Björn Ludwig

Application of a new viscoelastic finite element method model and analysis of miniscrew-supported hybrid hyrax treatment

INTRODUCTION In this study, we aimed to assess the ability of a new viscoelastic finite element method model to accurately simulate rapid palatal expansion with a miniscrew-supported hybrid hyrax appliance. METHODS A female patient received 3-dimensional craniofacial imaging with computed tomography at 2 times: before expansion and immediately after expansion, with the latter serving as a reference model for the analysis. A novel approach was applied to the finite element method model to improve simulation of the viscoelastic properties of osseous tissue. RESULTS The resulting finite element method model was a suitable approximation of the clinical situation and adequately simulated the forced expansion of the midpalatal suture. Specifically, it demonstrated that the hybrid hyrax appliance delivered a force via the 2 mini-implants at the center of resistance of the nasomaxillary complex. CONCLUSIONS The newly developed model provided a suitable simulation of the clinical effects of the hybrid hyrax appliance, which proved to be a suitable device for rapid palatal expansion.

Quantifying patient adherence during active orthodontic treatment with removable appliances using microelectronic wear-time documentation

OBJECTIVES The aim of this study was to quantify the wear times of removable appliances during active orthodontic treatment. MATERIALS AND METHODS The wear times of 141 orthodontic patients treated with active removable appliances in different locations were documented over a period of 3 months using an incorporated microsensor. Gender, age, treatment location, health insurance status, and type of device were evaluated with respect to wear time. Significant associations between wear times and patient factors were calculated using non-parametric tests. RESULTS The median daily wear time was 9.7 hours/day for the entire cohort, far less than the 15 hours/day prescribed. Younger patients wore their appliances for longer than older patients (7-9 years 12.1 hours/day, 10-12 years 9.8 hours/day, and 13-15 years 8.5 hours/day; P < 0.0001). The median wear time for females (10.6 hours/day) was 1.4 hours/day longer than males (9.3 hours/day; P = 0.017). Patients treated at different locations wore their devices with a difference of up to 5.0 hours/day. Privately insured patients had significantly longer median wear times than statutorily insured patients. No significant difference in wear time was noted according to device type. CONCLUSIONS The daily wear time of removable appliances during the active phase of orthodontic therapy can be routinely quantified using integrated microelectronic sensors. The relationship between orthodontist and patient seems to play a key role in patient adherence. Wear-time documentation provides the basis for more individualized wear-time recommendations for patients with removable appliances. This could result in a more efficient, shorter, and less painful orthodontic therapy.

Comparison of Bipartite Versus Tripartite Osteotomy for Maxillary Transversal Expansion Using 3-Dimensional Preoperative and Postexpansion Computed Tomography Data

PURPOSE To evaluate tripartite paramedian versus bipartite median osteotomy in surgically assisted rapid maxillary expansion. Tripartite osteotomy was performed between the lateral incisors and canines at the former premaxillary junction to avoid midline diastema, septal and columellar dislocation, and asymmetric expansion, minimizing high-distraction forces through bilateral doubled osteotomy on periodontia and thus reducing vestibular attachment loss and producing stable callus formation to avoid relapse. PATIENTS AND METHODS The preoperative and postexpansion computed tomography data from 50 patients were analyzed in multiplanar viewing for bodily segment movement, vestibular bone loss, and transverse skeletal and dental widening with predefined landmarks. Of the 50 patients, 22 had undergone tripartite and 28 had undergone bipartite osteotomy. RESULTS Using an independent t test, both osteotomies permitted adequate transverse skeletal expansion in the premolars, converging, however, in the molars. Bipartite osteotomy resulted in less symmetry in transverse skeletal widening, greater bodily segment movement in the first premolar/molar, and greater vestibular bone loss. Tripartite osteotomy resulted in greater overall expansion and less bone remodeling. On variance analysis, tripartite bone-borne distraction resulted in the greatest decrease of transverse expansion in patients older than 20 years. The tripartite osteotomy also provoked distractor- and age-independent outward segmental movement. Bipartite osteotomy resulted in distractor- and age-independent inward segmental movement. Bipartite osteotomy showed the greatest bone resorption in patients younger than 20 years old in the molars and tripartite osteotomy in patients older than 20 years in the premolars. CONCLUSIONS Tripartite paramedian osteotomy allowed greater overall symmetric expansion compared with bipartite median osteotomy, with, however, a decline in transverse widening to the posterior. Bipartite osteotomy should be preferred whenever good periodontal status permits greater vestibular bone loss and a midline diastema and asymmetric expansion and a midline shift will be tolerated by the patient. Tripartite osteotomy should be chosen whenever a midline diastema and shift, septal and columellar dislocation, asymmetric expansion, and larger distraction forces on the paradontia, resulting in vestibular attachment loss, are to be avoided.

Radiological location monitoring in skeletal anchorage: introduction of a positioning guide.

Background and Objective:As the insertion of miniscrews necessarily involves the risk of damaging the hard and soft tissues, particular attention must be paid to the diagnostics carried out prior to surgery, which include checking the insertion site radiologically by applying positioning devices. The placement of many common radiological positioning guides is difficult and timeconsuming, and some varieties must be specially constructed at great cost, which led us to develop in this study a simple and easily applicable X-ray aid offering the mandatory safety features in terms of reliability and forensics. We aimed to design a device as small as possible to avoid as many falsely-positive and falselynegative findings as possible with not-100% orthoradial dental films. We also wanted the device to be applicable in all potential insertion areas.Materials and Methods:We initially performed a thorough literature research for suggestions for radiological positioning guides in pre-operative diagnostics. Based on those descriptions, we fabricated two common positioning devices, which we then applied and tested clinically regarding their handling, general applicability, and quality.To meet the stringent demands made of pre-operative radiological diagnostics, we developed a positioning guide with probing function (“X-ray pin”). Its applicability and diagnostic value were examined in a clinical study of prospective design.Results and Conclusions:Our radiological positioning device has a total length of 3.5 mm and has a ball on its end, thus resembling conventional pins in principle. Due to its conical form, the device can be easily placed in the mucosa at the designated insertion site. The X-ray pin is reliably stable in position, guaranteeing an accurate assessment of the designated miniscrew position. There is no need for advance bending; or for later adjustment and attachment attempts. The pin can be inserted in all regions, including the palatal area. Our X-ray pin proved to be an easily affordable, clinically simple, and safe-to-apply alternative.ZusammenfassungHintergrund und Zielsetzung:Da bei der Insertion einer Minischraube die potentielle Gefahr einer Hart- bzw. Weichgewebeschädigung gegeben ist, sollte der Behandelnde besondere Sorgfalt auf die präoperative Diagnostik verwenden. Dazu trägt eine röntgenologische Lagekontrolle an der geplanten Insertionsregion unter Nutzung von Positionierungsvorrichtungen bei. Da viele bekannte Röntgenhilfen schwer und aufwendig zu platzieren sind und einige Varianten kostenintensiv laborgefertigt werden müssen, war es Ziel der Studie, eine einfach und schnell anzuwendende Röntgenhilfe zu entwickeln, die die nötige Sicherheit im Hinblick auf Aussagewert und Forensik bietet. Dabei sollte ein möglichst kleiner Behelf entstehen, der auch bei nicht absolut orthoradialen Zahnfilmen kaum falsch positive bzw. falsch negative Ergebnisse liefert. Des Weiteren sollte ein Einsatz in allen möglichen Planungsregionen möglich sein.Material und Methode:Vorab erfolgte eine gründliche Literaturrecherche nach Vorschlägen für Röntgenhilfsmittel zur präoperativen Diagnostik. Basierend auf diesen Beschreibungen wurden zwei gängige Modelle angefertigt, klinisch eingesetzt und in Bezug auf Handhabung, universelle Einsetzbarkeit und Ergebnisqualität getestet.Um einen Großteil der Anforderungen im Bereich der präoperativen Röntgendiagnostik zu erfüllen, wurde eine Orientierungshilfe mit Sondierungsfunktion („Röntgen-Pin“) entwickelt. Der Einsatz und diagnostische Wert wurden in einem klinisch prospektiven Studiendesign überprüft.Ergebnisse und Schlussfolgerung:Der entstandene Röntgenbehelf hat eine Gesamtlänge von 3,5 mm, trägt an seinem Ende eine Kugel und gleicht prinzipiell einer herkömmlichen Stecknadel. Durch die konische Form lässt er sich an der geplanten Insertionsstelle leicht in die Schleimhaut einbringen. Er ist zuverlässig lagestabil und gewährleistet eine gute Beurteilung der späteren Schraubenposition. Vorbiegungen, Justierungs- und Befestigungsversuche entfallen. Er kann in allen Regionen, so auch palatinal, eingesetzt werden. Klinisch zeigte er eine einfache und sichere Anwendbarkeit und erwies sich als eine kostengünstige Alternative.

Effects of Class II treatment with a banded Herbst appliance on root lengths in the posterior dentition

INTRODUCTION The aim of this study was a retrospective analysis of posterior teeth in 20 adolescents and young adults with Angle Class II Division 1 malocclusion treated with a banded Herbst appliance to check for inhibited root development and apical root resorption. METHODS Panoramic radiographs were taken of every patient at the beginning and after the completion of functional orthopedic treatment. The magnification of the area of the posterior teeth was determined individually for every radiograph. Then the vestibular lengths of the molars and premolars were assessed metrically. To assess root-length changes, the difference between the lengths of the teeth before and after treatment was calculated. RESULTS After treatment with a banded Herbst appliance, tooth length generally increased in the area of the anchorage. But there was a tendency toward root-length decrease in teeth immediately adjacent to the Herbst fittings in the vestibular roots of both the maxillary first molars (distovestibular, -0.02 ± 2.31 mm; mesiovestibular, -0.06 ± 2.05 mm) and the mandibular first premolars (-0.46 ± 3.53 mm). CONCLUSIONS The banded Herbst appliance might deliver unphysiologic forces to immediate anchor teeth, thereby exposing these to a higher risk of root resorption than in other teeth incorporated into the anchorage either directly via bands or indirectly via occlusal or approximal contacts. Looking at uncompromised root morphology in the area of the anchorage, we believe that early treatment with fixed functional appliances can be predicted to yield better outcomes than late treatment because of the higher biologic tolerance expressed by teeth with an apical latency.

Shear Bond Strength of Orthodontic Brackets Bonded with Self-etching Primer to Intact and Pre-conditioned Human Enamel

Objective:The purpose of this study was to evaluate the shear bond strength of orthodontic bracket when bonded to pre-conditioned and intact enamel using a self-etching primer within 6 hours and after thermal cycling.Material and Methods:One hundred and twenty freshly-extracted human teeth were divided into four groups according to how the buccal surface to be bonded had been pre-conditioned: 1) acid-etched with 37% phosphoric acid, 2) sand-blasted with 50 microns aluminum-oxide, 3) matted with diamond burr, and 4) intact enamel used as control. Orthodontic metal brackets were bonded to the teeth using the same composite resin (Transbond™ XT) and self-etching primer (Transbond™ Plus Self-Etching Primer). Brackets were debonded within 6 hours or after thermal cycling for 2500 times (5 °C – 37 °C – 55 °C). Shear bond strength was measured on a testing machine at a crosshead speed of 3 mm/min. The bracket-failure interface was quantified according to the modified adhesive remnant index score (ARI). Data were analyzed using the two-way ANOVA test, Scheffé confidence interval of differences of means, and the chi-square test (p < 0.05).Results:All the pre-conditioned groups showed significantly higher shear bond strength before and after thermal cycling than the control group. There was no significant correlation between thermal cycling and shear bond strength. The ARI scores revealed that the bond failed primarily on the adhesive-enamel interface in all groups before and after thermal cycling, with the exception of the acid-etched group, whose bonds failed mainly on the adhesive-bracket interface after thermal cycling.Conclusion:The authors recommend that the enamel be preconditioned before applying the self-etching primer when greater shear bond strength is desired.ZusammenfassungZiel:Ziel der Studie war die Ermittlung der Scherhaftfestigkeit von auf vor- und unbehandelten Schmelzoberflächen adhäsiv befestigten Brackets unter Verwendung eines selbstkonditionierenden Primers. Dabei waren die Versuche nach 6-stündiger Lagerung im Wasser bzw. nach Temperaturwechsel-Belastung der Proben angesetzt.Material und Methodik:Anhand der Konditionierung ihrer Bukkalflächen wurden 120 frisch extrahierte humane Zähne in vier Gruppen unterteilt: 1. konventionelle Ätzung der Schmelzoberfläche mit 37%iger Phosphorsäure, 2. gestrahlte Schmelzoberfläche mit 50 μm Aluminiumoxid-Partikeln, 3. Oberflächenbearbeitung mit diamantiertem Schleifkörper und 4. intakter Schmelz als Referenzgruppe. Unter Verwendung desselben Komposit klebers (Transbond™ XT) und selbstkonditionierenden Primers (Transbond™ Plus Self-Etching Primer) wurden Metallbrackets auf die Bukkalflächen der Zähne geklebt. Die Brackets wurden entweder nach 6 Stunden Wasserlagerung oder nach 2500 Zyklen einer Temperaturwechsel-Belastung (5 °C − 37 °C − 55 °C) wieder von den Zähnen abgelöst. Die Scherhaftung wurde in einer Materialprüfapparatur unter einer Vorschubgeschwindigkeit von 3 mm/min getestet. Das Versagen des Adhäsivverbundes am Schmelz-Bracket-Übergang wurde über eine modifizierte ARI-Skala (Adhesive remnant index score) erfasst. Die Ergebnisse wurden durch zweifaktorielle Varianzanalyse (ANOVA), den Signifikanztest nach Scheffé und den χ2-Test (p < 0,05) statistisch bewertet.Ergebnisse:Unabhängig von der beschriebenen Lagerung der Proben zeigten die Zähne aus den vorbehandelten Gruppen eine signifikant höhere Scherhaftfestigkeit als die Kontrollgruppe. Es war kein signifikanter Einfluss der Temperaturwechsel-Belastung auf die Scherhaftung nachweisbar. Die ARI-Bewertung zur Frakturanalyse belegte, dass in beiden Testreihen hauptsächlich die Adhäsiv-Schmelz-Verbindung versagte, mit Ausnahme der zusätzlich vorgeätzten Proben, bei denen der Frakturbereich nach Thermocycling meist an der Grenzfläche Bracket-Adhäsiv lag.Schlussfolgerung:Nach den vorliegenden Ergebnissen befürworten die Autoren zur Steigerung der Scherhaftung eine zusätzliche Schmelzkonditionierung vor dem Auftragen von selbstätzenden Primern.

Conservative Orthodontic Primary Care of Four Newborns with the Pierre-Robin Sequence Triad

Newborns with Pierre-Robin sequence often suffer from serious or even life-threatening obstructions in the respiratory tract resulting from anatomic malformations (micrognathia, glossoptosis and potentially a median cleft palate). Such babies require immediate effective therapeutic measures. Our case descriptions of four babies with the typical triad illustrate the application of a modified upper plate with an individually-adjustable pharyngeal spur. Precise and individually-modifiable adaptation of the plates pharyngeal parts – depending on the developmental stage – permit the narrow airway to be opened, which then affects the tongues position and the sagittal position of the mandible.ZusammenfassungNeugeborene mit Pierre-Robin-Sequenz haben durch die direkten Folgen ihrer anatomischen Fehlbildungen (Mikrogenie, Glossoptose und fakultativ mediane Gaumenspalte) häufig schwere bis lebensbedrohliche Atemwegsobstruktionen, die eine sofortige und effektive Einleitung therapeutischer Maßnahmen notwendig machen. Unsere Fallschilderungen von vier Säuglingen mit typischer Ausprägung der Trias beschreiben die Anwendung einer modifizierten Gaumenplatte mit individuell einstellbarem pharyngealem Sporn. Eine exakte und entwicklungsbedingt individuell modifizierbare Anpassung der pharyngealen Plattenanteile ermöglicht die Öffnung der verengten Atemwegspassage bei gleichzeitiger sukzessiver Beeinflussung der Zungenlage und der sagittalen Unterkieferposition.

Prevalence and development of KIG-relevant symptoms in primary school students from Frankfurt am Main.

Objective:To determine the actual need for orthodontic treatment in the late mixed dentition according to the German KIG system (Kieferorthopädische Indikationsgruppen = Orthodontic Indication Groups). By comparing the findings with those of the early mixed dentition, we aimed to evaluate whether a change in the spectrum of malocclusions would occur.Subjects and Methods:Dental check-ups took place in schools in Frankfurt am Main, during which the orthodontically-relevant symptoms of 1251 schoolchildren (female 49.5%, male 50.5%) in grades 4 and 5 were recorded and compared with findings documented 4 years earlier in the same classes at the same schools.Results:Of those orthodontic malocclusions in need of therapy and covered by the statutory health insurance, lateral crossbite and enlarged overjet (more than 6 mm) dominated by 9.2% and 8.7%, respectively, among the 9- to 11-year-old children. Of all the malocclusions recorded within the KIG-group showing a treatment need degree ≥ 3, category D4 (overjet greater than 6 mm) at 17.4% was the most frequent, followed by K4 (unilateral crossbite) at 15.3%, and M4 (negative overjet up to −3 mm) at 14.9%. 41.4% of all the children examined presented a treatment indication according to statutory health insurance directives (KIG ≥3). The 10% reduction in treatment cases financed by statutory health insurance has been achieved in any case [1], as mandated by health policy.Conclusions:Our comparison of results gathered from 2000 and 2004 showed that as the children grew older, the prevalence of already-enlarged overjets increased, as did the frequency of deep bite. We observed fewer frontal open bites and crossbites in late mixed dentition. Treatment need according to current statutory health insurance directives was clearly higher in the late mixed dentition (41.4%) than in the early mixed dentition (8%).ZusammenfassungZiel:Unter Berücksichtigung der Kieferorthopädischen Indikationsgruppen-(KIG-)Klassifikation sollte der aktuelle kieferorthopädische Behandlungsbedarf bei Kindern in der späten Wechselgebissphase bestimmt werden. Durch Gegenüberstellung der Daten mit den Befunden aus dem frühen Wechselgebiss ist eine mögliche Veränderung im Anomaliespektrum festzustellen.Probanden und Methodik:Im Rahmen der schulzahnärztlichen Untersuchung in Frankfurt am Main wurden bei 1251 Schülern (weiblich 49,5%, männlich 50,5%) der vierten und fünften Jahrgangsstufe kieferorthopädisch relevante Befunde erfasst und mit vor 4 Jahren an denselben Schulen und Klassen erhobenen Daten verglichen.Ergebnisse:Unter den festgestellten Zahnstellungs- und Kieferanomalien mit großer Therapiebedürftigkeit im Sinne einer von den Krankenkassen finanzierten Behandlung dominierten in der Gruppe der 9- bis 11-Jährigen der laterale Kreuzbiss mit 9,2% und die vergrößerte sagittale Frontzahnstufe (über 6 mm) mit 8,7%. Unter allen registrierten Anomalien der KIG-Gruppe ≥3 waren die Kategorien D4 (sagittale Stufe über 6 mm) mit 17,4%, K4 (einseitiger Kreuzbiss) mit 15,3% und M4 (mesiale Stufe bis −3 mm) mit 14,9% am häufigsten vertreten. Eine Behandlungsindikation im Sinne der gesetzlichen Krankenversicherung (KIG ≥3) fand sich in 41,4% aller untersuchten Fälle. Die gesundheitspolitisch gewollte Reduzierung der vertragszahnärztlichen Behandlungsfälle um 10% [1] ist somit in jedem Fall gelungen.Schlussfolgerungen:Der Vergleich der Ergebnisse aus den Jahren 2000 und 2004 zeigte, dass mit zunehmendem Alter die Prävalenz einer bereits vergrößerten Frontzahnstufe anstieg und die Häufigkeit eines tiefen Bisses zunahm. Im späten Wechselgebiss wurde eine geringere Anzahl an frontal offenen Bissen und generell an Kreuzbissen festgestellt. Die Behandlungsbedürftigkeit entsprechend den jeweils gültigen GKV-Richtlinien im späten Wechselgebiss war mit 41,4% deutlich höher als im frühen Wechselgebiss mit 8,0%.

Three dimensional anatomical exploration of the anterior hard palate at the level of the third ruga for the placement of mini-implants – a cone-beam CT study

AIM The aim of this retrospective investigation was to measure vertical bone thickness on the hard palate, determine areas with adequate bone for the insertion of orthodontic mini-implants (MIs), and provide clinical guidelines for identification of those areas. MATERIALS AND METHODS Pre-treatment records of 1007 patients were reviewed by a single examiner. A total of 125 records fulfilled the inclusion criteria and were further investigated. Bone measurements were performed on cone-beam computed tomography scans, at a 90° angle to the bone surface, on 28 predetermined and standardized points on the hard palate. Bone thickness at various areas was associated to clinically identifiable areas on the hard palate by means of pre-treatment plaster models. RESULTS Bone thickness ranged between 1.51 and 13.86 mm (total thickness) and 0.33 and 1.65 mm (cortical bone thickness), respectively. Bone thickness was highest in the anterior palate and decreased significantly towards more posterior areas. Plaster model analysis revealed that bone thickness was highest at the level of the third palatal ruga. CONCLUSIONS The areas on the anterior palate with adequate bone thickness for successful insertion of orthodontic MI correspond to the region of the third palatal ruga. These results provide stable and clinically identifiable landmarks for the insertion of palatal MIs.

The most distal palatal ruga for placement of orthodontic mini-implants

OBJECTIVE To evaluate the stability and bone availability of the most distal (third) palatal ruga, as an anatomical region for safe insertion of orthodontic mini-implants (OMIs) in the anterior palate. STUDY DESIGN Orthodontic records of 35 patients were analysed. Initial (T1) and final (T2) study models were bisected and the outline of the palatal contour was marked on the surface. Models were scanned and the palatal contours were superimposed on the palatal structures on the respective initial and final cephalometric images. Cephalometric measurements were used to assess vertical (3rdRug-PP, 2ndRug-PP, and 1stRug-PP), and oblique bone levels (3rdRug-U1, 2ndRug-U1, 1stRug-U1, and 3rdRug-U1(o)). Paired Students t-test was used to compare measurements between T1 and T2. RESULTS The position of the third palatal ruga remained stable during orthodontic treatment (Δ2ndRug-3rdRug P = 0.1mm; P = 0.61 and Δ1stRug-3rdRug P = 0.2mm; P = 0.39). Bone availability also remained adequate (3rdRug-U1T2 (o) = 9.9mm). CONCLUSION The third palatal ruga is a reliable clinical landmark to evaluate bone availability for the placement of OMIs in the anterior palate.