An electromyographic observation of the extensional labiobuccal flange lower complete denture

The electromyogram of the buccinator and the myoid muscles in 26 lower full denture patients with severe atrophic alveoli were measured separately in three groups: group one, the conventional dentures: group two, the extension flange dentures in preliminary stage after the denture insertion and group three, the extensional flange denture in forward stage. The main results showed that (1) the functional force, except on mouth opening, exerted by the buccinator muscles increased significantly in group two and three. (2) the functional force exerted by the mylohyoid muscles on mouth opening decreased significantly in group two and increased in group three which was similar to group one. There were no significant difference between these three groups on swallowing. (3) the functional force except on mouth opening, exerted by the buccinator and mylohyoid muscles between these three groups was no significant difference. These observations indicated that there was no significant interference in the physiological activities of the buccinator and the mylohyoid muscles with the extensional flange dentures. In addition, the extensional buccal flange may enhance the denture retention.     

Neue Drähte und deren Kraftabgabe-Konsequenzen für die kieferorthopädische Therapie

Zusammenfassung Nivellierungsbögen aus verseilten Stahldrähten wurden mit Nickel-Titanium-Drähten der neuen Generation, ausgezeichnet durch Formgedächtnis, Superelastizität und exzellentes Rückstellvermögen, verglichen. Die im Biegeversuch ermittelten Werte wurden statistisch aufbereitet und ergaben eine lineare Kraftweg-Kennlinie der verseilten Stahldrähte. Die Nickel-Titanium-Drähte zeigten aber eine deutliche Abweichung von der Linearität mit kurviger Verlaufsform. Neben der atypischen Kraftweg-Kennlinie mit einer konstanten Kraftabgabe im Mittel der Kurve gaben diese Drähte, unabhängig vom Aktivierungsgrad (das heißt unabhängig davon, ob die Stufe zwischen den Brackets 1 oder 4 mm betrug), dieselbe Kraft ab. Je größer die Aktivierung zwischen den Brackets war, desto länger stellte sich der Bereich der konstanten Kraftabgabe-die Superelastizität-im Diagramm dar. Daher eignen sich die Drähe für große Niveauunterschiede oder Deflektionen. Bei geringer Aktivierung verläuft die Kennlinie sehr steil und annähernd linear. In diesen Fällen ist verseilten Stahldrähten aufgrund ihrer kleineren Federrate und Flexibilität der Vorzug zu geben.

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Summary Levelling arches made of stainless-steel wires were compared with nickel-titanium wires of the new generation which are distinguished by their shape memory, superelasticity and their excellent spring-back. The data received from a bending test have been analysed statistically and revealed a linear unloading curve of the twisted stainless-steel wires. The nickel-titanium wires, however, showed a clear deviation form the linearity with a curviform course. Besides the unusual unloading curve with a constant force mechanism in the middle range of deactivation the wires give off the same amount of force irrespective of the degree of activation (that is to say, regardless whether the level difference between the brackets amounts to 1 or to 4 mm). The diagram shows that the greater the activity between the brackets, the longer the period of superelasticity. Therefore the nickel-titanium wires are suited for large level differences or deflections. At a low activation rate the characteristic line takes a very steep and almost linear deactivation curve. In these cases twisted stainless steal wires should be preferred because of their lower load deflection rate and flexibility.

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Résumé Les arcs de nivelage de fils d'acier tressés ont été comparés avec les fils nickel-titane de la nouvelle génération, se distinguant par leur mémoire de forme, superélasticité et capacité excellente de rappel. Les valeurs relevées au cours de l'essai de pliage ont été enregistrées statistiquement et ont montré une caractéristique linéaire du tracé de force des fils d'acier tressés. Les fils nickel-titane ont cependant montré une déviation significative en présentant non une linéarité mais un tracé curviligne. A côté de leur caractéristique atypique de leur tracé de force avec un dégagement constant de force au centre de la courbe, ces fils ont produit la même force, indépendamment, du degré d'activation (c.-à-d., indépendamment du fait que l'espace entre les brackets fut de 1 ou 4 mm). Plus l'activation était grande entre les brackets, plus la zone du dégagement de la force constante-la superélasticité, paraissait longue sur le diagramme. C'est pourquoi ces fils sont indiqués pour de fortes différences de niveau ou déflexions importantes. En cas d'activation peu considérable, le tracé est très raide et presque linéaire. Dans ces cas, la préférence doit être accordée aux fils d'acier tressés, en raison de leur force élastique et flexibilité inférieures.

     

Die Entwicklung des Parodontiums nach Zahnkeimtransplantationen im Rahmen der kieferorthopädischen Behandlung

Zusammenfassung Durch Tierversuche an jungen Beagle-Hunden konnte die normale Entwicklung des Parodontiums nach Zahnkeimtransplantationen histologisch nachgewiesen werden. Die klinisch-röntgenologischen Untersuchungen zeigten keine pathologischen Befunde im Parodontiumbereich nach Zahnkeimtransplantationen beim Menschen. Die transplantierten Zähne können wie die anderen kieferorthopädisch bewegt werden. In diesem Beitrag wird auf die häufigsten Indikationen von Zahnkeimtransplantationen von Molaren, Prämolaren und Eckzähnen hingewiesen.

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Summary The normal development of the periodontal structures was confirmed histologically on young Beagle-dogs following tooth-germ transplants. In humans, clinical and radiographic examinations revealed no pathology of the periodontium following transplantation of tooth germs. The grafted teeth could be moved orthodontically in the same way as any other teeth. No precautions need to be taken. This paper describes the most common indications for transplanting the tooth-germs of canines, bicuspids and molars.

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Résumé Dans les expérimentations animales chez de jeunes chiens-Beagles, on a prouvé que les structures parodontales sont normalement développées après la transplantation de germes dentaires. Les examens cliniques et radiologiques chez de jeunes sujets d'espèce humaine n'ont pas montré de résultats pathologiques au niveau du parodonte après la greffe de germes dentaires. Les dents transplantées peuvent être déplacées orthodontiquement comme les autres dents sans mesures spéciales. Dans cet article, on a donné les indications concernant les greffes des germes de molaires, prémolaires et canines.

     

Syndrompatienten im Rahmen der kieferorthopädischen Frühbehandlung von Säuglingen mit Lippen-Kiefer-Gaumen-Spalten

Zusammenfassung Die kieferorthopädische Säuglingsbehandlung widmet sich schwerpunktmäßig Neugeborenen mit orofazialen Spaltbildungen und Kindern mit Syndromen, vornehmlichDown-Syndrom. Über 100 Dysmorphiesyndrome können mit Spaltbildungen einhergehen.An klinischen Beispielen (Robin-Syndrom,Stickler-Syndrom) wird die Problematik der Syndromdiagnostik umrissen und an einem Fall (orofaziodigitales Syndrom) der Beitrag des in der Spaltfrührehabilitation tätigen Kieferorthopäden zur Syndromidentifikation aufgezeigt.

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Summary The orthodontist's early orthopaedic treatment of the newborn focuses on cleft palate infants and children withDowns syndrome. In more than 100 malformation syndromes, orofacial clefting occurs. The problem of syndrome diagnosis is discussed by way of clinical examples (Robin-syndrome,Stickler-syndrome).A case of oro-facial digital syndrome serves to demonstrate the orthodontists contribution to syndromic diagnosis in early cleft rehabilitation.

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Résumé Le traitement orthodontique précoce de nourrissons se voue dans le plus grand nombre des cas aux nouveaunés atteints de malformations orofaciales et aux enfants souffrant de syndromes, surtout du syndrome deDown (mongolisme). La formation de fentes peut être accompagnée de plus de 100 syndromes de malformations.La problématique du diagnostic de syndromes (séquence deRobin et syndrome deStickler) est esquissée à titre d'exemples cliniques et l'apport que l'orthodontiste s'occupant de la rééducation précoce de fentes labiomaxillaires peut faire à l'indentification de syndromes est mis en évidence à propos d'un cas spécifique (syndrome oro-facio-digital).

     

The fate of impacted lower third molars after the age of 20. A four-year clinical follow-up

Seventy dental students (mean age: 20 years) with 130 asymptomatic, non-ectopic, impacted mandibular 3rd molars were followed for 4 years. At the initial visit 26 were impacted in soft tissue, 30 were partially impacted in bone, and 74 were completely impacted in bone. The following items were registered at each visit: regional pocket depths, signs and symptoms of pathology, degree of impaction, presence of upper 3rd molar. No signs or symptoms of pathology were observed in any of the subjects at the 2 visits. The 4-year visit revealed that 49 3rd molars had been removed, the reason being pericoronitis or caries in 30%, mild symptoms in 39% and for prophylactic reasons in 31%. Of the remaining 81 3rd molars: 71% of the soft tissue impactions, 25% of partial bony impactions, and 8% of complete bony impactions showed complete and normal eruption. The remaining 3rd molars were either static or had advanced in the degree of eruption. It is concluded that non-ectopic, impacted 3rd molars in the given age group may have a chance to completely erupt. The treatment for asymptomatic impacted 3rd molars in young adults, therefore, might be observation instead of prophylactic removal.     

A new porcelain repair system with a silane coupler, ferric chloride, and adhesive opaque resin

A new porcelain repair system was developed which uses a two-liquid primer, self-cured opaque resin, and light-cured composite. The primer consisted of two liquids. One component was 4% 3-trimethoxysilylpropyl methacrylate in methyl methacrylate, and the other component was 0.5% ferric chloride in ethanol. A self-curing opaque resin, 4-META/MMA-TBB opaque resin, was used as an adhesive to bind the porcelain and the composite. Adhesive opaque resin was applied on the roughened and primed porcelain. Light-cured composite was placed over the 4-META opaque layer. A shear test was performed for investigation of the strength and durability of the bonding. The result was that for all specimens after 20,000 thermocycles, fracture or crack propagation during the shear test occurred in the porcelain, rather than in the bond. This system may be used to repair fractured porcelain facings without removal of prostheses.     

Burnishability of a nickel and a cobalt base casting alloys

A specially designed stainless steel split die capable of producing a total of 24 half cylindrical shaped wax patterns was used in this study. The burnishability of two non-precious casting alloys was evaluated following a proposed softening heat treatment technique. A practical easily applied burnishing tool was introduced. Results have shown that, both of the non-precious alloys were burnishable following softening heat treatment. However, nickel-chromium alloy was significantly more burnishable than the cobalt-chromium alloy. It is suggested that clinical implications of the developed technique in this study would be an important additive for more precision castings.