Heiner Wehrbein

Success rate of miniscrews relative to their position to adjacent roots.

The purpose of this study was to evaluate, histologically, root contact, proximity to a root, and proximity to marginal bone level as possible risk factors for the failure of mini-screws when inserted between neighbouring teeth. Twenty mini-screws were inserted into the mandible of five beagle dogs. Each dog received two bracket screw bone anchors in each lower quadrant, between the roots of the second and third, and third and fourth premolars. Every six weeks, apical radiographs were taken and vital stains were administered. Twenty-five weeks after insertion of the screws, the dogs were sacrificed and specimens prepared for histological evaluation. The distance between the screw and the roots and between the screw and the marginal ridge level (MRL) were measured on the histological slides. The presence or absence of root contact was evaluated histologically on serial sections. The number of screws was too small to allow for sound statistical analysis of the factors under investigation. During the evaluation period, 11 screws were lost. Six screws were in contact with a tooth root and five of these were lost. In five sites, the distance between the screw and the tooth was less than 1.0 mm, but only one of these screws was lost. The distance between the screw and the marginal bone level was less than 1.0 mm for nine screws and seven of these were lost. The results of this limited study suggest that root contact and marginal position might be major risk factors for screw failure.

Skeletal Anchorage in Orthodontics – Basics and Clinical Application

This review article describes the basics and clinical applications of skeletal anchorage in orthodontics, namely: areas of indication, anchorage devices, insertion areas, indications, potential complications, and their use in growing patients.The areas for skeletal anchorage include orthodontic-prosthetic anchorage, orthodontic anchorage, and skeletal anchorage in orthopedic therapy procedures. The anchorage devices currently available are: prosthetic implants, mini screws, palatal implants, onplants, bone anchors, zygoma wires and skeletally-supported distractors. The insertion areas described so far (according to therapeutic procedure and bone supply available) include edentulous jaw sections, the interdental septum, infra-apical and supra-apical areas, the palate (median, paramedian, lateral), the retromolar area, and the zygomatic bone. Force systems are applied (direct or indirect anchorage) according to surgical and orthodontic or orthopedic requirements. Skeletal anchorage devices should be selected according to the following criteria. Is the anchorage task unifunctional or multifunctional? How many anchorage devices are required for the therapy in question? What is the success rate of the various anchorage devices; what are the applicable biomechanics and soft tissue or hard tissue conditions in the insertion area? The success rates for miniscrews are currently between 80% and 90%, and over 90% for palatal implants.The potential of skeletal anchorage is broadening the current orthodontic treatment spectrum, guaranteeing the practitioner absolute control of anchorage by avoiding the unpredictable reactions of periodontal anchorage, leading to a reduction in unwanted side effects.ZusammenfassungDer vorliegende Artikel beschreibt die Grundlagen und die klinische Anwendung der skelettalen Verankerung in der Kieferorthopädie: Indikationsbereiche, Verankerungsmittel, Insertionsbereiche, Indikationen, potentielle Komplikationen und die Nutzung beim noch wachsenden Patienten.Als Indikationsbereiche der skelettalen Verankerung sind heute zu nennen: orthodontisch-prothetische Verankerung, orthodontische Verankerung und skelettale Verankerung bei kieferorthopädischen Behandlungsaufgaben. Als Verankerungsmittel stehen heute zur Verfügung: prothetische Implantate, Minischrauben, Gaumenimplantate, Onplants, Bone Anchors, Zygoma-Drähte und skelettal abgestützte Distraktoren. Je nach Behandlungsaufgabe und dem Knochenangebot wurden folgende Insertionsbereiche beschrieben: zahnloser Kieferabschnitt, interdentales Septum, infraund supraapikaler Bereich, Gaumen (median, paramedian, lateral), retromolarer Bereich sowie der Bereich des Os zygomaticum. Die Applikation des Kraftsystems (direkte/indirekte Verankerung) richtet sich nach den chirurgischen und orthodontischen/orthopädischen Erfordernissen. Die Selektion des skelettalen Verankerungsmittels sollte nach folgenden Kriterien erfolgen: uni- bzw. multifunktionelle Verankerungsaufgaben, Anzahl der notwendigen Verankerungselemente für die jeweilige Behandlungsaufgabe, Erfolgsrate der diversen Verankerungselemente, der zu applizierenden Biomechanik und der Weichgewebe- sowie Hartgewebebedingungen im Insertionsbereich. Die Erfolgsraten liegen heute bei Minischrauben bei 80–90%, bei Gaumenimplantaten bei über 90%.Die heutigen Möglichkeiten der skelettalen Verankerung erweitern das kieferorthopädische Behandlungsspektrum, garantieren eine absolute Kontrolle der Verankerung durch den Behandler, umgehen die unvorhersagbaren Reaktionen der desmodontalen Verankerung und führen zu einer Reduktion unerwünschter Nebenwirkungen.

Age-Related Changes in the Midpalatal Suture@@@Altersvernderungen der Sutura palatina mediana: A Histomorphometric Study@@@Eine histomorphometrische Studie

Aim:The issue of the present study was to register age-related morphological differences with reference to the mean sutural width (MSW) and the degree of obliteration (O) in the region of the human midpalatal suture.Material and Methods:22 human palate specimens from subjects of different ages (18–63 years) were available for this purpose. Three sections (anterior, median and posterior) from each specimen underwent histological preparation and staining with toluidine blue before being subjected to histological and histomorphometric analysis. Two age groups (≤ 25 years and ≥ 26 years) were formed.Results:The findings showed that the median sutural width in the younger group (≤ 25 years) was 211.20 µm versus only 161.16 µm in the older group. This difference was statistically significant (p = 0.05).The proportion of ossified tissue in the entire suture (obliteration) was low in all subjects. At 13.10%, the maximum obliteration measured was found in a 44-year-old man in the older age group. The median value of the ossification was 0% in the younger age group and 3.11% in the group ≥ 26 years. This difference was statistically significant (p = 0.036).The earliest ossification was registered in a 21-year-old man. The oldest subject without ossification was a 54-year-old man.In terms of local topography, no statistically significant differences between anterior, median and posterior palatal region were observed with respect to the two investigated parameters (MSW, O).Conclusion:These findings confirm that ossification of the midpalatal suture is not a valid reason for the increased transversal resistance encountered during rapid palatal expansion in younger subjects (≤ 25 years) as well as in many older persons.ZusammenfassungZiel:Das Ziel der vorliegenden Studie war es, altersabhängig morphologische Unterschiede in Bezug auf die mittlere suturale Breite (MSB) und den Obliterationsgrad (O) im Bereich der Sutura palatina mediana des Menschen zu erfassen.Material und Methoden:Zu diesem Zweck standen 22 humane Gaumenpräparate von Individuen unterschiedlichen Alters (18–63 Jahre) zur Verfügung. Von jedem Präparat wurden drei Abschnitte (anterior, median und posterior) histologisch aufbereitet, mit Toluidinblau gefärbt und dann histologisch und histomorphometrisch analysiert. Zwei Altersgruppen (≤ 25 Jahre und ≥ 26 Jahre) wurden gebildet.Ergebnisse:Nach den erhobenen Daten betrug die suturale Breite in der jüngeren Gruppe (≤ 25 Jahre) 211,20 µm im Median und in der älteren Gruppe nur 161,16 µm im Median. Der Unterschied war statistisch signifikant (p = 0,05).Der Anteil der verknöcherten Areale der gesamten Sutur (Obliteration) war bei allen Individuen gering. Die maximal gemessene Obliteration betrug 13,10% und wurde innerhalb der älteren Gruppe bei einem 44-jährigen Mann gefunden. Der Medianwert der Verknöcherung in der jüngeren Altersgruppe betrug 0% und in der Gruppe ≥ 26 Jahre 3,11%. Der Unterschied war statistisch signifikant (p = 0,036).Die früheste Verknöcherung wurde bei einem 21-jährigen Mann nachgewiesen. Die älteste Person ohne Verknöcherung war ein 54-jähriger Mann.Lokaltopographisch konnten bezüglich der beiden untersuchten Parameter (MSB, O) keine statistisch signifikanten Unterschiede zwischen anteriorem, medianem und posteriorem Gaumenbereich nachgewiesen werden.Schlussfolgerung:Diese Ergebnisse belegen, dass bei jüngeren (≤ 25 Jahre) und auch bei vielen älteren Erwachsenen die Verknöcherung der Sutura palatina mediana nicht als Grund für die erhöhte transversale Resistenz bei der schnellen Gaumennahterweiterung angesehen werden kann.

Der Einfluß des Kieferhöhlenbodens auf die orthodontische Zahnbewegung

ZusammenfassungDurch die Überlagerung von 40 prä- und posttherapeutischen, Orthopantomogrammen konnten der Grad der Kippung und die Art der Bewegung von 87 Zähnen in Abhängigkeit von Konfiguration und Ausdehnung der basalen Kieferhöhle quantitativ dargestellt werden. Es zeigte sich, daß bei eher vertikalem Kieferhöhlenbodenverlauf (VL=1) vor dem Zahn in Bewegungsrichtung mit einer deutlich höheren Kippung der Zähne zu rechnen ist; diese liegt um zirka 10° höher als bei Zähnen mit eher horizontalem oder schrägem Kieferhöhlenbodenverlauf (VL=2). Bei den Zähnen der Gruppe VL=1 besteht eine Abhängigkeit zwischen Tiefe des Rezessus und Grad der Kippung (p≦0,05), das heißt, je tiefer der Rezessus, desto größer die Kippung. Für die Gruppe VL=2 ist dieser Zusammenhang statistisch nicht gesichert. In der Gruppe VL=1 ist eine eher kippende und in der Gruppe VL=2 eine eher translatorische Bewegung zu erwarten.SummaryBy superimpositioning 40 pre-und posttherapeutic orthopantomograms the degree of tipping and kind of movement of 87 teeth could be described quantitatively, dependent on configuration and extension of the basal maxillary sinus. It has been shown that, with a more vertical extension (VL=1) in front of the tooth to be moved one can expect an obviously higher degree of tipping (about 10°) as compared to teeth moved through a more horizontal maxillary sinus base (VL=2). In the group of teeth VL-1 a correlation between the depth of the maxillary sinus recessus and the degree of tipping could be found (p≤0,05); i.e. the deeper the maxillary sinus recessus, the higher the degree of tipping. For VL=2 this correlation is statistically not significant. In the group VL=1 rather a tipping movement, in VL=2 a translatory movement can be expected.

Orthodontic anchorage implants inserted in the median palatal suture and normal transverse maxillary growth in growing dogs: a biometric and radiographic study.

Small osseointegrated implants inserted in the palate provide a reliable anchorage control during orthodontic treatment. When these implants are inserted in the median palatal suture in growing individuals, the possible effects on normal transverse maxillary growth are still unknown. Therefore, the aim of this study was to evaluate the influence of orthodontic anchorage implants on transverse maxillary growth when inserted in the median palatal suture of growing dogs. Five growing dogs were used, one of them randomly selected as a control dog. The test dogs each received two implants in the median palatal suture. Impressions and occlusal radiographs of the upper jaws were taken at baseline (TO), after 84 days (T1), and at the end of the study after 168 days (T2). Measurements to compare increases in maxillary width between test dogs and control dog were performed on study casts and occlusal radiographs at TO, T1, and T2. Restricted transverse growth was observed in the test dogs in the canine region. Transverse growth in the region of second and fourth premolars was similar for the test dogs and the control dog. These results may be of some clinical relevance when orthodontic anchorage implants are to be inserted in growing individuals. An alternative insertion site, for example the parasagittal region, should be considered in these cases, to avoid possible negative effects on normal transverse maxillary development.

Molar Distalization with a Modified Pendulum Appliance— In Vitro Analysis of the Force Systems and In Vivo Study in Children and Adolescents

The standard pendulum appliance was modified by integrating a distal screw into its base and by special preactivation of the pendulum springs. The suitability of this Pendulum K for the translatory distalization of maxillary molars was investigated in an in vitro analysis and in an in vivo study in children and adolescents. The in vitro measurement of the resulting force systems revealed that all forces and moments remained virtually constant over a three-mm simulated distalization increment. The transverse force, Fx, increased from two to 11 cN and the weakly intrusively acting force, Fy, from six to eight cN, but these increases were not statistically significant. The distalization force, Fz, initially 201 cN, was still 199 cN after a three-mm distalization increment. The mesially acting moment, My, rose from 1654 to 1834 cN mm, whereas the palatally acting moment, Mz, declined slightly from 229 to 164 cN mm. The slight, consistent distoinclinatory moment, Mx, initially 306 cN mm, was 310 cN mm after three mm. In parallel, the in vivo study with its collective of 66 patients confirmed that the Pendulum K allows a virtually translatory molar distalization with slight tippings of 4.75 degrees to the palatal plane and 4.25 degrees to the anterior basal plane. Palatal movements of the first molars were avoided. The proportion of molar distalization in the total movement was 73.53%.

Osteogenic differentiation of periodontal fibroblasts is dependent on the strength of mechanical strain

OBJECTIVE During orthodontic therapy the correct strength of mechanical strain plays a key role for bone remodelling during tooth movement. Aim of this study was to investigate the osteogenic differentiation of human periodontal ligament fibroblasts (HPdLF) depending on the applied strength of mechanical strain compared to osteoblasts (HOB). DESIGN HPdLF and HOB were loaded with different strengths (1%, 5% and 10%) of static mechanical strain (SMS) for 12h in vitro. Viability was verified by MTT and apoptosis by TUNEL assay. Gene expression of cyclin D1, collagen type-1 (COL-I), alkaline phosphatase (ALP), osteocalcin, osteoprotegerin (OPG) and receptor activator of the NF-κB ligand (RANKL) were investigated using RT-PCR. OPG and RANKL synthesis was measured by ELISA and ALP activity by colorimetric assay. RESULTS 10% of SMS led to a decrease in cell viability of both cells lines, but no increased rate of apoptosis. RT-PCR showed the highest increase of cyclin D1 expression for HPdLF and HOB when applied to 5% of SMS, and HOB showed a doubling of COL-I gene expression. HPdLF and HOB showed a strength-dependent synthesis of OPG and ALP activity, whereas HOB demonstrated a decrease in OPG synthesis and ALP activity when applied to 10% of SMS. CONCLUSION Osteogenic differentiation of HPdLF correlates with increasing strength of SMS. HOB show decreased activity when applied to high SMS, demonstrating potential damage to the bone remodelling due to strain of high strength. SMS up to 5% provides the best conditions for bone formation at the tension site of tooth movement.

Plaque levels of patients with fixed orthodontic appliances measured by digital plaque image analysis.

INTRODUCTION A digital plaque image analysis system was developed to objectively assess dental plaque formation and coverage in patients treated with fixed orthodontic appliances. METHODS The technique was used to assess plaque levels of 52 patients undergoing treatment with fixed appliances in the Department of Orthodontics at Johannes Gutenberg University in Mainz, Germany. RESULTS Plaque levels ranged from 5.1% to 85.3% of the analyzed tooth areas. About 37% of the patients had plaque levels over 50% of the dentition, but only 10% exhibited plaque levels below 15% of tooth coverage. The mean plaque coverage was 41.9% ± 18.8%. Plaque was mostly present along the gum line and around the orthodontic brackets and wires. CONCLUSIONS The digital plaque image analysis system might provide a convenient quantitative technique to assess oral hygiene in orthodontic patients with multi-bracket appliances. Plaque coverage in orthodontic patients is extremely high and is 2 to 3 times higher than levels observed in high plaque-forming adults without appliances participating in clinical studies of the digital plaque image analysis system. Improved hygiene, chemotherapeutic regimens, and compliance are necessary in these patients.

Clinical observations and success rates of palatal implants

INTRODUCTION Anchorage control is a challenge in orthodontics. Implants can be used to provide absolute anchorage.The aim of this study was to evaluate the success rates of palatal implants used for various anchorage purposes. METHODS Thirty-four palatal implants were placed in 33 patients. In the adults (n = 9), the implants (n = 9) were placed in the median palatal suture. In the adolescents (n = 24), the implants (n = 25) were placed in the paramedian region. The implants were used to support a transpalatal arch, a modified distal jet appliance, or a modified hyrax screw. An implant was considered successful if it could be used as planned throughout the orthodontic treatment. The patients were asked to evaluate their pain perception after placement and explantation procedures. RESULTS Three implants failed early (during the waiting period before orthodontic loading, within 3 months after placement). During the orthodontic loading period, no implants were lost. No statistically significant correlations were found between success rate and sex, age, primary stability, placement site (median or paramedian), implant size, or palatal depth. Pain perception after surgery was acceptable. The success rate of the palatal implants in this study was 91%. CONCLUSIONS Palatal implants are a reliable method of providing absolute anchorage control in a variety of patients for different indications. They can be loaded both directly and indirectly.

[Intrusion of the anterior teeth with the segmented-arch technic of Burstone--a clinical study].

ZusammenfassungDas Ziel der Untersuchung war es, die Effizienz der Intrusionsmechanik nachBurstone zu untersuchen. Bei 31 Tiefbißfällen mit einem frontalen Überbiß >- 4mm wurden zu Beginn und am Ende der Untersuchung Gebißmodelle, seitliche Fernröntgenaufnahmen und enorale Röntgenaufnahmen angefertigt. Es wurden erfaßt. 1. Ausmaß der Intrusion in Relation zum selektiven Kraftansatz, 2. Dauer der Intrusion und 3. Ausmaß der Wurzelresorption. Das durchsehnittliche Ausmaß der Intrusion lag im Oberkiefer bei 2,3 mm im Unterkiefer bei 3 mm und betrug pro Monat im Oberkiefer 0.53 mm, im Unterkiefer 0,54 mm Die Analyse des selektiven Kraftansatzes am Frontzahnblock ergab, daß das Widerstandszentrum weiter distal anzunehmen ist, als bisher vermutet wurde. Bei einer durchschnittlichen Behandlungsdauer von 4,3 Monaten im Oberkiefer und 5,5 Monaten im Unterkiefer konnten durch die Dosierung der Kraft bei einem berechenbaren Kräftesystem apikale Wurzelresorptionen gering gehalten werden. Der in drei Fällen angewandte bukkale Wurzeltorquebogen erlaubte bei Klasse-II/1-Dysgnathien, insbesondere bei aufgefächerten Frontzähnen, eine Kombinationsbewegung aus Lingualkippung der Krone und Intrusion, wobei die Intrasionskomponente im Vergleich zur Kippung deutlich verzögert war. Die segmentierte Bogentechnik erlaubt mittels eines selektiven Kraftansatzes und einer dosierten Kraftapplikation eine gezielte Intrusion von Frontzähuen.SummaryThe purpose of this study was to examine the efficiency of intrusion mechanics as described byBurstone. Thirty-one cases of deep bite with an overbite equal to or more than 4 mm were analysed by means of cast models, lateral cephalometric views and dental films of the front teeth prior to and after intrusion. The following parameters were considered: 1. Extent of the intrusion relative to a selective point of force application, 2. duration of the intrusion, and 3. amount of root resorption. The average extent of the intrusion in the case of the upper front teeth was 2.3 mm, and in the case of the mandible 3 mm. The rate of intrusion per month was 0.53 mm in the maxilla, and 0.54 mm in the mandible. Analysis of the point of force application showed that the centre of resistance must be presumed to be more distal than previously assumed. For an average treatment time of 4.3 months in the maxilla, and 5.5 months in the mandible, the apical root resorption was minimized by applying dosed force using a calculable force system. A buccal root torque arch employed in three cases permitted, in class II/1 cases, a combined movement comprising lingual tipping of the crown and intrusion, the intrusion component being clearly delayed in comparison with tipping. The segmented arch technique allows an objective intrusion of anterior teeth. This depends on choosing the appropriate point of force attachment and the correct amount of force.The purpose of this study was to examine the efficiency of intrusion mechanics as described by Burstone. Thirty-one cases of deep bite with an overbite equal to or more than 4 mm were analysed by means of cast models, lateral cephalometric views and dental films of the front teeth prior to and after intrusion. The following parameters were considered: 1. Extent of the intrusion relative to a selective point of force application, 2. duration of the intrusion, and 3. amount of root resorption. The average extent of the intrusion in the case of the upper front teeth was 2.3 mm, and in the case of the mandible 3 mm. The rate of intrusion per month was 0.53 mm in the maxilla, and 0.54 mm in the mandible. Analysis of the point of force application showed that the centre of resistance must be presumed to be more distal than previously assumed. For an average treatment time of 4.3 months in the maxilla, and 5.5 months in the mandible, the apical root resorption was minimized by applying dosed force using a calculable force system. A buccal root torque arch employed in three cases permitted, in class II/1 cases, a combined movement comprising lingual tipping of the crown and intrusion, the intrusion component being clearly delayed in comparison with tipping. The segmented arch technique allows an objective intrusion of anterior teeth. This depends on choosing the appropriate point of force attachment and the correct amount of force.