for this age group. We screened the literature for epidemiological, longitudinal and cross-sectional studies investigating healthy children 4 to 6 years old without abnormalities and orthodontic therapy. Radiographic cephalometry is a practical, valid tool for analyzing craniofacial structure and growth processes. But it has several disadvantages, including the use of ionizing radiation, measuring points that are difficult to locate, no means of radiographic enlargement without distorting reference values, and the data's two-dimensionality. Anthropometry is another procedure for creating reference values for the craniofacial structure in children. Its advantages over radiographic cephalometry include three-dimensional results and no radiation exposure. Moreover, it yields precise and valid results for a wide variety of potential applications.In addition to these procedures, there are other techniques with which cranial structure and growth development in children 4 to 6 years old can be investigated. Those reported in the literature in this connection include standardized photographs, the creation of computerized and magnetic resonance images, and investigations performed on dry skulls. In short, there is great demand nowadays for investigations aimed at developing reference values for Caucasian children 4 to 6 years old. Radiographic cephalometry and anthropometry are two very common methods. Anthropometry is expected to become increasingly important because it involves no exposure to radiation.     

Quantity and distribution of plaque in orthodontic patients treated with molar bands

Objective

The placement of orthodontic bands usually increases plaque accumulation due to numerous mechanical retention sites. The purpose of this investigation was to evaluate the amount and distribution pattern of biofilm in the oral (palatal and lingual) and interproximal regions surrounding orthodontic bands.

Materials and Methods

We evaluated the formation of biofilm on 32 orthodontic bands which had been placed intraorally for 6?C37?months. Two parameters were measured: the percentage of surface covered by biofilm (quantity) and the biofilm distribution pattern of accumulation. We measured these two parameters in four regions of interest: the mesial and distal interproximal regions, as well as the mesial and distal regions of the oral attachment.

Results

The quantity of biofilm formation was similar in all four regions of interest, ranging from 13.3% to 16.8%. In contrast to biofilm quantity, distribution patterns differed in the four regions. In the mesial and distal interproximal regions it appeared as extensive insular areas in 87.5% and 71.9%, respectively, whereas it appeared more often supragingival and linear in nature in regions adjacent to the oral attachment, i.e. in 65.6% and 68.8%, respectively.

Conclusion

Our results indicate that firstly, oral hygiene in the palatal and lingual regions of orthodontic bands seems as difficult as it is in the interproximal areas, thus requiring thorough hygiene in both areas. Secondly, orthodontic patients with a history of periodontal disease require special attention regarding the use of orthodontic bands.     

Zur Frage der Ausgleichsextraktion bei Nichtanlage oder traumatischem Verlust von Frontzähnen im Unterkiefer

Zusammenfassung Es wird über eigene Erfahrungen bei der kieferorthopädischen Behandlung der Nichtanlage bzw. des traumatischen Verlustes von Frontzähnen im Unterkiefer berichtet. Speziell wird auf die Problematik der Ausgleichsextraktion eingegangen. An Hand kasuistischer Beispiele werden die Behandlungsmöglichkeiten bei Fehlen eines, zweier bzw. dreier Frontzähne im Unterkiefer demonstriert.

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Summary The authors report on experiences with the orthodontic treatment of a missing anlage or of the traumatic loss, respectively, of frontal teeth in the lower jaw. In particular the problem of compensating extractions is dealt with. Cases are demonstrated to show the therapeutical possibilities with the absence of one, two or three frontal teeth of the lower jaw.

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Herrn Prof. Dr. Dr. Dr. h. c. mult. E. Reichenbach zum 75. Geburtstag     

Druckbelastung der Schneidezähne bei Dysfunktionen der mimischen Muskulatur

Zusammenfassung Die bei verschiedenen Dysfunktionen der mimischen Muskulatur (Lippenbeißen, Lippensaugen, Zungenpressen, anomales Schlucken) von seiten der Zunge und Lippen auf die Palatinal- bzw. Labialflächen oberer und unterer Incisivi einwirkende Druckbelastung wurde mittels speziell konstruierter Meßsonden registriert und statistisch ausgewertet.Die Untersuchung umfaßte drei Probandengruppen von jeweils 15 Kindern im Alter von 8 bis 12 Jahren. Während zwei Gruppen sich aus Probanden mit Fehlfunktionen der Zungenbzw. Lippenmuskulatur zusammensetzten, diente die dritten Gruppe der Kontrolle und dem statistischen Vergleich.Die Auswertung der Ergebnisse bestätigte die Vermutung, daß beim Vorliegen von Dysfunktionen der mimischen Muskulatur bereits während des Schluckaktes eine erhebliche Belastung der Incisivi auftritt. Die beim Lippenbeißen und maximalen Zungendruck registrierten Werte zeigten noch eine weitaus stärkere Ausprägung. Spitzenwerte von 1422 bzw. 2510 p/cm² sowie signifikante gruppenspezifische Unterschiede ließen erkennen, daß die beschriebenen Abweichungen vom normalen Funktionsmuster als eine wesentliche Ursache von Zahnfehlstellungen und parodontalen Schäden im Frontbereich angesehen werden müssen. Die auf Grund klinischer Beobachtungen vermuteten Zusammenhänge konnten somit durch die direkten Druckanalysen bestätigt und objektiviert werden.

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Summary Specially constructed measuring instruments have been developed in order to measure tongue and lip pressures on the labial and lingual surfaces of the anterior teeth. The instruments have been used to register pressures of the lip and tongue in various cases of abnormal oral habits such as lip biting, lip sucking, tongue thrusting and abnormal swallowing. The resulting measurements have been statistically evaluated. The study was composed of three groups of fifteen children each whose ages varied from 8 to 12 years. Two of the three groups had tongue and lip habits and the other group which had no obvious habits served as the control in order to have a statistical comparison.The evaluation of the results showed what was suspected and that is, that in patients with abnormal facial muscular habits there is, during swallowing, a definite increase in pressure on the incisors. With the lip biting and tongue thrusting patients there was an even larger increase in pressure. The cause of malposed teeth and peridontal problems in the anterior part of the dental arch can be seen when the differences of the maximum values of normal muscles are compared with the deviations of the maximum values of the habit groups (1422 to 2510 p/cm²). Clinical observations give one the idea that these relationships existed and now through the measuring instruments these can be proved and demonstrated.

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Häufigkeit und Folgen des frühzeitigen Verlustes von 6-Jahrmolaren

Zusammenfassung Nach vor allem aus eigenen statistischen Erhebungen entnommenen Angaben über die Häufigkeit des frühzeitigen Verlustes erster Molaren werden die Folgezustände aufgezeigt, die dieser Verlust nach sich zieht. An Hand der Analyse eines eigenen Patientengutes wird versucht, den für die weitere Gebißentwicklung günstigsten Zeitpunkt der Entfernung erster Molaren zu bestimmen und andere äußere Umstände dabei zu berücksichtigen.

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Summary Conditions resulting from the premature loss of the first molars are shown accordingly to data taken primarily from the authors' own statistic evaluations. Analizing their case material, the authors try to fix the optimum time for the removal of the first molars with regard to the further development of dentition, considering also other external conditions.

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Herrn Professor Dr. E. Hausser zum 60. Geburtstag     

Analysen und Ergebnisse nach Headgearbehandlung

Zusammenfassung Bei siebzig Patienten, die mit cervikalem Headgear behandelt wurden, haben wir anhand von speziellen Messungen im Fernröntgenseitenbild die Änderungen der Position der Sechsjahrmolaren vor und nach Behandlung verglichen. Die Lageänderung des Unterkiefers wurde untersucht, wobei wir in den meisten Fällen eine indirekte Beeinflussung beobachten konnten. Eine direkte dentale und basale Wirkung im Bereich des Oberkiefers wurde festgestellt.

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Summary In seventy patients all treated with cervical headgear, the position of the upper first permanent molar was compared before and after treatment by using special measurements on cephalographs. A direct dental and basal influence was detected in the upper jaw and indirect influence in the lower jaw.

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Résumé Nous rapportons les résultats obtenus chez 70 patients traités au moyen d'un headgear à traction cervicale. A l'aide de la téléradiographie sagittale nous avons observé le déplacement de la molaire de 6 ans au cours du traitement. La position de la mandibule est modifiée indirectement dans la majorité des cas. Au maxillaire, l'action se fait sentir tant au niveau dentaire que basal.

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Molar Distalization with Different Pendulum Appliances: In Vitro Registration of Orthodontic Forces and Moments in the Initial Phase

Abstract. Aim: Registration of the orthodontic forces and moments acting with different types of pendulum appliance for non-compliance upper molar distalization in an in vitro study. Material and Methods: The purpose-designed test set-up comprised the following components: artificial maxilla with anchorage unit and two electrothermodynamic (ETD) molars, electronic measuring unit for temperature control and regulation, and a sensor unit with force-moment sensor, analog/digital converter and data readout unit. This set-up permitted virtually authentic simulation of in vivo conditions on the one hand and precise determination of the force systems on the other.The appliances investigated were the standard pendulum appliance with U-loop activation according to Hilgers and with uprighting activation according to Byloff, the M-pendulum with U-loop activation according to Scuzzo, and the Pendulum K with initial uprighting activation, toe-in bend and incorporated distal screw according to Kinzinger. Results and Conclusions: The effects shown by the standard pendulum appliance and the M-pendulum over a 3 mm simulated distalization increment were a marked decrease in the distally directed forces, and an increase in the intrusive and palatally directed forces as well as in the distoinclinatory, mesially inward, and palatally rotating moments.Activations in the U-loop region of the pendulum springs induced an increase in distally and buccally directed forces and in uprighting and buccally rotating moments as well as a marked rise in extrusive forces. Whereas the activation described by Hilgers led to mesially outward rotating moments, activation according to Scuzzo resulted in a further increase in the mesially inward rotating moments.In the measured standard pendulum appliances, uprighting activation at the end of the pendulum according to Byloff led to an increase in distally and buccally directed as well as in mildly intrusive forces, and to an increase in uprighting as well as in buccally and mesially outward rotating moments.With the Pendulum K according to Kinzinger, the initial toe-in bend and uprighting activation in the region of the end of the pendulum spring together with regular adjustment of the incorporated distal screw permitted virtually translatory molar distalization: constantly distalizing forces with slight intrusive, buccally directed, and rotating side effects.     

In-vitro Investigation on Suitability of Light-cured Resins for Interocclusal Splints

OBJECTIVE: The aim of the present study was to determine the surface hardness of light- and auto-cured resins for the fabrication of occlusal splints employing Vickers hardness measurements. MATERIALS AND METHOD: In this study we used three auto-polymerized resins (Palapress, Orthocryl, Steady-Resin M) and four light-polymerized resins (Acrylight, Primosplint, Triad Tran- Sheet Colorless and Triad TranSheet Pink). The Vickers hardness measurement was carried out by means of a universal Durimet indenter applying a test load of 50 g for 30 seconds. The light-cured resins were polymerized in a Tagris Power light oven for 10 and 15 minutes each. Three separate test series were carried out (the hardness of plates under optimal conditions and of occlusal splints was measured, and the curing of light-polymerizing materials in layers of varying depth was evaluated). Data underwent statistical analysis via ANOVA and the Scheffé test. RESULTS: The microhardness determined in each case amounted to values between 10.4 HV 0.5 and 39.3 HV 0.5. The Vickers hardness determined for the plates that had been produced under optimal conditions demonstrated that their surface was significantly (p < 0.05) harder than that of cylinders and splints. The hardness values of the light-cured material Triad TranSheet Pink (39.3 HV 0.5) were significantly higher (p < 0.05) than those of all other resins. In all auto-polymerized resins, the surface hardness of the samples we examined (in the form of plates and splints) was significantly lower (p < 0.05) than that of the light-cured materials Triad TranSheet Pink and Colorless. CONCLUSION: The results we have obtained so far concerning surface hardness indicate that, in the fabrication of occlusal splints, light-cured resins may represent an alternative to auto-polymerizing materials.